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Articles 721 - 750 of 1876
Full-Text Articles in Physical Sciences and Mathematics
Influence Of Environmental Factors On The Seed Ecology Of Vallisneria Americana, Jessie J. Campbell
Influence Of Environmental Factors On The Seed Ecology Of Vallisneria Americana, Jessie J. Campbell
Dissertations, Theses, and Masters Projects
Environmental conditions may positively or negatively influence production, reproduction, and restoration of submerged aquatic vegetation (SAV). As SAV populations decline, it is important to understand the potential impacts of the environment on the natural processes of reproduction. The objectives of this study are to provide fundamental information on sexual reproduction in a dominant species of freshwater SAV, Vallisneria americana, in the Chesapeake Bay observe the changes in environmental conditions in an established V. americana bed over an entire growing season (April-October), quantify the effects of similar environmental conditions on V. americana seed germination under controlled laboratory conditions, and finally to …
An Investigation Of Programmer-Identified Concerns, Meghan Kathleen Revelle
An Investigation Of Programmer-Identified Concerns, Meghan Kathleen Revelle
Dissertations, Theses, and Masters Projects
No abstract provided.
Reproductive Attributes Of Polynoid Polychaetes From Hydrothermal Vents On The East Pacific Rise, Jessica Lynn Wallace
Reproductive Attributes Of Polynoid Polychaetes From Hydrothermal Vents On The East Pacific Rise, Jessica Lynn Wallace
Dissertations, Theses, and Masters Projects
No abstract provided.
Effects Of Human Disturbance On The Breeding Success Of Eastern Bluebirds (Sialia Sialis), Caitlin Rebecca Kight
Effects Of Human Disturbance On The Breeding Success Of Eastern Bluebirds (Sialia Sialis), Caitlin Rebecca Kight
Dissertations, Theses, and Masters Projects
No abstract provided.
Heavy Metal Complexes Of Mixed S,N Donor Ligands: X-Ray Crystallography And Solution-State 1h Nmr, Wei Lai
Heavy Metal Complexes Of Mixed S,N Donor Ligands: X-Ray Crystallography And Solution-State 1h Nmr, Wei Lai
Dissertations, Theses, and Masters Projects
No abstract provided.
Bi(Iii) Initiated Cyclization Reactions And Iodonium Fragmentation Kinetics, Yajing Lian
Bi(Iii) Initiated Cyclization Reactions And Iodonium Fragmentation Kinetics, Yajing Lian
Dissertations, Theses, and Masters Projects
No abstract provided.
Quantum Monte Carlo Method For Boson Ground States: Application To Trapped Bosons With Attractive And Repulsive Interactions, Wirawan Purwanto
Quantum Monte Carlo Method For Boson Ground States: Application To Trapped Bosons With Attractive And Repulsive Interactions, Wirawan Purwanto
Dissertations, Theses, and Masters Projects
We formulate a quantum Monte Carlo (QMC) method for calculating the ground state of many-boson systems. The method is based on a field-theoretical approach, and is closely related to existing fermion auxiliary-field QMC methods which are applied in several fields of physics. The ground-state projection is implemented as a branching random walk in the space of permanents consisting of identical single-particle orbitals. Any single-particle basis can be used, and the method is in principle exact. We apply this method to an atomic Bose gas, where the atoms interact via an attractive or repulsive contact two-body potential parametrized by the s-wave …
Photochemical Modification Of Polyethylene Terephthalate Surface, Zhengmao Zhu
Photochemical Modification Of Polyethylene Terephthalate Surface, Zhengmao Zhu
Dissertations, Theses, and Masters Projects
The prospect of obtaining desired surface-mediated characteristics while retaining bulk-mediated physical properties and avoiding potential environmental issues with wet chemical technology lends considerable appeal to photochemical approaches to surface modification.;We undertook a combined experimental and computational approach to investigate the effect of deep UV irradiation on the polyethylene terephthalate (PET) surface. its response to 172 nm UV from a xenon examiner lamp in the absence of oxygen was characterized with X-ray Photoelectron Spectroscopy (XPS), Time of Flight/Secondary Ion Mass Spectrometry (ToF/SIMS), transmission infrared spectroscopy (IR), and Atomic Force Microscopy (AFM). The surface chemistry details suggested that the primary photochemical reactions …
Characterization Of Ionic, Dipolar And Molecular Mobility In Polymer Systems, Zhenrong Guo
Characterization Of Ionic, Dipolar And Molecular Mobility In Polymer Systems, Zhenrong Guo
Dissertations, Theses, and Masters Projects
Changes in the ionic and dipolar molecular mobility in a polymer system are the basis for the changes in the dielectric mechanical properties of polymer materials. Frequency Dependent Dielectric Measurements (FDEMS) and Ion Time-of-Flight (ITOF) are two important techniques to investigate ionic and dipolar molecular mobility in polymer systems. The results can be related to the macro- and molecular dielectric, electrical and dynamic properties of polymeric materials. The combination of these two methods provides a full view of electric, dielectric and dynamic behavior for the systems as they undergo chemical and/or physical changes during polymerization crystallization, vitrification, and/or phase separation.;The …
Impact Of Large Scale Substrate Roughness On Giant Magnetoresistive Thin Films, Shannon M. Watson
Impact Of Large Scale Substrate Roughness On Giant Magnetoresistive Thin Films, Shannon M. Watson
Dissertations, Theses, and Masters Projects
This dissertation presents an investigation on the effects of large scale roughness on the properties of giant magnetoresistive multilayers. The large scale roughness (sigmarms > 5 nm) is introduced into giant magnetoresistive thin films through the substrate. Current-in-plane (CIP) and current-perpendicular-to-the-plane (CPP) thin films were deposited by dc magnetron and triode sputtering. All films were characterized for roughness, magnetic and electronic behavior.;Our research on both pseudo spin valves and exchange-biased spin valves shows that long length scale roughness does not have a significant detrimental effect on GMR thin films. For the CIP films, we find that a decrease in GMR correlates …
Nursery Delineation, Movement Patterns, And Migration Of The Sandbar Shark, Carcharhinus Plumbeus, In The Eastern Shore Of Virginia Coastal Bays And Lagoons, Christina L. Conrath
Nursery Delineation, Movement Patterns, And Migration Of The Sandbar Shark, Carcharhinus Plumbeus, In The Eastern Shore Of Virginia Coastal Bays And Lagoons, Christina L. Conrath
Dissertations, Theses, and Masters Projects
The identification and delineation of nursery areas and areas of aggregation of north Atlantic sharks has been identified as an important information need for future management efforts. The objectives of this project were to use a fishery-independent method to study the overwintering area of juvenile sandbar sharks, to spatially delineate the Eastern Shore nursery area, and to examine movement patterns and space use within this nursery area. Data from 21 satellite transmitters attached to large juvenile sandbar sharks revealed that these sharks primarily occurred off the outer banks of North Carolina, at deeper depths and colder water temperatures during the …
The Interaction Between Stratification, Circulation, And Sediment Transport In A Partially-Mixed Estuary, Malcolm E. Scully
The Interaction Between Stratification, Circulation, And Sediment Transport In A Partially-Mixed Estuary, Malcolm E. Scully
Dissertations, Theses, and Masters Projects
Detailed field observations from the York River estuary, Virginia are used to examine the processes governing vertical density stratification and to evaluate the importance of spatial and temporal variations in turbulent mixing on estuarine dynamics and sediment transport. Contrary to previous findings that suggest wind stress acts predominantly as a source of energy to mix away stratification, this study demonstrates that the wind can play a more important role in "straining" the along-channel estuarine density gradient. as a result, down-estuary winds enhance the tidally-averaged vertical shear, which interacts with the along-channel density gradient to increase stratification. Conversely, up-estuary winds tend …
Eye Pathologies Found In Several Decapod Crustaceans, Andrea M. Maniscalco
Eye Pathologies Found In Several Decapod Crustaceans, Andrea M. Maniscalco
Dissertations, Theses, and Masters Projects
No abstract provided.
Estimation Of Annual And Semi-Annual Survival Of Adult Female Blue Crabs And Assessment Of The Effectiveness Of The Virginia Blue Crab Sanctuary Using Tag-Return Methodology, Debra M. Lambert
Dissertations, Theses, and Masters Projects
The blue crab fishery is the most valuable commercial fishery in Chesapeake Bay. The Chesapeake Bay stock recently experienced a period of overfishing, which has resulted in below average abundances, and the spawning stock has experienced an 84 % decline in biomass relative to levels in the late 1980s. The status of the stock is determined by comparing current estimates of mortality to biological reference points. Given the current focus on blue crab conservation, there is a need to obtain reliable, empirical estimates of survival to compare to the biological reference points. A tagging program was initiated on the terminally-molted, …
Investigation Of The Life History Of The Cownose Ray, Rhinoptera Bonasus (Mitchill 1815), Donna S. Grusha
Investigation Of The Life History Of The Cownose Ray, Rhinoptera Bonasus (Mitchill 1815), Donna S. Grusha
Dissertations, Theses, and Masters Projects
No abstract provided.
Physiological Ecology Of The Cultured Hard Clam, Mercenaria Mercenaria: A Case Study In Cherrystone Inlet, Virginia, Elizabeth Darrow Condon
Physiological Ecology Of The Cultured Hard Clam, Mercenaria Mercenaria: A Case Study In Cherrystone Inlet, Virginia, Elizabeth Darrow Condon
Dissertations, Theses, and Masters Projects
No abstract provided.
Linking Framework Geology And Nearshore Morphology: Correlation Of Paleo-Channels With Shore-Oblique Sandbars And Gravel Outcrops, A. Grace Browder
Linking Framework Geology And Nearshore Morphology: Correlation Of Paleo-Channels With Shore-Oblique Sandbars And Gravel Outcrops, A. Grace Browder
Dissertations, Theses, and Masters Projects
No abstract provided.
Shore-Oblique Bars, Nearshore Gravel Outcrops, And Their Correlation To Shoreline Change, Courtney A. Schupp
Shore-Oblique Bars, Nearshore Gravel Outcrops, And Their Correlation To Shoreline Change, Courtney A. Schupp
Dissertations, Theses, and Masters Projects
No abstract provided.
Sources Of Sedimentary Organic Matter In The Mississippi River And Adjacent Gulf Of Mexico, Elizabeth J. Waterson
Sources Of Sedimentary Organic Matter In The Mississippi River And Adjacent Gulf Of Mexico, Elizabeth J. Waterson
Dissertations, Theses, and Masters Projects
The development of accurate carbon budgets, as well as global climate models with predictive capabilities, requires an understanding of the delivery and fate of terrigenous carbon in the environment. Understanding the extent to which estuarine and continental shelf processes alter carbon transfer between marine and terrestrial systems, including estimates of organic matter accumulation in coastal sediments, is poorly known. Organic carbon and nutrients exported to the adjacent Gulf of Mexico by the Mississippi River are influenced by biological and physical processes including remineralization, hydrodynamic sorting, seabed mixing and bioturbation, and burial. These complex processes make it difficult to know the …
Predicting Future Shoreline Condition Based On Land Use Trends, Logistic Regression, And Fuzzy Logic, Lynne M. Dingerson
Predicting Future Shoreline Condition Based On Land Use Trends, Logistic Regression, And Fuzzy Logic, Lynne M. Dingerson
Dissertations, Theses, and Masters Projects
The lower Chesapeake Bay and adjacent coastal waters serve as the primary summer nursery areas for juvenile sandbar sharks (Carcharhinus plumbeus) in the Northwest Atlantic Ocean. The large population of juvenile sandbar sharks in this ecosystem benefits from increased food availability that fuels rapid growth and from limited exposure to large shark predators. Juvenile growth and survival is the most critical life history stage for sandbar sharks, and juvenile nursery grounds will continue to play an important role in the slow recovery of this stock from severe population declines due to overfishing. The goal of this study was to assess …
A Molecular Phylogeny Of The Echeneoidea (Perciformes: Carangoidei) And An Investigation Of Population Structuring Within The Echeneidae, Kurtis N. Gray
A Molecular Phylogeny Of The Echeneoidea (Perciformes: Carangoidei) And An Investigation Of Population Structuring Within The Echeneidae, Kurtis N. Gray
Dissertations, Theses, and Masters Projects
No abstract provided.
Hypoxia In Shallow Coastal Waters: A Case Study In Onancock Creek, Virginia, Taiping Wang
Hypoxia In Shallow Coastal Waters: A Case Study In Onancock Creek, Virginia, Taiping Wang
Dissertations, Theses, and Masters Projects
No abstract provided.
Sonar Sensor Interpretation For Ectogeneous Robots, Wen Gao
Sonar Sensor Interpretation For Ectogeneous Robots, Wen Gao
Dissertations, Theses, and Masters Projects
We have developed four generations of sonar scanning systems to automatically interpret surrounding environment. The first two are stationary 3D air-coupled ultrasound scanning systems and the last two are packaged as sensor heads for mobile robots. Template matching analysis is applied to distinguish simple indoor objects. It is conducted by comparing the tested echo with the reference echoes. Important features are then extracted and drawn in the phase plane. The computer then analyzes them and gives the best choices of the tested echoes automatically. For cylindrical objects outside, an algorithm has been presented to distinguish trees from smooth circular poles …
Description And Evaluation Of The United States Coastal Pelagic Longline Fishery Interactions With Target And Non-Target Species In The Western North Atlantic, David. Kerstetter
Description And Evaluation Of The United States Coastal Pelagic Longline Fishery Interactions With Target And Non-Target Species In The Western North Atlantic, David. Kerstetter
Dissertations, Theses, and Masters Projects
Eighty-five monitored sets were used to investigate the interactions of pelagic fishes with commercial pelagic longline gear in the western North Atlantic during the fall mixed species fishery north of Cape Hatteras, North Carolina, and the spring swordfish fishery in the southern Gulf of Mexico and northern Caribbean Sea. This dissertation incorporates four components: (1) direct analyses of longline gear behavior using small time-depth recorders, (2) comparisons of catch rates and mortality of all species caught on size 16/0 non-offset circle and size 9/0 straight-shank J-style hooks, including analyses of time-of-capture utilizing electronic hook time recorders, (3) an evaluation of …
Simulation Of Turbidity Maximums In The York River, Virginia, Jae-Il Kwon
Simulation Of Turbidity Maximums In The York River, Virginia, Jae-Il Kwon
Dissertations, Theses, and Masters Projects
Two of the most important processes in cohesive sediment transport, erosion rate and settling velocity, were the focus of this study. Settling velocities were estimated by the Owen tube method and the acoustic Doppler velocimeter (ADV) method. A novel erosion model, namely a constant erosion rate model, was implemented in a three-dimensional hydrodynamic eutrophication model (HEM-3D) to simulate the turbidity maximums in the York River system, Virginia. Two one-month periods of model simulations were conducted to mimic typical dry (November--December, 2001) and wet (March--April, 2002) seasons. In order to have enough data to verify the model, four slack water surveys …
Application Of Survival Analysis Methods To Pulsed Exposures: Exposure Duration, Latent Mortality, Recovery Time, And The Underlying Theory Of Survival Distribution Models, Yuan Zhao
Dissertations, Theses, and Masters Projects
Ecotoxicologists adopted median lethal concentration (LC50) methods from mammalian toxicology. This conventional LC50 approach has shortcomings. Fixing the exposure duration and selecting the 50% mortality level result in loss of ecologically relevant information generated at all other times. It also ignores latent mortality that can manifest after exposure ends. as a result, it cannot adequately predict pulsed exposure effects in which concentration, duration, and frequency of pulses change through time. The underlying theory of the dose-response models used to calculate LC50 values, stochastic versus individual effective dose (IED) theory, has not been tested rigorously either. In this study, the effects …
Techniques Of Data Prefetching, Replication, And Consistency In The Internet, Xin Chen
Techniques Of Data Prefetching, Replication, And Consistency In The Internet, Xin Chen
Dissertations, Theses, and Masters Projects
Internet has become a major infrastructure for information sharing in our daily life, and indispensable to critical and large applications in industry, government, business, and education. Internet bandwidth (or the network speed to transfer data) has been dramatically increased, however, the latency time (or the delay to physically access data) has been reduced in a much slower pace. The rich bandwidth and lagging latency can be effectively coped with in Internet systems by three data management techniques: caching, replication, and prefetching. The focus of this dissertation is to address the latency problem in Internet by utilizing the rich bandwidth and …
Vibrational Lifetimes Of Hydrogen And Oxygen Defects In Semiconductors, Baozhou Sun
Vibrational Lifetimes Of Hydrogen And Oxygen Defects In Semiconductors, Baozhou Sun
Dissertations, Theses, and Masters Projects
Characterization of defect and impurity reactions, dissociation, and migration in semiconductors requires a detailed understanding of the rates and pathways of vibrational energy flow and of the coupling mechanisms between local modes and the phonon bath of the host material. Information on the inelastic microscopic interaction can be obtained by measuring the lifetime of local vibrational modes. This dissertation presents lifetime measurements of hydrogen and oxygen defects in semiconductors by means of time-resolved infrared pump-probe spectroscopy.;First, we measured the vibrational lifetime of H- and D-related bending modes in Si and other semiconductors. Time-resolved pump-probe and linewidth measurements reveal that the …
Monte Carlo Simulations Of Ferroelectric Crystal Growth And Molecular Electronic Structure Of Atoms And Molecules, Malliga Suewattana
Monte Carlo Simulations Of Ferroelectric Crystal Growth And Molecular Electronic Structure Of Atoms And Molecules, Malliga Suewattana
Dissertations, Theses, and Masters Projects
In this thesis, we explore two stochastic techniques to study properties of materials in realistic systems. Specifically, the kinetic Monte Carlo (KMC) method is utilized to study the crystal growth process of ferroelectric materials and the quantum Monte Carlo (QMC) approach is used to investigate the ground state properties of atoms and molecules.;In the growth simulations, we study the growth rates and chemical ordering of ferroelectric alloys using an electrostatic model with long-range Coulomb interactions. Crystal growth is characterized by thermodynamic processes involving adsorption and evaporation, with solid-on-solid restrictions and excluding diffusion. A KMC algorithm is formulated to simulate this …
Modifications Of Spacetime And Particle Physics Beyond The Standard Model, Justin M. Conroy
Modifications Of Spacetime And Particle Physics Beyond The Standard Model, Justin M. Conroy
Dissertations, Theses, and Masters Projects
In this dissertation we consider spacetime modifications that result in new physics beyond the standard model. We investigate various collider implications of a particular Lorentz-conserving formulation of QED in which spacetime coordinates are noncommuting. We also consider collider implications of Universal Extra Dimensions. Specifically, we address the possible formation of bound states involving the first quark KK-modes, i.e. KK-quarkonium. In addition, we consider the use of boundary conditions in extra dimensions to break gauge symmetries in unified theories. These boundary conditions can be related to a boundary Higgs sector that decouples from the theory. This technique of "Higgsless" symmetry breaking …