Physical Sciences and Mathematics Commons^™

Polycyclic Aromatic Hydrocarbon (Pah) Distributions Within Urban Estuarine Sediments, Siddhartha Mitra

Dissertations, Theses, and Masters Projects

Sediments and pore waters from two urban estuaries ranging in sediment mixing energy were studied to evaluate the potential release of contaminants from particles during sediment diagenesis. Two sites in Elizabeth River, VA and two tributaries in the Hudson River Watershed were sampled for polycyclic aromatic hydrocarbons (PAHs). Sediment age, total sediment organic carbon (TOC), carbon to nitrogen (C/N) ratios, and particle surface area (SA) were also sampled at these sites. In the Elizabeth River, both sites sampled (Site 1 and Site 2) have been non-depositional for the past 70 y or are comprised of old dredge spoil. PAH K&\sp\prime\sb{lcub}\rm …

The Synthesis Of Reflective And Electrically Conductive Polyimide Films Via An In Situ Self-Metallization Procedure Using Silver(I) Complexes, Robin Elaine Southward

Dissertations, Theses, and Masters Projects

Optically reflective polyimide films have been prepared by the incorporation of silver(I) acetate and a {dollar}\beta{dollar}-diketone solubilizing agent, hexafluoroacetylacetone (HFAH), into a dimethylacetamide solution of the poly(amic acid) formed from {dollar}3,3\sp\prime,4,4\sp\prime{dollar}-benzophenonetetracarboxylic acid dianhydride (BTDA) and {dollar}4,4\sp\prime{dollar}-oxydianiline {dollar}(4,4\sp\prime{dollar}-ODA). Optically reflective and conductive polyimide films have been prepared by replacing the {dollar}\beta{dollar}-diketone (HFAH), with the less substituted {dollar}\beta{dollar}-diketone, trifluoroacetylacetone (TFAH). The former system has been both cast directly from the poly(amic acid) resin and cast from the poly(amic acid) resin onto a fully imidized {dollar}\rm BTDA/4,4\sp\prime{dollar}-ODA base (forming a metallized topcoat). Thermal curing of the silver(I)-containing poly(amic acid) leads to imidization with …

Development Of Monitoring Protocol For Created Wetlands : Project Summary For 1997, James E. Perry

Reports

Appx. 1. Annotated bibliography -- Appx. 2. Field data sheet - Appx. 3.Monitoring protocol manual for created wetlands: draft manual.

The Synthesis Of 6a,6b-Dideoxy-6 A,6b-(9,10-Dicyanoanthracenyl-2,3-Dimethylene)-Beta-Cyclodextrin, Jonathan D. Tan

Dissertations, Theses, and Masters Projects

No abstract provided.

Collision-Induced Secondary Electron And Negative Ion Emission From Metallic Surfaces, John Christopher Tucek

Dissertations, Theses, and Masters Projects

Absolute yields of negative ions and secondary electrons resulting from collisions of positive sodium ions (Na{dollar}\sp{lcub}+{rcub}){dollar} with polycrystalline aluminum (Al) and molybdenum (Mo) surfaces and the Mo (100) surface have been measured as a function of the oxygen (O) coverage, from none up to several monolayers, for impact energies, E {dollar}<{dollar} 500 eV. Negative oxygen ions (O{dollar}\sp{lcub}-{rcub}){dollar} are found to be the dominant sputtered negative ions and for the three surfaces at all O coverages and Na{dollar}\sp{lcub}+{rcub}{dollar} impact energies. The O{dollar}\sp{lcub}-{rcub}{dollar} and secondary electron yields share a common impact energy threshold at {dollar}\rm E\sb{lcub}th{rcub}\approx 50{dollar} eV, and both have a strong dependence on the oxygen coverage of the surface.;The kinetic energy distributions of the secondary electrons and sputtered O{dollar}\sp{lcub}-{rcub}{dollar} were determined as functions of O coverages and impact energies. The O{dollar}\sp{lcub}-{rcub}{dollar} distributions are characterized by a narrow, low energy peak (at {dollar}\sim{dollar}1-2 eV) followed by a low level, high energy tail. The secondary electrons have a narrow (FWHM {dollar}\sim{dollar} 1-2 eV) kinetic energy distribution, centered essentially at the same most probable kinetic energy as the ions. The shapes of the respective distributions and the most probable kinetic energies are essentially invariant with the impact energy, O coverage and the metal surface.;The results were analyzed in terms of conventional collision cascade model, but the calculation could not be fitted to the experimental results. An electronic excitation mechanism is proposed to augment the collision cascade and to provide a mechanism for secondary electron emission. In the model, adsorbed O, which resides on the surface essentially as O{dollar}\sp{lcub}-{rcub},{dollar} is collisionally excited into an (MO{dollar}\sp{lcub}-{rcub})\sp*{dollar} repulsive state, and as the O{dollar}\sp{lcub}-{rcub}{dollar} exits the surface along the surface potential energy curve, it can decay by emission of an electron to the metal or to the vacuum, or it can survive as an ion. The parameters of this model can be adjusted such that the calculated kinetic energy distribution, together with that of the collision cascade, can reasonably reproduce the experimental observations for the ions and provide a reasonable fit to the corresponding electron kinetic energy distributions as well.

Thermal Lattice Boltzmann Simulations Of Variable Prandtl Number Turbulent Flow, Min Soe

Dissertations, Theses, and Masters Projects

With the advent of massively parallel processor machines, thermal lattice Boltzmann equation (TLBE) techniques offer an attractive way of handling turbulence simulations. TLBE is new form of DNS (direct numerical simulation method)--with the important advantages of being ideal for multi-parallel processors as well as being able to handle complicated geometries. Since there are many kinetic models that will reproduce the macroscopic nonlinear (compressible) transport equations, TLBE chooses that subset which can be readily solved on a discrete spatial lattice. The lattice geometry must be so chosen that the discrete phase representation of TLBE will not taint the rotational symmetric continuum …

Body Burden Of Polycyclic Aromatic Hydrocarbons And Tributyltin In Hard Clams, Mercenaria Mercenaria From The Elizabeth River, Va, Morris H. Roberts, Michael A. Unger

Reports

The Elizabeth River, contaminated with PAH, TBT, and heavy metals, is potentially home to a variety of estuarine invertebrates of commercial importance, notably oysters, hard clams, and crabs. Harvestable oysters have virtually disappeared from the system, but it has been rumored among commercial fishermen that a population of small (little neck to cherrystone) hard clams (Mercenaria mercenaria) exists within the Elizabeth River system. These clams are of serious interest to commercial clammers in the area as a previously unharvested source of market-size clams. Crabs of a harvestable size are also reasonably abundant throughout this river according to local fishermen.

The …

Distribution Of Freshwater Amphipoda In The Lake Matoaka/College Woods Area, Williamsburg, Virginia, Susan Alexandra Mahon

Dissertations, Theses, and Masters Projects

No abstract provided.

Characterization Of Epoxy-Amine Systems And Nylon-11 And Pvdf Degradation, Wendy Raquel Mahler

Dissertations, Theses, and Masters Projects

No abstract provided.

The Influence Of Microstructure On The Thermal Degradation Behavior Of Poly(Vinyl Chloride), Hoang Vi Tran

Dissertations, Theses, and Masters Projects

No abstract provided.

The Synthesis Of Benzophenone-3,5-Diacid Chloride For The Double Capping Of Beta-Cyclodextrin, Clyde Wesley Eargle

Dissertations, Theses, and Masters Projects

No abstract provided.

Microstructural Characterization Of An Ultra-High-Performance Polyimide, April Heather Baugher

Dissertations, Theses, and Masters Projects

The motivation for this study was to further characterize a relatively new high-temperature polymer for application as a matrix resin for carbon fiber composites. The two primary questions addressed in this study dealt with the structural and chemical changes occurring in these polymers on exposure to high temperature.;To investigate the structural changes in the heat-treated samples, a positron annihilation lifetime spectrometer was designed, built and optimized. Because the lifetime of a positron in a material reflects the electronic structure of the material in which it annihilates, measurements by positron annihilation lifetime spectroscopy can be used to investigate changes in a …

Radiation-Induced Luminescence In Terbium-Doped Silicate Glasses, Michael Stuart West

Dissertations, Theses, and Masters Projects

The purpose of this study is to characterize radiation-induced luminescence of terbium-doped silicate glasses. Experiments performed investigated the optical properties, isothermal time-evolution, and temperature dependence of the radiation-induced luminescence of two commercially available terbium-doped glasses. A problem common to this type of glass is the persistent luminescence, or afterglow, that occurs following the end of excitation from an external source of radiation. While the processes that govern characteristic luminescence of rare earth ions, including terbium, are well understood, the processes that give rise to afterglow in doped glasses are not. Identifying the source of long-term luminescence is essential for controlling …

Global State Predicates In Rough Real-Time, Jean Ann Mayo

Dissertations, Theses, and Masters Projects

Distributed systems are characterized by the fact that the constituent processes have neither common memory nor a common system clock. These processes communicate solely via message passing. While providing a number of benefits such as increased reliability, increased computational power, and geographic dispersion, this architecture significantly complicates many of the tasks of software development and verification, including evaluation of the program state. In the case of distributed systems, the program state is comprised of the local states of the constituent processes, as well as the state of the channels between processes, and is called the global state.;With no common system …

Cp Violation In K-Long Decays, Gregory Dominick Dorata

Dissertations, Theses, and Masters Projects

The main topic of this dissertation concerns alternative models of CP violation and the rates predicted by these models for the particular decay {dollar}K\sb{lcub}L{rcub}\to\pi\sp0\nu\bar\nu .{dollar} This decay is promising as a probe of the origin of CP violation in the kaon system. It is virtually free of hadronic uncertainties and its branching ratio would (along with a measurement of the CP asymmetry in {dollar}B\sbsp{lcub}d{rcub}{lcub}0{rcub}\to\psi K\sb{lcub}S{rcub}){dollar} allow a determination of all the elements of the CKM matrix (assuming all CP violation arises from the CKM matrix).;The first group of models of CP violation considered consists of three extensions of the Higgs …

Propagation Of Rayleigh Waves In Thin Films, Agus A. Ananda

Dissertations, Theses, and Masters Projects

With the advent of thin film technology and more recently its applications in microelectronics and control of surface properties, the interest in mechanical properties of thin films has grown tremendously. Mechanical defects such as creep, fracture and adhesion loss, play a very important role in physical instabilities of thin film materials. An acoustic microscope has been built to study mechanical properties of thin-films. The microscope operates at a nominal frequency of 50 MHz. Rayleigh surface waves velocities on the surface of film-substrate systems were measured from V(z) curves generated by the acoustic microscope. V(z) curves are produced from interference between …

The Synthesis, Characterization, And Molecular Modeling Of Cyclic Arylene Ether Oligomers, Sheeba Ahmed

Dissertations, Theses, and Masters Projects

Cyclophanes are a family of bridged cyclic aromatic compounds that have found extensive applications in host-guest chemistry, molecular recognition, biomimetics and most recently as precursors in ring-opening polymerizations.;This research presents the synthesis of several novel cyclic arylene ether oligomers, based on 1,3-bis(4-fluorobenzoyl) benzene and 3,3{dollar}\sp\prime{dollar}-methylene diphenol and 3,3{dollar}\sp\prime{dollar}-(ethylene dioxy) diphenol, and their characterization by LC-MS/MS, 1-D {dollar}\sp1{dollar}H-NMR and x-ray crystallography. Electrospray ionization (ES) along with MS/MS was used to characterize cyclic oligomers of molecular weight up to 1600 Da. The thermal properties of these cyclic oligomers were studied by differential scanning calorimetery (DSC) and thermal gravimetric analysis (TGA).;These cyclic oligomers …

A Study Of Poly(Vinyl Chloride) Microstructure, Vadim Guennadievich Zaikov

Dissertations, Theses, and Masters Projects

High-field {dollar}\sp{lcub}13{rcub}{dollar}C and {dollar}\sp1{dollar}H NMR spectroscopies were used to investigate some unusual features of the molecular microstructure of poly(vinyl chloride) (PVC).;Several model monochloroalkenes were synthesized in order to determine {dollar}\sp{lcub}13{rcub}{dollar}C shift increments for the replacement of H by Cl at positions that are near an isolated internal double bond. These increments then were used to predict the {dollar}\sp{lcub}13{rcub}{dollar}C shifts of the internal allylic chloride structure in PVC. The predictions were not satisfactory, because, as expected, the increments were not additive.;It was shown that during conventional VC polymerization, the chloroallylic chain end (-CH{dollar}\sb2{dollar}CH=CHCH{dollar}\sb2{dollar}Cl) does not copolymerize with the monomer and is …

Discrete-Time Linear And Nonlinear Aerodynamic Impulse Responses For Efficient Cfd Analyses, Walter A. Silva

Dissertations, Theses, and Masters Projects

This dissertation discusses the mathematical existence and the numerical identification of linear and nonlinear aerodynamic impulse response functions. Differences between continuous-time and discrete-time system theories, which permit the identification and efficient use of these functions, will be detailed. Important input/output definitions and the concept of linear and nonlinear systems with memory will also be discussed. It will be shown that indicial (step or steady) responses (such as Wagner's function), forced harmonic responses (such as Theodorsen's function or those from doublet lattice theory), and responses to random inputs (such as gusts) can all be obtained from an aerodynamic impulse response function. …

Winter/Spring Steady-State Water Balances For A Palustrine Forested Wetland Located In Southeastern Virginia, Daniel Otis Redgate

Dissertations, Theses, and Masters Projects

No abstract provided.

Effects Of Spot (Leisostomus Xanthurus) Induced Bioturbation And Suspension On The Transport And Fate Of Sediments And A Particle-Associated Organic Contaminant, Michele A. Horvath

Dissertations, Theses, and Masters Projects

No abstract provided.

New Data On Ichthyoplankton Of The Southwestern Pacific, Andrei V. Suntsov

Dissertations, Theses, and Masters Projects

No abstract provided.

Analysis Of Mercury Coordination Environments Of Tridentate And Tetradentate Nitrogen Based Ligands By Nmr Spectroscopy And X-Ray Crystallography, Rachel E. Freer

Dissertations, Theses, and Masters Projects

No abstract provided.

The Thermal Cure Of Phenylethynyl-Terminated Polyimides And Selected Model Compounds, Karen H. Wood

Dissertations, Theses, and Masters Projects

The ability to process high performance polymers into useful adhesives and high quality composites has been significantly advanced by synthetic techniques in which oligomers terminated with reactive groups cure or crosslink at elevated temperature after the article has been fabricated. Several matrix resin systems of considerable interest to the aerospace community utilize phenylethynyl terminated imide (PETI) technology developed at the Langley Research Center to achieve this advantage. This work addresses the cure chemistry of PETI oligomers.;The thermal cure of selected oligomers and model compounds was studied using a variety of analytical techniques including differential scanning calorimetry, high pressure liquid chromatography, …

Solar Infrared Relative Intensity Data From The Halogen Occultation Experiment, Philip Todd Spickler

Dissertations, Theses, and Masters Projects

Solar data from the Halogen Occultation Experiment (HALOE) were analyzed to determine the center-to-limb relative intensity and the vertical temperature profile for the quiet and active Sun over wavelengths from 2.4 to 10 {dollar}\mu{dollar}m. An algorithm that incorporated a nonlinear least squares procedure was developed that modeled the HALOE instrument during data acquisition. Data obtained from limb-to-limb scans along the solar equator on days of very low activity in May 1994 were analyzed to obtain coefficients of a function describing the relative intensity from center to limb. The relative intensities produced were precise to 0.1% (2{dollar}\sigma{dollar}) from the center to …

Spatial, Geostatistical, And Fractal Measures Of Seafloor Microtopography Across The Eel River Shelf, Off Northern California, George Randall. Cutter

Dissertations, Theses, and Masters Projects

No abstract provided.

Storm Surges In The Region Of Western Alaska, Warren Blier, Stanley Keefe, Wilson A. Shaffer, Sung C. Kim

VIMS Articles

Within the period of the historical record there have been several occurrences of extensive damage from storm-surge-related coastal flooding in the region of Nome, Alaska. The most recent of these events, although by no means the most destructive, occurred in association with the storm of 5–6 October 1992. Despite the small population of Nome (approximately 4000 people), total damage costs exceeded $6 million.

The research into the nature and causes of such flooding events has focused on this October 1992 case. The authors have, however, also examined a weaker, shorter-duration event that occurred on 20 August 1993 and, for contrast, …

Trophic Effects Of Sponge Feeding Within Lake Baikal's Littoral Zone .2. Sponge Abundance, Diet, Feeding Efficiency, And Carbon Flux, Aj Pile, Mark R. Patterson, M. Savarese, V I. Chernykh, V A. Fialkov

VIMS Articles

Endemic freshwater demosponges in the littoral zone of Lake Baikal, Russia, dominate the benthic biomass, covering 44% of the benthos. We measured in situ sponge abundance and,orating and calculated sponge-mediated Fluxes of picoplankton (plankton <2 mu m) for two common species, Baikalospongia intermedia and Baikalospongia bacillifera. By means of dual-beam how cytometry, we found retention efficiencies ranging from 58 to 99% for four types of picoplankton: heterotrophic bacteria, Synechococcus-type cyanobacteria, autotrophic picoplankton with one chloroplast, and autotrophic picoplankton with two chloroplasts. By using a general model for organism-mediated fluxes, we conservatively estimate that through active suspension feeding, sponges are a sink for 1.97 g C d(-1) m(-1), mostly from procaryotic cell types. Furthermore, grazing by these extensive sponge communities can create a layer of picoplankton-depleted water overlying the benthic community in this unique lake.

Virginia's Commercial Fishing Industry: Its Economic Performance And Contributions, James Kirkley

Reports

No abstract provided.

Virginia Game Fish Tagging Program Annual Report 1996, Cm Bain Iii, John A. Lucy

Reports

The Virginia Game Fish Tagging Program (VGFfP), a cooperative project of the Virginia Marine Resources Commission and the Virginia Institute of Marine Science (VIMS), enjoyed its second full year of operation in 1996. Participation in the project, which is funded with revenues generated by Virginia's saltwater recreational fishing license, nearly doubled with 127 anglers volunteering as taggers compared to 64 in 1995.