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Articles 451 - 480 of 1876
Full-Text Articles in Physical Sciences and Mathematics
Evaluating The Impact Of Stock Structure Uncertainty In Stock Assessments Of Sailfish In The Atlantic Ocean, Catarina Wor Lima
Evaluating The Impact Of Stock Structure Uncertainty In Stock Assessments Of Sailfish In The Atlantic Ocean, Catarina Wor Lima
Dissertations, Theses, and Masters Projects
No abstract provided.
Shedding Light On The Estuarine Coastal Filter: The Relative Importance Of Benthic Macroalgae In Shallow Photic Systems, Johnathan Daniel Maxey
Shedding Light On The Estuarine Coastal Filter: The Relative Importance Of Benthic Macroalgae In Shallow Photic Systems, Johnathan Daniel Maxey
Dissertations, Theses, and Masters Projects
No abstract provided.
Seed Burial In The Seagrass Zostera Marina: The Role Of Infauna, Natalia J. Blackburn
Seed Burial In The Seagrass Zostera Marina: The Role Of Infauna, Natalia J. Blackburn
Dissertations, Theses, and Masters Projects
In terrestrial systems, seed burial is widely recognized as a vital process that influences small- and large-scale plant population patterns. Despite its demonstrated importance in terrestrial literature, very little is known about seed burial in seagrasses. Zostera marina is a perennial seagrass found in northern temperate oceans worldwide, and is the dominant seagrass found in the Chesapeake Bay. In terrestrial systems, seed burial is frequently mediated by soil-dwelling invertebrates. The goal of this work was to determine the role that benthic infauna play in the burial of Z. marina seeds by addressing the following questions: 1. Are seeds on sediments …
Habitat Utilization And Trophic Interactions By Fauna In A Shallow Estuary: Comparisons Between Clam Aquaculture And Natural Sites, Lara Gates Kling
Habitat Utilization And Trophic Interactions By Fauna In A Shallow Estuary: Comparisons Between Clam Aquaculture And Natural Sites, Lara Gates Kling
Dissertations, Theses, and Masters Projects
Aquaculture of the hard clam, Mercenaria mercenaria, has steadily increased in the United States over the past 25 years. In some areas, including along Virginia’s coast, this industry has grown to such a scale that aquaculture systems now exist as agroecosystems within coastal waters. Several features of these aquaculture systems, such as high clam densities and protective mesh netting, may modify the availability of habitat, food, and nutrients and may be expected to affect benthic and nektonic community structure. Few studies, however, have evaluated these effects. We conducted seasonal (May – September) sampling in a tidal tributary of Chesapeake Bay …
Evaluating Persistent Organic Pollutants (Pops) And Mercury In The West Antarctic Peninsula (Wap) Food Web, With A Focus On Antarctic Fur Seals (Arctocephalus Gazella), Emily K. Brault
Dissertations, Theses, and Masters Projects
No abstract provided.
Mobile Animals As A Potential Dispersal Mechanism In Zostera Marina (Eelgrass), Sarah E. Sumoski
Mobile Animals As A Potential Dispersal Mechanism In Zostera Marina (Eelgrass), Sarah E. Sumoski
Dissertations, Theses, and Masters Projects
No abstract provided.
The Effects Of Salinity Pulses Of Varying Duration And Intensity On Three Freshwater Submerged Aquatic Vegetation Species, Rebecca Wright
The Effects Of Salinity Pulses Of Varying Duration And Intensity On Three Freshwater Submerged Aquatic Vegetation Species, Rebecca Wright
Dissertations, Theses, and Masters Projects
No abstract provided.
A Community-Based Participatory Assessment Of Fish Consumption And Dietary Mercury Exposure Along The Lower James River, Virginia Usa, Erica Lynnette Holloman
A Community-Based Participatory Assessment Of Fish Consumption And Dietary Mercury Exposure Along The Lower James River, Virginia Usa, Erica Lynnette Holloman
Dissertations, Theses, and Masters Projects
The use of community-based participatory research (CBPR) methods to conduct environmental exposure assessments provides valuable insight about disparities in fish consumption and contaminant exposure. Ninety-five community-specific fish consumption surveys were administered to low-income African American women (ages 16--49) residing in the Southeast community of Newport News, Virginia, USA, in 2008. The mean fish consumption rate for the women surveyed was 147.8 g/day (95% CI: 117.6-185.8), a rate substantially higher than the mean fish consumption rate reported for U.S. women (1.8 g/day 95% CI: 1.51-2.04). Through collaborative partnerships established between current researchers and The Moton Community House (a local community center), …
Effects Of Anthropogenic Stressors And Changes In Biodiversity On Lower Chesapeake Bay, Va Usa Seagrass Systems, Rachael E. Blake
Effects Of Anthropogenic Stressors And Changes In Biodiversity On Lower Chesapeake Bay, Va Usa Seagrass Systems, Rachael E. Blake
Dissertations, Theses, and Masters Projects
Anthropogenic stressors are increasingly changing conditions in coastal areas and impacting important habitats. But, when multiple stressors act simultaneously, their effects on ecosystems become more difficult to predict. In Chesapeake Bay, USA, predictions suggest that anthropogenic stressors from climate change, such as warming temperatures, may increase the frequency and severity of storm events, leading to increased freshwater, nutrient, and sediment inputs. Coastal development, another source of anthropogenic stressors, continues to increase with growing coastal populations, and may lead to altered sediment characteristics, habitat fragmentation, altered food webs, and loss of vegetated habitats. Community processes may interact with stressors, for example, …
A Case Study In The Effectiveness Of Marine Protected Areas (Mpas): The Islands Of Bonaire And Curacao, Dutch Caribbean, Noelle J. Relles
A Case Study In The Effectiveness Of Marine Protected Areas (Mpas): The Islands Of Bonaire And Curacao, Dutch Caribbean, Noelle J. Relles
Dissertations, Theses, and Masters Projects
The islands of Bonaire and Curacao, Dutch Caribbean, were both mapped along their leeward coasts for dominant coral community and other benthic cover in the early 1980s. This mapping effort offers a unique baseline for comparing changes in the benthic community of the two islands since that time, particularly given the marked differences between the two islands. Bonaire is well-protected and completely surrounded by a marine protected area (MPA), which includes two no-diving marine reserves; additionally, Bonaire's population is only around 15,000. In contrast, the island of Curacao is home to 140,000 inhabitants and marine protection is limited, with a …
Measurement Of Single And Double Spin Asymmetries In P(E, E' Pi(+/-,0))X Semi-Inclusive Deep-Inelastic Scattering, Sucheta Shrikant Jawalkar
Measurement Of Single And Double Spin Asymmetries In P(E, E' Pi(+/-,0))X Semi-Inclusive Deep-Inelastic Scattering, Sucheta Shrikant Jawalkar
Dissertations, Theses, and Masters Projects
Measurements in the late 1980s at CERN revealed that quark spins account for a small fraction of the proton's spin. This so-called spin crisis spurred a number of new experiments to identify the proton's silent spin contributors, namely, the spin of the gluons, which hold the quarks together, and the orbital angular momentum of both quarks and gluons. One such experiment was eg1-dvcs at the Thomas Jefferson National Accelerator Facility in Newport News, Va., which ran in 2009 and collected approximately 19 billion electron triggers for hydrogen. I will present new measurements of the single and double-spin asymmetries ALU, AUL …
The First Direct Measurement Of The Weak Charge Of The Proton, John Poague Leckey Iv
The First Direct Measurement Of The Weak Charge Of The Proton, John Poague Leckey Iv
Dissertations, Theses, and Masters Projects
Qweak is an experiment currently running at the Thomas Jefferson National Accelerator Facility that uses parity-violating elastic electron-proton scattering to measure the weak charge of the proton QPweak . Longitudinally polarized electrons are scattered off a liquid hydrogen target and pass through a toroidal-field magnetic spectrometer. This experiment is a sensitive test for physics beyond the Standard Model, as QPweak is well predicted in the Standard Model. This dissertation describes the first direct measurement of QPweak . The precision that will be generated by the final 4% measurement will allow the probing of certain classes of new physics up to …
Thermochemistry Of Amino Acids And Constrained Diamines, Erica Jane Tullo
Thermochemistry Of Amino Acids And Constrained Diamines, Erica Jane Tullo
Dissertations, Theses, and Masters Projects
The gas-phase proton affinities of several highly basic amino acids and diamines were determined using the extended kinetic method in an ESI-quadrupole ion trap instrument. The non-protein amino acid L-canavanine is structurally related to L-arginine with an oxygen substituted for the terminal methylene group of L-arginine and is highly toxic to humans. The proton affinity of L-arginine, a protein amino acid, was determined to be 1036 kJ mol -1, whereas the proton affinity of L-canavanine was determined to be 1005 kJ mol-1. Thus, substitution of an oxyguanidino group for the guanidine group in L-arginine results in a large decrease in …
Dark Matter In The Heavens And At Colliders: Models And Constraints, Reinard Primulando
Dark Matter In The Heavens And At Colliders: Models And Constraints, Reinard Primulando
Dissertations, Theses, and Masters Projects
In this dissertation, we investigate various aspects of dark matter detection and model building. Motivated by the cosmic ray positron excess observed by PAMELA, we construct models of decaying dark matter to explain the excess. Specifically we present an explicit, TeV-scale model of decaying dark matter in which the approximate stability of the dark matter candidate is a consequence of a global symmetry that is broken only by instanton-induced operators generated by a non-Abelian dark gauge group. Alternatively, the decaying operator can arise as a Planck suppressed correction in a model with an Abelian discrete symmetry and vector-like states at …
Understanding And Leveraging Virtualization Technology In Commodity Computing Systems, Duy Le
Understanding And Leveraging Virtualization Technology In Commodity Computing Systems, Duy Le
Dissertations, Theses, and Masters Projects
Commodity computing platforms are imperfect, requiring various enhancements for performance and security purposes. In the past decade, virtualization technology has emerged as a promising trend for commodity computing platforms, ushering many opportunities to optimize the allocation of hardware resources. However, many abstractions offered by virtualization not only make enhancements more challenging, but also complicate the proper understanding of virtualized systems. The current understanding and analysis of these abstractions are far from being satisfactory. This dissertation aims to tackle this problem from a holistic view, by systematically studying the system behaviors. The focus of our work lies in performance implication and …
Surface Impedance Of Superconducting Radio Frequency (Srf) Materials, Binping Xiao
Surface Impedance Of Superconducting Radio Frequency (Srf) Materials, Binping Xiao
Dissertations, Theses, and Masters Projects
Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. There remain many open questions, however, in developing a systematic understanding of the fundamental behavior of SRF materials, including niobium treated in different ways and various other bulk/thin film materials that are fabricated with different methods under assorted conditions. A facility that can measure the SRF properties of small samples in a range of 2∼40 K temperature is needed in order to fully answer these questions. The Jefferson Lab surface impedance characterization (SIC) system has been designed to attempt to meet this requirement. It consists of a sapphire-loaded cylindrical …
Towards Confident Body Sensor Networking, Zhen Ren
Towards Confident Body Sensor Networking, Zhen Ren
Dissertations, Theses, and Masters Projects
With the recent technology advances of wireless communication and lightweight low-power sensors, Body Sensor Network (BSN) is made possible. More and more researchers are interested in developing numerous novel BSN applications, such as remote health/fitness monitoring, military and sport training, interactive gaming, personal information sharing, and secure authentication. Despite the unstable wireless communication, various confidence requirements are placed on the BSN networking service. This thesis aims to provide Quality of Service (QoS) solutions for BSN communication, in order to achieve the required confidence goals.;We develop communication quality solutions to satisfy confidence requirements from both the communication and application levels, in …
Supersymmetric Leptophilic Models Of Electroweak Symmetry Breaking, Gardner Rush Marshall
Supersymmetric Leptophilic Models Of Electroweak Symmetry Breaking, Gardner Rush Marshall
Dissertations, Theses, and Masters Projects
Over the years, the Standard Model has proved itself to be an extremely durable theory. In spite of its success, very few empirical clues have emerged about the nature of the electroweak symmetry breaking that lies at its heart. With results from the LHC around the corner, this will hopefully change soon. In this dissertation we examine several possibilities for electroweak symmetry breaking and discuss various extensions to the Standard Model to resolve known problems. We begin by providing a brief overview of electroweak symmetry breaking, two Higgs doublet models, and supersymmetry. We then present a supersymmetric model that allows …
Studies Of Polarized And Unpolarized Helium -3 In The Presence Of Alkali Vapor, Kelly Anita Kluttz
Studies Of Polarized And Unpolarized Helium -3 In The Presence Of Alkali Vapor, Kelly Anita Kluttz
Dissertations, Theses, and Masters Projects
At the Thomas Jefferson National Accelerator Facility, glass target cells containing a high density of highly polarized 3He nuclei are used in electron scattering experiments studying the substructure of the neutron. In addition to 3He, these cells contain a small amount of rubidium (Rb), potassium (K), and nitrogen (N2), which facilitate the polarization process. The work presented here represents studies of the interactions between the alkali vapor and 3He nuclei when both are polarized and unpolarized.;Our investigations into the mechanisms responsible for the relaxation of the 3He polarization have measured unusually large polarization losses. In addition, most cells studied exhibited …
Automated Reductions Of Markov Chain Models Of Calcium Release Site Models, Yan Hao
Automated Reductions Of Markov Chain Models Of Calcium Release Site Models, Yan Hao
Dissertations, Theses, and Masters Projects
Markov chain models have played an important role in understanding the relationship between single channel gating of intracellular calcium (Ca2+) channels, specifically 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs), and the stochastic dynamics of Ca2+ release events, known as Ca2+ puffs and sparks. Mechanistic Ca2+ release site models are defined by the composition of single channel models whose transition probabilities depend on the local calcium concentration and thus the state of the other channels. Unfortunately, the large state space of such compositional models impedes simulation and computational analysis of the whole cell Ca2+ signaling in which the stochastic dynamics of …
Discovering New Vulnerabilities In Computer Systems, Zhenyu Wu
Discovering New Vulnerabilities In Computer Systems, Zhenyu Wu
Dissertations, Theses, and Masters Projects
Vulnerability research plays a key role in preventing and defending against malicious computer system exploitations. Driven by a multi-billion dollar underground economy, cyber criminals today tirelessly launch malicious exploitations, threatening every aspect of daily computing. to effectively protect computer systems from devastation, it is imperative to discover and mitigate vulnerabilities before they fall into the offensive parties' hands. This dissertation is dedicated to the research and discovery of new design and deployment vulnerabilities in three very different types of computer systems.;The first vulnerability is found in the automatic malicious binary (malware) detection system. Binary analysis, a central piece of technology …
Luminescent Nitrogen And Sulfure Adducts Of Cui Disubstituted Piperazine Complexes, Jason P. Safko
Luminescent Nitrogen And Sulfure Adducts Of Cui Disubstituted Piperazine Complexes, Jason P. Safko
Dissertations, Theses, and Masters Projects
No abstract provided.
Parity-Violating Asymmetry In The Nucleon To Delta Transition: A Study Of Inelastic Electron Scattering In The G0 Experiment, Carissa Lee Capuano
Parity-Violating Asymmetry In The Nucleon To Delta Transition: A Study Of Inelastic Electron Scattering In The G0 Experiment, Carissa Lee Capuano
Dissertations, Theses, and Masters Projects
The parity-violating asymmetry arising from inelastic electron scattering at backward angle (∼ 95??) near the Delta resonance has been measured for both hydrogen and deuterium targets as part of the G 0 experiment. For Q2 = 0.34 (GeV/c) 2 and W = 1.18 GeV, the asymmetries were found to be AHinel=-33.4+/-5 .3stat+/-5 .1sysppm, ADinel=-43.6+/-1 4.6stat+/- 6.2sysppm. .;From the hydrogen asymmetry, the axial transition form factor, GAND , can be extracted. GAND is related to probability of the quark spin-flip that occurs as the proton transitions to the Delta. From the measured asymmetry, the form factor is found to be GAND=-0.046+/- …
An Input Centric Paradigm For Program Dynamic Optimizations And Lifetime Evolvement, Kai Tian
An Input Centric Paradigm For Program Dynamic Optimizations And Lifetime Evolvement, Kai Tian
Dissertations, Theses, and Masters Projects
Accurately predicting program behaviors (e.g., memory locality, method calling frequency) is fundamental for program optimizations and runtime adaptations. Despite decades of remarkable progress, prior studies have not systematically exploited the use of program inputs, a deciding factor of program behaviors, to help in program dynamic optimizations. Triggered by the strong and predictive correlations between program inputs and program behaviors that recent studies have uncovered, the dissertation work aims to bring program inputs into the focus of program behavior analysis and program dynamic optimization, cultivating a new paradigm named input-centric program behavior analysis and dynamic optimization.;The new optimization paradigm consists of …
Searching, Selecting, And Synthesizing Source Code Components, Collin Mcmillan
Searching, Selecting, And Synthesizing Source Code Components, Collin Mcmillan
Dissertations, Theses, and Masters Projects
As programmers develop software, they instinctively sense that source code exists that could be reused if found --- many programming tasks are common to many software projects across different domains. oftentimes, a programmer will attempt to create new software from this existing source code, such as third-party libraries or code from online repositories. Unfortunately, several major challenges make it difficult to locate the relevant source code and to reuse it. First, there is a fundamental mismatch between the high-level intent reflected in the descriptions of source code, and the low-level implementation details. This mismatch is known as the concept assignment …
Rogue Fishermen: Codfish, Atlantic Items, And The Isles Of Shoals, Megan Victor
Rogue Fishermen: Codfish, Atlantic Items, And The Isles Of Shoals, Megan Victor
Dissertations, Theses, and Masters Projects
No abstract provided.
Charmed Hadron Spectrum And Interactions, Liuming Liu
Charmed Hadron Spectrum And Interactions, Liuming Liu
Dissertations, Theses, and Masters Projects
Studying hadrons containing heavy quarks in lattice QCD is challenging mainly due to finite lattice spacing effects. to control the discretization errors, mQa is required to be much less than 1, where mQ is the quark mass and a is the lattice spacing. For currently accessible lattice spacings, the charm quark mass doesn't satisfy this requirement. One approach to simulate heavy quarks on the lattice is non-relativestic QCD, which treats heavy quark as a static source and expand the lattice quark action in powers of 1mQa . Unfortunately, the charm quark is not heavy enough to justify this expansion. An …
The Impacts Of Shoreline Development On Shallow-Water Benthic Communities In The Patuxent River, Md, Cassie D. Bradley
The Impacts Of Shoreline Development On Shallow-Water Benthic Communities In The Patuxent River, Md, Cassie D. Bradley
Dissertations, Theses, and Masters Projects
Natural coastal habitats throughout Chesapeake Bay are increasingly threatened with shoreline modification due to population growth and rising rates of development. The replacement of these natural coastlines with hardened structures such as seawalls (bulkheads) and stone revetments (riprap) not only compromises vegetation at the land-water interface, but also can influence several elements of local aquatic food webs. Effects of these alterations have been well-studied with respect to fish assemblages and intertidal communities, particularly in conjunction with larger-scale watershed development, and recently, interest has shifted toward investigation of the effects of shoreline development on subtidal benthic infaunal communities.
This study evaluated …
Characterization Of Pa-11 Flexible Liner Aging In The Laboratory And In Field Environments Throughout The World, Arthur Jaeton Mitman Glover
Characterization Of Pa-11 Flexible Liner Aging In The Laboratory And In Field Environments Throughout The World, Arthur Jaeton Mitman Glover
Dissertations, Theses, and Masters Projects
Polyamide-11 (PA11) is a polymer of the Nylon family whose monomer is obtained from the castor bean, a renewable resource. It is widely used in offshore oil and gas production as a non-rigid flexible pipe liner, allowing for oil and gas transport from the wellhead to floating platforms for processing. The degradation of PA11 over time may lead to the pipe's failure, with possibly catastrophic results which include loss of life. Until now, the characterization of the degredative process has been limited to laboratory studies of the effects of water and temperature on the rate and degree of hydrolysis. In …
Net Microbial Activity, Vegetation Dynamics, And Ecosystem Function In Created And Natural Palustrine Forested Wetlands In Southeastern Virginia, Usa, Christian A. Hauser
Net Microbial Activity, Vegetation Dynamics, And Ecosystem Function In Created And Natural Palustrine Forested Wetlands In Southeastern Virginia, Usa, Christian A. Hauser
Dissertations, Theses, and Masters Projects
No abstract provided.