Digital Commons Network^™

Anaerobic Magnetite Production By A Marine, Magnetotactic Bacterium, Dennis A. Bazylinski, Richard B. Frankel, Holger W. Jannasch

Physics

Bacterial production of magnetite represents a significant contribution to the natural remanent magnetism of deep-sea and other sediments1–5. Because cells of the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum require molecular oxygen for growth and magnetite synthesis6, production of magnetite by magnetotactic bacteria has been considered to occur only in surficial aerobic sediments7. Moreover, it has been suggested that deposits of single-domain magnetite crystals are palaeooxygen indicators presumably having been formed under predominantly microaerobic conditions5–8. In contrast, some nonmagnetotactic, dissimilatory iron-reducing bacteria, such as the recently described strain GS-15 by Lovley et al. 7, synthesize extracellular magnetite from hydrous ferric oxide under …

Extrema Of The Magnitude And The Phase Of A Complex Function Of A Real Variable: Application To Attenuated Internal Reflection, R. M.A. Azzam

Electrical Engineering Faculty Publications

Given a complex function F(ω) = |F(ω)|exp[jΔ(ω)] of a real argument ω, the extrema of its magnitude |F(ω)| and its phase Δ(ω), as functions of ω, are determined simultaneously by finding the roots of one common equation, Im[G(ω)] = 0, where G= (F′/F)² and F′ = ∂F/∂ω. The extrema of |F| and Δ are associated with Re G < 0 and Re G > 0, respectively. This easy-to-prove theorem has a wide range of applications in physical optics. We consider attenuated internal reflection (AIR) as …

Simulation Of The Polarizable-Ion Dynamics Of Rb2Zncl4, P. J. Edwardson, John R. Hardy

John R. Hardy Papers

The promotion yet prevention of structural stability in the paraelectric phase of Rb₂ZnCl₄ by ionic polarizability is explored with both constant-lattice and variable-lattice simulations. As many as 168 ions ( 3 x 1 x 2 cells) under periodic boundary constraints are allowed to polarize in nonlinear response to forces which are obtained from the electron-gas model of Gordon and Kim. No assumption about the rigidity of the ZnCl₄^2- ion is made. The cause of polarization catastrophe in linear models is examined, and a cure is implemented via nonlinearity of the dipole moment versus field strength. …

Recoil Corrected Continuum Shell Model Form Factor Calculations For 4He(E,E’)4He(0+), Jiang Yu

Masters Theses

Charge form factor calculations for the electroexcitation of the ⁴He, 0⁺ state have been performed within the context of the recoil corrected continuum shell model. A pure Os⁴ ground state structure is assumed and full internal coordinate recoil corrections are made. The result is compared with available data. It is demonstrated that the 0+ state may be described in a 1p -1h shell model context. Inclusion of nsOs^-1 ground state correlations is suggested for further research.

The Effects Of Low Doses (1 To 500 Kilograys) Of 100-Kev Electrons On Four Polymers, Cynthia Anne Bradbury

Physics Theses & Dissertations

Commercial films of polyetherimide (PEI), polyetheretherimide (PEEI), polyethylene terephthalate (PET), and polycarbonate (PC) were exposed in vacuum to l 00-keV electron radiation to total absorbed doses of l, l 0, l 00, 300, and 500 kilograys. The concentration of radiation-generated radicals, as measured by electron paramagnetic resonance (EPR), increased by over an order of magnitude in all four polymers. Correspondingly, the intensity of the infrared absorption peaks increased uniformly for all doses. Solubility tests resulted in decreased solubility in all polymers. IR, EPR, and solubility suggest dehydrogenation of the aliphatic C-H and phenyl C-H sites. The data indicated that cross …

30th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 30th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, July 31 - August 5, 1988.

Variational Calculation Of Multiphoton Ionization Processes For The H Atom, Bo Gao, Anthony F. Starace

Anthony F. Starace Publications

Well-known variational principles for second-order perturbation matrix elements are extended to higher-order multiphoton processes for atomic hydrogen. Numerical applications to two- and three-photon ionization of the hydrogen ground state provide results comparable to those of analytic calculations, even near intermedaite-state resonances, yet without the complications involved in summation over intermediate states. Extensions to multiphoton processes for many-electron atoms are discussed briefly.

Erratum: Micellar-Shape Anisometry Near Isotropic–Liquid-Crystal Phase Transitions, Foek T. Hioe

Physics Faculty/Staff Publications

In lieu of an abstract, below is the first paragraph:

In our paper the binary sodium dodecyl (lauryl) sulfate (SLS)–water system was investigated by small-angle x-ray scattering in the isotropic (I) phase up to the I-hexagonal (H_a) transition and the ternary system (with decanol added to a binary system containing 26 wt% of SLS in water) up to what was considered to be an I-nematic cylindrical (N_c) phase transition. Our paper did not focus on the phase diagram of the studied system but rather on the detailed modeling of the …

Magnetic Properties Of Tunicate Blood Cells. I. Ascidia Nigra, Seunghee Lee, Kenneth Kustin, William E. Robinson, Richard B. Frankel, K. Spartalian

Physics

The magnetic properties of intact and freeze-dried blood cells of the tunicate Ascidia nigra and of model vanadium(III) and (IV) compounds as polycrystalline solids and in aqueous solution have been measured up to 50 kOe with a SQUID susceptometer. Corrections for the samples' diamagnetism were extracted from the temperature dependence of the data without any further assumptions. For vanadium(IV), measured values of the magnetic moment at different values of the applied magnetic field over the temperature range 2–100 K obey a Brillouin function with spin 1/2. For vanadium(III), the magnetic moment data did not obey a Brillouin function and were …

High-Pressure Neutron-Scattering Studies Of Graphite And Stage-Two Graphite-Sbcl₅, B. Alzyam, Clive H. Perry, C. Zahopoulos, Oran Allan Pringle, Robert M. Nicklow

Physics Faculty Research & Creative Works

The longitudinal-acoustic (LA) phonons propagating along the c axis in highly oriented pyrolytic graphite (HOPG) were investigated as a function of pressure up to 20 kbar using inelastic-neutron-scattering techniques. The phonon frequencies varied as (P,q)=A(P)sin[c(P)q/2], where A(P) and c(P) indicate the pressure dependences of the zone-center LO frequency of B_1g1 symmetry and of the c-axis lattice spacing, respectively. From the measurements, the mode Grüneisen parameter for the LA branch was estimated to be 1.5 x 10^-2 kbar^-1 (independent of q); the elastic constant C₃₃ for HOPG was found to be 3.40 x 10¹¹ dyn/cm …

Dynamics Of Antimatter-Atom Collisions, R. E. Olson, Timothy J. Gay

Timothy J. Gay Publications

Classical-trajectory Monte Carlo calculations have been used to study ionizing collisions between charged particles (p, p̅ , ℯ⁺, ℯ^-) and He atoms at an incident velocity of 2.83 a.u. While differences in the total single-ionization cross sections for these projectiles are small, our calculations reveal large effects at all angles in the ionized electron spectra, and provide qualitative evidence for a Barkas effect in p and p̅ collisions. Experimental data agree well with our fully classical calculations, including cross sections involving ejected electrons of long wavelength.

Magnetic Properties Of Magnetotactic Bacteria, B. M. Moskowitz, Richard B. Frankel, P. J. Flanders, R. P. Blakemore, Brian B. Schwartz

Physics

This paper reports on the magnetic properties of magnetosomes in the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum. The magnetosomes are well crystallized particles of magnetite with dimensions of 40 to 50 nm, which are arranged within the cells in a single linear chain and are within the single-magnetic-domain (SD) size range for magnetite. A variety of magnetic properties have been measured for two samples of dispersions of freeze-dried cells consisting of (1) whole cells (M-1) and (2) magnetosomes chains separated from cells (M-2). An important result is that the acquisition and demagnetization of various type of remanent magnetizations are markedly …

Calculations Of Three-Dimensional Transonic Flows Using The Implicit Formulation Of The Isenthalpic Euler Equations With Flux Vector Splitting, Frank E. Cannizzaro

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical method for solving three-dimensional transonic flows using the isenthalpic formulation of the Euler equations is developed. The method uses van Leer's flux vector splitting to solve the implicit formulation of the governing equations, which are applied to a cell centered finite-volume scheme. A three factor spatial approximate factorization is implemented in solving the implicit part of the governing equations. Time marching to a steady state solution requires short computational times due to the relative efficiency of the basic method. Computational times are further reduced by the implementation of the multigrid acceleration technique, which provided converged solutions in approximately …

Theory Of Alpha-Nucleus Collisions At High Energies, Francis A. Cucinotta

Physics Theses & Dissertations

The interaction of high energy alpha particles with atomic nuclei is considered using multiple scattering theories. Semi-classical solutions to coupled-channel equations derived from Watson's form of the nucleus-nucleus multiple scattering series are shown to be equivalent to the Glauber multiple scattering series. Second-order solutions for the elastic amplitude are developed and used to study the effects of short-range correlations in nuclear scattering. The Jastrow method is used to model the two-particle density for ⁴He and to construct one and two particle form factors. Excellent agreement with experimental data for angular distributions, and total and reaction cross sections is found. …

Three-State Systems Driven By Resonant Optical Pulses Of Different Shapes, C. E. Carroll, Foek T. Hioe

Physics Faculty/Staff Publications

New analytic solutions to the problem of a three-state system driven simultaneously by resonant optical pulses of different shapes are presented. The solutions are useful for prescribing the conditions for complete population transfer from one state to another or for complete population return.

Formation Of Ground And Excited States Of Antihydrogen, Sultana N. Nahar, J M. Wadehra

Physics and Astronomy Faculty Research Publications

Differential and integrated cross sections for the formation of antihydrogen by the impact of intermediate-energy (20–500 keV) antiprotons on positronium are calculated using the first Born approximation. The calculations are carried out for the formation of antihydrogen in ground and various excited electronic states (n=1–3) when positronium, the target atom, is in the ground state, and for the formation of antihydrogen in the ground state when the positronium is in various excited electronic states (n=1–2). The 1/n^3 behavior for the capture cross sections is used to calculate the total (that is, all states added together) integrated cross sections. The cross …

The Relationship Of Pore Volume And Pore Size Distribution To The Development Of Gloss And Scattering Coefficient, John A. Cook

Masters Theses

This study describes in a quantitative manner the relationships between coating structure and optical properties. Gloss, scattering coefficient and void volume were measured after applying different blends of polystyrene spheres to mylar film. Each coating was modeled using large spherical particles of the same size ratios to measure pore size distribution. The coating structure followed well with theoretical packing characteristics of spheres. Optical properties were related to changes in coating structure. Scattering coefficient and gloss correlated better with pore size distribution than particle size. Gloss increased when total void volume was reduced, while the scattering coefficient decreased.

Incommensurate Superlattice And 90° Twist Boundaries In The Superconducting Phase Of Bi-Sr-Ca-Cu-O, C.H. Chen, D.J. Werder, Sy_Hwang Liou, H.S. Chen, M. Hong

Sy-Hwang Liou Publications

We have observed an incommensurate superlattice structure in the Bi-Sr-Ca-Cu-O system using electron diffraction. The wave vector of the superlattice, q=(0,1/4.7,1), has an incommensurate component along the b axis and a commensurate component along the c axis. Twist boundaries perpendicular to the c axis, across which the crystallographic a and b axes are rotated 90°, are commonly observed in this system.

Single-Electron Capture And Loss Cross Sections Vs. Target Z For 1 Mev/U Oxygen Ions Incident On Gases, Scott Avery Boman

Masters Theses

Cross sections for 1 MeV/u oxygen projectile ions which have gained or lost an electron after passing through a gas target were measured as a function of target Z for several incident projectile charge states. The targets used were D_2, He, Ne, Ar and Kr, and the projectiles had charges of 5+, 6+, 7+ and 8+.

The electron capture measurements are generally in reasonable agreement with existing theoretical and empirical scaling rules. The electron loss cross sections differ appreciably from predictions of the PWBA, particularly for the heaviest targets studied. Empirical scaling relationships are derived for the present capture …

Electronic Excitations Of The Yba2Cu3O7-X Superconductor: A Study By Transmission Electron-Energy-Loss Spectroscopy With An Electron Microprobe, C.H. Chen, L.F. Schneemeyer, Sy_Hwang Liou, M. Hong, J. Kwo, H.S. Chen, J.V. Waszczak

Sy-Hwang Liou Publications

Interband and core-level transitions and plasmon resonance in the high-temperature oxide superconductor YBa₂Cu₃O_7-x were studied by transmission electron-energy-loss spectroscopy using an electron microprobe ∼5-10 Å in size. Both single-crystal and polycrystalline ceramic samples have been examined. No significant change in electronic structure was observed at the grain boundaries. A 13.5-eV interband-transition peak was found to be sensitive to damages created by ion-beam bombardment.

Ferroelectric Nematic Liquid Crystals: Realizability And Molecular Constraints, Rolfe G. Petschek

Faculty Scholarship

There is no fundamental reason that fluids should not be ferroelectric. However, the only knownferroelectric fluids are chiral smectic-C liquid crystals and related structures. We examine the possibility that molecules with permanent dipole moments can form a ferroelectric nematic phase, the least ordered conceivable ferroelectric phase. We show that reasonable electric dipole interactions between diskshaped molecules may lead to such a phase, and calculate the phase diagram using mean-field theory. Some constraints on the constituent molecules are discussed.

Thermodynamics Analysis Of Refrigeration, Joe Lam

Undergraduate Honors Capstone Projects

In this term paper, I will look indepth at refrigeration. Refrigeration is a rather long and complex topic. Therefore, I will only discuss it as detail as conditions permit. As for the parts where minute details required, I will refer you to the selected references. In discussing refrigeration, I will first look at the Carnot cycle as a fundamental issue for refrigeration.

Possible Origins Of High-Tc, Superconductivity, John R. Hardy, John W. Flocken

Physics Faculty Publications

A new mechanism is proposed to explain high-T, superconductivity in copper-oxide-based, open perovskitelike systems. It is shown that, should the oxygen ions be moving in a double-well potential, an order-of-magnitude enhancement of the electron-lattice coupling follows automatically from a consistent treatment of this motion. Both theoretical and experimental evidence for the presence of such double wells is cited.

Possible Origins Of High-TC, Superconductivity, John R. Hardy, J. W. Flocken

John R. Hardy Papers

A new mechanism is proposed to explain high-T_c superconductivity in copper-oxide-based, open perovskitelike systems. It is shown that, should the oxygen ions be moving in a double-well potential, an order-of-magnitude enhancement of the electron-lattice coupling follows automatically from a consistent treatment of this motion. Both theoretical and experimental evidence for the presence of such double wells is cited.

Y-Ba-Cu-O Films By Rf Magnetron Sputtering Using Single Composite Targets: Superconducting And Structural Properties, Sy_Hwang Liou, M. Hong, J. Kwo, B.A. Davidson, H.S. Chen, S. Nakahara, T. Boone, R.J. Felder

Sy-Hwang Liou Publications

High T_c superconducting Y-Ba-Cu-O films have been produced by rf magnetron sputtering using single unreacted composite targets of Y₂O₃, BaF₂, and CuO powders. Transport measurements of the films showed a sharp resistive T_c (R=0) at 89 K and a metallic behavior of resistivity versus temperature. The films show preferred orientations when deposited on single-crystal SrTiO₃ substrates (100) or (110) and followed by a post O₂ annealing at 825 °C.

Experimental Study Of Nonlinear Conductance In Small Metallic Samples, Richard A. Webb, S. Washburn, C. P. Umbach

Faculty Publications

We have directly observed current-dependent, nonlinear contributions to the conductance fluctuations of phase-coherent metallic wires and loops. The fluctuations in the current-voltage curves are reproducible, asymmetric about I=0, and in qualitative agreement with theoretical predictions. In ac measurements, the nonlinear terms also generate large harmonic signals of the conductance fluctuations whose dependence on the drive current can be understood qualitatively. The spectra of harmonics from loops and wires have different dependences on the voltage across the sample.

Modulated Phases In Thin Ferroelectric Liquid-Crystal Films, George A. Hinshaw Jr., Rolfe G. Petschek

Faculty Scholarship

We discuss modulated phases that can occur in thin liquid-crystal films composed of tilted, chiral molecules. While the phase diagram depends on all orders of a Landau expansion we find that either a striped phase of parallel defect walls or a lattice of hexagonal unit cells containing disclinations and bounded by intersecting walls can occur. The striped phase can occur with either a positive or negative bend elastic constant depending on the underlying microscopic parameters. The transition into the modulated phase is, in general, continuous with infinite defect separation at the transition.

Projectile-Charge Dependence Of Ejected-Electron Spectra, V. D. Irby, Timothy J. Gay, J. Wm. Edwards, E. B. Hale, M. L. Mckenzie, R. E. Olson

Timothy J. Gay Publications

We have studied H⁺+He and ³He⁺⁺+He ionizing collisions at intermediate energies (60 to 120 keV/amu) and have observed a significant shift in the velocity position of the maxima in forward-ejected electron spectra when changing projectiles from protons to α particles. In ionizing collisions, a large portion of the ejected electrons are stranded near the transitory equiforce, or saddle point, position between the target ion and receding projectile. The shift in the electron spectra maxima to smaller velocities, due to changing projectiles from protons to α particles, is consistent with the shift in the saddle-point velocity …

Hylleraas Variational Perturbation Theory: Application To Correlation Problems In Molecular Systems, Robert J. Cave, Ernest R. Davidson

All HMC Faculty Publications and Research

Hylleraas variational perturbation theory is applied through second order in energy to estimate the correlation energy in several molecular systems. The specific choices for H₀ and V which are made lead to equations nearly identical to the multireference linearized coupled‐cluster method of Laidig and Bartlett. The results obtained are in virtually exact agreement where comparisons have been made. Results from test calculations are presented for BeH₂, CH₂, and C₂H₄. In addition, the utility of perturbation theory for selecting correlating configurations is examined. This procedure is found to be quite accurate while …

Cayley-Tree Ising Model With Antiferromagnetic Nearest-Neighbor And Ferromagnetic Equivalent-Neighbor Interactions, Miron Kaufman, M. Kahana

Physics Faculty Publications

The phase diagram of the Ising model with antiferromagnetic nearest-neighbor interactions and ferromagnetic equivalent-neighbor interactions on the Cayley tree is determined exactly. A nonuniversal critical line separates the disordered and the ordered phases. A line of first-order transitions separating ferromagnetic order from antiferromagnetic order ends in the midst of the ordered phase at a classical ordered critical point. For a small range of values of the ratio of the two couplings, two transitions occur as the temperature is varied. In this case the uniform magnetization is not a monotonic function of the temperature.