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Nonlinear multi-fluid modeling of kinetic Alfvén waves in planetary magnetospheres
No full textUniversity of Minnesota Ph.D. dissertation. August 2025. Major: Physics. Advisor: Robert Lysak. 1 computer file (PDF); viii, 90 pages.Kinetic scale plasma effects are crucial for understanding energy transport in planetary magnetosphere systems, but due to the vast difference in length and time scales, they are challenging to capture in observation and simulation studies. This thesis presents the development and testing of a new nonlinear five-moment multifluid-Maxwell plasma model in a high resolution Finite Volume parallelized FORTRAN code to probe such phenomena. We test the code for cases of Earth-bound kinetic field line resonance (kFLR) evolution and Jovian Alfvénic filamentation in the Io flux tube. Our model reaches similar limits as existing fixed time-step Cartesian grid multifluid-Maxwell models used for other systems, such as Mercury, but the proof-of-concept is sound, and probes smaller length scales than previously attempted with fluid codes. The role of transverse ion convection in both test cases is evident, and suggests an avenue for future work in laboratory plasma experiments.West, Aaron. (2025). Nonlinear multi-fluid modeling of kinetic Alfvén waves in planetary magnetospheres. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278113
Making good memories: investigating the generation of protective and pathogenic memory CD8+ T cells
No full textUniversity of Minnesota Ph.D. dissertation. August 2025. Major: Microbiology, Immunology and Cancer Biology. Advisor: Stephen Jameson. 1 computer file (PDF); ix, 84 pages.CD8+ T cells are an important component of the adaptive immune system. Aneffective and durable memory CD8+ T cell response is critical to host immunity against intracellular pathogens and malignancy. Protective memory CD8+ T cells mount an efficient, antigen-specific response to a previously encountered infection, however there are numerous examples of CD8+ T cell mediated disease, either due to lack of responsiveness leading to immunodeficiency or hyperactivity leading to immunopathology. Key cytokines and transcription factors are important for the regulation of memory CD8+ T cell generation and function. STAT3 functions downstream of IL-6, IL-10, and IL-21 in CD8+ T cells, however previous studies using distinct models for STAT3 deletion reveal a discordant role for STAT3 in regulating activated CD8+ T cells and memory CD8+ T cell differentiation. To address this question of the role of STAT3, we used a CRISPR/Cas9 approach to ablate Stat3 in naïve T cells prior to acute viral infection. We found that loss of STAT3 in CD8+ T cells leads to inefficient production of a memory population without a qualitative change in CD8+ T cell differentiation. Transcriptional analysis at the effector phase revealed that loss of STAT3 did not skew CD8+ T cells toward a short-lived effector cell fate but instead displayed gene expression characteristics that aligned with early stages of CD8+ T cell exhaustion. An alternative function of memory CD8+ T cells is their ability to contribute to the immune response against an unrelated pathogen by bystander activation. Bystander CD8+ T cells bolster the overall immune response and provide additional protection in advance of an TCR-dependent CD8+ T cell response by sensing proinflammatory cytokines and by recognizing stress ligands on infected cells and employing innate-like killing functions through release of cytolytic granules, granzyme B and perforin, and the proinflammatory cytokine, IFNg. This is also generally considered to be a protective function of CD8+ T cells, however, there are some examples in mouse and human disease contexts that implicate a pathological bystander CD8+ T cell response. We developed two mouse models that had increased susceptibility to a bacterial infection with Listeria monocytogenes (Lm) in which mice had abundant populations of memory CD8+ T cells, generated by LCMV-Arm infection or with a subunit peptide vaccine (TriVax), suggesting a pathologic bystander CD8+ T cell mediated mechanism of disease. Determining the limits of protective bystander CD8+ T cell memory is imperative to determining therapeutic targets to prevent CD8+ T cell dysfunction in human disease states.Wall, Sarah. (2025). Making good memories: investigating the generation of protective and pathogenic memory CD8+ T cells. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278106
Toward the practical implementation of X-ray pulsar-based navigation in deep space
No full textUniversity of Minnesota Ph.D. dissertation. September 2025. Major: Aerospace Engineering and Mechanics. Advisor: Demoz Gebre-Egziabher. 1 computer file (PDF); xii, 135 pages.Deep space navigation has once again become a topic of concern as more missions aim to travel deeper into space with both autonomous and crewed missions. With this increase in volume of deep space missions comes strain on critical infrastructure used to support them, particularly the Deep Space Network (DSN). The DSN provides command, telemetry and navigation services to missions going to Earth’s moon and beyond, but due to limited time and resources, it is unable to keep up with this growing demand. This opens an opportunity for an autonomous method of navigation in deep space to supplement the DSN to relieve some of the strain imposed by increasing mission numbers. In particular, X-ray pulsar-based navigation (XNAV) presents a unique method for navigation using signals of opportunity. By observing these pulsar signals, a spacecraft is able to estimate its navigation states in deep space without needing to communicate with the Earth-based DSN. However, various practical issues stand in the way of the full implementation of XNAV in real spacecraft. Some of these include integer ambiguities, long integration times, and the use of very large detectors. In this dissertation, we target this set of issues to try and make progress towards XNAV’s practical implementation. First, we propose a method for estimating position using measurements of acceleration due to gravity. This is done with the aim of reducing the search space required for resolving integer ambiguities in the pulsar signal to be able to form an absolute range measurement. By narrowing the search space, the integer ambiguities can be more efficiently resolved on board the spacecraft using existing integer ambiguity resolution techniques. An Extended Kalman Filter is shown which processes measurements of gravitational acceleration and fuses them with a model of gravity to form position measurements. This filter is validated in two cases, a Lunar transfer and a Mars transfer, using Monte Carlo simulations. To compliment this filter, we present a method of measuring gravitational acceleration on orbit which cannot be achieved by traditional accelerometers. By measuring the rate of change of the Doppler shift in the pulsar signal, we are able to calculate the spacecraft acceleration during the observation interval. Next, we present an analysis showing the impact clock errors have on XNAV measurements. Due to the long stare times, oscillator stability has the potential to cause large problems in our estimate of spacecraft navigation states. While clock noise has direct impacts on the observed photon times, the noise does not necessarily present itself during batch processing algorithms like the Maximum Likelihood Estimator (MLE) that are used to form estimates of the navigation states for the observer. To test the impact clock noise has on these measurements, we generate simulated photon observations and corrupt them with clock noise generated using a random walk clock model. We choose different qualities of clock with different stability characteristics and perform Monte Carlo simulations to determine the effect oscillator stability has on the resulting navigation estimate by comparing estimate variance to the Cramer-Rao Lower Bound (CRLB). Finally, we characterize the performance of a small X-ray sensor called DESPINA. We present a series of trade studies across different design parameters including pulsar selection, field of view, detection area, pointing accuracy, and oscillator stability. We then present a case study of a full XNAV system in a Lunar transfer orbit with DESPINA as its lone sensor. This is once again tested using a Monte Carlo simulation environment to determine the performance of the XNAV system.Houser, Kyle. (2025). Toward the practical implementation of X-ray pulsar-based navigation in deep space. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278743
Defining the tumor transcriptome and systemic immune landscape of French bulldogs with high-grade gliomas: insights into breed-specific survival disparities
No full textUniversity of Minnesota Ph.D. dissertation. June 2025. Major: Comparative and Molecular Biosciences. Advisor: Liz Pluhar. 1 computer file (PDF); xvii, 266 pages.Canine high-grade glioma (HGG) is an aggressive primary brain tumor with few treatment options and a uniformly poor prognosis. It shares many features with glioblastoma (GB), the most common and aggressive primary brain tumor in people. In effect, clinical trials investigating novel therapies in pet dogs can benefit both patient populations. Immunotherapy trials in HGG-bearing pet dogs have provided strong preliminary data for similar clinical trials in people with GB. The suitability of the canine HGG model to predict GB treatment responsiveness hinges on continued characterization of shared features betweenthe two cancers. Relative to immunotherapy trials, exploring variables that contribute to interpatient tumor heterogeneity and classifying both the local and systemic immune landscape in HGG-bearing dogs are especially important for both canine HGG and human GB patients. In a translational clinical trial at our institution, we observed that HGG- bearing French bulldogs had a uniquely poor response to immunotherapy-based treatments. The cause of this survival disparity was unknown, but given that the observation was breed-exclusive, heritable underlying causes pertaining to the HGG and the immune system were suspected. The purpose of this research was to define the transcriptomes of French bulldog HGG and circulating peripheral immune cells as compared to breeds with favorable response to immunotherapy. First, the survival disparity was further defined by investigating survival outcomes between breeds and treatments. Pertaining to immunotherapy, French bulldogs were confirmed to have markedly worse survival outcomes than boxers and Boston terriers, two dog breeds in the same phylogenetic clade as French bulldogs and with similar HGG prevalence. Pertaining to French bulldogs treated with four different treatments, the median survival time of immunotherapy-treated dogs was not significantly different from those treated with palliative care. Both these groups had significantly worse median survival times than those treated with stereotactic radiation therapy or sonodynamic therapy. Regarding characterization of the French bulldog HGG transcriptome, two investigations were performed using RNA sequencing of formalin-fixed, paraffin- embedded HGG tissue to conduct differential gene expression analysis and geneset enrichment analysis (GSEA). First, the baseline differences in tumor transcriptomes between French bulldogs and other breeds was explored. Treatment-naïve French bulldog HGG samples were compared to treatment- naïve boxer and Boston terrier samples. Differential gene expression revealed 31 differentially expressed genes (DEGs), with many having critical roles in glioma malignancy in both GB and HGG. GSEA showed activated enrichment of 15 pathways pertaining to cell cycle progression, oncogenes, and immune pathways. Second, the evolution of HGG following immunotherapy treatment was explored. Paired analyses of post-immunotherapy HGG samples versus pre- treatment HGG were performed in French bulldogs and separately in boxers and Boston terriers to enable comparison of DEGs between the two breeds. Compared to boxers and Boston terriers, French bulldog HGG was associated with larger log2-fold change magnitude in DEGs, upregulation of known drivers ofglioma progression, and enrichment of immune-associated pathways associated with poor prognosis. Regarding characterization of the French bulldog peripheral immune landscape in the presence of HGG, RNA multiplex analysis using NanoString’s Canine Immuno-Oncology (IO) panel was used to quantify 800 genes across 47 annotated pathways in blood samples obtained from HGG-bearing and HGG-free French bulldogs and boxers and Boston terriers. Differential gene expression analysis showed that when compared to HGG-free French bulldogs, HGG-bearing French bulldogs displayed eight upregulated and 46 downregulated DEGs, many demonstrated to be similarly altered in human GB circulating immune cells. This research represents the first step in determining the molecular mechanisms that cause the survival disparity observed in HGG-bearing, immunotherapy-treated French bulldogs. This information is valuable not only for informing breed-specific treatment options for pet dogs with HGG, but also further refines the canine HGG model of human GB. Future studies to validate the observations of this research may identify key targets for novel therapy development for both dogs and people.Arnold, Susan. (2025). Defining the tumor transcriptome and systemic immune landscape of French bulldogs with high-grade gliomas: insights into breed-specific survival disparities. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278037
Petrofabric investigation of the sulfide-rich basal zone of the Duluth Complex
No full textUniversity of Minnesota M.S. thesis. June 2025. Major: Earth Sciences. Advisors: Christian Teyssier, Donna Whitney. 1 computer file (PDF); x, 150 pages.The South Kawishiwi Intrusion (SKI) of the 1.1 Ga Duluth Complex hosts significant Cu–Ni–PGE sulfide deposits concentrated within its basal contact zone. Although the geochemical signatures of these ores are well documented, the physical mechanisms responsible for focusing sulfur-rich melts remain unclear. This study investigates whether dynamic magma flow, characterized by shearing that produces mineral alignments or fabrics—influenced sulfide mineralization by transporting immiscible sulfide droplets within a flowing, crystal-rich mush prior to deposition.We analyzed oriented drill core samples from eleven closely spaced sites spanning mineralized and unmineralized zones in the SKI, including the unmineralized Duluth Layered Series (DLS) using a combination of techniques. Anisotropy of magnetic susceptibility (AMS) analysis identifies a well-developed, magnetite/titanomagnetite-dominated, pseudo-single-domain (grain size ~0.1–10 µm), oblate magnetic fabric in the mineralized zone, which is weaker in unmineralized rocks. Fabric orientations vary within the ore zone, reflecting highly dynamic and likely turbulent conduit flow capable of suspending and mixing immiscible sulfide droplets during ore formation. Bulk magnetic susceptibility (Kₘ) is variable in the SKI basal zone, reflecting lithological heterogeneity as confirmed by petrography, but uniformly high in distal zones such as the DLS.
Electron backscatter diffraction (EBSD) analyses show that crystallographic preferred orientations of silicate minerals are generally subparallel to magnetic lineations, confirming the magmatic origin of the magnetic fabric. X-ray computed tomography (XCT) reveals that, where silicate minerals are well-aligned, sulfides form interconnected, net-textured networks along grain boundaries, whereas in rocks with disordered textures, sulfides remain diffuse and disseminated. These integrated results support the hypothesis that magma-flow-induced fabrics within conduit-like segments of the SKI have a link to sulfide transport, segregation, and localization. The combined AMS, EBSD, and XCT methodologies thus provide a powerful and transferable toolkit for studying magmatic sulfide deposits and decoding magma-flow processes in layered mafic–ultramafic intrusions globally.Cobbinah, Ishmael. (2025). Petrofabric investigation of the sulfide-rich basal zone of the Duluth Complex. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/277951
Transportation Needs and Current Services in Mille Lacs and Kanabec Counties and the 5-County East Central Region
No full textFor many communities in rural America, transportation access proves to be a substantial obstacle to healthy, sustainable living. The necessity of vehicle ownership creates significant barriers to accessing employment opportunities, affordable grocery stores, medical and social services, and personal recreation and social connections. In East Central Minnesota, the East Central Regional Development Commission (ECRDC) and Lighthouse Child & Family Services have initiated a collaborative effort to assess current transportation infrastructure and identify gaps between existing services and community needs. This regional collaboration brings together transportation providers, riders, regional authorities, and social service stakeholders in a concerted effort to understand and address this multifaceted issue that profoundly impacts quality of life in the region.
Through both qualitative focus group analysis of focus groups and quantitative assessment of existing transportation services, this report presents differences between needs and existing services for residents of Mille Lacs and Kanabec Counties. Our findings show a lack of East to West transit options, impacting quality of life as it relates to healthcare access, affordable grocery access, and social and recreational opportunities. The analysis of the focus group discussions highlights temporal service deficiencies, the differences in opportunities offered by medical and non-medical transportation, and nuanced relationships with rural volunteer driver networks.
The quantitative analysis revealed that transit availability in East Central Minnesota is uneven and needs some improvements to align with travel demand, with pronounced gaps between key cross-county city pairs like Cambridge and Princeton. County-level discrepancies are also found in terms of local/regional transit coverage. Results indicate that targeted expansions in service areas and transfer facilitation would more effectively address regional mobility needs than frequency increases alone.
Based on the findings of our analyses, we recommend four transit service improvements to address existing service gaps. These were specifically identified through the transit service gap analysis. However, they are consistent with the findings from the focus group discussions.
This work should support future considerations for service expansion by transit providers, legislative actions, and grant application processes for addressing transportation needs.This is a co-publication of the University of Minnesota’s Empowering Small Minnesota Communities (ESMC) Program. This effort is made possible thanks to funding by the Minnesota State Legislature. The ESMC is coordinated by UMN partners at the Center for Transportation Studies, the Center for Ur/ban and Regional Affairs, the Humphrey School of Public Affairs, the Minnesota Design Center and UMN Extension Regional Sustainable Development Partnerships.Baek, Kwangho; Jessup, Theodore; Douma, Frank; Khani, Alireza; Darger, Michael. (2025). Transportation Needs and Current Services in Mille Lacs and Kanabec Counties and the 5-County East Central Region. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278236
Teacher decision-making using inclusive pedagogy in Ghana
No full textUniversity of Minnesota Ph.D. dissertation. 2025. Major: Organizational Leadership, Policy, and Development. Advisor: Christopher Johnstone. 1 computer file (PDF); ii, 207 pages.This study examines primary school teachers' decisions regarding inclusive pedagogy in Ghana. The study uses phronesis as a theoretical framework to analyze teacher decision-making. Teachers describe how they use diverse instructional approaches to meet the needs of struggling learners and students with possible disabilities in the classroom. Findings shed insight into the processes that inform teacher decisions, the way in which inclusion is understood in a context without reliable disability identification, and the diverse pedagogical approaches teachers utilize to meet the needs of all students, even in large classrooms.Niad, Hayley. (2025). Teacher decision-making using inclusive pedagogy in Ghana. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278052
AI Ethics: Data Feminism in a World of Power
No full textThis is a Cognitive Science Honors Thesis. Faculty Advisor: Dr. Alexis ElderRadford, Alexandra. (2025). AI Ethics: Data Feminism in a World of Power. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/272034
SAIL Showcase (2025-05-01)
No full textUniversity of Minnesota Duluth. Swenson College of Science and Engineering. (2025). SAIL Showcase (2025-05-01). Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/272193
AILRC Spring Feast (2025-03-25)
No full textTuesday-March 25th; 12:00-2:00 pm; UMD Ballroom; Light lunch servedDavid O'Connor, Bad River Band of Lake Superior Chippewa; Note: AIS will be Honoring the memory Professor John Red HorseAmerican Indian Learning Resource Center, Indigenous Student Organization, Department of American Indian StudiesUniversity of Minnesota Duluth. American Indian Learning Resource Center. (2025). AILRC Spring Feast (2025-03-25). Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/272305