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Full-Text Articles in Physics

Parity Violation In The N + 3he → 3h + P Reaction: Resonance Approach, Vladimir Gudkov Dec 2010

Parity Violation In The N + 3he → 3h + P Reaction: Resonance Approach, Vladimir Gudkov

Faculty Publications

The method based on microscopic theory of nuclear reactions has been applied for the analysis of parityviolatingeffects in few-body systems. Different parity-violating and parity-conserving asymmetries and theirdependence on neutron energy have been estimated for the n + 3He → 3H + p reaction. The estimated effectsare in a good agreement with available exact calculations.


Systematic Approach To Electrostatically Induced 2d Crystallization Of Nanoparticles At Liquid Interfaces, Sumit Kewalramani, Suntao Wang, Yuan Lin, Huong Giang Nguyen, Qian Wang, Masafumi Fukuto, Lin Yang Nov 2010

Systematic Approach To Electrostatically Induced 2d Crystallization Of Nanoparticles At Liquid Interfaces, Sumit Kewalramani, Suntao Wang, Yuan Lin, Huong Giang Nguyen, Qian Wang, Masafumi Fukuto, Lin Yang

Faculty Publications

We report an experimental demonstration of a strategy for inducing two-dimensional (2D)crystallization of charged nanoparticles on oppositely charged fluid interfaces. This strategy aims to maximize the interfacial adsorption of nanoparticles, and hence their lateral packing density, by utilizing a combination of weakly charged particles and a high surface charge density on the planar interface. In order to test this approach, we investigated the assembly of cowpea mosaic virus (CPMV) on positively charged lipid monolayers at the aqueous solution surface, by means of in situX-ray scattering measurements at the liquid–vapor interface. Theassembly was studied as a function of the solution …


Modeling-Free Bounds On Nonrenormalizable Isotropic Lorentz And Cpt Violation In Qed, Brett David Altschul Oct 2010

Modeling-Free Bounds On Nonrenormalizable Isotropic Lorentz And Cpt Violation In Qed, Brett David Altschul

Faculty Publications

The strongest bounds on some forms of Lorentz and CPT violation come from astrophysical data, and placing such bounds may require understanding and modeling distant sources of radiation. However, it is also desirable to have bounds that do not rely on these kinds of detailed models. Bounds that do not rely on any modeling of astrophysical objects may be derived both from laboratory experiments and certain kinds of astrophysical observations. The strongest such bounds on isotropic modifications of electron, positron, and photon dispersion relations of the form E^2 = p^2 + m^ 2 + epsilon p^3 come from data on …


Doping Dependence Of Electronic And Mechanical Properties Of Gase1−XTeX And Ga1−XInXSe From First Principles, Zs. Rak, S. D. Mahanti, K. C. Mandal, N. C. Fernelius Oct 2010

Doping Dependence Of Electronic And Mechanical Properties Of Gase1−XTeX And Ga1−XInXSe From First Principles, Zs. Rak, S. D. Mahanti, K. C. Mandal, N. C. Fernelius

Faculty Publications

No abstract provided.


Radical Spin Helix In Two-Dimensional Electron Systems With Rashba Spin-Orbit Coupling, Yuriy V. Pershin Dr, Valeriy A. Slipko Sep 2010

Radical Spin Helix In Two-Dimensional Electron Systems With Rashba Spin-Orbit Coupling, Yuriy V. Pershin Dr, Valeriy A. Slipko

Faculty Publications

We suggest a long-lived spin-polarization structure, a radial spin helix, and study its relaxation dynamics. For this purpose, starting with a system of equations for spin-polarization density, we find its general solution in the axially symmetric case. It is demonstrated that the radial spin helix of a certain period relaxes slower than homogeneous spin polarization and plain spin helix. Importantly, the spin polarization at the center of the radial spin helix stays almost unchanged at short times. At longer times, when the initial nonexponential relaxation region ends, the relaxation of the radial spin helix occurs with the same time constant …


Testing Photons' Bose-Einstein Statistics With Compton Scattering, Brett David Altschul Sep 2010

Testing Photons' Bose-Einstein Statistics With Compton Scattering, Brett David Altschul

Faculty Publications

It is an empirical question whether photons always obey Bose-Einstein statistics, but devising and interpreting experimental tests of photon statistics can be a challenge. The nonrelativistic cross section for Compton scattering illustrates how a small admixture ν of wrong-sign statistics leads to a loss of gauge invariance; there is a large anomalous amplitude for scattering timelike photons. Nevertheless, one can interpret the observed transparency of the solar wind plasma at low frequencies as a bound ν<10−25 if Lorentz symmetry is required. If there is instead a universal preferred frame, the bound is ν<10−14, still strong compared with …


Memristive Adaptive Filters, T. Driscoll, J. Quinn, S. Klein, H. T. Kim, B. J. Kim, Yuriy V. Pershin Dr, M. Di Ventra, D. N. Basov Aug 2010

Memristive Adaptive Filters, T. Driscoll, J. Quinn, S. Klein, H. T. Kim, B. J. Kim, Yuriy V. Pershin Dr, M. Di Ventra, D. N. Basov

Faculty Publications

Using the memristive properties of vanadium dioxide, we experimentally demonstrate an adaptive filter by placing a memristor into an LC contour. This circuit reacts to the application of select frequency signals by sharpening the quality factor of its resonant response, and thus “learns” according to the input waveform. The proposed circuit employs only analog passive elements, and may find applications in biologically inspired processing and information storage. We also extend the learning-circuit framework mathematically to include memory-reactive elements, such as memcapacitors and meminductors, and show how this expands the functionality of adaptive memory filters.


Faddeev-Type Equations For Three-Body Symmetry Violating Scattering Amplitudes, Vladimir Gudkov, Young-Ho Song Aug 2010

Faddeev-Type Equations For Three-Body Symmetry Violating Scattering Amplitudes, Vladimir Gudkov, Young-Ho Song

Faculty Publications

The equations which relate three-body and two-body symmetry violating scattering amplitudes are derivedin the first order of symmetry violating interactions. They can be used to obtain three-body symmetry violatingscattering amplitudes from two-body symmetry violating scattering amplitudes calculated in low energy effectivefield theory.


Laboratory Bounds On Electron Lorentz Violation, Brett David Altschul May 2010

Laboratory Bounds On Electron Lorentz Violation, Brett David Altschul

Faculty Publications

Violations of Lorentz boost symmetry in the electron and photon sectors can be constrained by studying several different high-energy phenomenon. Although they may not lead to the strongest bounds numerically, measurements made in terrestrial laboratories produce the most reliable results. Laboratory bounds can be based on observations of synchrotron radiation, as well as the observed absences of vacuum Cerenkov radiation. Using measurements of synchrotron energy losses at LEP and the survival of TeV photons, we place new bounds on the three electron Lorentz violation coefficients c(TJ ), at the 3 x 10-13 to 6 x 10-15 levels.


Solid-State Memcapacitive System With Negative And Diverging Capacitance, J. Martinez-Rincon, M. Di Ventra, Yuriy V. Pershin Dr May 2010

Solid-State Memcapacitive System With Negative And Diverging Capacitance, J. Martinez-Rincon, M. Di Ventra, Yuriy V. Pershin Dr

Faculty Publications

We suggest a possible realization of a solid-state memory capacitive (memcapacitive) system. Our approach relies on the slow polarization rate of a medium between plates of a regular capacitor. To achieve this goal, we consider a multilayer structure embedded in a capacitor. The multilayer structure is formed by metallic layers separated by an insulator so that nonlinear electronic transport (tunneling) between the layers can occur. The suggested memcapacitor shows hysteretic charge-voltage and capacitance-voltage curves, and both negative and diverging capacitance within certain ranges of the field. This proposal can be easily realized experimentally and indicates the possibility of information storage …


Reverberation-Chamber Test Environment For Outdoor Urban Wireless Propagation Studies, Helge Fielitz, Kate A. Remley, Christopher L. Holloway, Qian Zhang, Qiong Wu, David W. Matolak Mar 2010

Reverberation-Chamber Test Environment For Outdoor Urban Wireless Propagation Studies, Helge Fielitz, Kate A. Remley, Christopher L. Holloway, Qian Zhang, Qiong Wu, David W. Matolak

Faculty Publications

We introduce a test environment to replicate the well-known clustering of reflections in power delay profiles arising from late-time delays and reflections. Urban wireless propagation environments are known to exhibit such clustering. The test setup combines discrete reflections generated by a fading simulator with the continuous distribution of reflections created in a reverberation chamber. We describe measurements made in an urban environment in Denver, CO, that illustrate these multiple distributions of reflections. Our comparison of measurements made in the urban environment to those made in the new test environment shows good agreement.


Far-Field Optical Nanoscopy Based On Continuous Wave Laser Stimulated Emission Depletion, C. Kuang, Wei Zhao, Guiren Wang Jan 2010

Far-Field Optical Nanoscopy Based On Continuous Wave Laser Stimulated Emission Depletion, C. Kuang, Wei Zhao, Guiren Wang

Faculty Publications

Stimulated emission depletion (STED) microscopy is one of the breakthrough technologies that belong to far-field optical microscopy and can achieve nanoscale spatial resolution. We demonstrate a far-field optical nanoscopy based on continuous wave lasers with different wavelengths, i.e., violet and green lasers for excitation and STED, respectively. Fluorescent dyes Coumarin 102 and Atto 390 are used for validating the depletion efficiency. Fluorescent nanoparticles are selected for characterizing the spatial resolution of the STED system. Linear scanning of the laser beams of the STED system along one line of a microscope slide, which is coated with the nanoparticles, indicates that a …


Lorentz Violation With An Antisymmetric Tensor, Brett David Altschul, Quentin G. Bailey, Alan Kostelecky Jan 2010

Lorentz Violation With An Antisymmetric Tensor, Brett David Altschul, Quentin G. Bailey, Alan Kostelecky

Faculty Publications

Field theories with spontaneous Lorentz violation involving an antisymmetric 2-tensor are studied. A general action including nonminimal gravitational couplings is constructed, and features of the Nambu-Goldstone and massive modes are discussed. Minimal models in Minkowski spacetime exhibit dualities with Lorentz-violating vector and scalar theories. The post-Newtonian expansion for nonminimal models in Riemann spacetime involves qualitatively new features, including the absence of an isotropic limit. Certain interactions producing stable Lorentz-violating theories in Minkowski spacetime solve the renormalization-group equations in the tadpole approximation.


Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Cheettu Ammal, Andreas Heyden Jan 2010

Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Cheettu Ammal, Andreas Heyden

Faculty Publications

The interaction of Aun and Ptn (n=2,3) clusters with the stoichiometric and partially reduced rutile TiO2 (110) surfaces has been investigated using periodic slab and periodic electrostatic embedded cluster models. Compared to Au clusters, Pt clusters interact strongly with both stoichiometric and reduced TiO2 (110) surfaces and are able to enhance the reducibility of the TiO2 (110) surface, i.e., reduce the oxygen vacancy formation energy. The focus of this study is the effect of Hartree–Fock exchange on the description of the strength of chemical bonds at the interface of Au/Pt clusters and the TiO2 (110) surface. Hartree–Fock exchange helps describing …


Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Cheettu Ammal Jan 2010

Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Cheettu Ammal

Faculty Publications

The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the …