Physical Sciences and Mathematics Commons^™

A Comparison Of Haloe V19 With Sage Ii V6.00 Ozone Observations Using Trajectory Mapping, Gary A. Morris, James F. Gleason, James M. Russell Iii, Mark R. Schoeberl, M. Patrick Mccormick

Physics and Astronomy Faculty Publications

We apply trajectory mapping to an 8-year intercomparison of ozone observations from the Halogen Occultation Experiment (HALOE) (V19) and Stratospheric Aerosol and Gas Experiment (SAGE) II (V6.00) for the months March, May, June, September, October, and December from the period December 1991 to October 1999. Our results, which represent the most extensive such intercomparison of these two data sets to date, suggest a root-mean-square difference between the two data sets of >15% below 22 km in the tropics and of 4–12% throughout most of the rest of the stratosphere. In addition, we find a bias with HALOE ozone low relative …

Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev

Physics and Astronomy Faculty Patents

A system capable of pumping or mixing relatively warm fluids using a rotating magnetic element or bearing levitated by a cold superconducting element is disclosed. The magnetic element or bearing carries at least one impeller and is placed in a fluid vessel positioned external to the outer wall of a cryostat or other housing for the superconducting element. A separate cooling source thermally linked to the superconducting element provides the necessary cooling to create the desired superconductive effects and induce levitation in the magnetic element or bearing. The outer wall or housing defines a chamber around the cold superconducting element …

Large Force Fluctuations In A Flowing Granular Medium, Emily Longhi, Nalini Easwar, Narayanan Menon

Physics: Faculty Publications

We study fluctuations in the force at the boundary of a 2D granular flow. The forces are mainly impulsive at all flow rates. The probability distribution of impulses decays exponentially at large impulses, as do the forces in a static granular medium. At small impulses, the distribution evolves continuously with flow rate with no indication of the transition from collisional flow to intermittently jamming flows. However, the distribution of the time interval between collisions tends to a power law, P(τ)∼τ−3/2, showing a clear dynamical signature of the approach to jamming.

Comparison Of Heat Output And Microchemical Changes Of Palladium Cathodes Under Electrolysis In Acidified Light And Heavy Water, Conrado Salas Cano

Dissertations and Theses

Two experiments have been conducted to ascertain if a cell with a palladium cathode, a platinum anode, and a solution of H₂SO₄ in D₂O can produce excess heat under electrolysis compared to a similar cell with H₂O. In each experiment, two cells were connected in series with constant current. The two cells were identical except for the fact that the heavy water cell used D₂O instead of H₂O in the electrolyte. Both cells in each experiment employed Pd cathodes, Pt anodes, and H₂SO₄ in the solution. …

Asymmetries Between Strange And Antistrange Particle Production In Pion–Proton Interactions, Thomas D. Gutierrez, R. Vogt

Physics

Recent measurements of the asymmetries between Feynman x distributions of strange and antistrange hadrons in ∏−A interactions show a strong effect as a function of xn_F. We calculate strange hadron production in the context of the intrinsic model and make predictions for particle/antiparticle asymmetries in these interactions.

The Physical Conditions Within Dense Cold Clouds In Cooling Flows - Ii, Gary J. Ferland, A. C. Fabian, R. M. Johnstone

Physics and Astronomy Faculty Publications

This is a progress report on our numerical simulations of conditions in the cold cores of cooling flow condensations. The physical conditions in any non-equilibrium plasma are the result of a host of microphysical processes, many involving reactions that are research areas in themselves. We review the dominant physical processes in our previously published simulations, to clarify those issues that have caused confusion in the literature. We show that conditions in the core of an X-ray-illuminated cloud are very different from those found in molecular clouds, largely because carbon remains substantially atomic and provides powerful cooling through its far infrared …

Magnetochemical Origin For Invar Anomalies In Iron-Nickel Alloys, V. Crisan, P. Entel, H. Ebert, H. Akai, Duane D. Johnson, J. B. Staunton

Duane D. Johnson

Zero- and finite-temperature (T) first-principles calculations versus composition (c) show that magnetochemical effects lead to Invar anomalies in Fe-(Ni, Co, Pt) alloys. Chemical short- or long-range order and negative interatomic exchange interaction of electrons in antibonding majority-spin states force the face-centered-cubic lattice to compete simultaneously for a smaller volume (from antiferromagnetic tendencies) and a larger volume (from Stoner ferromagnetic tendencies). The resulting additional negative lattice anharmonicity is very large for Fe-(Ni, Co) while absent for Fe-Pt. Our results explain the T- and c-dependent behavior of Invar properties, including the lattice softening and thermal expansion of Fe-Ni. In addition, the occurrence …

A Problematic Set Of Two-Loop Self-Energy Corrections, Ulrich D. Jentschura, Jorg Evers, Christoph H. Keitel, Krzysztof Pachucki

Physics Faculty Research & Creative Works

We investigate a specific set of two-loop self-energy corrections involving squared decay rates and point out that their interpretation is highly problematic. The corrections cannot be interpreted as radiative energy shifts in the usual sense. Some of the problematic corrections find a natural interpretation as radiative nonresonant corrections to the natural line shape. They cannot uniquely be associated with one and only one atomic level. While the problematic corrections are rather tiny when expressed in units of frequency (a few hertz for hydrogenic P levels) and do not affect the reliability of quantum electrodynamics at the current level of experimental …

Coincident Fragment Detection In Strong Field Photoionization And Dissociation Of H₂, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner, Robert Moshammer, Alexander Dorn, Claus Dieter Schroter, Daniel Fischer, Jose R. Crespo Lopez-Urrutia, Paul B. Neumayer, J. Deipenwisch, C. Hohr, Bernold Feuerstein, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

An investigation of the correlated electronic and nuclear motion in fragmentation of H₂ in 4 x 10¹⁴ W/cm², fs laser pulses at 795 nm was presented using the electron-ion momentum spectroscopy. The channel selective electron energy distribution indicated assumption of a new H₂ ionization mechanism to interpret the differences found in the fragmentation channels. The results showed that the momentum distribution of H⁺ ions in the dissociation channels H(1s) + H⁺ + e^- and 2H⁺ + 2e^- was independent of the kinetic energy of photoelectrons.

Electric-Field-Induced Relativistic Larmor-Frequency Reduction, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

Using the numerical solution to the time-dependent Dirac equation we show that the effect of relativity on the usual Larmor period for an electron in a magnetic field can be enhanced drastically if a suitably scaled and aligned static electric field is added to the interaction. This electric field does not change the electron's speed but leads to an elliptical spin precession due to relativity. This spin precession is accompanied by a position-dependent spin distribution.

Search For New Physics In Photon-Lepton Events In Pp̅ Collisions At √S =1.8 1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present the results of a search in pp̅ collisions at √s =1.8 TeV for anomalous production of events containing a photon with large transverse energy and a lepton (e or m) with large transverse energy, using 86 pb^-1 of data collected with the Collider Detector at Fermilab during the 1994–1995 collider run at the Fermilab Tevatron. The presence of large missing transverse energy (E/_T), additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large E/_T , …

Sensitivity Comparison Of Ladar Receivers Designed To Detect Glint Targets, Christopher D. Brewer, Bradley D. Duncan, Edward A. Watson

Electro-Optics and Photonics Faculty Publications

We present four receiver designs for a ladar system, based on an optical parametric amplifier, that is designed to collect returns from glint targets. After coupling the return energy into periodically poled lithium niobate, the target backscatter is detected with either an infrared camera or a CCD array. Assuming reasonable detector and system characteristics, the sensitivity of each design is then evaluated by setting the receiver SNR detection threshold equal to one and using the minimum transmitted energy as the figure of merit. Through numerical analysis, we show that an upconversion receiver followed by a visible CCD array offers the …

Non-Dipolar Electron Angular Distributions From Fixed-In-Space Molecules, Renaud Guillemin, Oliver Hemmers, Dennis W. Lindle, E. Shigemasa, K. Le Guen, D. Ceolin, C. Miron, N. Leclercq, P. Morin, Marc Simon, P. W. Langhoff

Environmental Studies Faculty Publications

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N₂. Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.

Phase I: Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Randy Clarksean, Darrell Pepper

Fuels Campaign (TRP)

The proposed research would be conducted in 3 phases. Each of the phases would be carried out over a one-year period. Phase I includes model development, analysis, and the selection of a new casting furnace design. The work discussed in this report was completed as Phase I. Phase II of the program will lead to more modeling and validation to evaluate the proposed furnace concept. Phase III would be a joint effort between UNLV and Argonne National Laboratory (ANL) to demonstrate the acceptable use of the new furnace in a simulated remote environment.

The Phase III work would include the …

Longitudinal Ionosphericeffects In The South Atlantic Sector During Solar Maximum, E. R. De Paula, J. R. Souza, Bela G. Fejer, G. J. Bailey, R. A. Heelis

Bela G. Fejer

[1] Large-scale horizontal gradients in ion density and vertical drift observed by the Atmospheric Explorer E satellite in the South Atlantic region (latitudes 10°S–20°S, longitudes 50°W–10°E) during the June solstice at solar maximum are presented and analyzed. These features occur during the nighttime period. The observations near 450-km altitude show vertically downward ion drift velocities exceeding 120 m s−1 and depleted regions where the ion density is around 2 × 104 cm−3. It is shown, using values modeled by the Sheffield University Plasmasphere Ionosphere Model (SUPIM) along the satellite trajectory, that the large ion density depletions appear as a result …

Reflection-High Energy Electron Diffraction Study Of Si(100) Homoepitaxy By Femtosecond Pulsed Laser Deposition, Mohammed S. Hegazy

Electrical & Computer Engineering Theses & Dissertations

The dynamics of femtosecond pulsed laser deposition (fsPLD) of Si(!00)-1 x I and Si(!00)-2x I homoepitaxy are studied by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). The effects of substrate temperature, laser fluence and the pressure of a passive gas on the Si(!00)-1 x I growth mode are discussed. It is shown that films grow following the Volmer-Weber (3D) growth mode. The substrate temperature largely affects the morphology of the grown film. Below ~ 400 °C (at laser fluence of~ 1.9 J/cm²), randomly oriented 3D clusters are grown. This is shown …

Exclusive Photoproduction Of J/Ψ Mesons At Hera, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, 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, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi

Faculty Publications

The exclusive photoproduction of J/ψ mesons, γp → J/ψp, has been studied in ep collisions with the ZEUS detector at HERA, in the kinematic range 20 < W < 290 GeV, where W is the photon-proton centre-of-mass energy. The J/ψ mesons were reconstructed in the ninon and the electron decay channels using integrated luminosities of 38 pb-1 and 55 pb-1, respectively. The helicity structure of J/ψ production shows that the hypothesis of s-channel helicity conservation is satisfied within two standard deviations. The total cross section and the differential cross-section dσ/dt, where t is the squared four-momentum transfer at the proton vertex, are presented as a function of W, for |t| < 18 Ge2. The t distribution exhibits an exponential shape with a slope parameter increasing logarithmically with W with a value b = 4.15 ± 0.05(stat.)-0.18+0.30(syst.) GeV-2 at W = 90 GeV. The effective parameters of the Pomeron trajectory are αℙ(0) = 1.200 ± 0.009(stat.) -0.010+0.004(Syst.) and α′ℙ = 0.115 ± 0.018(stat.)-0.015+0.008(syst.) GeV-2.

In-Situ X-Ray-Absorption Spectroscopy Study Of Hydrogen Absorption By Nickel-Magnesium Thin Films, B. Farangis, Ponnusamy Nachimuthu, T. J. Richardson, J. L. Slack, Rupert C. Perera, Eric M. Gullikson, Dennis W. Lindle, M. Rubin

Chemistry and Biochemistry Faculty Research

Structural and electronic properties of co-sputtered Ni-Mg thin films with varying Ni to Mg ratio were studied by in-situ x-ray absorption spectroscopy in the Ni L-edge and Mg K-edge regions. Co-deposition of the metals led to increased disorder and decreased coordination around Ni and Mg compared to pure metal films. Exposure of the metallic films to hydrogen resulted in formation of hydrides and increased disorder. The presence of hydrogen as a near neighbor around Mg caused a drastic reduction in the intensities of multiple scattering resonances at higher energies. The optical switching behavior and changes in the x-ray spectra varied …

Efficient And Accurate Computation Of Non-Negative Anisotropic Group Scattering Cross Sections For Discrete Ordinates And Monte Carlo Radiation Transport, David W. Gerts

Theses and Dissertations

A new method for approximating anisotropic, multi-group scatter cross sections for use in discretized and Monte Carlo multi-group neutron transport is presented. The new method eliminates unphysical artifacts such as negative group scatter cross sections and falsely positive cross sections. Additionally, when combined with the discrete elements angular quadrature method, the new cross sections eliminate the lack of angular support in the discrete ordinates quadrature method. The new method generates piecewise-average group-to-group scatter cross sections. The accuracy and efficiency for calculating the discrete elements cross sections has improved by many orders of magnitude compared to DelGrande and Mathews previous implementation. …

Vibrational Modes Of Thin Oblate Clouds Of Charge, Thomas G. Jenkins, Ross L. Spencer

Faculty Publications

A numerical method is presented for finding the eigenfunctions (normal modes) and mode frequencies of azimuthally symmetric non-neutral plasmas confined in a Penning trap whose axial thickness is much smaller than their radial size. The plasma may be approximated as a charged disk in this limit; the normal modes and frequencies can be found if the surface charge density profile sigma(r) of the disk and the trap bounce frequency profile wz(r) are known. The dependence of the eigenfunctions and equilibrium plasma shapes on nonideal components of the confining Penning trap fields is discussed. The results of the calculation are compared …

Development Of An Efficient Ti:Sapphire Laser Transmitter For Atmospheric Ozone Lidar Measurements, Khaled A. Elsayed

Electrical & Computer Engineering Theses & Dissertations

The impetus of this work was to develop an all solid-state Ti:sapphire laser transmitter to replace the current dye lasers that could provide a potentially compact, robust, and highly reliable laser transmitter for differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 nm and 900 nm, with M² of 1.3, have been experimentally demonstrated and compared to model results. The Ti:sapphire lasers have shown the required output beam quality at maximum output pulse energy, 115 mJ at 867 nm and …

Improved W Boson Mass Measurement With The Dø Detector, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We have measured the W boson mass using the DØ detector and a data sample of 82 pb^-1 from the Fermilab Tevatron collider. This measurement uses W→eν decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such “edge” electrons have not been used in any previous DØ analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous DØ W boson mass …

Electron Correlation In Double Ionization Of Excited Helium By Fast Ion Impact, L. G. Gerchikov, S. A. Sheinerman, Michael Schulz, R. Moshammer, J. Ullrich

Physics Faculty Research & Creative Works

The correlation function between two emitted electrons has been calculated as a function of their momentum difference for double ionization of 1s2s excited He atoms by fast ion impact. A simple quantum mechanical approach is developed to take into account the dynamics of two-electron ejection as well as the effects of electron exchange and correlated electron motion in the final state. A clear difference between the correlation functions of the excited and ground state targets is reported.

Infrared Spectroscopy Of Aniline–Ne Clusters And The Corresponding Cluster Cations In The Nh2-Stretching Vibration Region, Naveed Piracha, T. Nakanaga

Naveed K. Piracha

The vibrational spectra of the NH2-stretching modes of aniline–Ne and aniline–Ne+ have been measured using infrared depletion spectroscopy and REMPI–TOF mass spectrometry. In the NH2-stretching vibration region of the aniline–Ne clusters, two absorption bands at 3422 and 3508cm−1 were observed. The frequency shifts from the monomer was found to be negligibly small. As for the aniline–Ne+ cluster cations, the observed frequencies of the vibrational modes were 3394 and 3488cm−1. These values agreed with ones observed for aniline–Ar+ cluster within the error limit. This fact suggests that the effect of neon to aniline in forming the cluster is not significant in …

Gev Electrons From Ultraintense Laser Interaction With Highly Charged Ions, S.X. Hu, Anthony F. Starace

Anthony F. Starace Publications

Ultraintense laser interactions with highly charged ions are investigated using three-dimensional Monte Carlo simulations. Results show that ultraenergetic GeV electrons may be produced for highly charged ions chosen so that their electrons remain bound during the rise time of the laser pulse, and so that the electrons are ionized when the laser is near its maximum amplitude, which satisfies the best injection condition for subsequent laser acceleration.

Electrical Characterization Of Gel Collected From Shark Electrosensors, Brandon R. Brown

Physics and Astronomy

To investigate the physical mechanism of the electric sense, we present an intial electrical characterization of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranchs (sharks, skates, and rays). We have collected samples of this gel, postmortem, from three shark species, and removed the majority of dissolved salts in one sample via dialysis. Here we present the results of dc conductivity measurements, low-frequency impedance spectroscopy, and electrophoresis. Electrophoresis shows a range of large protein-based molecules fitting the expectations of glycoproteins, but the gels of different species exhibit litttle similarity. The electrophoresis signature is unaffected by thermal cycling and …

Band Filling And Depletion Through The Doping Of Polyaniline Thin Films, B. Xu, Jaewu Choi, A. N. Caruso, Peter A. Dowben

Peter Dowben Publications

The position of the molecular orbitals of polyaniline, relative to the Fermi level, shifts with the doping of polyaniline by both charge donor and charge acceptor species. Sodium as an electron donor, when added to the polyaniline system, results in an increase in electron population in the polyaniline bands but a decrease in density of states near E_F . This is evident from the consistent shifts toward the greater binding energy of the occupied as well as unoccupied molecular orbitals, the valence bands and conduction band edges and characteristic core levels. In the case of iodine doping, an electron …

Piezoresponse Force Microscopy For Polarity Imaging Of Gan, B.J. Rodriguez, Alexei Gruverman, A. I. Kingon, R. J. Nemanich

Alexei Gruverman Publications

The polarity distribution of GaN based lateral polarity heterostructures is investigated by piezoresponse force microscopy (PFM). Simultaneous imaging of surface morphology, as well as the phase and magnitude of the piezoelectric response, is performed by PFM on a GaN film with patterned polarities on a c-Al₂O₃ substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution.

Polarization Jet Events And Excitation Of Weak Sar Arcs, S. Sazykin, Bela G. Fejer, Y. I. Galperin, S. A. Grigoriev, L. V. Zinin, M. Mendillo

Bela G. Fejer

[1] Polarization Jet (PJ), also known as Sub-Auroral Ion Drift (SAID), events are supersonic westward plasma drifts on the equatorward edge of the diffuse aurora in the evening and nighttime sector. Their optical F-region signatures are weak 630.0 nm red arcs colocated with regions of fast convection. These weak arcs resemble Stable Auroral Red (SAR) arcs observed during the recovery phase of magnetic storms, but have lower intensities, shorter lifetimes, and occur without a significant heat flux from the magnetosphere. Previous model studies underestimated the brightness of weak SAR arcs. We present calculations showing that ion-neutral collisional heating and ion …

Chemical Bonds Broken In Latent Tracks Of Light Ions In Plastic Track Detectors, R. Barillon, M. Fromm, Robert Katz, A. Chambaudet

Robert Katz Publications

When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear track detectors, this latent track can be specifically etched by an appropriate chemical solution. This enlargement process is due to a higher etch velocity (V_T) along the ion's path than in the non-damaged part of the detector. The etched track velocity is definitely linked to the damage created by the incoming ion in the detector material. A relationship between the physical parameters of the energy deposition and the variation in this etched track velocity with the ion energy cannot easily …