VTechWorks
VTechWorks provides global access to Virginia Tech scholarship, including journal articles, books, theses, dissertations, conference papers, slide presentations, technical reports, working papers, administrative documents, videos, images, and more by faculty, students, and staff. Faculty can deposit items to VTechWorks from Elements, including journal articles covered by the University open access policy. Email vtechworks@vt.edu for help.
Open Access Policy
Virginia Tech's open access policy enables researchers to deposit the accepted version of scholarly articles with no embargo.
Theses and Dissertations
Virginia Tech was first in the world to require ETDs in 1997, and continues to add scans of older theses and dissertations.
Open Textbooks
More than 50 freely available and openly licensed textbooks are among our most downloaded items.
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Recent Submissions
Assessing Healthy and Traditional Foods in Virginia Tribal Communities: Barriers and Facilitators from Lived Experiences
Powell, Tia (Virginia Tech, 2026-11-03)
Indigenous communities experience disproportionate rates of food insecurity, nutrition-related chronic diseases, and barriers to accessing both healthy and traditional foods. While these disparities have been well documented nationally, limited research has explored the unique experiences of Virginia’s Indigenous communities and how Virginia Cooperative Extension can support those communities. The purpose of this qualitative study was to examine the barriers and facilitators to accessing healthy and traditional foods through the lived experiences and stories of Indigenous community members in Virginia. Data collected through semi-structured interviews and a focus group discussion were analyzed using thematic analysis to identify common experiences, patterns, and emerging themes related to barriers and facilitators to access healthy and traditional foods. Participants identified barriers when accessing healthy and traditional foods, including rural food deserts, limited transportation, rising food costs, aging and physical limitations, historical loss of land, reduced opportunities for hunting, fishing, gardening, and food preservation, and the erosion of traditional ecological knowledge across generations. Participants also highlighted significant community strengths and facilitators to health and traditional food access, including strong family and community relationships, cultural revitalization efforts, community gardens, food forests, traditional food education, seed saving, food preservation, youth engagement, and collaborative partnerships with organizations such as Virginia Cooperative Extension. The findings demonstrate that Indigenous food sovereignty extends beyond food security to encompass cultural identity, self-determination, stewardship of ancestral knowledge, and community well-being. Based on the findings, recommendations are provided for culturally responsive nutrition education, community-engaged Cooperative Extension programming, and future partnerships that support Indigenous food sovereignty and improve access to healthy and traditional foods. By centering Indigenous voices and lived experiences, this research contributes to a growing body of knowledge that can inform public health practice, Extension programming, and policies that honor tribal priorities while promoting health equity.
The Presence and Bioactivity of Connexin-43 and Pannexin-1 in Milk-Derived Small Extracellular Vesicles
Amin, Md Ruhul (Virginia Tech, 2026-11-02)
Milk-derived small extracellular vesicles (mEVs) are an emerging platform for oral delivery of peptide therapeutics, but their potential as both an engineerable delivery vehicle and a naturally bioactive agent in their own right remains incompletely understood. This dissertation investigates the presence, delivery utility, and endogenous bioactivity of two channel-forming membrane proteins, Connexin 43 (Cx43) and Pannexin-1 (Panx1), in bovine mEVs, and tests the premise that channel-protein cargo defines functionally distinct, bioactive subpopulations within an otherwise heterogeneous mEV pool.
First, Pannexin-1 and Cx43 are shown to be present in a defined subpopulation of bovine mEVs, using western blotting, single-molecule localization microscopy, and flow cytometry-based single-vesicle detection, demonstrating mEV cargo heterogeneity. Secondly, an esterification-based strategy is developed for loading the Cx43 mimetic peptide αCT11 into mEVs. Orally administered, αCT11-loaded mEVs reduced infarct size by approximately 60% and preserved cardiac function in a murine model of ischemia-reperfusion injury, with efficacy retained when treatment was delayed by up to two hours after reperfusion. Finally, returning to the native, unloaded mEV population, a subpopulation intrinsically enriched in endogenous Cx43 is isolated using collagen-binding capacity as an indirect, function-based isolation strategy. This subpopulation was enriched approximately 22-fold in Cx43 relative to the unselected mEV pool and conferred significant radioprotection in a normal mammary epithelial cell model, exceeding that of unselected mEVs.
Together, these findings establish milk EVs as both a natural signaling reservoir, whose bioactivity is concentrated in cargo-defined subpopulations, and an engineerable oral delivery platform for Cx43-targeted peptide therapeutics. This dissertation further establishes collagen-affinity selection as a generalizable, peptide-free strategy for isolating functionally defined extracellular vesicle subpopulations that lack a directly targetable surface marker, with potential applications extending beyond this specific system.
Toward an Understanding of Empathic In-Vehicle Agents
Choe, Mungyeong (Virginia Tech, 2026-10-30)
Driver anger degrades vehicle control and safety, and in-vehicle conversational agents are increasingly proposed as a means of supporting drivers through emotionally difficult moments. Empathy is commonly treated as a desirable property of such agents, yet an agent has no emotional capacity in the sense the construct presupposes: what it has is a repertoire of utterances. This dissertation therefore operationalizes empathy as a verbal design strategy and asks which realization of it supports drivers, and whether the version that is best received is also the version that works best. Study 1 (N = 60) compared cognitive empathy, which names the driver's likely state and explains why the situation warrants it, against affective empathy, which expresses a parallel reaction of the agent's own, and against navigation-only speech, under a pre-drive anger induction. Study 2 (N = 48) then crossed the same three empathy conditions with agent embodiment, comparing a physically present humanoid robot against a voice-only agent. Study 3 (N = 48) crossed empathy condition with conversational interactivity, comparing a pre-scripted agent against one powered by a large language model while holding the robot, the voice, the timing, and the empathic utterances constant. All three studies measured self-reported affect, physiological response, perceptions of the agent, and vehicle control. The findings converge on a separation between how an agent is received and what it does. Cognitive empathy was associated with the most controlled vehicle handling in Study 1 and with the highest rate of active hazard response in Study 3, and it incurred far less of the penalty in perceived safety that emotionally expressive speech carried in Studies 2 and 3. Affective empathy, by contrast, was rated warmest, most animate, and most socially present, and was associated with faster cardiac settling in Study 1. However, it did not outperform cognitive empathy on any measure of vehicle control, and it reduced how safe the agent felt to be with in Studies 2 and 3. Embodiment lowered every dimension of perceived workload largely without changing how empathic content was evaluated. Conversational interactivity produced the strongest perceptual effects observed in this dissertation, nearly doubling perceived social presence, but these gains did not carry over: conversational capability had no effect on vehicle control and influenced physiological response only at the peak of the cardiac reaction. When drivers could converse freely with the agent, they asked overwhelmingly about information and company, with expressions of emotion accounting for a small fraction of what they said. Across the three studies, drivers' evaluations of the agent did not move together with their physiological responses or their driving behavior: ratings did not predict physiological response at the individual level, and the design that drivers judged warmest was not the design associated with the most controlled driving. On this basis, the dissertation argues that empathic in-vehicle agents should be evaluated on driver state and behavior rather than on social impression alone, that cognitive empathy offers the most defensible default for safety-critical settings, and that embodiment and conversational capabilities may contribute more to user acceptance than to physiological or behavioral regulation.
Multi-Fidelity Particle Flow Filters based on Log Homotopy
Bhattacharjee, Abhinab; Popov, Andrey A.; Subrahmanya, Amit N.; Sandu, Adrian (Virginia Tech. Computational Science Laboratory, 2026-10-27)
This work proposes a new Multi-Fidelity Particle Flow Filter (MFPFF) based on a linear control variate framework and multilevel Monte Carlo methods.
Conventional particle filters often suffer from weight collapse and particle degeneracy in high-dimensional spaces. Particle flow filters address this by smoothly transporting prior particles toward the posterior distribution, thereby avoiding the need for resampling. This work constructs multi-fidelity particle flow filters by augmenting a small number of expensive high-fidelity particles (full-order model runs) with a large number of inexpensive low-resolution particles (reduced-order surrogates constructed via intrusive Galerkin projection). These surrogates act as control variates to enhance the statistical estimate of the full-order posterior, yielding enhanced analysis accuracy at comparable computational cost. The work focuses on two particle flows based on log homotopy, the stochastic Gromov flow and deterministic Exact flow. Numerical experiments with the Korteweg-De Vries (KdV) and Quasi-Geostrophic (QG) test problems demonstrate that the proposed MFPFF achieves accuracy comparable to high-fidelity simulations while significantly reducing computational expense.
Exploring Organogenesis in American Chestnut
Kocz, Sebastian James (Virginia Tech, 2026-10-29)
American chestnut (Castanea dentata) was once a major presence in the forests of the Eastern United States. However, fifty years after chestnut blight, a canker disease caused by Cryphonectria parasitica, was first observed in the Bronx Zoo in 1904, the tree was considered functionally extinct. Efforts to increase disease resistance in the species via genetic engineering are ongoing, however they would be aided by improvements in the efficiency and speed of in vitro regeneration. To begin optimizing a de novo organogenesis regeneration protocol for C. dentata, we tested seven different callus induction media formulations as well as Agrobacterium-mediated transformation of explants with ten different morphogenic regulators (MRs) that had been reported to increase shoot induction when overexpressed in other plant species. We identified a high-performing callus induction media (WPM with 2 mg BAP and 0.5 mg NAA) that produced callus on 87.5% of C. dentata leaf explants after being kept in a dark environment for 3 weeks. In our three transformation experiments with MRs, while we found some MRs to cause significantly more callus to form than others, we found no significant improvement in callus induction in explants transformed with MRs compared to GFP-transformed controls. In some cases, the GFP-transformed control performed significantly better. Across both studies, four adventitious shoots were observed. These represent the first reported shoots formed by C. dentata through de novo organogenesis and give us optimism that with more optimization, a consistent protocol can be generated.