Dissertations
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Item Endogenous and exogenous control of polymers for spatiotemporally defined drug delivery(2025-01) Flowers, MarcusPolymeric ‘smart drug delivery systems’ respond to external and environmental stimuli to modulate drug release at the right time and in the right place. Here I present several polymer systems to overcome challenges in spatiotemporal control of drug delivery. First, a novel acid-labile liquid polymer responsive to endogenous pH conditions was synthesized and characterized for releasing poorly soluble drugs as an injectable depot, a photo-crosslinked implantable matrix, temporarily stable nanodroplets and stable nanogels. Second, two acid-labile biodegradable liquid polymers were investigated for pH-responsive intracellular delivery of the immunomodulator R848 (or Resiquimod), a poorly soluble adjuvant for a melanoma vaccine. Third, nanodroplets of one of the liquid polymers were embedded in mucoadhesive wafers and were evaluated for spatially defined drug delivery to engineered tissues. Lastly, exogenously controlled drug release was demonstrated using a novel gold-coated hydrogel and focused ultrasound. Together, these studies have presented new biomaterial systems as versatile tools for controlled drug delivery with potential applications in immunotherapy and tissue engineering.Item The making of Unapologetic Blackness: Black women, media, and meaning-making(2025-02) Evans, MonicaThis dissertation focuses on “restorying” Black women’s lives/media representations through the lens of reclamation, in opposition to AfroPessimistic approaches shaped by historical tropes, legacy stereotypes, and the hegemonic structures and processes of racial and gender inequality, creates a better understanding of the ways in which Black women navigate the world through joy by decentering strife and struggle. This project investigates Unapologetic Blackness through the use of two intersecting media case studies: from television—Harlem (2021), and from music—Jazmine Sullivan’s Heaux Tales (2021). The research illustrates the unique intersection between restoring Black women’s narratives and centering the present representations of Black women. Ultimately, this project argues that Unapologetic Blackness is an expression of Black sociality that is radical in its creation of unique temporalities and safe spaces for Black women to be their full selves—emotionally vulnerable and expressive of autonomy.Item Searches for Dark Matter production in two fixed target experiments: HPS and LDMX(2025-01) Eichlersmith, TomAstrophysical evidence strongly indicates the presence of particulate Dark Matter (DM) within our universe; however, the specific particle nature of DM is still unknown. The wide variety of possible DM particles produces a similar range of experiments focused on probing these different categories of possible DM. This work describes two experiments taking different approaches to search for Light DM residing in the 2MeV-1GeV mass range being produced by electron interactions. The Light Dark Matter eXperiment (LDMX) is a proposed fixed target experiment designed for a missing momentum search with an additional, orthogonal missing energy search channel described here. The Heavy Photon Search experiment (HPS) is another fixed target experiment designed for a displaced vertex search with distances of O(10cm) which are not probed by longer baseline experiments. Specifically, a search in HPS data for a specific Light DM model with a strongly-coupled dark sector enabling a higher expected production rate while keeping the characteristic decay length within HPS's acceptance is also presented.Item Sensing the markets: the crisis of Turkish financial markets(2024-08) Coral-Irwin, DenizThis dissertation investigates everyday practices of financial trading and expertise at the intersection of market technologies, intersubjective relations on the trading floors, and the volatile aftermath of the failed military coup in 2016 in Turkey. Inspired by Ann Cvetkovich, I ask: How does capitalism feel at the very heart of capitalism, that is, on the trading floors? I build an anthropologically informed interdisciplinary lens based on affect theory, film and media studies, psychoanalysis, and feminist theory, and use “affect” as a key analytic and site of the dissertation. I argue that traders’ interactions with financial markets are not simply taken-for-granted, mediating action between an unmarked user and replicable, conventionalized technologies. Instead, I show that these interactions are entangled with memories, other humans, technologies, and conditions. Traders’ engagements with markets do not exist in a bubble. Therefore, I use the socially, politically, and economically precarious aftermath of the failed coup, where the AKP government’s ideological pressure on the Turkish Central Bank caused traders to reconsider the mechanisms of the supposedly open and neoliberal Turkish economy and question the norms and ideals of finance, as a critical window into analyzing financial trading and expertise as being shaped not so much by seemingly universal, calculative agencies and technologies but rather by senses, imaginations, and embodied entanglements. I demonstrate that practices of financial trading and expertise are not atomistic and rational. Rather, it emerges from the collective that emerges from the dynamics on the trading floors and institutional, organizational, and political frameworks and ideologies of finance. Hence, Sensing the Markets: The Crisis of Turkish Financial Markets offers a conceptually and methodologically novel approach to the social scientific studies of finance, demonstrating that analyzing global mechanisms of finance capitalism, which are in constant flux and friction, requires an ethnographic methodology and writing that is similarly open to confusion, excess, and affective attunements.Item Clothing values of Anishinaabeg(2025) Davis, SageThis study explores an alternative fashion system by examining values through the lens of language and culture. This research aimed to understand the value of clothing in the Anishinaabe fashion system. Dialogue around the acquisition, use, and disposal of clothing was explored to un-derstand how clothing and language use reflects lifestyle, identity, and mindset. This research en-gages Anishinaabe language learners and speakers to explore how clothing acquisition, use, and disposal connects to language use. Participants chose Anishinaabe language phrases throughout the interview corresponding to insights shared in English. Using qualitative research grounded in In-digenous knowledge and methodologies, this research investigates two central questions: (1) How do Anishinaabeg use their clothing? and (2) How do Anishinaabeg value their clothing? Findings reveal distinct differences between the values expressed in English and An-ishinaabemowin. English language responses reflected individualistic and compartmentalized per-spectives, mirroring the separation prevalent in European American fashion systems. In contrast, Anishinaabemowin responses demonstrated interconnectedness, reflecting community-centered and holistic values. Additionally, spirituality emerged as a distinct and separate element in English themes but was integrated throughout Anishinaabemowin themes. Findings highlight the im-portance of detaching fashion from capitalistic values and the significance of exploring sustainable fashion systems that respect and integrate Indigenous worldviews and cultural practices.Item Vibro-tactile stimulation as a non-invasive treatment method for cervical dystonia(2023-02) Xu, JiapengCervical dystonia (CD) is a form of focal dystonia associated with involuntary cervical muscle contractions that lead to sustained or intermittent abnormal, painful head movements or postures, which severely affect a CD patient’s daily life. Current treatment opportunities for CD are limited and mainly consist of Botulinum toxin (BoNT) injections in the dystonic muscles or deep brain stimulation. Both methods are invasive, and BoNT is not tolerated by all CD patients. This dissertation examined if superficial, vibro-tactile stimulation (VTS) of the cervical muscles can be an alternative method to provide temporary symptom relief for people with CD. Method: A total of 66 CD participants (44 female; mean age ± SD: 61.2 ±12.6 years) participated in the study. All participants were seen within two weeks before or one week after their new BoNT injection (i.e., their symptomatic period). The most often affected cervical muscles, sternocleidomastoid and trapezius, were stimulated. Participants completed up to 9 randomly ordered stimulations under different conditions (stimulating a single muscle or the combination of two muscles) based on their clinical manifestations (e.g., torticollis, laterocollis). Under each stimulation condition, VTS was applied continuously for 5 minutes. A head angle index (HAI), a composite measure reflecting the head deviation across the three head axes, and a self-reported pain score (100-point scale) were the primary outcome measures. Results: First, 83% of the participants showed 10% or higher improvement in HAI with 39% showing improvement higher than 30% under at least one stimulation condition. Approximately 58% of participants who experienced pain showed at least 10% or higher of improvement in pain score under at least one stimulation condition. Second, both therapeutic effects in normalizing abnormal head posture and reducing pain persisted immediately after cessation of VTS. However, the head normalization effect decayed quickly. Retention of pain relief was more stable and was observable up to 20 minutes after the cessation of VTS. Third, each CD manifestation does not have a distinct optimal stimulation profile. For a specific manifestation, several stimulation conditions could induce similarly large relative improvements or response rate. Conclusion: In summary, the findings of this study provide evidence that VTS can be used as a potential new treatment method for CD. Improvements in abnormal head posture and pain were observed among a large portion of participants during the application of VTS.Item Semi-dry biofilm reactors for efficient gas phase bioprocessing applications(2025-01) Xu, ChaoTraditional liquid-phase bioprocessing systems face significant challenges in achieving efficient degradation of airborne volatile organic compounds (VOCs) and maximizing biofuel production, largely due to complex mass transfer resistances and kinetic limitations inherent in gas-liquid-solid reaction environments. These barriers result in reduced efficiency in VOC removal and restrict the potential productivity of biofuel fermentation processes. To address these challenges, this research explores innovative gas-phase bioprocessing strategies using biofilm reactors, aiming to enhance the efficiency of bioprocessing and overcome the limitations associated with liquid media. The initial part of the study focuses on VOC biofiltration and biodegradation, processes typically constrained by factors such as VOC aqueous solubility, mass transfer resistance across multiple layers, and cellular metabolic kinetics. Recent advancements in this field are analyzed to introduce a simplified evaluation framework that leverages inherent mass transfer and kinetic parameters to establish a universal space-time productivity (effectiveness) index. This index provides a standardized metric for comparing process efficiencies across various reaction systems, allowing for an objective assessment of different engineering designs. Such a standardized evaluation not only reveals the limitations of current technologies but also offers guidance for future research efforts to address critical engineering constraints, thus advancing the field of VOC biofiltration. Building on this analysis, the research presents an innovative “dry” biofilm reactor system to enhance VOC degradation efficiency by directly exposing Pseudomonas putida F1 biofilms, supported on carbonized cellulosic fibers, to gaseous VOC substrates. By eliminating the need for bulk aqueous-phase media, this approach removes aqueous-phase mass transfer resistance, facilitating more efficient VOC capture and degradation. Using toluene as a model VOC, the biofilm system achieved a specific growth rate of 0.425 day⁻¹ under optimal conditions (300 p.p.m. toluene and 80% relative humidity). Long-term degradation tests conducted in a tubular packed bed reactor demonstrated a toluene degradation rate of 2.5 mg gDCW⁻¹ h⁻¹ during the initial growth phase. Importantly, the biofilm retained its biodegradation activity in the stationary phase, achieving a toluene degradation rate of 1.9 mg gDCW⁻¹ h⁻¹, with simultaneous CO₂ release at 6.4 mg gDCW⁻¹ h⁻¹, indicating complete carbon conversion of the substrate. Operated without any bulk liquid medium phase, the biofilm achieved direct degradation of gas‐phase VOC at rates of about one order of magnitude higher than what has been previously reported for liquid culturing or immobilized cells. These findings demonstrate the potential of dry biofilm reactors to efficiently degrade VOCs without requiring large amounts of water, representing a significant advancement in sustainable air pollution control. The second part of this study addresses the productivity limitations in biofuel fermentation, particularly in ethanol production. Traditional liquid-phase fermentation has reached its productivity ceiling, prompting a shift to alternative methods. In this research, a hollow fiber membrane (HFM)-supported biofilm reactor was developed to enable ethanol biosynthesis under gas-phase conditions. This design minimizes reaction volume and allows in situ ethanol recovery, significantly enhancing productivity. Under optimal operating conditions, the gas-phase reactor achieved a volumetric ethanol productivity of 37.5 g LBiomass⁻¹ h⁻¹ during the microbial growth phase and maintained productivity at 19.1 g LBiomass⁻¹ h⁻¹ during the stationary phase, with specific productivity rates of 0.58 g gDCW⁻¹ h⁻¹ and 0.047 g gDCW⁻¹ h⁻¹, respectively. Long-term operations demonstrated stable ethanol production, underscoring the potential of gas-phase bioprocessing to surpass the productivity limitations of liquid-phase systems. This liquid-free approach presents substantial potential for enhancing the efficiency and scalability of biofuel production systems. In summary, gas-phase bioprocessing using biofilm reactors offers a transformative solution for both environmental remediation and biofuel production. By eliminating mass transfer limitations inherent in liquid-phase systems, the proposed gas-phase strategies provide an efficient and sustainable pathway for VOC degradation and biofuel synthesis, opening new avenues for advancing bioprocessing technology.Item Data-aware optimizations for efficient analytics over geo-distributed data(2024-12) Wolfrath, JoelModern applications process large volumes of data, which are analyzed and used to improve user experience, guide business decisions, and drive innovation. This data is increasingly generated and persisted across multiple geographical locations, which presents several challenges for traditional analytics systems designed to operate in a centralized fashion. First, the wide-area network links that connect these locations can be exceedingly slow and less reliable than high-speed networks in the cloud. Second, the ubiquity of smart devices has driven an increase in the volume of data available for processing. Third, several application domains process real-time data and require low-latency responses for queries. Finally, data sovereignty laws can further constrain the ability to transfer data for analysis. New approaches are required to deliver low-latency analytics over large data volumes distributed across the country or the globe. This thesis proposes utilizing data-awareness--the ability to observe properties of the data being processed--to improve the efficiency of geo-distributed analytics systems. If the system has some knowledge of the underlying data distributions, queries can be optimized to reduce latency and improve resource efficiency. For example, we show that identifying devices with similar data distributions can accelerate model training in federated learning. Knowledge of data similarity across geo-distributed data sources can also be exploited to improve wide-area network efficiency and reduce query latency. We also show that inference serving systems can produce higher-accuracy inferences by dynamically selecting a model based on the data. By considering the properties of geo-distributed data sources, systems can optimally navigate trade-offs between resource usage, accuracy, and latency.Item Phytoremediation of deicing salt from roadside soils(2024) van Lierop, LeifRock salt, consisting of primarily sodium chloride, is a low-cost and effectivedeicing agent for winter weather events in northern climates. However, most of the salt dissolves in melting snow and ice and eventually finds its way into soil, streams, lakes, wetlands and groundwater, causing negative impacts to aquatic life and plants. Like deicing salt, improper irrigation can also lead to salt contamination resulting in substantial global agricultural and economic losses. While many current forms of soil remediation are costly and disruptive, phytoremediation, on the other hand, is an inexpensive and environmentally friendly method. Phytoremediation uses salt tolerant plants to uptake sodium chloride into their aboveground biomass, which is then harvested and utilized for purposes such as animal feed or bioenergy. This research explores the viability of using salt tolerant plants to remove sodium chloride from Minnesota (MN) roadside soils, thus reducing the overall quantity of road salt in the environment. First, potential plant species were inventoried and screened for their potential for roadside phytoremediation using a decision matrix. Then, some of the highest rated species from the matrix were evaluated for their capability to uptake sodium and chloride from soil in a greenhouse screening experiment. The plants with the highest total salt uptake were the annual species common sunflower and pitseed goosefoot, followed closely by the perennial tall fescue turfgrass with showy goldenrod and weeping alkaligrass trailing slightly behind tall fescue. Perennial species are more desirable for roadside planting and management and therefore may be more likely candidates for phytoremediation of road salt from roadside soils. Another greenhouse study was performed on some commonly grown MN plants. Of the species tested, sugar beet showed the highest concentration of salt in itaboveground biomass with around 20% salt by dry mass when watered with a salt solution of 100 mM NaCl. The promising results of sugar beet led to the investigation of the phytoremediation ability of other beet crops and the potential salt uptake of sugar beet in an agricultural setting. All the beet crops tested showed similar salt uptake to sugar beet in a greenhouse experiment and could therefore also be potential strong candidates for phytoremediation. Testing of beet samples from agricultural soils found that the harvest of the aboveground biomass can extract around 50 g salt/m2 from slightly moderate to moderately saline soils. Also, the high salt uptake by common sunflowers led to a greenhouse experiment comparing common sunflower to the perennial Maximilian, tall, stiff, western, and sawtooth sunflowers. While the perennials had significantly lower salt uptake than common sunflower, they had higher salt extraction than many of the perennials tested in the previous experiments. Using the greenhouse study results, common sunflower was estimated to remove roughly 30 to 50 g salt/m2 in an agricultural setting with moderately saline soil. Two field studies were conducted using species identified as having high potential in the decision matrix. The low salt content of roadside soils at our testing sites led to additional salting of the roadside plots to determine potential salt uptake in a heavily salted roadside field condition. In the first roadside study at a road research facility, the site was not readily accessible throughout the experiment and therefore was not able to be easily maintained. Regardless, common sunflower showed high levels of survival and growth in the two types of plots tested; seeded plots and plots with transplants that were germinated in a greenhouse. In both the seeded and transplant plots, common sunflower showed the highest salt uptake of plants tested with an extraction potential of around 10 g salt/m2. The second roadside study at a different site the following year was more easily maintained through weed control and watering. Common sunflower showed the highest salt extraction potential in the seeded plots with again around 10 g salt/m2. In the transplant salted plots, pitseed goosefoot had much higher salt extraction potential with an average of nearly 50 g salt/m2. Overall, this research has found multiple annual and perennial species that are promising candidates for phytoremediation that should be further investigated for their ability to grow together in a species mixture in various field conditions. Also, it was determined that sugar beet and common sunflower have significant potential for salt remediation of agricultural soils. Therefore, this research has the potential to reduce the salinity of salt contaminated roadside and agricultural soils over time through harvest of aboveground biomass of the highest potential species tested.Item Hybrid molecular beam epitaxy of ultra-wide band gap semiconductors(2023-02) Truttmann, TristanPerovskite oxides exhibit a seemingly universal set of functionalities, blessing them with an alluring mystique that draws unending attention from academic researchers. And yet, one previously unrealized functionality in perovskite oxides is that of an ultra-wide band gap semiconductor: high room-temperature carrier mobilities with a band gap in the ultraviolet. Far from being an academic curiosity, the development of better ultra-wide band gap semiconductors is the key to the downsizing and cost improvement of power conversion devices that are becoming increasingly ubiquitous, and increasingly central to electrification and decarbonization. This thesis is an exploration into the semiconducting properties of perovskites with exceptionally wide band gaps, with the eventual goal of developing a semiconductor that is better for power switching than any existing one. To study these perovskites, I use the modular thin film deposition technique called molecular beam epitaxy (MBE). The exploration starts with the study of SrSnO3, a noncubic perovskite with a band gap substantially larger than that of the more commonly studied BaSnO3. First, I present a systematic study of how film thickness drives a complex interplay among crystal symmetry, strain, structural quality, and transport, with the conclusion that surface effects eclipse all other sources of disorder. With this lesson in mind, I next explore doping of SrSnO3 films exceeding 200-nm thickness, constituting the most extensive doping study of SrSnO3 to date. I achieve a record-high mobility of 72 cm2V-1s-1, and, with the help of collaborators, predict the phonon-limited mobility to be 75~140 cm2V-1s-1 suggesting limited but perhaps substantial room for improvement. Motivated by these encouraging results in SrSnO3, I venture deeper into the ultraviolet with CaSnO3, a material with an even wider band gap. I present not only the first successful growth of CaSnO3 with MBE, but also the first successful doping of CaSnO3 in any form, demonstrating, for the first time, that CaSnO3 is a semiconductor rather than an insulator. I conclude my experimental results with the growth of rutile Sn1-xGexO2 with metalorganic MBE, motivated by the goal of growing the alkaline earth germanates, a family of metastable perovskites that share many properties with the stannates.Item Molecular level investigation of the spatial and temporal nanoparticle-corona complex through the application of techniques used to investigate protein-protein interactions(2024-09) Northwick, AndrewEngineered nanoparticles have been part many advances in electronics, agriculture, and medicine off the back of the unique properties from their size. On this scale, these materials have direct interactions with proteins, cells, and other biomolecules and adsorb a coating called a corona. The corona modifies the nanoparticle surface and functionality and has been shown to impact colloidal stability and function. Research had identified that the surface charge of the nanoparticle affects the rate of corona adsorption and that the concentration of a protein in solution does not correlate to the concentration in the corona. However, many of these studies are hampered by the fact the corona adsorbs non-covalently and that techniques required to isolate the complex for analysis remove all but the strongest interactions. This is not a novel challenge; techniques have been developed to protein-protein interactions (PPI) at the molecular scale that interact through similar mechanisms. In this dissertation, we outline the adaptation of two techniques, protein footprinting and photoactivated crosslinking, to investigate two aspects of the corona that have gone uninvestigated, the spatial and temporal corona. We have previously shown that this can be achieved though lysine footprinting, looking for decreases in labeling representing a loss of solvent accessibility through the adsorption to the nanoparticle. Using cytochrome C as a model, we found two binding sites and that other sections of the protein deform and become more solvent accessible. We expand upon this work investigating how protein deformability and matrix effect change binding. We find that proteins prefer to adsorb to the surface of the nanoparticle through binding loop regions and that the observed protein deformation is likely the rotation of secondary structure to accommodate optimal binding. (Chapter 2). With a baseline of protein binding sights, we then investigate how protein-protein interactions alter the corona orientation to start applying this protocol to more biologically relevant conditions (Chapter 3). We find that the presence of multiple proteins does not change the binding sites but does impact the packing on the surface of the nanoparticles. Addressing how the corona changes as it develops the hard corona presents a more difficult challenge as any initial contacts are not strong enough to survive isolation from solution, much like PPI. To isolate these interactions, photoreactive crosslinkers have been developed to form a covalent bond between targets. We outline a design synthetic method to incorporate a photoreactive group into a ligand to incorporate onto the nanoparticle surface (Chapter 4). We also investigated a crosslinker with reported <1 min activation times to capture interactions as early as possible and found that the presence of nanoparticles provides interference. We also highlight the potential colorimetric assays to measure and optimize the activity of the photocrosslinkers pushing forward to investigate the corona formed from complex mixtures.Item Exploring the influence of magnetic fields and silica nanoparticles on the behavior of thermoresponsive polymer solutions(2024-02) Neal, ChristopherStimuli-responsive materials have recently sparked significant interest driven by growing demand for flexible electronics and wearable sensors. Among these, thermoresponsive polymer solutions stand out as a crucial class, comprising of a flexible polymer chain dissolved in a relatively low viscosity solvent. These materials can rapidly change their morphology and macroscopic properties in response to temperature fluctuations. Poly(N-isopropyl-acrylamide) (PNIPAM) and poloxamers are notable examples exhibiting thermoresponsive behavior in water, undergoing reversible dissolution-dehydration phase transitions. Both are amphiphilic polymers, containing hydrophobic and hydrophilic portions, leading to the formation of physical hydrogels at biologically-relevant temperatures. Despite previous studies on altering the phase transition behavior with silica nanoparticle (NP) additives and magnetic (B) fields in diamagnetic polymer solutions, the understanding of how these factors influence hydrogen bonding in polymer solutions remains incomplete. Therefore, developing methods to tune and characterize polymer-solvent interactions with NPs and B fields will significantly enhance the applicability and processability of these stimuli-responsive materials. The first goal of this thesis is to build an instrument capable of studying optical phase transitions of solutions under various concentrations of silica NPs and strengths of in-situ B fields. To do so, a turbidimeter will be designed, programmed and developed which can apply diverse and controlled temperature changes to solutions while simultaneously collecting light transmittance values. Turbidimetry studies the optical clarity of solutions; in polymer solutions, a 1- to 2-phase transition is often accompanied by a clear-to-cloudy transition, indicative of polymer dehydration. The modified turbidimeter (`magneto-turbidimeter') allows examinations into these polymer dehydration and aggregation mechanisms under different NP concentrations and B field strengths, revealing invaluable molecular-level insights about changes in interactions across these polymer phase transitions. The instrument was validated using aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions and compared to results collected manually by visually examining transmittance of vials of PNIPAM solution which were heated on a heating block. The second goal of this thesis is to study how B fields and silica NP additives impact the molecular level interactions in polymer solutions. Using a combination of calorimetric, spectroscopic and turbidimetric techniques--including the magneto-turbidimeter--the synergistic or antagonistic effects of silica NPs and B fields on the phase transition behavior of thermoresponsive polymer solutions are examined. Of particular interest is understanding how either NPs or B fields alter hydration shells or direct hydrogen bonds with PNIPAM side groups. While NP addition minorly impacts the PNIPAM thermodynamic and optical transitions, rheological transitions are dramatically altered and dependent upon NP quantity and shape. While NPs and B fields both reduce the phase separation energy barrier and lower optical transition temperatures by altering hydrogen bonding (H-bonding), infrared spectra demonstrate that the mechanism by which these changes occur is distinct. Magnetic fields primarily alter solvent polarization while NPs provide PNIPAM–NP H-bonding sites. Combining NP addition with field application uniquely alters the solution environment and results in field-dependent rheological behavior that is unseen in polymer-only solutions. Leveraging the insights of changes hydration with B fields, the third goal of this thesis is to study how the changes in polymer-solvent molecular interactions from B fields alter the rheological phase transition of PNIPAM solutions. Through the use of a magneto-rheological device, linearly-deforming oscillatory shear probed the formation of physical hydrogels from PNIPAM solutoins under various strengths of B fields. Here, we show that B fields weaken these physical hydrogels by limiting interactions between nearby PNIPAM-rich mesoglobules comprising the physical hydrogel network and by decreasing the size and water content of PNIPAM mesoglobules. Magnetic effects on hydrogel strength are also shown to depend upon the magnetization time and strength, as longer time and higher fields maximize B effects. Examinations of the two-step yielding behavior of PNIPAM hydrogels under various B field strengths suggest that B fields weaken mesoglobule-mesoglobule interactions without dramatic changes in the interaction length-scale. Conversely, B fields decrease the length-scale of longer-range mesoglobule correlations, likely due to a decrease in network connectivity from an increase in average inter-particle distance. Exploring the effects of B fields on the hydrogelation of PNIPAM solutions provides fundamental insight into the ability of B fields to interact with diamagnetic polymer solutions. The final goal of this thesis is to investigate the impact of B fields on the segmental dynamics of individual components in poloxamer solutions. Here, poloxamers are chosen as the material of interest over PNIPAM due to the highly uniform, ordered structures of the former, which minimize complications in QENS data. Through quasi-elastic neutron scattering (QENS) experiments conducted on aqueous poloxamer solutions, B fields increase the segmental dynamics of poly(ethylene oxide) (PEO) within the corona of poloxamer micelles. Curiously, diffusion of water molecules in the poloxamer corona was slightly slowed from magnetization, perhaps due to alterations in interactions between water-water H-bonding clusters due to magnetic polarization. Importantly, these changes in polymer and solvent dynamics are demonstrated to be independent of microstructural rearrangement, affirming that the application of a B field alters the interactions between polymer and solvent. The results of this thesis demonstrate that both B fields and hydrophilic silica nanoparticles are viable methods to alter the optical, thermodynamic, and rheological phase transition behavior of thermoresponsive polymer solutions. Exploring the manipulation of polymer-solvent interactions using these techniques expands their range of potential uses and reveals innovative pathways for crafting PNIPAM or poloxamer physical hydrogels. Specifically, understanding how nanoparticles or B fields alter polymer-solve hydrogen bonds offers novel avenues for tuning the directed assembly of soft matter systems.Item Experimental and numerical analysis of impacts, mass transfer, and deposition in dispersed phase systems(2024-02) Andrews, AustinMultiphase flows are fluid systems comprising at least two distinct phases that are transported jointly as a mixture. These systems pose challenges in engineering analysis and design due to the many permutations that arise from various mixture compositions and inter-phase interactions, often requiring case-specific analysis. The studies in this dissertation focus on experimental and numerical techniques to characterize dispersed phase systems, wherein the secondary phase(s) are dilute yet are able to greatly affect system behavior. Specific examples of such systems include (i) dusty high-speed flows where micrometer-sized atmospheric particles may lead to vehicle damage or failure, (ii) dissolved-ion transport in liquids near sensing membranes where coupled fluid flow and electrostatics can affect sensor performance, and (iii) nanometer to micrometer particle transport within electrostatic indoor air cleaners where device efficacy is directly related to particle size and composition. Motivated by these three examples, this thesis will be split into three main topics providing detail on (1) characterization of surface damage and erosion from high-speed particle impacts, (2) analysis of forced convection on ion-selective membranes using numerical solutions to the Navier-Stokes Nernst-Plank-Poisson system of equations, and (3) mass transfer analysis of particle collection with electrostatic precipitators using numerical methods developed from (2) alongside particle trajectory calculations. Through the study of these three topics, it was found that: (1) The extent of material damage from resulting high-speed particle impacts, as characterized by displaced material volume, can be collapsed into a single relationship for a wide range of impacting speeds and angles for ferrous sulfate projectiles onto Aluminum 6061-T6. (2) Phase boundary potentials in ion-selective membrane systems are influenced by external flow and can be described by unique dimensionless flow parameters such as the Debye length Reynolds number. (3) Newly developed approaches to describing particle mass transfer in electrostatic precipitators provide improvements in describing particle mass transfer rates in complex systems involving a combination of deterministic and stochastic particle motion.Item Metabolomic characterization of xenobiotic and nutrient metabolism events in pigs from dietary additives(2025) Mosher, WesleyDietary additives could benefit humans and production animals through their nutritional and non-nutritional functions. Diverse chemical and metabolic events in diet, digestive tract, and the post-absorption system could determine the efficacy of dietary additives. This dissertation investigated these events through metabolomics-based profiling and fingerprinting on three types of dietary additives, revealing chemical interactions of additives with food and feed, the disposition of additives in the gastrointestinal tract, and the metabolic influences of additives on the metabolism system and gut microbiome. The results provide useful insights on the mechanism of action as well as the biological and physiological consequences of consuming dietary additives. The values of the nutritional metabolomics approach as an effective tool for studying dietary additives are also highlighted by this dissertation research. In the first chapter, bisulfite-based mitigation of deoxynivalenol (DON), a highly reactive epoxy-sesquiterpenoid mycotoxin commonly present in cereal grains which are commonly used as animal feed ingredients, was evaluated. Dietary DON contamination negatively affects feed intake, growth, and health status in all stages of swine production. Both in vivo biotransformation, including somatic xenobiotic metabolism and microbial metabolism, and ex vivo chemical mitigation reactions, such as bisulfite-based sulfonation, have been shown to reduce the reactivity and bioavailability of DON in pigs. However, the influences of age and maturation on the disposition of DON and its chemical mitigation in pigs have not been examined previously. In this chapter, three animal studies were conducted: first, a comparison on the influence of age through two separate trials on nursery and finishing pigs, and then a follow up study on investigating the mass balance. The results revealed extensive interactions among maturation, DON disposition, and sulfonation treatment in pigs, and warrant further investigations to establish the reference values on the age of pigs, the level of DON contamination, and the dose of bisulfite agents to guide the mitigation practices in swine production. In the second chapter, the feasibility and efficacy of bile as a potential growth-promoting feed additive for nursery pigs was examined through chemometric characterization of bile from gilts, barrows, and sows to first evaluate the best choice for further study. There was particular interest in the HDCA content of the bile sources profiled based on previous studies in the literature connecting HDCA with response from antibiotic treatment. In the current study, the most HDCA-rich source was sow bile, which was collected for a feasibility trial to assess if nursery pigs would be receptive to its inclusion in their diets, as well as a long-term growth performance trial to understand the potential effects after feeding. The major findings from the studies include that nursery pigs are receptive to consuming up to 0.75% bile in their diets and that long-term feeding of bile acids can reduce the endogenous production of bile in nursery animals. The objective of the third study was to measure growth performance of nursery pigs fed three dietary concentrations of novel product containing extracted hydroxycinnamic acids and their oligomers and comparing these to a commercially available source of polyphenols. Overall, feeding the HCA supplemented diets had no significant effect on growth rate, feed intake, and gain efficiency regardless of dosage rate. Further, there were limited effects form feeding the HCA diets on the digesta and hepatic metabolome. The results from this evaluation indicate that HCA supplementation in weaned pig diets may have limited benefits for healthy nursery pigs in a clean environment, which represented the experimental conditions of this study. It is also important to note that dietary supplementation of a commercial polyphenolic-based feed additive at the recommended dosage provided no improvement in growth performance or metabolome response. Future studies are needed to evaluate if supplementing weaned pig diets with the HCA extract could improve the performance of the nursery pigs under health challenges and environmental stresses.Item Actin filament length regulation mediated by formin’s polymerization activities – nucleation and processive elongation(2025-02) Mahanta, BiswaprakashActin cytoskeletal organization governs essential cellular processes like cell motility, adhesion, cytokinesis, and morphogenesis. The assembly of actin filaments into higher order structures is regulated by a plethora of actin-binding proteins, which specialize the structures for specific functions. A significant fraction of these structures are assembled using unbranched actin filaments. The formin family of actin polymerases are uniquely responsible for polymerizing the majority of these unbranched filaments in cells. Formins function by binding the barbed end of filaments using their dimerized FH2 domains. They enhance the nucleation of filaments and facilitate monomer additions at the barbed end. The FH2 dimers step processively onto incoming actin monomers and stay bound to the barbed end to allow sustained filament growth. By remaining processively associated to the barbed end through thousands of cycles of subunit addition, formins protect filaments from capping and assemble filaments with physiologically relevant lengths. Despite its fundamental importance in actin cytoskeletal architecture, a clear understanding of formin’s processive elongation property remains elusive. Along with processive elongation, another way formins influence filament length is by nucleation of filaments. To understand how formins assemble filaments that attain precise lengths, we need an understanding of how both processive elongation and nucleation impact polymerization. To investigate how formin’s polymerization properties regulate filament length, we used in vitro actin reconstitution experiments, TIRF-microscopy based single molecule imaging, and stochastic modeling. We studied the budding yeast formin Bni1p to understand the regulation of formin processivity and found that the mechanism by which subunits are added to the filament barbed end has a vital role in dictating formin’s dwell time at the barbed end. Additionally, we uncovered a kinetic balance between formin-mediated nucleation and filament elongation, which is central to filament length regulation. Altogether, these findings provide novel insights into the workings of formins and advance the field in understanding their role in actin filament length regulation. This thesis provides a framework for future investigations to comprehend formin function and the roles played by other cellular factors in formin-mediated filament length regulation and actin cytoskeletal organization.Item Pd catalyzed carbonylation in the application of polymer synthesis via alkene/CO copolymerization and hydroesterification(2023-12) Lo, Shao-YuThe dissertation covers 4 projects centered on the utilization of Pd catalyst for copolymerization of carbon monoxide (CO) and olefin to synthesize polymers with diverse microstructures. The first 2 parts focus on the novel catalyst design to afford the chemo-selectivity between alkene/CO alternating copolymerization and hydroesterificaiton; meanwhile minimize side reaction such as alkene isomerization. The remaining 2 parts include a close look at alkene/CO copolymerization via more in-depth microstructure characterization of ethylene/CO or α-olefin/CO copolymer with various well-defined Pd catalysts.Item Driving pluripotent stem cell expansion to advance 3D cardiac tissue engineering(2024-02) Komosa, ElizabethRecent advancements in stem cell biology and biofabrication have greatly expanded the potential for creating complex, representative tissues for the study of nearly any system of the body and associated diseases. To better understand and treat cardiac diseases, which lead to over 600,000 deaths annually in the United States alone, our lab has developed a stem cell-derived, 3D-bioprinted chambered cardiac model, termed the human chambered muscle pump (hChaMP). In this model, human induced pluripotent stem cells (hiPSCs) are bioprinted in a cardiac bioink, expanded for two weeks, and then differentiated to the functional cells of the heart, cardiomyocytes. The resulting tissue is capable of generating macroscale contraction, allowing for measurement of clinically-relevant functional metrics. While the hChaMP is thus an exciting tool for improving cardiac modeling, limitations remain, including suboptimal thickness of viable tissue and insufficient reproducibility of hiPSC expansion and cardiac function. In this work, we develop a perfusion bioreactor that enables increased stem cell expansion in the hChaMP, with high distribution of cells across the tissue wall. We discuss initial attempts to differentiate the hiPSCs in the bioreactor and methods to improve the culture of cardiomyocytes under perfusion, with the goal of increasing viable tissue thickness and providing biomimetic load for improved cardiomyocyte maturation. We also uncover how stem cell expansion differs in the same scaffold from different vendors, as well as methods to enhance growth for improved consistency among bioprinted constructs. With improved and consistent hiPSC expansion, we aim to obtain a thick layer of cardiomyocytes, leading to reliable, physiologic function in the hChaMP. Future applications for hChaMP culture in the bioreactor, in addition to the potential for deriving pacemaker cardiomyocytes, are also outlined. The work described here will enable improved study of cardiac diseases, particularly cardiomyopathies, with the goal of informing therapies and reducing the global disease burden.Item Unraveling metabolic health and diabetes: insights into Placental mitochondrial programming, O-GlcNAc/mTORC1 dynamics, and pancreatic Beta-cell function(2025-01) Jo, SeokwonType 2 diabetes (T2D) is a condition characterized by impaired blood glucose regulation and is associated with comorbidities such as cardiovascular disease, nerve and kidney damage, and vision loss. The etiology of T2D is complex, involving both genetic predispositions and environmental factors, which can exert influence as early as pregnancy and extend into adulthood. Despite significant advances in T2D treatment since the discovery of insulin nearly a century ago, the disease continues to rise in prevalence. Pancreatic β-cells, responsible for insulin production, play a crucial role in T2D progression, as their dysfunction directly contributes to the disease. Understanding the timing of metabolic health programming and the mechanisms underlying β-cell failure is essential for advancing T2D therapies. This study aims to elucidate mechanisms behind the development of T2D and metabolic disorders, focusing on the role of in utero programming during critical developmental windows and nutrient sensor crosstalk in regulating pancreatic β-cell mass and function. Key findings include: 1) Placental mitochondrial dysfunction leads to fetal growth restriction, specifically in the females and alter offspring metabolic responses to stressors; 2) Disruptions in nutrient-driven O-GlcNAc and mTORC1 signaling contribute to β-cell failure through distinct and overlapping effects on glucose-stimulus coupling and β-cell proliferation; and 3) O-GlcNAc-dependent autophagy is essential for maintaining β-cell function and glucose homeostasis. This work suggests that metabolic trajectories are shaped as early as during pregnancy, through placenta, with distinct differences between males and females. Stressors in both early and later life can disrupt nutrient sensor pathways, such as O-GlcNAc and mTORC1 signaling, contributing to β-cell dysfunction and the progression of T2D. We emphasize that chronic disturbances, whether an increase or decrease, in these signaling pathways are detrimental to β-cell survival and function. Mechanistically, the findings highlight autophagy as a key downstream regulator of insulin secretion, controlled by nutrient sensor pathways.Item Balancing information mixing and optimality: a framework for robust and efficient distributed decision-making(2025-01) Khatana, VivekDriven by the need for resiliency, scalability, and plug-and-play operation, distributed decision-making is becoming increasingly vital. This thesis develops a comprehensive framework to address the challenges in distributed decision-making, focusing on distributed optimization and control of multi-agent networks. It combines theoretical insights, algorithmic tools, and experimental validation to enhance decision-making in networked dynamical systems (NDS) with applications aimed at advancing clean and renewable energy systems. The proposed solutions emphasize distributed consensus, distributed optimization under practical constraints, and resilience against malicious agents and natural disasters in modern power systems. Achieving consensus in multi-agent systems is a cornerstone of distributed decision-making. The first part of this thesis makes a significant contribution in the development of distributed average consensus algorithms in multi-agent networks. By analyzing the geometry of the ratio consensus algorithm, this thesis introduces a finite-time distributed stopping criterion that guarantees convergence within any specified tolerance, regardless of the dimensionality of the state variables. The approach leverages the monotonicity of network state polytopes indexed by time. Additionally, the thesis presents a finite-time stopping criterion for networks with dynamic interconnection topologies, demonstrating that global maximum and minimum values remain strictly monotonic, even with dynamic links. The practicality of these algorithms is showcased through MATLAB simulations and experiments with Node.js-based agents. To address communication noise in the cyber-physical components of NDS, a resilient average consensus algorithm is proposed. Each agent updates its estimates using local information while incorporating weighted, noise-free initial values during iterations. The resilient average consensus algorithm has a geometric rate of convergence under noiseless conditions and almost-sure consensus under noisy communication. Numerical experiments confirm its effectiveness under varying noise scenarios and parameters. Part two of this thesis introduces a framework for distributed multi-agent optimization problems involving a common decision variable. A novel optimize then agree approach decouples optimization and consensus steps, ensuring disagreement between agents’ estimates remains below a predefined tolerance; existing algorithms do not provide such a guarantee which is required in many engineering scenarios. For the class of distributed optimization problems with local linear equality, inequality, and set constraints, we develop an algorithm that works over directed communication topologies and accrues all the benefits of the Alternating Direction Method of Multipliers approach. The algorithms synthesize distributively, communication overhead remains within a log factor of the lower bound, and guarantees strong convergence properties, achieving global geometric convergence rates for strongly convex and Lipschitz differentiable functions and global sublinear convergence rates for general convex functions. The efficacy of this framework is demonstrated through comparisons with state-of-the-art algorithms on distributed optimization and learning problems. The last part of the thesis focuses on developing methods for clean and renewable energy adoption in power systems. We develop a distributed controller for secondary control in microgrids with grid-forming inverter-based resources (GFM IBRs). The controller uses distributed optimization, enabling decentralized measurements and neighborhood information exchange to achieve voltage regulation and reactive power sharing. Additionally, a framework for distributed detection and isolation of maliciously behaving agents is proposed for resilient power apportioning between distributed energy resources (DERs). To address challenges posed by the absence of power grids in catastrophic events, this thesis introduces a net-load management engine (horizon of viability (HoV) engine) that ensures reliable power supply to critical infrastructure over a given time-horizon by generating cost-optimal portfolios of local generation sources and loads using mixed-integer convex programming. Controller-hardware-in-the-loop (CHIL) platforms validate the proposed secondary controller, the resilient power apportioning protocol, and the HoV engine across diverse DERs and loads, demonstrating the robustness of the developed methods.Item Topologically-enhanced deep learning for spatial image processing and generation(2025-02) Ahmadkhani, MohsenThis dissertation explores the integration of topological awareness into deep learning frameworks for spatial image segmentation and generation. Addressing the critical need for topological consistency, the research develops novel methods to enhance the accuracy and reliability of segmentation outputs in geospatial and dendrological contexts. Key contributions include the introduction of TopoSinGAN, a topology-aware generative adversarial network, and TopoSegNet, a scalable segmentation model that incorporates topology-preserving loss functions. These models are evaluated across diverse datasets, including ultra-high-resolution tree-ring images and agricultural field boundaries. Building on the individual contributions of TopoSinGAN and TopoSegNet, the dissertation implements a comprehensive workflow that combines these models. TopoSinGAN is used to generate topologically consistent synthetic datasets, which are then employed to improve the training and accuracy of TopoSegNet. This integrated approach demonstrates significant advancements in segmentation performance, emphasizing the synergy between synthetic data generation and topological enhancement. The dissertation's findings establish a robust foundation for applying topological principles in deep learning, with implications for geospatial analysis, dendrochronology, and other domains requiring precise spatial delineation. By leveraging topology-aware techniques, this work advances the state-of-the-art in deep learning for image analysis, ensuring both geometric and structural fidelity in challenging applications.