Physical Sciences and Mathematics Commons^™

The Complex Neutral Gas Dynamics Of The Dwarf Starburst Galaxy Ngc 625, John M. Cannon, Naomi M. Mcclure-Griffiths, Evan D. Skillman, Stephanie Cote

John Cannon

No abstract provided.

Could Dark Energy Be Vector-Like?, Christian Armendariz-Picon

Physics - All Scholarship

In this paper I explore whether a vector field can be the origin of the present stage of cosmic acceleration. In order to avoid violations of isotropy, the vector has be part of a ``cosmic triad'', that is, a set of three identical vectors pointing in mutually orthogonal spatial directions. A triad is indeed able to drive a stage of late accelerated expansion in the universe, and there exist tracking attractors that render cosmic evolution insensitive to initial conditions. However, as in most other models, the onset of cosmic acceleration is determined by a parameter that has to be tuned …

Lattice Sigma Models With Exact Supersymmetry, Simon Catterall, Sofiane Ghadab

Physics - All Scholarship

We show how to construct lattice sigma models in one, two and four dimensions which exhibit an exact fermionic symmetry. These models are discretized and {\it twisted} versions of conventional supersymmetric sigma models with N=2 supersymmetry. The fermionic symmetry corresponds to a scalar BRST charge built from the original supercharges. The lattice theories possess local actions and in many cases admit a Wilson term to suppress doubles. In the two and four dimensional theories we show that these lattice theories are invariant under additional discrete symmetries. We argue that the presence of these exact symmetries ensures that no fine tuning …

Coherent Control Of Intersubband Optical Bistability In Quantum Wells, H. O. Wijewardane, Carsten A. Ullrich

Physics Faculty Research & Creative Works

The nonlinear intersubband (ISB) response of conduction electrons in quantum well were investigated. the coherent control of ISB optical biostability was analyzed using terahertz (THz) control pulses to induce picosecond switching between the bistable states. the switching speed was also determined by the ISB relaxation and decoherence times, T 1 and T 2. the results show that the shortest down-switching times of 50-6- ps are achieved by control pulses with intensity not far from the driving field, 30 W/cm 2.

Reaction Thresholds In Doubly Special Relativity, Daniel Heyman '03, F. Hinterleitner, Seth Major

Articles

Two theories of special relativity with an additional invariant scale, “doubly special relativity,” are tested with calculations of particle process kinematics. Using the Judes-Visser modified conservation laws, thresholds are studied in both theories. In contrast with some linear approximations, which allow for particle processes forbidden in special relativity, both the Amelino-Camelia and Magueijo-Smolin frameworks allow no additional processes. To first order, the Amelino-Camelia framework thresholds are lowered and the Magueijo-Smolin framework thresholds may be raised or lowered.

Biconformal Supergravity And The Ads/Cftconjecture, L. B. Anderson, James Thomas Wheeler

All Physics Faculty Publications

Biconformal supergravity models provide a new gauging of the superconformal group relevant to the Maldacena conjecture. Using the group quotient method to biconformally gauge SU(2,2|N), we generate a 16-dim superspace. We write the most general even- and odd-parity actions linear in the curvatures, the bosonic sector of which is known to descend to general relativity on a 4-dim manifold.

Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal

Articles

Results from the investigation of the diffusion processes in a dry acrylamide-based photopolymer system are presented. The investigation is carried out in the context of experimental work on optimization of the high spatial frequency response of the photopolymer. Tracing the transmission holographic grating dynamics at short times of exposure is utilized to measure diffusion coefficients. The results reveal that two different diffusion processes contribute with opposite sign to the refractive index modulation responsible for the diffraction grating build up. Monomer diffusion from dark to bright fringe areas increases the refractive index modulation. It is characterized with diffusion constant D0=1.6E-7 cm2/s. …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective of this project is to develop a method for the separation of Am from Cm based on electrochemical techniques. Electrochemical systems that allow the thermodynamics of actinide and lanthanide complexes to be systematically evaluated and tuned will be examined. The influence of complex formation on the ability to selectively isolate a given species electrochemically will be evaluated. Metal-ligand complex formation provides a useful derivation technique to increase solubility in solution environments that favor precipitation. In addition, the thermodynamic properties of a complex relative to the isolated species may be shifted to more suitably measurable electrochemical separation regimes. Electrochemical …

Design Concepts And Process Analysis For Transmuter Fuel Manufacturing, Georg F. Mauer

Fuels Campaign (TRP)

This proposal addresses the subject heading ‘Transmutation Fuel Development’ in the 2004 research topic list of the UNLV Transmutation Research Program (TRP) and DOE Advanced Fuel Cycle Initiative (AFCI). The large-scale deployment of remote fabrication and refabrication processes (with a capacity of approx. 100 metric tons of Minor Actinides (MA) annually) will be required for all transmutation scenarios. The objective of this project is the design, analysis, and evaluation of manufacturing processes for transmuter fuel fabrication. Fabrication processes for different fuel types differ in terms of equipment types, throughput, and cost. The evaluation of the fabrication processes will create a …

Growth And Transport Properties Of Complementary Germanium Nanowire Field Effect Transistors, Andrew B. Greytak, Lincoln J. Lauhon, Mark S. Gudiksen, Charles M. Lieber

Faculty Publications

n- and p-type Ge nanowires were synthesized by a multistep process in which axial elongation, via vapor–liquid–solid (VLS) growth, and doping were accomplished in separate chemical vapor deposition steps. Intrinsic, single-crystal, Ge nanowires prepared by Au nanocluster-mediated VLS growth were surface-doped in situ using diborane or phosphine, and then radial growth of an epitaxial Ge shell was used to cap the dopant layer. Field-effect transistors prepared from these Ge nanowires exhibited on currents and transconductances up to 850 µA/µm and 4.9 µA/V, respectively, with device yields of >85%.

Multistrange Baryon Production In Au-Au Collisions At √ SNn = 130 Gev, Star Collaboration, T.D. Gutierrez

Physics

The transverse mass spectra and midrapidity yields for Ξs and Ωs are presented. For the 10% most central collisions, the ¯Ξ¯+/h− ratio increases from the Super Proton Synchrotron to the Relativistic Heavy Ion Collider energies while the Ξ−/h⁻stays approximately constant. A hydrodynamically inspired model fit to the Ξ spectra, which assumes a thermalized source, seems to indicate that these multistrange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to π, K, p, and Λs.

Plasmaspheric Plumes: Crres Observations Of Enhanced Density Beyond The Plasmapause, Jeff Sanny, M. B. Moldwin, J. Howard, J. D. Bocchicchio, H. K. Rassoul, R. R. Anderson

Physics Faculty Works

CRRES plasma wave receiver density data were used to study the distribution and properties of dense plasmaspheric-like plasma observed outside the plasmapause. Our study indicates that outer plasmaspheric structure, often called plasmaspheric plumes, blobs, tails, or detached plasma regions, can exist at all local times under all levels of geomagnetic activity. Of the 558 CRRES orbits that had at least one clearly defined plasmapause, 169 (or 30%) had plasmaspheric-like density structures at higher L shells than the plasmapause. Most of the occurrences of plasmaspheric-like plasma observed by CRRES were in the noon-to-dusk sector in the aftermath of enhanced geomagnetic activity …

Moduli Stabilization With The String Higgs Effect, Scott Watson

Physics - All Scholarship

We review the notion of the Higgs effect in the context of string theory. We find that by including this effect in time dependent backgrounds, one is led to a natural mechanism for stabilizing moduli at points of enhanced gauge symmetry. We consider this mechanism for the case of the radion (size of the extra dimensions) and find that as decompactification of the large spatial dimensions takes place the radion will remain stabilized at the self dual radius. We discuss how this mechanism can be incorporated into models of string cosmology and brane inflation to resolve some outstanding problems. We …

Alpha And Gamma-Ray Spectroscopic Studies Of Au, Pt, And Ir Nuclei Near The Proton Dripline, Tuck-Meng Goon

Doctoral Dissertations

This dissertation reports the observation of α-decay and in-beam level structures in the neutron-deficient nuclei ^176,174Au, ^173,174Pt, and ¹⁷⁵Ir from an experiment which was performed at Argonne National Laboratory (ANL). A beam of ⁸⁴Sr projectiles was used to bombard ^92,94,96Mo targets. From these reactions, the ^176,178,180Hg compound nuclei were made which eventually decayed into more than 20 product nuclei. The experiment was performed with the Atlas accelerator and utilized the Gammasphere array at the target position in conjunction with the Fragment Mass Analyzer (FMA) for mass identification and a Double-Sided Silicon Strip Detector (DSSD), …

Spectral Characteristics Of Water Megamaser Galaxies. Ii. Eso103-G035, Txs 2226-184, And Ic1481, N. Bennert, H. Schulz, C. Henkel

Physics

Long-slit optical emission-line spectra of the H₂O megamaser galaxies ESO 103-G035, TXS 2226-184, and IC 1481 are evaluated in order to look for characteristics typical for water-megamaser galaxies. We present rotation curves, line ratios, electron densities, temperatures, and H luminosities. The successful line-profile decompositions rest on d-Lorentzians with an additional parameter d to adjust the wings, rather than Gaussians or Lorentzians as basic functions. No significant velocity gradient is found along the major axis in the innermost 2 kpc of TXS 2226-184. IC 1481 reveals a spectrum suggestive of a vigorous starburst in the …

Interaction Of Carbon Nanotubes With Saccharides: A Possible Route To Biocompatible Composites, Alan Casey, Jonathan Moghal, Gerald Farrell, Hugh Byrne, Gordon Chambers

Conference papers

Inclusion complexes of saccharides and HiPco Carbon Nanotubes (HCNT) were formed, resulting in water soluble complexes. These complexes were then characterised using a variety of spectroscopic techniques. Raman spectroscopy was used to probe changes in the vibrational character of both the host and guest species and also to assess if any selectivity of tube diameter occurred. UV-Vis-NIR and circular dichroic spectroscopies were used to assess the effect of inclusion on the electronic properties of the tubes. Spectroscopic analysis of these species showed clear evidence of an intermolecular interaction between the host material and the HCNT.

Anomalous Capture And Emission From Internal Surfaces Of Semiconductor Voids: Nanopores In Sic, David C. Look, Z-Q. Fang, S. Soloviev, T. S. Sudarshan, J. J. Boeckl

Physics Faculty Publications

Deep level transient spectroscopy in nanoporous, n-type SiC reveals a new type of deep (˜0.8 eV) trap that can hold more than 100 electrons and that has anomalous capture and emission behavior. Here we quantitatively explain these effects with a new, general formalism that treats both emission and capture in the presence of dynamic energy barriers, resulting from the charging and discharging of states on the internal surfaces of voids, such as pores or nanopipes. The capture kinetics display a logarithmic time dependence over a certain filling range, as has often been observed in connection with dislocation-related trapping.

Physics Department News, May 2004, College Of Arts And Sciences

Physics Newsletter

Contents from Volume 3, Issue 1:

• A Note from the Editor
• From the Chair
• What’s New at the University
• Faculty Highlights
• Staff Highlights
• Faculty Research
• PhysTEC
• Alumni News
• New Grants
• Student News
• Annual Student Awards
• Recent Graduates
• Department Roster
• Feedback/Update Reply Form

Self-Energy Correction To The Two-Photon Decay Width In Hydrogenlike Atoms, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We investigate the guage invariance of the leading logarithmic radiative correction to the two-photon decay width in hydrogenlike atoms, was investigated. The effective treatment of the correction using a Lamb-shift led to the equivalent results in both the length and velocity gages. The relevant radiative corrections were found to be related to the energies that entered into the propagator denominators, to the Hamiltonian, to the wave functions, and to the energy conservation condition, that holds between two photons. The results show that the dominant radiative correction to the 2S two-photon decay width is about -2.020 536(α/π)(Zα)² 1n[(Zα)^-2] …

Protonium Formation In The P̅-H Collision At Low Energies By A Diabatic Approach, M. Hesse, Anh-Thu Le, C. D. Lin

Physics Faculty Research & Creative Works

We present a diabatization technique in combination with the recently developed hyperspherical close coupling (HSCC) method. In contrast to the strict diabatization, our simple diabatization procedure transforms only sharp avoided crossings in the adiabatic hyperspherical potential curves into real crossings. With this approach, the weak collision channels can be removed from the close-coupling calculations. This method is used to study the antiproton-hydrogen collision at low energies. In the case of a scaled down (anti)proton mass, we show that a 10-channel calculation is enough to obtain converged cross sections at low energies. The results also indicate that protonium formation occurs mostly …

Mini-Conference And Related Sessions On Laboratory Plasma Astrophysics, H. Ji, Michael R. Brown, S. C. Hsu, H. Li, R. P. Drake

Physics & Astronomy Faculty Works

This paper provides a summary of some major physics issues and future perspectives discussed in the Mini-Conference on Laboratory PlasmaAstrophysics. This mini-conference, sponsored by the Topical Group on PlasmaAstrophysics, was held as part of the American Physical Society’s Division of Plasma Physics 2003 Annual Meeting (October 27–31, 2003). Also included are brief summaries of selected talks on the same topic presented at two invited paper sessions (including a tutorial) and two contributed focus oral sessions, which were organized in coordination with the mini-conference by the same organizers.

Investigation And Calculation Of Dose Coefficients For Radionuclides Produced In A Spallation Neutron Source Using The Ensdf And Nubase Nuclear Databases, Yayun Song

UNLV Theses, Dissertations, Professional Papers, and Capstones

Dose coefficients are useful for risk assessment during the design and siting of accelerator-driven nuclear facilities including the Spallation Neutron Source. There are seventy-two radionuclides with half-lives equal to or greater than one minute that will be produced by the spallation of a mercury target for which no published dose coefficients exist. Out of these seventy-two, twenty-four currently have conflicting published nuclear data in the Evaluated Nuclear Structure Data Files (ENSDF) and the NUBASE data files. In this research these twenty-four radionuclides have been studied. Because of missing ENSDF records, internal and external dose coefficients were determined for only six …

Design And Simulation Of An Induction Skull Melting System, Taide Tan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Incorporating volatile actinides, mainly americium into a metallic fuel pin (MFP) has been a serious problem due to americium’s high vapor pressure. An Induction Skull Melting (ISM) system was identified by Argonne National Laboratory (ANL) as a potential furnace design to cast MFPs. Through the development of the ISM system, the nuclear waste feedstock can be melted and injected into the mold for fabricating MFPs in the advanced nuclear fuel cycles. The main phenomena in this system include: induction melting process, casting process and mass transfer process of americium. Issues related to ISM system design for casting MFPs are discussed …

Computational Scattering Models For Elastic And Electromagnetic Waves In Particulate Media, Timothy Edwin Doyle

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Numerical models were developed to simulate the propagation of elastic and electromagnetic waves in an arbitrary, dense dispersion of spherical particles. The scattering interactions were modeled with vector multipole fields using pure-orbital vector spherical harmonics, and solved using the full vector form of the boundary conditions. Multiple scattering was simulated by translating the scattered wave fields from one particle to another with the use of translational addition theorems, summing the multiple-scattering contributions, and recalculating the scattering in an iterative fashion to a convergent solution. The addition theorems were rederived in this work using an integral method, and were shown to …

Mesospheric Temperature Climatology Above Utah State University, Joshua P. Herron

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A Rayleigh-scatter lidar has been in operation at Utah State University (41. 7° N, 111.8 ° W) starting in September 1993 until the present (October 2003). The return profiles from the atmosphere have been analyzed to provide temperature measurements of the middle atmosphere from 45 to 90 km. Various methods of averaging were used to construct a temperature climatology of the region based on these observations. The data analysis algorithm has been critically analyzed to find possible sources of error, and has been compared to an independently derived technique. The resulting temperatures have been compared to other mid-latitude lidars with …

Lidar Observations Of Oscillations In The Middle Atmosphere, Karen L. M. Nelson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The three major types of oscillations in the atmosphere are gravity waves, planetary waves, and tides. Identifying planetary waves and tides in nighttime-only lid are data is a challenge. The Lomb-Scargle method offers a possible solution to this problem, although aliasing is still a problem when tides are present in the data. The method has been applied to mesospheric Rayle high-scalier lidar temperature data taken at the Utah State University Atmospheric Lidar Observatory (ALO). This analysis is greatly enhanced by the length and completeness of the data set available through ALO, especially with regard to the identification of planetary waves. …

Diode Laser Microwave Induced Plasma Cavity Ringdown Spectrometer: Performance And Perspective, Chuji Wang, Sudip P. Koirala, Susan T. Scherrer, Yixiang Duan, Christopher B. Winstead

Faculty Publications

Recent studies combining an atmospheric-pressure plasma source (inductively coupled plasma or microwave induced plasma) with cavity ringdown spectroscopy (plasma-CRDS) have indicated significant promise for ultra-sensitive elemental measurements. Initial plasma-CRDS efforts employed an inductively coupled plasma as the atomization source and a pulsed laser system as the light source. In an effort to improve the portability and reduce the cost of the system for application purposes, we have modified our approach to include a compact microwave induced plasma and a continuous wave diode laser. A technique for controlling the coupling of the continuous wave laser to the ringdown cavity has been …

Search For Qcd-Instanton Induced Events In Eeep Inelastic Ep Scattering At Hera, S. Chekanov, M. Derrick, D. Krakauer, J. H. Loizides, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli

Faculty Publications

A search for QCD-instanton-induced events in deep inelastic ep scattering has been performed with the ZEUS detector at the HERA collider, using data corresponding to an integrated luminosity of 38 pb-1. A kinematic range defined by cuts on the photon virtuality, Q2 > 120 GeV 2, and on the Bjorken scaling variable, x > 10-3, has been investigated. The QCD-instanton induced events were modelled by the Monte Carlo generator QCDINS. A background-independent, conservative 95% confidence level upper limit for the instanton cross section of 26 pb is obtained, to be compared with the theoretically expected value of 8.9pb.

Behavior Of Coupled Automata, Reuben Gann, Jessica Venable, Eric J. Friedman, Adam S. Landsberg

WM Keck Science Faculty Papers

We study the nature of statistical correlations that develop between systems of interacting self-organized critical automata (sandpiles). Numerical and analytical findings are presented describing the emergence of "synchronization" between sandpiles and the dependency of this synchronization on factors such as variations in coupling strength, toppling rule probabilities, symmetric versus asymmetric coupling rules, and numbers of sandpiles.

Reduced Threshold Current Of A Quantum Dot Laser In A Short Period Superlattice Of Indirect-Band Gap, Greg Sun, Richard A. Soref, Jacob B. Khurgin

Physics Faculty Publications

We propose the idea of making quantum dot lasers by embedding direct-band gap quantum dots in a short period superlattice whose band gap is indirect. This technique reduces the threshold current and its temperature dependence. We show that a higher characteristic-temperature T₀ can be achieved in a quantum dot laser with indirect GaAs/AlAs superlattice barriers compared to that with direct GaAs barriers.