Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Series

1984

Discipline
Institution
Keyword
Publication

Articles 31 - 60 of 108

Full-Text Articles in Physics

Bags Vs. Strings: Hadrons In Type I And Type Ii Superconducting Vacua, V. Parameswaran Nair, C. Rosenzweig Aug 1984

Bags Vs. Strings: Hadrons In Type I And Type Ii Superconducting Vacua, V. Parameswaran Nair, C. Rosenzweig

Publications and Research

Two popular models for hadronic structure are bags and strings. Both involve analogies with superconductivity. We claim that the most appropriate analogies are type I superconductors for bags and type II superconductors for strings. The structures of hadrons is somewhat different for the two situations. In principle, and in practice in the real world, it is the similarities which are most important. These include linear confining potentials, linearly rising Regge trajectories and short distance Coulomb potentials. These are all generic properties of bound states in a superconductor and the main distinctions between bags and strings is under what circumstances these ...


Angular Differential And Total Cross Sections For The Excitation Of Atomic Hydrogen To Its N=2 Level By 25-150-Kev Hydrogen Molecular Ions, Jerry Peacher, Paul J. Martin, Denver G. Seely, Judith E. Aldag, Thomas J. Kvale, E. Redd, D. M. Blankenship, V. C. Sutcliffe, John T. Park Aug 1984

Angular Differential And Total Cross Sections For The Excitation Of Atomic Hydrogen To Its N=2 Level By 25-150-Kev Hydrogen Molecular Ions, Jerry Peacher, Paul J. Martin, Denver G. Seely, Judith E. Aldag, Thomas J. Kvale, E. Redd, D. M. Blankenship, V. C. Sutcliffe, John T. Park

Physics Faculty Research & Creative Works

Experimentally and theoretically determined differential and total cross sections are reported for excitation of atomic hydrogen to its n=2 level by 25-150-keV hydrogen molecular ions. The differential cross sections decrease 3-4 orders of magnitude over the measured center-of-mass scattering-angular range from 0 to 4.5 mrad. The results of a first Born approximation and two other theoretical calculations based upon the Glauber approximation are presented and compared with the experimental results. Both calculations based on the Glauber approximation agree fairly well with the experimental results. The Born approximation agrees moderately well with the experimental results at the very small ...


Inverting The Ratio Of The Complex Parallel And Perpendicular Reflection Coefficients Of An Absorbing Substrate Using A Transparent Thin-Film Coating, R. M.A. Azzam Jul 1984

Inverting The Ratio Of The Complex Parallel And Perpendicular Reflection Coefficients Of An Absorbing Substrate Using A Transparent Thin-Film Coating, R. M.A. Azzam

Electrical Engineering Faculty Publications

An absorbing substrate can be coated with a transparent thin film of refractive index N1 (within a certain range) and thickness d such that the ratio of complex reflection coefficients for the p_and s polarizations of the film-covered substrate ρ = Rp/Rs is the inverse of that of the film-free substrate ρ¯ = R¯p/R¯s at an angle of incidence ø. A method to determine the relationship among ø, N1, and d that inverts ρ (i.e., makes ρ = 1/ρ¯) for a given substrate at a given wavelength is described and is applied to ...


Yellow Giants In Young Clusters. I. Photometric Observations, Edward G. Schmidt Jul 1984

Yellow Giants In Young Clusters. I. Photometric Observations, Edward G. Schmidt

Edward Schmidt Publications

To enable a study of the properties of luminous yellow stars, a list has been compiled of 84 stars which appear to be in the appropriate region in the color-magnitude diagrams of 41 young clusters. Proper motions, radial velocities, UBV photometry, and spectral types from the literature have been used in those cases where such data are available to assign membership probabilities. DDO and uvby photometry have also been obtained of most of the stars in the list, and these data are analyzed to remove stars from the sample which have the wrong luminosity or the wrong color excess for ...


Magnetosome Dynamics In Magnetotactic Bacteria, S. Ofer, I. Nowik, E. R. Bauminger, G. C. Papaefthymiou, Richard B. Frankel, Richad P. Blakemore Jul 1984

Magnetosome Dynamics In Magnetotactic Bacteria, S. Ofer, I. Nowik, E. R. Bauminger, G. C. Papaefthymiou, Richard B. Frankel, Richad P. Blakemore

Physics

Diffusive motions of the magnetosomes (enveloped Fe3O4 particles) in the magnetotactic bacterium Aquaspirillum magnetotacticum result in a very broad-line Mössbauer spectrum (T ~ 100 mm/s) above freezing temperatures. The line width increases with increasing temperature. The data are analyzed using a bounded diffusion model to yield the rotational and translational motions of the magnetosomes as well as the effective viscosity of the material surrounding the magnetosomes. The results are <θ2>l/2 < 1.5° and <x2>1/2 < 8.4 Å for the rotational and translational motions, respectively, implying that the particles are fixed in whole cells. The effective viscosity is 10 cP at 295 K and increases with decreasing temperature. Additional Fe3+ material in the cell is shown to be associated with the magnetosomes. Fe2+ material in the cell appears ...


Onset Of Oscillations In Rayleigh-Benard Convection: Horizontally Unbounded Slab, Boyd F. Edwards, A. L. Fetter Jul 1984

Onset Of Oscillations In Rayleigh-Benard Convection: Horizontally Unbounded Slab, Boyd F. Edwards, A. L. Fetter

All Physics Faculty Publications

Rayleigh–Bénard convection in a laterally unbounded classical fluid layer with low Prandtl number P (ratio of kinematic viscosity to thermal diffusivity) is reexamined. An amplitude expansion with only a few normal modes yields lateral oscillations of the convective rolls, which are therefore only weakly nonlinear. For free boundary conditions, additional modes (absent for rigid boundaries) lead to long wavelength (‘‘hydrodynamic’’) oscillations, with explicit nonlinear distortions in the velocity and temperature fields. For oscillations with rigid boundaries, the finite critical wavenumbers are approximately independent of P for small P, and the calculated Rayleigh number, frequency, and wavenumber at onset agree ...


Full Second-Order Distorted-Wave Calculation Without Approximations For Atomic Excitation By Electron Impact, Don H. Madison Jul 1984

Full Second-Order Distorted-Wave Calculation Without Approximations For Atomic Excitation By Electron Impact, Don H. Madison

Physics Faculty Research & Creative Works

A new technique has been developed for evaluating second-order distorted-wave amplitudes for atomic excitation without making any approximations. By this technique, second-order amplitudes with arbitrary distorted waves and arbitrary Green's functions in the interaction can be evaluated with comparable difficulty. The utility of the method is demonstrated through a practical calculation of the second-order distorted-wave approximation for electron excitation of the 2p state of hydrogen.


Low-Temperature Magnetic Properties Of Submetallic Phosphorous-Doped Silicon, C. T. Murayama, W. G. Clark, Jeff Sanny Jun 1984

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 ...


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 Jun 1984

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 Te 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 distribution ...


Energy Losses Of Solar Neutrinos And The Oscillation Hypothesis, P.T. Leung, S. Boedo, M. L. Rustgi Jun 1984

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.


General Formula For The Inelastic Scattering Of Relativistic Spin-½ Particles By Heavy Atoms, P.T. Leung, M. L. Rustgi, S. A. Long Jun 1984

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.


A Simple Model For Impurity Photoabsorption In Silicon, Gust Bambakidis Jun 1984

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 ...


Narrow 0+ State In 20Ne And 06+ And 07+ Rotational Bands, H. T. Richards, G. Caskey, J. H. Billen, S. R. Riedhauser, Daniel J. Steck Jun 1984

Narrow 0+ State In 20Ne And 06+ And 07+ Rotational Bands, H. T. Richards, G. Caskey, J. H. Billen, S. R. Riedhauser, Daniel J. Steck

Physics Faculty Publications

A reanalysis of old data removes the (0+,2+) ambiguity for a very narrow state at Ex(20Ne)=11.55 MeV and gives a unique 0+ assignment. Such a 0+ state corresponds well to a predicted state at 11.494 MeV of unusually small reduced widths for decay to both the ground and first excited state of 16O. This new 0+ state is a better 06+ band head for the 8p-4h states at 15.159 MeV (6+) and 18.538 MeV (8+) than the currently accepted 0+ state at 12.44 MeV. Possible 2+ and 4 ...


Magnetic Guidance Of Organisms, Richard B. Frankel Jun 1984

Magnetic Guidance Of Organisms, Richard B. Frankel

Physics

No abstract provided.


Valence-Band Photoemission In La And Pr: Connections With The Ce Problem, David Michael Wieliczka, C. G. Olson, David W. Lynch Jun 1984

Valence-Band Photoemission In La And Pr: Connections With The Ce Problem, David Michael Wieliczka, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

Energy distribution curves from La and Pr were taken from 32 to 80 eV photon energies. Above 50 eV the valence-band photoemission in La is very weak, implying that previous studies of Ce have underemphasized the 4f contributions. Pr exhibits two peaks attributable to 4f electrons, similar to the structures in Ce.


Isotropy Group Description Of A Phase Transition In Nano3, W. Scott Stornetta, Dorian M. Hatch Jun 1984

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 May 1984

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.


Division-Of-Wave-Front Polarizing Beam Splitter And Half-Shade Device Using Dielectric Thin Film On Dielectric Substrate, R. M.A. Azzam May 1984

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.


Critical Points In Low-Energy Positron-Atom Scattering, J. M. Wadehra, T. S. Stein, W. E. Kauppila May 1984

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.


Temperature-Dependent Resistivity Of Highly Disordered Ni-Cr-Al Alloys , R. Hight, C. Plough, David J. Sellmyer May 1984

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(T22)], 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 Apr 1984

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.


The Chromospheres Of Classical Cepheids. 111. A Search For Transition Region Emission Lines, Edward G. Schmidt, Sidney B. Parsons Apr 1984

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 the ...


A Search For Chromospheric Emission In Tu Cassiopeiae Spectra, Arne A. Henden, Robert H. Cornett, Edward G. Schmidt Apr 1984

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, CanII 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.


The Chromospheres Of Classical Cepheids. 11. High-Resolution Profiles Of The Mg Ii H And K Lines, Edward G. Schmidt, Sidney B. Parsons Apr 1984

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 ...


An Spectrometer For Investigating The Spectral Momentum Density Of Thin Films, A. L. Ritter, Jr Dennison, J. Dunn Apr 1984

An Spectrometer For Investigating The Spectral Momentum Density Of Thin Films, A. L. Ritter, Jr 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 Å1. Preliminary coincidence data from an amorphous carbon film are presented.


Peccei-Quinn Symmetry As Flavor Symmetry And Grand Unification, Aharon Davidson, V. Parameswaran Nair, Kameshwar C. Wali Apr 1984

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 ...


What Becomes Of Global Color, Philip C. Nelson, Sidney Coleman Apr 1984

What Becomes Of Global Color, Philip C. Nelson, Sidney Coleman

Department of Physics Papers

The recent demise of certain global unbroken symmetry generators in the presence of a grand unified magnetic monopole leads us to consider more carefully the notion of charges associated with gauge symmetries. It turns out that global transformations associated with the generators of the gauge group, and their charges, make sense only for extended systems which are sufficiently localized. GUT monopoles fail this criterion. Detailed consideration of the monopole-antimonopole system helps remove apparent paradoxes related to the chromodyon excitations of a single monopole and agrees with the previous result that some, but not all, of the states naively expected do ...


Homogeneous Nucleation Rate For Water, Donald E. Hagen, James L. Kassner Apr 1984

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.


Mössbauer Study Of Sputtered Fe-Ti Alloys With Wide Composition Range, Sy_Hwang Liou, C.L. Chien Mar 1984

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

Si-Hwang Liou Publications

FexTi100-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., Tc) 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.


Magnetic Hardening In Rapidly Quenched Fe-Pr And Fe-Nd Alloys, David J. Sellmyer, A. Ahmed, G. Muench, George C. Hadjipanayis Mar 1984

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.