Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session H1: Poster Session I (2:00 - 5:00PM) |
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Room: Exhibit Hall EF |
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H1.00001: MATTER AT EXTREME CONDITIONS |
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H1.00002: A Practical Realization of the Delayed Choice Method with Haunted Quantum Entanglement for Choosing at a Distance an Overall Distribution Exhibiting Either Which-Way Information or Interference Douglas Snyder This method extends the idea of Greenberger and YaSin's haunted measurement to entanglement. There is a delayed choice whether or not to keep the entanglement between paired photons where an idler photon provides which way information to a distant signal photon. One can produce a ww distribution or a distribution showing interference in the signal photons at a distance by either keeping the paired idler photons or losing them in many other similar photons. Movable mirrors can either send an idler photon to one of two detectors along the two idler photon paths or instead send the idler photon into two optical microcavities filled with photons similar to the idler photon. The result is two different distributions depending on whether the paired idler photon is lost before the signal photon is detected. Ultrafast switches for single entangled photons can be used instead of mirrors to change the paths for the idler photon while the idler photon is in flight. References to the delayed choice method with haunted quantum entanglement: http://meetings.aps.org/link/BAPS.2012.MAR.K1.303, http://meetings.aps.org/link/BAPS.2011.APR.S1.23, http://meetings.aps.org/link/BAPS.2011.APR.S1.22. [Preview Abstract] |
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H1.00003: Rarefaction wave propagation and longitudinal sound velocities in shock compressed tantalum to 105 GPa Robert Scharff, Paulo Rigg, Robert Hixson The purpose of this work is to investigate the bcc to hexagonal structural phase transition recently reported for shock compressed tantalum. Longitudinal sound velocities were obtained using a velocimetry diagnostic to record the shock and rarefaction wave arrival times at the sample/anvil interface in the reverse-ballistic plate impact geometry. This approach allows for the determination of the sound speed as a function of pressure and is sensitive to volume changes associated with phase transition behavior. The authors demonstrate that if elastic -- plastic wave interactions are correctly determined, then the high pressure structural phase transition that has been previously reported is notably absent. [Preview Abstract] |
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H1.00004: Crystal structure and phase stability of tungsten borides Quan Li, Dan Zhou, Yanming Ma, Changfeng Chen We address the longstanding and controversial issue of ground-state structures of technically important tungsten borides using a first-principles structural search method via a particle-swarm optimization (PSO) algorithm. We have explored a large set of stable chemical compositions (convex hull) and clarified the ground-state structures for a wide range of boron concentrations, including W$_2$B, W$_3$B$_2$, WB, W$_2$B$_3$, WB$_2$, W$_2$B$_5$, WB$_3$, and WB$_4$. We further assessed relative stability of various tungsten borides and compared the calculated results with previously reported experimental data. The phase diagram predicted by the presented calculations may serve as a useful guide for synthesis of a variety of tungsten borides. [Preview Abstract] |
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H1.00005: Determination of Equations of State for AlF3 and AlI3: Semi-empirical Modeling of Extreme Condition Halide Chemistry Joseph Zaug, Elissaios Stavrou, Sorin Bastea, Jonathan Crowhurst, Aleaxander Goncharov, Sarah Roberts, Jonathan Plaue, Jeffrey Carter, Michael Armstrong Pressure dependent angle-dispersive x-ray powder diffraction measurements of alpha-phase aluminum trifluoride (alpha-AlF$_{\mathrm{3}})$ and separately, aluminum triiodide (AlI$_{\mathrm{3}})$ were conducted using a diamond-anvil cell. Results at 295 K extend to 50 GPa. The equations of state of AlF$_{\mathrm{3}}$ and AlI$_{\mathrm{3}}$ were determined through refinements of collected x-ray patterns. The respective bulk moduli and corresponding pressure derivatives using multiple orders of the Birch-Murngahan, Ff, and Gg EoS models will be discussed. Aluminum trifluoride exhibits no pressure induced structural phase transition while the triiodide data reveal a second-order iso-structural rearrangement: Applied stress transformed a monoclinicly distorted face centered cubic (FCC) structure into a perfect FCC structure. Results from semi-empirical thermochemical computations of energetic materials formulated with fluorine containing reactants will be presented. * This work was performed under the auspices of the U.S. Department of Energy jointly by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
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H1.00006: High-pressure Raman scattering spectrum of K$_{0.74}$Fe$_{1.67}$Se$_{1.6}$S$_{0.4}$ Yonghui Zhou, Li Li, Zhaorong Yang, Yuping Sun, Yuheng Zhang, Xiao-Jia Chen, Ho-kwang Mao We perform high-pressure Raman scattering measurements on K$_{0.74}$Fe$_{1.67}$Se$_{1.6}$S$_{0.4}$ single crystal up to 20 GPa at room temperature. Anomalous changes of both the A$_{\mathrm{g}}$ and B$_{\mathrm{g}}$ phonon modes are found at a critical pressure around 5.0 GPa. Above this pressure, all Raman modes exhibit a hardening behavior at higher pressures. The superconducting transition temperature of this compound was observed to decrease with increasing pressure and vanish at the critical pressure. These results suggest that the lattice modification and the associated electronic structure are important to understand the superconductivity in the FeSe-based superconductors. [Preview Abstract] |
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H1.00007: Pressure tuning of spin-phonon coupling in ZnCr$_{2}$Se$_{4}$ by Raman spectroscopy Xuliang Chen, Xiao-Jia Chen, Zhaorong Yang, Yuping Sun, Yuheng Zhang, Wenge Yang, Ho-kwang Mao Raman scattering measurements are performed to investigate the phonon spectra of ZnCr$_{2}$Se$_{4}$ single crystal as functions of pressure and temperature. We find that five characteristic phonon modes vary simultaneously by changing pressure and temperature. With decreasing temperature, the phonon modes show anomalous shifts at $T_{\mathrm{E}}$, corresponding to the temperature of negative thermal expansion of lattice. With the application of pressure, in addition to the enhancements of frequency of Raman modes, $T_{\mathrm{E}}$ shifts to higher temperature, indicative of strengthening of spin-phonon coupling. [Preview Abstract] |
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H1.00008: Pressure-induced disappearance of superconductivity across isostructural transition in underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta }$ Jian-Bo Zhang, Xiao-Jia Chen, Ling-Yun Tang, Zhen-Xing Qin, Jiang Zhang, Mikhail Eremets, Jing Liu, Jin-Sheng Wen, Zhi-Jun Xu, Genda Gu, Ho-Kwang Mao There exist rich phenomena in the underdoped regime of cuprate superconductors. An underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ single crystal is chosen to investigate the pressure-driven evolution of the superconducting behavior and structural properties by electrical resistance and synchrotron X-ray diffraction measurements. We find that an isostructural phase transition starts at 16.0 GPa and a structural collapse occurs at around 23.7 GPa. Meanwhile, superconductivity is observed to disappear and superconductor-insulator transition takes place across the phase transition. These results suggest that the Fermi surface topology could undertake some modification at high pressures. [Preview Abstract] |
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H1.00009: Structural and vibrational properties of NaFe$_0.925$Co$_0.075$As under pressure Liu-xiang Yang, Xiao-jia Chen, Ho-kwang Mao, A.F. Wang, Y.J. Yan, X.G. Luo, X.H. Chen We perform high-pressure Raman scattering and synchrotron X-ray diffraction measurements on an overdoped NaFe$_{0.925}$Co$_{0.075}$As single crystal up to 20 GPa at room temperature. Both phonon spectra and structural parameters exhibit abnormal behaviors at a critical pressure around 3.0GPa. The superconducting transition temperature was observed to have a maximum at the same critical pressure. Pressure-induced modification of the Fermi surface topology is suggested to account for the observed behaviors. These results offer a better understanding on the superconductivity in this system far away the complex of structural and spin density wave phase transitions in the underdoped regime. [Preview Abstract] |
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H1.00010: Fabrication of microcoined metal foil Rayleigh-Taylor targets Greg Randall, James Vecchio, Paul Fitzsimmons, Jack Knipping, Don Wall, Matthew Vu, Emilio Giraldez, Tane Remington, Brent Blue, Michael Farrell, Abbas Nikroo Rippled metal foils are currently sought for high strain rate material strength studies. For example, the growth of these ripples by the Rayleigh-Taylor instability after a laser-induced ramped compression yields strength behavior at extremely high strain rate. Because metals of interest (iron, tantalum, steel, etc.) typically cannot be diamond turned, we employ a microcoining process to imprint the $\sim$ 5 $\mu$m deep by $\sim$ 50 $\mu$m long ripples into the metal surface. The process consists of nitriding a steel die, diamond turning the die, and then pressing the die into a polished metal foil of choice (Seugling et al., Proc EUSPEN Int. Conference, 2010). This work details recent process developments, characterization techniques, and important physics for fabrication of these rippled metal targets. [Preview Abstract] |
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H1.00011: Molecular Simulations of Biological Systems under Extreme Conditions Yuko Okamoto I will present the results of generalized-ensemble simulations of proteins under extreme conditions, namely, high pressure, high temperature, etc. Generalized-ensemble algorithms that we employed were pressure simulated tempering (Y. Mori and Y. Okamoto, J. Phys. Soc. Jpn. 79, 074003 (2010)), multicanonical replica-exchange method (Y. Sugita and Y. Okamoto, Chem. Phys. Lett. 329, 261 (2000)), and replica-exchange umbrella sampling (Y. Sugita, A. Kitao, and Y. Okamoto, J. Chem. Phys. 113, 6042 (2000)). We compare the results with those of experiments. [Preview Abstract] |
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H1.00012: SURFACES, INTERFACES AND THIN FILMS |
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H1.00013: Electronic and Structural Properties of the Oxidized Cu(110) Surface Antoine Olenga, N.G. Fazleev The study of adsorption of oxygen on transition metal surfaces is important for the understanding of oxidation, heterogeneous catalysis, and metal corrosion. In this work we present an ab-initio investigation of stability and associated physical and electronic properties of different adsorption phases of oxygen on Cu(110). Especially, we focus on studies of changes in the work function, surface energy, electronic density, interlayer spacing, density of states, and band structure of the Cu(110) surface with oxygen coverage. We examine the cases of high oxygen coverage of the reconstructed Cu(110) surface when the oxygen atoms occupy on-surface as well as sub-surfaces sites. Calculations of electronic properties from first principles have been also performed for the (110) surface of Cu2O to use for comparison. The first-principles calculations in this work have been performed on the basis of density functional theory and using DMOl3 code. The obtained theoretical results have been compared with available experimental data. This work was supported in part by the National Science Foundation Grant DMR-0907679 and the GAANN grant P200A090284. [Preview Abstract] |
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H1.00014: Two-dimensional electrons on KTaO3 surfaces Pumsuk Park, Byounghak Lee The two-dimensional electron gas systems at the interface of polar/non-polar oxides interfaces, e.g. LaAlO$_3$(LAO)/SrTiO$_3$(STO), have received considerable attention due to interesting phenomena stemming from strong electron-electron interactions. A recent experiment [1] showed that the (001) surface of KTaO$_3$ (KTO) can induce two-dimensional electron gas even without external doping. KTO differs from widely studied STO in that KTO has more than 20 times stronger spin-orbit coupling. We carried out density functional theory calculations of vacuum-cleaved KTO surface structure to study the electronic and spin properties of the two-dimensional electrons. The electric field that arises from the surface polarization makes the conduction electrons near the surface, resulting in an orbital ordering similar to LAO/STO interface. Despite the strong spin-orbit coupling, about 400 meV, our result shows the Rashba spin splitting in this perovskite oxide is much smaller than that of conventional semiconductors, which is a good agreement with the angle-resolved photoemission measurement.[1] P. D. C. King, et al. Phys. Rev. Lett. 108, 117602 (2012). [Preview Abstract] |
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H1.00015: Electric multipole interactions in an extended BEG model Teresa Burns, JR Dennison General 2D dielectric phase diagrams and phase transitions for multipolar molecules adsorbed to a square ionic crystal are presented. The adsorbed molecules are modeled using a dilute spin-one Ising model in the Blume-Emery-Griffiths formalism, using a mean-field approximation. Physical constants such as the electric multipole moments and binding energies are used to uniquely determine the interaction parameters over the full range of physically-relevant values. We find that temperature- and coverage-dependent antiferroelectric to ferroelectric, coverage-dependent ferroelectric up to ferroelectric down, reentrant ferroelectric to ferrielectric, and order-disorder dipole phase transitions can occur. The results are presented as a quasi-continuous set of phase diagrams. Extensions into ferro-electric parameter space are discussed and connections to analytical solutions are explored. [Preview Abstract] |
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H1.00016: Study of positron annihilation with core electrons at the clean and oxygen covered Ag(001) surface P. Joglekar, K. Shastry, A. Olenga, N.G. Fazleev, A.H. Weiss In this paper we present measurements of the energy spectrum of electrons emitted as a result of Positron Annihilation Induce Auger Electron Emission from a clean and oxygen covered Ag (100) surface using a series of incident beam energies ranging from 20 eV down to 2 eV. A peak was observed at $\sim$ 40 eV corresponding to the N23VV Auger transition in agreement with previous PAES studies. Experimental results were investigated theoretically by calculations of positron states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the clean and oxygen covered Ag(100) surface. An ab-initio investigation of stability and associated electronic properties of different adsorption phases of oxygen on Ag(100) has been performed on the basis of density functional theory and using DMOl3 code. The computed positron binding energy, positron surface state wave function, and positron annihilation probabilities of surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, elemental content, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data. [Preview Abstract] |
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H1.00017: Evidence for a Large, Thermal-Activated Characteristic Length Scale in Unstable Homoepitaxial Growth on GaAs(001) Chuan-Fu Lin, Hung-Chih Kan, S. Kanakaraju, C.J. Richardson, Raymond Phaneuf We report on observations of unstable growth on GaAs(001) surfaces nanopatterned with grooves of varying length/width aspect ratios. For homoepitaxial growth at temperatures near 500${^\circ}$, we find that ridges build up at the upper long edges of grooves oriented along [110]. No ridges form at the long edges of grooves oriented [110]; instead cusps form at the bottoms of such grooves. Most interestingly, we find that the evolution of ridge heights during growth breaks into two distinct branches, with the separation occurring at a groove length of 7.5 $\pm$ 2.5 $\mu$m for growth at 525${^\circ}$, and at a length which is an order of magnitude smaller than this for growth at 460${^\circ}$. These observations indicate the presence of very large, thermally-activated characteristic lengths which governs the evolution of the topography during growth. [Preview Abstract] |
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H1.00018: Dynamics of STM-Induced Switching of Melamine/Cu(001) based on first-principles calculations Tatsuhiko Ohto, Ivan Rungger, Koichi Yamashita, Hisao Nakamura, Sanvito Stefano The manipulation or stimulation of molecules using Scanning Tunneling Microscopy (STM) is a technique that recently has deserved deep attention for its potential applications in molecular electronics. The melamine/Cu(001) system was found to show switching behavior in very wide range of applied bias. Although its mechanism was analyzed by a statistic model, the relationship between the switching rate and bias is still far to be fully clarified. In this context, we performed a campaign of exhaustive first-principles calculations to obtain most of the parameters for resonance model; such model is able to predict the switching rate as functions of bias and current. The energy barrier was calculated using the nudged elastic band method, with the aid of recent implementation of current-induced forces into SMEAGOL code, which is based on the nonequilibrium Green's function method with Density Functional Theory. The electron-phonon coupling and then the Inelastic Tunneling Spectroscopy signal are calculated to validate the one-phonon approximation. The spatial distribution of molecular orbitals and their coupling with vibrational modes are very useful to understand the switching behavior. [Preview Abstract] |
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H1.00019: Straining Nanomembranes via Highly Mismatched Heteroepitaxial Growth Frank Flack, Christoph Deneke, Francesca Cavallo, Max Lagally Semiconductor membranes (NMs) combine the high quality electronic properties of single crystalline material with the increased compliance of a thin sheet. Lately it has been demonstrated that these layers can be used as templates for the growth of self-assembled nanostructures (Ge islands) and the growth is heavily influenced by the compliant substrate. To quantify the interplay between strained growth and compliance, we examine the growth of highly strained InAs on Si NMs. The large lattice mismatch between these two materials causes the substrate to bend due to strain sharing between the film and substrate. Atomic force microscopy of the resulting curved surface shows continuous variation in island density, indicating local modifications of adatom diffusivity and critical film thickness. X-ray diffraction and finite element modeling show that islands near the apex of the bent surface are highly strained and those near the bound edges are fully relaxed. Finally, we present continuum elasticity calculations suggesting that InAs films could grow epitaxially on Si which is not possible on bulk Si. [Preview Abstract] |
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H1.00020: High-resolution TEM study of Mg-doped Aluminum Nitride Epilayers Bo Cai, Mim Nakarmi Transmission electron microscopy (TEM) has been employed to study the threading dislocations in Mg-doped Aluminum Nitride (AlN) epilayers grown by metal-organic chemical vapor deposition. The Mg-doped AlN epilayer samples were grown on high quality AlN/Sapphire template of AlN thickness $\sim$ 1 $\mu $m. Atomic Force Microscopy and X-ray Diffraction were employed to characterize the surface morphology and the crystalline properties respectively. In the AlN template layers, TEM revealed that the dominant threading dislocation is the edge type dislocation with the average dislocation density of screw and edge dislocation in the order of 10$^{7}$ and 10$^{9}$ cm$^{-2}$ respectively. In this study, we present our investigation of the threading dislocations associated with Mg-doping in AlN by analyzing the plan-view and cross-section view of TEM images taken under two-beam conditions. We will also use high-resolution dark field and bright field TEM images to investigate the origin and nature of the threading dislocations. Implementation of our finding to improve the quality of Mg-doped AlN epilayers will also be discussed. [Preview Abstract] |
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H1.00021: Short Perfluoroalkane adsorption on MgO (100) and graphite Nathaniel Bass, John Z. Larese There has been recent interest in the adsorption properties of C$_{2}$X$_{6}$ and C$_{3}$X$_{8}$ (X=H,F) adsorbates on graphite $[1]$, silica $[2]$ and Mo (100) $[3]$ surfaces. In particular, Bruch has examined the lattice structure for the monolayer solid, as well as, the area per molecule for each adsorbate on the basal plane of graphite $[1]$. We will present the result of our thermodynamic efforts to quantify these parameters experimentally on the graphite basal plane. Furthermore, we extend our thermodynamic investigation to the adsorption of these fluoroalkanes to the (100) MgO surface. We report on the thermodynamic properties for both systems including enthalpy, entropy, and isosteric heat of adsorption as calculated using an extensive set of volumetric adsorption isotherms. The wetting properties and a phase diagram for a representative C$_{N}$F$_{2N+2}$ layered system will also be presented. $[1]$ L. W. Bruch, J. Phys. Chem. C 113, 17399 (2009). $[2]$ G. M. Leuty, A. Abu-Nada, and M. Tsige, J. Phys. Chem. C 116, 14514 (2012). $[3]$ G. M. Leuty and M. Tsige, J. Phys. Chem. B 115, 12694 (2011). [Preview Abstract] |
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H1.00022: ABSTRACT WITHDRAWN |
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H1.00023: Dependence of the electronic transport on the microstructure in annealed Bi thin films Thanh Nhan Bui, Jean-Pierre Raskin, Loic Malet, Stephane Godet, Frederico Rodrigues Martins, Sebastien Faniel, Xavier Gonze, Damien Cabosart, Benoit Hackens Bi thin films, with a thickness ranging from 10 to 100 nm, are deposited by electron-beam evaporation on a thermally oxidized Si(100) substrate. The deposition parameters are optimized in order to maximize the grain size of the polycrystalline films. The evolution of the crystal orientation is examined as a function of the deposition and annealing parameters, by electron back scattering diffraction. Low temperature (21 mK - 150 K) magnetoresistance measurements (up to 15 T) on polycrystalline films reveal weak anti-localization, superimposed by the classical magnetoresistance. The analysis of the weak anti-localization allows us to extract quantum transport parameters, such as the phase coherence and the spin orbit coupling time. From the evolution of the broad magnetoresistance background, we infer the evolution of electronic transport parameters: the mobility, the charge carrier concentration and the mean free path. Magneto-transport and ab initio calculations are combined in order to investigate on the controversial existence of the semimetal-semiconductor transition. [Preview Abstract] |
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H1.00024: Diffusion of carbon oxides in SiO$_2$ during SiC oxidation Toru Akiyama, Kohji Nakamura, Tomonori Ito, Hiroyuki Kageshima, Masashi Uematsu SiC is a wide-band-gap semiconductor and has an advantage to fabricate electronic devices such as MOSFETs due to the ability to thermally oxidize to SiO$_2$. Despite many studies conducted on the oxidation of SiC, the kinetics such as diffusion and interface reaction is not fully understood. Here, we focus on the diffusion process during SiC oxidation, and clarify the diffusion mechanism of carbon oxides (CO and CO$_2$) in SiO$_2$ by means of density functional calculations. Our calculations demonstrate that the CO without any chemical bonds with host SiO$_2$ is stabilized while the CO$_2$ is incorporated between Si-O bonds of SiO$_2$ to form a carbonate group. The energy of CO$_2$ is found to be lower than that of CO by 3.7 eV, indicating that the most stable form of carbon oxides in SiO$_2$ is CO$_2$. Furthermore, the calculated energy barriers for diffusion of CO and CO$_2$ are found to be 0.1 and 1.8 eV, respectively. These results thus imply that CO molecules easily react with oxidant such as O$_2$ to form CO$_2$ and the outward diffusion of resultant CO$_2$ is rate-limiting. Indeed, the estimated activation energy for CO$_2$ diffusion (3.5 eV) reasonably agrees with that for Si-face SiC (3.1 eV) obtained by Deal-Grove model considering product gas out-diffusion. [Preview Abstract] |
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H1.00025: ABSTRACT WITHDRAWN |
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H1.00026: HAXPES analysis of materials for electronics applications Conan Weiland, Pat Lysaght, Joseph Woicik To continue the scaling of memory and logic devices, new materials must be employed to replace the traditional Si/SiO$_{2}$. However, detailed understanding of the chemical and electronic structures of the new materials and interfaces must be achieved for employment. X-ray photoelectron spectroscopy (XPS) is an excellent tool for studying such materials due to its unique ability to probe both the chemical and electronic structure of materials. However, XPS analysis is inherently limited by the short inelastic mean free paths (IMFPs) of the photoelectrons, limiting the probe depth to the near surface region. To overcome this limitation, XPS using hard X-rays (HAXPES) can be used, increasing the probe depth to technology relavent thicknesses. We present recent HAXPES results of materials and interfaces for electronics applications. [Preview Abstract] |
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H1.00027: Surface Electronic Structure of Gadolinium Nitride Zane Gernhart, Chin Li Cheung, Juan Col\'on Santana, Lu Wang, Wai-Ning Mei In this work, we report our finding of the surface electronic structure of high-quality [100]-textured gadolinium nitride (GdN) thin films made by a chemical vapor deposition method. The demonstrated ability to synthesize high-quality thin films has allowed for a detailed inverse photoelectron spectroscopy (IPES) study to elucidate the surface band structure of GdN. The results of our study indicate that the band gap of the GdN surface is about a few milli-electron volts. These findings agree well with the predictions of a small density of states at the Fermi level and an overlap of bands at the gamma point from our density functional theory calculations for GdN slab models of eleven to twenty layers. Although it is accepted that GdN is ferromagnetic semiconductor, reports on the nature of the electronic structure of GdN have ranged from insulating to semi-metallic. We attribute this lack of agreement in the literature is likely due to a wide variation in the quality of the analyzed samples and the inability to consistently synthesize high-quality GdN films. Hence it is our belief that our in-depth study will provide insight to this promising ferromagnetic material with semiconducting behavior. [Preview Abstract] |
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H1.00028: Functionally Graded Nickel Matrix Alumina Reinforced Nanocomposites Austin Young, Stephen Farias, Robert Cammarata Hierarchical structured nanocomposites are of great interest particularly in the fields of defense, aeronautics, and metamaterials. Previous work has demonstrated the ability to create uniform nickel matrices embedded with aluminum oxide nanoparticles via electrodeposition using a rotating disk electrode (RDE) [1]. This process allows for controlled enhancement of yield strength without negatively affecting other properties [2]. The speed of the RDE controls the rate of particle incorporation, and therefore, particle volume fraction. Hierarchical structures can be formed by simply changing the rotation rate during electrodeposition. This allows for controlled variations of composite structure throughout the material. Simply layered and functionally graded hierarchical materials have been produced using this method with structural resolution of the order of single microns. These layered structures produced unique mechanical properties, even exceeding those of uniformly dispersed composites.\\[4pt] [1] J.W. Kaczmar et al, The production and Application of metal matrix composite materials, 63 (2000)\\[0pt] [2] Ingrid, Synthesis and characterization of particle reinforced NiAl$_{2}$O$_{3}$ and FeCoTiO$_{2}$ nanocomposites, Ch.4. [Preview Abstract] |
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H1.00029: Spectroscopic Ellipsometry Measurements of Wurtzite Gallium Nitride Surfaces as a Function of Buffered Oxide Etch Substrate Submersion Chester Szwejkowski, Costel Constantin, John Duda, Patrick Hopkins Gallium nitride (GaN) is considered the most important semiconductor after the discovery of silicon. Understanding the optical properties of GaN surfaces is imperative in determining the utility and applicability of this class of materials to devices. In this work, we present preliminary results of spectroscopic ellipsometry measurements as a function of surface root mean square (RMS). We used commercially available 5mm x 5mm, one side polished GaN (3-7 $\mu$m)/Sapphire (430 $\mu$m) substrates that have a wurtzite crystal structure and they are slightly n-type doped. The GaN substrates were cleaned with Acetone (20 min)/Isopropanol(20 min)/DI water (20 min) before they were submerged into Buffered Oxide Etch (BOE) for 10s - 60s steps. This BOE treatment produced RMS values of 1-30 nm as measured with an atomic force microscope. Preliminary qualitative ellipsometric measurements show that the complex refractive index and the complex dielectric function decrease with an increase of RMS. More measurements need to be done in order to provide explicit quantitative results. [Preview Abstract] |
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H1.00030: High Surface Area Nanoporous Ti02 Coating for Effective Water Condensation. Mehmet Burak Kaynar, Mark Mcgarity, Emre Yassitepe, S. Ismat Shah A water collection device utilizing nanoparticles has been researched, towards the possible goal of providing water in much needed areas on Earth. Titanium dioxide nanoparticles were spray coated on stainless steel substrates to measure their effect on atmospheric water condensation. A simple thermoelectric cooler, also called a Peltier device, was used to lower the temperature of the coated and uncoated stainless steel substrates to below the dew point temperature of the surrounding air. The thickness of the spray coating was varied to measure its effect on water condensation. This increase in surface area had a direct effect on the amount of water condensed. Compared with bare stainless steel, the TiO2 spray coated stainless steel had a considerably smaller contact angle of H20 droplets. In addition, the super-hydrophilic properties of TiO2 allowed water to flow more easily off the device. [Preview Abstract] |
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H1.00031: Effects of epitaxial strain on oxygen vacancy ordering in LaCoO3 films Neven Biskup, Virat Mehta, Steven Pennycook, Yuri Suzuki, Maria Varela We report on atomically-resolved Z-contrast imaging and electron-energy-loss spectroscopy of epitaxial LaCoO3 thin films grown on SrTiO3, LaAlO3 and (LaAlO3)(SrTaO3) substrates. Regardless of the sign and magnitude of the epitaxial strain imposed by substrate, the LaCoO3 thin films contain oxygen vacancies to varying degrees. These oxygen vacancies tend to order parallel to the film/substrate interface in LCO films under tensile strain and perpendicular under compressive strain. Oxygen vacancy ordering results in charge ordering (CO) among the Co ions as observed by EELS through analysis of the Co L2,3 intensity ratio. We will discuss the amount of oxygen vacancies, the resulting superstructures and CO in the context of the ferromagnetismobserved in these films. [Preview Abstract] |
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H1.00032: Epitaxial Growth of Atomically Flat Yttrium Iron Garnet Thin Films on Gadolinium Gallium Garnet by Pulse Laser Deposition Tao Lin, Chi Tang, Jing Shi Yttrium iron garnet (YIG) is a ferrimagnetic insulator which is useful for magneto-optical, microwave, and more recently spintronic devices. Pulsed laser deposition (PLD) has emerged as a preferred technique to deposit complex oxide thin films, heterostructures, and superlattices with high quality. Deposition of YIG films using PLD has been reported by several groups. The layer-by-layer growth mode has been achieved with a high laser repetition rate. No details about surface morphology were discussed. Here we report our approach to grow YIG films with thickness ranging from 10 to 100 nm on (110)- and (111)-oriented gadolinium gallium garnet (GGG) substrates. In both orientations, we have successfully grown epitaxial YIG thin films confirmed by the patterns of the reflection high-energy electron diffraction. The magnetic properties are measured by a vibrating sample magnetometer. The in-plane easy-axis coercivity is less than 1 Oe, while the perpendicular saturation field is $\sim$ 2000 Oe. For both orientations, the atomic force microscopy images show that the YIG surface is extremely flat with roughness $\sim$ 0.6{\AA}. Flat terraces are found with the atomic step height in films with both orientations. This work paves the way to engineering anisotropy of the thin films for YIG-based magnetic devices. [Preview Abstract] |
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H1.00033: Investigation of CaMnO$_3$ Epitaxial Thin Films by High Resolution X-ray Diffraction and Atomic Force Microscopy Grace Yong, Tyler Goehringer, Evan Schulz, E. Kevin Tanyi, David Schaefer, Rajeswari Kolagani CaMnO$_{3}$ is a perovskite material of interest for its catalytic properties. As the surface characteristics are important in determining the catalytic properties of thin films, we are investigating the structural and morphological characteristics of epitaxial films thin films grown by Pulsed Laser Deposition. Film structure and morphology are sensitive to variations in the deposition conditions such as the deposition oxygen pressure. We are characterizing the films using high resolution x-ray diffraction in the reflectivity mode (low angle measurements) and using Atomic Force Microscopy. We will study Kiessig fringes as a function of film growth conditions. The film thickness can be determined from the period of the fringes and roughness can be characterized by the angular range of the fringes. We will compare the surface roughness obtained by x-ray reflectivity with those obtained using AFM (atomic force microscopy). [Preview Abstract] |
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H1.00034: Observation of growth of Si(111)-7x7 reconstructed surface with simultaneous step flow and nucleation Shin-ichiro Kobayashi, Masahi Matsushita, King Itaya The structure of Si(111)-7x7 surface (7x7) has been extensively investigated for five decades and established, both experimentally and theoretically, that the reconstructed surface is described by the dimer-adatom-staking fault model. Recently, we succeeded in observing the peculiar 7x7 surface in not only macroscopic area but also atomic level. Images by the leaser confocal microscopy (LCM)[1] provided us the alternative step structure in macroscopic area. By utilizing AFM, the step height almost corresponded to the step for ten layers of atomic step. This indicates that the step bunching by step flow was occurred by current heating to Si substrate. In addition, by investigating the atomic surface by STM in detail, we could find Si clusters or inlands with about 10 nm$^{\mathrm{2}}$ at the tip of the step as well as confirm the step bunching. The growth of this structure is originated from simultaneous nucleation by unit cell on 7x7 surface due to energy fluctuation and step flow by current heating. Observation of surface in wide range area by SPM and LCM is useful to understand the growth of mechanism of ultra-flat surface in semi-conductive and metallic surfaces. [1] S. Kobayashi et al, Electrochem. Solid-State Lett., 14, H351(2011) . [Preview Abstract] |
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H1.00035: Epitaxial growth mechanisms of graphene and effects of substrates V. Ongun Ozcelik, Seymur Cahangirov, Salim Ciraci Graphene growth and energy barrier calculations of defect healing were investigated using ab-initio MD calculations[1]. It was found that there are two mechanisms which play crucial roles in the growth of graphene. First mechanism is the formation of large carbon rings at the edges which eventually collapse to form honeycomb structure with defects. This collapse is found to be initiated by the new coming carbon atoms which replace one of the bonds in the ring, and expands it until the critical size is reached. Second mechanism is the formation of PH defects near the edge and their healing. We have shown that the energy barrier needed to overcome during healing of the PH defects are much lower than that of the SW defects. We have shown that the presence of a BN or Ni substrate have crucial effect on growth. These substrates guide the formation of honeycomb structures from carbon rings and enable the healing of specific defects as growth proceeds. We also studied graphene growth using carbon dimers as building blocks and found that defect formation is less frequent as compared to growth with monomers.\\[4pt] [1] V. Ongun Ozcelik, S. Cahangirov and S. Ciraci, Phys. Rev. B 85, 235456 (2012) [Preview Abstract] |
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H1.00036: Optical Properties of ZnO/Cu Nanolaminate Materials by Spectroscopic Ellipsometry Seth King, Loralee Bilke, Joseph Krueger, Elizabeth Tennyson, Benjamin Oleson Laminate materials in which ZnO and a metal are layered on the naonometer scale show great promise as transparent conducting oxides (TCO) [1,2]. However, for these materials to be employed in TCO applications a complete understanding of their optical properties must be gained. Specifically, the impact of varying the oxide and/or metal layer thickness, and the number of total laminations layers must be explored. In this study we employ UV -- Vis spectroscopy and spectroscopic ellipsometry to investigate variations in the index of refraction, transmittance, and the optical bandgap of ZnO/Cu nanolaminates as a function of Cu interlayer thickness. [1] J.S. Cho, S. Baek, and J.C. Lee; SOLAR ENERGY MATERIALS AND SOLAR CELLS, \textbf{95}, 7, 1852-1858 (2011) [2] J.G. Lu, X. Bie, Y.P. Wang, L. Gong, and Z.Z. Ye; JOURNAL OF VACUUM SCIENCE {\&} TECHNOLOGY A, \textbf{29}, 3, 03A115 (2011) [Preview Abstract] |
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H1.00037: STRONGLY CORRELATED SYSTEMS, INCLUDING QUANTUM FLUIDS AND SOLIDS |
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H1.00038: Magnetic and structural properties of BiFeO$_{3}$ thin films grown epitaxially on SrTiO$_{3}$/Si substrates Nikoleta Theodoropoulou, Daniel Currie, Ryan Laughlin, Rocio Contreras-Guererro, Aruna Dedigama, Weerasinghe Priyantha, Ravindranath Droopad, Peng Gao, Xiaoqing Pan The integration of oxides with semiconductors is important for the technological advancement of the next generation electronics. Concomitant ferroelectric and antiferromagnetic (AF) behavior is demonstrated in single crystal BiFeO$_{3}$ (BFO) films grown on 20 nm SrTiO$_{3}$ (STO) virtual substrates on Si (100) using MBE. Commensurate STO thin films are grown on Si in an oxide MBE chamber by co-deposition of Sr, Ti and molecular O$_{2}$. The STO/Si films are used as a virtual substrate for MBE deposition of BFO without breaking vacuum. The RHEED image of BFO shows a 2-D growth front with a 6-fold surface reconstruction under optimized conditions. Cross-sectional TEM confirms the high crystallinity of the films and shows sharp, atomically flat interfaces. The SADP reveals that BFO grows in a distorted rhombohedral crystal structure. XRD does not show formation of second phases and is consistent with the TEM and SADP results. The BFO films show AF behavior with a Neel temperature that exceeds 350 K and with a residual ferromagnetic behavior that decreases with film thickness. The saturation magnetization for a 20 nm film was 180 emu/cm$^{3}$. The ferroelectric behavior of the films was verified using Piezoresponse Force Microscopy. [Preview Abstract] |
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H1.00039: Hund's coupling and spin-orbit coupling in iridates revisited Hua Chen, Guru Khalsa, Allan H. MacDonald In recent years iridates have attracted a lot of interests because of unusual properties due to a combination of strong correlations and strong spin-orbit scattering. The magnetic properties of these materials are often analyzed theoretically by applying the Kugel-Khomskii model and specifically considering the $J=\frac{1}{2}$ subspace decoupled by strong spin-orbit coupling. It is not obvious that such an approach is always valid, however, given that the spin-orbit coupling, on-site correlation energies, intra-atom exchange energies, tetragonal splittings, etc. all have comparable strength. In this work we will revisit the magnetic interactions of these materials combining insights from an examination of the 2-electron multiplet structure of a $t_{2g}$ ion using the Slater theory of atomic structure, and ab initio electronic structure calculations. We will also discuss the the magnetic anisotropy and domain-wall energies of specific iridate materials implied by these magnetic interactions. [Preview Abstract] |
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H1.00040: Magnetic properties and compositional homogeneity in (Ce,La,Sr)(Ti,Fe)O$_3$ films Xueyin Sun, Peng Jiang, Lei Bi, Dong Hun Kim, Daming Jiang, Gaohui wu, G.F. Dionne, C.A. Ross Single crystal films of Sr(Ti$_{\mathrm{1-x}}$Fe$_{\mathrm{x}})$O$_{3}$ are magnetic well above room temperature with up to 0.8 $\mu_{\mathrm{B}}$/Fe and exhibit strong out-of-plane magnetoelastic anisotropy. The properties are governed by the Fe valence states which can be manipulated by substitution on the A-site. Here, $\sim$150 nm thick films of (A$_{\mathrm{y}}$Sr$_{\mathrm{1-y}})$(Ti$_{0.6}$Fe$_{0.4})$O$_{3}$ where A$=$La or Ce were grown on (LaAlO$_{3})_{0.3}$(Sr$_{2}$AlTaO$_{6})_{0.7}$ substrates by pulsed laser deposition. The La and Ce raised the saturation moment but lowered the optical transparency as the average Fe valence decreased. Theoptical band gap widened and the Fermi level moved toward the vacuum level with increased Ce or La content. The composition distribution in a film with 30{\%} Ce was analyzed by high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).The film showed columnar growth with homogeneous distribution of Ce, Fe, Ti and O, precluding the possibility of clustering or phase separation. [Preview Abstract] |
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H1.00041: Fluorination of epitaxial oxides: Creating ferrite and nickelate oxyfluoride films Steven May, Eun Ju Moon, Yujun Xie, David Keavney, Justin Goebel, Eric Laird, Christopher Li In ABO$_3$ perovskites, the physical properties are directly coupled to the nominal valence state of the B-site cation. In epitaxial thin films, the dominant strategy to control B-site valence is through the selection of a di- or trivalent cation on the A-site. However, this approach is limited, particularly when electron doping on the B-site is desired. Here we report a simple method for realizing oxyfluoride films, where the substitution of F for O is expected to reduce the B-site valence, providing a new means to tune electronic, optical and magnetic properties in thin films. Fluorination is achieved by spin coating an oxygen deficient film with poly(vinylidene fluoride). The film/polymer bilayer is then annealed, promoting the diffusion of F into the film. We have used this method to synthesize SrFeO$_{3-\delta}$F$_\delta$ and LaNiO$_{3-\delta}$F$_\delta$ ($\delta$ ? 0.5) films, as confirmed by x-ray photoemission spectroscopy and x-ray absorption spectroscopy. [Preview Abstract] |
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H1.00042: Coexistence of Ferromagnetism and Ferroelectric Polarization in Epitaxial NiTiO$_{3}$ thin films with the LiNbO$_{3}$-Type Structure Tamas Varga, Timothy Droubay, Mark Bowden, Scott Chambers, Robert Colby, Bernd Kabius, Edoardo Apra, William Shelton, Vaithiyalingam Shutthanandan In a search for new multiferroic materials where the direction of magnetization can be switched by an applied electric field, we have looked for materials in which polarization and magnetization are strongly coupled. Recent theory calculations predicted that the family of compounds MTiO$_{3}$ (M $=$ Mn, Fe, Ni), in a certain polymorphic structure (acentric \textit{R3c}), are promising candidates where a polar lattice distortion can induce weak ferromagnetism (WFM). Guided by these insights, the \textit{R3c} phase of NiTiO$_{3}$ has been prepared in epitaxial thin film form. The synthesis of these NiTiO$_{3}$ films, their full structural characterization, physical property measurements along with first-principles DFT calculations to predict the desired NiTiO$_{3}$ structure, its stability, and the effect electronic structure on the ferroic properties are presented. Optical SHG imaging of the NiTiO$_{3}$ films indicates a polar lattice. Temperature-dependent magnetization measurements suggest a Neel transition consistent with the \textit{R3c} structure. Our field-dependent magnetization results show a residual magnetism below the Neel temperature suggesting the presence of a ferromagnetic moment induced by the polar lattice distortion. These results validate theory predictions about the coexistence of WFM and ferroelectric polarization in MTiO$_{3}$ compounds with the \textit{R3c} structure. [Preview Abstract] |
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H1.00043: Trapping of three-dimensional Holstein polarons by various impurities Hadi Ebrahimnejad, Mona Berciu We study the bound states of a three-dimensional Holstein polaron near various kinds of single impurities, using the momentum-average approximation. We show that the electron-phonon coupling renormalizes the impurity potential into a strongly retarded effective potential, which describes essential physics ignored by ``instantaneous'' approximations. The accuracy of our method is gauged by comparison with results from diagrammatic Monte Carlo for the case of an impurity that modifies the on-site energy of the electron. We also discuss impurities that modify the local strength of the electron-phonon coupling as well as isotope substitutions that change both the electron-phonon coupling and the phonon frequency. For the latter, we recover a threshold value of the electron-phonon coupling below which, no matter how strong the impurity is, polaron can not be trapped. [Preview Abstract] |
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H1.00044: Electrical transport properties of BaTiO$_{3}$/LaAlO$_{3}$/SrTiO$_{3}$ heterostructure Thach Ngo, Lkhagvasureen Baasandorj, Jonghyun Song, Jinhee Kim Strongly correlated materials with incompletely filled d- of f-electron shells exhibit unusual electronic and magnetic properties, which cannot be effectively explained in terms of non-interacting electron model, and hence hold the promise of novel electronic applications. Here we report the tunneling measurement across BaTiO$_{3}$/LaAlO$_{3}$/SrTiO$_{3}$ heterostructure revealing the metal-insulator transition (MIT), at low temperatures, modulated by varying BaTiO$_{3}$ (BTO) layer thickness. Accordingly, we observed an Ohmic behavior at temperatures $>$ 200 K for all BTO thicknesses, this can be understood with thermoionic emission mechanism, and a clear rectification at low temperatures. The direct tunneling lends a good explanation for the structures with thin BTO layer ($<$ 8 unit cells) and the critical thickness for Zener tunneling contribution is 20 unit cells of BTO. The MIT was clearly observed in the structure with 18 unit cells of BTO. [Preview Abstract] |
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H1.00045: Effect of the substitution of Y, Nd, Sm and Eu for La in $La_{1.4}Ca_{1.6}Mn_2O_7$ on its structural and magneto-electrical properties at constant chemical pressure Cabir Terzioglu, Sevgi Polat Altintas A systematic study of the electrical and magnetic transport properties of the layered manganite $(La_{1-y}R_y)_{2-2x}Ca_{1+2x}Mn_2O_7$ (R=Y, Nd, Sm, Eu and x=0.3) is presented. The average A-site ionic radius $< r_A >$ is kept constant at 1.327 {\AA} and the role of the magnetic moment of rare earth ion has been studied by characterizing physical properties of the layered manganites. These materials were prepared by solid state reaction route and were characterized comparatively by X-ray diffraction (XRD), AC susceptibility and electrical resistivity measurements. The electrical resistivity in the entire temperature range is found to fit well with the phenomenological percolation model, which is based upon the phase segregation of ferromagnetic clusters and paramagnetic insulating regions. [Preview Abstract] |
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H1.00046: Structural and magneto-electrical properties of fluorine doped $La_{0.7}Ca_{0.3}MnO_3$ perovskite manganites Sevgi Polat Altintas, Nabil Mahamdioua, Cabir Terzioglu, Abderrezak Amira The role of fluorine doping for oxygen in $La_{0.7}Ca_{0.3}MnO_yF_x$ (x=0.0, 0.2, 0.4, 0.6) system has been investigated by means of X-ray diffraction, resistivity and susceptibility measurements. The oxygen content of the samples was determined by a redox back titration method and the Rietveld refinement was used to characterize structurally the manganites. The metal-insulator transition temperature T$_{MI}$ of all samples is found to increase by fluorine doping. In order to understand the conduction mechanism, the phenomenological percolation approach which depends on the phase segregation of ferromagnetic clusters and paramagnetic insulating regions was used. [Preview Abstract] |
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H1.00047: Two metal-insulator transitions in Iridates T. Das The experimental discovery of metal-insulator transition (MIT) in clean Iridates came as a surprise since electron-electron correlation is known to be weaker than the effective bandwidth of the extended 5d electrons of Iridium ion. Numerous studies indicate that the strong spin-orbit coupling in this system is responsible for the insulating behavior. Theories of MIT include strong coupling spin-liquid, Mott physics or weak-coupling Slater-type spin-ordering. Here we show that there exists another MIT in the spin-orbit density wave channel, which wither coexists with the spin-ordering insulator or phase separated in the parameter space of chemical potential, Coulomb interaction and spin-orbit coupling strength. The results are compared with various experimental data which support this proposal. [1] T. Das, Phys. Rev. Letts. (2012). Work is supported by US DOE. [Preview Abstract] |
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H1.00048: Vortex lattice disorder and the stability of nucleated topological liquids Ville Lahtinen, Andreas Ludwig, Simon Trebst When interacting non-Abelian anyons are arranged on a regular lattice, such as an Abrikosov lattice in a topological superconductor or a Wigner crystal in a fractional quantum Hall liquid, it has been shown that a new topological state is nucleated. Studying Majorana mode binding vortex lattices in Kitaev's honeycomb model, we show that the nucleated phases are stable with respect to both moderate vortex dimerization and local random disorder. In the limit of strong disorder, the first will recover the parent topological state, while the latter will drive the system into a gapless thermal metal state. [Preview Abstract] |
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H1.00049: Quantum order-by-disorder in an extended Shastry-Sutherland model Keola Wierschem, Pinaki Sengupta We show two examples of quantum order-by-disorder processes in an extended Shastry-Sutherland model. This model incorporates uniaxial exchange anisotropy along with additional next-nearest-neighbor bonds not present in the canonical Shastry and Sutherland model. Moreover, the transverse component of exchange is ferromagnetic, while the longitudinal component remains antiferromagnetic. This guarantees the model to be free of the quantum Monte Carlo sign problem, and we thereby explore two regions of the phase diagram that display the order-by-disorder phenomenon. In the first instance, we show that quantum fluctuations can turn a highly degenerate solid phase into a supersolid phase with higher degrees of diagonal order than the solid phase. In the second instance, the highly degenerate states along a phase boundary are lifted by quantum fluctuations and replaced by a striped solid phase. [Preview Abstract] |
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H1.00050: Indication of an internal field along the basal plane below the hidden order temperature in URu$_2$Si$_2$ from $^{29}$Si-NMR in a random powder sample Edith Soto, Oscar Bernal We present a study of the lineshape of $^{29}$Si NMR spectra in hidden-order URu$_2$Si$_2$ for relatively low applied fields (1 and 2~T) and temperatures from 5 to 300~K. The random-powder pattern we obtained changes considerably at the transition temperature (17.5~K). Fitting the spectra to a powder pattern of axial symmetry (for which one can define the parameters: $h_{||}$ and $h_{\bot}$ to locate the position of the spectral feature that corresponds to the orientation of the applied field parallel and perpendicular to the $c$-axis respectively) allows us to address the question of whether changes on the parameters imply an internal field throughout the sample. From these data we have been able to conclude that there is indeed a shift in the position of the line in the perpendicular geometry. The change in frequency units is between 3 and 4~kHz, which correspond to a field of about 4~G, just as we found previously for a single crystal. This is not the case for the parallel geometry, for which the strong $T$ dependence of the paramagnetic broadening and shift precludes us from making a similar conclusion. [Preview Abstract] |
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H1.00051: Electronic Tuning in CeCoIn$_{5}$ K. Gofryk, F. Ronning, J.-X. Zhu, M.N. Ou, P.H. Tobash, X. Lu, E.D. Bauer, J.D. Thompson, S.S. Stoyko, A. Mar, T. Park, Z. Fisk We report a globally reversible effect of electronic tuning on the magnetic phase diagram in CeCoIn$_{5}$ driven by electron (Pt and Sn) and hole (Cd, Hg) doping. Consequently, we are able to extract the superconducting pair breaking component for hole and electron dopants with pressure and codoping studies, respectively. We find that these nominally nonmagnetic dopants have a remarkably weak pair breaking effect for a $d$-wave superconductor. The pair breaking is weaker for hole dopants, which induce magnetic moments, than for electron dopants. Furthermore, both Pt and Sn doping have a similar effect on superconductivity despite being on different dopant sites, arguing against the notion that superconductivity lives predominantly in the CeIn$_{3}$ planes of these materials. In addition, we shed qualitative understanding on the doping dependence with density functional theory calculations. [Preview Abstract] |
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H1.00052: Torsion Pendulum energy dissipation due to $^3$He in aerogel. Dissipation signature of the A-phase Nikolay Zhelev, Robert Bennett, Johannes Pollanen, Eric Smith, William Halperin, Jeevak Parpia A torsion pendulum excited at acoustic frequencies was used to measure the dissipation $Q^{-1}$ and period shift of $^3$He confined in a 98\% open aerogel, compressed by 10\% along the axial direction. Data was taken in the range between 100mK and T$_c$, as well as below T$_c$ for a series of pressures. After accounting for bulk and empty cell contributions, $Q^{-1}$ is seen to be pressure and temperature independent in the normal state. The dissipation is larger than expected, which can be accounted for either by invoking a very long frictional relaxation time or by taking into account the internal friction in the aerogel that is affected by mass loading of $^3$He. In contrast, the dissipation in the superfluid state depends strongly on temperature and pressure. The A phase (observed on cooling) shows a higher dissipation than the B phase (observed on warming); the excess dissipation is greater at high pressures. [Preview Abstract] |
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H1.00053: A Study of the Superfluid Transition in Helium Films Adsorbed to a Rough CaF$_2$ Surface Over a Large Temperature Range Marty Schwarz, Laura Wadleigh, Dwight Luhman Rough two-dimensional substrates, such as thermally deposited CaF$_2$, have been shown to modify the experimental signatures of the superfluid transition in adsorbed thin helium films. Previous experiments have investigated a series of increasingly rough surfaces over a limited temperature range and found that the features at the superfluid transition become less defined as substrate roughness is increased. In this work we use a single rough CaF$_2$ substrate and study the superfluid transition in adsorbed helium films over a wide range of temperatures. Our results show that as the transition temperature increases the abrupt jump in superfluid density at the transition become less distinct. The changing characteristics of the transition on a single CaF$_2$ substrate with temperature suggest that the reduced observability of the transition on rough substrates cannot be explained entirely by simple surface geometry effects, such as tortuosity. [Preview Abstract] |
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H1.00054: Single-Photon-Sensitive Superconducting TES Sensors for EUV Photons in Superfluid Helium Faustin Carter, Scott Hertel, Daniel Prober, Daniel McKinsey Incident radiation can excite superfluid helium into a diatomic He2* excimer, which decays through the emission of a 15~eV photon. Such excimers have been used as tracers to measure the superfluid's quantum turbulence, thanks partly to the long half-life of the He2* triplet state ($\sim$13 seconds). However, the efficient detection of these excimers remains a challenge. This work presents two different detector designs capable of in-situ detection of the He2* excimers either directly, or by collecting the 15~eV emission upon decay. Both detectors are based on the superconducting transition edge sensor. One is designed to operate near 2~K, while the other is designed for $\sim$100 mK operation in a dilution refrigerator. We will discuss operating characteristics of both, and present preliminary data from the 2~K detector. [Preview Abstract] |
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H1.00055: INSULATORS AND DIELECTRICS |
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H1.00056: Band alignment in Ge/GeO$_{\mathrm{x}}$/HfO$_2$/TiO$_2$ heterojunctions as measured by hard x-ray photoelectron spectroscopy Abdul Rumaiz, Joseph Woicik, Conan Weiland, Q. Xie, Peter Siddons, Christophe Detavernier Hafnium based high-k materials have been widely studied to replaced SiO$_2$ as a gate insulator in field effect transistors. Apart from offering low equivalent oxide thickness, they also offer a favorable band offset with Si. The development in the field of high-k dielectrics has also reduced the significance of Si/SiO$_2$ interface, thus opening new possibilities with high mobility semiconductors such as Ge. It is well known that the leakage current of a gate stack is dependent on the dielectric constant and the tunnel barrier height. Based on the current scaling trend, an oxide with k $\sim$ 40 would be ideal. Among the widely studied oxides TiO$_2$ is known to have a very high dielectric constant. However the poor conduction band offsets with both Si and Ge, makes it completely impractical as a gate oxide material. The problem of poor conduction band offset has been addressed by introducing a suitable interlayer with higher conduction band offset. In our work we investigate the interlayer thickness dependence of band alignment in a germanium based bilayer metal-oxide-semiconductor sandwich with an amorphous HfO$_2$ and TiO$_2$ high k gate dielectric using hard x-ray photoelectron spectroscopy. We see a strong evidence of intermixing at Hf-Ge interface and a deviation from bulk offset for ultra thin HfO$_2$. [Preview Abstract] |
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H1.00057: Strain controlled ferroelectric switching time of BiFeO$_{3}$ capacitors Er-Jia Guo, Andreas Herklotz, Kathrin Doerr Recent advances in the epitaxial growth of complex oxide thin films made an artificial control of the strain states of ferroelectric (FE) films possible However, it is quite difficult to separate the intrinsic strain effects on FE switching from those effects resulting from the variable microstructures and defects. For this reason, the switching kinetics which is particularly sensitive to defects has not yet been investigated in controlled strain states. In this paper, we investigated the strain-dependent switching of BiFeO$_{3}$ capacitors grown on piezoelectric PMN-PT substrates at various temperatures. The FE switching exhibits good agreement with the KAI model. The strain-induced relative change of the switching time is different in the low and high electric field regions, showing a crossover from slowing down at low fields to acceleration of the switching at high fields under $\sim$0.1{\%} of reversible compressive strain. We attribute this behavior to the difference between the dynamics of domain-wall propagation in the creep and depinning regimes. As the temperature decreases, a tenfold strain-induced enhancement of the switching time was observed as a result of reduced thermal activation and the strain-induced rise of the pinning potential. This work will advance the fundamental understanding of the domain switching processes. The huge sensitivity of the switching time bears a strong potential for the optimization of FE devices. [Preview Abstract] |
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H1.00058: Domain formation and dielectric response in PbTiO$_3$: A first-principles free energy landscape analysis Anil Kumar, Karin Rabe, Umesh V. Waghmare We determine the relative thermodynamic stability of competing homogeneously and inhomogeneously ordered ferroelectric phases of PbTiO$_3$ using its free energy landscape, obtained from a newly developed method based on a combination of constrained polarization molecular dynamics simulations with a first-principles effective Hamiltonian and thermodynamic integration. While we find that the tetragonal structure is thermodynamical ly most stable at temperatures below the ferroelectric transition temperature ($T_0=660 K$), free energy of an ``orthorhombic-like'' 90$^{\circ}$ domain phase relative to the tetragonal phase almost vanishes at $T=540 K$, and remains small at all temperatures below $T_0$. In contrast to BaTiO$_3$, 90$^{\circ}$ domain walls are an order of magnitude lower in energy than 180$^{\circ}$ domain walls. We show that the computed dielectric response of the ``orthorhombic-like'' phase includes contributions from domain walls, and thus is significantly larger than that of the unifor mly polarized tetragonal phase of PbTiO$_3$. [Preview Abstract] |
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H1.00059: ABSTRACT WITHDRAWN |
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H1.00060: Probing laser induced space charge fields with Engineered Defects Hosanna Odhner, Greg Stone, Volkmar Dierolf We report on the ability to measure the buildup of space charge fields in ferroelectric materials with engineered defects, such as optically active rare earth ions. Analysis of the erbium emission reveals several changes in the intensity, frequency, and width of several peaks that occur on different time scales. Also, these changes are sensitive to the intrinsic defect concentration and the addition of extrinsic defects. Comparatively the magnitude of the spectral shifts for the different erbium peaks in erbium peaks are similar to those seen for an applied external electric field across the z-axis of the crystal. Also, several new peaks appear in the erbium emission demonstrating the ability to probe simultaneous changes in defect complexes. [Preview Abstract] |
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H1.00061: Structure and Properties of Hexagonal R$_{\mathrm{x}}$MnO$_{3+d}$ Trevor Tyson, Tian Yu, Catherine Dubourdieu Films of hexagonal Multiferroic RxMnO3$+$d (R$=$Dy and Er) have been prepared. Local atomic and electronic structure measurements have been utilized to probe the variation of properties of samples. The defect levels obtained, x $\sim$ 0.6 to x $\sim$ 1.2, correspond to systems with defect (voids) on the R sites and then the Mn sites. The spectroscopic studies are complemented by electronic structure calculations to predict the magnetic and electrical polarization properties as a function of defect level [Preview Abstract] |
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H1.00062: How Magnesium Substitution Changes the Magnetostrictive Properties of Cobalt Ferrite David C. Jiles, Cajetan Nlebedim, Ravi Hadimani, Ruslan Prozorov Materials based on cobalt ferrite are promising for magnetostrictive applications. Significant research effort has been invested towards understanding the effects of substituting different cations into the spinel crystal lattice of cobalt ferrite on its magnetostrictive properties. Al and Mg are the two cations that occupy the tetrahedral and octahedral sites of the spinel (MgAl$_{2}$O$_{4})$ from which cobalt ferrite derives its crystal structure. In our previous study, compared with other cation substituted cobalt ferrite studies, Al substitution resulted in the best compromise in magnetostriction and strain sensitivity. In this study, we present the effects of substituting Mg for Fe in cobalt ferrite. It was found that Mg substitution resulted in a near-linear decrease in magnetization of the samples. Remarkably, both magnetostriction and strain sensitivity showed a similar dependence on Mg substitution. This trend is unlike previous observations in which both properties show opposite dependence on cation substitution at lower concentrations of the substituted cations. [Preview Abstract] |
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H1.00063: EuTiO$_3$: a possible multiferroic material, structural, magnetic and dynamical characterization Zurab Guguchia, Hugo Keller, Juergen Koehler, Annette Bussmann-Holder Structural analogies between SrTiO$_{3}$ and EuTiO$_{3}$ suggest that other similarities exist, namely an oxygen octahedral rotational instability. This has been tested experimentally as well as theoretically by specific heat measurements [1], X-ray powder diffraction [2], EPR and $\mu $SR experiments [3], within the polarizability model and by ab initio calculations [4,5]. Earlier evidence for strong spin phonon coupling in EuTiO$_{3}$ [6] has been further explored for the high temperature instability at T$_{S}$ and is reflected in the magnetic field dependence of T$_{S}$ [7].\\[4pt] [1] A. Bussmann-Holder, J. K\"{o}hler, R. K. Kremer, J. M. Law, \textit{Phys. Rev. B} 2011, \textit{83,} 212102. [2] J. K\"{o}hler, R. Dinnebier, A. Bussmann-Holder, \textit{Phase Trans.} 2012, \textit{85,} 949. [3] Z. Guguchia, A. Shengelaya, H. Keller, J. K\"{o}hler, A.Bussmann-Holder, \textit{Phys. Rev. B} 2012, \textit{85,} 134113. [4] A. Bussmann-Holder, Z. Guguchia, J. K\"{o}hler, H. Keller, A Shengelaya, A. R. Bishop, \textit{New J. Phys.} 2012, \textit{14,} 093013. [5] J. L. Bettis, M.-H. Whangbo, J. K\"{o}hler, A. Bussmann-Holder, A. R. Bishop, \textit{Phys. Rev. B} 2011, \textit{84,} 184114. [6] T. Katsufuji, H. Takagi, \textit{Phys. Rev. B} 2001, \textit{64,} 054415. [7] Z. Guguchia, H Keller, J. K\"{o}hler, A. Bussmann-Holder, \textit{J. Phys.: Cond. Mat.} 2012, \textit{24,} 492201. [Preview Abstract] |
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H1.00064: Non-saturating Magneto-resistance up to 60 Tesla in Topological Insulator Bi2Te3 Thin Films Shixiong Zhang, Ross D. McDonald, Arkady Shekhter, Zhenxing Bi, Yan Li, Quanxi Jia, S.T. Picraux We report magneto-transport studies of topological insulator Bi2Te3 thin films grown by pulsed laser deposition. A non-saturating linear-like magneto-resistance (MR) was observed at low temperatures in the magnetic field range from a few Tesla up to 60 Tesla. Due to the large Fermi Surface, the magnetic field is not high enough to quantize all the surface Dirac Fermions into the lowest Landau level, which rules out the possibility of `quantum linear magnetoresistance'. We have further shown that the Linear MR may be associated with the weak antilocalization effect at high fields and can be described by the Hikami-Larkin-Nagaoka analysis providing the elastic scattering time is longer than the spin-orbit scattering time. [Preview Abstract] |
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H1.00065: Growth of topological insulators on Si(111)-(7$\times$7) surfaces by molecular beam epitaxy Anupam Roy, Sushant Sonde, Samaresh Guchhait, Sanjay Banerjee Following the theoretical prediction about Bi$_2$X$_3$ (X=Se, Te) being a topological insulator (TI) because of strong spin-orbit interactions, interest has grown in integrating these materials with Si technology for potential future devices. In this work, we will be presenting the epitaxial TI structures grown by molecular beam epitaxy (MBE) by codepositing high purity Bi and Se or Te onto the clean Si(111)-(7$\times$7) substrates under ultra-high vacuum (base pressure better than 1$\times$10$^{-10}$ mbar). In-situ studies show sharp streaky reflection high-energy electron diffraction (RHEED) patterns. Scanning tunneling microscopy (STM) studies show the growth of Bi$_2$Se$_3$ islands along the terraces. High resolution STM studies show hexagonal atomic structure of Bi$_2$Se$_3$. For Bi$_2$Te$_3$, STM shows that the growth follows a layer-by-layer mode with the height difference being same as the quintuple layer height of Bi2Te3. Spectroscopy studies of the grown film to confirm the chemical stoichiometry will also be presented. [Preview Abstract] |
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H1.00066: Phonon Dispersion, Electronic Structure and Photocatalytic Properties of Rutile TiO$_{2}$ doped with X-doped (X$=$N, B and Pt) Sanjeev K. Gupta, Prafulla K. Jha, Igor Luka\v{c}evi\'{c} First principles calculations were performed on the electronic, vibrational and Raman spectra of substitutional N, B and Pt-doped rutile titanium dioxide (TiO$_{2})$, within the density functional theory (DFT), using the plane-wave pseudopotential method as implemented in the ABINIT package. Of all the photocatalytic materials TiO$_{2}$ has been shown as the most useful one, with the most efficient photoactivity, the highest stability and the lowest cost. Moreover, it is safe for humans and the environment. The development of new types of photocatalytic cells is driven by the need for clean and sustainable energy. In this respect best doped materials are considered as a promising route for departing from the traditional photocatalytic cells. The physical insight provided by computational modeling may help in developing improved photocatalytic devices. To this end it is important to obtain an accurate description of the electronic structure and phonon dynamics, including the fundamental gaps and level alignment at the doped-TiO$_{2}$ interface. [Preview Abstract] |
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H1.00067: Structural, electronic, and optical properties of Ba$_{1-x}$Zn$_{x}$O Zeyad A. Alahmed, Hamad A. Albrithen, Ahmed M. El-Naggar We have investigated structural, electronic and optical properties of Ba$_{1-x}$Zn$_{x}$O alloy in the range of (0 $\le $ x $\le $ 1) in the zinc-blende phase. The all-electron full potential linearized augmented plane wave (FP-LAPW) method implemented in WIEN2k code was utilized in these calculations. Structural optimization of Ba$_{1-x}$Zn$_{x}$O alloy for the compositions x $=$ 0, 0.25, 0.50, 0.75, and 1.0 was carried out by minimizing the total energies as functions of the unit cell volume. The calculated equilibrium lattice constant $a$ and bulk modulus B for both binary BaO and ZnO compounds are found to be ($a=$6.04{\AA}, B$=$45.51GPa for BaO) and ($a=$4.689{\AA}, B$=$113.84GPa for ZnO), in good agreement with the values reported by different groups. We have observed a nonlinear behavior of the lattice constant $a$ as varying the composition x. The electronic structure and the band gap of different composition x are calculated using different types of exchange--correlation potentials. Additionally, we will present the electron charge density distribution for different crystallographic planes of the unit cell. Also, we will demonstrate the effects of variation of compositions x on the optical properties such as the complex dielectric function and refractive index of the alloy. [Preview Abstract] |
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H1.00068: The Image Potential for Spherical Conductors and Dielectrics Godfrey Gumbs, Antonios Balassis, Andrii Iurov, Paula Fekete We calculate the image potential for spherical conductors and dielectrics, such as fullerene buckyballs. Our calculations show that these structures can support electronic states which may be localized at some distance away from the surface. These ``spherical image states'' exist within extended surface potentials formed by the competition between the attractive image force, the external electron and its image charge in the spherical shell, and the repulsive centrifugal force arising from the angular motion. The effective potential leads to extended stable states away from the surface of the spherical shell. At low temperatures, this results in long lifetimes for the image states. We expect that spherical image states with binding energies of a few meV. The bound states may be formed with the aid of radiative recombination. [Preview Abstract] |
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H1.00069: Competing Mechanisms for Temperature-Dependant Electron Relaxation in Disordered SiO$_{2}$ Layers Under Electron Irradiation JR Dennison, Gregory Wilson, Amberly E. Jensen, Ryan Hoffmann High energy electrons incident on highly disordered insulating materials undergo quasielastic collisions that imparts both charge and energy to the material; this can excite multiple intrinsic electrons from valence band or low level trap states into the extended states of the conduction band. These excited electrons provide a significant conduction mechanism in insulators under the influence of applied fields, but quickly thermalize to shallow localized trap states just below the conduction band edge that are associated with structural (physical) or compositional (chemical) defects. Electrons in these shallow trap states can: (i) remain in these shallow trap states; (ii) be thermally re-excited into the conduction band, leading to thermally assisted charge transport, termed radiation induced conductivity (RIC); (iii) decay into deep traps well within the band gap, often emitting a photon which is termed cathodoluminescence; or (iv) decay to low level valence band or trap states through radiative or non-radiative processes. Simple theory based on thermally-assisted hopping conductivity and disordered band theory is used to link diverse temperature-dependant measurements to the transition mechanisms for electrons in the shallow states. [Preview Abstract] |
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H1.00070: Study of Insulator-Metal transition of VO$_{2}$ thin films with ultrafast optical pulses Elizabeth Radue, Lei Wang, Evan Crisman, Russell Wincheski, S. Kittiwatanakul, J. Lu, S.A. Wolf, Rosa Lukaszew, Irina Novikova VO$_{2}$ has been a popular material to study in the past few decades as it has a reversible insulator-metal transition (IMT) when heated past 340K or stimulated with an ultrafast optical pulse. The resistance and optical properties change by several orders of magnitude, making it an attractive candidate for low loss plasmonic devices, ultrafast switches, or smart windows. We study the dynamics of the transition of VO$_{2}$ thin films on different substrates with femtosecond pulses in a pump-probe experiment in order to better understand the mechanisms behind the transition. We have measured the IMT at several different temperatures to investigate any change in the dynamics of the transition. We also study the Raman spectroscopy of VO$_{2}$ thin films heated through the transition. The effects of the different substrates on the transition of the VO$_{2}$ thin film will be discussed. [Preview Abstract] |
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H1.00071: Direct Determination of Electric Current in Born-Oppenheimer Molecular Dynamics Tao Sun, Renata M. Wentzcovitch We introduce a new approach to calculate directly the electric current in Born-Oppenheimer molecular dynamics. In this approach the electric current is computed from the adiabatic variations of the Kohn-Sham eigenstates between consecutive time steps. This conceptually straightforward method is fairly efficient and can be easily implemented into existing electronic structure programs. We test the method in two representative systems: liquid D$_{2}$O and crystalline MgO. The polarization change and the electric current density computed from the present approach are in excellent agreement with those from the Berry phase method and explicit density functional perturbation theory calculations of Born-effective charges. [Preview Abstract] |
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H1.00072: Radio-frequency tunnel-junction shot noise thermometry and its application to the study of thermal properties at low temperature Jung Hwan Park, Dong-Gwang Ha, Woon Song, Yonuk Chong We developed a radio-frequency broadband measurement setup for shot noise thermometry in the temperature range from 0.1 K to 300 K. The noise power from a metallic tunnel junction was measured at 1 GHz with a bandwidth of 400 MHz. Very small noise signal from the tunnel junction was amplified by a cryogenic HEMT amplifier. The signal was then amplified by a room temperature amplifiers followed by a diode detector that converts the noise power into voltage output. Broadband measurement technique enables a fast measurement of RF signal. The shot noise thermometer directly measures the electron temperature and our measurement uncertainty is less than 3{\%} in the sub-Kelvin range. Because of the small size of the tunnel junction, local measurement of the temperature on a device is possible. Since we measure the electron temperature directly, we can apply this technique to the study of thermal properties at low temperature.We suggest a method of measuring electron temperature before and after a thermal process in a chip at low temperature, which will help understanding of the thermal properties of electron-phonon system at low temperature. [Preview Abstract] |
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H1.00073: Improved Atonic Mechanics Calculations and New Milieu Alfred Phillips Jr. We have devised a way for improving the accuracy of electron energy level calculations done in what we named Atonic mechanics. The more accurate calculations resulted from a new way of modeling magnetic effects. Prior to the improvement, the Atonic mechanic energy level calculation were about as accurate as conventional quantum mechanics for simple atoms. We have also created a more general milieu in which we can model the particle's motion. [Preview Abstract] |
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H1.00074: Investigation of Proton Dynamics in a (CH$_{3})_{4}$NCdCl$_{3}$ Single Crystal by using $^{1}$H Nuclear Magnetic Resonance Measurements Moohee Lee, Jung Seok Sim, Kihyeok Kang, Ho Hyoun Kim, Ae Ran Kim (CH$_{3})_{4}$NCdCl$_{3}$(TMCC) is reported to exhibit two first-order structural phase transitions. The crystal has a hexagonal structure in phase I at room temperature and then changes to a monoclinic one in phase II below 118 K. Finally a ferro-elastic monoclinic phase III appears below 104 K. The a- and c-axes of TMMC were found by using X-ray diffraction at room temperature. $^{1}$H NMR measurements of spectrum, spin-lattice relaxation time T$_{1}$ and rotating-frame relaxation time T$_{1\rho }$ were performed at 4.8 T parallel or perpendicular to the c-axis from 300 K down to 65 K. The spectrum shows no significant changes at both transition temperatures. T$_{1}$ and T$_{1\rho}$ monotonically decrease at low temperature and then show an abrupt decrease around 110 K. As the temperature decreases further, T$_{1}$ shows a minimum at 100 K and becomes longer whereas T$_{1\rho }$ continuously decreases. From these data, the proton dynamical behavior is analyzed and identified. [Preview Abstract] |
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H1.00075: Temperature Dependence of $^{7}$Li NMR Spectra in a Li$_{2}$KRb(SO$_{4})_{2}$ Single Crystal Moohee Lee, Ho Hyoun Kim, Kihyeok Kang, Jung Seok Sim, Ae Ran Lim Li$_{2}$KRb(SO$_{4})_{2}$ is a mixed crystal of LiKSO$_{4}$and LiRbSO$_{4}$. LiKSO$_{4}$ has a hexagonal symmetry at room temperature and undergoes four phase transitions at low temperature. On the other hand, LiRbSO$_{4}$ is pare-electric with a monoclinic symmetry at room temperature and then shows a phase transition above 400 K. In order to understand the microscopic details of structural phase transitions in the single crystal of Li$_{2}$KRb(SO$_{4})_{2}$, we have measured the temperature dependence of $^{7}$Li NMR spectrum at 8 T from 300 K down to 100 K. The $^{7}$Li NMR spectrum shows three resonance peaks, which is a typical shape from three nuclear Zeeman level splitting for the nuclear spin of I$=$3/2 with nuclear-quadruple interaction. The spectrum shows a different shape for 8T parallel and perpendicular to the c-axis. As temperature decreases, the spectrum shows no significant change whereas the $^{7}$Li nuclear quadrupole frequency increases monotonically. [Preview Abstract] |
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H1.00076: Quantum criticality in Kondo quantum dot coupled to helical edge states of interacting 2D topological insulators Chung-Hou Chung, Salman Silotri We investigate theoretically the quantum phase transition (QPT) between the one-channel Kondo (1CK) and two-channel Kondo (2CK) fixed points in a quantum dot coupled to helical edge states of interacting 2D topological insulators (2DTI) with Luttinger parameter $0 |
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H1.00077: The fate of Z$_2$ topological insulator in optical lattices with disorder Ahad Khaleghi Ardabili, Tekin Dereli, \"Ozg\"ur M\"ustecaplolu Topological insulator is considered to be very robust against any perturbation which Doesn't break time-reversal invariant and there are now many proposal about creating such systems in cold atom area which one can have very good control for tuning it. Here we investigate the effect of disorder in the TI Z$_2$ system proposed in B. Beri and N. R. Cooper PRL 107, 145301 (2011) We show that under a strong disorder the system undergoes a topological phase transition. [Preview Abstract] |
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H1.00078: Persistent currents in a Kane-Mele graphene ring with armchair edges Ming-Che Chang, Bor-Luen Huang, Chung-Yu Mou A graphene nano-ribbon with armchair edges is known to have no edge state. However, if the nano-ribbon is in the quantum spin Hall (QSH) state, then there must be helical edge states. By folding a graphene ribbon to a ring and threading it by a magnetic flux, we study the persistent charge and spin currents in the tight-binding limit. It is found that, for a broad ribbon, the edge spin current approaches a finite value independent of the radius of the ring. For a narrow ribbon, inter-edge coupling between the edge states could open the Dirac gap and reduce the overall persistent currents. Furthermore, by enhancing the Rashba coupling, we find that the persistent spin current gradually reduces to zero at a critical value, beyond which the graphene is no longer a QSH insulator. [Preview Abstract] |
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H1.00079: Electronic properties at an interface between Mott-insulator and topological-insulator Suguru Ueda, Norio Kawakami, Manfred Sigrist We investigated the correlated heterostructure of two-dimensional topological and Mott insulator with the inhomogeneous dynamical- mean-field theory combined with Lanczos exact diagonalization method. We focus on the proximity effects driven by the topological helical edge-state. It is elucidated that the edge state penetrates into the Mott insulator and induces a strongly renormalized in-gap state with helical energy spectrum We also address how the in-gap state is affected by the coupling between the Mott and topological insulators, and find the enhanced renormalization-effect caused by the band reconstruction at the interface. [Preview Abstract] |
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H1.00080: Quantum Network Models and Topological Insulators Monica Pate, Liang Fu We develop quantum network models for Anderson localization on the surface of weak topological insulators and topological crystalline insulators. These models represent systems in which delocalized helical electrons travel along contours that separate topologically distinct states. We perform numerical studies on random network systems to study the localization-delocalization transition in these materials. [Preview Abstract] |
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H1.00081: Three-dimensional Fermi surface in Cu$_{x}$Bi$_{2}$Se$_{3}$ Gang Li, Tomoya Asaba, Fan Yu, Benjamin Lawson, Ziji Xiang, Colin Tinsman, Adam Berkley, Yew San Hor, Lu Li To study the evolution of bulk electronic structure by copper doping in Bi$_{2}$Se$_{3}$, highly sensitive torque magnetometry measurements are carried out on a series of single crystals of different doping levels. By employing magnetic field up to 31 Tesla, we are able to observe de Hass-van Alphen oscillations from Field perpendicular to the basal plain (H$\parallel$c) up to the parallel configuration (H$\perp$c), and confirm the three-dimensional nature of the Fermi surface in the doped compounds. The quantum oscillation frequency varies and the Cu concentration changes. The anisotropy of the effective mass and the Fermi velocity will be also discussed. [Preview Abstract] |
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H1.00082: Nearly flat Andreev bound states in superconductor-topological insulator hybrid structures Mahmoud Lababidi, Erhai Zhao Exotic excitations arise at the interface between a three-dimensional topological insulator (TI) and superconductors. For example, Majorana fermions with a linear dispersion $E\sim k$ exist in a short $\pi$ Josephson junction on the TI surface. We show that in these systems, the Andreev bound state spectrum becomes nearly flat at zero energy when the chemical potential is sufficiently away from the Dirac point. The flat dispersion is well approximated by $E\sim k^N$, where $N$ scales with the chemical potential. A similar evolution from linear to flat dispersion also occurs for the subgap spectrum of a periodic superconducting proximity structure, such as a TI surface in contact with a stripe superconductor. [Preview Abstract] |
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H1.00083: Turning topological insulators `insulating' using irradiation with swift particle beams Lukas Zhao, Haiming Deng, M. Konczykowski, A. Hruban, Lia Krusin-Elbaum To understand the transport and quantum electronic behaviors of the topological Dirac surface states, it is essential to develop techniques that will unambiguously separate surface physics from that of the bulk. In the approaches taken thus far, such as nanostructured materials synthesis, doping, or compositional tuning, the complete elimination of the bulk conduction still remains a challenge. Here we present a different approach that uses swift particle beams to introduce controlled disorder into a bulk of topological insulators (TIs) thereby increasing bulk resistivity by orders of magnitude. The process creates Frenkel pairs, with charged vacancies stable up to room temperature. We report the results of irradiation of TIs Bi$_2$Te$_3$ and Sb$_2$Te$_3$ -- both \textit{p}-type in as-grown state -- with 2.5 MeV electrons performed at liquid hydrogen temperature (20~K). The longitudinal resistivity $\rho_{xx}$ monitored \textit{in-situ} as a function of particle fluence $\phi$ displays a maximum at which the hole (\textit{p}-type) conduction appears compensated; beyond $\phi_{max}$ a conversion to \textit{n}-type is obtained. The effect of this `compensation' on the surface states of the irradiated TIs probed in electric-field gated structures will be discussed. [Preview Abstract] |
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H1.00084: Polarization modulated diode effect in a ferroelectric tunnel capacitor with semiconducting BiFeO$_{3}$ barrier Guolei Liu, Shumin He, Shishou Kang, Yanxue Chen, Shishen Yan, Liangmo Mei Polarization modulated diode effect was investigated in a ferroelectric tunnel capacitor with semiconducting BiFeO$_{3}$ barrier, which was grown on a conductive Nb-SrTiO$_{3}$(001) substrate by oxygen plasma assisted molecular beam epitaxy. Switchable diode effect with a good rectifying property and large bipolar resistance switching observed. The on/off resistance ratio is larger than two orders of magnitude. The tunneling resistance was found to be dominated by the Schottky contact forming at BiFeO$_{3}$/Nb-SrTiO$_{3}$ interface, in the regime of Fowler-Nordheim tunneling across the Schottky-like barrier. The switchable diode effect was attributed to the Schottky barrier variations upon polarization reversal. The width variation of depletion layer was estimated about 8nm, which is comparable with the 25nm-thick BiFeO$_{3}$ barrier. [Preview Abstract] |
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H1.00085: UNDERGRADUATE RESEARCH SOCIETY / SOCIETY OF PHYSICS STUDENTS ABSTRACTS |
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H1.00086: Magnetic Behavior of Nanostructured Mn0.23TaS2 Near Ferromagnetic Transition Corey Cooling, Paul Shand, K.R. Boyle, Tim Kidd, Laura Strauss We have investigated the ferromagnetic transition for tantalum disulfide intercalated with 23{\%} manganese. The material was grown in the form of nanotube/nanowire structures with diameters ranging from 30nm to several hundred nanometers. These nanotube structures give the material a high anisotropy. The material was studied through Curie-Weiss analysis, dc magnetization, and ac susceptibility measurements. The ferromagnetic transition for Mn$_{0.23}$TaS$_{2}$ occurs around 85K and varies with the applied dc magnetic field. The ferromagnetic transition is characterized by a peak in the ac susceptibility. Analysis of the susceptibility peaks revealed atypically high critical exponent values when compared to other disordered ferromagnetic systems. The large exponents may be due to the existence of two transitions in close proximity. The first transition (at a higher temperature) is to a ferromagnetic state; the second is to a disordered magnetic state. Arrott-Noakes plotting provided further justification of a multicritical transition. Further work includes taking measurements on a bulk crystalline sample of similar concentration and comparing its properties to those of the nanostructured sample. [Preview Abstract] |
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H1.00087: Estimating the Distance and Metallicity of an RR Lyrae Star Shouvik Bhattacharya Minnesota State University Moorhead has a working observatory and recently renovated named the Paul P Feder Observatory at the Buffalo River State Park in the Northwest Minnesota. The observatory is equipped with a 16'' Cassegrain reflecting telescope, an Apogee Alta CCD camera, two research grade computers and the SBIG SGS Spectrograph, which was installed in the observatory facility in fall 2012. The student researcher used the facility and made photometric and spectroscopic observations of the RR Lyrae stars. The distance of the RR Lyrae star was estimated by analyzing the photometric data, extracting information about period and measured quantify brightness from the observed science images. High resolution spectroscopy was performed on the same star and its applicability to metallicity estimation will be reported. [Preview Abstract] |
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H1.00088: Do the Dark Matter Halos of Dwarf Galaxies share a Universal Core Radius? Liyang Yu, Caset R. Watson Recent observations suggest that dark-matter-dominated Milky Way dwarf satellite galaxies contain a universal mass of $\sim$ 10$^{7}$ M$_{\odot}$ within their innermost 300 pc. Additional observations suggest a universal, core dark matter (DM) surface density ($\mu_{0}$ = r$_{0} \rho_{0}$) for galaxies at all observed mass and luminosity scales. We demonstrate that the combination of these two results implies the existence of a universal DM halo core radius (r$_{0}$) for dwarf galaxies. To test this prediction, we compare the results of our calculations to existing dwarf galaxy data for Burkert and NFW DM density profiles. [Preview Abstract] |
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H1.00089: Does the Observed Phase Space Density of Dwarf Galaxies Indicate a Consistent Value for the Mass of the Dark Matter Particle? Joseph Cheeney, Casey Watson Recent studies have suggested that the phase space densities (Q) of Milky Way dwarf satellite galaxies imply a keV-scale dark matter particle mass. To go beyond this order-of-magnitude estimate, we examine trends in the phase space density data and consider their implications for the relationship between the primordial Q ($Q_P$), which depends directly on the dark matter particle mass, and the presently observed values of Q ($Q_0$). We then determine whether the application of a consistent $Q_P$-$Q_0$ relationship to the $Q_0$ data yields a consistent and more well-defined value of the dark matter particle mass. [Preview Abstract] |
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H1.00090: Probability Current in Hydrogen with Spin-Orbit Interaction William Hodge, Sam Migirditch, William Kerr The spin-orbit interaction is a coupling between a particle's spin and its motion. The Hamiltonian for a spin-$1/2$ particle which includes this coupling is \begin{equation} \mathcal{H} = \frac{\mathbf{p}^2}{2 m} + V(\mathbf{x}) + \frac{\nabla V (\mathbf{x}) \times \mathbf{p}}{2 m^2 c^2} \cdot \mathbf{S} . \end{equation} To describe the flow of probability in this system, we derive the continuity equation, which takes the usual form. In this case, however, we find the probability current density $\mathbf{j} (\mathbf{x}, t)$ to be the sum of two terms. The first term is the one obtained by most quantum mechanics textbooks during their derivation of the continuity equation. The second term, \begin{equation} \mathbf{j}_s (\mathbf{x}, t) = \frac{1}{2 m^2 c^2} \sum_{\sigma, \sigma' = \uparrow, \downarrow} \Big[ \psi^\ast (\mathbf{x}, \sigma, t) \langle \sigma | \mathbf{S} | \sigma' \rangle \psi (\mathbf{x}, \sigma', t) \Big] \times \nabla V(\mathbf{x}) , \end{equation} arises due to the inclusion of the spin-orbit term in the Hamiltonian and is small compared to the first. Using a perturbative treatment, we calculate $\mathbf{j} (\mathbf{x},t)$ for hydrogenlike atoms; for states with $\ell = 0$, we find that $\mathbf{j} (\mathbf{x}, t) = \mathbf{j}_s (\mathbf{x}, t)$. [Preview Abstract] |
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H1.00091: The Angular Momentum Flux in the Scalar Self-Force Problem Samuel Cupp, Peter Diener The scalar self-force problem consists of a scalar point charge orbiting a supermassive black hole. The object is small enough that the perturbation of space-time due to its mass is inconsequential, and the only forces are gravity and the self-force. The self-force is a force on the inspiraling particle that results from the back-scattering of the object's own field off of curved space-time. I derived an accurate calculation of the angular momentum flux for the scalar self-force problem and implemented it into a preexisting (3 spatial $+$1 time) dimensional code. We then compared our results to very precise frequency domain calculations. The angular momentum flux calculations yield results that converge to the actual value of 0.0124682173 M. However, the calculations currently converge at about .7 order, and the reasons for this extremely slow convergence is currently unknown. [Preview Abstract] |
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H1.00092: Development of Embedded Atom Potential for Aluminum for Simulation of Materials at extreme conditions Chance Brown, Brian Demaske, Vasily Zhakhovsky, Ivan Oleynik An embedded atom potential (EAM) potential for aluminum was developed by fitting a wide range of zero-temperature stress tensor components calculated using density functional theory (DFT). The theoretical stress tensor components were calculated for isotropic compressions as well as uniaxial deformations along three principal crystal axes. A number of experimental properties were included within the fitting database to ensure the accuracy of the potential near equilibrium conditions. Out of many candidate potentials, the one that most closely reproduced the experimental melting point and shock Hugoniot data was selected as the final potential. This potential gives a good description of aluminum under extreme pressures and temperatures, making it well-suited for atomistic simulations of laser-matter interactions and shock compression. [Preview Abstract] |
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H1.00093: Symmetries of Four Harmonically-Trapped Particles in One Dimension Brian Weinstein, Nathan Harshman, Jessica Uscinski We present a method for solving trapped, interacting, four-body systems in a one-dimensional harmonic trap. By expressing the particle coordinates in Jacobi spherical coordinates, we discover the underlying $O_h$ symmetry, i.e. tetrahedral symmetry with parity inversion. This symmetry provides an alternate method for describing particle configurations and clustering, and it simplifies numerical calculations of the energy eigenstates of the system for tunable interactions. [Preview Abstract] |
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H1.00094: Spin Noise Spectroscopy and Some Design Constraints on Spintronics Devices Amina Belkadi, A.F. Isakovic Spin noise spectra are obtained on GaAs samples with the standard setup. The spin spectral characteristics are studied in comparison with the spin transport efficiency for diodes fabricated on the same samples. It is shown that spectral characteristics of spin noise, such as FWHM and Q-factor are related to the spin transfer efficiency. Temperature and magnetic field dependence of the spin noise spectra are studied in the context of spin relaxation mechanisms. We also performed spin noise correlations analysis with respect to the volume effects motivated by the need to understand the design constraints on spintronics devices due to spin noise effects. [Preview Abstract] |
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H1.00095: Modeling Plasma Formation in a Micro-gap at Microwave Frequency Arthur Bowman, Stephen Remillard In the presence of a strong electric field, gas molecules become ionized, forming a plasma. The study of this dielectric breakdown at microwave frequency has important applications in improving the operation of radio frequency (RF) devices, where the high electric fields present in small gaps can easily ionize gases like air. A cone and tuner resonant structure was used to induce breakdown of diatomic Nitrogen in adjustable micro-gaps ranging from 13 to 1,156 $\mu $m. The electric field for plasma formation exhibited strong pressure dependence in the larger gap sizes, as predicted by previous theoretical and experimental work. Pressure is proportional to the frequency of collision between electrons and molecules, which increases with pressure when the gap is large, but levels off in the micro-gap region. A separate model of the breakdown electric field based on the characteristic diffusion length of the plasma also fit the data poorly for these smaller gap sizes. This may be explained by a hypothesis that dielectric breakdown at and below the 100 $\mu $m gap size occurs outside the gap, an argument that is supported by the observation of very high breakdown threshold electric fields in this region. Optical emissions revealed that vibrational and rotational molecular transitions of the first positive electronic system are suppressed in micro-gaps, indicating that transitions into the molecular ground state do not occur in micro-gap plasmas. Acknowledgements: National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811, the Provost's Office of Hope College, and the Hope College Division of Natural and Applied Sciences.~ [Preview Abstract] |
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H1.00096: Modeling Q-switched Laser Dynamics by State Space Methods Lameka Booker, Ikechukwu Ume, Makhin Thitsa Q-switched lasers are prevalent in applications that require high intensity laser in ultra-short pulses. In a solid state laser Q-switching regime, the laser rate equations are a set of nonlinear coupled differential equations involving photon flux $\phi_a$, instantaneous population inversion density $n_s$, and the absorption center density $n_a$. In this paper, the Q-switched laser is modeled by a system theoretic approach called state space method, where the three physical quantities: $\phi_a$, $n_a$, and $n_s$ are defined as the state variables of the system, the modulation function of the cavity losses, $\alpha(t)$ as the input function, and the laser output power as the output function of the system. First the system is Taylor linearized and the linearized system is simulated by MATLAB Simulink software. The full nonlinear system is also simulated in Simulink. The contribution to the output from the nonlinear components of the system is obtained from the difference between the outputs of the two models. [Preview Abstract] |
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H1.00097: All-optical quasi-phase matching of frequency doubling using counterpropagating light Rachel Myer, Allison Penfield, Etienne Gagnon, Amy Lytle Nonlinear optical frequency conversion is a useful method for creating coherent light sources with unique capabilities. The main challenge for conversion efficiency of processes like frequency doubling is the chromatic dispersion of the nonlinear medium. Successful techniques for correcting the phase mismatch between the different frequencies are often limited by the type of nonlinear medium that may be used. An all-optical method of quasi-phase matching using counterpropagating light has recently been demonstrated for high-order harmonic generation, an extreme nonlinear process. Sequences of counterpropagating pulses are used to interfere with the harmonic generation process periodically, correcting the phase mismatch and boosting efficiency. We report progress on an experimental investigation of the effect of counterpropagating light on the more commonly used low-order nonlinear optical processes. We present data showing the effects of a single counterpropagating pulse on the efficiency of frequency doubling of a Ti:sapphire ultrafast laser oscillator in beta-Barium Borate. [Preview Abstract] |
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H1.00098: Optical up-conversion in Er$^{3+}$:Y$_2$O$_3$ nanoparticles through spectral masking of broadband pump light Lauren Tulchinsky, Amy Lytle, Etienne Gagnon, Ken Krebs, Eliza Jonathan, Ann Silversmith Up-conversion photoluminescence (UC-PL) has been extensively studied for potential use in up-conversion lasers, IR to visible detectors, and high efficiency lighting applications. Here we report experimental results exploring the excited state absorption process behind the UC-PL of Er$^{3+}$ : Y$_{2}$O$_{3}$ nanoparticles under shaped-pulse laser excitation. By beginning with a broadband laser pulse and then spectrally shaping it to remove either the high or low energy part of the excitation, we examine the full width of the double resonance between the ground-to-excited state absorption and the excited state absorption of the impurity ions. We propose a model for the manifolds of the electronic energy states that treats each Stark level as a Gaussian of fixed width and then superimposes a Boltzmann distribution for the thermalized population of the levels. This simple model fits the experimental data well at room temperature, but begins to show expected differences at 78 K. [Preview Abstract] |
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H1.00099: Time-resolved Terahertz spectroscopy using a Ti:Sapphire laser oscillator Pradosh Kharel, Wassam Waquar, Etienne Gagnon In time-resolved terahertz spectroscopy, electromagnetic radiation in the frequency range 0.3 - 3 THz (corresponding to wavelengths of 0.1 - 1.0 mm) is used to probe the dynamic properties of charge carriers within materials. When a sample material is excited using an ultrafast optical laser pulse, the terahertz probe that passes through the sample a time later reveals the subsequent behavior of the charge carriers in the sample. Real-time mapping of the dynamics can then be achieved through a pump-probe delay experiment. To date, most time-resolved terahertz spectroscopy has relied on high-power laser systems in order both to excite the sample as well as to generate the probing terahertz radiation. Here, we investigate the feasibility of adapting this technology to a relatively less expensive Ti:sapphire laser oscillator. We present preliminary data and discuss challenges going forward. [Preview Abstract] |
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H1.00100: Construction and Characterization of a Nanosecond Nd:YAG Laser Pumped Distributed Feedback Dye Laser Generating Picosecond Pulses Timothy Clark, Chris Weckerly, Laszlo Ujj We have constructed a Distributed Feedback Dye Laser (DFDL) using interferometric pumping. DFDL works according to the dynamic modulation of the gain medium creating short pulses. Shortening of the pulses, stability, and dynamic range of the DFDL were investigated. Pulses were measured with the help of a photodiode with a 30 picosecond response time. Traces were recorded with a Tektronics DSA73304D (33GHz) digital serial analyser. The gain medium contains an ethanol solution of Rhodamine 590 dye and DODCI saturable absorber. Increasing the concentration of DODCI saturable absorber resulted in significant pulse shortening (150 to 54 picoseconds). Single pulse generation was achieved when the power of the pump laser was adjusted 10 percent above the laser threshold. The central wavelength of the laser pulses was 587 nm. The mathematical modeling, optical layout of the DFDL, and the results of the temporal and spectral characterization of the laser are presented on the poster. The development of the DFDL will lead to an extensive investigation of short pulse dye lasers for educational purposes and for applications in nonlinear spectroscopy. [Preview Abstract] |
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H1.00101: Characterizing the Effect of Surface Hydrophobicity on the Depletion Layer Erin Brown, Shannon Petersen, Jessica Jeroski, Ariel Statman, Adele Poynor When water is forced into contact with an extended hydrophobic surface, a uniform region of reduced density forms along the interface. We seek to identify both a qualitative and a quantitative relationship between the hydrophobicity of a surface and the characteristics of the corresponding depletion layer, specifically its thickness and density. We determine these qualities using surface plasmon resonance spectroscopy (SPR). We produce surfaces of different hydrophobicities through the formation of self-assembled monolayers of organothiols on gold-plated slides. Self-assembled monolayers (SAMs) of 1-octadecanethiol are used to produce surfaces with high hydrophobicity, as the terminal methyl group is highly nonpolar, while 11-mercapto-1-undecanol is used to produce surfaces with minimal hydrophobicity, as the terminal hydroxyl group is hydrophilic. Surfaces of intermediate hydrophobicity are fabricated using mixed SAMs of 1-octadecanethiol and 11-mercapto-1-undecanol. We measure surface hydrophobicity for the resulting SAM-coated slides by their contact angle with water droplets. In order to ensure an unchanging hydrophobicity throughout SPR trials, we analyze the stability of the surfaces to through repeated testing of contact angle variability over time and after extended submersion both in water and in ethanol. [Preview Abstract] |
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H1.00102: Computer Automated Contact Angle Measurement for Surface Plasmon Resonance Ariel Statman, Adele Poynor When water meets an extended hydrophobic surface, an ultra-thin, low density depletion layer is expected at the interface. Exactly how the depletion layer changes with change in hydrophobicity is still an open question. When studying the interaction between water and a hydrophobic surface, we need to be able to test the hydrophobicity of a self-assembled monolayer, and its stability over time. To do this, we take a series of images over time and determine whether the contact angle changes. [Preview Abstract] |
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H1.00103: Synthesis and characterization of iron platinum magnetic nanoparticles with controlled morphology and size Trinidy Combs, Hafsa Khurshid, Hariharan Srikanth We report the synthesis and characterization of monodispersed iron-platinum nanoparticles by the thermal decomposition of organometallic compounds. First, platinum (Pt) seeds were synthesized at 100C, followed by the addition of iron pentacarbonyl via injection method in the presence of oleic acid and oleylamine surfactants. An immediate injection after the decomposition of Pt acetylacetonate made alloy nanoparticles of Pt nanoparticles, whereas its injection after a prolonged period of time formed mixed particles of iron oxide and Pt. Particle shape was tuned from spherical to cubic by varying molar ratios of oleic acid to oleylamine during the reaction. The particles' size was controlled by varying the injection temperature of the iron precursor. XRD was used to confirm the crystallographic phases of the samples. Particle size and shape were investigated using TEM. Magnetic properties indicated that as-synthesized FePt nanoparticles are superparamagnetic with a blocking temperature of 64 K for 7 nm and shifted to 29 K for 3 nm. [Preview Abstract] |
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H1.00104: Structure and dynamics of Au/Fe nano-structures: results of molecular dynamics simulation Timothy Findling, Ahlam Al-Rawi Gold-plated iron nanostructures have chemical, optical, magnetic, and biomedical applications owing to the unique properties of the iron-gold combination. However, relatively little is known about the atomistic surface composition of these alloys. We have studied the structure and dynamics of Au/Fe nano-alloys using molecular dynamics simulations with an embedded-atom interaction potential [1]. We will present analyses of the structural composition as Au atoms are deposited on Fe facets, leading to locally optimal crystal structures for this alloy, as a function of composition and substrate temperature. We will also present a complete analysis of the stability of the resulting structures by calculating the vibrational density of state using velocity autocorrelation. The vibrational entropic contributions to the free energy of the Fe atoms and Au atoms in their vicinities will be evaluated as a function of the local surface geometry. The net outcome of this study is prediction of viable Au/Fe nanostructures. \\[4pt] [1] S. M. Foiles et al. Phys. Rev. B 33, 7983 (1986). [Preview Abstract] |
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H1.00105: Iron-Platinum Nanoparticles Dispersible in Aqueous Solutions Jason Huynh, Angshuman Pal, Hafsa Khurshid, George Hadjipanayis In this work, we have used a low temperature method that reduces Pt(acac)$_{\mathrm{2}}$ and thermally decomposes Fe(CO)$_{\mathrm{5}}$ in the presence of oleic acid (OA) and oleyl amine (OY) to fabricate monodispersed fcc FePt nanoparticles $^{\mathrm{[1]}}$. Adjusting the parameters, such as injection temperature and heating rate, could control the size and shape, respectively. The nanoparticles made for this study had a cubic shape and an average diameter of 5.3 nm. The particles were found to be superparamagnetic at room temperature with low coercivity. The aim of this project was to disperse nanoparticles in aqueous solutions. The surfactants (OA/OY) were then exchanged with tetramethylammonium hydroxide (TMAOH) to allow water phase transfer$^{\mathrm{\thinspace [2]}}$. After the transformation, the FePt nanoparticles were dispersed in 20 mL of a 0.01-wt {\%} TMAOH solution. The structural and magnetic properties were maintained as shown by X-Ray Diffraction and Vibrating Sample Magnetometer data. From these findings, the FePt nanoparticles are being modified for higher coercivity for potential use in hyperthermia studies. [1] L. Colak and G. C. Hadjipanayis, Nanotechnology 20 (2009) 485602. [2] V. Salgueiri\~{n}o-Maceira, L. M. Liz-Marz\'{a}n and M. Farle, Langmuir 20 (2004) 6947. [Preview Abstract] |
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H1.00106: Study of Hydrogen flame annealed Au thin-film surface morphology, integrity and film quality on various substrate surfaces Michael Schell, Indrajith Senevirathne Au thin-films have many applications in both industry and proof of concept investigations in device engineering. Typical Au depositions on substrate give rise to Stanski-Krastanov (SK) like growth while Frank-van der Merwe (FM) mode like growth is desired in many molecular self assembly and other engineering applications. Au films are magnetron sputter deposited at 100mtorr at low deposition rates ($\sim$ 1ML/min) on cleaved/fresh mica, glass microscopy slides and Si surfaces. Samples are hydrogen flame annealed to facilitate surface diffusion with minimal film contamination. Resulting Au surfaces were investigated and compared against purchased Au(111) on mica (standard) surface. Regular and custom built hydrophilic and hydrophobic AFM (Atomic Force Microcopy) probes were used in contact, and non contact AFM with topography and phase imaging to access the contamination and surface defects. Surface integrity, roughness, corrugation and morphology on Au surfaces were estimated. [Preview Abstract] |
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H1.00107: Structural Properties of Gold Thin Films Deposited on Technologically Important Substrates by Magnetron Sputtering Caleb Glaser, Michael Schell, Marian Tzolov, Indrajith Senevirathne, Moniruzzaman Syed Gold (Au) thin films offer a wide range of applications and may be used for memory storage, energy harvesting, nanosensors, optics, and biosensing devices. Au thin films are currently being studied more closely since they are highly conductive and yet not easily oxidized. Therefore, it is necessary to understand the growth mechanisms of film on various substrates. The structural properties of gold thin films also play an important role on the film quality, which may affect its' optical properties and the sensing capability of the device. In this study, Gold (Au) thin films were deposited on glass (SiO2), silicon (100) and other substrates at room temperature (RT) in an argon (Ar) gas environment as a function of deposition time. The structural properties and surface morphology of the Au thin film has been studied using an Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectrometry (EDX), and X-Ray Diffraction (XRD) measurements. The deposition rate was found to be decreased monotonically as deposition time increased for the films on glass substrates. The effect of the annealing temperature on the structural properties of the Au film deposited on the aforementioned substrates will also be discussed in this study. [Preview Abstract] |
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H1.00108: Characterization of Electrodeposited Nanoporous Ni and NiCu Films Kyla Koboski, Jennifer Hampton Nanoporous thin films are interesting candidates to catalyze certain reactions because of their large surface areas. This project focuses on the deposition of Ni and NiCu thin films on a Au substrate and further explores the catalysis of the hydrogen evolution reaction (HER). Depositions are created using controlled potential electrolysis. Samples are then dealloyed using linear sweep voltammetry. Before and after the dealloying, all the samples are characterized using multiple techniques. Electrochemical capacitance measurements allow comparisons of sample roughness. HER measurements characterize the reactivity of the sample with respect to the specific catalytic reaction. The Tafel equation is fit to the data to obtain information about the kinetics of the HER of the samples. Other methods for characterizing the samples include scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The use of SEM allows images to be taken of the deposition to determine the change in the structure pre- and post- dealloy of the sample. EDS allows the elemental composition of the deposition to be determined before and after the dealloy stage. [Preview Abstract] |
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H1.00109: Electrodeposition and Characterization of Nickel, Iron, Copper Thin Films and the Creation of Nanoporous Structures Jonathan Yarranton, Jennifer Hampton There has been much research in creating nanoporous platinum or gold thin films for catalysis, but there has not been as much work done with other, less noble metals. This research explored the deposition of nickel, iron, and copper ternary alloys using controlled potential electrolysis (CPE) and the selective removal of the copper with DC potential amperometry (DCPA) and linear sweep voltammetry (LSV) to create nanoporous structures. These structures have the advantage of increased surface area creating more efficient catalysts. All films were characterized before and after dealloying using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) for composition. The roughness of each of the films was characterized by the capacitance of the film, with higher capacitances indicating a higher electrochemical surface area. [Preview Abstract] |
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H1.00110: Effect of Carrier Doping on Nonlinearity of High Temperature Superconducting Thin Films Michael Bischak, Jinu Thomas, Stephen Remillard The nonlinearity of superconductors if found to depend on the sample's location on the phase diagram, and hence on the carrier doping. The doping level was tuned by annealing Tl$_{2}$Ba$_{2}$CaCu$_{2}$O$_{8-x}$ thin films in a reducing nitrogen atmosphere at temperatures ranging from 250$^{\circ}$C to 400$^{\circ}$C. Nonlinear microwave surface impedance of Tl$_{2}$Ba$_{2}$CaCu$_{2}$O$_{8-x}$ wafers in a 5.6 GHz sapphire dielectric resonator reveal dependence on carrier doping $x$, with fluxon hysteresis contributing more significantly in under-doped films (x greater than 0.1) at all temperatures and in more optimally doped films at high reduced temperature. With the critical temperature being used as the indicator of carrier density, it was found that under-doped samples have larger fluxon hysteresis losses as indicated by a one-to-one variation of surface reactance with surface resistance. This work was supported by the National Science Foundation under grants 1206149 and 1004811, and by the Research Corporation for Science Advancement. [Preview Abstract] |
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H1.00111: Ionic self-assembly of thin films: analytical and experimental results Vincent Kim, Will Banks, Andrew Seredinski, Brian Simpson, Dan Mazilu, Irina Mazilu Our work is motivated by the manufacturing process of self-assembled antireflective coatings using silica and titania nanoparticles. The properties of these coatings depend on the surface coverage of the substrate. During the manufacturing process, it is highly desirable to know the analytical relationship between the index of refraction and the particle density of the surface. We use a class of cooperative sequential adsorption models on a Cayley tree to model the self-assembly mechanism. Using the empty interval method, and generalizing results known from reaction--diffusion processes on Cayley trees, we calculate the time-dependent surface coverage. We compare our model to the experimental results obtained in the thin film lab. [Preview Abstract] |
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H1.00112: Analytical study of cooperative sequential adsorption models on Cayley trees and their applications to drug encapsulation of nanoparticles Andrew Seredinski, Vincent Kim, Brian Simpson, William Banks, Irina Mazilu, Dan Mazilu We present a class of cooperative sequential adsorption models on a Cayley tree with constant and variable attachment rates and their possible applications for drug encapsulation of nanoparticles. Using the empty interval method, and generalizing results known from reaction--diffusion processes on Cayley trees, we calculate a variety of quantities such as time-dependent surface coverage and time-dependent probabilities of certain particle configurations. [Preview Abstract] |
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H1.00113: Elucidating the Equilibrium States of C60 molecules on Ag(111) Stephanie Su, Renee Diehl, Katariina Pussi, Heekeun Shin, Hsin-I Li, Laura Serkovic, Ajay Shukla, Vincent Fournee, Julian Ledieu, Linlin Wang, Kristin Marino, Michael Snyder The properties of C$_{\mathrm{60}}$ on surfaces depend strongly on their local geometries, but until recently there were few quantitative studies for these structures. The interactions of C$_{\mathrm{60}}$ molecules on Ag(111) surface produce an interesting structural complexity that manifests as a competition between two geometrical states. We studied the most stable (2$\surd $3x2$\surd $3)R30$^{\mathrm{o}}$ phase of C$_{\mathrm{60}}$ on Ag(111) by using STM, LEED, and DFT. This phase consists of molecules in two different geometrical states - one sitting on a C-C bond on the top site and one sitting on a hex face on a vacancy. By measuring the dynamical equilibrium behavior of the system, we obtained detailed information on the energetics of two states. [Preview Abstract] |
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H1.00114: Fluorescent Quantum-Sized Carbon Dots Isolated in an rf Paul Trap Andrew Farr, Curtis Allen, Russell Hilleke, Robert Clark Quantum-sized carbon particles, known as carbon dots, exhibit strong wavelength- and size-dependent photoluminescence that makes them attractive candidates for many applications in nanoscale electronics and as biological markers. It has been shown that carbon dots become luminescent upon surface passivation with organic molecules; however, this property has never been verified outside of a chemical solution. To understand the mechanisms which underlie the photoluminescence, we are building an experiment to isolate single carbon dots in vacuum in an rf Paul trap and perform laser-induced fluorescence spectroscopy upon them. We report progress toward this goal, including the design and implementation of a custom electrospray ionization system. [Preview Abstract] |
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H1.00115: CVD graphene growth and transfer techniques for the fabrication of micromechanical resonators Daniel J. Losowyj, Isaac R. Storch, Thomas J. McCune, Paul L. McEuen Graphene's superlative mechanical strength, electrical mobility, low mass, and large surface area make it a prime candidate for use in micromechanical resonators [1,2], which have potential applications in mass and force sensing [3], radio frequency signal processing, and optomechanics [4]. Our resonators use graphene grown by chemical vapor deposition (CVD) and have excellent mechanical performance, but their electrical performance is comparatively worse than that of exfoliated graphene devices. We attribute these limitations to contamination from copper oxidation during the growth and solvents used in the transfer process. To remedy this, we have performed CVD growths on copper foils with long anneal times, confirming with Raman spectroscopy and SEM that the graphene is single layer and high quality. We have also found that graphene suspended on a substrate can survive high temperature air annealing, provided that the temperature ramp is gradual. Improving the electrical performance of these novel devices will facilitate their use in a variety of new experiments and applications. [1] J. S. Bunch \textit{et al}., Science (2007) [2] A. M. van der Zande \textit{et al}., Nano Lett. (2010) [3] C. Chen \textit{et al}., Nature Nanotechnology (2009) [4] R. A. Barton, \textit{et al}., Nano Lett. (2012) [Preview Abstract] |
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H1.00116: Effects of Recombination Processes on the Nonlinearity of Semiconductor Optical Amplifiers Ikechukwu Ume, Lameka Booker, Makhin Thitsa An optical signal traveling along the fiber often loses its strength and needs to be rejuvenated. Optical amplifiers perform amplification directly on the optical signal without optical-to-electrical and electrical-to-optical conversion. Especially, semiconductor optical amplifiers (SOA's), which use a semiconductor material as the laser gain medium could be integrated into monolithic photonic circuits. Therefore, SOA's are being considered as the building blocks of future all-optical networks. Since linear amplification of the signal is strongly desired for SOA's in many applications, it is important to determine the degree of nonlinearity in practical SOAs. In this paper the effects of recombination processes, namely: linear recombination, bimolecular recombination and Auger recombination on the nonlinearity of the SOA are investigated by using the Volterra series model. [Preview Abstract] |
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H1.00117: Relationship between shallow donors and H impurities in In$_{2}$O$_{3}$ from their behavior upon annealing Kirby Smithe, Weikai Yin, Michael Stavola, Lynn Boatner Indium oxide is a transparent conducting oxide used widely in modern electronics [1]. Theory predicts that interstitial H and H trapped by an oxygen vacancy act as shallow donors [2]. We have introduced H into In$_{2}$O$_{3}$ single crystals to produce O-H centers and also the broad IR absorption arising from free carriers. To investigate the relationship between the O-H centers and the shallow donors that are introduced by H, we have studied the annealing behavior of the O-H local vibrational modes and the free-carrier absorption by IR spectroscopy to determine how these spectral features are correlated. [1] M. McCluskey \textit{et al.}, J. Mater. Res. \textbf{27}, 2190 (2012) [2] S. Limpijumnong \textit{et al.}, Phys. Rev. B \textbf{80}, 193202 (2009). [Preview Abstract] |
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H1.00118: Characterization of Nickel-Zinc Electrodeposition Kevin Tkacz, Jennifer Hampton Nanoporous nickel serves as an interesting catalytic material due to its large surface area and therefore high reactivity. The purpose of this project is to develop a method for producing thin films of nanoporous nickel. This is done by the electrodeposition of a nickel-zinc alloy followed by the selective removal of zinc. A series of primarily sulfate baths were used for deposition in an attempt to produce samples ideal for selective removal of zinc. Deposition variables examined include metal concentration in the solution, ratio of metals in solution, deposition potential and solution pH. Depositions were characterized with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Linear sweep voltammetry was also used to characterize the dealloying process. It was determined that increasing the nickel concentration in solution also increased the concentration in the deposit. Uniform depositions with low nickel concentration were successfully made although attempts to increase the nickel concentration adversely affected the deposition quality. [Preview Abstract] |
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H1.00119: Ionic self-assembly of silica nanoparticles: time-dependence of surface coverage Katy Wilson, Brian Simpson, Vincent Kim, Andrew Seredinski, Will Banks, Dan Mazilu, Irina Mazilu We investigate the deposition by ionic self-assembly of alternating silica nanoparticle and poly(allyamine hydrochloride) layers. The optical properties of these coatings depend on the surface coverage of the substrate. We report experimental data for the surface coverage of the substrate as a function of dipping time. We model this process using a cooperative sequential adsorption model on a Cayley tree. We compare the analytical and experimental results and discuss possible generalizations of the model. [Preview Abstract] |
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H1.00120: Growth of Zinc Oxide Nanobelts Jamie Nowalk Zinc Oxide is a unique material that has a variety of applications in optoelectronics due to its piezoelectric, optical, and semiconducting properties. The carbothermal reduction of zinc oxide is a common technique used in chemical vapor deposition of nanostructures via the vapor transport mechanism. In this research project, the supply of zinc atom was successfully decoupled from the delivery of the oxidant, molecular oxygen. We have grown various forms of ZnO nanostructures at varying temperatures in a three-zone furnace. The reactions took place at a constant pressure of 200 torr on silicon substrates, each coated with a thin film of gold catalyst. Two-dimensional nano-ribbons were observed to grow best at higher temperatures between 800-1000 C, with the thinnest belts (30 nm) at 800 C. At 1000 C, the belts appear to taper off, resulting in shorter structures. One-dimensional wire growth was predominantly observed at 600 C. We compare our results with previously published syntheses of ZnO nanobelts. [Preview Abstract] |
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H1.00121: Low-energy electron diffraction study of the surface of SrTiO$_3$(001) Adam Bell, Kristin Marino, Renee Diehl Oxide materials having the perovskite structure have many intriguing physical properties, such as high-temperature superconductivity, colossal magnetoresistance, and ferroelectricity. These properties make them good candidates for applications such as hard drive read heads or random access memory. Although fabrication of such devices involves growing thin films, the characterization of the surface structures of perovskite materials has been slow. This is partly because they often have complex or unstable structures that can be difficult to prepare and maintain and partly because the electron or ion beams common in surface techniques can charge the surface and perturb the incident and scattered beams~This is particularly true of low-energy electron diffraction (LEED), the primary technique for determining the surface structures~~In this study, we have developed new methods to reduce the exposure of the insulating surface to electrons in a LEED experiment. These include using low incident beam currents, pulsing the electron beam and image enhancement techniques. We will carry out a LEED characterization of the SrTiO$_3$(001) surface structure, which has been the subject of some controversy concerning the terminating structure.\footnote{R. Herger et al., Phys. Rev. B 76, 195435 (2007).} [Preview Abstract] |
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H1.00122: Growth and Characterization of Mn-doped NaFeAs Nickolas Luttrell, Scott Carr, Yu Song, Chenglin Zhang, Pengcheng Dai We grew multiple dopings of Mn-doped NaFe As with the goal of observing a shift in the Tc from the NaFeAs parent compound as well as any structural transitions. A VSM was used to characterize the magnetic response of the samples. Results indicate slight Mn doping does not kill superconductivity immediately. We will make a direct comparison with Mn-doped BaFe2As2. [Preview Abstract] |
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H1.00123: NISXW study of Si adsorbed on an Al-Co-Ni quasicrystal Nick Stanisha, Anindita Chaudhuri, Julian Ledieu, Hsin Li, Stephanie Su, Andreas Mayer, Kevin Lovelock, Robert Jones, Lisa Wearing, David Woodruff, Renee Diehl The normal incidence standing x-ray wavefield (NISXW) technique has never before been applied to the determination of adsorption structures on quasicrystals, even though it is quite clear that, under the right conditions, x-ray standing waves do exist in quasicrystals. This omission may be due to a misconception that the relationship between the phase of the standing waves and the atoms at a quasicrystal surface is arbitrary. We have performed a NISXW experiment for the adsorption of Si atoms on the nominally 10-fold surface of the decagonal Al-Co-Ni quasicrystal. NISXW spectra were obtained for a Si coverage of about 0.3, for two different angles of incidence: normal to the 10-fold surface, and at an angle of about 60${\circ}$ from the surface normal. These angles correspond to two strong x-ray reflections of the quasicrystal. The intensity of the Si 1s photoemission signal was measured in order to determine the location of the Si atoms.order to accurately model the 5-fold symmetry of the surface, our analysis employed a 200 {\AA} x 200 {\AA} x 8 {\AA} structure model for the quasicrystal. The results indicate that the Si atoms have an average height of 1.80 {\AA} above the surface, and are arranged in 6-atom pentagonal clusters centered at points of 5-fold symmetry. This study demonstrates the feasibility for using NISXW as a structural tool for adsorbed atoms or molecules on quasicrystal surfaces. [Preview Abstract] |
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H1.00124: Magnetic Properties of Quasi-One-Dimensional Ca$_{3}$LiRuO$_{6}$ and CaFe$_{4}$As$_{3}$ Donovan Myers, Amar Karki, Rongying Jin Needle-like Ca$_{3}$LiRuO$_{6}$ and CaFe$_{4}$As$_{3}$ single crystals were grown using the flux method. While the structure of Ca$_{3}$LiRuO$_{6}$ is characterized by one-dimensional chains of alternating face-sharing LiO$_{6}$ trigonal prisms and RuO$_{6}$ octahedra along the $c$ axis, CaFe$_{4}$As$_{3}$ consists of edge-sharing FeAs$_{4}$ tetrahedra ribbons along the $b$ axis. Despite the one-dimensional nature, magnetization measurements reveal evidence of long-range magnetic ordering: Ca$_{3}$LiRuO$_{6}$ orders ferromagnetically below T$_{\mathrm{C}} =$ 120 K and CaFe$_{4}$As$_{3}$ undergoes two successive antiferromagnetic transitions at T$_{\mathrm{N1}} =$ 90 K and T$_{\mathrm{N2}} =$ 26 K. Possible magnetic interactions will be discussed. [Preview Abstract] |
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H1.00125: Exploring the variability of ion heating at reconnection events in MST M.S. Cartolano, D. Craig, D.J. Den Hartog, S.T.A. Kumar, M.D. Nornberg The variability of ion heating for individual reconnection events in the Madison Symmetric Torus (MST) is correlated with key plasma parameters to give insight into the process of ion heating. Magnetic reconnection is a process that converts energy stored in the magnetic field in the plasma into ion thermal energy. The change in impurity ion temperature during several thousand reconnection events was analyzed for standard plasmas in MST. These changes in the ion temperature were then correlated with various plasma parameters to try to understand the variations in the amount of heating. As expected, the change in ion temperature correlates strongly with the change in magnetic energy. Magnetic fluctuations in MST are thought to be responsible for driving reconnection, and larger amounts of ion heating do correspond to larger increases in the amplitudes of these magnetic fluctuations during an event. The strongest correlation is with the rate of change in the amplitude of magnetic fluctuations that are resonant in the edge of the plasma. Other anomalous behavior appears during reconnection, such as dynamo activity and electron thermal transport. When these activities are stronger, the amount of ion heating is stronger. Finally, a toroidal asymmetry to the ion heating is examined. [Preview Abstract] |
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H1.00126: Phase Dynamics in a Two-Plaquette Josephson Junction Array Zijie Poh, Ma'ayan Dagan, Jeanette Veldman, Brad Trees We study numerically and analytically the phase dynamics of two coupled plaquettes of Josephson junctions shunted by another junction. A plaquette is a square with a junction on each side. This geometry is motivated by single crystal Bismuth Strontium Calcium Copper Oxide (BSCCO), a layered high-$T_c$ superconductor consisting of hundred or thousands of intrinsic Josephoson junctions. The coupled plaquettes of our analysis are a simple model for two neighboring BSCCO crystals. We look for evidence of both frequency and phase synchronization in the dynamic (oscillating) junctions of the plaquettes. We find numerical evidence that intra-plaquette synchronization can be obtained even with weak coupling between the junctions in a plaquette and without the shunting junction. However, the shunting junction is crucial for synchronization between the junctions in neighboring plaquettes (inter-plaquette synchronization). Analytically, we use perturbation theory and a multiple time-scale analysis to predict the combinations of junction parameters for which phase synchronization appears in the array. By this analytical approach, we successfully capture the intra-plaquette synchronization behavior. The analytic study of inter-plaquette synchronization is still in progress. [Preview Abstract] |
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H1.00127: Measuring the off axis magnetic field within a Helmholtz Coil Edward Pluhar, Eric Martell Helmholtz coils are used because they produce nearly uniform magnetic fields on-axis. Prior research, namely Graf's thin coil experiment [The Physics Teacher, pp. 360 (2012)], has accurately measured the axial magnetic field produced by a thin coil; however, the magnetic field off-axis is known to be significantly more complicated and cannot be calculated analytically. In this research, I have numerically determined the magnetic field off-axis in the region between the two coils and compared those calculations with measured values. I then determined the effect the deviation from uniformity has on the behavior of a charged particle moving through this region, such as in the well-known electron charge-to-mass ratio experiment. [Preview Abstract] |
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H1.00128: Assessing the Reliability of Quantitative Imaging of Sm-153 Hannah Ponek, Michelle Chen, Eric Frey Samarium-153 is used for palliation of and recently has been investigated for therapy for bone metastases. Patient specific dosing of Sm-153 is based on quantitative single-photon emission computed tomography (SPECT) and knowing the accuracy and precision of image-based estimates of the in vivo activity distribution. Physical phantom studies are useful for estimating these in simple objects, but do not model realistic activity distributions. We are using realistic Monte Carlo simulations combined with a realistic digital phantom modeling human anatomy to assess the accuracy and precision of Sm-153 SPECT. Preliminary data indicates that we can simulate projection images and reconstruct them with compensation for various physical image degrading factors, such as attenuation and scatter in the body as well as non-idealities in the imaging system, to provide realistic SPECT images. [Preview Abstract] |
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H1.00129: Mechanical Properties of Chicken Embryo Somites to Analyze Cell Migration during Somitegenesis Sarit Zhukovsky, Lisa Taneyhill, Chyong Wu, Helim Aranda-Espinoza Somites develop as round segments on the sides of the neural tube and are responsible for the development of the vertebrae and other structures. Using Atomic Force Microscopy and Micropipette techniques, we were able to apply a known force to obtain data about the differences in the mechanical properties of the somites. Using contact mode in AFM, we obtained graphs that relate distance travelled by the cantilever versus deflection of the sample. We then used Matlab to analyze the data and find the material properties of the somites. We measured the Young's modulus of the anterior and posterior parts of the somites to be around 2 $\pm$ 0.8 kPa, but further data is needed to finalize our conclusion. Finding the mechanical properties of the posterior and anterior parts of the somites helped us to mimic those mechanical properties on polyacrylamide gels with different stiffness to determine the physiological functions of the somites and predict any mechanical abnormalities that might affect the migration of stem cells. By observing the major steps of migration, we were able to better understand how cell migration orchestrates embryonic morphogenesis with respect to their known mechanical properties. [Preview Abstract] |
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H1.00130: Mechanisms of stability of electrospun polypeptide fibers Alina Gitnik, Dhan B. Khadka, Michael C. Cross, Nicole K. Le, Donald T. Haynie Electrospun nano- and microfibers made of biodegradable and absorbable polymers are of great interest in biomedical engineering for tissue engineering, wound healing and other purposes. We have investigated physical properties of fibers made of the synthetic organic polymer co-poly(L-glutamic acid$_{\mathrm{4}}$, L-tyrosine$_{\mathrm{1}})$ (PLEY). This water-soluble polypeptide has a net negative charge at neutral pH. Dehydrated fibers are crosslinked with a diimide reagent dissolved in ethanol, giving a maximum average number of crosslinks of 1 per polymer molecule. Fiber integrity has been assessed in an aqueous medium at pH 2, 7 and 12, before and after crosslinking. Non-crosslinked fibers dissolved rapidly at all pH values, on a timescale of seconds to minutes. Crosslinked fibers dissolved completely at pH 12, but not at pH 2 or pH 7, the rate depending on the concentration of crosslinking reagent and therefore the density of crosslinks. Dissolution at pH 12 is attributable to ionization of the tyrosine side chain, which has a nominal pK$_{\mathrm{a}}$ of 10.4, an increase in electrostatic repulsion between side chains and the migration of counterions into the fiber. Fibers crosslinked in 50 mM EDC buckled on a timescale of minutes at pH 12 and dissolved shortly thereafter. [Preview Abstract] |
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H1.00131: SAM surface domains of 11-Mercapto-1-undecanol and 1-dodecanethiol mixtures on Au(111) investigated via hydrophilic and hydrophobic probes Indrajith Senevirathne, Mackenzie Maurer, Reshani Senevirathne SAM (Self Assembled Monolayer) surfaces may lead to many potential applications from polymer based electronics to sensor engineering. These devices may require a deeper understanding of the surface domain architecture of SAMs with multi component mixtures of thiols. Varying concentration mixed solutions of 11-Mercapto-1-undecanol (hydrophilic -OH end) and 1-dodecanethiol (hydrophobic --R), dissolved in 200 proof Ethanol with total 5mM concentration were prepared. These solutions were used in developing SAMs on clean flat Au(111) on mica. Resulting SAMs surfaces were investigated with regular and custom built hydrophobic and hydrophilic AFM (Atomic Force Microcopy) probes via contact, non contact and lateral force mode AFM with topography and phase imaging. Domains of distinct thiols were identified as selective self assembly on step edges and terraces. Surface roughness, corrugation and morphology at each domain were estimated. Total RMS surface roughness was estimated at $\sim$ 3.1nm for SAMs from unmixed (100{\%}) 11-Mercapto-1-undecanol with increasing RMS surface roughness estimates for SAMs from mixtures with increasing concentrations of dodecanethiol. [Preview Abstract] |
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H1.00132: Study of SAM surface morphology, integrity and film quality on various Au surfaces John Murphy, Indrajith Senevirathne SAM (Self Assembled Monolayer) surfaces have many possible applications from polymer based electronics to sensor engineering. Common substrate architecture for such systems happens to be Au(111) on mica. Au on layered mica lacks mechanical resilience towards engineering applications. Solutions of 1-dodecanethiol (hydrophobic --R), dissolved in 200 proof Ethanol with 5mM concentration were prepared. These solutions were used in developing SAMs on purchased, clean flat Au(111) on mica (standard), Au sputter deposited on mica, Hydrogen flame annealed Au layers on glass, and Hydrogen flame annealed Au layers on mica. Resulting SAM surfaces were investigated with regular and custom built hydrophilic and hydrophobic AFM (Atomic Force Microcopy) probes via contact, and non contact AFM with topography and phase imaging. Surface integrity, roughness, corrugation and morphology on SAM surfaces were estimated. Preliminary data indicated total RMS surface roughness at $\sim$ 2.8nm for SAMs on typical gold surfaces on mica purchased (standard) while varying RMS surface roughness estimates on subsequent surfaces with flame annealed samples showing similar RMS surface roughness. [Preview Abstract] |
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H1.00133: SAM surface domains of 6-Amino-1-hexanethiol hydrochloride and 1-dodecanethiol mixtures on Au(111) investigated via hydrophilic and hydrophobic probes Albert Foster, Reshani Senevirathne, Indrajith Senevirathne Amine terminated SAM (Self Assembled Monolayer) surfaces have shown to be bioactive. Hence similar systems can be exploited towards bioengineering applications. However a deeper understanding of the surface domain architecture of SAMs with multi component mixtures of such thiols is need. Varying concentration mixed solutions of 6-Amino-1-hexanethiol hydrochloride (hydrophilic --NH2 end) and 1-dodecanethiol (hydrophobic --R), dissolved in 200 proof Ethanol with total 5mM concentration were prepared. These solutions were used in developing SAMs on clean flat Au(111) on mica. Resulting SAMs surfaces were investigated with regular and custom built hydrophilic and hydrophobic AFM (Atomic Force Microcopy) probes via contact, non contact and lateral force mode AFM with topography and phase imaging. Domains of distinct thiols were identified as selective self assembly on step edges and terraces. Surface roughness, corrugation and morphology at each domain were estimated. Total RMS surface roughness was estimated at $\sim$ 3.75nm for SAMs from unmixed (100{\%}) 6-Amino-1-hexanethiol hydrochloride with increasing RMS surface roughness estimates for SAMs from mixtures with increasing concentrations of dodecanethiol. [Preview Abstract] |
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H1.00134: $p-n$ junction diodes fabricated from isolated electrospun fibers of (P(NDI2ODT2)) and an inorganic $p$-doped semiconductor Alexander Rosado, Nicholas Pinto A simple method to fabricate, under ambient conditions and within seconds, $p-n$ diodes using an individual electrospun poly\textbraceleft [N , N$'$-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5$'$-(2,2$'$-bithiophene)\textbraceright -(P(NDI2ODT2)) fiber and a commercially available $p$-doped Si/SiO$_{2}$ substrate is presented. Band bending at the fiber/Si$^{+}$ interface leads to asymmetric I-V characteristic curves resembling that of a diode. The diode turn-on voltage was in the range $\sim$1V and was unaffected via UV light irradiation. The rectification ratio however could be tuned reversibly thereby making this device multifunctional. In addition to being a rectifier, the advantage of our design is the complete exposure of the rectifying junction to the surrounding environment. This has the advantage of making them attractive candidates in the potential fabrication of low power, sensitive and rapid response photo-sensors. [Preview Abstract] |
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H1.00135: Polymer Films with Enhanced Light Emission Adam Thomas, Zac Barcikowski, Marian Tzolov Organic and polymer emitting diode degradation and efficiency are the main problem for industry in commercializing them as a product. This research focused on improving the efficiency of these devices with the main goal of tuning the emission spectrum of certain polymers to emit white light. By layering two polymers during the spin coating process of the device, the photoluminescence (PL) of the particular device was enhanced depending on the polymers we placed down and in particular order. This enhancement however did not occur when the same set of polymers that improved PL were mixed together in solution and then spin coated onto the device. The double layer structures with improved PL were evaluated using PL emission, excitation and optical absorption spectroscopy tests to determine how the polymers were interacting with each other. It was found that two polymers in one orientation would improve PL but wouldn't improve PL if the same polymers were spun in reverse order. As well as the second layer of polymer did not emit its own color but enhanced the under lying polymer layer. [Preview Abstract] |
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H1.00136: Direct Piezoelectricity of Soft Composite Electrospun Fibers Michael Varga, Jason Morvan, Nick Diorio, Ebru Buyuktanir, John Harden, John West, Antal Jakli Recently soft fiber mats electrospun from solutions of Barium Titanate (BT) ferroelectric ceramics particles and poly lactic acid (PLA) were found to have large (d33~1nm/V) converse piezoelectric signals offering a myriad of applications ranging from active implants to smart textiles. Here we report direct piezoelectric measurements (electric signals due to mechanical stress) of the BT/PLA composite fiber mats at various BT concentrations. A testing apparatus was designed and constructed solely for these measurements involving AC stresses provided by a speaker in 10Hz-10kHz frequency range. The piezoelectric constant d33 $\sim$1nC/N was found to be in agreement with the prior converse piezoelectric measurements. The largest signals were obtained with 6\% BT/PLA composites, probably because the BT particles at higher concentrations could not be dispersed homogeneously. Importantly the direct piezoelectric signal is large enough to power a small LCD by simply pressing a 0.2mm thick 2 cm2 area mat by a finger. We expect to use these mats in active Braille cells and in liquid crystal writing tablets.\\[4pt] Reference: J. Morvan, E. Buyuktanir, J.L. West, A. J\'akli, ``Highly-piezoelectric Biocompatible and Soft Composite Fiber Mats,'' Appl. Phys. Lett., 100, 063901-1-4 (2012) [Preview Abstract] |
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H1.00137: Growth and Characterization of PEDOT:PSS and Carbon Nanotube Composite Structures for Excitonic Solar Cells Constance Owens, Chaminda Hettiarachchi, Domingo Mateo-Feliciano, Robert Hyde, Sarath Witanachchi Harnessing solar energy is one of the most promising ways to tackle today's energy issues. Though solar cells are comprised of many different layers, our focus is on a single layer. The main goal of this study is to create thin film composite structures of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and carbon nanotubes (CNT), more specifically with multiple wall carbon nanotubes (MWCNT) by employing a spray method that utilizes Bernoulli's principle. We believe that a spray method will produce a better uniform layer than other methods that are utilized for creating thin films. Uniformity within a thin film is of the upmost importance because as uniformity is improved, many properties are enhanced. PEDOT:PSS was mixed separately with both dimethylformamide (DMF) and water. By the Dektak 3030ST, a profilometer device, it was discovered that the PEDOT:PSS containing DMF dispersed better than the PEDOT:PSS mixed with water, thus creating a more uniform film. Also it is well known that CNTs possess many excellent properties that can make them very useful in the field of solar technology. In this study we also combine MWCNTs into our thin films to see how they affect thickness, transparency and conductivity by using the Lambda 950, a UV/VIS spectrometer, and a four point probe. [Preview Abstract] |
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H1.00138: Electrical characterization of polymer solar cells Christopher Green, Zane Cohick, Marian Tzolov Polymer solar cell devices were fabricated using a mixture of the polymer PCPDTBT, PCBM, and 1,8-diiodooctane. The films were spin coated on ITO patterned substrates and covered with a hole injection layer. The film drying was performed at varied annealing temperatures and times. These devices were characterized utilizing current-voltage characteristics and the fill factor was determined. Devices were tested under dark and bright conditions using a xenon lamp. The current-voltage characteristics were modeled with an equivalent circuit yielding values for the shunt and series resistances. The variations in performance due to the changes in annealing temperatures and drying times were studied. Impedance spectroscopy was used to determine the dielectric constant of the active film. [Preview Abstract] |
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H1.00139: Photocurrent spectroscopy and structural studies of polymer solar cells Zane Cohick, Christopher Green, Marian Tzolov Polymer solar cells devices of the polymer mixture PCPDTBT:PCBM and 1,8-dioodooctane were created employing varied annealing temperatures and drying times. We used SEM and EDX to image the cross-section of the active layers and to identify separate phases. The short circuit photocurrent spectrum of the devices was measured and compared with the absorption spectrum of composite films and individual polymer films. The thicknesses of the solar cells were measured with a profilometer. Studies of the internal electric fields were performed using electroabsorption. [Preview Abstract] |
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H1.00140: Performance analysis of an inexpensive Direct Imaging Transmission Ion Microscope Patrick Barnes, Arthur Pallone A direct imaging transmission ion microscope (DITIM) is built from a modified webcam and a commercially available polonium-210 antistatic device mounted on an optics rail. The performance of the DITIM in radiographic mode is analyzed in terms of the line spread function (\textit{LSF}) and modulation transfer function (\textit{MTF}) for an opaque edge. Limitations of, potential uses for, and suggested improvements to the DITIM are also discussed. [Preview Abstract] |
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H1.00141: Testing the Accuracy of a Projectile Motion Apparatus Bret Henderson, Eric Martell The purpose of this research is to predict where a ball would land given initial velocity, angular velocity, and atmospheric conditions. A spinning spherical object flying through air is affected by gravity, quadratic drag forces, and the Magnus force. Mathematica was used to numerically solve predictions for the equations of motion. These predictions were compared with experimental data gathered by launching tennis balls, baseballs, and/or soccer balls from a machine we designed to propel the balls with a pre-determined initial velocity and initial angular velocity. [Preview Abstract] |
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H1.00142: Building and Testing a Superconductivity Measurement Platform for a Helium Cryostat Heath Rose, Joshua Ostrander, Jim Wu, Roberto Ramos Superconductivity experiments using Josephson junctions are an excellent environment to study quantum mechanics and materials science. A standard electrical transport technique uses filtered four wire measurement of these superconducting devices. We report our experience as undergraduates in a liberal arts college in building and testing an experimental platform anchored on the cold-finger of a helium cryostat and designed for performing differential conductance measurements in Josephson junctions. To filter out RF, we design, build and test cryogenic filters using ceramic capacitors and inductors and thermocoax cables. We also use fixed attenuators for thermal anchoring and use miniature connectors to connect wires and coax to a sample box. We report on progress in our diagnostic measurements as well as low-temperature tunneling experiments to probe the structure of the energy gap in both single- and multi-gapped superconductors. [Preview Abstract] |
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H1.00143: Dielectric Relaxation in Liquid Crystals 4'-Octyl-4-Cyanobiphenyl (8-CB) and C-16 Flourescent Dipyrrinone Chloe Renfroe, Andreiy Kondrat'yev, Caleb Morton, Preeyal Gupta, Aaron Wade, Chandra Prayaga, Micheal Huggins, Amy Renaud, Rebecca Chandler This paper reports the study of the dielectric relaxation time of the liquid crystal 4'-octyl-4-cyanobiphenyl (8-CB) in the smetic, nematic, and isotropic phases. The time constant of the decay was studied using a 10 mV square wave input signal. Large changes in the relaxation time were observed near the phase transitions. 8-CB was injected int a commercially available liquid crystal capacitor cell to act as a dielectric. The cell was housed in a temperature controlled environment constructed in the lab and an RC circuit was assembled using the 8-CB capacitor. The temperature of the capacitor was varied over the range 25$^{\circ}$C to 43$^{\circ}$C, covering all three phases. The sample was held at each temperature with a precision of 1mK using a temperature controller before measuring the voltage across the resistor with a digital oscilloscope. The input resistance (50$\Omega )$ of the oscilloscope was the resistance in the RC circuit. The recorded data was fitted to an exponential decay. These results give insight into the behavior of the time constant in the different phases and near the phase transitions. This method is used to study the dielectric relaxation of the new liquid crystal C-16 fluorescent dipyrrinone, synthesized in the Department of Chemistry, University of West Florida. [Preview Abstract] |
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H1.00144: Fabrication of a Liquid Crystal Capacitor Cell using Spin-Coating Logan Tate, Tabatha Ducharme, Chandra Prayaga, Aaron Wade, Michael Huggins, Rebecca Chandler, Amy Renaud This paper presents our work to fabricate and characterize a liquid crystal capacitor cell using novel liquid crystals. These LCs are not in their isotropic phase at room temperature and require the capacitor cells to be fabricated around them. This was done using spin coating where the samples were dissolved in Toluene, Anisole, or C$_{4}$CL. Next, the liquid crystals were spin-coated on either an ITO coated glass slide or a separate silicon wafer. This spin coating process was done in two stages where the first stage started at a slow speed to begin spreading the sample, and then during the second stage the spin coater ramped to a higher rpm to thin the sample while removing excess material. M-Line spectroscopy was used to determine the films thickness of the silicon substrate sample. To make the capacitor cell, a second ITO coated slide was placed on top of the first and the edges sealed with epoxy. Wires were soldered to the bus bars and the samples were mounted in a temperature controlled environment constructed in the lab and an RC circuit was assembled using the LC capacitor. Initial dielectric measurements were taken at room temperature to ensure the integrity of the cell. [Preview Abstract] |
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H1.00145: Compound droplet generation with viscoelastic interfaces Maxwell Collyard, Greg Randall, Brent Blue Compound droplets, or droplets-within-droplets, are traditionally key components in many applications ranging from the food and drug industries to inertial fusion targets. A microfluidic double T-junction can be used to create compound droplets, but each T-junction material typically must be carefully chosen so that the generated droplet does not spread on the walls. By introducing protein into the water shell and by heating simple off-the-shelf T-junctions to 70$^\circ$C, we were able to prepare oil-in-water-in-oil (O/W/O) droplets that were prevented from spreading on the channel walls. The stability is due to a thin, strong viscoelastic gel that forms on the oil/water interfaces. This is a path forward to mass fabrication of robust compound droplets since the proteins greatly stabilize the droplets near walls. Furthermore, these interfaces are less prone to deformation and useful for creation of uniform-walled shells using high electric fields. [Preview Abstract] |
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H1.00146: Dynamic Deformation of Theatrical Flats Jamiahus Walton, Eric Martell, Verda Beth Martell In theatre, flats are used as walls and background scenery. During construction, flats are often built on the ground and then ``walked up,'' where a group of stagehands manually lift one end while another anchors the other end in place. When flats are very large, they can deform during this process. Stiffeners are used to decrease the amount of deformation in the flat. The purpose of this research is to determine the strain along the flat during the process of raising it up with and without stiffeners. We will also explore the effect of the person anchoring the pivot edge of the flat and discuss the safety concerns this presents. This research is part of the Physics of Theatre Project, an interdisciplinary collaboration designed to improve safety, reduce costs, and increase knowledge of physics principles within the technical theatre community. [Preview Abstract] |
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H1.00147: Using IOLab to correct student misunderstandings of Newton's Third Law Nikki Tipsword, Eric Martell The Force Concept Inventory (FCI) is used at schools across the country as a tool to measure student conceptual understanding of Newtonian physics. One of the weaknesses commonly identified is in applications of Newton's Third Law. In this project, we are utilizing a recently-developed wireless data acquisition system, the IOLab, to attempt to rectify student misunderstandings regarding the Third Law. The subjects for this research came from calculus and algebra-based introductory physics courses. An assessment of the effectiveness of this teaching tool as well as a comparison between the two courses will be included. [Preview Abstract] |
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H1.00148: Using the Weather Research {\&} Forecasting Model (NACR) to Model the Atmosphere over the North Eastern United States and Investigate the Effects of Land Use on the Atmosphere Joseph Trout, Tiffany Lutes In this pilot project, the Weather Research {\&} Forecasting Model (WRF) from the National Center for Atmospheric Research was used to investigate the effects of land use on the weather and climate. New Jersey, especially New Jersey coastlines and NJ pine barrens have seen a rapid amount of development in a very short period. In this project, the WRF model is initialized with real. Observations and simulations are compared over areas of different land use. [Preview Abstract] |
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H1.00149: What does the Observed, Universal Dark Matter Surface Density of Galaxies tell us about Halo Substructure? Chris Pelikan, Casey Watson Recent observations suggest a universal, core dark matter (DM) surface density $({{\mu}_0} = {{\rho}_0}{r_0})$ for galaxies at all observed mass and luminosity scales. We show that this result emerges naturally if the gravitational field at the core radius of a DM halo is spherically symmetric. This result is independent of the scale of the DM halo core being considered as well as the assumed DM density profile. If a spherically symmetric gravitational field is the correct interpretation of the universal value of ${{\mu}_0}$, it implies that no dark matter substructure can exist, even within the largest core radius for which the universal ${{\mu}_0}$ relation holds, lest it spoil the symmetry -- except in the highly contrived scenario that substructure is symmetrically distributed in the cores of DM halos at all scales for which the universal ${{\mu}_0}$ relation is observed. Ignoring this extremely unlikely special case, the symmetry condition translates into an upper bound on the mass of the dark matter particle. Our result, which favors lower mass candidates, is consistent with the findings of several other recent studies. [Preview Abstract] |
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H1.00150: Zeta Potential Measurements of Glyoxalated Polyacrylamide (GPAM) Resins Sumit Libi, Apsana Shrestha, David Norwood, Steven Boone We will describe the use of a NICOMP 380 ZLS light scattering instrument (Particle Sizing Systems) to measure the zeta potential of glyoxalated polyacrylamide (GPAM) resins used in the paper industry. These experiments are part of a broader study of GPAM molecule properties (molecular weight, RMS radius, contour and persistence length) intended to understand differences in performance between various GPAM resins (specifically, differences in drainage performance during paper processing and wet/dry strength of paper). Additionally, zeta potential measurements help to understand the long term stability of these resins. Data and results obtained from the experiment will be presented. [Preview Abstract] |
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H1.00151: Magnetization reversal of patterned disks with perpendicular magnetic anisotropy Zhuyun Xiao, Xiao Wang, X.M. Cheng, Yaohua Liu, Suzanne G.E. te Velthuis, Daniel Rosenmann, Ralu Divan Magnetic vortex dynamics in magnetic disks have been extensively studied. However, spin dynamics in magnetic disks with perpendicular magnetic anisotropy (PMA) still remain to be fully understood. Magnetic configurations in disks with strong PMA are more complicated than magnetic vortices, resulting in novel spin dynamics with potential applications. In this work, we study the magnetization reversal of Co/Pd multilayered disks with PMA. Magnetic disks (3-8 microns in diameter) with the structure of [Co (0.3 nm)/Pd (0.5 nm)]$_{5}$/Co(0.3nm) were patterned on Si substrates via direct laser writing lithography, electron beam evaporation, and lift-off methods. A Kerr microscope was used to image magnetization reversal processes at various bias fields. The imaging results revealed a nucleation dominated magnetization reversal process with the growth of dendritic domains. The coercivity of the disks is significantly bigger than that of thin films with the same structure. Quantitative analysis of the real time Kerr imaging results shed light on the magnetization reversal mechanism of the patterned disks with PMA. Work at Bryn Mawr is supported by NSF under Grant No. 1053854. Work at Argonne National Laboratory and use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
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H1.00152: Apparent Sphere to Elongated particle transition of Elastin-Like Polypeptide Thermoreversible micelles Kaitlin Vandemark, Ali Ghoorchian, Nolan Holland, Kiril Streletzky Biosynthesized polymers can be designed to assemble into environmentally responsive nanoparticles. Such a system consisting of an oligomerization domain connecting three elastin-like polypeptide (ELP) chains has been developed. These polypeptides reversibly transition from aqueous soluble polymers to amphiphiles when the temperature is raised above the ELP transition temperature. As amphiphiles these can assemble into micelles under appropriate solution conditions. A particular system has been designed to reversibly form micelles at a neutral pH. However, the shape and size of micelles was found to depend strongly on salt concentration. We used polarized and depolarized dynamic light scattering to study temperature-driven formation of micelles of various geometries under different solvent conditions. We also monitored the sphere-to-elongated particle transition of the ELP micelles with addition of salt. The apparent dimensions, shape, and dynamics of micelles strongly depend on salt concentration, with two distinct salt regimes and a broad transition region observed. At low salt concentration (0-15 mM), largely spherical micelles were found with a hydrodynamic radius of 10-15 nm. At intermediate salt concentration (15-35 mM) the transition from spherical to elongated micelles is observed. At high salt concentrations (above 35 mM), the micelles again reach a stable structure consisting of highly anisotropic particles with an aspect ratio of higher than 10. [Preview Abstract] |
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H1.00153: Complex Refractive Index Structures in a Holographic Photopolymer Optimized for Optofluidic Devices Benjamin Cerjan, Andrew Peterson, Martha-Elizabeth Baylor We present complex refractive index features in a thiol-ene / methacrylate-based holographic photopolymer. Our photopolymer can fabricate coplanar optical features and fluid channels using three optical exposures. Previously with this material, we have fabricated linear multi-mode waveguides and 90-degree crossings of an optical waveguide and integrated fluidic channel. We now are using a simple photolithography system at 405 nm to create more interesting index structures. In this poster we present demonstrations of a variety of index structures (e.g., single mode waveguides, diffraction gratings, etc.) and explore the limitations of fabricating these structures. [Preview Abstract] |
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H1.00154: APPLICATIONS (IT, MEDICAL/BIO, PHOTONICS, ETC.) |
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H1.00155: Vacuum-Assisted Self-Assembly of Polymer Derived Siliconoxycarbide-Graphene Composite as Li-ion Battery Anode Lamuel David, Gurpreet Singh Exfoliated graphene oxide (GO) and polysiloxane were blended and pyrolyzed to synthesize freestanding SiOC-graphene composite papers ($\sim$ 10 $\mu$m thick). The structural and chemical characterization of the composite prepared with varying ceramic concentrations was carried out using electron microscopy, XRD, XPS and FT-infrared spectroscopy. High resolution microscopy images shows layer by layer stacking of GO sheets and an increase in interlayer spacing was observed by X-ray analysis. FTIR peaks at 3400 cm-1 (O-H), 1720 cm-1 (C$=$O), 1600 cm-1 (graphene), 3056 cm-1 (Si-CH$=$CH2) and 1034 cm-1 (Si-O-Si) confirmed the successful functionalization of SiOC with GO. Thermo-gravimetric analysis showed enhanced thermodynamic stability of the composite paper up to at least 700 $^{\circ}$C in flowing air. The SiOC/Graphene composite paper anodes showed stable electrochemical capacity of approx. 500 mAh/g which was twice that of free standing graphene anodes. The average coulombic efficiency (second cycle onwards) was observed to be approx. 97{\%}. [Preview Abstract] |
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H1.00156: Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes Carlos Paez, Peter Schulz, Rudolf Roemer, Neil Wilson In this work we numerically calculate the electric current through three kinds of DNA sequences (telomeric, $\lambda$-DNA, and p53-DNA) described by different heuristic models. A bias voltage is applied between two zig-zag edged graphene contacts attached to the DNA segments, while a gate terminal modulates the conductance of the molecule. The calculation of current is performed by integrating the transmission function (calculated using the lattice Green's function) over the range of energies allowed by the chemical potentials. We show that a telomeric DNA sequence, when treated as a quantum wire in the fully coherent low-temperature regime, works as an excellent semiconductor. Clear steps are apparent in the current-voltage curves of telomeric sequences and are present independent of lengths and sequence initialisation at the contacts. The current-voltage curves suggest the existence of stepped structures independent of length and sequencing initialisation at the contacts. We also find that the molecule-electrode coupling can drastically influence the magnitude of the current. The difference between telomeric DNA and other DNA, such as $\lambda$-DNA and DNA for the tumour suppressor p53, is particularly visible in the length dependence of the current. [Preview Abstract] |
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H1.00157: Interfacial energy level adjustment for ZnO/polymer electronics using triethoxysilane-based monolayers Thomas E. Furtak, T.M. Brenner, G. Chen, R.T. Collins, D.C. Olson Because of its large band gap and large ionization energy, together with its relatively large mobility and benign environmental character, ZnO is being increasingly employed in hybrid organic/inorganic electronics. It is commonly necessary to tailor the interfaces in these devices to optimize performance through surface treatment of the ZnO. Traditional molecular oxide modifiers, such as thiols and organic acids, etch ZnO, making it difficult to work with very thin ZnO films or nanostructures. To avoid etching we have developed a ZnO functionalization strategy based on siloxane-based molecular layers. We used this method to create monolayers on ZnO sol-gel films having variable average dipole character by mixing two molecules with different molecular dipoles. Samples were analyzed with IR spectroscopy and Kelvin probe measurements prior to being incorporated as the cathode in bulk heterojunction photovoltaic devices. We observed continuous tuning of the work function of treated ZnO over a range of 0.5~eV that is correlated with the composition of the monolayer. The open-circuit voltage of the devices was linearly proportional to the composition, although the magnitude of the change was much smaller than the change in work function.---Sponsored by NSF through DMR-0907409. [Preview Abstract] |
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H1.00158: Microwave pump-probe transmission x-ray microscopy for magnetization dynamics imaging Stefano Bonetti, Roopali Kukreja, Hendrik Ohldag, Richard Houanche, Jude Pinto, Josef Frisch, Jo Stohr, Hermann Durr The development of scanning transmission x-ray microscopy at synchrotron lightsources has seen a rapid development in recent years. The possibility of combined elemental specificity, nanometer resolution, magnetic sensitivity and even time-resolved capabilities, have made this imaging technique relevant for a large number of investigations in condensed matter physics. We further built up on these recent achievements by developing a new microwave ``pump-probe'' technique, where the ``pump'' is a continuous microwave source, precisely synchronized with the frequency of the synchrotron pulses, the ``probe''. Combined with the availability of low-alpha operation at Stanford Synchrotron Radiation Lightsource, that provides x-ray pulses as short as 10-15 ps FWHM, our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with 40 nm resolution, at x-ray energies in the 500-1000 eV range. When used together with circularly polarized x-rays, the above capabilities can be used in magnetism. In particular, they can be combined to study magnetic phenomena at microwave frequencies, such as spin waves or magnetization switching. Preliminary results on the imaging of spin waves emitted by spin transfer torque in nano-contacts will be discussed. [Preview Abstract] |
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H1.00159: Effective Mass and g-factor of 2D Electrons in a HgTe Quantum Well from THz Photoresponse Mehdi Pakmehr, A.V. Stier, H.D. Zhang, C. Bruene, H. Buhmann, L. Molenkamp, B.D. McCombe There is current interest in HgTe because of its interesting ``inverted'' band structure and large spin-orbit interaction, and because it is a topological insulator under quantum confinement, Well-widths close to that at which the band structure goes from the ``inverted'' to the normal structure are of particular interest. We have used photoresponse excited by several lines from an optically pumped THz laser and magnetotransport measurements to determine the cyclotron effective mass and g-factor of 2D electrons in the gamma\textunderscore 6 conduction band of a high quality HgTe quantum well (n$_{\mathrm{s}} =$ 1.55 x 10$^{12}$ cm$^{-2}$; 6 nm well) at low temperatures. One of the two samples studied was gated, which allowed density to be varied by over 30{\%}. We find m*$=$0.039m$_{\mathrm{e}}$ and g $=$ -18 at the highest density from fits to the PR with the field normal to the plane of the QW, and separately from CR transmission measurements and tilted field experiments. We will also discuss electron spin resonance measurements near filling factors 7 and 9. [Preview Abstract] |
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H1.00160: Temperature-Dependent Multi-Polarization Switching in VCSELs Yu-Fong Chen, Pei-Hou Chin, Cheng Hsu, Shaham Quadir, Yueh-Chen Li, Yu-Heng Wu, Tsu-Chiang Yen The multi-polarization switching (MPS) in vertical-cavity surface-emitting lasers (VCSELs) at constant temperature was investigated. The experiment was performed by triangular modulation signal at 100 Hz under 10 $^{\circ}$C and 7 $^{\circ}$C. The results show that the number of polarization switching (PS) was varied from single PS to five PSs and seven PSs at 10 $^{\circ}$C and 7 $^{\circ}$C, respectively. It also observed that the variation of PS in VCSEL was sensitive to the increasing and decreasing process of temperature. Rich results concluded that the substrate temperature play an significant role in MPS. [Preview Abstract] |
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H1.00161: Simulation of polarization switching of Vertical-Cavity Surface-Emitting Lasers at constant current Pei-Hou Chin, Wang-Chuang Kuo, Shaham Quadir, Yu-Heng Wu, Tsu-Chiang Yen The polarization switching (PS) in Vertical-Cavity Surface-Emitting Lasers (VCSELs) at constant bias current was investigated by numerical simulation in this research. The simulation was performed by Linear Current Gain model. The PS with a delay time at constant bias current was observed in the experiment which was performed by quasi-step current. The simulation results show that the PS delay time depends on the constant bias current and these results are matching well with experimental results. These results contribute to the understanding of the mechanism of VCSEL's polarization switching. [Preview Abstract] |
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H1.00162: Analysis of Multi-Polarization Switching in Vertical-Cavity Surface-Emitting Lasers Using Multi-peak gain model Chuan Hsu, Yu-Fong Chen, Pei-Hou Chin, Shaham Quadir, Yueh-Chen Li, Yu-Heng Wu, Tsu-Chiang Yen This research investigated the mulit-polarization switching (MPS) in vertical-cavity surface-emitting lasers (VCSELs) at constant temperature by simple multi-peak gain model.In experimental results, the phenomenon of the polarization switching (PS) in the VCSEL were arduous to definite quantitative analysis. A simple multi-peak gain model which included the temperature effect and current effect was established to match the MPS in the VCSEL. Simulation results match the experimental results well and shoe that the variation of temperature is a affecting factor of MPS. Therefore, the simple multi-peak gain model contributed a good understanding of multi-polarization switching in VCSELs. [Preview Abstract] |
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H1.00163: ABSTRACT WITHDRAWN |
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H1.00164: Critical Slowing Down of Relaxation Time in VCSEL's Polarization Switching Yueh-Chen Li, Wang-Chuang Kuo, Yu-Heng Wu, Tsu-Chiang Yen This study investigates the polarization switching (PS) of vertical-cavity surface-emitting lasers (VCSELs) approaching to criticality. The dynamical bifurcation of VCSEL's PS (VPS) which was researched in earlier investigations essentially differs from the static cases typically presented in thermodynamics. Therefore, a VCSEL is driven by quasi-increasing step current and quasi-decreasing step current instead of alternating current in this study. The results show a critical slowing down nearing PS, a power law and scaling law of the relaxation time which are the characteristics of second order phase transition. This investigation has potential for connecting the phase transition characteristics of VPS and quantum phase transitions (QPTs). [Preview Abstract] |
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H1.00165: Surface temperature measurement by optical self-interference of laser beam at the edge of a thermally sensitive thin film Phuong Anh Do, Mohamed Touabia, Alain Hache Measurement of surface temperature is problematic when the thermal mass of the probe (e.g. thermocouple or thermometer) is large relative to that of the sampled volume (e.g. thin film). With the goal of reducing thermal mass error, we developed a method using thermal probes in the form of thin films with materials exhibiting large physical and optical changes with temperature. Using chitosan, a polymer, as test material, we show that thermal expansion and refractive index changes in the film are detectable optically with a laser beam. When half of the Gaussian-shaped beam travels through the edge of the film and half of it does not, self-interference in the form of a fringe pattern is observed in the far field. With the fringe displacement correlated to phase variations and temperature changes, the calibration can be used to probe surface temperature on other samples. With the laser beam focused to 50 $\mu $m and chitosan films as thin as 100 nm, the method is adequate to measure temperature in the near vicinity of the surface. We provide a theory and numerical simulations to determine the ideal experimental conditions and parameters. [Preview Abstract] |
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H1.00166: Effect of doping on performance of IR quantum dot photodetector Guillaume Thomain, Vladimir Mitin, Victor Pogrebnyak, Andrei Sergeev We investigated the influence of the dopant position and dopant concentration on performance of InAs/Al$_{.22}$Ga$_{.78}$As quantum dot infrared photodetectors. We designed and fabricated three types of the QDIP with a InAs-dot sheet concentration of 1.04x10$^{11}$ cm$^{-2}$, which differ only in the position and density of a Si-dopant. In the first one, the dopant with a density of 5.4x10$^{11}$cm$^{-2}$ was placed directly into the QD layer; in the second, the same amount of the dopant was placed in the middle of the Al$_{.22}$Ga$_{.78}$As spacer between the QD layer in such a way that it was sandwich between the two undoped Al$_{.22}$Ga$_{.78}$As layers facing QD layers on both sides; in the third type, position of the dopant was the same as in the second device, but its concentration was 1.5 greater. The spectral, electrical, and temperature characterization of these devices demonstrated that device 3 had the largest responsivity and detectivity at 3.7 $\mu$m comparable with the best quantum well and MCT detectors. The experimental characterization along with simulations allowed us to analyze and explained the enhanced photoresponse of device 3. [Preview Abstract] |
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H1.00167: Toward terahertz heterodyne detection with superconducting Josephson junctions N. Bergeal, M. Malnou, C. Feuillet-Palma, A. Luo, T. Wolf, J. Lesueur, C. Ulysse, P. Febvre The terahertz region of the electromagnetic spectrum [0.3-10THz] has, so far, not been exploited fully due to the lack of suitable sources and detectors. Indeed, THz frequency lies between the frequency range of traditional electronics and photonics where the existing technology cannot be simply extended. SIS Niobium tunnel junctions that are currently used as mixing element in heterodyne receivers are intrinsically limited in frequency by the energy gap of Nb and operate only at low temperature (4.2K). An alternative to these devices consists of using High-Tc superconducting receivers. Over the past years, we have developed a new approach based on ion irradiation to make Josephson nano-junctions and SQUIDs with YBCO thin films [1,2]. In this talk, we will present a study of the high-frequency mixing properties of such junctions up to 400 GHz [3]. Conversion gain has been measured at frequencies spanning the range below and above the characteristic frequency fc $=$ (2e/h)IcRn of the junctions. The transition between two distinct mixing regimes has been clearly evidenced, in good agreement with the prediction of the three ports model. \\[4pt] [1] N. Bergeal et al., Appl. Phys. Lett. 87, 102502 (2005)\\[0pt] [2] N. Bergeal et al., Appl. Phys. Lett. 89, 1112515 (2006)\\[0pt] [3] Luo et al, arXiv:1203.1734 (2012) [Preview Abstract] |
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H1.00168: An Actively Shielded 1.5T MgB$_2$ MRI Magnet Design Michael Martens, Tanvir Baig, Mihai Cara, Robert Brown, David Doll, Michael Tomsic Superconducting magnets for MRI are often constructed with NbTi wire cooled below 4.2K using liquid helium. As helium costs have more than tripled in the last decade, there is a need for a cryogen-free conduction-cooled alternative. A key reason for pursuing MgB$_2$ superconductor wire in the design of MRI magnets is its superior critical current compared to NbTi over a temperature range of 10-15K. We present a 1.5T whole body actively shielded main magnet design assuming second-generation multifilament MgB$_2$ wire using an improved functional approach. The design exhibits 4 pairs of primary bundles and 1 pair of shielding bundles with an inner (outer) diameter of 1.1 (1.89)m and a length of 1.54m. The imaging volume is 45cm with a maximum of 9ppm inhomogeneity. The wire dimension is assumed to be 1mm$^2$ and the wire current is 135A. The maximum field on a wire is found to be 4.1T well below the critical field value of approximately 6T at 10K for the second-generation wire. The 5-Gauss footprint for the new magnet is found to be 2.7 (3.7)m in the radial (axial) direction. The maximum hoop stress and axial force on a bundle, respectively, are 82.9MPa and 2680.2kN. Trade-offs for the reduction of any given parameter are analyzed. [Preview Abstract] |
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H1.00169: Magnetic rotor flux observer of induction motors with fast convergence and less transient oscillation Chang-Woo Park, Jung-Hoon Hwang This paper presents an observer design for the estimation of magnetic rotor flux of induction motors. We characterize the class of MIMO induction motor systems that consists of the linear observable and the nonlinear part with a block triangular structure. The similarity transformation that plays an important role in proving the convergence of the proposed observer is generalized to the systems. Since the gain of the proposed observer minimizes a nonlinear part of the system to suppress for the stability of the error dynamics, it improves the transient performance of the high gain observer. Moreover, by using the generalized similarity transformation, it is shown that under some observability and boundedness conditions, the proposed observer guarantees the global exponential convergence to zero of the estimation error. Since the proposed scheme minimizes the nonlinearity of an induction motor system, it improves the transient performance of the observer and guarantees the global exponential convergence to zero of the estimation error. The estimation results of magnetic rotor fluxes through experiments are shown and it is presented that the proposed magnetic flux observer exhibits less transient oscillation and faster convergence time than the general observer. [Preview Abstract] |
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H1.00170: Energy Minimizers in Thin Ferromagnetic Nanorings with Four-Fold In-Plane Anisotropy Gabriel Chaves, Cyrill Muratov We present results obtained from micromagnetic simulations of thin ferromagnetic nanorings. We investigate annuli made of materials with non-negligible cubic anisotropy. In thin films the crystalline anisotropy favors magnetizations lying in the film plain along $\pm\hat{\mathbf{x}}$ or $\pm\hat{\mathbf{y}}$ directions. The magnetostatic energy separates into boundary and bulk terms. Our previous work provided a classification of remanent states based on the above contributions to the energy [1]. There are three regimes with distinct features of the remanent states depending on the dominant energy term. The magnetization configurations present four distinct domains. Different remanent states coexist in each of these regimes and they are characterized by the behavior of the domain walls spanning the annulus. Here, we compute the energies for these metastable states in a variety of ring dimensions and material parameters. In particular, we attempt to locate the ground state as a function of ring dimensions. This information is of importance for the design of magnetic storage devices based on configurations presenting $2\pi$ domain walls [2]. [1] G.D. Chaves-O'Flynn, C. Muratov. Submitted. IEEE Trans. Mag. [2] C. Muratov and V. Osipov. IEEE Trans. Mag, 45, p.3207 (2008) [Preview Abstract] |
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H1.00171: Development magnet for portable MRI device: Investigate skin cancer Nurcan Dogan Nuclear magnetic resonance (NMR) is well known from diagnostic medical imaging and analytical chemical spectroscopy. The sample is brought into the laboratory to be investigated with radio-waves inside stationary magnets. This paper describes a new approach useful to reduce the gradient strength of the magnetic field. Despite of the recent progress in magnet design, homogeneity of permenant magnet is still very limited. Fortunately for medical applications usually there is need in high-field homogeneity to obtain the high-resolution spectra that provide the detailed chemical shift and coupling-constant. In this work we discuss various permanent magnet design-without cooling system- for magnetic imaging. The magnet used for the present application consists of two units. The main unit is built from static magnet blocks and generates the main magnetic field. The second one is the shim unit. It consists of smaller movable magnets used to correct in a controlled manner the magnetic field generated by the main unit. By combining the two units, magnetic fields with defined spatial dependence can be generated with high accuracy. The performance of the magnet in terms of resolution and sensitivity is first evaluated and compared with conventional other magnets of higher gradient strength using phantoms of known geometry and relaxation times. After integration of magnet with spectrometer, Our new system is used to profile the structures of healty and unhealthy (cancer) human skins in vivo. To understand the contrast between the different skin type, the distribution of relaxation times T1 is spatially investigated. [Preview Abstract] |
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H1.00172: Human umbilical vein endothelial cell interaction with phospholipid polymer nanofibers coated by micro-patterned diamond-like carbon (DLC) Soki Yoshida, Terumitsu Hasebe, Tetsuya Suzuki, Atsushi Hotta Blood-contacting medical devices should possess the surface properties with the following two important characteristics: The first is the anti-thrombogenicity of the material surface and the second is the re-endothelialization over the device surface after long-term implantation, because endothelial cells have excellent anticoagulant properties in blood vessels. To develop highly hemocompatible materials that could promote surface endothelialization, we investigated biocompatible polymers coated with thin diamond-like carbon (DLC) film. In this research, we examined the viability of human umbilical vein endothelial cells (HUVECs) for hydrophilic 2-methacryloyloxyethyl phosphorylcholine (MPC) fibers with DLC coatings, both of which were known to be anti-thrombogenic. DLC was synthesized on MPC by varying the ratio of covered area by patterned DLC. HUVECs were seeded on DLC-coated MPC for 6 days. The results indicated that the MPC surface with DLC did not disturb HUVEC proliferation in 6 days of culture. Additionally, we are currently making strong efforts to fabricate MPC fibers with bFGF which is an important growth factor involved in cell proliferation. MPC containing bFGF with DLC coatings could be extensively utilized for blood-contacting medical devices. [Preview Abstract] |
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H1.00173: Theoretical Investigation of the Electronic Interaction between Au and TiO2 Nano-systems Andrew Rice The focus of this research is to theoretically study the underlying mechanisms of the enhanced catalytic properties presented by the oxide supported gold nanoparticles. Extensive studies have established that the interaction between the gold nanoparticles and the oxide substrates plays an important role in enhancing the catalytic performance. Several factors, such as geometry, electronic coupling and the charge transfer occurring between Au and TiO2 need to be considered in order to understand the interaction between Au and TiO2. One issue that will be discussed in this study is the bonding character between the Au/ TiO2 nanosystems. Experimentally, geometries on this subject have been researched. However, there is no clear picture of how the Au nanoparticles bonding to TiO2 surfcace in terms of the preference locations along certain orientation of TiO2 (anatase in our study). Using computational approaches, we are aiming to understand the bonding characters and the electronic properties of Au/ TiO2 nanosystems. The spherical shape of Au13 has been established. As for the TiO2 substrate, we considered three anatase nanoparticles with both (101) and (001) surface existence. Along with size increasing, the (001) surface tends to be the dominate surface of TiO2 nanoparticle. The reason we designed the TiO2 nanoparticle in this manner is that we are interested in the preferable locations of Au nanoclusters anchoring to TiO2. In our study, we found Au13 on all three TiO2 substrates showed geometric deformation. [Preview Abstract] |
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H1.00174: Temperature Dependence of the Single-Photon Sensitivity of a Quantum Dot, Optically Gated, Field-Effect Transistor Andrew Prudhom, Eric Gansen, Mary Rowe, Sean Harrington, John Nehls, Shelley Etzel, Sae Woo Nam, Richard Mirin The potential advantages that quantum communications and computing have over their conventional counterparts have seeded a growing interest in transmitting and processing information with individual photons. However, if these technologies are ever to reach their full potential, improved single-photon detectors will have to be developed. Here, I present a systematic study of the temperature dependence of the electrical noise in a quantum dot, optically gated, field-effect transistor (QDOGFET) and detail how the noise influences the sensitivity of this novel single-photon detector. Previous studies have shown that when cooled to 4K, QDOGFET's exhibit single-photon sensitivity and photon-number resolving capabilities; however, there has been no systematic study of how operating temperature affects their performance. Here, we measure the noise spectra of a device for a range of sample temperatures between 7K and 60K. We use the noise data to determine the signal-to-noise ratio of the optical response of the device for various temperatures and detection rates. Our analysis indicates that QDOGFET's can operate over a broad range of temperatures, where increased operating temperature can be traded for decreased sensitivity. [Preview Abstract] |
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H1.00175: Nanocomposite materials for radiation detection Sunil Sahi Colloidal quantum dots (CdTe, CdSe, and ZnO) have attracted tremendous interest in wide range of application from biological imaging, biosensing, solar cells to optoelectronic devices. However very few published reports on the radiation detection based on colloidal quantum dots. Quantum dots based nanocomposite materials could be a promising material for radiation detection because of their short luminescence life time and high quantum efficiencies as a consequence of quantum size confinement. However stopping power of most quantum dots is low and their scintillation luminescence is very weak. The combination of high stopping power of inorganic scintillator (CeF$_{3}$LaF$_{3}$: Ce, YAG:Ce) and high efficiency of quantum dot could potentially lead to a new class of scintillator. We have studied the nanocomposite of inorganic scintillator and quantum dot based on energy transfer principle and investigate the scintillation properties of nanocomposite scintillator. [Preview Abstract] |
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H1.00176: SHMUTZ {\&} PROTON-DIAMANT H$+$ Irradiated/Written-Hyper/Super-conductivity(HC/SC) Precognizance/Early Experiments Connections: Wet-Graphite Room-Tc {\&} Actualized MgB2 High-Tc: Connection to Mechanical Bulk-Moduli/Hardness: Diamond Hydrocarbon-Filaments, Disorder, Nano-Powders:C,Bi,TiB2,TiC Irwin Wunderman, Edward Carl-Ludwig Siegel, Thomas Lewis, Frederic Young, Adolph Smith, Gieselle Dresschhoff-Zeller SHMUTZ: ``wet-graphite''Scheike-\textellipsis .[Adv.Mtls.(7/16/12)]hyper/super-SCHMUTZ-conductor(S!!!) $=$ ``wet''(?)-``graphite''(?) $=$ ``graphene''(?) $=$ water(?) $=$ hydrogen(?) $=$ultra-heavy proton-bands(???)$=$ \textellipsis (???) claimed room/high-Tc/high-Jc superconductOR ``p''-``wave''/ BAND(!!!) superconductIVITY and actualized/ instantiated MgB2 high-Tc superconductors and their BCS- superconductivity: Tc Siegel[ICMAO(77);JMMM 7,190(78)] connection to SiegelJ.Nonxline-Sol.40,453(80)] disorder/amorphous-superconductivity in nano-powders mechanical bulk/shear(?)-moduli/hardness: proton-irradiated diamond, powders TiB2, TiC,\textbraceleft Siegel[Semis. {\&} Insuls.5:39,47, 62 (79)])-\textellipsis ``VS''/concommitance with Siegel[Phys.Stat.Sol.(a)11,45(72)]-Dempsey [Phil.Mag. 8,86,285(63)]-Overhauser-(Little!!!)-Seitz-Smith-Zeller-Dreschoff-Antonoff-Young-\textellipsis proton-``irradiated''/ implanted/ thermalized-in-(optimal: BOTH heat-capacity/heat-sink {\&} insulator/maximal dielectric-constant) diamond: ``VS'' ``hambergite-borate-mineral transformable to Overhauser optimal-high-Tc-LiBD2 in Overhauser-(NW-periodic-table)-Land: CO2/CH4-ETERNAL-sequestration by-product: WATER!!!: physics lessons from [Preview Abstract] |
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H1.00177: Very Early Prescient Experimental and Theoretical Nano/Microcluster-Scale-Physics Root-Cause Ultimate-Origins: History: EMET!!!/TRUTH!!! Victor Gregson, Ryogiro Kubo, Edward Carl-Ludwig Siegel Siegel[Phys.Stat.Sol.(a)11,45(72)] possibly first experimental nanoscale-physics/metallurgy/ceramics(VS CNRS Mdm.-Pres.resume-claims),following always-seminal Kubo[Phys. Lett.1,49(62);J.Phys.Soc.Jpn.:17,965(62); 21,1765(66); Comm.SS Phys.1,168 (68); J.Phys.Colloques,38,C2-69(77).]-Fulde[(1960s)]-Matsubara et. al.[(1960s]-Matsubara-Siegel[Intl.Conf.Lattice-Dym.(77);Statphys-13(77);ICMAO(77);Scripta Met.13,913(79)] as reviewed by Sugano[Microcluster-Physics(81)], very early experimental hardness/bulk-modului/shear-moduli versus/ connection to Dempsey[Phil.Mag. 8,86,285(63)] electrical-resistivity trends with cation-atomic-number of hot/cold-pressed ceramics versus Mott topological-disorder: Siegel: powders[Mtls.Sci.Eng.8,6 323(71);Phys.Stat.Sol .(a)11, 45(72) ;Semis, {\&}Insuls.5:39,47,62 (79)] /glasses[J.Nonxline-Sols.40,453(80); NYAS Conf.Atomic {\&} Molecular Glasses, Ann.NYAS(80); Ferroelectrics 34,1,127(81)]/ liquids[Phys.{\&} Chem.Liqs.:4(4)(75);5(1)(76)] / slushes (!!!)/ blends /ferrofluids[Intl Conf. Ferrofluids, M. Zahn ed.(84)]/nanophysics of Goudschmidt [Interstitial-Alloys,(69)] transition-metalloids: carbides, nitrides, borides, hydrides, carbon [Phys.Stat.Sol.(a)11,45(72); Semis.{\&}Insuls.5: 39,47,62(79)]) and proton-irradiated diamond Little[(1960s]-predicted hyper/superconducting polydiacetylene(???) quantum-wires [3rd World Cong.SC, Munich(92), Appl.-SC,1,10,1949(93); TWO OTHER PAPERS SPIKED BY ANL/DOE EDITORS!!! AS USUAL!!!: GOOGLE: [Preview Abstract] |
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H1.00178: Why a magnetized quantum wire can act as an optical amplifier M.S. Kushwaha Essentially, we embark on the device aspects of the intersubband collective (magnetoroton) excitations in a quantum wire characterized by a confining harmonic potential and subjected to a perpendicular magnetic field. The computation of the gain coefficient suggests a significant application: the electronic device based on such magnetoroton modes can act as an optical amplifier. [Preview Abstract] |
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H1.00179: Process simulation of carbon-based nanostructures in next-generation semiconductor integrated elements Yasunari Zempo, Takahisa Ohno The trend in semiconductor devices leads us to develop new materials such as CNT and graphene from the point of high electric conductivity, new CMOS channel and interconnect, and low-voltage operation. To realize the carbon-based nano device, we have established HPCI carbon-based nano structure material consortium with industries, universities and institutions, aiming for R\&D of nano electric fabrication. Our research is oriented to process simulations of nano structure manufacturing for optimal process design, property analyses for comprehensive assessment of the device applications, and providing industry-friendly environment that combines first principles and other methods (semi-empirical and classical). To promote device manufacturing with the help of HPCI (K computer), PHASE is our key software for electronic structure calculations based on DFT using plane wave base, which is not only wide applicable to various materials, and involves analytical tools for dielectric response, vibrational analysis, STM simulation, etc. but also compatible to wide range of platforms from note PC to SC, with well optimized parallel computation. Some of applications will be presented together with the scalability on K computer such as SiC defects, graphene growth, and conductivity analysis [Preview Abstract] |
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H1.00180: BIOLOGICAL PHYSICS |
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H1.00181: A More Practical Sort of Interstellar Travel? Robert Jones Various radio messages have been beamed toward nearby stellar systems. I contributed to one a couple years ago. (My contribution was a warning to anyone who got the message. I warned of humankind's rather imperfect value system.) But perhaps we should send the complete digital description of the human genome. Or perhaps those of various humans. Along with this would be an attempt to explain what the message is. One might hope that the recipients could then construct human beings at their end from atoms available there. Perhaps spaceships aren't needed. And perhaps a larger fraction of the space budget should be spent on seti. As a hedge against global catastrophe we should begin to send such signals now. [Preview Abstract] |
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H1.00182: Stochastic discrete-state simulation of cell population growth in different environments Merzu K. Belete, Rhys M. Admas, Gabor Balazsi Living cells possess low copies of many molecular components like DNA and proteins which cause stochastic fluctuations in gene expression. Gene expression affects cell phenotypes as a function of the environment.\footnote{Jacob F, Monod J. J Mol Biol \textbf{3}, 318-356 (1961)} Among all encoded phenotypes, fitness measures how well the organism survives in its environment. A number of experimental gene expression measurements confirmed that gene expression is a determinant factor for cellular fitness in various environments\footnote{Dekel E, Alon U. Nature \textbf{436}: 588-592 (2005)}. Yet, gene expression is a stochastic process better described by its probability distribution rather than its first moment. For bimodal gene expression, the individual cell gene expression is quite different from population average gene expression and it involves stochastic transitions between cellular states. Therefore, cell fitness is noisy and fluctuates randomly according to noisy gene expression. To address fitness in noise, we develop a stochastic model accounting different environments (combinations of drug and inducer). We found that the population fitness is nontrivial dependence on drug and inducer in agreement with our lab.\footnote{Nevozhay et al., PLoS Comp Bio (2012)} [Preview Abstract] |
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H1.00183: Simulations of single-molecule pulling experiments: equilibrium and non-equilibrium free-energy landscape trajectories Eric Copenhaver, Jutta Luettmer-Strathmann The response of a single molecule to an applied force is important for many biological processes. This response is often investigated via single-molecule pulling experiments, where a tension force is applied to the opposite ends of a biological chain molecule. In equilibrium conditions, the system follows a trajectory that may be predicted from the free-energy landscape. In non-equilibrium experiments, the pulling force varies too rapidly for the chain to explore all available configurations resulting in a deviation from the equilibrium trajectory. To gain a better understanding of the relationship between equilibrium and non-equilibrium processes, we investigate the effect of the pulling speed on the system's trajectory with two types of computer simulations of single-molecule experiments. We perform Wang-Landau simulations to determine the energy landscape and Langevin dynamics simulations to probe the dynamic response of the same bead-spring model of a biopolymer. After verifying that both simulation methods yield consistent equilibrium results, we study the effect of the pulling protocol on the free-energy landscape trajectories. The goal of this project is to devise an effective dynamic field that recreates the non-equilibrium pathway under equilibrium conditions. [Preview Abstract] |
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H1.00184: ABSTRACT WITHDRAWN |
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H1.00185: An Integrated Method for Quantification and Analysis of Motility in C. Elegans Frank Van Bussel, Amar Patel, Venkat Padmanabhan, Khan Zeina, Siva Vanapalli, Jerzy Blawzdziewicz Though the nematode C. Elegans is a model organism in many areas of biology, its most readily observed behaviors, crawling and swimming, have yet to be thoroughly described. The outcome of detailed studies, for example, on the relation of neural control to chemotaxis, or the effects of gene suppression as manifested in the behavior of mutant strains, depends upon the acquisition of detailed trajectory data over nontrivial time and length scales. Here we present a methodology for processing, quantifying, and analyzing nematode motion data both in terms of their shape over short time scales and their trajectories over long time scales. This method is based on a succinct representation of shape/trajectory information using piecewise-harmonic functions in curvature space, first described in [1]. The representation parameters are obtained through automated image processing techniques. Using this method we are able to analyze large amounts of nematode data relatively quickly, making it applicable to detailed worm-motion studies. References: 1. Padmanabhan V, Khan ZS, Solomon DE, Armstrong A, Rumbaugh KP, et al. (2012) Locomotion of C. elegans: A Piecewise-Harmonic Curvature Representation of Nematode Behavior. PLoS ONE 7(7): e40121. doi:10.1371/journal.pone.0040121 [Preview Abstract] |
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H1.00186: The Effect of Plasma on Tail Regeneration of Tadpoles \textit{Xenopus Laevis} Joyce June, Chima Amadi, Jaishri Menon, Kevin Martus Healthy wounds require a balanced combination of nutrients and growth factors for healing and tissue regeneration. Nitric oxide, (NO), is also crucial in wound healing processes and linked with production of several cytokines, interaction with other free radicals and influence on microcirculation. Hypothesize is that exposure to plasma will affect wound healing and tail regeneration in tadpoles \textit{Xenopus laevis} and plasma induced endogenous NO production may have an important role to play at the cellular level. Tail amputation was immediately followed by exposure of the wound to the helium plasma. For histological features, blastema (growing regenerate) was fixed in 4{\%} neutral buffer formalin for paraffin sections. \textit{In situ} staining for NO was carried out 5 days post amputation. The rate of the regenerating tail was proportional to the plasma exposure time at the expense of metamorphic rate. Histological features show that the tadpoles exposed to the plasma had a higher level of cellular proliferation and microvasculature in blastema. \textit{In situ} staining for NO indicated its increased endogenous production compared to the control. These findings suggest that accelerated wound healing and tail regeneration following exposure to the plasma may be due to its direct effect on cell proliferation and increased NO production which may be involved in microvascularization. [Preview Abstract] |
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H1.00187: Effect of substrate mechanical properties on T cell activation King Lam Hui, Arpita Upadhyaya T cell activation is a key process in cell-mediated immunity, and engagement of T cell receptors by peptides on antigen presenting cells leads to activation of signaling cascades as well as cytoskeletal reorganization and large scale membrane deformations. While significant advances have been made in understanding the biochemical signaling pathways, the effects imposed by the physical environment and the role of mechanical forces on cell activation are not well understood. In this study, we have used anti-CD3 coated elastic polyacrylamide gels as stimulatory substrates to enable the spreading of Jurkat T cells and the measurement of cellular traction forces. We have investigated the effect of substrate stiffness on the dynamics of T cell spreading and cellular force generation. We found that T cells display more active and sustained edge dynamics on softer gels and that they exert increased traction stresses with increasing gel stiffness. A dynamic actin cytoskeleton was required to maintain the forces generated during activation, as inferred from small molecule inhibition experiments. Our results indicate an important role for physical properties of the antigen presenting cell as well as cytoskeleton-driven forces in signaling activation. [Preview Abstract] |
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H1.00188: Physical controls on matrix mineralization Jinhui Tao, Mike Nielsen, Jim De Yoreo During biomineral formation, protein matrices impose order on nucleating mineral phases. While many studies have examined the structural relationships between mineral and matrix, few have explored the energetics. To address this gap we use \textit{in situ} TEM and AFM to investigate calcium phosphate nucleation and growth in collagen and amelogenin matrices. \textit{In situ} TEM results indicate that, in the absence of calcium, amelogenin nanospheres are loose aggregates of oligomers, while in the presence of calcium phosphate solution, can form chain-like structures and become mineralized with an amorphous phase before the appearance of crystalline phases. Results on collagen reveal the evolution of nucleation pathways from direct to indirect with increasing supersaturation and analysis of nucleation rates using classical theory demonstrates a reduction in interfacial energy due to matrix-mineral interactions. However, the calculated thermodynamic barriers are in contradiction to the observed pathways and well in excess of sensible values. We present a model based on cluster aggregation within the classical context that reconciles experiment and theory. [Preview Abstract] |
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H1.00189: X-ray absorption Studies of Zinc species in \textit{Centella asiatica} Sunil Dehipawala, Tak Cheung, Clayton Hogan, Yao Agoudavi, Sumudu Dehipawala Zinc is a very important mineral present in a variety of vegetables. It is an essential element in cellular metabolism and several bodily functions. We used X-ray fluorescence, and X-ray Absorption near Edge structure(XANES) to study the amount of zinc present in several leafy vegetables as well as its chemical environment within the plant. Main absorption edge position of XANES is sensitive to the oxidation state of zinc and is useful when comparing the type of zinc present in different vegetables to the standard zinc present in supplements. Normalized main edge height is proportional to the amount of zinc present in the sample. Several leafy greens were used in this study, such as \textit{Spinacia oleracea}, \textit{Basella alba}, \textit{Brassica oleracea}, \textit{Cardiospermum halicacabum }and \textit{Centella asiatica}. All of these plant leaves contained approximately the same amount of zinc in the leaf portion of the plant and a slightly lower amount in the stems, except \textit{Centella asiatica}. Both leaves and stems of the plant \textit{Centella asiatica} contained nearly two times the zinc compared to other plants. Further investigation of zinc's chemical environment within \textit{Centella asiatica} could lead to a much more efficient dietary consumption of zinc. [Preview Abstract] |
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H1.00190: A Minimal Model of the E. Coli Bacterium in Exponential Phase Growth Arijit Maitra, Ken Dill We study the fundamental process of exponential cell growth in the E. Coli bacterium under conditions of extracellular glucose limitations using a minimalistic reaction framework by accounting for energy metabolism and protein synthesis. The cell model has three nodes: ATP, the ribosomal and the non-ribosomal proteins. Their interdependencies and dynamics are wrapped in a system of ordinary differential equations. The formulations of their interactive fluxes capture the essence of cellular physiology under conditions of growth. We solve the model numerically for different glucose concentrations, and, where possible, explore the cell states analytically under steady state conditions. We verify the model predictions with available experimental data. The model lets us quantify the coupling between energy generation and biomass growth. An implication of this model is that it provides a layout to compute the fitness landscape in terms of the parameters of the cells, such as the protein translation rates, to make hypotheses about possible routes for cellular evolution under glucose limitation. [Preview Abstract] |
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H1.00191: DNA translocation through a nanopore in a single layered doped semiconductor membrane Ining A. Jou, Dmitriy V. Melnikov, Christopher R. McKinney, Maria E. Gracheva We have recently developed a computational model that allows us to study the influence a semiconductor membrane has on a DNA molecule translocating through a nanopore in this membrane. Our model incorporates both the self-consistent Poisson-Nernst-Planck simulations for the electric potential of a solid state membrane immersed in an electrolyte solution together with the Brownian Dynamics of the biomolecule. We study how the applied electrolyte bias, the semiconductor membrane bias and the semiconductor material type ($n$-Si or $p$-Si) affect the translocation dynamics of a single-stranded DNA moving through a nanopore in a single layered semiconductor membrane. Our results show that the type of semiconductor material has a prominent effect on the biomolecule's translocation time, with DNA exhibiting much longer translocation times through the $p$-type membrane than through the $n$-type at the same electrolyte and membrane potentials. In addition, we find the optimal combination for membrane/electrolyte system's parameters to achieve longest translocation time and largest DNA extension. With our single layered electrically tunable membranes, the DNA translocation time can be manipulated to have an order of magnitude increase. [Preview Abstract] |
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H1.00192: In-Situ Creation of Solid State Nanopores Kyle Briggs, Harold Kwok, Vincent Tabard-Cossa Recent advances in nanopore technology have demonstrated that they are a powerful tool for single biomolecule analysis, and great progress has been made toward the promise of nanopore-based DNA sequencing devices. A limiting factor in solid-state nanopore science is the complexity, throughput and cost of current fabrication methods, based on focused ion or election beam drilling, which require sophisticated equipment and highly trained personnel. Our laboratory at the University of Ottawa has demonstrated a simple and extremely low cost method to fabricate individual nanopores on thin solid-state membranes. By controlling an applied voltage across the membrane in aqueous salt solution, we are able to routinely create sub-5nm pores in dielectric membranes. In addition, the method can easily be extended to tune nanopore size with sub-nm precision. We will describe the fabrication method in detail, and present the effects of electric field strength, membrane material, solution salt composition, concentration and pH on the pore creation time and size distribution. These results allow us to elucidate the physical mechanisms responsible for nanopore formation. [Preview Abstract] |
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H1.00193: Dual mechanisms of DNA sequencing based on tunnelling between nitrogen-doped carbon nanotube electrodes Han Seul Kim, Yong-Hoon Kim The DNA sequencing approach based on the combination of nanopores and electron tunnelling has seen considerable advances in recent years, and particularly carbon nanomaterials have emerged as promising candidates to replace metal electrodes. Carrying out extensive first-principles calculations, we here show that two distinct DNA sequencing mechanisms can be achieved with different configurations of a single-type nitrogen-doped capped carbon nanotube (CNT) that has significantly enhanced transmission and chemical sensitivity over its pristine counterpart. With a small CNT-CNT gap size that induces face-on nucleobase configurations, we obtain a typical conductance ordering where the largest signal is induced from guanine due to its highest occupied molecular orbital energetic position higher than those of other bases. On the other hand, for a large CNT-CNT gap size that accommodates edge-on nucleobase configurations, we extract a completely different conductance ordering in which thymine results in the largest signal. We find that the latter novel nucleobase sensing mechanism originates from the nature of chemical connectivity between nitrogen-doped CNT caps and nucleobase functional groups that include the thymine methyl group. This work thus demonstrates the feasibility of a tunnelling-based dual-mode approach toward whole genome sequencing applications, detection of DNA base modifications, and single-molecule sensing in general. [Preview Abstract] |
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H1.00194: Charged Nanoparticle Translocation through Solid-State Nanopores Santoshi Nandivada, Ryan Rollings, Nathan Walsh, Jiali Li Solid-state nanopores are widely used for detection of biomolecules and small particles by measuring the pore resistance change when the molecules or particles are electrophoretically driven through. Using the same principle, in this study we look at the translocation of different size, around 10 nm in diameter, negatively charged nanoparticles through nanopores fabricated by combining ion beams and electron beams. We measure the relationship between the current blockage signal caused by pore resistance change with nanoparticle size and nanopore geometry. We also estimate the magnitude and duration of current blockage signal theoretically by relating the change in the resistance of the nanopore to the geometry of the pore and the particle. Preliminary results obtained from experiment and numerical simulation using finite element analysis software (Multiphysisc,COMSOL Inc) will be presented. [Preview Abstract] |
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H1.00195: High Temperature Baking as a Means of Controlling Solid-state Nanopore Fabrication and Stability Nathan Walsh, Denis Tita, Santoshi Nandivada, Ryan Rollings, Jiali Li Solid-state nanopores have been of interest in single biomolecule analysis due to their ability to be tunable in dimension and robust nature. The ability to withstand wide variations in temperature, salt, denaturing agent, and pH while maintaining pore stability has made it a promising technology in detecting biomolecules at the single molecule level. One of the current methods for fabricating these solid-state nanopores uses a low energy ion beam, $\sim$ 3 keV, incident on a 100nm diameter hole in a silicon nitride membrane to close it to a smaller diameter. Because of individual variability in between samples, the time taken for pore closure can vary from a matter of seconds to a few hours. Because the error in the measured final diameter of the nanopore is proportional to the closure rate, this causes a wide variability in final nanopore diameter. In addition, the variations in stability and electrical noise level of these nanopores at experimental solution condition have also been observed. Here we use a tube furnace to investigate adventitious carbon and its effects on the closure rate. We also use the tube furnace to bake the silicon nitride nanopores after fabrication and investigate the effects on the stability of the pore and electrical noise in solution. [Preview Abstract] |
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H1.00196: Cell mobility after endocytosis of carbon nanotubes Massooma Pirbhai, Thomas Flores, Sabrina Jedlicka, Slava V. Rotkin Directed cell movement plays a crucial role in cellular behaviors such as neuronal cell division, cell migration, and cell differentiation. There is evidence in preclinical in vivo studies that small fields have successfully been used to enhance regrowth of damages spinal cord axons but with a small success rate. Fortunately, the evolution of functional biomaterials and nanotechnology may provide promising solutions for enhancing the application of electric fields in guiding neuron migration and neurogenesis within the central nervous system. In this work, we studied how endocytosis and subsequent retention of carbon nanotubes affects the mobility of cells under the influence of an electric field, including the directed cell movement. [Preview Abstract] |
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H1.00197: Whole Protein Native Fitness Potentials Eshel Faraggi, Andrzej Kloczkowski Protein structure prediction can be separated into two tasks: sample the configuration space of the protein chain, and assign a fitness between these hypothetical models and the native structure of the protein. One of the more promising developments in this area is that of knowledge based energy functions. However, standard approaches using pair-wise interactions have shown shortcomings demonstrated by the superiority of multi-body-potentials. These shortcomings are due to residue pair-wise interaction being dependent on other residues along the chain. We developed a method that uses whole protein information filtered through machine learners to score protein models based on their likeness to native structures. For all models we calculated parameters associated with the distance to the solvent and with distances between residues. These parameters, in addition to energy estimates obtained by using a four-body-potential, DFIRE, and RWPlus were used as training for machine learners to predict the fitness of the models. Testing on CASP 9 targets showed that our method is superior to DFIRE, RWPlus, and the four-body potential, which are considered standards in the field. [Preview Abstract] |
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H1.00198: Directional Mechanosensing in Myosin VI Yubo Yang, Riina Tehver Myosin is a family of versatile motor proteins that perform various tasks, such as organelle transport, anchoring and cell deformation. Although the general mechanism of the motors has been fairly well established, details on dynamic aspects like force response of the motor, and force propagation are yet to be fully understood. In this poster, we present the response of the ATP binding region to force exerted on the tail domain in order to test the proposed tension-dependent gating mechanism of myosin VI processive motion. We employed the Self-Organized Polymer model in a computer simulation to explore the effect. Current results show that the ATP binding domain of myosin VI indeed exhibits tension dependence -- both structurally and dynamically. [Preview Abstract] |
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H1.00199: Aggregation of model amyloid insulin protein in crowding environments and under ac-electric fields Zhongli Zheng, Benxin Jing, Brian Murray, Mirco Sorci, Georges Belfort, Y. Elaine Zhu In vitro experiments have been widely used to characterize the misfolding/unfolding pathway characteristic of amylodogenic proteins. Conversion from natively folded amyloidogenic proteins to oligomers via nucleation is the accepted path to fibril formation upon heating over a certain lag time period. In this work, we investigate the effect of crowing environment and external electric fields on the pathway and kinetics of insulin, a well-established amyloid model protein by single fluorescence spectroscopy and imaging. With added co-solutes, such as glycerol and polyvinylpyrrolidone (PVP), to mimic the cellular crowding environments, we have observed that the lag time can be significantly prolonged. The lag time increases with increasing co-solute concentration, yet showing little dependence on solution viscosity. Conversely, applied ac-electric fields can considerably shorten the lag timewhen a critical ac-voltage is exceeded. The strong dependence of lag time on ac-frequency over a narrow range of 500 Hz-5 kHz indicates the effect of ac-electroosmosis on the diffusion controlled process of insulin nucleation. Yet, no conformational structure is detected with insulin under applied ac-fields, suggesting the equivalence of ac-polarization to the conventional thermal activation process for insulin aggregation. These finding suggest that at least the aggregation kinetics of insulin can be altered by local solution condition or external stimuli, which gives new insight to the treatment of amyloid related diseases. [Preview Abstract] |
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H1.00200: Conformational dynamics of amyloid proteins at the aqueous interface Matthew Armbruster, Nathan Horst, Brendy Aoki, Saad Malik, Patricia Soto Amyloid proteins is a class of proteins that exhibit distinct monomeric and oligomeric conformational states hallmark of deleterious neurological diseases for which there are not yet cures. Our goal is to examine the extent of which the aqueous/membrane interface modulates the folding energy landscape of amyloid proteins. To this end, we probe the dynamic conformational ensemble of amyloids (monomer prion protein and Alzheimer's Ab protofilaments) interacting with model bilayers. We will present the results of our coarse grain molecular modeling study in terms of the existence of preferential binding spots of the amyloid to the bilayer and the response of the bilayer to the interaction with the amyloid. [Preview Abstract] |
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H1.00201: Multiple attachments, heterogeneous binding and the high force tail in protein-protein binding force histograms Anwesha Sarkar, Edward Kramkowski, Essa Mayyas, Peter M. Hoffmann Atomic Force Microscopy (AFM) is a useful tool in measuring protein-protein interactions. However, a ``clean'' interpretation of the obtained data is not always easy. For instance, rupture force histograms generally do not fit simple theories. In particular, there is a high force tail that is not accounted for. This tail has variously been attributed to multiple binding (even though obvious multiple ruptures are excluded from analysis) or heterogeneity in the binding geometry. Here, we present a combined approach to answer the question of how much of the high force tail can be attributed to either cause. We used surfaces with well-controlled densities of active sites (biotin) to control multiple attachments with a functionalized tip (avidin). We found that the presence of multiple attachments, while significant, accounts for only a fraction of the events in the high force tail of the distribution. We also performed Monte Carlo simulations to match experimental results with theoretical expectations, confirming the importance of possible bond heterogeneity in these types of measurements. [Preview Abstract] |
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H1.00202: Study of the Agglomeration of 5 to 25nm Gold Nanoparticles as a Function of Viscosity and Ionic Concentration Adam Stefankiewicz, Tabbetha Dobbins Gold nanoparticles (AuNPs) attached to carcinoma cells and treated with light irradiation are able to convert the light into heat energy, thus killing those cells. In order to get the particles to the affected area, they may be entered into the circulatory system where the environment is highly viscous and comprised of high salt concentrations. This study examines the aggregation behavior of gold nanoparticles under those conditions. Surface charge creates coulombic repulsion between particles. Likewise, highly viscous solutions will prevent aggregation by limiting the rate of transport of gold through the solution. This study examines the aggregation behavior of gold nanopartilces as a function of viscosity (varied using polyethylene glycol). The study also examines the role of excess ions in the solution (varied using 5-Bromo-4-chloro-3-indolyl phosphate disodium salt). The aggregation phenomena was explored using dynamic light scattering for particle size analysis. Early results are presented here. [Preview Abstract] |
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H1.00203: Investigation of HT1080 tumor growth dynamics and ECM invasion in 3D Osman N. Yogurtcu, Angela M. Jimenez Valencia, Meng-horng Lee, Sean X. Sun, Denis Wirtz Tumors are complex arrangements of tissues made up of several components, including dense masses of cancer cells and re-organized extracellular matrix (ECM). Recent studies have revealed the crucial role that extracellular matrix components have on single cancer cell behavior, but how the interaction of ECM components affects the growth dynamics of an entire tumor is not fully understood. Here, we use human derived fibrosarcoma cell (HT1080) aggregates in combination with live cell imaging, cryo-stat sectioning, immunostaining, and confocal imaging to study changes in cell aggregate size, proliferation, and spatial distribution within 3 dimensional (3D) matrices. We compare our experimental observations with a coupled partial differential equations based mathematical model to predict cell aggregate growth and cell density distribution and determine how cell interactions play a significant role in this dynamic growth. Using this model, we investigate the distinct contributions from cell migration, proliferation, cell-matrix interactions, and matrix remodeling to the aggregate dynamics. [Preview Abstract] |
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H1.00204: Stochastic transcriptional activity results in precise RNA distribution profiles of Drosophila gap genes Mikhail Tikhonov, Shawn Little, Thomas Gregor How can biological systems reliably achieve a precise and reproducible response if they are constructed of noisy components? Using a novel single-molecule precision method in fixed Drosophila embryos we simultaneously measure the RNA distribution profiles and the transcriptional activity of individual nuclei in absolute units. We show that these RNA profiles of early patterning genes are precise at 8\% in absolute units, while the instantaneous activity of any one transcription site has an intrinsic noise exceeding 45\%. Thus the remarkable precision of Drosophila patterning system is already achieved at the RNA level and requires neither transcriptional feedback nor special mechanisms to reduce transcription noise. Instead, noise is filtered using straightforward spatiotemporal averaging. We further show that in regions where patterning genes are maximally expressed, they are all produced at the same absolute rate. This universality across gap genes suggests that the observed RNA production rate and noise are independent of promoter details and are inherent to transcription in Drosophila. [Preview Abstract] |
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H1.00205: Diblock organization of individual nucleoporin amino acid sequence determines overall structure and function of the nuclear pore complex David Ando, Yong Woon Kim, Roya Zandi, Ed Lau, Michael Colvin, Michael Rexach, Ajay Gopinathan The transport of cargo across the nuclear membrane is highly selective and accomplished by a poorly understood mechanism involving hundreds of nucleoporins within the nuclear pore complex (NPC). Currently, there is no clear picture of the overall structure formed by this collection of proteins within the pore, primarily due to their disordered nature. We perform coarse grained simulations of both individual nucleoporins and grafted rings of nups mimicking the {\it in vivo} geometry and supplement this with polymer brush modeling. Our results indicate that different regions or ``blocks'' of an individual NPC protein can have distinctly different forms of disorder and properties and that this appears to be a conserved feature. Furthermore, this block structure at the individual protein level is critical to the formation of a unique higher-order polymer brush architecture. Our results indicate that there exist transitions between distinct brush morphologies (open and closed states of the gate), which can be triggered by the presence of cargo with specific surface properties. The resulting transport mechanism, that we propose, is fundamentally different from existing models and points to a novel form of gated transport in operation within the NPC. [Preview Abstract] |
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H1.00206: Identification of low frequency intramolecular vibrational modes in crystalline adenosine via high pressure Raman spectroscopy Scott Lee, A. Anderson DNA is predicted to have an internal vibrational mode, below about 100 cm$^{-1}$, involving stretching motions of the hydrogen bonds between the basepairs. This mode is potentially important for mediating strand separation, an integral part of transcription and replication. Experiments are performed on ordered fibers and films containing many DNA molecules, while theoretical calculations are performed on single molecules. In addition to internal vibrations, solid samples also have external vibrations in which molecules within the unit cell vibrate against each other, meaning that the measured vibrational spectra will have both internal and external vibrations. Since these external vibrations are not calculated in theoretical calculations, the comparison between observed and calculated spectra is difficult. However, the restoring forces associated with the external modes are due to the long-range interactions between the neighboring molecules. Such modes are strongly affected by the application of high pressure. Internal modes are associated with much shorter ranged restoring forces, and are not affected so strongly by high pressure. Thus, high pressure experiments can determine whether the observed modes are internal or external in character. Here we report our high-pressure Raman studies of crystalline adenosine to reveal the nature of all the low-frequency vibrational modes. [Preview Abstract] |
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H1.00207: Raman spectroscopic determination of the hydrogen bond length for the water of hydration of DNA N.J. Tao, Scott Lee, Allan Rupprecht Raman spectroscopy is used to probe the nature of the hydrogen bonds which hold the water of hydration to DNA. The $\sim$ 3450 cm$^{-1}$ molecular O-H stretching mode shows that the first 6 water molecules per base pair of the primary hydration shell are very strongly bound to the DNA. The observed shift in the peak position of this mode permits a determination of the length of the hydrogen bonds for these water molecules. These hydrogen bonds appear to be about 0.3 {\AA} shorter than the hydrogen bonds in bulk water. The linewidth of this mode shows no significant changes above water contents of about 15 water molecules per base pair. This technique of using a vibrational spectroscopy to obtain structural information about the hydration shells of DNA could be used to study the hydration shells of other biomolecules. [Preview Abstract] |
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H1.00208: Stem Cell Physics. Multiple-Laser-Beam Treatment of Parkinson's Disease V. Alexander Stefan A novel method for the treatment of Parkinson's disease is proposed. Pluripotent stem cells are laser cultured, using ultrashort wavelength, (around 0.1 micron-ultraviolet radiation-with intensities of a few mW/cm$^2)$, multiple laser beams.\footnote{V. Stefan, B. I. Cohen, C. Joshi, \textit{Science}, 243, 4890, (Jan.27, 1989); Stefan et al., Bull. APS 32, No.9, 1713, (1987); Stefan APS March-2012, {\#} K1.00177; APS March-2011, {\#}S1.143; APS March-2009, {\#}K1.276.} The multiple-energy laser photons\footnote{V. Alexander Stefan, NEUROPHYSICS, STEM CELL PHYSICS, and GENOMIC PHYSICS: Beat-Wave-Driven-Free Electron Laser Beam Interactions with the Living Matter (S-U-Press, La Jolla, CA, 2012)} interact with the neuron DNA molecules to be cloned. The laser created dopaminergic substantia nigra neurons can be, (theoretically), laser transplanted, (a higher focusing precision as compared to a syringe method), into the striatum or substantia nigra regions of the brain, or both. [Preview Abstract] |
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H1.00209: Real-time autocorrelator for fluorescence correlation spectroscopy based on graphical-processor-unit architecture: method, implementation, and comparative studies Nicholas LaRacuente, Carl Grossman We developed an algorithm and software to calculate autocorrelation functions from real-time photon-counting data using the fast, parallel capabilities of graphical processor units (GPUs). Recent developments in hardware and software have allowed for general purpose computing with inexpensive GPU hardware. These devices are more suited for emulating hardware autocorrelators than traditional CPU-based software applications by emphasizing parallel throughput over sequential speed. Incoming data are binned in a standard multi-tau scheme with configurable points-per-bin size and are mapped into a GPU memory pattern to reduce time-expensive memory access. Applications include dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS) experiments. We ran the software on a 64-core graphics pci card in a 3.2 GHz Intel i5 CPU based computer running Linux. FCS measurements were made on Alexa-546 and Texas Red dyes in a standard buffer (PBS). Software correlations were compared to hardware correlator measurements on the same signals. [Preview Abstract] |
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H1.00210: Monte-Carlo Simulations of Drug Delivery on Biofilms Alper Buldum, Andrew Simpson The focus of this work is on biofilms that grow in the lungs of cystic fibrosis (CF) patients. A discrete model which describes the nutrient and biomass as discrete particles is created. Diffusion of the nutrient, consumption of the nutrient by microbial particles, and growth and decay of microbial particles are simulated using stochastic processes. Our model extends the complexity of the biofilm system by including the conversion and reversion of living bacteria into a hibernated state, known as persister bacteria. Another new contribution is the inclusion of antimicrobial in two forms: an aqueous solution and encapsulated in biodegradable nanoparticles. The bacteria population growth and spatial variation of drugs and their effectiveness are investigated in this work. [Preview Abstract] |
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H1.00211: Physical mode of bacteria and virus coevolution Pu Han, Liang Ren Niestemski, Michael Deem Single-cell hosts such as bacteria or archaea possess an adaptive, heritable immune system that protects them from viral invasion. This system, known as the CRISPR-Cas system, allows the host to recognize and incorporate short foreign DNA or RNA sequences from viruses or plasmids. The sequences form what are called ``spacers'' in the CRISPR. Spacers in the CRISPR loci provide a record of the host and predator coevolution history. We develop a physical model to study the dynamics of this coevolution due to immune pressure. Hosts and viruses reproduce, die, and evolve due to viral infection pressure, host immune pressure, and mutation. We will discuss the differing effects of point mutation and recombination on CRISPR evolution. We will also discuss the effect of different spacer deletion mechanisms. We will describe population structure of hosts and viruses, how spacer diversity depends on position within CRISPR, and match of the CRISPR spacers to the virus population. [Preview Abstract] |
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H1.00212: A Molecular Dynamics Investigation of the Physical-Chemical Properties of Calicivirus Capsid Protein Adsorption to Fomites David Peeler, Silvina Matysiak Any inanimate object with an exposed surface bears the possibility of hosting a virus and may therefore be labeled a fomite. This research hopes to distinguish which chemical-physical differences in fomite surface and virus capsid protein characteristics cause variations in virus adsorption through an alignment of in silico molecular dynamics simulations with in vitro measurements. The impact of surface chemistry on the adsorption of the human norovirus (HNV)-surrogate calicivirus capsid protein 2MS2 has been simulated for monomer and trimer structures and is reported in terms of protein-self assembled monolayer (SAM) binding free energy. The coarse-grained MARTINI forcefield was used to maximize spatial and temporal resolution while minimizing computational load. Future work will investigate the FCVF5 and SMSVS4 calicivirus trimers and will extend beyond hydrophobic and hydrophilic SAM surface chemistry to charged SAM surfaces in varying ionic concentrations. These results will be confirmed by quartz crystal microbalance experiments conducted by Dr. Wigginton at the University of Michigan. This should provide a novel method for predicting the transferability of viruses that cannot be studied in vitro such as dangerous foodborne and nosocomially-acquired viruses like HNV. [Preview Abstract] |
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H1.00213: Physics - The Difference between Life and Death: III. Great Height Saami J. Shaibani Although calculation of the maximum survivable height from which a human can fall is problematic, it is reasonable to opine that the probability of non-fatality in a descent of some 500 feet from the roof of a building is exceptionally low. When two brothers simultaneously experienced such an event, one lived and the other did not [1]. (Note: A nominally similar fall by another male also resulted in survival [2].) The general methodology for resolving such diverse outcomes is explained in other work [3,4], which provides some background for this study. Differentiation between the two subject adult males was limited by a lack of sufficient specificity in available data; however, it is still possible to consider the relevant physics principles and thereby examine the issues involved. Injury mechanisms are discussed and comparisons with other traumatic environments are made. The latter are included because their everyday nature provides a helpful illustration for learning.\\[4pt] [1] McFadden, R.D. (2007, December 8). The New York Times\\[0pt] [2] Rubinkam, M. (2008, April 25). USA Today\\[0pt] [3\&4] Bull Am Phys Soc, 48, 1348 \& 1349 (2003). [Preview Abstract] |
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H1.00214: Bone strength and athletic ability in hominids: \textit{Ardipithecus ramidus} to \textit{Homo sapiens} S.A. Lee The ability of the femur to resist bending stresses is determined by its midlength cross-sectional geometry, its length and the elastic properties of the mineral part of the bone. The animal's athletic ability, determined by a ``bone strength index,'' is limited by this femoral bending strength in relation to the loads on the femur. This analysis is applied to the fossil record for \textit{Homo sapiens, Homo neanderthalensis, Homo erectus, Homo habilis, Australopithecus afarensis} and \textit{ Ardipithecus ramidus}. Evidence that the femoral bone strength index of modern \textit{Homo sapiens} has weakened over the last 50,000 years is found. [Preview Abstract] |
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H1.00215: Modeling Light-Dependent Biofilm Morphology Chase Kernan, Jean Huang, Rebecca Christianson Bacterial aggregates on submerged substrates can produce complex biofilm morphologies that are subject to environmental and metabolic factors. We develop a reductionistic cellular automata model of these structures with the intent of guiding experimentation and explaining prior results. We focus on reproducing the columnar and ``mushroom'' phases of aerobic \emph{R. palustris} and light-sensitive anaerobic \emph{R. palustris}, respectively. This light sensitivity requires the novel inclusion of a characteristic light penetration depth in addition to surface tension and media penetration parameters. We quantitatively divide this parameter space into roughly four morphological phases---columnar, mushroom, uniform, and irregular---by examining the resultant convexity defect distribution, horizontal correlation, and coverage as a function of height. Finally, we both validate experimental evidence of these phases and suggest new parameter regimes to investigate empirically. [Preview Abstract] |
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H1.00216: Vision below threshold: why it can be beneficial to waste photons Moritz Kreysing, Kristian Franze, Mike Francke, Andreas Reichenbach, Jochen Guck Vision at low light intensities relies on photoreceptors being able to detect individual photons. As an accepted rule, the light sensitive portions of vertebrate rods and cones, namely outer segments, increase in volume the darker the animals' habitat gets in order to enhance the probability to capture incident photons. Consequently, the biggest outer segments are found in fish living in the deep sea. A peculiar exception to this rule are the eyes of some deep sea fish, as well as fish living in highly turbid rivers. In their retinas relatively short outer segments are bundled into spatially isolated groups, clearly not meant to maximize the probability of photon absorption. Based on a detailed morphological and optical study of multilayer light-collectors surrounding these segments [1], we argue that under extreme conditions in which quantum noise, i.e. the rate of spontaneous photo-pigment activation, becomes comparable to the rate of photon arrival, visual sensitivity cannot be achieved by large outer segments anymore. Instead the retinal focusing of light on very small receptors is the only way to lower the visual threshold further, or to see at near IR wavelengths, even though this means partial photon loss. References: 1. M.Kreysing et al., Science 336, no. 6089 (2012) [Preview Abstract] |
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H1.00217: Bioinspired quantum heat engines Dmitri Voronine, Konstantin Dorfman, Shaul Mukamel, Marlan Scully Quantum mechanics and thermodynamics have deep connections which govern the behavior of laser and photocell quantum heat engines (QHEs). We describe QHEs inspired by photosynthesis that operate under the natural conditions of incoherent excitation by sunlight. We investigate parameter regimes where large electric current yield enhancement and/or population oscillations are observed and identify noise-induced quantum coherence as the common origin of these effects. Quantum coherence plays a role in enhancing energy and charge transfer efficiencies and holds promise for improving the design and boosting the efficiencies of light-harvesting devices. A broad range of parameter regimes provides flexibility in designs and materials. [Preview Abstract] |
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H1.00218: PHYSICS EDUCATION |
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H1.00219: The Meaning of the Temperature Gregorio Ruiz-Chavarria While the concept of temperature is routinely used in daily life, its meaning is very confusing for the vast majority of ordinary humans. The main reason of this study is to provide a discussion about this concept in order to try to clarify its meaning. In most of the high school and college courses handled this concept saying that the temperature is a fraction of the average kinetic energy of the molecules that make up the body. Using this definition of temperature, a thermometer should then measuring the kinetic energy of the system under study, which does not. Then present a discussion about the meaning of temperature, analyzing which is the operating principle of some thermometers, leading the discussion in terms of the balance between two systems and we see that the interpretation of temperature as a fraction of the average kinetic energy, is an interpretation only at this level. [Preview Abstract] |
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H1.00220: Indiana Wesleyan University SPS Physics Outreach to Rural Middle School and High School Students Joshua Ostrander, Heath Rose, Robert Burchell, Roberto Ramos The Society of Physics Students chapter at Indiana Wesleyan University is unusual in that it has no physics major, only physics minors. Yet while just over a year old, IWU-SPS has been active in performing physics outreach to middle school and high school students, and the rural community of Grant County. ~Our year-old SPS chapter consists of majors from Chemistry, Nursing, Biology, Exercise Science, Computer Science, Psychology, Pastoral Studies, and Science Education, who share a common interest in physics and service to the community. IWU currently has a physics minor and is currently working to build a physics major program. Despite the intrinsic challenges, our multi-disciplinary group~has been successful at using physics demonstration equipment and hands-on activities and their universal appeal to raise the interest in physics in Grant County. We report our experience, challenges, and successes with physics outreach. We describe in detail our two-pronged approach: raising the level of physics appreciation among the IWU student community and among pre-college students in a rural community of Indiana. [Preview Abstract] |
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H1.00221: Investigation of Nematode Diversity using Scanning Electron Microscopy and Fluorescent Microscopy Taylor Seacor, Carina Howell Nematode worms account for the vast majority of the animals in the biosphere. They are colossally important to global public health as parasites, and to agriculture both as pests and as beneficial inhabitants of healthy soil. Amphid neurons are the anterior chemosensory neurons in nematodes, mediating critical behaviors including chemotaxis and mating. We are examining the cellular morphology and external anatomy of amphid neurons, using fluorescence microscopy and scanning electron microscopy, respectively, of a wide range of soil nematodes isolated in the wild. We use both classical systematics (e.g. diagnostic keys) and molecular markers (e.g. ribosomal RNA) to classify these wild isolates. Our ultimate aim is to build a detailed anatomical database in order to dissect genetic pathways of neuronal development and function across phylogeny and ecology. [Preview Abstract] |
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H1.00222: On-Ramp: Improving students' understanding of lock-in amplifiers Seth Devore, Chandralekha Singh, Jeremy Levy A lock-in amplifier is a powerful and versatile instrument which is used frequently in condensed matter physics research. However, many students struggle with the basics of a lock-in amplifier and they have difficulty in interpreting the data obtained with this device in diverse applications. To improve students' understanding, we are developing an ``On-Ramp'' tutorial based on physics education research which makes use of a computer simulation of a lock-in amplifier. During the development of the tutorial we interviewed several faculty members and graduate students. The tutorial is based on a field-tested approach in which students realize their difficulties after predicting the outcome of experiments that use a lock-in amplifier; students can check their predictions using simulations. The tutorial then guides students toward a coherent understanding of the basics of a lock-in amplifier. This poster will discuss the development and assessment process. [Preview Abstract] |
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H1.00223: Improving Performance through Motivation: Teaching Biology Pre-Med Students Physics Elena Gregg Several major factors which affect students' learning are assessed (curricula, different teaching approaches, assessment methods, engagement, and motivation). Direct connection between motivation, attitudes, self-confidence and achievement was established. It was demonstrated that improvement of motivation and self-confidence among students (particularly females, minorities and low achievers) is essential. Effectiveness of different instructional methods and motivational approaches was analyzed and evaluated in algebra-based Physics course for Biology pre-med undergraduate students. [Preview Abstract] |
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H1.00224: Using In-class Group Exercises to Enhance Lectures and Provide Introductory Physics Students an Opportunity to Perfect Problem Solving Skills through Interactions with Fellow Students Joseph Trout, Jared Bland In this pilot project, one hour of lecture time was replaced with one hour of in-class assignments, which groups of students collaborated on. These in-class assignments consisted of problems or projects selected for the calculus-based introductory physics students The first problem was at a level of difficulty that the majority of the students could complete with a small to moderate amount of difficulty. Each successive problem was increasingly more difficult, the last problem being having a level of difficulty that was beyond the capabilities of the majority of the students and required some instructor intervention. The students were free to choose their own groups. Students were encouraged to interact and help each other understand. The success of the in-class exercises were measured using pre-tests and post-tests. The pre-test and post-test were completed by each student independently. Statistics were also compiled on each student's attendance record and the amount of time spent reading and studying, as reported by the student. Statistics were also completed on the student responses when asked if they had sufficient time to complete the pre-test and post-test and if they would have completed the test with the correct answers if they had more time. The pre-tests and post-tests were not used in the computation of the grades of the students. [Preview Abstract] |
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H1.00225: Improving Science Teacher Preparation through the APS PhysTEC and NSF Noyce Programs Tasha Williams, Micheal E. Tyler, Andrea Van Duzor, Mel Sabella Central to the recruitment of students into science teaching at a school like CSU, is a focus on the professional nature of teaching. The purpose of this focus is twofold: it serves to change student perceptions about teaching and it prepares students to become teachers who value continued professional development and value the science education research literature. The Noyce and PhysTEC programs at CSU place the professional nature of teaching front and center by involving students in education research projects, paid internships, attendance at conferences, and participation in a new Teacher Immersion Institute and a Science Education Journal Reading Class. This poster will focus on specific components of our teacher preparation program that were developed through these two programs. In addition we will describe how these new components provide students with diverse experiences in the teaching of science to students in the urban school district. [Preview Abstract] |
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H1.00226: GENERAL |
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H1.00227: Resources for startup and growing businesses in the science and engineering sectors Joseph Sabol The American Chemical Society provides resources for members involved in forming startup and growing small businesses in the chemical and related sectors. In particular, the ACS Division of Small Chemical Businesses SCHB provides member benefits, informative programming at national and regional meetings, and networking opportunities for entrepreneurs. SCHB member benefits include listing in a directory of members' products and services, discounted expo booth rental at ACS national meetings, sponsorship to attend ACS leadership development courses, volunteer opportunities to shape and direct SCHB's operations, multiple social networking platforms, and professional networking opportunities with like-minded and similarly situated small business principals. SCHB's mission is ``To aid in the formation, development and growth of small chemical businesses.'' SCHB collaborates with other units in ACS, including local sections, the Chemical Entrepreneurship Council, the Division of Business Development \& Management, Entrepreneurial Initiative, and Career Services. SCHB helps chemists gain skills to translate research into commercially successful products; build strong, growing companies that create jobs; and collaborate with professionals outside the chemical community. [Preview Abstract] |
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H1.00228: The 2014 Gordon Research Conference: Physics Research {\&} Education: The Complex Intersection of Biology and Physics Mel Sabella, Matthew Lang The field of biological physics and the physics education of biology and medically oriented students have experienced tremendous growth in recent years. New findings, applications, and technologies in biological and medical physics are having far reaching consequences that affect and influence the science community, the education of future scientists and health-care workers, and the general population. As a result leaders in Physics Education Research have begun to focus their attention on the specific needs of students in the biological sciences, the different ways physicists and biologists view the nature of science and the interactions of scientists in these disciplines. In this poster we highlight some of these findings and pose questions for discussion. The Complex Intersection of Biology and Physics will be the topic of the next Gordon Research Conference on Physics Research and Education to be held in June 2014. The exact date and location are still to be determined. [Preview Abstract] |
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H1.00229: A Descriptive Approach to the Geometric Phase Matthew Rave, Jeff Lawson Geometric phase in a dynamical system can be visualized as the interplay between two characteristic periods of a closed orbit which go in and out of ``synch.'' We present several intuitive examples of such systems that are suitable for physics instruction. We then examine the details of a simple mechanical system on a torus to illustrate two specific approaches to determining the geometric phase: direct computation from the equations of motion, and the use of conservation laws. The elegance and simplicity of the latter approach can be explained by observing invariants under an action of the planar rotation group on the torus. We conclude by describing (in brief) how this approach extrapolates to the general method of reduction by symmetry. [Preview Abstract] |
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H1.00230: Spiral Galaxy Central Bulge Tangential Speed of Revolution Curves Laurence Taff The objective was to, for the first time in a century, scientifically analyze the ``rotation curves'' (sic) of the central bulges of scores of spiral galaxies. I commenced with a methodological, rational, geometrical, arithmetic, and statistical examination---none of them carried through before---of the radial velocity data. The requirement for such a thorough treatment is the paucity of data typically available for the central bulge: fewer than 10 observations and frequently only five. The most must be made of these. A consequence of this logical handling is the discovery of a unique model for the central bulge volume mass density resting on the positive slope, linear, rise of its tangential speed of revolution curve and hence---for the first time---a reliable mass estimate. The deduction comes from a known physics-based, mathematically valid, derivation (not assertion). It rests on the full (not partial) equations of motion plus Poisson's equation. Following that is a prediction for the gravitational potential energy and thence the gravitational force. From this comes a forecast for the tangential speed of revolution curve. It was analyzed in a fashion identical to that of the data thereby closing the circle and demonstrating internal self-consistency. This is a hallmark of a scientific method-informed approach to an experimental problem. Multiple plots of the relevant quantities and measures of goodness of fit will be shown. [Preview Abstract] |
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H1.00231: Sociological-Dysfunctionality(SD) Tyrrany-of-Arrogance((ToA) Versus (So Miscalled) "Wisdom-of-Crowds" Fascism; Jargonial-Obfuscation(JO) Egocentrism Enabling Would Be "Sciences" to be Alas Mere SEANCES!!!. John Bradshaw, Brian Martin, Edward Carl-Ludwig Siegel, Alexandria Euclid, Frederic Young, London Clay Bradshaw["Healing Shame That Binds You"]-"Brian Martin" SD ToA is via constant interminable media-hype spin-doctoring show-biz popularity promotion, witness ubiquitous talking-heads: "Kuku" sci.-guy(knows everything about everything), Green,Tyson, Alda, ,,, ad infinitum, ad nauseum!!!; worse still "scientific"-societies{\&}apos; seizing conferences/journals agendas, perverted into mere SEANCES: [Preview Abstract] |
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H1.00232: Self-OSTRICHIZED/OSTRACIZED-Criticality(sO/Oc) ``A TAD'' PRE-BAK HUYGENS-LEIBNITZ-NEWTON F $=$ ma With BEAK {\&} FEATHERS, Head BURIED in SANDPILE, TUCHIS Up in AIR: SCI-FI REwriting of CLASSIC(AL) PHYSICS HISTORY; ``BUZZWORDISM, BANDWAGONISM , SLOGANEERING for Fun, Profit, Survival, EGO(S) P.R.E. Bak-Beak, Frederic Young, Christian-Gottfried-Isaac Huygens-Leibnitz-Newtonon, David-Charles-Karl-Grover-Sheldon Koch-Rove-Norquist-Adelson, "Mutnick"-Willard-MittTheTwit-Ernie-Eddy Romney-Munster-Ryan, Edward Carl-Ludwig Siegel sO/Oc: SOC with a Beak and Feathers: first (so mis-called) ``Self-Organized-Criticality'' (SOC) [aka Burst Acoustic-Emission(BAE) from long long ago], then BNL/DOE Self-Organized (so mis-called) ``Punctuated-Equilibrium'', now/today (so mis-called) ``Self-Organized-(So Called)`Complexity' '', ... , ``tomorrow,... The World'': A Reich Is born via media-hype P. R. ``self-organization'' ``spin-doctoring'' localized -to- itinerant transition: Siegel ``BUZZWORDISM, BANDWAGONISM and SLOGANEERING for Fun [Preview Abstract] |
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H1.00233: ``Models'' CAVEAT EMPTOR!!!: ``Toy Models Too-Often Yield Toy-Results''!!!: Statistics, Polls, Politics, Economics, Elections!!!: GRAPH/Network-Physics: ``Equal-Distribution for All'' TRUMP-ED BEC ``Winner-Take-All''; ``Doctor Livingston I Presume?'' R.N.C.-Grover Preibus-Norquist, G.W.-Willard-Mitt Bush-Romney, J.P M.C Jamie Dimon, Sheldon-Charles-David-Sheldon Adelson-Koch, Paul-David Krugman-Axelrod, Edward Carl-Ludwig Siegel ``Models''? CAVEAT EMPTOR!!!: ``Toy Models Too-Often Yield Toy-Results''!!!: Goldenfeld[``The Role of Models in Physics'', in Lects.on Phase-Transitions {\&} R.-G.(92)-p.32-33!!!]: statistics(Silver\textbraceleft [NYTimes; Bensinger, ``Math-Geerks Clearly-Defeated Pundits'', LATimes, (11/9/12)])\textbraceright , polls, politics, economics, elections!!!: GRAPH/network/net/\textellipsis -PHYSICS Barabasi-Albert[RMP (02)] (r,t)-space VERSUS(???) [Where's the Inverse/ Dual/Integral-Transform???] (Benjamin)Franklin( 1795)-Fourier(1795; 1897;1822)-Laplace(1850)-Mellin (1902) Brillouin(1922)-\textellipsis (k, )-space, \textbraceleft Hubbard [The World According to Wavelets,Peters (96)-p.14!!!/p.246: refs.-F2!!!]\textbraceright ,and then (2) Albert-Barabasi[]Bose-Einstein quantum-statistics(BEQS) Bose-Einstein CONDENSATION (BEC) versus Bianconi[pvt.-comm.; arXiv:cond-mat/0204506; \textellipsis ] -Barabasi [???] Fermi-Dirac [Preview Abstract] |
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H1.00234: Undergraduate Physics Education at Radcliffe and Harvard 1895-1953 Joanna Behrman The effort to get more women to continue in physics is ongoing and many hypotheses exist as to why the gender ratio lags more in physics than in other fields. A historical investigation can offer insights to the origin of this persistent problem. Radcliffe College offered to female students an education supposedly equivalent to that offered to male students at Harvard. I track physics classes at Radcliffe and Harvard from Radcliffe's charter year to the year the physics classes fully merged. Data on instructors, enrollment, and later employment offers insights to trends in physics education over time and how the genders were affected differently even when multiple variables are isolated across the two single-gender groups. [Preview Abstract] |
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H1.00235: New research in Superconductivity Mona Khorrami Superconductors are materials that have no resistance to electricity's flow; they are one of the last great frontiers of scientific discovery. The theories that explain superconductor behavior seem to be constantly under review. In 1911 superconductivity was first observed in mercury by Dutch physicist Heike Kamerlingh Onnes When he cooled it to the temperature of liquid helium, 4 degrees Kelvin (-452F, -269C), its resistance suddenly disappeared. It was necessary for Onnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity. In 1933 German researchers Walther Meissner and Robert Ochsenfeld discovered that a superconducting material will repel a magnetic field. A magnet moving by a conductor induces currents in the conductor, but, in a superconductor the induced currents exactly mirror the field that would have otherwise penetrated the superconducting material - causing the magnet to be repulsed. This phenomenon is known as strong diamagnetism and is today often referred to as the ``Meissner effect'' (an eponym). Later on the theory developed by American physicists John Bardeen, Leon Cooper, and John Schrieffer together with extensions and refinements of the theory, which followed in the years after 1957, succeeded in explaining in considerable detail the properties of superconductors. [Preview Abstract] |
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H1.00236: ATOMIC, MOLECULAR AND OPTICAL (AMO) PHYSICS |
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H1.00237: Time-reversal-invariant Hofstadter-Hubbard model with ultracold fermions Peter P. Orth, Daniel Cocks, Stephan Rachel, Michael Buchhold, Karyn Le Hur, Walter Hofstetter We consider the time-reversal-invariant Hofstadter-Hubbard model which can be realized in cold-atom experiments [1]. In these experiments, an additional staggered potential and an artificial Rashba-type spin-orbit coupling are available. Without interactions, the system exhibits various phases such as topological and normal insulator, metal as well as semi-metal phases with two or even more Dirac cones. Using a combination of real-space dynamical mean-field theory and analytical techniques, we discuss the effect of on-site interactions and determine the corresponding phase diagram. In particular, we investigate the semi-metal to antiferromagnetic insulator transition and the stability of different topological insulator phases in the presence of strong interactions. We compute spectral functions which allow us to study the edge states of the strongly correlated topological phases. [1] Daniel Cocks, Peter P. Orth, Stephan Rachel, Michael Buchhold, Karyn Le Hur, and Walter Hofstetter, arXiv:1204.4171 (2012) (accepted for Phys. Rev. Lett.) [Preview Abstract] |
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H1.00238: Progress towards generating spin-squeezed sodium Bose-Einstein condensates Jie Jiang, Lichao Zhao, Micah Webb, Yingmei Liu A coherent spin-state is an unentangled state with all spins aligned in the same direction, while the spin degrees of freedom of atoms become entangled in spin-squeezed states. Spin-squeezing has attracted much attention for its potential to improve the sensitivity of spin-resonance measurements. We present the design and construction of a novel apparatus to generate spin-squeezing with sodium Bose-Einstein condensates (BECs) in optical lattices. Spin-squeezing requires an interaction among atoms to suppress spin noise. Different types of interactions in BECs are exploited in our system: atom-light interaction via a quantum non-demolition measurement, self interactions and elastic collisions controlled by spin-dependent potentials, and spin-exchange collisions. We will also discuss a possibility of using sequences of universal pulses to control loss of entanglement due to decoherence from environmental effects. [Preview Abstract] |
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H1.00239: ABSTRACT WITHDRAWN |
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H1.00240: Route to Observable Fulde-Ferrell-Larkin-Ovchinnikov Phases in 3D Spin-Orbit Coupled Degenerate Fermi Gases Zhen Zheng, Ming Gong, Xubo Zou, Chuanwei Zhang, Guangcan Guo The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, a superconducting state with non-zero total momentum Cooper pairs in a large magnetic field, was first predicted about 50 years ago. Recently, the possibility of observing FFLO states using ultracold degenerate Fermi gases has sparked tremendous interest. However, unambiguous experimental evidence for FFLO states is still elusive because of the stringent parameter requirement in experiments. Here, we show that a giant parameter regime for FFLO states can be obtained in 3D degenerate Fermi gases in the presence of spin-orbit coupling and an in-plane Zeeman field, two ingredients that were already developed for cold atoms in recent experiments. The predicted FFLO state is stable against quantum fluctuations due to the 3D geometry, and can be observed with experimentally already achieved temperature, thus opens a new fascinating avenue for exploring FFLO physics in degenerate Fermi gases. [Preview Abstract] |
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H1.00241: ABSTRACT WITHDRAWN |
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H1.00242: Quantum mechanical toolbox to study the dirty crossover in cold atomic gases B. Tanatar, Ayan Khan, Saurabh Basu We consider an ultracold atomic gas exhibiting the BCS-BEC crossover as the short-range interaction strength (characterized by the scattering length) is increased. In particular, we investigate the dirty crossover (for a disoredered gas) by means of the fidelity susceptibility (FS). Fidelity susceptibility is related to the overlap between the ground states of different phases. The disorder is incorporated in the mean-field formalism through Gaussian fluctuations. We observe a rise of asymmetric nature in the FS with increasing disorder which might be an indication for an impending quantum phase transition (QPT). We analyze our results for the FS and the density of states using the statistical tools such as skewness and kurtosis. [Preview Abstract] |
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H1.00243: Quench dynamics of interacting impurity boson in boson sea Huijie Guan, Deepak Iyer, Natan Andrei We use the Yudson Representation to study the quench dynamics of a system consisting of a one dimensional gas of interacting bosons and a mobile impurity boson. We are able to get an exact solution for finite coupling constant and finite time for two particles. To solve for more particles, long time approximation is made to simplify the calculation. We calculate the time evolution of impurity density and noise correlation and compare the results with experimental data. [Preview Abstract] |
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H1.00244: The physics of SU(4) alkaline-earth-atom-based Kondo lattice model at the Toulouse point Solomon F. Duki, Hong Ling The study of ultracold alkaline-earth atoms has gained significant attention due largely to recent efforts to employ ultracold alkaline-earth atoms as a unique platform to explore quantum computing and many-body physics. For alkaline-earth atoms, there is an almost perfect decoupling of the nuclear spin from the electronic angular momentum in both the ground and the metastable states. This along with the existence of relatively high nuclear spin degrees of freedom makes the cold alkaline-earth atoms an excellent candidate that one can employ to study Kondo effects with higher SU(N) spin degrees of freedom. In this work, we focus on a mixture of two-component fermionic alkaline-earth atoms loaded in external optical lattice potentials and treat it as an cold atom implementation of SU(4) Kondo lattice model. We apply bosonization and canonical transformation to obtain an exactly solvable point (the so-called Toulouse point). We study the physics of the system at the Toulouse point by calculating various correlation functions in the parameter regimes that are experimentally accessible to cold atom experiments. This work is supported by the US National Science Foundation and the US Army Research Office. [Preview Abstract] |
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H1.00245: MONTE-CARLO Simulations ``QUANTUM''-``NOISE'' POWER-SPECTRUM 0$=$(F$=$ma)$=$0 Uniform-Velocity Pareto/Red/Beethoven-Law VS 0$\ne $(F$=$ma)$\ne $0 Uniform-Acceleration/Deceleration/Bremsstrahlung Archimedes-(Euclid-Descartes)-Zipf/Pink/Flicker/Bach-Law UNIVERSALITY INEVITABILITY!!! T.T.L Louis, Edward Carl-Ludwig Siegel, Frederic Young, Adolph Smith Dynamics vs usual by-rote kinematics treatment/lack of understanding, via Siegel[AIP Shock-Physics Confs. Chicago(2011); Seattle(2013)] simple classical-mechanics/dynamics simple-insights]-Panofsky-Phillips[E{\&}M (1960s)],of Monte Carlo[Kaplan et.al.[PRL 107, 201601 (11)]:'''Noise', Sign-Problems {\&} Statistics'']-simulations' \textbraceleft Hamersley-Handscombe, Monte Carlo Methods, Methuen(64-75)\textbraceright ``noises'' power-spectra\textbraceleft SEMINAL Montroll [(60s-80s)\textbraceright -Boccara[ ``Modeling'' ``Complex''-Sys.(02)-ch.-8/p.-311]-West et.al.[Physics of Fractal-Operators, Springer(00)]-Shlesinger-Lindenberg-Handel-van Vliet-Jonscher-Ngai-\textellipsis -Siegel[Schrodinger Symp., Imperial-College (1987);Copenhagen-Onterp. 50-Yrs. After Como-Lect.,Symp.Fdns.Mod.Phys., Joensu(87)]\textbraceright , in the light of Siegel[MRS Fall-Mtgs. Boston: Symp. Fractals(89)-5-papers!!!; Symp. Scaling(90); Symp.Transport in Geometric-Constraints(90)] power-law decay algebraicity vs. white/flat/functionless [analogous to Fokker-Planck-eqn. two-terms Dichotomy, relatively: static/non-diffusive vs diffusive!!!] but dimensionality-dependence: first-odd-integer ${\rm Z}$ vs. first-even-integer ${\rm Z}$: 2-D bulk-region -area - dominated constant [Preview Abstract] |
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H1.00246: Bound states of fermions with short-range interactions in the presence of spin-orbit coupling and Zeeman fields Doga Murat Kurkcuoglu, C. A. R. Sa de Melo We discuss the emergence of two-particle bound states of spin-$1/2$ fermions in the presence of Zeeman fields for arbitrary mixtures of Dresselhaus and Rashba spin-orbit couplings, under the assumption that interactions are short-ranged and occur only in the s-wave channel. In this case, we calculate explicitly binding energies and effective masses and analyze their dependence on spin-orbit couplings, Zeeman fields and interactions. Finally, we note that such exact two-body results serve as important benchmarks for the construction of many-particle wavefunctions that recover the few-particle regime in the low density limit. [Preview Abstract] |
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H1.00247: Fractional topological phase in one-dimensional flat bands with nontrivial topology Huaiming Guo We show the existence of the fractional topological phase (FTP) in a one-dimensional interacting fermion model using exact diagonalization, in which the noninteracting part has flat bands with nontrivial topology. In the presence of the nearest-neighboring interaction $V_1$, the FTP at filling factor $\nu=1/3$ appears. It is characterized by the threefold degeneracy and the quantized total Berry phase of the ground states. The FTP is destroyed by a next-nearest-neighboring interaction $V_2$, and the phase diagrams in the $(V_1,V_2)$ plane are determined. We also present a physical picture of the phase and discuss its existence in the nearly flat band. Within the picture, we argue that the FTP at other filling factors can be generated by introducing proper interactions. The present study contributes to a systematic understanding of the FTPs and can be realized in cold-atom experiments. [Preview Abstract] |
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H1.00248: Manipulating Topological Edge Spins in One-Dimensional Optical Lattice Xiong-Jun Liu, Zheng-Xin Liu, Meng Cheng We propose to observe and manipulate topological edge spins in 1D optical lattice based on currently available experimental platforms. Coupling the atomic spin states to a laser-induced periodic Zeeman field, the lattice system can be driven into a symmetry protected topological (SPT) phase, which belongs to the chiral unitary (AIII) class protected by particle number conservation and chiral symmetries. In free-fermion case the SPT phase is classified by a $Z$ invariant which reduces to $Z_4$ with interactions. The zero edge modes of the SPT phase are spin-polarized, with left and right edge spins polarized to opposite directions and forming a topological spin-qubit (TSQ). We demonstrate a novel scheme to manipulate the zero modes and realize single spin control in optical lattice. The manipulation of TSQs has potential applications to quantum computation. [Preview Abstract] |
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H1.00249: Interference Signatures of Abelian and Non-Abelian Aharonov-Bohm effect on Neutral Atoms in Optical Lattices Ming-Xia Huo, Nie Wei, David A.W. Hutchinson, Leong Chuan Kwek We propose a scheme to generate an effective Abelian U(1) or non-Abelian SU(2) gauge field for cold neutral atoms in a ring- or square-shaped optical lattice by using Laguerre-Gauss lasers. The synthetic field produced is strongly localized, which allows us to study the Aharonov-Bohm effect on the neutral atoms. By preparing a coherent state of atoms initially and allowing them to evolve along two different paths enclosing the generated magnetic field, we obtain interference signatures of the Aharonov-Bohm effect with distinctly different patterns in the detection area for systems exposed to a zero, an Abelian U(1) or a non-Abelian SU(2) gauge field. [Preview Abstract] |
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H1.00250: Quantum Control of the Spin-Orbit Interaction Using the Autler-Townes Effect Ergin Ahmed, Sonia Ingram, Teodora Kirova, Omer Salihoglu, John Huennekens, Jianbing Qi, Yafei Quan, Marjatta Lyyra The interaction between the spin and the orbital angular momenta (spin-orbit interaction) of the electron in an atom or a molecule often can be neglected or treated as a perturbation. However, when relativistic effects are not negligible, the spin-orbit interaction must be taken into account. It can cause mixing of electronic states of different spin multiplicity, with the degree of mixing dependent on the strength of the spin-orbit interaction as well as the energy separation between the interacting states. It is also well known that, in the presence of strong electromagnetic fields, the energy levels in atoms or molecules experience shifts in their positions due to the Autler-Townes (AT) effect. Thus control of the spin-orbit interaction can be realized by using resonant or nonresonant laser fields as an external control mechanism. We have demonstrated [1] experimentally such control of the spin-orbit interaction using resonant cw optical field. We show that the enhancement of the spin-orbit interaction between a pair of weakly interacting singlet-triplet rovibrational levels, 1$^{\mathrm{3}}\Sigma _{\mathrm{g}}^{\mathrm{-}}$(v$=$1, $N=$21, $f)-G^1\Pi _{\mathrm{g}}$(v$=$12, $J=$21, $f)$, depends on the Rabi frequency (laser power) of the control laser. The increase in the spin-orbit interaction due to the control field is observed as a change in the spin character of the individual components of the perturbed pair. \\[0pt] [1] E. H. Ahmed, S. Ingram, T. V. Kirova, O. Salihoglu, J. Huennekens, and A. M. Lyyra, PRL, \textbf{107}, 163601 (2011). [Preview Abstract] |
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H1.00251: ABSTRACT WITHDRAWN |
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H1.00252: Lithium as a refrigerant for polar molecules A. Kaushik, S.K. Tokunaga, R.J. Hendricks, E.A. Hinds, M.R. Tarbutt Gases of ultracold polar molecules offer exciting new possibilities in many areas, including precision measurements [1], simulations of many-body quantum systems [2], and quantum information processing [3]. We aim to cool polar molecules by sympathetic cooling with ultracold atoms inside a suitable trap [4]. This poster presents our work on the production and transportation of a dense ultracold cloud of lithium for use as a refrigerant in sympathetic cooling. Up to $10^{10}$ lithium atoms are loaded from a Zeeman slower into a magneto-optical trap. Using a moving magnetic trap the atoms are transported to a separate chamber where they will later be co-trapped with molecules. We present the design of our setup and our recent results on transport. We also explore the possibility of electrically polarizing the lithium so that dipole-dipole interactions become important in the gas.\\[4pt] [1] J. J. Hudson, D. M. Kara, I. J. Smallman, B. E. Sauer, M. R. Tarbutt and E. A. Hinds, Nature 473, 493 (2011).\\[0pt] [2] A. Micheli, G. K. Brennen, and P. Zoller, Nature Physics 2, 341 (2006).\\[0pt] [3] D. DeMille, Phys. Rev. Lett. 88, 067901 (2002).\\[0pt] [4] S. K. Tokunaga, W. Skomorowski, P. S. \.{Z}uchowski, R. Moszynski, J. M. Hutson, E. A. Hinds and M. R. Tarbutt, Eur. Phys. J. D 65, 141 (2011). [Preview Abstract] |
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H1.00253: K-Shell Dielectronic Recombination for Si$^{5+}$ and Ar$^{9+}$ Ions Shahin Abdel-Naby, Fayez Shahin Dielectroinic recombination (DR) is the dominant electron-ion recombination process for most of the ions found in low density photoionized plasmas and low-to-medium density electron collisionally ionized plasmas. Accurate DR rate coefficients are needed for plasma modeling. We report on K-shell DR cross sections and rate coefficients of Si$^{5+}$ and Ar$^{9+}$ ions. The DR cross sections are calculated in the angular momentum average scheme. The dominant contributions to the DR cross sections and rate coefficients are obtained from the $1s2s^22p^6np$ resonant states. The total DR rates increase as the effective charge of the ions increases and the peaks of these rates are shifted toward higher incident electron energies as the degree of ionization increases. [Preview Abstract] |
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H1.00254: A spin-flip Zeeman slower controlled by a fast feedback circuit Lichao Zhao, Jie Jiang, Micah Webb, Yingmei Liu We present an effective setup for a spin-flip Zeeman slower controlled by a fast feedback circuit. Our experimental data demonstrate an efficient method to optimize the Zeeman slower for trapping more alkali atoms in a magneto-optical trap. In addition, we confirm that our feedback circuit can be applied to rapidly and simply control various magnetic fields used for creating atomic Bose-Einstein condensates and for studies related to magnetic Feshbach resonances. [Preview Abstract] |
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H1.00255: Laser cooling molecules Valentina Zhelyazkova, Aki Matsushima Laser cooling is a simple technique routinely used to cool atoms down to temperatures in the mK range. As the presence of a closed transition is essential for the cooling to work, laser cooling is usually not tractable in molecules due to their complex structure. Molecules can rotate and vibrate and usually only scatter a few photons before they end up in a dark state. In particular, the molecule often changes a vibrational state in the absorption-emission cycle. Recently, a whole class of polar molecules (e.g. CaF, SrF, BaF and TiO) has been shown to possess a highly diagonal Franck-Condon matrix, which makes them viable candidates to be laser cooled. We demonstrate a scheme for laser cooling of a supersonic beam of CaF and SrF radicals. The Franck-Condon factor for the relevant transition makes it possible for the molecules to scatter 10$^{4}$ photons with only one or two vibrational repump lasers. We show evidence of longitudinal slowing and cooling in CaF and beam brightening and cooling in SrF. [Preview Abstract] |
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H1.00256: Spectroscopic Characterization of Thulium doped Potassium Lead Chloride for Potential Applications in Optical Cooling Ei Brown, Herbert Brown, Uwe Hommerich, Althea Bluiett, Sudhir Trivedi Rare-earth doped solids have experienced increased attention for possible applications in anti-Stokes fluorescence cooling. Solid-state optical refrigeration offer several advantages over current bulky mechanical coolers including compact, lightweight, and vibration free. Most efforts have focused on optical cooling in Yb$^{3+}$ doped solids and cooling down to $\sim$155 K has been demonstrated. In this work, the optical properties of Tm$^{3+}$ doped KPC were evaluated as a potential solid-state material for laser cooling applications. Following 1907 nm excitation, Tm:KPC exhibited infrared emission with a center wavelength of 1806 nm arising from the $^{3}$F$_{4}\to $ $^{3}$H$_{6}$ transition of Tm$^{3+}$ ions. Under 1907nm pumping conditions, it was estimated that a quantum emission efficiency of at least 95{\%} is required to achieve a net cooling effect in Tm:KPC. Based on temperature dependent decay time studies the emission quantum efficiency of Tm:KPC was estimated to be only $\sim$75{\%}. Employing the energy-gap law, non-radiative decay through multi-phonon relaxation is predicted to be negligibly small in Tm:KPC. Concentration quenching effects and/or energy transfer processes to other defects seems most likely to be responsible for the low quantum efficiency. [Preview Abstract] |
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H1.00257: Infrared Emission and Upconversion Studies of Er$^{3+}$ Doped in the Low Phonon-Energy Hosts KPb$_{2}$Cl$_{5}$ and KPb$_{2}$Br$_5$ Althea Bluiett, Ei Ei Brown, Craig Hanley, Uwe Hommerich, Sudhir Trivedi There continues to be interests in Er$^{3+}$ doped materials that can generate efficient emission in the 1.5-1.6 um range for eye-safe laser applications and optical communications. Directly pumping the $^{4}$I$_{13/2}$ band of Er$^{3+}$ has been extensively studied in many hosts, such as YAG, however, it is well understood that the excitation of Er$^{3+}$ through this channel automatically generates unwanted upconversion emission, which depletes $^{4}$I$_{13/2}$ level of Er$^{3+}$ and moreover produces unwanted heating of the crystal. In this study, cw and pulsed laser excitation of the $^{4}$I$_{13/2}$ band of Er$^{3+}$ will be explored as a function of host material (KPb$_{2}$Cl$_{5}$ and KPb$_{2}$Br$_{5})$ rare-earth ion concentration, and temperature in the search for the optimum combination of variables to minimize upconversion and concurrently generate more efficient 1.5 $\mu$m emission from Er$^{3+}$. [Preview Abstract] |
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H1.00258: Progress Towards a Quantum Memory with Telecom-Wavelength Conversion Daniel Stack, Qudsia Quraishi, Ian Grissom, Ronald Meyers, Keith Deacon, Arnold Tunick, Patricia Lee Fiber-based transmission of quantum information over long distances may be achieved using quantum memory elements and quantum repeater protocols.\footnote{Duan et al., Nature {\bf 414}, 413-418 (2001)} However, atom-based quantum memories typically involve interactions with light fields outside the telecom window where attenuation in optical fibers is at a minimum. We report on progress towards a quantum memory based on the generation of 780 nm spontaneously emitted single photons by an off-resonant Raman beam interacting with a cold $^{87}$Rb ensemble. The single photons are then frequency converted into telecom photons (via four-wave mixing in a cold Rb sample), sent through a 13 km fiber, and then converted back to 780 nm photons (via sum frequency generation in a PPLN crystal). Finally, the atomic state is read out via the interaction of another off-resonant Raman beam with the quantum memory. With such a system it will be possible to realize a long-lived quantum memory that will allow transmission of quantum information over many kilometers with high fidelity, essential for a scalable, long-distance quantum network. [Preview Abstract] |
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H1.00259: Mimicking interacting relativistic theories with stationary pulses of light Dimitris G. Angelakis, Ming-Xia Huo, Darrick Chang, Leong Chuan Kwek, Vladimir Korepin Photonic quantum simulations of one dimensional many-body systems have attracted renewed interest lately with works on photon crystallization and Luttinger liquids. In this work we show that the quantum Thirring model for interacting fermions in (1$+$1) dimension can be realized using stationary polaritons in hollow waveguides filled with atoms. By controlling optical parameters such as one-photon detunings and external laser intensities, the massless and the massive Thirring models are realizable. Coherently mapping the polaritons into propagating photons allows for the direct probing of the relevant correlation functions and scaling behaviours characteristic of the underlying theories in question. [Preview Abstract] |
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H1.00260: Reduction of Cavity loss and Spontaneous Emission in Cavity QED Wayne Manrakhan An investigation of the entanglement dynamics of two atoms with a quantized cavity field in the presence of dissipation is undertaken. A study of the effects of spontaneous emission and cavity loss in our scheme shows how to reduce the effects of each independently in a bimodal cavity. Our computer numerical simulation results indicate that by choosing proper parameters one can reduce the effects of spontaneous emission and cavity loss. [Preview Abstract] |
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H1.00261: Non-Equilibrium Quantum Impurity Physics with Hybrid Light-Matter Systems Karyn Le Hur, Marco Schiro Recent advances in quantum electronics allowed to engineer hybrid nano devices made by coupling on chip a quantum dot to a microwave resonator as well as to electron reservoirs maintained at different bias voltages. These systems realize novel platforms to explore non equilibrium quantum impurity physics with light and matter. Focusing on a simple model of a biased quantum dot coupled to a photon mode we elucidate the signatures of the electronic correlations in the phase of the transmitted microwave signal. In addition we illustrate the effect of the electronic degrees of freedom on the photon field, giving rise to anharmonicity, damping and dissipation, and discuss how to control these effects by means of gate and bias voltages. [Preview Abstract] |
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H1.00262: A Luttinger liquid of photons and spin-charge separation in hollow-core waveguides Dimitris G. Angelakis, Ming-Xia Huo, Elica Kyoseva, Leong Chuan Kwek In this work we show that light-matter excitations (polaritons) generated inside a hollow one-dimensional fiber filled with two types of atoms, can exhibit Luttinger liquid behavior. We explain how to prepare and drive this quantum-optical system to a strongly interacting regime, described by a bosonic two-component Lieb Lininger model. Utilizing the connection between strongly interacting bosonic and fermionic systems, we show how spin-charge separation could be observed by probing the correlations in the polaritons. This is performed by first mapping the polaritons to propagating photon pulses and then measuring the effective photonic spin and charge densities and velocities by analyzing the correlations in the emitted photon spectrum. The necessary regime of interactions is achievable with current quantum optical technology. [Preview Abstract] |
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H1.00263: Efficient Non-Resonant Absorption in Thin Cylindrical Targets: Experimental Evidence Andrey Akhmeteli, Nikolay Kokodiy, Boris Safronov, Valeriy Balkashin, Ivan Priz, Alexander Tarasevitch A theoretical possibility of non-resonant, fast, and efficient (up to 40 percent) heating of very thin conducting cylindrical targets by broad electromagnetic beams was predicted in [Akhmeteli, arXiv:physics/0405091 and 0611169] based on rigorous solution of the diffraction problem. The diameter of the cylinder can be orders of magnitude smaller than the wavelength (for the transverse geometry) or the beam waist (for the longitudinal geometry) of the electromagnetic radiation. This can be used for numerous applications, such as pumping of active media of short-wavelength lasers, e.g., through efficient heating of nanotubes with laser radiation. Experimental confirmation of the above results is presented [Akhmeteli, Kokodiy, Safronov, Balkashin, Priz, Tarasevitch, arXiv:1109.1626 and 1208.0066]. Significant (up to 6\%) absorption of microwave power focused on a thin fiber (the diameter is three orders of magnitude less than the wavelength) by an ellipsoidal reflector is demonstrated experimentally. For the longitudinal geometry, preliminary experiments provide a qualitative confirmation of significant absorption of the power of a wide CO2 laser beam propagating along a thin wire (the diameter of the wire can be orders of magnitude less than the beam waist width). [Preview Abstract] |
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H1.00264: ABSTRACT WITHDRAWN |
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H1.00265: Spectroscopic methods for calculation of electron density and temperature in laser generated Hydrogen plasma Mohammadreza Rezaee, Christian Parigger Laser induced plasma spectroscopy has been around for several decades and has generated a lot of interest.Remote analyzing capability makes it favorable in applications where it is difficult to have an experimental probe physically there to do the measurements. One of these applications is in controlled fusion devices like Tokamaks in which Hydrogen and its isotopes are used as fuel. Having accurate knowledge of the plasma density and temperature is a key factor in plasma stability in confined plasma machines. Hydrogen lines are powerful tools in remote plasma diagnostics, and we can infer the plasma density and temperature from their broadening and shift. In a high power nanosecond-pulsed laser generated plasma, which is a transient phase and has a high electron density, Stark broadening is the dominant broadening mechanism and by measuring the FWHM of the broadened Hydrogen Balmer lines we calculated the electron density and temperature. We calculated the electron density by utilizing different available approaches and compared the results. There is difference between the electron density obtained from Stark broadened H$_{\alpha}$ at initial time after shot in comparison to that obtained from the H$_{\beta}$ and H$_{\gamma}$, which is related to the strong self-absorption. [Preview Abstract] |
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H1.00266: Colliding with the Speed of Light, Using Low-Energy Photon-Photon Collision Study the Nature of Matter and the universe Meggie Zhang Our research discovered logical inconsistence in physics and mathematics. Through reviewing the entire history of physics and mathematics we gained new understanding about our earlier assumptions, which led to a new interpretation of the wave function and quantum physics. We found the existing experimental data supported a 4-dimensional fractal structure of matter and the universe, we found the formation of wave, matter and the universe through the same process started from a single particle, and the process itself is a fractal that contributed to the diversity of matter. We also found physical evidence supporting a not-continuous fractal space structure. The new understanding also led to a reinterpretation of nuclear collision theories, based on this we succeeded a room-temperature low-energy photon-photon collision (RT-LE-PPC), this method allowed us to observe a topological disconnected fractal structure and succeeded a simulation of the formation of matter and the universe which provided evidences for the nature of light and matter and led to a quantum structure interpretation, and we found the formation of the universe started from two particles. However this work cannot be understood with current physics theories due to the logical problems in the current physics theories. [Preview Abstract] |
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H1.00267: MEST- avoid next extinction by a space-time effect Dayong Cao Sun's companion-dark hole seasonal took its dark comets belt and much dark matter to impact near our earth. And some of them probability hit on our earth. So this model kept and triggered periodic mass extinctions on our earth every 25 to 27 million years. After every impaction, many dark comets with very special tilted orbits were arrested and lurked in solar system. When the dark hole-Tyche goes near the solar system again, they will impact near planets. The Tyche, dark comet and Oort Cloud have their space-time center. Because the space-time are frequency and amplitude square of wave. Because the wave (space-time) can make a field, and gas has more wave and fluctuate. So they like dense gas ball and a dark dense field. They can absorb the space-time and wave. So they are ``dark'' like the dark matter which can break genetic codes of our lives by a dark space-time effect. So the upcoming next impaction will cause current ``biodiversity loss.'' The dark matter can change dead plants and animals to coal, oil and natural gas which are used as energy, but break our living environment. According to our experiments, which consciousness can use thought waves remotely to change their systemic model between Electron Clouds and electron holes of P-N Junction and can change output voltages of solar cells by a life information technology and a space-time effect, we hope to find a new method to the orbit of the Tyche to avoid next extinction. (see Dayong Cao, BAPS.2011.APR.K1.17 and BAPS.2012.MAR.P33.14) [Preview Abstract] |
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H1.00268: Pinning quantum phase transition of photons in a hollow-core fiber Ming-Xia Huo, Dimitris G. Angelakis The Bose-Hubbard and sine-Gordon models have been extremely successful in describing a range of quantum many body effects and especially quantum phase transitions. We show that a pinning transition for photons could be observed in a hollow-core one-dimensional fiber loaded with a cold atomic gas. Utilizing the strong light confinement in the fiber, a range of different strongly correlated polaritonic and photonic states, corresponding to both strong and weak interactions can be created and probed. We analyze the relevant phase diagram corresponding to the realizable Bose-Hubbard (weak) and sine-Gordon (strong) interacting regimes and conclude by describing the measurement process. The latter consists of mapping the stationary excitations to propagating light pulses whose correlations can be efficiently probed once they exit the fiber using available optical technologies. [Preview Abstract] |
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H1.00269: Information Theoretic Study of the Confined Harmonic Oscillator in Position, Momentum and Phase-Space Humberto Laguna, Robin Sagar The confined quantum harmonic oscillator (CHO) is an intermediate model which lies between the particle-in-a-box (PIAB), where the free particle is confined, and the quantum harmonic oscillator (HO) where the particle is not confined but is under the influence of a harmonic potential. Position and momentum space densities, and phase-space Wigner functions, are obtained for this system and analyzed using tools from information theory. Shannon entropies are used to gain insights into the localization of the particle in position, momentum and phase-space. The statistical correlation between the position and momentum of the particle is examined using the Wigner function and its mutual information. The analysis is performed as a function of the quantum number and of the box length, and the calculated quantities are compared to those of the PIAB and HO models. Our interests lie in determining similarities or differences among the different models and if there are regimes where the behavior of the CHO model more closely resembles either that of the PIAB or HO model. [Preview Abstract] |
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H1.00270: Bimodal Hong-Ou-Mandel Interferometry Deepika Sundarraman, Thomas Gilliss, Cody Leary We investigate two-photon Hong-Ou-Mandel interference in several interferometric systems, in which each of the two interfering input photons exist in arbitrary linear superpositions of the first-order Hermite-Gaussian modes $HG_{10}$ and $HG_{01}$. We find that if both input photons are in balanced superpositions of the $HG_{10}$ and $HG_{01}$ modes, the resulting two-photon interference can be engineered to transform these diagonal Hermite-Gaussian inputs into output modes of the Laguerre Gaussian type, which are entangled with respect to both output path and transverse spatial mode. We show that such two-photon interference effects can occur even if the input photons are prepared with \emph{distinguishable} transverse spatial states. [Preview Abstract] |
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H1.00271: Combinatorial Approach to Studying Metal Enhanced Fluorescence from Quantum Dots Nguyet Le, Timothy Corrigan, Michael Norton, David Neff Fluorescence is extensively used in biochemistry for determining the concentration or purity of molecules in a biological environment. In metal-enhanced fluorescence (MEF), the fluorescence molecules separated from a metal surface by several nanometers can be enhanced. The fluorescent enhancement is dependent on the size and spacing of the nanoparticles, as has been shown previously for a number of fluorophore molecules. Fluorescence from quantum dots is of particular interest because the quantum dots do not lose fluorescence ability when exposed to light and they have higher intensity of fluorescence. The purpose of this study is to determine the effect of size and spacing on fluorescence intensity when coupling gold nano-particles with quantum dots. We employ a combinatorial approach, depositing gold particles ranging in diameter from 30 nm to 130 nm with varied spacings onto the substrate, followed by a protein spacer-layer and quantum dots. The fluorescence signal from the metal enhanced quantum dots were determined by confocal microscopy. [Preview Abstract] |
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H1.00272: QUANTUM INFORMATION, CONCEPTS AND COMPUTATION |
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H1.00273: Electron Spin Relaxation due to Charge Noise Peihao Huang, Xuedong Hu It is widely accepted that for a single electron confined in a quantum dot, spin relaxation is dominated by spin-orbit interaction in combination with phonon emission. The effect of charge noise is usually considered to be small in the case of a single electron spin qubit, although it is never actually evaluated in a quantum dot. Here we examine the single-electron spin decoherence due to charge noise, mediated by the spin-orbit interaction. We find that at the lowest order, it is a relaxation channel, with $T_2=2T_1$, similar to the case of spin-orbit interaction and phonon scattering. The relaxation rate is linearly proportional to the applied magnetic field, in contrast to the 5th power magnetic field dependence in the phonon case. Our calculated spin relaxation time ranges from ms in GaAs to seconds in Si for 1 T field, making this relaxation channel at low field comparable or even more important than that due to phonon emission. The relaxation rate is inversely proportional to the 4th power of the dot confinement energy, so that increasing the confinement energy is an efficient way to suppress this relaxation channel. [Preview Abstract] |
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H1.00274: Characterization of rf-SSET in both in-plane and perpendicular magnetic fields Chunyang Tang, Zhen Yang, Mingyun Yuan, A.J. Rimberg, D.E. Savage, M.A. Eriksson Previous success in coupling an aluminum radio-frequency superconducting single electron transistor (rf-SSET) to quantum dots (QDs) has demonstrated use of the rf-SSET as an ultra-sensitive and fast charge sensor [1]. Since a magnetic field is usually necessary for quantum dot qubit manipulation, it is important to understand the effect of magnetic fields, either in-plane or perpendicular, on the performance of any charge sensor near the QDs. Here we report characterization of rf-SSETs in both in-plane and perpendicular magnetic fields. The rf-SSET works well in an in-plane fields up to 1 Tesla at a temperature of 30 mK. At 0.3K, in a perpendicular field generated by a stripline located 700 nm away, the rf-SSET charge sensitivity even shows improvement for up to 2.1 mA current through the stripline (corresponding roughly to a field of 6 Gauss). [1]M. Yuan et al, Appl. Phys. Lett. 101, 142103 (2012) [Preview Abstract] |
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H1.00275: DIGIT-PHYSICS: Digits Are Bosons Are Quanta Because (On Average) Quanta and Bosons Are and Always Were Digits!!!;Contra Wigner, ``On the Unreasonable Effectiveness of \textbf{\textit{Physics in}} Mathematics!''; Do Physics-NECESSARY-Averages Equal or VS. DIGITS-Log-LawS(!!!) Averages??? Hermon Chernoff, Edward Carl-Ludwig Siegel, Marvin Antonoff, Adolph Smith, Frederic Young Zurek(1981-\textellipsis ): ``Not Its But Bits''; Newcomb(1881)!!!: ``Not Bits But Its''!!! DIGITS?: ``For a Very Long Time Giving Us All The FINGER''!!!: ``DIGIT-\textbf{\textit{PHYSICS}}'': Contra Wigner, ``On the Unreasonable Effectiveness of \textbf{\textit{Physics in}} Mathematics!''; A Surprise in Theoretical/Experimental Physics and/or Ostensibly Pure-Mathematics: \textless PHYSICS: Q.-M./S.M.\textgreater $=$???$=$\textless DIGITS\textgreater -LAW(S) . DIGITS' ostensibly ``pure-mathematics'' \underline {Ne}wcomb[Am.J.Math.4,39(1\underline {\textbf{\textit{8}}}81)]-\underline {W}eyl[Math.Ann.,77,313 (\underline {\textbf{\textit{16}}})]-\underline {Be}nford[J.Am.Phil Soc,78,115(\underline {\textbf{\textit{38}}})] empirical inter-digit (\textit{on-average}) (DIGITS are \underline {\textbf{\textit{not}}} random-variables!!!) \textit{statistical}-correlations ``(\underline {NeWBe})-Logarithmic-Law'' $( \equiv <\omega >)(d)=\log_{10} \left( {+1+\frac{1}{d}} \right);d(\in Z)\in [0!,9];0\le ( \equiv \omega )(\notin Z)\le 1$ Hill [Proc. AMS 123, 887( 95)] vs, Jech[PSU/Brown!-(95)] root-cause ultimate-origin proof: scale-invariance $=$ base-invariance $=$ units-invariance proof)[N.Y.T. (8/4/'98); Am. Sci. (7-8/`98); New Sci. (7/10/'99)] sequential \textbf{\textit{INVERSION }} to \underline {\textbf{\textit{only}}} \textbf{\textit{Bose-Einstein}} \textit{quantum-statistics} (``\textit{Spin(}\underline {\textit{E}}\textit{)less-BoZos}''(``SoB'''s)) $\frac{1}{10^{ }-1}=d( )$, \textit{and} Taylor/power-series-$<\left( {( \equiv <\omega >)><<1} \right)$- \textbf{\textit{EXPANSION }}to $d\left( {( \equiv <\omega >} \right)=\frac{1}{10^{( \equiv \omega )}-1}\cong \frac{1}{[+1+( \equiv <\omega >)+...]-1}\cong \frac{1}{( \equiv <\omega >)}\approx \frac{"1"}{{\begin{array}{l} ( \equiv <\omega >) \\ ^{1.000...} \\ \end{array}}}$ \textbf{\textit{Hyperbolicity}} ``noise'' [Preview Abstract] |
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H1.00276: Counterfactual Assessment of Decoherence in Quantum Systems Onofrio Russo, Liang Jiang Quantum Zeno effect occurs when the system is observed for unusually short observation times, $t$, where the probability of the transition between different quantum states is known to be proportional to $t^{2}$. This results in a decrease in the probability of transitions between states and the consequent decrease in decoherence. We consider the conditions in which these observations are made counterfactual to assess whether this results in a significant change in decoherence. [Preview Abstract] |
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H1.00277: Universal set of quantum gates for electron defect spin qubits in diamond and silicon carbide Dmitry Solenov, Sophia E. Economou, Thomas L. Reinecke Electron spin qubits based on nitrogen-vacancy centers in diamond and defects in silicon carbide have become a rapidly developing direction in quantum information and computing due to their potential in room temperature quantum computing. While single-qubit manipulations have been proposed and experimentally realized, the design of a realistic deterministic two-qubit entangling gate currently remains an important challenge. We propose fast optically controlled design where a two-qubit gate between spatially separate qubits is mediated by a photonic microcavity mode. The proposed gate scheme is compatible with available single-qubit operations. In addition, our design provides an opportunity to perform individual single qubit operations without the need to spatially resolve the qubits. As a result, for the first time a universal set of deterministic gates is proposed that can be implemented with current experimental capabilities in these systems. [Preview Abstract] |
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H1.00278: Fabrication and characterization of transmon qubits and rectangular waveguide resonators for circuit quantum electrodynamics Dong-Gwang Ha, Jung Hwan Park, So-Yeon Jun, Woon Song, Yonuk Chong We present our design, fabrication and characterization of superconducting transmon qubits and resonators for circuit quantum electrodynamics (QED). We have made coplanar waveguide resonators and rectangular waveguide resonators. The characteristics of the resonators are well controlled by the design parameters, with the fundamental frequencies in the range of 1 to 8 GHz and the quality factors in the range of 10$^{2}$ to 10$^{6}$, respectively. We measured the resonator characteristics as a function of temperature. The excitation power dependence of the resonator characteristics was also investigated. For transmon qubits, we fabricated 100 nm-scale Al/Al$_{2}$O$_{\mathrm{x}}$/Al tunnel junctions with e-beam lithography and double angle evaporation. The junctions were characterized at low temperature down to 10 mK. Furthermore, quantum state measurement and manipulation in circuit QED structure will be discussed. [Preview Abstract] |
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H1.00279: Microwave Spectroscopy of a Josephson Junction Rhombi Chain Matthew Bell, Joshua Paramanandam, Lev Ioffe, Michael Gershenson It has been proposed that Josephson Junction (JJ) Rhombi chains can be used as a superconducting qubit symmetry protected from local noises [1]. We have studied the microwave response of a two-rhombi chain coupled to a lumped-element microwave resonator. The resonance frequency of this circuit was measured as a function of the phase $\varphi$ across the JJ Rhombi chain. The effective inductance of the JJ Rhombi as a function of $\varphi$ oscillates with a period $\Delta\varphi$=$\pi$ when the magnetic flux $\Phi$ in the Rhombi approaches half a flux quantum. In this regime, microwave spectroscopy of the first excited state of the JJ Rhombi was performed as a function of $\varphi$ and the gate-controlled charge on the central island of the two-Rhombi chain. The results of the microwave spectroscopy are in agreement with numerical simulations. We also discuss the results of time domain measurements of the Rhombi chain which establishes a baseline for the future coherence time measurements for longer (and, thus, more protected) chains. \\[4pt] [1] S. Gladchenko et al., ``Superconducting Nanocircuits for Topologically Protected Qubits,'' Nature Physics 5, 48 (2009). [Preview Abstract] |
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H1.00280: New Method for Determining the Quality Factor and Resonance Frequency of Superconducting Micro-resonators from Sonnet Simulation David Wisbey, Alexander Reinisch, Wesley Gardner, Jacob Brewster, Jiansong Gao Lithographed superconducting microwave resonators (micro-resonators) are useful in a number of important applications including microwave kinetic inductance detectors (MKIDs), as a memory element in quantum information, and readout of qubits and nanomechanical resonators. One of the major tasks in designing these devices is to find the resonance frequency (f$_{\mathrm{r}})$ and quality factor (Q) for these microwave circuits using EM simulation software such as Sonnet. The traditional method iteratively sweeps and zooms in frequency to fit simulated S$_{\mathrm{21}}$ data, which is often time consuming. In this work, we show a new---and much faster---method for determining f$_{\mathrm{r\thinspace }}$and Q by adding an internal (virtual) port in the Sonnet model and examining the input impedance through the added port. Accurate f$_{\mathrm{r}}$ and Q values can be retrieved from a single simulation with a wide frequency sweep. This is a robust method that works on many types of resonance circuits and eclipses the speed with which Q is traditionally extracted by eliminating the need for multiple frequency sweeps using Sonnet. [Preview Abstract] |
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H1.00281: Nonblinking green emission from single H3 color centers in nanodiamonds Jui-Hung Hsu, Wei-De Su, Kai-Lin Yang, Yan-Kai Tzeng, Huan-Cheng Chang We present a work that investigates the emission properties of single color centers in natural diamond nanoparticles for potential use as single photon sources and photostable biomarkers. Two emitters, H3 and H4, were identified by their sharp zero-phonon lines at 503 nm and 496 nm, respectively, in the photoluminescence spectra. Using a modified Hanbury Brown and Twiss setup, we observed complete photon antibunching for the H3 center. No fluorescence blinking was detected for a single H3 emitter on the ms timescale, indicating weak coupling between the electronic transition 1A1$\leftrightarrow $1B1 and adjacent metastable states of this nitrogen-vacancy-nitrogen point defect. [Preview Abstract] |
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H1.00282: Counting statistics and entanglement in a disordered free fermion system with a voltage bias Joseph Burg, Gregory Levine The Full Counting Statistics is studied for a disordered one-dimensional system of non-interacting fermions with and without a voltage bias. For two unbiased $L$ site lattices connected at time $t=0$, the charge variance increases as the natural logarithm of $t$, following the universal expression $\langle \delta N^2\rangle \approx \frac{1}{\pi^2}\log{t}$. Since the static charge variance for a length $l$ region is given by $\langle \delta N^2\rangle \approx \frac{1}{\pi^2}\log{l}$, this result reflects the conformal invariance and dynamical exponent $z=1$ of the disorder-free lattice. With disorder and strongly localized fermions, we have compared our results to a model with a dynamical exponent $z \ne 1$, and also a model for entanglement entropy based upon dynamical scaling at the Infinite Disorder Fixed Point (IDFP). The latter scaling, which predicts $\langle \delta N^2\rangle \propto \log\log{t}$, appears to better describe the charge variance of disordered 1-d fermions. When a bias voltage is introduced, the behavior changes dramatically and the charge and variance become proportional to $(\log{t})^{1/\psi}$ and $\log{t}$, respectively. The exponent $\psi$ may be related to the critical exponent characterizing spatial/energy fluctuations at the IDFP. [Preview Abstract] |
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H1.00283: New indicators of quantum phase transitions in several exactly solvable critical systems Ferdi Altintas, Resul Eryigit Quantum phase transitions (QPT) are the abrupt changes of the ground state of quantum systems as a consequence of a continous change of a tuning parameter (an external field or an anisotropy parameter). They are solely because of quantum fluctuations and occur at absolute zero temperature. The quantumness measures, such as entanglement and quantum discord (QD), are shown to be promising indicators of QPTs. In this presentation, we will introduce new indicators, such as Bell nonlocality as revealed by the viloation of CHSH inequality and measurement induced disturbance (MID), for characterizing quantum phase transitions in several exactly solvable critical systems, discuss their usefulness in capturing QPTs and compare the performance of these measures with that of the well known QPT-detectors. We have shown that although entanglement, QD and MID can partially indicate the QPTS (mostly model dependent), CHSH-Bell inequality can detect all QPTs of the considered models even when the relevant ground state is uncorrelated. [Preview Abstract] |
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H1.00284: Reduction of loss in quantum entanglement by temperature increase Julio Cesar Gonzalez Henao, Jose Antonio Roversi In this study we investigate the effect of coupling between a system of two qubits initially prepared in an entangled state and a nonlinear thermal bath. Under these conditions we can find an analytical solution for the system that allows us analyze the effects of temperature. We can also demonstrate that the increases of the thermal reservoir temperature produces a reduction of losses in the entanglement of the two-qubit system. [Preview Abstract] |
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H1.00285: FIRST Quantum-(19\underline {\textbf{\textit{80}}})-Computing DISCOVERY in Siegel-Rosen-Feynman-\textellipsis A.-I. Neural-Networks: Artificial(ANN)/Biological(BNN) and Siegel FIRST Semantic-Web and Siegel FIRST ``Page''-``Brin'' ``PageRank'' PRE-Google Search-Engines!!! Charles Rosen, Edward Carl-Ludwig Siegel, Richard Feynman, Irwin Wunderman, Adolph Smith, Vesco Marinov, Jacob Goldman, Sergey Brine, Larry Poge, Erich Schmidt, Frederic Young, William-Steven Goates-Bulmer, Thomas-Valerie-Genot Lewis-Tsurakov-Altshuler Belew[Finding Out About, Cambridge(2000)] and separately full-decade pre-Page/Brin/Google FIRST Siegel-Rosen(Machine-Intelligence/Atherton)-Feynman-Smith-Marinov(Guzik Enterprises/Exxon-Enterprises/A.-I./Santa Clara)-Wunderman(H.-P.) [IBM Conf. on Computers and Mathematics, Stanford(1986); APS Mtgs.(1980s): Palo Alto/Santa Clara/San Francisco/\textellipsis (1980s); MRS Spring-Mtgs.(1980s): Palo Alto/San Jose/San Francisco/\textellipsis (1980-1992) FIRST quantum-computing via Bose-Einstein quantum-statistics(BEQS) Bose-Einstein CONDENSATION (BEC) in artificial-intelligence(A-I) artificial neural-networks(A-N-N) and biological neural-networks(B-N-N) and Siegel[J. Noncrystalline-Solids 40, 453(19\underline {\textbf{\textit{80}}}); Symp. on Fractals\textellipsis , MRS Fall-Mtg., Boston(19\underline {\textbf{\textit{89}}})-5-papers; Symp. on Scaling\textellipsis , (19\underline {\textbf{\textit{90}}}); Symp. on Transport in Geometric-Constraint (19\underline {\textbf{\textit{90}}})] [Preview Abstract] |
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H1.00286: Fault-tolerent Holonomic Quantum Computation Based on Stabilizer Codes Yi-Cong Zheng, Todd Brun We present an all-geometric scheme for fault-tolerant holonomic quantum computation with stabilizer codes, based on non-Abelian adiabatic holonomies. This scheme implements a universal set of quantum gates by adiabatic deformation of the stabilizer eigenspaces (both the code space and error spaces) through the same closed path in the parameter space, so that each eigenspace obtains the same holonomy. This approach makes fault-tolerant error correction possible. We give examples to show how this scheme works for different stabilizer codes. [Preview Abstract] |
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H1.00287: Simulation of stochastic quantum systems using polynomial chaos expansions Kevin Young, Matthew Grace We present an approach to the simulation of quantum systems driven by classical stochastic processes that is based on the polynomial chaos expansion, a well-known technique in the field of uncertainty quantification. The polynomial chaos expansion represents the system density matrix as a series of orthogonal polynomials in the principle components of the stochastic process and yields a sparsely coupled hierarchy of linear differential equations. We provide practical heuristics for truncating this expansion based on results from time-dependent perturbation theory and demonstrate, via an experimentally relevant one-qubit numerical example, that our technique can be significantly more computationally efficient than Monte Carlo simulation. [Preview Abstract] |
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H1.00288: Quantum Knowledge Diagrams Douglas Snyder The principles behind quantum knowledge can be extracted from the specific empirical implementations so that pictorial elements can be developed representing fundamental concepts of quantum knowledge. With these elements, one can represent quantum knowledge principles underlying specific empirical implementations more simply and in a way that allows for a more direct comparison of quantum knowledge principles underlying various specific empirical implementations. These representations are quantum knowledge diagrams. Basic diagram elements include: 1) a which-way process; 2) a non-which-way process (showing interference); 3) availability, or lack thereof, of the which-way or non which-way information to the environment; 4) particles; 5) entanglement, or lack thereof, of 2 or more particles; 6) delayed choice. [Preview Abstract] |
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H1.00289: SEPHIROT: SCENARIO for CREATION AUTOMATICALLY from DIGITS AVERAGED-PROBABILITY Newcomb-Benford Log-Law: Inflation, BosonS, a Maxwell-Boltzmann Big-Bang Fireball, FermionS, HDE, HDM, CMB; UTTER-SIMPLICITY PURPOSELY SANS ANYthing!!!: It's a Jack-in-the-Box Univers: A Consciousness? EMET/TRUTH!!! Edward Carl-Ludwig Siegel Siegel[http://fqxi.org/community/forum/topic/1553]: TEN-DIGITS[0,\textellipsis ,9]; PROBABILITY AVERAGE LOG-Law SCALE-INVARIANCE; Utter-Simplicity: ``Complexity'' (Versus ``Complicatedness''); Zipf-law/ Hyperbolicity/ Inevitability (Archimedes), vs, Pareto-law, SCENARIO AUTOMATICALLY CREATES a UNIVERSE: inflation, a big-bang, bosons(E) $\to $Mellin-(c\textasciicircum 2)-tranform$\to $fermions(m), hidden-dark-energy(HDE), hidden-dark-matter(HDM), cosmic-microwave-background(CMB), supersymmetry(SUSY) PURPOSELY SANS ANY: theories, models, mechanisms, processes, parameters, assumptions,\textellipsis WHATSOEVER: It's a'' Jack-in-the-Box'' Universe!!! ONLY VIA: Bose-\textbraceleft Euler[(1732)] sum$=$product over-reals R-Riemann[Monats. Akad.,(1859)] sum$=$product over-complexs)-Bernoulli-Kummer\textbraceright -Newcomb[Am. J. Math. 4(1), 39(1881) THE discovery of the QUANTUM!!!]-\textbraceleft Planck(1901)]-Einstein(1905)]-Sommerfeld\textbraceright -Poincare[Calcul des Probabilit\'{e}s, 313 (1912)]-Weyl[Goett. Nach.(1914); Math. Ann. 77, 313(1916)]-(Bose(1924)-Einstein(1925)]-VS. [Preview Abstract] |
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H1.00290: Dynamic Localization of Particle Moving in Solid Film Gennadiy Filippov Calculation of the density matrix (DM) for a projectile during the passage through a solid film have shown progressive diminishing of the projectile's coherence length. For to find a more detail information about the projectile we perform a famous von Newmann's decomposition of DM on ``pure'' states and find an ambiguity of this approach. The unambiguous decomposition can be obtained if we introduce an additional coherence criterion: each term of the decomposition should conserve the shape of function of coherence. We use the next arguments: i) the function of coherence could be measured; ii) the parts of a wave field found in relation of mutual coherence belong to one particle and couldn't be separated from the particle; iii) the parts of a wave field which don’t find in relation of mutual coherence are belong to different particles and couldn't be associated with one particle. With the help of this approach one can find that during the penetration in a film the projectile undergo a significant spatial localization. The localized quasi-stationary state of projectile could conserve the information about the past interaction with environment. [Preview Abstract] |
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H1.00291: How to slow down light and where relativity theory fails Meggie Zhang Research found logical errors in mathematics and in physics. After discovered wave-particle duality made an assumption I reinterpreted quantum mechanic and I was able to find new information from existing publications and concluded that photon is not a fundamental particle which has a structure. These work has been presented at several APS meetings and EuNPC2012. During my research I also arrived at the exact same conclusion using Newton's theory of space-time, then found the assumptions that relativity theory made failed logical test and violated basic mathematical logic. And Minkowski space violated Newton's law of motion, Lorenz 4-dimensional transformation was mathematically incomplete. After modifying existing physics theories I designed an experiment to demonstrate where light can be slow down or stop for structural study. Such method were also turn into a continuous room temperature fusion method. However the discoveries involves large amount of complex logical analysis. Physicists are generally not philosophers, therefore to make the discovery fully understood by most physicists is very challenging. [Preview Abstract] |
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H1.00292: Classical Trajectories from Coherent Quantum Oscillations Alan M. Kadin In the conventional Copenhagen interpretation of quantum mechanics, classical behavior arises from microscopic coherent quantum systems only in the presence of decoherence on the macroscopic scale. On the contrary, we derive classical Hamiltonian trajectories for a confined quantum wave directly from coherent phase evolution on the microscopic scale, without decoherence or wavefunction collapse (see also [1]). This suggests that the basis for classical macroscopic physics, including relativity, lies in the microscopic behavior of coherently oscillating quantum fields. An outline of such a theory will be presented, which resolves longstanding paradoxes involving wave-particle duality, quantum entanglement, and the quantum-to-classical transition.\\[4pt] [1] A.M. Kadin, ``Waves, Particles, and Quantized Transitions: A New Realistic Model of the Microworld,'' http://arxiv.org/abs/1107.5794 (2011). [Preview Abstract] |
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H1.00293: The Physical Origin of the Feynman Path Integral Armin Nikkhah Shirazi The Feynman path integral is an essential part of our mathematical description of fundamental nature at small scales. However, what it seems to say about the world is very much at odds with our classical intuitions, and exactly why nature requires us to describe her in this way is currently unknown. We will describe here a possibility according to which the path integral may be the spacetime manifestation of objects existing in a lower-dimensional analog of spacetime until they give rise to the emergence of spacetime objects under a process that is currently labeled a ``Quantum Measurement.'' This idea is based on a mathematical distinction which at present does not appear to be widely appreciated [Preview Abstract] |
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H1.00294: Superconducting Qubit Readout Using Capture-Disperse-Release of Microwave Field Eric Mlinar We analyze a measurement scheme for superconducting qubits via controlled capture, dispersion, and release of a microwave field. The Purcell effect is circumvented by using a tunable coupler to decouple the microwave resonator from the transmission line during dispersive interaction with the qubit. We show that fast and high-fidelity qubit readout can be achieved for nonlinear dispersive qubit-resonator interaction and for sufficiently adiabatic tuning of the qubit frequency. The Jaynes-Cummings nonlinearity results in self-developing quadrature squeezing of the resonator field below the standard quantum limit, leading to a significant decrease in measurement error. [Preview Abstract] |
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H1.00295: Majorana-Fermions, Their-Own Antiparticles, Following Non-Abelian Anyon/Semion Quantum-Statistics : Solid-State MEETS Particle Physics Neutrinos: Spin-Orbit--Coupled Superconductors and/or Superfluids to Neutrinos; Insulator-Heisenberg-Antiferromagnet MnF2 Majorana-Siegel-Birgenau-Keimer - Effect E.-L. Majorana-Fermi-Segre, Marvin-Albert-Abdus Antonoff-Overhauser-Salam, Edward Carl-Ludwig Siegel Majorana-fermions, being their own antiparticles, following non-Abelian anyon/semion quantum-statistics: in Zhang et.al.-\textellipsis -Detwiler et.al.-\textellipsis ``Worlds-in-Collision'': solid-state/condensed-matter -- physics spin-orbit -- coupled topological-excitations in superconductors and/or superfluids -to- particle-physics neutrinos: ``When `Worlds' Collide'', analysis via Siegel[Schrodinger Centenary Symp., Imperial College , London (1987); in The Copenhagen-Interpretation Fifty-Years After the Como-Lecture, Symp. Fdns. Mod.-Phys., Joensu(1987); Symp. on Fractals, MRS Fall-Mtg., Boston(1989)-5-papers!!!] ``complex quantum-statistics in fractal-dimensions'', which explains hidden-dark-matter(HDM) IN Siegel ``Sephirot'' scenario for The Creation, uses Takagi[Prog.Theo.Phys. Suppl.88,1(86)]-Ooguri[PR D33,357(85)] - Picard-Lefschetz-Arnol'd-Vassil'ev[``Principia Read After 300 Years'', Not.AMS(1989); quantum-theory caveats comment-letters(1990); Applied Picard-Lefschetz Theory, AMS(2006)] -- theorem quantum-statistics , which via Euler- formula becomes which via de Moivre- -formula further becomes which on unit-circle is only real for only , i.e, for , versus complex with imaginary-damping denominator for , i.e, for , such that Fermi-Dirac quantum-statistics for [Preview Abstract] |
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H1.00296: FLUIDS |
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H1.00297: Electron Shock Waves with Current behind the Shock Front Mostafa Hemmati, W.C. Childs, H. Morris, P. Pinkston Electrical breakdown of a gas in a strong electric field is carried out by a wave with a strong discontinuity at the wave front, and traveling with speed comparable to speed of light. For theoretical investigation of electrical breakdown of a gas, we apply a one-dimensional, steady state, constant velocity, three component fluid model, and assume the electrons to be the main element in propagation of the wave. Our set of electron fluid-dynamical equations consists of the equations of conservation of mass, momentum, and energy plus the Poisson's equation. For breakdown waves with a significant current behind the shock front, in addition to the set of electron fluid dynamical equations, the shock condition on electron temperature need to be modified as well. Considering existence of current behind the shock front, we have derived the shock condition on electron temperature, and for a set of experimentally measured current values, we have been able to integrated the set of electron fluid dynamical equations through the dynamical transition region of the wave. Our results meet the expected conditions at the trailing edge of the wave. [Preview Abstract] |
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H1.00298: POST-DEADLINE ABSTRACTS |
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H1.00299: The dynamic and geometric phase transition in the cellular network of pancreatic islet Xujing Wang The pancreatic islet is a micro-organ that contains several thousands of endocrine cells, majority of which being the insulin releasing $\beta $-cells. $\beta $-cells are excitable cells, and are coupled to each other through gap junctional channels. Here, using percolation theory, we investigate the role of network structure in determining the dynamics of the $\beta $-cell network. We show that the $\beta $-cell synchronization depends on network connectivity. More specifically, as the site occupancy is reducing, initially the $\beta $-cell synchronization is barely affected, until it reaches around a critical value, where the synchronization exhibit a sudden rapid decline, followed by an slow exponential tail. This critical value coincides with the critical site open probability for percolation transition. The dependence over bond strength is similar, exhibiting critical-behavior like dependence around a certain value of bond strength. These results suggest that the $\beta $-cell network undergoes a dynamic phase transition when the network is percolated. We further apply the findings to study diabetes. During the development of diabetes, the $\beta $-cell network connectivity decreases. Site occupancy reduces from the reducing $\beta $-cell mass, and the bond strength is increasingly impaired from $\beta $-cell stress and chronic hyperglycemia. We demonstrate that the network dynamics around the percolation transition explain the disease dynamics around onset, including a long time mystery in diabetes, the honeymoon phenomenon. [Preview Abstract] |
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H1.00300: Numerical Modeling of Fluorescence Emission Energy Dispersion in Luminescent Solar Concentrator Lanfang Li, Xing Sheng, John Rogers, Ralph Nuzzo We present a numerical modeling method and the corresponding experimental results, to address fluorescence emission dispersion for applications such as luminescent solar concentrator and light emitting diode color correction. Previously established modeling methods utilized a statistic-thermodynamic theory (Kenard-Stepnov etc.) that required a thorough understanding of the free energy landscape of the fluorophores. Some more recent work used an empirical approximation of the measured emission energy dispersion profile without considering anti-Stokes shifting during absorption and emission. In this work we present a technique for modeling fluorescence absorption and emission that utilizes the experimentally measured spectrum and approximates the observable Frank-Condon vibronic states as a continuum and takes into account thermodynamic energy relaxation by allowing thermal fluctuations. This new approximation method relaxes the requirement for knowledge of the fluorophore system and reduces demand on computing resources while still capturing the essence of physical process. We present simulation results of the energy distribution of emitted photons and compare them with experimental results with good agreement in terms of peak red-shift and intensity attenuation in a luminescent solar concentrator. [Preview Abstract] |
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H1.00301: Micro Solar Cells with Concentration and Light Trapping Optics Lanfang Li, Eric Breuckner, Christopher Corcoran, Yuan Yao, Lu Xu, Ralph Nuzzo Compared with conventional bulk plate semiconductor solar cells, micro solar cells provide opportunity for novel design geometry and provide test bed for light trapping at the device level as well as module level. Surface recombination, however, will have to be addressed properly as the much increased surface area due to the reduced dimension is more prominent in these devices than conventional solar cells. In this poster, we present experimental demonstration of silicon micro solar cells with concentration and light trapping optics. Silicon micro solar cell with optimized surface passivation and doping profile that exhibit high efficiency is demonstrated. Effective incorporation of high quantum yield fluorescent centers in the polymer matrix into which micro solar cell was encapsulated was investigated for luminescent solar concentration application. Micro-cell on a semi-transparent, nanopatterned reflector formed by soft-imprint lithography was investigated for near field effect related solar conversion performance enhancement. [Preview Abstract] |
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H1.00302: Kagome-like Lattice Distortion in the Pyrochlore Material Hg$_2$Ru$_2$O$_7$ Joost van Duijn, Roc\'Io Ruiz-Bustos, Aziz Daoud-Aladine Hg$_2$Ru$_2$O$_7$ is one of the few pyrochlore materials known containing Ru$^{5+}$. It undergoes a first order metal to Mott insulator transition (MIT) at T= 107 K, below which the susceptibility is significantly reduced and appears to be nearly T independent. While initially it has been suggested that below 107 K the Ru S=3/2 moments are quenched into an antiferromagnetic spin singlet ground-state, similar as to what is observed in Tl$_2$Ru$_2$O$_7$, recent muon and polarized neutron diffraction experiments reveal the onset of long-range magnetic ordering below the MIT. In order to shed light on the magnetic interactions that give rise to the observed long-range ordering we have performed high resolution powder neutron diffraction experiments to determine the low temperature structure of Hg$_2$Ru$_2$O$_7$. Below the MIT the symmetry is lowered from cubic to monoclinic and the Ru-Ru bonds, which are equal in the pyrochlore phase, become split into short, medium and long bonds. As a result the exchange interactions between the Ru atoms become more two dimensional. The short and medium bonds form layers, which are separated by the long bonds, that run parallel to the monoclinic $ab$ plane. The low temperature structure can best be described as a stacking of Kagome-like layers. [Preview Abstract] |
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H1.00303: Non-equilibrium dynamics of isolated trapped ion chain Zhexuan Gong, Luming Duan We have studied the dynamics of an isolated trapped ion chain under a non-equilibrium initial state in both motional and internal degrees of freedom. For motional state, we find that the dynamics of temperature distribution is qualitatively different between axial and transverse direction, due to distinctive sound wave propagation. For internal state, we show that by engineering the effective Hamiltonian through laser field, we can get a variety of spin wave dynamics based on the range of effective spin-spin interaction. We also show that these interesting non-equilibrium dynamics can be readily tested with current ion-trap technology. [Preview Abstract] |
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H1.00304: Direct Measurement of the Pressure Dependence of the Glass Transition Temperature: A Comparison of Methods William Oliver III, Timothy Ransom, James Cooper III Two methods for the direct measurement of the pressure dependence of the glass-transition temperature T$_{\mathrm{g}}$ are presented and compared. These methods involve the use of the diamond anvil cell (DAC), and hence, enable the ability to measure T$_{\mathrm{g}}$(P) to record high pressures of several GPa. Such studies are increasingly relevant as new methods have pushed other high-pressure experimental investigations of glass-forming systems into the same pressure regime. Both methods use careful ruby fluorescence measurements in the DAC as temperature is increased from the glass (T\textless T$_{\mathrm{g}})$ to the viscous liquid (T\textgreater T$_{\mathrm{g}})$. Method 1 observes the disappearance of pressure gradients as the viscous liquid region is entered, whereas method 2 involves observation of slope changes in the P-T curve during temperature ramps. Such slope changes are associated with the significant change in the volume expansion coefficient between the highly viscous, metastable, supercooled liquid state and the solid glassy state. In most cases, the two methods yield good agreement in the T$_{\mathrm{g}}$(P) curve. Data will be presented for more than one glass-forming system, including the intermediate strength glass-forming system glycerol and the fragile glass former salol. [Preview Abstract] |
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H1.00305: Plasma assisted selenization for the preparation of CuInGaSe absorbers Zhi Huang, P.F. Luo, Z. Cevher, Y.H. Ren Cu(In,Ga)(S,Se)2 (CIGS) compound has attracted much attention most recently because of their application in high efficient photovoltaic devices. In order to obtain a decent CIGS photovoltaic device, it is very critical to optimize the metallic precursor layers and choose a suitable selenization technique. We demonstrate a plasma assisted selenium cracking method for preparing CIGS semiconductor films using elemental selenium vapor. The two stage selenization process includes the modification of the ionization state of Se species by radio frequency plasma and the deposition of a selenium cap layer above CuInGa metallic precursors. A CIGS absorber layer with improved homogeneity and crystallization is realized after a post annealing process. The result is explained by the enhancement of reaction kinetics between the reduced Se phase and metallic precursor layers. [Preview Abstract] |
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H1.00306: Transfer of Chirality from Molecule to Phase in Self-assembled Chiral Block Copolymers Rong-Ming Ho Here, we report the mechanisms of chiral transfer at various length scales in the self-assembly of enantiomeric chiral block copolymers (BCPs*). We show the evolution of homochirality from molecular chirality into phase chirality in the self-assembly of the BCPs*. The chirality of molecule in the BCP* is identified from circular dichroism (CD) spectra while the handedness of the helical conformation in the BCP* is determined from split-type Cotton effect in vibrational circular dichroism spectra. Microphase separation of the BCP* is exploited to form a helical (H*) phase, and the handedness of helical nanostructure in the BCP* is directly visualized from transmission electron microscopy tomography. As examined by CD and fluorescence experiments, significant induced CD signals and bathochromic shift of achiral perylene moiety as a chemical junction of the BCPs* can be found while the concentration of the BCPs* in toluene solution is higher than critical micelle concentration, suggesting a twisting and shifting mechanism initiating from microphase-separated interface of the BCPs* leading to the formation of the H* phase from self-assembly. The operation of the self-assembly of the BCP* may provide insights into morphological evolution from the molecular level via homochiral evolution, and give the appealing applications such as chiral metamaterials. [Preview Abstract] |
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H1.00307: Effect of Temperature on Nanophase-segregation and Transport in Polysulfone-Based Anion Exchange Membrane Fuel Cell: Molecular Dynamics Simulation Approach Kwan Ho Ko, Kyung Won Han, Ji Il Choi, Ying Chang, Chulsung Bae, Seung Soon Jang The effect of temperature on hydrated polysulfone-based anion exchange membrane is studied using molecular dynamics. Various temperature conditions such as 313K, 353 K and 393K with two different water contents (10 wt {\%} and 20 wt {\%}) are simulated. From the viewpoint of structure-property relationship, we scrutinize the change in the nanophase-segregated structure of membrane and transport of anionic charge carrier (hydroxide) as a function of temperature. Since it is well known that the anion transport is less than the proton transport, we attempt to pursue a fundamental understanding of the difference between anion transport and proton transport. For this purpose, we simulate the polysulfone-based proton exchange membrane that has the same molecular structure and molecular weight. By analyzing the pair-correlation of charge carriers, we observe the correlation among hydroxides is much stronger than that among hydroniums. The extent of nanophase-segregation is also analyzed using structure factor profile. [Preview Abstract] |
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H1.00308: On The Geometric Nature of ``Singlet Fission'' in Certain Crystalline Conjugated Polymers Noah Rahman ~In recent years, the coherent fission of low-lying singlet electronic excitations in conjugated polymers has attracted interest as a possible way to exceed the Shockley-Queisser limit in organic photovoltaics. Femtosecond spectroscopic and fluorescence measurements of such singlets and the resulting triplets in crystalline anthracene, tetracene and naphthalene reveal curious phenomena associated with certain vibrational modes, such as ultrafast propagation on a timescale inconsistent with conventional intersystem crossing, long-lived electronic coherence, and triplet magnetic anisotropy whose structure is consistent across all three materials. This conflicts with NRG and quantum chemical simulations, which posit isotropic triplets. I explain this by a dynamical Rashba spin-orbit interaction that decays as R$^{-6}$. This arises from a geometric SU(2) gauge potential generated by a nuclear-motion-induced parametric near-degeneracy of the molecular electronic states. The anisotropy is shown to follow from the work of Affleck and Oshikawa on spin one-half Heisenberg chains. Possible directions for future work are discussed, especially with regard to adiabatic pumping and topological insulators. [Preview Abstract] |
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H1.00309: Multiple Phase Transition of the Fulde-Ferrel-Larkin-Ovchinnikov States in two-band Superconductors Masahiro Takahashi, Takeshi Mizushima, Kazushige Machida The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states in the two-band superconductors are studied. FFLO states will be realized in superconductors with high external field or in ultracold atom gases with imbalanced population of the atoms for paring. In this study we focused on superconductors. We take into account the contribution of the 2nd band which has not been considered from the microscopic point of view. We extended the Bogoliubov-de Gennes equation for the multiple-band system and solved numerically with various parameters. As a result, the multiple phase transition from the BCS state to FFLO state, and in addition, between multiple FFLO states. The transition between states are 1st order, where usual BCS to FFLO phase transition is 2nd order. [Preview Abstract] |
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H1.00310: Spin Polarization Induced by Rashba Field and Electromagnetic Wave Katsuhisa Taguchi, Gen Tatara We theoretically show that the spin polarization is induced by the electric field of the electromagnetic wave in the presence of the Rashba spin-orbit interaction in metals. The spin is derived from the correlation function between the spin and electron's density and between the spin and electron's current. The correlation function is calculated by using the thermal Green's function, which includes non-perturbative Rashba spin-orbit interactions. The result shows that the spin is generated by electric field and Rashba fields. [Preview Abstract] |
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H1.00311: Google in a Quantum Network Giuseppe Paparo |
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H1.00312: Observation of fishtail effects in BaFe$_{2-x}$Ni$_{x}$As single crystals Ying Zi Zhang, Hi Qian Luo Isothermal magnetization loops were performed to characterize magnetic properties of three small chips of Bi$_{2 + x}$Sr$_{2 - x}$CuO$_{6 + \delta}$ single crystals in different temperatures, where $x$ = 0.10, 0.12, 0.14. All of the crystals show anomalous fishtail effects (second peak effects). We found that the second peaks can be described by thermal decoupling modal. The lowest crossover field from the first peak to the second peak is found as low as several Oe. We suggest that the crossover field is related to unbinding the vortex-antivortex pairs and building the vortex interaction from layer to layer. [Preview Abstract] |
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H1.00313: Phase separation dynamics in polymer blends close to Tg: aging and rejuvenating Gregoire Julien We extend the Percolation of Free Volume Distribution (PFVD) model developed by Long and co-workers to deal with polymer blends dynamics close to the glass transition. The dynamical model incorporates an extension of the Flory Huggins model to the case of compressible blends for calculating the driving forces. Spatial dynamics follows then from an Onsager like description. The model is solved on a 2D lattice corresponding to spatial scales of about a few tens to 100 nm and a resolution corresponding to the scale of dynamical heterogeneities, allowing to study phase separation close to Tg. We study also the reverse process, after the temperature is increased again in the totally miscible range. We observe a temporal asymmetry between the aging and the rejuvenation dynamics: the slow domains melt much faster than the elapsed time required to built them during the separation process and total miscibility is recovered after a much shorter time. [Preview Abstract] |
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H1.00314: Focused ion beam lithographically patterned growth of vertically aligned ZnO nanorods arrays on GaN Wing Lun Chung, Hua Sheng Wu Ordered ZnO nanorods were synthesized on GaN by using hydrothermal method via silicon dioxide template etched by focused ion beam nanolithography. Due to the nucleation site confinement, the as-grown ZnO nanorods were selectively budding inside the nanopattern. Scanning electron microscope image showed that the as-grown ZnO nanorods were highly ordered and exhibited hexagonal structure. This indicated the GaN substrate retained its crystalline orientation despite the destructive Focused ion beam lithography. [Preview Abstract] |
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H1.00315: First-Principles Calculations of Structural, Electronic and Optical Properties of CaTiO$_3$ Crystal Sub\^{e}nia Medeiros, Jusciane Silva, Eudenilson Albuquerque, Valder Freire The structural, electronic, vibrational, and optical properties of perovskite CaTiO$_3$ in the cubic, orthorhombic, and tetragonal phase are calculated in the framework of density functional theory (DFT) with different exchange-correlation potentials by CASTEP package. The calculated band structure shows an indirect band gap of 1.88 eV at the $\Gamma$-R points in the Brillouin zone to the cubic structure, a direct band gap of 2.41 eV at the $\Gamma-$$\Gamma$ points to the orthorhombic structure, and an indirect band gap of 2.31 eV at the M–$\Gamma$ points to the tetragonal phase. I have concluded that the bonding between Ca and TiO$_2$ is mainly ionic and that the TiO$_2$ entities bond covalently. Unlike some perovskites the CaTiO$_3$ does not exhibit a ferroelectric phase transition down to 4.2 K. It is still known that the CaTiO$_3$ has a static dielectric constant that extrapolates to a value greater than 300 at zero temperature. Our calculated lattice parameters, elastic constants, optical properties, and vibrational frequencies are found to be in good agreement with the available theoretical and experimental values. The results for the effective mass in the electron and hole carriers are also presented in this work. [Preview Abstract] |
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H1.00316: Spin torque switching and precession states in a spin Hall effect systems with perpendicularly magnetized ferromagnetic layer Shu Yan, Yaroslaw Bazaliy Magnetic switching in spin Hall effect (SHE) systems attracted some recent attention. Those bilayer systems consist of a perpendicularly polarized ferromagnetic (F) layer next to a non-magnetic metallic (N) layer with large SHE. A dc electric current flow along the layers was found to cause magnetic switching. One of the theoretical explanations proposed for this phenomenon is based on the emergence of a spin torque due to the spin polarized current coming from the N-layer into the F-layer. The latter current is produced by the SHE in N-layer. We study the influence of the external magnetic field on the current induced switching. It is shown that depending on the direction of the field the astroid curve describing magnetic switching can experience either a quantitative deformation, or a qualitative change with the emergence of stable precession cycles. These predictions allow us to suggest new test experiments designed to further probe the spin torque theory of SHE switching. [Preview Abstract] |
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H1.00317: Geometry in Biomimetic Network: Double Gyroid to Pseudo-Single Gyroid in Nanohybrid Materials Han-Yu Hsueh, Rong-Ming Ho, Yu-Chueh Hung, Yi-Chun Ling, Hirokazu Hasegawa Biological systems have developed delicately arranged micro- and architectures to produce striking optical effects since millions of years ago. Inspired by the textures of butterfly wings with single gyroid (SG) structure, herein, we aim to fabricate biocompatible and robust materials with SG-like structure in nanometer size so as to give new materials with unprecedented optical properties for applications. Biommicking from the biological photonic structures of butterfly wings, a double gyroid (DG) structure in nanometer size is obtained from the self-assembly of polystyrene-b-poly(L-lactide) (PS-PLLA). To acquire robust backbone networks, inorganic networks in polymer matrix are fabricated by using the hydrolyzed PS-PLLA with DG structure as a template for sol-gel reaction. Owing to the soft polymer matrix, two co-continuous inorganic networks embedded in the polymer matrix can be rearranged by thermal annealing at temperature above the glass transition of the polymer. Consequently, the rearrangement of these inorganic networks leads the formation of SG-like structure possessing unique nanohybrids with ordered texture. This unique nanomaterials with SG-like structure is referred as a pseudo-SG (p-SG) nanohybrids. [Preview Abstract] |
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H1.00318: Overlooked restrictions on Euler angles in quantum computation Mitsuru Hamada Let $X,Y,Z$ denote the Pauli matrices. For $\vec{n}=(n_x,n_y,n_z) \in {\bf R}^3$ with $n_x^2+n_y^2+n_z^2=1$ and $\theta\in{\bf R}$, put $R_{\vec{n}}(\theta)=\cos(\theta/2)I-i\sin(\theta/2)(n_x X+n_yY+n_z Z)$. Put $R_{y}(\theta)=R_{(0,1,0)}(\theta)$ and $R_{z}(\theta)=R_{(0,0,1)}(\theta)$. Theorem: Assume $\alpha,\gamma,\theta\in{\bf R}$, $\vec{n}=(n_x,n_y,n_z)\in{\bf R}^3$ and $n_x^2+n_y^2+n_z^2=1$. Then, there exists some $\beta,\delta\in{\bf R}$ satisfying $R_{\vec{n}}(\theta)=e^{i\alpha}R_{z}(\beta)R_{y}(\gamma)R_{z}(\delta)$ if and only if (iff) $e^{i\alpha}=1$ or $-1$, and $\sqrt{1-n_z^2}|\sin(\theta/2)|=|\sin(\gamma/2)|$. Corollary: Assume $\alpha,\gamma\in{\bf R}$, $\vec{n}=(n_x,n_y,n_z)\in{\bf R}^3$ and $n_x^2+n_y^2+n_z^2=1$. Then, there exist some $\beta,\delta,\theta\in{\bf R}$ such that $e^{i\alpha}R_{z}(\beta)R_{\vec{n}}(\theta)R_{z}(\delta)=R_{y}(\gamma)$ iff $e^{i\alpha}=1$ or $-1$, and $|\cos(\gamma/2)|\ge|n_z|$. This corollary shows a widespread fallacy on universal gates in quantum computation. Namely, when $|\cos(\gamma/2)|<|n_z|<1$, according to a claim often found in textbooks, $R_{y}(\gamma)$ could be written as $e^{i\alpha}R_{z}(\beta)R_{\vec{n}}(\theta)R_{z}(\delta)$ for some $\alpha,\beta,\delta,\theta\in{\bf R}$. This is untrue by the corollary. [Preview Abstract] |
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H1.00319: Fabrication of chalcopyrite light-absorbing layers based on nanoparticle and nanowire networks Yuhang Ren, Paifeng Luo, Bo Gao, Zehra Cevher, Chivin Sun We report on a method of preparing chalcopyrite, CuInGaSe2 (CIGS) light-absorbing layers using low cost air stable ink based on semiconductor nanoparticle and nanowires. The nanoparticles and nanowires are prepared from metal salts such as metal chloride and acetate at room temperature without inert gas protection. A uniform and non-aggregation CIGS precursor layer is fabricated with the formation of nanoparticle and nanowire networks utilizing ultrasonic spaying technique. We obtain a high quality CIGS absorber by cleaning the residue salts and carbon agents at an increased temperature and through selenizing the pretreated CIGS precursors. Our results offer an opportunity for the low-cost deposition of chalcopyrite absorber materials at large scale with high throughput. [Preview Abstract] |
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H1.00320: ABSTRACT WITHDRAWN |
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H1.00321: Quantum dots with light-hole exciton ground state Barbara Witek, Nika Akopian, Yongheng Huo, Santosh Kumar, Ricardo Cardenas, Gabriel Bester, Armando Rastelli, Oliver Schmidt, Val Zwiller A light-hole exciton is a quasiparticle formed from a single electron and a single light-hole (LH). This is a fundamental excitation in a semiconductor quantum dot (QD), which could potentially lead to new and simpler schemes in quantum information science and technology, However, it has not been explored so far because the ground state of a hole in a QD has dominant heavy-hole character. Here we develop a novel type of a QD system that allows us to engineer GaAs/ AlGaAs QDs with a light-hole (LH) ground state by embedding them in tensile strained membranes. We fully characterize LH exciton states in polarization resolved $\mu $-photoluminesce in the external magnetic field. LH exciton manifests itself in three orthogonally-polarized bright transitions and a large fine-structure. Further, we determine LH g-factor and observe different diamagnetic coefficients for LH p$_{x,y}$ and p$_{z}$ orbitals. Finally, we provide a comprehensive theoretical description of all the observed LH exciton properties: fine structure, polarization, oscillator strength and g-factors. Our work paves the way to explore the fundamental properties and potential relevance of LH-excitons in QD for quantum information technologies. [Preview Abstract] |
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H1.00322: Kinetic Potential Model of the Cloud-to-Drizzle Transition Robert McGraw, Yangang Liu, Edward Luke, Gunnar Senum It has been nearly a decade since the kinetic potential theory of drizzle formation in warm clouds was introduced [McGraw and Liu, Phys. Rev. Letts. 90, 018501 (2003)], and much progress in understanding the cloud-drizzle transition, especially regarding the role of turbulence, has been achieved within its framework. This poster will begin with an introduction to the kinetic potential idea, working up to the method it provides for predicting drizzle threshold conditions and rates, and concludes with an analysis this year of DOE/ARM cloud parcel vertical velocity measurements - discussing their implications for assessing turbulence fluctuations in water vapor saturation ratio and cloud droplet size. [Preview Abstract] |
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H1.00323: Non-Classical Order in Sphere Forming ABAC Tetrablock Copolymers Jingwen Zhang, Scott W. Sides, Frank S. Bates AB diblock and ABC triblock copolymers have been studied thoroughly. ABAC tetrablock copolymers, representing the simplest variation from ABC triblock by breaking the molecular symmetry via inserting some of the A block in between B and C blocks, have been studied systematically in this research. The model system is poly(styrene-b-isoprene-b-styrene-b-ethylene oxide) (SISO) tetrablock terpolymers and the resulting morphologies were characterized by nuclear magnetic resonance, gel permeation chromatography, small-angle X-ray scattering, transmission electron microscopy, differential scanning calorimetry and dynamic mechanical spectroscopy. Two novel phases are first discovered in a single component block copolymers: hexagonally ordered spherical phase and tentatively identified dodecagonal quasicrystalline (QC) phase. In particular, the discovery of QC phase bridges the world of soft matters to that of metals. These unusual sets of morphologies will be discussed in the context of segregation under the constraints associated with the tetrablock molecular architecture. Theoretical calculations based on the assumption of Gaussian chain statistics provide valuable insights into the molecular configurations associated with these morphologies. [Preview Abstract] |
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H1.00324: How does the host population's network structure affect the estimation accuracy of epidemic parameters? Kenta Yashima, Kana Ito, Kazuyuki Nakamura When an Infectious disease where to prevail throughout the population, epidemic parameters such as the basic reproduction ratio, initial point of infection etc. are estimated from the time series data of infected population. However, it is unclear how does the structure of host population affects this estimation accuracy. In other words, what kind of city is difficult to estimate its epidemic parameters? To answer this question, epidemic data are simulated by constructing a commuting network with different network structure and running the infection process over this network. From the given time series data for each network structure, we would like to analyzed estimation accuracy of epidemic parameters. [Preview Abstract] |
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H1.00325: Systematic Construction of Braids for Topological Quantum Computation Caitlin Carnahan, Daniel Zeuch, N.E. Bonesteel In topological quantum computation, quantum gates are carried out by braiding worldlines of non-Abelian anyons in 2+1 dimensional space-time. The simplest such anyons for which braiding is universal for quantum computation are Fibonacci anyons. Reichardt [1] has shown how to construct nontrivial braids for three Fibonacci anyons which yield $2 \times 2$ unitary operations whose off-diagonal matrix elements (in the appropriate basis) can be made arbitrarily small through a simple and efficient iterative procedure. A great advantage of this construction is that it does not require either brute force search or the Solovay-Kitaev method. There is, however, a downside---the phases of the diagonal matrix elements cannot be directly controlled. Despite this, we show that the resulting braids can be used to construct leakage-free entangling two-qubit gates for qubits encoded using four Fibonacci anyons each. We give two explicit constructions---one based on the ``functional braid" approach of Hu and Wan [2], and another based on the ``effective qubit" approach of Hormozi et al. [3]. \newline [1] B.W. Reichardt, Quant. Inf. and Comp. {\bf 12}, 876 (2012). \newline [2] H. Xu and X. Wan, PRA \textbf{78}, 042325 (2008). \newline [3] L. Hormozi et al., PRL {\bf 103}, 160501 (2009). [Preview Abstract] |
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H1.00326: Study of polymorphism of Atenolol and Captopril antihypertensives using x-ray powder diffraction and Rietveld refinement Juliana Sato, Fabio Ferreira Characterization of bulk drugs has become increasingly important in the pharmaceutical industry. X-ray powder diffractometry is an effective technique for the identification of crystalline solid-phase drugs. The technique is unique, since it combines specificity with a high degree of accuracy for the characterization of pharmaceuticals in solid state and is an especially useful method to describe the possible polymorphic behavior of drugs substances. In this work X-ray diffraction data have been obtained for two well-known antihypertensive drugs currently being administered in tablet form. They include atenolol and captopril. Atenolol and captopril were purchased from drugstore. The characterizations of the atenolol and captopril samples were carried out by FTIR spectroscopy and X-ray powder diffraction (XRPD). [Preview Abstract] |
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H1.00327: Solvation properties of C60 fullerene in water-DMSO mixtures Cleiton Maciel, Eudes Fileti Binary solvent mixtures present important properties that allow their use in wide field of applications. For instance, aqueous solutions of dimethyl sulfoxide have been use in biological systems due to the properties that can reach varying on the concentration of the compounds. Solvation properties in these mixtures have been explored but have never been reported investigations of solvation properties of large non polar solutes in that system. In this work, molecular dynamics simulations were employed to investigate the solvation properties of C60 fullerene immersed in water-DMSO binary mixtures. The role of DMSO as a cosolvent was studied modeling fullerene solutions varying the DMSO molar fraction from 0 to 1.0. Partial structural results showed a dense concentration of DMSO molecules around C60 at low DMSO content solutions. In high DMSO concentrations ($\sim$ 0.70) the average number of hydrogen bonds between DMSO and water molecules and the lifetime of these interactions were smaller and higher than poor DMSO solutions, respectively. Additionally, free energy calculations were performed and an increasing hydrophobic behavior of C60 was observed in DMSO rich solutions. [Preview Abstract] |
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H1.00328: Growth of Graphene by Catalytic Dissociation of Ethylene on CuNi(111) Parul Tyagi, Tyler Mowll, Zachary Robinson, Carl Ventrice Copper foil is one of the most common substrates for growing large area graphene films. The main reason for this is that Cu has a very low carbon solubility, which results in the self-termination of a single layer of graphene when grown using hydrocarbon precursors at low pressure. Our previous results on Cu(111) substrates has found that temperatures of at least 900 $^{\circ}$C are needed to form single domain epitaxial films. By using a CuNi alloy, the catalytic activity of the substrate is expected to increase, which will allow the catalytic decomposition of the hydrocarbon precursor at lower temperatures. In this study, the growth of graphene by the catalytic decomposition of ethylene on a 90:10 CuNi(111) substrate was attempted. The growths were done in an ultra-high vacuum system by either heating the substrate to the growth temperature followed by introducing the ethylene precursor or by introducing the ethylene precursor and subsequently heating it to the growth temperature. The growth using the former method results in a two-domain epitaxial graphene overlayer. However, introducing the ethylene before heating the substrate resulted in considerable rotational disorder within the graphene film. This has been attributed to the deposition of carbon atoms on the surface at temperatures too low for the carbon to crystallize into graphene. [Preview Abstract] |
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H1.00329: Exciton-induced degradation of photocurrent in small-molecule organic solar cells Xiaoran Tong, Nana Wang, Michael Slootsky, Stephen Forrest The reliability of organic photovoltaic cells (OPVs) has become a focus of research. In this work, the intrinsic degradation mechanism of archetypal subphthalocyanine/fullerene OPVs in the absence of water and oxygen is studied. We focus on the initial burn-in period (\textless 10h) during which there is no significant change in fill factor or open-circuit voltage, suggesting stable interfacial and bulk morphology. In planar OPVs employing C$_{\mathrm{60}}$ as the acceptor, the efficiency drop is primarily due to a reduction of photocurrent contributed by C$_{\mathrm{60}}$, as observed in the spectrally-resolved external quantum efficiency (EQE). The current loss occurs after the cell is illuminated in the C$_{\mathrm{60}}$ absorption range, regardless of intensity and proportional to the total number of C$_{\mathrm{60}}$-absorbed photons. The degradation over time is modeled as due to an increasing density of exciton-induced quenching sites that hinder exciton diffusion to the donor-acceptor interface. Experimentally, we find this mechanism can be effectively mitigated by employing a mixed donor-acceptor active layer where excitons are rapidly dissociated and the steady-state exciton density is reduced. The trap formation rate and exciton dynamics will be discussed in detail. Degradation of different OPV systems will be compared. [Preview Abstract] |
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H1.00330: ABSTRACT WITHDRAWN |
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H1.00331: Evaluation of the band-gap of Ruddlesden-Popper tantalates Juan Ramirez de Arellano, Sabina Ruiz Chavarria, Pablo de la Mora, Hoover A. Valencia, Gustavo Tavizon Tantalum-oxide based laminar compounds are suitable systems to perform water photo splitting reactions since the gap associated to the exciton formation has advantages over other systems. In the Ruddlesden-Popper series of compounds A'$_{2}$[A$_{\mathrm{n-1}}$B$_{\mathrm{n}}$O$_{\mathrm{3n+1}}$], where B$=$Ta and A$=$Lanthanide, for n$=$2 and 3, we have studied the effect of the A$=$ La, Nd and Pr on the gap value, and compare our results to the experimental values for those systems. We also discuss the experimental results of the water intercalated compounds in the water splitting reaction in light of our results on the electronic structure calculations. We have evaluated the band-gap of these compounds with the WIEN2k package using the modified Becke Johnson exchange potential. [Preview Abstract] |
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H1.00332: Photoionization of Ne~IV Fine Structure Levels Sultana Nahar Determination of Ne abundance, particularly in the sun, from the observed ionized neon lines has been a long standing problem. Ne~IV-V lines are detected requring accuate data for the atomic processes to carry out the spectral analysis. For precise astrophysical modelling, photoionization cross sections of Ne~IV have been calculated for a large number of fine structure levels in the relativistic Breit-Pauli R-matrix method. Resonances due to Rydberg series of auotionizaing states belonging to 19 excited core levels of configurations $2s^22p^2$, $2s2p^3$, and $2p^4$ are resolved with fine energy mesh. Near threshold resonances due to fine structure effects, not allowed in LS coupling, are found. Details of resonant structures and enhanced background due to Seaton resonances will be reported. [Preview Abstract] |
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H1.00333: Radiosensitization of high-Z compounds by medium-energy 160 kV vs. high-energy 6 MV X-rays for radiation therapy: Theoretical, in vitro and in vivo studies of platinum compounds activating glioma F98 cancer cells S. Lim, A. Pradhan, S. Nahar, M. Montenegro, R. Barth, R. Nakkula, C. Turro Energy dependence of X-ray irradiation of high-Z compounds for enhanced radiosensitization is explored thoeretically and via in vitro and in vivo experiments. The cell killing ability of medium-energy X-rays from 160 kV source are found to be more effective than 6 MV X-rays in activating high-Z contrast agents. Results are presented for a newly synthesized Pt compound, Pyridine Terpyridine Pt(II) Nitrate ([Pt(typ)(py)]) and carboplatin in treating F98 rat glioma. In-vitro results show considerable reduction in cell viability for radiosensitized cells irradiated with a 160 kV irradiator. Cells treated with 6 MV LINAC radiation find little variation with radiation dose. Maximum dose enhancement factors (DEFs) and minimum cancer cell survival fractions correspond to 50-200 keV range, and fall rapidly at higher energies. Theoretical calculations of photoelectric absorption vis-a-vis total scattering demonstrates this energy dependence. However, in vivo studies of rats treated with [Pt(tpy)(py)] had a severe negative neurotoxic response, confirmed by histopathological analysis. But subsequent in vivo studies using carboplatin showed very positive results in the treatment of F98 glioma bearing rats and potential clinical radiation therapy. [Preview Abstract] |
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H1.00334: The effective field induced by Rashba interaction in ferromagnetic systems Noriyuki Nakabayashi, Gen Tatara The spin motive force is widely used in spintronics. For example, it is demonstrated that domain wall motion is discussed by the spin motive force[1]. The spin mortive force should be devided into the two effective fields: the effective electric and magnetic field. The electric field induced by Rashba interaction is estimated from equation of motion of conduction electron[1,2], while estimating the effective magnetic field in the same way are somewhat difficult. We estimate the effective magnetic field which is estimated by calculating the electric current[3]. The electirc current is calculated in ferromagnetic metals in the presence of Rashba interaction. \\[4pt] [1] K.-W. Kim, S.-M. Seo, J. Ryu, K.-J. Lee, and H.-W. Lee, Phys. Rev. B 85, 180404 (May 2012).\\[0pt] [2] G. Tatara, N. Nakabayashi, and K.-J. Lee, arXiv:1211.5205 [cond-mat.mes-hall] (Nov 2012).\\[0pt] [3] A. Takeuchi and G. Tatara, J. Phys. Soc. Jpn. 81, 033705 (2012). [Preview Abstract] |
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H1.00335: Geometry and surface controlled formation of nanoparticle helical ribbons Jonathan Pham, Jimmy Lawrence, Dong Yun Lee, Gregory Grason, Todd Emrick, Alfred Crosby Helical structures are interesting because of their space efficiency, mechanical tunability and everyday uses in both the synthetic and natural world. In general, the mechanisms governing helix formation are limited to bilayer material systems and chiral molecular structures. However, in a special range of dimensions where surface energy dominates (i.e. high surface to volume ratio), geometry rather than specific materials can drive helical formation of thin asymmetric ribbons. In an evaporative assembly technique called flow coating, based from the commonly observed coffee ring effect, we create nanoparticle ribbons possessing non-rectangular nanoscale cross-sections. When released into a liquid medium of water, interfacial tension between the asymmetric ribbon and water balances with the elastic cost of bending to form helices with a preferred radius of curvature and a minimum pitch. We demonstrate that this is a universal mechanism that can be used with a wide range of materials, such as quantum dots, metallic nanoparticles, or polymers. Nanoparticle helical ribbons display excellent structural integrity with spring-like characteristics and can be extended high strains. [Preview Abstract] |
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H1.00336: Non-Gaussian statistics and spatially-organized extreme events on experimental fracture surfaces Laurent Ponson The measurement of an abnormally high roughness exponent $\zeta \simeq 0.80$ on fracture surfaces of a large range of materials has been a long standing open question. Here, we revisit the roughness of cracks in metallic alloys and mortar where this value were reported, and show that this behavior is intimately connected with a non-Guaussian statistics of the height fluctuations of the fracture surfaces. The fat tails observed on the roughness distribution are shown to result from spatially organized domains where the local slope is abnormally large. This network of extreme events is characterized by long-range spatial correlations and power law statistics, and their scale of observations suggest that they are signature of microcracking in the material. Our findings support that damage is the central mechanism at the origin of the universal scaling behavior with $\zeta \simeq 0.80$ and open new perspectives in the quantitative investigation of microscopic failure processes from the analysis of fracture surfaces. [Preview Abstract] |
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H1.00337: Alignment of Magnetic Nanoparticles in Polymer Films Ecem Yarar, Deniz Rende, Seyda Bucak Polymer nanocomposites are advanced materials, which are obtained by the addition of natural or synthetic nanosized inorganic fillers into the polymeric material. The addition of trace amounts of nanoparticles could enhance the polymer's mechanical, thermal, electrical and optical properties due to their size and high surface area/volume ratio. In this work, magnetite/PMMA nanocomposites were prepared either by randomly dispersing or by aligning magnetite nanoparticles in the matrix using an external magnetic field. Oleic acid coated iron oxide nanoparticles (magnetite) were used as nanofiller. 7-9 nm iron oxide nanoparticles were synthesized by co-precipitation method with different surfactant amounts and at different synthesis temperatures. Superparamagnetic property of bare iron oxides was confirmed by Vibrating Sample Magnetometer (VSM) analysis. Thermogravimetric Analysis (TGA) measurements were used to calculate the surface coverage of the oleic acid on iron nanoparticles, which increases with increasing oleic acid concentration and consistent across synthesis temperature. Dispersion and alignment of nanoparticles through the polymer film were investigated with TEM and SEM. Results showed that magnetic nanoparticles formed under the influence of an external magnetic field were aligned and formed rods consisting of individual nanoparticles. [Preview Abstract] |
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H1.00338: Disordered Floquet topological insulators Shirit Baruch, Tami Pereg-Barnea In the presence of an external periodic field some materials become Floquet topological insulators. Introducing disorder into these systems may alter their electronic properties, which may critically affect their applications. We investigate the effects of disorder on Floquet topological insulators using a Green's function formalism. We find that in the presence of disorder, the transport properties of Floquet topological insulators differ from those of standard topological insulators. We further investigate the robustness of the topological phase to disorder. [Preview Abstract] |
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H1.00339: Method for Reducing the Nano-Cracks on the Surface of the Heterostructure Gagik Shmavonyan, Ovsanna Zadoyan The sizes of dislocations in the hetero-interface and nano-cracks on the surface of the heterostructure conditioned by lattice mismatch of semiconductors are sometimes close to those of nano-layer structures made up of a few atomic layers. Elimination of such defects becomes important in the elaboration of high quality semiconductor nanostructured optoelectronic devices. So, it is actual to develop new technological processes and elaborate adequate regimes, which will allow decreasing the sizes of defects in the heterointerface from the characteristic sizes of the structure. The method of reducing the dislocations in the heterointerface and nano-cracks on the surface of the heterostructure grown on the substrate is suggested: applying substrates with high crystallographic indices (bent substrate) and then depositing various buffer nano-layers based on compositionally graded films to the bent substrate. By solving the problem of obtaining high-quality hetero-interface and surface through epitaxial technologies it is possible to a) decrease mechanical and thermal strain in the heterointerface, b) obtain relaxed and high-quality nanoheterostructures based on big lattice mismatch. [Preview Abstract] |
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H1.00340: Effect of Subelement Size, Strand Size and RRR on Stability of RRP Nb3Sn Wires Emanuela Barzi, Simone Moio, Alexander Zlobin Using ample statistics gathered from state-of-the-art Nb3Sn strands of different designs and sizes developed by Oxford Superconductor Technology (OST), the effects on the strand current density of subelement size, Residual Resistivity Ratio (RRR) of the copper matrix, and strand size were measured, analyzed and compared with the predictions of a stability model. The data confirmed a strong dependence of the instability current density on the subelement size, but also hinted at effects of non-uniform current distribution in the wire. The data also show that the instability current relates so weakly to RRR that it is possible to cleanly identify a common instability behavior as a function of subelement size and of strand size despite an ample range of RRR. This analysis was performed both at 4.2 K and 1.9 K. [Preview Abstract] |
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H1.00341: Physics of ON-OFF Switching Mechanism of ReRAM via Oxygen Vacancy Based Conducting Channels Katsumasa Kamiya, MoonYoung Yang, Blanka Magyari-Kope, Masaaki Niwa, Yoshio Nishi, Kenji Shiraishi Resistive--Random--Access--Memories (ReRAMs) have attracted increased attention as a promising candidate for the next generation of non-volatile memories. It has been pointed out that the ON-OFF switching in ReRAMs is governed by the formation and disruption of oxygen vacancy conducting filaments. However, the origin of this formation-isolation transition is still unclear. We thus studied the ON-OFF switching mechanism of ReRAM using first-principles calculations. We found that electron-captured oxygen vacancies tend to form a cohesive conductive filament (``ON''-state), while the filament is disrupted when electrons are removed from the oxygen vacancies (``OFF''-state). We concluded that this cohesion and isolation transition of the oxygen vacancies upon carrier injection and removal is the physical origin of the ON-OFF switching in ReRAMs. This concept is also applicable for other binary-oxide-based ReRAMs, since the physics is inherently related to the properties of the oxygen vacancies. Based on this physics, we proposed a guiding principle for stack-structures of ReRAMs, which has been very recently shown to improve ReRAM properties drastically. [Preview Abstract] |
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H1.00342: Evidence of a Liquid-Liquid Phase Transition Hot Dense Hydrogen Isaac Silvera, Vasily Dzyabura, Mohamed Zaghoo We use pulsed laser heating of hydrogen at static pressures in the megabar pressure region generated in a diamond anvil cell to search for the plasma phase transition (PPT) to liquid atomic metallic hydrogen. Heating the sample substantially above the melting line we observe a plateau in a temperature vs laser power curve that otherwise increases with power. This anomaly in the heating curve is closely correlated with theoretical predictions for the PPT, falling within the theoretically predicted range and having a negative slope with increasing pressure. Details will be presented. [Preview Abstract] |
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H1.00343: Magnetic Properties of nickel hydroxides layers 30A apart obtained by intercalation with dodecyl sulfate ion Mohindar Seehra, Vivek Singh Magnetic systems with reduced dimensionality make good test beds for checks on theoretical models [1]. Here, changes in the nature of magnetic ordering in quasi-2d system of layered Ni hydroxides (LH-Ni-) with variations in the interlayer spacing c are investigated. Magnetic properties of LH-Ni-DS with c $\approx $ 30 A$^{\circ}$ synthesized by intercalating dodecyl sulfate ion, (C$_{12}$H$_{25}$OSO$_{3})^{-}$ between the layers are compared with those of LH-Ni-Ac (c $\approx $ 8.5 A$^{\circ}$ ) containing the acetate (Ac) ligand [2]. Measurements included those of magnetization M vs. T and H, ac susceptibilities (f $=$ 0.1 Hz - 1000 Hz) and EMR (Electron Magnetic Resonance) spectra at 9.28 GHz. Results show that just like LH-Ni-Ac, LH-Ni-DS also orders ferromagnetically but with T$_{c\, }\approx $ 23 K about 45 {\%} larger than T$_{c\, }\approx $ 16 K reported for LH-Ni-Ac.[2]. In EMR studies, linewidth is strongly temperature-dependent, decreasing with decreasing T from 300 K, reaching a minimum near 45 K and then increasing sharply for T \textless\ 45 K, the latter due to short range magnetic ordering. These results differ with the model of Drillon et al [3] in which interlayer dipolar interaction between clusters of correlated spins in the layers yields T$_{C}$ nearly independent of c. Roles of magnetic anisotropy and exchange constants in determining T$_{C}$ in the LH-Ni systems is discussed.\\[4pt] [1]. ``Magnetic properties of layered transition metal compounds'' L.J. deJongh , Editor.\\[0pt] [2]. J.D. Rall {\&} M.S. Seehra, J. Phys.:Condens.Matter 24, 076002(2012).\\[0pt] [3]. M. Drillon et al, Phys.Rev.B65, 104404 (2002). [Preview Abstract] |
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H1.00344: A dictionary of behavioral motifs reveals clusters of genes affecting C. elegans locomotion Andre Brown, Eviatar Yemini, Laura Grundy, Tadas Jucikas, William Schafer Visible phenotypes based on locomotion and posture have played a critical role in understanding the molecular basis of behavior and development in \textit{C. elegans} and other model organisms. However, it is not known whether these human-defined features capture the most important aspects of behavior for phenotypic comparison nor whether they are sufficient to discover new behaviors. Here we show that four basic shapes, or eigenworms, previously described for wild type worms also capture mutant shapes, and that this representation can be used to build a dictionary of repetitive behavioral motifs in an unbiased way. By measuring the distance between each individual's behavior and the elements in the motif dictionary, we create a fingerprint that can be used to compare mutants to wild type and to each other. This analysis has revealed previously undescribed phenotypes and has allowed clustering of mutants into related groups. Behavioral motifs provide a compact and intuitive representation of behavioral phenotypes. [Preview Abstract] |
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H1.00345: Effect of solvent on the structure of a protein (H3.1) with a coarse-grained model with knowledge-based interactions Ras Pandey, Barry Farmer Quality of solvent plays a critical role in modulating the structure of a protein along with the temperature. Using a coarse-grained Monte Carlo simulation based on three knowledge-based contact potentials (MJ[1], BT[2], BFKV[3]) we examine the structure and dynamics of a histone (H3.1). The empty lattice sites constitute the effective solvent medium in which the protein is embedded. Residue-solvent characteristic interaction is based on the hydropathy index while the residue-residue interaction is used from the knowledge-based contact matrices derived from ensembles of protein structures in the protein data bank. Large scale simulations are performed to analyze the structure of protein for a range of residue-solvent interaction strength, a measure of the solvent quality with each potential. Unlike the monotonic thermal response, the radius of gyration of the protein exhibits non-monotonic dependence of the solvent strength. Quantitative comparison of the structure and dynamics emerging from three knowledge-based potentials will be presented in this talk. \\[4pt] [1] S. Miyazawa and R.L. Jernigan, Macromolecules 18, 534 (1985).\\[0pt] [2] M.R. Betancourt and D. Thirumalai, Protein Sci. 2, 361 (1999).\\[0pt] [3] U. Bastolla et al. Proteins 44, 79 (2001). [Preview Abstract] |
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H1.00346: Thermoelectric properties of AgSbTe$_2$ from first-principles calculations Hadi Akbarzadeh, Nafiseh Rezaei, S. Javad Hashemifar, Keivan Esfarjani Recently, novel thermoelectric materials are extensively investigated for providing sustainable energy resource. In this regard, AgSbTe$_{2}$ as a p-type semiconductor is widely investigated due to its low lattice thermal conductivity and relatively large Seebeck coefficient. We study electronic, vibrational, and thermoelectric properties of FCC and rhombohedral structures of AgSbTe$_{2}$ by first-principles calculations. The hybrid HSE03 functional is employed to correct wrong prediction of semimetal behavior in GGA and obtain a band gap of about 0.5 eV. The Seebeck coefficient, electrical conductivity, and electronic part of thermal conductivity are calculated by using a combination of maximally localized Wannier functions and semi-classical Boltzmann equation. By matching the calculated Seebeck coefficient with the experimental data, we predict the carrier concentration and band gap of several experimental samples. Our results indicate that the band gap and hole concentration of pure samples should be in the range of 0.2-0.5 eV and 2-5 $\times$ 10$^{19}$ holes/cm$^{3}$. Finally, we use the experimental electrical conductivity and the constant relaxation time assumption to estimate the relaxation time of this compound. [Preview Abstract] |
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