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Portland State University

1992

Articles 1 - 10 of 10

Full-Text Articles in Physics

Explosion Of A Liquid Film In Contact With A Pulse-Heated Solid Surface Detected By The Probe-Beam Deflection Method, P.T. Leung, Andrew C. Tam, Nhan Do, Leander Klees, Wing P. Leung Dec 1992

Explosion Of A Liquid Film In Contact With A Pulse-Heated Solid Surface Detected By The Probe-Beam Deflection Method, P.T. Leung, Andrew C. Tam, Nhan Do, Leander Klees, Wing P. Leung

Physics Faculty Publications and Presentations

The threshold for explosive vaporization of a liquid layer on an opaque solid surface heated by an ultraviolet excimer pulsed laser is studied by a photoacoustic probe-beam deflection method. The probe beam traverses the liquid in the vicinity of the laser-heated liquid-solid interface. Below the explosion threshold, photoacoustic generation in the solid occurs only through a thermoelastic mechanism, which results mainly in shear waves that do not couple well into the liquid. Above the explosion threshold, photoacoustic pulses in the solid are also produced by explosive recoil, hence producing longitudinal pulses in the solid that couple well into the liquid …

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Correction Of Chromatic Aberration With An Electron Mirror, Michael Stewart Mauck Dec 1992

Correction Of Chromatic Aberration With An Electron Mirror, Michael Stewart Mauck

Dissertations and Theses

The theoretical basis for using electron mirrors as correctors of chromatic aberration is presented and an experimental verification of correction of chromatic aberration is demonstrated. A hyperbolic electrostatic electron mirror operating in its converging range and at unity magnification was used as a corrector. A novel separating system with deflections taking place at image planes was developed to implement the mirror without impairing the resolution. Correction was demonstrated in an electron optical probe system. The chromatic aberration was measured by means of the shadows cast by a fine mesh placed near the final image. The experimental method and equipment are …

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A Technique For The Evaluation Of Double Excitation Of Atoms By Fast Protons And Antiprotons, Jack C. Straton, James H. Mcguire, Zheng Chen Nov 1992

A Technique For The Evaluation Of Double Excitation Of Atoms By Fast Protons And Antiprotons, Jack C. Straton, James H. Mcguire, Zheng Chen

Physics Faculty Publications and Presentations

A technique for evaluating cross sections for two-electron excitation in collisions of atoms with fast particles of charge ZP is presented. The atomic wave function is approximated by a sum of pair products of one-electron wave functions, with the coefficients chosen by diagonalizing the fully correlated twoelectron Hamiltonian. Thus spatial correlation is included in both the asymptotic and scattering regions by using these configuration-interaction (Cl) wave functions for initial, intermediate, and final states. Use of CI wave function also allows the first-order contributions to be expressed in closed, analytical form. Both the energy-conserving and energy-nonconserving parts of the second-order amplitude …

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Binary Mixtures Near Surfaces, Patrick Dunn Aug 1992

Binary Mixtures Near Surfaces, Patrick Dunn

Dissertations and Theses

This paper presents an approach to modeling a binary mixture near a surf ace. The approach used is based on statistical mechanics. The Cluster Variation (CV) method is used to solve an Ising-like model with a cluster size of two (neighboring lattice points). The free energy of the system is expressed in terms of the probabilities of occurrences of particular clusters. The CV method is first developed for a homogeneous system which leads to a set of three non-linear partial differential equations. The surface boundary is then introduced and the CV method is developed for this system which leads to …

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Flux Trapping In Superconducting Pellets, Andreas Straub Jul 1992

Flux Trapping In Superconducting Pellets, Andreas Straub

Dissertations and Theses

This research concerns the effects on samples of nominal composition Bil.8Pb0.2Sr2Ca2cu30y which were exposed to hot, dense argon in a ballistic compressor. The investigations were concentrated on two specimens which were exposed to hot, dense argon at about 1800 K (peak pressure 330 atm) and 1500 K (peak pressure 230 atm), respectively. Sample Bi #1 showed a completely melted surface structure after triple exposure in the ballistic compressor at 1800 K while the surface of sample Bi #7 was just partly melted after double exposure at 1500 K. Changes in flux trapping capability and qualitative Meissner effect were investigated in …

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Transmission Studies Of Explosive Vaporization Of A Transparent Liquid Film On An Opaque Solid Surface Induced By Excimer-Laser-Pulsed Irradiation, P.T. Leung, Nhan Do, Leander Klees, Wing P. Leung, Frank Tong May 1992

Transmission Studies Of Explosive Vaporization Of A Transparent Liquid Film On An Opaque Solid Surface Induced By Excimer-Laser-Pulsed Irradiation, P.T. Leung, Nhan Do, Leander Klees, Wing P. Leung, Frank Tong

Physics Faculty Publications and Presentations

Examines the dynamics of the explosion of a liquid film by an ultraviolet excimer pulsed laser studied experimentally on top of an amorphous silicon film deposited on fused quartz. Background on thermal physics of superheated pure or mixed liquids; Techniques for surface temperature measurement; Experimental of probe laser and pulsed excimer laser.

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Proteolytic Modification Of The Ca²-Release Mechanism Of Sarcoplasmic Reticulum In Skeletal Muscle, Ute Goerke Jan 1992

Proteolytic Modification Of The Ca²-Release Mechanism Of Sarcoplasmic Reticulum In Skeletal Muscle, Ute Goerke

Dissertations and Theses

Calcium ions are important mediators in the mechanism of contraction and relaxation of muscle fibers. Depolarization of sarcolemma and transverse tubule causes an increase of myoplasmic ca2+ concentration which induces contraction of the myofibrils. In skeletal muscle fibers, the intracellular Ca2+ concentraton is regulated by an extensive membrane system, the sarcoplasmic reticulum (SR). Ca2+-release from SR is initiated by depolarization of the transverse tubule via a process referred to as excitation-contraction coupling. The Ca2+ - release channel located in the junctional SR plays an important role in this mechanism.

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Diffraction Of Light By A Focused Ultrasonic Wave, J. Huang, Joel Alan Nissen, Erik Bodegom Jan 1992

Diffraction Of Light By A Focused Ultrasonic Wave, J. Huang, Joel Alan Nissen, Erik Bodegom

Physics Faculty Publications and Presentations

The measurement of the acoustic pressure of a planar ultrasonic wave by light diffraction is well established. The ability to do similar measurements in the case of spherical waves has been doubted. However, we show that the range of validity can be extended to the focal region of a spherical concave piezoelectric transducer. Light is passed through the focal plane of a spherical concave transducer and is diffracted as a result of the variation in the index of refraction. The peak pressure can be calculated from the diffraction intensity by making the following simplification. We assume that in the focal …

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Nonlinear Dynamics In Oscillating Waterfalls, Michael Schumann Jan 1992

Nonlinear Dynamics In Oscillating Waterfalls, Michael Schumann

Dissertations and Theses

The concern of this thesis was to investigate the nonlinear dynamics inherent in oscillating waterfalls.

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Adsorption Of Halogenated Phenolate Ions To Egg-Phosphatidylcholine Vesicles, Andreas Blochel Jan 1992

Adsorption Of Halogenated Phenolate Ions To Egg-Phosphatidylcholine Vesicles, Andreas Blochel

Dissertations and Theses

In this study, parameters for the adsorption of several halogenated phenolate ions to egg-phosphatidylcholine vesicles have been determined by microelectrophoresis.

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