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Faculty Publications

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1993

Articles 1 - 30 of 41

Full-Text Articles in Physical Sciences and Mathematics

Plate Motions In The North Andean Region, Jeffrey T. Freymueller, James N. Kellogg, Victor Vega Dec 1993

Plate Motions In The North Andean Region, Jeffrey T. Freymueller, James N. Kellogg, Victor Vega

Faculty Publications

Repeated geodetic measurements with the Global Positioning System (GPS) provide direct measurements of displacements due to plate motions and active crustal deformation in Central America and northern South America, an area of complex interaction of the Nazca, Cocos, Caribbean and South American plates. The displacement rates for the period 1988-1991, obtained from the results of the first three Central And South America (CASA) GPS campaigns, are in general agreement with the predictions of the NUVEL-1 plate motion model, but there are differences in detail between the observations and the model. The Nazca-North Andes convergence rate vector measured by GPS is …

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Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein Dec 1993

Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein

Faculty Publications

It is shown that the analysis of surface layers by neutron reflection interferometry is considerably enhanced by performing the reflectometry with phase information. We discuss two methods of providing such information. One method involves physically adding an extra reference layer, whose amplitude and phase are known theoretically. The other uses the Lloyd's mirror configuration, in which a directly propagating ray that interferes with the reflected ray supplies the phase information. The methods have much in common with holography.

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Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James N. Kellogg Dec 1993

Seismic Evidence For Blind Thrusting Of The Northwestern Flank Of The Venezuelan Andes, Bruno De Toni, James N. Kellogg

Faculty Publications

Surface geology and seismic and well data from the northwestern flank of the Venezuelan Andes indicate overthrusting of Andean basement rocks toward the adjacent Maracaibo Basin along a blind thrust fault. The frontal monocline is interpreted as the forelimb of a northwestward verging fault-related fold deformed over a crustal-scarle map. The Andean block has been thrust 20 km to the northwest and uplifted 10 km on a ramp that dips about 20o-30o southeastward. The thrust fault ramps up through crystalline basement rocks to a decollement horizon within the shaly units of the Cretaceous Colon-Mito Juan formations. Backthrusts …

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The Importance Of Using Multiple Styles Of Generalization, Tony R. Martinez, D. Randall Wilson Nov 1993

The Importance Of Using Multiple Styles Of Generalization, Tony R. Martinez, D. Randall Wilson

Faculty Publications

There are many ways for a learning system to generalize from training set data. There is likely no one style of generalization which will solve all problems better than any other style, for different styles will work better on some applications than others. This paper presents several styles of generalization and uses them to suggest that a collection of such styles can provide more accurate generalization than any one style by itself. Empirical results of generalizing on several real-world applications are given, and comparisons are made on the generalization accuracy of each style of generalization. The empirical results support the …

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Towards A General Distributed Platform For Learning And Generalization, Brent W. Hughes, Tony R. Martinez Nov 1993

Towards A General Distributed Platform For Learning And Generalization, Brent W. Hughes, Tony R. Martinez

Faculty Publications

Different learning models employ different styles of generalization on novel inputs. This paper proposes the need for multiple styles of generalization to support a broad application base. The Priority ASOCS model (Priority Adaptive Self-organizing Concurrent System) is overviewed and presented as a potential platform which can support multiple generalization styles. PASOCS is an adaptive network composed of many simple computing elements operating asynchronously and in parallel. The PASOCS can operate in either a data processing mode or a learning mode. During data processing mode, the system acts as a parallel hardware circuit. During leaming mode, the PASOCS incorporates rules, with …

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Purification And Characterization Of A Gamma-Like Dna-Polymerase From Chenopodium Album L., K. Meißner, Sabine Heinhorst, Gordon C. Cannon, T. Börner Oct 1993

Purification And Characterization Of A Gamma-Like Dna-Polymerase From Chenopodium Album L., K. Meißner, Sabine Heinhorst, Gordon C. Cannon, T. Börner

Faculty Publications

A DNA polymerase activity from mitochondria of the dicotyledonous angiosperm Chenopodium album L. was purified almost 9000 fold by successive column chromatography steps on DEAE cellulose, heparin agarose and ssDNA cellulose. The enzyme was characterized as a gamma-class polymerase, based on its resistance to inhibitors of the nuclear DNA polymerase alpha and its preference for poly(rA).(dT)12-18 over activated DNA in vitro. The molecular weight was estimated to be 80,000 - 90,000. A 3' to 5' exonuclease activity was found to be tightly associated with the DNA polymerase activity through all purification steps. This is the first report of an association …

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Driven Diffusion Of Particles, First-Passage Front, And Interface Growth, R. Bidaux, Ras B. Pandey Oct 1993

Driven Diffusion Of Particles, First-Passage Front, And Interface Growth, R. Bidaux, Ras B. Pandey

Faculty Publications

We study a computer-simulation model for driven particles on a discrete lattice where a fraction p of the lattice sites is randomly occupied by frozen impurities (barriers), and an imposed bias governs the particles’ hopping through the lattice. These particles (the carriers) are initially released from a source of wetting fluid from one end of the lattice in order to wet and the dry lattice on their trails. We study the transport of particles, frontier of their trail, and the growth of the interface between the wet and dry regions as a function of the biased field and the number …

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Rsvp: A New Resource Reservation Protocol, Daniel Zappala, Stephen Deering, Deborah Estrin, Scott Shenker, Lixia Zhang Sep 1993

Rsvp: A New Resource Reservation Protocol, Daniel Zappala, Stephen Deering, Deborah Estrin, Scott Shenker, Lixia Zhang

Faculty Publications

The current Internet architecture, embodied in the Internet Protocol (IP) network protocol, offers a very simple service model: point-to-point best-effort service. In recent years, several new classes of distributed applications have been developed, such as remote video, multimedia conferencing, data fusion, visualization, and virtual reality. It is becoming increasingly clear that the Internet’s primitive service model is inadequate for these new applications. This inadequacy stems from the failure of the point-to-point best-effort service model to address two application requirements. First, many of these applications are very sensitive to the quality of service their packets receive. For a network to deliver …

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Classification Of The Tor-Algebras Of Codimension Four Almost Complete Intersections, Andrew R. Kustin Sep 1993

Classification Of The Tor-Algebras Of Codimension Four Almost Complete Intersections, Andrew R. Kustin

Faculty Publications

Let (R, m, k) be a local ring in which 2 is a unit. Assume that every element of k has a square root in k . We classify the algebras Tor'(R/J, k) as J varies over all grade four almost complete intersection ideals in R. The analogous classification has already been found when J varies over all grade four Gorenstein ideals [21], and when J varies over all ideals of grade at most three [5, 30]. The present paper makes use of the classification, in [21], of the Tor-algebraso f codimension four Gorenstein rings, as well as the (usually …

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Radially Symmetrical Flow Of Reacting Liquid With Changing Viscosity, S.E. Solovyov, V.A. Volpert, S.P. Davytan Aug 1993

Radially Symmetrical Flow Of Reacting Liquid With Changing Viscosity, S.E. Solovyov, V.A. Volpert, S.P. Davytan

Faculty Publications

Frontal regimens for one-dimensional flow of reacting liquid with changing viscosity are studied. Stationary solutions are investigated for the case of narrow reaction zones that shrink to a front. The results of numerical solution of the nonstationary problem are presented. Complex oscillations resulting from period-doubling bifurcations are found.

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Driven Diffusion, Kawasaki Dynamics, Mixing, And Spatial Ordering In An Interacting Lattice-Gas, Yan He, Ras B. Pandey Jul 1993

Driven Diffusion, Kawasaki Dynamics, Mixing, And Spatial Ordering In An Interacting Lattice-Gas, Yan He, Ras B. Pandey

Faculty Publications

Kawasaki dynamics is used to study the transport properties of a nonequilibrium steady state system of interacting lattice gas of oppositely charged particles in a linear gradient field in two dimensions. The rms displacements show unusual nondiffusive transport. The effective conductivity varies with the temperature which deviates from the Arrhenius law and depends on the range of interaction. Density of a fully mixed state decays with temperature with a power law. Onset of spatial ordering occurs in a certain temperature range at a fixed range of interaction.

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Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal Jul 1993

Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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Electronegativity And Bond Type 2. Evaluation Of Electronegativity Scales, Gordon Sproul Jul 1993

Electronegativity And Bond Type 2. Evaluation Of Electronegativity Scales, Gordon Sproul

Faculty Publications

No abstract provided.

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Formation Of O-Tyrosine And Dityrosine In Proteins During Radiolytic And Metal-Catalyzed Oxidation, Thomas G. Huggins, Mary C. Wells-Knecht, Nicholas A. Detorie, John W. Baynes, Suzanna R. Thorpe Jun 1993

Formation Of O-Tyrosine And Dityrosine In Proteins During Radiolytic And Metal-Catalyzed Oxidation, Thomas G. Huggins, Mary C. Wells-Knecht, Nicholas A. Detorie, John W. Baynes, Suzanna R. Thorpe

Faculty Publications

To evaluate their usefulness as chemical indicators of cumulative oxidative damage to proteins, we studied the kinetics and extent of formation of ortho-tyrosine (0-Tyr), dityrosine (DT), and dityrosine-like fluorescence (Ex = 3 17 nm, E,,, = 407 nm) in the model proteins RNase and lysozyme exposed to radiolytic and metalcatalyzed (H20z/Cu2+) oxidation (MCO). Although there were protein-dependent differences, o-Tyr, DT, and fluorescence increased coordinately during oxidation of the proteins in both oxidation systems. The contribution of DT to total dityrosine-like fluorescence in oxidized proteins varied from 2-10070, depending on the protein, type of oxidation, and extent of oxidative damage. In …

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Oxidized Amino Acids In Lens Protein With Age: Measurement Of O-Tyrosine And Dityrosine In The Aging Human Lens, Mary C. Wells-Knect, Thomas G. Huggins, Daniel G. Dyer, Suzanne R. Thorpe, John W. Baynes Jun 1993

Oxidized Amino Acids In Lens Protein With Age: Measurement Of O-Tyrosine And Dityrosine In The Aging Human Lens, Mary C. Wells-Knect, Thomas G. Huggins, Daniel G. Dyer, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

The concentrations of ortho-tyrosine (o-Tyr) and dityrosine (DT) were measured in noncataractous human lenses in order to assess the role of proteinoxidation reactions in the aging of lens proteins. The measurements were conducted by selected ion monitoring-gas chromatography/mass spectrometry using deuterium-labeled internal standards, which provided both high sensitivity and specificity for the quantitation of o-Tyr and DT. Between ages 1 and 78 years, the o-Tyr concentration in lens proteins varied from 0.3 to 0.9 mmol of o-Tyr/mol of Phe (n = 19), while DT ranged from 1 to 3 mumol of DT/mol of Tyr (n = 30). There were no …

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Ordering Processes In Porous-Media, J.C. Lee Jun 1993

Ordering Processes In Porous-Media, J.C. Lee

Faculty Publications

The ordering processes in a binary liquid mixture confined in a Vycor type of pore and at temperatures near the transition temperature of the pure system Tc are studied using a kinetic Ising model and the method of Monte Carlo simulations. The results for dynamics show quite clear signatures of the pore width but no notable difference between T > Tc and T < Tc. In the results for statics, the small angle part of the structure factor increases rapidly as T approaches Tc in the one-phase region. This suggests the onset of ordering but the fluctuation of …

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Maillard Reaction Products And Their Relation To Complications In Insulin-Dependent Diabetes Mellitus, David R. Mccance, Daniel G. Dryer, John A. Dunn, Karen E. Bailie, Suzanne R. Thorpe, John W. Baynes, Timothy J. Lyons Jun 1993

Maillard Reaction Products And Their Relation To Complications In Insulin-Dependent Diabetes Mellitus, David R. Mccance, Daniel G. Dryer, John A. Dunn, Karen E. Bailie, Suzanne R. Thorpe, John W. Baynes, Timothy J. Lyons

Faculty Publications

Glycation, oxidation, and browning of proteins have all been implicated in the development of diabetic complications. We measured the initial Amadori adduct, fructoselysine (FL); two Maillard products, N epsilon-(carboxymethyl) lysine (CML) and pentosidine; and fluorescence (excitation = 328 nm, emission = 378 nm) in skin collagen from 39 type 1 diabetic patients (aged 41.5 +/- 15.3 [17-73] yr; duration of diabetes 17.9 +/- 11.5 [0-46] yr, [mean +/- SD, range]). The measurements were related to the presence of background (n = 9) or proliferative (n = 16) retinopathy; early nephropathy (24-h albumin excretion rate [AER24] > or = 20 micrograms/min; n …

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Large Amplitude L=1 Coherent Structures In Non-Neutral Plasmas Confined In A Cylindrical Trap, Ross L. Spencer, Grant W. Mason Jun 1993

Large Amplitude L=1 Coherent Structures In Non-Neutral Plasmas Confined In A Cylindrical Trap, Ross L. Spencer, Grant W. Mason

Faculty Publications

The computation of l= 1 coherent structures in non-neutral plasmas with arbitrary density profiles and for large displacements of the plasma from the symmetry axis of a confining cylindrical trap is described. As the structures are displaced from the axis, they revolve about the symmetry axis with a frequency that typically increases with displacement. The plasma also is distorted into an approximately elliptical shape. The frequency shifts and the eccentricities as a function of displacement, plasma size, and the shape of the density profile are both computed numerically and calculated analytically. The results are shown to be consistent with data …

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Accumulation Of Maillard Reaction Products In Skin Collagen In Diabetes And Aging, Daniel G. Dyer, John A. Dunn, Suzanne R. Thorpe, Karen E. Bailie, Timothy L. Lyons, David R. Mccance, John W. Baynes Jun 1993

Accumulation Of Maillard Reaction Products In Skin Collagen In Diabetes And Aging, Daniel G. Dyer, John A. Dunn, Suzanne R. Thorpe, Karen E. Bailie, Timothy L. Lyons, David R. Mccance, John W. Baynes

Faculty Publications

To investigate the contribution of glycation and oxidation reactions to the modification of insoluble collagen in aging and diabetes, Maillard reaction products were measured in skin collagen from 39 type 1 diabetic patients and 52 nondiabetic control subjects. Compounds studied included fructoselysine (FL), the initial glycation product, and the glycoxidation products, N epsilon-(carboxymethyl) lysine (CML) and pentosidine, formed during later Maillard reactions. Collagen-linked fluorescence was also studied. In nondiabetic subjects, glycation of collagen (FL content) increased only 33% between 20 and 85 yr of age. In contrast, CML, pentosidine and fluorescence increased five-fold, correlating strongly with age. In diabetic patients, …

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Fast Accurate Simulation Of Large Shared Memory Multiprocessors, Bob Boothe Phd Jun 1993

Fast Accurate Simulation Of Large Shared Memory Multiprocessors, Bob Boothe Phd

Faculty Publications

Fast computer simulation is an essential tool in the design of large parallel computers. Our Fast Accurate Simulation Tool, FAST, is able to accurately simulate large shared memory multiprocessors and their execution of parallel applications at simulation speeds that are one to two orders of magnitude faster than previous comparable simulators. The key ideas involve execution driven simulation techniques that modify the object code of the application program being studied. This produces an augmented version of the code that is directly executed and performs much of the work of the simulation. We extend the previous work by introducing several new …

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Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred May 1993

Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred

Faculty Publications

We have studied at cryogenic temperatures photoluminescence features which lie more than 0.15 eV below the band edge in ZnxCd1-xTe (0≤x≤0.09) crystals. The same features, namely a defect band which lies at about 0.13-0.20 eV below the band-gap energy and a peak at 1.1 eV, that are observed in pure CdTe samples are observed in these alloy materials. In annealed samples we observe that the 1.1 eV feature, which has been attributed to tellurium vacancies, increases with fast cooling. Increased concentrations of tellurium vacancies can be understood in terms of the phase diagram of CdTe which indicates that higher concentrations …

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Development Of New Methods For Assessing Solidification/Stabilization Of Hazardous Waste Using Solid-State Nuclear Magnetic Resonance Techniques (Ph.D Dissertation, Lsu), Michael A. Janusa May 1993

Development Of New Methods For Assessing Solidification/Stabilization Of Hazardous Waste Using Solid-State Nuclear Magnetic Resonance Techniques (Ph.D Dissertation, Lsu), Michael A. Janusa

Faculty Publications

New methods for assessing solidification/stabilization (S/S) of hazardous waste using solid-state nuclear magnetic resonance are developed for the purpose of diagnosing on a microscopic level the performance of S/S as a hazardous waste disposal technique. There are four techniques developed and described in this dissertation: (1) Solid-state deuterium NMR spectroscopy is used to determine if a particular deuterated organic waste is effectively solidified/stabilized and to determine the lower limit of the bond strength between the waste and the cement matrix; (2) Constant time pulsed field gradient ^ NMR spectroscopy is tested on a liquid waste encapsulated within a solidified matrix …

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Scaling Water And Energy Fluxes In Climate Systems: Three Land-Atmospheric Modeling Experiments, Eric F. Wood, Venkataraman Lakshmi May 1993

Scaling Water And Energy Fluxes In Climate Systems: Three Land-Atmospheric Modeling Experiments, Eric F. Wood, Venkataraman Lakshmi

Faculty Publications

The effects of small-scale heterogeneity in land-surface characteristics on the large-scale fluxes of water and energy in the land-atmosphere system have become a central focus of many of the climatology research experiments. The acquisition of high-resolution land-surface data through remote sensing and intensive land-climatology field experiments(like HAPEX and EIFE) has provided data to investigate the interactions between microscale land-atmosphere interactions and macroscale models. One essential research question is how to account for the small-scale heterogeneities and whether `effective' parameters can be used in the macroscale models. To address this question ofscaling, three modeling experiments were performed and are reviewed in …

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Evidence Of A Nondiffusive Transport In A Monodisperse Screened Coulomb System By A Molecular-Dynamics Simulation, Michael Wild, Ras B. Pandey May 1993

Evidence Of A Nondiffusive Transport In A Monodisperse Screened Coulomb System By A Molecular-Dynamics Simulation, Michael Wild, Ras B. Pandey

Faculty Publications

A molecular-dynamics simulation is carried out for particles (tracers) interacting with a screened Coulomb potential in three dimensions. A phase transition is observed from a liquid to an fcc solid on reducing the temperature at a fixed density, consistent with previous studies. In the liquid phase, the variation of the rms displacement Rtr of the charged particles with time seems to depend on the density and the temperature. In the short-time regime, the effective exponent k for the subdiffusive power-law behavior, i.e., Rtr∼tk, decreases on increasing the density and lowering the temperature. A crossover from …

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Cp-Odd Nucleon Potential, Vladimir Gudkov, Xiao-Gang He, Bruce H.J. Mckellar May 1993

Cp-Odd Nucleon Potential, Vladimir Gudkov, Xiao-Gang He, Bruce H.J. Mckellar

Faculty Publications

The P-odd and CP-odd nucleon potential for different models of CP violation in the one-meson exchange approximation is studied. It is shown that the main contribution is due to the π-meson exhcange which leads to a simple one-parameter CP-odd nucleon potential.

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On The Distribution Of Sums Of Residues, Jerrold R. Griggs Apr 1993

On The Distribution Of Sums Of Residues, Jerrold R. Griggs

Faculty Publications

No abstract provided.

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Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández Mar 1993

Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández

Faculty Publications

In the first-order Raman spectrum of amorphous carbon (a-C) there is a low-frequency feature in the 200-900-cm-1 region. This feature is characteristic of the highly disordered amorphous-carbon materials. We note that the intensity of this feature is very sensitive to the thermal history of samples, thus suggesting that it is an important measure of the degree of disorder of the a-C materials. We also discuss the relationship between this feature and the phonon density of states of graphite.

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Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet Mar 1993

Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet

Faculty Publications

Numerical investigations of a warm-fluid model with an isothermal equation of state for the perpendicular dynamics of an axisymmetric, magnetically confined pure electron plasma predict an exponentially unstable, l=1, diocotron mode for hollow density profiles. The unstable mode can be identified with a stable, nonsmooth mode that exists in cold drift models but which is destabilized by finite temperature effects. The unstable mode has many properties similar to the experimental results reported by Driscoll [Phys. Rev. Lett. 64, 645 (1990)].

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In-Medium Behavior Of The Qcd ϴ Term And The Value Of Cp Violation In Nuclei, Vladimir Gudkov Feb 1993

In-Medium Behavior Of The Qcd ϴ Term And The Value Of Cp Violation In Nuclei, Vladimir Gudkov

Faculty Publications

The expectation value of the θ term in QCD for nuclear matter is estimated in the nucleon gas approximation. There is no significant renormalization (to an accuracy ∼10%) of the CP violation in nuclei due to the similar behaviors for the in-medium values of the θ term and quark condensates.

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Precision Spectroscopy Using The Lamb Dip In A Pure Ion Plasma, P. N. Barnes, Grant W. Hart Feb 1993

Precision Spectroscopy Using The Lamb Dip In A Pure Ion Plasma, P. N. Barnes, Grant W. Hart

Faculty Publications

The use of the Lamb dip as a technique for precision spectroscopy in a non-neutral plasma is explored through computer modeling. Using singly ionized magnesium as the ion and under typical pure ion plasma conditions, the measurement appears to be feasible. Under the conditions calculated here, the Lamb dip is only 4% wider than the natural linewidth of the transition.

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