Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session S1: Poster Session III (1:00 pm - 4:00 pm) |
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Room: Exhibit CD |
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S1.00001: POLYMER AND SOFTER MATTER PHYSICS II |
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S1.00002: Origin of translocation barriers for polyelectrolyte chains Rajeev Kumar, Murugappan Muthukumar For single-file translocations of a charged macromolecule through a narrow pore, the crucial step of arrival of an end at the pore suffers from free energy barriers, arising from changes in intrachain electrostatic interaction, distribution of ionic clouds and solvent molecules, and conformational entropy of the chain. All contributing factors to the barrier in the initial stage of translocation are evaluated by using the self-consistent field theory for the polyelectrolyte and the coupled Poisson-Boltzmann description for ions, without radial symmetry. The barrier is found to be essentially entropic, due to conformational changes. For moderate and high salt concentrations, the barriers for the polyelectrolyte chain are quantitatively equivalent to that of uncharged self-avoiding walks. Electrostatic effects are shown to increase the free energy barriers, but only slightly. The degree of ionization, electrostatic interaction strength, decreasing salt concentration and the solvent quality all result in increases in the barrier. [Preview Abstract] |
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S1.00003: The complex band perspective of self-localization in conducting polymers Qing Lu, Minghai Li, Lauren O'Malley, Xi Lin The complex band is an extension of the conventional band structure to allow Bloch wavevector being a complex number, so that energy becomes a continuous function of the complex wavevector. Imaginary wavevectors mark the characteristic wavefunction decay rate for those states existing in the forbidden gaps, and thus provide the localization perspective of these defect states. This view, however, has been rarely discussed concerning of self-localized solitons and polarons in conducting polymers. In this work, we use the Su-Schrieffer-Heeger (SSH) model and its extended model to compute the complex band structures of the defect-free \textit{trans}-polyacetylene ($t$-PA) and poly-(p-phenylene-vinylene) (PPV) chains, respectively. We find the complex wavevectors predicted by the complex band structure computations agree excellently with the decay rates of the soliton wavefunction in $t$-PA and the bipolaron wavefunction in PPV. From this complex band perspective, our recently revealed multiple self-localized electronic states induced by either the electron correlation or the Peierls twin instability can be easily understood. [Preview Abstract] |
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S1.00004: Morphologies in Sulfonated Styrenic Pentablock Copolymer Membranes Jae-Hong Choi, Matt Bramson, Karen I. Winey Membranes of pentablock and triblock copolymers consisting of poly(\textit{tert}-butyl styrene) (TBS), hydrogenated polyisoprene (HI), and partially sulfonated poly(styrene-\textit{ran}-styrene sulfonate) (SS) were studied using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The TBS-HI-SS-HI-TBS pentablock and TBS-HI-SS triblock copolymer membranes exhibit anisotropic microphase separated morphologies. Because the pentablock and triblock copolymers can be expected to have complex morphologies, thermal annealing was conducted to promote well-defined morphologies. The annealed membranes exhibit stronger peaks and more high order reflections in SAXS patterns, as well as better defined microstructures in the TEM. Electron microcopy studies with various staining protocols are underway to establish the morphology of the pentablock copolymer membranes including the size and shape of the three microdomains (TBS, HI and SS). We gratefully acknowledge Kraton Polymers, Inc. for materials. [Preview Abstract] |
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S1.00005: Effect of the Electrostatic Interactions on Stretching of Semiflexible and Biological Polyelectrolytes Jan-Michael Carrillo, Andrey Dobrynin Using combination of the molecular dynamics simulations and theoretical calculations we have shown that the bending rigidity of biological and semiflexible polyelectrolytes is force dependent. The effective chain bending rigidity decreases with increasing the value of the applied force. At small and intermediate force magnitudes a semiflexible polyelectrolyte behaves similar to a neutral chain with the effective bending rigidity equal to the sum of the bare chain and electrostatic bending rigidities which has a well known Odijk-Skolnick-Fixman (OSF) form with a quadratic dependence on the Debye radius. However, in the limit of the large forces when the magnitude of the applied force exceeds an electrostatic force responsible for the local chain stretching the effective chain's bending rigidity is determined by the bare chain's elastic properties. This dependence is a result of the scale dependent effect of the electrostatic interactions on the chain bending and elastic properties that can be approximated by two characteristic length scales. One describes the chain's elasticity at the distances along the polymer backbone shorter than the Debye radius while another controls the long-scale chain's orientational correlations. By stretching a semiflexible polyelectrolyte one probes different chain's deformation modes. [Preview Abstract] |
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S1.00006: Peptide and micelle morphologies in ionic liquid Ashley Montgomery, Sandeep Naik, Jacob Ray, Daniel Savin Ionic liquids (ILs) are considered ``green'' solvents that have shown interesting properties in polymeric solutions; however, potential screening effects in polyelectrolytes remain largely unexplored. These studies intend to compare the solution behavior of traditional polyelectrolytes like poly(styrene sulfonate) in ionic liquid and water. This will be extended into charged polypeptides such as poly(L-lysine) (PK) and PK-containing block copolymers. In particular, we are interested in the solution chain dimensions and secondary structure of the polypeptide and how it can potentially influence micelle morphologies in ionic liquids. Circular dichroism, dynamic light scattering and electron microscopy were used for characterization of peptide secondary structure and aggregate morphology respectively. The aggregation in ionic liquids will be compared with their aqueous counterparts. [Preview Abstract] |
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S1.00007: Stimuli-responsive polypeptide-based triblock copolymers Jacob Ray, Sandeep Naik, Daniel Savin Stimuli-responsive copolymers demonstrate diverse aggregation behavior in aqueous solution, where the molecular architecture and hydrophilic/hydrophobic content influences morphology. The solution morphology of poly(lysine)-b-poly(propylene oxide)-b-poly(lysine) (KPK) triblock copolymers with high lysine content ($>$ 75 wt.\%) will be compared with complementary KP diblock copolymers in the same phase range. Light scattering and TEM were used to determine aggregate size and morphology as a function of pH and temperature; furthermore, circular dichroism was used to measure helix-to-coil transitions of the K blocks. PK diblocks in this composition range yield spherical micelles over the entire pH range whereas KPK systems appear to exhibit morphological transitions with changing pH. [Preview Abstract] |
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S1.00008: Morphological and physical behavior of styrenic, phosphonium-containing ionomers Rick Beyer, Kristoffer Stokes Despite many years of effort, a clear understanding of the factors controlling morphology in Nafion and other ionomers has not been achieved. The increasing need for fuel cell technology continues to drive efforts to develop materials having better performance characteristics even though fundamental structure-property relationships remain unclarified. Alkaline fuel cells (AFCs) present several benefits over proton exchange membrane (PEM) fuel cells, including cost of manufacture (less expensive catalysts) and a significantly shorter path to commercialization. Here we present the most recent findings from our efforts to examine structure-morphology-property relationships for a series of model cationic ionomers. A series of statistical copolymers of styrene and p-vinylbenzyl-trimethyl-phosphonium chloride have been prepared via RAFT polymerization, allowing us to investigate the effect of ion content on physical behavior. Chemical, physical, and morphological characterization has been undertaken using NMR, TGA, DSC, SAXS, and TEM. [Preview Abstract] |
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S1.00009: \textit{p}H-Triggered ``Explosions'' of Dually Responsive Polymer Micelles: Solutions \textit{versus} Surfaces Svetlana Sukhishvili, Li Xu, Oleg Borisov, Ekaterina Zhulina We report on a $p$H-induced micelle-to-micelle phase transition of dually pH- and temperature-responsive spherical block copolymer micelles (BCMs) with weak polyelectrolyte coronae in solutions and at surfaces. In solutions, dynamic and static light scattering confirmed that sharp changes in micellar hydrodynamic size and aggregation number occur in a narrow $p$H range, $\Delta p$H $<$ 0.1. In agreement with theory, $\zeta $-potential measurements indicated an abrupt change in ionization of polymer chains in the micellar corona at the transition $p$H. At surfaces, monolayers of adsorbed micelles retained their inherent $p$H and temperature response properties, but in contrast to solution, the monolayer response was irreversible. Self-assembly of BCMs with polyanions inhibited the pH-induced transition, while self-assembled films showed reversible, temperature-induced swelling transitions. [Preview Abstract] |
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S1.00010: Variable pressure NMR self-diffusion studies of fuel cell polymer electrolyte membrane Bruno Pinto, Jaime Farrington, Phil Stallworth, Steve Greenbaum The purpose of this study is to characterize water diffusion in polymer electrolyte membranes for hydrogen fuel cell applications under varying temperature and pressure. Measurement of the diffusion coefficient is accomplished by performing an NMR spin echo sequence in a large static magnetic field gradient. Variable pressure measurements allow the evaluation of the activation volume, which yields insight to the water mobility and proton conduction mechanism. Measurements were performed on NAFION {\textregistered} samples containing different levels of nanoscopic tin dioxide (SnO2) with water content of 10{\%} and 25 {\%} by mass. Results show that pressure has a larger effect on the sample with 10{\%} water content, as demonstrated by a larger activation volume, than the 25{\%} hydrated samples. This suggests that polymer segmental motion is involved in water molecular transport at lower water content. The effect of SnO2 content on activation volume will also be presented. [Preview Abstract] |
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S1.00011: None-Affine Multiaxial Deformation of Polymer Networks Nikolay Oskolkov, Sergei Panyukov, Michael Rubinstein We develop a theory of multiaxial deformation of polymer network based on the non-affine slip-tube model of rubber elasticity. The effect of entanglements on a network strand is represented through a constraining potential (tube), which changes with network deformation. In addition, the stored length of network chains is allowed to redistribute between different directions along the contour of the tube upon multiaxial deformation. The dependence of stress on strain is calculated and compared with experimental data. [Preview Abstract] |
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S1.00012: Polyelectrolytes in electric fields: An explicit solvent simulation study Hongjun Liu, Edward Maginn, Y. Elaine Zhu We use a coarse-grained molecular dynamics model to study the electrophoretic behavior of a flexible polyelectrolyte chain in a salt-free solution. The explicit solvent is used to recover the hydrodynamic interaction. Our results show the an excellence correspondence of simulation to experimental observations when the hydrodynamic interaction is considered. Electrophoretic mobility increases with the increasing chain length, passes through a maximum and reaches a plateau for the long polymers. Effective charge and effective friction are also investigated to provide the physical insight. [Preview Abstract] |
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S1.00013: Kinetic Monte Carlo Simulation of Cation Diffusion in Yttria-Stabilized Zirconia Brian Good Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating. In such an application, the inhibition of oxygen diffusion is a major concern, and this issue has been addressed via molecular dynamics and kinetic Monte Carlo simulation. However, the mechanical integrity of such coatings can be affected by processes involving diffusive motion on the cation lattice. In this work, we perform kinetic Monte Carlo simulations to investigate cation diffusion in YSZ. We obtain diffusive migration barrier energies ab initio calculations; these barriers are considerably larger than those for oxygen diffusion, and consequently the calculated cation diffusivities are much smaller than oxygen diffusivities from earlier KMC simulations. We report on the effects on cation diffusivity of cation sublattice vacancy concentration, and of Y concentration (and the related oxygen vacancy concentration). [Preview Abstract] |
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S1.00014: Theory of self-healing polymer networks with reversible bonding Evgeny Stukalin, Arun Kumar N, Ludwik Leibler, Michael Rubinstein The polymer networks formed by reversible bonds, e.g., hydrogen bonds, feature the striking ability to restore their structural integrity after damage. This self-healing effect is sustainable following an appreciable waiting time after the fracture. The ability of these polymers to self-repair is attributed to very slow decay of non-equilibrium concentration of broken bonds during the waiting time followed by an efficient re-formation of bonds across the interface after two fractured surfaces are brought into contact. This process is distinct form self-adhesion which proceeds at equilibrium (very low) density of broken bonds. By means of analytical theories and scaling arguments we study the reaction kinetics of polymer chain systems that can form reversible bonds. The importance of anomalous diffusive motions of ``stickers'' as portions of dangling chains and reaction kinetics of bonding events including renormalization of bond lifetime and sticker partner exchange have been established for the self-healing process. Theoretical modeling that maps the results of MD/MC simulations onto kinetic models are used to capture the self-healing mechanism and its dynamics. [Preview Abstract] |
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S1.00015: Random networks of cross-linked directed polymers Panayotis Benetatos, Stephan Ulrich, Annette Zippelius We consider a system of directed polymers confined between two planes with their end-points free to slide on them and we introduce random permanent cross-links. We treat the cross-links as quenched disorder and we use a semimicroscopic replica field theory to study the structure and elasticity of this system. Starting from the sol phase and increasing the cross-link density, we get a continuous gelation transition signaled by the emergence of a finite in-plane localization length. The distribution of localization length turns out to depend on the height along the preferred direction of the directed polymers. The gelation transition also gives rise to a finite in-plane shear modulus which we calculate and turns out to be universal, i.e., independent of the energy and length scales of the polymers and the cross-links. Using a symmetry argument, we show that cross-links of negligible extent along the preferred axis of the directed polymers do not cause any renormalization to the tilt modulus of the un- cross-linked system. [Preview Abstract] |
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S1.00016: Improving self-healing behavior of dually cross linked nanogels that encompass nanoparticles Solomon Duki, German Kolmakov, Krzysztof Matyjaszewski, Anna Balazs Numerical studies of nanogels that are cross-linked by stable and labile bonds have shown that the material can withstand significantly high stresses before it undergoes fracture. The mechanical integrity of such materials is preserved through structural rearrangement of the nanogel particles; this structural rearrangement is facilitated by the making and breaking of the labile bonds. Apart from the bond properties, the stiffness and flexibility of the nanogel is crucial to determine the mechanical properties of these self healing novel materials. Our simulations show that the mechanical property of the entire sample is significantly improved by introducing hard core nanoparticles into the structural units. Through numerical modeling of hard core-soft shell nanogel material we identify the region of parameters (the nanogel size and core/shell ratio) at which the sample demonstrates optimal stability and self-healing behavior. [Preview Abstract] |
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S1.00017: Stiffening, Fracture, and Friction of Physically Associating Networks by Shear Rheometry Kendra A. Erk, Kenneth R. Shull The mechanical strength, toughness, and frictional properties of soft viscoelastic networks are characterized with shear rheometry. A physically associating acrylic triblock copolymer solution is utilized as a model system. At elevated temperatures these solutions are viscoelastic liquids with near Maxwellian relaxation. The relaxation time increases dramatically as temperature is reduced, such that at room temperature the solutions effectively become viscoelastic networks. When deformed over a range of shear rates, these networks demonstrate elastically driven behavior that can be quantified via rheometry and modeled with an exponential strain energy function. During fast deformation (i.e.,Weissenberg number, Wi, greater than unity), strain-stiffening followed by softening is observed, reminiscent of fluid fracture. At decreased rates (Wi less than unity), evidence of viscoelastic- and liquid-like instabilities is observed. Additionally, post-fracture stress plateaus are found to be related to the frictional stress at the sliding fracture-like interface. [Preview Abstract] |
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S1.00018: Study on hierarchical structure of polyethylene under uniaxial stretch by using USAXS, SAXS and WAXS Sumiaki Fujii, Shotaro Nishitsuji, Mikihito Takenaka, Hirokazu Hasegawa In this study, we have investigated the structural changes of two kind of linear low density polyethylene (LLDPE) under uniaxial stretch in the order of submicron by using two-dimensional ultra small angle X-ray scattering (2D-USAXS) ,to nm scale small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) Before stretch, the density fluctuations exist in the order of submicron scale. The circular-averaged scattering profiles of both samples exhibit the power-law behaviours of $q$ as mass fractal properties. 2D-USAXS pattern of LLD-a, which has higher molecular weight than LLD-b after stretch is elongated perpendicular to the stretch direction. This change is caused by the elongation of the branch structures homogeneously. The pattern of LLD-b after stretch has been elongated parallel to stretch direction, and exhibit butterfly pattern It is known that the heterogeneous deformation associating with deformation causes this pattern. The difference in structural change between two samples originates from the difference in the molecular weight. However they show same tendency in SAXS and WAXS regions [Preview Abstract] |
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S1.00019: Melting and Crystalline Properties of Isotactic Poly(propylenes) with 1,3 Defects Carolina Ruiz-Orta, Juan P. Fernandez-Blazquez, Rufina G. Alamo, Amelia M. Anderson, Geoffrey W. Coates Polypropylenes synthesized with a chiral diimine Ni(II) catalyst and MAO produce isotactic poly(propylenes) with random 1,3 enchainments and offer the opportunity to study the effect of this defect on iPP crystallization in reference to the effect given by 1-alkene comonomers. The type and content of 1,3 insertions was obtained from high resolution 13 C NMR spectra. Both, the 1,3 insertion and the ethylene comonomer add similar methylene sequences to the isotactic iPP chain; however, iPP with isolated 1,3 defects melt and crystallize at lower temperatures than matched propylene ethylene copolymers. The melting behavior is similar to propylene 1-octene copolymers, reflecting the exclusion of the 1,3 defect from the crystals. Compared to copolymers with 1-octene or 1-hexene units, the methylene enchainment and change in chirality caused by the 1,3 defect leads to a lower degree of crystallinity and different polymorphic behavior. [Preview Abstract] |
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S1.00020: Real-Time FTIR Spectroscopic Study of the Crystallization Process of Random Isotactic Propylene-1-Alkene Copolymers Rufina G. Alamo, Juan P. Fernandez-Blazquez, Eduardo Pereira, Carolina Ruiz-Orta The real-time evolution of IR regularity bands during isothermal crystallization of random propylene copolymers confirm the beginning of crystallization at a critical helical sequence length (n*) of about 12 isotactic units, corresponding to a vibrational frequency of 841 cm-1. The evolution with time of concentration of helical sequences below and above n* allows to infer the details of helical organization at the early stages of crystallization. The concentration of helices of 10 isotactic units prior start of crystallization is at equilibrium. When spatial fluctuations of these helices allow the formation of a critical nucleus, growth to longer helices proceeds spontaneously, as indicated by identical kinetics of the 998 (n = 10), 841 (n = 12) and 1220 ( n $>$ 12) cm-1 bands. Furthermore, their final value correlates with the degree of crystallinity obtained by WAXD. All comonomer types hinder the formation of iPP helical sequences as observed by the strong decrease of concentration of helices $<$ n* with increasing comonomer content before crystallization is arrested. Comonomers that disrupt the TG conformational regularity, such as the ethylene unit, require a different IR-WAXD crystallinity calibration. [Preview Abstract] |
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S1.00021: Effect of crystalline form on phase transformation kinetics of poly(l-lactic acid) Jeffrey Kalish, Shaw Ling Hsu Films of poly(l-lactic acid) (PLLA) were crystallized from the amorphous solid phase at various temperatures. At crystallization temperatures lower than 120$^{\circ}$C, the disordered alpha' phase appears, but at crystallization temperatures greater than 120$^{\circ}$C, the alpha crystal forms. Crystallization kinetics was followed using far infrared (FIR) spectroscopy. Vibrations in the FIR range can be used to directly assess the interchain interactions which are sensitive to changes in chain conformation. Interactions involving carbonyl and methyl functional groups have previously been observed in PLLA crystals. The relative rates of formation of the crystalline trans-gauche-trans conformation versus the interchain interactions were also investigated. Coexistence of the two crystalline forms has been investigated at crystallization temperatures near 120$^{\circ}$C. The alpha' crystalline form shows weaker interactions and lower thermal stability. By annealing at elevated temperatures, interchain interactions strengthened continuously. [Preview Abstract] |
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S1.00022: Understanding and Controlling Scrolled Polymer Single Crystal Habits in Isotactic Polybutene-1 Hao-Jan Sun, Bernard Lotz, Stephen Cheng The origin of non-planar polymer crystal habit, lamellar twisting and scrolling, still remains unclear. In this study, isotactic polybutene-1 (iPBu-1) was chosen as a model compound to investigate the precise relationship between the building molecules and the scrolled morphology. The scrolled micro-tubular iPBu-1 Form III single crystals have been successfully produced through dilute solution crystallization. TEM observation confirmed the edges are the (110) growth faces and that the scroll axis is along (320) plane. Polyethylene decoration experiments showed the lozenge shape crystal has four sectors with fold direction in each sector along the (110) growth surface. TEM and AFM studies also showed that the micro-tube size can be controlled by lamellar thickness which is dependent on crystallization temperature. Based upon these observations, a mechanism for lamellar scrolling is proposed where the asymmetric chain folds on opposite fold surfaces could be introduced by the isochiral 4$_{1}$ helical packing scheme in the unit cell. These asymmetric chain folds along the growth direction can generate unbalanced surface stresses to make the lamellar scrolling. [Preview Abstract] |
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S1.00023: A 2D Synchrotron X-Ray Study on Stress-Induced Crystallization of Propylene-1-Butylene Random Copolymer: Polymorphism and Preferred Orientation Yimin Mao, Christian Burger, Xiaowei Li, Benjamin Hsiao, Derek Thurman, Andy Tsou Crystallization process of propylene-1-butylene (P-B) random copolymer during mechanical stretching was investigated in real time using synchrotron x-ray scattering technique. Scattering data was studied based on 2D whole pattern analysis. Before stretching, the crystalline phase in P-B copolymer was a mixture of $\alpha $ and $\gamma $ phases of isotactic polypropylene homopolymer. Upon stretching, the c-axis of both $\alpha $- and $\gamma $-phase became aligned with the stretching direction (fiber axis). At high strains, $\gamma $-phase gradually transformed to $\alpha $-phase. A mesomorphic phase featured with strong diffuse scattering in equatorial direction was observed at high strains at low temperature. However, it was not observed at high temperatures because of high chain mobility. In this case, a secondary crystallization of alpha phase crystal appeared at high strains. The newly grown daughter lamellae exhibited an 81$^{o}$ tilting angle with respect to the fiber axis, resulting in the a-axis orientation of alpha phase. [Preview Abstract] |
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S1.00024: Nanoparticle-arrested phase separation of polymer blends Le Li, Xuan Ding, Caroline Miesch, P.K. Sudeep, Todd Emrick, Ryan Hayward, Thomas Russell Under appropriate conditions, polymer blends undergo demixing by a spinodal decomposition (SD) mechanism, leading to an interpenetrating, bicontinuous morphology with a characteristic wavelength that coarsens over time to reduce interfacial energy. Nanoparticles added to the polymer mixture can segregate to one of the phases or to the interfaces between the phases. Jamming of the nanoparticles within one of the domains or at the interface can arrest this phase separation process, trapping the interpenetrating morphology. We have studied the thermodynamics and kinetics of phase separation of polystyrene/poly(vinyl methyl ether) (PS/PVME) blends in the presence of CdSe nanoparticles and nanorods. For appropriate choices of particle size, shape and ligand coverage, nanoparticles were found to effectively arrest spinodal phase separation in the bicontinuous state. [Preview Abstract] |
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S1.00025: Multicompartment Micelles from pH Responsive Block Terpolymers Chun Liu, Marc Hillmyer, Timothy Lodge The self-assembly of multiblock copolymers into multicompartment micelles whose cores are subdivided into distinct subdomains is an exciting area of polymer science due to potential applications, foremost of which is in advanced drug delivery. Herein, we describe the synthesis of a series SODA block terpolymers (S: poly(styrene); O: poly(ethylene oxide); DA: poly[2-(dimethylamino)ethyl acrylate]) with varied architectures (miktoarm u-SODA and linear SODA and OSDA terpolymers). DA is a weak polybase that is hydrophilic at low pH and hydrophobic at high pH. It is also immiscible with the S block, a feature desirable for the formation of multicompartment micelles. As pH increases from 2.6 to 9.0, u-SODA micelles in water evolve from mixed corona (O + DA corona) spherical micelles to multicompartment (S + DA core) wormlike and spherical micelles. A similar evolution is also observed for linear OSDA and SODA terpolymers, except that some SODA multicompartment micelles are cross-linked together by sharing the middle O block. This type of pH-triggered evolution could be useful for sequential drug release. [Preview Abstract] |
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S1.00026: Scaling model for symmetric star polymers Ram Ramachandran, Durgesh K. Rai, Gregory Beaucage Neutron scattering data from symmetric star polymers with six poly (urethane-ether) arms, chemically bonded to a C-60 molecule are fitted using a new scaling model and scattering function. The new scaling function can describe both good solvent and theta solvent conditions as well as resolve deviations in chain conformation due to steric interactions between star arms. The scaling model quantifies the distinction between invariant topological features for this star polymer and chain tortuosity which changes with goodness of solvent and steric interaction. Beaucage G, \textit{Phys. Rev. E} \textbf{70} 031401 (2004).; Ramachandran R, et al. \textit{Macromolecules} \textbf{41} 9802-9806 (2008).; Ramachandran R, et al. \textit{Macromolecules}, \textbf{42} 4746-4750 (2009); Rai DK et al. \textit{Europhys. Lett.}, (Submitted 10/2009). [Preview Abstract] |
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S1.00027: Dynamic microscopy method for the characterization of nano-sized particles Beom-Jin Yoon, Jung O.K. Park, Mohan Srinivasarao, Michael H. Smith, L. Andrew Lyon We demonstrate optical microscopic method to characterize nano-sized particles. Light scattering has been used to analyze particles when the size is smaller than the resolution of microscope. Herein, we describe our study on dynamics of polystyrene particles and poly(N-isopropylacryamide) (pNIPAM) based microgel particles using real space observation with optical microscopy. Fourier analysis and image processing were done to the time and spatial series of real space images taken by optical microscope with general white light illuminations. While other real space analysis, such as atomic force microscope and electron microscope, gave the information of collapsed particles only, we acquired equivalent information to the hydrodynamic properties provided by light scattering experiments through direct observation of nano-sized particles. [Preview Abstract] |
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S1.00028: Glass Transition Temperature of Polystyrene Films on Preferential Substrate Hoyeon Lee, Sudhakar Naidu, Eunhye Kim, Du Yeol Ryu In thin films, the interfacial interactions at the substrate/polymer and polymer/air influence the transition behavior. When a polymer chains is placed on the substrate of the same chemical identity, an autophobic behavior has been observed. In the present study, glass transition behavior of polystyrene (PS) film on the PS-brush substrates was investigated by the volumetric changes with in-situ ellipsometry, where the brush thicknesses (or grafting densities) are varied. Thickness dependence of transition behavior indicates that a decrease of glass transition temperature with decreasing film thickness was significant in the short PS-brush surface. [Preview Abstract] |
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S1.00029: Differential AC/scanning chip nanocalorimeter for in-situ measurements of vapor deposited glasses Mathias Ahrenberg, Heiko Huth, Christoph Schick, Katie Whitaker, Mark D. Ediger We use nanocalorimetry to investigate the formation of extraordinarily stable glasses prepared by vapor deposition. For that purpose we've built a vapor deposition chamber that allows in-situ characterization of vapor-deposited organic molecules. The use of commercially available nanocalorimeter sensors permits us to measure the temperature at the sample position directly via heater resistivity. The calibration of this method was done with the melting point of several metals. This was applied to investigate vapor deposition of glass formers as a function of time as well as vapor deposited samples as a function of temperature. [Preview Abstract] |
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S1.00030: Observing the Twinkling Fractal Nature of the Glass Transition Joseph Stanzione III, Richard Wool, Kenneth Strawhecker The main idea underlying the Twinkling Fractal Theory (TFT) of the glass transition is the development of dynamic percolating solid fractal structures near $T_{g}$, which are in dynamic equilibrium with the surrounding liquid. Solid and liquid clusters interchange at a frequency \textit{$\omega $}$_{TF}$, which is controlled by the population of intermolecular oscillators in excited energy levels in accord with the Orbach vibrational density of states for a particular fractal cluster \textit{g($\omega )$} $\sim $ \textit{$\omega $}$^{df-1}$, where the fracton dimension $d_{f}$ = 4/3. To an observer, these clusters would appear to be ``\textit{twinkling}.'' A time-lapse tapping-mode atomic force microscopy (AFM) technique has been developed in order to experimentally confirm such phenomena. The \textit{twinkling} behavior of amorphous, atactic polystyrene with $M_{W}$ = 194,000 g/mol, PDI = 1.07 (GPC) and $T_{g}$ = 375 K (DSC-heating rate of 3 K/min) has been captured above (383 K), below (358 K), and well below (298 K) its $T_{g}$. Two-dimensional space images reveal fractal dimensions consistent with the TFT. The \textit{twinkling} behavior was analyzed using a statistical autocorrelation function in conjunction with the apparent stretched exponential Kohlrausch-Williams-Watts relaxation function. [Preview Abstract] |
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S1.00031: Effect of Nanoconfinement on the Glass Transition Temperature and Small Molecule Diffusion in Polymers of Varying Backbone Stiffness Hui Deng, Manish Mundra, John Torkelson Fluorescence spectroscopy was used to determine the glass transition temperature in ultrathin supported bisphenol-A polysulfone (BPAPS) and bisphenol-A polycarbonate (BPAPC) films and compared to previous results for ultrathin supported polystyrene (PS) films. BPAPC and BPAPS are more rigid than PS due to the presence of aromatic rings in their polymer backbones. A dramatic increase in Tg-reduction upon confinement was seen for polymers with increased backbone stiffness. A fluorescence-multilayer film technique was then used to determine the diffusion coefficient of a small molecule probe in ultrathin supported PS films. A decrease in the diffusion coefficient of the probe was observed upon confinement of the PS films. This procedure is also being applied to ultrathin supported BPAPC and BPAPS films to explore the impact of polymer backbone rigidity on small molecule diffusion in nanoconfined polymers. [Preview Abstract] |
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S1.00032: Residual Stress in Floating Polymer Sheets Kamil Toga, Jiangshui Huang, Benny Davidovitch, Narayanan Menon, Thomas Russell Capillary wrinkling of floating polystyrene (PS) sheets offers a simple methodology to investigate the properties of polymers without the constraint of adhesion to an underlying substrate. A radially symmetric wrinkle pattern forms when a small water droplet is placed at the center of a floating circular film. Residual biaxial tension resulting from preparation conditions and the line tension imposed by the three-phase contact line at the droplet and film edges can be quantified by observing the film topography under the water droplet. Fluorescent PS films of varying thicknesses were prepared by spin coating and transferred to the water surface. The residual stress were measured an order of magnitude smaller than that reported for films on solid substrates. A strong dependency on film thickness and weak molecular weight dependence were found. The length of wrinkles radiating from the droplet was accurately calculated; residual stress determined in this manner. [Preview Abstract] |
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S1.00033: Bonding Structure of Phenylacetylene on Hydrogen-Terminated Si(111) and Si(100): Surface Photoelectron Spectroscopy Analysis and Ab-Initio Calculation Masakazu Kondo, Edward Kramer Organic monolayers formed by reaction on hydrogen-terminated silicon have potential in future device applications. Although previous studies showed that monolayers may be fabricated via a surface hydrosilylation reaction scheme, controversy exists regarding the bonding structure at the interface. In the present study, we shed light on the interfaces between phenylacetylene (PA) and two different H-terminated silicon surfaces, H:Si(111) and H:Si(100). We utilize X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy for the purpose. Features arising from the valence/unoccupied bands in photoelectron spectra suggest that a large number of the PA molecules retain their $\pi$-electronic character for both of the systems. We further discuss these experimental findings and their interpretation based on ab-initio quantum chemical calculations. [Preview Abstract] |
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S1.00034: Mechanics of Thin Film Buckling Yuri Ebata, Alfred Crosby Buckling of thin polymer films can be used to fabricate unique patterned surfaces while also providing fundamental insights into molecular mechanisms associated with nonlinear deformation processes. In this study, thin polystyrene films with thickness ranging from 50nm to 800nm are attached to patterned polydimethylsiloxane substrates and compressed uniaxially. At low applied strains, the polystyrene film wrinkles above the patterned depressions and a scaling relationship between the number of wrinkles and the pattern size is found. At higher compression, the polystyrene film localizes the strain by proceeding into a series of sharp folds. Observed strains in the polystyrene film along the fold ridge approach 50{\%}. The reversibility of these sharp features is studied. [Preview Abstract] |
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S1.00035: Self Wrinkling of UV-cured Polymer Films Alfred J. Crosby, Dinesh Chandra We report~the~formation of surface wrinkle patterns associated with the curing of polymer films. Taking advantage of a thin layer of liquid on the surface of a polymer film, we swell the underlying substrate-constrained film, resulting in surface wrinkles due to the resulting compressive stress. The wrinkles evolve from isolated dimples at short times to elongated wrinkles with a defined length. ~The wavelength of the wrinkles is proportional to the film thickness and is stable at long times.~The wrinkle amplitude increases with time after curing due to~diffusion of the liquid, reaching a state of equilibrium swelling at long times. The characteristic time for amplitude evolution increases with increasing crosslink density. [Preview Abstract] |
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S1.00036: Improving Plasmonic Enhancement of Spectroscopic Signals from Polymer Analytes Rebecca Agapov, Andrey Malkovskiy, Carlos Barrios, Alexei Sokolov, Mark Foster Tip enhanced Raman spectroscopy (TERS), an emerging technique that combines optical microscopy and scanning probe microscopy, provides the sensitivity and selectivity necessary for high-resolution chemical imaging of polymer surfaces. An unprecedented 20 nm lateral resolution for the chemical imaging has been achieved. Unfortunately, the fragile plasmonic structures used to enhance the electric field are prone to mechanical, chemical, and thermal degradation. Developing robust noble metal nanostructures with stable plasmonic resonance is essential to reliable high resolution chemical imaging. Covering the metal layer with protective ultrathin coatings is being investigated to extend the plasmonic activity of the engineered nanostructures. Addition of an ultrathin aluminum oxide (Al$_{2}$O$_{3})$ coating to a silver-coated scanning probe microscopy tip for TERS significantly improves plasmonic structure stability without sacrificing the initial enhancement efficiency. The properties of this coating, the structure of its interface with the plasmonic structure, and its effect on the optical properties of the metal-coated tip are being investigated. [Preview Abstract] |
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S1.00037: Complex Interfaces: Gradient Libraries and Measurement Advances John Howarter, Edwin Chan, Jun Young Chung, Peter Johnson, Jennifer Kelly, Joonsung Yoon, Christopher Stafford The structure and properties of polymer interfaces play an integral role in many technological applications, particularly in the areas of coatings and adhesives. Interfacial interactions depend on factors including interfacial energy, roughness, surface chemistry, mechanical properties, and the defect population. We have developed measurement approaches that quantify the effects of these factors on interactions of soft materials at or near rigid interfaces such as found in many nanocomposites or coatings. To complement the measurement techniques, we designed combinatorial libraries that express incremental variation in key factors governing interfacial properties. There is an additional challenge of measuring and predicting degradation of material at interfaces, which can include both surface and sub-surface structures. Novel metrologies developed for this purpose include a surface indention array for measurement of creep and relaxation behavior of thin films; sub-surface AFM techniques for the detection and mechanical testing of subsurface features; multiple wrinkling based metrologies which can be used to characterize thermal and mechanical response; and cantilever peel adhesion test which is used to measure interfacial fracture toughness and anisotropic adhesion. [Preview Abstract] |
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S1.00038: Pattern Formation During Phase Separation of Polymer-Ionic Liquid Co-Solutions Zhiyong Meng, Chinedum Osuji Co-solutions of polystyrene (PS) with a 1-butyl-3-methylimidazolium based ionic liquid (IL) in DMF phase separated into IL-rich and PS-rich domains on solvent evaporation. Over a limited range of polymer molecular weights and substrate temperatures, a variety of striped and cellular or polygonal structures were found on the resulting film surface, as visualized using bright-field and phase-contrast optical microscopy. This effect appears to be due to a Benard-Marangoni instability at the free surface of the liquid film as it undergoes evaporation, setting up convection rolls inside the fluid which become locked in place as the system vitrifies on solvent removal. Differential scanning calorimetry shows that the IL does not significantly plasticize the polymer, suggesting that the viscosity of the polystyrene solution itself controls the formation of this instability. [Preview Abstract] |
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S1.00039: Polystyrene / Polybutadiene Thin Film Polymer Blends Studied by Atomic Force Microscopy: Dewetting and Copolymer Compatibilization Dean Waldow, Luke Latimer Thin film blends of polystyrene and polybutadiene with and without copolymers were studied using atomic force microscopy. The polymer blend system was chosen to match previous bulk measurements where the homopolymers are below their respective entanglement molecular weights. The blends were studied as binary blends and with a low concentration of added diblock, random, and two arm graft copolymers. Initially, the surface morphology relating to dewetting and phase separation of the binary blend was studied as a function of time and film thickness. The film thicknesses ranged from about 10 nm to 100 nm. Surface roughness, lateral domain size, and contact angle were used to characterize the thin film blends as a function of time, initial film thickness, and composition. The thinnest films were very mobile and dewetted much faster than the thicker films. The dewetting results are analyzed in terms of scaling behavior versus time as well as with regard to the thickness dependence of the polystyrene glass transition temperature. The thin films with added copolymers substantially modified the kinetics of dewetting with the diblock copolymer having the greatest effect on reducing film dewetting. [Preview Abstract] |
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S1.00040: Self-Assembly of Submonolayer-Coverage Organic Films T.P. Corrales, P. Homm, P. Ferrari, M.J. Retamal, E.A. Cisternas, V. del Campo, U.G. Volkmann, H. Taub, F.Y. Hansen We used velocity controlled dip-coating to adsorb of $n$-dotriacontane onto silicon substrates coated with their native oxide film ($\sim $15 {\AA}). The withdrawal velocity of the samples is varied from 0.2 cm/min to 6 cm/min and the films were studied using SEM and AFM after coating. We observe the formation of monolayered structures with different coverage and morphology depending on the withdrawal velocity. Between 0.2 cm/min and 0.5 cm/min we observe an abrupt decrease in the coverage of the monolayered structures, reaching a minimum at 1cm/min. Above 1cm/min we observe a rise in coverage, reaching a plateau around 6 cm/min. We relate this behavior to the transition from a gravity driven film growth to an entrained film regime proposed by M. Ghosh et al. [1]. We also find that the morphology of these structure depend strongly on the pulling velocity. \\[4pt] [1] M. Ghosh, F. Fan, K.J. Stebe, Langmuir \textbf{23} (4), 2007. [Preview Abstract] |
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S1.00041: A NEXAFS Characterization of Vapor Deposited Monolayer and Submonolayer films on Si, SiO$_{2 }$and Al$_{2}$O$_{3}$ Cherno Jaye, Daniel A. Fischer, Benjamin M. DeKoven, Jeffrey D. Chinn A large number of microelectromechanical systems (MEMS) are fabricated using semiconductor and ceramic materials such as Si, SiO$_{2}$, and Al$_{2}$O$_{3}$ which are hard, brittle materials. MEMS components are very small and lack power when in motion; and are highly susceptible to the influence of adhesive and surface forces. To mitigate this challenge MEMS lubrication schemes involving vapor phase lubrication have been proposed as a means of continuously replenishing lubricant films on MEMS surfaces. We present synchrotron based near edge x-ray absorption fine structure (NEXAFS) spectroscopy results of vapor deposited monolayers and submonolayers on Si, SiO$_{2}$ and Al$_{2}$O$_{3}$ substrates under different process condition. Carbon K-NEXAFS revealed that the vapor deposited fluorodecyltrichlorosilane (FDTS) molecules on silica and alumina substrates produced self-assembled monolayered films that not only have high surface coverage but are highly oriented. Orientation and coverage comparisons for other pre-cleaning methods as well as directly vapor deposited FDTS will be presented. [Preview Abstract] |
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S1.00042: A polymeric nanocoating on carbon nanotube arrays for developing imprinted protein sensor L. Ren, H.Z. Zhao, C.J. Xu, Y. Yu, H.Z. Wang, Y.C. Lan, D. Wagner, M.J. Naughton, Z.F. Ren, T.C. Chiles, D. Cai Polyphenol (PPn) was electrodeposited on carbon nanotubes (CNT) arrays at nanoscale thickness. PPn is a non-conductive polymer, so increase of sensor impedance was observed with high density CNT array, low density CNT array, and tip-polished CNT array (tCNTA), while tCNTA was determined to be the best nanosensor platform to incorporate the imprinted PPn coating due to the highest impedance increase. The PPn was characterized by transmission electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry for its thickness, uniformity, stability, resistivity and permittivity etc., as well as the protein entrapment and removal process. The density of the imprint was also evaluated by a PPn refilling experiment. Finally, ferritin was used as the template to develop a highly sensitive and selective protein nanosensor. Therefore, a novel strategy was demonstrated here to deposit and characterize polymeric nanocoating, also to evaluate imprints and detect proteins. [Preview Abstract] |
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S1.00043: The Acoustic Characterization of the Hydrophobic and Hydrophilic Films Xiaohua Wang, Xin Wang, Rodolfo Fernandez, Mingdi Yan, Andres La Rosa In living systems, essential water-related phenomena occur in restricted geometries. The stability of biological systems is controlled by the subtle hydrophilic-hydrophobic interplay, which makes their study of paramount importance. However, a limitation in current experimental strategies is that only the forces acting on the probe are sensed, the effects on the substrate and its absorbed layer are missed. Herein we introduce a novel acoustic-based technique able to simultaneously and independently monitor the effects that surface interactions exert on both the probe and sample. Our homemade shear force/acoustic microscope comprises a piezoelectric tuning fork (to which a gold tip is attached) and an acoustic transducer (placed underneath the substrate). While the tip is laterally oscillating and brought into the adsorbed layer, both the ultrasonic waves generated at the fluid-like layer and the damping effect on the tip are detected as a function of the tip-sample separation. Polymer samples with tailor made hydrophilic/hydrophobic characteristics are analyzed, as a previous step towards the acoustic characterization of protein-sugar molecular interactions. [Preview Abstract] |
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S1.00044: Arrangement of block copolymer microdomains confined at hemi-spherical substrates with different brush layers Du Sik Bae, Won Chul Joo, Jin Seok Byun, Gumhye Jeon, Jin Kon Kim The arrangement of the microdomains in block copolymers changes significantly from that in bulk, when they are confined at certain geometric constraints. Although many research works have been reported on microdomain arrangement at one-dimension, two-dimension, and three-dimension confinement, the hemi- spherical geometry has been never employed for this purpose. Here, we study, via scanning and transmission electron microscopy, the arrangement of the microdomains of polystyrene- block-poly(methyl methacrylate) copolymer (PS-b-PMMA) confined at a hemi-sphere wall. This constraint was introduced by using anodic aluminum oxide template. The inner wall surface of the hemi-sphere was further modified by three different brush layers: (1) PS, (2) PMMA, and (3) neutral brushes on PS and PMMA. We observed some interesting morphologies which have not been reported. [Preview Abstract] |
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S1.00045: Probing 2D Order in Block Copolymer Monolayers Patterned by Graphoepitaxy Adetunji Onikoyi, Edward Kramer We evaluate different experimental strategies for probing the 2D ordering and melting of a topographically constrained spherical morphology diblock copolymer (BCP) monolayer. Diamond and square wells of various dimensions are constructed either on Si or on an electron transparent silicon nitride membrane by electron beam lithography using hydrogen silsesquioxane (HSQ) resist. The walls of the patterned wells are a monolayer thick and are preferentially wetted by the short segment of the BCP. In addition to scanning force microscopy (SFM), transmission electron microscopy (TEM) can be used to determine the domain positions in the wells after thermal annealing. Results show that a near perfect hexagonal 2D lattice can be obtained in small diamond shaped wells of appropriate dimensions. Perfect six-fold symmetry is disfavored in square wells and regions of metastable square packing or defect dense regions of hexagonal packing have been observed as the well dimensions shrink. Further studies are being performed to understand effects of homopolymer addition on the graphoepitaxially patterned BCP films. [Preview Abstract] |
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S1.00046: A Quantitative Determination of Parameters Governing Reaction Products in Emulsion Based Systems Casey Kimball, Shaw Ling Hsu Investigation of reacting blends containing an aqueous latex base (Poly(Styrene-co-Butadiene), Poly (Methyl Methacrylate) and Poly(Ethylene-co-Vinyl Acetate) respectively) and Poly(Vinyl Alcohol) as a crosslinking agent with a multifunctional isocyanate shows the formation of different chemical products using Time Resolved Fourier Transform Infrared Spectroscopy. The formation of functional groups that contribute to crosslinking (i.e. the urethane and urea linkages from the resultant urethane chemistry) is dependent upon the miscibility of the three reactive functional groups in the blends, namely, the water, the hydroxyl and the isocyanate groups. For the first time, using an internal standard, it is possible to determine the relative composition of the products formed in a quantitative fashion as well as the reaction kinetics. The differences in observed reactivity can be accounted for by different dispersion states of the reactive groups in the blend. Dispersion on the molecular level is governed by the miscibility of the components and therefore is different in each of the three systems depending on their latex base. [Preview Abstract] |
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S1.00047: Surface composition and morphology of dendronized perfluoro poly(2-vinylpyridine) in a poly(2-vinylpyridine) homopolymer Michael Dimitriou, Robert Vestberg, Kristin Schmidt, Craig Hawker, Edward Kramer Surface segregation of end-functional, dendronized poly(2-vinylpyridine) in a blend with P2VP was measured by X-ray photoelectron spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS). A series of chain end functionalized P2VP dendritic-linear copolymers were synthesized \emph{via} either anionic polymerization or Reversible Addition Fragmentation Chain Transfer polymerization with one, two, or four perfluorinated hexyl chains, P2VP-(C$_{6}$F$_{13}$)$_{n}$ where n = 1, 2 and 4 attached at a single chain end. For a given wt\% of added surfactant, XPS shows higher -C$_{6}$F$_{13}$ concentrations on the surface with increasing n. For n = 2 and 4 a saturation of -C$_{6}$F$_{13}$ on the surface was achieved above 10wt\% of added surfactant. For n = 2 this result is independent of spin coating solvent while for n = 4 this value depends on solvent volatility and selectivity. NEXAFS spectroscopy confirmed no orientation of the perfluorinated chains for all wt\% of the added surfactant. [Preview Abstract] |
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S1.00048: Observation of \textit{Fddd} structure in SI diblock copolymer/homopolymer blends Myung Im Kim, Satoshi Akasaka, Tsutomu Wakada, Mikihito Takenaka, Hirokazu Hasegawa We previously reported the discovery of a novel bicontinuous microdomain structure with \textit{Fddd} symmetry in polystyrene-\textit{block}-polyisoprene (SI) diblock copolymer. Then we confirmed the stability of \textit{Fddd} structure and found \textit{Fddd} structure exists as an equilibrium structure in SI diblock copolymer. Also we determined the stable region of \textit{Fddd} structure in the phase diagram of SI diblock copolymers. It is well known that blending homopolymer with diblock copolymer causes order-order transition under wet brush condition. We can anticipate that homopolymer - diblock copolymer blend exhibits \textit{Fddd} structure even though the neat block copolymer does not have \textit{Fddd} region. In this study, we, hence, investigated the phase behaviors of SI diblock copolymer-PS homopolymer blends with various compositions by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) and explored how blending homopolymer affects the \textit{Fddd} region. Consequently, we could confirm that addition of polystyrene homopolymer (hPS) induces morphology transformation and determine the region of \textit{Fddd} phase in the SI diblock copolymer/hPS blends that is similar to that of SI diblock copolymers we reported. [Preview Abstract] |
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S1.00049: Direct measurement of deformation-induced molecular mobility in polystyrene glasses Benjamin Bending, Hau-Nan Lee, Mark Ediger We use an optical photobleaching method to measure the molecular mobility during active deformation of lightly cross-linked polystyrene glass. We see a factor of 1000 mobility enhancement during deformation using a constant engineering stress of 16 MPa at Tg-16 K. Additionally, we observe a significant narrowing of the distribution of relaxation times in the flow regime which we interpret as increasingly homogeneous dynamics in the polystyrene glass. After accounting for the Tg shift, we obtain similar results for 2 and 4 percent cross-linking density of polystyrene. Qualitatively similar mobility results are observed during deformation of polystyrene and poly(methyl methacrylate) glasses. These results imply that the prominent beta relaxation in poly(methyl methacrylate) does not play a role in the observed deformation-induced mobility and thus changes in the alpha segmental relaxation control the non-linear mechanical response. [Preview Abstract] |
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S1.00050: Stable organic glasses transform into unusually mobile liquids via growth growth fronts Mark Ediger, Stephen Swallen, Thomas Mates Physical vapor deposition onto substrates near 0.85 Tg can prepare organic glasses with low enthalpy, high density, and high thermal stability. Secondary ion mass spectrometry on isotopically labeled multilayer films of tris-naphthylbenzene and indomethacin stable glasses is used to study the evolution of these materials upon heating above Tg. In contrast to ordinary glasses, when stable glasses are held above Tg they transform to a liquid via a growth front mechanism. In these experiments, growth fronts are initiated at the free surface of the glass and in some cases at the glass/substrate interface or an internal interface in the glass. Diffusion in the liquid that results from the growth front is initially 2-5 times faster than for the equilibrium supercooled liquid at the same temperature; the nature of this liquid is unclear. Under some circumstances, the slow evolution of this unusually mobile liquid into the equilibrium supercooled liquid can be observed. [Preview Abstract] |
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S1.00051: Synthesis and Phase Behavior of Well Defined Coil-Rod-Coil Block Copolymer Composed of Regioregular Poly(3-hexyl thiophene) Hong Chul Moon, Arockiam Anthonysamy, Youngmin Lee , Jin Kon Kim We synthesized coil-rod-coil triblock copolymers composed of regioregular poly(3-hexyl thiopene) (P3HT) block via anionic coupling reaction. Two different coil blocks (poly(2-vinyl pyridine) (P2VP) and polyisoprene (PI)) were selected. P2VP-b- P3HT-b-P2VP copolymer was synthesized in a polar solvent of tetrahydrofurane, while PI-b-P3HT-b-PI copolymer was synthesized in a nonpolar solvent of benzene. For the synthesis of both block copolymers, the chain ends of the P3HT were capped by the aldehyde group. When the excess amount of the living P2VP (or PI) anions was used, all of aldehyde-capped P3HT were completely reacted with P2VP (or PI) anions, without leaving any P3HT homopolymer in the product. We also investigated the phase behavior of synthesized block copolymers with various molecular weights and volume factions of each block component. [Preview Abstract] |
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S1.00052: MD simulations of the effect of grafted charged polymer coatings on electro-osmotic flow Owen A. Hickey, James L. Harden, Christian Holm, Gary W. Slater Using conventional molecular dynamics simulations with explicit solvent we examine how grafted charged polymer coatings affect the electro-osmotic flow (EOF) in a circular capillary. First and foremost we compare the electro-osmotic properties of the polymer coating to the electrophoretic properties of the polymers which make up the layer. We find that the speed of the bulk electro-osmotic flow is actually slightly higher than the electrophoretic speed of the polymers which make up the coating. We compare this to similar experimental results where the electrophoretic speed was found to be slightly higher than the speed of the EOF generated by the same polymers when used as a coating. We show evidence which suggests that this is due to the incomplete screening of EOF caused by the underlying layers in the polymer coating. We also present other interesting results like the fact that an interface which is electrically neutral can generate a non-zero EOF. [Preview Abstract] |
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S1.00053: Low-q X-ray scattering behavior in polymers Amanda McDermott, Gregory Tudryn, Jan Ilavsky, Andrew Allen, Ralph Colby, James Runt Many polymer systems display low-q scattering following a power law, and ultra-small-angle X-ray scattering reveals that this behavior persists at scattering wavevectors corresponding to length scales of several microns. Amorphous homopolymers are expected to be homogeneous at these scales, so the identity of the phases required to account for such scattering is an unresolved question. Our investigation of both ionomer and polymer/salt systems suggests that ions can change the morphology of large-scale inhomogeneities as well as increasing the scattering contrast. However, it is difficult to draw quantitative conclusions without first understanding the phenomenon in ion-free polymers. We discuss recent data on homopolymers of varying thermal history, tacticity, and molecular weight in relation to theoretical models, including the Fischer cluster mode observed in light scattering studies. [Preview Abstract] |
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S1.00054: Manipulation of surface crystalline structures of ultrathin PEO films using supercritical carbon dioxide So King Lam, Mitsunori Asada, Peter Gin, Maya Endoh, Tadanori Koga, Sushil Satija Crystallization of polymeric materials in nanoconfined geometries has attracted considerable attention in the past decade. In this talk, we will present the effect of supercritical carbon dioxide as an environmentally ``green'' alternative to typical external fields, i.e. high temperature annealing, to control the melting/crystallization behavior of semicrystalline polymer thin films. Poly(ethylene oxide) (PEO) thin films with thickness of 10nm-100nm were used for this study. Various scCO$_{2 }$conditions, including the density fluctuation ridge where anomalous plasticization effects can be observed in various polymer thin films, were applied to the PEO thin films. The surface structures before and after exposure were then investigated by using atomic force microscopy and grazing incidence small angle X-ray scattering and diffraction techniques. The results clearly showed the surface crystalline structures could be altered significantly by the use of scCO$_{2}$. [Preview Abstract] |
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S1.00055: First Order Phase Transition of Primary and Secondary Decanol Inside Nanoporous Silica Samuel Amanuel The roles of OH side groups in influencing the first order phase transition of structural isomers of Decanol are determined from calorimetric measurements. Our calorimetric measurements revealed that the melting temperature of 1-decanol and 2-decanol to be 6.3\r{ }C and -2.5\r{ }C, respectively. While there is 1-2\r{ }C hysteresis between the melting and freezing temperatures of 1-decanol, there is about 20\r{ }C hysteresis between the melting and freezing temperature of 2-decanol. These structural isomers clearly behave differently in bulk, namely difference in their transition temperature, hysteresis in the transition temperatures, and viscosity. How physical confinement influences and affects their melting and freezing behavior will be presented in this presentation. Comparative measurement on these primary and secondary can possibly elucidate whether the presence of plausible non-freezing layer argument used to explain the reduction in the apparent $\Delta $H with respect to physical size is generally valid for different structural isomers. [Preview Abstract] |
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S1.00056: Hierarchical Structure on Nanofiber via Combination of Electrospinning and Polymer Crystallization Xi Chen, Bingbing Wang, Christopher Li We report the formation of hierarchically ordered polymer nanofiber structures, named as nano fiber shish kebabs (NFSKs), by combining electrospinning and controlled polymer crystallization methods. We have proved that it is a general method that can be applied to a number of polymers, both homopolymer and block copolymers.Electrospun poly caprolactone (PCL) nanofibers serve as the shish and a secondary polymer (PCL homopolymer or PCL-related block copolymers) is decorated on the nanofiber in the form of single crystal lamellae by either an incubation (slow crystallization), or a solvent evaporation (fast crystallization) method. This hierarchical architecture is found potential application as a platform for incorporating inorganic nanoparticles into nanoscale polymer fibers in an ordered fashion. [Preview Abstract] |
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S1.00057: Crystallization Control of Hard and Soft Segments of Polyurethanes via Controlled Placement of Surface Functionalized Nanoparticles Matthew A. Hood, James M. Sands, John J. La Scala, Frederick Beyer, Christopher Y. Li Segmented polyurethanes (SPUs) phase separate into hard and soft domains, due to differences in segment composition, resulting in extraordinary properties. We synthesized a SPU composed of PTMO-HDI-BDO and demonstrated that addition of 12nm silica nanoparticles (SiNPs) will have drastic effects on mechanical and morphological properties. Moreover, SiNPs with specific surface chemical groups (i.e. hydroxyl, amine, etc.) have been synthesized in order to tailor the interaction between NPs and soft/hard domains of SPU. Thermal, mechanical and diffraction experiments along with electron microscopy have been used to characterize these systems and compare them to neat SPU and as-received SiNP/SPU composites. By controlling the particle placement within the SPU a systematic structure-processing-properties relationship can be inferred for use in the design of more complex NP/SPU composites. [Preview Abstract] |
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S1.00058: Polystyrene-Polylactide Bottlebrush Block Copolymer at the Air/Water Interface Lei Zhao, Myunghwan Byun, Javid Rzayev, Zhiqun Lin Hydrophobic ultrahigh molecular weight bottlebrush block copolymer and linear block copolymer of polystyrene-polylactide (PS-PLA) were shown to be capable of forming Langmuir monolayers and exhibiting unique assembly behaviors at the air/water interface, which cannot be addressed by the classic theory of Langmuir monolayer of amphiphilic copolymers. New models were proposed to illustrate these intriguing surface behaviors. The self-assembled structure of Langmuir monolayer of bottlebrush block copolymer was determined by a combination of AFM measurement, thermal annealing, and enzymatic degradation experiment. To the best of our knowledge, this is among few studies on hydrophobic block copolymers at the air/water interface. As such, it not only complements the well-known models of self-assembly of amphiphilic block copolymers at the air/water interface but also expands the use of Langmuir-Blodgett (LB) technique to hydrophobic block copolymers. [Preview Abstract] |
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S1.00059: Metal Nanoparticle Arrays Templated by Block Copolymer Sphere Monolayers Hiroyuki Ishii, Edward Kramer Making well-ordered arrays of metal nanoparticles has attracted a lot of interest due to its potential application in nanoelectronics and nanooptics. We fabricated well-ordered gold nanoparticle arrays using an ordered block copolymer monolayer film as a template. After the thermal self-assembly of a polystyrene-b-poly(2-vinylpyridine) (PS-P2VP) monolayer containing P2VP spheres, the sample was soaked in a solution containing HF to charge the P2VP and metal salts which can coordinate with P2VP. Subsequently the sample was treated with an oxygen plasma to reduce metal salts and remove polymer. The array structure was characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). While the interparticle distance can be controlled by changing molecular weight of block copolymer, access of the solution to the P2VP spheres, which have a PS matrix layer on top, is not always successful. Strategies for improving such access will be discussed. [Preview Abstract] |
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S1.00060: Synthesis and Co-assembly of Cyclopeptide-Polymer Conjugates with Block Copolymers Rami Hourani, Nana Zhao, Brett Helms, Ting Xu Thin films containing sub-nanometer channels aligned normal to the surface constitute promising materials for selective transport of small molecules for industrial and biological applications. The co-assembly of cyclopeptide-polymer conjugates with block copolymers (BCPs) allows the generation of such materials with molecular level control over the assemblies. The number, type, and dimensions of conjugated polymer chains influence the thermodynamics governing the microphase separation of BCPs, and the surface energy required to stabilize such small channels to obtain well-defined pore diameters at the sub-nanometer level. Coupling different synthetic homopolymers to a preformed cyclic (D-alt-L)-R-octapeptide, allowed the generation of coil-ring-coil conjugates. The co-assembly of blends of such conjugates with block copolymers was investigated, and the effect of the size, type and number of conjugated polymer chains on the thickness and packing of thin films was demonstrated. This study provides a general and reliable methodology to generate well-defined hierarchically structured nanoporous materials for ions and gas transport. [Preview Abstract] |
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S1.00061: Enhancement light-emission of GaN via surface-nanopatterning Mansik Park, Bongseok Kim, Soohwan Hwang, Minsik Cho, Kyusoon Shin In this presentation, we are going to suggest a method to improve the light-extraction efficiency of an inorganic substrate by simple surface-patterning. We fabricated a nanoporous pattern via blockcopolymer lithography on the light emitting GaN semiconductor. Tuning of refractive index of thin films on GaN was available by choosing block copolymer with a suitable composition. We believe the light-extraction efficiency was able to be enhanced due to insertion of the nanoporous film that changes the refractive indices from GaN substrate to air in the middle of the path of light. Detailed method will be introduced in the presentation. [Preview Abstract] |
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S1.00062: PS-b-PDMS Block Copolymer Thin Film: Pattern Formation and Phase Behavior I-Fan Hsieh, Stephen Z.D. Cheng, Feng Chen, Qiang Fu Recently, block copolymer thin films are of great interest for their applications in surface patterning, and thin films of diblock copolymers with cylindrical microdomains normal to the surface are more attractive due to the tenability of large aspect ratios of the cylindrical microdomains. Within various kind of block copolymer, PS-b-PDMS is chosen due to an extremely large $\chi $ value between PS and PDMS. PS-b-PDMS can be transformed into silicon oxide under UV/O$_{3}$ exposure, and a layer of silicon oxide with the self-assembled block copolymer patterns can be made. In our work, utilizing PGMEA as solvent and its vapor as spin casting atmosphere, we found an effective approach to obtain the PDMS cylinders oriented normal to the substrate. Furthermore, during benzene solvent annealing, PDMS cylinders' orientation transfers from perpendicular to parallel and then back to perpendicular again. By changing the cylinders orientation alternatively, the lateral order of cylinder packing gradually improved. By investigating this morphology evolution, the mechanism and free energy pathway for PS-b-PDMS thin film morphology transition during solvent annealing can be constructed. [Preview Abstract] |
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S1.00063: Quantitative study of temperature-dependent order in thin films of cylindrical morphology block copolymer Vindhya Mishra, Edward Kramer Disordering and defect generation in block copolymer systems at high temperatures is of significance to get a better understanding of the physics governing these systems, which can also direct efforts to minimize them. We have studied the smectic-nematic-isotropic transition in confined monolayers and bilayers of cylindrical morphology poly (styrene-b-2vinyl pyridine) diblock copolymer. Previous studies of melting phenomena in block copolymer thin films have relied on quantitative AFM studies alone. We have supplemented AFM studies with grazing incidence small angle X-ray diffraction lineshape analysis to quantify the decay of translational and orientational order with increasing temperature. The results have been interpreted in the context of the Toner-Nelson theory of melting for layered systems. [Preview Abstract] |
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S1.00064: Square and Rectangular Arrays from Directed Assembly of Sphere-forming Diblock Copolymers in Thin Films Shengxiang Ji, Umang Nagpal, Wen Liao, Juan de Pablo, Paul Nealey Patterns of square and rectangular arrays with nanoscale dimensions are scientifically and technologically important. Fabrication of square array patterns in thin films has been demonstrated by directed assembly of cylinder-forming diblock copolymers on chemically patterned substrates, supramolecular assembly of diblock copolymers, and self-assembly of triblock terpolymers. However, a macroscopic area of square array patterns with long-range order has not been achieved, and the fabrication of rectangular arrays has not been reported so far. Here we report a facile approach for fabricating patterns of square and rectangular arrays by directing the assembly of sphere-forming diblock copolymers on chemically patterned substrates. On stripe patterns, a square arrangement of half spheres, corresponding to the (100) plane of the body-centred cubic (BCC) lattice, formed on film surfaces. When the underlying pattern periods mismatched with the copolymer period, the square pattern could be stretched (up to $\sim $60{\%}) or compressed ($\sim $15{\%}) to form rectangular arrays. Monte Carlo simulations have been further used to verify the experimental results and the 3-dimensional arrangements of spheres. [Preview Abstract] |
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S1.00065: Dynamics of Main Chain Liquid Crystalline Polysiloxanes Containing $p$-Phenyleneterephthalate Mesogens Kevin Masser, Harshad Patil, Ronald Hedden, James Runt The dynamics of three main-chain liquid crystalline polysiloxanes were investigated using broadband dielectric relaxation spectroscopy. The liquid crystalline polymers (LCP) differ regarding the substituents on the rigid mesogens, and the nature of the substituents is found to influence the relaxation behavior. Within the temperature and frequency range examined, five relaxations are observed; two glassy state processes are associated with motions of the spacer segments (gamma relaxation) and the substituted phenyl rings (beta relaxation). The segmental (alpha) relaxation time changes with the nature of the mesogen substituent. A relaxation assigned to interfacial polarization between domain boundaries was observed, which disappears at the LCPs clearing temperature. [Preview Abstract] |
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S1.00066: Effect of pressure on orientational order in fluids of semiflexible polymer chains – A Monte Carlo simulation study Kiran Khanal, Jutta Luettmer-Strathmann Semiflexible polymer chains in solution show orientational order at sufficiently high concentrations and low temperatures. In melts of semiflexible chains, we expect packing effects to lead to an increase in orientational order with increasing pressure. In this work, we investigate this effect with Monte Carlo simulations of a lattice model for semiflexible polymer chains. The model is an extension of Shaffer's bond-fluctuation model and includes attractive interactions between monomers and an adjustable bending penalty that determines the Kuhn segment length. This allows us to model melts of flexible, semiflexible, and rodlike chains. For this work, we performed Monte Carlo simulations for polymer melts with a range of bending parameters and densities. We determined the pressure in the athermal limit from chain and bead-insertion methods and use thermodynamic integration to obtain the equation of state at finite temperatures. We measure the orientational order parameter to describe long-range order in the system and we also determine local packing of chain segments. [Preview Abstract] |
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S1.00067: Time evolution study of anisotropy of P3HT film formation using \textit{In-Situ} polarized Raman Spectroscopy Min Sang Park, Avishek Aiyar, Jung Ok Park, Elsa Reichmanis, Mohan Srinivasarao The charge transport properties of self-organized conjugated polymer films are strongly dependent on the molecular ordering during the solution casting process. We studied how the chain orientation of poly(3-hexylthiophene) (P3HT) is altered as function of evaporation time using polarized micro-Raman spectroscopy and POM. The time evolution of anisotropy of P3HT films prepared by drop-casting with 1,2,4-trichlorobenzene indicates that directional preference of P3HT chain alignment occurs only during the specific time duration. No anisotropy was detected either before or after this duration. These results were compared with the \textit{in-situ} current measurements of P3HT solution during evaporation, and interpreted in terms of the solvent evaporation induced self organization. Based on these results, the mechanism of film formation by solvent evaporation is proposed and supported with morphologies of polymer film induced by different solvent evaporation forces by means of AFM. The information of chain ordering in this study addresses the question of whether conjugated polymer films by solution casting can have nematic ordering with non-separable anisotropic interactions where mean field theory predicts ordering. [Preview Abstract] |
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S1.00068: Molecular Dynamics Simulations of Gas Transport in Polymer Films David Whitley, Simon Butler, David Adolf Parallel molecular dynamics simulations have been carried out to determine the permeability of O$_{2}$ and N$_{2}$ through polyethylene terephthalate, polypropylene and cis(1-4) polybutadiene. The permeability of both mixed and unmixed gas penetrants is studied within films of these well known gas barrier polymers. Results are obtained either through the solubility and diffusion (i.e. $P=D*S$) or via the permeability directly. Encouraging results are obtained. Additional analysis focuses on ``unmixed/mixed gas'' intracomparisons of the simulated permeability data in addition to corresponding penetrant and host polymer local dynamics. [Preview Abstract] |
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S1.00069: Self-Consistent PRISM Theory-Monte Carlo Simulation of Functionalized Nanoparticles in a Polymer Matrix Nitish Nair, Arthi Jayaraman Functionalizing nanoparticles with small ligands or polymers is an effective way to tune the interfacial interactions between nanoparticles and in turn their spatial organization in a solvent or polymer matrix. We integrate Polymer Reference Interaction Site Model (PRISM) theory and Monte Carlo (MC) simulations to study copolymer-functionalized nanoparticles embedded in a polymer melt. While PRISM theory can be applied to dense systems with minimal computational effort, it involves approximations, e.g. the use of ideal conformations for the grafted and free polymers. On the other hand, MC simulations of polymer melts are computationally intensive but devoid of the approximations of PRISM. Therefore, we combine the advantages of each method by presenting a self-consistent PRISM-MC approach which gives us theoretical results that are more accurate than pure PRISM theory at packing fractions that are hard to access with pure MC simulations. Using this self-consistent PRISM-MC approach, we have studied the effect of packing fraction and the sequence of the grafted polymers on the potential of mean force between two copolymer-grafted nanoparticles in a homopolymer matrix. [Preview Abstract] |
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S1.00070: Generating self avoiding walks by Markov dependent elongations Kazuhito Shida Generation of long self-avoiding walks (SAW) is still a difficult problem, because any loops in the walk must be checked and avoided. When self-avoiding walks are sampled on lattice model by elongating the walk into randomly selected free (not already occupied by a segment of the walk) sites, the efficiency is improved but some chains are extremely oversampled. We have been investigating a very simple method to solve this problem. In this method, successive elongations of the walk follow an order k Markov model, defined in such a way that final emission rates of various walk configurations are as equal as possible. Markov model can prohibit some transitions corresponding to short loops, though long loops must be checked by conventional method. Since Markov dependence will be forgotten after k elongations, no net bias is caused on resultant walk configurations. This is the first method proposed for SAW oversampling that uses neither of recursive adjustments nor ordinary MCMC. [Preview Abstract] |
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S1.00071: Role of hydrophobic interactions in the self-assembly of alternating copolymers Cecile Malardier-Jugroot, Anita S.W. Chan, Michael N. Groves New nanomaterials already play a key role in several emerging technologies. Among the methods used to fabricate new nanomaterials, the most successful in producing precise structure is the bottom-up method. The materials obtained by self-assembly are ordered on different scales and respond and adapt to the presence of other molecules in their environment [1] and can therefore be used as probes, sensors or switches [2]. In this paper, we will describes the self-assembly of amphiphilic alternating copolymers into nanoarchitectures in aqueous solution. To investigate the role of the nature of the hydrophobic groups on the association, the self-assembly of two polymers are compared: poly(isobutylene-alt-maleic anhydride) (IMA) and poly(styrene-alt-maleic anhydride) (SMA) [3, 4]. The theoretical prediction is also compared to experiment and the characterization using Small Angle Neutron Scattering, Dynamic Light Scattering and High Resolution Transmission Electron Microscopy will be presented in detail. [1] S. Zhang, \textit{Nature Biotechnology}, 21, 10, 1171, 2003. [2] F. Patolsky, \textit{et al.}, \textit{Nanomedicine}, 1, 51-65, 2006 [3] C. Malardier-Jugroot, \textit{et al.,} \textit{J. of Phys. Chem. B}, 109(15), 7022-7032, 2005 [4] A.S.W. Chan, \textit{et al.}, \textit{Mol. Sim.}, accepted for publication, 2009. [Preview Abstract] |
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S1.00072: Studying Soft Materials with Soft Potentials -- Fast Monte Carlo Simulations Jing Zong, Xinghua Zhang, Pengfei Zhang, Yuhua Yin, Baohui Li, Qiang Wang The basic idea of fast Monte Carlo (FMC) simulations\footnote{\textit{Q. Wang and Y. Yin}, \textbf{J. Chem. Phys., 130}, 104903 (2009); \textit{Q. Wang}, \textbf{Soft Matter, 5}, 4564 (2009).} is to use soft potentials that allow particle overlapping, instead of hard repulsions (e.g., the Lennard-Jones potential in continuum or the self- and mutual-avoiding walks on a lattice) used in conventional molecular simulations. This gives orders of magnitude faster/better sampling of configurational space. In addition, since soft potentials are commonly used in polymer field theories, using the same Hamiltonian in both FMC simulations and the theories thus allow stringent test of the latter, without any parameter-fitting, to unambiguously and quantitatively reveal the consequences of theoretical approximations. Here we use several systems, ranging from small-molecule liquid crystals to homopolymer solutions and brushes, to demonstrate these great advantages of FMC simulations performed both in continuum and on a lattice. [Preview Abstract] |
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S1.00073: Visual-Analytics Tools for Analyzing Polymer Conformational Dynamics Sidharth Thakur, Syamal Tallury, Melissa Pasquinelli The goal of this work is to supplement existing methods for analyzing spatial-temporal dynamics of polymer conformations derived from molecular dynamics simulations by adapting standard visual-analytics tools. We intend to use these tools to quantify conformational dynamics and chemical characteristics at interfacial domains, and correlate this information to the macroscopic properties of a material. Our approach employs numerical measures of similarities and provides matrix- and graph-based representations of the similarity relationships for the polymer structures. We will discuss some numerical measures that encapsulate geometric and spatial attributes of polymer molecular configurations. These methods supply information on global and local relationships between polymer conformations, which can be used to inspect important characteristics of stable and persistent polymer conformations in specific environments. Initially, we have applied these tools to investigate the interface in polymer nanocomposites between a polymer matrix and carbon nanotube reinforcements and to correlate this information to the macroscopic properties of the material. The results indicate that our visual-analytic approach can be used to compare spatial dynamics of rigid and non-rigid polymers and properties of families of related polymers. [Preview Abstract] |
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S1.00074: Supramolecular Assembly of Tripodal Trisamides Li Feng A series of tripodal trisamide compounds have been synthesized from tris(2-aminoethyl)amine (TREN) by condensation with different acid chlorides. Gelation of organic solvents with these compounds was investigated as a function of concentration and solvent solubility parameter. Compounds made with linear acid chlorides were poor gelators. A gelator made with 2-ethylbutyryl chloride (TREN-EB) was an excellent gelator for many organic solvents. It was found that the minimum gelation concentration of TREN-EB increased with increasing solubility parameter of the solvent. Thin films samples were prepared by spin-coating mixtures of TREN-EB and a poly(acrylate). Scanning force microscopy measurements showed that TREN-EB formed nanofibrillar network structures. In addition a dependence of the network morphology on the casting solvent was found. [Preview Abstract] |
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S1.00075: Small Angle X-ray Scattering (SAXS) to Probe the Mullins Effect in Filled Elastomers Arthur Scholz, Ed Kramer The addition of nanosized filler particles to elastomers has long been known to improve fracture energy and increase energy dissipation. A characteristic strain softening observed during cyclic mechanical loading (``Mullins effect'') is largely responsible. SAXS using synchrotron X-radiation allows us to characterize the structural changes that occur in the scale of the particles during cyclic mechanical loading and thus probe the origins of the Mullins effect. In crosslinked silica-filled siloxane elastomers the scattering is mainly due to the electron density difference between the particles and the siloxane. The symmetric SAXS pattern at zero strain is transformed into a ``butterfly'' SAXS pattern at true tensile strains of order 2, clear evidence of non-affine deformation of the filled elastomer, and the SAXS invariant after a cycle as well as that at the maximum strain in the cycle, increases as this maximum strain increases, strong evidence of void formation. [Preview Abstract] |
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S1.00076: The Effects of the Thickness and Type of Silicone Coating Materials on the Swelling Behaviour of Hydrogels Zamri Radzi, J. Hannah Lee, Marc Swan, Tim Goodacre, David Bucknall, Jan Czernuszka Encapsulation is one of the methods to control the degree of hydrogel swelling. In certain medical applications the hydrogels are required to undergone slow initial swelling before they start to gradually swell up to their maximum swelling capacity. Using a dip coating technique, the anisotropic hydrogels were coated with different types of silicone dispersion formulations. The hydrogels were swelled and measured by determining the mass change as a function of time. By varying the coating thickness and concentration of silicone we found that it is possible to slow down the initial swelling and allow the subsequent swelling process to gradually take place to physiologically acceptable levels. This behaviour has been analysed in terms of the permeability to water of the silicone membranes and their mechanical properties. [Preview Abstract] |
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S1.00077: Monte Carlo study of confinement effects on controlled radical polymerization reactions Salomon Turgman-Cohen, Jan Genzer Bulk- and surface-initiated controlled radical polymerization (CRP) in implicit solvents is modeled using a stochastic Monte Carlo algorithm by implementing the bond-fluctuation model scheme. We study the effect of system parameters, including: bulk vs. surface initiation, surface density of initiators, substrate geometry, solvent quality, and the ratio between surface and bulk polymers on the molecular weight and polydispersity index (PDI) of the resulting polymers. To better understand the effect of geometry and steric hindrance on the polymerization we calculate the sizes and shapes of the growing polymers and monitor the various reactive species located near the reactive polymer chain-ends. Our results indicate that confinement of the growing chains has detrimental consequences on the ability of CRP to yield nearly monodisperse polymers; i.e., confining polymers to impenetrable surfaces and/or decreasing solvent quality decreases the rate of polymerization and increases the PDI. [Preview Abstract] |
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S1.00078: MAGNETISM |
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S1.00079: Deriving a functional form of anhysteretic magnetization function for Jiles-Atherton theory of hysteresis David Jiles, Arun Raghunathan, Yevgen Melikhov, John Snyder The Jiles-Atherton (JA) theory explains the ferromagnetic hysteresis through contributions of irreversible and reversible magnetization components [1]. Anhysteretic magnetization function, a function of energy of the moments in a domain, forms a basic building block of this model. This function has known forms for specific cases of anisotropy: axially anisotropic (one-dimensional), planar anisotropic (two-dimensional), and isotropic (three-dimensional) [1, 2]. Hence there is a need to generalize anhysteretic magnetization function to extend JA theory to other forms of anisotropy. In this work, a functional form of anhysteretic magnetization function has been derived. It was shown that this functional form of anhysteretic magnetization with necessary boundary conditions can be reduced to the familiar specific model equations in the particular cases. This work extends the applicability of the JA model to systems with various anisotropy dependences. This research was supported by the UK EPSRC (EP/D057094) and the US NSF (DMR-0402716). [1] D. C. Jiles et. al., JMMM. \textbf{61}, 48 (1986). [2] Y. M. Shi et. al., JMMM. \textbf{187}, 75 (1998). [Preview Abstract] |
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S1.00080: A simple model for the magnetoelectric interaction in multiferroics C.J. Calderon, G.E. Barberis The (anti)ferromagnetic and ferroelectric transitions in some magnetoelectric compounds seem to be strongly correlated. Even for systems that do not show spontaneous ferroelectricity such as the LiMPO$_{4}$ (M = Mn, Fe, Co, Ni) compounds, the coupling between magnetic and electric degrees of freedom is evident experimentally. Here, we present a simple numerical calculation to simulate this coupling that leads to the two transitions. We assume a magnetic sublattice consisting of magnetic moments coupled to a separated non-magnetic sublattice consisting of classical electric dipoles. The coupling between them is realized using the phenomenological spin - lattice Hamiltonian method, where the magnetic moment in each site of the lattice is coupled to strains, and the minimum of energy obtained through the Monte Carlo method. In the simplest version, the magnetic system is 2D Ising (anti)ferromagnetic lattice, with nearest neighbors interactions only, and the electric moments are non-coupled, permanent moments. Within this approximation, the second order magnetic transition induces ferroelectricity in the electric dipoles. We show that these calculations can be extended to other magnetic systems, (x-y model and \ 3D Heisenberg) with coupling to the electric moments will, so they can be applied to model realistic systems such as the olivines mentioned above. [Preview Abstract] |
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S1.00081: Phase transitions of high and fractional order Vladimir Udodov On the basis of exact solution it was concluded for the first time that the traditional one-dimensional Ising model (1D IM) has phase transitions (PT) of arbitrarily high order, including fourth-, fifth- and sixth-order phase transitions, according to the Baxter's classification. Moreover, this model also exhibits PT's of fractional order. It was rigorously proved that in the Baxter's approach the order of a PT in 1D IM can be any real number that is not less than the unit. We show further how such an order can be defined consistently. Finally, using the thermodynamic arguments we demonstrate that superconductors can undergo third and higher (including fractional) order PT's within the meaning of Erenfest as the temperature tends to zero. It is established relation wish critical exponent of specific heat and critical magnetic field for superconductor as the temperature tends to zero. [Preview Abstract] |
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S1.00082: Investigation of cubic particles with uniaxial anisotropy using M$^{3 }$- a Matlab based micromagnetic code Angelique Montgomery, Claudia Mewes, Tim Mewes We have developed a Matlab based micromagnetic code (M$^{3})$ to simulate three dimensional magnetic structures. We find that the mathematical notation and the multidimensional capabilities of Matlab greatly simplify code development and maintenance compared to other programming languages. Here we report on the investigation of the magnetic states of cubic particles with a reduced size L and a uniaxial anisotropy of relative strength Q=K$_{u}$/K$_{d}$ (K$_{u}$: uniaxial anisotropy, K$_{d}$: magnetostatic energy density) along one of the cube axis in zero field. As can be expected using estimates of the energy based on domain theory, we find single domain states for small L with a transition to a vortex state for small Q and to a two domain state for large Q. Increasing L further eventually leads to the formation of three and multidomain states. We have also investigated the influence of the boundary conditions for the 26 neighbor method on the resulting magnetic states. [Preview Abstract] |
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S1.00083: Domain Wall Magnetism in Multiferroic BiFeO3 Qing He, S.-Y. Yang, C.-H. Yang, P. Yu, J. Wu, Z. Q. Qiu, R. Ramesh, M. Daraktchiev, G. Catalan, J. Scott, E. Arenholz, A. Scholl, A. Fraile-Rodriguez, D. Lee, S. X. Wang, L. Martin, Y.-H. Chu Through a combination of theoretical calculations and experimental studies, a holistic picture of the connection between processing, structure, and properties brings to light the role of magnetism at ferroelectric domain walls in determining the magnetic properties in BiFeO$_{3}$. By controlling domain structures through epitaxial growth constraints and probing these domain walls with exchange bias studies, x-ray magnetic dichroism based spectromicroscopy, and high resolution transmission electron microscopy we demonstrate that the formation of certain types of ferroelectric domain walls (i.e., 109$^{\circ}$ walls) can lead to enhanced magnetic moments in BiFeO$_{3}$. This work is supported by the Department of Energy. [Preview Abstract] |
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S1.00084: Numerical simulation of magnetic domain evolution in Co/Pd thin films Daniel Parks, Sujoy Roy, Keoki Seu, Run Su, Erik Shipton, Eric Fullerton, Stephen Kevan We report on the development of a novel algorithm for the numerical simulation of two-dimensional magnetic domain patterns. By allowing an arbitrary function to act as a constraint on the envelope of the fourier modulus of the simulated domain pattern, we are able to use experimentally observed scattering patterns to guide the evolution of the simulation. Here we show the results of simulations on magnetic domain growth in Co/Pd thin films. [Preview Abstract] |
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S1.00085: Spin blockade, orbital occupation, and charge ordering in La$_{1.5}$Sr$_{0.5}$CoO$_{4}$ Chun-Fu Chang, Zhiwei Hu, Hua Wu, Tobias Burnus, Nils Hollmann, Thomas Lorenz, Arata Tanaka, Hong-Ji Lin, Chien-Te Chen, Liu Hao Tjeng Using Co-$L_{2,3}$ and O-$K$ x-ray absorption spectroscopy, we reveal that the charge ordering in La$_{1.5}$Sr$_{0.5}$CoO$_{4}$ involves high spin ($S$=3/2) Co$^{2+}$ and low spin ($S$=0) Co$^{3+}$ ions. This provides evidence for the spin blockade phenomenon as a source for the extremely insulating nature of the La$_{2-x}$Sr$_{x}$CoO$_{4}$ series. The associated $e_g^2$ and $e_g^0$ orbital occupation accounts for the large contrast in the Co-O bond lengths and, in turn, the high charge ordering temperature. Yet, the low magnetic ordering temperature is naturally explained by the presence of the non-magnetic ($S$=0) Co$^{3+}$ ions. From the identification of the bands we infer that La$_{1.5}$Sr$_{0.5}$CoO$_{4}$ is a narrow band material. [Preview Abstract] |
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S1.00086: $\mu^{+}$SR Investigation of CaCrO$_{3}$ Oren Ofer, Jun Sugiyama, Martin M{\aa}nsson, Kim H. Chow, Eduardo J. Ansaldo, Jess H. Brewer, Masahiko Isobe, Yutaka Ueda We investigated the magnetic phase of the perovskite CaCrO$_3$ by using the muon spin relaxation technique. A static antiferromagnetic order is revealed with distinct multiple internal fields which are experienced in the muon interstitial sites. Above $T_N$, lattice deformations are indicated by field $\mu$SR suggesting a magneto-elastic mechanism. [Preview Abstract] |
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S1.00087: Spin temperature and thermalization in spin valves Tero Heikkil\"a, Moosa Hatami, Gerrit E.W. Bauer We study the concept of spin temperature in excited spin valves, more precisely the effective electron temperature that may become spin dependent, both in linear response and far from equilibrium. A temperature or voltage gradient create non-equilibrium energy distributions of the two spin ensembles in the normal metal spacer, which approach Fermi-Dirac functions through energy relaxation mediated by electron-electron and electron-phonon coupling. Both mechanisms also exchange energy between the spin subsystems. This spin thermalization may strongly affect thermoelectric properties spin valves, leading, e.g., to violations of the Wiedemann-Franz law.\footnote{Tero T. Heikkil\"a, Moosa Hatami and Gerrit E.W. Bauer, [arXiv:0910.4867].} [Preview Abstract] |
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S1.00088: Magnetization and magnetoresistance of ZnO thin film D. F. Wang, V. T. T. Thuy, Y. S. Lee, T. W. Eom, G. H. Kim, Y. P. Lee A ZnO film was deposited on a silicon wafer by magnetron sputtering, and the magnetic and the electronic properties have been studied. The magnetic property measurements show that the ZnO film is ferromagnetic at room temperature. The magnetoresistance (\textit{MR}) measurement reveals a positive \textit{MR} of 23.3{\%} at 2 K, which is due to the spin splitting induced by the \textit{sd} exchange interaction. Aging effect, however, was observed when the sample was put under the air for a month. The ferromagnetism disappears and the \textit{MR} becomes negative, too. It is explained by the modification of the defects in ZnO. The huge magnitude of the spin-dependent \textit{MR} as well as the aging effect of \textit{MR} demonstrates that the observed ferromagnetism in ZnO is intrinsic, not from impurity or contamination. [Preview Abstract] |
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S1.00089: Giant-Magnetoresistance(GMR) Siegel KEY FIRST Experimental Discovery Decade-Earlier PRE-``Fert"-``Gruenberg" in Nuc"el"ar ``Super"alloys: Science?;``SEANCE!!!; Ethics?; SHMETHICS!!! R. Hoffman, E. Siegel (So MIScalled) ``Fert"-``Grunberg"[PRL(1988;1989)] GMR 2007 physics Nobel/Wolf/Japan-Prizes VS. decade-earlier(1973-1977) KEY FIRST Siegel at:Westin"kl"ouse/PSEG/IAEA/ABB[google:``Martin Ebner"(94-04) in financial media]/Vattenfall/Wallenbergs/nuc"el"ar-DoE Labs[at flickr.com, search on ``Giant- Magnotoresistance''; find: Intl.Conf.Mag.Alloys \& Oxides(ICMAO), Haifa(Aug./1977); J.Mag.Mag.Mtls,(JMMM)7,312(1978)``unavailable: not yet scanned''/modified(last R(H) GMR Figs(7;8) deleted!!!) on JMMM/Reed-Elsevier website until 7/29/08 conveniently one- half-year after last (Nobel)award(12/2007); conveniently effectively deleted!!!; google: ``If Leaks Could Kill''; many APS/MRS Mtgs(1970s)$<<<$1988/1989] decade-earlier GMR: (1978)$<<<$ (1988); 1988-1978 =10 years = one full decadeprecedence!!!] first experimental discovery in (so MIScalled) ``super''alloys [182/82, Hastelloy-X, 600, 690(!!!), Stainless-Steels: ANY/ALL!!!] generic endemic Wigner's[JAP,17,857(1946)]- disease/Ostwald-ripening/spinodal-decomposition/overageing- embrittlement/ thermo-mechanical-INstability! [Preview Abstract] |
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S1.00090: Spin-disorder resistivity of heavy rare-earth metals from Gd to Tm: An ab-initio study James Glasbrenner, Kirill Belashchenko Electrical resistivity of heavy rare-earth metals has a dominant contribution from thermal spin disorder scattering. In the paramagnetic state, this spin-disorder resistivity (SDR) decreases through the Gd-Tm series. Models based on the assumption of fully localized 4f states treated as S or J multiplets predict that SDR is proportional to S$^{2}$ (S is the 4f shell spin) times a quantum correction (S+1)/S or (J+1)/J. The interpretation of this correction using experimental results is ambiguous. Since the 4f bandwidth is not small compared to the multiplet splitting, it is not clear whether the 4f shells in rare-earth metals behave as if they were fully localized and have a good quantum number S or J. To address this issue, in this work we calculate the paramagnetic SDR of the rare-earth metal Gd-Tm series using a non-collinear implementation of the tight-binding linear muffin-tin orbital method. The conductance is found using the Landauer-B\"{u}ttiker approach applied to the active region of a varying size, averaging the conductance over random spin-disorder configurations and fitting its size dependence to Ohm's law. The results are compared with experiment and discussed. The sensitivity to basis set and the treatment of the 4f electrons, as well as the role of exchange enhancement in the conduction band is considered. The issue of the quantum correction is examined in light of the new results. [Preview Abstract] |
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S1.00091: Manifestation of electron-electron interactions in time-resolved ultrafast pump-probe spectroscopy in C$_{60}$ Guoping Zhang, Thomas F. George The electron-electron interaction EEI is at the core of modern physics from high-temperature supercon- ductivity to giant magnetoresistance. Nanostructures, in general, and $\rm C_{60}$, in particular, open a new frontier for the study of the electron correlation effect in quasi-zero-dimensional materials. Here, a direct investigation of the time-resolved pump-probe signal in $\rm C_{60}$ shows [1] that the on-site electron-electron interaction manifests itself in two aspects in the early stage of ultrashort laser excitation. First, it pushes the signal peak to an earlier time delay for below-resonance excitation and narrows the peak-time change with probe detuning [2]. Second, it shortens the quasiparticle lifetime and, if the interaction is strong enough, it diminishes the spike in the lifetime at resonance. These features are detectable experimentally, and the findings here suggest a different route to detect dynamical EEI in nanostructure [3].\\[0pt] [1] Zhang and George, Phys. Rev. B {\bf 76}, 085410 (2007); [2] Zhang and George, J. Opt. Soc. Am. B {\bf 24}, 1150 (2007); [3] Zhang {\it et al.}, J. Phys. Chem. A {\bf 113}, 1175 (2009) [Preview Abstract] |
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S1.00092: Demagnetization field of conic domains Ross Dickinson, Timothy Royappa, Guoqing Wu The demagnetization field associated with a sample geometry is of particular interest in NMR spectroscopy and Knight shift analysis. The distribution of a non-uniform demagnetization field is calculated for samples with conical shapes. The results are compared for samples with paraboloid, ellipsoid and hyperboloid geometries at similar aspect ratios. We find that the demagnetization field is enhanced at the vicinity of the sample surface with the largest values found in the paraboloid geometry. [Preview Abstract] |
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S1.00093: Decay of Rabi spin oscillations generated by the acoustic wave in single-molecule magnets Gwang-Hee Kim We study the decay of Rabi spin oscillations generated by the sound wave close to the resonance. The analytical form of decay is obtained as a function of the phenomenological coupling constant whose internal dynamics is mainly caused by phonon coupling of single-molecule magnets. It is shown that the starting condition produced by the longitudinal magnetic field plays an important role in changing the oscillation period and the amplitude. The form of decay and the adjustable starting condition can be used to observe the oscillations of the magnetization of the sample in experiment. [Preview Abstract] |
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S1.00094: Ultrafast magnetization and spin oscillation in thin Ni/Fe film Joo In Lee, Chan Yong Hwang We investigated the electron and spin dynamics in thin Ni/Fe film by means of time-resolved magneto-optical Kerr effect (MOKE). The magnetization of the film changes rapidly during the subpicosecond, including the spin relaxation and electron-phonon coupling. We observed the spin oscillations in the MOKE signal varying the polarization angle between the pump and probe beams. The period of the spin oscillations was about 200 fs. It is supposed that this is not only related to the polarization in film induced ultrafast optical field but mediated also the spin-obit coupling. [Preview Abstract] |
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S1.00095: On chip detection of magnetic dynamics of single microscopic magnetic dot Xin Fan, Rong Cao, Yaping Zhang, Takahiro Moriyama, John Xiao Fast magnetic switching in data storage and microwave spintronic devices demand the understanding of magnetic dynamics in microscopic magnetic elements. Ferromagnetic resonance (FMR) spectrum measured with a microwave cavity or transmission line is one of the most popular tools to investigate the magnetic dynamics. These types of measurements usually require that at least one of the sample dimensions should be comparable to the microwave wavelength. Here we present an induction-based detection to obtain the ferromagnetic resonance spectrum from a single microscopic magnetic dot. A magnetic dot with a lateral size of 40 $\times $ 40 $\mu m^2$ and a thickness of 40 nm is lithographically patterned on top of a coplanar waveguide (CPW). A coplanar airprobe is positioned over the sample and perpendicular to the underlying CPW to pick up the microwave signal. With this setup, we are able to measure the FMR spectrum of the magnetic dot with very strong signal (15dB change in S21). Such direct detection of a single microscopic magnetic element also provides a simple way to investigate the nonlinear spin dynamics. This work was supported by NSF DMR Grant No. 08242249. [Preview Abstract] |
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S1.00096: Laser induced ultrafast magnetization reorientation in two dimensional arrays of Fe nanoparticles Zehra Cevher, Yu Gong, Wei Lai, Yuhang Ren, C. Kim, S. Delikanli, Hao Zeng We report on our recent study of ultrafast demagnetization and reorientation dynamics induced by femtosecond optical pulses in two dimensional arrays of magnetic nanoparticles. The transient Faraday rotation signal and magnetic hysteresis loops were acquired with a probe beam following excitation by pump pulses in the 50-nm Fe nanoparticle arrays. We observed rapid change and recovery of magnetization hysteresis loops of about 50 fs along with excitation of 50 fs optical pulses under Voigt geometry. The processes are consistent with the ultrafast coherent magnetic responses of the sample and clearly show that the mechanisms of optomagnetic interactions do not rely on laser-induced heating but have a nonthermal origin. Our results clearly show the feasibility of ultrafast optical control of both the magnetization and the magnetocrystalline anisotropy. [Preview Abstract] |
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S1.00097: ABSTRACT HAS BEEN MOVED TO X35.00013 |
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S1.00098: Effect on chemical substitution on properties of magnetoelastic properties of cobalt ferrite David Jiles, Naresh Ranvah, Ikenna Nlebedim, Yevgen Melikhov, John Snyder, Anthony Moses, Paul Williams There has been a recent interest in magnetic materials that can be used to sense or produce stress. Cobalt ferrite has emerged as a candidate material for these sensor and actuator applications because of its high magnetostrictive sensitivity and low hysteresis. However, there have been several studies to improve the properties of cobalt ferrite by chemical substitution. Substitutions of M$^{3+}$, where M=Mn, Cr, and Ga, have been tried along with Co$^{+2}$/Ge$^{4+}$ co-substitution in place of some of Fe$^{3+}$ in cobalt ferrite. The mechanisms by which these chemical substitutions change the magnetomechanical properties of cobalt ferrite depend on the site occupancy of these ions and their contribution to the moment of that site. These moment contributions in turn affect properties such as anisotropy, magnetization, Curie temperature and magnetostriction. In the current study the effect of site occupancy of different dopant ions on the magnetoelastic properties of cobalt ferrite has been analyzed. Anisotropy, magnetization and magnetostriction have been measured between 10 and 400~K. These properties have then been correlated to the site occupation preference of different dopant ions. [Preview Abstract] |
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S1.00099: Unexpected size and temperature dependence of the magnetic switching field of individual Co nanoislands D. Sander, G. Rodary, S. Wedekind, H. Oka, C. Etz, J. Kirschner We present results on the magnetic switching field of individual, nm small Co islands on Cu(111), which we obtained by low temperature spin-polarized STM in magnetic fields. We find that the magnetic switching field of the islands depends on both island size and temperature. A transition from a superparamagnetic to a blocked magnetization state is found with increasing islands size for islands with appr. 800 atoms at 8 K. The maximum switching field reaches 2.2 T for islands with 5000 atoms, and it decreases for larger islands. The switching field of an island decreases with increasing temperature. A quantitative analysis reveals the failure of the N\'eel-Brown model of thermally assisted magnetization reversal by coherent rotation, which has been successfully applied to similar systems. Our calculations find a spatial variation of the magnetic anisotropy and of the magnetization within a Co island. The implication of the inhomogeneous magnetic properties for the field-induced magnetization reversal is discussed. [Preview Abstract] |
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S1.00100: Preparation of Co nanoparticles embedded in anatase matrix by pulsed laser deposition Katsura Ikemiya, Yasushi Hirose, Toshihiro Shimada, Tetsuya Hasegawa Co nanoparticles embedded in anatase matrix were successfully obtained by pulsed laser deposition. LaSrAlO$_{4}$(001) was used as the substrate, on which a thin epitaxial seed layer of (001) oriented anatase TiO$_{2}$ was fabricated. When depositing Ti$_{1-x}$Co$_{x}$O$_{2}$ on the seed layer, phase separation into anatase TiO$_{2}$ and Co metal took place, and Co nanoparticles were dispersed in an anatase matrix. The TiO$_{2}$ seed layer substantially improved the crystallinity of anatase phase, which is speculated to promote the segregation of Co metal from anatase. TEM-EDS measurements revealed that the size of Co particles increased with increasing film growth temperature. Furthermore, we found that coercivity changed as a function of the particle size, as predicted by theoretical calculations. [Preview Abstract] |
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S1.00101: Dynamics of Spin Glass in NiFe$_{2}$O$_{4 }$Nanoparticle Y. Ying, T. W. Eom, J. M. Kim, Y. P. Lee, J. H. Kang The dynamic magnetic properties of spin glass in NiFe$_{2}$O$_{4}$ nanoparticles have been investigated. The strong irreversibility in the zero-field-cooled and the field-cooled temperature-dependent magnetizations implies the spin glass. The real part of the ac susceptibility$_{ }\chi '(T)$ curve shows a pronounced peak. With increasing frequency, the peak ($T_{f})$ shifts to a higher temperature, which is a characteristic of spin glass. The frequency-dependent $T_{f}$ data is fitted by a critical power law: $\tau =\tau _0 (T_f /T_g -1)^{-z\upsilon }$. The spin-glass transition temperature$ T_{g}$ is 290 K. The microscopic flipping time $\tau _0 $ of the fluctuating spins and the critical parameter $z\upsilon $ are obtained to be 10$^{-10}$ s and 8.3 respectively. They are both within the ranges typical for spin glasses (10$^{-10}$ - 10$^{-12 }$s for $\tau _0 $ and 5 - 10 for $z\upsilon )$, confirming the nature of spin glass. The excellent fit by the Vogel-Fulcher model, revealing the existence of the inter-particle interaction, exhibits that spin glass rather than superparamagentism exists in NiFe$_{2}$O$_{4}$ nanoparticles. [Preview Abstract] |
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S1.00102: Studies on the magnetic reversal properties of cobalt anti-dot micropatterned arrays N. G. Deshpande, M. S. Seo, X. R. Jin, S. J. Lee, Y. P. Lee, J. Y. Rhee, K. W. Kim Large-area micropatterned arrays of cobalt anti-dots with different lattice symmetries (square and rhomboid geometry) and periodicities were fabricated by using the CMOS process. The surface morphology as well as the surface topography was checked by scanning electron microscopy and atomic force microscopy, and the magnetic properties were studied by MOKE and magnetic force microscopy (MFM). A systematic study on the magnetic-reversal mechanism, the in-plane anisotropy and the switching-field properties were carried out, together with the OOMMF simulations. It was found from the MOKE measurements that different lattice geometries induce different anisotropies with changes in the easy and the hard axes. In addition, the inclusion of non-magnetic holes in the uniform magnetic film, with modified lattice geometry and periodicity not only changes the domain configuration but also drastically affects the switching field. The MFM images in the remanent state show well-defined domain structures which are periodic in nature according to the lattice geometry. The observed change in the magnetic properties is closely related to the fact that the inclusion of non-magnetic vacancies hinders the domain wall motion, and to the geometrical variation giving rise to different anisotropy. [Preview Abstract] |
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S1.00103: Size Distribution and Anisotropy of Self-assembled MnAs Nanoparticles in GaAs Robert DiPietro, Hannah Johnson, Steve Bennett, Tom Nummy, Laura Lewis, Don Heiman The size distribution and anisotropy of composite films of MnAs nanoparticles in a GaAs matrix have been determined by \textit{thermomagnetic} measurement and subsequently confirmed by electron microscopy studies. The composite was fabricated from a homogeneous Ga$_{0.9}$Mn$_{0.1}$As film grown by MBE and annealed at 520-570\r{ }C to produce superparamagnetic particles of diameter 10-50 nm. Magnetization measurements show a peak in the temperature-dependent zero field cooling (ZFC) moment, $m_{ZFC}$(T), near the system blocking temperature T$_{B}$. The distribution in T$_{B}$ was first obtained from $f$(T$_{B})\propto $ d/dT [T$\cdot m_{ZFC}$(T)], derived assuming that the moment of a particle below its blocking temperature is zero and varies as 1/T above the blocking temperature. The distribution in particle diameter $f$(D) was obtained using the usual relation between blocking temperature and particle volume, K$_{eff}$V/k$_{B}$T$_{B}$=25, where K$_{eff}$ is the effective MnAs anisotropy constant. A value for the anisotropy constant was obtained by comparing the thermomagnetic $f$(D) with the size distribution obtained visually from SEM micrographs, where $<$D$>$=12 nm and width $\Delta $D=7nm for a 50-nm-thick film. The visual and thermomagnetic size distribution functions are found to be nearly identical using K$_{eff}$=160,000 erg/cm$^{3}$. Work supported by NSF DMR-097007. [Preview Abstract] |
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S1.00104: First principles calculations of the thermodynamics of magnetic nanoparticles using the Wang-Landau Embedded Cluster Method Markus Eisenbach, Balazs Ujfalussy Calculations of the ground states of magnetic nanoparticles can be performed reliably both non-relativistically as well as by solving the Dirac equation using Density Functional Theory. Here we present a method that allows us to calculate the free energy and magnetization of nanoscale systems on surfaces by combining the relativistic embeded cluster method [B. Lazarovits, L. Szunyogh, and P. Weinberger, Phys Rev B 65 (2002)] with the Wang-Landau method [F. Wang and D. P. Landau, PRL 86, 2050 (2001)]. We show results for the thermodynamic properties and finite temperature magnetization of surface nanostractures, in particular monatomic magnetic chains on surfaces. [Preview Abstract] |
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S1.00105: Anomalous thermal expansion in iron-nickel alloys:\ {\it ab initio\/} calculations and the relation to magnetism Fran{\c c}ois Liot, Chris Hooley The thermal expansion of ferromagnetic disordered iron-nickel alloys at various temperatures is studied, using an approach based on Ising magnetism and first-principles calculations of the disordered local moment (DLM) type. The theory correctly describes the strong increase of the thermal expansion coefficient with increasing nickel concentration from 0.35 to 0.8 at room temperature. It also reproduces the Invar effect for $x=0.35$. These results are analyzed, and the effect of the magnetic free energy contribution on the thermal expansion is discussed. Furthermore, a simple relationship between anomalous thermal expansion and magnetism is presented. It is argued that an alloy shows the Invar effect if the concentration of nearest-neighbor iron-iron pairs with anti-parallel local moments increases sufficiently rapidly with temperature over a broad temperature interval. [Preview Abstract] |
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S1.00106: Spin glass behavior of Mn-intercalated TiS$_{2}$ Paul Shand, Michael Streicher, Sofya Markova, Tyler Rash, Laura Strauss, Tim Kidd We have performed extensive magnetic measurements on Mn$_{0.09}$TiS$_{2}$ to determine the nature of the low-temperature transition previously observed in this intercalated dichalcogenide. Zero-field cooled and field-cooled dc magnetization measurements exhibit a cusp and bifurcation at $T_{g}$ = 5.5 K. The real and imaginary parts of the ac susceptibility also show peaks in the vicinity of $T_{g}$. The peaks shift with frequency, with the magnitude of the shift being similar to those observed in RKKY-mediated spin glasses. Time-dependent dc magnetization measurements suggest aging behavior at temperatures lower than $T_{g}$, consistent with non-equilibrium dynamics. The totality of the evidence suggests that Mn$_{0.09}$TiS$_{2}$ is a spin glass similar to canonical RKKY spin glasses such as Cu$_{1-x}$Mn$_{x}$. [Preview Abstract] |
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S1.00107: Electrically Tunable Y-type Hexaferrite-Piezoelectric Microwave Resonator Alexander Tatarenko, G. Srinivasan An electrically tunable Y-type hexaferrite-piezoelectric resonator has been designed and characterized. Such Y-type hexagonal ferrites have large in-plane anisotropy that would facilitate the observation of ferromagnetic resonance (FMR) over 5-25 GHz with external bias fields of 0-5 kOe. In a ferrite-piezoelectric bilayer the FMR could be tuned with an electric field E applied to the piezoelectric layer. The piezoelectric deformation manifests as an internal magnetic field in the ferrite and will lead to a shift in FMR. Single crystal ferrites of the composition Ba$_{2}$Zn$_{2}$Fe$_{12}$O$_{22}$ (Zn$_{2}$Y) were used. The crystals were grown by the floating zone technique. The resonator consisted of a 100 micron thick 1 mm x 3 mm Zn$_{2}$Y bonded to 10 mm diameter ,200 micron thick lead zirconate titanate (PZT). The resonator was placed in a micorstripline and excited with 1 mW of microwaves. The reflected or transmitted power was measured with a a vector network analyzer. Reflected power versus frequency profiles at 5-25 GHz for a series of in-plane bias magnetic field $H$ showed an increase in the FMR frequency by 60 MHz for E = 7 kV/cm. These resonators can be used as filters or phase shifters. -- work supported by grants from ARO and ONR. [Preview Abstract] |
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S1.00108: Magnetoelectric characterization of magnetostrictive-piezoelectric semi-ring structure V.M. Petrov, I.N. Soloviev, Ning Zhang, G. Srinivasan Resonant modes and magnetoelectric (ME) performance of piezoelectric semi-ring with magnetostrictive insert are considered. The magnetostrictive rod is supposed to match the diameter of the semi-ring. The ac magnetic field is applied along the rod so that demagnetizing effects are minimized. The output voltage is induced in the radial direction of the piezoelectric semi-ring. Using such a structure enables effective transfer of mechanical strain and strong ME coupling. Theoretical modeling of resonant modes for in-plane bending vibration in the semi-ring was applied to PZT ring and Terfenol-D rod. The estimates agree with measured values of 70 V/(cm$\cdot $Oe). Such semi-ring ME structures are useful for magnetic field sensor applications. -- work supported by grants from DARPA and NSF. [Preview Abstract] |
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S1.00109: Domain-wall motion across geometrical nanoconstrictions in GaMnAs nanowire Dong-Hyun Jang, Sung Un Cho, Yun Daniel Park We report on the domain wall traversing across a GaMnAs nanowire with geometrical nanoconstrictions in series. The nanowire is patterned from 100 nm GaMnAs/GaAs(001) prepared by low-temperature molecular beam epitaxy (LT-MBE). From SQUID magnetization measurements as well as magnetotransport measurements, the magnetic ordering temperature is found to be 80 K. Series of nanoconstrictions, equally spaced (2 microns) and equally designed widths ($<$ 40 nm), are patterned by e-beam lithography and realized by chemical etching processes. Electrical probes are e-beam patterned and are realized by Au/Ti e-beam evaporation and subsequent lift-off. By monitoring the resistance across the nanowire while sweeping the magnetic field along the wire axis, we observe change in resistance steps, which number corresponds to number of nanoconstrictions. Furthermore, we will discuss the resistance changes across each constriction to verify the domain wall movement across the nanowire. [Preview Abstract] |
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S1.00110: Physical and microwave characteristics of Gd-doping yttrium iron garnet (YIG) M.F. Tai, K.Z. Wang, L.R. Hong, C.J. Wu, L.C. Lin, H.C. Ku, S.Z. Liu, K.M. Kwo Ferrimagnetic insulating yttrium iron garnet (YIG) are widely used in microwave devices due to their unique magnetic, electrical and microwave properties. The substitution of rare earth ion for the Y$^{3+}$ ion can modulate or improve its high-frequency properties for microwave application. We prepared a serial of single-phased polycrystalline Y$_{3-x}$Gd$_{x}$Fe$_{5}$O$_{12}$ garnet samples with $x $= -- 3.0 by the conventional ceramic technique. The refinement of X-ray diffraction patterns of the samples shows them to crystallize in a centrosymmetrically cubic structure with a\textit{ Ia3d} space group. Both the lattice constant and dc saturation magnetization at room temperature decrease with increasing Gd$^{3+}$ We also measured the low- and high-frequency dielectric constant and tangent loss. As well, the spin wave line width $\Delta $H$_{k}$ regarding the ferromagnetic resonance behavior is on progress. These results are important to develop high-power circulators and isolators in microwave range. [Preview Abstract] |
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S1.00111: Observation of surface polarization in a diluted magnetic semiconductor GaMnAs/GaAs(111) Changsoo Park, H.K. Choi, C.U. Yang, Y. Shon, J. Y. Son, Y.D. Park We report ferromagnetic and ferroelectric behaviors of a Mn doped GaAs epilayer grown on a GaAs (111) substrate by low-temperature molecular beam epitaxy. We confirmed structure and ferromagnetic properties of the Mn doped GaAs layer by high resolution x-ray diffraction and superconducting quantum interference device measurements. We estimated the ferromagnetic Curie temperature to be 110K from both anomalous Hall effect and magnetization temperature dependence measurements. Electric force microscopy at room temperatures show enhanced ferroelectric switching behaviors on the surface of the Mn doped GaAs (111). [Preview Abstract] |
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S1.00112: Novel mechanism of reversible photoinduced magnetism in Prussian blue analogs Mukul Kabir, Krystyn J. Van Vliet Prussian blue (PB) crystals are metallorganic materials that exhibit several modes of inducible changes in oxidation state, and thus changes in physical and functional properties. Reversible switching of magnetic state by external stimuli has been demonstrated experimentally for PB and PB analogs, with many potential applications including information storage and processing. For example, at low temperature, illumination of visible light (500-700 nm) induces bulk magnetization in KCo[Fe(CN)$_6$]:5H$_2$O, which can be eliminated by near-IR wavelengths of $\sim$ 1319 nm). However, the molecular-scale mechanisms by which such magnetic state switching occurs have not yet been elucidated, and are required to facilitate design of this and other such magnetic switch-inducible materials. Here we report our simulations and proposed switching mechanism for this PB analog crystal. We apply density functional theory, corrected for on-site Coulomb interaction (DFT+U), to describe the structure and energetic ground state of anhydrate KCo[Fe(CN)$_6$]. This ground state has large octahedral ligand-field splitting, and consequently exhibits a low-spin structure. We find that the low-spin to high-spin transition is a two step process involving charge transfer between the metal atoms via the carbon-nitrogen ligand, followed by electron transfer within the cobalt atom. This spin-crossover results in 10\% increase in C-N bondlength, and proceeds via a strong Jahn-Teller active metastable intermediate state. [Preview Abstract] |
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S1.00113: Correlation of magnetic properties, morphology and structural parameters in Mn$_{0.5}$Zn$_{0.5}$Fe$_{2}$O$_{4}$ nanoparticles P. Prieto, J. Prado, J. Lopez, M.E. Gomez, G.A. Mendoza The effect of structural and morphology parameters on the magnetic behavior of Mn$_{0.5}$Zn$_{0.5}$Fe$_{2}$O$_{4}$ Nanoparticles is presented. The samples were prepared by chemical co-precipitation method on mica substrates at temperatures between 60-90 \r{ }C. The particle sizes were obtained using AFM ($\sim $ 3-15 nm) and MFM. Magnetization measurements have been adjusted for a system of non-interacting nanoparticles with a volume distribution according to: $M(T,H,t)=\frac{m_o ^2H}{2T}\int\limits_0^{V_C } {dVf(V)} V^2$ Where m$_{o}$ is magnetization of the single particle, V$_{c}$ is critical volume and $f(V)$ is distribution size function. Blocking temperature T$_{B}$, magnetization of the single particle, anisotropy energy density and size distribution were obtained as function of the average particle size. The dependence of parameters such as M$_{s}$ and H$_{c}$ has been determines as function of the temperature and correlated with the particle sizes. [Preview Abstract] |
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S1.00114: Investigating the Effective Hydrodynamic Size of Dextran Coated Iron Oxide Nanoparticles Prem Vaishnava, Vikas Gumber, Rajesh Regmi, Correy Black, Ambesh Dixit, Vaman Naik, Chandran Sudakar, Ratna Naik, Gavin Lawes We report synthesis and functionalization of magnetite nanoparticles by coating with dextran having 5, 15-20, 60-90, and 670 kDa molecular weights. The hydrodynamic radii of the functionalized nanoparticles suspended in water measured by dynamic light scattering technique assuming the bulk value for viscosity, were 91, 100, 106, and 132 nm, respectively. By measuring the ac magnetic loss, we determined the effective sizes to be 105, 113, 122, and 136 nm, respectively. The sizes measured by these techniques are approximately twice as large as expected given the iron oxide nanoparticle size and surfactant molecular chain length, at least for the lower molecular weight dextran. Comparing the results of hydrodynamic sizes studies, we conclude that the effective viscosity for the coated nanoparticles may be different than the bulk viscosity of the carrier liquid. [Preview Abstract] |
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S1.00115: Microwave assisted switching in individual and interacting magnetic nanowires D. Grundler, D. Heitmann, J. Topp Recent spin dynamics experiments have shown that microwave assisted switching (MAS) occurs if a magnet is excited at large excitation amplitudes, i.e., in the non-linear regime.[1,2] MAS has reduced the coercive fields $H_c $. We studied the MAS process on arrays of nanopatterned permalloy wires (20 nm thick, 300 nm wide, and 180 $\mu $m long) where we varied the edge-to-edge separation $d$ between 100 and 700 nm. MAS was found to reduce $H_c $ resonantly at the quantized center-mode eigenfrequency of the nanowires. MAS also narrowed the distribution of $H_c $ of the nanowires. The efficiency for the MAS process depended on, both, the applied in-plane field and separation $d$. To model this behavior we considered the effect of dipolar interactions. [3] MAS was most efficient for $d$ = 100 nm and reduced $H_c $ by about a factor of two. Our observations are relevant if MAS is considered for encoding information in magnetic bits of high density. [1] J. Podbielski et al., Phys. Rev. Lett. 99, 207202 (2009). [2] G. Woltersdorf et al., Phys. Rev. Lett. 99, 227207 (2009).[3] J. Topp et al., in press. [Preview Abstract] |
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S1.00116: Modification of edge mode dynamics by oxidation in Ni$_{80}$Fe$_{20}$ thin film edges Meng Zhu, Robert McMichael As magnetic storage and logic devices scale down to the sub-micron level, the effect of edge oxidation on magnetic properties needs to be identified. We use ``edge mode'' ferromagnetic resonance (FMR) to probe the magnetic properties of oxidized Ni$_{80}$Fe$_{20}$ (Py) nanostripe edges. The oxidation is carried out using either oxygen plasma or thermal annealing in oxygen. For both treatments, the edge saturation field decreases with oxidation. However, the effects of the two oxidation methods on the effective out-of-plane anisotropy field show opposite trends. Bulk mode resonance shifts and micromagnetic simulations suggest that a reduction in the bulk magnetization occurs during thermal annealing. Linewidth measurements show that plasma oxidation produces little change in damping, but thermal annealing increases effective damping. [Preview Abstract] |
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S1.00117: ABSTRACT WITHDRAWN |
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S1.00118: Structural stability of Ni quantum point contacts under electrical stresses Kenji Yoshida, Akinori Umeno, Shuichi Sakata, Kazuhiko Hirakawa We have investigated the structural stability of quantum point contacts (QPCs) of ferromagnetic metals under electrical stresses, using a spectroscopic method called ``electromigration (EM) spectroscopy[1]''; i. e., we have applied a feedback-controlled electrical break junction method to Ni QPC samples and obtained a histogram of the critical junction voltages, $V_{c}$, at which there occurred one-by-one atom removal due to EM. The obtained histogram shows that $V_{c}$ is distributed over a range of from 0.2 $\sim $ 0.4 V, which are consistent with the surface diffusion potential, $E_{D}$, of Ni. It was found that, although the local current density through the Ni QPCs is higher than 10$^{10}$ A/cm$^{2}$, the Ni QPC is stable, as long as the junction voltage is less than a certain threshold voltage determined by $E_{D}$ of Ni. The present result indicates that the junction voltage, rather than the current density, plays a critical role in EM in metallic QPCs and that the EM spectroscopy is a powerful tool for determining the structural stability of electrically-biased atomic-scale systems. [1] A. Umeno and K. Hirakawa, Appl. Phys. Lett. 94, 162103 (2009) [Preview Abstract] |
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S1.00119: Surface Induced Suppression of Magnetization and Surface magnetization Reversal in Magnetic Nanoparticles Chaehyun Kim, Wei Lai, Renat Sabirianov, Yuhang Ren, Hao Zeng Ferrite nanoparticles show strong size and surface dependent magnetic properties. These manifest themselves as a reduced magnetization with decreasing size and an unconventional temperature dependence of magnetization. These effects can be attributed to competing exchange interactions that contribute differently at the nanoparticle surface and interior, leading to reduced ferromagnetic order at the surface. A simple model is constructed that are consistent with experimental observations and further predict an independent magnetization reversal mode for surface spins. This prediction is verified by magnetic second harmonic generation measurements. [Preview Abstract] |
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S1.00120: Synthesis and Physical Properties of Sulfur Doped Iron Nanoparticles M. Tarsem Singh, H. Han, Y. Qiang, D. Baer, J. Amonette, P. Nachimuthu, C. Wang, M. Engehard We have studied the physical properties of iron magnetic nanoparticles (MNPs) and sulfur doped iron MNPs. Both types of MNPs were synthesized under the same conditions using magnetron sputtering gas-aggregation nanocluster source. For sulfur doped particles, 5 sccm of hydrogen sulfide gas was used in the aggregation chamber where it reacts with iron and forms sulfur doped iron particles. XPS results show the presence of sulfate and sulfide peak. TEM images indicate that iron sulfide particles are bigger in size than pure iron particles. This result is consistent with the magnetization measurement as coercive field is higher for sulfur doped particles. Our aim is to study the physical behavior of sulfur doped iron particles and find out its exact crystal structure. This type of MNPs is mainly used to study the effects of sulfur on the corrosion and reactivity of iron nanoparticles in water remediation. [Preview Abstract] |
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S1.00121: Effect of oxidation on interlayer exchange coupling in Fe$\vert $MgO$\vert $Fe tunnel junctions H.-X. Yang, M. Chshiev, A. Kalitsov, A. Schuhl, W.H. Butler The interlayer exchange coupling (IEC) in MgO-based magnetic tunnel junctions (MTJ) is a subject of major interest for spintronics community [1,2]. Recent experiments demonstrated that oxydation conditions strongly affect the character of the IEC in Fe/MgO/Fe(001) MTJs [3]. In order to elucidate the effect of over- and under-oxidation on the nature of the IEC in Fe$\vert $MgO$\vert $Fe MTJs, we performed systematic studies of the influence of O impurities and vacancies on the IEC using ab-initio and tight-binding approaches. We found that the O vacancies cause strong AF IEC in agreement with previous studies [2-4]. Furthermore, an additional O atom at the Fe$\vert $MgO interface makes the IEC ferromagnetic in for 3ML and above MgO thicknesses in agreement with experiment [3]. We demonstrate also that the full structural relaxation of ideal Fe$\vert $MgO$\vert $Fe MTJs may lead to the antiferromagnetic IEC. Tight-binding calculations of the IEC in the framework of the Keldysh formalism were also performed. The results obtained support our first principles calculations. [1] J. Faure-Vincent et al, Phys. Rev. Lett. 89, 107206 (2002); [2] T. Katayama et al., Appl. Phys. Lett. 89, 112503 (2006); [3] Y.F. Chiang et al, Phys. Rev. B 79, 184410 (2009); [4] M.Y. Zhuravlev et al, Phys. Rev. Lett. 94, 026806 (2005). [Preview Abstract] |
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S1.00122: Magnetic and dielectric phase diagrams of Tb$_{1-x}$Eu$_{x}$MnO$_{3}$ ${(0 \leq x \leq 1)}$ Y.Y. Hsu, H.C. Hsu, C.D. Yang, W.Y. Tseng, H.C. Ku The dependence of dielectric and magnetic properties with structural parameters have been investigated for the mixed- crystal system Tb$_{1-x}$Eu$_{x}$MnO$_{3}$ ${(0 \leq x \leq 1)} $. Since the ferroelectricity observed is originated from the incommensurate antiferromagnetism of Mn$^{3+}$ ions, the magnetic interaction strength should pronouncedly affect these properties. The interaction strength is dominated by the Mn-O bond length and Mn-O-Mn bond angle thus makes the structural discussion substantial. The Reitveld refinement showed an $ab$- plain Mn-O-Mn bond angle increases smoothily, as $x$ increased, with a slight jump around $x$ = 0.4-0.5, which is close to the disappearance of ferroelectricity, while the magnetic ordering temperature $T_N$ almost not changed. The phase diagrams observed in magnetism and dielectricity with $x$ indicate enriched magnetic and electric structures in this system and will be discussed in details. [Preview Abstract] |
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S1.00123: Role of cationic/oxygen vacancies in transport and magnetic properties of NiFe$_{2}$O$_{4}$ thinfilms prepared by pulsed laser deposition G. Hassnain Jaffari, Safia Anjum, Abdul K. Rumaiz, S. Ismat Shah Non-stoichometric NiFe$_{2}$O$_{4}$ thin films have been synthesized pulsed laser deposition. We have found monotonic increase in saturation magnetization and non-monotonic increase in conductivity as a function of oxygen pressure during growth of the samples. Substantial reduction in magnetization is found which varies from 0.4{\%} to 40{\%} of bulk value as a function of oxygen partial pressure during the growth of the samples. Three orders of magnitude increase in the conductivity of the sample prepared at an excessive oxygen deficient environment. These variations in saturation magnetization and conductivity as been discussed within the framework of cation/oxygen vacancies in inverse spinel NiFe$_{2}$O$_{4}$ structure. The changes in the electronic structures due to the presences of the vacancies have been investigated using X-ray Photoelectron spectroscopy. [Preview Abstract] |
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S1.00124: Optical Properties and Electronic Structures of NiFe$_{2}$O$_{4}$ and CoFe$_{2}$O$_{4}$ Thin Films R.C. Rai, S. Wilser, M. Guminiak, M.L. Nakarmi We present the growth and investigation of inverse spinel ferrite NiFe$_{2}$O$_{4}$ and CoFe$_{2}$O$_{4}$ thin films. An electron beam deposition system was used to prepare ferrite thin films in the oxygen environment on sapphire and STO single crystal substrates. We measured a variable temperature (80 - 500 K) transmittance of these films to investigate their optical and electronic structures. The optical spectra of thin film samples show insulating characters with several electronic transitions, such as on-site metal $d$ to $d$ and charge transfer oxygen 2$p$ to metal 3$d$ transitions. Electronic transitions have been assigned based on the first principles calculations and comparison with chemically similar Ni and Co-containing compounds. [Preview Abstract] |
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S1.00125: Spin-current induced dissipation in metals Ashwin A. Tulapurkar, Yoshishige Suzuki By using the Boltzmann`s transport equations, we calculate the rate at which entropy is produced when spin-polarized current flows through a metal. A new pair of thermodynamic force and current is required to describe the entropy production. The dissipation, which is related to the entropy production, can be interpreted in terms of a simple circuit model which is also used to describe the giant magneto-resistance (GMR) effect. As an application of these results, we find that when current is passed through an interface between two oppositely magnetized ferromagnets, the extra dissipation produced due to the GMR effect is more localized than the variation of spin-dependent electrochemical potentials. [Preview Abstract] |
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S1.00126: First-principles quantification of the non-adiabatic spin torque parameter in Fe and Ni Keith Gilmore, Ion Garate, Allan MacDonald, Mark Stiles We have used density functional methods to evaluate the non-adiabatic spin-transfer torque parameter $\beta$ for Fe and Ni as a function of the electronic scattering rate. Like the damping parameter $\alpha$, $\beta$ contains contributions due to both intraband and interband electronic transitions. For both Fe and Ni, the intraband terms are proportional and have a ratio of approximately 1 for Fe and about 2.1 for Ni. We separate the numerically challenging interband contribution into two terms, one that we show is qualitatively and quantitatively similar to the interband contribution of $\alpha$, and one that is small, but non-zero. Our calculations indicate that $\beta$ is interband dominated at scattering rates consistent with room temperature for Fe and Ni, as is the case for $\alpha$. From this, we expect the two dynamic parameters to be approximately equal for both metals. [Preview Abstract] |
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S1.00127: Growth of Single-Crystalline, Atomically Smooth MgO Films on Ge(001) by Molecular Beam Epitaxy Wei Han, Yi Zhou, Yong Wang, Yan Li, Jared Wong, Keyu Pi, Adrian Swartz, Kathy McCreary, Faxian Xiu, Kang Wang, Jin Zou, Roland Kawakami Developing single-crystalline FM/MgO/Ge(001) heterostructures is essential for Ge-based spintronics. We investigate the growth of MgO thin films on Ge(001) via molecular beam epitaxy and find that the growth temperature plays a key role in the quality of MgO thin films. Reflection high-energy electron diffraction (RHEED) and atomic force microscopy show that the single-crystal quality and atomically smooth morphology are optimized for a growth temperature of 250\r{ }C. RHEED and transmission electron microscopy indicate that the MgO is (001)-oriented and the MgO unit cell has a 45\r{ } in-plane rotation with respect to that of Ge, providing a high quality film and interface for potential spin injection experiments. [Preview Abstract] |
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S1.00128: Characterization of Aluminum Oxide Tunnel Barrier for use in a Non-Local Spin Detection Device Joseph Abel, John Garramone, Ilona Sitnitsky, Vincent LaBella Aluminum oxide can be utilized as an interface layer between ferromagnetic metals and silicon to achieve spin injection into silicon. The goal of our research is to inject and readout spins using a non-local measurement device that utilizes 1-2~nm aluminum oxide interface layers as tunnel barriers. An important step of fabricating a non-local measurement device out of silicon is the growth of an aluminum oxide tunnel barrier\footnote{O. van't Erve, A. Hanbicki, M. Holub, C. Li, C. Awo-Affouda, P. Thompson and B. Jonker, Appl. Phys. Lett. 91, 212109 (2007).}. Aluminum Oxide thin films where grown using a Knudsen cell to deposit 1 nm, 2 nm, and 3 nm of aluminum. The films were then oxidized in O$_2$. X-ray photoelectron spectroscopy (XPS) was performed to characterize the film stoichiometry, and the band gap. We will also report on current voltage measurements of these films after they have been capped with metal and compare the resistance area product to those calculated for spin injection into silicon\footnote{B.-C. Min, K. Motohashi, C. Lodder, and R. Jansen, Nat. Mater. 5, 817 (2006). }. [Preview Abstract] |
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S1.00129: Atomic and magnetic structures of (CuCl)LaNb$_2$O$_7$ and (CuBr)LaNb$_2$O$_7$: Density functional calculations Chung-Yuan Ren, Ching Cheng The atomic and magnetic structures of (Cu$X$)LaNb$_2$O$_7$ ($X$=Cl and Br) are investigated using the density-functional calculations. Among several tens of the examined structures, an orthorhombic distorted $2\times 2$ structure, in which the displacement pattern of $X$ halogens resembles the model conjectured previously based on the empirical information is identified as the most stable one. The displacements of $X$ halogens, together with those of Cu ions, result in the formation of $X$-Cu-$X$-Cu-$X$ zigzag chains in the two materials. The nearest-neighbor interaction within the zigzag chains are determined to be antiferromagnetic (AFM) for (CuCl)LaNb$_2$O$_7$ but ferromagnetic (FM) for (CuBr)LaNb$_2 $O$_7$. On the other hand, the first two neighboring interactions between the Cu cations from adjacent chains are found to be AFM and FM respectively for both compounds. The magnitudes of all these in-plane exchange couplings in (CuBr)LaNb$_2$O$_7$ are evaluated to be about three times those in (CuCl)LaNb$_2$O$_7$. In addition, a sizable AFM inter-plane interaction is discovered between the Cu ions separated by two NbO$_6$ octahedra. The present study strongly suggests the necessity to go beyond the square $J_1-J_2$ model in order to correctly interpret the magnetic property of (Cu$X)$LaNb$_2$O$_7$. [Preview Abstract] |
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S1.00130: Effects of disorder and bond angle on the magnetic properties of ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$-like materials Tyrel McQueen, Danna Freedman, Robin Chisnell, Tiaheng Han, Young Lee, Daniel Nocera The mineral herbertsmithite, ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$, contains two-dimensional Kagome layers of Cu$^{2+}$ (S=1/2) ions. It is a candidate for the long-sought-after spin-liquid ground state as no long range magnetic order is found above T = 50 mK despite strong antiferromagnetic interactions, $\theta _{CW} \quad \sim $ -300 K. However, it is difficult to determine how Zn-Cu site mixing affects the ground state properties, due to difficulties in quantifying the degree of Zn-Cu disorder. Here the structural and magnetic properties on chemically related systems in which Zn$^{2+}$ is replaced by Mg$^{2+}$ and Cd$^{2+}$ are presented. These results permit direct identification of the effect of disorder on the observed magnetic behavior, and highlight the importance of the Cu-O-Cu bond angle in determining the magnetic coupling between Cu$^{2+}$ ions within each layer. [Preview Abstract] |
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S1.00131: ESR Studies of the Quantum Spin-Ladder System BPCB Sergei Zvyagin, E. \v{C}i\v{z}m\'{a}r, M. Ozerov, J. Wosnitza Magnetic excitations in the spin-ladder material (C$_5$H$_{12}$N)$_2$CuBr$_4$ (known as BPCB) have been probed by means of electron spin resonance (ESR). A pronounced anisotropy ($\sim 5\%$ of the rung interaction) was revealed. Our observations are in contrast to the isotropic spin-ladder model, previously employed for analysis of magnetic properties and the phase diagram of this compound. It is argued that such an anisotropy in BPCB is determined by the substantial spin-orbit coupling illuminating the importance of anisotropy effects in BPCB and other spin systems with the cooperative ground state. Details of the ESR magnetic excitation spectrum in BPCB are discussed. [Preview Abstract] |
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S1.00132: Magnetoresistance effects in phthalocyanine based magnetic tunnel Junctions C. Barraud, R. Mattana, P. Seneor, S. Fusil, K. Bouzehouane, C. Deranlot, F. Petroff, A. Fert, J.B. Beaufrand, D.J. Kim, R. Rakshit, J. Arakski, S. Boukari, M. Bowen, E. Beaurepaire We will report on the fabrication and magneto-transport properties of nanometer size organic magnetic tunnel junctions based on the cobalt-phthalocyanine organic semiconductor. We will present spin dependent transport measurements in Co/CoPc/Co magnetic tunnel junctions where the thickness of the organic semiconductor is only few nm. We have observed a significant magnetoresistance effect at low temperature. Two contributions to the magnetoresistance are isolated: a tunnel anisotropic magnetoresistance (TAMR) and a spin valve effect associated to the magnetic configuration of Co electrodes (parallel and antiparallel magnetic configurations). Strong variations of coercive fields with respect to angle measurements and to the bias voltage were observed. The bias dependence of MR effects was also studied and revealed an interesting new behavior compared to standard inorganic magnetic tunnel junctions. All these results will be discussed. [Preview Abstract] |
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S1.00133: Single Molecule Manipulation of Co-Salophene-Br$_2$ Andrew DiLullo, Shih-Hsin Chang, Germar Hoffman, Roland Wiesendanger, Saw-Wai Hla Using Low Temperature Scanning Tunneling Microscopy (LT-STM) manipulation we studied the system of individual Co-Salophene-Br$_2$ molecules adsorbed on a Au(111) surface. Co-Salophene-Br$_2$ has a metallic ion caged on three sides, and two of three $\pi$-rings have bromine termination. This molecule adsorbs onto Au(111) in a planar orientation and forms ordered molecular clusters. With the STM tip single molecules were pulled out from molecular clusters and then the bromine atoms were individually dissociated to form Co-Salophene molecules having two, one, or zero attached bromine atoms. The bond dissociation was selectively done by locally injecting tunneling electrons. In conjunction with our manipulation studies Kondo resonances of the intact and de-brominated molecules were probed by means of local tunneling spectroscopy and spectroscopic mapping. This work is a step towards the engineering of molecular systems on a surface from basic molecular units. [Preview Abstract] |
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S1.00134: INSULATORS AND DIELECTRICS |
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S1.00135: Time-Domain Thermoreflectance Measurements of Thermal Transport in Amorphous SiC Thin Films Brian Daly, Donald Hondongwa, Sean King We present ultrafast optical pump-probe measurements of thermal transport in a series of amorphous SiC samples. The samples were grown on Si wafers by plasma enhanced chemical vapor deposition utilizing various combinations of methylsilanes and H$_{2}$ and He diluent gases. The sample films were well characterized and found to have densities (1.3 -- 2.3 g cm$^{-3})$ and dielectric constants (4.0 -- 7.2) that spanned a wide range of values. Prior to their measurement, the samples were coated with 40-70 nm of polycrystalline Al. The pump-probe measurements were performed at room temperature using a modelocked Ti:sapphire laser that produced sub-picosecond pulses of a few nJ. The pulses heat the Al coating, causing a transient reflectivity change. As the Al film cools into the SiC film, the reflectivity change can be measured, giving a measure of the thermal effusivity of the SiC film. We then extract values for the thermal conductivity of the SiC films and find that it varies from less than half of the thermal conductivity of amorphous SiO$_{2}$ for the lower density materials to somewhat larger than amorphous SiO$_{2}$ for the highest density films. [Preview Abstract] |
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S1.00136: Ion conductivity relaxation and specific heat close to the first-order phase transition of $\gamma -$RbAg$_{4}$I$_{5}$ Ruben A. Vargas, Hernando Correa, Diego Pe\~na Lara We report on simultaneous measurements of specific heat at normal pressure and ac conductivity in single-crystalline $\gamma $-RbAg$_{4}$I$_{5}$ close to and below its $\gamma $-to-$\beta $ first order phase transition at 121 K. We found an accurate proportionality between the specific heat, \textbf{\textit{c}}$_{P}$, and the temperature derivative of the product \textbf{\textit{nE}}$_{\sigma }$, where \textbf{\textit{$\beta $ =1- n}}, is the Kohlrausch stretching exponent for the conductivity relaxation and \textbf{\textit{E}}$_{\sigma }$\textbf{\textit{ = d(ln$\sigma )$/d(T}}$^{-1}$\textbf{\textit{)}} is the dc conductivity activation energy, which is non-Arrhenius. Thus, our results show that the dc conductivity activation energy \textbf{\textit{E}}$_{\sigma }$\textbf{\textit{(T)}} includes, besides the true microscopic energy ``barrier'' for independent ionic motion, \textbf{\textit{(1-n) E}}$_{\sigma}$ (according the coupling model), an additional contribution from the enthalpy of the mobile Ag-ions defects, \textbf{\textit{h}}. [Preview Abstract] |
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S1.00137: The Crystal Structure of Lanthanide Zirconates Richard Clements, Brendan Kennedy, Christopher Ling, Anton P.J. Stampfl The lanthanide zirconates of composition Ln$_{2}$Zr$_{2}$O$_{7}$ (Ln = La-Gd) are of interest for use in inert matrix fuels and nuclear wasteforms. The series undergoes a pyrochlore to fluorite phase transition as a function of the Ln atomic radii. The phase transition has been attributed to disordering of both the cation and the anion [1]. We have undertaken a synthesis of the lanthanide zirconate series Ln$_{2}$Zr$_{2}$O$_{7}$ (Ln = La-Gd), Ln$_{0.2}$Zr$_{0.8}$O$_{1.9}$ (Ln = Tb-Yb) and Nd$_{x}$Ho$_{2-x}$Zr$_{2}$O$_{7}$ (0$<$x$<$2) via a solid state oxide technique. We have performed neutron powder diffraction on selections of the series, using ANSTO's new high resolution powder diffractometer Echidna, in order to obtain accurate data on atomic displacement parameters and O 48f position across the series. These results will be presented, along with details of the analysis and synthetic techniques used. [Preview Abstract] |
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S1.00138: The fluctuation of charge/orbital/spin ordering structure in Sm$_{1-x}$Sr$_{x}$MnO$_{3}$ (x = 0.55 and 0.6) Xiuzhen Yu, Yasuhide Tomioka, Toru Asaka, Koji Kimoto, Yoshinori Tokura, Yoshio Matsui In over-doped Sm$_{1-x}$Sr$_{x}$MnO$_{3 }(x \quad >$ 0.5), the disorder due to ionic size mismatch of Sm and Sr cations is very large. A large disorder decreases the electronic correlation length and induces the electronic structure competition and hence the spatial phase fluctuation. In this study, the charge/orbital ordering (CO/OO) structure and magnetic domain structure in Sm$_{1-x}$Sr$_{x}$MnO$_{3}$ with doping levels of 0.55 and 0.6 have been examined by transmisstion electronic microscopy (TEM). For $x$ = 0.55, the CO/OO structure with commensurate modulation vector \textbf{\textit{Q}} = (0, 1/3, 0) is seen above the A-type transition temperature ($T_{NA} \quad \sim $ 180 K) and that with the incommensurate one below $T_{NA}$. For $x$ = 0.6, typical 180-degree magnetic domains were observed in the (110) plane below 50 K, indicating the canted AFM structure. This AFM structure locally collapses because of the existence of short-range CO. [Preview Abstract] |
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S1.00139: Characterization of charge trapping in Eu doped Al$_{2}$O$_{3}$ and its application to a nonvolatile memory. Dong Hak Kim, Daeyong Lim Charge trapping and luminescence properties of Eu ions at different charge states have been investigated for Eu-doped-Al$_{2}$O$_{3}$/SiO$_{2}$/Si structure. X-ray photoelectron spectroscopy and photoluminescence spectra studies showed that doped Eu ions mainly exist in Eu$^{3+}$ state for samples annealed at low temperature. When charges were injected by Fowler-Nordheim tunneling, Eu doped Al$_{2}$O$_{3}$ layer showed a strong electron trapping behavior. After high temperature thermal annealing in reducing ambient gas, the luminescence spectra changed into those of Eu$^{2+}$. However, charge trapping was negligible. Our experimental results indicate that Eu$^{3+ }$ion in Al$_{2}$O$_{3}$ behaves as a strong electron trap while Eu$^{2+ }$ion formed after high temperature thermal annealing behaves as a strong luminescent center. As an application, we fabricated a non-volatile memory MOS structure using Eu doped Al$_{2}$O$_{3}$ as a charge trapping layer and obtained good memory properties. [Preview Abstract] |
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S1.00140: Ta doped TiO$_{2}$: substitutionality and bandgap variation A. Roy Barman, S. Dhar, M. Motapothula, T.K. Chan, M. Breese, G. Osipowicz, T. Venkatesan We report on the growth of high quality single crystal anatase Ta$_{x}$Ti$_{1-x}$O$_{2}$ films on (001) LaAlO$_{3}$ substrate by Pulsed Laser Deposition at various substrate temperatures, O$_{2}$ partial pressures, and Ta concentrations. We use X-Ray diffraction and Rutherford backscattering-ion channeling experiments to study the epitaxial film growth and Ta substitutionality. Ta is found to be almost completely substituted in the Ti sites resulting in the expansion of the TiO$_{2}$ lattice constant with Ta concentration. A strong oxygen pressure and temperature dependence of the Ta substitution is also noticed. The bandgap of the doped TiO$_{2}$, measured by UV-Vis spectroscopy, shows a blue shift. This appears to be more consistent with the formation of an alloy Ta$_{x}$Ti$_{1-x}$O$_{2}$ with a bandgap given by a linear combination of the bandgaps of the TiO$_{2}$ and Ta$_{2}$O$_{5}$, in accordance with the Vegard's law rather than the band filling effects (Moss-Burstein shift). The origin of this blue shift will be presented and discussed along with the experimental results. [Preview Abstract] |
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S1.00141: Optical Wave Propagation in Epitaxial Nd:Y$_{2}$O$_{3 }$Planar Waveguides Wei Li, Scott Webster, Raveen Kumaran, Shawn Penson, T Tiedje Optical wave propagation in neodymium doped yttrium oxide (Nd:Y$_{2}$O$_{3})$ films grown on R-plane sapphire substrates by molecular beam epitaxy has been studied by the prism coupler method. The measurements yield propagation loss data, precise values for the refractive index and the dispersion relation. The refractive index of the Nd:Y$_{2}$O$_{3}$ at 632.8nm is found to be 1.909, which is close to the available data for bulk Y$_{2}$O$_{3}$ crystal (1.923 at 645nm from Handbook of Optical Constants of Solids II). The lowest propagation loss measured is 0.9$\pm $0.2 cm$^{-1}$ at 1046 nm with a spin-on polymethyl-methacrylate top cladding layer on a film with 6 nm RMS surface roughness. The loss measurements suggest the majority loss of this planar waveguide sample is due to scattering from surface roughness. The loss measurements are in good agreement with the model of Payne and Lacey (Opt. and Quantum Electron \textbf{26} (1994) 977-986) in which we use the experimental value for the surface autocorrelation obtained from AFM measurements. [Preview Abstract] |
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S1.00142: Band gap and wavelength dependent refractive indices of pulsed laser deposited LaGdO3 high-k dielectric films on quartz substrates Shojan Pavunny, Reji Thomas, Ram Katiyar Inter-lanthanide oxide, LaGdO3 (LGO) has been considered for the high-k gate oxide application. However, its optical properties like, band gap (Eg), refractive index (n) and extinction coefficients (k) are not studied so far. Highly oriented LGO thin films were deposited on quartz (0001) substrates by pulsed laser deposition and evaluated its optical properties by employing UV-visible transmission spectroscopy (190-800nm). The structure, morphology, composition and valency-state were studied using XRD, AFM, EDX and XPS respectively. The thickness, Eg, n, and k of the film were extracted from the transmission spectra. The optical band gap for the film was calculated by considering a direct transition between valence and conduction bands, and found to be 5.44 eV, satisfying the band-offset requirement with Si for the gate-oxide application. The variation of n and k with wavelength and thickness will also be discussed. [Preview Abstract] |
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S1.00143: Lead-free piezoelectrics; Raman delineation of phase boundaries Joe Trodahl, Ben Wylie-van Eerd, Naama Klein, Dragan Damjanovic, Nava Setter There is a need to identify ferroelectrics with strong temperature-independent piezoelectric responses to replace the ubiquitous PbZr$_{x}$Ti$_{1-x}$O$_{3}$ (PZT). It is central in this search to establish the phase diagram of candidate materials, especially the existence of a temperature-independent phase boundary similar to that in PZT. We will report Raman investigations of a number of target materials, and report clear evidence of such a boundary in one of them and weaker, as yet incomplete evidence in another. [Preview Abstract] |
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S1.00144: A novel colossal magnetodielectric effect in Er$_{2}$O$_{3}$ nanoparticle embedded SiO$_{2}$ glass matrix around room temperature Sudip Mukherjee, Ching Hsuan Chen, Chih Chieh Chou, Bijay Krishna Chaudhuri, Hung-Duen Yang An intriguing colossal magnetodielectric (MD) behavior is observed in nanocrystalline Er$_{2}$O$_{3}$ (0.5 mol{\%}) embedded SiO$_{2}$ glass matrix synthesized via sol-gel route. At around 9 T magnetic field, the dielectric constant of this superparamagnetic Er$_{2}$O$_{3}$ nanoparicle ($\sim $5 nm) composite reached almost \textit{$\sim $}2.75 times the corresponding value of pure Er$_{2}$O$_{3}$. The MD effect arising due to the strong coupling between the magnetic moment and the lattice strain depends on the nanoparticle size and separation, which can be controlled by proper annealing. This novel MD system might be treated as a potential candidate for device miniaturization. [Preview Abstract] |
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S1.00145: Magnetic field dependent ferroelectric like behavior in glass S. Mukherjee, C.H. Chen, C.C. Chou, H.D. Yang, B.K. Chaudhuri Lines first proposed the possibility of ferroelectricity (FE) in glass polar or nonpolar medium. However, so far no such material has been developed showing FE in glass. We developed some novel rare earth oxide ($\sim $0.4 mol{\%}) : SiO$_{2}$ glasses which show FE like behavior (with FE loop and Curie Weiss behavior) around ambient temperature. The observed colossal dielectric constant depends on magnetic and electric fields. No signature of structure was detected by XRD. However, long time annealing ($\sim $700 ${^\circ})$ small number of rare earth oxide nanoparticles ($\sim $3 nm) appear as observed from high resolution electron micrograph but here also no sigh of crystalline peak in the XRD micrographs. We believe this is the first report supporting the possibility of FE in glass as proposed by Lines with no long range order. The origin of this dielectric instability is considered to be due to the strong coupling of the magnetic spin with the ?dielectrically soft? local O-Si-O structural unit (configuration) which causes micro- stress and an anisotropic strain developed during glass network formation with magnetic impurity ions. The stress released by annealing the glass and hence destroys the FE feature. A model with glass network structure has also been proposed. [Preview Abstract] |
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S1.00146: Evidence of magneto-electric coupling on YMnO$_3$ thin films capacitors Jackeline Narvaez, Juan Ramirez, Maria Gomez We report synthesis of phase pure multiferroic YMnO$_3$ thin films. Films were prepared by using rf magnetron sputtering technique using ultra high purity Argon gas at 0.07mbar at substrate temperature around 850$^{\circ}$C over Pt/TiO$_2$/SiO$_2$/Si substrates. Films were characterized by x-ray diffraction (XRD), Scanning electron microscopy (SEM), temperature-dependent magnetization curves by using a Vibrating sample magnetometer (VSM), Atomic force microscopy (AFM) and temperature-dependent polarization measurements of Au/YMnO$_3$/Pt capacitor heterostructures. Temperature dependence capacitance measurements show an anomaly close to the N\'{e}el temperature (70K) which is corroborated by electrical polarization hysteresis loops. We found a effect on the ferroelectric properties (saturation polarization and coercitive electric field) only explained by the antiferromagnetic phase of YMnO$_3$. We model the ferroelectric hysteresis loops by using a series of resistance-capacitor elements. [Preview Abstract] |
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S1.00147: $^{87}$Rb Nuclear Magnetic Resonance Measurements of RbKSO$_{4}$ Single Crystal Moohee Lee, Kihyeok Kang, B. J. Mean, Sung Hoon Kim, Ae Ran Lim $^{87}$Rb Nuclear Magnetic Resonance (NMR) measurements have been performed on a single crystal of ferroelectric RbKSO$_{4}$ at 4.8 and 8.0 T from room temperature down to 70 K. Two first-order phase transitions were reported to occur at 116 and 820 K. The crystal axes of RbKSO$_{4}$ single crystal are well defined by XRD and NMR measurements. NMR spectrum, shift, linewidth, spin-lattice relaxation rate 1/T$_{1}$ and spin-spin relaxation rate 1/T$_{2}$ are measured as a function of temperature and rotation angle of the crystal axis to the magnetic field. The central peak of $^{87}$Rb NMR spectrum at room temperature shows a different behavior for the three crystal axes. The satellite peaks are extremely broad compared with the central peak. The spin-lattice relaxation rate 1/T$_{1}$ significantly decreases as temperature goes down. The spin-spin relaxation rate 1/T$_{2}$ is almost same and independent of the temperature variation. [Preview Abstract] |
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S1.00148: Interfacial polarization and High Frequency ($>$100 MHz) Stable Capacitor Functions of Nanodielectric BaTiO3 Composites Ataur Chowdhury, Abhijit Biswas, I. Bayer, A. Tripathi, E. Lock, S. Walton, M. Norton, D. Avasthi, D. Dahanayaka, D. Bumm, E. Suhir, R. Gupta We report fabrication of nanodielectric composites of barium titanate (BTO) in LiF and PMMA dielectric materials by electron-beam-assisted vapor-phase codeposition at temperature ($\sim$35 $^{\circ}$C). The fabricated nanodielectric composites showed unique nanometric interfacial polarization properties that resulted in very promising high-frequency ($>$ 100 MHz) capacitor functions. The best capacitor performance was achieved from as-deposited BTO-LiF nanodielectric systems that exhibited a flat capacitance density of about 10 nF/cm$^2$ with the self resonance frequency occurring at around 150 MHz along with a low loss tangent of about 0.1 at 100 MHz, thus verifying the high-quality of the device structures. [Preview Abstract] |
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S1.00149: Shell model for BaTiO$_3$-Bi(Zn$_{1/2}$Ti$_{1/2})$O$_3$ perovskite solid solutions J. Vielma, D. Jackson, D. Roundy, G. Schneider Even though the composition of BaTiO$_3$-Bi(Zn$_{1/2}$Ti$_{1/2})$O$_3$ perovskite solid solutions is similar to other ferroelectric compounds, the dielectric response is unusual. Results of permittivity measurements as a function of temperature show a diffuse phase transition indicative of a weakly coupled relaxor behavior.\footnote{C. C. Huang and D. P. Cann, J. Appl. Phys. {\bf 104}, 024117 (2008)} To investigate the weakly coupled relaxor behavior in these materials at intermediate length scales we are developing a newly calibrated shell model based on first-principles supercell calculations of both the solid solution and its compositional endpoints. Initial results for its phase diagram will presented. [Preview Abstract] |
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S1.00150: Properties of ferroelectric multilayer materials Mandana Meisamiazad, Alexei Grigoriev, Daniel Tinberg, Susan Trolier-McKinstry, Tara Dwenski, Donald Walko In this work, we analyze polarization switching and elastic strain properties of ferroelectric multilayer materials. These properties depend on electrostatic coupling between ferroelectric layers. The coupling can be affected by the dielectric properties and geometry of individual ferroelectric layers and by the electrical charges at the interfaces between the layers. The goal is to describe the properties of a ferroelectric multilayer system using the Landau-Ginzburg-Devonshire theory and compare the calculations with the results of piezoelectric strain measurements by time-resolved X-ray diffraction. The potential implications of our work in nanoelectronics and nanoelectromechanical systems include the development of new multistate memory devices and advanced piezoelectric materials. [Preview Abstract] |
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S1.00151: Photo-induced poly-domain to mono-domain switching in ultrathin PbTiO$_{3}$ films A. Vailionis, R. Meyer, P.C. McIntyre Ferroelectric (FE) domain structures play a crucial role in polarization switching dynamics, ferroelectric random access memory (FRAM) data retention and polarization fatigue and it is therefore of practical importance to gain a more fundamental understanding of the origin of the transition between poly-domain and mono-domain states. Methods that promote the mono-domain state in the FE films are also of interest for model studies of ferroelectricity and its dimensional scaling. We investigate a novel poly-domain to mono-domain (P-M) switching mechanism in thin ferroelectric PbTiO$_{3}$ (PTO) films induced by ultraviolet (UV) light illumination. The switching occurs within minutes if a sample is irradiated with light of wavelength $<$ 390 nm which corresponds to a photon energy that is roughly equivalent to the band gap of PbTiO$_{3}$ (3.2 eV). Based on a developed electrostatic model, we show that the observed phenomenon is related to photo generation of free carriers at the PbTiO$_{3}$/SrTiO$_{3}$ interface which effectively screens the PTO polarization charge at the interface and therefore promotes the transition of the ferroelectric film from a poly-domain to a mono-domain state. The model successfully describes not only the observed illumination effects on PTO stripe domain patterns but also a longer-term poly-domain to mono-domain (P-M) transition that occurs without intentional illumination. [Preview Abstract] |
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S1.00152: Specific heat and magnetoelectric study of the YMn$_{1-x}$Ti$_{x}$ solid solution A. Duran, C. Ochoa, G. Guzman, S. Cardena, F. Morales, R. Escamilla, R. Escudero Multifunctional materials have received wide attention in the last few years. In particular, biferroics where both ferromagnetism and ferroelectricity coexist in the same volume of the same substance. The coupling between these two order parameters is of fundamental interest because of open routes for technological applications. One of these compounds is the YMnO$_{3}$ where has been observed the ferromagnetic and ferroelectric coupling at 80 and about 913 K, respectively. We have studied here, the crystal structure, magnetic, and dielectric properties of the solid solution of YMnO$_{3}$:Ti synthesized by solid state reaction. We have found that the doped-system retains its hexagonal structure (P63/mmc) up to 10 {\%} of Ti. Afterwards of this concentration, a rhombohedral phase (R3c) takes place. The susceptibility and specific heat measurements indicated that the magnetic signal and the magnetic entropy at T$_{N}$ decreases as Ti is replaces by Mn ion. We believe that the distribution of the Ti (d$^{0})$ on the Mn (d$^{4})$ sites dilutes the Mn-Mn interaction decreasing the magnetic fluctuation around of the T$_{N}$. [Preview Abstract] |
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S1.00153: PUBLIC POLICY |
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S1.00154: AUDITING for VERACITY ``DUE-DILIGENCE" RIGOROUS-HONESTY!!!: ETHICS??? DIGITS? For A Very-Long Time Giving Us All THE FINGER!!! DOES ``MEAN" MEAN MEAN!!!??? Brian Martin, E. Siegel BAD-scienceS UNethics FLOOD: Pilkey[UseLESS-Arithmetic(2007)]- Park[Vodoo Science(2006)]-Dewedny[Yes We Have NO Neutrons(1997)] -LeVay[When Science Goes WRONG(2008)-LBNL/DOE IMAGINARY-element -``118")]Bell-Labs/Alcatel-Lucent/Thales-Group/France: L'AffairS: Jan Hendrik Schoen; Giant-Magnetoresistance: ``Fert"-``Gruenberg" [PRL(1988;1989)]Kern(KFZ)/Reed-Elsevier/Wallenbergs/Enskilda- Bank/InvestorAB/Sweden:LONG-AFTER Siegel[flickr.com, search on ``Giant-Magnetoresistance": find: ICMAO,Haifa(1977); J.Mag.Mag. Mtls.(JMMM)7,312(1978): 1978$<<<$1988: (1988-1978)=10 years= one full decade!!!-SANS CRUCIAL last-2-R(H)-Figures MISSING-ONLY SCANNED online(7/2008)conveniently 1/2-year AFTER 2007-Physics: Wolf/Japan/Nobel-prizes(12/2007)]-Revkin[dot.earth,NYT(8/2009)] ``Sea-level-Rise Predictions HALVED"(=50\%-error:by coin-toss Bern oulli ``super-computer"(SC)!!!)-McNeil[NY(8/2009]``H1N1-Flu (Langer-Carlson-Bak forest-fire SOC:Vespigniani-Germann)epidem- iology-models predicted cases: $\sim$1,000-3,000 max. VS. same-week CDC-data~100,000-300,000"(=100\%-error: by drunk dart-throws New- ton F=ma``SC"(!!!)-Financials(2008)!!!: AD INFIN-ITUM AD NAUSEUM !!! Statistical-lawS[Biostatistics(1998)]:``TRUST, BUT VERIFY !!!": ABSOLUTELY MANDATORY!!! [Preview Abstract] |
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S1.00155: FRAMING Linguistics: ``SEANCES"(!!!) Martin-Bradshaw-Siegel ``Buzzwordism, Bandwagonism, Sloganeering For:Fun, Profit, Survival, Ego": Rampant UNethics Sociological-DYSfunctionality!!! John Bradshaw, E. Siegel ``Sciences''/SEANCES(!!!) rampant UNethics!!! WITNESS: Yau v Perelman Poincare-conj.-pf. [Naser, NewYorker(8/06)]; digits log- law Siegel[AMS Nat.Mtg.(02)-Abs.973-60-124] inversion to ONLY BEQS: Newcomb(1881)$<<<$Planck(01)$<$Einstein(05)$<<<$Bose(24): quanta/bosons=digits!!!; Wolf(DARPA)-Awshalom(UCSB) (so MIS- called) ``spintronics'' copy of Overhauser(54)-(Slichter)-effect: 54$<<<$90s!!!; Siegel [AMS Nat.Mtg.(02)-Abs.973-03-126] proof: Fermat's: Last-Theorem = Least-Action Ppl:64$<<<$94(Wiles); ``Bak''/BNL (so called) ``SOC''= F=ma REdiscovery, copying Siegel [PSS(71);...] acoustic-emission:71$<<<$88: ``Per Bak''?, PRE Bak!!!; ``Bednorz''(v Raveau-Chu) high-Tc cuprate SC Nobel; ``Emery''($\sim$93)/ BNL high-Tc SC 3-band Hubbard-model v Siegel generic multi-(2- 10)-band spin-orbital-degeneracy(SOD)[Ph.D.,MSU(70);PSS(72;73); JMMM(76-80);World Cong.SC,Munich(92)]:70$<<<$93!!!; Anderson [1/3$<$1] failed cuprate high-Tc SC ``RVB'' v Overhauser correct cuprates/pnictides SSDWs:[(60s)$<<<$(87)];(so called) ``Anderson'' [1/3$<$1;PRL(58)] localization REdiscovery v Rayleigh(1881)``short- CUT'' graph-theory method[Doyle-Snell, Random-Walks/Electric-Nets (81)]: 1881$<<<$58; ``Fert''[PRL(88)] 07-Nobel copying v Siegel[at flickr.com,search on ``GMR''; google: ``If Leaks Could Kill'']: [(78)$<<<$(88)]!!!: Marti[google: ``Brian Martin'']-Bradshaw [Healing the SHAME that BINDS You(80s)]: Ethics? SHMETHICS!!! [Preview Abstract] |
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S1.00156: QUANTUM INFORMATION, CONCEPTS, AND COMPUTATION |
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S1.00157: The Neutrosophic Logic View to Schr\"{o}dinger Cat Paradox, Revisited Florentin Smarandache, Vic Christianto The present article discusses Neutrosophic logic view to Schr\"{o}dinger's cat paradox. We argue that this paradox involves some degree of indeterminacy (unknown) which Neutrosophic logic can take into consideration. To make this proposition clear, we revisit a previous paper of ours by offering an illustration using modified coin tossing problem, known as Parrondo's game. [Preview Abstract] |
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S1.00158: Physics Proofs of Four Millennium-Problems(MP) via CATEGORY-SEMANTICS(C-S)/F=C Aristotle SQUARE-of-OPPOSITION(SoO) DEduction-LOGIC DichotomY L. Clay, E. Siegel Siegel-Baez C-S/F=C tabular list-format matrix truth-table analytics SoO jargonial-obfuscation elimination query WHAT? yields four ``pure''-maths MP ``Feet of Clay!!!'' proofs:(1)Siegel [AMS Natl.Mtg.(2002)-Abs.\#:973-03-126:(@CCNY;1964!!!)$<<<$(1994; Wiles)]Fermat's: Last-Theorem = Least-Action Principle; (2) P=/=NP TRIVIAL simple Euclid geometry/dimensions: NO computer anything;``Feet of Clay!!!''; (3)Birch-Swinnerton-Dyer conjecture; (4)Riemann-hypotheses via combination of: Siegel [AMS Natl.Mtg. (2002)-Abs.\#:973-60-124 digits logarithmic-law simple algebraic- inversion to ONLY BEQS with ONLY zero-digit BEC, AND Rayleigh [(1870);graph-theory ``short-CUT method''[Doyle- Snell,Random- Walks \& Electric-Networks,MAA(1981)]-``Anderson'' [PRL(1958)] critical-strip 1/2 complex-plane localization!!! SoO DichotomY (``v'') IdentitY: numbers(Euler v Bernoulli) = (Sets v Multisets) = Quantum-Statistics(F.-D. v B.-E.) = Power- Spectra(1/f$^(0)$ v 1/f$^(1.000...)$ = Conic-Sections(Ellipse v (Parabola) v Hyperbola) = Extent(Locality v Globality); Siegel [MRS Fractals Symp.(1989)](so MIScalled)``complexity'' as UTTER- SIMPLICITY (!!!) v COMPLICATEDNESS MEASURE(S) definition. [Preview Abstract] |
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S1.00159: Allowed Quantum States for Two Coupled Quantum Dots via Vacuum Vijay Kasisomayajula, Onofrio Russo We consider a system containing two similar isolated nano-structures such as quantum dots in a vacuum. The Planck radiation law which contains the $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $ $\hbar \omega $ term, which is the energy density per photon per mode for the zero point energy, creates concern when it is realized that the total energy in the vacuum summing all field modes leads to an infinite energy. Even when a high frequency cutoff is introduced, the calculated energy in the vacuum is dramatically larger than that observed. When the Hamiltonian H is defined for the structure-vacuum system, it is separated into the unperturbed Hamiltonian H$_{u }$ and the perturbation term of the form \[ \int {g_a (\omega )} \hbar \omega \left( {a(\omega )^\dag a(\omega )} \right)d\omega +\mbox{i}\left( {s^\dag +s} \right)\int {g_b (\omega )} k(\omega )\left( {a(\omega )-a(\omega )^\dag } \right)d\omega \] respective bosonic creation and annihilation operators satisfying [a($\omega )$, a($\omega \prime )^{\dag }$] = $\delta (\omega -\omega \prime )$, s and s$^{\dag }$ the system operators that couple the structures to the vacuum, k($\omega )$ the frequency dependent coupling constant, and the g$_{a}(\omega )$ and g$_{b}(\omega )$, functions necessary to insure a finite energy density. The state of the system can then be realized when the condition meets the requirement that the medium which is the vacuum be considered to be at the flat white noise limit. [Preview Abstract] |
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S1.00160: Coordination of time-stamps in optical communication experiments without clock signal sending Kiyotaka Hammura, David Williams The problem is how to implement coordination of time-stamps shared between sender and receiver in optical communications without clock signal sending. The coordination is essential for sharing time sequence information between the two. Clock signal free implementation of it will save the cost for implementing the clock signal channel. In our experiment, we devised a special bit sequence and put the sequence on top of data sequence to be sent, then the whole sequence was sent to receiver along a single optical channel. In theory, thanks to the specialty of the pattern embedded, the first data bit at the sender side will be identified on the receiver's time axis. The results were as expected. We succeeded in demonstrating our theory. The method has a potential to saving a great deal of cost and physical burden, including implementing various transmission channels. The nearest next target is to incorporate this method into a quantum cryptography system. [Preview Abstract] |
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S1.00161: Negativity and phase transitions in Spin-1 anisotropic Heisenberg model with Longitudinal Crystal Field Armen Kocharian, Nerses Ananikyan, Lev Ananikyan, Vahagn Abgaryan Quantum entanglement which refers to quantum correlations has emerged as one of the important sign of critical behavior in various many-body quantum mechanical systems. We analyze the behavior of entanglement and concurrence for sign of quantum phase transition by exact diagonalization technique in small bipartite and frustrated Heisenber-like clusters. The quantum entanglement, particle and spin susceptibilities in bipartite and frustrated qubits for spin-1 anisotropic Heisenberg model with biquadratic exchange, longitudinal crystal and magnetic fields are calculated in terms of negativity for ferromagnetic and antiferromagnetic exchange interactions. The correlation between the plateaus behavior, the conditions for a high density quantum entanglement and lines with continuously- varying quantum critical points are found for ordered phases with different spin concentrations in assembled spin-1 nanoclusters and bosonic particles in the optical lattices. [Preview Abstract] |
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S1.00162: An Exact Mapping from Navier-Stokes Equation to Schr\"{o}dinger Equation via Riccati Equation Vic Christianto, Florentin Smarandache In the present article we argue that it is possible to write down Schr\"{o}dinger representation of Navier-Stokes equation via Riccati equation. The proposed approach, while differs appreciably from other method such as what is proposed by R. M. Kiehn, has an advantage, i.e. it enables us extend further to quaternionic and biquaternionic version of Navier-Stokes equation, for instance via Kravchenko's and Gibbon's route. Further observation is of course recommended in order to refute or verify this proposition. [Preview Abstract] |
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S1.00163: Quantum Computing using Molecular Vibrational and Rotational Modes of the Open-shell $^{14}$N$^{16}$O Molecule Kenji Mishima, Koichi Yamashita We demonstrate the possibility of using internal molecular vibrational and rotational modes of an open-shell molecule for one of the most important quantum algorithms: the Deutsch-Jozsa algorithm. The molecular system of interest is one of the representative open-shell molecules: $^{14}$N$^{16}$O. The gate pulses are constructed by utilizing multi-target optimal control theory (MTOCT). The gate fidelities of each quantum gate are more than 95.23{\%}. Upon implementing the Deutsch-Jozsa algorithm combining these elementary gates, we obtained fidelity of at least 94.76{\%}. This indicates that vibrational and rotational qubits of the open-shell $^{14}$N$^{16}$O molecule are about as promising for processing quantum algorithms as those of the closed-shell molecule $^{12}$C$^{16}$O that we studied earlier. [Preview Abstract] |
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S1.00164: Towards Quantum Chemistry on a Quantum Computer Alan Aspuru-Guzik The fundamental problem faced in quantum chemistry is the calculation of molecular properties, which are of practical importance in fields ranging from materials science to biochemistry. Recently, an efficient algorithm has been proposed enabling a quantum computer to overcome this problem by achieving only a polynomial resource scaling with system size. Such a tool would therefore provide an extremely powerful tool for new science and technology. Here we present a photonic implementation for the smallest problem: obtaining the energies of H2, the hydrogen molecule in a minimal basis. We perform a key algorithmic step - the iterative phase estimation algorithm - in full, achieving a high level of precision and robustness to error. We implement other algorithmic steps with assistance from a classical computer and explain how this non-scalable approach could be avoided. Finally, we provide new theoretical results which lay the foundations for the next generation of simulation experiments using quantum computers. We have made early experimental progress towards the long-term goal of exploiting quantum information to speed up quantum chemistry calculations. [Preview Abstract] |
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S1.00165: The Free Will Theorem and Limits on Realistic Theories Christopher Godfrey The rGRWf model (Tumulka 2006) is a proposed solution of the measurement problem of quantum mechanics involving a stochastic nonlinear wave equation embedded in a relativistic framework. Its primary feature is a mechanism that suppresses superpositions of macroscopically different states for macroscopic systems. However, the Free Will Theorem (FWT) proposed by Conway and Kochen (Conway and Kochen 2007, 2009) purports to prove that no theory that is both non-deterministic and relativistic can reproduce all possible measurement results on a system of two entangled spin-one particles. Here we examine both the rGRWf model and the FWT. It is demonstrated that underlying assumptions in the postulates of the FWT rule out certain classes of realistic physical theories. These underlying assumptions and the characteristics of physical theories permitted by the FWT axioms are discussed. [Preview Abstract] |
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S1.00166: Optimal control of charge transfer in coupled quantum dots Esa Rasanen, Antti Putaja Theoretical design of an external field to drive a quantum system from an initial state to a given target state can be achieved within quantum optimal control theory. We aim at designing laser-driven quantum bits (qubits) by applying optimal control to models of semiconductor nanodevices such as quantum dots and quantum rigs. Here we have constructed a coherent and precise charge-switching scheme on coupled quantum dots. The charge transfer can be controlled in an arbitrary way by exploiting the superpositions of the eigenstates. For example, we are able to achieve 100 sequential charge-switch operations with more than $90\,\%$ fidelity in a few picoseconds. The fidelity is not dramatically affected by realistic filtering of the pulse frequencies. We also demonstrate a two-particle control schme in a one-dimensional model system with a soft-Coulombic interaction operator. [Preview Abstract] |
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S1.00167: Investigating Possible Quantum Metastable States in Graphene-based Josephson Junctions Joseph Lambert, Steven Carabello, Zechariah Thrailkill, Thilanka Galwaduge, Roberto Ramos Recently, superconducting tunneling currents have been measured in graphene devices consisting of two parallel superconducting leads contacted by single- and few-layer graphene flakes. The current-voltage characteristic curves of these devices are hysteretic and Shapiro steps appear when the device is irradiated with microwaves. Thus, there is evidence of both the d.c. and a.c. Josephson effects. The graphene devices have shown to have strong quantum coherence as indicated by a Fraunhofer-like pattern in the current versus external magnetic field plot. These effects motivate us to investigate the presence of quantum metastable states similar to those found in conventional current-bias Josephson junctions. We present work investigating the nature of these metastable states and the implications of ballistic versus diffusive graphene Josephson junctions. We also present experimental progress studying the nature of switching from the superconducting to the normal state in these devices. [Preview Abstract] |
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S1.00168: Exploiting Kerr Cross Non-linearity in Circuit Quantum Electrodynamics for Non-demolition Measurements Shwetank Kumar, David DiVincenzo High quality factor microwave resonators are versatile devices which find many applications in circuits for scalable quantum computing architectures. We will present a novel circuit for dispersive readout of energy stored in one mode of a nonlinear superconducting ring resonator by detecting frequency shift of a second mode coupled to the first via Kerr nonlinearity. Symmetry is used to enhance the circuit responsivity by minimizing the nonlinear terms that do not contribute to the detector response. Assessment of the signal to noise ratio indicates that the scheme will function at the single photon level, allowing quantum non-demolition measurement of the photon number state of one resonator mode. Experimental data from a simplified version of the device demonstrating the principle of operation will be presented. Extensions of this work to implement on-chip superconducting beam splitters with applications towards linear optics qubit schemes will be discussed. [Preview Abstract] |
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S1.00169: Coplanar waveguides as bandpass filter Fabio Altomare, Raymond Simmonds Coplanar waveguides have been used as a bus to exchange coherent interaction between phase qubits, and to mediate the interaction between transmon. Here we show how a coplanar waveguide can be used to effectively reduce the measurement crosstalk between two flux biased phase qubits [Preview Abstract] |
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S1.00170: Mirror Symmetry of Matter and Antimatter Robert Close Physical processes involving weak interactions have mirror images which can be mimicked in the natural universe only by exchanging matter and antimatter. This experimental observation is easily explained by the hypothesis that spatial inversion exchanges matter and antimatter. Yet according to conventional theory, the parity operator $P$ does not exchange matter and antimatter but instead yields phenomena which have never been observed. We examine the conventional derivation of the Dirac parity operator and find that it is based on the speculative assumption that the unit imaginary is always a true scalar rather than a pseudoscalar. This assumption incorrectly requires that the matrix $\gamma^0$ preserve its sign under spatial inversion. This requirement results in a mixed-parity vector space defined relative to velocity, which is otherwise isomorphic to the spatial axes. We derive a new spatial inversion operator $M$ (for mirroring) by requiring that for any set of orthogonal basis vectors, all three must have the same parity. A pseudoscalar unit imaginary is defined in terms of Dirac matrices. The $M$ operator is a symmetry of the Dirac equation. It exchanges positive and negative energy eigenfunctions, consistent with all experimental evidence of mirror symmetry between matter and antimatter. This result provides a simple reason for the apparent absence in nature of mirror-like phenomena, such as right-handed neutrinos, which do not exchange matter and antimatter. [Preview Abstract] |
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S1.00171: Quantum stochastic walks: A generalization of classical random walks and quantum walks Alan Aspuru-Guzik We introduce the quantum stochastic walk (QSW), which determines the evolution of generalized quantum mechanical walk on a graph that obeys a quantum stochastic equation of motion. Using an axiomatic approach, we specify the rules for all possible quantum, classical and quantum-stochastic transitions from a vertex as defined by its connectivity. We show how the family of possible QSWs encompasses both the classical random walk (CRW) and the quantum walk (QW) as special cases, but also includes more general probability distributions. As an example, we study the QSW on a line, the QW to CRW transition and transitions to genearlized QSWs that go beyond the CRW and QW. QSWs provide a new framework to the study of quantum algorithms as well as of quantum walks with environmental effects. [Preview Abstract] |
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S1.00172: GENERAL THEORY |
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S1.00173: Steinberg ``AUDIOMAPS" Music Appreciation-Via-Understanding: Special-Relativity + Expectations "Quantum-Theory": a Quantum-ACOUSTO/MUSICO-Dynamics (QA/MD) R. Steinberg, E. Siegel ``AUDIOMAPS'' music enjoyment/appreciation-via-understanding methodology, versus art, music-dynamics evolves, telling a story in (3+1)-dimensions: trails, frames, timbres, + dynamics amplitude vs. music-score time-series (formal-inverse power- spectrum) surprisingly closely parallels (3+1)-dimensional Einstein(1905) special-relativity ``+'' (with its enjoyment- expectations) a manifestation of quantum-theory expectation- values, together a music quantum-ACOUSTO/MUSICO-dynamics (QA/MD). Analysis via Derrida deconstruction enabled Siegel- Baez ``Category-Semantics'' ``FUZZYICS''=``CATEGORYICS (``SON of 'TRIZ") classic Aristotle ``Square-of-Opposition" (SoO) DEduction-logic, irrespective of Boon-Klimontovich versus Voss- Clark[PRL(77)] music power-spectrum analysis sampling- time/duration controversy: part versus whole, shows that ``AUDIOMAPS" QA/MD reigns supreme as THE music appreciation-via- analysis tool for the listener in musicology!!! Connection to Deutsch-Hartmann-Levitin[This is Your Brain on Music,(2006)] brain/mind-barrier brain/mind-music connection is both subtle and compelling and immediate!!! [Preview Abstract] |
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S1.00174: The mass, energy, space and time systemic theory-MEST-the Theory of Relativity of Einstein Dayong Cao Things have their physical system of the mass, energy, space and time of themselves-MEST. The time is from the frequency of wave, the space is from the amplitude of wave. So the wave is like the space-time. In the wave-particle duality, the wave like the space-time, the particle like the mass-energy. The nature of the macrosubstance is mainly mass-energy while space-time are ancillary. Their physical systemic moel like that the mass-energy is center and the space-time is around, the particle is center and the wave is around. The quality of radiate wave mainly is quantum space-time while its mass-energy is ancillary. Their physical systemic moel like that the space-time is center and the mass-energy is around, and the wave is center and the particle is around. When a train run with a high speed up, why can a drosophila stopped in the mid-air of the train cars? Because the train cars have the space-time (wave) of itselves. And its space-time will be changed in the trip. Also its space-time be changed, they have the same formula of the physical laws-the Theory of Relativity of Einstein. Everything have relatively independent system of MEST, and have their relatively independent character. Also things have different space-time and MEST of themselves, but they have the same formula of the physical systemic laws. [Preview Abstract] |
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S1.00175: Approximation Methods Applied to the Pullen-Edmonds Hamiltonian R.K. Murawski, J. Erickson, S.P. Bowen, V. Fessatidis, J.D. Mancini In this work we have studied the Hamburger theorem sequence which uses the moments of the Hamiltonian evaluated for a particular state, as well as a variety of approximation schemes derivable from the \emph{t}-expansion and also a Lanczos tridiagonalization scheme. Each of these calculational schemes has been applied to the well-studied Pullen-Edmonds Hamiltonian for the representation of a $2D$ isotropic harmonic oscillator with an interaction potential of the form $x^{2}y^{2}$. We further investigate truncated approximations from moments, matrix truncations relative to the natural $2D$ simple harmonic oscillator states $|n_{x}n_{y}>$, and a class of analytic truncations in the spirit of Feenberg perturbation theory. Each of these different approximation schemes will be compared with respect to effort, accuracy, and calculational problems. [Preview Abstract] |
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S1.00176: A Variational Approach To Complex Periodic Potentials With Real Band Spectra J. Mikalopas, F. Corvino, J.D. Mancini, V. Fessatidis, S.P. Bowen In this paper we study a class of complex \emph{PT}--symmetric periodic potentials possessing real band structures. In particular we shall investigate the potentials $V(x)=i\sin^{2N+1}(x)$ ($N=0,1,2,\ldots$) which are known to have infinitely many gaps. We note for such potentials, that at the band edges there are periodic wave functions with no anti-periodic ones. We will apply a recently developed variational ansatz wherein a finite (variational) basis is constructed with respect to a variational parameter $\lambda$, according to the schema $\psi_{n}=\partial^{n}_{\lambda}\psi_{0}\left( x,\lambda\right) $. Comparisons are then made to both numerical analysis as well as higher-order WKB techniques. [Preview Abstract] |
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S1.00177: Finite matrix Methods Applied to the Hubbard Model R.K. Murawski, W.J. Massano, V. Fessatidis, J.D. Mancini, S.P. Bowen For a number of years, finite matrix methods, have provided theorists with a viable methodology for calculating ground state energies in many body systems. In particular, those schemes derivable from the \textquotedblleft% \emph{t}-expansion\textquotedblright\ of Horn and Weinstein [Phys.~Rev.~\textbf{D30}, 1256 (1984)]: Connected Moments Expansion (CMX), Alternate Moments Expansion (AMX), Generalized Moments Expansion (GMX) and the Canonical Sequence Method (CSM) have yielded viable results in a variety of fields such as atomic, nuclear and molecular physics. In this study we wish to expound upon the work of Lee and Lo [Nuovo Cimento \textbf{15D}, 1483 (1993)] who applied the CMX to evaluate the ground state energy of the half-filled Hubbard model for both the linear chain and the square lattice. Here we will apply the recently derived GMX to this system as well as the CSM scheme. These results will then be compared to a Lanczos tridiagonalization calculation. Comments will then be made regarding the usefulness of such methods to true many body systems. [Preview Abstract] |
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S1.00178: The unified approach to motion of quasi-particles in crystal lattice and parametric resonance Irina Bariakhtar, Victor Baryakhtar, Alexander Nazarenko The mathematical identity of the description of the motion of an electron in the periodic field of a crystal lattice and the motion of an oscillator with periodically changing eigen frequency due to the external field is demonstrated. The band approach, well suited for description of quasi-particles in a crystal, is applied to description of parametric resonance. This gives the possibility to calculate the properties of increments of parametric oscillations close to the band edges. The increment of parametric oscillation is calculated in two approximations: the weak and strong external limits. [Preview Abstract] |
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S1.00179: All-electron KKR Calculations for Metallic Systems with Thousands of Atoms Per Cell via Sparse Matrix Iterative Solvers Suffian Khan, Duane Johnson To perform electronic-structure calculations for inherently large systems, such as a quantum dots with heterogeneous interfaces, we must perform the calculations over very large unit cells (10$^{4}$ to 10$^{8}$ atoms). KKR methods typically solve for G by direct inversion G$^{-1}$, with known analytic form. Using a screened, k-space hybrid KKR, we solve Dyson's equation for the Green's function using a reference state via G = G$_{ref}$ [ I - (t - t$_{ref}$) G$_{ref}$]$^{-1}$, scattering matrices t and t$_{ref}$ are known and the non-Hermitian tensor G$_{ref}$ is chosen for convenience and sparsity [1]. The approach is O(N) for bandgap materials, whereas it is O(N$^2$) for metals but with a potentially large prefactor. We use Krylov-space solvers to reduce storage and exploit known symmetries. Parallel iterative and energy contour solves are made also. We explore the numerical efficiency and scaling versus atoms per unit cells. \newline [1] Smirnov and Johnson, Comp! $^1$Phys. Comm. 148, 74-80 (2002). [Preview Abstract] |
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S1.00180: Exchange-correlation energy functionals for electrons in two dimensions. S. Pittalis, E. Rasanen, C. Proetto, M. Marques, E.K.U. Gross Two-dimensional (2D) electronic systems have attracted vast interest in condense matter physics since the beginning of semiconductor technology. Density-functional theory (DFT) is among the available theoretical and computational methods to deal with many-electron systems. Fundamental quantity in DFT is the exchange-correlation (xc) energy functional. In practice, this functional needs to be approximated. Many approximations have been developed for three-dimensional (3D) systems that, unfortunately, are inadequate for 2D systems. Hence, there is a clear need for new approximations specifically designed for 2D systems. Following this important need, efficient and practical expressions for the xc-energy of electrons in 2D are presented. Numerical results for finite systems show that the proposed functionals outperform the standard 2D local-spin-density approximation. [Preview Abstract] |
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S1.00181: Exploring the Dependence of the Exchange-Correlation Energy on the Laplacian of the Electron Density Seth Ross, A.C. Cancio It has been observed that the deviation of exchange-correlation (XC) energy from the local density approximation (LDA) model in quantum Monte Carlo simulations of several systems correlates to the local Laplacian of the density [1] in a roughly linear fashion. We examine the effects on the prediction of typical material properties of the linear dependence of the XC energy density on the Laplacian of the density. To do this we focus on slowly varying systems within LDA and generalized gradient approximation models and compare these models using the Laplacian. We use the pseudopotential code Abinit to examine selected systems such as the AE6 test set and some typical solids such as Si, Cu, Na and NaCl. We then observe the differences between predictions of properties, particularly atomization energies and bond lengths of molecules and cohesive energies and lattice constants of solids, between standard DFT models and models using the Laplacian.\\[4pt] [1] A. C. Cancio and M. Y. Chou, Phys. Rev. B. 74, 081202 (2006) [Preview Abstract] |
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S1.00182: Non-linear optics and local-field factors in liquid chloroform: A time-dependent density-functional theory study David A. Strubbe, Xavier Andrade, Angel Rubio, Steven G. Louie Chloroform is often used as a solvent when measuring non-linear optical properties of organic molecules. We assess the influence of the solution environment on the molecular properties by calculating directly the non-linear susceptibilities of liquid chloroform at optical frequencies. We use the Sternheimer equation in time-dependent density-functional theory [J. Chem. Phys. 126, 184106 (2007)], on snapshots from ab initio molecular dynamics. We compare the results to those in the gas and solid phases, and to experimental values. We also calculate ab initio local-field factors, used to analyze electric-field-induced second-harmonic generation (EFISH) and hyper-Rayleigh scattering (HRS) experiments. [Preview Abstract] |
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S1.00183: Concept of mass and the generalized form of law of Motion. Akm Harun-Ar-Rashid Newton's laws of motion play a vital role in classical physics and astronomy. However, Newton's second law of motion is found crippling and MOdified Newtonian Dynamics (MOND) is proposed. The above law is also considered the limiting case of Einstein's relativistic motion for small velocity compared to the speed of light $\left( {v^2/c^2<<1} \right)$. This study proposes a generalized form of law of motion $vF=ma$ and hence, $v=v_0 e^{\frac{F}{m}t^{_0 }\sqrt {1-\frac{v^2}{c^2}} }$ which gives both Newton's law and Einstein's law of relativity as the limiting case. The above equation can explain the real world applications. The concept of mass in mechanics is also important. However, there is still debate over the relativistic and non-relativistic masses. If the concept of mass in mechanics is not clear, the application of these laws would produce huge controversial results. This study has provided the clear idea about mass which may help to get conclusion of the debate. [Preview Abstract] |
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S1.00184: Gravity Driven Universe Roy Masters Flowing global gravitation initially produced space without time or mass. Space-time and mass are properties of flowing global gravitation. From its fabric, primal mass spins spontaneously giving rise to local gravitational space-time curvatures. Global gravity is the unifying background field. Gravity began flowing from its singularity with a big whoosh. It curves with angular rotational precession, creating a spatial geometry similar to the windings of a ball of string. Three-dimensional global gravity swirls locally into massive densities. Concurrently with these densities, local gravity curvatures of space-time arise. The expanse between celestial objects is not completely empty, void space as generally believed; it is antecedent gravity, a prerequisite associated field necessary for originating the first quantum particles. Gravity is dark energy; gravity's spin, as the second fundamental force, is electromagnetic dark matter. Electromagnetic masses attract then gravity compresses hot, dense and small$---$then bang, the first hydrogen star of which there are many. There may have been many big bangs, but no Big Bang that ultimately created the universe. [Preview Abstract] |
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S1.00185: Atonic Mechanics and Special Relativity Alfred Phillips Jr The value of Atonic Mechanics is the ease of atomic spectral calculations, as previously demonstrated for helium (see Part Two on the web at sourceinstitute dot org). Atonic mechanics spectral calculations have the same accuracy as those of the Schrodinger Theory but without the mathematical tedium. We show that Atonic mechanics can be put into Special Relativity. [Preview Abstract] |
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S1.00186: Total Relativistic Kinetic Energy Must Include Rotational and Vbrational as Well As Linear Kinetic Energy Stewart Brekke All masses will have no motion, linear, vibrational and/or rotational kinetic energy singly/and or in some combination. Therefore, the mass-energy equivalence must include these factors. The basic equation for E-zero is therfore $E_0= m_0c^2 + 1/2m_0v^2 + 1/2I\omega^2 + 1/2kx^2$. Since $K= (m-m_0)c^2$, the total kinetic energy of a relativistic mass must therefore be described in the following manner. $K=mc^2 + mv^2 + 1/2I_1\omega^2 + 1/2k_1x_1^2 - m_0c^2 - 1/2m_0v^2 -1/2I_2\omega^2 -1/2k_2x_2^2$. [Preview Abstract] |
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S1.00187: Numerical Study of Spin-1/2 XXZ Model on Square Lattice from Tensor Product States Pochung Chen, Chen-Yen Lai, Min-Fong Yang By means of the recently proposed algorithm based on the tensor product states, the magnetization process of the spin-1/2 anti-ferromagnetic XXZ model on a square lattice is investigated. In the large spin-anisotropy limit, clear evidence of a first-order spin-flip transition is observed as an external magnetic field is increased. Our findings of the critical field and the discrete jumps in various local order parameters are in good agreement with the quantum Monte Carlo data in the literature. Our results imply that this algorithm can be an accurate and efficient numerical approach in studying first-order quantum phase transitions in two dimensions. [Preview Abstract] |
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S1.00188: GPU accelerated self-consistent calculation of the Hall potential in semiconductor devices Tobias Kramer, Viktor Krueckl, Christoph Kreisbeck, Eric J. Heller, Robert E. Parrott The usage of teraFLOPS graphics processing units allows us to run efficiently classical many-body simulation of semiconductor devices at realistic electron densities. As an application, we study the necessary conditions for the formation of the Hall potential: (i) Ohmic contacts with metallic reservoirs, (ii) electron-electron interactions, and (iii) confinement to a finite system. By propagating thousands of interacting electrons over million time-steps we capture the build-up of the self-consistent potential, which resembles results obtained by conformal-mapping methods. As shown by a microscopic model of the current injection, the Hall effect is linked to specific boundary conditions at the particle reservoirs. References: http://www.quantumdynamics.de/publications.html [Preview Abstract] |
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S1.00189: Quantum dynamics of H2+ in an atto-second laser pulse Nicholas Vence, Robert Harrison, Predrag Krstic We demonstrate a highly-accurate numerical procedure to investigate the quantum dynamics of single electron, single- and two-center wave functions in a strong, sub-femtosecond, few-cycles laser pulse. The non-perturbative time evolution does not rely on an eigenfunction basis set. The multiresolution numerical techniques from [Harrison et. al., J. Chem. Phys. 121, 2866 (2004)] are used for spatial discretization. These calculations observe excitation and ionization in the hydrogenic systems up to lithium++ along with the molecular hydrogen ion. This study will serve as a benchmark for future multielectron calculations. This research is supported by the U.S. Department of Energy. [Preview Abstract] |
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S1.00190: ABSTRACT WITHDRAWN |
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S1.00191: Finite Difference Solution of the Quantum Wigner Function in the Presence of a Magnetic Field: PML Absorbing Boundary Condition Tomas Materdey Numerical results using a perfectly matching layer (PML) absorbing boundary condition for the finite-difference time evolution of the quantum Vlasov equation are presented. Comparisons with previous results based on the constant flux approach are discussed. [Preview Abstract] |
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S1.00192: Two -- phase direct simulation of remediation of snow drifting around buildings in three dimensions E. Maldonado, M.W. Roth We present the results of two - phase numerical simulations of controlling snow drifting around buildings in three dimensions with deflection fins. The first phase involves numerical calculation of the air velocity profile around the building and fin using a velocity -- pressure Navier -- Stokes solver, while the second phase involves direct classical simulation of snowfall with particle - particle interactions introduced to control clumping and drifting. We are able to consider deflection fins having novel shapes as well as the effect of crosswinds. [Preview Abstract] |
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S1.00193: Testing for superconductivity with normal state properties O. Paul Isikaku-Ironkwe One of the challenging problems in the search for superconductors is determining from the chemical formula whether a material will be a superconductor or not. Superconductivity correlates with normal state properties such as electronegativity, valence electron count and mass (atomic number). Using these normal state properties we study known superconductors, non-superconductors and semiconductors. We find that for most superconductors, the ratio of average electron count (Ne), to the square root of the average atomic number (Z), is usually less than 1, but greater than 0.5. We find too that when this applies and the electronegativity is higher than 1.5, we are likely to get a superconductor. We propose here that this relationship could be used as a semi-empirical test for superconductivity, knowing just a materials formula. Except for carbon-based superconductors and some unconventional superconductors, most non-superconductors have Ne over the square root of Z greater than 1 or less than 0.5. [Preview Abstract] |
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S1.00194: New Generally Covariant Generalization of the Dirac Equation Not Requiring Gauges David Maker We introduce a new pde ($\Sigma _{\mu }\surd \kappa _{\mu \mu }$\textit{$\gamma $}$_{\mu }$\textit{$\partial \psi $/$\partial $x}$_{\mu }$\textit{-$\omega \psi $=0}) with spherically symmetric diagonalized $\kappa _{00}$ = 1-r$_{H}$/r=1/$\kappa _{rr}$ giving it general covariance. If r$_{H}$ =2e$^{2}$/m$_{e}$c$^{2}$ this new pde reduces to the standard Dirac equation as r$\to \infty $. Next we solve this equation directly using separation of variables (e.g., 2P, 2S, 1S terms). Note metric time component $\kappa _{oo}$ =0 at r=r$_{H}$ and so clocks slow down with \textit{baryon stability} the result. Note also that near r$_{H}$ the 2P$_{3/2}$ state for this new Dirac equation gives a azimuthal trifolium, 3 lobe shape; so this \textbf{ONE} charge$ e$ (so don't need \textit{color} to guarantee this) spends $1/3$ of its time in each lobe (\textit{fractionally charged} lobes), the lobe structure is locked into the center of mass \textbf{(}\textit{asymptotic freedom}), there are \textit{six }2P states (corresponding to the 6 flavors);~the P wave scattering gives the \textit{jets}\textbf{,} all these properties together constituting the~\textit{main properties of quarks!}~without invoking the many free parameters, gauge conditions of QCD. Also the 2S$_{1/2}$ is the\textbf{ }\textit{tauon} and the 1S$_{\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} }$is the \textit{muon} here. The S matrix of this new pde gives the \textit{W and Z as resonances and does not require renormalization counterterms or free parameters. } Thus we get nuclear, weak and E{\&}M phenomenology as\textit{ one} step solutions of this new pde. [Preview Abstract] |
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S1.00195: A Quantized Metric As an Alternative to Dark Matter Joel Maker The cosmological spherical symmetry background metric coefficient (g$_{44}\equiv )$ g$_{00}$= 1-2GM/c$^{2}$r should be inserted into a Dirac equation $\Sigma _{\mu }(\surd $g$_{\mu \mu }\gamma ^{\mu }\partial \psi $/$\partial $x$_{\mu })-\omega \psi $ = 0 (1,Maker) to make it generally covariant. The spin of this cosmological Dirac object is nearly unobservable due to inertial frame dragging and has rotational L(L+1) $\Delta \varepsilon $ and oscillatory $\varepsilon $ interactions with external objects at distance away r$>>$10$^{10 }$LY. The inside and outside frequencies $\omega $ match at the boundary allowing the outside metric eigenvalues to propagate inside. To include the correct 3 lepton masses in this Dirac equation we must use ansatz g$_{oo}$= e$^{i(2\varepsilon +\Delta \varepsilon )}$ with $\varepsilon $=.06, $\Delta \varepsilon $=.00058. For local metric effects our ansatz is g$_{oo}=_{ }$e$^{i\Delta \varepsilon }$. Here the metric coefficient g$_{oo}$ levels off to the quantized value e$^{i\Delta \varepsilon }$ in the galaxy halo: g$_{oo}$=1-2GM/rc$^{2}\to $ rel(e$^{i\Delta \varepsilon })$ \textbf{=}cos($\Delta \varepsilon )$= 1-($\Delta \varepsilon )^{2}$/2 $\to (\Delta \varepsilon )^{2}$/2=2GM/rc$^{2}$ for this circular motion v$^{2}$/r=GM/r$^{2}$=c$^{2}(\Delta \varepsilon )^{2}$/4r $\to $v$^{2 }$=c$^{2}(\Delta \varepsilon )^{2}$/4 =87km/sec)$^{2} \quad \approx $\textbf{100km/sec})$^{2}$. So the metric acts to quantize v. Note also there is rotational energy quantization for the $\Delta \varepsilon $ rotational states that goes as: (L(L+1)) $\propto $ $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $mv$^{2} \quad \to \sqrt {L(L+1)} \quad \propto $v. Thus differences in v are proportional to L, L being an integer. Therefore $\Delta $v = kL so v = 1k, v = 2k, v = 3k, v = 4k{\ldots}. v=N (the above $\sim $100km/sec) with \textit{dark matter then not required} to give these high halo velocities. Recent nearby galaxy Doppler halo velocity data \textbf{\textit{strongly support}} this velocity quantization result. [Preview Abstract] |
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S1.00196: Atom Wavelike Nature Solved Mathematically Charles Sven Like N/S poles of a magnet the strong force field surrounding, confining the nucleus exerts an equal force [noted by this author] driving electrons away from the attraction of positively charged protons force fields in nucleus -- the mechanics for wavelike nature of electron. Powerful forces corral closely packed protons within atomic nucleus with a force that is at least a million times stronger than proton's electrical attraction that binds electrons. This then accounts for the ease of electron manipulation in that electron is already pushed away by the very strong atomic N/S force field; allowing electrons to drive photons when I strike a match. Ageless atom's electron requirements, used to drive light/photons or atom bomb, without batteries, must be supplied from a huge, external, super high frequency, super-cooled source, undetected by current technology, one that could exist 14+ billion years without degradation -- filling a limitless space prior to Big Bang. Using only replicable physics, I show how our Universe emanated from that event. [Preview Abstract] |
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S1.00197: Mass, Energy, Space And Time Systemic Theory--MEST-- heat and cold, positive electron and negative electron Dayong Cao Things have their physical system of the mass,energy, space and time of themselves-MEST. The time is from the frequency of wave, the spac is from the amplitude of wave. Also they have different space-time and MEST of themselves, but all of them have the balance system of MEST In the solar system, there is the ``quantization'' model of the planets, $ V^2\approx \frac{1}{n^2}0.92\times 10^4km^2/s^2,{\begin{array}{*{20}c} \hfill \\ \end{array} }r\approx n^2\times 14.5\times 10^6km,{\begin{array}{*{20}c} \hfill \\ \end{array} }2\pi t\approx n^2\times 1.89\times 10^6s,(n=2,{\begin{array}{*{20}c} \hfill \\ \end{array} }3,{\begin{array}{*{20}c} \hfill \\ \end{array} }4...)$ And there is the balance energy equation of planet (with a Round revolution orbit), $ \frac{1}{2}mv^2+m'c^2=-G\frac{Mm}{r},{\begin{array}{*{20}c} \hfill \\ \end{array} }\frac{1}{2}mv^2=\frac{1}{2n^2}mv_0 ^2,{\begin{array}{*{20}c} \hfill \\ \end{array} }m'c^2=\frac{1}{n^2}m_0 'c^2,{\begin{array}{*{20}c} \hfill \\ \end{array} }G\frac{Mm}{r}=\frac{1}{n^2}G\frac{Mm}{r_0 }.$ Among it, ``$m'c^2$'' is the energy of space-time of planet, ``$\frac{1}{2}mv^2$'' is the kinetic energy of planet, ``$G\frac{mM}{r}$'' is potential energy of planet. In atomic system, there is the ``quantization'' model of the electron, $ v_e ^2\approx \frac{1}{n^2}v_0 ^2,{\begin{array}{*{20}c} \hfill \\ \end{array} }r_e \approx n^2r_{e0} ,{\begin{array}{*{20}c} \hfill \\ \end{array} }2\pi t_e \approx n^22\pi t_{e0} (n=2,{\begin{array}{*{20}c} \hfill \\ \end{array} }3,{\begin{array}{*{20}c} \hfill \\ \end{array} }4...)$ And there is the balance energy equation of the electron of Hydrogen (with a Round revolution orbit), $ \frac{1}{2}m_e v_e ^2+m_e 'c^2=-\frac{1}{4\pi \varepsilon _0 }\frac{q_1 q_2 }{r_e },{\begin{array}{*{20}c} \hfill \\ \end{array} }\frac{1}{2}m_e v_e ^2=\frac{1}{2n^2}m_{e0} v_{e0} ^2,{\begin{array}{*{20}c} \hfill \\ \end{array} }m_e 'c^2=\frac{1}{n^2}m_{e0} 'c^2,{\begin{array}{*{20}c} \hfill \\ \end{array} }\frac{1}{4\pi \varepsilon _0 }\frac{q_1 q_2 }{r_e }=\frac{1}{n^2}\frac{1}{4\pi \varepsilon _0 }\frac{q_1 q_2 }{r_{e0} }.$ Among it, ``$m_e 'c^2$'' is the energy of space-time of the electron, ``$\frac{1}{2}m_e v_e ^2$'' is the kinetic energy of the electron, ``$\frac{1}{4\pi \varepsilon _0 }\frac{q_1 q_2 }{r_e }$'' is electric potential energy. [Preview Abstract] |
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S1.00198: APPLICATIONS |
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S1.00199: Quantum dot photodetectors: Structures with collective potential barriers Andrei Sergeev, Li-Hsin Chien, Vladimir Mitin, Serge Oktyabrsky Major restrictions of room-temperature semiconductor photodetectors and some other optoelectronic devices are caused by short photoelectron lifetime, which strongly reduces the photoresponse. We report our research on advanced optoelectronic materials, which combine manageable photoelectron lifetime, high mobility, and quantum tuning of localized and conducting states. These structures integrate quantum dot (QD) layers and correlated QD clusters with quantum wells (QWs) and heterointerfaces. The integrated structures provide many possibilities for engineering of electron states as well as specific kinetic and transport properties. The main distinctive characteristic of the QD structures with collective potential barriers is an effective control of photoelectron capture due to separation of highly mobile electrons transferring the photocurrent along heterointerfaces from the localized electron states in the QD blocks (rows, planes, and various clusters). Besides manageable photoelectron kinetics, the advanced QD structures will also provide high coupling to radiation, low generation-recombination noise, and high scalability. [Preview Abstract] |
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S1.00200: Millimeter and sub-millimeter heterodyne mixing based on 2DEG hot-electron bolometers Kai Wang, Matthew Bell, Rahul Ramaswamy, Andrei Sergeev, Gottfried Strasser, Vladimir Mitin We investigate GHz and THz heterodyne mixer based on the electron heating effect of a two-dimensional electron gas (2DEG) by electromagnetic radiation at liquid nitrogen temperatures (77K). The devices are fabricated from AlGaAs/GaAs heterostructures with a channel width of 150 $\mu $m and lengths varying from 3-20 $\mu $m. Steady-state measurements are used to investigate electron heating in these devices and determine basic parameters, such as electron-phonon energy relaxation time and electron heat capacity. We perform mixing experiments at $\sim $100 GHz frequency range with two Gunn diodes as the radiation sources, and find that electron heating is the primary mixing mechanism at these frequencies. For the mixing experiments at $\sim $ 2 terahertz range, a quantum cascade laser (QCL) is employed as the local oscillator. To optimize our device, we also investigate electron kinetics and transport properties in the 2DEG hot-electron bolometer. [Preview Abstract] |
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S1.00201: Effects of disorder on performance of 2DEG hot-electron mixer Rahul Ramaswamy, Kai Wang, Andrei Sergeev, Gottfried Strasser, Vladimir Mitin, Matthew Bell, Aleksandr Verevkin The hot electron bolometer is a detector of choice to be integrated with quantum cascade laser (QCL) to constitute as a mixer. This pair is a promising candidate for a sensitive terahertz mixer operating at liquid nitrogen temperatures. To get effective coupling to the electromagnetic radiation and to avoid significant kinetic inductance at THz frequencies we use low mobility specially fabricated 2DEG structures. The disorder was introduced by low energy electron irradiation onto the sample by electron beam lithography process. We also reduced the spacer thickness in the AlGaAs/GaAs heterostructures to increase ionized impurity scattering. Our fabricated bolometer micro bridges are 150 $\mu $m wide and vary in length from 3 to 20 $\mu $m. We investigate electron heating in these devices at THz frequencies and determine basic kinetic and transport parameters, such as electron-phonon relaxation time, electron heat capacity and bandwidths achievable in such mixers. [Preview Abstract] |
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S1.00202: Titanium-Silicon Dioxide as a Transparent Conducting Oxide and an Anti-Reflection Contact for Photovoltaic Applications John Chivers, Thomas Vandervelde We report on the use of Earth-abundant silicon-dioxide and titanium-dioxide as a transparent conducting oxide (TCO) and antireflective (AR) coating. The varied band gap and index of refraction conditions inherent in the SiTiO$_{2}$ system allow controlled variation of material properties during monolithic growth. TCOs are a critical component in modern photovoltaic devices, used as a front-side contact that won't block incident light. At present, many TCOs require rare-Earth materials (e.g. Indium), which is problematic for large-scale manufacturing. The abundant, well characterized materials used here can be integrated into an existing product line quickly and cheaply. Some TCOs may also act as an AR coating, further increasing light absorption. The ideal AR coating would gradually change from the index of refraction of air to that of the underlying semiconductor. Most AR coatings used today make this transition in a small number of steps, which limits their efficacy. In this work, we use a deposition process that slowly grades the index of refraction while maintaining conductivity and transparency. [Preview Abstract] |
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S1.00203: ABSTRACT HAS BEEN MOVED TO K1.00296 |
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S1.00204: Accessing nanomechanical resonators via a fast microwave circuit Mika Sillanpaa, Jaakko Sulkko, Jayanta Sarkar, Juha Muhonen, Pertti Hakonen We demonstrate how to fully electrically detect the vibrations of conductive nanomechanical resonators up to the microwave regime. We use the electrically actuated vibrations to modulate an LC tank circuit which blocks the stray capacitance, and detect the created sideband voltage by a microwave analyzer. We show the novel technique up to mechanical frequencies of 200 MHz and femto-meter displacement sensitivities. Finally, we estimate how one could approach the quantum limit of mechanical systems. [Preview Abstract] |
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S1.00205: Switching transition between bi-stable memory switching and mono-stable threshold switching based on ion migration in a NiO thin film Inrok Hwang, Myung-Jae Lee, Gyoung-Ho Buh, Jinsik Choi, Jin-Soo Kim, Sahwan Hong, Sang-ho Jeon, Yeon Soo Kim, Ik-Su Byun, Seung-Woong Lee, Seung-Eon Ahn, Bo Soo Kang, Sung-Oong Kang, Bae Ho Park We have investigated a transition of resistive switching behaviors between bi-stable memory switching and mono-stable threshold switching in a NiO film, which was controllable by the polarity and width of applied electric pulse. Macroscopic model was proposed to explain the polarity- and width-dependence of electrical transition that provided experimental evidences for migration of oxygen ions (O2-) to be responsible for the filamentary resistive switching mechanism [Preview Abstract] |
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S1.00206: Transport phenomena in a gate selective vertical double quantum dot Victoria Russell, Simon Chorley, Francois Sfigakis, Stuart Holmes, David Anderson, Geb Jones, Crispin Barnes, Ian Farrer, Charles Smith, David Ritchie, Michael Pepper Certain proposals for a spin qubit require gate control of the position of an electron in a selected 2DEG composition. Conventionally this depends upon patterning of both top and backgates on to a substrate to a precision of within a few nanometres, a non-trivial process. Here we report an attempt to control relative population of two vertical quantum dots using only surface gates. The dots are defined using electrostatic surface gates on a double GaAs quantum well structure with a 7nm barrier. An additional top gate is used to control electron density and coupling between the two dots and hence the dominant transport path. In the crossover regime we observe Fano resonances and charge detection signatures in the conductance through the double dot. This is the first step towards control of the position of a single electron in a vertical double quantum dot composed of different semiconductor materials using only surface gates. [Preview Abstract] |
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S1.00207: Localised magnetic fields in arbitrary directions using patterned nanomagnets Robert McNeil, R.J. Schneble, M. Kataoka, T. Kasama, R.E. Dunin-Borkowski, J.M. Feinberg, R.J. Harrison, C.J.B. Ford, C.H.W. Barnes, D.H.Y. Tse, T. Trypiniotis, J.A.C. Bland, D. Anderson, G.A.C. Jones, M. Pepper Controllable local electric fields on nanometer length scales have revolutionised quantum electronics, but local magnetic fields are less well developed. Nanometer-scale magnets may be engineered to give qualitatively different behaviour from that seen in larger similar shapes. We present designs of patterned magnetic elements that can produce remnant fields of 50 mT (potentially 200 mT) confined to chosen, submicron regions, in directions perpendicular to an external initializing field. We have fabricated an example to confirm the modeling, and have imaged the resulting magnetic field using electron holography. A wide variety of magnetic-field profiles on nanometer scales can be produced and the ability to apply electric fields, for example to move a quantum dot between regions of differing magnetic-field strength or direction, makes this a powerful technique. [Preview Abstract] |
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S1.00208: Innovative Technologies: Hyperpolarized Noble Gases for Enhanced MRIs P.E. Cladis, James Daniels An update is given of Daniels' novel method to measure gas magnetization by measuring the frequency jump between two coupled oscillating systems. [Preview Abstract] |
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S1.00209: Characteristics of oscillating magnetic field-actuated microvalve response time Jonathan Kessler, Santaneel Ghosh, Jian Peng, Clayton Schenk Magnetically responsive thermo-active hydrogels offer several potential advantages over other bio-material systems for the controlled release applications for micro- and nanofluidic devices. Volume phase transition of the thermo-sensitive gels is controlled by the change in entropy of the system induced by the hysteresis loss of embedded ferromagnetic nanoparticles modulated by an ac magnetic field. It has been shown in [1], a poly(N-isopropylacrylamide) (PNIPAM) based thermo-responsive system provides controlled heating and volumetric changes with a significantly faster response time through magnetic actuation owing to its smaller dimension. Moreover, it is extremely easy to modulate the field and frequency. Varying the flow rate, channel diameter, and valve width, we characterize the response time of the microvalve for drug delivery applications. [1] S. Ghosh, C. Yang, T. Cai, Z. Hu, and A. Neogi\textit{, J. Phys. D: Appl. Phys. }\textbf{42} (2009) 135501 [Preview Abstract] |
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S1.00210: Conducting the lasing of single transverse modes in a commercial multi-mode VCSEL by the beam-profile adapted optical feedback Yu-Heng Wu, Chuan-Pi Hsu, Da-Long Cheng, Wang-Chuang Kuo, Tsu Chiang Yen This work studied the generation of single high-order transverse modes in a commercial multi-transverse mode VCSEL by applied beam-profile adapted optical feedback. To adapt the beam profile, the multi-transverse-mode beam profile of the solitary VCSEL was launched into a single-mode fiber, resulting in a quasi-Gaussian beam profile at the exit of fiber. The adapted beam passed through a spatial light modulator (SLM) and was then fed back into the laser's cavity. The SLM was designed to have the beam profile of a high-order transverse mode. The VCSEL would lasing the designated single transverse mode with a side-mode suppression ratio about 20 dB by the optical feedback. More experimental details will be presented and these results will help to expand the application of VCSELs. [Preview Abstract] |
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S1.00211: Production of Molecular Oxygen using a Capacitevly-Coupled Radio-Frequency Discharge in a Carbon Dioxide Gas Mixture George Brooke, Berley Rister, James Ray We have studied the production of molecular oxygen using a radio-frequency capacitively-coupled discharge in a simulated Martian atmosphere (95{\%} CO$_{2}$, $\sim $5 torr). The concentration of molecular oxygen within the chamber was measured using continuous-wave cavity ring-down spectroscopy (CW-CRDS). Oxygen concentration measurements were made at discharge powers ranging from approximately 5 W to 10 W. The discharge temperature was monitored using the CO rotational emission spectrum.. [Preview Abstract] |
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S1.00212: The self-focusing and the optical breathers in tunable waveguide arrays Yi-Hsiu Wu, Shuan-Yu Huang, Chie-Tong Kuo A voltage-controlled waveguide array in planar nematic liquid crystals is employed to investigate the phenomena of self-focusing and optical breathers. The multiple focal points appearing along the propagating axis can be adjusted their beam undulation by the applied voltage. The breathing period resulting from a periodic refractive-index modulation can be induced by a spatially periodic electric-field distribution. The polarization dependence of breathing period in a waveguide array is also discussed. [Preview Abstract] |
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S1.00213: Atomistic Modeling of the Thermoelectric Properties in Silicon Nanowires Abhijeet Paul, Gerhard Klimeck The thermoelectric properties of Silicon can be improved due to nano-sized structuring and modulation. The effect of crystal orientation, cross-sectional dimension and source-drain doping on Seebeck coefficient (S) and electronic conductance ($\sigma$) in silicon nanowires is studied theoretically in this work. From the electronic structure obtained using an atomistic 10 band $sp^{3}d^{5}s^{*}$ Tight-Binding model with spin orbit coupling, we calculate these parameters using the Landauer formula. Conductivity increases with increasing cross-section size since the number of modes per energy increases. Different orientations show different conductivity. However, Seebeck coefficient is quite independant of the orientation and cross-section size. But, the power factor ($S^{2}\sigma$), can be improved with size and orientation mainly due to the improvement in conductivity. In these nanowires, phonon scattering at the wire boundary further reduces the lattice thermal conductivity ($\kappa_{l}$) which plays a positive role in improving the thermoelectric figure of merit (ZT) bringing it close to 1 at 300K. [Preview Abstract] |
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S1.00214: ABSTRACT WITHDRAWN |
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S1.00215: Two Dimensional Plasmonic Cavities on Moire Surfaces Sinan Balci, Askin Kocabas, Mustafa Karabiyik, Coskun Kocabas, Atilla Aydinli We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements. [Preview Abstract] |
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S1.00216: Porous Anodic Aluminum Oxide with Serrated Nanochannels Dongdong Li, Liang Zhao, Jia G. Lu Self-assembled nanoporous anodic aluminum oxide (AAO) membrane with straight channels has long been an important tool in synthesizing highly ordered and vertically aligned quasi-1D nanostructures for various applications. Recently shape-selective nanomaterials have been achieved using AAO as a template. It is envisioned that nanowires with multi-branches will significantly increase the active functional sites for applications as sensors, catalysts, chemical cells, \textit{etc}. Here AAO membranes with serrated nanochannels have been successfully fabricated via a two-step annodization method. The serrated channels with periodic intervals are aligned at an angle of $\sim $25$^{circ}$ along the stem channels. The formation of the serrated channels is attributed to the evolution of oxygen gas bubbles and the resulted plastic deformation in oxide membrane. In order to reveal the inside channel structure, Platinum are electrodeposited into the AAO template. The as-synthesized serrated Pt nanowires demonstrate a superior electrocatalytic activity. This is attributed to the enhanced electric field strength around serrated tips as shown in the electric field simulation by COMOSL. Moreover, hierarchical serrated/straight hybrid structures can be constructed using this simple and novel self assembly technique. [Preview Abstract] |
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S1.00217: A study of the structural, optical, and electronic properties of diamond nanoparticles R. Chakraborty, J. Kyle LaRoque, Suresh Sharma We present extended results on the structure and optical properties of nanometer-size (10-100 nm) diamond particles. Samples were grown on silicon substrates by hot-filament assisted chemical vapor deposition (HFCVD) and characterized by using AFM, SEM, Raman and photoluminescence (PL) spectroscopies [1, 2]. AFM and SEM measurements show that the samples contain particles ranging in diameter from 10 to 100 nm. The Raman spectroscopy data confirm through the $\sim $ 1332 cm$^{-1}$ characteristic line that the samples contain diamond nanoparticles. We examine details of the Raman spectra (asymmetrical shape and shift from the 1332 cm$^{-1}$ line) and correlations of these features with the properties of diamond nanoparticles [3]. The PL spectra show bands arising from structural defects in the Si/SiO$_{2}$ substrate and diamond nanoparticles. \\[4pt] [1] S. C. Sharma et al., J. Materials Research, \textbf{5}, 2424 (1990)\\[0pt] [2] R. Chakraborty, K. LaRoque, and S. C. Sharma, TSAPS, D1.00023, October (2009)\\[0pt] [3] A. Stacey, I. Aharonvich, S. Prawer, J. E. Butler, Diam and Rel. Maters. \textbf{18}, 51 (2009) [Preview Abstract] |
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S1.00218: Quantum Dot Nanostructures: HREM Charactrization and Perspectives in Applications for Soalr Energy Conversion Sergei Rouvimov, Mikhail Maximov, Victor Ustinov, S.A. Blokhin, A.R. Kovsh The paper reviews the progress in growth and characterization of quantum dot (QD) nanostructures, and the perspectives of their application in multi-layer semiconductor solar energy converters. While unique electronic properties of QDs have been already successfully utilized in novel high-speed quantum dot lasers [1], QDs seem to be promising for novel solar cells due to tunable bandgap and energy level structure [2]. High resolution electron microscopy (HREM) played an important role in understanding of self organization phenomena and QD properties as well as in optimization, control and engineering of QD nanostructures (tuning QD size and density, using stacked multilayered QD structures and controlling vertical and lateral coupling) to superior laser performance (temperature-independent, low threshold currents, high differential gain). The paper addresses current developments and challenges in application of QD nanostructures to solar energy conversion as well as progress and perspectives in HREM analysis of quantum dot structures. [1] V.M. Ustinov, et al \textit{Electronics Letters}, 34, 670-672 (1998) [2] A. Nozik, in \textit{Nanostructured and Photochemical systems for solar photon conversion}, World Scientific Publ., 2008, p.147 [Preview Abstract] |
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S1.00219: The effect of surface heterogeneity on the mechanical properties of single wall carbon nanotube carpets E.C. Maldonado, M.W. Roth The results presented and discussed involve Material Point Method (MPM) simulations of single wall carbon nanotube (SWNT) carpets with varying surface heterogeneity. Specifically, we use deterministic MPM simulations to explore the effect of the degree of randomness of the SWNT array on peeling and adhesive properties as well as the degree clumping of the carpets acting under the constraint of guided motion of the carpet substrate. The bulk elastic properties of the tubes and substrate are taken into account and the system's behavior is characterized through calculations involving dynamics and energetics. [Preview Abstract] |
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S1.00220: Physical properties of poly(lactic-co-glycolic) and poly(ethylene glycol) nanoparticles for drug delivery using atomic force microscopy (AFM) and electrostatic nanolithography Sergei Lyuksyutov, Igor Fedin, Victoria Nedashkivska, Caterina Lyuksyutova, Werner Geldenhuys, Vijay Sutariya Nanoparticles (NP) of biodegradable polymers poly(lactic-co-glycolic)(PLGA) and poly(ethylene glycol) (PEG) are potential drug delivery components for biomedical applications. The NP based on PLGA or PEG can be directed to accumulate in cancer tumor cells with the use of anti-bodies which are conjugated to the NP. The NP's size distribution is the critical property for biochemical affinity and therefore delivery to the specific target organs. We used an atomic force microscopy (AFM) to characterize the NP size and AFM electrostatic nanolithography (AFMEN) to study the behavior of PEG-PLGA NP under the extreme electric fields exceeding 10$^{9}$ V m$^{-1}$. AFMEN allows the displacement of molecules along the lines of the electric field due to electrostatic polarization. This study has an important practical application for the optimum design of NP with the correct characteristics for drug delivery. [Preview Abstract] |
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S1.00221: Computational study of hydrogen adsorption on silica-based nanosprings Yingqian Zhan, Marty Ytreberg Silica-based nanosprings were recently synthesized and characterized by McIlroy and collaborators.1 Further experimental studies on these nanosprings revealed a high adsorption rate of hydrogen gas at room temperature (data not published). In this study, computer simulation was used to understand the hydrogen adsorption properties of silica nanosprings. The interaction between the nanomaterial and hydrogen molecules was described using classical approximations. Different orientations and positions of the hydrogen molecule relative to the nanosprings were tested and the effect of the separation between the two nanowires was studied. The results suggest that the hydrogen molecule tends to be trapped between the nanosprings, i.e., that the unique geometry of the nanosprings is the cause for the high rate of adsorption. References 1.Lidong Wang, D Major, P Paga, D Zhang, M G Norton and D N McIlroy. Nanotechnology, 2006, 17, S298-S303 [Preview Abstract] |
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S1.00222: Hydrogen Materials Compatibility in Piezoelectrics Kyle Alvine, Stan Pitman, Charles Henager, Vaithiyalingam Shutthanandan, Craig Brown, Madhu Tyagi, Tim Jenkins, Terry Udovic Hydrogen materials compatibility is an important materials science issue for hydrogen storage and delivery in hydrogen vehicle technology and infrastructure and to a lesser degree the microelectronics industry where hydrogen passivation is required. Piezoelectrics are one such material. They are used in direct injection hydrogen internal combustion engines (H2ICE) as actuators but tend to foul rapidly in high pressure hydrogen. Ferroelectric random access memory (FERAM) also suffers similar degradation issues. We present high pressure hydrogen absorption and diffusion findings for PZT and BaTiO3 piezoelectric materials. Data is based on quasi-elastic neutron (QENS) scattering and elastic recoil detection analysis (ERDA). [Preview Abstract] |
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S1.00223: Organic solar array with transparent contacts by spray Jason Lewis, Jian Zhang, Xiaomei Jiang Organic solar cells (OSC) based on pi-conjugated polymers (e.g., poly-3-hexylthiophene, P3HT) and fullerene derivatives (e.g.,6,6 -phenyl C61 butyric acid methyl ester, PCBM) have attracted attention over the past decades because they may provide a cost-effective route to wide use of solar energy for electrical power generation.These organic semiconductors have the advantage of being chemically flexible for material modifications, as well as mechanically flexible for the prospective of low-cost, large scale processing such as solution-cast on flexible substrates. However, one of the major challenges preventing the realization of complete solution-processable manufacturing of OSC is the metal cathode depostion invoving high vacuum. Althrough there have been several reports about apraying a thick layer of PEDOT:PSS as a replacement, the sacrifice of transparency will be problematic in certain appliactions such as window technology. Furthermore, fabrication of organic solar array (OSA) using spray method is still in its early stage. We have developed a novel procedure to fabricate transparent-contacts OSA using layer-by-layer spray technique, with a balance between conductivity and transparency for the spray-on contacts. Spray-on OSA performance will be compared side by side with OSA fabricated by conventional spin-coating and metal desposition procedure. [Preview Abstract] |
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S1.00224: ABSTRACT WITHDRAWN |
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S1.00225: Improved solar cell based on ZnO nanowires and CdSe quantum dots Athavan Nadarajah, Robert C Word, Rolf Konenkamp We report a solar cell nanostructure that incorporates CdSe quantum dots embedded in a ZnO nanowire film and a hole-conducting polymer layer. This arrangement allows for enhanced light absorption and efficient collection of the carriers. Microscopic studies show the conversion of CdSe quantum dots into an inter-connected and continuous polycrystalline thin film upon annealing in cadmium chloride ambient. This structural change of the quantum dot layer destroys the quantum confinement and improves the charge transport in the layer significantly. It also provides for improved charge transfer to the adjacent contacting layers. The optimized solar cell exhibits an external quantum efficiency of 65 percent and an energy conversion efficiency above 2 percent. [Preview Abstract] |
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S1.00226: Dye Sensitized Solar Cells Based on Free-standing TiO2 Nanotube Chaehyun Kim, Savas Delikanli, Samanthe Perera, Hao Zeng Dye-sensitized solar cells based on free-standing TiO2 nanotube arrays as electrodes have been fabricated. It was shown that highly ordered vertically oriented TiO2 nanotube arrays offer a large surface area for adsorption of dye molecules or quantum dots and provide a direct pathway for fast electron transport. This cuts down carrier recombination and enhances photoconversion efficiency. TiO2 nanotube arrays were obtained by potentiostatic anodization of titanium foil in fluoride-based ehylene glycol electrolyte. TiO2 nanotube arrays can be detached from the titanium foil by chemical etching and annealed at high temperatures to obtain highly crystalline anatase phase without cracking, since there is no strain induced between TiO2 and Ti foil. Solar cells based on free-standing dye-sensitized solar cells reveal much higher overall efficiency than those with nanotubes attached to the Ti foil, due to the improved crystallinity and front side illumination. J. Phys. Chem. C 2009, 113, 6310--6314 [Preview Abstract] |
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S1.00227: Electronic transport of femtosecond-laser created sub-bandgap absorbers Meng-Ju Sher, Mark Winkler, Eric Mazur Femtosecond laser irradiation can dope silicon with sulfur to concentrations above the Mott transition threshold. This material exhibits near-unity, broadband absorption for photon energies lower than 0.5 eV, deep below the silicon bandgap, and is potentially useful for photovoltaic applications. In addition, this material exhibits metallic-like conduction. The unusual optical and electronic properties of femtosecond laser-doped silicon suggest the formation of an intermediate band. In this poster, we will report on the femtosecond laser doping technique, as well as temperature-dependent Hall measurements on silicon doped with varying sulfur concentrations. These measurements reveal on the nature of electronic transport in this novel material, as well as identify the energy states of the sulfur donors and hence the location of the intermediate band. We will also discuss potential applications for intermediate band photovoltaics. [Preview Abstract] |
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S1.00228: Optical and Transport Properties of SnZrCh$_{3}$ (Ch = S, Se) Daniel Harada, Annette Richard, Andriy Zakutayev, Doug Keszler, Janet Tate SnZrS$_{3}$ is a semiconductor that crystallizes in the NH$_{4}$CdCl$_{3}$ crystal structure. It is studied as a possible solar cell absorber. We report on the synthesis and transport properties of SnZrS$_{3}$ and isostructural SnZrSe$_{3}$. The optical band gaps are measured by diffuse reflectance, a gap of 1.5 eV is found for SnZrS$_{3}$. Seebeck measurements indicate that both SnZrS$_{3}$ and SnZrSe$_{3}$ are p-type semiconductors at room temperature. The measured resistivity for SnZrS$_{3}$ is 36 Mohm cm, and for SnZrSe$_{3}$ it is 1 Mohm cm. [Preview Abstract] |
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S1.00229: Study of Dynamic Properties of Ferrocene Molecular Rotors on Au(1,1,1) U.G.E. Perera, Y. Zhang, H.R. Kersell, G. Rapenne, S-W. Hla Dynamic properties of 4Fe3Set double decker molecular rotor adsorbed on a Au(111) surface were studied by using a low temperature scanning tunneling microscopy at 75 K. Due to thermal excitation, most of the molecular rotors are found to be spinning on the surface at this temperature. Moreover, lateral motion of the spinning rotors across the surface were occasionally observed in the sequence of STM images. Molecules can move both along and across the surface Herring bone reconstructions. Furthermore, using STM lateral manipulation scheme, relocation of the spinning rotors can also be performed. At higher bias voltages above -2.4V, the molecules disintegrate on the surface. [Preview Abstract] |
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S1.00230: FLUIDS AND SOFT MATTER III |
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S1.00231: Adsorption of Electrolytes within Narrow Slit-Shaped Silica Pores: Molecular Dynamics Simulation Results to Design Separation Strategies Alberto Striolo, Dimitrios Argyris We report equilibrium molecular dynamics simulation results for structural and dynamic properties of aqueous electrolyte solutions confined within narrow pores. The slit-shaped pores are carved from cristobalite silica and show various degrees of hydroxylation. The pore width is in the range 08 -- 2.0 nm. The aqueous solutions contain NaCl, CsCl, CaCl$_{2}$, and SrCl$_{2}$ electrolytes at 1M concentration or larger. Simulations are performed at ambient conditions within the NVT ensemble. The results are analyzed in terms of density profiles away from the solid substrates, self diffusion coefficients in the direction parallel to the solid substrate, and residence time at contact with the solid substrate. The data suggest the formation of layered structures, consistent with results obtained for thin films of solution supported on free-standing surfaces. Because the self-diffusion coefficient is faster as the distance from the solid increases, the ions that are at the pore center diffuse more quickly through the pore than those adsorbed closer to the wall. Further, our results are important for exploring and understanding Hofmeister effects under confinement, and also for deploying a number of practical applications including water desalination, remediating nuclear waste sites, and designing nanofluidic devices. [Preview Abstract] |
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S1.00232: ABSTRACT HAS BEEN MOVED TO K1.293 |
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S1.00233: Mesoscopic Hydrodynamic Theory of Electric-Field Driven Water Pumping Through Nanochannels Angbo Fang We develop a mesoscopic hydrodynamic theory for water flow through nanochannels. The physical meaning of vortex flux, which is responsible for translation-rotation (T-R) dynamic coupling, is analyzed and shown to be relevant only at mesoscopic length and time scales. Then we apply a variational approach to derive the hydrodynamic equations of motion along with consistent hydrodynamic boundary conditions, taking into account the important T-R coupling in surface layers. Analytic solutions for the velocity profile are obtained and analyzed for general fluid-solid interfacial dynamic properties. Under a homogenous rotating electric field, the water pumping efficiency is dominated by the mismatch degree of dynamic properties (such as slip length and surface layer thickness) of the two opposite interfaces confining the nanochannel. The averaged flow velocity is in general shown to be independent of the channel width. [Preview Abstract] |
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S1.00234: Enhancement of charged macromolecule capture by nanopores in a salt gradient Tom Chou We propose a simple electrokinetic mechanism of enhanced charged particle capture to nanopores that connect two reservoirs of different ionic strength. The mechanism relies on the electrostatic potential near the pore mouths. For long pores with diameter much greater than the local screening length, we obtain accurate analytic expressions showing how salt gradients control the local conductivity which can lead to increased local electrostatic potentials and charged analyte capture rates. We also find that the attractive electrostatic potential may be balanced by an outward, repulsive electro-osmotic flow that can in certain cases conspire with the salt gradient to further enhance the analyte capture rate. [Preview Abstract] |
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S1.00235: pH/ion nanosensors with optical tweezers in a lab-on-a-chip Mark Kendrick, Whitney Shepherd, Jessica Gifford, Daniel Gruss, David McIntyre, Oksana Ostroverkhova, Valeriya Bychkova, Alexey Shvarev, Natalia Pylypuik, Myra Koesdjojo, Vincent Remcho, Shalini Prasad, Scott Reed We present a lab-on-a-chip measurement platform for monitoring pH and other ion concentrations of solutions in a microfluidic device or within biological cells, with high spatial resolution. We have developed a variety of polymeric pH/ion sensitive nanoparticles (ion optodes), or `nanosensors', that can be synthesized \textit{in situ }within a microfluidic device. These ion optodes exhibit fluorescence spectra that change with the pH/ion concentration of the surrounding environment. We optically trap and manipulate several nanosensors, either in microfluidic channels or within biological cells, using holographic optical tweezers and simultaneously monitor fluorescence emission spectra from individual nanosensors. Changes in the fluorescence spectra of the optically trapped ion optodes provide information on spatial and temporal changes in either the pH or ion concentrations in the microfluidic channel or biological cell. [Preview Abstract] |
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S1.00236: Power and Pressure Fluctuations in Elastic Turbulence Yonggun Jun, Victor Steinberg Power $P$ fluctuations injected to the system and pressure $p$ fluctuations in a swirling flow of polymer solutions in a wide range of polymer concentrations $c$ were simultaneously measured in elastic turbulence regime. They show non-Gaussian statistics that strongly resemble statistical behavior of $P$ and $p$ in hydrodynamic turbulence. Together with this fact, weak dependence of the statistics of rescaled variables on $c$ may suggest that there are universal mechanisms determining the intermittent statistics of $P$ and $p$. We also show that the study of the statistics of $p$ provides a way to study statistics of the elastic stresses in elastic turbulence otherwise currently unattainable. [Preview Abstract] |
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S1.00237: Dynamical Scaling in Wave Turbulence Colm Connaughton, Paul Krapivsky, Alan Newell Wave turbulence concerns itself with the non-equilibrium statistical mechanics of ensembles of nonlinearly interacting dispersive waves in the presence of external forcing and damping. In the limit of weakly interacting waves, one may consistently derive a kinetic equation describing the evolution of the wave spectrum. The stationary solution of this equation, the Kolmogorov--Zakharov (KZ) spectrum, describes a cascade of wave energy from the forcing scale to the dissipation scale. We present a mixture of numerical and asymptotic results which show that dynamical scaling solutions the 3-wave kinetic equation can be non-trivial. Firstly, the transient spectrum which precedes the establishment of the KZ spectrum in the case of forced turbulence is shown to be steeper than that predicted by KZ theory in the finite capacity case. Secondly, the transient relaxation spectrum in the case of decaying turbulence can exhibit non-trivial logarithmic corrections to the expected dynamical scaling laws. [Preview Abstract] |
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S1.00238: SUPPLEMENTAL |
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S1.00239: Finding Your Literature Match - A Physics Literature Recommender System Edwin Henneken, Michael Kurtz A recommender system is a filtering algorithm that helps you find the right match by offering suggestions based on your choices and information you have provided. A latent factor model is a successful approach. Here an item is characterized by a vector describing to what extent a product is described by each of N categories, and a person is characterized by an ``interest'' vector, based on explicit or implicit feedback by this user. The recommender system assigns ratings to new items and suggests items this user might be interested in. Here we present results of a recommender system designed to find recent literature of interest to people working in the field of solid state physics. Since we do not have explicit feedback, our user vector consists of (implicit) ``usage.'' Using a system of N keywords we construct normalized keyword vectors for articles based on the keywords of that article and its bibliography. The normalized ``interest'' vector is created by calculating the normalized frequency of keyword occurrence in the papers cited by the papers read. [Preview Abstract] |
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S1.00240: \textbf{Mass, Energy, Space And Time Systemic Theory }---MEST--- some suppose Dayong Cao Like charges repel each other, unlike charges attract, Like magnetic attract, unlike magnetic repel each other; By the same way, Like energy (like cold and heat) repel each other, unlike energy (as temperature, like cold and heat) attract, Like mass attract, unlike mass repel each other; so the dark mass-energy can give the planet the press like the gravity. Like revolution repel each other, unlike revolution attract, Like autorotation attract, unlike autorotation repel each other; By the same way, Like isospin repel each other, unlike isospin attract, Like spin attract, unlike spin repel each other; In the solar system, the mass-energy is center and the space-time is around. So sun absorb the mass-energy and radiate the light (space-time). In the black hole system, the space-time is center and the dark mass-energy is around. So black hole absorb the light and radiate the dark mass-energy. The dark mass-energy can go into sun. It can ignite the nuclear fission of sun. And the nuclear fission can ignite it's nuclear fusion ; The light can go into the black hole. It can ignite the ``nuclear fission'' of space-time of the black hole. And the ``nuclear fission'' can ignite the ``nuclear fusion'' of space-time of the black hole. When we get The Unification of Physics of MEST, we will get The Return-To-Zero of Physics of MEST. \[ f(x^{(M,E,S,T)})=(0,1) \] [Preview Abstract] |
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S1.00241: Microtubule Dynamics Interacting with Stabilizing Agents in a Cell-like Environment Mitra Shojania Feizabadi Microtubules, key components of the cytoskeleton, are involved in several biological functions. They are highly dynamic polymers that stochastically switch between growing and shrinking phases. Due to their critical role in the process of cell division, they are the target of anti-cancer drugs. Antimitotic drugs usually suppress the dynamic instability of microtubules and, therefore, affect the process of cell division. In this work, the dynamic of microtubules interacting with catastrophe suppressing drugs as stabilizing agents, introduced by Mishra et al. (Phys. Rev. E. 72, 51914, 2005), is modified in a confined geometry and associated with the obtained and analyzed steady state solutions. [Preview Abstract] |
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S1.00242: POST-DEADLINE ABSTRACTS |
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S1.00243: Inhomogeneous magnetic phases: a LOFF-like phase in Sr$_3$Ru$_2$O$_7$ Andrew Berridge, Santiago Grigera, Ben Simons, Andrew Green The phase diagram of Sr$_3$Ru$_2$O$_7$ contains a metamagnetic transition that bifurcates to enclose an anomalous phase with intriguing properties - a large resistivity with anisotropy that breaks the crystal-lattice symmetry - and an interesting entropic landscape. We propose that this is a magnetic analogue of the spatially inhomogeneous superconducting Fulde-Ferrel-Larkin-Ovchinnikov state. Based on a microscopic theory of Stoner magnetism we derive a Ginzburg-Landau expansion where the magnetisation transverse to the applied field can become spatially modulated. We show that this reproduces the observed phase diagram of Sr$_3$Ru$_2$O$_7$. We consider the dependence of the system on the angle of the applied magnetic field and calculate the signatures of the metamagnetic transition and inhomogeneous phase in the entropy and specific heat. These results are compared with the experimental observations. [Preview Abstract] |
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S1.00244: Paired states of crystalline electrons in two dimensions Francisco Claro, Daniel Souza We show that in a perfect crystalline environment two electrons may pair to form a bound state. Such states form a band whose energy above the Bloch band center scales like the strength of the interaction. The pairs obey the dynamics of a composite particle. This is shown by considering an external electric field and verifying that there are Bloch oscillations corresponding to an object of charge 2e. If the strength of the interaction is comparable to the band width, or smaller, the Bloch and paired states bands may overlap, suggesting that in the ground state a bosonic fluid could be formed. The pair problem is equivalent to that of a single particle in a 4D lattice with a surface. The paired states correspond to surface states in such equivalent problem and decay exponentially as the particles move away from each other. [Preview Abstract] |
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S1.00245: Prediction of the Viscoelastic Bulk Modulus Jiaxi Guo, Sindee Simon The bulk and shear viscoelastic responses for several materials appear to arise from the same molecular mechanisms at short times, i.e., Andrade creep where the KWW beta parameter is approximately 0.3. If this is indeed the case, prediction and placement of the bulk viscoelastic response can be made simply by knowing the limiting elastic and rubbery bulk moduli and the viscoelastic shear response. The proposed methodology, which uses only easily measured functions, is considerably less time- and labor-intensive than direct measurement of the viscoelastic bulk modulus. Here we investigate this hypothesis and compare the calculated viscoelastic bulk responses for several materials to existing data in the literature. [Preview Abstract] |
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S1.00246: Tg Depression and Reactivity of Nanoconfined Monocyanate Ester and its Trimer Yung P. Koh, Sindee Simon The effects of nanoconfinement on the reaction kinetics and the Tg depression of a monocyanate ester and the resulting cyanurate trimer are studied using differential scanning calorimetry (DSC). The monocyanate ester is imbibed in the nanopores of controlled pore glass. The reaction rate is found to increase with decreasing nanopore size without a change in reaction mechanism based on both dynamic heating scans and isothermal reaction studies. Both the monocyanate ester reactant and cyanurate trimer product show reduced Tgs compared to the bulk; the Tg depression increases with conversion and is more pronounced for the fully reacted product, suggesting that molecular stiffness influences the magnitude of nanoconfinement effects. Confinement of the cyanurate trimer synthesized in the bulk and then imbibed in the nanopores indicates that the Tg depression is not due to a change in chemical structure. The results of imbibement studies will also be discussed. [Preview Abstract] |
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S1.00247: Photoconductivity of nanowires that are self-assembled from chiral porphyrins J.G. Menko, W.F. Smith, Y. Lu, A.T. Johnson, P. Iavicoli Recently synthesized chiral porphyrin molecules\footnote{M. Linares, P. Iavicoli, K. Psychogyiopoulou, D. Beljonne, S. De Feyter, D. B. Amabilino, and R. Lazzaroni, Langmuir \textbf{2008}, $24$, 9566-9574.} in a methlocyclohexane solvent self-assemble into aggregates which appear as a network of nanoscale filaments when deposited onto oxidized silicon. We have shown in preliminary experiments conducted in air that the aggregates are photoconductive, with an action spectrum (photoconductivity vs. wavelength) that matches the in-solution absorbance curve. We discuss these results, and also experiments conducted in a dry nitrogen environment. [Preview Abstract] |
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S1.00248: Using the Second Law to Develop Non-equilibrium Thermodynamics and Absence of Entropy Loss in a Phase Space Confinement Puru Gujrati We start from the second law of thermodynamics applied to an isolated system consisting of the system surrounded by an extremely large medium, and formulate a general non-equilibrium thermodynamic description of the system when it is out of thermal and mechanical equilibrium with the medium. Our approach allows us to identify the correct form of the non-equilibrium entropy, Gibbs free energy and enthalpy of the system under all conditions including possible ergodicity braking due to phase space confinement. We find that there is never any loss of entropy. We also obtain an extension of the classical non-equilibrium thermodynamics due to de Donder in which one normally assumes thermal and mechanical equilibrium with the medium. We find that the temperature and pressure differences between the system and the medium act as thermodynamic forces, which are normally neglected in the classical non-equilibrium thermodynamics. These forces play an important role in relaxation processes in addition to other internal order parameters. We apply our approach to study the general trend during structural relaxation in glasses and establish the phenomenology behind the concept of the fictive temperature on firmer theoretical foundation. [Preview Abstract] |
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S1.00249: The Influence of Interference on the Kondo Effect Justin Malecki, Ian Affleck Semi-conductor quantum dots with an odd number of electrons are known to exhibit the Kondo effect when embedded between two leads. We study how the Kondo effect is influenced by the presence of an additional transport path between the two leads, allowing for the possibility of electron interference. It is shown that Kondo screening of the quantum dot still occurs but at a reduced Kondo temperature that is independent of a magnetic flux between the two tunneling pathes. We describe the various phases of the system and have determined the low-energy effective model which does exhibit flux dependence. All results are supported by data from the numerical renormalization group (NRG). [Preview Abstract] |
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S1.00250: Dark current non-linearities in CCD imagers Justin Dunlap, Erik Bodegom, Morley Blouke, Ralf Widenhorn It is generally assumed that the dark count due to thermally excited electrons increases linearly with exposure time. We studied two scientific Charge-Coupled device (CCD) imagers and found that a significant number of pixels have non-linear dark current behavior. Furthermore, we found that non-linear pixels fall into specific categories. In a related experiment we also observed that the dark current response varied as we exposed the imagers to different levels of light. The characterization of the dark current response of a pixel can give additional information about the impurity that is responsible for the increased dark count. This information cannot be obtained by the typical methods of varying the temperature of the chip and analyzing the dark current response. Complications arise for pixels with non-linear dark current, as linear behavior is often assumed in dark current correction. [Preview Abstract] |
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S1.00251: Strong diamagentism in Cuprate Kai-Yu Yang Strong diamagnetism signal in pseudogap state has been reported recently in toque magnetometry experiment. A boson-fermion model is established based on the anisotropy of the state in $\mathbf{k}$-space, i.e. cooperons on antinodes and holes on nodes, to study this phenomenon. An algorithm of continuous time diagrammatic determinant quantum monte carlo is developed to simulate this model. The renormalization of the cooperon's band gives arise to large diamagnetism in agreement with experiments. [Preview Abstract] |
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S1.00252: ABSTRACT WITHDRAWN |
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S1.00253: Path integral approach to random motion with nonlinear friction Adrian Baule Using a path integral approach, we derive an analytical solution of a nonlinear and singular Langevin equation, which has been introduced previously by P.-G. de Gennes as a simple phenomenological model for the \textit{stick-slip} motion of a solid object on a vibrating horizontal surface. We show that the optimal (or most probable) paths of this model can be divided into two classes of paths, which correspond physically to a sliding or slip motion, where the object moves with a non-zero velocity over the underlying surface, and a stick-slip motion, where the object is stuck to the surface for a finite time. These two kinds of basic motions underlie the behavior of many more complicated systems with solid/solid friction and appear naturally in de Gennes' model in the path-integral framework. [Preview Abstract] |
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S1.00254: Study of Casimir Effect in Nanosystems Samina Masood The Casimir effect is a cause of Casimir force for nano-systems. We explicitly show that the Casimir force depends on the physical properties of nano-systems like temperature and chemical potential. The possible applications of Casimir force on nanosystem is also discussed. [Preview Abstract] |
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S1.00255: Nonlinear and nonlocal effects on dispersion relation for surface plasmon at a metal/Kerr medium interface Railing Chang, Jung-Hao Huang, Pui-Tak Leung We present an analytical calculation for the dispersion relation of SP at a metal/Kerr medium interface where the metal is treated by local (Drude) as well as nonlocal (hydrodynamic) models for comparison. In the local model the dispersion relation exhibits prominent change as the field intensity increases, with SP frequency for large wave number shifted negatively (positively) for positive (negative) Kerr coefficient (KC). As the intensity increases to certain critical value, the negative KC results in the disappearance of SP mode. In the nonlocal model, all the nonlinear phenomena observed continue to exist but are significantly weakened, indicating that nonlinearity and nonlocality are two mutually counteracting effects. [Preview Abstract] |
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S1.00256: Progress Report on Closing the Quantum Metrological Triangle Mikko Paalanen, O. Hahtela, A. Kemppinen, V. Maisi, A. Manninen, A. Satrapinski, J. Hassel, P. Helisto, H. Seppa, P. Hakonen, S. Kafanov, M. Mottonen, J. Pekola, D. Averin, Y. Pashkin, J. Tsai Quantum Metrological Triangle is made out of three components: Josephson voltage standard, Quantum Hall resistance standard and an accurate current pump. Closing the Triangle consists of applying Ohm's law with great accuracy on the three devices, which are based on fundamental physical phenomena and quantities, such as Planck's constant and electron charge. The first two devices are already accepted international metrological standards. We will report on our recent progress in developing an accurate current pump, based on a hybrid single electron transistor, and compare it with other current pumps. We will also report on new ideas in developing the low noise current amplifier, needed for testing the Ohm's law, and describe our overall plans for closing the Triangle along with the expected uncertainties. [Preview Abstract] |
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S1.00257: A first-order phase transition at the random close packing of hard spheres Hernan Makse, Yuliang Jin Randomly packing spheres of equal size into a container consistently results in a static configuration with a density of $\sim$64\%. The ubiquity of random close packing (RCP) rather than the optimal crystalline array at 74\% begs the question of the physical law behind this empirically deduced state. Indeed, there is no signature of any macroscopic quantity with a discontinuity associated with the observed packing limit. Here we show that RCP can be viewed as a manifestation of a thermodynamic singularity, which defines it as the ``freezing point'' in a first-order phase transition between ordered and disordered packing phases. Despite the athermal nature of granular matter, we show the thermodynamic character of the transition in that it is accompanied by sharp discontinuities in volume and entropy at a critical compactivity, which is the intensive variable that plays the role of temperature in granular matter. Our results predict the experimental conditions necessary for the formation of a jammed crystal by calculating the analogue of the `entropy of fusion'. This approach is useful since it maps out-of-equilibrium problems in complex systems onto simpler established frameworks in statistical mechanics. [Preview Abstract] |
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S1.00258: Self-Assembly of 3D Non--Close-Packed Colloidal Structures Vyom Sharma, Deying Xia, Craig Carter, Yet-Ming Chiang The ability to direct the position of colloidal particles in a 3-dimensional structure has led to the formation of non--close-packed structures which exhibit complete photonic-band gap. Currently, researchers use templates to make these structures and position colloidal particles one-by-one. Here, we show that by manipulating the electrical potential and concentration within a binary system of colloidal particles, it is possible to create a non--close-packed layer of binary particles through self-assembly. On repeating the above steps, we show that a second layer was obtained on top of the first layer. Finally, by burning off one kind of particle-type in the end, we obtain the first two layers of a diamond cubic unit cell. Our method relies on controlling the electrical potential of the system and the concentration of particles only. As a result, we show that by using different kinds of templates, structures with different symmetries can be obtained. To our knowledge this is the first demonstration of colloidal self-assembly to obtain non--close-packed structures 3D structures. [Preview Abstract] |
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S1.00259: Barrier evolution of magnetic tunnel junction by annealing and under biased condition Yuzi Liu, Amanda K. Petford-Long Energy-filtered transmission electron microscopy (EFTEM) and in-situ electron holography were applied to study changes to the tunnel barrier behavior of CoFe/MgO$_{x}$/CoFe magnetic tunnel junctions (MTJs) as a function of annealing and applied electrical bias. During annealing oxygen moved to the MgO$_{x}$ to form a more stoichiometric and homogenous crystalline tunnel barrier, and Co diffused into the barrier. There is no significant change in Fe distribution. Annealing also results in a reduction of the barrier height. The effect of varying the bias voltage from -1.5 V--1.5 V is to change barrier asymmetry and to decrease the effective barrier width. These changes are a result of charge accumulation at the interface. Argonne National Laboratory is operated under Contract No. DE-AC02-06CH11357 by U.S. DOE. The electron microscopy was accomplished in the Argonne National Laboratory Electron Microscopy Center for Materials Research. [Preview Abstract] |
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S1.00260: Is it really a small world - network connectivity revisited Baruch Barzel, Ofer Biham Networks are useful for describing systems of interacting objects, the applications include chemical and metabolic systems, food webs as well as social networks. Lately, it was found that many of these networks display some common topological features, such as high clustering, small average path length and a power-law degree distribution. These topological features are commonly related to the network's functionality. However, the topology alone does not account for the nature of the interactions in the network and their strength. In this talk we will introduce a method for evaluating the correlations between pairs of nodes in the network. These correlations depend both on the topology and on the functionality of the network. A network with high connectivity displays strong correlations between its interacting nodes and thus features small-world functionality. The method can be used to obtain the correlation matrix or to evaluate the correlation function of the network. Certain networks display a typical correlation length. The connectivity of a network is then defined as the ratio between this correlation length and the average path length of the network. Using this method one can distinguish between a topological small world and a functional small world, where the latter is characterized by long range correlations and high connectivity. Clearly, networks which share the same topology, may have different connectivities, based on the nature and strength of their interactions. [Preview Abstract] |
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S1.00261: Experimental Phase Diagram of the $\nu=1/2$ Bilayer Electron System Koji Muraki Experimental phase diagram of the bilayer electron system at total filling $\nu=1/2$ is investigated through magnetotransport measurements on a series of double-quantum- well samples with different tunneling gap $\Delta_{\rm{SAS}}$ and tunable densities. A $\nu=1/2$ fractional quantum Hall (QH) effect is observed over a wide, and previously unexplored, region of the phase diagram described by the interlayer tunneling and layer distance. The $\nu=1/2$ QH liquid phase in our double quantum wells is connected to the region where the $\nu=1/2$ QH effect is reported for wide single quantum wells and is bounded by a compressible composite-Fermion liquid phase at lower densities and by an insulating phase at higher densities. Furthermore, we find a striking impact of the interlayer tunneling on the competition between the QH liquid and the insulating phases; the QH phase is taken over by the insulating phase in the limit of small tunneling, suggesting a crucial role of tunneling on the stability of a bilayer Wigner crystal. [Preview Abstract] |
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S1.00262: Band structure calculations of Mo$_{2}$BC under pressure R. Falconi, F. Alvarez, R. Escamilla, R. Escudero Mo$_{2}$B is a superconductor with a Tc of about 5.8 K and a body centered tetragonal cristalline structure. When carbon is added to the structure it is formed the intermetallic Mo$_{2}$BC compound, which is a superconductor with a Tc of about 7 K and has a crystalline face centered orthorhombic structure. In this work we make ab initio calculations of the electronics bands for Mo$_{2}$BC at several pressures up to 5 GPa in order to explain why chemical pressure, generated by decreasing the carbon concentration, decreases T$_{C}$ in a non linear rate. The density of state at the Fermi level is reduced in a non monotonic way suggesting some correlation. We complement the study with high pressure electrical resistivity measurements up to 4.8 GPa which reveal a decreasing of Tc at the rate dT$_{C}$/dP = - 0.03 K/GPa. [Preview Abstract] |
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S1.00263: First principles analysis of Hedvall's magnetocatalytic effect in subnanometre base metal clusters Daniel Torres, Jeffrey Greeley Magnetic order is destroyed in a ferromagnetic material warmed above its Curie temperature. This loss of order leads to a number of old-known phenomena, such as the Hedvall's magnetocatalytic effect: an abrupt change in the rate of a chemical reaction on a magnetic surface at the Curie point. Here, we present a relationship between catalytic activity and magnetic properties of the catalyst. Using the methanation reaction as the example, we suggest that the magnetic transition of small base metals clusters significantly affects catalytic activity. These results provide an unambiguous case of Hedvall's magnetocatalytic effect produced by soft ferromagnets. [Preview Abstract] |
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S1.00264: Nucleation and Freezing of Colloidal Microgel Monolayer Ziren Wang, Ahmed Alsayed, Arjun Yodh, Yilong Han We studied the crystallization of two-dimensional colloidal crystals composed of diameter tunable microgel spheres. The critical nucleation size, surface and line tensions were measured, and four empirical 2D criteria for freezing were experimentally tested. These freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystals. At the freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing. [Preview Abstract] |
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S1.00265: Block copolymer structures in nano-pores Marco Pinna, Xiaohu Guo, Andrei Zvelindovsky We present results of coarse-grained computer modelling of block copolymer systems in cylindrical and spherical nanopores on Cell Dynamics Simulation. We study both cylindrical and spherical pores and systematically investigate structures formed by lamellar, cylinders and spherical block copolymer systems for various pore radii and affinity of block copolymer blocks to the pore walls. The obtained structures include: standing lamellae and cylinders, ``onions,'' cylinder ``knitting balls,'' ``golf-ball,'' layered spherical, ``virus''-like and mixed morphologies with T-junctions and U-type defects [1]. Kinetics of the structure formation and the differences with planar films are discussed. Our simulations suggest that novel porous nano-containers can be formed by confining block copolymers in pores of different geometries [1,2]. \\[4pt] [1] M. Pinna, X. Guo, A.V. Zvelindovsky, Polymer 49, 2797 (2008).\\[0pt] [2] M. Pinna, X. Guo, A.V. Zvelindovsky, J. Chem. Phys. 131, 214902 (2009). [Preview Abstract] |
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S1.00266: Soliton self-frequency shift in non-uniform fiber tapers: analytical description through an improved moment method Zhigang Chen, Antoinette Taylor, Anatoly Efimov We develop an improved moment method derived from the generalized nonlinear Schr\"{o}dinger equation to model soliton propagation in optical fibers. We account for the full Raman gain spectrum of the material and derive a system of coupled differential equations describing the evolution of the five moments of the optical pulse, valid for arbitrary soliton durations. We further simplify the equations by casting them into a moving frequency frame that follows the central frequency of the Raman-shifting soliton. We show that for short solitons there exists a non-negligible Raman-induced chirp, which contributes to slowing down the soliton self-frequency shift. By comparing with the numerical solution of the generalized nonlinear Schr\"{o}dinger equation, the improved moment method is shown to accurately represent soliton self-frequency shift under higher order dispersion, self-steepening and pulse chirp. Numerical examples are presented for a dispersion-shifted fused silica fiber and a ZBLAN non-uniform fiber taper. The latter demonstrates enhanced soliton self-frequency shift through axial dispersion and nonlinearity engineering along the taper length. [Preview Abstract] |
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S1.00267: Scaling study of Kondo effect in a quantum dot embedded in an Aharonov-Bohm interferometer Ryosuke Yoshii, Mikio Eto The Kondo effect is theoretically investigated in a quantum dot embedded in an Aharonov-Bohm (AB) ring, using the ``poor man's'' scaling method. First, we construct an equivalent model in which a quantum dot is coupled to a single lead. The AB interference effect is involved in the magnetic-flux dependence of the density of states in the lead. The scaling analysis of this model yields analytical expressions for the Kondo temperature $T_{\rm K}$ and logarithmic corrections to the conductance at temperatures $T \gg T_{\rm K}$.\footnote{R.\ Yoshii and M.\ Eto, J.\ Phys.\ Soc.\ Jpn.\ {\bf 77}, 123714 (2008).} We find that (i) $T_{\rm K}$ is significantly modulated by the magnetic flux penetrating the ring when the ring size $L$ is much smaller than the size of Kondo cloud, $L_{\rm K}=\hbar v_{\rm F}/T_{\rm K}$, with $v_{\rm F}$ being the Fermi velocity. $T_{\rm K}$ is hardly affected by the flux when $L \gg L_{\rm K} $. (ii) When $L \ll L_{\rm K}$, the flux dependence of $T_{\rm K}$ is the smallest around the center of Coulomb valley and becomes remarkable near the edges of the valley.\footnote{R.\ Yoshii and M.\ Eto, Physica E, in press.} [Preview Abstract] |
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S1.00268: Superfocusing the light through the nanosize slit via photonic tornado Seong Soo Choi, Vinaya Jha, Om Suwal, Myoung Jin Park, Nam Kyu Park, DaiSik Kim The macro size pyramidal horn probe such as klystron horn antenna has been used to provide the excellent focusing capabilities in microwave region. In the similar way, the pyramidal probe with the micron size mirror (pyramidal horn probe) has been fabricated with a nano-size aperture with diameter ranging from $\sim $1 nm to $\sim $30 nm. Light transmission through the micro-fabricated pyramidal horn probe has been measured to enhance the light transmission due to resonant effects between the cavity mode and the slit modes in the probe, along with improved directionality of the transmitted beam. The resonant tunneling between two standing waves in the input groove and in the output groove can provide the transmission enhancements. With decreasing slit width, the transmission is found to increasing tremendously.[1] The transmission is measured to be inversely proportional to the area.[2,3] References:[1] R. Gordon, Phys. Rev. B 73, 153405 (2006).[2] R. Harrington, IEEE Trans. Antennas Propagat. Ap-30, 205(1982).[3] Y Leviatan, R. Harrington, J. Maut, IEEE Trans. Antennas Propagat. Ap-30, 1533(1982) [Preview Abstract] |
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S1.00269: Humidity dependence of optical property of a DNA fiber: first-principles and molecular dynamics studies Takenori Yamamoto, Tsuyoshi Uda, Takahisa Ohno We present first-principles and molecular dynamics studies for humidity dependence of optical property of a deoxyribonucleic acid (DNA) double helix fiber. The first-principles electronic structure and the molecular dynamics simulations reveal that the electronic structure of the DNA fiber is varied by the hydration amount or the relative humidity. We show that the ultraviolet optical conductivity is influenced by the hydration structure and the DNA deformation, and that our findings agree with other theoretical results and experimental observations. The infrared (IR) optical conductivity is calculated by the molecular dynamics approach. The humidity dependence of the optical conductivity due to the dipole relaxation of water is in close agreement with experimental observations. The IR absorption spectrum due to DNA vibrations agrees with the experimental spectrum in feature. [Preview Abstract] |
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S1.00270: Droplet Detachment in Confined Gaseous Microchannel Flows Brian Carroll, Carlos Hidrovo Multiphase flows are ubiquitous in microfluidic applications for lab-on-a-chip and micro total analysis systems, particularly those with micromixing capabilities. Significant advancement has been achieved recently for both active and passive micromixers. Increasing the Reynolds number prior to mixing, however, remains relatively unchartered due to the large fluid viscosities typically involved. By using a gaseous flow to detach and transport liquid droplets, Reynolds numbers in excess of 100 can be achieved. This allows droplet interaction and mixing to take place under highly inertial conditions with potentially increased mixing rates. Since droplet detachment and entrainment is a prerequisite for droplet mixing, an experimental investigation is performed and presented for liquid droplet detachment in confined microchannel gas flows. Gas flow rate and channel aspect ratios were varied to determine influence on detached droplet characteristics. Preliminary results indicate that two distinct force balance regions exist and are delineated according to Reynolds number. Increasing the Reynolds number increases the droplet aspect ratio, yielding longer slug-like droplets that may oppose favorable mixing conditions. [Preview Abstract] |
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S1.00271: Optical orientation due to phonon-assisted indirect transitions in Silicon Pengke Li, Hanan Dery We study the circular polarization of the photoluminescence due to phonon-assisted indirect optical transitions in Silicon. The band structure is calculated by empirical pseudopotential method with the spin-orbit interaction. Phonon modes are obtained by the adiabatic bond charge model and the $\Delta$ - $\Gamma$ electron-phonon matrix elements are calculated within the rigid-ion approximation. We quantify the circular polarization of various phonon-assisted optical transitions and we show that the circularity of the dominant transverse phonon peaks is due to electrons from valleys perpendicular to light propagation. [Preview Abstract] |
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S1.00272: Permeability Characterization of Capillary Flow through Vertically Aligned Pillars Conan Zhang, Carlos Hidrovo Darcy's law is a constitutive equation that relies on an empirical value, the permeability ($\kappa )$, to correlate the flow rate with the pressure gradient within the porous structures. The permeability is primarily dependent on the microstructural details such as the tortuosity and porosity, which are statistical in nature. With the advent of micromanufacturing techniques, it is now possible to create porous structures with regular and well defined features. This opens the possibility of creating structures that have been optimized for capillary performance. In this research, an analytical model was developed to simulate capillary flow through an array of vertically aligned pillars. The analysis is based on a quasi-steady state balance between viscous and capillary forces on a substrate consisting of alternating micropillar and flat surface regions. The model is used to predict the capillary limit of micropillar arrays under thermal loads for heat pipe applications and validated against experimental data of silicon samples in an open loop setup. It is shown that the optimal pillar spacing is directly related to its aspect ratio. [Preview Abstract] |
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S1.00273: Direct observation of magnetic monopole defects in an artificial spin-ice system Sam Ladak, Dan Read, Garry Perkins, Will Branford, Lesley Cohen Frustration is the inability to satisfy the bonding requirements of all pairs in a system. Spin-ice materials have proven to be a model system to study frustration, and more recently they have been shown both theoretically and experimentally to be home to exotic excitations, whereby the atomic magnetic moments fractionalize into monopoles. Two-dimensional Kagome and square lattice systems have been shown to capture the physics of frustration and reproduce the ice-rules. In this study we have carried out magnetic force microscopy (MFM) at remanence in order to understand the magnetic reversal of an artificial kagome ice structure. We find that during the switching process ice-rule violating defects which carry magnetic charge are created and hop through the lattice with further increments to the magnetic field. These defects are the two-dimensional equivalent of magnetic monopoles in bulk spin-ice and hence are defined as monopole defects. The dynamics of the monopole defects through the artificial spin ice system will be discussed. High resolution MFM imaging at vertices and OOMMF simulations allow the micro-magnetic configuration of a monopole defect to be resolved. [Preview Abstract] |
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S1.00274: Sample Collection for the National Ignition Facility Sarah Nelson, Dawn Shaughnessy, Ken Moody, Lee Bernstein, Darren Bleuel, Richard Fortner, Dieter Schneider, Wolfgang Stoeffl, Mark Stoyer, Gary Grim, Robert Rundberg, Uwe Greife The National Ignition Facility (NIF) is slated to come online in 2010. A variety of experiments are planned for the facility, and diagnostic techniques such as gas- and solid-phase capsule debris analysis may prove to be successful methods for establishing the success or failure of ignition experiments at NIF. Samples in the gas phase offer the most direct method of collection by simply pumping out the large target chamber following a NIF shot. The target capsules will be prepared with dopants which will produce radioactive noble gas isotopes upon activation with neutrons. We have designed the Radchem Apparatus for Gas Sampling (RAGS) in order to collect post-shot gaseous samples for NIF capsule diagnostics. We will present preliminary results of the gas collection (or separation) efficiency, as well as a construction update. The ability to collect solid debris following a NIF capsule shot will also be required. We are currently developing a solid debris collection capability, and various design ideas will be presented. In addition, experimental results will be discussed. LLNL-ABS-413318. [Preview Abstract] |
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S1.00275: Improvement of the polymer composite:ZnO-nanocolumn solar cell performance through surface modification Fang-Chi Hsu, Chiang-Ting Chen, Shang-Wei Kuan, Wei-Fang Su, Yang-Fang Chen Incorporating ordered inorganic nanostructures into polymer matrix has been considered as one of the methods to improve the charge collection efficiency of the photogenerated carriers. However, the surface states of the inorganic nanostructure could serve as the charge trapping center for free carriers. We use a conductive ligand, amine terminated 3-hexylthiophene (oligomer 3HT-NH$_{2})$, to modify the surface of ZnO-nanocolumn embedded in poly(3-hexylthiophene)/(6,6)-phenyl C$_{61}$ butyric acid methyl ester (P3HT/PCBM) composite. We found that the addition of oligomer 3HT-HH$_{2}$ ligand layer between the polymer composite and the ZnO-nanocolumn structures improves the short circuit current ($J_{SC})$ and open circuit voltage ($V_{OC})$ of the devices resulting in a 25{\%} increment in the power conversion efficiency before device optimization. [Preview Abstract] |
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S1.00276: Polarization dependent X-ray absorption and resonant inelastic X-ray scattering studies at Cu K-edge in quasi-one-dimensional cuprate LiCu$_{2}$O$_{2}$ single crystals Ku-Ding Tsuei, Cheng-Mau Cheng, Chia-Wei Hu, Kuo Wei Yeh, Mau-Kuen Wu We have carried out a polarization dependent X-ray absorption (XAS) and the resonant inelastic X-ray scattering (RIXS) experiments on LiCu2O2 single crystals near the Cu K-edge. The XAS measurement reveals absorption peaks associated with Cu+ and Cu2+ 4$p$ unoccupied states respectively. A pre-edge peak can be assigned to quadrupole transition at the Cu2+ site. In the RXIS measurement, the incident energy dependent spectra disclose three energy loss peaks at 3.6 eV, 6.1 eV and 4.9 eV. The energy loss of 3.6 eV and 6.1 eV are the charge transfer states from O 2$p $nonbonding and bonding states to the Cu2+ 3$d $states and resonate at two incident energies. The third peak at 4.9 eV can be associated with Cu+ 4\textit{px,y}; we argue that this feature is generated by the Cu+ 3$d $state coupled with Cu2+ 3$d $state through the shared O 2$p $bonding. In addition, the 3.6 eV and 6.1 eV energy loss peaks are nearly dispersionless in momentum dependent spectra. [Preview Abstract] |
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S1.00277: Signification of preparative continuous system for precision particle size fractionation and investigation of the principles for its realization Jun-ichi Kawahara, Yoichiro Ito To begin with, signification of preparative continuous system for precision particle size fractionation is to be discussed from fundamental points of view. Next, typical system presently envisioned for continuous particle size fractionation is to be analytically evaluated. Although it would be a right strategy to set separation direction perpendicular to the flow of carrier medium (namely, liquid), it seems to have some fundamental problems. First, gravity is too weak as a separation force for submicron or smaller particles. Second, high resolution would never be obtained due to its structural reasons. Third, during the continuation of the separation process, it would be difficult to keep the linear velocity of the carrier medium in the separation channel unchanged due to the deposition of larger particles, since the separation channel is quite narrow in the separation direction. Then, the principles to realize the continuous precision size fractionation for submicron and smaller particles by solving these problems are to be discussed. [Preview Abstract] |
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S1.00278: Market mechanism based on the endogenous changing of game types such as Minority-Majority games Sanghyun Ahn, Gyuchang Lim, Sooyong Kim, Kyungsik Kim In many social and biological systems agents simultaneously and adaptively compete for limited resources, thereby altering their environment. We propose a evolution function extending Minority-Majority Games that captures the competition between agents to make money. The dynamics changes the ratio of two types of boundedly rational traders, fundamentalists and chartists with the payoff function endogenously. In the previous game theories, the best strategies are not always targeting the minority but are shifting opportunistically between the minority and the majority. And using a mixture of local bifurcation theory and numerical methods, there are possible bifurcation routes to complicated asset price dynamics, chaotic attractors. Hereby we improve the thinking logic of the atoms for attaching the dynamics to the market. This working shows that removing unrealistic features of the game theories leads to models which reproduce a behavior close to what is observed in real markets. [Preview Abstract] |
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S1.00279: Study of the Magnetic Phase Transition in Hubbard Model on the Triangular Lattice at 1/3 Electron Density Shan Dai, Richard Scalettar The recent discovery of sodium cobaltate (Na$_{x}$CoO$_{2}$) has caught strong scientific interest. To gain qualitative understanding of its properties, we study the transition between the magnetic and paramagnetic phases in the triangular lattice Hubbard model at 1/3 filling, using mean field theory. At this density, the electrons can avoid magnetic frustration through localization on a honeycomb sublattice. That is, charge ordering might arise through minimizing the magnetic exchange energy J=4$t^{2}$/U (at the expense of a higher kinetic energy t). We find that such charge ordering does indeed occur at sufficiently low temperature T, and that, within the magnetic phase, the spin order parameter increases with a critical exponent beta=1/2 near T$_{c}$. In contrast, the the charge order parameter increases linearly with T$_{c}$-T. In the ground state, the system is always in the paramagnetic phase when U/t $<$ 4.5. [Preview Abstract] |
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S1.00280: Diabolical point and conical diffraction in periodic plasmonic nanostructures Sung Hyun Nam, Antoinette Taylor, Anatoly Efimov We present formation of a singular (diabolical) point in k-space of a periodic metal-dielectric waveguide array. The singularity originates from the balance in the alternating normal and anomalous coupling. We numerically demonstrate a strong diffraction anomaly (conical-like diffraction) near the singular point. We also show the evolution of the diffraction pattern with band deformation. The peculiar propagation dynamics of surface plasmon polaritons could provide a new toolset for manipulating light on the nano-scale. [Preview Abstract] |
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S1.00281: Jamming transition in plowed granular media Nick Gravish, Paul Umbanhowar, Daniel I. Goldman We demonstrate in a three-dimensional laboratory plate drag experiment that a granular medium (250~$\mu$m glass beads) exhibits a bifurcation from fluid-like to jammed flow as the volume fraction ($\phi$) is increased above a critical value $\phi_c=0.603 \pm 0.0025$. We measure the force $F_d$ on a flat plate (3.8~cm width, 10.0~cm depth) dragged at constant velocity $v$ through the surface of a granular medium for $0.57<\phi<0.63$. For $\phi<\phi_c$, $F_d$ is independent of time and particle image velocimetry indicates that the flow of the granular media is uniform around the plate. For $\phi>\phi_c$, $F_d$ displays large periodic fluctuations which correspond to the formation of shear bands. Surface profile measurement of the post-drag net displaced volume $\Delta V$ of the granular material reveals that the medium compacts ($\Delta V<0$) in response to drag for $\phi<\phi_c$ and expands ($\Delta V>0$) for $\phi>\phi_c$. Thus the transition to jammed flow at $\phi_c$ is marked by the onset of dilation in granular media. [Preview Abstract] |
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S1.00282: Charge State Studeis at the University of Notre Dame Chris Schmitt, Jay LaVerne, Daniel Robertson, Matthew Bowers, Wenting Lu, Philippe Collon Equilibrium charge state distributions have been measured for 3 -- 7 MeV lithium, boron, and carbon ions passing through carbon foils. The data are compared to the predictions of several semi-empirical models of charge equilibrium in the $\le $ 1MeV/u regime. The current work underscores the general problem of extrapolating models developed for high-Z projectiles to ions of low-Z. A compilation of experimental data for low-Z ions in the low energy regime has been used to re-parameterize a few of the charge equilibrium models for carbon foils. Experimental techniques, comments and suggestions on the nature of the equilibrium charge states of low-Z ions are presented. [Preview Abstract] |
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S1.00283: Efficient spin filter utilizing antidot potential in semiconductor heterostructures Tomohiro Yokoyama, Mikio Eto We propose a highly efficient spin filter using artificial potential created by an antidot gate-electrode, STM tip, etc., in semiconductor heterostructures in the presence of spin-orbit interaction. The strength of such a potential is electrically tunable and it can be attractive as well as repulsive. In our previous paper,\footnote{M.\ Eto and T.\ Yokoyama, J.\ Phys.\ Soc.\ Jpn.\ {\bf 78}, 073710 (2009).} we formulated the spin Hall effect due to the scattering by the potential in terms of phase shifts and showed that it is extremely enhanced by the resonant scattering when an attractive potential is properly tuned. In the present study, we examine three- and four-terminal devices including an artificial potential as a spin filter. We numerically evaluate the spin polarization of the output current when an unpolarized current is injected from a terminal. With an axially symmetric potential, we observe the spin polarization of more than 50\%.\footnote{T.\ Yokoyama and M.\ Eto, Phys.\ Rev.\ B {\bf 80}, 125311 (2009).} Although the polarization is smaller when the axial symmetry is broken, we find that realistic devices could work well as an efficient spin filter.\footnote{T.\ Yokoyama and M.\ Eto, Physica E, in press.} [Preview Abstract] |
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S1.00284: Computer Simulation of Hydrogen Storage Capacity in Hydrogen Storage Materials Masahiko Katagiri, Vasileios Tserolas, Shigeki Saito, Yasushi Takeuchi, Jun Nakamura, Hiroshi Ogawa Metal hydrides are the most promising materials for hydrogen storage, especially the lightweight metal alloy hydrides. Getting high hydrogen uptake is a part of the problem. The recent developments in the field of fuel cells and more particularly hydrogen storage under solid form have underlined the usefulness of the Pressure-Composition-Temperature (PCT) curves. For the calculation of PCT of RNi5 (R = La, Pr, Nd, and Sm), we consider a simple model on the basis of statistical mechanics. In addition, Molecular Dynamics (MD) simulations and grand canonical Monte Carlo (MC) simulations are performed to predict PCT curves. Molecular dynamics is a powerful tool in calculating free energy, including the fluctuation effects. However, the problem in MD is the accuracy. Then the grand canonical MC is also used to check the accuracy. We also demonstrate the first principle calculations on RNi5 and V-based materials with zero-point vibration effect. [Preview Abstract] |
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S1.00285: On conjectured local generalizations of anisotropic scale invariance and their implications Hans Werner Diehl, Sergei Rutkevich, Mykola Shpot The theory of generalized local scale invariance of strongly anisotropic scale invariant systems proposed some time ago by Henkel [Nucl.\ Phys.\ B \textbf{641}, 405 (2002)] is examined. The case of so-called type-I systems is considered. This was conjectured to be realized by systems at $m$-axial Lifshitz points; in support of this claim, scaling functions of two-point cumulants at the uniaxial Lifshitz point of the three-dimensional ANNNI model were predicted on the basis of this theory and found to be in excellent agreement with Monte Carlo results [Phys. Rev. Lett.\textbf{87}, 125702 (2001)]. The consequences of the conjectured invariance equations are investigated. It is shown that fewer solutions than anticipated by Henkel generally exist and contribute to the scaling functions if these equations are assumed to hold for all (positive and negative) values of the $d$-dimensional space (or space time) coordinates $(t,\mathbf{r})\in R \times R^{d-1}$. Renormalization-group improved perturbation theory in $4+m/2-\epsilon$ dimensions is used to determine the scaling functions of the order-parameter and energy-density two-point cumulants in momentum space to two-loop order. The results are incompatible with Henkel's predictions. [Preview Abstract] |
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S1.00286: The Structure and Gelation Mechanism of Tunable Guanosine-Based Supramolecular Hydrogels Z. Li, L. Buerkle, M. Orseno, K.A. Streletzky, S. Seifert, A.M. Jamieson, S.J. Rowan SLS experiments on 50/50 mixtures of Guanosine (\textbf{G}) and 2',3',5'-Tri-O-Acetylguanosine (\textbf{TAcG)} in aqueous 0.354 M KCl show a sudden increase in molecular weight between c of 0.1 and 0.2 wt{\%}, indicating the critical concentration (Cc) for self-association of \textbf{G/TAcG} quartets into columnar assemblies. Guinier plot of SLS data above Cc indicates a radius of gyration that decreases with c and unphysically small values of molecular weight, suggesting that SLS is probing internal structure of microgel particles. Polarized and depolarized DLS indicate translational and rotational diffusion of a bimodal distribution of particles. The fast DLS modes appear to originate from fibrillar agglomerates of \textbf{G/TAcG} columnar quartet assemblies, and the slow modes from microgel domains. SAXS probes structure of individual columnar \textbf{G/TAcG} quartet assemblies, and indicates that, above Cc it is described by c-independent rigid cylinder, whose dimensions are consistent with earlier SANS results. Collectively, the experiments suggest that sol and microgel phases coexist in solution below macroscopic gel point, and that sol phase contains individual columnar stacks of \textbf{G/TAcG} quartets and fibrillar aggregates formed via lateral aggregation of these columnar assemblies. With increasing c, DLS indicates progressive increase in the volume fraction of microgel domains, which ultimately leads to macroscopic gelation. [Preview Abstract] |
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S1.00287: A Method for Calculation of the Upper Limit of Mendeleev's Periodic Table Albert Khazan 40 years ago some scientists claimed that elements heaviest than No.110 are impossible. The technics got much progress in the last years: element 118 has already been registered. Now, the researchers of Joint Inst. for Nuclear Research (Dubna, Russia) claim that the Periodic Table will end with element 150. However they do not provide theoretical proofs to this claim, because the stability limits of electronic shells they calculated by means of Quantum Mechanics do not answer this question in exact. In contrast, I focused onto the contents of chemical compounds along the Table. The used method is as follows. First, it was found that, given any chemical compound, the contents of any element in it (per 1 gram-atom) is described by the equation of a equilateral hyperbola Y=K/X. Then the scaling coefficient was deduced for the hyperbolas, thus the atomic mass of the last (heaviest) element, 411.66, was found as the abscissa of the ultimate point of the arc drawn by the tops of the hyperbolas. With it, the number of the last element, 155, was found as a consequence. See: Khazan A. Upper Limit in Mendeleev's Periodic Table --- Element No.155. Svenska fysikarkivet, 2009. [Preview Abstract] |
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S1.00288: The Strong Coupling Limit of the Hubbard Model Li Liu, Hong Yao, Steve Kivelson We carry out a coordinated study of the two dimensional Hubbard model in the extreme strong-coupling limit, $\frac{U}{t}\to \infty $. The resulting problem has no parameters other than the mean electron concentration per site, n. As is well known, for n=1, the infinite U limit is singular, in that interactions of order$\frac{t^2}{U}$ must be included to resolve the $2^N$ fold degeneracy of the ground state found for infinite U. For any other value of n, however, the infinite U limit is well behaved, but incompletely understood. We have applied a combination of exact diaganolization and variational methods to explore the phase diagram of this paradigmatic model of strongly interacting electrons. [Preview Abstract] |
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S1.00289: High pressure structure and Thermal properties of Gallium and Indium Telluride compounds Matthew Jacobsen, Ravhi Kumar, Andrew Cornelius III-V compounds of In and Ga are promising materials for optoelectronic, thermoelectric and nuclear power engineering applications. Pressure induced structural changes have been reported previously for InTe, In$_{2}$Te$_{3}$, GaTe, and Ga$_ {2}$Te$_{3}$ at ambient temperature at lower pressure ranges. We have synthesized and investigated these compounds extensively under pressure up to a limit of 20 GPa and report the pressure induced structural sequences for the previously mentioned compounds and solid solutions of them. The transition pressure and bulk modulus are obtained for all compositions. Further we also present specific heat measurements carried out at ambient pressure to assist in the understanding of the electrical and structural properties. [Preview Abstract] |
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S1.00290: Optimization of microwave antenna design for millikelvin quantum coherence experiments Dili Wang The dilute Ising magnet LiHo$_{0.045}$Y$_{0.955}$F$_{4}$ forms clusters of isolated spins which can be excited into individually addressable states by applying a nonlinear ac magnetic field at resonant frequencies which depend on the cluster size. The dynamics and decoherence of these cluster states are determined, in part, by hyperfine interactions between the electronic and nuclear spins. These interactions create a ladder of states spaced at approximately 6 GHz, opening the possibility of using microwave pumping to probe the dynamics of this hyperfine splitting and the effects that it has on the larger cluster state. We have investigated a range of microwave antenna designs for optimizing this pumping mechanism, focusing on single-arm spiral geometries for both transmitter and receiver. The broadband transmission efficiency in near-field distances was studied, and it was found that the turn count of the spiral was the primary variable determining the efficiency, with the ratio between trace width and trace gap an important secondary factor. [Preview Abstract] |
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S1.00291: Geometrically frustrated pyrochlores $Bi_{2-y}Sr_yIr_2O_7$, a solid solution with non-large magnetic order Carlos Cosio Casta\~{n}eda, Gustavo Tavizon, Pablo de la Mora, Francisco Morales, Roberto Escudero The $Bi_{2-y}Sr_yIr_2O_7$ solid solutions were synthesized by solid state reaction and characterized by Rietveld analysis with x-ray powder diffraction data. DC magnetic susceptibilities of these compounds, which crystallize in $\alpha$-pyrochlore, were measured in a SQUID magnetometer with an applied magnetic field of 1 kOe. Magnetic analyses indicate that antiferromagnetic interactions between iridium moments are present but no magnetic transition was observed in the range of 2-300K. Unexpectedly, in the high-temperature region, the compounds display a linear temperature dependence that increases with the Sr contents, hence the magnetic susceptibilities are not Curie-Weiss-like magnets. This deviation from the simple Curie-Weiss law can be assigned to short-range order effects. For the $y=0$ compound, AC magnetic susceptibility was determined in a 10 Oe magnetic field with a frequency of 1 kHz. The temperature dependence of the real part of this susceptibility does not show a spin-freezing temperature. This behavior indicates the absence of a transition towards a long- range order or spin-glass-like state above 2 K. In conclusion, the remaining paramagnetic state, in spite of antiferromagnetic correlations, could be indicative of the presence of a spin liquid or a cooperative paramagnetic state. [Preview Abstract] |
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S1.00292: A Versatile Apertureless Near-field and Far-field Spectroscopic Microscope for Biological and Material Applications Derek Nowak, A.J. Lawrence, Erik S\'{a}nchez Traditional light microscopy suffers from the diffraction limit, which limits the spatial resolution to $\lambda $/2. Near-field optical microscopes allow for imaging at resolutions lower than the diffraction limit. Using a combination of a hybrid atomic force microscope and an inverted optical microscope, resolutions below 20 nm have been demonstrated. The imaging probes for the AFM are specially shaped metal tips that are illuminated with the excitation light. This technique has been named tip enhanced near-field optical microscopy (TENOM). We are developing a system that will allow the imaging of the fluorescence from almost any visible chromophore without changing filters or excitation wavelength for resolutions below 20 nm, using two-photon excitation. The microscope's ability to image samples at atmospheric pressure, room temperature, and in solution makes it a very promising tool for the biological and material science communities. A single computer, simple control circuits, FPGA data acquisition, and a simplified optical system control the microscope. This versatility will enable the end user to custom design experiments from con-focal far-field single molecule imaging to high resolution scanning probe microscopy imaging. [Preview Abstract] |
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S1.00293: Atomic Ytterbium Beam Experiments at an Undergraudate Physics Laboratory Rabin Paudel, Lucian Lupinski, Jonathan Barlow, Scott Pond, Martin Madsen We report on progress towards producing cold Ytterbium atoms in an undergraduate laboratory. We constructed a low-cost Zeeman slower designed to slow Yb atoms from 325 m/s to $\sim$ 1 cm/s on the $^{1}S_{0}$ to $^{1}P_{1}$ atomic transition, accessible by a direct-diode laser at 398.8 nm. We propose using the spectrally-resolved spontaneous emission from a long-lived decay channel ($\tau\sim$ 1$\mu$s) to measure the Yb beam velocity. [Preview Abstract] |
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S1.00294: Vorono{\"\i} cell sizes distribution of two-dimensional granular packings and parking lot model Kevin Hernandez Pardo, Leonardo Reyes In 1989, Edwards and Oakeshott proposed a statistical mechanics description for granular packings in mechanical equilibrium. In this approach, the volume of the bulk plays the role of the energy in thermal systems and an analogous of the temperature, called compactivity, arises. In 2007, Aste \emph{et al.} found a gamma distribution of Vorono{\"\i} cell-sizes in granular packings which seems independent of preparation and history of the system. The parking lot model (PLM) is an stochastic system in which particles are thrown over a line at random continuous positions. Particles can be adsorbed with a rate $p_+$ plus a volume exclusion principle, and particles in the line can be desorbed with a rate $p_-$. Other than desorption, particles cannot move within the line. It is known that after a transient the system fluctuates around a density which depends only on the parameter $K=p_+/p_-$. Nowak \emph{et al.} introduced this model in the context of granular materials in 1998. Tarjus and Viot studied the PLM in the context of the statistical mechanics proposed by Edwards. We have found that, for high densities, the distribution of Vorono{\"\i} cell lengths in the one-dimensional PLM is also a gamma distribution. In this work we compare the distribution of local Vorono{\"\i} cell sizes of molecular dynamics simulations of soft discs in two dimensions and Monte Carlo simulations of the two-dimensional PLM. [Preview Abstract] |
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S1.00295: TDDFT Simulation of Organic EL Materials for Optical Properties Yasunari Zempo Organic EL is expected to be a break-through for next-generation flat panel displays. There are lots of advantages from the point of production cost as a large scale display, because its device structure is quite simple. For the material development, it is quite important to analyze spectra in emission/absorption processes. It is of current interest for the emission efficiency to use not only fluorescent but also phosphorous processes. Time dependent density functional theory (TDDFT) has applied to study the optical responses of the conjugated polymers and complex molecules such as poly(9,9-dialkyl-fluorene) and Ir(PPY)$_{3}$. It provides us predictably emission spectra quite effectively. In our study, real-space and real-time calculation techniques are applied to describe the electronic states instead of conventional basis-expansion techniques. This method ensures more efficiently in relatively small number of spatial meshes to obtain results with reasonable accuracy. The development and performance of our code, taking spin-orbit interactions into account, will be also discussed. [Preview Abstract] |
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