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Articles 181 - 210 of 2339
Full-Text Articles in Physical Sciences and Mathematics
On-Road Remote Sensing Of Heavy-Duty Diesel Truck Emissions In The Austin- San Marcos Area: August 1998, Jerome A. Morris, Gary A. Bishop, Donald H. Stedman
On-Road Remote Sensing Of Heavy-Duty Diesel Truck Emissions In The Austin- San Marcos Area: August 1998, Jerome A. Morris, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Do Interactions Increase Or Reduce The Conductance Of Disordered Electrons? It Depends!, Thomas Vojta, Frank Epperlein, Michael Schreiber
Do Interactions Increase Or Reduce The Conductance Of Disordered Electrons? It Depends!, Thomas Vojta, Frank Epperlein, Michael Schreiber
Physics Faculty Research & Creative Works
We investigate the influence of electron-electron interactions on the conductance of two-dimensional disordered spinless electrons. We present an efficient numerical method based on diagonalization in a truncated basis of Hartree-Fock states to determine with high accuracy the low-energy properties in the entire parameter space. We find that weak interactions increase the dc conductance in the strongly localized regime while they decrease the dc conductance for weak disorder. Strong interactions always decrease the conductance. We also study the localization of single-particle excitations at the Fermi energy which turns out to be only weakly influenced by the interactions.
Essential Role Of Correlations In Governing Charge Transport In Disordered Organic Materials, Sergei V. Novikov, David H. Dunlap, Vasudev M. Kenkre, Paul Ernest Parris, Anatoly V. Vannikov
Essential Role Of Correlations In Governing Charge Transport In Disordered Organic Materials, Sergei V. Novikov, David H. Dunlap, Vasudev M. Kenkre, Paul Ernest Parris, Anatoly V. Vannikov
Physics Faculty Research & Creative Works
The transport of photoinjected charges in disordered organic films is often interpreted using a formula based on a Gaussian disorder model (GDM) that neglects spatial correlations due to charge-dipole interactions, even though such correlations have recently been shown to explain the universal electric field dependence observed in these systems. Based on extensive computer simulations of a 3D disorder model that includes such correlations, we present a new formula for analyzing experiments that accurately describes transport in these materials.
Comparison Of Electron-Atom Collision Parameters For S To P Transitions Under Reversal Of Energy Transfer, Max Shurgalin, Andrew James Murray, William R. Macgillivray, M. C. Standage, Don H. Madison, Kathrin D. Winkler, Igor Bray
Comparison Of Electron-Atom Collision Parameters For S To P Transitions Under Reversal Of Energy Transfer, Max Shurgalin, Andrew James Murray, William R. Macgillivray, M. C. Standage, Don H. Madison, Kathrin D. Winkler, Igor Bray
Physics Faculty Research & Creative Works
Inelastic and superelastic electron scattering from the optically prepared 32P3/2 state of sodium has enabled atomic collision parameters to be deduced for the 4S-3P deexcitation and the 3S-3P excitation processes. These data are compared with convergent close coupling and second order distorted wave Born calculations. For excitation, both theories agree with experiment, whereas for deexcitation the close coupling theory is in better agreement. A long-standing proposal relating to the sign of the transferred angular momentum is not supported.
A Late Cambrian Positive Carbon-Isotope Excursion In The Southern Appalachians: Relation To Biostratigraphy, Sequence Stratigraphy, Environments Of Deposition, And Diagenesis, Bosiljka Glumac, Kenneth R. Walker
A Late Cambrian Positive Carbon-Isotope Excursion In The Southern Appalachians: Relation To Biostratigraphy, Sequence Stratigraphy, Environments Of Deposition, And Diagenesis, Bosiljka Glumac, Kenneth R. Walker
Geosciences: Faculty Publications
A positive carbon-isotope excursion is recorded within the Upper Cambrian sedimentary succession in the southern Appalachians that consists of the Nolichucky Shale, the Maynardville Formation, and the Copper Ridge Dolomite. The lower part of the succession contains Aphelaspis zone fauna (Early Steptoean). The extensively dolomitized and poorly fossiliferous nature of the upper part of the succession precludes any detailed biostratigraphic determinations. Correlation with similar positive carbon-isotope excursions in coeval successions elsewhere suggests that this excursion represents a perturbation in the global cycling of carbon. Comparison of excursions at different localities in North America provides a means for the application of …
Analysis Of Multiphoton Ionization Of Metal Atoms In The Saturation Regime Using Subpicosecond Krf Laser Pulses, B. Witzel, Cornelis J. Uiterwaal, H. Schröder, D. Charalambidis, K.-L. Kompa
Analysis Of Multiphoton Ionization Of Metal Atoms In The Saturation Regime Using Subpicosecond Krf Laser Pulses, B. Witzel, Cornelis J. Uiterwaal, H. Schröder, D. Charalambidis, K.-L. Kompa
C.J.G.J. Uiterwaal Publications
Singly and multiply charged ion yield curves are reported for resonant and nonresonant two photon- ionization processes for a collection of 31 metal atoms. The atoms are created by sputtering from a solid target using an Ar-ion gun. Single and multiple ionization of these atoms is performed using linearly polarized 248.6-nm (KrF) laser pulses with a full width at half maximum duration of 500 fs, employing intensities between 109 and 1012 W cm-2. A four-grid high-resolution reflecting time-of-flight spectrometer is used for ion detection. This advanced spectrometer has a well-defined and small source volume, enabling absolute …
Unidirectional Anisotropy In Ultrathin Transition-Metal Films , Ralph Skomski, H.-P. Oepen, J. Kirschner
Unidirectional Anisotropy In Ultrathin Transition-Metal Films , Ralph Skomski, H.-P. Oepen, J. Kirschner
Ralph Skomski Publications
Unidirectional magnetic anisotropies in low-symmetry magnetic thin films such as cobalt on vicinal copper surfaces are investigated. Possible explanations of the observed uniaxial anisotropies are competing anisotropy (CA) coefficients and Dzyaloshinskii-Moriya (DM) interactions. Unidirectional CA is an interesting mechanism occurring in low-symmetry magnets and involves neither antiferromagnetic exchange nor spin canting. It is visible in the easy-cone regime and decides, for example, whether the preferential magnetization direction points up or down a stepped surface. In the case of Co/Cu(11n) films, however, the anisotropy direction speaks in favor of DM-type interactions.
Ionization Dynamics In Fast Ion-Atom Collisions. I. Energy And Angular Distributions Of Low-Energy Electrons Emitted In Ionization Of He By Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, L. Gulyas, M. Eugene Rudd
Ionization Dynamics In Fast Ion-Atom Collisions. I. Energy And Angular Distributions Of Low-Energy Electrons Emitted In Ionization Of He By Bare Carbon Ions, Lokesh C. Tribedi, P. Richard, Y. D. Wang, C. D. Lin, L. Gulyas, M. Eugene Rudd
M. Eugene Rudd Publications
We have studied the two-center effect (TCE) in ion-atom ionization by measuring the energy and angular distributions of the double-differential cross sections (DDCSs) (d2σ/dεdΩ) of the low-energy electrons emitted in a collision of He atoms with 2.5 MeV/nucleon C6+ ions. The electrons with energies between 0.1 and 300 eV were detected for 13 different emission angles between 15° and 160°. From the measured DDCSs we have deduced the single differential cross sections such as dσ/dΩ and dσ/dε and the total cross section. The data have been …
Radiative Decay Modes Of The D0 Meson, D. M. Asner, Kenneth A. Bloom, Cleo Collaboration
Radiative Decay Modes Of The D0 Meson, D. M. Asner, Kenneth A. Bloom, Cleo Collaboration
Kenneth Bloom Publications
In this paper we describe a search for four radiative decay modes of the D0 meson: D0 → φγ, D0 → ωγ, D0 → K-*γ, and D0 → ρ0γ . We obtain 90% C.L. upper limits on the branching ratios of these modes of 1.9 X 10-4, 2.4 X 10-4, 7.6 X 10-4, and 2.4 X 10-4, respectively.
Comment On "Beach Water Table Fluctuations Due To Wave Run-Up: Capillarity Effects" By L. Li Et Al., Vitaly A. Zlotnik
Comment On "Beach Water Table Fluctuations Due To Wave Run-Up: Capillarity Effects" By L. Li Et Al., Vitaly A. Zlotnik
Department of Earth and Atmospheric Sciences: Faculty Publications
Vitaly A. Zlotnik's comment on "Beach water table fluctuations due to wave run-up: Capillarity effects" by L. Li, D. A. Barry, J.-Y. Parlange, and C. B. Pattiaratchi, published in Water Resources Research (1997) 3(5): 935-945.
Accurate Classification Of Juvenile Weakfish Cynoscion Regalis To Estuarine Nursery Areas Based On Chemical Signatures In Otoliths, Simon R. Thorrold, Cynthia M. Jones, Peter K. Swart, Timothy E. Targett
Accurate Classification Of Juvenile Weakfish Cynoscion Regalis To Estuarine Nursery Areas Based On Chemical Signatures In Otoliths, Simon R. Thorrold, Cynthia M. Jones, Peter K. Swart, Timothy E. Targett
OES Faculty Publications
We investigated the ability of trace element and isotopic signatures in otoliths to record the nursery areas of juvenile (young-of-the-year) weakfish Cynoscion regalis from the east coast of the USA. Juvenile C. regalis were captured with otter trawls at multiple sites in Doboy Sound (Georgia), Pamlico Sound (North Carolina), Chesapeake Bay (Virginia), Delaware Bay (Delaware) and Peconic Bay (New York), from July to September 1996. One sagittal otolith from each specimen was assayed for Mg/Ca, Mn/Ca, Sr/Ca and Ba/Ca ratios using inductively coupled plasma mass spectrometry (ICP-MS), while delta 13 C and delta 18 O values from the other sagittal …
A Framework For Sharing Handwritten Notes, Richard C. Davis, James Lin, Jason A. Brotherton, James A. Landay, Morgan N. Price, Bill N. Schilit
A Framework For Sharing Handwritten Notes, Richard C. Davis, James Lin, Jason A. Brotherton, James A. Landay, Morgan N. Price, Bill N. Schilit
Research Collection School Of Computing and Information Systems
NotePals is an ink-based, collaborative note taking application that runs on personal digital assistants (PDAs). Meeting participants write notes in their own handwriting on a PDA. These notes are shared with other participants by synchronizing later with a shared note repository that can be viewed using a desktop-based web browser. NotePals is distinguished by its lightweight process, interface, and hardware. This demonstration illustrates the design of two different NotePals clients and our web-based note browser.
Notepals: Sharing And Synchronizing Handwritten Notes With Multimedia Documents, James A. Landay, Richard C. Davis, Victor Chen, Jonathan Huang, Rebecca B. Lee, Francis Li, James Lin, Charles B. Morrey, Ben Schleimer
Notepals: Sharing And Synchronizing Handwritten Notes With Multimedia Documents, James A. Landay, Richard C. Davis, Victor Chen, Jonathan Huang, Rebecca B. Lee, Francis Li, James Lin, Charles B. Morrey, Ben Schleimer
Research Collection School Of Computing and Information Systems
NotePals is an ink-based, collaborative note taking application that runs on personal digital assistants (PDAs). Meeting participants write notes in their own handwriting on a PDA. These notes are shared with other participants by synchronizing later with a shared note repository that can be viewed using a desktop-based web browser. NotePals is distinguished by its lightweight process, interface, and hardware. This demonstration illustrates the design of two different NotePals clients and our web-based note browser.
Web Bags: Are They Useful In A Web Warehouse?, Sourav S. Bhowmick, Sanjay Kumar Madria, Wee-Keong Ng, Ee Peng Lim
Web Bags: Are They Useful In A Web Warehouse?, Sourav S. Bhowmick, Sanjay Kumar Madria, Wee-Keong Ng, Ee Peng Lim
Research Collection School Of Computing and Information Systems
Sets and bags are closely related structures. A bag is different from a set in that it is sensitive to the number of times an element occurs while a set is not. In this paper, we introduce the concept of web bag in a web warehouse as a part of our Web Information Coupling System(WICS). Informally, a web bag is a web table which allows multiple occurrences of identical web tuples. Web bag helps to discover useful knowledge from a web table such as visible documents (or web sites), luminous documents and luminous paths. We formally discuss the semantics and …
A Global Object Model For Accommodating Instance Heterogeneities, Ee Peng Lim, Roger Hsiang-Li Chiang
A Global Object Model For Accommodating Instance Heterogeneities, Ee Peng Lim, Roger Hsiang-Li Chiang
Research Collection School Of Computing and Information Systems
To completely address database integration problems in the context of multidatabase [10] and data warehousing systems, one has to examine various integration and query requirements. Due to various reasons such as poor data quality in local databases, ongoing local database updates, and instance heterogeneities, some instance differences have to be accommodated by the integrated databases. We have therefore proposed a new object-oriented global data model, called OORA, that can accommodate attribute and relationship instance heterogeneities in the integrated database. In addition, the OORA model has been designed to allow database integrators and end users to query both the local and …
Web Warehousing System: Design And Issues, Wee-Keong Ng, Ee Peng Lim, Sourav S. Bhowmick, Sanjay Kumar Madria
Web Warehousing System: Design And Issues, Wee-Keong Ng, Ee Peng Lim, Sourav S. Bhowmick, Sanjay Kumar Madria
Research Collection School Of Computing and Information Systems
The World Wide Web is a distributed global information resource. It contains a large amount of information that have been placed on the web independently by different organizations and thus, related information may appear across different web sites. To manage and access heterogeneous information on WWW, we have started a project of building a web warehouse, called Whoweda (Warehouse of Web Data). Currently, our work on building a web warehousing system has focused on building a data model and designing a web algebra. In this paper, we discuss design and research issues in a web warehousing system. The issues include …
Searches For The Neutral Higgs Bosons Of The Mssm In E+E- Collisions At Centre-Of-Mass Energies Of 181-184 Gev, Barate, R.; Et Al., M. Thulasidas
Searches For The Neutral Higgs Bosons Of The Mssm In E+E- Collisions At Centre-Of-Mass Energies Of 181-184 Gev, Barate, R.; Et Al., M. Thulasidas
Research Collection School Of Computing and Information Systems
The data collected by ALEPH at LEP at centre-of-mass energies ranging from 181 to 184 GeV, corresponding to an integrated luminosity of 57 pb−1, are analysed to search for pair-produced neutral Higgs bosons h and A, in the bb̄bb̄ and τ+τ−bb̄ final states. Two events are found in the data with 2.5 expected from standard model processes. When combined with the lower energy data collected by ALEPH and with earlier reported searches for associated hZ production, these analyses are interpreted in the context of the minimal supersymmetric extension of the standard model (MSSM). For standard choices of MSSM parameter sets, …
Interior Blowup In A Convection-Diffusion Equation, Christopher P. Grant
Interior Blowup In A Convection-Diffusion Equation, Christopher P. Grant
Faculty Publications
This paper addresses the qualitative behavior of a nonlinear convection-diffusion equation on a smooth bounded domain in Rn, in which the strength of the convection grows superlinearly as the density increases. While the initial-boundary value problem is guaranteed to have a local-in-time solution for smooth initial data, it is possible for this solution to be extinguished in nite time. We demonstrate that the way this may occur is through nite-time "blow up," i.e., the unboundedness of the solution in arbitrarily small neighborhoods of one or more points in the closure of the spatial domain. In special circumstances, such as the …
Modelling Direct Episodic Recharge In The Western Australian Wheatbelt, F Lewis, Cooperative Research Centre For Catchment Hydrology (Australia)
Modelling Direct Episodic Recharge In The Western Australian Wheatbelt, F Lewis, Cooperative Research Centre For Catchment Hydrology (Australia)
Resource management technical reports
In agricultural regions of Western Australia, salinity is spreading. This is because the area taken up by groundwater discharge is increasing as a result of increased groundwater recharge following the replacement of native vegetation systems by annual crops and pasture species. Attempts to reduce groundwater recharge are now being made as it is hoped that this will decrease the rate of land salinisation. At several sites, average recharge rates have been estimated to be from 2% to 13% of the average annu ter hydrographs from the agricultural regions indicate that at some sites recharge does not occur as small amounts …
Structural Biology Metaphors Applied To The Design Of A Distributed Object System, Ladislau Bölöni, Ruibing Hao, Kyungkoo Jun, Dan C. Marinescu
Structural Biology Metaphors Applied To The Design Of A Distributed Object System, Ladislau Bölöni, Ruibing Hao, Kyungkoo Jun, Dan C. Marinescu
Department of Computer Science Technical Reports
No abstract provided.
State To State He-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane
State To State He-Co Rotationally Inelastic Scattering, Stiliana Antonova, Ao Lin, Antonis P. Tsakotellis, George C. Mcbane
Peer Reviewed Articles
Relative integral cross sections for rotational excitation of CO in collisions with He were measured at energies of 72 and 89 meV. The cross sections are sensitive to anisotrophy in the repulsive wall of the He-CO interaction. The experiments were done in crossed molecular beams with resonance enhanced multiphoton ionization detection. The observed cross sections display interference structure at low Δj, despite the average over the initial CO rotational distribution. At higher Δj, the cross sections decrease smoothly. The results are compared with cross sections calculated from two high quality potential energy surfaces for the He-CO …
Field Trip Guide: Illinois River Summary, National Poultry Water Management Symposium, Kenneth F. Steele
Field Trip Guide: Illinois River Summary, National Poultry Water Management Symposium, Kenneth F. Steele
Arkansas Water Resources Center Technical Reports
No abstract provided.
A Continuum Analysis Of The Chemotactic Signal Seen By Dictyostelium Discoideum, J. C. Dallon, H. G. Othmer
A Continuum Analysis Of The Chemotactic Signal Seen By Dictyostelium Discoideum, J. C. Dallon, H. G. Othmer
Faculty Publications
We develop a mathematical model of cell-to-cell-signalling in Dictyostelium discoideum that predicts the cAMP signal seen by individual cells in early aggregation. The model employs two cells on a plane and is designed to predict the space-time characteristics of both the extracellular cAMP signal seen by one cell when a nearby cell relays, and the intracellular cAMP response produced by the stimulus in the receiving cell. The effect of membrane bound phosphodiesterase is studied and it is shown that cells can orient effectively even in its absence. Our results give a detailed picture of how the spatio-temporal characteristics of the …
Flux Measurements And Sampling Strategies: Applications To Methane Emissions From Rice Fields, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer
Flux Measurements And Sampling Strategies: Applications To Methane Emissions From Rice Fields, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer
Physics Faculty Publications and Presentations
The emissions of methane from rice fields and other sources are often measured by placing chambers on the surface and taking sequential samples. Although static chambers pose several problems that affect the accuracy of the data, there are a few parameters that, if carefully chosen, can improve the reliability of the data and reduce the uncertainties. These parameters are the length of time the chamber is kept on the rice plants, the number of samples that are drawn to estimate the flux, the basal area and height of the chamber, the frequency of measurements during the growing season, and the …
Effects Of Production And Oxidation Processes On Methane Emissions From Rice Fields, M. Khalil, R. A. Rasmussen, Martha J. Shearer
Effects Of Production And Oxidation Processes On Methane Emissions From Rice Fields, M. Khalil, R. A. Rasmussen, Martha J. Shearer
Physics Faculty Publications and Presentations
The emission of methane from rice fields is the difference between the amount produced in the anaerobic zone below the soil and the amount oxidized in the root zone. Plants can also contribute to methane production by exuding organic compounds that may be utilized by methanogenic bacteria. We measured methane emissions from rice fields at Tu Zu in China between 1988 and 1994, which gave average emissions of about 30 mg m⁻² h⁻¹. We estimate that 45-60% of the methane produced was oxidized before reaching the atmosphere; and root exudates may have contributed of the order of 10% of the …
Factors Affecting Methane Emissions From Rice Fields, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer, R. W. Dalluge, Lixin Ren, Chang-Lin Duan
Factors Affecting Methane Emissions From Rice Fields, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer, R. W. Dalluge, Lixin Ren, Chang-Lin Duan
Physics Faculty Publications and Presentations
Methane emissions from rice fields are affected by a number of environmental and agricultural factors. We have analyzed our 7-year data set on methane emissions from rice fields in Tu Zu, China, to delineate the relationships between emissions and a number of variables that were measured at the same time. Our work was done in fields that were managed under prevailing agricultural practices of the region. Consequently, only the effect of factors that vary from year to year or during the growing season can be calculated. In our study we measured the effects of environmental variables (soil temperature, wind speed, …
Measurements Of Methane Emissions From Rice Fields In China, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer, R. W. Dalluge, Lixin Ren, Chang-Lin Duan
Measurements Of Methane Emissions From Rice Fields In China, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer, R. W. Dalluge, Lixin Ren, Chang-Lin Duan
Physics Faculty Publications and Presentations
Rice fields have always been regarded as one of the largest anthropogenic sources of atmospheric methane. Here we report the results of a 7-year study of methane emissions from rice fields in the Sichuan Province of China. In this region, there is one crop of rice per year, the fields are continuously flooded from transplanting to harvest, and there is heavy use of organic fertilizers. Emissions over the entire growing season were measured from each of up to 24 plots. Environmental variables were measured and relevant supporting data on the agricultural practices were recorded. The fields were studied under prevailing …
Target Dependence Of The Triply Differential Cross Section For Low Energy (E, 2e) Processes, Cheng Pan, Anthony F. Starace
Target Dependence Of The Triply Differential Cross Section For Low Energy (E, 2e) Processes, Cheng Pan, Anthony F. Starace
Anthony F. Starace Publications
The main purpose of this chapter is to review our calculations, whose aim is to explain the target dependence of the triply differential cross sections that has been observed in a number of recent experiments performed at relatively low energies above the ionization threshold for the two outgoing electrons leaving in opposite directions (θ12 = π). One reason for focusing on this θ12 = π geometry is that it is the most important geometry for near-threshold double-escape processes in the WPR theory. Another reason is that up to now, except for H and He targets, the triply differential …
The Electromagnetic Field Near A Dielectric Half-Space, Andrew Lang, Dr. Adam D. Helfer
The Electromagnetic Field Near A Dielectric Half-Space, Andrew Lang, Dr. Adam D. Helfer
College of Science and Engineering Faculty Research and Scholarship
We compute the expectations of the squares of the electric and magnetic fields in the vacuum region outside a half-space filled with a uniform non-dispersive dielectric. This gives predictions for the Casimir-Polder force on an atom in the "retarded" regime near a dielectric. We also find a positive energy density due to the electromagnetic field. This would lead, in the case of two parallel dielectric half-spaces, to a positive, separation-independent contribution to the energy density, besides the negative, separation-dependent Casimir energy. Rough estimates suggest that for a very wide range of cases, perhaps including all realizable ones, the total energy …
Stochastic Methods For Evaluating The Potential For Wetland Rehydration In Covered-Karst Terranes, Christian David Langevin
Stochastic Methods For Evaluating The Potential For Wetland Rehydration In Covered-Karst Terranes, Christian David Langevin
USF Tampa Graduate Theses and Dissertations
Augmentation with reclaimed water is one method for rehydrating wetlands damaged by water-level declines. Augmentation with reclaimed water has been proposed for rehydrating a wetland in the covered-karst terrane of west-central Florida. There is concern because reclaimed water may contain harmful agents that could flow from the wetland 1.4 km to a municipal wellfield that withdraws 30,000 m3/day. Estimates of groundwater flow velocities were calculated from the results of detailed field studies at the wetland. Results indicate that groundwater flows downward in the surficial aquifer at rates of 0.1 to 0.2 m/day and horizontally in the Floridan aquifer …