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The effect of warming, drought, and elevated carbon dioxide on the germination, growth, and survival of Quercus macrocarpa acorns from across a North American latitudinal gradient
No full textUniversity of Minnesota M.S. thesis. August 2025. Major: Natural Resources Science and Management. Advisors: Peter Reich, Jeannine Cavender-Bares. 1 computer file (PDF); xi, 107 pages.Forests are being increasingly impacted by climate change, as warmer and drier conditions accelerate both tree mortality and subsequent shifts in species composition. Seedlings play an outsize role in this process, and so predicting the effect of changing climate conditions on seedling performance is essential to understanding the future of forests. Bur oak (Quercus macrocarpa) is especially important for this process at the boreal-temperate ecotone in northern Minnesota, and given their wide latitudinal distribution, bur oaks may have developed local adaptation in response to climate. We measured the germination, growth, and survival of Q. macrocarpa acorns from Minnesota (MN), Illinois (IL), and Oklahoma (OK), in two open-air global change experiments in Minnesota, USA, that manipulate above and below ground temperature, rainfall, and atmospheric CO2. The TeRaCON experiment in central Minnesota includes a fully factorial design with two levels of warming (ambient, +2.5°C), rainfall reduction (ambient, –30% by volume), and elevated atmospheric CO2 (ambient at 414ppm, elevated at 511ppm). The B4WarmED experiment also has a fully factorial design with three levels of warming (ambient, +1.7°C, +3.3°C) and two levels of rainfall (ambient, –30% by volume). We hypothesized that: (1) Greater warming and drought will be associated with reduced germination success, survival and growth, but that (2) elevated CO2 will be associated with increased performance. (3) Larger acorns will grow into taller seedlings, even if growth is limited under warmer and drier conditions. (4) Acorns from more arid climates (IL, OK) will perform better than those from MN when under warmer and drier conditions. (5) Acorns from more arid climates will germinate later in the season than those from farther north.
In central MN, warming and drought reduced overall first season survival as expected (by –13% and –14% respectively), while eCO2 increased it (+14%). However, farther north at B4WarmED, moderate warming had a marginally significant positive effect on survival (+17%). OK acorns germinated three weeks later at both sites, and had 30% lower survival at B4WarmED, as compared to acorns from MN and IL. In summary, we find that while climate change will likely impair Q. macrocarpa establishment in central Minnesota, it may potentially benefit establishment in northern Minnesota. There was not clear evidence of a locally adapted germination or survival advantage for acorns from IL and OK when planted in Minnesota, even under the warmer and drier conditions anticipated for the near future. Indeed, while Q. macrocarpa acorns from Oklahoma can germinate and survive equally well as native populations in central Minnesota, even under future warming northern Minnesota will likely remain too cool for acorns from Oklahoma to establish themselves as successfully as their local counterparts.Larson, Andrew. (2025). The effect of warming, drought, and elevated carbon dioxide on the germination, growth, and survival of Quercus macrocarpa acorns from across a North American latitudinal gradient. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278718
Developing RF safety strategies at high field and ultra-high field MRI
No full textUniversity of Minnesota Ph.D. dissertation. July 2025. Major: Physics. Advisor: Yigitcan Eryaman. 1 computer file (PDF); vii, 91 pages.Radiofrequency (RF) safety remains a critical concern in high field and ultra-high field magnetic resonance imaging (MRI), especially for patients with implanted medical devices such as deep brain stimulation (DBS) systems. This thesis addresses two central aims which are improving RF safety for patients with DBS implants and demonstrating the feasibility of conducting RF safety assessment beyond traditional scanner-based methods. Chapter 2 validates a patient-specific heating prediction workflow in a bilateral DBS configuration using an anthropomorphic phantom to accurately estimate heating near the electrical contacts for varying bilateral trajectories. Chapter 3 extends this validation to in vivo and postmortem swine models, accounting for tissue heterogeneity and perfusion effects, and further explores the use of a toroidal transceiver for artifact-reduced imaging near the DBS electrode in intraoperative MRI. Chapter 4 presented an implant-friendly (IF) RF excitation optimization workflow as a technique to reduce RF artifacts and heating risk in both phantom and patient imaging studies. Chapter 5 focused on presenting different RF safety validations that were conducted in a controlled B0-free RF safety lab across multiple frequencies, including SAR distribution mapping, DBS transfer function measurement, and hardware failure analysis. The validation results across all chapters highlight practical solutions to current RF safety limitations.Zulkarnain-Lemke, Nur Izzati Huda. (2025). Developing RF safety strategies at high field and ultra-high field MRI. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278135
An exploration of microbial motility and active fluids through the lens of 3D flow visualization
No full textUniversity of Minnesota Ph.D. dissertation. October 2025. Major: Chemical Engineering. Advisors: Xiang Cheng, Satish Kumar. 1 computer file (PDF); x, 133 pages.The study of microbial motility has progressed significantly in the past decade in nosmall part due to experimental visualization of the flow induced by freely swimming microorganisms, yet such visualizations have been constrained to two dimensions and many three-dimensional swimming behaviors remain inadequately defined. This thesis combines experimental visualization, hydrodynamic modeling, and numerical simulations to characterize microbial flow fields in three dimensions and changes to such flow fields due to various factors. First, we present the first experimental measurements of the three-dimensional (3D) flow field of freely swimming Chlamydomonas reinhardtii, visualized by holographic microscopy.
The characterized flow field revealed how the well-known 2D flow structures extend to 3D in both time-averaged and time-resolved, revealing complex structures that otherwise remain unclear from visualization of the 2D flow. In particular, the time-resolved vortex structures in 3D exhibit dynamics that are rich and unexpected in inertialess flow. The characterized 3D flow field also yields a more rigorous quantification of the energy expenditure, along with both the swimming and feeding efficiencies of the alga, providing a more accurate estimate of measures of physiological metric related to motility. Thus, complete characterization of the 3D flow field around C. reinhardtii advances our understanding of its motility and provides a powerful method to experimentally visualize flows around microorganisms in 3D.
Second, we examine the changes in C. reinhardtii flow fields due to physical changes to the cell, namely through two mutations in the length of its two flagella, one for shorter length and another for longer. Our measurements show, on time average, the forward shift of lateral vortex and hyperbolic stagnation point, along with the change in vortex orientation as the flagella length increases. The time-resolved flow fields show a similar change from puller to pusher flow between the mutants and the wild-type, though with notably different structures during the transition arising from the differing flagellar waveforms. From the characterized time-resolved flow fields, we quantify the changes in metrics such as swimming and feeding efficiencies to gain insight into physiological changes brought about by the change of flagella length.Third, we turn our attention into the propulsion of the bacterium Escherichia coli in the bulk and near a solid surface, utilizing hydrodynamic modeling to predict its 3D flow field. We extend upon the classic force dipole representation of the bacterium by adding two point torques, allowing us to capture the near-field rotational flow induced by the rotation of the body and flagella while preserving the far-field structure of a pusher-type force dipole flow in the bulk. Close to a solid surface, the characterized flow structure loses its mirror symmetry along the y = 0 and x = 0 planes, resulting in a clockwise ”twist” in the in-plane flow structure, providing us with an explanation to why the bacterium constantly turns clockwise while swimming next to a solid surface.
Lastly, we expand beyond the scope of a single swimming microorganism and probe the collective effect of numerous microswimmers inducing flow in a thin liquid film. Through both linear stability analysis and nonlinear simulations, we find that contractile active units have a destabilizing effect on the film, introducing new instabilities not commonly seen in passive films, while extensile active units have the opposite effect. This suggests a promising route to mitigate instabilities by introducing some level of extensile activity to an otherwise passive thin liquid film. Together, the work detailed in this thesis advances our understanding of microbial
motility through the characterization of the induced flow, providing insight into the hydrodynamic and biological aspects of the propulsion of a freely swimming microorganism.Pradipta, Gregorius. (2025). An exploration of microbial motility and active fluids through the lens of 3D flow visualization. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278796
Minutes: Senate Committee on Student Academic Integrity (SAIC): November 12, 2025
No full textIn these minutes: Welcome; Presidential AI Task Force Report UpdateUniversity of Minnesota: Senate Committee on Student Academic Integrity. (2025). Minutes: Senate Committee on Student Academic Integrity (SAIC): November 12, 2025. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278925
Effects of a feed sanitizer and an appetite stimulant on reproductive performance of sows
No full textUniversity of Minnesota M.S. thesis. July 2025. Major: Animal Sciences. Advisors: Lee Johnston, Andres Gomez Zapata. 1 computer file (PDF); vi, 154 pages.PROJECT ONE- Reduced microbial and pathogen content in feed is hypothesized to improve performance of sows and their nursing litters. The objective of this study was to evaluate the effects of a formaldehyde, propionic acid, and terpene-based feed sanitizer, on performance, health, and gut microbiome of sows and their nursing piglets. Two contemporary groups of sows, (n = 107 mixed parity Topigs Norsvin TN70 females) were divided across two dietary treatments which included a commercially relevant corn-soybean meal-based diet (Control; n=53) or the Control diet containing 0.55% sanitizer powder (5.5 kg of Termin-8 per metric ton; Treatment; n=54). Dietary treatments began on day 80 of gestation and continued through lactation to weaning. Sows were moved to individual farrowing stalls at approximately day 109 of pregnancy. Sows received 2.72 kg daily of their assigned lactation diet from entry to farrowing accommodations until farrowing. After farrowing, sows had ad libitum access to feed and water until weaning on approximately day 19 postpartum. Piglets were cross-fostered within dietary treatments within 24 hours of birth to equalize litter size. DNA for microbiome analyses was extracted from fecal swabs collected from sows before administration of diets and at weaning, and from piglets at weaning. Statistical analysis of data was conducted using the GLIMMIX procedure of SAS with a statistical model that included treatment as a fixed effect, group as a random effect, and sow parity as a covariate. Qiime2 and various R packages were used to analyze 16S rRNA MiSeq Illumina sequence data (V4 region). Dietary feed sanitizer had no significant effects on sow body weight or backfat depth, average daily feed intake of sows, wean-to-estrus interval, litter size or weight at weaning, or incidence of diarrhea in piglets. We observed decreased weight of stillborn pigs for sows fed sanitized diets compared to sows fed Control diet (P = 0.010). Gut microbiome composition (beta diversity) of both sows fed Control (PERMANOVA, F = 23.854, R2 = 0.271, P = 0.001) and sanitized diets (PERMANOVA, F = 13.371, R2 = 0.203, P = 0.001) changed from gestation to weaning in a similar manner, except for some distinctions in the taxa driving these differences. There were significant compositional differences in gut microbiomes between sows fed Control and sanitized diets at weaning (PERMANOVA, F= 11.354, R2 = 0.231, P= 0.001). Except for a few differentially abundant bacterial taxa, there were no significant compositional differences between the gut microbiome of piglets from sows fed either the Control or sanitized diets. No differences in alpha diversity were observed in sows or piglets at weaning, except for Chao1 richness of Control sows at gestation. In conclusion, supplementing sanitizer to sow diets did not significantly impact overall sow and piglet performance or piglet health; but did influence their gut microbiome to a moderate extent. This finding warrants further investigation into potential functional implications between effects of formaldehyde-based feed sanitizer and changes in the microbiome in the context of sow and piglet performance and health.
PROJECT TWO- Evaluation of a biogenic compound in heat-stressed lactating sows: Researchers have hypothesized that biogenic compounds may enhance voluntary feed intake of lactating sows, which is particularly beneficial during heat stress when feed consumption usually declines. The objectives of this study were to evaluate the effects of a proprietary blend of umami and truffle flavors with biogenic compounds, on voluntary feed intake and performance of lactating sows housed under heat-stress conditions. Four contemporary cohorts of mixed parity sows (n=224; Topigs Norsvin TN70 females) were allocated randomly within parity to 1 of 2 dietary treatments. Treatments were corn-soybean meal-based diets (Control; n=111) or the Control diet containing 0.075% Luctamax® SowVive (Lucta US, Mahwah, New Jersey; Treatment; n=113). Sows were moved into individual farrowing stalls at about day 109 of pregnancy, and offered their assigned treatment diets. To create heat stress, farrowing rooms were maintained at 29°C from 0600 h to 2100 h and 24 °C at night. Sows received 2.72 kg daily of their assigned lactation diet from entry to farrowing accommodations until farrowing. After farrowing, sows had ad libitum access to feed and water until weaning on about day 20 ± 1.2 postpartum. Piglets were cross-fostered within dietary treatments within 24 hours of birth to equalize litter size. Statistical analysis of performance data was conducted using the GLIMMIX procedure of SAS with treatment and sow parity-group (Parity 0-1; 2-4; 5+) as fixed effects, and cohort group as a random effect. Treatment diets had no significant effects on sow performance at weaning (P > 0.20). Average daily feed intake during lactation ranged from 4.0-5.1 kg/day for control sows and 3.6-5.4 kg/day for treatment sows (P = 0.357). Litter size at weaning ranged from 10.8-12.6 pigs per litter for control groups and 11.1-12.4 pigs per litter for treatment groups, and litter weight at weaning was similarly unaffected by flavored biogenic compound supplementation (P > 0.20). We observed decreased weight of stillborn pigs for sows fed the Treatment diet compared to sows the Control diet (P = 0.008). In conclusion, under the conditions of this experiment, feeding this combination of biogenic compounds to lactating sows experiencing heat stress did not influence voluntary feed intake of sows or sow and litter performance.Williams, Sara. (2025). Effects of a feed sanitizer and an appetite stimulant on reproductive performance of sows. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278017
Seasonal Ice phenology of high-latitude fresh and salt water lakes using SMAP satellite data
No full textUniversity of Minnesota M.S. thesis. August 2025. Major: Civil Engineering. Advisor: Ardeshir Ebtehaj. 1 computer file (PDF); ix, 77 pages.Accurate monitoring of lake ice dynamics is essential for understanding the lake-atmosphere interactions and net primary productivity, especially under global warming and permafrost thawing. This study demonstrates the first application of spaceborne L-band passive radiometry to retrieve large lake ice phenology, offering advantages over higher microwave frequencies and optical sensing systems due to deeper penetration depth and less background noise and interference. Anautomated algorithm using the Soil Moisture Active Passive (SMAP) satellite observations is proposed that relies on kernel-based change detection methodology for daily monitoring of more than 65 seasonal northern freshwater lakes. To evaluate retrieval accuracy, we performed detailed inter-sensor comparisons with MODIS optical imagery, AMSR2 microwave observations, and the NOAA IMS product. A spatially consistent pixel-level comparison framework was devel-oped to address differences in resolution, enabling robust statistical assessment of SMAP-derived ice-on and ice-off dates across twelve representative lakes. Results show high temporal agreement with AMSR2 (correlation coefficients often exceeding 0.95) and moderate agreement with IMS, with SMAP demonstrating enhanced sensitivity to transitional melt and freeze states. Trend analysis of phenological metrics across eighteen lakes revealed coherent signals of climate-driven change, including earlier spring melt and delayed freeze-up in many regions, consistent with ERA5 temperature-based metrics. While most trends were not statistically significant over the nine-year period, the observed directional patterns align with regional warming trends and highlight SMAP’s value for climate-sensitive lake ice monitoring. Overall, this work establishes SMAP L-band radiometry as a unique and effective tool for daily, all-season observation of lake ice dynamics at continental scale.Zuber, MD. (2025). Seasonal Ice phenology of high-latitude fresh and salt water lakes using SMAP satellite data. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278022
Influence of food composition on taste perception
No full textUniversity of Minnesota M.S. thesis. August 2025. Major: Food Science. Advisor: Devin Peterson. 1 computer file (PDF); vii, 92 pages.Molecular interactions among food ingredients are hypothesized to have a big impact on flavor perception affecting the release of taste compounds. It is challenging to calculate how much of the added flavor in the food formulation is being perceived. This thesis investigates the molecular interactions of taste compounds with food ingredients in both fresh and aged food products. Chapter 1 includes a general introduction about food processing, definition of the problem and general objectives.
Chapter 2 includes literature review about flavor perception, taste, tastants, taste receptors, taste qualities covered in this study such as saltiness, bitterness and sweetness. Also includes, the potential molecular interactions that can take place between macromolecules (carbohydrates, protein, lipids) with taste compounds and how those interactions could affect the final taste perception.
Chapter 3 presents the evaluations of interactions of simple ingredients such as starch, protein with tastants such as salt (sodium) and bitter compound (pinellic acid); as well as interactions with actual food system, refined and whole wheat bread, and the subsequent taste release in model systems under storage conditions.
Chapter 4 includes sensory Time Intensity evaluation, total chemical taste (sodium, pinellic acid, tryptophan, glucose and fructose) quantification in bread and saliva extracts after mastication after storage conditions and finally the correlation between sensory and chemical evaluation.
Chapter 5 includes future work suggestions.Anguaya Velasquez, Cesar Armando. (2025). Influence of food composition on taste perception. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/277957
Design of hydraulically actuated small-scale bubble generator & study of oxygen dissolution at elevated pressure
No full textUniversity of Minnesota M.S.M.E. thesis. July 2025. Major: Mechanical Engineering. Advisor: James Van de Ven. 1 computer file (PDF); xiv, 129 pages.Small-scale bubbles have become a highly studied field of research in previous decades and have shown potential in applications across several sectors including agriculture, wastewater treatment, and medicine. Several approaches including venturi nozzles, mixing mechanisms and electrolysis have been studied in the past but have failed to achieve small-scale bubble concentrations presented in thesis. The contribution of this thesis is an incremental step in the design of a hydraulically actuated small-scale bubble generator capable of treating hypoxia in humans through intravenous delivery of a super-oxygenated saline solution. The novel small-scale bubble generator is presented detailing its design, functionality and method of operation. The developed small-scale bubble generator regulates quantities of oxygen and saline to a controlled ratio, which are compressed and held at pressures up to 100 ATM until the oxygen is completely dissolved in saline. Upon complete dissolution, the high pressure homogenous solution is expanded through a restrictive orifice plate to atmospheric pressure resulting in the creation of small-scale bubbles as a result of degassing effects. An experimental study and mathematical model of dissolution and diffusion behavior of oxygen in water at elevated pressure utilizing the small-scale bubble generator are presented. The experimental study and mathematical model estimated values of dissolution and diffusion coefficients to be 6.1379 x 10⁻⁵ m/s and 2.8548 x 10⁻⁹ m²/s for the experimental data collected over three trials for nine hour periods. Estimated values are compared with a theoretical mass transfer model in which variances from theoretical outcomes are discussed. Experimental trials yielded dissolution and diffusion coefficients that agree with expected results for similar instances of mass transfer at the prescribed pressure, volume and system geometry. The results of this work indicate that achieving high levels of oxygen concentration in water at elevated pressure takes over nine hours to achieve due to the slow mechanism of diffusion through the liquid column. The time to reach 95% saturation is estimated to be 10.6 days (256 hours) using the geometry and test conditions of the designed system. The implications of these experiments are discussed in the treatment of hypoxia. This work can be used in future research to optimize the design of small-scale bubble generators utilizing the same approach, and as a benchmark for dissolution and diffusion behavior of oxygen in water at elevated pressure.Schommer, Nicholas. (2025). Design of hydraulically actuated small-scale bubble generator & study of oxygen dissolution at elevated pressure. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278005
Bad at love: treating heartache through love addiction recovery
No full textUniversity of Minnesota Ph.D. dissertation. September 2025. Major: Sociology. Advisors: Teresa Gowan, Kathy Hull. 1 computer file (PDF); ix, 251 pages.Love in late modernity is marked by both more freedom and more insecurity. On the one hand, we have more choice in who and how to love. On the other hand, these choices get commodified under capitalism and constrain us. The romance industry is a major engine of romantic commodification: it sells fantasies of passionate love and profits when these fantasies spin out of control. An ostensible refuge from this commodification is the “healthy love” industry, a branch of therapy culture, which promises to help us reap the benefits of romantic freedom without losing our sense of self-control. But how well does this work, and for whom? This dissertation analyzes the healthy love industry as a both a limited solution to the pain of modern love and a gendered form of social control. Through a mixed qualitative case study of “love addiction” recovery groups, a quintessential space of healthy love, I show how lovers come to think of themselves as unhealthy and work to get healthy, and how women’s oppression gets reproduced in the process. I make a central argument: the healthy love industry can empower people as they muck through the uncertainty of modern romance, but these effects are not equal, nor are they permanent. “Getting healthy” for men is about emotionalizing the self, while women, already stereotyped as overly-emotional, must work to rationalize the self and set stronger boundaries against romance. But since romantic love continues to be held up as central to women’s self-worth, women oscillate between the goals of romance and health, blaming themselves when they fail to achieve either. Ultimately, healthy love further constrains women’s romantic options while offering men expanded access to romance. My analysis contributes to debates around the potential for therapy culture to ease gendered oppression and highlights one critical way in which it falls short.Nelson, Tayler. (2025). Bad at love: treating heartache through love addiction recovery. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278756
Minutes: Student Senate Consultative Committee: October 9, 2025
No full textIn these minutes: P&A Senate Update; Internal Committees Update; Campus Reports; Chair’s ReportUniversity of Minnesota: Student Senate Consultative Committee. (2025). Minutes: Student Senate Consultative Committee: October 9, 2025. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/278941