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Articles 34351 - 34380 of 36545

Full-Text Articles in Physical Sciences and Mathematics

Radial Distribution Of Dose And Cross-Sections For The Inactivation Of Dry Enzymes And Viruses, Zhang Chunxiang, D. E. Dunn, Robert Katz Jan 1985

Radial Distribution Of Dose And Cross-Sections For The Inactivation Of Dry Enzymes And Viruses, Zhang Chunxiang, D. E. Dunn, Robert Katz

Robert Katz Publications

A new semi-empirical algorithm for the radial distribution of dose is compared with available data. The algorithm is used to calculate the inactivation cross section for dry enzymes and viruses using an extended target model of a 1-hit detector. Agreement with data is at about the 15% level, approximating the precision of the data itself.

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The Vibrational Distribution Of N2+ In The Terrestrial Ionosphere, Jane L. Fox, Alexander Dalgarno Jan 1985

The Vibrational Distribution Of N2+ In The Terrestrial Ionosphere, Jane L. Fox, Alexander Dalgarno

Physics Faculty Publications

The densities and vibrational distributions of N2+ in the X²Σg+, A²Πu, and B²Σu+ states in the daytime terrestrial ionosphere are computed for both low and high solar activity. Altitude profiles of the relative populations of the vibrational levels of N2+X²Σg+ are presented. The fraction of vibrationally excited N2+ varies from 5% at 100 km to 50% at 450 km. Several models are examined in which loss of N2+(v) is enhanced for v > 0 and in …

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Semiclassical Calculation Of Quantum-Mechanical Wave Functions For A Two-Dimensional Scattering System, Stephen Knudson, John B. Delos, B. Bloom Jan 1985

Semiclassical Calculation Of Quantum-Mechanical Wave Functions For A Two-Dimensional Scattering System, Stephen Knudson, John B. Delos, B. Bloom

Arts & Sciences Articles

The semiclassical theory developed by Maslov and Fedoriuk is used to calculate the wave function for two‐dimensional scattering from a Morse potential. The characteristic function S and the density Jacobian J are computed in order to obtain the primitive wave function. The incident part shows distorted plane‐wave behavior and the scattered part shows radially outgoing behavior. A uniform approximation gives a wave function that is well‐behaved near the caustic.

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Summary Abstract: Computerized Scanning Auger Microprobe, T. J. Sommerer, Edward Boyd Hale Jan 1985

Summary Abstract: Computerized Scanning Auger Microprobe, T. J. Sommerer, Edward Boyd Hale

Physics Faculty Research & Creative Works

No abstract provided.

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Spin-1 Exchange-Interaction Model Of Ferromagnetism, Harry A. Brown Jan 1985

Spin-1 Exchange-Interaction Model Of Ferromagnetism, Harry A. Brown

Physics Faculty Research & Creative Works

The spin-exchange operator for spin S=1 and a constant-coupling-like approximation are used to evaluate the thermodynamic properties of a system described by a two-spin Hamiltonian that includes dipole and quadrupole interactions. The dipole and quadrupole moments and the exchange energy are found as functions of temperature. There is a critical temperature, Tc, which depends on the coordination number of the lattice at which the system undergoes a second-order phase transition. Below Tc, both magnetic moments, simultaneously, take on nonzero values and have infinite derivatives there while the derivative of the exchange energy is discontinuous. Comparison is made with other results …

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Electron Capture In Pseudo-Two-Electron Systems: Ar8++He, M. Kimura, Ronald E. Olson Jan 1985

Electron Capture In Pseudo-Two-Electron Systems: Ar8++He, M. Kimura, Ronald E. Olson

Physics Faculty Research & Creative Works

Molecular-structure calculations using the pseudopotential method have been performed on the (ArHe)8+ system. The cross section for single-electron capture in Ar8++He collisions was calculated for energies from 20 eV to 10 keV/amu. The perturbed-stationary-state method [M. Kimura, H. Sato, and R. E. Olson, Phys. Rev. A 28, 2085 (1983)], modified to include electron translation factors appropriate to two-electron systems, was used. The total cross section is relatively energy independent with a value of approximately 2.5x10-15 cm2. The n=4 level of Ar7+ is found to be preferentially populated, with the 4f level being dominant. © 1985 The …

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A Continental Well-Aged Aerosol In The Guinean Savannah At The Level Of A Trough Along The Itcz, F. Desalmand, Josef Podzimek, R. Serpolay Jan 1985

A Continental Well-Aged Aerosol In The Guinean Savannah At The Level Of A Trough Along The Itcz, F. Desalmand, Josef Podzimek, R. Serpolay

Physics Faculty Research & Creative Works

Simultaneous measurements of Aitken nuclei, cloud condensation nuclei and aerosol particles sizes larger than 0.3 μm in the Guinean savannah during the dry season show an aerosol of very exceptional physical properties: numerous cloud condensation nuclei (2000-3000 per cm3) active at low supersaturation (or slight 'undersaturation'), absence of very small Aitken nuclei active at 180% of supersaturation and concentrations of large aerosol particles (D > 0.3 μm) between 30 and 60 per cm3. The analysis of the aerosol behavior during a 'typical' 24-hr period of the dry season and during a fog situation indicates that (1) the aerosol is a very …

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Effects Of Iron Implantation On The Aqueous Corrosion Of Magnesium, S. Akavipat, Edward Boyd Hale, C. E. Habermann, P. L. Hagans Jan 1985

Effects Of Iron Implantation On The Aqueous Corrosion Of Magnesium, S. Akavipat, Edward Boyd Hale, C. E. Habermann, P. L. Hagans

Physics Faculty Research & Creative Works

The influence of the implantation of iron ions on the corrosion of magnesium and an AlZn-rich magnesium alloy (AZ91C) has been studied. Anodic polarization measurements in a dilute chloride-containing alkaline solution were used to evaluate corrosion resistance. A range of ion energies (50-180 keV) and doses (1016-2 x 1017 Fe+ ions cm-2) have been evaluated. Both the iron-implanted pure magnesium and the alloy AZ91C gave improved polarization measurements. A systematic positive shift of the open-circuit potential with increasing iron dose was found. In AZ91C at a dose of 1017 Fe+ ions cm-2, there was a + 0.6 V more noble …

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Neutron-Diffraction Study Of The Magnetic Ordering In Ni(Ch₂Co₂Nh₂)₂ 2h₂O, Akifumi Onodera, Yorihiko Tsunoda, Nobuhiko Kunitomi, Oran Allan Pringle, Robert M. Nicklow, Ralph M. Moon Jan 1985

Neutron-Diffraction Study Of The Magnetic Ordering In Ni(Ch₂Co₂Nh₂)₂ 2h₂O, Akifumi Onodera, Yorihiko Tsunoda, Nobuhiko Kunitomi, Oran Allan Pringle, Robert M. Nicklow, Ralph M. Moon

Physics Faculty Research & Creative Works

The magnetic structure of Ni(CH2CO2NH2)2 2 H2O has been determined by the analysis of neutron-diffraction data from powder and single-crystal samples. Ni(CH2CO2NH2)2 2 H2O orders at a Néel temperature of 0.88 K. The magnetic structure consists of antiferromagnetically coupled layers having a canted ferromagnetic ordering within layers, with a moment of (2.33 ± 0.14)μB per Ni2+ ion. The magnetic unit cell is composed of two crystallographic unit cells, and contains four nickel atoms. The moment direction is not simply related …

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Erratum: Normalized Line Shapes For Far-Wing Continuum Spectra: The Rb-Xe Satellite Band (Physical Review A(1985) 32, 5 (3150-3152)), Ronald James Bieniek Jan 1985

Erratum: Normalized Line Shapes For Far-Wing Continuum Spectra: The Rb-Xe Satellite Band (Physical Review A(1985) 32, 5 (3150-3152)), Ronald James Bieniek

Physics Faculty Research & Creative Works

Recent advances in experimental spectroscopy offer the promise of yielding much detailed information about molecular potentials and collisional interactions from a study of the light emitted or absorbed in the far wings of atomic lines. However, readily manipulable, accurate theoretical expressions and methods are needed to extract such knowledge. Straightforward formulas, based on the distorted-wave approximation, for the normalized emission intensity in the far wing of a pumped atomic line are given here. By normalizing theoretical spectra with respect to the strength of the atomic line, one obtains a convenient form for the analysis of experimental differential spectra that are …

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Faraday's Law Demonstration, Richard Sankovich Jan 1985

Faraday's Law Demonstration, Richard Sankovich

Physics Faculty Research & Creative Works

No abstract provided.

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The Spin‐Exchange Ferromagnet With Dipole And Quadrupole Interactions, Harry A. Brown Jan 1985

The Spin‐Exchange Ferromagnet With Dipole And Quadrupole Interactions, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

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Satellite Structure In Laser-Assisted Charge-Transfer Cross Sections, Y. P. Hsu, Ronald E. Olson Jan 1985

Satellite Structure In Laser-Assisted Charge-Transfer Cross Sections, Y. P. Hsu, Ronald E. Olson

Physics Faculty Research & Creative Works

A six-state coupled-channel calculation has been performed on the laser-assisted charge-transfer collision H++Na+Latin small letter h with stroke. A greatly enhanced charge-transfer cross section is observed for low-energy collisions if the photon energy is matched to the classical satellite frequency. This frequency is determined by the location of an extremum in the difference of potential energies between the laser-pumped initial and final molecular states. The stationary-phase method has been used to reproduce the general features and the magnitude of the cross-section structure. © 1985 The American Physical Society.

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Spin-Exchange Cross Sections For Hydrogen-Atomalkali-Metal-Atom Collisions, H. R. Cole, Ronald E. Olson Jan 1985

Spin-Exchange Cross Sections For Hydrogen-Atomalkali-Metal-Atom Collisions, H. R. Cole, Ronald E. Olson

Physics Faculty Research & Creative Works

The pseudopotential molecular-structure method has been used to calculate the X1 and a3 interaction potentials for the alkali-metal-atom hydrogen-atom systems. These potentials were then used in a quantum-mechanical calculation to determine the spin-exchange cross sections in the energy range from 2.5x10-4 eV to 2.5 eV. The cross sections follow the general form Q1/2=a-b lnv. However, abundant structure on the cross sections is present due to orbiting resonances induced by the deeply bound well of the X1 molecular state. The spin-exchange cross sections range from 17x10-16 to 25x10-16 cm2 at room temperature for H(F=1) transferring to H(F=0) in collision with unpolarized …

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Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Thermal Stress Analysis, A. Ballantyne, H.A. Hyman, Clive L. Dym, R.C. Southworth Jan 1985

Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Thermal Stress Analysis, A. Ballantyne, H.A. Hyman, Clive L. Dym, R.C. Southworth

All HMC Faculty Publications and Research

This paper examines the effects of thermal loading and time history upon the thermal stresses developed in lithographic mask structures as would be expected under irradiation by intense soft x rays. The objective of this work was to examine the phenomenology of the interaction and to evaluate the limits placed upon mask dosage. The mechanics of mask failure are examined in terms of single pulse and cumulative, or fatigue, effects. A number of prototypical mask structures are investigated, which show that the application of intense pulsed sources to x‐ray lithography does not reduce the potential utility of the techique. However, …

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Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Dynamic Response, Clive L. Dym, A. Ballantyne Jan 1985

Response Of Lithographic Mask Structures To Repetitively Pulsed X-Rays: Dynamic Response, Clive L. Dym, A. Ballantyne

All HMC Faculty Publications and Research

This paper addresses the issue of the dynamic response of thin lithographic mask structures to thermally induced stress fields. In particular, the impact of repetitively pulsed x‐ray sources are examined: the short duration (1–100 nsec) pulses induce large step changes in mask temperatures, which can, in turn, induce a dynamic response. The impact of conductive cooling of the mask is to reduce the repetitively pulsed problem to a series of isolated nearly identical thermal impulses of duration approximately equal to the cooling time. The importance of self‐weight and prestress is examined, and an analysis of the nonlinear dynamic response to …

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Cross Sections For Ionization Of Water Vapor By 7-4000-Kev Protons, M. Eugene Rudd, T. V. Goffe, R. D. Dubois, L. H. Toburen Jan 1985

Cross Sections For Ionization Of Water Vapor By 7-4000-Kev Protons, M. Eugene Rudd, T. V. Goffe, R. D. Dubois, L. H. Toburen

M. Eugene Rudd Publications

Cross sections for production of electrons and positive ions by proton impact on water vapor have been measured from 7-4000 keV by the transverse-field method.

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The Rotated Diffraction Grating: A Laboratory Experiment, James A. Lock Jan 1985

The Rotated Diffraction Grating: A Laboratory Experiment, James A. Lock

Physics Faculty Publications

No abstract provided.

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Charge Transfer Of Hydrogen Ions And Atoms In Metal Vapors, T. J. Morgan, Ronald E. Olson, A. S. Schlachter, J. W. Gallagher Jan 1985

Charge Transfer Of Hydrogen Ions And Atoms In Metal Vapors, T. J. Morgan, Ronald E. Olson, A. S. Schlachter, J. W. Gallagher

Physics Faculty Research & Creative Works

Cross sections and equilibrium fractions for energetic H+, H−, and H0 in collisions with metal vapor targets have been compiled and evaluated. Both experimental and theoretical results are reported. Sources of errors are discussed, and recommended values for the data are presented. © 1985, American Institute of Physics for the National Institute of Standards and Technology. All rights reserved.

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Effect Of The Interplanetary Magnetic Field Y Component On The High‐Latitude Nightside Convection, O. De La Beaujardiere, Vincent B. Wickwar, J D. Kelly, J H. King Jan 1985

Effect Of The Interplanetary Magnetic Field Y Component On The High‐Latitude Nightside Convection, O. De La Beaujardiere, Vincent B. Wickwar, J D. Kelly, J H. King

All Physics Faculty Publications

Sondrestrom radar observations reveal that the dawn‐dusk (By) component of the interplanetary magnetic field (IMF) strongly influences the nightside polar convection. This effect is quite complex. The convection for one orientation of By is not the mirror image of the other orientation. A positive By (i.e., pointing toward dusk) seems to organize the velocities such that, at all local times, they are predominantly westward within the radar field‐of‐view (≃68°‐to‐82° invariant latitude). Between dusk and midnight, on one such occasion, sunward flow is observed within the polar cap. In the midnight and dawn sectors, when By …

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Theoretical Study Of Anomalously High F Region Peak Altitudes In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk Jan 1985

Theoretical Study Of Anomalously High F Region Peak Altitudes In The Polar Ionosphere, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

During the last solar maximum period several observations of anomalously high F region peak altitudes have been made by the high latitude incoherent scatter radars. The observations indicate that there are several distinctive features associated with these high hmF2 ionospheric profiles: (1) they are observed near midnight with the plasma flowing out of the polar cap, (2) NmF2 ranges from 105 to 106 cm−3, (3) hmF2 ranges from 400 to 500 km, (4) below 300 km the profile is devoid of ionization, and (5) the observations are for solar maximum conditions. …

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Refilling Of Geosynchronous Flux Tubes As Observed At The Equator By Geos 2, Jan Josef Sojka, G. L. Wrenn Jan 1985

Refilling Of Geosynchronous Flux Tubes As Observed At The Equator By Geos 2, Jan Josef Sojka, G. L. Wrenn

All Physics Faculty Publications

During periods of extended quiet geomagnetic activity the geosynchronous satellite orbit lies inside the plasmasphere. Five such periods were observed by the GEOS 2 satellite. During the initial 48 hours of such periods the equatorial plasma flux tube density increases at 30 to 50 cm−3/day. However, on reaching ∼100 cm−3 the refilling rate decreases, and refilling is limited. Only when the density reaches ∼100 cm−3 do the plasma characteristics and fluctuations appear to be plasmaspheric and the flow predominantly corotational. The “hot outer zone” of the plasmasphere is highly structured in density and temperature when viewed …

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Universal Time Dependence Of Nighttime F Region Densities At High Latitudes, O De La Beaujardiere, Vincent B. Wickwar, G Caudal, J Holt, J D. Craven, L A. Frank, L Brace, D Evans, J D. Winningham, R A. Heelis Jan 1985

Universal Time Dependence Of Nighttime F Region Densities At High Latitudes, O De La Beaujardiere, Vincent B. Wickwar, G Caudal, J Holt, J D. Craven, L A. Frank, L Brace, D Evans, J D. Winningham, R A. Heelis

All Physics Faculty Publications

Coordinated EISCAT, Chatanika, and Millstone Hill incoherent scatter radar observations have revealed that in the auroral zone, the nighttime F region densities vary substantially with the longitude of the observing site: EISCAT’s densities are the largest and Millstone Hill’s are the lowest. The nighttime F region densities measured by the individual radars are not uniform: the regions where the densities are maximum are the so-called “blobs” or “patches” that have been reported previously. The observations are consistent with the hypothesis that the nighttime densities are produced in significant amounts not by particle precipitation, but by solar EUV radiation, and that …

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A Theoretical Study Of The Global F Region For June Solstice, Summer Maximum, And Low Magnetic Activity, Jan Josef Sojka, Robert W. Schunk Jan 1985

A Theoretical Study Of The Global F Region For June Solstice, Summer Maximum, And Low Magnetic Activity, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

We constructed a time-dependent, three-dimensional, multi-ion numerical model of the global ionosphere at F region altitudes. The model takes account of all the processes included in the existing regional models of the ionosphere. The inputs needed for our global model are the neutral temperature, composition, and wind; the magnetospheric and equatorial electric field distributions; the auroral precipitation pattern; the solar EUV spectrum; and a magnetic field model. The model produces ion (NO+, O2+, N2+, N+, O+, He+) density distributions as a function of time. For our …

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Symmetry Behavior Of The Static Taub Universe: Effect Of Curvature Anisotropy, T. C. Shen, B. L. Hu, D. J. O'Connor Jan 1985

Symmetry Behavior Of The Static Taub Universe: Effect Of Curvature Anisotropy, T. C. Shen, B. L. Hu, D. J. O'Connor

T. -C. Shen

Using the static Taub universe as an example, we study the effect of curvature anisotropy on symmetry breaking of self-interacting scalar field. The one-loop effective potential of a λφ4 field with arbitrary coupling (ξ) is computed by ζ-function regularization. It is expressed as a perturbative series in a small anisotropy parameter α measuring the deformation from the spherical Einstein universe with radius of curvature α. This result is used for analyzing the symmetry behavior of such a system as a function of the geometric (α,α) and field (ξ,λ) parameters. The result is also used to address the question of …

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Theory Of Spectral Asymmetries And Nonlinear Currentsin The Equatorial Electrojet, E. Kudeki, D. T. Farley, Bela G. Fejer Jan 1985

Theory Of Spectral Asymmetries And Nonlinear Currentsin The Equatorial Electrojet, E. Kudeki, D. T. Farley, Bela G. Fejer

Bela G. Fejer

The spectral up-down asymmetry of type 1 echoes returned from the equatorial electrojet irregularities is shown to be a consequence of the nonlinear development of the horizontally propagating large scale primary waves which dominate the k spectrum of the electrojet turbulence. The waves reduce the vertical electric polarization field of the electrojet and suffer second harmonic distortion as they grow. These effects together could cause an asymmetry exceeding 20% between the upward and downward components of the relative (to the ions) electron velocity associated with the primary waves. This asymmetry, which changes its direction from day to night as does …

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Turbulent Disruptions From The Strauss Equations, Jill Potkalitsky Dahlburg Jan 1985

Turbulent Disruptions From The Strauss Equations, Jill Potkalitsky Dahlburg

Dissertations, Theses, and Masters Projects

The subject of this thesis is an analysis of results from pseudospectral simulation of the Strauss equations of reduced three-dimensional magnetohydrodynamics. We have solved these equations in a rigid cylinder of square cross section, a cylinder with perfectly conducting side walls, and periodic ends. We assume that the uniform-density magnetofluid which fills the cylinder is resistive, but inviscid. Situations which we are considering are in several essential ways similar to a tokamak-like plasma; an external magnetic field is imposed, and the plasma carries a net current which produces a poloidal magnetic field of sufficient strength to induce current disruptions. These …

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Stability And Transition Of The Driven Magnetohydrodynamic Sheet Pinch, Russell B. Dahlburg Jan 1985

Stability And Transition Of The Driven Magnetohydrodynamic Sheet Pinch, Russell B. Dahlburg

Dissertations, Theses, and Masters Projects

The stability and transition properties of a bounded, current carrying magnetofluid are explored, using the hydrodynamic theory developed for plane shear flows as a guide. A driven magnetohydrodynamic sheet pinch equilibrium is employed. A sixth order, complex eigenvalue equation which governs the normal modes of small oscillations is derived, and solved numerically by the Chebyshev tau method. Eigenfunctions are shown, as well as the curve of neutral stability. The locus of critical Lundquist numbers has the form of a hyperbola. The nonlinear stability of a primary disturbance of the system is considered. For regions in parameter space close to criticality, …

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Relative Fluorescence Efficiencies For The Dissociative Excitation Of Some Hg-Halides By N2(A ³Σu+), Laird D. Schearer Jan 1985

Relative Fluorescence Efficiencies For The Dissociative Excitation Of Some Hg-Halides By N2(A ³Σu+), Laird D. Schearer

Physics Faculty Research & Creative Works

No abstract provided.

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Raman Studies Of Heavily Implanted, Dye-Laser-Annealed Gaas, H. D. Yao, A. Compaan, Edward Boyd Hale Jan 1985

Raman Studies Of Heavily Implanted, Dye-Laser-Annealed Gaas, H. D. Yao, A. Compaan, Edward Boyd Hale

Physics Faculty Research & Creative Works

Raman scattering is used to study the annealing behavior produced by 10 nsec, 565 nm dye laser pulses in high dose ion-implanted GaAs. Samples were prepared with Sn and Cd implantations of 2, 5, and 10 x 1015 cm2. The Raman spectra indicate that the threshold for epitaxial growth lies between 0.2 - 0.3 J cm2. Best carrier activation (∼ 2%), however, is achieved at ∼1.6 J cm2 for the Sn-implanted sample (n-type). For Cd implantation the electrical activation appears to be very high ({greater-than or approximate} 50%) for low pulse energies({less-than or approximate} 0.3 J cm2) but decreases for …

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