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Articles 31 - 60 of 370
Full-Text Articles in Physics
Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler
Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler
Theses and Dissertations
An understanding of spontaneous emission processes within microcavities is crucial in addressing the need to make tomorrow's microlasers more efficient. One approach to improving the device efficiency is to reduce the threshold input energy at which lasing begins to occur. It has been suggested that the threshold in a microcavity laser can be decreased by increasing the fraction of spontaneous emission into the lasing mode, this can be accomplished by preferentially coupling the gain medium of the laser to the electromagnetic cavity mode of interest. It therefore becomes necessary to understand the mechanism by which this coupling takes place. This …
Photolithographic Patterning Of Vacuum-Deposited Organic Light Emitting Devices, Peifang Tian, P. E. Burrows, S. E. Forrest
Photolithographic Patterning Of Vacuum-Deposited Organic Light Emitting Devices, Peifang Tian, P. E. Burrows, S. E. Forrest
Peifang Tian
We demonstrate a photolithographic technique to fabricate vacuum-deposited organic light emitting devices. Photoresist liftoff combined with vertical deposition of the emissive organic materials and the metal cathode, followed by oblique deposition of a metal cap, avoids the use of high processing temperatures and the exposure of the organic materials to chemical degradation. The unpackaged devices show no sign of deterioration in room ambient when compared with conventional devices fabricated using low-resolution, shadow mask patterning. Furthermore, the devices are resistant to rapid degradation when operated in air for extended periods. This work illustrates a potential foundation for the volume production of …
Observation Of Scaling Violations In Scaled Momentum Distributions At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti
Observation Of Scaling Violations In Scaled Momentum Distributions At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti
Faculty Publications
Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of x and Q2 using the ZEUS detector. The evolution of the scaled momentum, xp, with Q2, in the range 10 to 1280 GeV2, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of Q2. © 1997 Elsevier Science B.V.
Low-Field Hole Mobility In A Photorefractive Polymer, Arosha Goonesekera, Stephen Ducharme, James M. Takacs, Lei Zhang
Low-Field Hole Mobility In A Photorefractive Polymer, Arosha Goonesekera, Stephen Ducharme, James M. Takacs, Lei Zhang
Stephen Ducharme Publications
We present the time-of-flight measurements of hole mobility in a photorefractive polymer composite as a function of temperature and applied electric field. The analysis shows that the temperature dependence of the low-field mobility is in apparent disagreement with the predictions of the Gaussian disorder model and also with polaron models.
Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes
Impedance Spectroscopy Of Bilayer Lipid Membranes And Tio₂ Based Solar Cells, Uwe Hermes
Dissertations and Theses
It has been proposed in the literature that a novel class of biosensors can be based on a bimolecular layer of lipids supported on one side by a metallic surface. In order to estimate the potential of this system for the design of membrane sensors, we have studied properties of a two-electrode system consisting of a tefion insulated metallic wire and a Ag/ AgCl electrode, both immersed in KCl solution. The lipid bimolecular layer was formed on the metal surface of the cut tefion insulated wire. The electrical conductivity properties of such a device were studied in the frequency range …
Study Of The Decay Τ-→2Π-Π+3Π0ΝΤ, S. Anderson, Kenneth A. Bloom, Cleo Collaboration
Study Of The Decay Τ-→2Π-Π+3Π0ΝΤ, S. Anderson, Kenneth A. Bloom, Cleo Collaboration
Kenneth Bloom Publications
The decay τ-→2π-π+3π0ντ has been studied with the CLEO II detector at the Cornell Electron Storage Ring. The branching fraction is measured to be (2.85 ± 0.56 ± 0.51) X 10-4. The result is in good agreement with the isospin expectation but somewhat below the conserved-vectorcurrent prediction. We have searched for resonance substructure in the decay. Within the statistical precision, the decay is saturated by the channels τ-→π-2π0ωντ, 2π-π+ωντ, and π-2π0ων …
Limit On The Two-Photon Production Of The Glueball Candidate FJ(2220) At The Cornell Electron Storage Ring, R. Godang, Kenneth A. Bloom, Cleo Collaboration
Limit On The Two-Photon Production Of The Glueball Candidate FJ(2220) At The Cornell Electron Storage Ring, R. Godang, Kenneth A. Bloom, Cleo Collaboration
Kenneth Bloom Publications
We use the CLEO detector at the Cornell e+e- storage ring, CESR, to search for the two-photon production of the glueball candidate fJ (2220) in its decay to KsKs. We present a restrictive upper limit on the product of the two-photon partial width and the KsKs branching fraction, (Γγγ BKsKs)fJ(2220). We use this limit to calculate a lower limit on the stickiness, which is a measure of the two-gluon coupling relative to the two-photon coupling. This limit on stickiness …
Upper Limits To The Outflow Of Ions At Mars: Implications For Atmospheric Evolution, Jane L. Fox
Upper Limits To The Outflow Of Ions At Mars: Implications For Atmospheric Evolution, Jane L. Fox
Physics Faculty Publications
Escape of ions is potentially important for the evolution of volatiles on Mars, but the mechanisms and rates of ion escape processes are not fully understood. Instruments on the Russian Phobos 2 orbiter have, however, measured fluxes of heavy ions apparently of ionospheric origin in the optical shadow of Mars. These ions are assumed to arise from escape processes induced by the interaction of the solar wind with the ionosphere. We determine here upper limits to the ion loss rates by imposing upward flux boundary conditions on models of the low and high solar activity Mars ionosphere. The maximum fluxes …
Characterizing The Coherence Of Bose-Einstein Condensates And Atom Lasers, R. J. Dodd, Charles W. Clark, Mark Edwards, Keith Burnett
Characterizing The Coherence Of Bose-Einstein Condensates And Atom Lasers, R. J. Dodd, Charles W. Clark, Mark Edwards, Keith Burnett
Department of Physics and Astronomy Faculty Publications
For a dilute, interacting Bose gas of magnetically-trapped atoms at temperatures below the critical temperature T 0 for Bose-Einstein condensation, we determine the second-order coherence function g (2)(r 1, r 2) within the framework of a finite-temperature quantum field theory. We show that, because of the different spatial distributions of condensate and thermal atoms in the trap, g (2)(r 1, r 2) does not depend on |r 1 - r 2| alone. This means that the experimental determinations of g (2) reported to date give only its spatial average. Such an average may underestimate the degree of coherence attainable in …
Observation Of Isolated High-ET Photons In Photoproduction At Hera: Zeus Collaboration, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti
Observation Of Isolated High-ET Photons In Photoproduction At Hera: Zeus Collaboration, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti
Faculty Publications
Events containing an isolated prompt photon with high transverse energy, together with a balancing jet, have been observed for the first time in photoproduction at HERA. The data were taken with the ZEUS detector, in a γp centre of mass energy range 120-250 GeV. The fraction of the incoming photon energy participating in the production of the prompt photon and the jet, xγ, shows a strong peak near unity, consistent with LO QCD Monte Carlo predictions. In the transverse energy and pseudorapidity range 5 ≤ EγT < 10 GeV, -0.7 ≤ ηγ < 0.8, EjetT ≥ 5 GeV, and -1.5 ≤ ηjet ≤ 1.8, with xOBSγ > 0.8, the measured cross section is 15.3 ± 3.8 ± 1.8 pb, in good …
Hands-On Phasors And Multiple-Slit Interference, Rand S. Worland, Matthew J. Moelter
Hands-On Phasors And Multiple-Slit Interference, Rand S. Worland, Matthew J. Moelter
Physics
No abstract provided.
Teaching College Physics To A Blind Student, Michelle Parry, Mark Brazier, Ephraim Fischbach
Teaching College Physics To A Blind Student, Michelle Parry, Mark Brazier, Ephraim Fischbach
Chemistry & Physics Faculty Publications
No abstract provided.
Empirical Models Of Storm-Time Equatorial Zonal Electric Fields, Bela G. Fejer, L. Scherliess
Empirical Models Of Storm-Time Equatorial Zonal Electric Fields, Bela G. Fejer, L. Scherliess
Bela G. Fejer
Ionospheric plasma drifts often show highly complex and variable signatures during geomagnetically active periods due to the effects of different disturbance processes. We describe initially a methodology for the study of storm time dependent ionospheric electric fields. We present empirical models of equatorial disturbance zonal electric fields obtained using extensive F region vertical plasma drift measurements from the Jicamarca Observatory and auroral electrojet indices. These models determine the plasma drift perturbations due to the combined effects of short-lived prompt penetration and longer lasting disturbance dynamo electric fields. We show that the prompt penetration drifts obtained from a high time resolution …
Spectrum Of Hot O At The Exobases Of The Terrestrial Planets, Jane L. Fox, Aleksander B. Hać
Spectrum Of Hot O At The Exobases Of The Terrestrial Planets, Jane L. Fox, Aleksander B. Hać
Physics Faculty Publications
The distribution of energetic O produced in dissociative recombination of O2+ at the exobases of the terrestrial planets is important in determining the structure of the outer hot O coronas and for the escape flux of O from Mars. Using recently measured values for the branching ratios of the energetically allowed channels in O2+ dissociative recombination, along with models of the vibrational distribution of O2+, we compute the velocity distribution of hot O atoms produced at the exobases of Mars, Venus, and Earth. We take into account the effects of the ion and …
Search For The Decay Τ-→4Π-3Π+(Π0)ΝΤ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration
Search For The Decay Τ-→4Π-3Π+(Π0)ΝΤ, K. W. Edwards, Kenneth A. Bloom, Cleo Collaboration
Kenneth Bloom Publications
We have searched for the decay of the τ lepton into seven charged particles and zero or one π0. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.61 fb-. No evidence for a signal is found. Assuming all the charged particles are pions, we set an upper limit on the branching fraction B(τ-→4π-3π+(π0) ντ) < 2.4X10-6 at the 90% confidence level. This limit represents a significant improvement …
New Upper Limit On The Decay Η→E+E-, T. E. Browder, Kenneth A. Bloom, Cleo Collaboration
New Upper Limit On The Decay Η→E+E-, T. E. Browder, Kenneth A. Bloom, Cleo Collaboration
Kenneth Bloom Publications
We have searched for the rare decay of the η meson η→e+e- using the CLEO II detector. The η’s were produced in e+e- collisions with 10 GeV center-of-mass energy at the Cornell Electron Storage Ring (CESR). We find with 90% confidence the upper limit on the branching fraction B (η→e+e-)<7.7×10-5. The application of conventional elementary particle theory to this decay predicts a branching fraction of about 10-9.
Determination Of The Michel Parameters And The Τ Neutrino Helicity In Τ Decay, J. P. Alexander, Kenneth A. Bloom, Cleo Collaboration
Determination Of The Michel Parameters And The Τ Neutrino Helicity In Τ Decay, J. P. Alexander, Kenneth A. Bloom, Cleo Collaboration
Kenneth Bloom Publications
Using the CLEO II detector at the Cornell Electron Storage Ring operated at √s =10.6 GeV, we have determined the Michel parameters ρ, ξ, and δ in τ±→l±νν̅ decay as well as the τ neutrino helicity parameter hvτ in τ±→π±π0ν decay. From a data sample of 3.02×106 produced τ pairs we analyzed events of the topologies e+e-→τ+τ-→(l±νν̅)(π±π0ν) and e+e-→τ+τ-→(π±π0ν̅)(π±π0ν). …
Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xi. Intensive Monitoring Of The Ultraviolet Spectrum Of Ngc 7469, I. Wanders, Bradley M. Peterson, D. Alloin, T.R. Ayres, J. Clavel, D. Michael Crenshaw, K. Horne, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Paul T. O'Brien, G.A. Reichert, P.M. Rodriguez-Pascual, W. Wamsteker, T. Alexander, K. S.J. Anderson, E. Benitez, N.G. Bochkarev, A.N. Burenkov, F.-Z. Cheng, S.J. Collier, A. Comastri, M. Dietrich, D. Dultzin-Hacyan, B.R. Espey, A. V. Filippenko, C. Martin Gaskell, I.M. George, M.R. Goad, L.C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, Ari Laor, G.M. Macalpine, M. Mignoli, S.L. Morris, K. Nandra, S. Penton, Richard William Pogge, R.L. Ptak, J.M. Rodriguez-Espinoza, M. Santos-Lleo, A.I. Shapovalova, J.M. Shull, Stephanie A. Snedden, L.S. Sparke, G.M. Stirpe, W.-H. Sun, T.J. Turner, M.-H. Ulrich, T.-G. Wang, C. Wei, W.F. Welsh, S.-J. Xue, Z.-L. Zhou
Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xi. Intensive Monitoring Of The Ultraviolet Spectrum Of Ngc 7469, I. Wanders, Bradley M. Peterson, D. Alloin, T.R. Ayres, J. Clavel, D. Michael Crenshaw, K. Horne, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Paul T. O'Brien, G.A. Reichert, P.M. Rodriguez-Pascual, W. Wamsteker, T. Alexander, K. S.J. Anderson, E. Benitez, N.G. Bochkarev, A.N. Burenkov, F.-Z. Cheng, S.J. Collier, A. Comastri, M. Dietrich, D. Dultzin-Hacyan, B.R. Espey, A. V. Filippenko, C. Martin Gaskell, I.M. George, M.R. Goad, L.C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, Ari Laor, G.M. Macalpine, M. Mignoli, S.L. Morris, K. Nandra, S. Penton, Richard William Pogge, R.L. Ptak, J.M. Rodriguez-Espinoza, M. Santos-Lleo, A.I. Shapovalova, J.M. Shull, Stephanie A. Snedden, L.S. Sparke, G.M. Stirpe, W.-H. Sun, T.J. Turner, M.-H. Ulrich, T.-G. Wang, C. Wei, W.F. Welsh, S.-J. Xue, Z.-L. Zhou
C. Martin Gaskell Publications
From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes. From the time delays, one can estimate the size of the region dominating the production of the UV emission lines in this source. We find the strong UV emission lines to respond to continuum variations with time delays of about 2.d3-3.d1 for Lyα, 2.d7 for C IV λ1549, 1.d9-2.d4 for N IV λ …
Dispersion Coefficients For Highly Excited Molecular States Of K2, Mircea Marinescu, Anthony F. Starace
Dispersion Coefficients For Highly Excited Molecular States Of K2, Mircea Marinescu, Anthony F. Starace
Anthony F. Starace Publications
We report results of theoretical calculations for the dispersion coefficients associated with the long-range interaction of two 39K atoms in the states 39K(4s)- 39K(5d,6d,7s). These results have been found by Wang et al. [Phys. Rev. Lett. 78, 4173 (1997)] to be in a good agreement with their measurements.
Molecular Fluorescence At A Rough Surface: The Orientation Effects, P.T. Leung, W. L. Blacke
Molecular Fluorescence At A Rough Surface: The Orientation Effects, P.T. Leung, W. L. Blacke
Physics Faculty Publications and Presentations
The problem of the dynamical interaction between an emitting dipole and a metallic grating surface is considered with particular interest in the effects due to different orientations of the dipole with respect to the substrate surface. Our previous perturbative theory is extended to treat both parallel and perpendicular dipoles and the results are applied to the study of modified fluorescence characteristics for admolecules in the vicinity of a rough metal surface modeled as a grating. Numerical results show that some of the characteristics are very sensitive to the molecular orientation and the one along the grating direction is manifested with …
A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby
A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby
Theses and Dissertations
The most current version of the Parameterized Real-time Ionospheric Specification Model (PRISM), version 1.7b, was validated using Digital Ionospheric Sounding System (DISS) measurements of F2 layer critical frequency (foF2) and F2 peak electron density height (hmF2) as the "ground truth." PRISM was executed, first, with no real-time input parameter and, second, with Global Positioning System (GPS) Total Electron Content (TEC) measurements as the sole real-time parameter. Hourly values of hmF2 and foF2 over 123 days in 1994-1996 (solar minimum conditions) and covering three seasons (equinox, summer solstice, and winter solstice) were compared for Wallops Island, Virginia, and Point Arguello, California, …
Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces, R. E. Davies, John R. Dennison
Evolution Of Secondary Electron Emission Characteristics Of Spacecraft Surfaces, R. E. Davies, John R. Dennison
All Physics Faculty Publications
Secondary electron emission (SEE) plays a key role in spacecraft charging [Garrett, 1981; Frooninckx and Sojka, 1992] . As a result, spacecraft charging codes require knowledge of the SEE characteristics of various materials in order to predict vehicle potentials in various orbital environments [Katz, et. al., 1986]. Because SEE is a surface phenomenon, occurring in the first few atomic layers of a material, the SEE characteristics of a given surface are extremely sensitive to changes in surface condition--e.g., the addition or removal of surface contaminants, or changes in surface morphology. That spacecraft surfaces can and generally do undergo significant evolution …
Observational Evidence Of Wave Ducting And Evanescence In The Mesosphere, J. R. Isler, Michael J. Taylor, D. C. Fritts
Observational Evidence Of Wave Ducting And Evanescence In The Mesosphere, J. R. Isler, Michael J. Taylor, D. C. Fritts
All Physics Faculty Publications
A collaborative radar and imaging study of gravity waves over the Hawaiian Islands was performed during October 1993 as part of the Airborne Lidar and Observations of Hawaiian Airglow 1993/Coupling and Dynamics of Regions Equatorial (ALOHA-93/CADRE) campaign to investigate the propagation characteristics of short-period (<1 hour) waves at nightglow altitudes. The horizontal wavelengths and apparent phase speeds of quasi-monochromatic wave events were measured in four separate nightglow emissions using data obtained by a high-resolution CCD imager. This information was correlated with simultaneous MF radar wind measurements over the same height interval (∼80–100 km) to infer intrinsic wave parameters in each case. Correlating the two data sets allowed the determination of the local vertical wavenumber for each event, in particular whether it be real (indicative of freely propagating waves) or imaginary (indicative of ducted or evanescent waves). The results of this study indicate a preponderance of ducted or evanescent waves at 80–100 km during the time of the observations, with up to ∼75% of the events recorded exhibiting ducted or evanescent behavior. Also noted was a tendency for ducted behavior to be more prevalent among waves with shorter horizontal wavelengths, in agreement with Doppler ducting theory. These results suggest that ducted waves are relatively common in the upper mesosphere and lower thermosphere region, at least over the mid-Pacific Ocean. As small-scale waves which are ducted have the potential to travel much longer horizontal distances than freely propagating waves, the frequency of their occurrence should be taken into account in efforts to quantify gravity wave effects at these altitudes.
Nonlinear Response Theory: Transport Coefficients For Driving Fields Of Arbitrary Magnitude, Paul Ernest Parris, Marek Kus, David H. Dunlap, Vasudev M. Kenkre
Nonlinear Response Theory: Transport Coefficients For Driving Fields Of Arbitrary Magnitude, Paul Ernest Parris, Marek Kus, David H. Dunlap, Vasudev M. Kenkre
Physics Faculty Research & Creative Works
A theory of nonlinear response is developed for driving fields of arbitrary magnitude. Exact and usable expressions are provided for electrical and thermal mobility, and related transport coefficients, in terms of correlation functions of the system. A generalization into the nonlinear domain is provided of the Wiedemann-Franz law connecting electrical and thermal response and of the Einstein relation relating the diffusion constant and the mobility.
Image Measurements Of Short Period Gravity Waves At Equatorial Latitudes, Michael J. Taylor, W. R. Pendleton Jr., S. Clark, H. Takahashi, D. Gobbi, R. A. Goldberg
Image Measurements Of Short Period Gravity Waves At Equatorial Latitudes, Michael J. Taylor, W. R. Pendleton Jr., S. Clark, H. Takahashi, D. Gobbi, R. A. Goldberg
All Physics Faculty Publications
A high-performance, all-sky imaging system has been used to obtain novel data on the morphology and dynamics of short-period (<1 hour) gravity waves at equatorial latitudes. Gravity waves imaged in the upper mesosphere and lower thermosphere were recorded in three nightglow emissions, the near-infrared OH emission, and the visible wavelength OI (557.7 nm) and Na (589.2 nm) emissions spanning the altitude range ∼80–100 km. The measurements were made from Alcantara, Brazil (2.3°S, 44.5°W), during the period August-October 1994 as part of the NASA/Instituto Nacional de Pesquisas Espaciais “Guara campaign”. Over 50 wave events were imaged from which a statistical study of the characteristics of equatorial gravity waves has been performed. The data were found to divide naturally into two groups. The first group corresponded to extensive, freely propagating (or ducted) gravity waves with observed periods ranging from 3.7 to 36.6 min, while the second group consisted of waves of a much smaller scale and transient nature. The later group exhibited a bimodal distribution for the observed periods at 5.18 ± 0.26 min and 4.32 ± 0.15 min, close to the local Brunt-Vaisala period and the acoustic cutoff period, respectively. In comparison, the larger-scale waves exhibited a clear tendency for their horizontal wavelengths to increase almost linearly with observed period. This trend was particularly well defined around the equinox and can be represented by a power-law relationship of the form λ h = ( 3.1 ± 0.5 ) τ ob 1.06 ± 0.10 , where λ h is measured in kilometers and τob in minutes. This result is in very good agreement with previous radar and passive optical measurements but differs significantly from the relationship λ h ∝ τ105 ob inferred from recent lidar studies. The larger-scale waves were also found to exhibit strong anisotropy in their propagation headings with the dominant direction of motion toward the-NE-ENE suggesting a preponderance for wave generation over the South American continent.
Analysis Of Uranium Oxide Weathering By Molecular Spectroscopy, Matthew S. Zickafoose
Analysis Of Uranium Oxide Weathering By Molecular Spectroscopy, Matthew S. Zickafoose
Theses and Dissertations
A preliminary study of the weathering of uranium oxide particles diluted in diamond dust at ambient environmental conditions is presented. The primary weathering reaction is oxidation of the uranium from the 4 to 6 oxidation state, although formation of compounds such as carbonates and hydroxides is possible. Identification of the state of uranium oxide has been attempted using luminescence spectroscopy and diffuse reflectance Fourier transform infrared spectroscopy DRIFTS. Luminescence spectra of nominal samples of three common oxides, UO3, U3O8, and UO2, have been measured showing significant spectral differences in peaks at 494 nm, 507 nm, 529 nm, and 553 nm. …
Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker
Hybrid Quantum And Molecular Mechanics Embedded Cluster Models For Chemistry On Silicon And Silicon Carbide Surfaces, James R. Shoemaker
Theses and Dissertations
Fabrication of silicon carbide SiC semiconductor devices are of interest for aerospace applications because of their high-temperature tolerance. Growth of an insulating SiO2 layer on SiC is a poorly understood process, and sometimes produces interface defects that degrade device performance. Accurate theoretical models of surface chemistry, using quantum mechanics QM, do not exist because of the huge computational cost of solving Schroedingers equation for a molecular cluster large enough to represent a surface. Molecular mechanics MM, which describes a molecule as a collection of atoms interacting through classical potentials, is a fast computational method, good at predicting molecular structure, …
Role Of Multiple Scattering In Cross-Correlated Light Scattering With A Single Laser Beam, James A. Lock
Role Of Multiple Scattering In Cross-Correlated Light Scattering With A Single Laser Beam, James A. Lock
Physics Faculty Publications
Previous systems for measuring cross-correlated light scattering by small particles suspended in a liquid with multiple-scattering suppression have illuminated the particles with two laser beams. It is shown that multiple-scattering suppression should also occur in cross correlation for a system that employs a single laser beam and two closely spaced detectors with wide fields of view. The single-scattering, double-scattering, and single-double-scattering cross-term contributions to the intensity cross-correlation function are calculated. It is found that the two cross terms, when added together, are unimportant for both autocorrelation and cross correlation. The amplitude of the double-scattering term can be greatly diminished by …
Multiple-Scattering Suppression By Cross Correlation, William V. Meyer, David S. Cannell, Anthony E. Smart, Thomas W. Taylor, Padetha Tin
Multiple-Scattering Suppression By Cross Correlation, William V. Meyer, David S. Cannell, Anthony E. Smart, Thomas W. Taylor, Padetha Tin
Physics Faculty Publications
We describe a new method for characterizing particles in turbid media by cross correlating the scattered intensity fluctuations at two nearby points in the far field. The cross-correlation function selectively emphasizes single scattering over multiple scattering. The usual dynamic light-scattering capability of inferring particle size from decay rate is thus extended to samples that are so turbid as to be visually opaque. The method relies on single-scattering speckle being physically larger than multiple-scattering speckle. With a suitable optical geometry to select nearby points in the far field or equivalently slightly different scattering wave vectors (of the same magnitude), the multiple-scattering …
Hybrid Reflection-Transmission Surface Light-Scattering Instrument With Reduced Sensitivity To Surface Sloshing, William V. Meyer, James A. Lock, H. Michael Cheung, Thomas W. Taylor, Padetha Tin, J. Adin Mann
Hybrid Reflection-Transmission Surface Light-Scattering Instrument With Reduced Sensitivity To Surface Sloshing, William V. Meyer, James A. Lock, H. Michael Cheung, Thomas W. Taylor, Padetha Tin, J. Adin Mann
Physics Faculty Publications
A hybrid reflection-transmission surface light-scattering instrumental design is presented, examined theoretically, and tested experimentally. The purpose of the design is to reduce the sensitivity of the instrument to vibration in general and surface sloshing in particular while sacrificing Little performance. Traditional optical arrangements and two new optical configurations with varying trade-offs between slosh resistance and instrumental simplicity and accuracy are examined by use of Fourier optics methods. The most promising design was constructed and tested with acetone, ethanol, and water as subject fluids. The test involved backcalculation of the wave number of the capillary wave examined with the known physical …