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Dissertations, Theses, and Masters Projects

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Articles 811 - 840 of 1876

Full-Text Articles in Physical Sciences and Mathematics

The Effect Of An Adsorbate Upon Secondary Emission Properties Of Low -Energy Ion Bombarded Metallic And Semiconductor Substrates, Wendy Sara Vogan Jan 2003

The Effect Of An Adsorbate Upon Secondary Emission Properties Of Low -Energy Ion Bombarded Metallic And Semiconductor Substrates, Wendy Sara Vogan

Dissertations, Theses, and Masters Projects

The absolute probabilities for low energy ion bombardment induced secondary emission of electrons and anions have been measured as a function of adsorbate coverage of the surface. The primary ion beams were incident at less than 500 eV on metallic, semiconducting and insulating surfaces. The adsorbate used was chiefly oxygen, and the coverage range studied was zero to about one monolayer. The presence of an adsorbate was observed to significantly enhance secondary emission of electrons and anions in the case of O - and Na+ impacting metallic (W, Al) and semiconducting (Si) substrates; the effect of the adsorbate was little …


A Mycobacterium-Inducible Nramp In Striped Bass Morone Saxatilis, Erin Jeffrey Burge Jan 2003

A Mycobacterium-Inducible Nramp In Striped Bass Morone Saxatilis, Erin Jeffrey Burge

Dissertations, Theses, and Masters Projects

In mammals, the natural resistance-associated macrophage protein 1 gene, Nramp1, plays a major role in resistance to mycobacterial infections. Chesapeake Bay (USA) striped bass, Morone saxatilis, are currently experiencing an epizootic of mycobacteriosis that threatens the health of this ecologically and economically important species. This dissertation characterizes an Nramp gene in this species (MsNramp ) and provide evidence for induction following Mycobacterium exposure. The striped bass MsNramp gene and 554 amino acid sequence contain all the signal features of the Nramp family, including a topology of 12 transmembrane domains (TM), the transport protein specific 'binding-protein-dependent transport system inner membrane component …


Ecosystem Gas Exchange In Natural And Created Tidal Salt Marshes Of Tidewater, Virginia, Molly Mitchell Roggero Jan 2003

Ecosystem Gas Exchange In Natural And Created Tidal Salt Marshes Of Tidewater, Virginia, Molly Mitchell Roggero

Dissertations, Theses, and Masters Projects

No abstract provided.


Genetic Variation Within And Among The Suminoe Oyster (Crassostrea Ariakensis) Populations And Stocks As Assessed By Molecular Markers, Qian Zhang Jan 2003

Genetic Variation Within And Among The Suminoe Oyster (Crassostrea Ariakensis) Populations And Stocks As Assessed By Molecular Markers, Qian Zhang

Dissertations, Theses, and Masters Projects

No abstract provided.


Automated Fish Species Classification Using Artificial Neural Networks And Autonomous Underwater Vehicles, Daniel Foster Doolittle Jan 2003

Automated Fish Species Classification Using Artificial Neural Networks And Autonomous Underwater Vehicles, Daniel Foster Doolittle

Dissertations, Theses, and Masters Projects

No abstract provided.


Imposex As An Indication Of Butyltin Exposure In The Veined Rapa Whelk (Rapana Venosa), A Chesapeake Bay Invader, Ethan Alexander Jestel Jan 2003

Imposex As An Indication Of Butyltin Exposure In The Veined Rapa Whelk (Rapana Venosa), A Chesapeake Bay Invader, Ethan Alexander Jestel

Dissertations, Theses, and Masters Projects

No abstract provided.


Ann Wave Prediction Model For Winter Storms And Hurricanes, Jun-Young. Kim Jan 2003

Ann Wave Prediction Model For Winter Storms And Hurricanes, Jun-Young. Kim

Dissertations, Theses, and Masters Projects

Currently available wind-wave prediction models require a prohibitive amount of computing time for simulating non-linear wave-wave interactions. Moreover, some parts of wind-wave generation processes are not fully understood yet. For this reason accurate predictions are not always guaranteed. In contrast, Artificial Neural Network (ANN) techniques are designed to recognize the patterns between input and output so that they can save considerable computing time so that real-time wind-wave forecast can be available to the navy and commercial ships. For this reason, this study tries to use ANN techniques to predict waves for winter storms and hurricanes with much less computing time …


Biology Of Mated Triploid Crassostrea Ariakensis In Multiple Environments: Gametogenesis, Sex Ratio, Disease Prevalence, And Reversion, Alan J. Erskine Jan 2003

Biology Of Mated Triploid Crassostrea Ariakensis In Multiple Environments: Gametogenesis, Sex Ratio, Disease Prevalence, And Reversion, Alan J. Erskine

Dissertations, Theses, and Masters Projects

No abstract provided.


An Evaluation Of The Accuracy Of The Growing Season Used For Wetland Delineation In Se Virginia, Rebecca L. Arenson Jan 2003

An Evaluation Of The Accuracy Of The Growing Season Used For Wetland Delineation In Se Virginia, Rebecca L. Arenson

Dissertations, Theses, and Masters Projects

No abstract provided.


Sublethal Effects Of Sediment Contamination On An Estuarine Amphipod, Bruce W. Vogt Jan 2003

Sublethal Effects Of Sediment Contamination On An Estuarine Amphipod, Bruce W. Vogt

Dissertations, Theses, and Masters Projects

No abstract provided.


Analysis Of Prey Selection In Black Skimmer, Rynchops Niger, Adults And Chicks Using Continuous Video Monitoring, Renae Joyce Held Jan 2003

Analysis Of Prey Selection In Black Skimmer, Rynchops Niger, Adults And Chicks Using Continuous Video Monitoring, Renae Joyce Held

Dissertations, Theses, and Masters Projects

No abstract provided.


Comparison Of Mussel-Bed Faunas At Blake Ridge And Florida Escarpment Seeps, Kathleen Elizabeth Knick Jan 2003

Comparison Of Mussel-Bed Faunas At Blake Ridge And Florida Escarpment Seeps, Kathleen Elizabeth Knick

Dissertations, Theses, and Masters Projects

No abstract provided.


Avian Communities Of Created And Natural Wetlands: Saltmarshes Of Southeast Virginia, David William Desrochers Jan 2003

Avian Communities Of Created And Natural Wetlands: Saltmarshes Of Southeast Virginia, David William Desrochers

Dissertations, Theses, and Masters Projects

No abstract provided.


Metal Concentrations In Deep-Sea Mussels From A Hydrothermal Vent And Cold Seep, Shana Rapoport Jan 2003

Metal Concentrations In Deep-Sea Mussels From A Hydrothermal Vent And Cold Seep, Shana Rapoport

Dissertations, Theses, and Masters Projects

No abstract provided.


Laboratory Oxide Coatings: Physical Form And Surface Chemistry, Kea U. Duckenfield Jan 2003

Laboratory Oxide Coatings: Physical Form And Surface Chemistry, Kea U. Duckenfield

Dissertations, Theses, and Masters Projects

The impact of dissolved trace metals on aquatic ecosystems and human health is controlled by sorption, i.e., binding to the surfaces of environmental particles. Since many environmental particles are coated with highly reactive substances, and since discrepancies in trace metal sorption behavior persist between oxides developed in the laboratory and environmental oxide phases, it was hypothesized that the physical form of oxide coatings may influence the chemical properties of the coated particle. Therefore, relationships between the physical forms of several different Fe(III) oxide coatings and the Cu(II) sorption behavior of the coated solids were investigated in comparison with the component …


A Theoretical And Experimental Study Of Allee Effects, Joanna Gascoigne Jan 2003

A Theoretical And Experimental Study Of Allee Effects, Joanna Gascoigne

Dissertations, Theses, and Masters Projects

Allee effects occur when fitness suffers at low population size or density. This can lead to reduced population growth rate and a critical density below which extinction occurs. Allee effects can occur in reproduction or survival. Critical densities are higher in reproductive Allee effects than in juvenile survival Allee effects, making reproductive Allee effects more severe (higher extinction probability). In terms of the critical Allee effect threshold, reproductive Allee effects are more severe in r-selected populations, while juvenile survival Allee effects are more severe in K-selected populations. For populations with negative density dependence, there is a maximum critical Allee threshold, …


An Analysis Of Wetland Patterns And Functions At The Watershed And Sub-Watershed Scales, With *Policy Applications, Jennifer Newton Bissonnette Jan 2003

An Analysis Of Wetland Patterns And Functions At The Watershed And Sub-Watershed Scales, With *Policy Applications, Jennifer Newton Bissonnette

Dissertations, Theses, and Masters Projects

This dissertation addresses the need to define potential impacts of recent and proposed changes in federal wetland regulation in a quantifiable manner. Consideration was made not only of total wetland acreage and wetland types that could sustain losses, but also to categorize the effect such losses would have in terms of wetland functions, at the watershed scale. This work took a Geographic Information Systems (GIS) approach, and included employing a best-professional judgment model for scoring habitat, water quality and flood attenuation functions to determine potential cumulative impacts; a water quality study which related wetland and watershed variables to nutrient and …


Historical Diet Analysis Of Loggerhead (Caretta Caretta) And Kemp's Ridley (Lepidochelys Kempi) Sea Turtles In Virginia, Erin E. Seney Jan 2003

Historical Diet Analysis Of Loggerhead (Caretta Caretta) And Kemp's Ridley (Lepidochelys Kempi) Sea Turtles In Virginia, Erin E. Seney

Dissertations, Theses, and Masters Projects

The Chesapeake Bay and coastal waters of Virginia, U.S.A. serve as foraging grounds for loggerhead (Caretta caretta) and Kemp’s ridley (Lepidochelys kempi) sea turtles from approximately May to October each year. Both loggerheads and Kemp’s ridleys are known to feed primarily on benthic invertebrates as juveniles and adults, but specific prey preferences vary between geographic regions. The Virginia Institute of Marine Science Sea Turtle Program has collected diet data and gut samples from stranded and incidentally caught sea turtles in Virginia since 1979. Examination of turtles that stranded in Virginia during the late 1970s and early 1980s indicated that loggerheads …


A Genetic Investigation Of Population Structure And Phylogenetics Of The Benthic Polychaete Paraprionospio Pinnata In Chesapeake Bay, Julie Beck Stubbs Jan 2003

A Genetic Investigation Of Population Structure And Phylogenetics Of The Benthic Polychaete Paraprionospio Pinnata In Chesapeake Bay, Julie Beck Stubbs

Dissertations, Theses, and Masters Projects

No abstract provided.


Bacterial Properties And Dissolved Organic Matter Distributions In The Black Sea, Jessica A. Morgan Jan 2003

Bacterial Properties And Dissolved Organic Matter Distributions In The Black Sea, Jessica A. Morgan

Dissertations, Theses, and Masters Projects

No abstract provided.


Taxonomic Composition And Growth Rates Of Phytoplankton Assemblages At The Subtropical Convergence East Of New Zealand, Liza M. Delizo Jan 2003

Taxonomic Composition And Growth Rates Of Phytoplankton Assemblages At The Subtropical Convergence East Of New Zealand, Liza M. Delizo

Dissertations, Theses, and Masters Projects

No abstract provided.


Inverse Model Analysis Of Plankton Food Webs In The North Atlantic And Western Antarctic Peninsula, Robert M. Daniels Jan 2003

Inverse Model Analysis Of Plankton Food Webs In The North Atlantic And Western Antarctic Peninsula, Robert M. Daniels

Dissertations, Theses, and Masters Projects

No abstract provided.


The Wind Effects On The Evaluation Of Proposed Craney Island Expansions In The Lower James And Elizabeth Rivers, Momo Chen Jan 2003

The Wind Effects On The Evaluation Of Proposed Craney Island Expansions In The Lower James And Elizabeth Rivers, Momo Chen

Dissertations, Theses, and Masters Projects

No abstract provided.


Investigations Into The Etiology Of Ulcerative Lesions In Atlantic Menhaden, Brevoortia Tyrannus, Raemarie Ann Johnson Jan 2003

Investigations Into The Etiology Of Ulcerative Lesions In Atlantic Menhaden, Brevoortia Tyrannus, Raemarie Ann Johnson

Dissertations, Theses, and Masters Projects

No abstract provided.


Socioeconomic Effects Of Area Management And The Potential For Community-Based Co-Management: A Case Study Of The Atlantic Sea Scallop Fishery, Winifred L. Ryan Jan 2003

Socioeconomic Effects Of Area Management And The Potential For Community-Based Co-Management: A Case Study Of The Atlantic Sea Scallop Fishery, Winifred L. Ryan

Dissertations, Theses, and Masters Projects

Community concerns regarding natural resource management may be addressed in several forms. The community may participate as part of the public in the management process; community concerns may be included in social impact assessment; and communities may directly participate as managers of resources whether on their own or in conjunction with higher levels of government. In fisheries, typically community concerns are addressed through social impact assessment which is perceived to be lacking in social theory, history, and often effect (Boggs 1994, Little and Krannich 1989). More recent activity and newer regulations show success with co-management, a management regime of shared …


Polycyclic Aromatic Hydrocarbon Sources And Distribution In An Urban Estuary, Shelby E. Walker Jan 2003

Polycyclic Aromatic Hydrocarbon Sources And Distribution In An Urban Estuary, Shelby E. Walker

Dissertations, Theses, and Masters Projects

As part of the assessment of the potential risk posed by contaminated sediments to the environment and human health, the United States Environmental Protection Agency (USEPA) is developing a set of sediment quality criteria (SQC) that are based on equilibrium partitioning (EqP). While EqP theory has often been used to predict contaminant concentrations within a factor of two for a range of sediment types, substantial deviations from predicted values have also been documented. The objective of this research was to evaluate the influence of PAH source on PAH sediment-pore water partitioning and distribution in sediments. The Elizabeth River is one …


Multinuclear Nmr Studies Of Relaxor Ferroelectrics, Donghua Zhou Jan 2003

Multinuclear Nmr Studies Of Relaxor Ferroelectrics, Donghua Zhou

Dissertations, Theses, and Masters Projects

Multinuclear NMR of 93Nb, 45Sc, and 207Pb has been carried out to study the structure, disorder, and dynamics of a series of important solid solutions: perovskite relaxor ferroelectric materials (1-x) Pb(Mg1/3Nb 2/3)O3-x Pb(Sc1/2Nb1/2)O 3 (PMN-PSN).;93Nb NMR investigations of the local structure and cation order/disorder are presented as a function of PSN concentration, x. The superb fidelity and accuracy of 3QMAS allows us to make clear and consistent assignments of spectral intensities to the 28 possible nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb), where each number ranges from 0 to 6 and their sum is 6. For most of the …


Magnetohydrodynamic Turbulence: The Development Of Lattice Boltzmann Methods For Dissipative Systems, Angus Ian Duncan Macnab Jan 2003

Magnetohydrodynamic Turbulence: The Development Of Lattice Boltzmann Methods For Dissipative Systems, Angus Ian Duncan Macnab

Dissertations, Theses, and Masters Projects

Computer simulations of complex phenomena have become an invaluable tool for scientists in all disciplines. These simulations serve as a tool both for theorists attempting to test the validity of new theories and for experimentalists wishing to obtain a framework for the design of new experiments. Lattice Boltzmann Methods (LBM) provide a kinetic simulation technique for solving systems governed by non-linear conservation equations. Direct LBMs use the linearized single time relaxation form of the Boltzmann equation to temporally evolve particle distribution functions on a discrete spatial lattice. We will begin with a development of LBMs from basic kinetic theory and …


Time-Resolved Optical Studies Of Colossal Magnetoresistance And Charge -Density Wave Materials, Yuhang Ren Jan 2003

Time-Resolved Optical Studies Of Colossal Magnetoresistance And Charge -Density Wave Materials, Yuhang Ren

Dissertations, Theses, and Masters Projects

This thesis presents measurements of collective modes and ultrafast carrier relaxation dynamics in charge-density-wave (CDW) conductors and colossal magnetoresistance (CMR) manganites. A femtosecond laser pump pulse excites a broad frequency spectrum of low-energy collective modes and electron-hole pairs thereby changing its optical properties. The low-energy collective excitations and quasiparticle relaxation and recombination processes are monitored by measuring the resulting photoinduced absorption as a function of probe pulse wavelength and time delay.;A general model was developed for the photogeneration and detection mechanism of collective modes based on light absorption in two-color pump-probe experiments. A broad spectrum of collective modes (phasons and …


Power Considerations For Memory-Related Microarchitecture Designs, Zhichun Zhu Jan 2003

Power Considerations For Memory-Related Microarchitecture Designs, Zhichun Zhu

Dissertations, Theses, and Masters Projects

The fast performance improvement of computer systems in the last decade comes with the consistent increase on power consumption. In recent years, power dissipation is becoming a design constraint even for high-performance systems. Higher power dissipation means higher packaging and cooling cost, and lower reliability. This Ph.D. dissertation will investigate several memory-related design and optimization issues of general-purpose computer microarchitectures, aiming at reducing the power consumption without sacrificing the performance. The memory system consumes a large percentage of the system's power. In addition, its behavior affects the processor power consumption significantly. In this dissertation, we propose two schemes to address …