Physical Sciences and Mathematics Commons^™

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 …

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 …

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 …

Habitat Complexity As A Determinant Of Juvenile Blue Crab Survival, Jessica L. Schulman

Dissertations, Theses, and Masters Projects

No abstract provided.

Autoecology Of Paraprionospio Pinnata (Polychaeta: Spionide) Along An Estuarine Gradient, Elizabeth K. Hinchey

Dissertations, Theses, and Masters Projects

No abstract provided.

An Analysis Of The Effects Of Sea Level Rise On The Salt Marshes Of Cape Hatteras National Seashore, North Carolina, Christopher Robert Perle

Dissertations, Theses, and Masters Projects

No abstract provided.

A Comparison Of Natural And Laboratory Diets For The Culture Of Marine Invertebrate Larvae American Oyster, Crassostrea Virginica, Queen Conch, Strombus Gigas, And Milk Conch, Strombus Costatus, Sandra Dawn Brooke

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

Dissertations, Theses, and Masters Projects

No abstract provided.

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 …

Perkinsus Marinus Extracellular Proteases: Modulation Of Production By Environmental Factors And Effects On The Host Defense Parameters Of The Eastern Oyster Crassostrea Virginica, Kathleen A. Garreis

Dissertations, Theses, and Masters Projects

No abstract provided.

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 …

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 …

Selective Inversion In Solid-State Deuteron Nmr, Marco J. Brown

Dissertations, Theses, and Masters Projects

Deuteron NMR selective inversion (SI) is developed to study slow molecular motions in solids. Theoretical and practical aspects of selective inversion of spin-1 nuclei in solids are presented. Differences between powdered solids and liquids are considered. Double sideband modulated (DSBM) shaped pulses are shown to improve the performance of SI pulses. DSBM and DANTE selective pulses are compared for off-resonance SI applications. Common spin-{dollar}{lcub}1{rcub}\over{lcub}2{rcub}{dollar} shaped pulses are tested for suitability to solid state deuteron NMR. Simple, short pulses are shown to be most effective due to fast spin-spin relaxation and large underlying homogeneous linewidths in solids.;The power and utility of …

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.

Patterns Of Phytoplankton Abundance And Nutrient Concentration In The York River Estuary, Virginia: 1984-1994, Yongsik Sin, Richard L. Wetzel

Reports

No abstract provided.

Hydrodynamics Of Sediment Suspensions In The Littoral Zone Of The Lower York River - Phase Ii, John D. Boon

Reports

This report covers the second year (Phase II) of a two-year study. An earlier contract report (Boon,1996) was submitted in January, 1996, to the Virginia Coastal Resources Management Program covering the first year (Phase I) results of a wave , current and suspended sediment monitoring study conducted at the mouth of the York River (Figure 1).

The purpose of the monitoring study , as originally planned , was to investigate processes governing sediment suspension within the shallow waters of the littoral zone (depths< 2m) in coastal estuaries. These are regions in which bottom sediment, in the absence of vegetative cover and depending on sediment grain sizes present, has the potential to be actively eroded and entrained in the water column by wind waves and/or currents. Suspended sediment has the further potential to impact water quality and promote eutrophication through nutrient enrichment processes (Kemp et al., 1983; Orth and Moore, 1983). High sediment loadings also lead to light reduction in the photic zone which can impact the growth or survival of submerged aquatic vegetation (De Groot and de Jonge, 1990) .

Hydrodynamics Of Sediment Suspensions In The Littoral Zone Of The Lower York River - Phase I, John D. Boon

Reports

Motivation for this study derives from a need to know more about processes governing sediment suspension within the shallow waters of the littoral zone (depths< 2m) in coastal estuaries. These are regions in which bottom sediment, in the absence of vegetative cover and depending on grain sizes present, has the potential to be actively eroded and entrained in the water column by wind waves and/or currents. Suspended sediment has the further potential to impact water quality and promote eutrophication through nutrient enrichment processes (Kemp et al., 1983; Orth and Moore, 1983). High sediment loadings also lead to light reduction in the photic zone which can impact the growth or survival of submerged aquatic vegetation (De Groot and de Jonge, 1990).

Virginia Wetlands Management Handbook 2nd Edition, Wetlands Program, Virginia Institute Of Marine Science, Thomas A. Barnard

Reports

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

Dissertations, Theses, and Masters Projects

No abstract provided.

Contributions To The Life History Of Juvenile Blueback Herring (Alosa Aestivalis): Phototactic Behavior And Population Dynamics, Douglas A. Dixon

Dissertations, Theses, and Masters Projects

This research investigated the relationship between juvenile abundance indexes (JAIs) for anadromous blueback herring (Alosa aestivalis) and abiotic factors (river flow and temperature) during the spawning and nursery period in the tidal freshwater areas of James, Pamunkey, Mattaponi, and Rappahannock Rivers in Virginia. Accomplishing this objective required the evaluation of the JAI methodology, specifically the effect of phototactic behavior on diel changes in the surface availability to the pushnet sampling gear, and obtaining population dynamics information (hatch dates, growth, natural mortality) during early life history from otolith microstructure of samples collected in 1991 and 1992. Mean catch-per-unit effort (CPUE) at …

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 …

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 …

Modeling Storm-Induced Sediment Transport On The Inner Shelf: Effects Of Bed Microstratigraphy, Baeck Oon Kim

Dissertations, Theses, and Masters Projects

Sediment transport during a storm event on the inner continental shelf was detailed through the development of models based on field experiments conducted at Duck, North Carolina in October 1994. A vertical one-dimensional model (1DV model) was developed by coupling the Grant and Madsen (1986) model with bed stratigraphy to consider real seabeds. Sediment was divided into seven size classes and fractional transport was estimated. Mixing depth and total depth from a simplified sediment conservation equation provided the basis for changing bottom sediment, sediment availability for transport, and armoring processes. These processes involve a feedback between hydrodynamics and bed stratigraphy. …

Demersal Predator Exposure To Toxic Organic Contaminants: Direct Effects Of Macrofauna In Trophic Transfer, Patrick Winfield Lay

Dissertations, Theses, and Masters Projects

The bioaccumulation and metabolism of organic contaminants (PAH, PCB) by three estuarine polychaetes, Nereis succinea (Frey and Leuckart 1847), Paraprionospio pinnata (Ehlers 1901) and Polydora ligni (Webster 1879), and by the fish predator, spot (Leiostomus xanthurus Lacepede 1802), were examined in laboratory experiments. Variations in trophic transfer of these contaminants resulting from differences in prey and contaminant type were also investigated. Toxicokinetic modeling reveals that metabolism of organic contaminants by invertebrate species result in variations in uptake, metabolism and elimination rate constants. Incorporation of prey metabolism potential in kinetic models increases the latter's predictability of biota-sediment accumulation factors (BSAFs), or …

The Development Of Affinity Maturation In Rainbow Trout Oncorhynchus Mykiss, Ing Wei Khor

Dissertations, Theses, and Masters Projects

No abstract provided.

Lipid Class Composition Of Oysters, Crassostrea Virginica, Exposed To Sediment-Associated Pahs, Tong Li

Dissertations, Theses, and Masters Projects

No abstract provided.

The Influence Of Location, Seagrass Species And Water Depth On The Settlement And Distribution Of Early Stage Blue Crabs, Renee A. Pardieck

Dissertations, Theses, and Masters Projects

No abstract provided.

Growth Dynamics Of A York River Estuary Heterotrophic Dinoflagellate Grazing Katodinium Rotundatum, Angela Denise Smith

Dissertations, Theses, and Masters Projects

No abstract provided.

Exchanges Of Dissolved Inorganic Nitrogen And Dissolved Organic Carbon Between Salt Marsh Sediments And Overlying Tidal Water, Betty Berry Neikirk

Dissertations, Theses, and Masters Projects

No abstract provided.

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.