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Functional Polymer Composites for Clinical and Engineering Challenges
No full textDoctor of PhilosophyThis dissertation presents the design and development of novel polymers engineered to outperform widely used commercial materials across a range of demanding applications. The central theme of this work is the deliberate tuning of polymer structure, identity, and architecture to achieve targeted functional and mechanical properties—such as resilience in extreme environments, antimicrobial activity, and selective drug capture. Through several projects and collaborations, these efforts resulted in first-generation materials that offer potential improvements for technologies spanning aerospace propulsion, neurosurgery, and infectious disease prevention.
The first half of the dissertation (Chapters 2–5) focuses on the synthesis and control of flexible, rubber-like polymers for high-resolution 3D printing, inspired by the widely used solid-propellant binder hydroxyl-terminated polybutadiene. The insights gained from this work enabled the creation of materials capable of being printed into complex, compliant geometries suitable for soft biomedical applications. The second half (Chapters 6–9) shifts from fundamental structure–property relationships to the design of materials for specific medical technologies. These advances include a chemotherapy drug–capture agent, an antimicrobial catheter coating, and a neurosurgical adhesive for sealing dura mater defects. Developed in collaboration with clinicians at Carilion Clinic, these projects highlight how chemists can tailor material properties by incorporating design principles and clinical constraints provided by physicians. Together, these studies demonstrate how molecular-level polymer engineering can translate into practical solutions for pressing healthcare challenges and support the development of the next generation of advanced functional materials
Introducing WebPdL2Ork
No full textIn the following paper, we present WebPdL2Ork, a WebAssemblybased runtime environment for the Pd-L2Ork ecosystem that enables easy deployment of patches or code snippets inside a Web browser. Below, we outline and compare its approach to other similar implementations and highlight its unique affordances, some that are inherited from Pd-L2Ork, and others developed to address idiosyncrasies associated with the Web browser’s sandboxed environment. Lastly, we evaluate its implementation using learning modules developed as part of the VT Waves project designed to promote connections between wave physics concepts and music, and the L2Ork Tweeter Pd-L2Ork app, the most complex patch that is included with Pd-L2Ork and is designed to enable EDM-style musicking over the internet while maintaining perfect sync.Published versio
Exploring Audience-Centered Experience (ACE) Interpretation: A study of visitor interests and live program outcomes in the U.S. National Park Service
No full textThe National Park Service (NPS) has recently shifted interpreter training toward an audience-centered approach, emphasizing participation and personal sharing rather than one-way knowledge delivery to achieve more socially-focused program outcomes. However, the extent to which visitors want programs that invite personal sharing remains unclear. Survey data from nine NPS sites indicate that most visitors, across demographic groups, tend to prefer traditional interpreter-led programs over those involving open sharing of ideas among visitors. To better understand when these methods may be effective, this study also draws on systematic observations of 48 programs across 28 NPS units that incorporated deeper audience sharing, along with post-program surveys. Programs that emphasized human stories, connected sharing prompts to the program's theme, and fostered a safe environment to share tended to perform more strongly, though these qualities did not consistently produce improved social outcomes. Findings highlight both the potential and the limitations of audience-centered interpretation and offer guidance for future practice and research.Master of ScienceThe National Park Service (NPS) has recently encouraged interpreters to create public programs that are more participatory rather than a traditional presentation. This newer approach invites the audience to share their own ideas, stories, and perspectives during programs. To understand visitors' perspectives of this shift, we surveyed visitors at nine NPS units and found that most prefer more traditional programs rather than the more modern participatory programs. To learn more about when interactive approaches work well, we also observed 48 programs across 28 parks that encouraged deeper sharing among visitors. Programs tended to be more successful when interpreters focused on human stories, clearly connected personal sharing to the central theme, and created a welcoming, comfortable environment. However, these qualities did not always lead to stronger social outcomes. Findings highlight both the potential and the limitations of audience-centered interpretation and offer guidance for future practice and research
Journal of Peacebuilding and Development
No full textThis paper examines how rural collective organization shapes patterns of violence and peacebuilding in conflict-affected Colombia. It combines municipal-level panel data (2016–2022) with qualitative analysis of testimonies from the Colombian Truth Commission (1958–2016) and a regional case of agricultural cooperatives in Sur del Tolima. The quantitative analysis identifies where collective organization is associated with variation in victimization, showing that agricultural cooperative membership is linked to lower victimization only in PDET municipalities—the territories most affected by conflict and institutional weakness—while peasant associations exhibit no robust protective relationship once structural controls are included. The qualitative analysis then examines how this conditional protection is produced in practice, identifying three mechanisms: strategic noncooperation, social cohesion and trust, and economic alternatives. Together, the findings suggest that institutionalized cooperation can function as civilian infrastructure for protection and recovery, while remaining contingent on baseline security, political recognition, and sustained support. The study contributes to peacebuilding scholarship by linking civilian agency with Latin American debates on the social and solidarity economy, showing how cooperatives translate solidarity into stability within fragile governance environments.Submitted versio
On the Need to Acquire Data for the Advancement of Shock Prediction
No full textToday, most shock propagation predictions are empirically based, resulting from a single study done by Martin Marietta in 1970. That work examined a body of shock data available at the time to create empirically derived guidance on how shock magnitude propagates through joints and distance. Most space programs use this Martin Marietta data until final shock validation testing where actual propagation is observed and defined. At this point, exceedances can be costly. Modern shock prediction techniques exist, but these are not proven for official use because existing data is either too simple, the analysis is stymied by an insufficient finite element model, or the results of prior work are proprietary. This report demonstrates that even on a simple structure, 1) the historical empirical technique does not correctly predict the environment, and 2) basic linear and non-linear analysis is not sufficient for analysis of shock. This work sets the foundation for improving shock prediction by gathering and releasing open-source, high quality shock data that can be used by anyone to validate new techniques.Master of ScienceWhen designing rockets and their payloads, analysis is performed to predict the forces that will act on the various components of the system. This analysis ensures the design is adequate for the complex structures to survive their journey. Once the structure is assembled, it is subjected to testing that replicates the variety of harsh environments that it will be subjected to on its way to space. If the forces were under-predicted, expensive one-of-a-kind equipment like a telescope lens or solar panel could be damaged. If they are over-predicted, additional mission objectives, like additional scientific sensors, will be needlessly left behind on Earth to offset the additional weight of the larger-than-necessary structures. This report uses a simple structure to demonstrate that 1) conventional wisdom regarding the type of force known as a mechanical shock may not accurately predict the forces the structure will see, and 2) modern techniques that have been successfully applied to other use cases may be inadequate for the prediction of shock. This work sets the foundation for improving shock prediction by gathering and releasing open-source, high quality shock data that can be used by anyone to validate new techniques
Nature
No full textRiver deltas sustain dense human populations, major economic centres and vital ecosystems worldwide1,2. Rising sea levels and subsiding land threaten the sustainability of these valuable landscapes with relative sea-level rise and associated flood, land loss and salinization hazards1-3. Despite these risks, vulnerability assessments are impeded by the lack of contemporary, high-resolution, delta-wide subsidence observations4. Here we present spatially variable surface-elevation changes across 40 global deltas using interferometric synthetic aperture radar. Using this dataset, we quantify delta surface-elevation loss and show the prevalence and severity of subsidence in river deltas worldwide. Our analysis of three key anthropogenic drivers of delta elevation changes shows that groundwater storage has the strongest relative influence on vertical land motion in 10 of the 40 deltas. The other deltas are either influenced by multiple drivers or dominated by sediment flux or urban expansion. Furthermore, we find that contemporary subsidence surpasses absolute (geocentric) sea-level rise as the dominant driver of relative sea-level rise for most deltas over the twenty-first century. These findings suggest the need for targeted interventions addressing subsidence as an immediate and localized challenge, in parallel with broader efforts to mitigate and adapt to climate change-driven global sea-level rise.Published versio
Water Research
No full textNon-targeted analysis of complex per- and polyfluoroalkyl substances (PFAS) via Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) promises unprecedented insights into the "fluorinome", i.e., the complete set of organofluorine compounds in a given sample. In this study, we present a Python-based workflow developed in parallel with a carefully constructed PFAS formula database comprising ∼ 20 million entries to facilitate the assignment of chemical formulas to ultrahigh-resolution mass spectra. PFAS assignments based on the analysis of complex aqueous film-forming foam (AFFF) on the world's highest-resolving 21 tesla FT-ICR MS were compared to quadrupole time-of-flight (QTOF) MS data, validating 22 common and discovering 19 previously undetected PFAS classes. We then explored the viability of ultrahigh-resolution FT-ICR MS analysis for forensic profiling purposes on PFAS-impacted groundwater samples, identifying bis-perfluoroalkyl sulfonimides (bis-FASIs) as long-suspected ingredients of electrochemical fluorination AFFFs. While our newly developed workflow may also be used for other types of high-resolution mass spectrometers such as QTOF and Orbitrap, this work leverages the unique ultrahigh-resolving power, sub-ppm mass measurement accuracy, and high dynamic range of 21 tesla FT-ICR mass spectrometry to maximize information from complex contaminant mixtures in environmental samples.Published versio
Applied Network Science
No full textThere are myriad real-life examples of contagion processes on human social networks, e.g., spread of viruses and mis/dis/information, joining groups, and social unrest. Also, there are many methods to control or block undesirable contagion spread on networks. In this work, we introduce a novel method of blocking contagions that uses nodes from dominating sets (DSs). This is the first work to use DS nodes to block contagions. Finding minimum dominating sets of graphs is an NP-Complete problem, so we generalize a well-known heuristic, enabling us to customize its execution. Our method produces a prioritized list of dominating nodes, which is, in turn, a prioritized list of blocking nodes. Given a network, we compute this list of blocking nodes and we use it to block contagions for all blocking node budgets, contagion seed sets, and parameter values of the contagion model. We provide examples to illustrate the issues associated with DS-based contagion blocking. We report on computational experiments of the blocking efficacy of our approach using seven mined networks. Among the results is that the heuristic generalization is important for improved blocking performance. We also demonstrate the effectiveness of our approach by comparing blocking results with those from the high degree heuristic, which is a common standard in blocking studies. We discuss how our general DS-based method recovers the high degree heuristic as a special case.Published versio
Quarterly Review of Distance Education
No full textIn this paper, the authors examine the complex relationship between class size and the design of online courses in higher education. Drawing on recent research, industry reports, and U.S. government regulations, it explores how optimal class sizes vary based on course objectives, student engagement needs, and instructional approaches. The analysis reveals that effective online class sizes generally range from 12 to 30 students but can differ significantly depending on course design, subject matter, and program type. Recommendations include that institutions must balance pedagogical best practices and regulatory requirements when determining online class sizes, emphasizing the need for flexible, context-specific approaches that align with broader institutional strategies for online learning while considering faculty workload and the time to adjust course design to accommodate changing class sizes.Accepted versio
Investigating Hfq-dependent Small Regulatory RNA, Bsr34, and Its Roles in Brucella abortus Physiology and Pathogenicity
No full textBrucellosis, a debilitating zoonotic disease caused by the facultative intracellular pathogen Brucella, relies on rapid gene regulation for survival within host cells. Small regulatory RNAs (sRNAs), often chaperoned by Hfq, are key post-transcriptional regulators of bacterial virulence and stress adaptation, yet remain largely uncharacterized in Brucella. Following the identification of Hfq-associated sRNA candidates in B. suis, this study provides the first functional characterization of Bsr34, an Hfq-dependent sRNA in B. abortus 2308. We confirmed that Bsr34 expression is entirely Hfq-dependent. Phenotypic analysis of a Δbsr34 mutant revealed no defects in in vitro growth or general stress survival but showed significant attenuation in a murine infection model, indicating a specific role in virulence. While an initial chloramphenicol sensitivity phenotype was inconsistent, expression profiling demonstrated that Bsr34 is specifically downregulated under envelope stress (polymyxin B) and acidic pH, but not under oxidative or nutrient stress. Collectively, these findings establish Bsr34 as a bona fide Hfq dependent sRNA involved in host-specific adaptation and stress response, laying the groundwork for future studies to identify its regulatory targets and elucidate its precise role in Brucella pathogenesis.Master of ScienceBrucellosis is a serious infectious disease transmitted from infected animals to humans, causing debilitating flu-like symptoms and fever. Despite prolonged antibiotic treatment, brucellosis frequently relapses, and no available drug regimen is capable of fully eradicating the infection.
The bacterium responsible, Brucella abortus, has a remarkable ability to survive inside host cells where it faces numerous environmental challenges including acidic conditions, nutrient limitation, and attack by the immune system. To rapidly adapt to these hostile conditions, Brucella uses specialized molecular tools called small regulatory RNAs (sRNAs), short nucleotide fragments that act like switches to quickly turn genes on or off in response to stress.
Bsr34 is one such small RNA that was discovered in Brucella but has never been studied in detail. We hypothesized that Bsr34 plays an important role in helping the bacteria survive stress and cause disease.
To test this, we created a mutant strain of B. abortus lacking Bsr34 and compared its behavior to normal bacteria. Our experiments revealed several important findings: First, we confirmed that Bsr34 requires a helper protein called Hfq to remain stable without Hfq, Bsr34 completely disappears. Second, Bsr34 is present in all Brucella species but not in other bacteria, suggesting a Brucella-specific function. Third, while bacteria lacking Bsr34 grew normally under laboratory conditions, Bsr34 levels dropped dramatically when bacteria faced envelope stress or acidic environments, conditions encountered inside host cells. Most importantly, when tested in mice, Brucella lacking Bsr34 showed significantly reduced ability to colonize and persist in the spleen at both 1 week and 4 weeks post-infection. This demonstrates that Bsr34 is specifically required for survival and disease within the host, even though it isn't essential for basic survival in the laboratory.
These discoveries provide the first glimpse into how Bsr34 functions as a specialized tool for infection rather than general bacterial survival. However, many questions remain unanswered.
We still don't know exactly which genes Bsr34 controls or the precise molecular mechanisms by which it helps bacteria adapt to the host environment. Future research will focus on identifying Bsr34's target genes and understanding how this small RNA coordinates the bacteria's response to the stresses encountered during infection. Understanding these small RNA regulators could eventually lead to new strategies for treating or preventing brucellosis by targeting the molecular switches that help Brucella survive inside host cells and cause disease