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Articles 1 - 30 of 45
Full-Text Articles in Physical Sciences and Mathematics
A Bio-Economic Feasibility Model For Remote Setting: Potential For Oyster Aquaculture In Virginia, Michael Spohn Congrove
A Bio-Economic Feasibility Model For Remote Setting: Potential For Oyster Aquaculture In Virginia, Michael Spohn Congrove
Dissertations, Theses, and Masters Projects
No abstract provided.
A Molecular Analysis Of Atlantic Menhaden (Brevoortia Tyrannus) Stock Structure, Abigail J. Lynch
A Molecular Analysis Of Atlantic Menhaden (Brevoortia Tyrannus) Stock Structure, Abigail J. Lynch
Dissertations, Theses, and Masters Projects
Atlantic menhaden is an ecologically and economically important species along the U.S. east coast. As a filter-feeder and key prey fish, it provides a critical link between primary production, phytoplankton, and larger piscivorous predators, such as striped bass, bluefish, and weakfish. The species is also the target of one of the largest commercial fisheries in the country. Menhaden are assessed as a single, coastwide stock, and recent assessments indicate that it is not overfished. However, there is very limited population genetics data to support the assumption of a single stock. Additionally, the recent consolidation of the fishery and localization of …
Twine-Top Modifications Of Sea-Scallop Dredges: Reducing Yellowtail-Flounder Bycatch, Kelli A. Milleville
Twine-Top Modifications Of Sea-Scallop Dredges: Reducing Yellowtail-Flounder Bycatch, Kelli A. Milleville
Dissertations, Theses, and Masters Projects
No abstract provided.
Broad Spatial Trends In Osprey Provisioning, Reproductive Success, And Population Growth Within Lower Chesapeake Bay, Kenneth Andrew Glass
Broad Spatial Trends In Osprey Provisioning, Reproductive Success, And Population Growth Within Lower Chesapeake Bay, Kenneth Andrew Glass
Dissertations, Theses, and Masters Projects
No abstract provided.
Idiopathic Lesions And Visual Deficits In The American Lobster (Homarus Americanus) From Longs Island Sound, Ny, Christopher Robert Magel
Idiopathic Lesions And Visual Deficits In The American Lobster (Homarus Americanus) From Longs Island Sound, Ny, Christopher Robert Magel
Dissertations, Theses, and Masters Projects
In 1999 a mass mortality of the American lobster (Homarus americanus) occurred in western Long Island Sound (WLIS). Although the etiology remains unknown, warm bottom water temperature, hypoxia, heavy metal poisoning, and pesticides have been suggested as casual factors. Subsequently, lobsters from WLIS have continued to display symptoms of morbidity that include lethargy and cloudy grey eyes, caused by idiopathic lesions. The effects of these lesions on lobster vision are unknown. We therefore used electoretinography (ERG) to document changes in visual function in lobsters obtained from WLIS, while simultaneously using histology to quantify the extent of damage. Of the lobsters …
Influences Of Habitat Conditions On Submerged Aquatic Vegetation Development In The Chickahominy River And Other Virginia Tributaries Of The Chesapeake Bay, Erin C. Shields
Dissertations, Theses, and Masters Projects
Recently, there has been an expansion of submerged aquatic vegetation (SAV) in the tidal fresh and oligohaline portions of lower Chesapeake Bay tributaries. Much like the resurgence seen in the Potomac in the 1980’s, this spread of SAV in Virginia systems such as the Mattaponi, Pamunkey and Chickahominy seems to have been initiated by the introduction and spread of the invasive species Hydrilla verticillata, and appears to have been rapid. However the resurgence in the Piankatank has occurred in the absence of the introduction of this species. The factors that are influencing the growth of SAV in these tributary environments, …
Variability In Geologic Framework And Shoreline Change: Assateague And Wallops Islands, Eastern Shore Of Virginia, Geoffrey L. Wikel
Variability In Geologic Framework And Shoreline Change: Assateague And Wallops Islands, Eastern Shore Of Virginia, Geoffrey L. Wikel
Dissertations, Theses, and Masters Projects
No abstract provided.
Sediment Transport And Erodibility In The York River Estuary: A Model Study, Jeffrey Paul Rinehimer
Sediment Transport And Erodibility In The York River Estuary: A Model Study, Jeffrey Paul Rinehimer
Dissertations, Theses, and Masters Projects
A cohesive sediment bed model was implemented in the Community Sediment Transport Modeling System (CSTMS) to examine processes influencing sediment erodibility and suspended sediment concentrations. Estimates of eroded mass from the sediment bed model were calibrated and verified with erosion chamber measurements from the York River, Virginia, a tidally-dominated environment. A constant erosion rate parameter combined with depth-varying critical shear stress was sufficient to model erosion observations of depth-limited sediment cores. Sensitivity of total eroded mass to seasonal variations in erodibility and changes in consolidation time scale was evaluated during spring-neap variations in bottom stresses. Differences were greatest during spring …
Natural Mortality Of Blue Crab: Estimation And Influence On Population Dynamics, David A. Hewitt
Natural Mortality Of Blue Crab: Estimation And Influence On Population Dynamics, David A. Hewitt
Dissertations, Theses, and Masters Projects
The blue crab Callinectes sapidus supports one of the most important fisheries in the Chesapeake Bay and is the leading contributor to blue crab landings in the United States. Assessment and management of blue crab stocks has been hampered by a lack of estimates of natural mortality rates, a key parameter in assessment models. In Chapter 2, we demonstrate that the approach used for estimating natural mortality that had been used in past assessments was flawed, and provide justification for a superior alternative. In Chapter 3, we synthesize our current understanding of natural mortality rates in adult blue crab and …
Surface Study Of Niobium For Superconducting Radio Frequency (Srf) Accelerators, Hui Tian
Surface Study Of Niobium For Superconducting Radio Frequency (Srf) Accelerators, Hui Tian
Dissertations, Theses, and Masters Projects
Niobium rf superconductivity is a near-surface phenomenon because of the shallow rf penetration depth. Accordingly, the performance of Nb SRF accelerator cavities is strongly impacted by the topmost few nanometers interior surface, especially as impacted by the final surface conditioning treatments.;Surface topography impacts performance through local loss of superconductivit caused by intrusion of the rf magnetic field, which is enhanced at sharp protrusions. "Sharpness" comprises both vertical and lateral aspects, requiring development a new characterization approach beyond the familiar roughness measurements (Ra, Rz), which view only the vertical component. Stylus profilomety and atomic force microscopy traces view surface topography from …
Time-Resolved Magnetic Flux And Ac-Current Distributions In Superconducting Yttrium Barium Copper Oxide Thin Films And Multifilaments, Ran Yang
Dissertations, Theses, and Masters Projects
Time-resolved magneto-optical imaging (TRMOI) technique allows dynamic ac transport measurements on superconductors. The high time and spatial resolutions of the measurements also offer good quantitative data analysis of the MO images. YBa2Cu 3O7-delta (YBCO) was discovered as a high-temperature superconductor (HTSC) which has wide applications due to its high critical temperature of Tc = 91 K, and high critical current density Jc in the order of 106-7 Acm-2. Many of the applications require high ac current load and a high magnetic field. We study the interaction behavior of YBCO thin films in an ac transport current and a dc magnetic …
Effects Of Urban Development On Breeding Bird Diversity: The Role Of Diet And Migration, Elise Anne Larsen
Effects Of Urban Development On Breeding Bird Diversity: The Role Of Diet And Migration, Elise Anne Larsen
Dissertations, Theses, and Masters Projects
No abstract provided.
Age, Growth, And Demography Of The Sandbar Shark, Carcharhinus Plumbeus, Over Temporal And Spatial Scales, Jason G. Romine
Age, Growth, And Demography Of The Sandbar Shark, Carcharhinus Plumbeus, Over Temporal And Spatial Scales, Jason G. Romine
Dissertations, Theses, and Masters Projects
Numbers of sandbar sharks, Carcharhinus plumbeus, in the Northwest Atlantic have experienced drastic declines since the early 1980's reaching their minima during the early 1990's. Catch rates in the early 1990's were a mere 25% of those during the 1980's. Such drastic reductions in other fish stocks have often caused compensatory responses, most notably the cod stocks in the Northwest Atlantic. Compensatory responses in depressed populations may include decreased natural mortality, increased fecundity, or increased growth rates. Compensation for population fluctuations below carrying capacities have been recognized for many terrestrial and oceanic r-selected organisms, but few instances have been noted …
Topics In Mode Conversion Theory And The Group Theoretical Foundations Of Path Integrals, Andrew Stephen Richardson
Topics In Mode Conversion Theory And The Group Theoretical Foundations Of Path Integrals, Andrew Stephen Richardson
Dissertations, Theses, and Masters Projects
This dissertation reports research about the phase space perspective for solving wave problems, with particular emphasis on the phenomenon of mode conversion in multicomponent wave systems, and the mathematics which underlie the phase space perspective. Part I of this dissertation gives a review of the phase space theory of resonant mode conversion. We describe how the WKB approximation is related to geometrical structures in phase space, and how in particular ray-tracing algorithms can be used to construct the WKB solution. We further review how to analyze the phenomena of mode conversion from the phase space perspective. By making an expansion …
Controls On Continental Shelf Stratigraphy: Waiapu River, New Zealand, Heidi M. Wadman
Controls On Continental Shelf Stratigraphy: Waiapu River, New Zealand, Heidi M. Wadman
Dissertations, Theses, and Masters Projects
A quantitative understanding of the processes controlling sediment transport and deposition across the land/sea interface is crucial to linking terrestrial and marine environments and understanding the formation of marine stratigraphy. The nature and distribution of terrestrial-derived sediment preserved in shelf stratigraphy in turn provides insight into the complex linkages inherent in source-to-sink sediment dynamics. Located inboard of an actively subducting plate boundary and characterized by one of the highest sediment yields in the world, the open-shelf setting off of the Waiapu River in New Zealand presents an excellent location to improve our understanding of the factors controlling the formation of …
Nearshore Morphology And Lithology: Links To Framework Geology And Shoreline Change, Jennifer L. Miselis
Nearshore Morphology And Lithology: Links To Framework Geology And Shoreline Change, Jennifer L. Miselis
Dissertations, Theses, and Masters Projects
Despite evidence of the geologic and morphologic complexity of inner shelves worldwide, there is a paucity of observations from the nearshore, inhibiting direct comparison of these factors to coastal change. Using geophysical instruments to characterize the geology of the nearshore, this research focuses on the relationships between nearshore stratigraphy, sediment heterogeneity, shoreface morphology and shoreline behavior. While generally not considered in engineering models of shoreline evolution, these factors influence nearshore processes. Overall, the findings presented highlight the importance of nearshore geology, both at the seafloor and underlying it, in contributing to modem sediment transport processes affecting beaches. Shallow, sub-seafloor geology …
Bottom-Up And Top-Down Controls On Sedimentary Ecosystem Functioning In A Seagrass Habitat, Amanda C. Spivak
Bottom-Up And Top-Down Controls On Sedimentary Ecosystem Functioning In A Seagrass Habitat, Amanda C. Spivak
Dissertations, Theses, and Masters Projects
Coastal seagrass ecosystems are complex habitats that are increasingly influenced by human perturbations. Disturbances that affect the strength of bottom-up (i.e. resource availability) and top-down (i.e. consumer) controls may also influence biomass distribution between trophic levels, sediment biogeochemistry, and seagrass ecosystem metabolism. Here, I experimentally tested how top-down and bottom-up perturbations interact with community structure (diversity, food chain length of epibenthic consumers) to alter sediment biogeochemistry and ecosystem metabolism in an experimental eelgrass (Zostera marina ) system. My data indicated that resource availability influenced SOM composition and ecosystem metabolism. Light availability tended to be a stronger determinant of SOM composition …
Acoustic Measurements Of Cohesive Sediment Transport: Suspension To Consolidation, Ho Kyung Ha
Acoustic Measurements Of Cohesive Sediment Transport: Suspension To Consolidation, Ho Kyung Ha
Dissertations, Theses, and Masters Projects
This dissertation aims at utilizing the acoustic approach to measure cohesive sediment behaviors including (1) suspension, (2) settling, (3) deposition and (4) consolidation. The first two processes were attempted to interpret by means of backscattered signal analysis, while the last two processes were done by echo signal analysis. The acoustic instruments used in this study include Acoustic Doppler Velocimeter (ADV), Pulse Coherent Acoustic Doppler Profiler (PC-ADP) and Micro-Chirp system. Used sediments are pure kaolinite and in-situ sediments collected from Mai Po and Clay Bank. 5-MHz ADV was used to estimate the suspended sediment concentration (SSC) and settling velocity (ws). For …
Methods For Stabilizing High Reynolds Number Lattice Boltzmann Simulations, Brian Robert Keating
Methods For Stabilizing High Reynolds Number Lattice Boltzmann Simulations, Brian Robert Keating
Dissertations, Theses, and Masters Projects
The Lattice Boltzmann Method (LBM) is a simple and highly efficient method for computing nearly incompressible fluid flow. However, it is well known to suffer from numerical instabilities for low values of the transport coefficients. This dissertation examines a number of methods for increasing the stability of the LBM over a wide range of parameters. First, we consider a simple transformation that renders the standard LB equation implicit. It is found that the stability is largely unchanged. Next, we consider a stabilization method based on introducing a Lyapunov function which is essentially a discrete-time H-function. The uniqueness of an H-function …
Mercury Levels In Newly Independent Songbirds, Anne Moire Condon
Mercury Levels In Newly Independent Songbirds, Anne Moire Condon
Dissertations, Theses, and Masters Projects
No abstract provided.
Effects Of Metal-Based Montmorillonite Clay And Zeolite Additives On The Fire Retardance And Smoke Suppression Of Poly(Vinyl Chloride), Alexander George Zestos
Effects Of Metal-Based Montmorillonite Clay And Zeolite Additives On The Fire Retardance And Smoke Suppression Of Poly(Vinyl Chloride), Alexander George Zestos
Dissertations, Theses, and Masters Projects
No abstract provided.
Organotitanium-Aluminum Promoted Carbometalations Of Alkynols: Substituent Effects, Nikola A. Nikolic
Organotitanium-Aluminum Promoted Carbometalations Of Alkynols: Substituent Effects, Nikola A. Nikolic
Dissertations, Theses, and Masters Projects
No abstract provided.
Community Dynamics In Submersed Aquatic Vegetation: Intermediate Consumers As Mediators Of Environmental Change, James G. Douglass
Community Dynamics In Submersed Aquatic Vegetation: Intermediate Consumers As Mediators Of Environmental Change, James G. Douglass
Dissertations, Theses, and Masters Projects
Natural ecosystems are strongly affected by changes in resource supply (bottom-up forces) and by changes in upper trophic levels (top-down forces). The extent to which these processes impact a system depends largely on the responses of organisms at middle trophic levels. In seagrass beds, a group of mid-level consumers known as mesograzers form a critical link in the chain of impact, connecting seagrass and epiphytic algae with predatory fishes and crustaceans. I observed dramatic seasonal and interannual changes in mesograzer abundance and species composition in eelgrass (Zostera marina) beds of lower Chesapeake Bay, Virginia, and endeavored to explain the top-down …
Mesopelagic Zooplankton Feeding Ecology And Effects On Particle Repackaging And Carbon Transport In The Subtropical And Subarctic North Pacific Ocean, Stephanie E. Wilson
Mesopelagic Zooplankton Feeding Ecology And Effects On Particle Repackaging And Carbon Transport In The Subtropical And Subarctic North Pacific Ocean, Stephanie E. Wilson
Dissertations, Theses, and Masters Projects
Differences in zooplankton community structure and diet within the mesopelagic zone (base of euphotic zone to 1000 m) play a key role in affecting the efficiency by which organic matter is exported to depth, but how the structure of mesopelagic food webs change with depth or location is poorly known. I examined how mesopelagic zooplankton affect particle export in an oligotrophic (Hawaii Ocean Time-series site ALOHA) compared to a mesotrophic (Japanese time series site K2) open-ocean system. In the first part of the study, I investigated how fecal pellet characteristics change with depth in order to quantify the extent of …
Factors Controlling Tidal Flat Morphology In South San Francisco Bay Between The 1890s And 2005, Joshua Alexander Bearman
Factors Controlling Tidal Flat Morphology In South San Francisco Bay Between The 1890s And 2005, Joshua Alexander Bearman
Dissertations, Theses, and Masters Projects
There is currently a project underway to restore many of the man-made salt ponds along the shores of South San Francisco Bay (SSFB) back to tidal marsh, potentially reestablishing these areas as sinks for SSFB sediments. While there have been recent studies examining the evolution of newly restored marsh areas in SSFB, there have been no recent projects focusing on the expected response of valuable tidal flat environments adjacent to the restored marshes. To help fill this void, this project seeks to characterize SSFB tidal flat morphodynamics, both spatially and temporally, through examination of historic morphologic variability and change along …
Novel Use Of A Natural Isotope Signature To Track Recruitment And Evaluate Age Determination Methods For The 2002 Year Class Of American Shad In The York River, Sally A. Upton
Dissertations, Theses, and Masters Projects
No abstract provided.
A Modern Sediment Budget For The Continental Shelf Off The Waipaoa River, New Zealand, Andrea J. Miller
A Modern Sediment Budget For The Continental Shelf Off The Waipaoa River, New Zealand, Andrea J. Miller
Dissertations, Theses, and Masters Projects
No abstract provided.
Synthesis And Field Emission Properties Of Carbon Nanostructures, Kun Hou
Synthesis And Field Emission Properties Of Carbon Nanostructures, Kun Hou
Dissertations, Theses, and Masters Projects
This dissertation focuses on developing carbon nanostructures for application as the electron emissive material in novel back-gated triode field emission devices. The synthesis, characterization, and field emission properties of carbon nanostructures, including 1-D carbon nanofibers (CNF), 2-D carbon nanosheets (CNS), and chromium oxide coated carbon nanosheets (CrOx-CNS), are presented in this work.;First, we have fabricated aligned carbon nanofiber based back-gated triode field emission devices and confirmed the operation of these devices. 1-D carbon nanofibers were directly synthesized on blank TiW substrates using direct current plasma enhanced chemical vapor deposition. It was found that the morphology of carbon nanofibers could be …
Correction Of Finite Size Errors In Many-Body Electronic Structure Calculations, Hendra Kwee
Correction Of Finite Size Errors In Many-Body Electronic Structure Calculations, Hendra Kwee
Dissertations, Theses, and Masters Projects
Electronic structure calculations using simulation cells for extended systems typically incorporate periodic boundary conditions as an attempt to mimic the real system with a practically infinite number of particles. Periodic boundary conditions introduce unphysical constraints that give rise to finite-size errors. In mean-field type calculations, the infinite size limit is achieved by simple quadrature in the Brillouin zone using a finite number of k-points. Many-body electronic structure calculations with explicit two-particle interactions cannot avail themselves of this simplification. Direct extrapolation is computationally costly while size correction with less accurate methods is frequently not sufficiently accurate. The Hartree-Fock method neglects the …
The Survival Benefit Of Benthic Macroalgae Gracilaria Vermiculophylla As An Alternative Nursery Habitat For Juvenile Blue Crabs, Justin A. Falls
The Survival Benefit Of Benthic Macroalgae Gracilaria Vermiculophylla As An Alternative Nursery Habitat For Juvenile Blue Crabs, Justin A. Falls
Dissertations, Theses, and Masters Projects
The Chesapeake Bay blue crab is in decline. One of the threats to it is the loss of its once plentiful nursery habitat, seagrass, due to baywide eutrophication and climate change. The emergence of the non-native benthic macroalga Gracilaria vermiculophylla may offer the blue crab an alternative nursery if it can provide juvenile crabs a refuge from predation. The ability of Gracilaria to protect juvenile blue crabs was investigated in mesocosm and field survival studies, which were combined into a larger dataset. All of these studies used tethering and therefore a tethering validation study in mesocosms accompanied these experiments. In …