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Afm And C-Afm Studies Of Gan Films, Katherine Cooper

Theses and Dissertations

This thesis uses the techniques of atomic force microscope (AFM) and conductive AFM (C-AFM) to study the conduction properties of n-type GaN films. A total of 16 samples were examined and grouped according to their surface morphologies and conduction behaviors. The most common type of surface morpliology was that of Ga-rich samples having undulating "hillocks" with interspersed holes. Although most of the samples had this common morphology, their local conduction behaviors were not all similar. Local I-V spectra of the tip-sample Schottky contact could be grouped according to three major types: low leakage, high leakage, and "p-type". The highest quality …

Erythrocyte-Associated Transients In Capillary Po2 In The Rat Spinotrapezius Muscle During Hemodilution With Hespan And A Hemoglobin-Based Oxygen Carrier, Matthew Barker

Theses and Dissertations

Hemoglobin-based oxygen carriers for use as transfusion fluids have emerged as a leading technology directed at stemming shortages of a safe blood supply and providing a readily available resuscitation fluid in various trauma situations. The purpose of this investigation was to determine the effects of isovolemic hemodilution with Hespan and a hemoglobin-based oxygen carrier (HBOC) on erythrocyte-associated transients (EATs) in capillary PO2. The particulate nature of blood flow in capillaries, when observed from a stationary observation point, results in fluctuations of PO2 as alternating red blood cells and plasma gaps move through the detection region. Therefore, through experimental methods which …

Infant Oral Health: A Survey Of General Dentists, Pediatric Dentists, And Pediatricians In Virginia, Rhea Delcastillo Davis

Theses and Dissertations

Purpose: The purpose of this study was to examine the knowledge, attitudes, and experiences related to infant oral health for both dental and medical providers.Methods: A survey of infant oral health care was sent to 300 randomly selected general dentists, 300 randomly selected pediatricians, and all pediatric dentists in Virginia. The survey contained questions regarding the providers' routine infant oral health care regimen. In addition demographic data from the provider was collected. Responses to the questionnaire were tabulated and percent frequency distributions for responses to each item computed. Percents for all items were based on the total number of respondents …

Assessing The Relationship Between Socioeconomic Variables And Risk Of Overweight Among Children 6 Years Of Age, Marilyn Cochon Batan

Theses and Dissertations

Background: The percentage of overweight children has tripled in the last thirty years. Inconsistent findings are published regarding the relationship between socioeconomic variables and being overweight in childhood.Objective: To determine whether socioeconomic variables are associated with risk of being overweight among six year olds. Methods: Six year olds with BMI data were selected from the National Survey of Children's Health (n=4,362). Variables were coded and a low socioeconomic index was created. Using population weights, descriptive statistics were generated and regression was utilized to assess the relationship between socioeconomic variables and being 'at risk' for overweight. Socioeconomic variables were also compared …

Cytokine And Chemokine Profiles In A Rat Model Of Hemorrhagic Shock After Immuno-Modulation By Androstenetriol, Kristin E. Paccione

Theses and Dissertations

Further understanding of the cellular and molecular mechanisms involved in traumatic injury, and how they are modulated during drug interaction, can facilitate novel treatment strategies for future trauma patients. We hypothesize that the pharmacological agent, Androstenetriol (AET), up regulates host immune response by modulating the continued expression of mediators, including cytokines. In a double-blinded experiment, rats were hemorrhaged, driven by volume or pressure conditions, then resuscitated with fluids and packed red blood cells following a subcutaneous injection of either vehicle or drug. Blood was collected at various time points and cytokine levels were determined by analyses with both multiplex and …

Genetic Variability, Pathogen Susceptibility, Subspecies Identity And Conservation Of The Endangered Northern Flying Squirrel (Glaucomys Sabrinus) In Virginia, James Lincoln Sparks Jr.

Theses and Dissertations

I examined the population genetic structure of three known subspecies of Glaucomys sabrinus from Appalachia, Washington State, and two previously unexamined populations from Mount Rogers National Recreation Area (MRNRA) in Southwestern Virginia. Mean FST (0.107) and an AMOVA (P G. sabrinus subspecies populations in the southern Appalachians are genetically differentiated. Glaucomys sabrinus at MRNRA were less inbred than expected. Gene flow, a consensus tree based on Nei's genetic distance, elevated heterozygosity and morphometric data suggest that the MRNRA G. sabrinus population is an intergrade of the two recognized Appalachian subspecies, G. s. fuscus and G. s. coloratus. I compared inbreeding …

An Exploration Of Impediments To Attachment In A Juvenile Offender Population: Comparisons Between Juvenile Sex Offenders, Juvenile Violent Offenders And Juvenile Non-Sex, Non-Violent Offenders, Sharon Kay Funari

Theses and Dissertations

This current study addresses potential impediments to attachment that may differentiate between incarcerated juveniles who have committed sexual crimes and incarcerated juveniles who have not committed such offenses. The exploration of such potential barriers to attachment has been organized around Bronfenbrenner's Ecological Model. Subjects were 2948 incarcerated male adolescents adjudicated to the Virginia Department of Juvenile Justice and were divided based solely upon adjudicating offense: Juvenile non-violent, non-sexual offenders (JNVNSO, n=1149), Juvenile violent, non-sexual offenders (JVNSO, n=1433) and Juvenile sexual offenders (JSO, n=366). Results indicated that JSOs differed from JNVNSOs and JVNSOs in their histories of sexual abuse as well …

Predictors Of Induced Abortion Among Female Youth Center Users In Port-Au-Prince, Haiti, Rachel Barker

Theses and Dissertations

Objective: Induced abortions occur in every country in the world. However sixty percent of the world's women live in countries where abortion is illegal. 19 million pregnancies end in unsafe and/or illegal abortions. Annually, 68,000 women die from unsafe abortions. Legal or not, unsafe abortion is one of the great neglected problems of health care in developing countries like Haiti and is a serious concern to women during their reproductive lives. Methods: The data for this study was collected from youth centers (ages 15-24) and used to estimate percentage distributions of abortion ratios by selected characteristics of women, particularly age …

Material And Acoustic Properties Of Swimbladders Of Tilapia And Channel Catfish, Mohammed Ali Nawaz

Theses and Dissertations

Acoustically, teleost swimbladders have been considered resonant underwater bubbles. Contrary results indicating that bladders are tuned less sharply than such a bubble have been explained by damping of surrounding fish tissue. Recent findings in toadfish and weakfish, however, suggest that the bladder is a highly damped structure and that the frequency of the fish sounds is deternlined as a forced response to sonic muscle movement rather than by resonance of the bladder. In this study I examined acoustics and material properties of swimbladders in Tilapia (an auditory generalist) and the channel catfish (an auditory specialist). The swimbladder was struck with …

Building Hypertext In The Elementary School Art Classroom: An Integrated Approach To Learning And Curriculum, Talitha Church

Theses and Dissertations

In response to the many demands and pressures faced by both students and teachers in public schools, the art teacher in this action research study searched for ways to change her teaching practices to facilitate active inquiry. She utilized Thinking Maps®, a specialized form of graphic organizers, and Inspiration®, a hypertext linking program to promote interdisciplinary teaching and learning. The goals of the study were to increase student engagement, improve learning, and promote higher order thinking in elementary school art classes. The target group was comprised of the third grade students at Saunders Elementary School in Newport News, Virginia. Each …

The Effects Of Footshock On The Reinforcing Efficacy Of Cocaine In Male Long-Evans Rats, Elizabeth S. Hendrick

Theses and Dissertations

Many links exist between cocaine abuse and stress. The literature and laboratory studies in rats suggest that this could be because stress increases the reinforcing efficacy of cocaine. Using male Long-Evans rats, experiments in this thesis tested effects of footshock on the reinforcing efficacy of cocaine using a progressive ratio schedule of reinforcement. They also examined effects of footshock on the reinforcing efficacy of a half-maximal dose of cocaine. Finally, they tested the effects of footshock on cocaine self-administration in rats initially resistant to acquisition of cocaine self-administration. Footshock did not increase reinforcing efficacy of cocaine on a PR schedule …

Analysis And Shape Modeling Of Thin Piezoelectric Actuators, Makram Mouhli

Theses and Dissertations

The field of smart materials is an increasingly growing area of research. In aerodynamics applications especially, transducers have to fulfill a series of requirements such as light weight, size, energy consumption, robustness and durability. Piezoelectric transducers, devices which transform an electrical signal into motion, fulfill many of these requirements. Specifically, piezoelectric composites are of interest due to their added toughness and ease of integration into a structure. Resulting composites have a characteristic initial curvature with accompanying residual stresses that are responsible for enhanced performance, relative to flat actuators, when the active material is energized. A number of transducer designs based …

The Relationship Between Breastfeeding And The Development Of Asthma In Early Childhood, River Anne Pugsley

Theses and Dissertations

Purpose: Asthma can have significant adverse effects on the health and quality of life of children, and the prevalence of this condition continues to rise. Breastfeeding may protect against asthma, but some uncertainty remains. The purpose of this study was to further examine the relationship between breastfeeding and the risk of developing asthma in early childhood. Methods: Data were collected from the State and Local Area Integrated Telephone Survey: National Survey of Children's Health, 2003. The study population consisted of 33,315 children ages 0 to 5 years. Prevalence rates of asthma and breastfeeding ,were calculated, as were crude and Mantel-Haenszel …

Daubechies And Quadratic B-Spline Wavelets For Automated Early Diagnosis Of Alzheimer's Disease, Genevieve Jacques

Theses and Dissertations

Alzheimer's disease is a neurological disorder characterized by nerve degeneration and neuronal death. The diagnosis of Alzheimer's disease at an early stage is a major concern due to the lack of a standard and effective diagnosis procedure available to community healthcare providers, as well as the increasing numbers of the elderly population affected. Clinical evaluation, the standard AD diagnostic procedure conducted at major university hospitals and research clinics, achieves, on average, a positive predictive value of 93%, with a sensitivity of 83%, specificity of 55% and an overall accuracy of 75%. An effective and objective tool for early diagnosis of …

An Investigation Of Multi-Dimensional Evolutionary Algorithms For Virtual Reality Scenario Development, Scott Papson

Theses and Dissertations

Virtual reality (VR) has emerged as a powerful visualization tool for design, simulation, and analysis in modem complex industrial systems. The primary motivation for this thesis is to develop a framework for the effective use of VR in design-simulation-analysis cycles, particularly in situations involving large, complex, multi-dimensional data-sets. This thesis develops a framework that is intended to support not only the integration of such data for visual, interactive, and immersive displays, but also provides a method for performing risk analysis. Previously "static" VR environments are enhanced with time-evolutionary capabilities. Four candidate algorithms are evaluated for this purpose – deterministic modeling, …

The Effect Of Prostaglandin Inhibitor On Pregnancy Rates Of Heifer Embryo Transfer Recipients, Jared William Mcnaughtan

Theses and Dissertations

Manipulation of the reproductive tract results in increased levels of prostaglandin, which may, in turn, reduce pregnancy rates in embryo recipients. Administration of a prostaglandin inhibitor prior to embryo transfer improves pregnancy rates in cows. Embryo transfer into heifers is more difficult and often requires additional manipulation of the uterus. This study was designed to determine whether administration of the prostaglandin inhibitor, flunixin meglumine, immediately prior to embryo transfer increases pregnancy rates in heifers. Heifers (n=466) were divided into two equal groups based on BCS (range=6-7) and weight (range=256-455). Estrus was synchronized in heifers by giving two injections of prostaglandin …

New Product Launch Decisions Under Competition And Uncertainty: A Real Options And Game-Theoretic Approach To New Product Development, James O. Ostler

Theses and Dissertations

New product development is central to many firms' future success. Not only as a means to continue to maintain their piece of the market, but product development can also be a strategic means for a company to diversify, and/or alter focus to adapt to changing market conditions.

Most of the research in new product development has been on how to do it cheaper and faster than the next guy. However, early commercialization does not guarantee a position of strength in the market. Failures of EMI in CT scanners and Xerox in personal computers illustrate that being first to market does …

An In Vitro Evaluation Of Chitosan As A Biomaterial Focusing On The Effects Of The Degree Of Deacetylation, Virginia Hamilton

Theses and Dissertations

The material characteristics play a role in the suitability of chitosan for biomedical applications. This is not surprising since the degree of deacetylation of chitosan influences antimicrobial activity, degradation rate, immune reaction and mechanical properties such as strength and elongation. This study examines chitosans of variable material characteristics for wound and bone healing applications. Chitosan films of 76, 78, 80, 87, 91, 92, and 95% degree of deacetylation were tested in vitro for cellular responses by fibroblast and bone cell lines. The in vitro responses were compared to the material characteristics of molecular weight, degree of deacetylation, swelling index, and …

Development Of A Distributed Model For The Biological Water Processor Of The Water Recovery System For Nasa Advanced Life Support Program, Sachin Vishwas Puranik

Theses and Dissertations

The Water Recovery System (WRS) is one of the necessary subsystems in an Advanced Life Support program. It regenerates potable water by processing wastewater generated on a space shuttle or on a space station. The Biological Water Processor (BWP) is one of the complex subsections of WRS that involves processes described by continuous time as well as discrete event dynamics. Such systems can be modeled as hybrid dynamical systems in MATLAB/Stateflow. The following state variables of the BWP have been simulated in MATLAB: Pressure drop across Organic Carbon Oxidation Reactor (OCOR), Pressure drop across nitrification reactor, nitrifier flow rate, total …

Microbially Mediated Porosity Enhancement In Carbonate Reservoirs: Experiments With Samples From The Salem, Sligo, And Smackover Formations, Melody Roy Coffey

Theses and Dissertations

This study used petrographic thin sections, scanning electron microscopy, and confocal laser microscopy to document microbially mediated dissolution of carbonate reservoir rocks. The samples studied came from three carbonate units that are hydrocarbon reservoirs; the Salem, Sligo, and Smackover formations. These samples were inoculated with bacteria, and then treated with nutrient solutions followed by ethanol to promote generation of acetic acid by bacteria. Dissolution occurred in calcite-dominated rocks and in dolomitized rocks. Noticeable changes first occurred after nine weeks of ethanol treatment and significant change only occurred after twelve weeks of ethanol treatment. The size of the vuggy pores created …

Imposing Cyclic Strain On Osteogenic Stem Cells: The Effects Of Strain Levels And Repetition Of Cyclic Strain In An Implant Environment, Daniel Henlee Smith

Theses and Dissertations

Bone and bone cells have been shown to respond to mechanical forces placed upon them. Particularly, strain plays an important role in osteogenic differentiation of marrow cells around artificial implants in bone. These strains, depending on their magnitude, duration, and repetition, can alter the proliferation and matrix synthesis of osteoblasts. To test how strain parameters influence osteoblast behavior, a four-point bending apparatus was used to impose cyclic strain on osteogenic stem cells isolated from rats and seeded on titanium plates. Cells were stimulated at 1 Hz for 15 minutes daily and compared to an unstrained control. Stimulation occurred at two …

Predicting Open-Source Software Quality Using Statistical And Machine Learning Techniques, Amit Ashok Phadke

Theses and Dissertations

Developing high quality software is the goal of every software development organization. Software quality models are commonly used to assess and improve the software quality. These models, based on the past releases of the system, can be used to identify the fault-prone modules for the next release. This information is useful to the open-source software community, including both developers and users. Developers can use this information to clean or rebuild the faulty modules thus enhancing the system. The users of the software system can make informed decisions about the quality of the product. This thesis builds quality models using logistic …

Visualization Of Computer-Modeled Forests For Forest Management, Mahnas Jean Mohammadi-Aragh

Theses and Dissertations

Forest management is a costly and time-consuming activity. Remote sensing has the potential to improve the process by making it cheaper and more efficient, but only if appropriate characteristics can be determined from computer-models. This thesis describes the implementation of a forest visualization system and a corresponding user study that tests the accuracy of parameter estimation and forest characterization. The study uses data obtained from field-surveys to generate a computer-modeled forest. Five different stands were tested. Based on the quantitative results obtained, generally, there is no statistically significant difference in parameter estimation when comparing field-recorded movies and computer-generated movies.

Towards A Methodology For Interactive Virtual Design Assessment, Kang Li

Theses and Dissertations

Complex interactive behaviour involves cognitive, sensation and motor behaviour and may consist of several sub interactive behaviours. It needs to be examined from different points of view. Although explaining everything in one model is not currently possible, it is possible to connect information from different sources to get a better understanding of the interaction to benefit product design. The long-term objective of our study is to develop a methodology for interactive virtual design assessment to study the interactive behaviour and achieve compatibility. This study summarized two experiments which covered many aspects of interactive behaviours in seated posture. Experiment one addressed …

Ecological And Genetic Consequences Of Seasonal Drought On Stream Communities Inhabiting Pool Refugia, Joseph William Love

Theses and Dissertations

In intermittent streams, hydrological variation is probably the single-most important factor affecting fish assemblage structure. While the response of aquatic assemblages to seasonal or annual variation in hydrology is well-known, less attention has been devoted to how assemblages respond to natural, intraseasonal drought. To explore this question, I conducted summer surveys of fish and aquatic insect assemblages occupying pool refugia in first to third order, intermittent streams in the Saline river drainage in the Ouachita highlands (central Arkansas, U.S.A.)(2001?2003). The goals of this project were: 1) to relate assemblage variability of fishes and aquatic insects to environmental gradients during summer …

Gas Hydrates To Capture And Sequester Co2, Tao Ding

Theses and Dissertations

Reducing atmospheric CO2, a main source of greenhouse gas, has been accentuated recently. One focus is capture, separation, and sequestration of industrial CO2. As a hydrate former, CO2 forms hydrates at moderate temperatures and pressures. This phenomenon could be utilized to capture and separate CO2 from flue gases, and also has the potential to sequester CO2 in the deep sds. This research investigated the CO2-N2 separation efficiency of gas hydrates; it investigated the sequestration potential of CO2 hydrates in ocean sediments. The catalytic effect of surfactants in these processes was investigated. A fluorosurfactant FS-62 was mixed with SDS at 100ppm/1000ppm …

A Study Of The Impact Of The Mississippi Writing Project Summer Institute On Teacher Efficiency In Writing, Susan Gregory Dillard

Theses and Dissertations

In order to provide evidence of the worth of the Summer Institute of the National Writing Project, this study sought to determine whether participation in the professional development would increase feelings of teacher efficacy in writing. The Summer Institute professional development is consistent with recommendations of researchers in teacher efficacy and in professional development. Albert Bandura?s social cognitive theory provides a contextual framework for both teacher efficacy and the Summer Institute. The study compared the pre- and posttest scores on the Teacher Efficacy Scale for Writing and Writing Orientation Scale (Graham, S., Harris, K. R., Fink, B. & MacArthur, C., …

Investigation Of Inductively Coupled Plasma As An Atomization Source For Analytical And Fundamental Measurements Using Cavity Ringdown Spectroscopy, Fabio Jerome Mazzotti

Theses and Dissertations

Analytical as well as fundamental measurements were performed with an inductively coupled plasma (ICP) using the novel technique of cavity ringdown spectroscopy. A newly designed ICP torch was presented. Limits of detection were measured for elemental mercury, both in an ICP as well as in a cold mercury chemical generator. The efficiency of the technique was compared with laser-induced fluorescence (LIF) in the ICP. Isotopically resolved spectra of uranium were collected with this technique and results were compared to previous studies using LIF. Gas temperature and electron density estimations were done by lineshape measurements on lead atoms in the ICP. …

Site-Specific Prediction And Measurement Of Cotton Fiber Quality, Rui Wang

Theses and Dissertations

Maintaining cotton fiber quality is crucial for the survival of the U.S. cotton industry. Previous studies have indicated that spatial variability of fiber quality parameters exists in cotton fields. If site-specific measurement and prediction of quality is possible, then fiber could be segregated during the harvesting process, thus increasing the overall price a producer would receive for his crop. Because of the importance of fiber micronaire to the textile industry, the fact that micronaire exhibits moderate variation in the field, and the fact that it has been shown to be related to optical properties of cotton fibers, micronaire measurement was …

Atomic Force Microscope Conductivity Measurements Of Single Ferritin Molecules, Degao Xu

Theses and Dissertations

Conductive Atomic Force Microscope (c-AFM) was used to measure the conductivity of single horse spleen ferritin (HoSF) and azotobacter vinelandii bacterial ferritin (AvBF) molecules deposited on flat gold surfaces. A 500 micron diameter gold ball was also used as a contact probe to measure the conductivity of a thin film of ferritin molecules. The average current measured for holo HoSF was 13 and 5 times larger than that measured for apo HoSF as measured by c-AFM at 1V and gold ball at 2V and respectively, which indicates that the core of ferritin is more conductive than the protein shell and …