Physical Sciences and Mathematics Commons^™

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.

Magnetic Guidance Of Organisms, Richard B. Frankel

Physics

No abstract provided.

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 …

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 …

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.

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.

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.

Short-Range And Infinite-Range Bond Percolation, Miron Kaufman, Mehran Kardar

Miron Kaufman

A method for generalizing bond-percolation problems to include the possibility of infinite-range (equivalent-neighbor) bonds is presented. On Bravais lattices the crossover from nonclassical to classical (mean-field) percolation criticality in the presence of such bonds is described. The Cayley tree with nearest-neighbor and equivalent-neighbor bonds is solved exactly, and a nonuniversal line of percolation transitions with exponents dependent on nearest-neighbor bond occupation probability is observed. Points of logarithmic and exponential singularity are also encountered, and the behavior is interpreted as dimensional reduction due to the breaking of translational invariance by bonds of Cayley-tree connectivity.

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.

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.

Critical Amplitude Of The Potts Model: Zeroes And Divergences, Miron Kaufman, David Andelman

Miron Kaufman

The critical amplitude of the q-state Potts-model free energy is studied as a function of q in two dimensions and on the diamond hierarchical lattice. The amplitude diverges at an infinite number of q values, qn,introducing logarithmic terms in the free energy. We expect that in each interval (qn,qn+1) there is a q value where the amplitude vanishes, affecting the singularity of the free energy as a function of temperature. Possible consequences for gelation and vulcanization of polymers are discussed.

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.

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 …

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 …

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.

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 …

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.

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. …

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 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 …

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 …

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 …

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.

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.

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.

Construction Of A Multidimensional Potential Energy Surface From An Energy Spectrum, Robert Leonard Waterland, John B. Delos

Arts & Sciences Articles

A method for the systematic construction of a multidimensional potential energy surface from an energy spectrum is presented. We show that if the Hamiltonian and the energy spectrum satisfy certain conditions then there is an inversion technique which gives a potential energy function from the spectrum. The method proceeds via a sequence of canonical transformations and leads to a potential energy which is symmetric in all its variables. We test the procedure for one‐ and two‐dimensional examples and show that it gives reasonable results. However, the method does not give a unique result and we discuss two types of nonuniqueness …

Relativistic Invariance And Zitterbewegung, James A. Lock

Physics Faculty Publications

We examine the question of what it is about the structure of relativistic quantum mechanics that causes the nonintuitive phenomenon of the Zitterbewegung of particle position to exist. Further, we examine various assumptions concerning the measurement process which are implicit in the observation of Zitterbewegung.

Precipitation Of Fe3O4 In Magnetotactic Bacteria, Richard B. Frankel, Richard P. Blakemore

Physics

The magnetotactic bacterium A. magnetotacticum contains ferrous ions, a low density hydrous ferric oxide, a high density hydrous ferric oxide (ferrihydrite) and Fe₃O₄, which is precipitated by partial reduction of the ferrihydrite precursor.

Comment On Criticality Of The Anisotropic Quantum Heisenberg Model On A Self-Dual Hierarchical Lattice, Miron Kaufman, Mehran Kardar

Miron Kaufman

No abstract provided.