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Full-Text Articles in Physics

Diffusion And Drift In Terahertz Emission At Gaas Surfaces, James Heyman, N Coates, A Reinhardt, G Strasser Dec 2003

Diffusion And Drift In Terahertz Emission At Gaas Surfaces, James Heyman, N Coates, A Reinhardt, G Strasser

James Heyman

No abstract provided.


Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher Dec 2003

Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher

Jeffrey Dyck

We have measured electrical and magnetic properties of single crystals of Sb2_xMnxTe3 with x =0 – 0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2– VI3 diluted magnetic semiconductors, at least ...


The Recent Evolution Of The Dwarf Starburst Galaxy Ngc 625 From Hubble Space Telescope Imaging, John M. Cannon, R C. Dohm-Palmer, E D. Skillman, D J. Bomans, S Cote, B W. Miller Nov 2003

The Recent Evolution Of The Dwarf Starburst Galaxy Ngc 625 From Hubble Space Telescope Imaging, John M. Cannon, R C. Dohm-Palmer, E D. Skillman, D J. Bomans, S Cote, B W. Miller

John Cannon

No abstract provided.


Effects Of Substrate Temperature And Near-Substrate Plasma Density On The Properties Of Dc Magnetron Sputtered Aluminum Doped Zinc Oxide, Nathan Schmidt, Thomas Totushek, William Kimes, David Callender, James Doyle Oct 2003

Effects Of Substrate Temperature And Near-Substrate Plasma Density On The Properties Of Dc Magnetron Sputtered Aluminum Doped Zinc Oxide, Nathan Schmidt, Thomas Totushek, William Kimes, David Callender, James Doyle

James R. Doyle

No abstract provided.


Monday Night Football: Physics Decides Controversial Call, Gregory A. Dilisi, Richard A. Rarick Oct 2003

Monday Night Football: Physics Decides Controversial Call, Gregory A. Dilisi, Richard A. Rarick

Gregory A. DiLisi

A problem regarding a controversial refereeing decision of a videotaped football play is discussed. Vector analysis is used to show that the refereeing decision was correct; the camera's projection of the play onto the football field created an observational error.


Light Propagation In Variable-Refractive-Index Materials With Liquid-Crystal-Infiltrated Microcavities, Bin Wang, Philip Bos, Charles D. Hoke Oct 2003

Light Propagation In Variable-Refractive-Index Materials With Liquid-Crystal-Infiltrated Microcavities, Bin Wang, Philip Bos, Charles D. Hoke

Philip J. Bos

A liquid-crystal-infiltrated microcavity structure is proposed as a variable-refractive-index material. It has the advantages over previously considered nanostructured materials of having a larger phase-angle change and lower driving voltage. Two-dimensional liquid-crystal director and finite-difference time-domain optical simulations are used to select liquid crystal material parameters and optimize the dimension of the microcavity structured material.


Quantum Corrections To The Schwarzschild And Kerr Metrics, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein Oct 2003

Quantum Corrections To The Schwarzschild And Kerr Metrics, N. E. J. Bjerrum-Bohr, John Donoghue, Barry R. Holstein

John Donoghue

We examine the corrections to the lowest order gravitational interactions of massive particles arising from gravitational radiative corrections. We show how the masslessness of the graviton and the gravitational selfinteractions imply the presence of nonanalytic pieces ;A2q2,;q2ln2q2, etc., in the form factors of the energy-momentum tensor and that these correspond to long range modifications of the metric tensor gmn of the form G2m2/r2,G2m\/r3, etc. The former coincide with well known solutions from classical general relativity, while the latter represent new quantum mechanical effects, whose strength and form is necessitated by the low energy quantum nature of ...


Spectral Representation Of The Electrical Properties Of Layered Materials., Anthony Day, A. Mcgurn, D. Bergman, M. Thorpe Sep 2003

Spectral Representation Of The Electrical Properties Of Layered Materials., Anthony Day, A. Mcgurn, D. Bergman, M. Thorpe

Anthony Roy Day

We present a spectral representation for the effective conductivity of two homogeneous layers joined at a rough interface. This spectral representation is closely related to the Bergman-Milton spectral representation for bulk composites, and is easily extended to multilayered materials. By comparing the layered system to a reference layered system that has a flat interface, we form a surface spectral density that captures all the effects of surface structure on the effective conductivity of the layered sample, and is independent of the conductivities of the two layers. Because of the anisotropy of the layered system there are two surface spectral densities ...


Effect Of Parallel Velocity Shear On The Electrostatic Ion-Cyclotron Instability In Flamentary Current Channels, Erick Agrimson, Su-Hyun Kim, Nicola D'Angelo, Robert L. Merlino Sep 2003

Effect Of Parallel Velocity Shear On The Electrostatic Ion-Cyclotron Instability In Flamentary Current Channels, Erick Agrimson, Su-Hyun Kim, Nicola D'Angelo, Robert L. Merlino

Erick Agrimson

No abstract provided.


Threshold Electrodisintegration Of 3he, R S. Hicks, A Hotta, S Churchwell, X Jiang, Gerald Alvin Peterson, J Shaw, B Asavapibhop, M C. Berisso, P E. Bosted, K Burchesky, R A. Miskimen, S E. Rock Jun 2003

Threshold Electrodisintegration Of 3he, R S. Hicks, A Hotta, S Churchwell, X Jiang, Gerald Alvin Peterson, J Shaw, B Asavapibhop, M C. Berisso, P E. Bosted, K Burchesky, R A. Miskimen, S E. Rock

Gerald Alvin Peterson

Cross sections were measured for the near-threshold electrodisintegration of 3He at momentum transfer values of q=2.4, 4.4, and 4.7fm-1. From these and prior measurements the transverse and longitudinal response functions RT and RL were deduced. Comparisons are made against previously published and new nonrelativistic A=3 calculations using the best available nucleon-nucleon NN potentials. In general, for q<2fm-1 these calculations accurately predict the threshold electrodisintegration of 3He. Agreement at increasing q demands consideration of two-body terms, but discrepancies still appear at the highest momentum transfers probed, perhaps due to the neglect of relativistic dynamics, or to the underestimation of high-momentum wave-function components.


Femtosecond Phase-Coherent Two-Dimensional Spectroscopy, Peifang Tian, Dorine Keusters, Yoshifumi Suzaki, Warren S. Warren May 2003

Femtosecond Phase-Coherent Two-Dimensional Spectroscopy, Peifang Tian, Dorine Keusters, Yoshifumi Suzaki, Warren S. Warren

Peifang Tian

Femtosecond phase-coherent two-dimensional (2D) spectroscopy has been experimentally demonstrated as the direct optical analog of 2D nuclear magnetic resonance. An acousto-optic pulse shaper created a collinear three-pulse sequence with well-controlled and variable interpulse delays and phases, which interacted with a model atomic system of rubidium vapor. The desired nonlinear polarization was selected by phase cycling (coadding experimental results obtained with different interpulse phases). This method may enhance our ability to probe the femtosecond structural dynamics of macromolecules.


Mobility Of Taxol In Microtubule Bundles, Jennifer Ross, D. Kuchnir Fygenson May 2003

Mobility Of Taxol In Microtubule Bundles, Jennifer Ross, D. Kuchnir Fygenson

Jennifer Ross

Mobility of taxol inside microtubules was investigated using fluorescence recovery after photobleaching on flowaligned bundles. Bundles were made of microtubules with either GMPCPP or GTP at the exchangeable site on the tubulin dimer. Recovery times were sensitive to bundle thickness and packing, indicating that taxol molecules are able to move laterally through the bundle. The density of open binding sites along a microtubule was varied by controlling the concentration of taxol in solution for GMPCPP samples. With [63% sites occupied, recovery times were independent of taxol concentration and, therefore, inversely proportional to the microscopic dissociation rate, koff. It was found ...


Brane Dynamics From Nonlinear Realizations, T Clark, M Nitta, Tonnis Ter Veldhuis Apr 2003

Brane Dynamics From Nonlinear Realizations, T Clark, M Nitta, Tonnis Ter Veldhuis

Tonnis ter Veldhuis

No abstract provided.


Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher Apr 2003

Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher

Jeffrey Dyck

We examine the effect of alloying Sn on the Sb site of ytterbium-filled skutterudites, a promising class of thermoelectric materials. We report measurements of the Hall effect, electrical resistivity, Seebeck coefficient, and thermal conductivity between 2 and 300 K on two series of samples having different ytterbium filling fractions: Yb0.19Co4Sb12-xSnx, with x=0, 0.05, 0.1, and 0.2, and Yb0.5Co4Sb12-xSnx, with x=0.5, 0.6, 0.8, 0.83, and 0.9. We find that the substitution of Sn does not lower the electron concentration of these samples, but rather gives rise to a p-type ...


Dynamics Of Conformal Maps For A Class Of Non-Laplacian Growth Phenomena, Martin Z. Bazant, Jaehyuk Choi, Benny Davidovitch Mar 2003

Dynamics Of Conformal Maps For A Class Of Non-Laplacian Growth Phenomena, Martin Z. Bazant, Jaehyuk Choi, Benny Davidovitch

Benny Davidovitch

Time-dependent conformal maps are used to model a class of growth phenomena limited by coupled non-Laplacian transport processes, such as nonlinear diffusion, advection, and electro- migration. Both continuous and stochastic dynamics are described by generalizing conformal- mapping techniques for viscous fingering and diffusion-limited aggregation, respectively. A gen- eral notion of time in stochastic growth is also introduced. The theory is applied to simulations of advection-diffusion-limited aggregation in a background potential flow. A universal crossover in mor- phology is observed from diffusion-limited to advection-limited fractal patterns with an associated crossover in the growth rate, controlled by a time-dependent effective Peclet number ...


Search For Neutral Baryon Resonances Below Pion Threshold, X Jiang, R Gilman, R Ransome, P Markowitz, T H. Chang, C C. Chang, Gerald Alvin Peterson Feb 2003

Search For Neutral Baryon Resonances Below Pion Threshold, X Jiang, R Gilman, R Ransome, P Markowitz, T H. Chang, C C. Chang, Gerald Alvin Peterson

Gerald Alvin Peterson

The reaction p(e,e′π+)X0 was studied with two high-resolution magnetic spectrometers to search for narrow baryon resonances. A missing mass resolution of 2.0 MeV was achieved. A search for structures in the mass region of 0.97


Photoproduction Of The Ω Meson On The Proton At Large Momentum Transfer, M Battaglieri, M Brunoldi, R De Vita, B Asavapibhop, R S. Hicks, D Lawrence, R Miskimen, Gerald Alvin Peterson Jan 2003

Photoproduction Of The Ω Meson On The Proton At Large Momentum Transfer, M Battaglieri, M Brunoldi, R De Vita, B Asavapibhop, R S. Hicks, D Lawrence, R Miskimen, Gerald Alvin Peterson

Gerald Alvin Peterson

The differential cross section, dσ/dt, for ω meson exclusive photoproduction on the proton above the resonance region (2.6


A Comparative Study Of Interatomic Potentials For Copper And Aluminum Gas Phase Sputter Atom Transport Simulations, Keith Kuwata, Rachel Erickson, James Doyle Dec 2002

A Comparative Study Of Interatomic Potentials For Copper And Aluminum Gas Phase Sputter Atom Transport Simulations, Keith Kuwata, Rachel Erickson, James Doyle

James R. Doyle

No abstract provided.


Ultrafast Two-Photon Free Induction Decay, D. Keusters, Peifang Tian, W. Warren Dec 2002

Ultrafast Two-Photon Free Induction Decay, D. Keusters, Peifang Tian, W. Warren

Peifang Tian

No abstract provided.


A Comparison Of Semi-Analytical And Numerical Solutions For The Microwave Heating Of A Lossy Material In A Three-Dimensional Waveguide, Prof. Tim Marchant Dec 2002

A Comparison Of Semi-Analytical And Numerical Solutions For The Microwave Heating Of A Lossy Material In A Three-Dimensional Waveguide, Prof. Tim Marchant

Tim Marchant

The microwave heating of a three-dimensional block in an infinitely long rectangular waveguide propagating the TE10 mode is considered. The electrical conductivity (the dielectric loss) is assumed to be a function of temperature, and modelled by the Arrhenius law. A coupled set of equations is obtained that describes the electromagnetic fields and the temperature distribution in the block. The numerical solutions of this problem are obtained by two methods, the well known FD-TD scheme and a frequency domain method which makes the further assumption that a single TE10 mode exists in the waveguide and material. The results show that an ...


Dynamic-Stochastic Modeling Of A Municipal Water Supply System In Stella, Stephen Mecca, R. Lamontagne Dec 2002

Dynamic-Stochastic Modeling Of A Municipal Water Supply System In Stella, Stephen Mecca, R. Lamontagne

Stephen J. Mecca

A dynamic-stochastic model of a reservoir and municipal water system has been developed and studied. The overall structure of the model, which is written in Stella?, is presented; the physical- environmental- and end- use- segments are outlined and sample simulation results are presented. The flexibility of the model to encompass physical changes in the system is highlighted. Alternative representations of end-use are outlined and the applications of this type of modeling for policy analysis and water resources management is suggested. The design and status of on-going studies to validate key components of the model are discussed.


Micro Thermoelectric Cooler Fabrication: Growth And Characterization Of Patterned Sb2te3 And Bi2te3 Films ., Luciana Da Silva, M. Kaviany, A. Dehennis, Jeffrey Dyck Dec 2002

Micro Thermoelectric Cooler Fabrication: Growth And Characterization Of Patterned Sb2te3 And Bi2te3 Films ., Luciana Da Silva, M. Kaviany, A. Dehennis, Jeffrey Dyck

Jeffrey Dyck

A column-type micro thermoelectric cooler is being fabricated using p-type Sb2Te3 and n-type Bi2Te3 films (approximately 4 μm thick). The films are grown by thermal co-evaporation and patterned on Cr/Au/Ti/Pt (hot) connectors, which are deposited onto a silicon dioxide coated wafer. The column height is limited by control of the Te deposition rate. Although a high substrate temperature during thermoelectric film deposition is desired, it has been limited by the degradation of the photoresist used for patterning. The measured Seebeck coefficient and electrical resistivity of the thermoelectric films are reported, and preliminary results show that excess tellurium ...


Femtosecond Pulse Shaping Approaches To Multiphoton Imaging., W. Warren, W. Wagner, Peifang Tian, T. Ye Dec 2002

Femtosecond Pulse Shaping Approaches To Multiphoton Imaging., W. Warren, W. Wagner, Peifang Tian, T. Ye

Peifang Tian

No abstract provided.


Transport Coefficients Of Titanium-Doped Sb2te3 Crystals., P. Svanda, P. LošŤÁK, Č. Drašar, Jeffrey Dyck Dec 2002

Transport Coefficients Of Titanium-Doped Sb2te3 Crystals., P. Svanda, P. LošŤÁK, Č. Drašar, Jeffrey Dyck

Jeffrey Dyck

Titanium-doped single crystals (cTi = 0 to 2×1020 atoms cm-3) were prepared from the elements Sb, Ti, and Te of 5N purity by a modified Bridgman method. The obtained crystals were characterized by measurements of the temperature dependence of the electrical resistivity, Hall coefficient, Seebeck coefficient and thermal conductivity in the temperature range of 5-300 K. It was observed that with an increasing Ti content in the samples the electrical resistance, the Hall coefficient and the Seebeck coefficient increase. This means that the incorporation of Ti atoms into the Sb2Te3 crystal structure results in a decrease in the concentration of ...


Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde Dec 2002

Infrared-Active Vibron Bands Associated With Substitutional Impurities In Solid Parahydrogen, Robert Hinde

Robert Hinde

We present a model for the line shapes of infrared-active Q1(0) vibron bands observed in solid parahydrogen doped with low concentrations of spherical substitutional impurities. The line shapes are highly sensitive to the H2 vibrational dependence of the dopant–H2 interaction. When this vibrational dependence is strong, the dopant can trap the infrared-active vibron in its first solvation shell; in this case, the trapped vibron manifests itself in the absorption spectrum as a narrow feature to the red of the pure solid’s vibron band.


Bogomol'nyi, Prasad And Sommerfield Configurations In Smectics, Christian Santangelo, Randall D. Kamien Dec 2002

Bogomol'nyi, Prasad And Sommerfield Configurations In Smectics, Christian Santangelo, Randall D. Kamien

Christian Santangelo

It is typical in smectic liquid crystals to describe elastic deformations with a linear theory when the elastic strain is small. In smectics, certain essential nonlinearities arise from the requirement of rotational invariance. By employing the Bogomol’nyi, Prasad, and Sommerfield decomposition and relying on boundary conditions and geometric invariants, we have found a large class of exact solutions. We introduce an approximation for the deformation profile far from a spherical inclusion and find an enhanced attractive interaction at long distances due to the nonlinear elasticity, confirmed by numerical minimization.


Improved Determination Of The Electroweak Penguin Contribution To E’/E In The Chiral Limit, Vincenzo Cirigliano, John Donoghue, Eugene Golowich, Kim Maltman Dec 2002

Improved Determination Of The Electroweak Penguin Contribution To E’/E In The Chiral Limit, Vincenzo Cirigliano, John Donoghue, Eugene Golowich, Kim Maltman

John Donoghue

We perform a finite energy sum rule analysis of the flavor ud two-point V-A current correlator, Delta Pi (Q^2). The analysis, which is performed using both the ALEPH and OPAL databases for the V-A spectral function, Delta rho, allows us to extract the dimension six V-A OPE coefficient, a_6, which is related to the matrix element of the electroweak penguin operator, Q_8, by chiral symmetry. The result for a_6 leads directly to the improved (chiral limit) determination epsilon'/epsilon = (- 15.0 +- 2.7) 10^{-4}. Determination of higher dimension OPE contributions also allows us to perform an independent test ...


Ground State Numerical Study Of The Three-Dimensional Random Field Ising Model, I. Dukovski, Jonathan Machta Dec 2002

Ground State Numerical Study Of The Three-Dimensional Random Field Ising Model, I. Dukovski, Jonathan Machta

Jonathan Machta

The random field Ising model in three dimensions with Gaussian random fields is studied at zero temperature for system sizes up to 603. For each realization of the normalized random fields, the strength of the random field, Δ and a uniform external, H is adjusted to find the finite-size critical point. The finite-size critical point is identified as the point in the H−Δ plane where three degenerate ground states have the largest discontinuities in the magnetization. The discontinuities in the magnetization and bond energy between these ground states are used to calculate the magnetization and specific heat critical exponents ...


Novel Examples Of Achiral Bent-Core Azo Compounds Exhibiting B1 And Anticlinic-Antiferroelectric B2 Mesophases, Veena Prasad, Shin-Woong Kang, Satyendra Kumar Dec 2002

Novel Examples Of Achiral Bent-Core Azo Compounds Exhibiting B1 And Anticlinic-Antiferroelectric B2 Mesophases, Veena Prasad, Shin-Woong Kang, Satyendra Kumar

Satyendra Kumar

The first examples of achiral bent-core molecules consisting of an azo linkage and five aromatic rings exhibiting bent-core mesophases are reported. They exhibit B1 and B2 phases as identified by optical microscopy, differential scanning calorimetry, X-ray diffraction, and electro-optical techniques. The B2 phase of these materials is identified to be the anticlinic–antiferroelectric, SmCAPA phase. The mesophases of these compounds have relatively low transition temperatures and wide temperature ranges. The observation of bent-core phases in azo compounds assumes significance from the fact that the introduction of the –NN– linkage adds a new dimension, namely photochromism, to this field.


Connection Between Adam-Gibbs Theory And Spatially Heterogeneous Dynamics, N. Giovambattista, S. V. Buldyrev, Francis W. Starr, H. E. Stanley Dec 2002

Connection Between Adam-Gibbs Theory And Spatially Heterogeneous Dynamics, N. Giovambattista, S. V. Buldyrev, Francis W. Starr, H. E. Stanley

Francis Starr

No abstract provided.