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Single Ionization Of Ne By Intense Laser Fields, C. R. Feeler, Ronald E. Olson Jun 2000

Single Ionization Of Ne By Intense Laser Fields, C. R. Feeler, Ronald E. Olson

Physics Faculty Research & Creative Works

A three-dimensional classical Monte Carlo method has been used to examine the final state electron dynamics after single ionization of neon in an electric field generated by a short-pulse high-intensity laser. Linearly and circularly polarized fields were studied. Intensities ranging from 3 x 1014 to 3 x 1015 W cm-2 were used with a wavelength of 800 nm and a full-width at half-maximum of 30 fs. At these values, the Keldysh parameter is less than one, making the classical approximation valid. A potential determined by Hartree-Fock calculations has been used to model the Ne atom. A kinematically complete picture …

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Dimethylsulfoxide Reductase: An Enzyme Capable Of Catalysis With Either Molybdenum Or Tungsten At The Active Site, Lisa J. Stewart, Susan Bailey, Brian Bennett, John M. Charnock, C. David Garner, Alan S. Mcalpine Jun 2000

Dimethylsulfoxide Reductase: An Enzyme Capable Of Catalysis With Either Molybdenum Or Tungsten At The Active Site, Lisa J. Stewart, Susan Bailey, Brian Bennett, John M. Charnock, C. David Garner, Alan S. Mcalpine

Physics Faculty Research and Publications

DMSO reductase (DMSOR) from Rhodobacter capsulatus, well-characterised as a molybdoenzyme, will bind tungsten. Protein crystallography has shown that tungsten in W-DMSOR is ligated by the dithiolene group of the two pyranopterins, the oxygen atom of Ser147 plus another oxygen atom, and is located in a very similar site to that of molybdenum in Mo-DMSOR. These conclusions are consistent with W LIII-edge X-ray absorption, EPR and UV/visible spectroscopic data. W-DMSOR is significantly more active than Mo-DMSOR in catalysing the reduction of DMSO but, in contrast to the latter, shows no significant ability to catalyse the oxidation of DMS.

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Terdiurnal Oscillations In Oh Meinel Rotational Temperatures For Fall Conditions At Northern Mid-Latitude Sites, W. R. Pendleton Jr., Michael J. Taylor, Larry Gardner Jun 2000

Terdiurnal Oscillations In Oh Meinel Rotational Temperatures For Fall Conditions At Northern Mid-Latitude Sites, W. R. Pendleton Jr., Michael J. Taylor, Larry Gardner

All Physics Faculty Publications

High‐precision (∼0.5 K) measurements of OH Meinel (M) (6,2) rotational temperatures above the Bear Lake Observatory, UT (42°N, 112°W) during October 1996 have revealed an interesting and unexpected mean nocturnal pattern. Ten quality nights (>100 h) of data have been used to form a mean night for autumnal, near‐equinoctial conditions. The mean temperature and RMS variability associated with this mean night were 203 ± 5 K and 2.4 K, respectively, and compare very favorably with expectations based on Na‐lidar measurements of mean tidal temperature perturbations over Urbana, IL (40°N, 88°W) during the fall 1996. Furthermore, this comparison shows that …

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Comments On D Branes And The Renormalization Group, Vatche Sahakian Jun 2000

Comments On D Branes And The Renormalization Group, Vatche Sahakian

All HMC Faculty Publications and Research

We review the de Boer-Verlinde-Verlinde formalism for the renormalization group in the context of Dp-brane vacua for p < 5. We comment on various aspects of the dictionary between bulk and boundary and relate the discussion to the Randall-Sundrum scenario. We find that the gravitational coupling for the Randall-Sundrum gravity on the Dp-brane worldvolume is dressed by the c-function of the Yang-Mills theory. We compute the beta function and find the expected uneventful flow prescribed by the classical dimension of the Yang-Mills operator.

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Control And Data Acquisition For An Electron Spectrometer System, Stanislav Rumega Jun 2000

Control And Data Acquisition For An Electron Spectrometer System, Stanislav Rumega

Masters Theses

An electron spectrometer system, installed on one of the beam lines in the WMU Van de Graaff accelerator laboratory, consists of two 45o parallel-plate electrostatic analyzers, a decelerating grid, and a channeltron. It allows the energy analysis, angular analysis, and the detection of continuum electrons ejected following the bombardment of a target with accelerated ions or electrons. First, the principles of operation of the spectrometer itself are discussed with emphasis on the energy analysis. Next, the electronics and computer interfacing required for control of the spectrometer functions and for acquisition of data are described. Finally, the control and data …

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Reversible Carbon Monoxide Binding And Inhibition At The Active Site Of The Fe-Only Hydrogenase, Brian Bennett, Brian J. Lemon, John W. Peters Jun 2000

Reversible Carbon Monoxide Binding And Inhibition At The Active Site Of The Fe-Only Hydrogenase, Brian Bennett, Brian J. Lemon, John W. Peters

Physics Faculty Research and Publications

Carbon monoxide binding and inhibition have been investigated by electron paramagnetic resonance (EPR) spectroscopy in solution and in crystals of structurally described states of the Fe-only hydrogenase (CpI) from Clostridium pasteurianum. Simulation of the EPR spectrum of the as-isolated state indicates that the main component of the EPR spectrum consists of the oxidized state of the “H cluster” and components due to reduced accessory FeS clusters. Addition of carbon monoxide to CpI in the presence of dithionite results in the inhibition of hydrogen evolution activity, and a characteristic axial EPR signal [geff(1), geff(2), and …

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Photoionization And Photofragmentation Of Gaseous Toluene Using 80-Fs, 800-Nm Laser Pulses, A. M. Müller, Cornelis J. Uiterwaal, B. Witzel, J. Wanner, K.-L. Kompa Jun 2000

Photoionization And Photofragmentation Of Gaseous Toluene Using 80-Fs, 800-Nm Laser Pulses, A. M. Müller, Cornelis J. Uiterwaal, B. Witzel, J. Wanner, K.-L. Kompa

C.J.G.J. Uiterwaal Publications

This paper presents ion yields resulting from multiphoton ionization and fragmentation of gaseous toluene (C7H8) in the focus of an 80 fs Ti:sapphire laser beam (λ = 800 nm) with a sufficiently small B-integral [Siegman, Lasers (University Science Books, Mill Valley, CA, 1986)]. The peak intensity was varied between 1.9x1013 and 2.8x1013Wcm-2, and both linear and circular polarization were used. Over the whole range of intensities studied, only the singly charged parent ion and its fragment, C7H7+, are found. Although the Keldysh adiabaticity parameter equals …

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System Architecture And Hardware Design Of The Cdf Xft Online Track Processor, S. Holm, J.R. Dittman, J. Freeman, R. Klein, J.D. Lewis, T.M. Shaw, T. Wesson, C. Ciobanu, J. Gerstenslager, J. Hoftiezer, R. Hughes, M. Johnson, P. Koehn, C. Neu, C. Sanchez, B.L. Winer, Kenneth A. Bloom, D. Gerdes, J.W. Dawson, W.N. Haberichter Jun 2000

System Architecture And Hardware Design Of The Cdf Xft Online Track Processor, S. Holm, J.R. Dittman, J. Freeman, R. Klein, J.D. Lewis, T.M. Shaw, T. Wesson, C. Ciobanu, J. Gerstenslager, J. Hoftiezer, R. Hughes, M. Johnson, P. Koehn, C. Neu, C. Sanchez, B.L. Winer, Kenneth A. Bloom, D. Gerdes, J.W. Dawson, W.N. Haberichter

Kenneth Bloom Publications

A trigger track processor is being designed for CDF Run 2. This processor identifies high momentum (PT > 1.5 GeV/c) charged tracks in the new central outer tracking chamber for the CDF I1 detector. The design of the track processor, called the extremely Fast Trackcr (XFT), is highly parallel and handle an input rate of 183 Gbitslsec and output rate of 44 Gbitdsec. The XFT is pipclined and reports the results for a new event every 132ns. The XFT uses threc stages, hit classification, segment finding, and segment linking. The pattem recognition algorithm for the three stages are implemented …

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A Look At What Is (And Isn't) Known About Quasar Broad Line Regions And How Narrow-Line Seyfert 1s Fit In, C. Martin Gaskell Jun 2000

A Look At What Is (And Isn't) Known About Quasar Broad Line Regions And How Narrow-Line Seyfert 1s Fit In, C. Martin Gaskell

Department of Physics and Astronomy: Faculty Publications

The evidence is reviewed that the Broad Line Region (BLR) probably has two distinct components located at about the same distance from the central black hole. One component, BLR II, is optically-thick, low-ionization emission at least some of which arises from a disc and the other, BLR I, is probably optically-thin emission from a more spherically symmetric halo or atmosphere. The high Fe II/Hβ ratios seen in Narrow-Line Seyfert 1 galaxies (NLS1s) are not due to strong Fe II emission, as is commonly thought, but to unusually weak Balmer emission, probably caused by higher densities. NLS1s probably differ from non-NLS1s …

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Time Domain Measurement Of The Nonlinear Refractive Index In Optical Fibers And Semiconductor Film, Hernando Garcia May 2000

Time Domain Measurement Of The Nonlinear Refractive Index In Optical Fibers And Semiconductor Film, Hernando Garcia

Dissertations

A new technique to measure the nonlinear refractive index n2 in optical fibers and semiconductor films has been developed. It is based on the time delay two-beam coupling of very intense picosecond laser pulses that have been self-phase modulated in the nonlinear optical medium. The two beams are coupled in a slow responding medium that is sensitive to time dependent phase distortions. We determine that the amount of phase distortion experienced by the pulse is proportional to the nonlinear refractive index of the medium, This time domain approach can also be applied to optical fiber amplifiers in the presence …

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Diffractive Dijets With A Leading Antiproton In P̅P Collisions At √S = 1800 Gev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration May 2000

Diffractive Dijets With A Leading Antiproton In P̅P Collisions At √S = 1800 Gev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report results from a study of events with a leading antiproton of beam momentum fraction 0.905 <xF < 0.965 and 4-momentum transfer squared |t|< 3 GeV2 produced in p̅p collisions at √s =1800 GeV at the Fermilab Tevatron collider. Approximately 2% of the events contain two jets of transverse energy ETjet > 7 GeV. Using the dijet events, we evaluate the diffractive structure function of the antiproton and compare it with expectations based on results obtained in diffractive deep inelastic scattering experiments at the DESY ep collider HERA.

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Measurement Of Inclusive(D(S)(±)) Photoproduction At Hera Zeus Collaboration, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti May 2000

Measurement Of Inclusive(D(S)(±)) Photoproduction At Hera Zeus Collaboration, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The first measurement of inclusive D(s)(±) photoproduction at HERA has been performed with the ZEUS detector for photon-proton centre-of-mass energies 130 < W < 280GeV. The measured cross section for 3 < p (is perpendicular to)/(D(s)) < 12GeV and |η(D(s))| < 1.5 is σ(ep → D(s)X) = 3.79 ± 0.59(stat.) -0.46/+0.26 (syst.) ± 0.94(br.)nb, where the last error arises from the uncertainty in the D(s)(±) decay branching ratio. The measurements are compared with inclusive D*(±) photoproduction cross sections in the same kinematic region and with QCD calculations. The D(s)(±) cross sections lie above a fixed-order next-to-leading order calculation and agree better with a tree-level O(αα(s)/3) calculation that was tuned to describe the ZEUS D*(±) cross sections. The ratio of D(s)(±) to D*(±) cross sections is 0.41 ± 0.07 (stat.) -0.05/+0.03 (syst.) ± 0.10(br.). From this ratio, the strangeness-suppression factor in charm photoproduction, within the LUND string fragmentation model, has been calculated to be γ(s) = 0.27 ± 0.05 ± 0.07(br.). The cross-section ratio and γ(s) are in good agreement with those obtained in charm production in e+e- annihilation. (C) 2000 Elsevier Science B.V.

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An Improved Limit On The Rate Of The Decay K^+ -> Pi^+ Mu^+ E^-, Duncan Brown, R. Appel May 2000

An Improved Limit On The Rate Of The Decay K^+ -> Pi^+ Mu^+ E^-, Duncan Brown, R. Appel

Physics - All Scholarship

The experiment E865 at BNL places an upper limit on the branching ratio for the decay K+ -> pi+ mu+ e- of 3.9x10^-11 (90% C.L.). Along with with other results this yields a combined upper limit on this branching ratio of 2.8x10^-11. A new upper limit on the branching ratio for pi0 -> mu+ e- of 3.8x10^-10 (90% C.L.) is also established. The experiment and analysis are described.

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Renormalization Scale Invariant Pqcd Predictions For R(E+ E-) And The Bjorken Sum Rule At Next-To-Leading Order, Michael Binger, Chueng-Ryong Ji, David G. Robertson May 2000

Renormalization Scale Invariant Pqcd Predictions For R(E+ E-) And The Bjorken Sum Rule At Next-To-Leading Order, Michael Binger, Chueng-Ryong Ji, David G. Robertson

Physics Faculty Scholarship

We discuss the application of the physical QCD effective charge αV, defined via the heavy-quark potential, in perturbative calculations at next-to-leading order. When coupled with the Brodsky-Lepage-Mackenzie prescription for fixing the renormalization scales, the resulting series are automatically and naturally scale and scheme independent, and represent unambiguous predictions of perturbative QCD. We consider in detail such commensurate scale relations for the e+e− annihilation ratio Re+e− and the Bjorken sum rule. In both cases the improved predictions are in excellent agreement with experiment.

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Low Temperature Anomaly In Mesoscopic Kondo Wires, P. Mohanty, Richard A. Webb May 2000

Low Temperature Anomaly In Mesoscopic Kondo Wires, P. Mohanty, Richard A. Webb

Faculty Publications

We report the observation of an anomalous magnetoresistance in extremely dilute quasi-one-dimensional AuFe wires at low temperatures, along with a hysteretic background at low fields. The Kondo resistivity does not show the unitarity limit down to the lowest temperature, implying uncompensated spin states. We suggest that the anomalous magnetoresistance may be understood as the interference correction from the accumulation of geometric phase in the conduction electron wave function around the localized impurity spin.

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Sulfite: Cytochrome C Oxidoreductase From Thiobacillus Novellus, Ulrike Kappler, Brian Bennett, Jörg Rethmeier, Günter Schwarz, Rainer Deutzmann, Alistair G. Mcewan, Christiane Dahl May 2000

Sulfite: Cytochrome C Oxidoreductase From Thiobacillus Novellus, Ulrike Kappler, Brian Bennett, Jörg Rethmeier, Günter Schwarz, Rainer Deutzmann, Alistair G. Mcewan, Christiane Dahl

Physics Faculty Research and Publications

Direct oxidation of sulfite to sulfate occurs in various photo- and chemotrophic sulfur oxidizing microorganisms as the final step in the oxidation of reduced sulfur compounds and is catalyzed by sulfite: cytochrome c oxidoreductase (EC1.8.2.1). Here we show that the enzyme from Thiobacillus novellus is a periplasmically located αβ heterodimer, consisting of a 40.6-kDa subunit containing a molybdenum cofactor and an 8.8-kDa mono-heme cytochrome c 552 subunit (midpoint redox potential, E m8.0 = +280 mV). The organic component of the molybdenum cofactor was identified as molybdopterin contained in a 1:1 ratio to the Mo content of the enzyme. Electron …

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“The Way Of The Scientist Deepens Beauty By Increasing Understanding”: Teaching Physics As An Aesthetic Form, Claudine Indigo Kavanagh May 2000

“The Way Of The Scientist Deepens Beauty By Increasing Understanding”: Teaching Physics As An Aesthetic Form, Claudine Indigo Kavanagh

Dissertations and Theses

Educators have struggled to find an appropriate and efficacious method to engage students of science in their classrooms and lecture halls, This investigation presents a theoretical foundation for the use of aesthetic criteria when teaching physics in high school or undergraduate settings and suggests that this may be an effective learning tool. The relationship between science aesthetics and science literacy is pursued here. Included in this study are discussions of the applications of aesthetic judgement by theoretical physicists in the 20th century and and methods for bringing a dialogue concerning natural philosophy and beauty in the science classroom. While many …

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A Spectroscopic Redshift For The Cl 0024+16 Multiple Arc System: Implications For The Central Mass Distribution, Tom Broadhurst, Xiaosheng Huang, Brenda Frye, Richard Ellis May 2000

A Spectroscopic Redshift For The Cl 0024+16 Multiple Arc System: Implications For The Central Mass Distribution, Tom Broadhurst, Xiaosheng Huang, Brenda Frye, Richard Ellis

Physics and Astronomy

We present a spectroscopic redshift of z = 1.675 for the well-known multiply lensed system of arcs seen in the z = 0.39 cluster Cl 0024+16. In contrast to earlier work, we find that the lensed images are accurately reproduced by a projected mass distribution which traces the locations of the brightest cluster elliptical galaxies, suggesting that the most significant minima of the cluster potential are not dynamically erased. The averaged mass profile is shallow and consistent with predictions of recent numerical simulations. The source redshift enables us to determine an enclosed cluster mass of M(<100 kpc h-1) = …

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Snapover: Anomalous Plasma Current Collection By Positively Biased Conductors When Surrounded By A Dielectric, Clint Thomson, John R. Dennison May 2000

Snapover: Anomalous Plasma Current Collection By Positively Biased Conductors When Surrounded By A Dielectric, Clint Thomson, John R. Dennison

All Physics Faculty Publications

Over the last decade, high-powered spacecraft have been designed that will operate at voltages greater than 100 V. At these voltages, the solar arrays can undergo both destructive arcing at negative biases, and plasma electron current collection at positive biases. Furthermore, above some critical positive bias voltage (~100 V), the electron current collected by the array interconnects increases dramatically through a phenomenon termed Asnapover@. During snapover, large portions of the solar array cover glass charge positively, and begin to draw electron current from the plasma as if it were a conducting surface. This leads to substantial power losses for the …

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Effects Of Ga Substitution For Fe On The Structure And Magnetic Properties Of Nd8.4Fe87.1-XGaXB4.5 (X = 0–2.2) Alloys Prepared By Mechanical Alloying, B.Z. Cui, X.K. Sun, W. Liu, Z.D. Zhang, D.Y. Geng, X.G. Zhao, J. Ping Liu, David J. Sellmyer May 2000

Effects Of Ga Substitution For Fe On The Structure And Magnetic Properties Of Nd8.4Fe87.1-XGaXB4.5 (X = 0–2.2) Alloys Prepared By Mechanical Alloying, B.Z. Cui, X.K. Sun, W. Liu, Z.D. Zhang, D.Y. Geng, X.G. Zhao, J. Ping Liu, David J. Sellmyer

David Sellmyer Publications

The effects of a partial substitution of Ga for Fe on the structure and magnetic properties of mechanically alloyed Nd8.4Fe87.1B4.5 were studied. With increasing Ga content, the magnetic properties of the nanocomposite magnets first improve, reach maxima at 1.1 at.% Ga, and then degrade. The addition of Ga helps to control the morphology, especially the grain sizes of both α -Fe and Nd2Fe14B.

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Curie Temperature Of Multiphase Nanostructures, Ralph Skomski, David J. Sellmyer May 2000

Curie Temperature Of Multiphase Nanostructures, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

The Curie temperature and the local spontaneous magnetization of ferromagnetic nanocomposites are investigated. The macroscopic character of the critical fluctuations responsible for the onset of ferromagnetic order means that there is only one Curie temperature, independent of the number of magnetic phases present. The Curie temperature increases with the grain size and is, in general, larger than predicted from the volume averages of the exchange constants. However, the Curie-temperature enhancement is accompanied by a relative reduction of the spontaneous magnetization. Due to the quadratic dependence of the permanent-magnet energy product on the spontaneous magnetization, this amounts to a deterioration of …

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Instrumentation And Measurement Of Secondary Electron Emission For Spacecraft Charging, Neal Nickles, John R. Dennison May 2000

Instrumentation And Measurement Of Secondary Electron Emission For Spacecraft Charging, Neal Nickles, John R. Dennison

All Physics Faculty Publications

Secondary electron emission is an important physical mechanism in the problem of spacecraft charging. The NASA Space Environments and Effects branch is currently revising NASA’s strategy for mitigating damage due to spacecraft charging. In an effort to substantially improve the modeling of spacecraft charging, measurements of secondary electron emission parameters are being made. The design of the apparatus needed to measure these parameters is discussed in detail. Various measurement techniques are explained and conclusions are drawn about the suitability of the final design.

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Simple Model For Mixing At Accelerated Fluid Interfaces With Shear And Compression, John D. Ramshaw May 2000

Simple Model For Mixing At Accelerated Fluid Interfaces With Shear And Compression, John D. Ramshaw

Physics Faculty Publications and Presentations

A simple model was recently described for predicting linear and nonlinear mixing at an unstable planar interface between two fluids of different density subjected to an arbitrary time-dependent variable acceleration history [J. D. Ramshaw, Phys. Rev. E 58, 5834 (1998)]. Here we generalize this model to include the Kelvin-Helmholtz (KH) instability resulting from a tangential velocity discontinuity delta u, as well as the effects of a uniform anisotropic compression or expansion of the mixing layer as a whole. The model consists of a second-order nonlinear ordinary differential equation of motion for the half-width h of the mixing layer. This equation …

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Annealed Disorder, Rare Regions, And Local Moments: A Novel Mechanism For Metal-Insulator Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta May 2000

Annealed Disorder, Rare Regions, And Local Moments: A Novel Mechanism For Metal-Insulator Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

It is shown that, for noninteracting electron systems, annealed magnetic disorder leads to a new mechanism, and a new universality class, for a metal-insulator transition. The transition is driven by a vanishing of the thermodynamic density susceptibility rather than by localization effects. The critical behavior in d = 2 + ∈ dimensions is determined, and the underlying physics is discussed. It is further argued that annealed magnetic disorder, in addition to underlying quenched disorder, describes local magnetic moments in electronic systems.

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Hysteresis-Loop Overskewing In The Light Of A Novel Nucleation Mode, Ralph Skomski, J. Ping Liu, David J. Sellmyer May 2000

Hysteresis-Loop Overskewing In The Light Of A Novel Nucleation Mode, Ralph Skomski, J. Ping Liu, David J. Sellmyer

David Sellmyer Publications

It is demonstrated that the magnetostatic demagnetizing factor is not the only sample-shape dependent contribution to the hysteresis loop. There are also exchange contributions, which lead to interesting effects, particularly in nanostructures. An example is the recently discovered bulging mode in two-phase nanomagnets. The bulging mode exhibits the angular symmetry of the coherent mode, but it is incoherent due to its radial variation and gives rise to negative demagnetizing factors.

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Measurement Of The Differential Dijet Mass Cross Section In Pp̅ Collisions At √S =1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration May 2000

Measurement Of The Differential Dijet Mass Cross Section In Pp̅ Collisions At √S =1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the cross section for production of two or more jets as a function of dijet mass, based on an integrated luminosity of 86 pb-1 collected with the Collider Detector at Fermilab. Our dijet mass spectrum is described within errors by next-to-leading order QCD predictions using CTEQ4HJ parton distributions, and is in good agreement with a similar measurement from the DØ experiment.

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The Influence Of Both Coordination Number And Lattice Constant On The Nonmetal To Metal Transition, I.N. Yakovkin, Peter A. Dowben May 2000

The Influence Of Both Coordination Number And Lattice Constant On The Nonmetal To Metal Transition, I.N. Yakovkin, Peter A. Dowben

Peter Dowben Publications

We show that both coordination and lattice constant can have an important influence on the nonmetal to metal transition and the two parameters are not easily separated. Using example theoretical calculations for barium, we provide a compelling case that atomic coordination is a critical factor in determining the critical lattice constant for the nonmetal to metal transition. A comparison between the nonmetal to metal transition three-dimensional and two-dimensional systems is not possible on the basis of the atomic coordination alone. This is discussed in the context of a comparison of the available experimental data for both elemental expanded fluids (three-dimensional) …

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Comparative Thermal-Expansion Study Of Β″-(Et)2sf5ch2cf2so3 And Κ-(Et)2cu(Ncs)2: Uniaxial Pressure Coefficients Of Tc And Upper Critical Fields, J. Müller, M. Lang, F. Steglich, J. A. Schlueter, A. M. Kini, U. Geiser, Javid Mohtasham, Rolf Walter Winter, Gary L. Gard, T. Sasaki, N. Toyota May 2000

Comparative Thermal-Expansion Study Of Β″-(Et)2sf5ch2cf2so3 And Κ-(Et)2cu(Ncs)2: Uniaxial Pressure Coefficients Of Tc And Upper Critical Fields, J. Müller, M. Lang, F. Steglich, J. A. Schlueter, A. M. Kini, U. Geiser, Javid Mohtasham, Rolf Walter Winter, Gary L. Gard, T. Sasaki, N. Toyota

Chemistry Faculty Publications and Presentations

We report high-resolution measurements of the coefficient of thermal expansion, α=l⁻¹ x (δl/δΤ), on single crystals of the organic superconductors β″-(ET)₂SF₅CH₂CF₂SO₃ and κ-(ET)₂Cu(NCS)₂. For both salts we find large and highly anisotropic phase-transition anomalies at Tc. Combining these data with literature results on the specific heat via the Ehrenfest relation, the uniaxial pressure coefficients of Tc can be determined. Most remarkably, a strikingly similar in-plane vs out-of-plane anisotropy is found for both compounds: the strong suppression of Tc observed in hydrostatic-pressure experiments is dominated by a huge negative uniaxial stress effect perpendicular to the conducting planes. Therefore we expect that …

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Imaging The Phase Of An Evolving Bose-Einstein Condensate Wave Function, J. E. Simsarian, J. Denschlag, Mark Edwards, Charles W. Clark, L. Deng, E. W. Hagley, K. Helmerson, S. L. Rolston, W. D. Phillips Apr 2000

Imaging The Phase Of An Evolving Bose-Einstein Condensate Wave Function, J. E. Simsarian, J. Denschlag, Mark Edwards, Charles W. Clark, L. Deng, E. W. Hagley, K. Helmerson, S. L. Rolston, W. D. Phillips

Physics & Astronomy: Faculty Publications

We demonstrate a spatially resolved autocorrelation measurement with a Bose-Einstein condensate and measure the evolution of the spatial profile of its quantum mechanical phase. Upon release of the condensate from the magnetic trap, its phase develops a form that we measure to be quadratic in the spatial coordinate. Our experiments also reveal the effects of the repulsive interaction between two overlapping condensate wave packets and we measure the small momentum they impart to each other.

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Manganese Surface Segregation In Nimnsb, Delia Ristoiu, J. P. Nozie`Res, C.N. Borca, B. Borca, Peter A. Dowben Apr 2000

Manganese Surface Segregation In Nimnsb, Delia Ristoiu, J. P. Nozie`Res, C.N. Borca, B. Borca, Peter A. Dowben

Peter Dowben Publications

A quantitative analysis of the surface composition of the Heusler alloy NiMnSb has been undertaken using angle-resolved x-ray photoemission spectroscopy and the surface composition characterized. With sufficient annealing cycles, the stoichiometric surface evolves to a surface that is manganese rich. This indicates that the surface enthalpy is different from the bulk for the Heusler alloy NiMnSb. ©2000 American Institute of Physics.

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