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Articles 2731 - 2760 of 4602

Full-Text Articles in Physical Sciences and Mathematics

Oyster Reef Restoration In Virginia: Broodstock Addition & Nutrient Exchanges, Laurie Ann Sorabella Jan 2002

Oyster Reef Restoration In Virginia: Broodstock Addition & Nutrient Exchanges, Laurie Ann Sorabella

Dissertations, Theses, and Masters Projects

No abstract provided.

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Supplemental Data: Effects Of Physical Mixing On The Attenuation Of Polycyclic Aromatic Hydrocarbons In Estuarine Sediments., Krisa M. Arzayus, Rebecca M. Dickhut, Elizabeth A. Canuel Jan 2002

Supplemental Data: Effects Of Physical Mixing On The Attenuation Of Polycyclic Aromatic Hydrocarbons In Estuarine Sediments., Krisa M. Arzayus, Rebecca M. Dickhut, Elizabeth A. Canuel

Reports

To examine the role of physical disturbance on the long-term preservation of polycyclic aromatic hydrocarbons (PAHs) in sediments, cores were collected from two sites removed from point sources of PAHs and representing contrasting seabed mixing regimes. Although SPAH concentrations in sediments over the past 50 years were not significantly different between the two sites, several PAH isomer ratios were significantly different (p

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Accomack County Shoreline Situation Report, Marcia Berman, Harry Berquist, Sharon Dewing, J. B. Glover, Carl Hershner, Tamia Rudnicky, Daniel E. Schatt Jan 2002

Accomack County Shoreline Situation Report, Marcia Berman, Harry Berquist, Sharon Dewing, J. B. Glover, Carl Hershner, Tamia Rudnicky, Daniel E. Schatt

Reports

No abstract provided.

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Ring Diameter And Closed Area Scallop Fisheries: The Performance Of A Dredge With 4" Rings In The Atlantic Sea Scallop (Placopecten Magellanicus) Fishery, In The Context Of An Area Rotation Management Scheme, Kevin D. Goff Jan 2002

Ring Diameter And Closed Area Scallop Fisheries: The Performance Of A Dredge With 4" Rings In The Atlantic Sea Scallop (Placopecten Magellanicus) Fishery, In The Context Of An Area Rotation Management Scheme, Kevin D. Goff

Dissertations, Theses, and Masters Projects

No abstract provided.

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Comparisons Of Community Structure Between Seep And Vent Mussel-Beds, Mary Parker Turnipseed Jan 2002

Comparisons Of Community Structure Between Seep And Vent Mussel-Beds, Mary Parker Turnipseed

Dissertations, Theses, and Masters Projects

No abstract provided.

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Development Of A Technique To Isolate Measurement Of Ionic Mobility, Jie Guo Jan 2002

Development Of A Technique To Isolate Measurement Of Ionic Mobility, Jie Guo

Dissertations, Theses, and Masters Projects

No abstract provided.

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Effects Of Urbanization And Land Use On Pah Accumulation In Wetland Sediments, Kimani L. Kimbrough Jan 2002

Effects Of Urbanization And Land Use On Pah Accumulation In Wetland Sediments, Kimani L. Kimbrough

Dissertations, Theses, and Masters Projects

The relationship between wetland polycyclic aromatic hydrocarbon (PAH) concentrations and adjacent land use was assessed using surface sediments, sediment cores and global information systems (GIS) in the Elizabeth River, Virginia, an urbanized subestuary of the Chesapeake Bay. Wetlands adjacent to parking lots and petroleum industrial sites exhibited the highest PAH concentrations of all land uses in surfaces sediment and historically. Automobile and coal are the dominant sources of PAHs in wetland sediments historically as determined by relative concentration, fingerprinting and source specific compounds. An analysis of variance (ANOVA) test used to compare sixteen surface sediment sites based on land use …

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Organic Matter Cycling In The York River Estuary, Virginia: An Analysis Of Potential Sources And Sinks, Leigh Mccallister Jan 2002

Organic Matter Cycling In The York River Estuary, Virginia: An Analysis Of Potential Sources And Sinks, Leigh Mccallister

Dissertations, Theses, and Masters Projects

A study of the organic matter (OM) sources and biogeochemical and physicochemical sinks was undertaken in the York River estuary, Virginia. The reactivity of dissolved organic carbon (DOC) was enhanced from ∼25--68% by the combined effects of exposure to natural sunlight and bacterial decomposition. In contrast, sunlight exposure decreased the bioreactivity of DOC in the higher salinity lower York by a factor of five. The combined effects of photochemical and bacterial processing were found to modify both the bioavailability and metabolic fate of OM (e.g. respiration vs. biomass). Stable isotopic (delta13C, delta15N) and radiocarbon (Delta14C) values of bacterial nucleic acids …

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Genetic Stock Structure Of The Sailfish, Istiophorus Platypterus, Based On Nuclear And Mitochondrial Dna, Jan Renee Mcdowell Jan 2002

Genetic Stock Structure Of The Sailfish, Istiophorus Platypterus, Based On Nuclear And Mitochondrial Dna, Jan Renee Mcdowell

Dissertations, Theses, and Masters Projects

The results of life history studies involving the sailfish, Istiophorus platypterus, from the Atlantic, Pacific, and Indian oceans were reviewed. Results of studies agree on several aspects of sailfish biology; sailfish exhibit opportunistic feeding behavior, follow the 28??C isotherm, spawn in summer mature at approximately age 3, and are the least migratory of the billfishes. However, results are in conflict concerning sex ratio and whether sailfish are single or multiple spawners. Although many researchers have reported that sailfish are sexually dimorphic, their fragile otoliths make them difficult to age, aging studies have not been validated, and sexual dimorphism has not …

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Fate Of Organic Compounds Associated With Extractable And Bound Phases Of Estuarine Sediments Deposited Under Varying Depositional Regimes, Krisa Murray Arzayus Jan 2002

Fate Of Organic Compounds Associated With Extractable And Bound Phases Of Estuarine Sediments Deposited Under Varying Depositional Regimes, Krisa Murray Arzayus

Dissertations, Theses, and Masters Projects

Surficial sediments and sediment cores were collected from two distinct depositional regimes of the York River subestuary of Chesapeake Bay to document seasonal inputs, spatial variability, and longer-term (>40 years) fate of total organic carbon (TOC), lipid biomarker compounds and polycyclic aromatic hydrocarbons (PAHs). These regimes included biological mixing in the lower York and episodic mixing at the mid river site. Compounds were selected to represent a range of chemical reactivities, biological and anthropogenic sources, and modes of entry to the environment. The depositional environments were characterized with a suite of analytical tools: x-radiographs, Eh, 210Pb and 137Cs, total …

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Effects Of Habitat Fragmentation On The Utilization Of Eelgrass (Zostera Marina) By Mobile Epifauna And Macrofauna, Scott R. Marion Jan 2002

Effects Of Habitat Fragmentation On The Utilization Of Eelgrass (Zostera Marina) By Mobile Epifauna And Macrofauna, Scott R. Marion

Dissertations, Theses, and Masters Projects

The threat to biodiversity posed by increasing rates of anthropogenic habitat fragmentation necessitates an understanding of the consequences of spatial pattern for natural communities. Reduction of patch size, loss of habitat, changes in the quantity and proportion of habitat edge, and reduced connectivity among habitats can all shape ecological processes and faunal behavior. Seagrass habitats provide a natural model system for examining spatial inf1uences on marine fauna, but separating the effects of habitat structure, environmental conditions, and spatial pattern is difficult because shoot density, percent cover, and hydrodynamic regime often co-vary with patch size. This study used experimentally manipulated seagrass …

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Comparison Of The Fate Of Dissolved Organic Matter In Two Coastal Systems: Hog Island Bay, Va (Usa) And Plum Island Sound, Ma (Usa), Tami L. Lunsford Jan 2002

Comparison Of The Fate Of Dissolved Organic Matter In Two Coastal Systems: Hog Island Bay, Va (Usa) And Plum Island Sound, Ma (Usa), Tami L. Lunsford

Dissertations, Theses, and Masters Projects

No abstract provided.

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The Development Of A Water Quality Model In Baltimore Harbor, Back River, And The Adjacent Upper Chesapeake Bay, Hui Liu Jan 2002

The Development Of A Water Quality Model In Baltimore Harbor, Back River, And The Adjacent Upper Chesapeake Bay, Hui Liu

Dissertations, Theses, and Masters Projects

No abstract provided.

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Distribution, Fluxes, And Bacterial Utilization Of Different Molecular Weight Fractions Of Dissolved Organic Matter In The York River Estuary, Carol J. Pollard Jan 2002

Distribution, Fluxes, And Bacterial Utilization Of Different Molecular Weight Fractions Of Dissolved Organic Matter In The York River Estuary, Carol J. Pollard

Dissertations, Theses, and Masters Projects

No abstract provided.

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Nekton Utilization Of Intertidal Fringing Salt Marsh And Revetment Hardened Shorelines, Robert A. Carroll Jan 2002

Nekton Utilization Of Intertidal Fringing Salt Marsh And Revetment Hardened Shorelines, Robert A. Carroll

Dissertations, Theses, and Masters Projects

No abstract provided.

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Temporal And Spatial Variation In Reproductive Output Of The Veined Rapa Whelk (Rapana Venosa) In The Chesapeake Bay, Catherine C. Ware Jan 2002

Temporal And Spatial Variation In Reproductive Output Of The Veined Rapa Whelk (Rapana Venosa) In The Chesapeake Bay, Catherine C. Ware

Dissertations, Theses, and Masters Projects

No abstract provided.

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Diet Composition Of Young-Of-The-Year Bluefish, Pomatomus Saltatrix, In The Lower Chesapeake Bay And Virginia's Coastal Ocean, James Gartland Jan 2002

Diet Composition Of Young-Of-The-Year Bluefish, Pomatomus Saltatrix, In The Lower Chesapeake Bay And Virginia's Coastal Ocean, James Gartland

Dissertations, Theses, and Masters Projects

No abstract provided.

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An Evaluation Of Closed Area Boundaries Of The Sea Scallop Stock In The Middle Atlantic Bight, John David Lange Jan 2002

An Evaluation Of Closed Area Boundaries Of The Sea Scallop Stock In The Middle Atlantic Bight, John David Lange

Dissertations, Theses, and Masters Projects

No abstract provided.

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Estimating Commercial Scallop Dredge Efficiency Through Vessel Tracking, Catch Data, And Depletion Models, Todd Gedamke Jan 2002

Estimating Commercial Scallop Dredge Efficiency Through Vessel Tracking, Catch Data, And Depletion Models, Todd Gedamke

Dissertations, Theses, and Masters Projects

No abstract provided.

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Coastal Zone Landscape Classification Using Remote Sensing And Model Development, Kevin R. Slocum Jan 2002

Coastal Zone Landscape Classification Using Remote Sensing And Model Development, Kevin R. Slocum

Dissertations, Theses, and Masters Projects

Coastal zone landscape characterization and empirical model development were evaluated using multi-spectral airborne imagery. Collectively, four projects are described that address monitoring and classification issues common to the resource management community. Chapter 1 discusses opportunities for remote sensing. Chapter 2 examines spectral and spatial image resolution requirements, as well as training sample selection methods required for accurate landscape classification. Classification accuracy derived from 25nm imagery with 4m pixel sizes outperformed 70nm imagery with 1m pixel sizes. Eight natural and five cultural landscape features were tested for classification accuracy. Chapter 3 investigated the ability to characterize 1m multispectral imagery into rank-ordered …

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The Ground State Of Two-Dimensional Hubbard-Like Models, Eric Christopher Allman Jan 2002

The Ground State Of Two-Dimensional Hubbard-Like Models, Eric Christopher Allman

Dissertations, Theses, and Masters Projects

We present results from a constrained path Monte Carlo (CPMC) study of a modified two-dimensional Hubbard model. We include more general forms of the band structure and electron interaction in order to examine their effects on ground-state properties, such as electron pairing correlations. Both next-nearest neighbor hopping, t', and third-nearest neighbor hopping, t″, are introduced in the Hamiltonian. A nearest neighbor interaction of strength V is also included. We carry out CPMC calculations on system sizes up to 16 x 16, at various electron fillings, to investigate the ground state of the model for different values of these parameters. For …

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Adaptive And Secured Resource Management In Distributed And Internet Systems, Li Xiao Jan 2002

Adaptive And Secured Resource Management In Distributed And Internet Systems, Li Xiao

Dissertations, Theses, and Masters Projects

The effectiveness of computer system resource management has been always determined by two major factors: (1) workload demands and management objectives, (2) the updates of the computer technology. These two factors are dynamically changing, and resource management systems must be timely adaptive to the changes. This dissertation attempts to address several important and related resource management issues.;We first study memory system utilization in centralized servers by improving memory performance of sorting algorithms, which provides fundamental understanding on memory system organizations and its performance optimizations for data-intensive workloads. to reduce different types of cache misses, we restructure the mergesort and quicksort …

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Simulation Techniques In An Artificial Society Model, Barry Glenn Lawson Jan 2002

Simulation Techniques In An Artificial Society Model, Barry Glenn Lawson

Dissertations, Theses, and Masters Projects

"Artificial society" refers to a generic class of agent-based simulation models used to discover global social structures and collective behavior produced by simple local rules and interaction mechanisms. Artificial society models are applicable in a variety of disciplines, including the modeling of chemical and biological processes, natural phenomena, and complex adaptive systems. We focus on the underlying simulation techniques used in artificial society discrete-event simulation models, including model time evolution and computational performance.;Although for some applications synchronous time evolution is the correct modeling approach, many other applications are better represented using asynchronous time evolution. We claim that asynchronous time evolution …

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Effects Of Longitudinal Disorder On The Magnetic Field Distribution In Bismuth Strontium Calcium Copper Oxide, Xuewen Wan Jan 2002

Effects Of Longitudinal Disorder On The Magnetic Field Distribution In Bismuth Strontium Calcium Copper Oxide, Xuewen Wan

Dissertations, Theses, and Masters Projects

Transverse Field muon spin relaxation (TF-muSR) experiments were performed in external magnetic fields 1.0, 2.7, 3.0, 4.5, 5.5, 6.0 and 7.0 T along the Bi2212 crystalline c-axis. For the first time, the heterodyned fitting analysis technique shows that the field profiles on the ab basal planes of single crystal Bi2212 are symmetric in all experimental fields 1.0--7.0 T and at all experimental temperatures 2.0-90.0 K. The muon spin relaxation rates due to the mixed state of Bi2212 were found to increase linearly from 0 mus-1 at the transition temperature, 90.0 K, to about 1.0 mus -1 at the lowest temperature, …

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Aggregate Matrix-Analytic Techniques And Their Applications, Alma Riska Jan 2002

Aggregate Matrix-Analytic Techniques And Their Applications, Alma Riska

Dissertations, Theses, and Masters Projects

The complexity of computer systems affects the complexity of modeling techniques that can be used for their performance analysis. In this dissertation, we develop a set of techniques that are based on tractable analytic models and enable efficient performance analysis of computer systems. Our approach is three pronged: first, we propose new techniques to parameterize measurement data with Markovian-based stochastic processes that can be further used as input into queueing systems; second, we propose new methods to efficiently solve complex queueing models; and third, we use the proposed methods to evaluate the performance of clustered Web servers and propose new …

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Simulation And Numerical Solution Of Stochastic Petri Nets With Discrete And Continuous Timing, Robert Linzey Jones Iii Jan 2002

Simulation And Numerical Solution Of Stochastic Petri Nets With Discrete And Continuous Timing, Robert Linzey Jones Iii

Dissertations, Theses, and Masters Projects

We introduce a novel stochastic Petri net formalism where discrete and continuous phase-type firing delays can appear in the same model. By capturing deterministic and generally random behavior in discrete or continuous time, as appropriate, the formalism affords higher modeling fidelity and efficiencies to use in practice. We formally specify the underlying stochastic process as a general state space Markov chain and show that it is regenerative, thus amenable to renewal theory techniques to obtain steady-state solutions. We present two steady-state analysis methods depending on the class of problem: one using exact numerical techniques, the other using simulation. Although regenerative …

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Causes Of Submerged Aquatic Vegetation Declines In Tangier Sound, Chesapeake Bay, Robert J. Orth, Kenneth Moore, James Fishman, David J. Wilcox, Lee Karrh, Thomas Parham Jan 2002

Causes Of Submerged Aquatic Vegetation Declines In Tangier Sound, Chesapeake Bay, Robert J. Orth, Kenneth Moore, James Fishman, David J. Wilcox, Lee Karrh, Thomas Parham

Reports

No abstract provided.

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A Summary Of Methods For Controlling Phragmites Australis, Libby Norris, James E. Perry, Kirk J. Havens, Virginia Institute Of Marine Science, Wetlands Program Jan 2002

A Summary Of Methods For Controlling Phragmites Australis, Libby Norris, James E. Perry, Kirk J. Havens, Virginia Institute Of Marine Science, Wetlands Program

Reports

No abstract provided.

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Evaluation Of Striped Bass Stocks In Virginia, Monitoring And Tagging Studies, 1999-2003 Annual Report, 1 September 2000 - 31 October 2001, Philip W. Sadler, Robert J. Latour, Robert E. Harris, John E. Olney Dec 2001

Evaluation Of Striped Bass Stocks In Virginia, Monitoring And Tagging Studies, 1999-2003 Annual Report, 1 September 2000 - 31 October 2001, Philip W. Sadler, Robert J. Latour, Robert E. Harris, John E. Olney

Reports

This report presents the results of striped bass (Marone saxatilis) tagging and monitoring activities in Virginia during the penod 1 September 2000 through 31 October 2001. It includes an assessment of the biological characteristics of striped bass taken from the 2001 spring spawning run, estimates of annual survtval based on annual spring tagging, and the results of the fall 2000 directed mortality study that is cooperative with the Maryland Department of Natural Resources. The information contained in this report is required by the Atlantic States Marine Fisheries Commission and is used to implement a coordinated management plan for striped bass …

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Tracking The Fate Of A High Concentration Groundwater Nitrate Plume Through A Fringing Marsh: A Combined Groundwater Tracer And In Situ Isotope Enrichment Study, Cr Tobias, Sa Macko, Iris C. Anderson, Elizabeth A. Canuel, Jw Harvey Dec 2001

Tracking The Fate Of A High Concentration Groundwater Nitrate Plume Through A Fringing Marsh: A Combined Groundwater Tracer And In Situ Isotope Enrichment Study, Cr Tobias, Sa Macko, Iris C. Anderson, Elizabeth A. Canuel, Jw Harvey

VIMS Articles

A groundwater plume enriched in (15)NO(3)(-) was created upgradient of a mesohaline salt marsh. By measuring the changes in concentration and isotopic enrichment of NO(3)(-), N(2)O, N(2), NH(4)(+), and particulate organic nitrogen (PON) during plume transport through the marsh, in situ rates of dissimilatory nitrate reduction to ammonium (DNRA) and denitrification (DNF) were estimated, as well as N storage in the reduced N pools. For groundwater discharge within the top 10 cm of marsh, NO(3)(-) removal was 90% complete within the 50 cm of marsh nearest the upland border. The peak NO(3)(-) loss rate from the plume ranged from 208 …

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