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.
Communities in VTechWorks
Select a community to browse its collections.
Recent Submissions
Connecting the Opens: Open Access Week 2026
Lener, Edward F.; Walz, Anita R.; Borunda, Luis; Sadler, Jesse; Petters, Jonathan L.; Surprenant, Aimée (Virginia Tech, 2026-10-19)
The 2026 Connecting the Opens panel discussion features brief overviews of open access, open educational resources, open publishing, and open data to provide some general information on the topics. Finally, presenters will discuss how aspects of open have impacted their career development as well as how they have incorporated open practices into their research and scholarship, and the audience will be invited to participate in the conversation.
Rootstock Effects on Flower Bud Mortality in ‘Gala’ and ‘Fuji’ Apples Under Natural Spring Frost Conditions (2021–2023)
Saini, Amolpreet Kaur; Jahed, Khalil R.; Sherif, Sherif M. (Virginia Cooperative Extension, 2025-06-30)
From Reaganism to Trumpism: Anti-Government Narratives and the U.S. Federal Career Service
Abdelrasol, Saifeleslam Tarek Shahata (Virginia Tech, 2026-10-28)
One of the most critical foundations of the United States governance system is the non-partisanship of the federal career service, which has faced intensifying attacks powered by presidential anti-government narratives. This dissertation examines the anti-government narratives of Presidents Ronald Reagan and Donald Trump, as two prominent conservative presidents who have championed anti-government narratives and actions, and their relationship to federal career employees' organizational commitment and retention decisions. The dissertation argues that these two presidential narratives evolved from one another but also differ in degree and kind. The study analyzed ninety-nine presidential written documents and three hundred ninety-one speeches through manifest, latent, and cross-application coding, complemented by semi-structured interviews with current and former federal career employees. The analysis shows that presidential anti-government narratives have shifted from Reagan's structural and abstract criticism to Trump's personal delegitimization of federal career employees. Trump's narrative includes multiple conspiratorial framings of federal employees as part of the deep state, which has no precedent in Reagan's anti-government narrative. The dissertation aims at systematically examining the relationship between presidential narratives and federal workforce dynamics. This relationship is critical for sustaining a competent, non-partisan career federal workforce. The dissertation finds that the sustained attacks on the legitimacy of the federal career employees from the head of the executive branch might relate strongly to their organizational commitment and, ultimately, their decisions to remain in federal service. Finally, this dissertation could work as a guide for future presidents and policymakers to understand the power of words on the attitudes and decisions of the federal workforce.
Ultrasound Wave-Matter Interactions in Soft Matter
Kulkarni, Hrishikesh (Virginia Tech, 2026-10-28)
Soft materials that undergo controlled shape change in response to external stimuli are foundational to emerging technologies in soft robotics, minimally invasive medicine, and adaptive biomedical devices. However, most existing actuation strategies rely on embedded electronics, optical fibers, or magnetic fillers, which complicate fabrication, limit miniaturization, and restrict operation in confined or deep-tissue environments. This dissertation establishes focused ultrasound (FUS) as a unified, non-invasive mechanism for remotely and programmably actuating soft matter, advancing ultrasound-responsive polymers, architected locally resonant metamaterials, and hierarchical structures while developing predictive multi-physics and multi-fidelity modeling frameworks. The first part investigates 4D-printed shape memory polymers (SMPs) actuated by FUS. A systematic spatiotemporal characterization links printing parameters, thermomechanical properties, and ultrasound exposure conditions to shape recovery response. Experiments show that FUS generates localized heating, accesses intermediate configurations, and achieves full recovery in functional structures, with optimized conditions yielding >95% recovery while delineating degradation thresholds governed by thickness and acoustic intensity. The second part introduces liquid crystal elastomers (LCEs) as intrinsically anisotropic, ultrasound-responsive materials. Pre-programmed LCE strips exhibit rapid, reversible bending under FUS, driven solely by viscoelastic dissipation and nematic–isotropic transitions, without the need for embedded optical or magnetic components. The dependence of actuation kinetics on geometry, crosslinking density, and ultrasound parameters is quantified through coupled thermal and mechanical measurements. Building on these material-scale insights, the third part develops a locally resonant metamaterial (LRM) comprising a PDMS matrix with polyurethane-filled Nylon 6,6 fibers housing central tungsten microspheres. Finite-element simulations that couple pressure acoustics, viscoelastic solid mechanics, and transient heat transfer reveal deeply subwavelength dipolar resonances and hybrid fiber–cavity modes that concentrate shear, enhance dissipation, and increase local heat generation by an order of magnitude. The fourth part introduces multi-fidelity machine learning framework that predicts ultrasound-driven deformation and shape morphing by integrating geometric, material, and acoustic parameters. Finally, the fifth part extends the framework to biological soft matter, developing a multiphysics multiscale k-space pseudospectral model of tendon to elucidate how focused ultrasound interacts with anisotropic, hierarchical, tissue architectures. The model captures aberrated focusing, harmonic generation, micro-mechanics, and shear-dominant effects, deformations under impulsive acoustic loading, providing mechanistic insight relevant to therapeutic ultrasound. Together, these studies establish a cohesive experimental, computational, and data-driven foundation for ultrasound-responsive soft matter laying the groundwork for remotely powered soft robots, actuators, adaptive implants, and programmable therapeutic systems.
Anthropogenic Food Waste and the Ecology of Foodborne Pathogens at the Wildlife–Domestic animal–Human Interface
Patino Westermann, Lena Carolina (Virginia Tech, 2026-10-28)
Anthropogenic waste can create persistent food subsidies that draw wildlife and domestic animals into close contact with humans and with one another, creating opportunities for exposure to foodborne bacterial pathogens across shared landscapes. The goal of this dissertation was to investigate patterns of carriage and diversity of two such pathogens, non-typhoidal Salmonella (NTS) and Campylobacter, among wildlife, domestic animals, humans, and the environment in northern Botswana, a landscape where protected, rural, and urban areas remain closely connected. Using bacterial isolates, molecular detection, longitudinal surveillance, and genomic analysis, this work characterized pathogen presence across this system through four complementary studies.
Chapter 2 screened fecal samples from facultative scavengers with access to human waste (banded mongoose, marabou stork, domestic dog, chicken) and wildlife species without access to such waste (hippo, elephant) in Kasane, northern Botswana (n=797), for NTS. Facultative scavengers were approximately nine times more likely to carry NTS than non-scavenging species (p=0.0001), with prevalence ranging from 5% in marabou storks to 26% in domestic dogs; NTS was not detected in chickens or elephants. Serotyping of six banded mongoose isolates identified serovars Agona (n=5) and Jedburgh var 15+ (n=1), and phenotypic resistance testing found low antimicrobial resistance overall, with no multidrug resistance. NTS carriage tracked a trophic gradient of waste exposure, present in species accessing mixed or meat-derived waste but absent in chickens feeding primarily on grain and vegetable material, suggesting that waste composition, not scavenging status alone, shapes NTS exposure risk.
Chapter 3 used longitudinal PCR-based surveillance to examine Campylobacter carriage in marabou storks foraging at the Kasane municipal landfill between April 2018 and July 2023 (n=1,003). Campylobacter genus DNA was detected in 24.3% of samples, with no evidence of a seasonal pattern. Detection odds were lower during the COVID-19 disruption period (2020–2021) than during the other sampled years (OR=0.456, 95% CI: 0.264–0.787, p=0.0048), while stork counts at the landfill also declined during this period (incidence rate ratio = 0.62, 95% CI: 0.45–0.86, p=0.004). These concurrent changes may have been associated with the hypothesized reduction in commercial food-waste inputs following the collapse of regional tourism, although waste volume and composition were not directly measured. Species-specific PCR and partial atpA sequencing identified C. coli, C. jejuni, C. lari, C. upsaliensis, and C. volucris, establishing a baseline description of Campylobacter species circulating in this stork population. To our knowledge, this represents the first report of C. volucris in sub-Saharan Africa.
Chapter 4 combined culture-based isolation and molecular detection to characterize Campylobacter diversity across humans, domestic animals, wildlife, retail chicken products, and wastewater in the same system. Culture recovered Campylobacter from domestic animals, wildlife, wastewater, and retail chicken products, but not from human stool, and species composition differed among host groups. Several detected species, including C. lanienae, C. ureolyticus, and C. vicugnae, are rarely reported in the region, extending their known ecological and geographic distributions. Molecular detection identified Campylobacter genus DNA in 65.7% of human stool samples (165/251) and revealed a broad range of species, including non-thermophilic and fastidious taxa, with C. ureolyticus being the most frequently identified taxon. In chickens, this approach detected DNA from more than one Campylobacter species in individual samples. These findings indicate that conventional culture-based surveillance may underestimate Campylobacter diversity in this system and demonstrate the value of integrating complementary detection methods into One Health surveillance.
Chapter 5 analyzed whole-genome sequencing data from C. jejuni and C. upsaliensis isolated from marabou storks foraging at a municipal landfill, comparing them against 124 previously published African C. jejuni genomes and 7 C. upsaliensis genomes. The C. jejuni isolate belonged to the host-generalist ST-206 clonal complex, clustering with human isolates from multiple African regions and showing extensive recombination characteristic of widely circulating lineages; the stork isolate lacked the principal fluoroquinolone- and tetracycline-resistance determinants that were prevalent in the examined C. jejuni from other African locations and sources. These genomic relationships were consistent with the broad host and geographic distribution of this lineage but did not establish direct transmission between storks and humans. In contrast, the C. upsaliensis isolate formed a deeply divergent lineage relative to South African human isolates, with low recombination, a novel partial sequence type, and no acquired resistance determinants. These findings provide the first genomic characterization of Campylobacter from marabou storks and suggest contrasting evolutionary trajectories, with C. jejuni belonging to a broadly distributed host-generalist lineage and C. upsaliensis potentially representing an underrecognized, wildlife-associated lineage. Future studies will build upon these C. upsaliensis findings by expanding the sample size and geographic distribution of examined genomes from Africa.
Together, these findings suggest that anthropogenic waste creates opportunities for pathogen exposure that vary by waste type, pathogen, and lineage, rather than acting as a uniform driver of risk. The integration of culture, molecular detection, longitudinal surveillance, and whole-genome sequencing revealed complementary dimensions of pathogen carriage, species diversity, temporal variation, and population structure. These results extend prior evidence of anthropogenic connectivity in this system, previously documented for E. coli, to NTS and Campylobacter, while showing that patterns observed at shared human–animal–environment interfaces cannot be assumed to generalize across pathogens, methods, or even closely related species. This work supports the inclusion of wildlife, environmental sources, and anthropogenic waste interfaces in One Health surveillance while emphasizing the need for source-resolved sampling and broader genomic representation to determine transmission pathways.