Physical Sciences and Mathematics Commons^™

Quantum Manifestations Of Bifurcations Of Classical Orbits: An Exactly Solvable Mode, Aaron D. Peters, Charles Jaffé, John B. Delos

Arts & Sciences Articles

We examine photodetachment of H− in parallel electric and magnetic fields, hν+H−→H+e− using semiclassical approximations. The fields cause the electron to return to the atom, producing recurrences that are visible as interference oscillations in the photodetachment cross section. As the energy is varied, new returning orbits are created through bifurcations. Each such new recurrence increases the complexity of the absorption spectrum, and each bifurcation causes a local failure of the semiclassical approximation. The failure is repaired by a Fresnel diffraction integral.

The Virginia Wetlands Report No. 94-9, Virginia Institute Of Marine Science, Center For Coastal Resources Management

Virginia Wetlands Reports

• Birds of the Eastern Shore. Julie G.Bradshaw

• Virginia’s Eastern Shore: Gone to the Birds. Jill Barnard

• VIMS Wetlands Education Program Notes. Maryann Wohlgemuth

• Bluefish. Lyle Varnell

• The Virginia Geographic Information Network (VGIN). Marcia Berman

• York River State Park. Pam Mason

• New Brochure Encourages “Green” Solutions to Shoreline Erosion. Jill Barnard

• Marsh Grass Planting: Shoreline Stability Without Structure. Walter I. Priest, III

Environmental Education Resources Directory : A Guide To Environmental Information And Educational Resources In Virginia, Department Of Environmental Quality, Commonwealth Of Virginia, Virginia Institute Of Marine Science

Reports

No abstract provided.

Water Quality Conditions In The Tidal Rappahannock River: Longitudinal And Dome Surveys In 1993, Kyeong Park, Albert Y. Kuo

Reports

Previous field surveys and modeling studies (Kuo et al. 1991; Park et al. 1993) indicated the presence of three different water quality regimes in the tidal Rappahannock River (Fig. 1), a western shore tributary of Chesapeake Bay: : Region I - hypoxic conditions during summer in the bottom water between km 0-55 : Region II - high chlorophyll concentration between km 80-147 : Region III - waste water discharges from sewage treatment plants To study the differences among these 3 reaches of the river, two types of field surveys were conducted during the summer of 1993: 1) longitudinal surveys in …

Status Of The Major Oyster Diseases In Virginia 1993 A Summary Of The Annual Monitoring Program, Eugene M. Burreson, Lisa M. Ragone Calvo

Reports

No abstract provided.

Wetland Mitigation, Megan Greiner, Virginia Institute Of Marine Science, Wetlands Program

Reports

No abstract provided.

The Virginia Wetlands Report No. 94-6, Virginia Institute Of Marine Science

Virginia Wetlands Reports

• Sea Ducks: Scoters and Oldsquaw. Julie G. Bradshaw
• Death on the Chesapeake Bay: The 1994 Avian Cholera Outbreak. Julie G. Bradshaw
• Wetlands Education Program Survey. Maryann Wohlgemuth
• Red Drum. Lyle Varnell
• Wetlands Management Symposium A Success. Tom Barnard
• Dismal Swamp National Wildlife Refuge (Part 2). Pam Mason
• Gabions. Walter I. Priest, III

Water Quality In Chesapeake Bay : Virginia Portion, Water Year 1993 : A Report To The Virginia Department Of Environmental Quality, Kevin Curling, Bruce Neilson

Reports

The Chesapeake Bay Water Quality Monitoring Program (WQMP) has three main objectives: (1) characterization of water quality conditions, (2) detection of temporal and spatial trends in water quality, and (3) creation of a data base that furthers our understanding of the processes that control water quality in the Chesapeake Bay system. The purpose of this report is to characterize water quality conditions in the Virginia portion of Chesapeake Bay during the 1993 water year, which runs from October 1992 through September 1993. These monitoring efforts have been conducted with funding from the US Environmental Protection Agency and the Commonwealth of …

York Estuary Sediments, Carl H. Hobbs Iii

Reports

This report presents the results of the analyses of a suite of sediment samples that was collected from the York River Estuary, including portions of the Mattaponi and Pamunkey Rivers. Samples from the York were taken in November, 1991, the Pamunkey in December, 1991, and Mattaponi in February, 1992. The intent of the project was to obtain an archive of "background" and "status" information on the bottom sediments of the system.

Tidal Propagation In Strongly Convergent Channels, Carl T. Friedrichs, David G. Aubrey

VIMS Articles

Simple first‐ and second‐order analytic solutions, which diverge markedly from classical views of cooscillating tides, are derived for tidal propagation in strongly convergent channels. Theoretical predictions compare well with observations from typical examples of shallow, “funnel‐shaped” tidal estuaries. A scaling of the governing equations appropriate to these channels indicates that at first order, gradients in cross‐sectional area dominate velocity gradients in the continuity equation and the friction term dominates acceleration in the momentum equation. Finite amplitude effects, velocity gradients due to wave propagation, and local acceleration enter the equations at second order. Applying this scaling, the first‐order governing equation becomes …

Transport Of Particles Across Continental Shelves, Ca Nittrouer, Ld Wright

VIMS Articles

Transport of particulate material across continental shelves is well demonstrated by the distributions on the seabed and in the water column of geological, chemical, or biological components, whose sources are found farther landward or farther seaward. This paper addresses passive (incapable of swimming) particles and their transport across (not necessarily off) continental shelves during high stands of sea level. Among the general factors that influence across-shelf transport are shelf geometry, latitudinal constraints, and the timescale of interest. Research studies have investigated the physical mechanisms of transport and have made quantitative estimates of mass flux across continental shelves. Important mechanisms include …

A Profile Of The Oyster Industry Northeastern United States, Douglas Lipton, James Kirkley

Reports

This is a critical period for the future of the east coast oyster industry. This report documents the dramatic decline in industry output which has been the impetus for a publicly funded program to "revtalize" the industry. Oyster biologists argue over the severityy of the decline and the cause, and also the potential remedies. Should non-native oysters, specifically Crassostrea gigas, be introduced into the region to replace the native oyster production? Are there ways to manage around the devastating oyster diseases MSX and Dermo? Will large populations of oysters significantly improve the water quality in currentiy degraded areas?

While these …

Resonances And Recurrences In The Absorption Spectrum Of An Atom In An Electric Field, J. Gao, John B. Delos

Arts & Sciences Articles

We use closed-orbit theory to study the absorption spectrum of an atom in an electric field. In previous work we examined absorption spectra above the zero-field ionization threshold. Only one closed orbit exists there, and it is unstable. Now we examine the situation below threshold. Here, the orbit parallel to the electric field is stable and, as the energy decreases, many other closed orbits bifurcate out of it. These closed orbits have simple patterns, and the associated recurrences are most clear if the absorption spectrum is measured using a scaled-variables method. The relation between the semiclassical Einstein-Brillouin-Keller-Marcus (EBKM) theory and …

Recurrence Spectroscopy: Observation And Interpretation Of Large-Scale Structure In The Absorption Spectra Of Atoms In Magnetic Fields, J. Main, G. Wiebusch, K. Welge, J. Shaw, John B. Delos

Arts & Sciences Articles

Measurements were made of the absorption spectrum of hydrogen atoms to levels near the ionization threshold in a strong magnetic field. Taking advantage of a classical scaling law, we varied the photon energy and the magnetic-field strength simultaneously, and measured absorption versus B−1/3 at fixed scaled energy, ɛ=E/(B/Bo)2/3. The absorption rate has sinusoidal fluctuations which are correlated with closed classical orbits of the electron. Fourier transformation of this signal gives peaks, which we interpret as ‘‘recurrence strength,’’ as a function of the classical action of the closed orbit. Closed-orbit theory gives formulas for these recurrence strengths. …

The Virginia Wetlands Report No. 94-2, Virginia Institute Of Marine Science

Virginia Wetlands Reports

• American Oystercatcher. Julie G. Bradshaw
• White Perch. Lyle Varnell
• Using Photography for Mapping. Marcia Berman
• Analysis of Functional Assessment Accuracy for Constructed Wetlands. M. Fox, Julie G. Bradshaw, and Jim Perry
• Habitat Restoration is Focus of Newly Formed Bay Program Workgroup. Carl Hershner
• Virginia Association of Wetlands Professionals.
• Dismal Swamp National Wildlife Refuge (Part 1). Pam Mason
• Bulkheading with Plastic.Walter I. Priest, III

General Methods For Analyzing Machine Learning Sample Complexity, Christoph Cornelius Michael

Dissertations, Theses, and Masters Projects

During the past decade, there has been a resurgence of interest in applying mathematical methods to problems in artificial intelligence. Much work has been done in the field of machine learning, but it is not always clear how the results of this research should be applied to practical problems. Our aim is to help bridge the gap between theory and practice by addressing the question: "If we are given a machine learning algorithm, how should we go about formally analyzing it?" as opposed to the usual question: "how do we write a learning algorithm we can analyze?".;We will consider algorithms …

Comparative Toxicity Of Creosote And Creosote Contaminated Sediments, Padma T. Venkatraman

Dissertations, Theses, and Masters Projects

No abstract provided.

In Vitro And In Vivo Effects Of Chemotherapeutants On The Oyster Parasite, Perkinsus Marinus, Gustavo W. Calvo

Dissertations, Theses, and Masters Projects

To investigate the potential of chemotherapeutants to control the oyster pathogen Perkinsus marinus, anticoccidial and antifungal compounds were tested in vitro on infected hemolymph and cultured P. marinus cells and in vivo on infected oysters. In addition, acute toxicity to oysters was determined for six anticoccidials. In vitro experiments with infected hemolymph consisted of 24 h exposure of 0.2 mL hemolymph aliquots to concentrations ranging from 100 mg/L to 0.01 mg/L of amphotericin-B, amprolium, arprinocid, cycloheximide, lasalocid, malachite green, monensin, sulfadimethoxine, and a potentiated sulfadimethoxine, followed by incubation in fluid thioglycollate medium (FTM) to determine prezoosporangia abundance. Lasalocid, malachite green, …

Deuteron Nuclear Magnetic Resonance Studies Of Molecular Motion In Solids, Tak Yan Tse

Dissertations, Theses, and Masters Projects

$\sp2$H-NMR is a powerful spectroscopic technique for investigating dynamics in solids. to extend the range of motional rates that can be quantitatively investigated, a new approach for measuring the quadrupolar spin-lattice relaxation time $T\sb{1Q}$ was developed. This uses a Broadband Jeener-Broekaert (BBJB) sequence with echo-detection, which avoids the frequency-discriminated excitation profile and spectral baseline distortion intrinsic to the conventional Jeener-Broekaert (JB) experiment. By combining the BBJB experiment with an Inversion-Recovery sequence with Quadrupole-Echo detection (IRQE), two independent longitudinal relaxation times, $T\sb{1Q}$ and $T\sb{1Z}$, can be measured. Spectral densities of motion $J\sb1(\omega\sb{o}$) and $J\sb2(2\omega\sb{o}$) are extracted from these relaxation times. The …

Inverse Estimation Of Horizontal Pressure Gradients And Vertical Eddy Viscosity Profiles In Shallow Waters, Bohyun Bang

Dissertations, Theses, and Masters Projects

A least-squares inverse method was devised to estimate horizontal pressure gradients and vertical eddy-viscosity profiles simultaneously, from current profiles. The method was designed mostly for observations of deterministic or near-deterministic wave currents. Tidal-current observations were chosen for the present study. The inverse system was constructed from a linearized momentum equation. The viscosity was modeled with a time-constant and harmonic function in time, but without its vertical structure predefined. The least-squares problem was solved with the singular value decomposition, by taking current harmonic profiles as input. at first, the method was tested with current profiles simulated by a numerical model employing …

Characterization And Modeling Of Amino Epoxide Resins, Maria Anastasia Argiriadi

Dissertations, Theses, and Masters Projects

No abstract provided.

Global Phylogeography Of Yellowfin Tuna, Thunnus Albacares, And Mackerels Of The Genus Scomber, Daniel R. Scoles

Dissertations, Theses, and Masters Projects

Intraspecific genetic relationships within yellowfin tuna, Thunnus albacares, and three mackerels of the genus Scomber were studied by restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA). The comparison of these scombrids, with different larval distributions, adult distributions, and vagilities, served to investigate the hypothesis that population structure in marine fishes results from geographic and physical oceanographic processes that limit dispersal of early life history stages. Samples of 20 yellowfin tuna were examined from each of five Pacific locations and one Atlantic location. MtDNA analysis with 12 informative restriction endonucleases demonstrated considerable genetic variation, as evidenced by overall nucleon …

Food, Feeding, And Length-Weight Relationships Of Young-Of-The-Year Striped Bass, Morone Saxatilis And Young-Of-The-Year White Perch, Morone Americana, Paul J. Rudershausen

Dissertations, Theses, and Masters Projects

No abstract provided.

The Role Of Predation On Zostera Marina L (Eelgrass) Seed Abundance, James Fishman

Dissertations, Theses, and Masters Projects

No abstract provided.

Toxicity Resistance In Mummichog (Fundulus Heteroclitus) From A Chemically Contaminated Environment, Cynthia A. H. Williams

Dissertations, Theses, and Masters Projects

No abstract provided.

A Gis Spatial Analysis Of The Potential Conflict Between Submerged Aquatic Vegetation Management And The Development Of Shellfish Aquaculture In The Lower Chesapeake Bay, Laura Ann Grignano

Dissertations, Theses, and Masters Projects

No abstract provided.

Predation On Juvenile Blue Crabs, Callinectes Sapidus Rathbun, In Lower Chesapeake Bay: Patterns, Predators, And Potential Impacts, Kirt E. Moody

Dissertations, Theses, and Masters Projects

Various investigations of the population dynamics of blue crabs in Chesapeake Bay indicate that predator-induced mortality in the juvenile phase may determine year-class strength. In a tethering study, which spanned three seasons in shallow-water habitats of the lower York River, daily mortality rates of juvenile crabs were measured across three variables: crab size (30-70 mm carapace width), habitat type (seagrass, mud, and sand), and month (May-November). Vulnerability to predation was consistently lower for larger crabs, approaching a size refuge from predation at approximately 90 mm carapace width. Predation was most intense in unvegetated sand habitats, and significantly lower in seagrass …

Investigations Into Cataract Formation In Sciaenid Fish Species From The Elizabeth River, Chesapeake Bay, Virginia, Christopher D. Williams

Dissertations, Theses, and Masters Projects

Cataract formation in the Elizabeth River (ER) has been reported since 1986. Previous studies have concentrated on describing cataract as a function of exposure to polluted sediments, especially polycyclic aromatic hydrocarbons (PAH). These studies, however, have not examined what processes might be involved in fish cataractogenesis. The overall objective of this research was to identify important processes associated with the early development of cataract in feral fish populations. Field studies were used to systematically examine cataract development. Cataract in sciaenids was not associated with previously described cataractogenic factors, but could be linked to contaminated sediments of the ER. Cataract was …

Correlation Between Electron Capture Negative Chemical Ionization Mass Spectrometric Fragmentation And Calculated Internal Energies For Polychlorinated Biphenyls, John Greaves, Ellen Harvey, William G. Macintyre

VIMS Articles

Correlations between molecular structure and fragmentation observed in electron capture negative chemical ionization mass spectra (moderator gas = methane) of 49 selected tetrachlorinated, pentachlorinated, and hexachlorinated biphenyls have been investigated by using molecular modeling. The semiempirical general molecular orbital program MOPAC was used to calculate molecular properties for biphenyl and the 209 polychlorinated biphenyls. The mass spectrometric ionization and fragmentation processes were found to be linked to the number of chlorine atoms present on the biphenyl, and to the number of those chlorine atoms in the ortho (2, 2', 6, and 6') positions. The intensity of molecular ions increased with …

Directional Wave Spectra Using An Acoustic Doppler Current Profiler, William T. Stockhausen

Dissertations, Theses, and Masters Projects

No abstract provided.