Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

Physics

Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 28471 - 28500 of 34246

Full-Text Articles in Entire DC Network

Experimental Studies Of Magnetic Reconnection, Michael R. Brown May 1999

Experimental Studies Of Magnetic Reconnection, Michael R. Brown

Physics & Astronomy Faculty Works

Laboratory magnetic reconnection experiments have been performed for nearly 20 years. Elegant experiments by Stenzel and Gekelman [R. L. Stenzel and W. Gekelman, Phys. Rev. Lett. 42, 1055 (1979); W. Gekelman and R. L. Stenzel, Phys. Rev. Lett. 54, 2414 (1985)] focused on the measurement of field quantities with a single movable probe in a highly reproducible plasma. Observations included a very thin current sheet (on the order of c/ωpe), accelerated electrons, and whistler waves. The argon ions were unmagnetized in these experiments. Recent magnetohydrodynamic (MHD) experiments by Yamada and Ono have used merging plasmoids [M. Yamada, Y. Ono, A. …

Go to article

Neutron Resonance Spectroscopy Of 117sn From1 Ev To 1.5 Kev, D A. Smith, J D. Bowman, Bret E. Crawford, C A. Grossmann, T Haseyama, Mikkel B. Johnson, A Masaike, Y Matsuda, G E. Mitchell, V A. Nazarenko, S I. Penttila, N R. Roberson, S J. Seestrom, E I. Sharapov, L M. Smotritsky, Sharon L. Stephenson, V W. Yuan May 1999

Neutron Resonance Spectroscopy Of 117sn From1 Ev To 1.5 Kev, D A. Smith, J D. Bowman, Bret E. Crawford, C A. Grossmann, T Haseyama, Mikkel B. Johnson, A Masaike, Y Matsuda, G E. Mitchell, V A. Nazarenko, S I. Penttila, N R. Roberson, S J. Seestrom, E I. Sharapov, L M. Smotritsky, Sharon L. Stephenson, V W. Yuan

Physics and Astronomy Faculty Publications

Parity violation has been studied recently for neutron resonances in 117Sn. The neutron resonance spectroscopy is essential for the analysis of the parity violation data. We have measured neutron resonances in 117Sn for neutron energies from 1 to 1500 eV using the time-of-flight method and the (n,γ) reaction. The sample was enriched to 87.6% 117Sn. Neutron scattering and radiative widths were determined, and orbital angular momentum assignments were made with a Bayesian analysis. The s-wave and p-wave strength functions and average level spacings were determined.

Go to article

Hydrologic Time Series Forecasting With Specialized Autoregressive Neural Networks, Paul Edward Roundy May 1999

Hydrologic Time Series Forecasting With Specialized Autoregressive Neural Networks, Paul Edward Roundy

Undergraduate Honors Capstone Projects

Interannual forecasts of hydrologic time series are important for water supply management.  Specialized neural network algorithms for such forecasts are developed here.  These methods are based on  the principles of nonlinear dynamics and an autoregresive backpropogation training algorithm.  The applicable nonlinear methods are described, as well as the algorithm.  Some of the problems of these networks are summarized, along with some of their positive attributes.  Tests showed that they may be able to learn and forecast some hydrologic data.  These networks were most successful for  forecasting the flows of the Colorado River.  Some example forecasts are given, including the peaks …

Go to article

Black Holes And The Sym Diagram. Ii, Emil Martinec, Vatche Sahakian May 1999

Black Holes And The Sym Diagram. Ii, Emil Martinec, Vatche Sahakian

All HMC Faculty Publications and Research

The complete phase diagram of objects in M theory compactified on tori Tp,p=1,2,3, is elaborated. Phase transitions occur when the object localizes on cycle(s) (the Gregory-Laflamme transition), or when the area of the localized part of the horizon becomes one in string units (the Horowitz-Polchinski correspondence point). The low-energy, near-horizon geometry that governs a given phase can match onto a variety of asymptotic regimes. The analysis makes it clear that the matrix conjecture is a special case of the Maldacena conjecture.

Go to article

The Effect Of Laser Bandwidth On The Signal Detected In Two-Color, Resonant Four-Wave Mixing Spectroscopy, F. Di Teodoro, Elizabeth Mccormack May 1999

The Effect Of Laser Bandwidth On The Signal Detected In Two-Color, Resonant Four-Wave Mixing Spectroscopy, F. Di Teodoro, Elizabeth Mccormack

Physics Faculty Research and Scholarship

The effect of laser line shape and bandwidth on the signal detected in two-color, resonant four-wave mixing (TC-RFWM) spectroscopy is determined by means of an ab initio calculation of the third-order polarization based on diagrammatic perturbation theory. Modifications to the approach previously used for the case of delta-function laser line shapes are made by introducing a different treatment of the rotating wave approximation and phase-matching conditions. A three-level excitation scheme for double-resonance spectroscopy of bound and quasibound states is analyzed. In the case of Lorentzian laser line shapes, analytic expressions for the signal line profile are obtained for each excitation …

Go to article

Kinematics Of Tt̅ Events At Cd, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration May 1999

Kinematics Of Tt̅ Events At Cd, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

The kinematic properties of tt̅ events are studied in the W + multijet channel using data collected with the CDF detector during the 1992–1995 runs at the Fermilab Tevatron collider corresponding to an integrated luminosity of 109 pb-1. Distributions of a variety of kinematic variables chosen to be sensitive to different aspects of tt̅ production are compared with those expected from Monte Carlo calculations. A sample of 34 events rich in tt̅ pairs is obtained by requiring at least one jet identified by the silicon vertex detector (SVX) as having a displaced vertex consistent with the decay of …

Go to article

Modes And Quasi-Modes For M = 1,2 In A Gyrokinetic Model For A Non-Neutral Plasma, S. Neil Rasband, Ross L. Spencer May 1999

Modes And Quasi-Modes For M = 1,2 In A Gyrokinetic Model For A Non-Neutral Plasma, S. Neil Rasband, Ross L. Spencer

Faculty Publications

Modes and quasi-modes for m = 1,2 are studied in a gyro-kinetic model for a pure-electron plasma. Only z-independent perturbations are considered. Numerical methods are used to solve the relevant differential equations for smooth, analytic density profiles. Different temperatures and representative profiles are considered and comparison is made with the familiar cold fluid model from which the results depart but little, except at higher temperatures. A continuum component to the spectrum, present in the cold-fluid model, remains in the gyro-kinetic model to the order considered.

Go to article

Near-Field Fluorescence Microscopy Based On Two-Photon Excitation With Metal Tips, Erik J. Sánchez, Lukas Novotny, X. Sunney Xie May 1999

Near-Field Fluorescence Microscopy Based On Two-Photon Excitation With Metal Tips, Erik J. Sánchez, Lukas Novotny, X. Sunney Xie

Physics Faculty Publications and Presentations

We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with femtosecond laser pulses of proper polarization. The strongly enhanced electric field at the metal tip (ap15 nm end diameter) results in a localized excitation source for molecular fluorescence. Excitation of the sample via two-photon absorption provides good image contrast due to the quadratic intensity dependence. The spatial resolution is shown to be better than that of the conventional aperture technique. We used the technique to image fragments of photosynthetic membranes, as well as j-aggregates with spatial resolutions on the order of 20 nm.

Go to article

Measurement Of Angle-Resolved Secondary Electron Spectra, Robert Davies May 1999

Measurement Of Angle-Resolved Secondary Electron Spectra, Robert Davies

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Theoretical formulations of secondary electron emission over the past 20 years have exceeded the confirming ability of available measurements. An instrument has been developed and tested for the purpose of obtaining simultaneous angle- and energy-resolved (AER) secondary and backscattered electron measurements for energetic electrons incident on conducting surfaces. The instrument is found to be in good working order and the data quality found to be excellent for nearly all angles and energies investigated. A representative set of AER measurements has been acquired for 1500 eV electrons normally incident on polycrystalline gold. The data have been used to construct angle-resolved (AR) …

Go to article

Effects Of Resonant Tunneling In Electromagnetic Wave Propagation Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky May 1999

Effects Of Resonant Tunneling In Electromagnetic Wave Propagation Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky

Physics Faculty Research & Creative Works

We consider tunneling of electromagnetic waves through a polariton band gap of a one-dimensional chain of atoms. We analytically show that a defect embedded in the structure gives rise to the resonance transmission at the frequency of a local polariton state associated with the defect. Numerical Monte Carlo simulations are used to examine properties of the electromagnetic band arising inside the polariton gap due to finite concen-tration of defects.

Go to article

Defect-Induced Resonant Tunneling Of Electromagnetic Waves Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky May 1999

Defect-Induced Resonant Tunneling Of Electromagnetic Waves Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky

Physics Faculty Research & Creative Works

We consider tunneling of electromagnetic waves through a polariton band gap of a 1-D chain of atoms. We analytically demonstrate that a defect embedded in the structure gives rise to the resonance transmission at the frequency of a local polariton state associated with the defect.

Go to article

Photodetachment Of Na-, Chien-Nan Liu, Anthony F. Starace May 1999

Photodetachment Of Na-, Chien-Nan Liu, Anthony F. Starace

Anthony F. Starace Publications

Eigenchannel R-matrix calculation results are presented for the photodetachment partial cross sections of Na- for energies up to the Na(5p) threshold. The photoelectron angular distribution asymmetry parameter for the process Na-+γ→Na(3p)+e- is also presented over the same energy range. Detailed analyses and identifications of 1P0 resonance structures are presented and compared with corresponding ones in H- and Li-. Our results are compared with works of others, including the four-state close-coupling results of Moores and Norcross [Phys. Rev. A 10, 1646 (1974)], the resonances observed by Johnston and …

Go to article

Phase Control Of X-Ray–Atom Scattering In The Presence Of A Bichromatic Laser Field, Dejan B. Miloševíc, Anthony F. Starace Apr 1999

Phase Control Of X-Ray–Atom Scattering In The Presence Of A Bichromatic Laser Field, Dejan B. Miloševíc, Anthony F. Starace

Anthony F. Starace Publications

We consider the scattering of 50 eV x-rays by hydrogen atoms in the presence of a bichromatic, linearly polarized laser field with frequencies ω and rω, where r = 2, 3, ω = 1.17 eV, and with relative phase &#; between the bichromatic laser field components. Numerical results for the differential cross-section (DCS) as a function of the number n, where nω is the energy exchanged with the laser field, are presented. For either a monochromatic laser field or a bichromatic laser field with the frequencies ω and 3ω, the integer n can only be even, while for a bichromatic …

Go to article

The Influence Of Surface Terminal Layer And Surface Defects On The Electronic Structure Of Cmr Perovskites: La0.65A0.35Mno3 (A = Ca, Sr, Ba), Jaewu Choi, Hani Dulli, Sy-Hwang Liou, Peter A. Dowben, Marjorie Langell Apr 1999

The Influence Of Surface Terminal Layer And Surface Defects On The Electronic Structure Of Cmr Perovskites: La0.65A0.35Mno3 (A = Ca, Sr, Ba), Jaewu Choi, Hani Dulli, Sy-Hwang Liou, Peter A. Dowben, Marjorie Langell

Peter Dowben Publications

The electronic structure near to the Fermi level of the colossal magnetoresistance (CMR) perovskite manganite materials, La0.65A0.35MnO3 (A = Ca, Sr, Ba), has been studied using both photoemission and inverse photoemission spectroscopy. The electronic structure for all three materials is very similar and consistent with an Mn–O terminal layer regardless of dopant. Small differences in the electronic structure among the materials are, however, observed. The observed band gap is not significant for La0.65A0.35MnO3 and La0.65A0.35MnO3 while there is a gap, about 1.5 eV, for La …

Go to article

The Pg X-Ray Qso Sample: Links Between The Ultraviolet-X-Ray Continuum And Emission Lines, Beverley J. Wills, A. Laor, M. S. Brotherton, D. Wills, B. J. Wilkes, Gary J. Ferland, Zhaohui Shang Apr 1999

The Pg X-Ray Qso Sample: Links Between The Ultraviolet-X-Ray Continuum And Emission Lines, Beverley J. Wills, A. Laor, M. S. Brotherton, D. Wills, B. J. Wilkes, Gary J. Ferland, Zhaohui Shang

Physics and Astronomy Faculty Publications

Two sets of relationships relate QSO UV to soft X-ray continua with the broad-line region. These are (i) the Baldwin relationships, which are inverse relationships between the broad-line equivalent width and the continuum luminosity, and (ii) Boroson & Green's optical "Principal Component 1'' relationships, linking steeper soft X-ray spectra with narrower Hβ emission, stronger Hβ blue wings, stronger optical Fe II emission, and weaker [O III] λ5007 lines. In order to understand these relationships, we extended the spectra into the UV for 22 QSOs with high-quality soft X-ray spectra. These are from the complete sample of QSOs from the Bright …

Go to article

Natural Emissions Of Chlorine-Containing Gases: Reactive Chlorine Emissions Inventory, M. A. K. Khalil, R. M. Moore, D. B. Harper, J. M. Lobert, D. J. Erickson, V. Koropalov, W. T. Sturges, W. C. Keene Apr 1999

Natural Emissions Of Chlorine-Containing Gases: Reactive Chlorine Emissions Inventory, M. A. K. Khalil, R. M. Moore, D. B. Harper, J. M. Lobert, D. J. Erickson, V. Koropalov, W. T. Sturges, W. C. Keene

Physics Faculty Publications and Presentations

Although there are many chlorine-containing trace gases in the atmosphere, only those with atmospheric lifetimes of 2 years or fewer appear to have significant natural sources. The most abundant of these gases are methyl chloride, chloroform, dichloromethane, perchloroethylene, and trichloroethylene. Methyl chloride represents about 540 parts per trillion by volume (pptv) Cl, while the others together amount to about 120 pptv Cl. For methyl chloride and chloroform, both oceanic and land-based natural emissions have been identified. For the other gases, there is evidence of oceanic emissions, but the roles of the soils and land are not known and have not …

Go to article

Search For Third-Generation Leptoquarks From Technicolor Models In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Apr 1999

Search For Third-Generation Leptoquarks From Technicolor Models In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report the results of a search for technicolor using 110 pb-1 of pp̅ collisions recorded by the Collider Detector at Fermilab (CDF). In technicolor models containing a technifamily, color-octet technirhos enhance the pair production of color-triplet technipions, which behave as third-generation leptoquarks. From our previously reported search for third-generation leptoquarks, we present constraints on the production of color-triplet technipions and color-octet technirhos as a function of their masses.

Go to article

Structural And Magnetic Properties Of Nanocomposite Co:C Films, M. Yu, Yi Liu, David J. Sellmyer Apr 1999

Structural And Magnetic Properties Of Nanocomposite Co:C Films, M. Yu, Yi Liu, David J. Sellmyer

David Sellmyer Publications

The structural and magnetic properties of Co:C nanocomposite films at room temperature were investigated as functions of annealing temperature, Co concentration, and film thickness. The as-deposited films, which were cosputtered from Co and C onto water-cooled glass substrates, are nonmagnetic amorphous Co–C alloys. Hexagonal-close-packed (hcp) Co grains are formed in 100 nm films annealed at 300 °C and most Co takes this structure when annealed at higher temperatures. The sizes of the Co grains range from 10 to 25 nm, with larger grain size resulting from higher annealing temperature and higher Co concentration. With the increase of annealing temperature and …

Go to article

Strain Dependence Of The Magnetic Properties Of Nm Fe Films On W(100), Axel Enders, D. Sander, J. Kirschner Apr 1999

Strain Dependence Of The Magnetic Properties Of Nm Fe Films On W(100), Axel Enders, D. Sander, J. Kirschner

Axel Enders Publications

The thickness dependence of the magneto-elastic coupling B1, the intrinsic film stress, and the magnetic in-plane anisotropy K4 of Fe films on W(100) are measured with an in situ combination of a highly sensitive optical deflection technique with magneto-optical Kerr-effect measurements. We find that both B1 and K4 depend strongly on the Fe film thickness. The thickness dependence of B1 can be described by considering a second order magneto-elastic coupling constant D = GJ/m3 as a strain dependent correction of B1. We tentatively ascribe the deviation of K4 from its …

Go to article

Enhancement Of Coercivity In Nanometer-Size Copt Crystallites, Sy_Hwang Liou, S. Huang, Elizabeth S. Klimek, Roger D. Kirby Apr 1999

Enhancement Of Coercivity In Nanometer-Size Copt Crystallites, Sy_Hwang Liou, S. Huang, Elizabeth S. Klimek, Roger D. Kirby

Roger Kirby Publications

In this study, we showed that a magnetic coercivity (Hc) as high as 37 kOe was obtained in a CoPt thin film that contains separated nanometer-size CoPt crystallites. We prepared CoPt thin films with thicknesses of 5 and 175 nm by magnetron sputtering. After annealing in an Ar/H2 atmosphere at temperatures from 650 to 750 °C for 3–12 h, we measured the magnetic properties and found that magnetic Hc relates to annealing temperature, annealing time and film thickness. From atomic force microscopy and magnetic force microscopy studies, the magnetic single domain size of CoPt is …

Go to article

Magnetic Hardening In SmcoX–Co Multilayers And Nanocomposites, J. Ping Liu, Yi Liu, Ralph Skomski, David J. Sellmyer Apr 1999

Magnetic Hardening In SmcoX–Co Multilayers And Nanocomposites, J. Ping Liu, Yi Liu, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

SmCox–Co (x = 3.5, 4, and 5) nanostructured multilayers have been prepared by dc and rf sputtering. Magnetic hardening has been found in the as-deposited thin films. The effects of the Co and hard-phase layer thicknesses and the effect of the Cr underlayer have been studied. Further magnetic hardening has been achieved by heat treating the samples. A remarkable increase of the coercivity has been obtained in the nanocomposite films, with coercive force up to 40 kOe. Transmission electron microscopy, atomic force microscopy, and magnetic force microscopy observations have been performed to understand the nanostructure and the domain …

Go to article

Effects Of Layer Thickness On Orientation Distribution And Magnetic Properties Of Cocrta/Cr Films, Z. S. Shan, H. Zeng, C. X. Zhu, M. Azarisooreh, K. Honardoost, Yi Liu, David J. Sellmyer Apr 1999

Effects Of Layer Thickness On Orientation Distribution And Magnetic Properties Of Cocrta/Cr Films, Z. S. Shan, H. Zeng, C. X. Zhu, M. Azarisooreh, K. Honardoost, Yi Liu, David J. Sellmyer

David Sellmyer Publications

No abstract provided.

Go to article

Magnetic And Structural Properties Of Mg–Co Nanostructures Fabricated, E.M. Kirkpatrick, Diandra Leslie-Pelecky, S.-H. Kim, R.D. Rieke Apr 1999

Magnetic And Structural Properties Of Mg–Co Nanostructures Fabricated, E.M. Kirkpatrick, Diandra Leslie-Pelecky, S.-H. Kim, R.D. Rieke

Diandra Leslie-Pelecky Publications

Reductive chemical synthesis is a versatile tool for fabricating elemental nanostructures; however, less work has been completed on understanding and controlling alloy formation. Magnetic Mg–Co and Mg–Co–C nanocomposites have been fabricated using a reductive chemical synthesis designed to produce highly active metals. The as-synthesized powder was annealed at temperatures from 150 to 650 °C. Samples were investigated using x-ray diffraction, alternating gradient force magnetometry, and superconducting quantum interference device magnetometry. X-ray diffraction indicates that the resulting structures are multiphase with MgCo2, MgCo3C0. 5, fcc Co, Mg, MgO, and Li2CO3 present depending on …

Go to article

Activation Entropy, Activation Energy, And Magnetic Viscosity, Ralph Skomski, Roger D. Kirby, David J. Sellmyer Apr 1999

Activation Entropy, Activation Energy, And Magnetic Viscosity, Ralph Skomski, Roger D. Kirby, David J. Sellmyer

Roger Kirby Publications

Starting from an exact quantum-statistical description, the influence of the shape of the energy landscape on the magnetic viscosity is investigated. Magnetic phase-space analysis based on Kramers’ escape-rate theory of chemical reaction kinetics theory shows that the activation entropy associated with thermally activated hopping modifies the magnetic viscosity by reducing the attempt-frequency prefactor compared to an earlier prediction by Brown [W. F. Brown, Phys. Rev. 130, 1677 (1963)]. Energetic contributions are analyzed in terms of a model applicable to a range of coherent and noncoherent magnetization processes, and in the long-time limit deviations from the linear logarithmic magnetic-viscosity law are …

Go to article

Dielectric Tensor For Magneto-Optic Nimnsb, Xiang Gao, John A. Woollam, Roger D. Kirby, David J. Sellmyer, C. T. Tanaka, J. Nowak, Jagadeesh S. Moodera Apr 1999

Dielectric Tensor For Magneto-Optic Nimnsb, Xiang Gao, John A. Woollam, Roger D. Kirby, David J. Sellmyer, C. T. Tanaka, J. Nowak, Jagadeesh S. Moodera

Department of Physics and Astronomy: Faculty Publications

The diagonal component ɛxx and off-diagonal component ɛxy of the complex dielectric tensor for the ferromagnetic compound NiMnSb are determined using ex situ spectroscopic ellipsometry and magneto-optic analysis over the spectral range from 0.7 to 6.2 eV. The effects of the overcoat on the raw data are removed by the analysis. First, the complex ɛxx of thin-film NiMnSb were determined by ex situ spectroscopic ellipsometry; then ɛxy was determined by analyzing Kerr rotation and ellipticity data using the determined ɛxy data. Lorentz oscillators were used to model peaks seen in the ɛxx spectra. The …

Go to article

Effects Of Layer Thickness On Orientation Distribution And Magnetic Properties Of Cocrta/Cr Films, Z.S. Shan, H. Zeng, C.X. Zhu, M. Azarisooreh, K. Honardoost Apr 1999

Effects Of Layer Thickness On Orientation Distribution And Magnetic Properties Of Cocrta/Cr Films, Z.S. Shan, H. Zeng, C.X. Zhu, M. Azarisooreh, K. Honardoost

David Sellmyer Publications

Evolution of orientation distribution of Co(110) crystal planes was determined by x-ray rocking curves. It has been found that: (i) The full-width at half maximum W of the Co(110) rocking curve decreases with both increasing Cr underlayer thickness dcr, and increasing CoCrTa magnetic layer thickness dco, especially in the thin layer regime. (ii) For the thin dcoregime, the interlayer diffusion between the Cr underlayer and the magnetic layer affects the rocking curves and magnetic properties significantly. (iii) Film magnetic properties, e.g., a significant jump in coercivity with increasing magnetic layer thickness in the thin …

Go to article

K-Inflation, Christian Armendariz-Picon, T. Damour, V. Mukhanov Apr 1999

K-Inflation, Christian Armendariz-Picon, T. Damour, V. Mukhanov

Physics - All Scholarship

It is shown that a large class of higher-order (i.e. non-quadratic) scalar kinetic terms can, without the help of potential terms, drive an inflationary evolution starting from rather generic initial conditions. In many models, this kinetically driven inflation (or "k-inflation" for short) rolls slowly from a high-curvature initial phase, down to a low-curvature phase and can exit inflation to end up being radiation-dominated, in a naturally graceful manner. We hope that this novel inflation mechanism might be useful in suggesting new ways of reconciling the string dilaton with inflation

Go to article

Applications Of Amorphous Track Models In Radiation Biology, Francis Cucinotta, Hooshang Nikjoo, Dudley A. Goodhead Apr 1999

Applications Of Amorphous Track Models In Radiation Biology, Francis Cucinotta, Hooshang Nikjoo, Dudley A. Goodhead

Robert Katz Publications

The average or amorphous track model uses the response of a system to gamma-rays and the radial distribution of dose about an ion’s path to describe survival and other cellular endpoints from proton, heavy ion, and neutron irradiation. This model has been used for over 30 years to successfully fit many radiobiology data sets. We review several extensions of this approach that address objections to the original model, and consider applications of interest in radiobiology and space radiation risk assessment. In the light of present views of important cellular targets, the role of target size as manifested through the relative …

Go to article

Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott Apr 1999

Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott

AFIT Patents

An improved intracavity sensor based output power control for microcavity light emitting devices. An improved phototransistor transducer is both configured and physically disposed so that it passively transmits the spurious optical energy output of the microcavity light emitting device while simultaneously generating a light determined electrical signal of easily used large magnitude that is nearly free of error. The base-collector region of the transistor is disposed with a quantum well absorbing layer and produces a signal responsive to a selected emission wavelength. The configuration of the optical energy communicating transducer is arranged so that it is improved in sensitivity and …

Go to article

Excitation Of Morphology-Dependent Resonances And Van De Hulst's Localization Principle, James A. Lock Apr 1999

Excitation Of Morphology-Dependent Resonances And Van De Hulst's Localization Principle, James A. Lock

Physics Faculty Publications

When a laser beam scatters from a microparticle whose shape deviates from that of a sphere, a number of partial waves of the incident beam couple to a given partial wave of the scattered and interior fields. As a result, partial-wave coupling caused by small surface irregularities of a liquid droplet provides the mechanism for exciting low-radial-order morphology-dependent resonances. (C) 1999 Optical Society of America.

Go to article

First Prev Next Last