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Magnetic Guidance Of Organisms, Richard B. Frankel

Physics

No abstract provided.

A Simple Model For Impurity Photoabsorption In Silicon, Gust Bambakidis

Physics Faculty Publications

A simple model for absorption of infrared radiation by impurity atoms in silicon crystals has been developed and applied to electronic excitations ofthe Group V donors Bi, Sb, As, and P, and the Group III acceptors B, AI, Ga, and In. The model is based on the quantum-defect method for approximating bound donor or acceptor wave functions outside the core region of the impurity. For each donor species, the relative oscillator strengths have been calculated for the transitions from the ground state to the first four excited levels. For each acceptor species, the relative oscillator strengths were calculated for transitions …

Iue Observations Of Dq Herculis And Its Nebula, And The Nature Of The Cold Nova Shells, Gary J. Ferland, R. E. Williams, D. L. Lambert, G. A. Shields, M. Slovak, P. M. Gondhalekar, J. W. Truran

Physics and Astronomy Faculty Publications

The nebula ejected in the 1934 outburst of the classical nova DQ Her is remarkable for its unprecedentedly low temperature of T_e 500 K as measured by Williams et al. (1978). In this paper, IUE observations are combined with Steward optical spectra. It is confirmed that the gas is quite cold. It is further shown that the gas is ionized by the radiation field of the central object. X-ray, ultraviolet, optical and infrared observations of the underlying binary are combined with the extreme-ultraviolet continuum deduced from the level of ionization of the nebula to obtain a composite energy …

General Formula For The Inelastic Scattering Of Relativistic Spin-½ Particles By Heavy Atoms, P.T. Leung, M. L. Rustgi, S. A. Long

Physics Faculty Publications and Presentations

A general differential-cross-section formula for the inelastic scattering of relativistic spin-½ particles by heavy atoms is derived in the Born approximation and the structure and polarization of the incident particle is incorporated. The results reduce to those of Fano (1963) and of Turner et al. (1973) in well-known limiting cases.

Low-Temperature Magnetic Properties Of Submetallic Phosphorous-Doped Silicon, C. T. Murayama, W. G. Clark, Jeff Sanny

Physics Faculty Works

Measurements of the electron-spin-resonance properties of Si:P with dopant concentration of n=2.05×10¹⁸ cm⁻³ (somewhat below the metal-insulating transition) at low temperatures (0.035 to 4.2 K) and low frequencies (11.5-58.2 MHz) are reported. They show a substantial deviation from Curie-law behavior for the susceptibility, in agreement with previous static experiments. An internal field is observed to develop as the temperature is lowered. At 35 mK, the internal field has a magnitude of 2.1 Oe and is directed opposite to the externally applied field. The buildup of the internal field is accompanied by an increase in the resonance linewidth. Both …

Energy Losses Of Solar Neutrinos And The Oscillation Hypothesis, P.T. Leung, S. Boedo, M. L. Rustgi

Physics Faculty Publications and Presentations

A formula for the stopping power of neutrinos interacting via the standard weak-interaction model, but incorporating the possibility of neutrino oscillations among the three flavors, is derived. The results are applied to study the solar-neutrino anomaly and it is found that the anomaly cannot be accounted for by many orders of magnitude from consideration of the energy losses of the neutrinos interacting with the solar matter, even if the oscillation hypothesis is found to be valid.

Isotropy Group Description Of A Phase Transition In Nano3, W. Scott Stornetta, Dorian M. Hatch

Faculty Publications

Predictions of the possible post-transition symmetries of an R 3c zone center continuous phase transition are made using recent extensions of the Landau theory. The Landau theory is summarized and direct group theoretical methods are applied to the R 3c phase. General techniques for solving systems of nonlinear polynomial equations are reviewed and these techniques are applied to the minimization of the free energy F for the aforementioned possible symmetries. The results of the direct methods and the minimization procedures are shown to be compatible. It is shown that the transition to R 3c in NaNO3 is consistent with the …

Effect Of Nickel Impurities On Charge-Density-Wave Formation In Tas3, M.H. Rashid, David J. Sellmyer, Roger D. Kirby

Roger Kirby Publications

Introduction of nickel impurities into TaS₃ has the effect of smearing the charge-density-wave transitions in TaS₃ of both orthorhombic and monoclinic phases. The orthorhombic doped crystals show non-Ohmic conductivity beyond threshold fields that are much larger than the threshold field of the pure phase, possibly due to additional pinning of the charge-density wave by nickel impurities. The charge-density-wave state is completely destroyed as 10 at % or more Ta atoms are replaced by Ni atoms and metallic behavior between 4.2 and 30 K is observed in these cases.

Critical Points In Low-Energy Positron-Atom Scattering, J. M. Wadehra, T. S. Stein, W. E. Kauppila

Physics and Astronomy Faculty Research Publications

Critical points, which represent minima in differential scattering cross sections as a function of scattering angle and incident projectile energy, are theoretically predicted for elastic scattering of low-energy positrons by Ar, Kr, and Xe. It is demonstrated that these points arise due to low-energy positron diffraction effects.

Feasibility Studies Of Conversion Electron Mössbauer Spectroscopy (Cems) Of Iron-Doped Inp, Gilbert R. Hoy, Desmond C. Cook, Edward Agyekum

Physics Faculty Publications

An electron detector for conversion electron Moessbauer spectroscopy CEMS has been designed and built. Tests have been performed to study the effects on the detector resolution with respect to high voltage, gas flow rate, and counting rate. These parameters have been optimized to detect the 7.3keV conversion electrons emitted following resonant absorption of the 14.4keV source gamma rays associated with the Moessbauer effect using Fe57. CEMS spectra have been obtained using standard Fe57 enriched and natural iron samples. CEMS spectra have also been obtained for InPFe samples supplied by the Naval Research Laboratory. So far we have only been successful …

Division-Of-Wave-Front Polarizing Beam Splitter And Half-Shade Device Using Dielectric Thin Film On Dielectric Substrate, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

Temperature-Dependent Resistivity Of Highly Disordered Ni-Cr-Al Alloys , R. Hight, C. Plough, David J. Sellmyer

David Sellmyer Publications

Measurements are reported on the electrical resistivity of highly disordered Ni-Cr-Al films between 4.2 and 300 K. X-ray diffraction measurements show the films to be crystalline with a bcc structure. Negative temperature coefficients are observed and the resistivity data above about 50 K can be fitted by the expression ρ(T)=ρ₀ [1-cln(T²+Δ²)], where Δ depends on the heat treatment of the sample.

Mixing Angles, B-Meson Life-Time In The Six-Quark Model Based On So(10) X U(1)Pq, V. Parameswaran Nair, Louis Michel, Kameshwar C. Wali

Publications and Research

We show that a recently proposed multigenerational, grand unified model with three parameters (top-quark mass and two phases of Higgs vacuum expectation values) yields results in good agreement with the most recent phenomenological limits placed on the weak mixing angles of the quarks. These limits take into account the experimental value for B-meson life-time.

Nonlinear Effects In Supercritical Quenches Of A Binary Fluid, Rolfe G. Petschek

Faculty Scholarship

We report on a study of the evolution of the structure factor S(k,t) of a binary fluid mixture near the consolute critical point after rapid quenches which kept the system in the stable, one-phase region. S(k,t) always relaxed more slowly than expected on the basis of linear response and, under certain conditions, overshot the equilibrium value. A nonlinear theory without adjustable parameters, based on the Langevin equations for order-parameter fluctuations near the critical point, agreed with the data.

The Chromospheres Of Classical Cepheids. 11. High-Resolution Profiles Of The Mg Ii H And K Lines, Edward G. Schmidt, Sidney B. Parsons

Edward Schmidt Publications

High-resolution spectra have been obtained with the long-wavelength camera of the International Ultraviolet Explorer for five Cepheids at a number of phases each. These data were used to study the profiles of the Mg _II h and k lines near 2900 Å. An emission feature often appears at the centers of the two lines. There are also central absorption features due to circumstellar or interstellar gas. They are often multiple and may or may not divide the emission into two peaks. The velocities of the circumstellar absorption components imply that they originate in a region which is at least several …

A Search For Chromospheric Emission In Tu Cassiopeiae Spectra, Arne A. Henden, Robert H. Cornett, Edward G. Schmidt

Edward Schmidt Publications

We have searched high-resolution spectra of the multimode cepheid TU Cas for evidence of chromospheric emission. Spectral regions covered include the Ca _II near-IR triplet near 8600 Å, Hα, Can_II H and K, Mg _II h and k; phase coverage in both primary and secondary modes was reasonably complete. There was no evidence for changes other than those caused by temperature variation. The observed lack of emission makes unlikely current mass loss (and resulting helium enrichment) by means of stellar winds.

An Spectrometer For Investigating The Spectral Momentum Density Of Thin Films, A. L. Ritter, John R. Dennison, J. Dunn

All Physics Faculty Publications

An (e, 2e) spectrometer has been constructed for detecting scattered and recoiling electrons from a thin solid film. The cross section for observing the two electrons in coincidence is proportional to the spectral momentum density of the target. In this spectrometer the energy of the incident electron beam is 25 keV and the beam current is approximately 40 μA. The energy resolution (FWHM) is ≤4 eV. The momentum resolution (FWHM) can be varied from 0.2 to 1.0 Å⁻¹. Preliminary coincidence data from an amorphous carbon film are presented.

The Chromospheres Of Classical Cepheids. 111. A Search For Transition Region Emission Lines, Edward G. Schmidt, Sidney B. Parsons

Edward Schmidt Publications

In previous studies of Cepheid chromospheres with the IUE, we found that the chromospheric emission is strongly dependent on the period of the star and varies substantially through the cycle. For the shortest period star in our sample, δ Cep, we were able to detect little significant chromospheric emission in the short wavelength region, and we were only able to detect transition region emission in the longest period star, 1 Car. However, the upper limits on these emissions were slightly above expected flux levels for nonvariable stars. To detect them or place lower and physically more interesting limits on …

Homogeneous Nucleation Rate For Water, Donald E. Hagen, James L. Kassner

Physics Faculty Research & Creative Works

Homogeneous nucleation rate data for water extending over an exceptionally large domain of rate (J), supersaturation ratio (S), and temperature (T) was recently published. Because it spans a large J-S-T surface, this data constitutes a good test of nucleation theory. Here classical nucleation theory is used to analyze this data. By adjusting only the sticking coefficient, we are able to obtain a good fit between theory and experiment. It was necessary to include an increase in the water molecular density associated with the finite water compressibility.

Peccei-Quinn Symmetry As Flavor Symmetry And Grand Unification, Aharon Davidson, V. Parameswaran Nair, Kameshwar C. Wali

Publications and Research

We consider the possibility of identifying the Peccei-Quinn (PQ) symmetry as also the flavor symmetry in multigenerational grand unification schemes. The essential ingredient, a global, axial U(1) symmetry in the PQ mechanism to avoid the strong CP-violation problem provides useful constraints on the fermion —Higgs-boson couplings in the theory, thereby leading to identical "canonical" forms for fermion mass matrices in both the charged sectors. These forms are the conjectured Fritzsch-type matrices exhibiting the "nearest-neighbor" interactions in generation space. From among the popular schemes for grand unification, SO(10) emerges as one which has several advantages over the others for constructing multigenerational …

A Quantitative Study Of The Copper Content In Granite Rocks, Samir F. Al-Mandwee

Masters Theses

A spectrographic analysis was conducted on ten granite samples of different geological origin from the Pioneer Mountains in Central Idaho. A qualitative analysis was performed first and then a quantitative analysis to determine the presence and relative amounts of copper in the various samples. This spectrographic analysis employed a direct current arc source of 340 volts and 4 amperes to excite the samples which were dissolved in acid and dried on the ends of high purity carbon electrodes. The emitted light passed through a step sector and a medium quartz spectrograph to a photographic plate. The optical density of the …

Partial Radiative Recombination Cross Sections For Excited States Of Hydrogen, Patricia M. Fazio

Physics Theses & Dissertations

In calculating the radiative recombination cross sections for interstellar H II regions usually only the electric dipole term in the expansion of the interaction Hamiltonian is kept. However, conditions present in these regions permit recombination into highly excited states and the "effective size" of the atom is not much less than the wavelength of the emitted photon. These physical conditions do not meet the requirements for making the dipole approximation. A higher order approximation is to keep an additional term in the expansion of the Hamiltonian, and, therefore, to include contributions of quadrupole transitions in the calculation of the partial …

A Theoretical Model For Calculation Of Molecular Stopping Power, Yuan-Jian Xu

Physics Theses & Dissertations

A modified local plasma model based on the work of Linhard-Winther, Bethe, Brown, and Walske is established. The Gordon-Kim's molecular charged density model is employed to obtain a formula to evaluate the stopping power of many useful molecular systems. The stopping power of H₂ and He gas was calculated for incident proton energy ranging from 100 KeV to 2.5 MeV. The stopping power of O₂, N₂ and water vapor was also calculated for incident proton energy ranging from 40 keV to 2.5 MeV. Good agreement with experimental data was obtained.

A discussion of molecular effects leading …

An Investigation Of Refractive Index Of Solutions Of Ammonia And Water At Various Concentrations And Temperatures, Effendy Arif

Mechanical & Aerospace Engineering Theses & Dissertations

Refractive index of ammonia-water solutions is investigated experimentally (for (lamda) = 632.8 nm) and semi-empirically (for (lamda) = 589.3 and 632.8 nm) in ammonia-weight concentration of up to 30%, over a temperature range of 20 to 60(DEGREES)C. The experiment employs a specially designed and built refractometer that measures the displacement of a laser beam due to refraction in the test solution. The refractive index is then deduced from the beam displacement. Based on the experimental data, the refractive index is correlated empirically with the concentration and temperature. A semi-empirical investigation is developed based on the Lorentz-Lorenz equation and the additive …

The Development Of A Microprocessor Controlled Linearly Actuated Valve Assembly, Raymond H. Wall

Mechanical & Aerospace Engineering Theses & Dissertations

The development of a proportional fluid control valve/assembly is presented. This electro-mechanical system is needed for space applications to replace the current proportional flow controllers that use bulky hydraulic or pneumatic actuation systems. The flow is controlled by a microprocessor system that monitors the control parameters of upstream pressure and requested volumetric flow rate. The microprocessor achieves the ·proper valve stem displacement by means of a digital linear actuator. A linear displacement sensor is used to measure the valve stem position. 'Ibis displacement is monitored by the microprocessor system as a feedback signal to close the control loop. With an …

A Plasma Focus Interrupting Switch, Gregory Francis Knapp

Electrical & Computer Engineering Theses & Dissertations

The feasibility of using a dense plasma focus (DPF) as a current interrupting device has been investigated. Specifically, a 34-kJ, Mather-type DPF was modified to accept a third electrode so that a discharge could be created between this electrode and the center electrode of the DPF by a 10-kJ inductive energy storage circuit. It was anticipated that the accelerating mechanisms of the DPF pinch, which are known to cause a rapid reduction in the DPF current, would interrupt the 1-kA to 10-kA secondary discharge current thus forcing the secondary current through an external load and hence result in power amplification. …

Weak Localization Of Two-Dimensional Conduction Holes, S. Washburn, Richard A. Webb, E. E. Mendez, L. L. Chang, L. Esaki

Faculty Publications

We report transport measurements which we interpret as weak localization of two-dimensional conduction holes in a GaSb-InAs-GaSb quantum-well structure. This system is unique in that it has parallel conduction channels containing both holes and electrons. The longitudinal resistance of the sample was measured for temperatures between 0.006 and 25 K; the magnetoresistance was measured in a perpendicular magnetic field. Weak localization of the holes was indicated by negative magnetoresistance and by a large logarithmic correction to the conductivity.

Magnetic Hardening In Rapidly Quenched Fe-Pr And Fe-Nd Alloys, David J. Sellmyer, A. Ahmed, G. Muench, George C. Hadjipanayis

David Sellmyer Publications

We report studies of high-field magnetization and thermomagnetic effects in rapidly quenched and heat treated alloys based on Fe-Pr and Fe-Nd. Coercivities up to ~40 kOe and large energy products result from the precipitation of a finely dispersed crystalline phase. Studies of varying the alloy composition and heat treatment are reported. Journal of Applied Physics is copyrighted by The American Institute of Physics.

Spin-Glass-Like Freezing In Disordered Mnpd3 And Crpd3 Alloys, M.H. Rashid, David J. Sellmyer

David Sellmyer Publications

We report studies of dc and ac susceptibility and high-field magnetization on disordered samples of MnPd₃ and CrPd₃. Both samples undergo spin-glass-like transitions, as is evident from susceptibility peaks at 45 and 37 K, respectively. The effective paramagnetic moments deduced from Curie–Weiss fits of the susceptibility in the paramagnetic region are 0.38µ_B/Mn and 0.4µ_B/Cr. Both materials show saturation effects at high applied fields and a flat χ(T) below the spin-freezing temperature in the field-cooled state. The data are discussed in terms of a cluster-glass model with local antiferromagnetic interactions. Journal of …

Mössbauer Study Of Sputtered Fe-Ti Alloys With Wide Composition Range, Sy_Hwang Liou, C.L. Chien

Sy-Hwang Liou Publications

Fe_xTi_100-x alloys over a wide composition range has been made by high-rate sputtering and studied by ⁵⁷Fe Mössbauer spectroscopy. Samples with 30 ≤ x ≤ 80 are amorphous whereas samples with x ≥ 85 are metastable crystalline bcc alloys. Large differences in magnetic properties (e.g., T_c) and hyperfine interactions (Heff, isomer shift) are found between the amorphous and bcc alloys. Comparison of FeTi and Fe₂Ti in amorphous and crystalline states show that the short-range order in the amorphous state has no resemblence to that of the crystalline compounds.