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Articles 1 - 30 of 49
Full-Text Articles in Physical Sciences and Mathematics
Radical Environmentalism And Religion, Evelyn Louise Bush
Radical Environmentalism And Religion, Evelyn Louise Bush
Dissertations, Theses, and Masters Projects
No abstract provided.
Structured Eigenvectors, Interlacing, And Matrix Completions, Brenda K. Kroschel
Structured Eigenvectors, Interlacing, And Matrix Completions, Brenda K. Kroschel
Dissertations, Theses, and Masters Projects
This dissertation presents results from three areas of applicable matrix analysis: structured eigenvectors, interlacing, and matrix completion problems. Although these are distinct topics, the structured eigenvector results provide connections.;It is a straightforward matrix calculation that if {dollar}\lambda{dollar} is an eigenvalue of A, x an associated structured eigenvector and {dollar}\alpha{dollar} the set of positions in which x has nonzero entries, then {dollar}\lambda{dollar} is also an eigenvalue of the submatrix of A that lies in the rows and columns indexed by {dollar}\alpha{dollar}. We present a converse to this statement and apply the results to interlacing and to matrix completion problems. Several corollaries …
Effects Of Periodic Environmental Hypoxia On Predator Utilization Of Macrobenthic Infauna, Janet A. Nestlerode
Effects Of Periodic Environmental Hypoxia On Predator Utilization Of Macrobenthic Infauna, Janet A. Nestlerode
Dissertations, Theses, and Masters Projects
Hypoxia and anoxia have significant deleterious ecological effects on living resources throughout many estuarine and marine ecosystems worldwide. Brief periods of low oxygen facilitate transfer of benthic production to higher trophic levels as many benthic infaunal species have shallower sediment depth distributions during hypoxic events. A baited time-lapse camera equipped with a water quality datalogger was used to document in situ exploitation of oxygen-stressed benthic invertebrate prey organisms by mobile fish and crustacean predators during alternating normoxia-hypoxia cycles in the York River. Based on photographic and diver observations, this hypoxiainduced benthic-pelagic transfer of production is more likely to occur when …
Temporal Variablity Of The Pycnocline In The Mid-Chesapeake Bay, Linda Jane Frizzell-Makowski
Temporal Variablity Of The Pycnocline In The Mid-Chesapeake Bay, Linda Jane Frizzell-Makowski
Dissertations, Theses, and Masters Projects
Mixing and dispersion in a partially mixed estuary are driven by, among other processes, the gravitational circulation, wind-events and tides. These processes are important in the vertical and horizontal distribution and exchange of salinity, oxygen, nutrients, and organisms. The objective of this research was to examine the temporal variability of the pycnocline in the mid-Chesapeake Bay in response to forcing at subtidal and higher frequencies as observed in the spring of 1993. The largest change in the pycnocline was associated with meteorological forcing. Up-Bay wind stress and subsequent abatement of the wind stress produced a 5 meter displacement of the …
The Role Of Epibenthic Predators In Structuring Marine Soft-Bottom Communities Along An Estuarine Gradient, Rochelle D. Seitz
The Role Of Epibenthic Predators In Structuring Marine Soft-Bottom Communities Along An Estuarine Gradient, Rochelle D. Seitz
Dissertations, Theses, and Masters Projects
A unifying theory of community regulation in soft-bottom systems remains elusive, despite extensive field studies on factors controlling community structure. Here, I have (1) reviewed models of community regulation, (2) examined the role of predation in controlling benthic diversity along a salinity gradient, (3) examined effects of predation upon an abundant bivalve, Macoma balthica, and (4) revised a model of community regulation in an estuarine soft-bottom system. The Menge and Sutherland (MS) "consumer stress model" posits that consumers feed ineffectively in harsh environments, and the importance of physical disturbance, competition and predation varies with recruitment, environmental conditions, and trophic position. …
Water Quality Modeling As An Inverse Problem, Jian Shen
Water Quality Modeling As An Inverse Problem, Jian Shen
Dissertations, Theses, and Masters Projects
An inverse mathematical estuarine eutrophication model has been developed. The model provides a framework to estimate unknown parameters by assimilation of the concentration data of those state variables. The inverse model developed is a laterally integrated, two-dimensional, real-time model which consists of a hydrodynamic model, an eutrophication model and an adjoint model. The hydrodynamic model provides the dynamic fields for both the eutrophication model and the adjoint model. The eutrophication model simulates eight water quality state variables which are phytoplankton, organic nitrogen, ammonium nitrogen, nitrite-nitrate nitrogen, organic phosphorus, inorganic (ortho) phosphorus, carbonaceous biochemical oxygen demand and dissolved oxygen. The adjoint …
Field And Laboratory Evidence Of Pheromone Mediated Mating Behavior In The Blue Crab, Callinectes Sapidus, Donald S. Gibbs
Field And Laboratory Evidence Of Pheromone Mediated Mating Behavior In The Blue Crab, Callinectes Sapidus, Donald S. Gibbs
Dissertations, Theses, and Masters Projects
No abstract provided.
Synthesis And Characterization Of Cyclic Arylene Ether Oligomers, David Lewis Eldridge
Synthesis And Characterization Of Cyclic Arylene Ether Oligomers, David Lewis Eldridge
Dissertations, Theses, and Masters Projects
No abstract provided.
Synthesis And Characterization Of Boron-Containing Polymeric Materials For Neutron Shielding Applications, Michael B. Glasgow
Synthesis And Characterization Of Boron-Containing Polymeric Materials For Neutron Shielding Applications, Michael B. Glasgow
Dissertations, Theses, and Masters Projects
The development of boron-containing polymeric materials for neutron shielding applications was undertaken. Three types of materials were characterized for physical and thermal properties: boron powder-filled epoxy composites, carborane polyamides having boron chemically bonded into the polymer, and boron-loaded polyimide thin films. Addition of amorphous submicron boron powder did not affect significantly the thermal performance of the epoxy. The 17% boron loading produced a 26% increase in compressive failure strength and a 68% increase in the compressive modulus. 0.125 inch thick specimens containing 17% boron absorbed 92% of incident neutrons from a 5-Curie Pu/Be source compared with {dollar}<{dollar}1% for the neat epoxy. Dispersion of the boron in the epoxy was improved with the addition of larger size crystalline boron powders. Carborane polyamides containing up to 35% boron were thermally stable up to 400{dollar}\sp\circ{dollar}C in air. The polymers had hydrogen/boron ratios from 2.0 to 3.8 and were soluble in several organic solvents. Polymer solutions were processed into clear, colored thin films. Boron-filled polyamic acid solutions of a PMDA-ODA polyimide containing up to 10% boron were processed into thin films. Neutron absorption of the opaque films measured in a 5-Curie Pu/Be neutron source was linear with boron concentration and film thickness. The fraction of neutrons absorbed varied linearly with boron concentration and film thickness. The applicability of boron-containing materials to the aerospace, nuclear power and accelerator industries was investigated.
The Strong Force: Two Calculations Of Strong Interaction Phenomena, Richard L. Kahler
The Strong Force: Two Calculations Of Strong Interaction Phenomena, Richard L. Kahler
Dissertations, Theses, and Masters Projects
Because the theory of strong interactions is mathematically intractable, it is necessary to make approximations which preserve phenomenological features of the theory in order to get answers to practical questions. This thesis explores two such techniques: (1) the chiral bag model is used to investigate the nucleon-nucleon potential and (2) perturbative QCD is used to investigate the pion form factor. An extensive introduction is presented to make the thesis more understandable to a wider audience of people otherwise unfamiliar with particle physics.
A Grammar-Based Technique For Genetic Search And Optimization, Clayton Matthew Johnson
A Grammar-Based Technique For Genetic Search And Optimization, Clayton Matthew Johnson
Dissertations, Theses, and Masters Projects
The genetic algorithm (GA) is a robust search technique which has been theoretically and empirically proven to provide efficient search for a variety of problems. Due largely to the semantic and expressive limitations of adopting a bitstring representation, however, the traditional GA has not found wide acceptance in the Artificial Intelligence community. In addition, binary chromosones can unevenly weight genetic search, reduce the effectiveness of recombination operators, make it difficult to solve problems whose solution schemata are of high order and defining length, and hinder new schema discovery in cases where chromosome-wide changes are required.;The research presented in this dissertation …
The Meteorological Effects Of The Kuwait Oil Fires, Patrick Kevin Dowling
The Meteorological Effects Of The Kuwait Oil Fires, Patrick Kevin Dowling
Dissertations, Theses, and Masters Projects
No abstract provided.
Breeding Ecology, Success, And Population Management Of The Piping Plover (Charadrius Melodus) At Chincoteague National Wildlife Refuge, Virginia, Robert Richard Cross
Breeding Ecology, Success, And Population Management Of The Piping Plover (Charadrius Melodus) At Chincoteague National Wildlife Refuge, Virginia, Robert Richard Cross
Dissertations, Theses, and Masters Projects
No abstract provided.
Low-Valent Metal Complexes As Reductive Coupling Agents For Smoke Suppression In Poly(Vinyl Chloride), Panagiotis Ioannou Kourtesis
Low-Valent Metal Complexes As Reductive Coupling Agents For Smoke Suppression In Poly(Vinyl Chloride), Panagiotis Ioannou Kourtesis
Dissertations, Theses, and Masters Projects
No abstract provided.
Synthesis And Characterization Of Poly(Carborane-Sulfone), Beth Le Ogura
Synthesis And Characterization Of Poly(Carborane-Sulfone), Beth Le Ogura
Dissertations, Theses, and Masters Projects
No abstract provided.
Transport In Chaotic Systems, Xian Zhu Tang
Transport In Chaotic Systems, Xian Zhu Tang
Dissertations, Theses, and Masters Projects
This dissertation addresses the general problem of transport in chaotic systems. Typical fluid problem of the kind is the advection and diffusion of a passive scalar. The magnetic field evolution in a chaotic conducting media is an example of the chaotic transport of a vector field. In kinetic theory, the collisional relaxation of a distribution function in phase space is also an advection-diffusion problem, but in a higher dimensional space.;In a chaotic flow neighboring points tend to separate exponentially in time, exp({dollar}\omega t{dollar}) with {dollar}\omega{dollar} the Liapunov exponent. The characteristic parameter for the transport of a scalar in a chaotic …
Fate And Transport Processes For Polycyclic Aromatic Hydrocarbons In The Surface Microlayer Of Southern Chesapeake Bay, Kewen Liu
Dissertations, Theses, and Masters Projects
Surface microlayer (SM) samples were collected with a rotating cylinder sampler from the York and Elizabeth River estuaries of southern Chesapeake Bay every other month from May 1994 through June 1995. Total suspended particle concentration (TSP) concentrations in the SM were found to be up to 1000 times higher than in the corresponding subsurface water, and to be exponentially associated with the wind speed at sampling. A relatively larger POC/TN ratio in the Elizabeth River SM compared with that in the York River SM was also observed. No seasonal trends were noticed in the SM characteristics; however, TSP, POC, and …
The Role Of Microbial Food Webs In Benthic-Pelagic Coupling In Freshwater And Marine Ecosystems, Adele J. Pile
The Role Of Microbial Food Webs In Benthic-Pelagic Coupling In Freshwater And Marine Ecosystems, Adele J. Pile
Dissertations, Theses, and Masters Projects
A majority of carbon in freshwater and marine ecosystems is in the form of ultraplankton, heterotrophic and autotrophic plankton &<&5 &\mu&m including heterotrophic bacteria, Prochlorococcus, cyanobacteria, and autotrophic eucaryotes. However, ultraplankton and subsequently microbial food webs have yet to be incorporated into models of benthic-pelagic coupling despite the preponderance of macroinvertebrates with the capacity to feed on ultraplankton. I have examined the role of microbial food webs in benthic-pelagic coupling in three ecosystems: Lake Baikal, Siberia, Russia; Gulf of Maine, Northwest Atlantic Ocean; and Conch Reef, Florida Keys, USA. Using sponges as a model organism and in situ measurements, I have quantified (1) suspension feeding on ultraplankton and (2) release of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) resulting in direct evidence that benthic macroinvertebrates do occupy the level of primary consumer within the microbial food web. Dual-beam flow cytometry was employed to quantified sponge suspension feeding on five types of ultraplankton: heterotrophic bacteria, Synechococcus-type cyanobacteria, autotrophic picoplankton &<&3 &\mu&m, autotrophic eucaryotes 3-10 &\mu&m, and in marine ecosystems Prochlorococcus. Grazing by the freshwater sponges Baikalospongia intermedia and B. bacilliferia and the boreal marine sponge, Mycale lingua, was unselective for all types of ultraplankton with efficiencies ranging from 63-99%. This is the first time that grazing on Synechococcus-type cyanobacteria and Prochlorococcus by macroinvertebrates has been quantified in freshwater and marine ecosystems. Conversely, the coral reef sponges Ircinia felix and I. strobilina release significant amounts of DIN and DIP as a result of grazing on procaryotic plankton. Using a general model for organism-mediated fluxes, it is conservatively estimated that through active suspension feeding sponges in Lake Baikal retain 1.97 g C day&\sp{lcub}-1{rcub}& m&\sp{lcub}-2{rcub}& and M. lingua retains 29 mg C day&\sp{lcub}-1{rcub}& m&\sp{lcub}-2{rcub}& while at Conch Reef sponges released 204 &\mu&mol DIN day&\sp{lcub}-1{rcub}& m&\sp{lcub}-2{rcub}& and 48 &\mu&mol DIP day&\sp{lcub}-1{rcub}& m&\sp{lcub}-2{rcub}&. A majority of the carbon retained at all three locations was from procaryotic cell types suggesting that ultraplankton are an important overlooked component of benthic-pelagic coupling.
Gaseous Flux And Distribution Of Polycyclic Aromatic Hydrocarbons Across The Air-Water Interface Of Southern Chesapeake Bay, Kurt E. Gustafson
Gaseous Flux And Distribution Of Polycyclic Aromatic Hydrocarbons Across The Air-Water Interface Of Southern Chesapeake Bay, Kurt E. Gustafson
Dissertations, Theses, and Masters Projects
Gaseous fluxes of polycyclic aromatic hydrocarbons (PAHs) across the air-water interface of Southern Chesapeake Bay were calculated for the period January 1994 through May 1995 using a modified two-film model. Additionally, the distributions of PAHs between the vapor and aerosol phase in the atmosphere, and between the freely dissolved and suspended particulate phase in the water column were investigated. Net instantaneous gaseous fluxes of PAHs were determined to vary in direction and magnitude both spatially and temporally across the air-water interface of Southern Chesapeake Bay at four sites ranging from remote to urban and highly industrialized. The magnitude of gas …
Age, Growth, And Reproductive Biology Of Blackcheek Tonguefish, Symphurus Plagiusa (Cynoglossidae: Pleuronectiformes), In Chesapeake Bay, Virginia, Mark Richard Terwilliger
Age, Growth, And Reproductive Biology Of Blackcheek Tonguefish, Symphurus Plagiusa (Cynoglossidae: Pleuronectiformes), In Chesapeake Bay, Virginia, Mark Richard Terwilliger
Dissertations, Theses, and Masters Projects
No abstract provided.
Lipid Class Composition Of Oysters, Crassostrea Virginica, Exposed To Sediment-Associated Pahs, Tong Li
Lipid Class Composition Of Oysters, Crassostrea Virginica, Exposed To Sediment-Associated Pahs, Tong Li
Dissertations, Theses, and Masters Projects
No abstract provided.
Autoecology Of Paraprionospio Pinnata (Polychaeta: Spionide) Along An Estuarine Gradient, Elizabeth K. Hinchey
Autoecology Of Paraprionospio Pinnata (Polychaeta: Spionide) Along An Estuarine Gradient, Elizabeth K. Hinchey
Dissertations, Theses, and Masters Projects
No abstract provided.
The Effects Of A Regulatory Gear Restriction On The Harvest Of The Recruiting Year Class In The Offshore Sea Scallop, Placopecten Magellanicus, Fishery, Jeffrey C. Brust
The Effects Of A Regulatory Gear Restriction On The Harvest Of The Recruiting Year Class In The Offshore Sea Scallop, Placopecten Magellanicus, Fishery, Jeffrey C. Brust
Dissertations, Theses, and Masters Projects
No abstract provided.
Potential For Population Regulation Of The Zebra Mussel, Dreissena Polymorpha, In The Hudson River, Larry C. Boles
Potential For Population Regulation Of The Zebra Mussel, Dreissena Polymorpha, In The Hudson River, Larry C. Boles
Dissertations, Theses, and Masters Projects
No abstract provided.
Effects Of Electron Irradiation And Percent Composition On The Glass Transition Temperature And Damping Of Boron-Epoxy Composites, Ian Ivan Nieves
Effects Of Electron Irradiation And Percent Composition On The Glass Transition Temperature And Damping Of Boron-Epoxy Composites, Ian Ivan Nieves
Dissertations, Theses, and Masters Projects
No abstract provided.
Spectroscopic Characterization Of Hg(Ii) Coordination Complexes, Sharon Rosemary Fitzhenry
Spectroscopic Characterization Of Hg(Ii) Coordination Complexes, Sharon Rosemary Fitzhenry
Dissertations, Theses, and Masters Projects
No abstract provided.
A Bipartite Model Of Distributed Systems: Possibilities And Implications, Anna Karin Brunstrom
A Bipartite Model Of Distributed Systems: Possibilities And Implications, Anna Karin Brunstrom
Dissertations, Theses, and Masters Projects
Networking software is generally designed in layers. User processes exist at the application layer. They rely on the transport layer to provide them with end-to-end communication. In the distributed systems literature communication is traditionally viewed from the application layer. at the application layer we have no knowledge of the whereabouts of a message once a send operation is completed. at the transport layer, on the other hand, information about the delivery of a message to the transport layer in the receiving host is often available. We believe transport layer information can be better utilized in distributed systems design. This dissertation …
Analysis Of (Iso)Surface Reconstructions: Quantitative Metrics And Methods, Tracey Allen Beauchat
Analysis Of (Iso)Surface Reconstructions: Quantitative Metrics And Methods, Tracey Allen Beauchat
Dissertations, Theses, and Masters Projects
Due to sampling processes volumetric data is inherently discrete and most often knowledge of the underlying continuous model is not available. Surface rendering techniques attempt to reconstruct the continuous model, using isosurfaces, from the discrete data. Therefore, it natural to ask how accurate the reconstructed isosurfaces are with respect to the underlying continuous model. A reconstructed isosurface may look impressive when rendered ("photorealism"), but how well does it reflect reality ("physical realism")?;The users of volume visualization packages must be aware of the short-comings of the algorithms used to produce the images so that they may properly interpret, and interact with, …
The Projector Basis Method For Electronic Band Structure Calculations, Christopher Haas
The Projector Basis Method For Electronic Band Structure Calculations, Christopher Haas
Dissertations, Theses, and Masters Projects
Over the last several decades, two methods have emerged as the standard tools for the calculation of electronic band structures. These methods, the Car-Parinello plane wave method and the linear augmented plane wave method (LAPW), each have strengths and weaknesses in different regimes of physical problems. The Car-Parinello algorithm is ideal for calculations with soft pseudopotentials and large numbers of atoms. The LAPW method, on the other hand, easily handles all-electron and hard-core pseudopotential calculations with a small number of atoms. The projector basis method, presented here, is a hybrid mixed basis method which allows the calculation of moderately large …
Surface Reflection Hyperthermal Neutral Stream Source, Christopher A. Nichols
Surface Reflection Hyperthermal Neutral Stream Source, Christopher A. Nichols
Dissertations, Theses, and Masters Projects
A novel source of hyperthermal (1-30 eV) reactive neutrals based on the surface-reflection-neutralization technique is described. This source is potentially capable of minimizing the charge-induced damage associated with plasma based semiconductor processing steps. The goal of this thesis is to investigate the issues involved in scale-up of this technology for processing of 8{dollar}\sp{lcub}\prime\prime{rcub}{dollar} diameter wafers used today in the semiconductor industry. This includes modeling the plasma ion source and trajectory simulations of the reflected neutral flux. A prototype source was constructed for experimental verification of the plasma model.;An inductively coupled plasma (ICP) source is used to provide a source of …