University of Tennessee Institute of Agriculture
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Investigating the Chemical Recycling of Polyesters and Polycarbonates: the Factors that Control the Depolymerization Rate and the Formation of Nanoplastics
No full textThe increasing demand for synthetic polymers is not being met with a corresponding rise in recycling, with only 9% of plastics being recycled annually. Consequently, the management of polymer waste is unsustainable, as most polymers end up in landfills or are incinerated. This research project examines Polyethylene Terephthalate (PET), Polycarbonate (PC), and TritanTM from Eastman Chemical Company, aiming to make recycling processes more sustainable. The focus is on understanding chain structure evolution during depolymerization, the impact of functional groups on depolymerization rates, polymer solvent compatibility, polymer crystal size\u27s influence on depolymerization kinetics, and imaging nanoplastics from environmental samples. It further seeks to utilize telechelics formed during depolymerization for repolymerization or to create value-added products, ultimately advancing sustainable polymer recycling and developing economically viable materials from polymer waste streams.
This project aims to depolymerize polymers into oligomers for next-generation materials. My first project (Chapter II) revealed that annealing PET before depolymerization increased crystallinity and altered crystal structure, enabling the production of desirable dihydroxy-terminated oligomers with limited post-depolymerization reactions. Chapter III demonstrated that diol/polymer compatibility directs the rate of heterogeneous phase depolymerization, although the carbonyl carbon\u27s reactivity also plays a role. Improved solubility (e.g., bisphenol-A) enhances the transition to a homogeneous phase, while poorer solubility (e.g., ethylene glycol) inhibits it. Chapter IV examines how crystallinity and crystal size impact the depolymerization of PET, enabling isolation of telechelic oligomers. The final project discussed (Chapter V) explores visualizing microplastics and nanoplastics using transmission electron microscopes and investigating how solubility affects the shape of formed nanoplastics
Templating the Assembly of Metal-Organic Frameworks on Cellulose for Multifunctional Materials
Get PDFMetal-organic frameworks (MOFs) are a class of crystalline materials that have been of immense interest due to their highly porous nature and multifunctional properties. However, the scalable production and applications of MOFs are hindered by their insolubility in water, tendency to precipitate and aggregate, and lack of processability. The combination of flexible cellulose macromolecules and rigid MOF crystals to form functional composites offers a promising solution to overcome these challenges. While recent studies have witnessed a fast evolution of cellulose/MOF functional material development, interfacial behavior and inherent mechanisms of hybridization between the two phases are relatively less clear. The current dissertation aims to unravel the inherent interaction between the two components and offer guidelines for rational fabrication of functional cellulose/MOF composites. The templating capability of cellulose was first demonstrated by using different modified forms of nanocellulose to hybridize with MOFs. Both sulfonated and carboxylated cellulose successfully directed the in situ formation of MOFs on the fibrils. The sulfonated cellulose/MOF was processed into freestanding aerogels with promising adsorption capacity for methylene blue. In the meantime, carboxylated cellulose templated the growth of fluorescent MOFs, which was subsequently designed into a sensing pad to detect pesticide methyl parathion. To enhance the cellulose/MOF compatibility and processability, the ionic liquid-induced spinning process was used. This enabled MOFs to be evenly incorporated into the regenerated cellulose filament matrix after dissolution and spinning. The interfacial compatibility between cellulose and MOFs was thoroughly investigated from the bulk morphology to the molecular level. Lastly, the mechanism of MOFs assembly on the carboxylated cellulose was investigated using molecular dynamics simulations. It is found that MOF precursors form coordination and hydrogen bonds with cellulose. These interactions provide binding sites for MOFs, guiding the in situ assembly of MOFs on the cellulose matrix
Modeling the Opioid Epidemic in Vulnerable Subpopulations and a Multiscale Mixed Modeling Approach to Parasitoid Wasp Dispersal with Host Interaction
Get PDFThe opioid epidemic has severely impacted the United States for decades. A rise in opioid prescriptions during the 1990s led to increased non-medical heroin use and, more recently, fentanyl use. This surge in both prescription and illicit opioids has contributed to a sharp increase in overdoses nationwide. In this study, we present a two-part compartmental model to better understand opioid use and overdose dynamics, focusing on two key factors influencing a vulnerable subpopulation: (1) the overall prevalence of opioid use in the broader community and (2) the availability of targeted resources for the subcommunity. Through mathematical analysis and comparison with population-level data, we assess how different subcommunity scenarios compare to the larger community and how these broader trends influence them.
Parasitoid wasps play a crucial role as agricultural biocontrol agents. However, modeling the spatial movement of these insects is challenging. These wasps are often very small, but their flight is primarily wind-driven, allowing them to travel kilometers from their release point. This results in a complex, multiscale modeling problem. In this study, we build upon an existing mathematical model of parasitoid wasp dispersal to explore the spatial dynamics between the wasps and their hosts. By combining analytical solutions with finite-difference approximations and incorporating half-hourly wind velocity data, we develop a coupled, two-dimensional spatial-temporal model to simulate the dispersal of the parasitoid wasps and their host. We then simulate various scenarios of parasitoid and host dynamics, generating visualizations of their dispersal patterns over time across a field. These simulations offer valuable insights into the complex interactions between the wasps and their hosts, advancing our understanding of their dispersal behavior and the potential for biocontrol applications
Revisiting the Schreiter Collection: A Multi-Proxy Study of Genomic Diversity, Paleodiet, and Geographic Mobility in the South-Central Andes
No full textAndean societies have been shaped by complex population movements, interaction networks, and cultural particularities since early periods of occupation. Despite the growing body of biomolecular research on past Andean lifeways, areas such as Northwest Argentina (NWA) remain underexplored. Positioned at a geographic intersection between the Andean Cordillera and the eastern lowlands of the Southern Cone, this region is essential for understanding past population dynamics across the continent. This research applies stable isotope analyses, complete mitochondrial genome sequencing, and radiocarbon dating to study pre-colonial individuals from the Schreiter Collection, an archaeological assemblage from the Quebrada de Villa Vil in NWA, to investigate paleodiet, mobility, and genomic diversity among ancient South-Central Andeans. This study arises from the interests of Argentine archaeologists to recontextualize individuals from the Schreiter Collection as part of ongoing research and community engagement efforts in the High Valleys of NWA, and research outcomes will support local communities in knowledge production and identity-building.
Stable isotope analyses (δ13C, δ15N, and δ18O) suggest heavy maize consumption, camelid protein supplementation, and crop fertilization practices, distinct weaning diets with increased C3 plant consumption, and minimal geographic mobility. Individuals from the Schreiter Collection exhibit mtDNA haplogroups A2+64 (66.67%), D1g5a (16.67%), and C1b (16.67%), which indicates genetic differentiation from Central Andean populations. Shared haplotypes with ancient individuals from Quebrada de Humahuaca and Calchaquí Valley suggest integration into regional exchange networks that facilitated gene flow, and a D1g5a mitogenome closely related to ancient individuals from Central Argentina and the Pampas supports evidence for population interactions between the South-Central Andes and the eastern lowlands. Isotopic uniformity and a regionally-distinct distribution of matrilines suggests a cohesive and well-established community identity in Quebrada de Villa Vil, while affinities with other ancient populations emphasize the differing scales of regional interaction networks
The Summer School of the South: Cultural Foundations of the Southern Education Movement in the Progressive Era, 1902-1912
Get PDFThis examination of The Summer School of the South explores how southern education reformers sought to ameliorate the South’s social problems through a cultural model of public education aimed at inspiring democratically conscious citizenship. From 1902-1912, teachers from across the South attended the six-week residential liberal arts program which blended ideals from the mid-nineteenth century common school movement with breakthroughs in the social sciences. The result was a curiosity-driven model for education that elevated individuals and fostered democratically conscious citizens. The Summer School platformed a liberal humanist vision of progressive education that over time was obscured by managerial progressives’ dual emphases on social efficiency and the modern research academy. This thesis traces how participating teachers and faculty used the Summer School of the South to claim cultural respectability, and professional status, aligning themselves with the emerging national middle class of progressives. In doing so, it situates the southern education movement within the broader trajectory of the Progressive Era
Evaluating Digital Health Record Systems: Utility, Security, Deployability and Usability
Get PDFThis thesis presents a comprehensive evaluation of the security foundations in modern Electronic Health Record (EHR) systems, emphasizing the persistent gap between usability-driven deployments and robust data protection. We assessed leading opensource and commercial EHR platforms—including OpenMRS, GNU Health, Epic, Cerner, and NextGen through a structured taxonomy of security, utility, deployability, and usability properties. Our evaluation revealed that while these systems offer mature interfaces and scalable deployments, they commonly lack critical protections such as record-level confidentiality, tamper-evident audit logs, and mechanisms for patient-controlled access. To address these shortcomings, we designed a cryptographically secure EHR architecture. Our approach enables fine-grained access policies, enforces per-record encryption using distinct keys, and ensures that only authorized parties can decrypt patient data. This system prioritizes patient sovereignty, minimizes insider threat vectors, and provides verifiable provenance across access events. Through comparative analysis and architectural modeling, we identify trade-offs in emergency access, metadata privacy, and clinical usability. The findings underscore the need for rethinking EHR security from the ground up, embedding cryptographic assurances without compromising operational workflows. This thesis contributes a modular framework for secure EHR design using cryptography and outlines future work on protocol standardization and usability optimization for deployment in real-world healthcare settings
The Impact of Food Loss and Waste Reduction Practices on Consumer Grocery Store Choice
Get PDFEfforts to reduce food loss and waste (FL&W) have gained increasing attention in both policy and retail settings, yet little is known about how such initiatives influence consumer behavior in grocery store selection. To address this limitation, we conducted a discrete choice experiment to determine how consumers respond to grocery stores committing to varying levels of FL&W reduction, different FL&W verification methods (self-reported, third-party, or government-certified), and benefit framings of why to reduce FL&W (hunger versus environmental impact) when selecting a grocery store. Using the results of a mixed logit model, we predicted the probability of store choice under two scenarios: one which varied the level of FL&W reduction and another which varied the verification mechanism. Government verification positively influenced store choice, while third-party verification had no statistically significant impact. Additionally, framing FL&W reduction as addressing hunger leads to a stronger consumer grocery store preference than environmental framing. Traditional factors like product variety, overall shopping expenses, and travel time impacted choice, highlighting a retailer’s need to balance these factors with FL&W reduction elements. Results can inform policymakers and retailers interested in designing effective FL&W reduction strategies that can offer a competitive advantage
Optimizing Corn Production in Tennessee: Enhancing Yield Potential and Nitrogen Use Efficiency
No full textCorn production is critical to the livelihood of producers and consumers, alike. Through global and domestic production of corn grain, every-day products are made possible, including, but not limited to food products, livestock/animal feed, and ethanol.
Corn is considered a high nitrogen feeder; thus, fertilizer N is a high direct cost input for growers. The use of nitrogen for production is essential; however, there are repercussions associated with the overuse and underuse of fertilizer N agronomically, economically, and environmentally. Fertilizer recommendations vary per geographical area and the nitrogen recommendation for Tennessee was developed decades ago. While the recommendation and reliance on nitrogen in a production system remains unchanged, genetics and hybrid selection continue to improve, thus the need for reassessment. The interconnection of production decisions, such as water input, hybrid selection, and nitrogen application rate, have the potential to influence the end results of yield, quality, and input efficiency. The study objectives include: determine the effect of water management, hybrid selection, nitrogen application rate, and the potential interactions thereof, on the agronomic yield and quality metrics of harvested grain as well as evaluate multiple nitrogen use efficiency indices in relation to water management, hybrid selection, and nitrogen application rate, to gain insight into the influence management practices have on the efficient utilization of nitrogen. The study aims to provide growers and researchers insight into the interworking of efficient management practice decision making in a corn production system in west Tennessee
Using Fatal Crash Data to Analyze Nationwide Trends in Pedestrian Safety at Bus Stops
No full textThe multimodal nature of public transit requires bus stops to be safely accessible to passengers who begin and end their trips as pedestrians. Prior studies have analyzed bus stop safety using crash data, but many of these studies assume that all crashes within a given distance of a bus stop are directly related to the stop itself. This is likely due to the limited availability of data that specifically identifies transit bus stop-related crashes, which this study confirmed through an examination of transit-related information in safety various safety datasets. This thesis begins to address this gap by analyzing fatal transit bus stop-related pedestrian crashes reported in the Fatality Analysis Reporting System (FARS) and comparing them with other nearby fatal pedestrian crashes. The data was preprocessed to include only fatal transit bus stop-related crashes and other fatal pedestrian crashes within a quarter- and half-mile radii. Then, a binary logit model and hierarchical clustering compared fatal transit bus stop-related crashes with other nearby fatal pedestrian crashes. Last, an inventory of bus stop infrastructure was manually compiled to assess fatal transit bus stop-related crashes. The binary logit model indicated that midblock stops, pedestrians on the roadside, and bus-involved crashes are strong indicators of fatal transit bus stop-related crashes. The cluster analysis revealed three fatal transit bus stop-related crash scenarios: (1) crossing to/from an intersection stop, (2) waiting on the roadside at a midblock stop, and (3) crossing to/from a midblock stop. The clustering of both transit bus stop-related and other nearby crashes showed that fatal crashes involving a pedestrian waiting at a midblock stop clustered separately from other nearby fatal crashes. Finally, the inventory revealed that bus stop infrastructure generally improved after the crash, but disparities exist between crossing- and waiting-related crash locations. This thesis reveals how fatal transit bus stop-related crashes compare to other nearby fatal crashes, helping identify countermeasures specific to transit stops. Crossing improvements may benefit both transit passengers and other pedestrians in the immediate areas. Relocating transit stops to signalized intersections and converting in-lane stops to curbside pull-out stops may enhance bus stop safety
The Effect of Tillage Practice and Cover Cropping Systems on Yield, Leaf Quality, and Angular Leaf Spot Occurrence in Dark Tobacco in Tennessee
No full textAngular Leaf Spot (ALS) (Psuedomonas syringae pv. tabaci) has become an increasingly important disease in Mid-South tobacco production since 2015. Current recommendations for the control and spread of ALS are selection of tobacco varieties with low susceptibility and the use of chemical preventions, such as agricultural streptomycin. Tobacco producers have limited options in weed management and rely heavily on tillage implementation and few pre-emergent herbicides. Cover crops have proven to be beneficial at decreasing weed biomass, improving soil health, and reducing soil borne pathogens in many crops. The objectives of this project are to evaluate the impact of cover crops and tillage type in tobacco production systems on ALS occurrence, tobacco yield, and leaf quality. Field plots were arranged in a split block design with four replications. Tillage type (conventional and no tillage) was applied to the main plot and cover crop treatment (cereal rye, crimson clover, hairy vetch, and fallow) to the sub-plot. Field inoculations of ALS were applied to tobacco in 2022 and 2023 at growth stages 1108 to 1110. Inoculated tobacco was harvested and left in the experimental area to serve as ALS inoculum for the following tobacco crop. Tobacco yield was impacted by tillage type, but disease progression was not statistically influenced by cover crops or tillage type during the first year of this study. During the second year, tillage influenced disease progression with conventional tillage having lower disease than no-tillage. Research has explored mostly chemical control methods of ALS with limited success. Additional research studying the impacts of other methods, such as cultural methods, should be conducted