Bulletin of the American Physical Society
2015 Annual Spring Meeting of the APS Ohio-Region Section
Volume 60, Number 3
Friday–Saturday, March 27–28, 2015; Kent, Ohio
Session C1: Poster Session |
Hide Abstracts |
Chair: Michael Strickland, Kent State University Room: KSU Student Center 2nd Floor Lobby |
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C1.00001: Sonification of Time-series Data Sets Haowen Xi, Andrew Kelley The purpose of our research is to create an efficient and straightforward sonification algorithm to convert any time-series data set into sound. This allows for data to be communicated through non-speech audio and understood alongside typical visualization techniques, although no widely available or easily understood program currently exists. The time-series data that can be analyzed ranges from stock market prices to atmospheric temperature or neural activity in the brain. This algorithm was accomplished with MATLAB computational software utilizing uncomplicated yet unique mappings of values to determine frequency, duration and dynamic contrast and was coded in such a way as to be easily applied in its current form or replicated in other software languages. Our approach to presenting data has the advantages of being able to easily identify patterns in large data sets, clarifying complex and hard-to-understand data, as well as bringing abstract and intricate scientific data down to an approachable level for the general public. We hope to provide a flexible tool for sonification research and data exploration as well as solve some of the problems that have arisen in this new field. [Preview Abstract] |
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C1.00002: Nonlinear normal modes of the double and triple planar pendulum Alex Jurgens, Cavendish McKay Nonlinear normal modes (NNMs) are a nonlinear extension of the classical normal modes of linear vibration theory, capable of demonstrating nonlinear behaviors including bifurcations, internal resonance, and modal interactions. However, use of NNMs in structural dynamics remains limited due to difficulties in computation. Previous research has shown successful computation of NNMs using a numerical algorithm combining a shooting method with a continuation technique. We apply this algorithm to the double and triple planar pendulum, connecting a staple problem in nonlinear dynamics with a fresh analytical perspective. [Preview Abstract] |
(Author Not Attending)
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C1.00003: Crab Nebula Significance Map with HAWC data Gilgamesh Luis-Raya, Roberto Arceo, Eucario G. P\'erez-P\'erez, Nazario Bautista-Elivar, Luis Alberto Zamora-Campos, Francisco Marroqu\'In-Guti\'errez The all-sky observatory HAWC (The High Altitude Water Cherenkov) is a large field of view instrument which operates 24 hr/day by observing $\sim $2sr of the sky. The experiment is located on Sierra Negra volcano at 4100 m above the sea level in the border between Puebla and Veracruz states in Mexico. The full array contains 300 water Cherenkov detectors with an effective area of 22,000 m$^{2}$ and a total number of 1200 PMTs (4 in each tank). The HAWC detector is sensitive to gamma and cosmic rays in the energy range between 100GeV and 100TeV being perfect to analyze gamma ray sources like the supernova remnant NGC1952 also known as Crab Nebula. In this work, we show significance map in the direction of the Crab nebula calculated from gamma ray data taken during 2014 with HAWC. [Preview Abstract] |
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C1.00004: Dynamical Evolution of Open Star Clusters of Varying Initial Mass Functions in STARLAB Nicholas Miller, Ann Bragg, Cavendish McKay N-body simulations are widely used to model the dynamical evolution of a variety of systems, among them star clusters. Much of our understanding of star cluster evolution rests on the results of N-body simulations, providing insight in the structural evolution of these systems, as well as a detailed study of mass segregation. Observations show that the more massive members of a star cluster aggregate toward the center, while less massive members tend to move farther away from the center. Using the N-body code STARLAB/KIRA we construct a large number of open star cluster models with various initial mass functions: a Saltpeter mass function (power law with exponent $\alpha= -2.35$), a series of additional power law functions with each exponent increasing by 0.2 from the last ($\alpha = -2.15,-1.95,-1.75$) and a Miller-Scalo mass function. For each mass function, we simulate an ``ensemble'' of 160 individual clusters each containing 2600 stars. We compare the time evolution within these simulations to models that begin with mass segregation by combining two different simulated clusters. With a ``hybrid'' of the two dynamical models we perform a comparison to determine what effect joining together simulations has on cluster evolution and our ability to replicate observational data. [Preview Abstract] |
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C1.00005: Detuning Enhanced Cavity Spin Squeezing Yan-Lei Zhang, Chang-Ling Zou, Xu-Bo Zou, Liang Jiang, Guang-Can Guo We have theoretically analyzed the experimental method [1] to squeeze unconditionally the collective spin of an atomic ensemble in a driven optical cavity. We find that strong atom-cavity coupling weakens the spin squeezing and the large detuned laser driving can improve the scaling of spin squeezing to $S^{-2/3}$, which is the ultimate limit of the ideal one-axis twisting spin squeezing. From our numerical solutions and analytical analysis, the large detuning is very important as the squeezing originates from the laser induced spin state dependent geometry phase. We also study the influence of scattering of photon into free space due to imperfect Raman scattering, and demonstrate that the optimal spin squeezing can be obtained with appropriate detuning. This improvement of spin squeezing by detuning is very feasible for experiments, without the requirement of preparation or post-selection of photon state. The detuning enhanced cavity spin squeezing can also be applied to other systems, such as nitrogen-vacancy centers in diamond, to prepare SSS for quantum metrology.\\[4pt] [1] I. D. Leroux, M. H. Schleier-Smith, and V. Vuleti\'{c}, Phys. Rev. lett \textbf{104}, 073602 (2010). [Preview Abstract] |
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C1.00006: Two-axis spin squeezing of two-component BEC via a continuous driving Huang Wen In two-component BEC, the one-axis twisting Hamiltonian leads to spin squeezing with the limitation that scales with the number of atoms as $N^{-\frac{2}{3}}$. We propose a scheme to transform the one-axis twisting Hamiltonian into a two-axis twisting Hamiltonian, resulting in enhanced spin squeezing $\propto N^{-1}$ approaching the Heisenberg limit. Instead of pulse sequences, only one continuous driving field is required to realizing such transforming, thus the scheme is promising for experiment realizations, to an one-axis twisting Hamiltonian. Quantum information processing and quantum metrology may benefit from this method in the future. Besides, our scheme is spin number in- dependent and needs a shorter evolution time compared with [1]. \\[4pt] [1] C. Shen and L. M. Duan, Phys. Rev. A \textbf{87}, 051801 (2013). [Preview Abstract] |
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C1.00007: Using Go-Model Simulation to Capture the Complexity of the $\alpha$-Spectrin Daniel Gavazzi, John Portman The protein $\alpha$-spectrin is composed of a repeating helical structure that can be separated into three domains named R15, R16, and R17. Although each domain is highly homologous, the folding mechanism and kinetics are distinct. Most strikingly, the folding time of R15 is three orders of magnitude larger than R16, with R17 being the slowest. The origin of this wide range of rates has been attributed to roughness in energy landscapes and internal friction. We show that a simple analytic model is able to capture the subtleties of folding each domain, despite their structural similarities. In particular, our model predicts the increasing complexity from R15 to the R16 and R17 domains which explains the kinetic trends seen in experiments. [Preview Abstract] |
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C1.00008: Simulating light propagation in brain tissue using ray tracing Thomas Sauer, Winslow Cotton, Peifang Tian, Anna Devor, Anders Dale, Lana Ruvinskaya, David Boas, Sava Sakadzic The advent of two-photon fluorescence microscopy (TPFM) has opened great opportunities in neurosciences. However, data interpretation of TPFM on dyes with small signal changes such as beta-nicotinamide adenine dinucleotide (NADH) face enormous challenges because the measured signal change is distorted by hemodynamic changes. Prior work by Baraghis et al corrected for this using a single value found empirically. We calculate the point to point correction factor using a 3D microvasculature and check the validity of the single value correction scheme. We use ray tracing scheme to simulate two-photon fluorescence and consider light scattering and absorption due to blood vessels. We calculated the correction factors of NADH signal in a rat model and found that the correction factor was homogeneous beyond 140 microns below the cortical surface, indicating that a single value correction scheme may be adequate in deeper tissues. We will present our new results on a mouse model to test the generality of the single value correction scheme. Our study allows more accurate interpretation of functional imaging studies. [Preview Abstract] |
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C1.00009: Phase diagram for a multi-domain heteropolymer: A computer simulation study Su Latt, Mark Taylor Many biological macromolecules such as proteins and RNA fold into well-defined three-dimensional conformations that are closely related to their function. In this research, we study folding transitions of a simple two-domain heteropolymer chain. The model chain consists of two alternating AB sections (A=square-well sphere, B=hard sphere) linked by a section of B monomers. In this AB model, A-sites act as hydrophobic monomers and B-sites act as hydrophilic monomers. We use Wang-Landau computer simulations to compute the density of states of this model polymer, which allows us to construct the canonical partition function and single chain specific heat. We present a conformational phase diagram for the chain $(AB)_{32}(B)_{10}(AB)_{32}$ as a function of temperature and square-well interaction range. With decreasing temperature the AB-domains undergo simultaneous collapse transitions forming compact rod-like structures with an A-bead (hydrophobic) core and a B-bead (hydrophilic) exterior. There is evidence for a secondary transition in which the two collapsed AB domains join forming a single rod-like structure. For sufficiently long-range interactions there is also a low-temperature freezing transition in which the A-beads form a crystalline disk core with B-bead exterior. [Preview Abstract] |
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C1.00010: GEOMETRIC ENGINEERING, From METAMATERIALS To PLASMID STABILITY Through MULTIFRACTALS Fauzan Faizal-Imaduddin As gauge/group theory inherent with ``geometric engineering'', instead metamaterials are engineered upon its geometrical factor, in effort to resembles ``plasmons in SERS/surface enhanced Raman scattering geometries''-Stefan A. Maier: \textbf{``Plasmonics: Fundamentals {\&} Applications'', }Springer,.., 165, herewith J. Bernstein {\&} AT Hagler: \textbf{``Polymorphism {\&} isomorphism as a tool to study th relationship between Crystal Force {\&} Molecular Conformations''}, \underline {Crystal {\&} Liquid Crystal, }v 50, 1979 retrieved by HE. Mr. Prof. Pantur SILABAN. Ever proven by Arthur Cayley whereas multifractals can be related to the /Gauge/group theory, evolving occurrence in improvement from classical genetics to genetic engineering- RP Elande {\&} SJ Chiang in Ales Prokop, \textit{et.al}(e.):\textbf{''Recombinant DNA technology and Application'', }McGrawHill Inc., 1991, 153 have promising Fusion mechanism not again depends of ``expensive'' Laser- beams. Replace this text with your abstract body. [Preview Abstract] |
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C1.00011: STM study of short chain hydrophobic thiol SAMs on Au capped HOPG under ambient conditions Alexis Bowers, Mackenzie Maurer, Indrajith Senevirathne Self Assembled Monolayer(SAM) surfaces provide common architecture in many device applications including sensor engineering. The conductivity characteristics and surface molecular structure or orientation of these SAMs are important physiochemical properties which are dependent on the surface arrangement. SAMs used in this study are short chain --R terminated (hydrophobic) 1-Butanethiol on thermally annealed Au thin film capped on Highly Oriented Pyrolitic Graphite(HOPG). Scanning Tunneling Microscopy (STM) and contact angle measurements are used to assess the SAM layered surfaces. Solutions of 1-Butanethiol, dissolved in 200 proof Ethanol with 5mM concentration were prepared for the self-assembly process. These solutions were used in developing SAMs on purchased, freshly cleaved HOPG substrates. Au thin films were sputter deposited on HOPG and subsequently annealed. Initial data shows low Au deposition yields rougher inconsistent surfaces. Ambient conditions under which data was obtained impose fresh surfaces for each investigation. Tentative surface structure, consistency and thiol molecular arrangement of the SAM layer on Au capped HOPG will be discussed. [Preview Abstract] |
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C1.00012: Spectral analysis of dynamic scattering mode in nematic liquid crystals James Gleeson, Mansoureh Shasti Dynamic Scattering Mode (DSM) is a switchable, optically cloudy state that has various applications. We study this effect as a means to develop an ultimate application: switchable eyewear to control the transmission of the light. Since our eyes are sensitive to a specific frequency range, we measure the Fourier transform of the signal. Also, calculating the auto-correlation signal gives us this ability to predict the signal in time and see how the scattered signal is correlated in time. [Preview Abstract] |
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C1.00013: Temperature Dependence of Topological Defect in the Twist-Bend Nematic Liquid Crystal Droplets Dispersed in Isotropic Fluid Greta Cukrov, Young-Ki Kim, Oleg D. Lavrentovich We investigate the temperature dependence of topological defect in the liquid crystal droplets exhibiting nematic ($\mbox{N})$ and underlying twist-bend nematic ($\mbox{N}_{\mbox{tb}} )$ phases with a use of polarizing optical microscopy. In this study, we adopt two surface anchoring boundary conditions: 1) tangential (director $\mathbf{\hat{{n}}}$ is parallel to the droplet's surface) and 2) homeotropic ($\mathbf{\hat{{n}}}$ is perpendicular to the droplet's surface). In N phase of the studied material, the droplets with a tangential anchoring possess two point defects, boojums, of strength 1 at the poles, while the ones under a homeotropic condition show a point defect, hedgehog, of strength 1 at the center of the droplets. These defects are normal topological features in the nematic phase. As the temperature $T$ approaches the $\mbox{N}\;\mbox{-}\,\mbox{N}_{\mbox{tb}} $ transition temperature ($T_{\mbox{N-Ntb}} )$, however, the hedgehog in the droplets with a homeotropic anchoring splits into two point defects. As $T$ is lowered further, the split defects move toward the poles of the droplet and are eventually located at poles in the $\mbox{N}_{\mbox{tb}} $ phase. We ascribe the transition to the significant drop of the bend elastic constant $K_{3} $ near $T_{\mbox{N-Ntb}} $. Further experiments are in progress to verify how the intriguing features of the elastic constant in the $\mbox{N}_{\mbox{tb}} $ phase affect the director configuration and topological behavior in the droplets. [Preview Abstract] |
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C1.00014: Mesothermy in the Mesozoic: Mass gain curves in dinosaurs Scott Lee Thermal regulation is an important property of animals. Most extant (i.e., living today) animals use either endothermy (in which the body temperature is kept very close to a certain value) or ectothermy (in which the body temperature varies greatly and can be as low as ambient temperature). In order to maintain their high body temperature, extant endotherms have a much higher metabolic rate than extant ectotherms. This permits endotherms to grow much faster than ectotherms. A small number of extant animals (echidna, leatherback turtles, and certain tuna and sharks) use mesothermy in which their body temperature varies by as large as 10 $^{\circ}$C or is kept warmer than ambient by a certain amount). A model based on conservation of energy is used to determine the growth of extant animals and dinosaurs. Of particular interest is the maximum growth rate of the animal which is correlated with metabolism. Extant animals show that the maximum growth rate is about an order of magnitude higher in endotherms then it is in ectotherms. Maximum growth rates of twenty different dinosaur species are found to be intermediate between extant endotherms and ectotherms. This argues that dinosaurs used mesothermy to regulate their body temperature. [Preview Abstract] |
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C1.00015: A Twist in the Nematic Phase of Mixtures of Achiral Cyanobiphenyl Dimer Mesogens G. Singh, D. Kooijman, M. Fisch, M. Vengatesan, J.K. Song, S. Kumar The twist-bend nematic (N$_{\mathrm{tb}})$ phase characterized by a heliconical structure forms below the regular uniaxial nematic (N) phase in achiral mesogens, CB~(CH$_{2})_{\mathrm{n~}}$CB, constituted of two cyanobiphenyl (CB) moieties connected by a alkyl linkage with odd number $n$ of --CH$_{2}$-- segments. This phase is absent in the homologs with even $n$. The precise structure of the N$_{\mathrm{tb}}$ phase in these and other systems is intriguing and remains under investigation. To gain an insight into the N$_{\mathrm{tb}}$ phase, we studied the pure and mixtures of odd ($n~=$~7) and even ($n~=$~6) homologues using polarizing optical microscopy and high-resolution x-ray diffraction. The latter technique was used to calculate the orientational order parameters $\langle $P$_{2}$(cos$\theta )\rangle $, $\langle $P$_{4}$(cos$\theta )\rangle $, and $\langle $P$_{6}$(cos$\theta )\rangle $ as functions of temperature in the two nematic phases. The results show that order parameter $\langle $P$_{2}\rangle $ and its higher moment $\langle $P$_{4}\rangle $ increase with decreasing temperature in N phase as expected. The value of $\langle $P$_{6}\rangle $ remains relatively small at all temperatures in the two phases. In the N$_{\mathrm{tb}}$ phase, $\langle $P$_{4}\rangle $ decreases and eventually becomes negative. This behavior is consistent with heliconical arrangement of dimer molecules. The phase diagram, temperature-dependent heliconical tilt, and the pitch were measured optically. The behavior of the order parameters qualitatively remains the same in mixtures of CB (CH$_{2})_{7}$ CB and CB (CH$_{2})_{6}$ CB while their values vary with concentration. [Preview Abstract] |
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C1.00016: Stress and Structure Relaxations in Smectic Liquid Crystal Elastomers Dena Mae Agra-Kooijman, Michael Fisch, Wanting Ren, Philip MacMullan, Anselm Griffin, Satyendra Kumar Randomly oriented smectic domains (polydomain) in liquid crystal elastomer orient under uniaxial stress to form an optically monodomain sample. We studied the dynamics of stress relaxation and how it depends on the changes in microscopic elastomer structural during the polydomain to monodomain (PM) transition by x-ray diffraction. The results of stress relaxation data can be well approximated by a double exponential equation, $\sigma $(t) $=$ $\sigma_{1}$exp(-t/$\tau_{1}) \quad + \quad \sigma_{2}$exp (t/$\tau _{2})$ involving short ($\tau_{1}$ $\sim$ 1 min), and long ($\tau_{2})$ relaxation times. The long relaxation time, $\tau $2 is strain dependent and it decreases exponentially from 18 to 10 min with increasing strain. The structural relaxation is well described by a single exponential function with constant, $\tau_{\alpha }$, which is $\sim$ 45 min in the polydomain region, and $\sim$ 8 min in the monodomain state. The difference between the stress and structural relaxations is attributed to the underlying factors involved during the PM transition. The stress relaxation is associated with the slippage of polymer chains, while structural relaxation is attributed to the rotation of the smectic domains. [Preview Abstract] |
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C1.00017: Stability Analysis of Metal Oxide Catalyst Using Computational Method Kwangjin An, Richard Kyung, Terri T. Hahn, Gabor A. Somorjai To actualize green energy in the hydrogenation/dehydrogenation reactions, study on the mechanisms of selectivity and specific analysis on the molecular stability of the product are required. Porous oxide supports and metal nanoparticles can increase catalytic selectivity to obtain desirable products. In this experiment, n-Hexane isomerization as a multipath reaction was carried out over 2.7 nm Pt nanoparticles on five kinds of oxide supports over the temperature range of 240$-$360 $^{\circ}$C in 140 Torr n-hexane and 620 Torr H$_{2}$. Under these reaction conditions, multiple products were generated through four distinct reaction pathways: branched isomers via isomerization, methylcyclopentane and cyclohexane via cyclization, benzene via dehydrogenation of cyclohexane (aromatization), and cracked hydrocarbons with short chains (C1$-$C5) via hydrogenolysis. For the stability analysis, the chemical catalytic efficiency and physical activities of proposed metal oxide compounds are modeled and analyzed using computational simulations. The oxide compounds' chemical and physical properties, such as repulsive forces, electron structures, and bond strengths are studied using computational quantum mechanical modelling method. [Preview Abstract] |
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C1.00018: Circular arrangements of atoms: solving Schr\"{o}dinger's equation for the energy spectrum Matthew Golden, Mellita Caragiu Placing atoms in a circular arrangement enables us to use Schr\"{o}dinger's time-independent equation in combination with specific boundary conditions in order to solve for the system's energy spectrum. In addition, symmetry constraints facilitate the investigation of various configurations of atoms, including the situation in which atoms are of different species. We use MAPLE to represent graphically the solutions of the resulting transcendent equations. [Preview Abstract] |
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C1.00019: Using Metastable Energy States of Lanthanide Metals as Sensors for Radical Oxygen Brendan Graziano Singlet molecular oxygen, the lowest excited state denoted O$_{\mathrm{2}}(^{\mathrm{1}}\Delta_{\mathrm{g}})$, presents a potential hazard as a byproduct of various biochemical reactions. Currently, the best method for detection of singlet oxygen is to monitor its 1240 nm emission, which is not sensitive. Our research examines indirect sensing of this low-lying state through laser-based spectroscopy of lanthanide-ion complexes whose energy levels closely correlate to that of the singlet oxygen. Specifically, tris(tetramethyl heptanedianato) dysprosium(III) has been explored as a potential sensor because of its matching low-energy states and its highly emissive $^{\mathrm{4}}$F$_{\mathrm{9/2}}$ level at 574 nm. Through two-color, time-resolved transient fluorescence, we hope to measure the rate constant for quenching by non-singlet oxygen, effectively making a metastable detector. [Preview Abstract] |
(Author Not Attending)
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C1.00020: Evidence for re-entrant, zero field quantum critical point, with chemical tuning in Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$ Y.P. Singh, D.J. Haney, X.Y. Huang, B.D. White, M.B. Maple, M. Dzero, C.C. Almasan We performed specific heat and electronic transport studies on single crystals of Ce$_{1-x}$Yb$_{x}$CoIn$_{5}$ alloys with the motivation to probe further, some of the previously reported unusual behaviors, such as robust coherence and superconductivity, persistent non-Fermi liquid (NFL) behavior, and the possibility of quantum criticality in higher Yb doping. These measurements are performed in temperatures as low as 0.5 K and magnetic fields up to 14 T. Our analysis of specific heat and resistivity data unveils the presence of a crossover in the properties of x $=$ 0.54 doping crystals, from a high temperature NFL behavior to Fermi-liquid (FL) behavior at lower temperatures. We show that the origin of the NFL behavior is a result of quantum fluctuations. Our analysis also establishes that the alloy with x $=$ 0.54 Yb concentration is quantum critical, i.e., x$_{\mathrm{c}} = $ 0.54. [Preview Abstract] |
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C1.00021: Non-Fermi liquid properties of Ni$_{1-x}$V$_{x}$ close to the disordered ferromagnetic quantum critical point Mitch Powers, Dekrayat Almaalol, Ruizhe Wang, Sean Pavlak, Ted Otieno, Brendan Wyatt, Sara Ubaid-Kassis, Almut Schroeder, Thomas Vojta Resistivity and magnetization data of the d-metal alloy Ni$_{1-x}$V$_{x}$ are presented in the vicinity of the critical Vanadium concentration of $x_{c}\approx $11.6{\%} where the onset of long-range ferromagnetic order is suppressed to zero temperature. The resistivity ($\rho )$ displays power laws in temperature (T) ($\rho $-$\rho_{o}$ $\sim$ T$^{n})$ with non-Fermi liquid values of n(x)\textless 2 close to x$_{c}$. Above x$_{c}$ the dependence of the magnetic susceptibility on T and magnetic field is best described by simple, non-universal, power laws with a Griffiths exponent $\alpha $(x), indicating fluctuating magnetic clusters are still present in the paramagnetic phase. Below x$_{c}$ similar $\alpha $(x) exponents reveal clusters in the FM phase, as well. Both $\alpha $(x) and n(x) vary with x and display a minimum at x$_{c}$. These exponents observed in this disordered quantum phase transition are significantly different than the critical exponents expected for a clean ferromagnet. [Preview Abstract] |
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C1.00022: Evolution of magnetic order in the anisotropic Kondo insulator Ce(Ni,Cu)Sn Adane Gebretsadik, Almut Schroeder, T. Miokovic, R. Vollmer, H. V. Lohneysen, Y. Echizen, T. Takabatake, J. Lynn, G. Aeppli, E. Bucher The characteristic feature of a Kondo insulator is the energy gap forming in the low temperature (T) coherent regime. An example is CeNiSn, which exhibits sharp gaps at particular wave vectors in the magnetic excitation spectrum as observed by neutron scattering and reduced low energy excitations as observed in thermodynamic quantities such as specific heat (C) and magnetic susceptibility ($\chi$) best described in terms of a pseudo gap due to the anisotropic hybridization in this compound. We present C, $\chi$ and neutron data of CeNi$_{1-x}$Cu$_{x}$Sn to see how magnetic order forms in such an anisotropic Kondo insulator upon doping. The magnetic gap seems to have collapsed already for x$=$0.13 as the magnetic correlation have become quasielastic. The long range magnetic order below T$_{N}=$1.4K is described by the same wave vector as the dominant inelastic correlations in x$=$0. For x$=$0.078, $\chi$ (T) shows still a shoulder at 4K reminiscent of a pseudo gap. At lower T, $\chi$ (T) and C(T) exhibit a maximum at T$_{N}=$0.4K indicating magnetic order, confirmed by neutron scattering. The magnetic order occurs at x$_{c}=$0.07 before the gap vanishes at x$_{g}\approx $0.1. The transition at x$_{c}$ shows signs of a disordered quantum phase transition. [Preview Abstract] |
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C1.00023: Electrophoresis and sedimentation of colloidal particles with normal anchoring in cholesteric liquid crystal Taras Turiv, Oleg Lavrentovich We study sedimentation and electrophoresis of dielectric colloidal spheres with homeotropic anchoring through a cholesteric liquid crystal (CLC) with the pitch larger than the particle diameter. The driving force (gravity or the electric field) is applied parallel to the cholesteric axis. The particle follows a helicoidal (rather than linear) trajectory showing the components of velocity that are parallel and perpendicular to the helcioidal axis of the cholesteric. The handedness of the helicoidal trajectory corresponds with the handedness of the cholesteric material. The effect nonzero velocity perpendicular to the cholesteric axis is explained as the result of broken symmetry of the director field around the particle. [Preview Abstract] |
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C1.00024: Fabrication and characterization of bulk heterojunction solar cells Raquel Cossel, Max McIntyre, Marian Tzolov Bulk heterojunction solar cells were fabricated using PCPDTBT and PCDTBT polymers, and PCBM in inert atmosphere. We characterized the devices using current-voltage characteristics, impedance spectroscopy, spectrally resolved photocurrent measurements, optical absorption spectroscopy, and film thickness measurements. We will present results of the open circuit voltage, short circuit current and fill factor of the devices. The impedance data allowed us to determine the existence of very thin depletion region in the solar cells. These data are supported by impedance measurements on structures of very thick films of the same material. The correlation between the photocurrent spectra and the optical absorption allows to conclude that the absorption in the polymer as well as in the PCBM leads to photocurrent generation. We have explored ways to increase the thickness of the polymer films for improved light utilization. [Preview Abstract] |
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C1.00025: Investigating consistency and physical properties of ambient Cr thin-films on different substrate support Daniel Turner, Indrajith Senevirathne Study of adhesion, consistency and structure of multilayer, noble/wider-refractory metallic films are increasingly important industry and surface engineering/physics. In this study Cr/substrate thin-films are studied for their consistency and structure. Soda lime glass and polycrystalline quartz were used for substrate support. Substrates were removed of organic impurities. Typical Cr depositions on substrates above shown to give rise to Stranski - Krastanov (SK) like growth. Cr was thermally evaporated with varying thicknesses of 85nm - 145nm. These systems were investigated without annealing via Scanning Electron Microscopy (SEM) to examine the surface consistency and possible oxidization. Further, the ambient contamination, elemental composition and thermal diffusion were investigated via Energy Dispersive X-ray spectroscopy (EDX). Cr film has a high affinity to ambient Oxygen and shown to form jagged distributed surface irregularities. These were observed to be dependent on substrate consistency/uniformity and the degree of initial contamination. [Preview Abstract] |
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C1.00026: Nanopowder Synthesis and Characterization of Bismuth Telluride Nanoparticles for Prospective Thermoelectric Materials Zachary S. Bukszar, Paul C. Challen, C. Virgil Solomon, Jeffrey S. Dyck The demand for high efficiency thermoelectric devices is on the rise as they provide a means for clean renewable energy. Bismuth telluride (Bi$_{2}$Te$_{3})$ is an efficient room temperature thermoelectric material that can be synthesized through scalable bottom-up wet-chemical methods. In this study, nanocrystal growth is accomplished through microwave stimulation of organically dissolved bismuth and tellurium precursors within reaction times on the scale of two minutes. The use of this method helps in achieving commercial viability due to the low time and energy costs required. The aim of our studies has been to synthesize nanocrystalline Bi$_{2}$Te$_{3}$, and characterize the nanoparticles by Inductively Coupled Plasma Spectroscopy (ICP-OES), Powder X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). By altering stoichiometric ratios of tellurium/bismuth in the precursor solutions, we obtain different product stoichiometries that could be understood to fit within the infinitely adaptive series (Bi$_{2})$m(Bi$_{2}$Te$_{3})$n. With appropriate choice of concentration for precursor solutions we obtain fairly pure Bi$_{2}$Te$_{3}$. The structure shown through SEM and XRD corresponds to $\sim$ 10nm thick hexagonal platelets of Bi$_{2}$Te$_{3}$ with the possibility of Bi$_{2}$ blocks integrating themselves into the structure as the ratio of m:n increases. [Preview Abstract] |
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C1.00027: Modeling Thermal Conductivity of Organic-Inorganic Hybrid Perovskite Methylamine Lead Iodide Gage T. Marek, Anton Kovalsky, Lili Wang, Clemens Burda, Jeffrey S. Dyck Organic-Inorganic hybrid Perovskite Methylamine Lead Iodide (CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}})$ is being studied for its promise as high quality photovoltaic material. This material provides advantages like the use of inexpensive base materials, similar manufacturing to modern thin-film materials, and has shown relatively high conversion efficiency of 16{\%}. For use in real world application the effect of radiant heat from the sun cannot be ignored as it has profound effects on output efficiency due to thermally-induced structural degradation, and photovoltage reduction. Thermal conductivity measurements on dense, pressed pellets of polycrystalline CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$ were taken over the temperature range 10-300K, and extremely low thermal conductivity values were found. It is a compelling question whether or not the local vibrational modes of the methylamine ion are responsible for the low thermal conductivity. The data were compared to a simple model of the lattice thermal conductivity that takes into account various mechanisms of phonon scattering. We find that we obtain excellent fits of the data to the model by taking into account only point defect, grain boundary, and three-phonon Umklapp scattering. In particular, we do not find that it is necessary to include resonant phonon scattering due to the methylamine ion. [Preview Abstract] |
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C1.00028: Strategy to study Nucleation and Growth of Nanoparticles using Plasmon Absorbance of Au and Ag Narayan Sharma, Amit Acharya, Prakash Adhikari Noble metallic nanoparticles show interesting absorbance and scattering properties due to Plasmon resonance which occur when their electron density interact with the incident electromagnetic radiation of wavelength that are far larger than the particle size. Due to these properties, such nanoparticles have been the subject of interest for researchers around the world. Here, we present a method that can experimentally show nucleation and growth of nanoparticles merely by looking at the Plasmon absorbance profile. Gold nanoparticles of nearly 5 nm sizes was synthesized and silver shell was grown over gold under different conditions. The choice of gold and silver nanoparticles in this experiment lies on the fact that these two nanoparticles have very similar lattices while their Plasmon absorbance peaks are at different wavelengths. The eventual goal of this work is to develop an experimental strategy for monitoring the time-dependent monomer concentration during the hot-injection synthesis of Ag nanoparticles. [Preview Abstract] |
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C1.00029: Electrical Characterization of Be-Doped InAs/InAsSb Superlattices Henry Bourassa, Arthur Siwecki, Mo Ahoujja, Said Elhamri, Elizabeth Steenbergen, William Mitchel, Shin Mou, Gail Brown The InAs/InAsSb type-II superlattice materials studied to date for infrared detector applications have been residually n-type, but p-type absorber regions with minority carrier electrons can result in increased photodiode quantum efficiency, R$_{\mathrm{o}}$A, and detectivity. Therefore, Be-doped InAs/InAsSb superlattices were investigated to determine the p-type InAs/InAsSb superlattice material transport properties essential to developing high quality photodiode absorber materials. Hall measurements performed at 10K revealed that the superlattice converted to p-type with Be-doping of 3 x10$^{\mathrm{16}}$ cm$^{\mathrm{-3}}$ and the hole mobility reached 24 400 cm$^{\mathrm{2}}$/Vs. Photoresponse measurements at 10K confirmed the 175 meV bandgap and material optical quality. [Preview Abstract] |
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C1.00030: Impact of the substrate on the transport parameters of InAs/In$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$Sb Superlattices Arthur Siwecki, Henry Bourassa, R. Berney, Mo Ahoujja, Said Elhamri, William Mitchel, Heather Haugan, Shin Mou, Gail Brown It is shown that n-type InAs/InGaSb superlattices can be electrically isolated from lightly doped n-type GaSb substrates at much higher temperatures than from the more common p-type GaSb substrates without the use of a large bandgap insulating layer. Transport measurements show superlattice conduction up to near room temperature. It is argued that the isolation is due to the n/p/n junction created by the substrate/buffer layer superlattice structure. [Preview Abstract] |
(Author Not Attending)
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C1.00031: Crystal modification and preferred orientation studies of 1,$\omega $-alkanediols ($\omega =$10-13) obtained from rapid glancing incidence X-ray diffraction experiments Gilgamesh Luis-Raya, Marius Ram\'Irez-Cardona, Eucario G. P\'erez-P\'erez, Nazario Bautista-Elivar, Luis Alberto Zamora-Campos, Francisco Marroqu\'In-Guti\'errez The crystal structure determination of four polycrystalline samples of 1,$\omega $-alkanediols (CnH2n$+$2O2 with n $=$ 10, 11, 12 ,13) was achieved from Glancing Incidence X-ray Diffraction (GIXD) data by combining lattice energy optimization, molecular replacement and rigid-body structural Rietveld refinements. The occurrence of either monoclinic (P21/c, Z$=$2) or orthorombic (P212121, Z$=$4) polymorphs is explained as function of a constant hydrogen bond energy (28.5 kJ/mol per molecule) in the series, the differences on hydrogen patterns and the different herringbone grade on the bilayer arrangement. From a multi-axial March-Dollase treatment, energetic and structural features yield remarkably differences on the textural behavior as well as on morphology of crystallites. In this work we show that crystalline structures of medium complexity and their microstructures can be solved from short counting times of GIXD experiments from standard radiation, and a molecular replacement procedure using crystal structures of compounds with higher chain lengths as reference data. [Preview Abstract] |
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C1.00032: Calibration Aspects of STAR experiment's Heavy Flavor Tracker (HFT) Ayman Hamad The Heavy Flavor Tracker (HFT[1]) is a silicon detector in the STAR experiment at RHIC. It consists of three subsystems and four layers of silicon detectors. The heart of the system is the two inner layers of PXL (pixel) detector. The PXL uses ultra thin sensors 50 microns with 20x20 microns active pixel MAPS (Monolithic Active Pixel Sensors) technology. The air-cooled lightweight pixel detector is surrounded by two subsystems; the SSD (Silicon Strip Detector) and IST (Intermediate Silicon Tracker). These two layers of silicon help us interface and connect the PXL hits to the Time Projection Chamber (TPC) tracks. The full system is capable of a track pointing (DCA) resolution of about 30 microns for 1 GeV/c pions. In Spring-2014 the HFT system had its first physics run with Au$+$Au collisions at 200 GeV/c. In this poster we report on several performance and calibrations efforts like masking, alignment and track pointing resolution. \\[4pt] [1] STAR Heavy Flavor Tracker Technical Design Report: ~https://drupal.star.bnl.gov/STAR/starnotes/public/sn0600~ [Preview Abstract] |
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C1.00033: A Group Theoretic Development of Isospin and Low Isospin Multiplets Ashley Ernst The concept of isospin~is developed using second quantization creation/annihilation operators forming the su(3) Lie algebra. Isospin is then applied using direct sum decomposition of Kronecker products to three isospin systems. [Preview Abstract] |
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C1.00034: Experimental characterization of the plasma sheath using two dust particles Nicholas R. Weiner, T.E. Sheridan Plasma is an ionized gas that exhibits long-range particle-particle interactions which are manifested in collective behavior such as the plasma sheath. The plasma sheath is the boundary layer between plasma and a material wall. The sheath has a large electric field that confines highly mobile electrons and forces positively charged ions out of the plasma. For a horizontal electrode, the sheath's upward electric force can balance the weight of small dust particles and cause them to levitate near the sheath-plasma interface. The motion of these levitating particles can be used to characterize the plasma sheath. A rectangular depression placed on an rf-powered electrode has been used to create a plasma sheath. Two dust particles were trapped in the plasma sheath and the normal mode frequencies of the two-particle cluster allow us to determine the ellipticity of the sheath edge, the Debye length, the dust charge and the vertical electric field. [Preview Abstract] |
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C1.00035: Exploration of stable, metastable and unstable configuration states of dust clusters Andrew A. Kurtz, T.E. Sheridan A small number of identical dust particles are confined in a two-dimensional biharmonic well inside an electron-ion plasma. In steady state, the dust particles form a strongly-coupled elliptical cluster. Clusters are heated by a quick change in the plasma density and then cool rapidly, leading to configuration states that may be stable, metastable or unstable. We directly observe the relaxation of unstable states to equilibria. We will compare observed configuration states to computed states and look for qualitatively different regimes as a function of dust particle number and potential well anisotropy. [Preview Abstract] |
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C1.00036: Experimental measurement of plasma sheath overlap T.E. Sheridan The plasma sheath is the boundary layer that separates a plasma from a surface such as an electrode or wall. The sheath adjacent to a large flat surface has a characteristic width $s_0$, which is the planar sheath width. If the surface has a step of height $d$, then some length scale $t_0$ describes the lateral transition at the sheath edge from one level to the other. Two parallel steps separated by a distance $W$ form a trench. When $W < t_0$, we expect that the sheaths from the two steps overlap and the sheath is pushed out of the trench. We have measured sheath overlap for a trench with variable width $W$ using a two dust particles. The dust particles float at the sheath edge, so their height above the electrode gives a quantitative measure of the sheath width. When $W\gg s_0$ the cluster height is independent of $W$. When $W < s_0$ the dust particles move upward, indicating that sheath overlap is occurring. [Preview Abstract] |
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C1.00037: Synchronization of Huygens' Clocks: An Elementary Treatment Ulrich Zurcher, Laura Karle, Andrew Slfikin Huygens proposed a general model to explain the synchronization of two oscillators. We describe synchronization of two pendulums mounted on a cart. The cart moves along the horizontal: the motion is damped. We show that the principle of conservation of momentum can be used to describe an escapement mechanism. Simple graphical methods are used to show that the motion of the two pendulums can be described in terms of a symmetric and anti-symmetric ``mode.' We quantify the damping of the pendulums and show that the two modes are described by two different damping constants. We discuss that this property explains why only the anti-symmetric mode ``survives'' for long time; i.e., the two pendulums are synchronized. We discuss direction for future investigation. [Preview Abstract] |
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C1.00038: Novel Photo- patterning of Organic Semiconductors Shiyi Liu, Akram Al-shadeedi, Bj\"orn L\"ussem Charge carrier mobility in organic semiconductors (OSCs) has been increased significantly over the last decade. Recently, a carrier mobility up to 43 cm$^{2}$/Vs was reported by Yongbo et al [Yuan, Yongbo, et al, \textit{Nature communications}~5:3005 (2014)]. Despite this increase in charge carrier mobility, high- resolution patterning of organic semiconductors is still challenging. Here we report on a novel patterning method---Double Layer Lithography (DLL) based on optical lithography and dry chemical etching. Recently, a set of fluorinated photoresist system was developed, which is compatible with most organic materials [Zakhidov, AlA., et al. \textit{Advanced Materials} 20 (2008), 3481], thus open the possibility to utilize optical lithography to achieve high- resolution patterning and high yield of devices. Introducing protection layers in the process, we are able to pattern the structures using dry chemical etching, which provides reliable and fast pattern transfer and allows for large- scale integrated circuits. To demonstrate the versatility of the DLL method, we will discuss OFETs based on pentacene and DNTT. Despite the dry etching step, high charge carrier mobility and low hysteresis of the transfer characteristic are obtained. Due to the high yield, we are able to extract the contact resistance of the DNTT based OFETs with high precision. The DLL structuring method developed by us is a key technology for the development of novel organic device concepts. In particular the high yield and reproducibility will allow for building more reliable and powerful organic transistors and to integrate them into larger circuits. [Preview Abstract] |
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C1.00039: Doped Ambipolar Organic Field-Effect Transistors Akram Al-shadeedi, Shiyi Liu, Scott Bunge, Bj\"orn L\"ussem Organic doping leads to significantly improved performance of organic devices such as organic light emitting diodes (OLEDs) and organic solar cells. Doping improves the injection of charge carriers into organic semiconductors and significantly increases the conductivity of organic layers, which allows for the design OLEDs operating at very low voltages and high power efficiency. Doping in organic transistors is more seldom used, but first studies show that it will be highly beneficial here as well. In this contribution, we show for the first time that organic ambipolar transistors can be realized by doping the contact and channel region of organic field-effect transistors (OFETs). The OFETs consist of pentacene as a matrix material, insulating tetratetracontance (TTC) as passivation layer, and Al2O3 as gate oxide. The source and drain regions are doped by the n-dopant W2(hpp)4 to improve carrier injection. Furthermore, the channel region is slightly doped (1wt{\%}) by the same dopant. The results discussed in this contribution open a new approach to design and optimize organic circuits. As an example, the design of an organic inverter consisting of two doped OFETs layers will be discussed and it will be shown that the switching voltage of the inverter can be precisely controlled by the doping ratio in the organic channel. [Preview Abstract] |
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C1.00040: Restoration of a Scanning Electron Microscope for Undergraduate Research Joseph Andler, Dennis Kuhl We report on the rehabilitation of an ETEC Autoscan Scanning Electron Microscope for use in undergraduate research. The production, measurement, and control of high vacuum and electron beams are discussed. General troubleshooting techniques for specific equipment such as pneumatic valves, mechanical and diffusion pumps, and thermocouple and ion gauges are investigated. [Preview Abstract] |
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C1.00041: A Comparative Study of Dwarf Spherical Galaxy Evolution Utilizing Newtonian, Dark Matter and MONDian Theory Matthew Walentosky, Benjamin Blankartz, Stephen Alexander Modified Newtonian Dynamics (MOND) is the only viable alternative to the dark matter paradigm to explain the observed speed discrepancies of stars in spiral galaxies. Originally proposed by Mordehai Milgrom, this alternative theory to dark matter proposes that at extremely low accelerations, Newtonian gravity requires slight modifications to Newton's Second Law. While the theory of dark matter is currently the most widely accepted theory in explaining the missing mass phenomenon, MOND's success at predicting rotation curves of spiral galaxies cannot be ignored and thus must be investigated further. We present numerical simulations of dwarf spherical galaxies similar in properties to those orbiting our own Milky Way galaxy and provide side-by-side comparisons when Newtonian, Dark Matter and MOND physics are applied to the same galaxy. The results of this study have potential implications on the understudied topic of tidal effects acting on dwarf spherical galaxies. [Preview Abstract] |
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C1.00042: Pressure dependences of the vibrational modes of crystalline adenosine as studied by infrared spectroscopy Carl Starkey, Scott Lee The vibrational modes of nucleic acids are of great interest since some of them are believed to be involved in the conformational transitions of DNA. We report the pressure dependences of the infrared-active vibrational modes of crystalline adenosine up to pressures above 9 GPa. In order to provide information about the eigenvectors of the vibrational modes, we evaluate the logarithmic derivatives with respect to pressure of these modes. Some of the hydrogen-stretching modes show a negative pressure derivative, indicating a weakening of the molecular bond as the hydrogen bond strengthens. The results are used to shed light on the conformational transitions of DNA. [Preview Abstract] |
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