Physical Sciences and Mathematics Commons^™

Critical Dynamics Of Superconductors In The Charged Regime, Courtney Lannert, Smitha Vishveshwara, Matthew P.A. Fisher

Physics: Faculty Publications

The charged regime of the superconductor-metal transition was analyzed by applying a finite temperature critical dynamics. A transverse gage field coupling was applied to the superconducting order parameter. A new dynamic universality class characeterized by a finite fixed point ratio between the transport coefficients associated with the order parameter and gage fields was found by assuming relaxational dynamics for both the order parameter and gage fields within a renormalization group scheme. It was found that various features of the dynamic universality class of the charged superconductor appeared in measurable quantities.

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence, A.S. Green, Gordon A. Gallup, Mark A. Rosenberry, Timothy J. Gay

Gordon Gallup Publications

We have measured the circular polarization of light emitted from both atomic H and molecular H₂ after bombarding H₂ with longitudinally polarized electrons. For both atomic and molecular fluorescence near threshold we observe a circular polarization as great as 10% of the electron polarization. This represents the first direct observation of spin transfer in electron-molecule collisions.

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence, A. S. Green, Gordon A. Gallup, Mark A. Rosenberry

Timothy J. Gay Publications

We have measured the circular polarization of light emitted from both atomic H and molecular H₂ after bombarding H₂ with longitudinally polarized electrons. For both atomic and molecular fluorescence near threshold we observe a circular polarization as great as 10% of the electron polarization. This represents the first direct observation of spin transfer in electron-molecule collisions.

Relativistic Allowed And Forbidden Transition Probabilities For Fluorine-Like Fe Xviii, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, P. A. M. Van Hoof, Gary J. Ferland, K. M. Aggarwal, R. Kisielius, P. H. Norrington

Physics and Astronomy Faculty Publications

Energy levels and the corresponding transition probabilities for allowed and forbidden transitions among the levels of the ground configuration and first 23 excited configurations of fluorine-like Fe XVIII have been calculated using the multiconfigurational Dirac-Fock GRASP code. A total of 379 lowest bound levels of Fe XVIII is presented, and the energy levels are identified in spectroscopic notations. Transition probabilities, oscillator strengths and line strengths for electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transitions among these 379 levels are also presented. The calculated energy levels and transition probabilities are compared with experimental data.

Afci Quarterly Input – Unlv January Through March, 2004, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Doubly Differential Multiple Ionization Of Krypton By Positron And Electron Impact, Kay Dubois, Antonio C. Santos, Ahmad Hasan

Physics Faculty Research & Creative Works

Measurements of doubly differential single and multiple ionization of krypton atoms have been performed for 750 eV positron and electron impact. Data were measured as a function of projectile energy-loss and scattering angle. For electrons, the energy-loss range was 0-85% of the initial projectile energy and scattering angles were between ±22°. Following the procedure adopted previously for argon, the electron impact data were placed on an absolute scale by normalizing to total ionization cross sections available in the literature. The present results for krypton show differences between positron and electron impact that are less pronounced than was found for argon. …

Magnetosome Formation In Prokaryotes, Dennis A. Bazylinski, Richard B. Frankel

Physics

Magnetotactic bacteria were discovered almost 30 years ago, and for many years and many different reasons, the number of researchers working in this field was few and progress was slow. Recently, however, thanks to the isolation of new strains and the development of new techniques for manipulating these strains, researchers from several laboratories have made significant progress in elucidating the molecular, biochemical, chemical and genetic bases of magnetosome formation and understanding how these unique intracellular organelles function. We focus here on this progress.

The Electrochemical Separation Of Curium And Americium: Quaterly Report January - March 2004, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

This research report outlines the current status and progress associated with the electrochemical separation of Curium and Americium.

Data collection and analysis of the Ce³⁺/Ce⁴⁺ redox couple in various supporting electrolytes has continued. All electrolyte systems were investigated at Pt, Au, and Glassy Carbon working electrodes. Analysis of these data was accomplished by performing appropriate background subtractions to reveal net peaks due to Ce redox behavior. Successful identification of the Ce redox couple was achieved with all electrolyte/electrode systems, although a decline in peak resolution was observed with increasing acid concentration. Optimal conditions in this experiment were …

A Rapidly-Converging Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab Geometry, Nicholas J. Wager

Theses and Dissertations

I present a numerical technique to solve the time independent Boltzmann Transport Equation for the transport of neutrons and photons. The technique efficiently solves the discrete ordinates equations with a new iteration scheme. I call this new scheme the angle space distribution iteration method because it combines a non-linear, high angular-resolution flux approximation within individual spatial cells with a coarse angular-resolution flux approximation that couples all cells in a spatial mesh. This shown to be an efficient alternative to source iteration. The new method is implemented using the step characteristic and exponential characteristic spatial quadrature schemes. The latter was introduced …

Student Explorations Of Quantum Effects In Leds And Luninescent Devices, Lawrence Escalada, N. Sanjay Rebekki, Dean A. Zollman

Faculty Publications

We developed activity-based instructional units to introduce basic quantum principles to students with limited physics and mathematics backgrounds. To emphasize the practical applications of contemporary physics, we introduced concepts using the contexts of light-emitting devices such as light-emitting diodes (LEDs), fluorescent lamps, and glow-in-the-dark toys. As our standard of living becomes more dependent on the latest developments in science and technology, our students' literacy must be at a level that enables them to make educated decisions on science- and technology-related issues and their everyday applications. Students need to have at least a basic understanding of 20th-century physics and its applications …

Neutron Cross Sections For He-3 At Epithermal Energies, C. D. Keith, Z. Chowdhuri, D. R. Rich, W. M. Snow, J. D. Bowman, S. L. Penttila, D. A. Smith, M. B. Leuschner, V. R. Pomeroy, Gordon L. Jones, E. I. Sharapov

Articles

High accuracy, absolute measurements of the neutron total cross section for He-3 are reported for incident neutron energies 0.1-400 eV. The measurements were performed at the LANSCE short-pulse neutron spallation source. Using the previously determined cross section for neutron elastic scattering, 3.367+/-0.019 b, we extract a new value for the energy dependence of the He-3(n,p)He-3 reaction cross section, sigma(np)=(849.77+/-0.14+/-1.02)E-1/2-(1.253+/-0.00+/-(+0.008)(-0.049))b, where the neutron energy is expressed in eV. The first uncertainty is statistical, the second systematic.

Analysis Of Uncertainties In Infrared Camera Measurements Of A Turbofan Engine In An Altitude Test Cell, Thomas A. Morris

Theses and Dissertations

This research investigated the uncertainties in measuring the IR signature of a General Electric F110-GE-129 turbofan engine inside an altitude test cell. The requirements for the measurement system include the intensity and radiance of the engine surfaces in three bands of operation, two Medium Wave IR (MWIR) bands and one Long Wave IR (LWIR) band. The altitude test cell provides a venue for measuring the IR signature in simulated altitude operation, but the imaging process is laden with measurement uncertainty due to stray radiation from the facility structure, hot exhaust gases, and the measurement equipment itself. The atmosphere and a …

Spectral Dependence Of Coherent Backscattering Of Light In A Narrow-Resonance Atomic System, D. V. Kupriyanov, I. M. Sokolov, N. V. Larionov, P. Kulatunga, C. I. Sukenik, S. Balik, M. D. Havey

Physics Faculty Publications

We report a combined theoretical and experimental study of the spectral and polarization dependence of near-resonant radiation coherently backscattered from an ultracold gas of 85Rb atoms. Measurements in a 6 MHz range about the 5s 2S1/25p 2P3/2, F=3F'=4 hyperfine transition are compared with simulations based on a realistic model of the experimental atomic density distribution. In the simulations, the influence of heating of the atoms in the vapor, magnetization of the vapor, finite spectral bandwidth, and other nonresonant hyperfine transitions are considered. Good agreement is found between the simulations and measurements.

The Second Law Mystique, Alexey V. Nikulov, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

No abstract provided.

Infrared Laser Spectroscopy Of Jet Cooled Cobalt Tricarbonyl, Kyle Trauth, William A. Burns, Ginger Berry, Scott Reeve

Scott Reeve

No abstract provided.

Surface Photovoltage Effects On The Isomeric Semiconductors Of Boron-Carbide, A. N. Caruso, Snjezana Balaz, Bo Xu, Peter A. Dowben, A.S. Mcmullen-Gunn, Jennifer I. Brand, Yaroslav B. Losovyj, D.N. Mcilroy

Peter Dowben Publications

During exposure to synchrotron radiation, closo 1,7-dicarbadodecaborane (metacarborane) and closo 1,2-dicarbadodecaborane (orthocarborane) decompose, and are accompanied by increasingly evident photoemission surface photovoltage effects. We show that metacarborane and orthocarborane form self-doped n-type and p-type boron-carbides, respectively. Surface photovoltage effects dominate the photoemission final state, not the changes in electronic structure due to decomposition. © 2004 American Institute of Physics. [DOI: 10.1063/1.1648136]

Leptonic Cp Violation Phases Using An Ansatz For The Neutrino Mass Matrix And Application To Leptogenesis, Joseph Schechter, Salah Nasri, Sherif Moussa

Physics - All Scholarship

We further study the previously proposed Ansatz, Tr(M)=0, for a prediagonal light Majorana type neutrino mass matrix. If CP violation is neglected this enables one to use the existing data on squared mass differences to estimate (up to a discrete ambiguity)the neutrino masses themselves. If it is assumed that only the conventional CP phase is present, the ansatz enables us to estimate this phase in addition to all three masses. If it is assumed that only the two Majorana CP phases are present, the Ansatz enables us to obtain a one parameter family of solutions for the masses and phases. …

Infrared Depletion Spectroscopy Of Aniline–Toluene Cluster: The Investigation Of The Red Shifts Of The Nh2 Stretching Vibrations Of Aniline–Aromatic Clusters, Naveed Piracha, F. Ito, T. Nakanaga

Naveed K. Piracha

The infrared spectra of the NH2 stretching vibrations of aniline–toluene cluster and corresponding cluster cation have been measured by the infrared depletion method. The NH2 stretching vibrations of aniline–toluene cluster were observed at 3393 and 3468 cm−1. The red shifts from the corresponding bands of aniline monomer are 29 and 40 cm−1, respectively, for the NH2 symmetric and anti-symmetric stretching vibrations. The magnitudes of the red shifts are similar to those of other aniline–aromatic clusters. The structure of this cluster has been found to be a sandwich type, that is, the two aromatic rings are parallel in the cluster and …

Three-Dimensional High-Resolution Reconstruction Of Polarization In Ferroelectric Capacitors By Piezoresponse Force Microscopy, B. J. Rodriguez, Alexei Gruverman, A. I. Kingon, R. J. Nemanich, J. S. Cross

Alexei Gruverman Publications

A combination of vertical and lateral piezoresponse force microscopy (VPFM and LPFM, respectively) has been used to map the out-of-plane and in-plane polarization distribution, respectively, of (111)-oriented Pb(Zr,Ti)O₃-based (PZT) ferroelectric patterned and reactively-ion-etched capacitors. While VPFM and LPFM have previously been used to determine the orientation of the polarization vector in ferroelectric crystals and thin films, this is the first time the technique has been applied to determine the three-dimensional polarization distribution in thin-film capacitors and, as such, is of importance to the implementation of nonvolatile ferroelectric random access memory. Sequential VPFM and LPFM imaging have been performed …

Electronic Structure Of Nuclear-Spin-Polarization-Induced Quantum Dots, Yuriy V. Pershin Dr

Faculty Publications

We study a system in which electrons in a two-dimensional electron gas are confined by a nonhomogeneous nuclear-spin polarization. The system consists of a heterostructure that has nonzero nuclei spins. We show that in this system electrons can be confined into a dot region through a local nuclear-spin polarization. The nuclear-spin-polarization-induced quantum dot has interesting properties indicating that electron energy levels are time dependent because of the nuclear-spin relaxation and diffusion processes. Electron confining potential is a solution of diffusion equation with relaxation. Experimental investigations of the time dependence of electron energy levels will result in more information about nuclear-spin …

Slow Spin Relaxation In Two-Dimensional Electron Systems With Antidots, Yuriy V. Pershin Dr, Vladimir Privman

Faculty Publications

We report a Monte Carlo investigation of the effect of a lattice of antidots on spin relaxation in twodimensional electron systems. The spin relaxation time is calculated as a function of geometrical parameters describing the antidot lattice, namely the antidot radius and the distance between their centers. It is shown that spin polarization relaxation can be efficiently suppressed by the chaotic spatial motion due to the antidot lattice. This phenomenon offers a new approach to spin coherence manipulation in spintronics devices.

Non-Adiabatic Perturbations From Single-Field Inflation, Christian Armendariz-Picon

Physics - All Scholarship

If the inflaton decays into several components during reheating, and if the corresponding decay rates are functions of spacetime-dependent quantities, it is possible to generate entropy perturbations after a stage of single-field inflation. In this paper, I present a simple toy example that illustrates this possibility. In the example, the decay rates of the inflaton into ``matter'' and ``radiation'' are different functions of the total energy density. In particular cases, one can exactly solve the equations of motion both for background and perturbations in the long-wavelength limit, and show that entropy perturbations do indeed arise. Beyond these specific examples, I …

Bond Breaking And Temporary Anion States In Uracil And Halouracils: Implications For The Dna Bases, Adam M. Scheer, Kayvan Aflatooni, Gordon A. Gallup, Paul Burrow

Paul Burrow Publications

Low energy electrons are capable of breaking bonds in gas phase DNA bases by means of the dissociative electron attachment process.With the aid of new total scattering data in the halouracils and input from quantum chemical calculations, we describe the dipole bound and valence anion states in these compounds and present assignments for the two types of structure appearing in the cross sections. A clear distinction between the two mechanisms for bond breaking is necessary for an understanding of electron induced damage to DNA.

Nondipole Effects In Photo-Double-Ionization Of He By A Vuv Photon, Andrei Y. Istomin, N. L. Manakov, A. V. Meremianin, Anthony F. Starace

Department of Physics and Astronomy: Faculty Publications

We present a dynamical model-independent, ab initio parametrization of the quadrupole transition amplitude for photo-double-ionization of He. An asymmetry of the triple differential cross section induced by the nondipole corrections is discussed and shown to be significant even for an excess energy as low as 80 eV. We provide predictions for two different kinds of experiments in which nondipole effects should be observable with current experimental capabilities.

Azimuthal Anisotropy At The Relativistic Heavy Ion Collider: The First And Fourth Harmonics, Star Collaboration, T.D. Gutierrez

Physics

We report the first observations of the first harmonic (directed flow, v₁) and the fourth harmonic (v₄), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v₂) generated at RHIC. From the correlation of v₂ with v₁ it is determined that v₂ is positive, or in-plane. The integrated v₄ is about a factor of 10 smaller than v₂. For the sixth (v_{6 …}

Reply To Comment By R. Bousquet Et Al. On “Subduction Factory: 1. Theoretical Mineralogy, Densities, Seismic Wave Speeds And H2O Contents”, Bradley R. Hacker, Geoffrey A. Abers, Simon M. Peacock, Scott Joshnston

Physics

No abstract provided.

High Resolution Measurements Of Kinetic Energy Release Distributions Of Neon, Argon, And Krypton Cluster Ions Using A Three Sector Field Mass Spectrometer, K. Gluch, S. Matt-Leubner, L. Michalak, Olof E. Echt, A. Stamatovic, P. Scheier, T. D. Mark

Physics & Astronomy

Using a newly constructed three sector field mass spectrometer (resulting in a BE1E2 field configuration) we have measured the kinetic energy release distributions of neon, argon, and krypton cluster ions. In the present study we used the first two sectors, B and E1, constituting a high resolution mass spectrometer, to select the parent ions in terms of mass, charge, and energy, and studied the decay of those ions in the third field free region. Due to the improved mass resolution we were able to extend earlier studies carried out with a two sector field machine, where an upper size limit …

Search For Pair Production Of Scalar Top Quarks In R-Parity Violating Decay Modes In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present the results of a search for pair production of scalar top quarks (t̅₁) in an R-Parity violating supersymmetry scenario in 106 pb^-1 of pp̅ collisions at √s=1.8 TeV collected by the Collider Detector at Fermilab. In this mode each t̅₁ decays into a τ lepton and a b quark. We search for events with two τ's, one decaying leptonically (e or µ) and one decaying hadronically, and two jets. No candidate events pass our final selection criteria. We set a 95% confidence level lower limit on the t̅₁ mass at 122 GeV/ …

Proposal For No-Cost Extension And Re-Scope For Unlv Trp Project: Neutron Multiplicity Measurements For The Afci Program (Advanced Fuel Cycle Initiative), Denis Beller

Transmutation Sciences Physics (TRP)

The U.S. Advanced Fuel Cycle Initiative (AFCI) is a program to develop economic and environmental methods to reduce the impact of waste from commercial nuclear fuel cycles. One concept for near-complete destruction of waste isotopes from used nuclear fuel is accelerator-driven transmutation. High-power accelerators would be used to produce high-energy charged particles, which then collide with heavy metal targets to create a cascade of neutrons. These neutrons then cause a nuclear chain reaction in subcritical systems. Fission neutrons then transmute fissile waste isotopes as well as other problematic isotopes such as technetium-99 and iodine-129. To design these systems, complex reactor …

Cubic : Bulk Thermoelectric Materials With High Figure Of Merit, Kuei Hsu, Sim Loo, Fu Guo, Wei Chen, Jeffrey Dyck, Cterid Uher, Tim Hogan, E. Polychroniadis, Mercouri Kanatzidis

Jeffrey Dyck

The conversion of heat to electricity by thermoelectric devices may play a key role in the future for energy production and utilization. However, in order to meet that role, more efficient thermoelectric materials are needed that are suitable for high-temperature applications. We show that the material system may be suitable for this purpose. With m = 10 and 18 and doped appropriately, n-type semiconductors can be produced that exhibit a high thermoelectric figure of merit of ~2.2 at 800 kelvin. In the temperature range 600 to 900 kelvin, the material is expected to outperform all reported bulk thermoelectrics, thereby earmarking …