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2001

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Physics

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Articles 361 - 378 of 378

Full-Text Articles in Physical Sciences and Mathematics

Electronic Structures And Magnetism Of Lani₅₋ₓfeₓ Compounds, Jinbo Yang, Chiu-Ying Tai, G. K. Marasinghe, George Daniel Waddill, Oran Allan Pringle, William Joseph James Jan 2001

Electronic Structures And Magnetism Of Lani₅₋ₓfeₓ Compounds, Jinbo Yang, Chiu-Ying Tai, G. K. Marasinghe, George Daniel Waddill, Oran Allan Pringle, William Joseph James

Physics Faculty Research & Creative Works

A systematic study of the magnetic moments and hyperfine interactions of the LaNi5-xFex compounds was performed using the spin-polarized tight-binding-linear-muffin-tin-orbital methods (TBLMTO). The calculated results were compared with neutron diffraction and Mössbauer experimental data and found to be in good agreement. Fe atoms exhibit more localized magnetic moments in LaNi5-xFex when the Fe content x is lower than 1.0. The calculated magnetic moments of the Fe atoms approach values as large as 2.5μB due to the dilution effect. The strong s-d hybridization between the Ni and La atoms and the neighboring Fe in …

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Molecular Simulations Of Sound Wave Propagation In Simple Gases, Alejandro Garcia, N. Hadjiconstantinou Jan 2001

Molecular Simulations Of Sound Wave Propagation In Simple Gases, Alejandro Garcia, N. Hadjiconstantinou

Faculty Publications

Molecular simulations of sound waves propagating in a dilute hard sphere gas have been performed using the direct simulation Monte Carlo method. A wide range of frequencies is investigated, including very high frequencies for which the period is much shorter than the mean collision time. The simulation results are compared to experimental data and approximate solutions of the Boltzmann equation. It is shown that free molecular flow is important at distances smaller than one mean free path from the excitation point.

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Quasirandom Distributed Gaussian Bases For Bound Problems, Sophya V. Garashchuk, J. C. Light Jan 2001

Quasirandom Distributed Gaussian Bases For Bound Problems, Sophya V. Garashchuk, J. C. Light

Faculty Publications

We introduce quasirandom distributed Gaussian bases (QDGB) that are well suited for bound problems. The positions of the basis functions are chosen quasirandomly while their widths and density are functions of the potential. The basis function overlap and kinetic energy matrix elements are analytical. The potential energy matrix elements are accurately evaluated using few-point quadratures, since the Gaussian basis functions are localized. The resulting QDGB can be easily constructed and is shown to be accurate and efficient for eigenvalue calculation for several multidimensional model vibrational problems. As more demanding examples, we used a 2D QDGB-DVR basis to calculate the lowest …

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Semiclassical Application Of The Mo/Ller Operators In Reactive Scattering, Sophya V. Garashchuk, J. C. Light Jan 2001

Semiclassical Application Of The Mo/Ller Operators In Reactive Scattering, Sophya V. Garashchuk, J. C. Light

Faculty Publications

Mo/ller operators in the formulation of reaction probabilities in terms of wave packet correlation functions allow us to define the wave packets in the interaction region rather than in the asymptotic region of the potential surface. We combine Mo/ller operators with the semiclassical propagator of Herman and Kluk. This does not involve further approximations and can be used with any initial value representation (IVR) semiclassical propagator. Time propagation in asymptotic regions of the potential due to Mo/ller operators reduces the oscillations of the propagator integrand and improves convergence of the results with respect to the number of trajectories. The effectiveness …

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Measurement Of Open Beauty Production In Photoproduction At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari Jan 2001

Measurement Of Open Beauty Production In Photoproduction At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari

Faculty Publications

The production and semi-leptonic decay of heavy quarks have been studied in the photoproduction process e+p → e+ + dijet + e- + X with the ZEUS detector at HERA using an integrated luminosity of 38.5 pb-1. Events with photon-proton centre-of-mass energies, Wγp, between 134 and 269 GeV and a photon virtuality, Q2, less than 1 GeV2 were selected requiring at least two jets of transverse energy Ejet1(2)T > 7(6) GeV and an electron in the final state. The electrons were identified by employing the ionisation energy loss measurement. The contribution of beauty quarks was determined using the transverse momentum of …

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Corrected Article: Exclusive Electroproduction Of ᵠ Mesons At 4.2 Gev [Physical. Rev. C 63, 065205, (2001)], M. Bektasoglu, L. Ciciani, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, Et Al., The Clas Collaboration Jan 2001

Corrected Article: Exclusive Electroproduction Of ᵠ Mesons At 4.2 Gev [Physical. Rev. C 63, 065205, (2001)], M. Bektasoglu, L. Ciciani, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, S. E. Kuhn, L. M. Qin, F. Sabatié, L. B. Weinstein, Et Al., The Clas Collaboration

Physics Faculty Publications

We studied the exclusive reaction ep → e' p' ᵠ using the ᵠ →K+K- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Our experiment covers the range in Q2 from 0.7 to 2.2 GeV2and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of ᵠ production on the proton. Our measurement shows the expected decrease of the t slope with the vector-meson formation time c Δ t …

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A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali Jan 2001

A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Design and analysis of a new compensating element for improving the electron pulse front and compressing the pulse duration in a femtosecond photoelectron gun are described. The compensating element is a small metallic cylindrical cavity in which an external voltage is applied in such a way that a special electric field forms and interacts with the electron pulse. This electric field reduces the distances between the faster and slower electrons inside the cavity and efficiently compensates for electron pulse broadening caused by the photoelectron energy spread and space charge effects. Poisson's equation and the equation of motion are solved to …

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Group Invariant Solutions In Mathematical Physics And Differential Geometry, Ian M. Anderson, Mark E. Fels, Charles G. Torre Jan 2001

Group Invariant Solutions In Mathematical Physics And Differential Geometry, Ian M. Anderson, Mark E. Fels, Charles G. Torre

All Physics Faculty Publications

This is a brief overview of our work on the theory of group invariant solutions to differential equations. The motivations and applications of this work stem from problems in differential geometry and relativistic field theory. The key feature in our theory is that we allow for non-transverse symmetry group actions, which are very common in applications.

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Retrieval And Validation Of Mesospheric Temperatures From Wind Imaging Interferometer Observations, M G. Shepherd, B Reid, S Zhang, B H. Solheim, G G. Shepherd, Vincent B. Wickwar, Joshua P. Herron Jan 2001

Retrieval And Validation Of Mesospheric Temperatures From Wind Imaging Interferometer Observations, M G. Shepherd, B Reid, S Zhang, B H. Solheim, G G. Shepherd, Vincent B. Wickwar, Joshua P. Herron

All Physics Faculty Publications

A method has been developed for the retrieval of mesospheric temperatures in the 65–90 km altitude range from satellite observations made by the Wind Imaging Interferometer (WINDII) aboard the Upper Atmosphere Research Satellite (UARS). Retrieved temperatures are derived from Rayleigh scattered sunlight observed in a wavelength band centered at 553 nm. Integrated line-of-sight radiance observations are inverted to tangent height volume scattering profiles, which are proportional to atmospheric density. From these, absolute temperature profiles are calculated using a technique derived from established Rayleigh lidar retrieval methods assuming that the atmosphere is in hydrostatic equilibrium and that it obeys the ideal …

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Time-Resolved Structural Study Of Low-Index Surfaces Of Germanium Near Its Bulk Melting Temperature, Xinglin Zeng, H. E. Elsayed-Ali Jan 2001

Time-Resolved Structural Study Of Low-Index Surfaces Of Germanium Near Its Bulk Melting Temperature, Xinglin Zeng, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The structure of the low-index surfaces of germanium near its bulk melting temperature is investigated using 100-ps time-resolved reflection high-energy electron diffraction. The surface is heated by 100-ps laser pulses while a synchronized electron beam probes the structure. Ge(111)was observed to remain in its incomplete melting structure up to at least Tm + 134 ± 40 K when heated by a 100-ps laser pulse. Both the Ge(100) and Ge(110) surfaces are observed to melt near the bulk melting temperature when heated with 100-ps laser pulses. Because of the low-diffraction intensity-to-background ratio at high temperatures and because of the temperature …

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Study Of Dynamics And Mechanism Of Metal-Induced Silicon Growth, Elena A. Guliants, Wayne A. Anderson Jan 2001

Study Of Dynamics And Mechanism Of Metal-Induced Silicon Growth, Elena A. Guliants, Wayne A. Anderson

Electrical and Computer Engineering Faculty Publications

The present study addresses the mechanism of metal-induced growth of device-quality silicon thin films. Si deposition was performed by magnetron sputtering on a 25-nm-thick Ni prelayer at 525–625 °C and yielded a continuous, highly crystalline film with a columnar structure. A Ni disilicide intermediate layer formed as a result of the Ni reaction with Si deposit provides a sufficient site for the Si epitaxial growth because lattice mismatch is small between the two materials. The reaction between Ni and Si was observed to progress in several stages. The NixSiy phase evolution in a Ni:Si layer was studied by x-ray photoelectron …

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Electron Cyclotron Resonance Heating In Spherical Plasmas: O-X-Ebw Mode Conversion In Mast, Josef Preinhaelter, M. A. Irzak, Linda L. Vahala, George Vahala Jan 2001

Electron Cyclotron Resonance Heating In Spherical Plasmas: O-X-Ebw Mode Conversion In Mast, Josef Preinhaelter, M. A. Irzak, Linda L. Vahala, George Vahala

Electrical & Computer Engineering Faculty Publications

Using a full wave solution, the O-X-EBW mode conversion is examined for density and magnetic profiles in MAST. The effects of magnetic shear and the sharp density pedestal for H-mode operation are considered with an eye to understanding both electron cyclotron emission (ECE) and electron cyclotron resonance heating (ECRH).

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Measurement Of The Neutral Current Cross Section And F2 Structure Function For Deep Inelastic E+P Scattering At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci Jan 2001

Measurement Of The Neutral Current Cross Section And F2 Structure Function For Deep Inelastic E+P Scattering At Hera, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci

Faculty Publications

The cross section and the proton structure function F2 for neutral current deep inelastic e+p scattering have been measured with the ZEUS detector at HERA using an integrated luminosity of 30 pb-1. The data were collected in 1996 and 1997 at a centre-of-mass energy of 300 GeV. They cover the kinematic range 2.7 < Q2 < 30000 GeV2 and 6-10-5 < cursive Greek chi < 0.65. The variation of F2 with cursive Greek chi and Q2 is well described by next-to-leading-order perturbative QCD as implemented in the DGLAP evolution equations.

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Polymer Depletion Interaction Between Two Parallel Repulsive Walls, F. Schlesener, Andreas Hanke, R. Kimpel, S. Dietrich Jan 2001

Polymer Depletion Interaction Between Two Parallel Repulsive Walls, F. Schlesener, Andreas Hanke, R. Kimpel, S. Dietrich

Physics and Astronomy Faculty Publications and Presentations

The depletion interaction between two parallel repulsive walls confining a dilute solution of long and flexible polymer chains is studied by field-theoretic methods. Special attention is paid to self-avoidance between chain monomers relevant for polymers in a good solvent. Our direct approach avoids the mapping of the actual polymer chains on effective hard or soft spheres. We compare our results with recent Monte Carlo simulations [A. Milchev and K. Binder, Eur. Phys. J. B 3, 477 (1998)] and with experimental results for the depletion interaction between a spherical colloidal particle and a planar wall in a dilute solution of nonionic …

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Assimilation Ionosphere Model: Development And Testing With Combined Ionospheric Campaign Caribbean Measurements, Jan Josef Sojka, D. C. Thompson, Robert W. Schunk, T. W. Bullett, J. J. Makela Jan 2001

Assimilation Ionosphere Model: Development And Testing With Combined Ionospheric Campaign Caribbean Measurements, Jan Josef Sojka, D. C. Thompson, Robert W. Schunk, T. W. Bullett, J. J. Makela

All Physics Faculty Publications

Assimilation Ionosphere Model (AIM) is a physics-based, global, ionospheric specification model that is currently under development. It assimilates a diverse set of real-time (or near-real-time) measurements, such as ionograms, GPS slant total electron content (TEC), and in situ plasma measurements. This study focuses on a middle latitude ionosonde assimilation capability in both local and regional forms. The models described are capable of using theƒ0 F 2 and h m F 2 from ionograms to generate either a local or a regional distribution of the induced plasma drift. This induced drift is usually caused by the meridional neutral wind. Results …

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Space Missions To Detect The Cosmic Gravitational-Wave Background, Neil J. Cornish, Shane L. Larson Jan 2001

Space Missions To Detect The Cosmic Gravitational-Wave Background, Neil J. Cornish, Shane L. Larson

All Physics Faculty Publications

It is thought that a stochastic background of gravitational waves was produced during the formation of the universe. A great deal could be learned by measuring this Cosmic Gravitational-wave Background (CGB), but detecting theCGB presents a significant technological challenge. The signal strength is expected to be extremely weak, and there will be competition from unresolved astrophysical foregrounds such as white dwarf binaries. Our goal is to identify the most promising approach to detect the CGB. We study the sensitivities that can be reached using both individual, and cross-correlated pairs of space based interferometers. Our main result is a general, coordinate …

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Mesospheric Temperature Observationsat The Usu / Cass Atmospheric Lidar Observatory (Alo), Vincent B. Wickwar, T D. Wilkerson, M Hammond, Joshua P. Herron Jan 2001

Mesospheric Temperature Observationsat The Usu / Cass Atmospheric Lidar Observatory (Alo), Vincent B. Wickwar, T D. Wilkerson, M Hammond, Joshua P. Herron

All Physics Faculty Publications

The Center for Atmospheric and Space Sciences (CASS) at Utah State University (USU) operates the ALO for studying the middle atmosphere from the stratosphere to the lower thermosphere. ALO’s mid-latitude location (41.74°N, 111.81°W, 1466 m) is very unique in that it is in the middle of an extensive set of rugged mountains, the Rocky Mountains, which are a major orographic source of gravity waves that may give rise to a longitudinal variation in the mesospheric structure. Mesospheric observations between approximately 45 and 90 km have been carried out on many clear nights with the ALO Rayleigh- scatter lidar since late …

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Gps Normalization And Preliminary Modeling Results Of Total Electron Content During A Midlatitude Space Weather Event, J. J. Makela, M. C. Kelley, Jan Josef Sojka, X. Pi, A. J. Mannucci Jan 2001

Gps Normalization And Preliminary Modeling Results Of Total Electron Content During A Midlatitude Space Weather Event, J. J. Makela, M. C. Kelley, Jan Josef Sojka, X. Pi, A. J. Mannucci

All Physics Faculty Publications

On November 22–23, 1997, a geomagnetic storm occurred during a period of excellent viewing conditions over the Arecibo Observatory in Puerto Rico. Here we explore the total electron content (TEC) registered by Global Positioning System (GPS) receivers located close to the Cornell All-Sky Imager (CASI) at the Arecibo Observatory. The storm began with the equatorward surge of a very high (100% increase) TEC enhancement stretching for many hours of local time on the dayside. At dusk the TEC over the Caribbean remained elevated with levels equal to the noontime monthly averages. During the event the TEC was highly structured and …

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