Digital Commons Network^™

Study Of The Effects Of Initial-Bred Nuclei On Zeolite Naa Crystallization By Quasi-Elastic Light Scattering Spectroscopy And Electron Microscopy, Leszek Gora, Kiril A. Streletzky, Robert W. Thompson, George D.J. Phillies

Physics Faculty Publications

Synthesis studies have been conducted at 25, 60, and 80 °C with a clear solution batch composition that produces zeolite NaA. Aluminosilicate precursor material was added to promote the synthesis and to evaluate the effects of adding initial-bred nuclei that were created by a precursor “seed” reaction. It is shown that the initial-bred nuclei promoted the crystallization rate, that the crystalline mass produced was increased when using the initial-bred nuclei, and that the nucleation of a second population was not inhibited by the addition of initial-bred nuclei as seeds.

Nonlinear Front Evolution Of Hydrodynamic Chemical Waves In Vertical Cylinders, J. W. Wilder, D. A. Vasquez, Boyd F. Edwards

All Physics Faculty Publications

The nonlinear stability of three-dimensional reaction-diffusion fronts in vertical cylinders is considered using the viscous hydrodynamic fluid equations in the limit of infinite thermal diffusivity. A nonlinear front evolution equation is presented and used to examine the transition from nonaxisymmetric to axisymmetric convection observed in experiments performed in cylinders. Comparisons with experiments show excellent agreement in both the shape and speed of the front.

High Quality Interfaces In Gaas-Alas Quantum Wells Determined From High Resolution Photoluminescence, D. C. Reynolds, David C. Look, B. Jogai, R. Kaspi, K. R. Evans, M. Estes

Physics Faculty Publications

No abstract provided.

Defect Donor And Acceptor In Gan, David C. Look, D. C. Reynolds, Joseph W. Hemsky, J. R. Sizelove, R. L. Jones, Richard J. Molnar

Physics Faculty Publications

No abstract provided.

Lamb Shift Of 3p And 4p States And The Determination Of Α, Ulrich D. Jentschura, Gerhard Soff, Peter J. Mohr

Physics Faculty Research & Creative Works

The fine-structure interval of P states in hydrogenlike systems can be determined theoretically with high precision, because the energy levels of P states are only slightly influenced by the structure of the nucleus. Therefore a measurement of the fine structure may serve as an excellent test of QED in bound systems, or alternatively as a means of determining the fine-structure constant a with very high precision. In this paper an improved analytic calculation of higher-order binding corrections to the one-loop self-energy of 3P and 4P states in hydrogenlike systems with a low nuclear charge number Z is presented. The method …

Hydrocarbon Ions In The Ionosphere Of Titan, Jane L. Fox, Roger V. Yelle

Physics Faculty Publications

We have constructed a new model of the ionosphere of Titan that includes 67 species and 626 reactions. Although N₂⁺ is the major ion produced over most of the ionosphere, the ionization flows to ions whose parent neutrals have lower ionization potentials and to ions formed from species with large proton affinities. In contrast to other models, which have predicted that HCNH⁺ should be the major ion, our calculations suggest that the major ions at and below the ion peak are hydrocarbon ions, and H, C, and N-containing ions. Our predicted peak electron density for a solar …

Ion Acceleration And Anomalous Transport In The Near Wake Of A Plasma Limiter, D. P. Sheehan, J. Bowles, R. Mcwilliams

Physics and Biophysics: Faculty Scholarship

Ion acceleration and anomalous transport were studied experimentally in the near wake region of an electrically floating disk limiter immersed in two different types of collisionless, supersonically flowing, magnetized plasmas: the first initially quiescent, the second initially turbulent. Ion densities and velocity distributions were obtained using a nonperturbing laser induced fluorescence diagnostic. Large-amplitude, low-frequency turbulence was observed at the obstacle edge and in the wake. Rapid ion and electron configuration space transport and ion velocity space transport were observed. Configuration space and velocity space transport were similar for both quiescent and turbulent plasma-obstacle systems, suggesting that plasma-obstacle effects outweigh the …

Remanence Enhancement And Exchange Coupling In Prco/Co Films, J. Ping Liu, Yi Liu, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

PrCo/Co multilayer thin films have been prepared by sputtering. After heat treatment, high coercivity is developed and the remanence is enhanced for the insertion of the CO layers and the exchange coupling between the hard phase and the soft phase, which leads to high energy products of the composite magnets. The nanostructure of the films has been studied by TEM. It is found that the grain size of the films with high energy products is in the range from 10 to 25 nanometers.

Quantum Coulomb Glass Within A Hartree-Fock Approximation, Frank Epperlein, Michael Schreiber, Thomas Vojta

Physics Faculty Research & Creative Works

We study the influence of electron-electron interactions on the electronic properties of disordered materials. In particular, we consider the insulating side of a metal-insulator transition where screening breaks down and the electron-electron interaction remains long ranged. The investigations are based on the quantum Coulomb glass, a generalization of the classical Coulomb glass model of disordered insulators. The quantum Coulomb glass is studied by decoupling the Coulomb interaction by means of a Hartree-Fock approximation and exactly diagonalizing the remaining localization problem. We investigate the behavior of the Coulomb gap in the density of states when approaching the metal-insulator transition and study …

Magnetic And Structural Properties Of Sm2Fe10Co7/MXCY Thin Films, I.A. Al-Omari, N. J. Cunningham, David J. Sellmyer

David Sellmyer Publications

The structural and magnetic properties of Sm₂Fe₁₀Co₇/M_xC_y (M=A1 and Si; x≥0 and y≥0) multilayer films with Ta underlayers and overlayers before and after annealing at 700 °C for 5-12 min have been fabricated and studied. Structural studies show evidence of layer diffusion upon annealing. X-ray diffraction shows that the samples after annealing consist of a soft phase, α -Fe, and a hard phase with the 2-17-type structure. The samples studied have in-plane anisotropy with single hysteresis loops indicating that the two phases are strongly exchange coupled. After annealing, the coercivity of …

A Football Chase On Video, Norman F. Derby, Robert Fuller, Thomas A. Summers

Robert G. Fuller Publications

At some universities, football examples are used to motivate students in physics courses to study the law of kinematics and collisions. (In fact, it has been rumored that the number of such examples is inversely related the national ranking of the local football team.) In addition, pursuit-and-evasion strategies are often introduced in beginning calculus courses as a device for teaching mathematical modeling and problem solving. Some recent papers describe theoretical strategies for pursuit-and-evasion that are appropriate for a one-on-one situation in a football game. But what do players actually do in a real football game? We decided to look into …

Symmetry, Symmetry Breaking, And The Current View Of The Dirac Monopole, Erik Kristian Leder

Dissertations and Theses

The ideas of symmetry and symmetry breaking are considered in the context of classical gauge theory. Local U(l) symmetry is developed for a complex scalar field and electromagnetism is identified as the associated gauge field. Local S0(3) theory for a triplet of real scalar fields is derived and the incorporation of additional gauge fields is demonstrated. Symmetry breaking for the S0(3) gauge theory is performed and the gauge fields are shown to acquire mass by the Higgs mechanism. The equations of the t'Hooft-Polyakov monopole are derived and compared to those of the magnetic monopole of Dirac.

High Temperature Superconducting Josephson Junctions In A Stacked Bicrystal Geometry, H.Q. Li, R.H. Ono, L.R. Vale, D.A. Rudman, Sy_Hwang Liou

Sy-Hwang Liou Publications

Bicrystal grain boundary Josephson junctions were fabricated in a stack of two layers of YBa₂Cu₃O_χ separated by epitaxial SrTiO₃. Weak link behavior was observed in the bridges formed in both layers that had similar shunted-junction characteristics but significantly different critical currents. Characteristic voltages up to 1.9 mV were measured at 4.5 K. The resonant structure was seen in the current–voltage characteristics of the upper-layer junctions, and interactions between junctions in the two layers were evident.

Observation Of The Decay DS+ → Ωπ+, R. Balest, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using e⁺e^- annihilation data collected by the CLEO II detector at CESR, we have observed the decay D_s⁺ → ωπ⁺. This final state may be produced through the annihilation decay of the i>D_s⁺, or through final state interactions. We find a branching ratio of γ(D_s⁺ → ωπ⁺)/γ(D_s⁺ →ηπ⁺) = 0.16±0.04±0.03, where the first error is statistical and the second is systematic.

Toy Model For Breaking Super Gauge Theories At The Effective Lagrangian Level, Joseph Schechter, Francesco Sannino

Physics - All Scholarship

We propose a toy model to illustrate how the effective Lagrangian for super QCD might go over to the one for ordinary QCD by a mechanism whereby the gluinos and squarks in the fundamental theory decouple below a given supersymmetry breaking scale m. The implementation of this approach involves a suitable choice of possible supersymmetry breaking terms. An amusing feature of the model is the emergence of the ordinary QCD degrees of freedom which were hidden in the auxiliary fields of the supersymmetric effective Lagrangian.

Forming B1-XCX Semiconductor Layers By Chemical Vapor Deposition, Peter A. Dowben

Peter Dowben Publications

Active semiconductor devices including heterojunction diodes and thin film transistors are formed by PECVD deposition of a boron carbide thin film on an N-type substrate. The boron to carbon ratio of the deposited material is controlled so that the film has a suitable band gap energy. Boron carbides such as B_4.7C, B_7.2C and B₁₉C have suitable band gap energies between 0.8 and 1.7 eV. The stoichiometry of the film can be selected by varying the partial pressure of precursor gases, such as nido pentaborane and methane. The precursor gas or gases are energized. e.g., …

Search For Neutrinoless Τ Decays Involving Π0 Or Η Mesons, G. Bonvicini, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for lepton flavor violating decays of the τ lepton using final states with an electron or a muon and one or two π⁰ or η mesons but no neutrinos. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.68 fb^-1. No evidence for signals was found, resulting in much improved limits on the branching fractions for the one-meson modes and the first upper limits for the two-meson modes.

Numerical Observation Of A Tubular Phase In Anisotropic Membranes, Mark Bowick, Marco Falcioni, Gudmar Thorleifsson

Physics - All Scholarship

We provide the first numerical evidence for the existence of a tubular phase, predicted by Radzihovsky and Toner (RT), for anisotropic tethered membranes without self-avoidance. Incorporating anisotropy into the bending rigidity of a simple model of a tethered membrane with free boundary conditions, we show that the model indeed has two phase transitions corresponding to the flat-to-tubular and tubular-to-crumpled transitions. For the tubular phase we measure the Flory exponent \nu_F and the roughness exponent \zet. We find \nu_F=0.305(14) and \zeta=0.895(60), which are in reasonable agreement with the theoretical predictions of RT --- \nu_F=1/4 and \zeta=1.

Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = ³/₂ Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with g_eff values of 2.20, 3.92, and …

Search For The Decays B0 → D (*)+D (*)-, D. M. Asner, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using the CLEO-II data set we have searched for the decays B⁰ → D^(*)+D^(*)-. We observe one candidate signal event for the decay B⁰ → D^*+D^*- with an expected background of 0.022 ± 0.011 events. This yield corresponds to a branching fraction of B(B⁰ → D^*+D^*-) = [5.317_-3.7^+7.1(stat) ± 1.0(syst)] x 10^-4 and an upper limit of B(B⁰ → D^*+D^*-) < 2.2 X 10^-3 at the 90% C.L. We see no significant excess of signal above …

39th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Preliminary program and registration information for the 39th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 3-7, 1997.

Magneto-Aerotaxis In Marine Coccoid Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Mark S. Johnson, Barry L. Taylor

Physics

Magnetotactic cocci swim persistently along local magnetic field lines in a preferred direction that corresponds to downward migration along geomagnetic field lines. Recently, high cell concentrations of magnetotactic cocci have been found in the water columns of chemically stratified, marine and brackish habitats, and not always in the sediments, as would be expected for persistent, downward-migrating bacteria. Here we report that cells of a pure culture of a marine magnetotactic coccus, designated strain MC-1, formed microaerophilic bands in capillary tubes and used aerotaxis to migrate to a preferred oxygen concentration in an oxygen gradient. Cells were able to swim in …

Spurious Electrons In Electron Spectrometers And Their Effect On Differential Electron Impact Ionization Cross-Section Measurements, M. Eugene Rudd

M. Eugene Rudd Publications

The effect of the nonideal response characteristics of electrostatic analyzers is described and equations are derived, which allow a calculation of the distortion that this causes in measurements of angular and energy distributions of electrons from atomic collisions, especially in electron impact. Examples are given that show how a contamination as small as 10^-5 from spurious electrons generated inside an analyzer can explain the peak seen at zero angle in some angular distribution measurements and the filling in of the minimum in the energy distributions in others.

Experimental Investigation Of Nonlinear Dynamics In Single Mode Semiconductor Laser Diodes With Phase Conjugate Feedback, Gordon T. Hengst

Theses and Dissertations

The semiconductor laser diode offers a unique system to investigate nonlinear dynamics when optical feedback is applied. Although there is extensive research of laser diodes with optical feedback from normal dielectric mirrors, very little has been done experimentally to analyze the effects of degenerate phase conjugate feedback from a BaTiO₃ crystal. This research experimentally investigated the dynamics of a single-mode laser diode with weak phase conjugate feedback using both the self-pumped and double phase conjugate geometries. The experimental results validated a mathematical model which numerically evaluates the Lang-Kobayahsi coupled differential equations. The model simulated the nonlinear behavior of a …

Magnetism In One Dimension: Fe On Cu(111), J. Shen, Ralph Skomski, M. Klaua, H. Jenniches, S. Sundar Manoharan, J. Kirschner

Ralph Skomski Publications

The magnetism and the morphology of one-dimensional Fe stripes on a Cu(111) vicinal surface with perpendicular magnetization are investigated. Scanning tunneling microscopy shows that the Fe stripes have nanometer width and are aligned in parallel along the [011] direction. From the magnetization curves it is inferred that the stripes exhibit a ferromagnetic behavior well below the nominal thickness of one monolayer. In contrast to two-dimensional films, the magnetization of the stripes is not only temperature but also time dependent. The dynamics of the stripes have been described by a micromagnetic Ising model with Glauber dynamics, yielding an effective anisotropy constant …

Simulation Of A Microdosimetry Problem: Behavior Of A Pseudorandom Series At A Low Probability, P. Meyer, J. E. Groetz, Robert Katz, M. Fromm, A. Chambaudet

Robert Katz Publications

The carcinogenic effects for low dose irradiations are not very well known. Estimations usually are made based on the effects observed at high doses that are then extrapolated to low doses. To estimate low dose effects, the ICRP (International Commission on Radiological Protection) uses a linear extrapolation matched with a dose-rate reduction factor equal to two. This proportionality of the effect and dose, even for the lowest doses and dose-rates, leads to two assumptions which must be questioned :
1. the efficiency of DNA repair in cells does not vary with the dose and the dose-rate,
2. when one single …

Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes

Dissertations and Theses

It has been proposed in the literature that a novel class of biosensors can be based on a bimolecular layer of lipids supported on one side by a metallic surface. In order to estimate the potential of this system for the design of membrane sensors, we have studied properties of a two-electrode system consisting of a teflon insulated metallic wire and a Ag/AgCl electrode, both immersed in KCl solution. The lipid bimolecular layer was formed on the metal surface of the cut teflon insulated wire. The electrical conductivity properties of such a device were studied in the frequency range 20 …

Vacuum Structure Of Two-Dimensional Gauge Theories On The Light Front, Gary Mccartor, David G. Robertson, Stephen S. Pinksy

Physics Faculty Scholarship

We discuss the problem of vacuum structure in light-front field theory in the context of (1+1)-dimensional gauge theories. We begin by reviewing the known light-front solution of the Schwinger model, highlighting the issues that are relevant for reproducing the θ structure of the vacuum. The most important of these are the need to introduce degrees of freedom initialized on two different null planes, the proper incorporation of gauge field zero modes when periodicity conditions are used to regulate the infrared, and the importance of carefully regulating singular operator products in a gauge-invariant way. We then consider SU(2) Yang-Mills theory in …

Bern Porter International: Volume 1 Number 1 (Summer, 1997), Bern Porter, Sheila Holtz, Natasha Bernstein

Newsletters

A Literary Newspaper

Featuring the Bern Porter International mission statement with an introduction to the Institute of Advanced Thinking and Porter's literary philosophy.

Resonance Feature In Al- Photodetachment Below The Al(3S24S 2S) Threshold, B.J. Davies, C.W. Ingram, D.J. Larson, Chien-Nan Liu, Anthony F. Starace

Anthony F. Starace Publications

Photodetachment of Al-(3s²3p²³ 3P) near the threshold of the first excited state of neutral aluminum has been studied both experimentally and theoretically. A 19-keV mass-resolved Al- beam was intersected by a frequency-doubled neodymium-doped yttrium aluminum garnet pumped dye-laser beam, and the fast atoms created by detachment processes were detected. Measurements just below the threshold of the first excited state, Al(3s²4s²S), find a large resonance peak in the detachment signal. An eigenchannel R-matrix calculation generates a resonance structure that is qualitatively similar to the data and identifies the large resonance …