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2004

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Articles 121 - 150 of 609

Full-Text Articles in Physics

Distal Placement Of An End-To-Side Bypass Graft Anastomosis A 3-D Computational Study, John Robert Di Cicco Oct 2004

Distal Placement Of An End-To-Side Bypass Graft Anastomosis A 3-D Computational Study, John Robert Di Cicco

Mechanical & Aerospace Engineering Theses & Dissertations

A three-dimensional computational fluid dynamics study of blood flow through stenotic arteries has been conducted. Flow phenomena, such as separation regions and turbulence, can be found distal to an arterial stenosis. Frequently, a bypass graft using an end-to-side technique is attached to a stenotic artery to restore adequate blood flow. However, a significant percentage of these grafts fail after thirty postoperative days due to intimal hyperplasia development around the distal anastomosis. Moreover, aberrant wall shear rates have been implicated as a factor in the development of intimal hyperplasia. Thus, the present study examines whether placement of the distal end of …

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Thermoelectricity In Natural And Synthetic Hydrogels, Brandon R. Brown Sep 2004

Thermoelectricity In Natural And Synthetic Hydrogels, Brandon R. Brown

Physics and Astronomy

We describe a technique for measuring a Seebeck effect in gels and present data for three systems. notably distinct signals are obtained for gel originating in the electrosensitive organs of marine sharks, syntehtic collagen-based gel, and as a control, seawater, the gels' seawater simply confirms that gels suppress mass transport. The difference between synthetic gel and the gel of sharks shows that the charged polymers of the shark gel restrict mass transport much more successfully than the polumers of the collagen gel, and we submit that this sort of ion localization is key to the emergence of thermoelectricity in a …

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Production Of E+E− Pairs Accompanied By Nuclear Dissociation In Ultraperipheral Heavy-Ion Collisions, Star Collaboration, T.D. Gutierrez Sep 2004

Production Of E+E− Pairs Accompanied By Nuclear Dissociation In Ultraperipheral Heavy-Ion Collisions, Star Collaboration, T.D. Gutierrez

Physics

We present data on e+e− pair production accompanied by nuclear breakup in ultraperipheral gold-gold collisions at a center of mass energy of 200GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order diagrams for pair production should be enhanced. We compare the data with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED). The data distributions agree with both calculations, except that the pair transverse momentum spectrum disagrees with the equivalent photon approach. We set limits on higher-order contributions to the cross section.

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Production Of A Kev X-Ray Beam From Synchrotron Radiation In Relativistic Laser-Plasma Interaction, Antoine Rousse, Kim Ta Phuoc, Rahul Shah, Alexander Pukhov, Eric Lefebvre, Victor Malka, Sergey Kiselev, Frederic Burgy, Jean-Philippe Rousseau, Donald P. Umstadter, Daniele Hulin Sep 2004

Production Of A Kev X-Ray Beam From Synchrotron Radiation In Relativistic Laser-Plasma Interaction, Antoine Rousse, Kim Ta Phuoc, Rahul Shah, Alexander Pukhov, Eric Lefebvre, Victor Malka, Sergey Kiselev, Frederic Burgy, Jean-Philippe Rousseau, Donald P. Umstadter, Daniele Hulin

Donald Umstadter Publications

We demonstrate that a beam of x-ray radiation can be generated by simply focusing a single high-intensity laser pulse into a gas jet. A millimeter-scale laser-produced plasma creates, accelerates, and wiggles an ultrashort and relativistic electron bunch. As they propagate in the ion channel produced in the wake of the laser pulse, the accelerated electrons undergo betatron oscillations, generating a femtosecond pulse of synchrotron radiation, which has keV energy and lies within a narrow (50 mrad) cone angle.

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Polarization-Dependent Electron Affinity Of Linbo3 Surfaces, W.-C. Yang, B. J. Rodriguez, Alexei Gruverman, R. J. Nemanich Sep 2004

Polarization-Dependent Electron Affinity Of Linbo3 Surfaces, W.-C. Yang, B. J. Rodriguez, Alexei Gruverman, R. J. Nemanich

Alexei Gruverman Publications

Polar surfaces of a ferroelectric LiNbO3 crystal with periodically poled domains are explored using UV-photoelectron emission microscopy (PEEM). Compared with the positive domains (domains with positive surface polarization charges), a higher photoelectric yield is found from the negative domains (domains with negative surface polarization charges), indicating a lower photothreshold and a corresponding lower electron affinity. The photon-energy-dependent contrast in the PEEM images of the surfaces indicates that the photothreshold of the negative domains is ~4.6 eV while that of the positive domains is greater than ~6.2 eV. We propose that the threshold difference between the opposite domains can be …

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First Principles Study Of Transition-Metal Substitutions In Sm–Co Permanent Magnets, Renat F. Sabirianov, Arti Kashyap, Ralph Skomski, Sitaram Jaswal, David J. Sellmyer Sep 2004

First Principles Study Of Transition-Metal Substitutions In Sm–Co Permanent Magnets, Renat F. Sabirianov, Arti Kashyap, Ralph Skomski, Sitaram Jaswal, David J. Sellmyer

David Sellmyer Publications

The microchemistry and magnetism of conventional and high-temperature Sm–Co permanent magnets are investigated by first-principles calculations. Particular emphasis is on the site preference for the substitution of Cu, Ti, and Zr in SmCo5 and Sm2Co17 compounds. Cu substitution is more favorable in the 1:5 phase, in agreement with experimental findings. Titanium and zirconium have positive solution energies for both the phases, with Ti(Zr) having slight preference for the 1:5 (2:17) phase. Some Zr may segregate to the phase boundaries because of its large solution energy. For Ti and Zr the dumbbell site of the 2:17 phase …

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Stark Width And Shift Of The Neutral Argon 425.9 Nm Spectral Line, Vladimir Milosavljevic, Vida Zigman, Stevan Djenize Sep 2004

Stark Width And Shift Of The Neutral Argon 425.9 Nm Spectral Line, Vladimir Milosavljevic, Vida Zigman, Stevan Djenize

Articles

The Stark parameters, the width (W) and the shift (d), of the neutral argon (Ar I) 425.9 nm spectral line have been studied in a linear, low-pressure, optically thin pulsed arc discharge. The line shapes are measured in three different plasmas at about 16,000 K electron temperature (T) and about 7.0×1022 m−3 electron density (N). The separate electron and ion contributions to the total Stark width (Wt), i.e. We and Wi, as well as to the total Stark shift (dt), i.e. …

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Superconducting Transition Edge Sensor Using Dilute Almn Alloys, S. W. Deiker, W. Doriese, G. C. Hilton, K. D. Hilton, W. H. Rippard, J. N. Ullom, L. R. Vale, S. T. Ruggiero, A. Williams, Betty A. Young Sep 2004

Superconducting Transition Edge Sensor Using Dilute Almn Alloys, S. W. Deiker, W. Doriese, G. C. Hilton, K. D. Hilton, W. H. Rippard, J. N. Ullom, L. R. Vale, S. T. Ruggiero, A. Williams, Betty A. Young

Physics

We have fabricated a bolometer using a transition-edge sensor (TES) made of Al doped with Mn to suppress the superconducting critical temperature (Tc) of Al from ∼1Kto∼100mK. The resulting detector exhibits low-frequency noise consistent with theory, with a noise-equivalent power of 7.5×10−18W/√Hz. The addition of Mn impurities did not significantly increase the heat capacity of the TES. In addition, the detector is surprisingly insensitive to applied magnetic fields. The use of AlMn alloy films in arrays of TES detectors has advantages in simplicity of fabrication when compared to traditional bilayer fabrication techniques.

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Polarization Of Nuclear Spins From The Conductance Of Quantum Wires, James A. Nesteroff, Yuriy V. Pershin Dr, Vladimir Privman Sep 2004

Polarization Of Nuclear Spins From The Conductance Of Quantum Wires, James A. Nesteroff, Yuriy V. Pershin Dr, Vladimir Privman

Faculty Publications

We devise an approach to measure the polarization of nuclear spins via conductance measurements. Specifically, we study the combined effect of external magnetic field, nuclear spin polarization, and Rashba spin-orbit interaction on the conductance of a quantum wire. Nonequilibrium nuclear spin polarization affects the electron energy spectrum making it time dependent. Changes in the extremal points of the spectrum result in time dependence of the conductance. The conductance oscillation pattern can be used to obtain information about the amplitude of the nuclear spin polarization and extract the characteristic time scales of the nuclear spin subsystem.

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Oscillator Damped By A Constant-Magnitude Friction Force, Avi Marchewka, David S. Abbott, Robert J. Beichner Sep 2004

Oscillator Damped By A Constant-Magnitude Friction Force, Avi Marchewka, David S. Abbott, Robert J. Beichner

Dartmouth Scholarship

Although a simple spring/mass system damped by a friction force of constant magnitude shares many of the characteristics of the simple and damped harmonic oscillators, its solution is not presented in most texts. Closed form solutions for the turning and stopping points can be found using an energy-based approach. A dynamical approach leads to a closed form solution for the position of the mass as a function of time. The main result is that the amplitude of the oscillator damped by a constant magnitude friction force decreases by a constant amount each swing and the motion dies out after a …

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Application Of Microgels For Optical Tagging, J. Michael Carthcart, L. Andrew Lyon, Marcus Weck, Robert D. Bock Sep 2004

Application Of Microgels For Optical Tagging, J. Michael Carthcart, L. Andrew Lyon, Marcus Weck, Robert D. Bock

Biology, Chemistry, and Environmental Sciences Faculty Books and Book Chapters

In this paper we present results from our research into the use of microgel-based photonic crystals in an optical tagging application. The basis for this research is the phenomena of self-assembly of hydrogel nano- and microparticles (i.e., microgels) into colloidal crystal Bragg reflectors. Previous research has demonstrated the assembly of Bragg structures that are sensitive in the visible spectral region. This current research focuses on the extension of this process into the infrared regime and the use of these infrared-sensitive structures in the creation of an optical tag. In particular, the research effort emphasizes two primary areas: the development of …

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An Earlier Lidar Observation Of A Noctilucent Cloud Above Logan, Utah (41.7°N), Joshua P. Herron, Vincent B. Wickwar Sep 2004

An Earlier Lidar Observation Of A Noctilucent Cloud Above Logan, Utah (41.7°N), Joshua P. Herron, Vincent B. Wickwar

Posters

The Atmospheric Lidar Observatory (ALO) Rayleigh-scatter lidar has been operated for 11 years on the Utah State University (USU) campus (41.7o N 111.8o W). During the morning of 22 June 1995 a noctilucent cloud (NLC) was observed with the lidar well away from the twilight periods when NLCs are visible. It lasted for approximately one hour. This observation and a second in 1999 [Wickwar et al., 2002] are very significant because they show the penetration of NLCs equatorward of 50°, which may have important implications for global change. Temperature profiles calculated at hourly intervals were at least 20 …

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Dirac-Fock Energy Levels And Transition Probabilities For Oxygen-Like Fe Xix, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington Sep 2004

Dirac-Fock Energy Levels And Transition Probabilities For Oxygen-Like Fe Xix, V. Jonauskas, F. P. Keenan, M. E. Foord, R. F. Heeter, S. J. Rose, Gary J. Ferland, R. Kisielius, Peter A. M. Van Hoof, P. H. Norrington

Physics and Astronomy Faculty Publications

Multiconfigurational Dirac-Fock calculations are reported for 656 energy levels and the 214 840 electric dipole (E1), electric quadrupole (E2) and magnetic dipole (M1) transition probabilities in oxygen-like FeXIX. The spectroscopic notations as well as the total transition probabilities from each energy level are provided. Good agreement is found with data compiled by NIST.

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Simulations Of Resonant Alfvén Waves Generated By Artificial Hf Heating Of The Auroral Ionosphere, D Pokhotelov, W Lotko, A V. Streltsov Sep 2004

Simulations Of Resonant Alfvén Waves Generated By Artificial Hf Heating Of The Auroral Ionosphere, D Pokhotelov, W Lotko, A V. Streltsov

Dartmouth Scholarship

Numerical two-dimensional two-fluid MHD sim- ulations of dynamic magnetosphere-ionosphere (MI) cou- pling have been performed to model the effects imposed on the auroral ionosphere by a powerful HF radio wave trans- mitter. The simulations demonstrate that modifications of the ionospheric plasma temperature and recombination due to artificial heating may trigger the ionospheric feedback in- stability when the coupled MI system is close to the state of marginal stability. The linear dispersion analysis of MI coupling has been performed to find the favorable conditions for marginal stability of the system. The development of the ionospheric feedback instability leads to the generation …

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Exclusive Electroproduction Of J/Ψ Mesons At-Hera, S. Chekanov, M. Derrick, J. H. Loizides, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, 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, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, L. Rinaldi Sep 2004

Exclusive Electroproduction Of J/Ψ Mesons At-Hera, S. Chekanov, M. Derrick, J. H. Loizides, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, 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, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, L. Rinaldi

Faculty Publications

The exclusive electroproduction of J/ψ mesons, ep→epJ/ψ, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15

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Lattice Supersymmetry Via Twisting, Simon Catterall Sep 2004

Lattice Supersymmetry Via Twisting, Simon Catterall

Physics - All Scholarship

We describe how the usual supercharges of extended supersymmetry may be {\it twisted} to produce a BRST-like supercharge Q. The usual supersymmetry algebra is then replaced by a twisted algebra and the action of the twisted theory is shown to be generically Q-exact. In flat space the twisting procedure can be regarded as a change of variables carrying no physical significance. However, the twisted theories can often be transferred to the lattice while preserving the twisted supersymmetry. As an example we construct a lattice version of the two-dimensional supersymmetric sigma model

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High-Energy Ion Generation By Short Laser Pulses, Anatoly Maksimchuk, K. Flippo, H. Krause, G. Mourou, K. Nemoto, D. Schultz, Donald P. Umstadter, R. Vane, V. Yu. Bychenkov, G.I. Dudnikova, V.F. Kovalev, K. Mima, V.N. Novikov, Y. Sentoku, S.V. Tolokonnikov Sep 2004

High-Energy Ion Generation By Short Laser Pulses, Anatoly Maksimchuk, K. Flippo, H. Krause, G. Mourou, K. Nemoto, D. Schultz, Donald P. Umstadter, R. Vane, V. Yu. Bychenkov, G.I. Dudnikova, V.F. Kovalev, K. Mima, V.N. Novikov, Y. Sentoku, S.V. Tolokonnikov

Donald Umstadter Publications

This paper reviews the many recent advances at the Center for Ultrafast Optical Science (CUOS) at the University of Michigan in multi-MeV ion beam generation from the interaction of short laser pulses focused onto thin foil targets at intensities ranging from 1017 to 1019 W/cm2. Ion beam characteristics were studied by changing the laser intensity, laser wavelength, target material, and by depositing a well-absorbed coating. We manipulated the proton beam divergence using shaped targets and observed nuclear transformation induced by high-energy protons and deuterons. Qualitative theoretical approaches and fully relativistic two-dimensional particle-in-cell simulations modeled energetic ion …

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Lognormal X-Ray Flux Variations In An Extreme Narrow-Line Seyfert 1 Galaxy, C. Martin Gaskell Sep 2004

Lognormal X-Ray Flux Variations In An Extreme Narrow-Line Seyfert 1 Galaxy, C. Martin Gaskell

Department of Physics and Astronomy: Faculty Publications

We show that the large variations in the X-ray flux of the extreme narrow-line Seyfert 1 galaxy IRAS 13224– 3809, measured during a 10 day ASCA observation, have a two-parameter lognormal distribution of multiplicative standard deviation σmult = 2.7 and that the amplitude of variability at any given moment is proportional to the flux level. We find similar behavior in earlier ROSAT soft X-ray monitoring. There is no evidence of a nonvariable component. The flux-dependent behavior of the variability rules out linear shot-noise models. Although at first glance the variations of the ASCAlight curve for IRAS 13224–3809 appear …

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Visualizing Early Frog Development With Motion-Sensitive 3-D Optical Coherence Microscopy, Richard C. Haskell, Mary E. Williams, Daniel C. Petersen, Barbara M. Hoeling, Andrew J. Schile, J. D. Pennington, M. G. Seetin, J. M. Castelaz, Scott E. Fraser, Cyrus Papan, Hongwu Ren, Johannes F. De Boer, Zhongping Chen Sep 2004

Visualizing Early Frog Development With Motion-Sensitive 3-D Optical Coherence Microscopy, Richard C. Haskell, Mary E. Williams, Daniel C. Petersen, Barbara M. Hoeling, Andrew J. Schile, J. D. Pennington, M. G. Seetin, J. M. Castelaz, Scott E. Fraser, Cyrus Papan, Hongwu Ren, Johannes F. De Boer, Zhongping Chen

All HMC Faculty Publications and Research

A motion-sensitive en-face-scanning 3-D optical coherence microscope (OCM) has been designed and constructed to study critical events in the early development of plants and animals. We describe the OCM instrument and present time-lapse movies of frog gastrulation, an early developmental event in which three distinct tissue layers are established that later give rise to all major organ systems. OCM images constructed with fringe-amplitude data show the mesendoderm migrating up along the blastocoel roof, thus forming the inner two tissue layers. Motion-sigma data, measuring the random motion of scatterers, is used to construct complementary images that indicate the presence of Brownian …

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A Simple Design For An Electronic Speckle Pattern Interferometer, Thomas R. Moore Sep 2004

A Simple Design For An Electronic Speckle Pattern Interferometer, Thomas R. Moore

Faculty Publications

An electronic speckle pattern interferometer suitable for use in an undergraduate laboratory is described. This interferometer can be built for a small fraction of the cost of a commercial version and is simple and inexpensive to build and understand. The interferometer is useful for visualizing the normal modes of vibrating objects as well as changes in index of refraction.

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Enhancement Of Curie Temperature In Ga1−XMnXAs Epilayers Grown On Cross-Hatched InYGa1−YAs Buffer Layers, O. Maksimov, B.L. Sheu, G. Xiang, N. Keim, P. Schiffer, N. Samarth Sep 2004

Enhancement Of Curie Temperature In Ga1−XMnXAs Epilayers Grown On Cross-Hatched InYGa1−YAs Buffer Layers, O. Maksimov, B.L. Sheu, G. Xiang, N. Keim, P. Schiffer, N. Samarth

Physics

Relaxed InyGa1−yAs epilayers grown on (0 0 1) GaAs are known to exhibit a cross-hatched surface with ridges running along the [1 1 0] and directions. We find that Ga1−xMnxAs epilayers grown on such buffer layers can have as-grown Curie temperatures (TC) that are higher than the as-grown 110 K value typical of Ga1−xMnxAs/GaAs heterostructures. Further, low-temperature annealing leads to only modest additional increases in TC, contrasting with the behavior in Ga1−xMnxAs/GaAs where TC …

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Immunogold Labeling To Enhance Contrast In Optical Coherence Microscopy Of Tissue Engineered Corneal Constructs, Chris B. Raub, Elizabeth J. Orwin, Richard C. Haskell Sep 2004

Immunogold Labeling To Enhance Contrast In Optical Coherence Microscopy Of Tissue Engineered Corneal Constructs, Chris B. Raub, Elizabeth J. Orwin, Richard C. Haskell

All HMC Faculty Publications and Research

Our lab has used an optical coherence microscope (OCM) to assess both the structure of tissue-engineered corneal constructs and their transparency. Currently, we are not able to resolve cells versus collagen matrix material in the images produced. We would like to distinguish cells in order to determine if they are viable while growing in culture and also if they are significantly contributing to the light scattering in the tissue. In order to do this, we are currently investigating the use of immunogold labeling. Gold nanoparticles are high scatterers and can create contrast in images. We have conjugated gold nanoparticles to …

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Volume Holographic Recording And Readout For 90-Deg Geometry, Partha P. Banerjee, Monish Ranjan Chatterjee, Nickolai Kukhtarev, Tatiana Kukhtareva Sep 2004

Volume Holographic Recording And Readout For 90-Deg Geometry, Partha P. Banerjee, Monish Ranjan Chatterjee, Nickolai Kukhtarev, Tatiana Kukhtareva

Electrical and Computer Engineering Faculty Publications

When a prerecorded cross-beam hologram is reconstructed (so-called edge-lit readout) with a uniform plane wave and a point source, the resulting exact solutions reveal Bessel-function-type diffracted beam profiles, which are fundamentally modified under weak propagational diffraction. The case of a profiled beam readout with propagational diffraction may be analyzed using a transfer function approach based on 2-D Laplace transforms. In a second series of investigations, dynamic readout from a cross-beam volume hologram recorded with two orthogonal uniform plane waves is considered for various dependences of the refractive index modulation with intensity. Typically, refractive index profiles that are proportional to the …

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Modeling And Propagation Of Near-Field Diffraction Patterns: A More Complete Approach, Glen D. Gillen, Shekhar Guha Sep 2004

Modeling And Propagation Of Near-Field Diffraction Patterns: A More Complete Approach, Glen D. Gillen, Shekhar Guha

Physics

We discuss the origins and regions of validity of various near-field diffraction models. The complete Rayleigh–Sommerfeld model is found to accurately represent intensity distributions for axial distances up to and including the location of the aperture, a region where commonly used models fail. We show that near-field diffraction theory can be applied to the refraction of light at an interface between two different media yielding results that demonstrate the validity of Snell’s law in the presence of diffraction. Calculations using near-field diffraction and Fourier optics are compared to experimentally measured intensity distributions

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Electronic Structure Properties And Bcs Superconductivity In Ss-Pyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman Sep 2004

Electronic Structure Properties And Bcs Superconductivity In Ss-Pyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman

Physics Faculty Research & Creative Works

We report a first-principles density-functional calculation of the electronic structure and properties of the recently discovered superconducting β-pyrochlore oxide KOs2O6. We find that the electronic structure near the Fermi energy EF is dominated by strongly hybridized Os 5d and O 2p states. A van Hove singularity very close to Ef leads to a relatively large density of states at EF, and the Fermi surface exhibits strong nesting along several directions. These features could provide the scattering processes leading to the observed anomalous temperature dependence of the resistivity and to the rather large …

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Breakup Of H₂ In Singly Ionizing Collisions With Fast Protons: Channel-Selective Low-Energy Electron Spectra, Christina Dimopoulou, Robert Moshammer, Daniel Fischer, C. Hohr, Alexander Dorn, Pablo Daniel Fainstein, Jose R. Crespo Lopez-Urrutia, Claus Dieter Schroter, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich Sep 2004

Breakup Of H₂ In Singly Ionizing Collisions With Fast Protons: Channel-Selective Low-Energy Electron Spectra, Christina Dimopoulou, Robert Moshammer, Daniel Fischer, C. Hohr, Alexander Dorn, Pablo Daniel Fainstein, Jose R. Crespo Lopez-Urrutia, Claus Dieter Schroter, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

The dissociation of H2 in singly ionizing collisions with fast protons was analyzed using channel-selective low-energy electron spectra. Dissociative and nondissociative single ionization of H2 by 6MeV proton impact was described in a kinematically by determining momentum vectors of electron and H+ fragment of H2+ target ion, respectively. The electron spectra exhibited role of autoionization of doubly and singly excited states of H2. The doubly and singly excited states of H2 involve coupling between electronic and nuclear motion of molecule.

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Electron Loss From 1.4-Mev / U U4,6,10+ Ions Colliding With Ne, N₂, And Ar Targets, Robert D. Dubois, Antonio C. Santos, Th. Stohlker, F. Bosch, A. Brauning-Demian, A. Gumberidze, S. Hagmann, C. Kozhuharov, R. Mann, A. Orsic Muthig, U. Spillman, S. Tachenov, W. Bart, L. Dahl, B. Franzke, J. Glatz, L. Groning, S. Richter, D. Wilms, K. Ullmann, O. Jagutzki Sep 2004

Electron Loss From 1.4-Mev / U U4,6,10+ Ions Colliding With Ne, N₂, And Ar Targets, Robert D. Dubois, Antonio C. Santos, Th. Stohlker, F. Bosch, A. Brauning-Demian, A. Gumberidze, S. Hagmann, C. Kozhuharov, R. Mann, A. Orsic Muthig, U. Spillman, S. Tachenov, W. Bart, L. Dahl, B. Franzke, J. Glatz, L. Groning, S. Richter, D. Wilms, K. Ullmann, O. Jagutzki

Physics Faculty Research & Creative Works

Absolute, total, single- and multiple-electron-loss cross sections are measured for 1.4-MeV / u U4,6,10+ ions colliding with neon and argon atoms and nitrogen molecules. It is found that the cross sections all have the same dependence on the number of electrons lost and that multiplying the cross sections by the initial number of electrons in the 6s, 6p, and 5f shells yields good agreement between the different projectiles. By combining the present data with previous measurements made at the same velocity, it is shown that the scaled cross sections slowly decrease in magnitude for …

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Below Band Gap Photoreflectance Transitions In Epitaxial Gan, Phil W. Yu, Jerry D. Clark, David C. Look, C. Q. Chen, Jinwei Yang, Edmundas Koutstis, M. Asif Khan, Denis V. Tsvertkov, Vladimir A. Dmitriev Sep 2004

Below Band Gap Photoreflectance Transitions In Epitaxial Gan, Phil W. Yu, Jerry D. Clark, David C. Look, C. Q. Chen, Jinwei Yang, Edmundas Koutstis, M. Asif Khan, Denis V. Tsvertkov, Vladimir A. Dmitriev

Physics Faculty Publications

A photoreflectance (PR) and photoluminescence (PL) study has been performed on a Si-doped epitaxial GaN layer that contains impurity or defect related below band gap features in its PR spectrum. In the 300 K PR spectrum, these features appear at energies of 3.26 and 3.33 eV, respectively, but below 180 K they can no longer be seen. The 3.26 eV line evidently corresponds to a donor acceptor pair transition, also seen in PL. The origin of the 3.33 eV line is uncertain, but may correspond to a transition involving the nitrogen vacancy.

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Map Estimation For Hyperspectral Image Resolution Enhancement Using An Auxiliary Sensor, Russell C. Hardie, Michael T. Eismann, Gregory L. Wilson Sep 2004

Map Estimation For Hyperspectral Image Resolution Enhancement Using An Auxiliary Sensor, Russell C. Hardie, Michael T. Eismann, Gregory L. Wilson

Electrical and Computer Engineering Faculty Publications

This paper presents a novel maximum a posteriori (MAP) estimator for enhancing the spatial resolution of an image using co-registered high spatial-resolution imagery from an auxiliary sensor. Here we focus on the use of high-resolution panchomatic data to enhance hyperspectral imagery. However, the estimation framework developed allows for any number of spectral bands in the primary and auxiliary image. The proposed technique is suitable for applications where some correlation, either localized or global, exists between the auxiliary image and the image being enhanced. To exploit localized correlations, a spatially varying statistical model, based on vector quantization, is used. Another important …

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Volume Holographic Optical Elements, Ching-Cherng Sun, Partha P. Banerjee Sep 2004

Volume Holographic Optical Elements, Ching-Cherng Sun, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

The final two papers are concerned with the analysis of novel holograms. Banerjee et al. investigate holographic recording and reconstruction for edge-lit holograms recorded in a 90-degree geometry. Various cases of recording and readout that incorporate propagational diffraction have been modeled. It is shown that the 90-degree geometry can result in beam shaping, as evidenced through preliminary experimental results with photorefractive lithium niobate. Nguyen et al. propose a new approach for designing computer-generated holograms. An artificial neural network is used to initiate the genetic algorithm so that the high computation cost of genetic algorithms for synthesizing holograms is significantly reduced …

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