Physics Commons^™

Direct Observation Of Molecular Cooperativity Near The Glass Transition, E. Vidal Russell, N. E. Israeloff

Nathan Israeloff

We describe direct observations of molecular cooperativity near the glass transition in poly-vinyl-acetate (PVAc), through nanometer-scale probing of dielectric fluctuations. Molecular clusters switched spontaneously between two to four distinct configurations, producing complex random-telegraph-signals (RTS). Analysis of the RTS and their power spectra shows that individual clusters exhibit both transient dynamical heterogeneity and non-exponential kinetics.

Correlated Hip Motions During Quiet Standing, R. K. Koleva, A. Widom, D. Garelick, Meredith Harris, Claire Gordy, Mia Jackson

Meredith Harris

Kinematic measurements of two simultaneous coordinates from postural sway during quiet standing were performed employing multiple ultrasonic transducers. The use of accurate acoustic devices was required for the detection of the small random noise displacements. The trajectory in the anteroposterior - mediolateral plane of human chest was measured and compared with the trajectory in anteroposterior direction from the upper and lower body. The latter was statistically analyzed and appeared to be strongly anti-correlated. The anticorrelations represent strong evidence for the dominance of hip strategy during an unperturbed one minute stance. That the hip strategy, normally observed for large amplitude motions, …

Dry Friction Due To Adsorbed Molecules, C. Daly, J. Zhang, J. Sokoloff

Christopher Daly

Using an adiabatic approximation method, which searches for Tomlinson model-like instabilities for a simple but still realistic model for two crystalline surfaces in the extremely light contact limit, with mobile molecules present at the interface, sliding relative to each other, we are able to account for the virtually universal occurrence of "dry friction." The model makes important predictions for the dependence of friction on the strength of the interaction of each surface with the mobile molecules.

Nanotopography Influences Adhesion, Spreading, And Self-Renewal Of Human Embryonic Stem Cells, Weiqiang Chen, Luis G. Villa-Diaz, Yubing Sun, Shinuo Weng, Jin Koo Kim, Raymond H. W. Lam, Lin Han, Rong Fan, Paul H. Krebsbach, Jianping Fu

Weiqiang Chen

Human embryonic stem cells (hESCs) have great potentials for future cell-based therapeutics. However, their mechanosensitivity to biophysical signals from the cellular microenvironment is not well characterized. Here we introduced an effective microfabrication strategy for accurate control and patterning of nanoroughness on glass surfaces. Our results demonstrated that nanotopography could provide a potent regulatory signal over different hESC behaviors, including cell morphology, adhesion, proliferation, clonal expansion, and self-renewal. Our results indicated that topological sensing of hESCs might include feedback regulation involving mechanosensory integrin-mediated cell matrix adhesion, myosin II, and E-cadherin. Our results also demonstrated that cellular responses to nanotopography were cell-type …

Measurement Of The Neutron F2 Structure Function Via Spectator Tagging With Clas, N. Baillie, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

We report on the first measurement of the F₂ structure function of the neutron from semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲ 100° MeV/c and their angles to ≳ 100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The Fⁿ₂ data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q² < 4.52 GeV², with uncertainties from nuclear corrections estimated to be less than …

Functional Magnetic Nanoparticles, James Gass

USF Tampa Graduate Theses and Dissertations

Nanoparticle system research and characterization is the focal point of this research and dissertation. In the research presented here, magnetite, cobalt, and ferrite nanoparticle systems have been explored in regard to their magnetocaloric effect (MCE) properties, as well as for use in polymer composites. Both areas of study have potential applications across a wide variety of interdisciplinary fields.

Magnetite nanoparticles have been successfully dispersed in a polymer. The surface chemistry of the magnetic nanoparticle proves critical to obtaining a homogenous and well separated high density dispersion in PMMA. Theoretical studies found in the literature have indicated that surface interface energy …

Mechanical Writing Of Ferroelectric Polarization, Haidong Lu, C.-W. Bark, D. Esque De Los Ojos, J. Alcala, Chang-Beom Eom, G. Catalan, Alexei Gruverman

Alexei Gruverman Publications

Ferroelectric materials are characterized by a permanent electric dipole that can be reversed through the application of an external voltage, but a strong intrinsic coupling between polarization and deformation also causes all ferroelectrics to be piezoelectric, leading to applications in sensors and high-displacement actuators. A less explored property is flexoelectricity, the coupling between polarization and a strain gradient. We demonstrate that the stress gradient generated by the tip of an atomic force microscope can mechanically switch the polarization in the nanoscale volume of a ferroelectric film. Pure mechanical force can therefore be used as a dynamic tool for polarization control …

Observations With The Most Sensitive Rayleigh-Scatter Lidar, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham

Leda Sox

The mesosphere is the most unexplored region of the atmosphere. Its altitude range of 50-85 km lies in between the reaches of data collecting instruments like weather balloons and satellites. For this reason, remote sensing systems, such as lidar, which are able to employ ground-based instruments to make extensive measurements in this difficult to detect region. The Rayleigh-scatter lidar at USU is currently being redeveloped to be the most powerful and sensitive of its kind. This type of lidar exploits light and particle interactions, like those that account for the blue color of the sky, to make relative density and …

Multi-State Analysis Of The Ocs Ultraviolet Absorption Including Vibrational Structure, Johan A. Schmidt, M. S. Johnson, George C. Mcbane, Reinhard Schinke

Peer Reviewed Articles

The first absorption band of OCS (carbonyl sulfide) is analyzed using potential energy surfaces and transition dipole moment functions of the lowest four singlet and the lowest four triplet states. Excitation of the 2¹A' state is predominant except at very low photon energies. It is shown that the vibrational structures in the center of the band are due to excitation of the 2³A" triplet state, whereas the structures at the very low energies are caused by bending excitation in the potential wells of states 2¹A' and 1¹A".

Electron Energy Dependent Charging Effects Of Multilayered Dielectric Materials, Gregory Wilson, Jr Dennison, Amberly Evans Jensen, Justin Dekany

Presentations

No abstract provided.

Observations With The Most Sensitive Rayleigh-Scatter Lidar, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham

Graduate Student Posters

The mesosphere is the most unexplored region of the atmosphere. Its altitude range of 50-85 km lies in between the reaches of data collecting instruments like weather balloons and satellites. For this reason, remote sensing systems, such as lidar, which are able to employ ground-based instruments to make extensive measurements in this difficult to detect region. The Rayleigh-scatter lidar at USU is currently being redeveloped to be the most powerful and sensitive of its kind. This type of lidar exploits light and particle interactions, like those that account for the blue color of the sky, to make relative density and …

Quantum Mutual Information Capacity For High-Dimensional Entangled States, P. Ben Dixon, Gregory A. Howland, James Schneeloch, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

High-dimensional Hilbert spaces used for quantum communication channels offer the possibility of large data transmission capabilities. We propose a method of characterizing the channel capacity of an entangled photonic state in high-dimensional position and momentum bases. We use this method to measure the channel capacity of a parametric down-conversion state by measuring in up to 576 dimensions per detector. We achieve a channel capacity over 7  bits/photon in either the position or momentum basis. Furthermore, we provide a correspondingly high-dimensional separability bound that suggests that the channel performance cannot be replicated classically.

The Discrete Yang-Fourier Transforms In Fractal Space, Yang Xiao-Jun

Xiao-Jun Yang

The Yang-Fourier transform (YFT) in fractal space is a generation of Fourier transform based on the local fractional calculus. The discrete Yang-Fourier transform (DYFT) is a specific kind of the approximation of discrete transform, used in Yang-Fourier transform in fractal space. This paper points out new standard forms of discrete Yang-Fourier transforms (DYFT) of fractal signals, and both properties and theorems are investigated in detail.

Magnetic Properties And Defects In Iron Implanted Strontium Titanate Single Crystals And Thin Films, Misha Chavarha

Electronic Thesis and Dissertation Repository

Physical vapor deposition was used to grow good quality crystalline stoichiometric SrTiO₃ thin films on Si(001) substrate using a systematic approach starting from understanding of kinetics and thermodynamics of the system and finishing with the development of procedure for high quality SrTiO₃/Si interface. Growth of optimized SrTiO₃ perovskite structure on Si requires careful transformation of a thin interfacial SrSix layer into the initial SrTiO₃ lattice cells. The critical aspects of the growth, such as low temperature and low oxidant partial pressure, are explained in details. Crystallinity and stoichiometry of SrTiO₃ were verified using powder …

Implementation And Testing Of The First Prompt Search For Gravitational Wave Transients With Electromagnetic Counterparts, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, Shaon Ghosh, Rodica Martin

Department of Physics and Astronomy Faculty Scholarship and Creative Works

Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify …

Using Radial Basis Functions To Interpolate Along Single-Null Characteristics, Maria Babiuc-Hamilton, Clyde E. Meador

Physics Faculty Research

The Cauchy-Characteristic Extraction (CCE) technique is the most precise method available for the computation of the gravitational waves obtained from numerical simulations of binary black hole mergers. This technique utilizes the characteristic evolution to extend the simulation to null infinity, where the waveform is computed in inertial coordinates. Although we recently made CCE publicly available to the numerical relativity community, there is still room for improvement, and the most important is enhancing the overall accuracy of the code, by upgrading the numerical methods used for interpolation and differentiation. One of the most promising ways is to use the Radial Basis …

Electron Momentum-Space Densities And Fermi Surface Of Li100-Xmgx (0 <~ X <~ 40) Alloys: Compton Scattering Experiment Versus Theory, G. Stutz, F. Wohlert, A. Kaprolat, W. Schulke, Y. Sakurai, Y. Tanaka, M. Ito, H. Kawata, N. Shiotani, S. Kaprzyk, A. Bansil

Arun Bansil

Directional Compton profiles (CP's) of Li₁₀₀₋ₓMgₓ(0≤x≤40) were measured for (11)12 directions of the momentum transfer q with (0.14) 0.16 a.u. (a.u. = atomic units: h = e = m = 1) momentum space resolution using synchrotron x rays, monochromatized to (31) 59 keV (values in brackets refer to x = 0). The total experimental valence electron CP's, their second derivatives, and the associated directional differences were compared with the corresponding Korringa-Kohn-Rostoker-coherent-potential-approximation-local-density-approximation (KKR-CPA-LDA) computations. Discrepancies between measurements and calculations are partly traced back to an inadequate treatment of electron correlation effects within the LDA framework. The three-dimensional (3D) valence-electron momentum density, …

Site-Selectivity Properties Of The Angle-Resolved Photoemission Matrix Element In Bi₂Sr₂Cacu₂O₈, S. Sahrakorpi, M. Lindroos, A. Bansil

Arun Bansil

We show that the angle-resolved photoemission (ARPES) spectra for emission from the bonding as well as the antibonding Fermi-surface sheet in Bi₂Sr₂CaCu₂O₈ possess remarkable site, selectivity properties, in that the emission for photon energies less than 25 eV is dominated by pd excitations from just the O sites in the CuO₂ planes. There is little contribution from Cu electrons to the ARPES intensity, even though the initial states at the Fermi energy contain an admixture of Cu-d and O-p electrons. We analyze the origin of this effect by considering the nature of the associated dipole matrix element in detail and …

A Novel Direct Method Of Fermi Surface Determination Using Constant Initial Energy Angle-Scanned Photoemission Spectroscopy, M. Lindroos, A. Bansil

Arun Bansil

We show that a constant initial energy, angle-scanned (CIE-AS) photoemission spectrum for emission from the Fermi energy (EF) contains Fermi surface (FS) signatures which originate from density of states type indirect transitions. Such previously unrecognized FS features in a CIE-AS spectrum would provide a robust and straightforward means of determining Fermi surfaces. Furthermore, the associated photointensity should yield a new window on k⊥, dispersion related issues in materials. Extensive simulations of CIE-AS spectra from low index faces of Cu are presented within the framework of the one-step photoemission model in order to delineate the nature of these new spectral features.

X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr

Arun Bansil

We present results for realistic modeling of the x-ray absorption near edge structure (XANES) of the overdoped high-Tc superconductor La₂₋ₓSrₓCuO₄ in the hole doping range x = 0.20 - 0.30. Our computations are based on a real-space Green's function approach in which strong-correlation effects are taken into account in terms of a doping-dependent self-energy. The predicted O K-edge XANES is found to be in good accord with the corresponding experimental results in this overdoped regime. We find that the low energy spectra are dominated by the contribution of O atoms in the cuprate planes, with little contribution from apical O …