Award-winning Theses and Dissertations

Permanent URI for this collection

https://hdl.handle.net/10919/71751

Every year, the Virginia Tech Graduate School honors several outstanding theses and dissertations, and some theses and dissertations have won external awards. Browse these works here.

2016: "Virginia Tech Graduate School honors top scholars of the 2015-16 academic year"
2013: "Laura Gambrel, Justin Lemkul receive 2013 Outstanding Dissertation Award"
2012: "Robert Neal and Catherine Larochelle receive 2012 Outstanding Dissertation Awards from Graduate School"
2011: "Nikkhah wins best dissertation for identification of cell biomechanical signatures"
2011: "Graduate students receive William Preston Society Thesis awards"
2010: "Graduate School selects outstanding master's research from Class of 2010"

Read about applying for thesis and dissertation awards at graduateschool.vt.edu/academics/awards/.

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Now showing 1 - 20 of 34

ACADIA: Efficient and Robust Adversarial Attacks Against Deep Reinforcement Learning
Ali, Haider (Virginia Tech, 2023-01-05)
Existing adversarial algorithms for Deep Reinforcement Learning (DRL) have largely focused on identifying an optimal time to attack a DRL agent. However, little work has been explored in injecting efficient adversarial perturbations in DRL environments. We propose a suite of novel DRL adversarial attacks, called ACADIA, representing AttaCks Against Deep reInforcement leArning. ACADIA provides a set of efficient and robust perturbation-based adversarial attacks to disturb the DRL agent's decision-making based on novel combinations of techniques utilizing momentum, ADAM optimizer (i.e., Root Mean Square Propagation or RMSProp), and initial randomization. These kinds of DRL attacks with novel integration of such techniques have not been studied in the existing Deep Neural Networks (DNNs) and DRL research. We consider two well-known DRL algorithms, Deep-Q Learning Network (DQN) and Proximal Policy Optimization (PPO), under Atari games and MuJoCo where both targeted and non-targeted attacks are considered with or without the state-of-the-art defenses in DRL (i.e., RADIAL and ATLA). Our results demonstrate that the proposed ACADIA outperforms existing gradient-based counterparts under a wide range of experimental settings. ACADIA is nine times faster than the state-of-the-art Carlini and Wagner (CW) method with better performance under defenses of DRL.
Active Dynamic Analysis and Vibration Control of Gossamer Structures Using Smart Materials
Ruggiero, Eric John (Virginia Tech, 2002-05-07)
Increasing costs for space shuttle missions translate to smaller, lighter, and more flexible satellites that maintain or improve current dynamic requirements. This is especially true for optical systems and surfaces. Lightweight, inflatable structures, otherwise known as gossamer structures, are smaller, lighter, and more flexible than current satellite technology. Unfortunately, little research has been performed investigating cost effective and feasible methods of dynamic analysis and control of these structures due to their inherent, non-linear dynamic properties. Gossamer spacecraft have the potential of introducing lenses and membrane arrays in orbit on the order of 25 m in diameter. With such huge structures in space, imaging resolution and communication transmissibility will correspondingly increase in orders of magnitude. A daunting problem facing gossamer spacecraft is their highly flexible nature. Previous attempts at ground testing have produced only localized deformation of the structure's skin rather than excitation of the global (entire structure's) modes. Unfortunately, the global modes are necessary for model parameter verification. The motivation of this research is to find an effective and repeatable methodology for obtaining the dynamic response characteristics of a flexible, inflatable structure. By obtaining the dynamic response characteristics, a suitable control technique may be developed to effectively control the structure's vibration. Smart materials can be used for both active dynamic analysis as well as active control. In particular, piezoelectric materials, which demonstrate electro-mechanical coupling, are able to sense vibration and consequently can be integrated into a control scheme to reduce such vibration. Using smart materials to develop a vibration analysis and control algorithm for a gossamer space structure will fulfill the current requirements of space satellite systems. Smart materials will help spawn the next generation of space satellite technology.
The AFM Study of Ovarian Cell Structural Mechanics in the Progression of Cancer
Ketene, Alperen Nurullah (Virginia Tech, 2011-05-06)
According to the American Cancer Society, Cancer is the second most common cause of death in the United States, only exceeded by heart disease. Over the past decade, deciphering the complex structure of individual cells and understanding the symptoms of cancer disease has been a highly emphasized research area. The exact cause of Cancer and the genetic heterogeneity that determines the severity of the disease and its response to treatment has been a great challenge. Researchers from the engineering discipline have increasingly made use of recent technological innovations, namely the Atomic Force Microscope (AFM), to better understand cell physics and provide a means for cell biomechanical profiling. The presented work's research objective is to establish a fundamental framework for the development of novel biosensors for cell separation and disease diagnosis. By using AFM nanoindentation, several studies were conducted to identify key distinctions in the trends of cell viscoelasticity between healthy, nontumorigenic cells and their malignant, highly tumorigenic counterparts. The possibility of identifying useful 'biomarkers' was also investigated. Due to the lack of an available human ovarian cell line, experiments were done on a recently developed mouse ovarian surface epithelial (MOSE) cell line, which resembles to human cell characteristics and represents early, intermediate, and late stages of the ovarian cancer. Material properties were extracted via Hertz model contact theory. The experimental results illustrate that the elasticity of late stage MOSE cells were 50% less than that of the early stage. Cell viscosity also decreased by 65% from early to late stage, indicating that the increase in cell deformability directly correlates with increasing levels of malignancy. Various cancer treatment and component-specific drugs were used to identify the causes for the changes in cell biomechanical behavior, depicting that the decrease in the concentration levels of cell structural components, predominantly the actin filament framework, is directly associated with the changes in cell biomechanical property. The investigation of MOSE cells being subject to multiple mechanical loads illustrated that healthy cells react to shear forces by stiffening up to 25% of their original state. On the other hand, cancerous cells are void of such response and at times show signs of decreasing rigidity. Finally, deformation studies on MOSE cancer stem cells have shown that these cells carry a unique elasticity profile among other cell stage phenotypes that could allow for their detection. The results herein carry great potential into contributing to cell separation methods and analysis, furthering the understanding of cell mechanism dynamics. While prior literature emphasizes on the elastic modulus of cells, the study of cell viscosity and other key material properties holds a critical place in the realistic modeling of these complex microstructures. A comprehensive study of individual cells holds a great amount of promise in the development of effective clinical research in the fight against cancer.
Behavioral Training of Reward Learning Increases Reinforcement Learning Parameters and Decreases Depression Symptoms Across Repeated Sessions
Goyal, Shivani (Virginia Tech, 2023-12)
Background: Disrupted reward learning has been suggested to contribute to the etiology and maintenance of depression. If deficits in reward learning are core to depression, we would expect that improving reward learning would decrease depression symptoms across time. Whereas previous studies have shown that changing reward learning can be done in a single study session, effecting clinically meaningful change in learning requires this change to endure beyond task completion and transfer to real world environments. With a longitudinal design, we investigate the potential for repeated sessions of behavioral training to create change in reward learning and decrease depression symptoms across time. Methods: 929 online participants (497 depression-present; 432 depression-absent) recruited from Amazon’s Mechanical Turk platform completed a behavioral training paradigm and clinical selfreport measures for up to eight total study visits. Participants were randomly assigned to one of 12 arms of the behavioral training paradigm, in which they completed a probabilistic reward learning task interspersed with queries about a feature of the task environment (11 learning arms) or a control query (1 control arm). Learning queries trained participants on one of four computational-based learning targets known to affect reinforcement learning (probability, average or extreme outcome values, and value comparison processes). A reinforcement learning model previously shown to distinguish depression related differences in learning was fit to behavioral responses using hierarchical Bayesian estimation to provide estimates of reward sensitivity and learning rate for each participant on each visit. Reward sensitivity captured participants’ value dissociation between high versus low outcome values, while learning rate informed how much participants learned from previously experienced outcomes. Mixed linear models assessed relationships between model-agnostic task performance, computational model-derived reinforcement learning parameters, depression symptoms, and study progression. Results: Across time, learning queries increased individuals’ reward sensitivities in depression-absent participants (β = 0.036, p =< 0.001, 95% CI (0.022, 0.049)). In contrast, control queries did not change reward sensitivities in depression-absent participants across time ((β = 0.016, p = 0.303, 95% CI (-0.015, 0.048)). Learning rates were not affected across time for participants receiving learning queries (β = 0.001, p = 0.418, 95% CI (-0.002, 0.004)) or control queries (β = 0.002, p = 0.558, 95% CI (-0.005, 0.009). Of the learning queries, those targeting value comparison processes improved depression symptoms (β = -0.509, p = 0.015, 95% CI (-0.912, - 0.106)) and increased reward sensitivities across time (β = 0.052, p =< 0.001, 95% CI (0.030, 0.075)) in depression-present participants. Increased reward sensitivities related to decreased depression symptoms across time in these participants (β = -2.905, p = 0.002, 95% CI (-4.75, - 1.114)). Conclusions: Multiple sessions of targeted behavioral training improved reward learning for participants with a range of depression symptoms. Improved behavioral reward learning was associated with improved clinical symptoms with time, possibly because learning transferred to real world scenarios. These results support disrupted reward learning as a mechanism contributing to the etiology and maintenance of depression and suggest the potential of repeated behavioral training to target deficits in reward learning.
Biaxial Mechanical Behavior of Swine Pelvic Floor Ligaments: Experiments and Modeling
Becker, Winston Reynolds (Virginia Tech, 2014-06-08)
Although mechanical alterations to pelvic floor ligaments, such as the cardinal and uterosacral ligaments, are one contributing factor to the development and progression of pelvic floor disorders, very little research has examined their mechanical properties. In this study, the first biaxial elastic and viscoelastic tests were performed on uterosacral and cardinal ligament complexes harvested from adult female swine. Biaxial elastic testing revealed that the ligaments undergo large strains and are anisotropic. The direction normal to the upper vagina was typically stiffer than the transverse direction. Stress relaxation tests showed that the relaxation was the same in both directions, and that more relaxation occurred when the tissue was stretched to lower initial strains. In order to describe the experimental findings, a three-dimensional constitutive model based on the Pipkin-Rogers integral series was formulated and the parameters of such model were determined by fitting the model to the experimental data. In formulating the model, it was assumed that the tissues consist of a ground substance with two embedded families of fibers oriented in two directions and that the ligaments are incompressible. The model accounts for finite strains, anisotropy, and strain-dependent stress relaxation behavior. This study provides information about the mechanical behavior of female pelvic floor ligaments, which should be considered in the development of new treatment methods for pelvic floor disorders.
Carve That Opossum and Plucky, Ducky Underwear: A Narrative Inquiry of Laughter in a Preschool Classroom
Smidl, Sarah Lynn (Virginia Tech, 2003-05-06)
This thesis is a narrative inquiry of laughter in a University Lab School preschool classroom that describes the many situations in which children laugh as well as laughter's importance for the children, for me, and for all of us as a whole within the context of our classroom. To date, there is a paucity of research on children's laughter, especially in young children. The majority of research that has been conducted has been quantitative in nature, with few attempts to comprehensively describe the many situations in which laughter occurs. For my study, I felt it crucial to look at, document, and describe preschoolers' laughter, taking into consideration the many facets of their school day including free play, story time, playground time, and snack time. My sample included all of my 14 preschoolers, who ranged in age from 3 years to 4 years, 4 months at the outset of the study. I also deemed it important to look at what these laughter-producing situations meant to me and the children in my classroom, including what deeper worth laughter for all of us, how we used it in the classroom, and how it helped me to grow both personally and professionally through my research.
A Catalyst for the Development of Human Rights: German Internment Practices in the First World War,1914-1929
Vick, Alison Marie (Virginia Tech, 2013-06-17)
This thesis is a transnational study of the military actions and responses related to prisoners of war in World War I. Building on the works human rights scholars, I explore the how the collective rights afforded to prisoners of war under the 1906 Geneva Convention and 1907 Hague Convention served as a precursor to the concept of human rights that emerged after World War II. I argue that German military treated prisoners of war according to national interest, rather than international law. Specifically, I explore how the concepts of "military necessity" and "reciprocity" drove German internment practices, and how German internment practices escalated in violence during the last two years of the war. The violent practices committed by the Germans against prisoners of war produced an international demand to hold the perpetrators of wartime atrocities accountable for their actions in the postwar period.
Dammed If You Don't: The Palmertown Tragedy of 1924 in Collective Memory
Bolt, Carmen (Virginia Tech, 2016-06-24)
On December 24, 1924, a wall of water and alkali muck engulfed Palmertown, a small community in Saltville, Virginia. Houses were swept away and by the time all of the bodies were pulled from the wreckage, the death toll had reached 19-an immense loss for the tight-knit community. A dam, owned by Mathieson Alkali Works, loomed approximately 100 feet above Palmertown, keeping at bay the chemical muck produced by the company plants. Despite the extent of the damage, the flood is largely absent from discourse and no historical marker exists to memorialize the tragedy. Furthermore, Palmertown and neighboring Henrytown were expunged in the mid-twentieth century when Olin Corporation rebuilt the dam overtop of the town sites. Stories of the event have been passed down for generations, immortalizing a specific story of the disaster in the memories of many local residents of Saltville, so why is it not memorialized? The cultural framework of Saltville determined how and why this disaster and others have been remembered or forgotten. In 1924, Saltville residents were accustomed to tragic events; to some extent these events were seen as part and parcel of life in a company town in Appalachia. Yet, nearly a century after the tragedy, the process of unearthing of difficult events can illuminate much of the community's collective history and restore the fragmented communal memory. The memorialization of the Palmertown Tragedy of 1924 establishes a framework for acknowledging an arduous past and identifying the roots of a town's resilience.
Economic costs of extreme heat on groundnut production in the Senegal Groundnut Basin
Sembene, Maguette (Virginia Tech, 2023-09-01)
Groundnut production is vital to the Senegalese agricultural economy, particularly in the Groundnut Basin. However the region is increasingly affected by climate change and associated rising temperatures. This study investigates long-term changes in the frequency of extreme temperatures in the Groundnut Basin and the impact of extreme temperatures on groundnut production. The current economic costs of extreme temperatures on groundnut farmers and potential future additional economic costs associated with climate change are then calculated. The study uses a two-year panel dataset from 1,123 households in the Groundnut Basin and weather data from meteorological stations and the ERA5 climate database. Results identify a significant increasing trend in extreme temperatures across the Groundnut Basin and a negative relationship between extreme temperatures and groundnut yield. This leads to financial losses for farmers, with adaptation strategies such as input level adjustments providing partial mitigation. Future projections indicate further increases in extreme heat degrees days, resulting in significant yield losses by 2050. But the implications of extreme heat also extend beyond agriculture, affecting human habitation and exacerbating societal inequalities. The findings highlight the potential long-term effects of increasing temperatures on agricultural practices in the Groundnut Basin and underscore the need for adaptation and mitigation strategies to cope with the impacts of climate change.
Effect of Ornamentation on the Emotion Response and Perception of Motion Graphics
Musselman, Ryan William (Virginia Tech, 2013-06-24)
This study explores the effect of ornamentation on the emotional response and perception of motion graphics. A series of motion graphics were created, eye tracked, and tested for changes in emotional responses and perceptions based on the amount of ornamentation in the design. This study collected both quantitative and qualitative data to gain a better understanding of the viewer's overall emotional responses and perceptions of each video. Eye tracking data was studied to validate focal points and areas of interest. The quantitative data was analyzed by looking for correlations and trends. The qualitative data was analyzed for trends and reoccurring ideas. This study found that the amount of ornamentation in logo animations has a direct effect on the viewer's emotional responses and perceptions. More ornamentation led to overall positive changes in the emotional responses and perceptions of the brand or message, however there can be a turning point where the ornamentation can cause a negative response from the viewer.
Federal and Local Acceptance of Refugees: The Dual Structures Promoting Community Inclusion
Garrett, Benjamin Troy (Virginia Tech, 2019-07-11)
This thesis asks the question: what roles do local governments and nongovernmental organizations play in resettling refugees in U.S. cities? To answer this question, I conducted a case study of the refugee resettlement structure and process as it occurs in the city of Roanoke, Virginia. I find that two governance structures dictate how refugees are resettled into the city. The first stems from federal refugee policy, which establishes the use of a public-private partnership between federal and state governments and federated civic organizations. The second is an evolving local-level grassroots organizational structure that assesses the needs of refugees in Roanoke following their initial resettlement. In the case study on Roanoke I examine the support roles and practices of government institutions and nongovernmental organizations during the initial refugee resettlement period. Additionally, I examine aspects of long-term service provision and additional supports that move refugees towards social and economic inclusion. I conducted interviews with government and non-governmental leaders to grasp their understandings of existing practices and norms of local-level refugee resettlement. I also examined local survey data, economic and demographic data, media reports, and other public documents prepared by government agencies and nonprofit organizations. I identify who offers, or influences decisions about, specific supports for refugees at different times throughout the resettlement/integration process. I will suggest further implications of the supports provided for how they structure the pattern of refugees' economic and social inclusion. This thesis is designed to contribute to the limited literature on the process of local-level refugee resettlement in U.S. cities.
High-Resolution Mapping of the Region around the Soybean Virus Resistance Genes, Rsv1 and Rpv1
Gore, Michael Allen (Virginia Tech, 2000-07-28)
Soybean mosaic virus (SMV) and peanut mottle virus (PMV) are potyviruses that can cause serious yield reductions in soybean [Glycine max (L.) Merr.]. Virus resistant soybean cultivars have been released with alleles at the Rsv1 and Rpv1 locus that confer resistance to SMV and PMV, respectively. A high-resolution map-based cloning approach was undertaken to isolate Rsv1 and Rpv1 from soybean, with hopes of providing insight into this host-pathogen relationship. A mapping population of 1,056 F2 individuals was constructed from the cross of the resistant cultivar PI 96983 (Rsv1 and Rpv1) by the susceptible cultivar Lee 68 (rsv1 and rpv1). Ninety-one of the 1,056 F2 individuals had a cross-over (recombination) in the chromosomal region between microsatellite, or simple sequence repeat (SSR) marker loci Hsp176 and Sat120, and these 91 recombinant lines (RLs) were selected for further genetic analysis. Genotypes of Rsv1 and Rpv1 for the 91 RLs were obtained by inoculating their F2:3 progeny with SMV-G1 and PMV-P1, respectively. The 91 RLs also were used for mapping one random amplified polymorphic DNA (RAPD), five SSR, and 21 restriction fragment length polymorphism (RFLP) markers. Included in these RFLP markers were seven resistance gene candidate (RGC) and five resistance gene candidate flanking (RGCF) markers. RGC probes encode a protein with homology to previously cloned plant disease resistance genes, and RGCF probes are sequences obtained from the flanking regions of candidate disease resistance genes. The resultant high-resolution map consisted of 41 marker loci detected by 27 molecular markers. Rsv1 and Rpv1 cosegregated with one or more RFLP bands detected by RGCF probes: GG27-1a, 3gG2SP, and/or T3G. Analyses of the disease reaction and molecular marker data from seven RLs suggested that the map position of Rsv1 should be at a locus different from that designated by the linkage analysis software, Mapmaker 3.0. Compared to the other 89 RLs, a high percentage (>34%) of F3 plants grown from four of these seven RLs gave a necrotic reaction when inoculated with SMV-G1. From this evidence, we believed that another locus independent of Rsv1 was involved in PI 96983's response to SMV-G1. The two loci conferring resistance to SMV-G1 were designated Rsv1a and Rsv1b.
A Holistic Approach to Taxonomic Evaluation of Two Closely Related Endangered Freshwater Mussel Species, the Oyster Mussel (Epioblasma capsaeformis) and Tan Riffleshell (Epioblasma florentina walkeri) (Bivalvia: Unionidae)
Jones, Jess W. (Virginia Tech, 2004-03-19)
Primers for 10 polymorphic DNA microsatellite loci were developed and characterized for the endangered oyster mussel Epioblasma capsaeformis from the Clinch River, TN. Microsatellite loci also were amplified for individuals collected from the following additional populations or species: (1) E. capsaeformis from Duck River, TN; (2) E. florentina walkeri from Indian Creek, upper Clinch River, VA; (3) E. florentina walkeri from Big South Fork Cumberland River, TN; and (4) E. torulosa rangiana from Allegheny River, PA. Allelic diversity ranged from 9-20 alleles/locus, and averaged 13.6/locus for all 5 populations investigated. Average expected heterozygosity (HE) per locus ranged from 0.78-0.92, and averaged 0.86. A genetic characterization of extant populations of E. capsaeformis and E. florentina walkeri was conducted to assess taxonomic validity and to resolve conservation issues related to recovery planning. These mussel species exhibit pronounced phenotypic variation, and are difficult to characterize phylogenetically using DNA sequences. Monophyletic lineages, congruent with phenotypic variation among species, were obtained only after extensive analysis of combined mitochondrial (1378 bp of 16S, cytochrome-b, ND1) and nuclear (515 bp of ITS-1) DNA sequences. In contrast, analysis of variation at 10 hyper variable DNA microsatellite loci showed moderate to highly divergent populations based on FST values, which ranged from 0.12-0.39. Quantitative genetic variation was observed in fish host specificity, with transformation success of glochidia of E. capsaeformis significantly greater (p<0.05) on the greenside darter Etheostoma blennioides, and that of E. f. walkeri significantly greater (p<0.05) on the fantail darter E. flabellare. Lengths of glochidia differed significantly (p<0.001) between species, with sizes ranging from 241-272 μm. Underwater photographs of mantle-pads and micro-lures of female mussels documented fixed phenotypic variation between species. The texture and color of the mantle-pad of E. capsaeformis is smooth and bluish-white, while that of E. f. walkeri is pustuled and brown, with tan mottling. Based on extensive molecular, morphological, and life history data, a population of E. capsaeformis from the Duck River, TN is described and proposed as a separate species, and a population of E. f. walkeri from the upper Clinch River, VA is described and proposed as a separate subspecies. Genetic management guidelines were developed to assess taxonomic status, genetic variation of donor-recipient populations targeted for augmentation, and field and laboratory protocols to maximize genetically effective population size, minimize genetic changes in captive-reared progeny, and prevent the release of juvenile mussels into non-native drainages. A pragmatic approach to species recovery is advocated; one that incorporates the principles of conservation genetics into breeding programs, but prioritizes the immediate demographic needs of critically endangered mussel species.
Home and Community-Based Service Use by Vulnerable Older Adults
Weaver, Raven H. (Virginia Tech, 2014-04-25)
Home and community based services (HCBS) are designed to provide services that meet the increasing and diverse needs of the older adult population who wish to age-in-place for as long as possible in their homes and community. Yet, little is known about the choices people make when selecting services. The purpose of this study was to assess HCBS use among vulnerable older adults. Andersen’s (1995) behavioral model of health services use provided theoretical guidance for selecting and explaining predisposing, enabling, and need-based variables associated with service use within the Community Living Program (CLP) federal initiative. Through consumer direction of services, 18 routine or one-time services were offered to 76 participants enrolled in the Virginia CLP. Two-step cluster analysis identified four distinct profiles of service users, ranging in size from 7 to 34 members. Services used within the groups ranged from 11 to 16 services. Use of personal care services (p=.033) and respite (p=.010) were significantly associated with group membership differentiation. Within each cluster, the percentage of participants using each service varied greatly. The most important variables that differentiated service user membership were caregiver relationship to participant, participant living arrangement, participant disability type, and length of time caregiver provided care. Between-cluster membership was significantly different with regard to average service cost per day for services used (p=.002) and the likelihood of moving to a nursing home if services were not provided (p=.034). Findings inform future research and have implications for practitioners assisting vulnerable older adults in selecting services to meet different care needs.
Hypolimnetic Oxygenation Mitigates the Effects of Nutrient Loading on Water Quality in a Eutrophic Reservoir
Gerling, Alexandra Beth (Virginia Tech, 2015-09-03)
Climate change is predicted to have many diverse effects on freshwater lakes and reservoirs by increasing both hypolimnetic hypoxia and runoff, which will increase nutrient concentrations and degrade water quality. Hypoxic conditions can trigger the release of metals and nutrients from the sediments, i.e., internal loading, while storms can increase external nutrient loading to a waterbody. One potential solution for combating hypoxia is to use side stream supersaturation (SSS), a novel form of hypolimnetic oxygenation. First, in Chapter 1, I tested the efficacy of SSS operation to improve water quality in Falling Creek Reservoir (FCR), a shallow, eutrophic, drinking water reservoir. I found that SSS operation successfully increased hypolimnetic oxygen concentrations in FCR and suppressed internal loading of iron, manganese, and phosphorus. In Chapter 2, I manipulated inflow volumes to FCR and used SSS as a tool to alter hypolimnetic oxygen conditions in whole-ecosystem manipulations of internal and external nutrient loading. I observed that internal nitrogen and phosphorus loading during hypoxic conditions largely controlled the hypolimnetic mass of nutrients in FCR, regardless of inflow volumes, presumably as a result of the accumulated nutrients in its sediment from historical agriculture. Additionally, FCR consistently functioned as net sink of N and P throughout almost all of the treatments and substantially reduced nutrient export to downstream ecosystems. In summary, my research demonstrates the sensitivity of reservoir water quality to global change.
Incorporating Motives into the Theory of Planned Behavior: Implications for Reducing Alcohol Abuse among College Students
Smith, Ryan Christopher (Virginia Tech, 2011-04-18)
College alcohol abuse continues as a major public-health concern. Theory-driven research is necessary to address the severe negative consequences of this college drinking. One theory that offers particular promise is the theory of planned behavior (TPB). This theory posits that attitudes, perceived behavioral control, subjective norms, and intentions are the causal underpinnings of behavior. The current research investigates the utility of this theory in predicting college-student drinking behavior and investigates the potential benefit of including "motives" as an additional theoretical construct. In total, 316 students completed two electronic surveys. The first survey measured participants" standing on TPB constructs and motives. The second survey, administered two weeks later, asked participants about their alcohol consumption over the prior two weeks. Results not only shed light on the severity of the college drinking culture, but also offered a potential theoretical mechanism to promote positive behavior change. While the average participant reported consuming alcohol at binge drinking levels, the TPB with the inclusion of motives offered promise. Using structural equation modeling, this proposed model explained 71% of the variance in drinking intentions and 83% of the variance in self-reported drinking behavior in the follow-up survey. Motives added significantly to this model, indicating future TPB studies may benefit from including motives as an additional theoretical construct.
The Influence of Mild Cognitive Impairment (MCI) on Marital Relationships
Winston, Brianne L. (Virginia Tech, 2005-05-12)
The purpose of this study was to examine the influence of mild cognitive impairment (MCI) on marital relationships. MCI refers to age-related decline in memory and other cognitive processes that do not necessarily interfere with daily activities or the maintenance of social relationships with others (Petersen et al., 1999). Using social exchange theory as the theoretical framework to guide this qualitative study, aspects of the marital relationship explored from the nonimpaired spouses’ perspective were couple interaction, intimacy, and the division of household labor. In-depth interviews were conducted with five husbands and five wives (M age = 76.6 yrs., S.D. = 6.64). Open-ended interview questions that focus on issues specific to the marital relationship included: (a) range of activities participated in as a couple, (b) ways of showing care or affection toward one another, and (e) management of everyday life. In addition to participating in the semi-structured interviews, the spouses completed three standardized scales (e.g., Revised Memory & Behavior Problems Checklist, Zarit Burden Interview, Center for Epidemiological Studies-Depression Scale). Their responses to these measures provided information about the memory and behavioral changes of the elder as it related to the outcomes for and responses of the spouse. Spouses noted both change and stability within their marriages. They expressed “mixed emotions” concerning the influence of MCI on both them as individuals and on their relationship. Husbands’ responses focused on the negative relationship outcomes (e.g., frustration, stress) associated with caring for a spouse with memory loss; however, wives reported higher levels of burden and depression on the standardized measures than did the husbands. Gender differences were found regarding how husbands and wives view their roles in context to the caregiving situation, as well as how they adapt and cope. Longitudinal research is needed to examine the changes in the dynamics of these late-life marital relationships over time.
Interactive Interfaces for Capturing and Annotating Videos of Human Movement
Zilevu, Kobla Setor (Virginia Tech, 2019-07-11)
In this thesis, I describe the iterative service design process I used in identifying and understanding the needs of diverse stakeholders, the development of technologies to support their mutually beneficial needs, and the evaluation of the end-user experience with these technologies. Over three iterative design cycles, the set of identified end-user customers expanded to include the patient, the supervising therapist, the annotating therapist, and other members of the development team. Multiple versions of interactive movement capture and annotation tools were developed as the needs of these stakeholders were clarified and evolved, and the optimal data forms and structures became evident. Interactions between the stakeholders and the developed technologies operating in various environments were evaluated and assessed to help improve and optimize the entire service ecosystem. Results and findings from these three design cycles are being used to direct and shape my ongoing and future doctoral research
MEMS-Based Micro Gas Chromatography: Design, Fabrication and Characterization
Zareian-Jahromi, Mohammad Amin (Virginia Tech, 2009-05-22)
This work is focused on the design, fabrication and characterization of high performance MEMS-based micro gas chromatography columns having wide range of applications in the pharmaceutical industry, environmental monitoring, petroleum distillation, clinical chemistry, and food processing. The first part of this work describes different approaches to achieve high-performance microfabricated silicon-glass separation columns for micro gas chromatographic (µgC) systems. The capillary width effect on the separation performance has been studied by characterization of 250 Âµm-, 125 Âµm-, 50 Âµm-, and 25 Âµm-wide single-capillary columns (SCCs) fabricated on a 10Ã 8 mm2 die. The plate number of 12500/m has been achieved by 25 Âµm-wide columns coated by a thin layer of polydimethylsiloxane stationary phase using static coating technique. To address the low sample capacity of these narrow columns, this work presents the first generation of MEMS-based "multicapillary" columns (MCCs) consisting of a bundle of narrow-width rectangular capillaries working in parallel. The second contribution of this work is the first MEMS-based stationary phase coating technique called monolayer protected gold (MPG) for ultra-narrow single capillary (SCC) and multicapillary (MCC) microfabricated gas chromatography (μGC) columns yielding the highest separation performance reported to date. This new μGC stationary phase has been achieved by electrodepositing a uniform functionalized gold layer with an adjustable thickness (250nm-2Âµm) in 25μm-wide single columns as well as in four-capillary MCCs. The separation performance, stability, reproducibility and bleeding of the stationary phase have been evaluated over time by separating n-alkanes as non-polar and alcohols as polar gas mixtures.
Negotiating Sovereignty: Resistance and Meaning Making at the Bear Mountain Mission in Early-Twentieth Century Virginia
Blake, Erica Nicole (Virginia Tech, 2022-06-16)
In 1907, the Episcopal Church established a mission in the heart of the Native Monacan community on Bear Mountain in Amherst County, Virginia. The Bear Mountain Mission operated a church, day-school, and clothing bureau until 1965, when the day-school closed after the integration of Amherst County Public Schools. This thesis investigates how Native Monacan congregants negotiated sovereignty, enacted resistance against the assimilating efforts of the Episcopal Church, and maintained group identity and safety at the Mission during the first three decades of the twentieth century. Monacan congregants utilized the inherently colonial nature of the Mission's structure in ways that allowed them access to influential white Protestant networks, as well as validation by the mission workers who lived in and around the Bear Mountain community. I argue that Monacan people used strategies such as the refashioning of Mission teachings, anonymous and signed letter-writing to the Bishop, and communal protests to ensure that the Mission remained a safe space that worked for their Native community during a time of immense racial animosity. Using the personal correspondence between women mission workers, church leadership, and Monacan congregants, I examine the inner workings of the Bear Mountain Mission, and the beliefs and actions of mission workers and Monacan people alike. This thesis challenges the history of Bear Mountain Mission, and Native missions within the United States more broadly, to consider the unique and numerous ways that Native peoples enacted resistance strategies in order to ensure that Protestant Missions worked in ways that benefited their communities.

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