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Articles 34981 - 35010 of 36535

Full-Text Articles in Physical Sciences and Mathematics

Spin-Glass-Like Behavior In Very Dilute Pdfe At Very Low Temperatures, Richard A. Webb, G. W. Crabtree, J. J. Vuillemin Sep 1979

Spin-Glass-Like Behavior In Very Dilute Pdfe At Very Low Temperatures, Richard A. Webb, G. W. Crabtree, J. J. Vuillemin

Faculty Publications

Measurements of the electrical resistivity of palladium, residual resistivity ratio ∼22 500, containing 1.7 ppm of Fe have been made from 5.5 K to 1.8 mK. 15 Hz ac susceptibility measurements from 1 K to 1.8 mK together with the resistivity data suggest that a transition into a spin-glass state occurs near 7 mK.

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Brownian Motion In A Flowing Fluid, John D. Ramshaw Sep 1979

Brownian Motion In A Flowing Fluid, John D. Ramshaw

Physics Faculty Publications and Presentations

A phenomenological theory is developed for Brownian motion in a flowing incompressible fluid. The Brownian particles are regarded as an ideal gas subject to a position- and time-dependent force field that represents interactions with the host fluid. This approach immediately leads to deterministic partial differential equations of motion for the Brownian particles. These equations are then examined in the limit of large friction, in which they imply an expression for the diffusional mass flux of Brownian particles. This expression is a sum of terms representing concentration, forced, thermal, and pressure diffusion. Comparisons are made with earlier work, and with the …

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Doubly Differential Cross Sections For Proton-Impact Ionization Of Argon, Don H. Madison, Steven Trent Manson Sep 1979

Doubly Differential Cross Sections For Proton-Impact Ionization Of Argon, Don H. Madison, Steven Trent Manson

Physics Faculty Research & Creative Works

Proton-impact-ionization cross sections for argon which are differential in the energy and angle of the ejected electron have been calculated within the framework of the Born approximation using both Hartree-Slater and Hartree-Fock wave functions for the ejected electron. Results of the two types of calculations are compared with each other and with experiment. Differential cross sections for all five sub shells of argon are examined and particular attention is given to some interesting features of the K-shell cross sections. The range of applicability of the theoretical models is discussed.

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Photoionization Of Chalcogen And Halogen Atoms: Cross Sections And Angular Distributions, Steven T. Manson, Alfred Msezane, Anthony F. Starace, Siamak Shahabi Sep 1979

Photoionization Of Chalcogen And Halogen Atoms: Cross Sections And Angular Distributions, Steven T. Manson, Alfred Msezane, Anthony F. Starace, Siamak Shahabi

Anthony F. Starace Publications

The authors present a survey of the photoionization cross sections and photoelectron angular distributions for the outer p subshell of the chalcogen atoms O, S, Se, and Te and the halogen atoms F, Cl, Br, and I. Results are presented in the Hartree-Fock approximation as well as in the central-potential-model approximation. An extensive analysis and comparison of the results obtained is presented which finds that exchange-interaction effects are strongest for the n=3 row elements.

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Physical Consequences Of Anomalies In Nonlocal Potential Problems, L. L. Foldy, James A. Lock Aug 1979

Physical Consequences Of Anomalies In Nonlocal Potential Problems, L. L. Foldy, James A. Lock

Physics Faculty Publications

An s-wave two-body separable potential may give rise to several phenomena which are absent for nonsingular local potentials. We examine the physical implications of a well known example of such phenomena, the continuum bound state, as well as of two lesser known anomalies, the so-called positive energy spurious state and negative energy bound states with improper long-range behavior. By examining these anomalies in light of Levinson's theorem, Wigner's phase shift inequality, and the effect of a perturbation on the anomalous states by their insertion in a three-body scattering situation, we find in agreement with previous studies that the continuum bound …

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The Wavelength Dependence Of Herpes Simplex Viral Inactivation & Ultraviolet Enhanced Reactivation, Richard Detsch Aug 1979

The Wavelength Dependence Of Herpes Simplex Viral Inactivation & Ultraviolet Enhanced Reactivation, Richard Detsch

Masters Theses & Specialist Projects

The degrees of Ultraviolet Enhanced Reactivation (UVR) by mammalian cells of Heroes simplex virus inactivated by different wavelengths of far ultraviolet radiation were measure'. The wavelength dependence of UVR is presented for the wavelength region 238 nm to 297 nm. The shape of the UVR curve suggests that virus directed repair is less dependent on the wavelength of UV radiation than are cellular repair mechanisms. The wavelength dependence of Herpes simplex inactivation by far UV radiation is also presented. The shape of the virus inactivation curve suggests the involvement of both DNA and protein.

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21st Rocky Mountain Conference On Analytical Chemistry Jul 1979

21st Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Abstracts and meeting program from the 21st annual meeting of the Rocky Mountain Conference on Analytical Chemistry, 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 30 - August 1, 1979.

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Magnetically Dilute Metallic Glasses. Ii. 4F Moments, G.R. Gruzalski, David J. Sellmyer Jul 1979

Magnetically Dilute Metallic Glasses. Ii. 4F Moments, G.R. Gruzalski, David J. Sellmyer

David Sellmyer Publications

Magnetic-susceptibility and high-field magnetization measurements are presented for amorphous Zr40Cu600-xMx (M denoting Gd and Tb), with x ranging from zero to ten. Effective moments of magnetic solutes were determined by fitting susceptibility data to the Curie-Weiss expression. The moments of Gd and Tb are very close to those expected for trivalent ions and the paramagnetic Weiss temperatures are positive. Saturation did not occur in any of the samples, even at 80 kOe and 1.3 K; however, the alloys containing Gd approached normalized magnetization values of unity. High-field hysteresis loops were used to obtain the …

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Magnetically Dilute Metallic Glasses. I. 3D Moments, G.R. Gruzalski, David J. Sellmyer Jul 1979

Magnetically Dilute Metallic Glasses. I. 3D Moments, G.R. Gruzalski, David J. Sellmyer

David Sellmyer Publications

Magnetic-susceptibility and high-field magnetization measurements are presented for amorphous Zr40Cu50M10 (M denoting Fe, Mn) and Nb50Ni50-xFex, with x ranging from zero to about ten. Curie-Weiss fits to the susceptibility data were made to determine effective moments peff and paramagnetic Weiss temperatures, ⊖. The small values of peff suggest the presence of moment instabilities depending on local environment, and the negative ⊖ values suggest antiferromagnetic local-moment-conduction-electron interactions. The Fe alloys develop hysteresis at low temperatures indicating the presence of a magnetically ordered state. These alloys can be …

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Direct Relation Between Fresnel’S Interface Reflection Coefficients For The Parallel And Perpendicular Polarizations, R. M.A. Azzam Jul 1979

Direct Relation Between Fresnel’S Interface Reflection Coefficients For The Parallel And Perpendicular Polarizations, R. M.A. Azzam

Electrical Engineering Faculty Publications

We have found a significant relation, rp = rs (rs -cos2ϕ)/(1-rs cos2ϕ), between Fresnel’s interface complex-amplitude reflection coefficients rp and rs for the parallel (p) and perpendicular (s) polarizations at the same angle of incidence ϕ. This relation is universal in that it applies to reflection at all interfaces between homogeneous isotropic media collectively and, of course, throughout the electromagnetic spectrum. We investigate the properties of this function, rp = f (rs), and its inverse,rs = g (rp), as …

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Photometric Measurements Of Thin Tracks In Nuclear Emulsion, Robert Katz Jul 1979

Photometric Measurements Of Thin Tracks In Nuclear Emulsion, Robert Katz

Robert Katz Publications

Difficulties observed in the application of track theory to CNO particles are attributed to problems in the application of a light scattering correction in microphotometry.

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Relations Between Amplitude Reflectances And Phase Shifts Of The P And S Polarizations When Electromagnetic Radiation Strikes Interfaces Between Transparent Media, R. M.A. Azzam Jun 1979

Relations Between Amplitude Reflectances And Phase Shifts Of The P And S Polarizations When Electromagnetic Radiation Strikes Interfaces Between Transparent Media, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

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Ab Initio Treatment Of Final-State Spin-Orbit Interactions: Photoionization Of The 6S Electron In Cesium, Keh-Ning Huang, Anthony F. Starace Jun 1979

Ab Initio Treatment Of Final-State Spin-Orbit Interactions: Photoionization Of The 6S Electron In Cesium, Keh-Ning Huang, Anthony F. Starace

Anthony F. Starace Publications

Ab initio theoretical calculations are presented for the cross section, photoelectron angular distribution, and photoelectron spin polarization resulting from photoionization of the 6s electron of cesium. Starting from an initial basis of nonrelativistic Hartree-Fock wave functions, the effect of final-state spin-orbit interaction in the Breit-Pauli approximation is treated exactly. The effect of core relaxation is also examined. Our calculated results agree with recent experimental measurements of the photoionization cross section and the photoelectron spin polarization. Comparison is made with other theoretical calculations. Finally, the length form of the electric dipole interaction operator is shown to be consistent with gauge invariance …

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Resonant Contributions To Single Charge Transfer Between He++ And He, J. N. Bardsley, James S. Cohen, J. M. Wadehra May 1979

Resonant Contributions To Single Charge Transfer Between He++ And He, J. N. Bardsley, James S. Cohen, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

Energy levels and lifetimes are calculated for the resonant states that are important in radiative single charge transfer in He2+-He collisions at thermal energies. The resonant contribution to the charge-transfer rate decreases with increasing temperature and is approximately 12% of the total rate at 300 K.

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Magnetic Properties Of Iron-Doped Layer-Structure Dichalcogenides , S.J. Hillenius, R.V. Coleman, E.R. Domb, David J. Sellmyer May 1979

Magnetic Properties Of Iron-Doped Layer-Structure Dichalcogenides , S.J. Hillenius, R.V. Coleman, E.R. Domb, David J. Sellmyer

David Sellmyer Publications

Magnetic-susceptibility measurements have been made on dilute excess Fe alloys of the layer-structure crystals TaSe2, NbSe2, and TaS2. The 2H selenides show local-moment formation and obey a Curie-Weiss law in the range 300-30 K with effective moments in the range (2.5-4.5)μB. For 2H-FexTaSe2 a strong susceptibility maximum is observed at low temperature and at low fields the maximum has a cusplike shape characteristic of a "spin-glass" type transition. The temperature of the maximum scales approximately linearly with Fe concentration and reaches 13 K for x=0.10. …

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Simulative Investigation Of The Detection Of Modes Of Luminosity Variation In Astrophysical Sources, James Collins May 1979

Simulative Investigation Of The Detection Of Modes Of Luminosity Variation In Astrophysical Sources, James Collins

Masters Theses & Specialist Projects

Five astronomical data analysis methods were evaluated, using computer simulation techniques, for minimum detection levels, periodicity detection, and parameter estimation sensitivities. The evaluation of these methods was accomplished using three basic waveforms with the addition of ten “random” noise samples from a Gaussian distribution of known parameters. The chi-square and t-test methods were evaluated in detecting low-amplitude variability and brightness level shifts. Results indicate both methods have a strong dependence on the estimation of the standard deviation (σ) where a 0.1 change in σ will affect detection rates by ten to twenty-five percent at the ninety-five percent confidence level. The …

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Franck Condon Factors And R-Centeroids For Six Diatomic Molecules, Patricia M. Fazio May 1979

Franck Condon Factors And R-Centeroids For Six Diatomic Molecules, Patricia M. Fazio

Physics Theses & Dissertations

The Franck Condon factor is defined as the square of the overlap integral and is so named because of its ties with the Franck Condon Principle. The r-centroid is the internuclear separation associated with the electronic transition of the diatomic molecule. The physical meaning of these integrals is discussed. Two methods for construction of the wavefunctions are presented. Both methods employ the Morse Potential Energy function. The first method calculates the integrals using the analytic wavefunction of Morse and the second method has numerically constructed wavefunct!ons. The twelve transitions and six diatomic molecules studied include; B 2Σ+ to X …

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Electronic Properties And Superconductivity Of Zr-Pd Glasses, G.R. Gruzalski, J.A. Gerber, David J. Sellmyer Apr 1979

Electronic Properties And Superconductivity Of Zr-Pd Glasses, G.R. Gruzalski, J.A. Gerber, David J. Sellmyer

David Sellmyer Publications

Electrical-resistivity measurements between 1.4 and 300 K and room-temperature magnetic-susceptibility measurements were performed on the metallic glasses ZrxPd1-x, for x=0.59, 0.63, 0.67, and 0.70. The samples, prepared by a modified hammer-anvil technique, exhibit negative temperature coefficients of the resistivity at temperatures from about 10 to 300 K. These data can be understood in terms of the extended Ziman theory if it is assumed that Zr and Pd contribute about 2 and 1 conduction electrons, respectively. Assuming that the magnetic susceptibility is a qualitative measure of the electronic density of states at the Fermi level, N …

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Transformation Of Fresnel’S Interface Reflection And Transmission Coefficients Between Normal And Oblique Incidence, R. M.A. Azzam Apr 1979

Transformation Of Fresnel’S Interface Reflection And Transmission Coefficients Between Normal And Oblique Incidence, R. M.A. Azzam

Electrical Engineering Faculty Publications

If w denotes an interface Fresnel reflection or transmission coefficient for s- or p-polarized light at an oblique angle of incidence ø, and z denotes the same coefficient at normal incidence, we find that w is an analytic function of z, w = ƒ(z), that depends on ø but not on the specific optical properties of the two media on both sides of the interface. All four functions that correspond to the four distinct Fresnel coefficients and their inverses are determined. We single out for detailed examination, as an example, the relationship between the reflection of s -polarized light at …

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Type Conversion In Electron‐Irradiated Gaas, J. W. Farmer, David C. Look Apr 1979

Type Conversion In Electron‐Irradiated Gaas, J. W. Farmer, David C. Look

Physics Faculty Publications

The unambiguous type conversion of GaAs by electron irradiation is reported here for the first time. Several high‐quality n‐type vapor‐phase epitaxial layers (ρ?3 Ω cm and μ?7000 cm2/V sec at 300 K) were converted by 1‐MeV electrons to high‐quality p‐type layers (ρ?30 Ω cm and μ?400 cm2/V sec). Temperature‐dependent Hall‐effect data show energy levels at 0.5, 0.3, and about 0.1 eV above the valence band. Evidence is presented to indicate that the failure of some of our samples (and, perhaps, other samples reported in the literature) to convert to low‐r …

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Effect Of Magnetic Fields On Drug Induced Contractility And Mortality In Spirostomum, Angela Ripamonti, Richard B. Frankel, E. M. Ettienne Apr 1979

Effect Of Magnetic Fields On Drug Induced Contractility And Mortality In Spirostomum, Angela Ripamonti, Richard B. Frankel, E. M. Ettienne

Physics

The influence of homogeneous magnetic fields up to 5.5 T on contractile frequency and mortality in the ciliate protozoan spirostomum ambiguum stimulated by 2,2′ PDS is reported. Magnetic fields are observed to decrease contractile frequency and to significantly increase mortality.

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The Effects Of Proton Irradiation On The Absorption Of Multi Component Glasses, Marcia Frances Bartusiak Apr 1979

The Effects Of Proton Irradiation On The Absorption Of Multi Component Glasses, Marcia Frances Bartusiak

Physics Theses & Dissertations

Three Schott glasses typically used in space technology -­ LaK 21, KzFS N4, and LF 5 -- were irradiated with 85 MeV protons. Induced absorption spectra were determined for each glass after varying fluences of radiation. It was found that the spectra for each glass can be fitted with three Gaussian shaped bands in the near ultraviolet-visible region, while a fourth Gaussian characterizes the absorption edge. For doses up to 107 rads, the dependence of the induced absorption a on total dose is accurately described by the saturating exponential function a(Φ)= as (1 - e--b Φ ) …

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Photoconductivity And Photovoltaic Studies On Some Ii-Vi Compounds, Challa Nagesh Apr 1979

Photoconductivity And Photovoltaic Studies On Some Ii-Vi Compounds, Challa Nagesh

Masters Theses

The photoconductivity spectra of ultra-pure single crystals of CdS in the range 500-575 nm, CdSe in the range 700-900 nm, ZnSe in the range 420-570 nm and ZnS in the range 300-450 nm have been studied using an improved A.C. method of detection. The sensitivity of the apparatus is high enough to study weak photoconductors like ZnS. The photoconductivity spectrum of each substance showed a peak at the wavelength corresponding to the energy band gap of the substance. The energy band gaps obtained from the spectra are 2.35 eV for CdS, 1.6 eV for CdSe, 2.7 eVfor ZnSe and 3.6 …

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Atomic Hydrogen In A Uniform Magnetic Field: Low-Lying Energy Levels For Fields Below 109 G, Anthony F. Starace, Gary L. Webster Apr 1979

Atomic Hydrogen In A Uniform Magnetic Field: Low-Lying Energy Levels For Fields Below 109 G, Anthony F. Starace, Gary L. Webster

Anthony F. Starace Publications

The wave function for an electron in combined Coulomb and uniform magnetic fields is expanded in oblatespheroidal angle functions. The resulting Schrödinger equation for the radial function is solved for the energy levels by means of two different adiabatic approximations, which yield rigorous lower and upper bounds on the lowest exact energy levels for each symmetry state of the system. Results are presented for the level and binding energies of hydrogenic 1s, 2s, and 2p levels for magnetic fields in the range 107≤B≲1011 G and compared with results of other …

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Magnetite In Freshwater Magnetotactic Bacteria, Richard B. Frankel, Richard P. Blakemore, Ralph S. Wolfe Mar 1979

Magnetite In Freshwater Magnetotactic Bacteria, Richard B. Frankel, Richard P. Blakemore, Ralph S. Wolfe

Physics

A previously undescribed magnetotactic spirillum isolated from a freshwater swamp was mass cultured in the magnetic as well as the nonmagnetic state in chemically defined culture media. Results of Mössbauer spectroscopic analysis applied to whole cells identifies magnetite as a constituent of these magnetic bacteria.

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Abstract: Fe Hyperfine Fields In Fe3 _ XVXSi Alloys, T. J. Burch, C. A. Weiler, K. Raj, J. I. Budnick, V. Niculescu, C. C. Papefthymiou, Richard B. Frankel Mar 1979

Abstract: Fe Hyperfine Fields In Fe3 _ XVXSi Alloys, T. J. Burch, C. A. Weiler, K. Raj, J. I. Budnick, V. Niculescu, C. C. Papefthymiou, Richard B. Frankel

Physics

No abstract provided.

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Reflection Of An Electromagnetic Plane Wave With 0 Or Π Phase Shift At The Surface Of An Absorbing Medium, R. M.A. Azzam Mar 1979

Reflection Of An Electromagnetic Plane Wave With 0 Or Π Phase Shift At The Surface Of An Absorbing Medium, R. M.A. Azzam

Electrical Engineering Faculty Publications

An electromagnetic plane wave incident obliquely from a transparent medium onto the surface of an absorbing medium can be reflected with 0 or π phase shift if (i) the wave is p (TM) polarized, and (ii) the complex relative dielectric function ε is such that 0 ≤|ε| 2/2Re(ε) ≤ 1. Furthermore, the locus of ε such that the reflection coefficient for the p polarization is real at the same angle of incidence, is a circle, and that of ε½ (the complex relative refractive index) is Bernoulli’s lemniscate.

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Temperature Dependence Of Alignment Production In He I By Beam-Foil Excitation, Timothy J. Gay, H. G. Berry Mar 1979

Temperature Dependence Of Alignment Production In He I By Beam-Foil Excitation, Timothy J. Gay, H. G. Berry

Timothy J. Gay Publications

We have measured the dependence upon target-foil temperature of the linear polarization fraction (M / I) of the 2s1S-3p1P, 5016-Å transition in He I for ion energies between 60 and 180 keV. The thin carbon exciter foils were heated externally by Nichrome resistance elements. The measurements of Hight et al. are duplicated; the energy and current dependencies of M / I are the same, assuming correspondence between beam heating and external heating. We also observe that γ, the number of secondary electrons produced per incident ion, decreases with increasing foil …

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Magnetic Properties Of The Rare-Earth Glasses (R65Fe35)100-XBX, J.A. Gerber, S.G. Cornelison, W.L. Burmester, David J. Sellmyer Mar 1979

Magnetic Properties Of The Rare-Earth Glasses (R65Fe35)100-XBX, J.A. Gerber, S.G. Cornelison, W.L. Burmester, David J. Sellmyer

David Sellmyer Publications

Results are reported on the magnetic properties of (R65Fe35)100-xBx glasses, where R denotes Y, Gd, and Er, and x is 10 or 20. Curie-Weiss fits were made to high temperature susceptibility data to determine average effective moments per magnetic ion and Weiss temperatures. Hysteresis loops and modified Arrott plots were used to determine the spontaneous magnetizations, coercive forces, and ordering temperatures. The effective moments and spontaneous moments are compared with those calculated on the assumption of local moments on both magnetic subnetworks, and assuming various spin structures. There is evidence for moment instabilities …

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Comments On The Theory Of Dipolar Fluids, John D. Ramshaw Feb 1979

Comments On The Theory Of Dipolar Fluids, John D. Ramshaw

Physics Faculty Publications and Presentations

The theory of dipolar fluids posbulated by Chan, Mitchell and Ninham is commented upon.

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