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- ACADIA: Efficient and Robust Adversarial Attacks Against Deep Reinforcement LearningAli, 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 MaterialsRuggiero, 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 CancerKetene, 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.
- Amplifying the Griot: Technology for Preserving, Retelling, and Supporting Underrepresented StoriesKotut, Lindah Jerop (Virginia Tech, 2021-05-24)As we develop intelligent systems to handle online interactions and digital stories, how do we address those stories that are unwritten and invisible? How do ensure that communities who value oral histories are not left behind, and their voices also inform the design of these systems? How do we determine that the technology we design respect the agency and ownership of the stories, without imposing our own biases? To answer these questions, I rely on accounts from different underrepresented communities, as avenues to examine how digital technology affect their stories, and the agency they have over them. From these stories, I elicit guidelines for the design of equitable and resilient tools and technologies. I sought wisdom from griots who are master storytellers and story-keepers on the craft of handling both written and unwritten stories, which instructed the development of the Respectful Space for technology typology, a framework that informs our understanding and interaction with underrepresented stories. The framework guided the approach to understand technology use by inhabitants of rural spaces in the United States--particularly long-distance hikers who traverse these spaces. I further discuss the framework's extensibility, by considering its use for community self-reflection, and for researchers to query the ethical implications of their research, the technology they develop, and the consideration for the voices that the technology amplifies or suppresses. The intention is to highlight the vast resources that exist in domains we do not consider, and the importance of the underrepresented voices to also inform the future of technology.
- Application of Artificial Intelligence to Wireless CommunicationsRondeau, Thomas Warren (Virginia Tech, 2007-09-20)This dissertation provides the theory, design, and implementation of a cognitive engine, the enabling technology of cognitive radio. A cognitive radio is a wireless communications device capable of sensing the environment and making decisions on how to use the available radio resources to enable communications with a certain quality of service. The cognitive engine, the intelligent system behind the cognitive radio, combines sensing, learning, and optimization algorithms to control and adapt the radio system from the physical layer and up the communication stack. The cognitive engine presented here provides a general framework to build and test cognitive engine algorithms and components such as sensing technology, optimization routines, and learning algorithms. The cognitive engine platform allows easy development of new components and algorithms to enhance the cognitive radio capabilities. It is shown in this dissertation that the platform can easily be used on a simulation system and then moved to a real radio system. The dissertation includes discussions of both theory and implementation of the cognitive engine. The need for and implementation of all of the cognitive components is strongly featured as well as the specific issues related to the development of algorithms for cognitive radio behavior. The discussion of the theory focuses largely on developing the optimization space to intelligently and successfully design waveforms for particular quality of service needs under given environmental conditions. The analysis develops the problem into a multi-objective optimization process to optimize and trade-of of services between objectives that measure performance, such as bit error rate, data rate, and power consumption. The discussion of the multi-objective optimization provides the foundation for the analysis of radio systems in this respect, and through this, methods and considerations for future developments. The theoretical work also investigates the use of learning to enhance the cognitive engine's capabilities through feed-back, learning, and knowledge representation. The results of this work include the analysis of cognitive radio design and implementation and the functional cognitive engine that is shown to work in both simulation and on-line experiments. Throughout, examples and explanations of building and interfacing cognitive components to the cognitive engine enable the use and extension of the cognitive engine for future work.
- Assessment of the Jones Act Waiver Process on Freight Transportation Networks Experiencing DisruptionFialkoff, Marc Richard (Virginia Tech, 2017-10-27)In October 2012, Hurricane Sandy caused massive disruption and destruction to the Mid-Atlantic region of the United States. The intensity of the storm forced the Port of New York and New Jersey to close, forcing cargo diversion to the Port of Norfolk in Virginia. Because of the Jones Act restriction on foreign vessels moving between U.S. ports, the restriction on short sea shipping was viewed as a barrier to recovery. Much of the critical infrastructure resilience and security literature focuses on the "hardening" of physical infrastructure, but not the relationship between law, policy, and critical infrastructure. Traditional views of transportation systems do not adequately address questions of governance and behaviors that contribute to resilience. In contrast, recent development of a System of Systems framework provides a conceptual framework to study the relationship of law and policy systems to the transportation systems they govern. Applying a System of Systems framework, this research analyzed the effect of relaxing the Jones Act on freight transportation networks experiencing a disruptive event. Using WebTRAGIS (Transportation Routing Analysis GIS), the results of the research demonstrate that relaxing the Jones Act had a marginal reduction on highway truck traffic and no change in rail traffic volume in the aftermath of a disruption. The research also analyzed the Jones Act waiver process and the barriers posed by the legal process involved in administration and review for Jones Act waivers. Recommendations on improving the waiver process include greater agency coordination and formal rulemaking to ensure certainty with the waiver process. This research is the first in studying the impact of the Jones Act on a multimodal freight transportation network. Likewise, the use of the System of Systems framework to conceptualize the law and a critical infrastructure system such as transportation provides future opportunities for studying different sets of laws and policies on infrastructure. This research externalizes law and policy systems from the transportation systems they govern. This can provide policymakers and planners with an opportunity to understand the impact of law and policy on the infrastructure systems they govern.
- Atomic Force Microscopy Study of Clay Mineral DissolutionBickmore, Barry Robert (Virginia Tech, 1999-12-09)An integrated program has been developed to explore the reactivity of 2:1 phyllosilicates (biotite and the clays montmorillonite, hectorite, and nontronite) with respect to acid dissolution using in situ atomic force microscopy (AFM). Three techniques are described which make it possible to fix these minerals and other small particles to a suitable substrate for examination in the fluid cell of the atomic force microscope. A suite of macros has also been developed for the Image SXM image analysis environment which make possible the accurate and consistent measurement of the dimensions of clay particles in a series of AFM images, so that dissolution rates can be measured during a fluid cell experiment. Particles of biotite and montmorillonite were dissolved, and their dissolution rates normalized to their reactive surface area, which corresponds to the area of their edge surfaces (Ae). The Ae-normalized rates for these minerals between pH 1-2 are all ~10E-8 mol/m2*s, and compare very well to other Ae-normalized dissolution rates in the literature. Differences between the Ae-normalized rates for biotite and the BET-normalized rates (derived from solution chemical studies) found in the literature can be easily explained in terms of the proportion of edge surface area and the formation of leached layers. However, the differences between the Ae-normalized montmorillonite rates and the literature values cannot be explained the same way. Rather, it is demonstrated that rates derived from solution studies of montmorillonite dissolution have been affected by the colloidal behavior of the mineral particles. Finally, the dissolution behavior of hectorite (a trioctahedral smectite) and nontronite ( a dioctahedral smectite) were compared. Based on the differential reactivity of their crystal faces, a model of their surface atomic structures is formulated using Hartman-Perdock crystal growth theory, which explains the observed data if it is assumed that the rate-determining step of the dissolution mechanism is the breaking of connecting bonds between the octahedral and tetrahedral sheets of the mineral structure.
- Bacteriophage Felix O1: Genetic Characterization and Bioremedial ApplicationWhichard, Jean Marie (Virginia Tech, 2000-10-16)Bacteriophage Felix O1 was studied for applicability as a Salmonella intervention. Felix O1's potential as a Salmonella therapeutic was explored, as was its utility as a food application. Felix O1 is specific for and infects most serovars within the genus Salmonella. The entire 86.155-kb sequence of the phage's linear, double-stranded chromosome was determined. 213 open reading frames (ORFs) were found, including 23 homologues of phage genes (e<0.008). Homology searches do not indicate genes that would be expected to increase virulence of Salmonella. Thirteen T4 homologues were found, including rIIA and rIIB, rapid lysis genes of T-even phages. Site-directed mutagenesis of the rIIB region was attempted by homologous recombination with plasmids containing luxAB of Vibrio harveyi. No DrIIB luxAB+ recombinants resulted from the methods tried. Serial in vivo passage was used to select for a longer-circulating Felix O1 mutant using the modified methods of Merril et al., (1996). No difference was found in the clearance of wild-type (WT) and Felix O1 following nine serial passages. Injection of 10⁹pfus yielded 24-hour concentrations of 6.5 and 4.9 log10 pfus/ml plasma for WT and 9th passage, respectively. Both isolates were undetectable in plasma by 72 hours, but remained in spleens at 96 hours. A large-plaque Felix O1 variant (LP) isolated during in vivo serial passage was compared with WT for Salmonella growth suppression. Spectrophotometric measurement of BHI cultures indicated greater suppression of S. typhi by LP than by WT, a difference not seen with S. typhimurium DT104. Both isolates suppressed 24-hour S. typhimurium DT104 growth on experimentally-contaminated chicken frankfurters at 22°C. Untreated frankfurters yielded 6.81 log10 Salmonella cfus/g, whereas WT and LP-treated samples yielded 5.01 and 4.70 log10 cfus/g, respectively. Both phages suppressed the Salmonella typhimurium DT104 growth (p<0.0001), but the isolates did not perform differently (p=0.5088). Presence of Salmonella caused a higher yield of WT phage than from the uninoculated group (p=0.0011), but did not affect LP yield (p=0.4416). With Salmonella present, the 24-hour LP concentration was lower than WT concentration. This supports the surmised LP rapid-lysis phenotype since T4 rapid-lysis mutants typically exhibit lower burst sizes than wild-type phage.
- Between Discipline and Profession: A History of Persistent Instability in the Field of Computer Engineering, circa 1951-2006Jesiek, Brent K. (Virginia Tech, 2006-12-13)This dissertation uses a historical approach to study the origins and trajectory of computer engineering as a domain of disciplinary and professional activity in the United States context. Expanding on the general question of "what is computer engineering?," this project investigates what counts as computer engineering knowledge and practice, what it means to be a computer engineer, and how these things have varied by time, location, actor, and group. This account also pays close attention to the creation and maintenance of the "sociotechnical" boundaries that have historically separated computer engineering from adjacent fields such as electrical engineering and computer science. In addition to the academic sphere, I look at industry and professional societies as key sites where this field originated and developed. The evidence for my analysis is largely drawn from journal articles, conference proceedings, trade magazines, and curriculum reports, supplemented by other primary and secondary sources. The body of my account has two major parts. Chapters 2 through 4 examine the pre-history and early history of computer engineering, especially from the 1940s to early 1960s. These chapters document how the field gained a partially distinct professional identity, largely in the context of industry and through professional society activities. Chapters 5 through 7 turn to a historical period running from roughly the mid 1960s to early 1990s. Here I document the establishment and negotiation of a distinct disciplinary identity and partially unique "sociotechnical settlement" for computer engineering. Professional societies and the academic context figure prominently in these chapters. This part of the dissertation also brings into relief a key argument, namely that computer engineering has historically occupied a position of "persistent instability" between the engineering profession, on the one hand, and independent disciplines such as computer science, on the other. In an Epilogue I review some more recent developments in the educational arena to highlight continued instabilities in the disciplinary landscape of computing, as well as renewed calls for the establishment of a distinct disciplinary and professional identity for the field of computer engineering. I also highlight important countervailing trends by briefly reviewing the history of the software/hardware codesign movement.
- Biaxial Mechanical Behavior of Swine Pelvic Floor Ligaments: Experiments and ModelingBecker, 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.
- Brazil Comes to the Future: Living Time and Space in the International Order of CompetitionRossone de Paula, Francine (Virginia Tech, 2016-06-20)The rise of Brazil as an economic power in the last decade has been celebrated by politicians and analysts as an opportunity for the country to take advantage of its visibility and bargaining power in order to effectively advocate for and promote an institutional and normative reform of the international order toward a less asymmetric and exclusionary space for politics. This dissertation aims to examine the spatial and temporal assumptions in these recent discourses about Brazil's emergence to the global stage and Brazil']s disposition towards the future. Departing from an understanding that there are scripts governing the realm of the possible and the visible in international politics, this dissertation proposes an analysis of what defines the conditions of possibility for Brazil's emergence to the global stage. By looking at discourses about Brazil's position and positioning in international politics, this study explores implicit and explicit rules defining the possibilities for one to be seen as a legitimate presence in the future and what these spatiotemporal constructs reveal about what is allowed as repetition and as change in the world. Contrary to many optimistic accounts of Brazil's emergence as a transformational leader from the developing world, I argue that it is only possible for Brazil to be discursively represented as an emerging global player and/or a country of the future that may have finally arrived because of the same limiting spatial and temporal discursive representations in world politics that translate difference into hierarchy and that contain and define intelligible possibilities for an alternative political order.
- Carve That Opossum and Plucky, Ducky Underwear: A Narrative Inquiry of Laughter in a Preschool ClassroomSmidl, 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,1914-1929Vick, 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.
- Citizen Soldiers and Professional Engineers: The Antebellum Engineering Culture of the Virginia Military InstituteMiller, Jonson William (Virginia Tech, 2008-09-17)The founders and officers of the Virginia Military Institute, one of the few American engineering schools in the antebellum period, embedded a particular engineering culture into the curriculum and discipline of the school. This occurred, in some cases, as a consequence of struggles by the elite of western Virginia to gain a greater share of political power in the commonwealth and by the officers of VMI for authority within the field of higher education. In other cases, the engineering culture was crafted as a deliberate strategy within the above struggles. Among the features embedded was the key feature of requiring the subordination of one’s own local and individual interests and identities (class, regional, denominational, etc.) to the service of the commonwealth and nation. This particular articulation of service meant the performance of “practical” and “useful” work of internal improvements for the development and defense of the commonwealth and the nation. The students learned and were to employ an engineering knowledge derived from fundamental physical and mathematical principles, as opposed to a craft knowledge learned on the job. To carry out such work and to even develop the capacity to subordinate their own interests, the cadets were disciplined into certain necessary traits, including moral character, industriousness, selfrestraint, self-discipline, and subordination to authority. To be an engineer was to be a particular kind of man. The above traits were predicated upon the engineers being white men, who, in a new “imagined fraternity” of equal white men, were innately independent, in contrast to white women and blacks, who were innately dependent. Having acquired a mathematically-intensive engineering education and the character necessary to perform engineering work, the graduates of VMI who became engineers were to enter their field as middle-class professionals who could claim an objective knowledge and a disinterested service to the commonwealth and nation, rather than to just their own career aspirations.
- Coalition Networks and Policy Learning: Interest Groups on the Losing Side of Legal ChangeMillar, Ronald B. (Virginia Tech, 2005-12-07)Network, organizational, and policy learning literatures indicate that when interest groups face failure they will seek out alternative ideas and strategies that will enhance their potential for future success. Research with regard to interest groups and legal change has found that interest groups, using arguments that were once accepted as the legal standard for Supreme Court decisions, were unwilling or unable to alter their arguments when the Court reversed its position on these legal standards. This research project examined the conflicting findings of these literatures. Using the Advocacy Coalition Framework as a guide, this project studied the separationist advocacy coalition in cases regarding state aid to elementary and secondary sectarian schools from 1971 to 2002. The legal briefs filed by members of the separationist advocacy coalition with the Court were examined using content analysis to track changes in their legal arguments. Elite interviews were then conducted to gain an understanding of the rationale for results found in the content analysis. The research expectation was that the separationist advocacy coalition would seek out and incorporate into their briefs new and innovative legal arguments to promote their policy goals. The research results demonstrated that prior to legal change interest groups did seek out and incorporate new legal arguments borrowed from other fora and sought to expand or reinterpret established legal arguments to better aid their policy goals. The changes that seemed to have the potential for adoption by the Court were quickly incorporated into the briefs of the other members of the coalition. Following legal change interest groups continued to analyze the decisions of the Court in order to seek out the best possible legal arguments to use in their briefs; however, the main focus of legal arguments examined and used by the coalition narrowed to those cited by the swing justice in the funding cases. Two innovative arguments were developed, but were either ignored or considered unsuitable, and were not used by the other members of the coalition. Counter to this project's research expectations new and innovative legal arguments were not adopted by the coalition. As the Court discontinued the use of various legal arguments the coalition quickly responded to these changes and dropped those obsolete legal arguments. Therefore, contrary to prior research, the interest groups and the coalition altered their arguments following legal change. Only those interest groups who no longer participated in coalition discussions reverted back to using pre-legal change arguments. Learning continued to occur in the coalition following legal change; however, the focus of analysis and the pool of arguments deemed worthy of use narrowed considerably.
- Confronting the West: Social Movement Frames in 20th Century IranPoulson, Stephen Chastain (Virginia Tech, 2002-12-06)The Iranian Revolution of 1979 received considerable attention from modern social scientists who study collective action and revolution because it allowed them to apply their different perspectives to an ongoing social event. Likewise, this work used the Iranian experience as an exemplar, focusing on a sequence of related social movement frames that were negotiated by Iranian groups from the late 19th through the 20th century. Snow and Benford (1992) have proposed that cycles of protest are associated with the development of a movement master frame. This frame is a broad collective orientation that enables people to interpret an event in a more or less uniform manner. This study investigated how movement groups in Iran developed master frames of mobilization during periodic cycles of protests from 1890 to the present. By investigating how master frames were negotiated by social movement actors over time, this work examined both the continuity and change of movement messages during periods of heightened social protest in Iran.
- Consequences of avian parental incubation behavior for within-clutch variance in incubation temperature and offspring behavioral phenotypesHope, Sydney Frances (Virginia Tech, 2020-01-17)Parents can have large effects on their offspring by influencing the early developmental environment. In birds, a major way that parents can influence the early developmental environment is through egg incubation. Not only is incubation necessary for hatching success, but small changes of <1C in average incubation temperature have large effects on post-hatch offspring morphology and physiology. However, incubation is energetically costly and time-consuming for parents, and thus parents must allocate resources between incubation and self-maintenance. This can lead to differences in parental incubation behavior and egg temperatures among and within populations. Understanding which factors influence incubation, and the subsequent effects for offspring, is crucial for understanding parental effects, non-genetic drivers of phenotypic variation, and how environmental changes affect avian populations. I used wood ducks (Aix sponsa) as a study species to investigate how factors (disturbance, clutch size, ambient temperature) that influence parental demands may affect parental incubation behavior, physiology, and egg temperatures, and subsequently how egg temperatures affect offspring behavior and physiology. In a field experiment, I found that nest disturbance (i.e., capture) reduced both parent prolactin concentrations and the amount of time that parents spent incubating (Chapter 1). Further, ambient temperature was positively and clutch size negatively related to egg temperatures. Notably, in large clutches, differences in average incubation temperature among eggs within nests were large enough (i.e., >1C) to lead to different offspring phenotypes within broods (Chapter 2). Then, in a series of experiments in which I controlled incubation temperature, I provided evidence that lower average incubation temperatures lead to a reduced ability of ducklings to exit the nest cavity (Chapter 3), a more proactive behavioral phenotype (Chapter 4), a smaller body size, and a reduced efficiency in food consumption (Chapter 5), compared to those incubated at higher temperatures. Together, my dissertation illustrates how disturbances, clutch size, and ambient temperature can influence an important aspect of avian parental care, which has wide-ranging effects on offspring traits and fitness. This has broad implications for understanding the evolution of clutch size, development of behavior, and the effects of anthropogenic changes on wildlife.
- Dammed If You Don't: The Palmertown Tragedy of 1924 in Collective MemoryBolt, 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.
- Development and testing of recombinant B. abortus RB51 vaccine strains carrying M. tuberculosis protective antigensAl Qublan, Hamzeh (Virginia Tech, 2015-06-23)Tuberculosis, caused by Mycobacterium tuberculosis, is one of the most prevalent infectious diseases inflicting humankind. The World Health Organization estimates that one third of the world's population, approximately 2.2 billion people, is infected with TB with a mortality of 1.7 million people annually. Currently, the WHO estimates that each year more than 9 million people develop TB. Bacille Calmette-Guérin (BCG), an attenuated strain of M. bovis, is the only licensed TB vaccine in the world. Clinical studies have shown childhood vaccination with BCG to be protective against disseminating and meningeal forms of TB. However, the efficacy of BCG against pulmonary TB in adults has been variable and inconsistent (0-80%). The objective of this study is to develop and test the efficacy of the B. abortus vaccine strain RB51 as a platform for expression of M. tuberculosis antigens (Ag85B, ESAT6 and Rv2660c) and induction of a protective immune response against M. tuberculosis and B. abortus challenge in mice. Here we report the construction of two recombinant strains of B. abortus vaccine strain RB51 capable of expressing mycobacterial antigens Ag85B, ESAT6 and Rv2660c. Our studies show that expression of mycobacterial antigens in strain RB51 lead to induction of antigen-specific immune responses characterized by secretion of IgG2a antibodies as well as of IFN- and TNF-α. Mice immunized with a combination of two strains of RB51 in equal numbers, one carrying Rv2660c-ESAT6 and another carrying Ag85B, led to a 0.90 log reduction in CFU burden with significance nearly reaching borderline (p = 0.052). However, when mice were primed with the same strains of RB51 and boosted with proteins Ag85B and ESAT6, a significant level of protection (1 log reduction) compared to the PBS vaccinated group was achieved. The protection levels conferred by this vaccination strategy was similar to that conferred by BCG vaccine. In conclusion, we have shown that recombinant RB51 strains expressing mycobacterial protective antigens result in stimulation of antigen specific immune response without altering the vaccine efficacy in protecting against the more virulent strain of B. abortus 2308. These recombinant vaccines could potentially be used to protect against M. tuberculosis infection.
- Disaggregating Within-Person and Between-Person Effects in the Presence of Linear Time Trends in Time-Varying Predictors: Structural Equation Modeling ApproachHori, Kazuki (Virginia Tech, 2021-06-01)Educational researchers are often interested in phenomena that unfold over time within a person and at the same time, relationships between their characteristics that are stable over time. Since variables in a longitudinal study reflect both within- and between-person effects, researchers need to disaggregate them to understand the phenomenon of interest correctly. Although the person-mean centering technique has been believed as the gold standard of the disaggregation method, recent studies found that the centering did not work when there was a trend in the predictor. Hence, they proposed some detrending techniques to remove the systematic change; however, they were only applicable to multilevel models. Therefore, this dissertation develops novel detrending methods based on structural equation modeling (SEM). It also establishes the links between centering and detrending by reviewing a broad range of literature. The proposed SEM-based detrending methods are compared to the existing centering and detrending methods through a series of Monte Carlo simulations. The results indicate that (a) model misspecification for the time-varying predictors or outcomes leads to large bias of and standard error, (b) statistical properties of estimates of the within- and between-person effects are mostly determined by the type of between-person predictors (i.e., observed or latent), and (c) for unbiased estimation of the effects, models with latent between-person predictors require nonzero growth factor variances, while those with observed predictors at the between level need either nonzero or zero variance, depending on the parameter. As concluding remarks, some practical recommendations are provided based on the findings of the present study.