Physical Sciences and Mathematics Commons^™

Gas Permeation Measurements On Small Polymer Specimens, Karen S. Burns

Chemistry & Biochemistry Theses & Dissertations

Mass spectrometry was used to measure oxygen and nitrogen permeabilities while polarography was used to measure oxygen permeabilities for several contact lens materials. Applicable sample holders were designed and fabricated to accommodate curved and flat specimens with surface areas of 0.5 cm² and 1.0 cm² and thicknesses between 0.025 mm and 0.500 mm. A prepared standard was used to calibrate the mass spectrometric analyses.

The oxygen permeability values determined by mass spectrometry were significantly greater than those determined by polarography. This was attributed to the phase boundary phenomena and the limiting oxygen permeance of water inherent in the …

Sediment Budgets And Shoreline Dynamics Cape Henry, Virginia, Marcia R. Berman

OES Theses and Dissertations

Analysis of 1183 beach profiles from Cape Henry, Virginia indicated that the recession-erosion ''rule" established by the Army Corps of Engineers underestimates the short-term response of the shoreline to changes in sediment volume.

Correlation between bi-weekly backshore volume change and the change in high water line (HWL) position was stronger (0.67 < r < 0.88) than correlation between bi-weekly total volume change and the change in mean low water (MLW) shoreline position (0.33 < r < 0.52). The short-term change in position of MLW is influenced by minor features such as bars. The position of the HWL is controlled by volume change at the backshore.

Correlation between change in HWL and MLW shoreline positions improved from r = 0.01 tor·= 0.67 for intervals of two weeks to two years, respectively. This suggests parallel-shore retreat only may be operable for greater than two-year periods.

A Study Of Flow Separation In Transonic Flow Using Inviscid And Viscous Cfd Schemes, James Andrew Rhodes

Mechanical & Aerospace Engineering Theses & Dissertations

A comparison of flow separation in transonic flows is made using various computational schemes which solve the Euler and the Navier-Stokes equations of fluid mechanics. The flows examined are computed using several simple two-dimensional configurations including a backward facing step and a bump in a channel. Comparison of the results obtained using shock fitting and flux vector splitting methods are presented and the results obtained using the Euler codes are compared to results on the same configurations using a code which solves the Navier-Stokes equations.

Phytoplankton Dynamics In The Very Low Salinity Region Of The James River Estuary, Virginia, U.S.A., Changho Moon

OES Theses and Dissertations

During summer and autumn discharge from the James River estuary, Virginia, was less than 120 _m³sec^-1. There was a peak phytoplankton biomass in the very low salinity region (defined as the location where surface salinity measured less than 0.5$ 0/00) and this peak represented five to ten times greater biomass than adjacent waters. The peak biomass occurred independent of the tidal state and the location of nutrient inputs. It disappeared during winter and spring, and nutrient limitation was not responsible for the low phytoplankton biomass, indicating there were physical, not chemical controlling factors.

The peak biomass …

Sulfide In Shelf/Slope Waters Of The Western Atlantic, Christian F. Krahforst

OES Theses and Dissertations

Sulfide in the surface ocean has been recently considered as a source of hydrogen sulfide gas in the marine boundary layer. This "oxic" sulfide may also be important as a ligand in trace metal complexation. In the absence of actual data, the existence of sulfide in the ocean mixed layer remains speculative. The purpose of this study was to develop a sensitive technique (having picomolar detection limits) for the determination of sulfide in seawater, and to investigate the distribution of sulfide in the surface ocean.

In order to assess the abundance and distribution of sulfide in surface waters, samples were …

Investigation Of Complex Formation By Oligomers Of Cytosine And Guanosine, Steven Roberts Davis

Chemistry & Biochemistry Theses & Dissertations

Duplex formation between oligo(C:G) _n where n=3 to 4 was shown not to occur under conditions favorable for duplex formation between poly G and poly C. Instead, a stable guano sine self-structure was found to form which a T_m of 50°C for (Gp)₃ and 80°C for (Gp)₄ at strand concentrations of 10^-5M in 1M NaCl. Neither a duplex nor a self-structure formed in the absence of salt.

Oligomers of guanosine and cytosine were obtained by basic hydrolysis and separated according to chain length using DEAE Sephadex column chromatography. Separation of cytosine oligomers with chain lengths …

Discrimination Of Subparallel Beach Ridges Using Detrital Ilmenite Composition And Fourier Shape Analysis, Allen E. Evans Jr.

OES Theses and Dissertations

Elemental composition (Fe, Ti, Mn, Mg, V, Cu, Ni, Zn, and Cr) and Fourier shape analysis of magnetically separated detrital ilmenite from seven Pleistocene and modern beach sand deposits of the Southeastern Virginia Coastal Plain were used to distinguish each deposit. Geomorphic expression, crosscutting relationships and proximity to the present shoreline differentiates the relative age of the seven sampled beach deposits. Analysis of ilmenite elemental composition, independent of geomorphic expression, distinguished beach sands of

different age and was successful in determining that each beach contained ilmenite similar in composition. Of the seven beach ridges tested, subtle yet significant differences in …

Molting In The Mature Female Blue Crab, Callinectes Sapidus, Rathbun, Kirk J. Havens

OES Theses and Dissertations

The present study examines the hypothesis that mature female blue crabs, Callinectes sapidus, do not have a terminal anecdysis. Induced molting via eyestalk ablation, size frequency distributions and gonad and limb regeneration indices from field collected animals are used as indicators of potential post maturity molts.

Eyestalk ablation of mature females resulted in ecdysis approximately 51 days after ablation, indicating a physiological ability if mature females to complete ecdysis. Analysis of size frequency distributions indicates two distinct shifts from smaller to larger females, one in early spring and a second in early fall. While migration of larger females into …

Large Deviation Local Limit Theorems For Ratio Statistics, Sanjeev V. Sabnis

Mathematics & Statistics Theses & Dissertations

Let {T„, n > 1} be an arbitrary sequence of non-lattice random variables and {S_n, n > 1} be another sequence of positive non-lattice random variables. Let the two sequences be independent. Let Ø_1n and Ø_2n be the moment genereating functions of {Tn, n > 1} and { S_n,n > 1} respectively. Let {a_n} be a sequence of real numbers such that a_n —»• oo.

Cross-Shore Sediment Transport In Relation To Waves And Currents In A Groin Compartment, Hyo Jin Kang

OES Theses and Dissertations

In nearshore areas waves are generally irregular, and the irregular wave-induced currents have different peak velocities (magnitude asymmetry) and durations (duration asymmetry) between forward and backward motions. These asymmetries may produce a net cross-shore sediment transport in one direction. The sediment transport mostly occurs as bedload where the waves are non-breaking.

Sediment transport on a sloping bed is also affected by gravity, and accordingly the Shields parameter should be re-evaluated for a grain on a sloping bed. It was also found that the affect of a steady current that interacts nonlinearly with the waves was important for the cross-shore sediment …

Synthesis Of Potential Long Acting Calcium Channel Antagonists: A Study Of 1,4-Dihydropyridine Analogs, Thomas E. Christos

Chemistry & Biochemistry Theses & Dissertations

An investigation was undertaken to synthesize and evaluate longer acting analogs to the antihypertensive agent nifedipine. Analogs that are capable of covalent bonding to the nifedipine receptor were considered. These compounds may show increased activity as they will remain at the receptor for a longer period of time.

During the course of this study, previously unreported and unexpected products were encountered and lead to a more intense examination of the Hantzsch synthesis. Of particular interest was the oxazolidine 25 which was a major component of the Hantzsch synthesis when ethanolamine was used instead of ammonium hydroxide. Also isolated during this …

Analysis Of Phytoplankton And Particle Variability At A Warm Core Ring/Shelf Break Front Using Flow Cytometry, Kimberly G. Davis

OES Theses and Dissertations

Particle variability at a Gulf Stream warm core ring/ shelf break front on 09 Nay 1985 was analyzed. Single particle measurements of fluorescence, perpendicular light scatter, and volume were made using a FACS Analyzer flow cytometer. Advantages and disadvantages of at-sea use of the instrument are described. To evaluate the flow cytometry data, individual particle data were compared with bulk phytoplankton and particle measurements. Abundance and size distributions of fluorescent and non-fluorescent particles indicated a convergence zone at the front while upwelling was likely within the ring perimeter. Variability in fluorescence (approximating chlorophyll A) and cell biovolume exposed regions of …

Growth Potential Of Young Black Sea Bass, Centropristis Striata, In Artificial Environments, Joung Won Kim

OES Theses and Dissertations

The growth potential of the commercially important marine finfish, black sea bass (Centropristis striata), was examined for aquaculture under controlled conditions. The effect of food and body weight on growth was evaluated using juveniles and young black sea bass cultured with a natural diet and a commercial diet at various feeding levels.

Growth was affected by type of food, food consumption rate, and fish body weight. For fish having positive weight gain, absolute growth rate (gram/day) increased exponentially as food consumption rate (percent of body weight per day) and/or body weight increased. Instantaneous growth rate (percent of body weight per …

The Geochemistry Of Selenium And Sulfur In A Coastal Salt Marsh, David Jay Velinsky

OES Theses and Dissertations

Investigation of the various chemical forms of selenium and sulfur in sediments and pore waters can provide information about various oxidation/reduction processes. Five cores were obtained from the Great Marsh, from April 1985 to June 1986. Sampling times coincided with the seasonal redox cycle known to occur within the marsh system. Sediments were analyzed for various selenium and sulfur phases.

Iron monosulfides and elemental sulfur both display large seasonal changes in concentration and distribution with depth, indicating a coupling with redox conditions. In contrast, the depth distribution of greigite did not show appreciable changes with season. Pyrite underwent large concentration …

An Annual Study Of Phytoplankton Composition And Associated Environmental Conditions Of Lake Trashmore, Virginia Beach, Virginia, Seba B. Sheavly

Biological Sciences Theses & Dissertations

A 12 month study of Lake Trashmore was conducted on phytoplankton composition, inorganic nutrients and their seasonal associations. The dominant phytoplankton groups observed were diatoms, chlorophyceans and cyanobacteria. Phytoplankton assemblage patterns were coupled with pH, temperature, dissolved oxygen, nitrites and silicates. Diatoms dominated during periods of high nutrient concentrations, cooler temperatures and an unstable water column. Cyanobacteria forms dominated during periods of warmer temperatures, higher pH and decreased nitrogen and dissolved oxygen concentrations. A seasonal community shift occurred from cyanobacterial dominance to chlorophycean dominance when pH levels decreased. The lake is eutrophic based on indices of chlorophyll a concentrations, transparency …

Reactions Of Organic N-Chloramines In The Gastric Fluid Of The Rat, Kathryn E. Mazina

Chemistry & Biochemistry Theses & Dissertations

Using chlorine as a drinking water disinfectant may have potential health effects due to its reactivity with organic amino nitrogen compounds found in the stomach. Organic N-chloramines have been shown to form in the stomachs of laboratory rats. The possible reactions of N-chloramines in the stomach fluid were examined in this study using a model radiolabeled N-chloramine. ³⁶Cl-N-Chloropiperidine, was synthesized and purified to remove ³⁶Cl-chloride. Stomach fluid was obtained from Sprague-Dawley rats which had been first fasted for 24 or 48 hours and then administered 3 mL of deionized water. Different concentrations of radiolabeled chloramine were reacted with …

A Comparison Of Potential Fishing Methods Associated With Fish Aggregating Devices Off The Northeast Coast Of Puerto Rico, Alan M. Friedlander

OES Theses and Dissertations

Six fish aggregating devices (FADs) were deployed in June and monitored through December 1986. Emphasis was placed on trolling, live-bait handlining and longlining.

There was a significant difference (x2 = 7.815, pCoryphaena hippurus) which made up 64.2% of the catch.

Handlining at night around inshore buoys for one boat yielded 82.7 kg per trip. Pelagic fish comprised 83.9% of the catch, with the majority (81.4%) being kingfish (Scomberomorous cavalla). Catch rates were 50% higher and the species diversity much greater on the FADs versus control during experimental nightfishing, but the difference was not significant.

Longlining resulted in 3.4 …

Processes Which Create And Destroy Stratification In The South Atlantic Bight During Gabex Ii, Rebecca Lynn Lovingood

OES Theses and Dissertations

The stratification present on the South Atlantic Bight (SAB) during the summertime is influenced by creative forces, namely surface heating, precipitation, fresh water runoff and advection of Gulf Stream water, and destructive forces, these being wind, bottom currents, tides, evaporation and cooling. During the summer of 1981 the Georgia Bight Experiment II (GABEX II) was conducted to evaluate the Gulf Stream intrusions on the shelf dynamics. Calculations using potential energy as an indicator of stratification showed that the mixing forces were strong enough to destroy the stratification if the advection of buoyancy is ignored. During this period, however, the potential …

Laminar Viscous Effects On Longitudinal Dispersion In Tidal Froude Models, Larry H. White

OES Theses and Dissertations

A laboratory investigation was designed to test the ability of a tidal Froude model operated according to the minimum Reynolds number criterion of 1400 to simulate the longitudinal dispersion of its turbulent, laboratory prototype in the absence of depth distortion and density stratification. To examine the model's performance, comparative tracer-dye dispersion tests were conducted in the model and in the prototype to determine spatial and temporal longitudinal dye distributions. Froude similitude of cross-sectional mean tide heights and current velocities was achieved. The minimum Reynolds number criterion did not guarantee turbulent flow throughout all tidal stages, prolonged periods of laminar flow …

Determination Of Amino Acids And Chloramino Acids In Municipal Wastewater, Jeffrey Taylor Jewell

Chemistry & Biochemistry Theses & Dissertations

It is well known that unchlorinated municipal wastewater contains high levels of organic and inorganic amino nitrogen compounds, the single most abundant amino-N species being ammonia. Upon chlorination, these compounds are transformed almost instantaneously and quantitatively into N-chloramino derivatives. The organic chloramines have been shown to

interfere with disinfection and have lower disinfection capacities than their inorganic counterpart monochloramine. The environmental effects imposed by the discharge of these compounds into natural receiving waters is unknown. This study has shown that amino acid precursors for N-chloramino acids range in concentration from 1.4 X 10^-7 M to 9.0 X 10^{-7 …}

On A Moving Boundary Problem Of Transitional Ballistics, Jen-Ing G. Hwang

Mathematics & Statistics Theses & Dissertations

A major problem which arises in computer simulation of the firing of a gun weapon is the development of numerical schemes which effectively account for the physics of projectile motion. The chief difficulty is that away from the projectile the calculation is ordinarily accomplished on a fixed numerical grid, whereas due to projectile movement some cells of the grid near the projectile undergo volume changes as the calculation proceeds. A local finite volume scheme is developed which accounts for the expansion or compression of cells fore-and-aft of the projectile. Through the process of numerical experiment, the effectiveness of the scheme …

Provenance Of Sands Within The Lower Chesapeake Bay Based On Ilmenite Composition, Edward Augustus Council Iii

OES Theses and Dissertations

Surficial sands deposited in the Chesapeake Bay are a mixture of sands derived from the bay's shorelines, from offshore, and from relict deposits. Direct fluvial input is probably minor except from the James River, which may serve as a local source of sands in the Thimble Shoals area. Sands in the western half of the bay are primarily derived from the erosion of the adjacent shoreline. In contrast, the eastern half of the bay has two major sources of sand. Shoreline erosion is the dominant source north of the town of Eastville, Virginia, while the offshore is the major source …

A Simple Numerical Model For The Study Of Baroclinic Estuarine Shelf Interactions, Thomas J. Berger

OES Theses and Dissertations

A one and a half layer nonlinear f-plane numerical model was used to study estuarine-shelf interactions. The single active layer covered a domain consisting of a 100 km long by 20 km wide channel discharging onto a 100 km wide by 300 km long shelf. Channel and "western” shelf boundaries were no-slip, "eastern" or oceanic boundary was free-slip and "northern" and "southern" shelf boundaries were open. The channel was forced with a constant inflow velocity spun up from 2 cm s^-1 to 27 cm s^-1over five days. The model initial conditions were a flat interface at …

A Numerical Study Of Three-Dimensional Vortex Breakdown, Robert Edward Spall

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical simulation of vortex breakdown using the time-dependent Navier-Stokes equations was performed. Unlike previous studies, the numerical algorithm, formulated in terms of the velocity and vorticity, was not restricted to axisymmetric flows. Prototype vortices were parameterized in terms of their Reynolds number and Rossby number. Two cases were studied extensively. In one case, a vortex was imbedded in a uniform free stream. In the other case, the axial velocity of the free stream was decelerated in the streamwise direction. For both cases breakdown occurred when the Rossby number was below a critical value. Vortex lines, particle traces and velocity …

Studies Of Radiation Effects In Three High Polymers, Heidi Rene-Mitchell Ries

Physics Theses & Dissertations

Three high polymers, Mylar®, Ultem®, and Kapton®, were irradiated to total doses of 1, 5, and 9.5 gigarad using 1-MeV electrons. The glass transition temperatures (T_g) of the materials before and after irradiation were measured using an AC electrical dissipation factor technique. From the T_g data, it was found that the electron radiation at these total doses results in net chain scissioning in Mylar and net crosslinking in Ultem, while self-mending is predominant in Kapton. The dielectric constant was measured before and after irradiation, but no significant changes due to irradiation were observed. Electron paramagnetic resonance (EPR) …

Groin-Associated Rip Currents Measured Using A New Digital Current Meter, Dennis L. Lundberg

OES Theses and Dissertations

Rip currents have often been noted in physical model studies of groins and their effectiveness. Nevertheless, detailed field investigations of rip currents along a groin wall have not been heretofore conducted. A new digital current meter system was designed and built to study the groin-associated rip currents in a test groin compartment at Willoughby Spit, Norfolk, VA. Six ducted impeller current meters are controlled by a data acquisition system that utilizes an onboard microprocessor and solid state memory. The new system provides high quality data on horizontal water velocities associated with wave action. The velocities stored are time mean velocities …

The Stratigraphy Of Late Quaternary Deposits In The Payan Mining District, Narino, Colombia, South America, Richard Alan Barringer

OES Theses and Dissertations

Late Quaternary terrace deposits along the Rio Magui consist of cobble or pebble gravels with thick volcanic ash caps. These gravel terrace deposits unconformably overlie a cemented volcanic tuff (Ananias Formation), and are subdivided into two formations (Antigua and Panambi formations) based on the cobble lithology and size, depth of weathering, geomorphic relationships, and heavy mineral assemblages. Carbon-14 dates from wood suggest that the Antigua fan deposits are older (greater than 40,000 YBP) than the lower Panambi alluvium (less tahn 25,000 YBP) which is restricted to lower terraces within the modern river valleys.

Two separate ash units identified by differences …

Depositional And Diagenetic History Of The Middle Ordovician Carbonates Of The Shenandoah Valley, Northern Virginia, Lynn Ellen Weyenberg

OES Theses and Dissertations

An examination of the Middle Ordovician carbonates in northwest Virginia has revealed a particularly sensitive record of deposition and subsidence. Two-hundred acetate peels from six measured stratigraphic sections in Shenandoah County, Virginia were examined to interpret the depositional and diagenetic history. Two major lithofacies have been recognized within the New Market Limestone and three have been recognized in the Lincolnshire Formation. These five lithofacies represent an overall transgressive sequence. This transgression was not uniform but paused several times to allow carbonate deposition to reach sea-level. These shoaling events suggest a slowly subsiding basin in this region. The carbonate rocks within …

On The Thermal Stresses Due To A Uniform Heat Flow Past A Circular Hole With A Radial Edge Crack, George F. Edmonds

Mathematics & Statistics Theses & Dissertations

The problem solved in this dissertation is that of finding the stresses in an isotropic, linear, thermoelastic solid when a uniform heat flow is disturbed by the presence of an insulated circular hole with a radial edge crack. By superimposing a Mellin transform solution of the equations of thermoelasticity on a Michell series solution the author reduces the problem to a pair of singular integral equations which are then solved numerically. The stress intensity factors and crack formation energies, quantities of interest to workers in fracture mechanics, are then calculated.

The Hydrogeology Of Nags Head Woods, Dare County, North Carolina, Janet Salyer Emry

OES Theses and Dissertations

Nags Head Woods, a coastal maritime forest located on a barrier island in eastern North Carolina, stabilizes a back-barrier dune system bordering a tidal marsh. The purpose of this study is to provide basic information about the groundwater geology in Nags Head Woods and to predict the effects upon water levels due to municipal pumping of Fresh Pond, a large lake near the center of the island.

Clean, fine-to-medium sands dominate the top of the surficial (water table) aquifer, underlain by silty fine-to-coarse sands at -4 m elevation. A silty clay bed of very low permeability is present at -12 …