Master's Theses (Plan A and Professional Engineering Design Projects)

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Load Rating of Reinforced Concrete Box Culverts During Springtime Thaw Conditions
(2024-07) DeGonda, John
As Minnesota’s bridge inventory continues to age and climate conditions become more extreme, it becomes increasingly important to characterize bridge strength under adverse conditions. Cast-in-place (CIP) reinforced concrete box culverts (RCBC) are some of the older bridge-classified structures in Minnesota, and their continued functioning under spring-thawing soil conditions is essential to many common transportation routes. Four cast-in-place reinforced concrete box culverts were selected for field testing out of a sample of ten box culverts representative of the Minnesota inventory. Using data from field testing, three-dimensional finite element models of the culverts were created and calibrated by changing material properties to match field deflections and strains. Calibrated models were modified to match two cases of spring-thawing soil conditions, and load rating factors were generated for normal and thawed soil conditions. Load rating factors calculated using calibrated models were compared with rating factors generated using AASHTO BrR 7.5. Results indicated that thawed soil conditions result in a lower load rating compared to normal soil conditions, and rating factors from BrR 7.5 were conservative compared to calibrated model rating factors.
Stewarding Floodplain Forests in a Changing Climate: Assisted Migration and Spring Tree Phenology in an Urban Climate Change Experiment and Monitoring for Floodplain Tree Regeneration
(2024) Daniel, Abby
As climate change continues to affect the world’s ecosystems, land managers seek to determine the best actions to maintain or adapt their forests to the current and projected climatic shifts. Floodplain forests are an ecosystem of interest for mitigating the effects of climate change, primarily through increased critical habitat and biodiversity, reduced nutrient input in riverine systems, and carbon sequestration. These unique forests are critical in climate action plans, but they are also facing increasing stressors due to severe weather events, nonnative species, and landscape alterations, resulting in the need to support these forests through a changing climate. Chapter 1 of this thesis focuses on the spring phenology of trees planted in an urban floodplain forest climate change experiment in Saint Paul, MN. Specifically, we examined the bud break and leaf out of trees in the Adaptive Silviculture for Climate Change (ASCC) project to determine if resident tree species, southern tree species, and populations of trees from USDA Hardiness Zones 4, 5, and 6 differed in the timing of these phenophases. We found that novel southern tree species who were moved northward via assisted species migration and range expansion leafed out significantly later than all other species. We did not find many significant differences among trees within the same species who were sourced from different hardiness zones, with the exception of eastern cottonwood (Populus deltoides) trees from hardiness zone 5 breaking bud and leafing out later than those from zone 4. Our findings suggest that the movement of species northward from outside of their natural range may have implications for their successful growth and survival due to the potentially altered timing in key leaf phenological events and subsequent mismatch with the growing season at the site of relocation. Chapter 2 is focused on a collaboration with Prairie Island Indian Community to monitor floodplain forests to support the Tribe’s reforestation efforts. The overarching goal of monitoring was to support healthy and resilient floodplain forests through providing information that will assist in identifying successful tree planting locations for diverse and climate-resilient tree species derived from the “Resilience” management approach of the ASCC project. Planting of diverse tree species in canopy openings was desired to maintain a forest canopy and other ecosystem services after the removal of green ash (Fraxinus pennsylvanica) trees impacted by the nonnative insect emerald ash borer (Agrilus planipennis). We developed a monitoring plan to sample the understory vegetation and overstory light levels at sites deemed a priority for planting or for management actions to reduce reed canary grass (Phalaris arundinacea) abundance. While specific results and management recommendations will not be shared in this published thesis, we assessed the potential success of enrichment plantings as well as the impacts of reed canary grass in 19 canopy gaps. These included gaps where ash were harvested, where ash will be harvested, and pre-existing canopy gaps. We identified suitable sites and locations within gaps to plant a diverse set of floodplain tree species that will create and maintain forest canopy, provide habitat, and potentially increase resilience to the impacts of climate change.
Detangling Knots of Trauma: Intergenerational Transmission of Racial Trauma Through Hair Care Processes Between Mothers and Daughters In African American Families
(2024) De Souza Ramos, Gabriela
Black Hair has emerged as a significant topic in contemporary Critical Race discussions, fostering positive societal changes aimed at combating racism and supporting Black women in their struggles. This has led to the implementation of laws and programs, such as the Crown Act(Lee & Nambudiri, 2021), designed to address hair discrimination., designed to address hair discrimination. However, there remains a need to address various assumptions regarding the symbolism of Black hair in society. Hair discrimination and racist dynamics based on uninterrogated assumptions have resulted in racial trauma, which has profoundly affected Black women and their relationships with their mothers and with their Black Hair. This study explored the intergenerational transmission of racial trauma within African American families, focusing on mother-daughter hair care practices. Studies have shown that internalized racism can exacerbate racial trauma through intergenerational transmission within African American families (Watson, 2023); many Black women recall their first encounters with hair-related questioning within their families during their initial experiences with hair relaxers (Norwood, 2018). Grounded in a phenomenological approach, I conducted 10 interviews with African American women born and raised in the United States to understand their lived experiences about their hair, asking them to consider how racism, discrimination, and stigma affected their feelings about their hair and hair care, and how messages from their mothers during hair-caring interactions affected their feelings and experiences with their Black hair. Narrative analysis revealed that racial trauma was perpetuated through hair care interactions in families, specifically from mothers to daughters. Older women felt pressure to heed their mothers’ advice and conform to society’s white standard of beauty. Younger women were caught in the middle. Discrimination and racial trauma were real for them, yet they were empowered by recent societal changes to push back against white Supremacy norms to join the natural Black hair movement. The voices in the narratives of the Black women are reflected in this study. They are presented here to celebrate Black hair and advocate for anti-racist parenting as a contribution toward healing and breaking the cycle of intergenerational pain within Black communities. Key words: Black Hair, intergenerational transmission of racial trauma, mother - daughter relationships, discrimination, anti-racism, phenomenology
MORPHOLOGICAL, PHENOLOGICAL, AND TRANSPIRATIONAL DIFFERENTIATION IN POPULATIONS OF QUERCUS MACROCARPA AND QUERCUS RUBRA
(2024-05) Bergen, Erin
The characteristics and consequences of climate change are unfolding with unprecedented speed worldwide, and few places are changing faster than northern Minnesota. This study takes a unique approach to quantifying arboreal variation in physical plant traits and plant water use in the context of climate change. Two populations, northern and southern, of two species, Quercus macrocarpa and Quercus rubra, were grown in a common garden experiment at a northern field site and compared for climatic suitability. Traits that are known to have adaptive value, such as growth, leaf attributes, and phenological traits, were measured and compared. In addition, the transpiration rates of these populations were captured via portable rapid evapotranspiration chamber for comparison. Trees in a forested watershed can be responsible for up to 70% of the ecosystem’s water loss. Population-level differentiation in transpiration has ramifications for water cycling and may be an important but understudied consideration in climate-forward forest management practices. Rather than struggling in an adverse environment, these two species maintained their cohorts well, indicating that climate shifts have created hospitable long-term conditions for these species. There was genetic differentiation between the two populations for each species for traits that are important for climate adaptation. These differences were especially strong for fall phenology traits and notable for physiological traits linked to water use adaptation, such as specific leaf area. Importantly, measured transpiration varied at a population level for both species. In late August 2020 and 2021, Q. macrocarpa populations significantly differed in their transpiration rate and therefore water use. Furthermore, in a year with more water stress, Q. rubra also demonstrated significant population differentiation in midsummer transpiration. This suggests true population differences, a pattern that may become more evident over time or if additional sites from the original experiment are measured. A model constructed using field precipitation, discharge, and transpiration measurements demonstrated that each population for each species would have a unique impact on the discharge of the Stewart River. This study is one of the known few to demonstrate population differentiation in tree transpiration rates, particularly in Q. macrocarpa and Q. rubra. Taken altogether, this study demonstrates that northern populations may be falling out of alignment with local climate, at the cost of lost growth opportunities and greater winter stresses at the margins of the growing season, and that tree cover can have distinct impacts on ecosystem water balances even at a population scale. This presents an opportunity to counteract the desynchronization of climate shifts with local adaptations, especially in heavily forested regions such as northern Minnesota, and highlights the need for further investigation of water use impacts of trees chosen for planting.
A Multi-Value Macrophyte Based Assessment for Lakes in the Twin Cities Metro, Minnesota
(2024-07) Weaver, Maija
Macrophytes are an important component of lake ecosystems and approaches to assess their community are needed. Previously published aquatic macrophyte based indices often fail to address invasive species, single-species dominance, and mean rake density. Indices also have a single number output, which may be too general to accurately portray all aspects of the macrophyte community. My study developed a comprehensive multi-value aquatic macrophyte-based assessment for lakes in the Twin Cities Metro area of Minnesota, integrating metrics of invasive species, mean rake density, and species dominance. A database of 438 point-intercept surveys across 131 lakes in the seven-county metro area was used to evaluate existing indices and individual metrics. Among available indices of macrophyte community health I focused on two, Beck’s Index of Biotic Integrity (B-IBI) and the Aquatic Macrophyte Community Index (AMCI). Both were similar and highly correlated, but B-IBI was developed for Minnesota and does not confound invasives species with community health. I then created two additional indices, one for Invasive Species and another for Single-Species Dominance. The Invasive Species Index includes three metrics: frequency of occurrence of invasive macrophytes, mean rake density of curlyleaf pondweed, and mean rake density of Eurasian watermilfoil. The Single Species Dominance Index uses two metrics: the frequency of occurrence of the most abundant species relative to the littoral area vegetated and mean rake density of the most abundant species. The two new indices were used in conjunction with B-IBI, which accurately summarized general macrophyte community health, to create our multi-value assessment of individual lakes. Case studies involving lakes subjected to alum and herbicidal treatments demonstrate the indices' responsiveness to management actions. For instance, invasive species scores and dominance scores decreased in lakes treated with herbicides, reflecting effective invasive species control. Conversely, alum treatments primarily enhanced macrophyte community health without significantly impacting invasive species or dominance scores. My approach allows for the retrospective analysis of management practices, offering insights into the effectiveness of different interventions as well as prospective assessments for management outcomes. Overall, the multi-value assessment framework provides a useful tool for lake managers and regulators, enabling more informed decisions about aquatic macrophyte management and health.
Acoustic conditioning in common carp (Cyprinus carpio) to accelerate removal and reduce cost
(2024-07) Bullers, Rebecca
The common carp (Cyprinus carpio) is one of the most widely distributed invasive fish species in North America. Bait-and-removal strategies, which employ carp-specific bait and pop-up nets, face limitations due to the variability in size and duration of carp feeding aggregations. Acoustic conditioning, training carp to associate an acoustic signal with bait delivery, may enhance this strategy by promoting more synchronized aggregations. Two studies were conducted to examine this. In a controlled laboratory setting, carp subjected to partial reinforcement during acoustic conditioning exhibited behaviors more resistant to extinction than those under continuous reinforcement. In a natural lake, while carp did not significantly respond to the acoustic cue alone, pairing the cue with bait increased new carp recruitment to the site, accelerated the rate at which peak activity was reached, and resulted in tighter aggregations. These results suggest that acoustic conditioning can improve the efficiency and cost-effectiveness of bait-and-removal strategies.
Chemicals of Emerging Concern in Minnesota Subsurface Sewage Treatment Systems
(2023) Boor, Elizabeth
Subsurface Sewage Treatment Systems (SSTS) effectively treat traditional wastewater contaminants like organic matter, nitrogen, and phosphorous. However, they are not designed to treat contaminants of emerging concern (CEC). As the scientific community has discovered, CEC are prevalent in our environment. This paper includes two studies aiming to quantify concentrations of CEC in and coming from SSTS. The first study includes in-field data of CEC in septage, septic tank effluent, groundwater, and soil around three MNDOT rest area SSTS and one septage field application site. The second study is a complimentary laboratory soil column study that quantified CEC concentrations within a soil column and corresponding wheat samples following a known septage application. Both studies used mass spectrometry to quantify CEC in collected samples. The field study revealed that SSTS effluent and septage field application contribute to CEC concentrations found in the environment. SSTS do offer partial treatment of CEC, but many CEC escape secondary treatment and are found in the shallow groundwater near soil treatment areas. The Secondary Treatment Unit at the Rum River rest area significantly decreased severalCEC concentrations but did not fully degrade any target compounds. SSTS primary treatment—solids removal—also decreases the concentration of many CEC. However, the septage generated from solids removal is often land applied in Minnesota which then reintroduces removed CEC back into the environment. The soil column study showed detects of target CEC in groundwater, soil, and plant samples. However, poor recoveries in lab analysis resulted in high uncertainty in CEC concentrations. Because of the poor recoveries, a fate and transport analysis was not possible.
RET Kinase is transcriptionally regulated by ASCL1 in Neuroendocrine Prostate Cancer and Small Cell Lung Cancer
(2024-07) Tengse, Sachi Bhalchandra
Resistance to second-generation androgen deprivation therapies often causes neuroendocrine prostate cancer (NEPC), an aggressive disease variant, in castration-resistant prostate cancer patients. Due to low survival outcomes and limited therapeutic interventions for patients, it is imperative to study the molecular basis of NEPC. Studies have shown that NEPC can be categorized into two subtypes based on the expression of ASCL1 or NEUROD1, two proneuronaltranscription factors. In this study, we aim to find cell surface markers specific to ASCL+ NEPC which can be used as a biomarker or a druggable target. Analysis of parental and siASCL1 NCIH660 cells nominated RET as the top hit gene strongly correlated to ASCL1. In previous studies, we have shown that RET kinase is implicated as a mechanism of treatment resistance contributing to NEPC survival or growth. Here, we see that RET gene expression strongly correlates to ASCL1 but not NEUROD1 in various NEPC patient samples and mouse models. This data was corroborated by scRNA-seq data in CRPC-NEPC samples, whereas there was no expression of RET or ASCL1 in CRPC-Adeno samples. We also analyzed temporal gene expression data from PARCB xenograft models, and observed that the gene expression of RET mirrors the gene expression of ASCL1, and increases as the tumor progresses towards a neuroendocrine phenotype. Informatics modeling of whole transcriptome sequencing data from patient samples indicates that RET and ASCL1 has substantially similar gene network signatures in NEPC than ADCA, implying that these genes reside in the same gene ecosystem in NEPC. Remarkably, we did not notice correlations between RET and NEUROD1 gene networks in both subtypes. We saw increased ASCL1 recruitment and H3K27ac marks at the RET transcription sites in ASCL1- positive PDXs, but not in CRPC or NEUROD1-positive PDXs. We also demonstrated a similar relationship between RET and ASCL1 in Small Cell Lung Cancer, a neuroendocrine cancer type using publicly available bulk RNA-seq, scRNA-seq, as well as ChIP-seq data. These results highlight the critical role of ASCL1 in mediating RET signaling in NEPC and will be crucial to stratify patients and develop novel therapeutic interventions.
Optimizing Training Resources Used in Neural Architecture Search- A Balancing Act Between Performance and Training Units.
(2024-05) Armah, Lovis
Recent works have introduced novel training methods in neural network architecture search (NAS) aimed at reducing computational costs. So, Le and Liang (ICML 2019) introduced the PDH Evolution (PDH-E) method for training the Evolved Transformer, on the computationally expensive WMT 2014 English-German translation task, and reported significant reductions in the number of models evaluated. Additionally, other studies have explored partial training, which involves training candidate models with fewer training steps, resulting in notable improvements in computational efficiency. However, a comparative analysis of the performance and computational efficiency of these methods against full training approaches, which utilize the entire dataset to train candidate models, is yet to be thoroughly explored in theliterature. In this study, we employ a micro-genetic algorithm to compare the performance of three training approaches: partial training, full training, and PDH-E. We define TU as the cumulative number of training steps required for NAS models to be evaluated to determine the best candidate. Using the MNIST dataset, we demonstrate that PDH-E, compared to full training, can achieve a performance improvement of 0.2% with an accuracy of 98.71%, while also realizing a 48% reduction in TU. However, we also highlight that poorly chosen training step configurations in PDH-E may result in the utilization of more TUs than necessary, with a 3.6% surplus compared to full training, achieving an accuracy of 98.74%. Moreover, we illustrate that partial training can achieve an accuracy of 98.05% with a configuration that yields a 96% reduction in TU.
The Impacts of Trypanosoma cruzi Strain Variability on Metabolism and Genetic Manipulation
(2024-07) Syeda, Nooreen Fatima
This research aimed to investigate how natural genetic variations in the eukaryotic unicellular parasite Trypanosoma cruzi, the causative agent of Chagas disease, impact its metabolism and ability to be genetically manipulated. To achieve this goal, the study focused on metabolic flexibility, antibiotic susceptibility, and the development of new tools for T. cruzi genetic manipulation. We examined ATP generation across three metabolic pathways in four T. cruzi strains: Esmeraldo, Sylvio-X10, CL Brener, and Tulahuen. Our findings revealed strain-specific variations, indicating two strains in particular preferentially utilize different metabolic pathways to maintain crucial ATP levels. This diversity of the T. cruzi species suggests a complex metabolic landscape with potential implications for parasite survival and pathogenicity within its host. Furthermore, we investigated antibiotic susceptibility among these four strains, and found significant variations in their susceptibility towards commonly used antibiotics for genetic manipulation. This demonstrates that empirically determining optimal selection markers for the strain being modified is very important. Notably, we found that genetic relatedness does not necessarily correlate with antibiotic susceptibility, as strains belonging to the same discrete typing units (DTUs) showed great variability in their responses to antibiotics. To facilitate future genetic studies in T. cruzi, we successfully developed a robust and flexible methodology for generating donor DNA constructs for CRISPR/Cas9-mediated gene editing. This approach, utilizing the NEBuilder HiFi DNA assembly method, enables the efficient assembly of complex donor DNA constructs from multiple fragments, streamlining the process of genetic manipulation in this parasite.Overall, this study provides a foundation for understanding the interplay between genetic variation, metabolism, and drug susceptibility in T. cruzi. Our long-term goal is to link strain-specific amino acid substitutions with different metabolic outcomes, ultimately leading to a more comprehensive understanding of T. cruzi biology and potentially revealing novel therapeutic targets for Chagas disease.
Balancing Art and Science: Guiding the Responsible Use of AI Systems in the Context of Art
(2024-05) Raines, Aaron
This thesis examines the transformative role of Artificial Intelligence in the realm of art, exploring its capabilities as both a creative tool and a disruptive force. It situates AI within the historical context of technological impacts on art, analyzing how AI redefines artistic processes, challenges traditional practices, and raises ethical questions. Through an examination of AI’s applications across various art forms, this study not only highlights the innovative potential of AI but also addresses the critical ethical implications it poses in art creation.Central to this thesis is the development of an ethical framework tailored for people integrating AI into their artistic processes. This framework provides guidance on maintaining artistic integrity while leveraging AI’s capabilities for novel artistic expression. The thesis further discusses the broader cultural impacts of AI in art, particularly its potential to democratize artistic creation and its risks, such as the undermining of authenticity and originality. The contributions of this research are threefold: it delineates AI’s role as a powerful catalyst in the creation of new art forms; it develops a comprehensive set of ethical guidelines for using AI in art; and it assesses AI’s cultural impact, advocating for responsible engagement with AI technologies in the art community. The study calls for ongoing dialogue and adaptive ethical practices as AI technologies continue to evolve. This research aims to equip artists with the insights necessary to navigate the evolving intersection of AI and art responsibly.
The Effects Of Ketogenic Diet On Lipid Metabolism In The Liver In Lipocalin 2 Knockout Mice
(2024-05) Peng, Huanzhao
Ketogenic diet is known to have benefits for epilepsy treatment and weight loss. However, long-term health outcomes of ketogenic diet remain debated. Lipocalin 2 (Lcn2) is a secreted protein known for its role in lipid metabolism by regulating mitochondrial function. In our previous studies, we observed that Lcn2 knockout (KO) mice had reduced levels of serum ketone bodies and increased liver lipid accumulation after receiving a long-term ketogenic diet feeding compared with wild-type (WT) mice. The current study was carried out to further investigate the role of Lcn2 in lipid metabolism in the liver under a long-term ketogenic diet feeding. We hypothesize that Lcn2 plays a crucial role in modulating the adverse effects of long-term ketogenic diet feeding on lipid accumulation in the liver. Specifically, we anticipate that Lcn2 deficiency will exacerbate hepatic lipid accumulation and impair ketogenesis in response to prolonged ketogenic diet consumption. Both Lcn2 KO mice and WT mice were examined after receiving either regular chow diet or ketogenic diet for 10 weeks. As liver is the principal site for ketogenesis, we examined the expression of genes involved in ketogenesis, mitochondrial fatty acid oxidation, lipogenesis, lipolysis, and oxidative stress to investigate how Lcn2 deficiency impacts the ketogenic diet-induced lipid metabolism in the liver. Our results showed that there was increased lipid accumulation and increased triglyceride levels in the liver in Lcn2 knockout mice fed a ketogenic diet for 10 weeks. In addition, the gene expression results indicate that the ketogenesis was altered and mitochondrial fatty acid oxidation was reduced in Lcn2 KO mice fed a ketogenic diet. Additionally, the results suggest that Lcn2 KO mice have reduced lipogenesis and increased lipolysis in the liver upon ketogenic diet feeding. Moreover, Lcn2 KO mice showed higher levels of oxidative stress in the liver under the ketogenic diet-fed condition compared with WT mice. In conclusion, Lcn2 deficiency impairs mitochondria function, which results in altered ketogenesis and reduced mitochondrial fatty acid oxidation capacity. Due to impaired mitochondrial function, Lcn2 deficiency leads to increased oxidative stress. Together, Lcn2 deficiency exacerbates the detrimental effects of long-term ketogenic diet on lipid metabolism in the liver, leading to fatty liver.
Multi-sink audio transmission in Pepper, a Humanoid Robot
(2024-07) Rao, Hritik
SoftBank Robotics Pepper, the Humanoid Robot, lacks simultaneous audio transmission and is limited in its connectivity choices. This study explores the development of audio protocols facilitating simultaneous audio transmission through multi-device/mode (loudspeaker, wireless modules) for Pepper in large group settings.The main goal of this exploratory study is to propose a new communication model to interact with Pepper and measure the acceptability metric to analyze users' willingness to adopt a wireless communication system with the robot. The proposed new model is user accessible for people with mild to moderate age-related hearing loss and provides an alternative to the traditional method using a radio frequency transmission system, overcoming the limitation of the onboard Bluetooth V4 driver of the current model. The RF audio transmission model splices the audio signal from the Pepper mainboard and sends it to an external BT module that captures and forwards it to an RF transmitter and receiver system so that the audio can be simultaneously transmitted to multiple receivers in group settings as well as multi-mode transmission where the standard Pepper communication protocol can be used in parallel with the new system which is more beneficial for people with low to moderate hearing impairment. The exploratory study was deployed in an Alzheimer/Dementia memory unit in Superior, Wisconsin. The participants recruited were in regular contact with Pepper for various activities and games for four weeks prior to this study to analyze the receptivity of the communication mode without any bias seen in the initial acclimation period with humanoid robots.
Stabilizer States and the Holographic Entropy Cone
(2024-07) Osthus, Noah
The quantum entropy cone encapsulates all possible entropic structures for quantum states. The linear entropy inequalities that define it are a subset of those that define the analogous structure for holographic states: the holographic entropy cone. We define and review all of these concepts. Given the connection between AdS/CFT holography and quantum error correction, we seek to characterize the holographic entropy cone through a class of quantum states primarily used in quantum error correcting codes: qudit stabilizer states. We develop prerequisite formalism for the analysis of stabilizer states and especially their entanglement entropies. Then, we focus on a subset of stabilizer states called XZ-separable stabilizer states in order to simplify the expression for entanglement entropy. Finally, we look at ways of constructing XZ-separable states from entropy vectors, and apply this to many of the extreme rays of the 5-region holographic entropy cone.
Morphological and Mechanical Performance of Unstressed and Stressed Pipe-Grade High-Density Polyethylene Exposed to Chlorinated Environment
(2024-07) Motta, Grace
High-density polyethylene (HDPE) is used in various industries, including pipes for carrying potable water, which creates an oxidative environment. This work investigates oxidative degradation of bimodal pipe-grade HDPE with short chain branches placed on the higher molecular weight chains. These short chain branches are intended to enhance pipe resistance to environmental stress corrosion cracking and are hypothesized to prevent oxidized polymer chains from migrating from the amorphous region to the crystalline region. This study evaluates the effect of stress on the morphological and mechanical performance of pipe-grade HDPE exposed to an oxidative environment. Extruded film HDPE samples are exposed to a 5ppm chlorinated water bath at 60℃ for up to 1500 hours. An apparatus is designed to keep the samples submerged in the bath while applying a constant load. During exposure, samples are subjected to a continuous stress (creep loading) of 0, 3, 5 or 6 MPa. Mechanical performance of the samples is evaluated by creep behavior during exposure (percent elongation vs. exposure time) and tensile tests after exposure (strain at break, strength, and modulus of toughness, which is the material’s capacity to absorb energy in plastic deformation). Morphology is assessed by Fourier-Transform infrared spectroscopy (carbonyl index), differential scanning calorimetry (crystallinity), and strain hardening modulus (entanglement molecular weight). The data is analyzed by grouping the samples into two sets based on thickness: “thin” (49µm to 63µm) and “thick” (79µm to 109µm). To account for variation in thickness among samples, a normalized exposure time (a function of Tref/T^2), referenced to a 90µm thick sample, is calculated. Key findings of this study are as follows: All samples, regardless of the application of stress, exhibit surface degradation. The carbonyl index (CI) increases up to 189% after 1500 hours of exposure. For thick samples, crystallinity remains constant, ranging from 62% to 64%, regardless of the application of stress. Only thick samples exposed for 1500 hours with an applied stress of 5MPa show evidence of degradation through the thickness. Entanglement molecular weight and mechanical performance are “bulk” (through-the-thickness) properties. For these thick samples with an applied stress of 5MPa, after 1500 hours of exposure, entanglement molecular weight increases by 58%, ultimate tensile strength decreases by 48%, and percent elongation at break decreases by 50%. This pilot study demonstrates the feasibility of constant loading during exposure and the importance of sample thickness. The thin sample set may have exhibited signs of degradation in some regions, but due to the variation in thickness across the film, the data are inconsistent. Data from the thick samples show greater consistency; however, the exposure time is insufficient to produce a brittle sample in the absence of applied stress. Future studies should include longer exposure times and additional molecular weight measurements, including molecular weight distribution and polydispersity index using gel permeation chromatography; due to the limited number of testing stations, a single stress level of 5MPa should be applied.
Fluorescence Microscopy Visualization of DNA Breakage in Extensional Flows of Microfluidic Devices
(2024-07) Onyango, Clive
Scission of DNA into smaller fragments is an important step in next-generation sequencing, with hydrodynamic breakage being a preferred method. Previous studies on flow-induced scission of DNA (and polymers in general) have focused on observing the distribution of scission products to infer the breakage mechanism and kinetics. Few studies have directly visualized the breakage of individual molecules in a flow of controlled type.We employed fluorescence microscopy to image the breakage dynamics of labelled DNA molecules in the extensional flow of microfluidic devices. By observing the distribution of breakage locations for 29 molecules and comparing breakage probability in extensional versus channel flows, we reveal that mechanical stretching at the tested conditions does not sufficiently weaken the backbone bond, and breakage is caused solely by photocleavage. Ligated DNA molecules broke less frequently than those from the stock solution, indicating that nicking increases the breakage probability. Increasing the mechanical stretching force through viscosity enhancement would be worthy of study to test whether strong stretching can lead to midpoint breakage of molecules.
Characterizing phosphorus impacts on crop yields, soil nutrient profiles, and water quality in soils at risk of flooding for several phosphorus-based fertilizers of varying source and rate
(2024-07) Malone, Rory
In the Red River Valley of northwestern Minnesota, phosphorus (P) is the main nutrient of concern that threatens the Lake Winnipeg watershed. Climate change has altered crop production in the Northern Great Plains, as increased summer temperatures have brought corn and soybean rotations to northern regions. Consequentially, farmers in the Red River Valley are implementing P rates for two years at once on corn-soybean rotations which do not have long-established fertility documentation in the region. Additionally, soluble orthophosphate (ortho-P) release from calcareous, alkaline soils to spring floodwater over agricultural fields is understudied. To characterize the impact of phosphorus-based fertilizers by source and rate on crop yields, soil nutrient concentrations, biomass nutrients, and nitrogen mineralization, field trials with corn and soybean rotations were conducted over two years at the University of Minnesota’s Northwest Research & Outreach Center, followed by a laboratory incubation study to characterize dissolved P release from the treatments over eight weeks of a cool, anaerobic, saturated environment designed to replicate spring flooding. Treatments included the following commonly used fertilizers: monoammonium phosphate (MAP, NPK: 11-52-0), MicroEssentials SZ (MESZ, NPK-Zn: 12-40-0-10S-1), and 25% Struvite/Crystal Green (NPK: 5-28-0). While increased fertilizer rates resulted in slightly higher yields for some datasets, two-year rates of P-based fertilizer did not make differences in crop yields. These field trials indicate that applying excess phosphorus to save time does not impact yields, but simply increases phosphorus available in soil water to run off under flooded conditions. Laboratory incubation of mesocosms from field samples by fertilizer source and rate at two depths (0-15 cm and 15-30 cm) showed distinct release of soluble P from the soil to water between treatments. Ortho-P release from soil to surface water and pH increased over time, with ortho-P being greater in concentration in the surface layer. The 3-week mark was a significant point in spikes of ortho-P release in both surface and subsurface soil layers, which characterizes a timeline for water quality concerns in spring flooding of agricultural fields, after iron reduction occurs and previously sorbed phosphorus is released. MAP + Struvite and MESZ at double rates had consistently higher dissolved ortho-P release, possibly due to the addition of magnesium and zinc. While double rates were not noticeable by crop yield in a second-year soybean rotation, double rates showed distinct risk of runoff to floodwaters in simulated conditions.
Dentists' Attitudes and Perspectives on Viewing Cone-beam Computed Tomography of Impacted Teeth in Virtual Reality
(2024-06) Liu, Deborah
Introduction: Three-dimensional (3-D) radiographic imaging has transformed the dental field since its inception by giving clinicians a wealth of data impossible to glean from two-dimensional (2-D) imaging. However, current viewing modalities were designed for 2-D and analog data, with no way to view 3-D imaging in its natural 3-D state, such as the case with cone-beam computed tomography (CBCT). Virtual reality (VR) has become increasingly widespread in recent years and poises itself as a new potential tool for viewing volumetric datasets.Aim: The aim of this study is to evaluate dentists’ attitudes and perspectives on using VR medical imaging application Medicalholodeck to view CBCT of impacted teeth using Oculus Quest 2 immersive VR headsets. This study also aims to investigate whether viewing 3-D data in VR allows for improved visualization and/or efficiency compared to 2-D viewing modalities. Methods: CBCT datasets of three patients with impacted teeth were uploaded to Quest 2 headsets. Participants underwent a VR tutorial and viewing session to become familiar with navigating 3-D data in VR and then completed a survey on their experience. As a proof-of-concept study, data were descriptive in nature and no statistical hypotheses were tested. Results: Results revealed varying perceptions of visualization and/or accuracy for impacted teeth and their surrounding craniofacial structures when viewed in VR. For many factors that oral surgeons, orthodontists, and periodontists consider in treating cases with impacted teeth, clinicians found VR to be beneficial, especially when used in conjunction with traditional 2-D viewing modalities. Clinicians perceived VR to provide heightened global visualization with its immersive capabilities, to be easy to use, and highly enjoyable. Current shortcomings of VR include its accompanying learning curve, mediocre resolution, and decreased ability to visualize small structures. Conclusions: Few studies have been completed thus far evaluating VR as a tool for viewing 3-D data in dentistry. Data from this study showed VR has promise for enhanced viewing of CBCT images, despite not currently being perceived to improve clinicians’ efficiency. Dentists believed VR provided improved visualization for certain morphological characteristics and will likely be most useful as an adjunctive tool for complex cases. As this study was descriptive in nature, further in-depth research is needed to provide additional insight on the clinical utility of viewing 3-D data in VR.
Social Reproduction in Education: A Comparative Study of Middle-Class Parenting in South Korea and the US
(2024-05) Lee, Yoosong
Is education the great equalizer? Education has long been considered to play a crucial role in promoting social mobility, providing individuals with equal opportunities and hope for a better life. However, numerous studies have shown that education can also serve as a means for maintaining social standing within the middle or wealthier class, who transmit privilege and advantages to the next generation through their own cultural strategy of education and parenting. Taking the cases of focal children in Unequal Childhoods by Annette Lareau as a reference to US middle-class parenting, and drawing on the researcher’s self-narrative of educational experience in the US and South Korea, this thesis investigates and compares how the cultural logic of middle-class parents in two different cultures permeates their children’s everyday life, accumulating transferrable and durable privilege. The comparisons are centered on three points; 1. parents’ engagement in formal learning, 2. parents’ engagement in informal learning, and 3. parents’ engagement in nonformal learning. This paper also proposes further discussion on alternative parenting strategies that could substitute for the prevailing ideology of middle-class parenting, and suggests how education institutions serve to close the educational gap between social classes.
Understanding the role of Pentraxin 3 in senescence and fibrogenesis in adipose tissue and liver during aging
(2022-07) Lee, Hsin-Ching
The inflammaging is defined as chronic and low-grade inflammation when aging. The pathogenesis of age-related diseases largely results from the development of inflammaging. Interestingly, patients with obesity share largely similar phenotypes with aging and both obesity and aging are accompanied by progressive inflammation in adipose tissue. Pentraxin 3 (PTX3) is a soluble pattern recognition receptor and plays an important role in the innate immune system. Moreover, PTX3 can be induced by different inflammatory stimuli in adipocytes. The change levels of plasma PTX3 has been observed in patients with metabolic diseases or aging individuals, however, investigating the role of PTX3 in adipose tissue and liver during inflammation and aging is still needed since the mechanism is not completely understood. My research is focused on understanding the role of PTX3 in senescence and fibrogenesis in adipose tissue and liver during aging. In the first project, we investigated the effect of PTX3 deficiency on cellular senescence and fibrogenesis of stromal vascular (SV) cells of brown adipose tissue (BAT) and inguinal (ING) white adipose tissue (Ing-WAT) from old female mice, and we found out that PTX3 deficiency results in increased senescence and fibrogenesis in SV cells of subcutaneous adipose tissue. In the second project, we determined the direct role of PTX3 in senescence and fibrogenesis by investigating the reversal effect of recombinant mouse PTX3 (rmPTX3) on senescence and fibrogenesis in SV cells. Unfortunately, we didn’t see the reversal effect of recombinant mouse PTX3 (rmPTX3) on senescence and fibrogenesis in SV cells. In the third project, we examined whether PTX3 deficiency impacts senescence and lipogenesis in liver in vivo, and we demonstrated that PTX3 deficiency itself significantly downregulated gene expression in lipogenesis, lipolysis, and mitochondria function in liver. Also, PTX3 deficiency attenuated fibrogenesis and gluconeogenesis in liver. In summary, my master research reveals that PTX3 deficiency results in increased senescence and fibrogenesis in SV cells of subcutaneous adipose tissue in old female mice and PTX3 deficiency attenuates lipid transport and oxidation, fibrogenesis, and gluconeogenesis in the liver.

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