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Articles 3691 - 3720 of 4602

Full-Text Articles in Physical Sciences and Mathematics

Laser-Induced Collisional Detachment, D. Luo, John B. Delos, S. Geltman Apr 1988

Laser-Induced Collisional Detachment, D. Luo, John B. Delos, S. Geltman

Arts & Sciences Articles

A theoretical study is presented of the process of photodetachment of a negative ion by sub-threshold-frequency radiation in the presence of a simultaneous collision. Calculations are carried out for the H−-He case and the resulting cross section is compared with other competing processes, such as two-photon photodetachment and nonradiative collisional detachment.

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Semiclassical Interpretation Of Eigenvectors For Excited Atoms In External Fields, Robert Leonard Waterland, M. L. Du, John B. Delos Feb 1988

Semiclassical Interpretation Of Eigenvectors For Excited Atoms In External Fields, Robert Leonard Waterland, M. L. Du, John B. Delos

Arts & Sciences Articles

Eigenvectors for an electron in an atom in parallel electric and magnetic fields are calculated, and a semiclassical interpretation of their behavior is obtained. Eigenvectors can in this case be regarded as ‘‘wave functions in angular momentum space.’’ The matrix equation defining the eigenvectors is written as a difference equation, and then converted to a pseudodifferential equation; a systematic procedure is then used to construct a semiclassical approximation. It is found that the same classical Hamiltonian that has been previously used to calculate semiclassical eigenvalues provides a WKB-type representation of the eigenvectors. The development sheds new light on action-angle formulations …

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Late Pleistocene Barrier-Island Sequence Along The Southern Delmarva Peninsula: Implications For Middle Wisconsin Sea Levels, Kenneth Finkelstein, Michael S. Kearney Jan 1988

Late Pleistocene Barrier-Island Sequence Along The Southern Delmarva Peninsula: Implications For Middle Wisconsin Sea Levels, Kenneth Finkelstein, Michael S. Kearney

VIMS Articles

Evidence for a middle Wisconsin sea-level high at or above modern limits along the east coast of the United States has long been controversial. Most reports have been dismissed as poorly dated or lacking unequivocal documentation of a marine transgression. We describe here a 14C-dated, middle Wisconsin transgressive sequence with an extant subaerial barrier facies along the southern Delmarva Peninsula. This sequence indicates that sea levels were near their present position between ca. 23 and 34 ka; it may correlate with other inferred similar-age littoral deposits of the area, and it suggests that the evidence for glacioeustatic fluctuations during the …

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The Formation Of Longitudinal Fronts In A Coastal Plain Estuary, Linda M. Huzzey, John M. Brubaker Jan 1988

The Formation Of Longitudinal Fronts In A Coastal Plain Estuary, Linda M. Huzzey, John M. Brubaker

VIMS Articles

Longitudinal estuarine fronts, aligned parallel to the axis of the estuary, are characteristic of the York River. Their time scale for genesis and decay is of the order of hours; they are usually located at the inner edge of the shoals or over the main channel. Field measurements have shown marked intratidal differences in density and current speeds across this estuary. These can be correlated with changes in depth and the strength of the advective processes. Differential advection between the channel and shoal regions, when acting upon a constant longitudinal density gradient, is shown to be of sufficient magnitude to …

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Determination Of Tributyltin In The Marine-Environment, Rg Huggett, Michael A. Unger, Fa Espourteille, Cd Rice Jan 1988

Determination Of Tributyltin In The Marine-Environment, Rg Huggett, Michael A. Unger, Fa Espourteille, Cd Rice

VIMS Articles

Tributyltin (TBT) is a biocide used in antifouling paints to protect hulls from nuisance organisms such as barnacles, worms and algae. The use of TBT paints has increased over the past decade due to its effectiveness as an antifoulant which is related to its toxicity. Water concentrations of less than 100 ng L- have been shown to harm some aquatic species in laboratory tests and observations in the natural environment indicate that levels below 10 ng L- may be harmful. Tributyltin is bioconcentrated by many species to levels of one thousand, or more, times ambient water concentrations. Sediment-water partitioning coefficients …

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Recalibration Of Pagan River Water Quality Model, Albert Kuo, Gamble M. Sisson, Bruce J. Neilson Jan 1988

Recalibration Of Pagan River Water Quality Model, Albert Kuo, Gamble M. Sisson, Bruce J. Neilson

Reports

Two water quality models of the Pagan River were developed in the 1970s by the Virginia Institute of Marine Science. The first model was developed under the CSA (cooperative state agencies) program (Kuo, Lewis and Fang, 1976). It simulated the oxidation of organic matter and the effect that, and reaeration, had on the dissolved oxygen regime of the river. The model included four water quality parameters: salinity, dissolved oxygen, carbonaceous oxygen demand and nitrogenous oxygen demand. A later model, developed as part of the Hampton Roads 208 studies, was an expansion of the first one. It included the nitrogen and …

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Analysis Of Effluents And Associated Sediments And Tissue For Toxic Organic Compounds, 1987-1988 : Final Report To Virginia State Water Control Board, Robert Hale, Craig L. Smith Jan 1988

Analysis Of Effluents And Associated Sediments And Tissue For Toxic Organic Compounds, 1987-1988 : Final Report To Virginia State Water Control Board, Robert Hale, Craig L. Smith

Reports

Effluent and sediment samples were collected from 30 point source discharge sites within tributaries to the Chesapeake Bay, and analyzed for the presence of toxic organic compounds. The facilities selected included: municipal treatment plants, oil refining and storage operations, shipyards, military bases, paper companies, electrical power generators and various other manufacturing enterprises. In addition to sediment, shellfish were collected from the receiving streams. Unfortunately, environmental conditions in the vicinity of many of the facilities were unsatisfactory for the long-term survival of shellfish. As a consequence their availability was limited. ....

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The Influence Of Post-Settlement Mortality On Recruitment Patterns In A Soft-Bottom Habitat, Erick Christian Zobrist Jan 1988

The Influence Of Post-Settlement Mortality On Recruitment Patterns In A Soft-Bottom Habitat, Erick Christian Zobrist

Dissertations, Theses, and Masters Projects

No abstract provided.

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Predator-Prey Dynamics Between The Blue Crab: Callineates Sapidus Rathbun, And Juvenile Oysters Crassostrea Virginica (Gmelin), David B. Eggleston Jan 1988

Predator-Prey Dynamics Between The Blue Crab: Callineates Sapidus Rathbun, And Juvenile Oysters Crassostrea Virginica (Gmelin), David B. Eggleston

Dissertations, Theses, and Masters Projects

No abstract provided.

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Development, Test And Application Of A New Method Of Particle Shape Analyses Based On The Concept Of The Fractal Dimension, Adam Arthur Frisch Jan 1988

Development, Test And Application Of A New Method Of Particle Shape Analyses Based On The Concept Of The Fractal Dimension, Adam Arthur Frisch

Dissertations, Theses, and Masters Projects

Shape analysis methods based on the concept of the fractal dimension are emerging as a new method of quantifying complex particle shapes. The concept of the fractal dimension stems from the approximately linear relationship between the logarithm of the particle perimeter and the logarithm of the step length or unit of measure. as step length is shortened, the resulting particle perimeter is lengthened. The fractal dimension (D) is defined as 1 {dollar}-{dollar} b, where b is the slope of the log/log plot of perimeter against step length. Using two dimensional projected particle outlines measured by a video image digitizing system, …

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Availability Of Lead, Zinc, Copper, And Cadmium To The Peregrine Falcon (Falco Peregrinus) From Waterfowl Of The Craney Island Disposal Area, Douglas Stephen Davis Jan 1988

Availability Of Lead, Zinc, Copper, And Cadmium To The Peregrine Falcon (Falco Peregrinus) From Waterfowl Of The Craney Island Disposal Area, Douglas Stephen Davis

Dissertations, Theses, and Masters Projects

No abstract provided.

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The Synthesis Of Quinone-Capped Cyclodextrins, Michael Vernie Cossette Jan 1988

The Synthesis Of Quinone-Capped Cyclodextrins, Michael Vernie Cossette

Dissertations, Theses, and Masters Projects

No abstract provided.

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Investigation Of Tributyltin: Water/Sediment Interactions, Michael A. Unger Jan 1988

Investigation Of Tributyltin: Water/Sediment Interactions, Michael A. Unger

Dissertations, Theses, and Masters Projects

Tributyltin (TBT) and its degradation products dibutyltin (DBT) and monobutyltin (MBT) have been quantitatively analyzed in environmental water samples using gas chromatography with flame photometric detection and gas chromatography/mass spectrometry (GC/MS). The butyltins were extracted from environmental samples with hexane/0.2% tropolone and derivatized with hexyl magnesium bromide to form hexylbutyltins. Full scanning GC/MS was used for confirmation of peak identifications and quantification was done by selective ion monitoring (methane chemical ionization) at m/z 319 (TBT) and m/z 347 (DBT, MBT and tripentyltin, the internal standard). Calibration curves were linear and detection limits were less than 2 ngL&\sp{lcub}-1{rcub}&. GC/MS and GC …

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Modes Of Longshore Variability In The Development Of A Bar-Trough Morphology, Rebecca Jo Savage Jan 1988

Modes Of Longshore Variability In The Development Of A Bar-Trough Morphology, Rebecca Jo Savage

Dissertations, Theses, and Masters Projects

No abstract provided.

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Population Status Of Five Potentially Threatened Vascular Plants From Coastal Plain Tidal Rivers In Virginia, Carl Hershner, James Perry Jan 1988

Population Status Of Five Potentially Threatened Vascular Plants From Coastal Plain Tidal Rivers In Virginia, Carl Hershner, James Perry

Reports

Work is underway to clarify the population status of Virginia's biota that have been considered rare, endangered, or of an unknown population status by earlier scientists (Porter, 1979). The purpose of the current study was to investigate the population status and areal distribution of five of these plant species found on the tidal rivers of the Coasta1 Plain in Virginia. Although only a small portion of a much larger effort, it is hoped that this work will help fill some of the gaps that exist in our data base on these species. Furthermore, it is hoped that the following information …

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Sedimentation And Its Role In The Nutrient Dynamics Of A Tidal Freshwater Marsh, Jane M. Ledwin Jan 1988

Sedimentation And Its Role In The Nutrient Dynamics Of A Tidal Freshwater Marsh, Jane M. Ledwin

Dissertations, Theses, and Masters Projects

No abstract provided.

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The Effects Of Salinity On Cadmium Toxicity To The Bay Mysid, Mysidopsis Bahia Molenock, Peter F. De Lisle Jan 1988

The Effects Of Salinity On Cadmium Toxicity To The Bay Mysid, Mysidopsis Bahia Molenock, Peter F. De Lisle

Dissertations, Theses, and Masters Projects

The effects of salinity on cadmium toxicity to the bay mysid, Mysidopsis bahia Molenock were studied in a series of experiments examining salinity tolerance, effect of salinity on intermolt period, osmoregulatory capacity, interaction of salinity with acute cadmium toxicity, role of changes in cadmium speciation, modification due to calcium antagonism and effects of cadmium on osmoregulatory ability. Upper and lower tolerance limits increased with increasing acclimation salinity. Intermolt duration decreased slightly with increasing salinity. Mysidopsis bahia osmoregulates at salinities from 5 to 37&\perthous& and exhibits an isosmotic point of 24&\perthous&. Hemolymph osmolality attained steady-state condition by 95 min post-transfer to …

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Long Wave Generation By Wave Groups In The Nearshore, Jeffrey H. List Jan 1988

Long Wave Generation By Wave Groups In The Nearshore, Jeffrey H. List

Dissertations, Theses, and Masters Projects

This study investigates the forcing of leaky mode long wave by incident wave groups in the nearshore. Using both field and model data, two previously proposed generation models are evaluated: the bounded long wave of Longuet-Higgins and Stewart (1964), and the breakpoint-forced long wave of Symonds et al. (1982). New methods of parameterizing incident wave height modulations are proposed, including an amplitude time series and a clearly defined groupiness factor. Cross-correlations between observed amplitude and low frequency time series clearly document the release and shoreline reflection of a group-forced long wave. The shallow water amplification of the component identified as …

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Distribution And Taxonomy Of Endolithic Algae Occurring In The Shells Of Crassostrea Virginica Throughout The Lower James River, Virginia, Ellen Pafford Snyder Jan 1988

Distribution And Taxonomy Of Endolithic Algae Occurring In The Shells Of Crassostrea Virginica Throughout The Lower James River, Virginia, Ellen Pafford Snyder

Dissertations, Theses, and Masters Projects

No abstract provided.

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Response Of A Partially Mixed Coastal Plain Estuary To Storm Events, Daniel Ary Hepworth Jan 1988

Response Of A Partially Mixed Coastal Plain Estuary To Storm Events, Daniel Ary Hepworth

Dissertations, Theses, and Masters Projects

No abstract provided.

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The Effects Of At-Sea Killing And Storage Methods On The Quality Of Recreationally-Caught Northern Bluefin Tuna, Thynnus Thynnus, Nancy Jeanne Chartier Jan 1988

The Effects Of At-Sea Killing And Storage Methods On The Quality Of Recreationally-Caught Northern Bluefin Tuna, Thynnus Thynnus, Nancy Jeanne Chartier

Dissertations, Theses, and Masters Projects

No abstract provided.

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Swimming Responses Of Larvae Of Three Mactrid Bivalves To Different Salinity Gradients, Bernardita Campos Maia Jan 1988

Swimming Responses Of Larvae Of Three Mactrid Bivalves To Different Salinity Gradients, Bernardita Campos Maia

Dissertations, Theses, and Masters Projects

No abstract provided.

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Swash Induced Zonation Of A Foreshore Sediment Size Distribution, Mary Sue Jablonsky Moustafa Jan 1988

Swash Induced Zonation Of A Foreshore Sediment Size Distribution, Mary Sue Jablonsky Moustafa

Dissertations, Theses, and Masters Projects

No abstract provided.

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Assessing Environmental Stress On The Loggerhead Sea Turtle (Caretta Caretta) In Virginia Waters, Sarah A. Bellmund Jan 1988

Assessing Environmental Stress On The Loggerhead Sea Turtle (Caretta Caretta) In Virginia Waters, Sarah A. Bellmund

Dissertations, Theses, and Masters Projects

No abstract provided.

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An Assessment Of Tributyltin Contamination In Sediments And Shellfish In The Chesapeake Bay, Francois A. Espourteille Jan 1988

An Assessment Of Tributyltin Contamination In Sediments And Shellfish In The Chesapeake Bay, Francois A. Espourteille

Dissertations, Theses, and Masters Projects

No abstract provided.

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Seasonal Changes In Fecundity Of Oysters Crassostrea Virginica (Gmelin): From Four Oyster Reefs In The James River, Virginia, Carrollyn Cox Jan 1988

Seasonal Changes In Fecundity Of Oysters Crassostrea Virginica (Gmelin): From Four Oyster Reefs In The James River, Virginia, Carrollyn Cox

Dissertations, Theses, and Masters Projects

No abstract provided.

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Semantic Specification Using Tree Manipulation Languages, Randall Paul Meyer Jan 1988

Semantic Specification Using Tree Manipulation Languages, Randall Paul Meyer

Dissertations, Theses, and Masters Projects

Software tools are used to generate compilers automatically from formal descriptions of languages. Methods for specifying the syntax of languages are well-established and well-understood; however, methods for formal semantic specification are not. The method most commonly used for semantic specification is an attribute grammar.;This thesis examines an alternative method of semantic specification. TreeSem is defined as a Tree Manipulation Language applicable to semantic specification. A TreeSem program is easier to read and to write than a corresponding attribute grammar specification.;Algorithms for translation of a TreeSem program into an equivalent attribute grammar specification, and for translation of an attribute grammar specification …

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The Measurement Of Strong Interaction Effects In High-Z Sigma Hyperonic Atoms, William Clarke Phillips Jan 1988

The Measurement Of Strong Interaction Effects In High-Z Sigma Hyperonic Atoms, William Clarke Phillips

Dissertations, Theses, and Masters Projects

Strong-interaction effects have been observed in the X-ray spectra of atoms formed with {dollar}\Sigma\sp-{dollar} in lead and tungsten.;In the experiment, performed at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, negative kaons were brought to rest in a novel laminar target consisting of thin sheets of high-Z material in a liquid hydrogen bath. The geometry of the target was designed to optimize the production of high-Z {dollar}\Sigma\sp-{dollar} atoms and the detection of their subsequent de-excitation X rays. A method of identifying the energetic {dollar}\pi\sp+{dollar} from the production reaction K{dollar}\sp-{dollar}+ p {dollar}\to\Sigma\sp- +\pi\sp+{dollar} resulted in a factor of 15 improvement in …

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Statistically Constrained Decimation Of A Turbulence Model, Timothy Joe Williams Jan 1988

Statistically Constrained Decimation Of A Turbulence Model, Timothy Joe Williams

Dissertations, Theses, and Masters Projects

The constrained decimation scheme (CDS) is applied to a turbulence model. The CDS is a statistical turbulence theory formulated in 1985 by Robert Kraichnan; it seeks to correctly describe the statistical behavior of a system using only a small sample of the actual dynamics. The full set of dynamical quantities is partitioned into groups, within each of which the statistical properties must be uniform. Each statistical symmetry group is then decimated down to a small sample set of explicit dynamics. The statistical effects of the implicit dynamics outside the sample set are modelled by stochastic forces.;These forces are not totally …

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The Development And Application Of A Helium Discharge Detector For Gas Chromatography, Margaret Laverne Ware Jan 1988

The Development And Application Of A Helium Discharge Detector For Gas Chromatography, Margaret Laverne Ware

Dissertations, Theses, and Masters Projects

No abstract provided.

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