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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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Advances In Verification Technology, David W. Hafemeister Jan 1985

Advances In Verification Technology, David W. Hafemeister

Physics

The alleged limits of verification techniques have been used to justify lack of action at the negotiating table, but advances in computer science and optics should help dispel doubts about the verifiability of treaties

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Microaerobic Conditions Are Required For Magnetite Formation Within Aquaspirillum Magnetotacticum, R. P. Blakemore, K. A. Short, D. A. Bazylinski, Charles Rosenblatt, Richard B. Frankel Jan 1985

Microaerobic Conditions Are Required For Magnetite Formation Within Aquaspirillum Magnetotacticum, R. P. Blakemore, K. A. Short, D. A. Bazylinski, Charles Rosenblatt, Richard B. Frankel

Physics

The amount of magnetite (Fe3O4) within magnetosomes of the microaerophilic bacterium Aquaspirillum magnetotacticum varies with oxygen and nitrogen supply. The development of optical methods for directly measuring cell magnetism in culture samples has enabled us to quantitate bacterial Fe3O4 yields. We measured final cell yields, average cell magnetic moments, and magnetosome yields of growing cells. Cultures were grown with NO3-, NH4+, or both, in sealed, unshaken vials with initial headspace Po2 values ranging from 0 (trace) to 21 kPa.

More than 50% of cells had detectable …

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The Production Of Highly Unidirectional Lower-Hybrid Waves, R. Mcwilliams, M. Okubo, R. C. Platt, D. P. Sheehan Jan 1985

The Production Of Highly Unidirectional Lower-Hybrid Waves, R. Mcwilliams, M. Okubo, R. C. Platt, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

The development of a highly unidirectional lower-hybrid wave source would improve the electron current drive efficiency in tokamaks. Lower-hybrid waves launched from a phased wave array are shown to be reflected from a grid placed in a cold, low-density plasma. The antenna-grid combination results in highly unidirectional lower-hybrid waves.

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Measurement Of The Far Infrared Optical Properties Of Steel, Aluminum, Evaporated Iron, And Teflon Fep, Raymond E. Paul Jan 1985

Measurement Of The Far Infrared Optical Properties Of Steel, Aluminum, Evaporated Iron, And Teflon Fep, Raymond E. Paul

Doctoral Dissertations

"The optical properties of low-carbon shim steel, aluminum foil, and Teflon FEP have been measured in the 20 cm-1 to 70 cm-1 range. In particular, measurements of surface impedance for aluminum and low-carbon steel were used to calculate the imaginary part of the dielectric constant (&m, 2). The resulting values of &m, 2 were of order 106 for aluminum, and 105 for steel. The imaginary part of the dielectric constant for metals is several times greater in magnitude than the real part in the frequency range of this experiment. Calculations of &m, …

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Optical Properties Of Natural Minerals In The Far-Infrared, Larry Lavern Long Jan 1985

Optical Properties Of Natural Minerals In The Far-Infrared, Larry Lavern Long

Doctoral Dissertations

"The reflectivity of natural mineral powders were measured in the far infrared. The complex indices of refraction were then determined by Kramers-Kronig analysis or dispersive analysis. The samples were constructed by pressing the powdered sample into a 13 mm diameter pellet. A few of the samples that were measured were kaolin, illite, and montmorillonite, clay samples that could not be obtained in large single crystals. For calcite and gypsum crystals a comparison between the single crystal measurements and powder measurements was done to determine the effect of sample preparation on the measured spectra"-- Abstract, p. ii

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Corrosion In Magnesium And A Magnesium Alloy (Az91c) As Modified By Ion Implantation, Sanay Akavipat Jan 1985

Corrosion In Magnesium And A Magnesium Alloy (Az91c) As Modified By Ion Implantation, Sanay Akavipat

Doctoral Dissertations

"Magnesium and a magnesium alloy (AZ9 1C) have been ion implanted over a range of ion s energies (50 to 150 keV) and doses (1 x 1016 to 2 x 1017 ions/cm2) to modify the corrosion properties of the metals. The corrosion tests were done by anodic polarization in chloride -free and chloride containing aqueous solutions of a borated-boric acid with a pH of 9.3. Anodic polarization measurements showed that some implantations could greatly reduce the corrosion current densities at all impressed voltages and also increased slightly the pitting potential, which indicated the onset of the …

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Quantum Electrodynamics Based On Self-Energy: Lamb Shift And Spontaneous Emission Without Field Quantization, A. O. Barut, Jean F. Van Huele Jan 1985

Quantum Electrodynamics Based On Self-Energy: Lamb Shift And Spontaneous Emission Without Field Quantization, A. O. Barut, Jean F. Van Huele

Faculty Publications

The theory of radiative processes in quantum theory is formulated on the basis of self-energy, in analogy to classical radiation theory, and is explicitly carried out for the calculation of the Lamb shift and spontaneous emission.

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A Study Of Controlling Variables Using A Microcomputer Program Compared To The Piagetian Bending Rods Task, Rita Arlene Hrecz Jan 1985

A Study Of Controlling Variables Using A Microcomputer Program Compared To The Piagetian Bending Rods Task, Rita Arlene Hrecz

Dissertations and Theses @ UNI

This study compared two formats of controlling variables. Subjects' performance of controlling variables in the Piagetian Bending Rods Task was compared to their performance of controlling variables in the microcomputer interactive program called Measuring Gravitational Forces. The correlation result (0.78 on the Spearman rho and the Pearson Product Moment correlations) and results of the nonparametric Wilcoxon t test and the parametric correlated t indicated no statistically significant difference of subjects' performance of controlling variables in either task. No statistically significant gender difference of subjects' performance of either the Bending Rods Task or the Measuring Gravitational Forces computer program was found. …

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Evidence For Uncorrelated Electron Capture And K-Shell Excitation In S13++He Collisions, J. A. Tanis, E. M. Bernstein, M. W. Clark, W. G. Graham, Robert H. Mcfarland, T. J. Morgan, B. M. Johnson, K. W. Jones, M. Meron Jan 1985

Evidence For Uncorrelated Electron Capture And K-Shell Excitation In S13++He Collisions, J. A. Tanis, E. M. Bernstein, M. W. Clark, W. G. Graham, Robert H. Mcfarland, T. J. Morgan, B. M. Johnson, K. W. Jones, M. Meron

Physics Faculty Research & Creative Works

Evidence is presented for a two-step process in ion-atom collisions in which two independent interactions occur in a single encounter. Measurements for 15200-MeVS13++He collisions indicate that uncorrelated projectile K-shell excitation and capture of a target electron occur in a single collision with one target atom. The results are in reasonable qualitative agreement with theoretical predictions of this two-step process. © 1985 The American Physical Society.

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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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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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Electron Capture By Slow Alq+ Ions Colliding With Hydrogen, R. A. Phaneuf, M. Kimura, H. Sato, Ronald E. Olson Jan 1985

Electron Capture By Slow Alq+ Ions Colliding With Hydrogen, R. A. Phaneuf, M. Kimura, H. Sato, Ronald E. Olson

Physics Faculty Research & Creative Works

Total electron-capture cross sections have been measured for collisions of Alq+ (q=210) with H and H2 in the 20120-eV/amu energy range. The general trend of the cross sections for both H and H2 is an approximately linear increase with ionic charge state. The Al2++H and Al3++H systems were investigated theoretically using the molecular-orbital method with a pseudopotential to represent the Al3+ ion core. Coupled-channel calculations realize good agreement with experiment. An anomalously small cross section for Al2++H is attributed to the fact that of the 1 and 3 entrance channels, only the 1 …

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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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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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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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Lattice Dynamics Of Mixed Crystals Of Tise2, Roger D. Kirby, G.A. Freund, Jr. Dec 1984

Lattice Dynamics Of Mixed Crystals Of Tise2, Roger D. Kirby, G.A. Freund, Jr.

Roger Kirby Publications

We present the results of Raman scattering measurements on the mixed-crystal systems TiSe2-xSx, TiSe2-xTex, ZrxTi1-x Se2. At room temperature with the pure compounds all have crystal structures represented by the D3d(P3̃m1) space group with three atoms per unit cell. There are two Raman-active k=0 phonons, one of A1gˉ symmetry and one of Eg symmetry. In the TiSe2-xTex system, the A1gˉ and Egˉ phonon frequencies shift smoothly with concentration, and the shifts are well described by a simple virtual-crystal …

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A Model For Orientation Effects In Electron‐Transfer Reactions, Paul Siders, Robert J. Cave, R.A. Marcus Dec 1984

A Model For Orientation Effects In Electron‐Transfer Reactions, Paul Siders, Robert J. Cave, R.A. Marcus

All HMC Faculty Publications and Research

A method for solving the single‐particle Schrödinger equation with an oblate spheroidal potential of finite depth is presented. The wave functions are then used to calculate the matrix element TBA which appears in theories of nonadiabatic electron transfer. The results illustrate the effects of mutual orientation and separation of the two centers on TBA. Trends in these results are discussed in terms of geometrical and nodal structure effects. Analytical expressions related to TBA for states of spherical wells are presented and used to analyze the nodal structure effects for TBA for the spheroidal wells.

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(Super)Conformal Symmetry Breaking, Andrew Strominger, V. Parameswaran Nair Dec 1984

(Super)Conformal Symmetry Breaking, Andrew Strominger, V. Parameswaran Nair

Publications and Research

We argue that the only consistent way to break conformal invariance in a quantum theory of gravity is spontaneously in a finite locally conformal supersymmetric theory. This generically occurs whenever scalar fields are present. Covariant surface-integral expressions for the super-charge and four-momentum in terms of asymptotically constant spinor fields are derived. These are used to discuss stability and other aspects of the theory.

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Segregation Of Copper To The Surface Of Copper-Nickel Alloys, Peter A. Dowben Dec 1984

Segregation Of Copper To The Surface Of Copper-Nickel Alloys, Peter A. Dowben

Peter Dowben Publications

Copper segregation profiles at the surfaces of Cu17Ni83(111) and Cu17Ni83(100) have been calculated by a semiempirical procedure based upon previously published data. These profiles indicate that surface enrichment of copper is not limited only to the topmost layer but occurs for several layers away from the surface as well. A comparison of the calculated segregation profiles based upon the experimental results for the (100) and (111) surfaces of Cu17Ni83 do not agree with predictions based upon thermodynamic models of segregation.

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Threshold Effect In Mg-Doped Lithium Niobate, K. L. Sweeney, L. E. Halliburton, D. A. Bryan, R. R. Rice, Robert Gerson, H. E. Tomaschke Dec 1984

Threshold Effect In Mg-Doped Lithium Niobate, K. L. Sweeney, L. E. Halliburton, D. A. Bryan, R. R. Rice, Robert Gerson, H. E. Tomaschke

Physics Faculty Research & Creative Works

Optical absorption spectra were obtained after reducing (i.e., vacuum annealing) a series of LiNbO3 crystals grown from melts having various Mg concentrations and Li/Nb ratios. A band peaking at 500 nm, and assigned to oxygen vacancies containing two electrons, was the only absorption present in one set of crystals following reduction. In contrast, two overlapping bands peaking near 1200 and 760 nm were present in the other set of crystals immediately after the reduction. The 1200-nm band is assigned to a previously unreported electron trap and the 760-nm band to oxygen vacancies containing only one electron. These data are interpreted …

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A Study Of Integral Equations For Computing Radial Distribution Functions, Robert C. Scherzer Dec 1984

A Study Of Integral Equations For Computing Radial Distribution Functions, Robert C. Scherzer

Masters Theses

The use of integral equations to find radial distribution functions for computing thermodynamic properties is examined. The system considered is a simple classical fluid with interactions according to the Lennard-Jones (6-12) pair potential function. Two parametric integral equations (C and T) are studied in detail. Derivation of equation T and a power series solution are given. Computer solutions at several different temperatures, densities, and parameter values are obtained. Comparisons are made betv/een these results and results from integral equation N, PY, and HNC, and results from Monte Carlo, molecular dynamics, and power series methods. Equations C and N are found …

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Semiflexible Self-Avoiding Polymers, Rolfe G. Petschek Dec 1984

Semiflexible Self-Avoiding Polymers, Rolfe G. Petschek

Faculty Scholarship

A simple two dimensional model for semiflexible polymers is discussed. A rigorous lower bound is obtained for the free energy and a rigorous upper bound is obtained for the energy. These bounds evaluated for infinite systems are shown to be in serious conflict with results obtained by a Monte Carlo simulation of a finite system.

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Increased Optical Damage Resistance In Lithium Niobate, D. A. Bryan, Robert Gerson, H. E. Tomaschke Dec 1984

Increased Optical Damage Resistance In Lithium Niobate, D. A. Bryan, Robert Gerson, H. E. Tomaschke

Physics Faculty Research & Creative Works

We have confirmed greatly improved resistance to photorefractive damage in compositions of lithium niobate containing 4.5 at. % MgO or more. Holographic diffraction measurements of photorefraction demonstrated that the improved performance is due to a hundredfold increase in the photoconductivity, rather than a decrease in the Glass current. The diffraction efficiency shows an Arrhenius dependence on temperature, with an activation energy of 0.1 eV for the damage-resistant compositions, compared with 0.5 eV for undoped or low-magnesium compositions. The damage-resistant compositions are distinguished by a 2.83-μm absorption line instead of the usual 2.87-μm line due to the OH-stretch vibration.

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Microprocessor-Based Pressure Controller, E. Redd, John T. Park Dec 1984

Microprocessor-Based Pressure Controller, E. Redd, John T. Park

Physics Faculty Research & Creative Works

A device for automatic control of pressure in an ion-atom scattering experiment has been constructed. The system was modeled to achieve the minimum time for transition from one pressure to another. The pressure controller "learns" the system response and iterates the parameters used in "profiling" the valve voltage to reduce the transition time. The device has been used with two different scattering chambers and has worked well with both.

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Yellow Giants In Young Clusters. Ii. A Comparison Of Observation With Theory, Edward G. Schmidt Dec 1984

Yellow Giants In Young Clusters. Ii. A Comparison Of Observation With Theory, Edward G. Schmidt

Edward Schmidt Publications

Luminosities and effective temperatures are calculated for 17 nonvariable yellow giants and supergiants and nine Cepheids which were previously identified as members of open clusters. These stars are identified as being in the helium core burning stage of evolution. A comparison with the predictions of pulsation theory does not show any disagreement. On the other hand, several comparisons with the theory of stellar evolution produce discrepancies which suggest that effects neglected in the calculations may play an important role in the evolution of these stars.

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Model Calculations Of The Micrometer To Millimeter Intrinsic Absorption For Simple Ceramics, John R. Hardy, P. J. Edwardson, J. A. O'Gara Nov 1984

Model Calculations Of The Micrometer To Millimeter Intrinsic Absorption For Simple Ceramics, John R. Hardy, P. J. Edwardson, J. A. O'Gara

John R. Hardy Papers

A systematic study has been made of the strength of the intrinsic absorption, or loss, for millimeter to micrometer electromagnetic radiation propagating in simple ceramic materials. This study employed a number of model diatomic systems whose simplicity enabled the basic two-phonon decay process, responsible for this intrinsic loss, to be computed with precision, even at the lowest frequencies, on a dedicated microcomputer. It was found that, at least at low frequencies, the loss was a relatively structureless universal function of the atomic mass ratio, in general agreement with earlier results for real alkali halides. In particular, it was found that, …

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Absence Of Minimum Metallic Conductivity In Gd(3-X)Vxs4 At Very Low Temperature And Evidence For A Coulomb Gap, S. Washburn, Richard A. Webb, S. Von Molnar, F. Holtzberg Nov 1984

Absence Of Minimum Metallic Conductivity In Gd(3-X)Vxs4 At Very Low Temperature And Evidence For A Coulomb Gap, S. Washburn, Richard A. Webb, S. Von Molnar, F. Holtzberg

Faculty Publications

Gd(3-x)vxS4 provides a convenient analog of a compensated semiconductor in which, for x≃0.3, the mobility edge can be tuned smoothly through the Fermi energy by the application of a magnetic field. The results of a search for a minimum metallic conductivity demonstrate that, down to T=6 mK, the metal-insulator transition is smooth. In the insulating regime, the temperature dependence of the conductivity was more consistent with the theory of mutual interactions than with the theory of pure localization.

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String Induced Space Compactification, P. G. Freund, P. Oh, James Thomas Wheeler Nov 1984

String Induced Space Compactification, P. G. Freund, P. Oh, James Thomas Wheeler

All Physics Faculty Publications

Motivated by the possibility of a finite theory of gravity provided by superstrings in ten space-time dimensions, we analyze the problem of space compactification in the context of string dynamics. Such an analysis is hampered by conceptual and technical problems, stemming from the existence of the quantum string's own graviton mode on the one hand, and from Witten's observation of anomalies in a not specially chosen curves space-time on the other hand. Still, in the context of a classical local field presentation of string theory à la Nambu and Hosotani, supplemented by gravitational and Kalb-Ramond interactions, we are able to …

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Central-Peak-Soft-Mode, Coupling In Ferroelectric Gd2(Moo4)3, J. Petzelt, F. Smutny, V. Katkanant, F. G. Ullman, John R. Hardy, A. A. Volkov, G. V. Kozlov, S. P. Lebedev Nov 1984

Central-Peak-Soft-Mode, Coupling In Ferroelectric Gd2(Moo4)3, J. Petzelt, F. Smutny, V. Katkanant, F. G. Ullman, John R. Hardy, A. A. Volkov, G. V. Kozlov, S. P. Lebedev

John R. Hardy Papers

Transmission measurements on Gd2(MoO4)3 in the ( 5-50)-cm-1 region were performed with use of tunable backward-wave oscillator sources (5-30 cm>-1) and a Fourier spectrometer (30-50 cm>-1). The resulting dielectric spectra show an additional low-frequency dispersion which was fitted with a standard central-peak model. Its characteristic relaxation frequency is ~20 cm>-1 and the coupling between the soft mode and central mode increases near the transition temperature. This model also accounts very well for the weak anomaly in the clamped permittivity Ec measured at 63 MHz. The same central mode …

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