Driven by Light: An Ultrafast Look into the Bright Future of Photosensitizers

University of Minnesota Ph.D. dissertation. April 2024. Major: Chemistry. Advisor: David Blank. 1 computer file (PDF); xiii, 339 pages.This thesis investigates various strong light-absorbing molecules that have potential applications in furthering our progress into replacing fossil fuels with clean energy resources and remediating harmful chemicals in the environment. The research presented in this thesis employs a range of spectroscopic techniques, complemented with computational predictions, to characterize the light absorption and excited state dynamics of newly developed chromophores that have shown promise in these various applications. Chapter 3 investigates a BODIPY-fullerene dyad designed to be used in organic photovoltaics as a triplet sensitizer to form longer-lived excitons. This triplet sensitization occurs via a ping-pong energy transfer mechanism between the BODIPY and fullerene, resulting in a long-lived BODIPY triplet (>1 µs). Chapters 4 and 5 investigate the MB-DIPY chromophore that could potentially displace fullerene as a strong and more versatile electron acceptor in organic photovoltaics. In Chapter 4, the redox potentials and photophysics of four MB-DIPY analogs are explored. The MB-DIPYs had comparable reduction potentials to fullerene and demonstrated efficient intersystem crossing to form long-lived triplet states (>10 µs). In Chapter 5, the MB-DIPY is functionalized with ferrocene, a strong electron donor, and demonstrated sub-ps charge-transfer from the ferrocene to the MB-DIPY followedby charge recombination in 12 ps. Chapters 6 and 7 investigate the Rh-Ga and Co-Ga heterobimetallic photocatalysts that can access challenging bonds via a photoredox mechanism. The excited state nature of these photocatalysts is first explored in Chapter 6. The results were consistent with the naked anionic catalyst being the active participant in the photocatalytic cycle. Chapter 7 investigates the reactivity of the photocatalysts with a chloroadamantane substrate. The results suggested that the substrate binds to the anionic rhodium photocatalyst and that the photocatalytic reactivity is not diffusion-limited. In contrast, the anionic cobalt catalyst was converted into the chlorinated precatalyst upon the addition of the substrate, demonstrating that the chemical reactivity of the rhodium and cobalt photocatalysts differ with this substrate.Schaffner, Jacob. (2024). Driven by Light: An Ultrafast Look into the Bright Future of Photosensitizers. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/264361

Biochar And Ecosystem Recovery: Evaluating Artificial Regeneration Outcomes And Understory Plant Community Dynamics In Response To Top-Dress Amendments In Northern Minnesota

University of Minnesota M.S. thesis. May 2024. Major: Natural Resources Science and Management. Advisor: Marcella Windmuller-Campione. 1 computer file (PDF); viii, 112 pages.Recurring and severe droughts present significant obstacles to successful forest regeneration. Biochar soil amendments have emerged as a promising possible solution, providing the dual benefit of mitigating climate change through carbon sequestration while enhancing forest soil health in areas facing regeneration challenges. These amendments improve seedling drought resilience through enhanced cation exchange capacity, water retention, and nutrient availability. However, existing research in forested systems is limited, and primarily focuses on short-term impacts of the amendment on soil nutrients, physical properties, and microbial communities. Researchers have identified a need for long-term, site-specific research regarding how biochar affects forests' growth and stand dynamics. Over a five-year period, we investigated the effects of two different doses of top-dressed biochar soil amendments on tree growth across four different species. Our study did not reveal significant positive effects of biochar on seedling growth or survival over this period. However, it also did not indicate any negative influence on seedling survival or growth. Notably, each species exhibited distinct response patterns, suggesting potential trends deserving further investigation and emphasizing the importance of temporal scale in such studies. Additionally, our analysis of vegetative community composition and structure in response to the biochar amendments revealed distinct species-community responses, indicating complex underlying mechanisms warranting further investigation. In summary, this study contributes to a deeper understanding of biochar’s role in post-disturbance vegetation recovery and sheds light on the variability in seedling response patterns influenced by biochar soil amendment. Emphasizing the significance of species-specific responses, as well as the potential ecosystem-wide cascading effects, our findings highlight the complexity of biochar applications and their interactions with both tree species and understory vegetation over time. This research adds to the growing body of knowledge on biochar applications in forestry, underscoring its potential benefits in reforestation and carbon sequestration efforts. Furthermore, it enhances our understanding of the potential long-term effects of biochar soil amendments on forest health, stand dynamics, and sustainable forest management practices in a changing climate.Ackerman, Sophie. (2024). Biochar And Ecosystem Recovery: Evaluating Artificial Regeneration Outcomes And Understory Plant Community Dynamics In Response To Top-Dress Amendments In Northern Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/264251

Minutes: Senate Committee on Finance and Planning: January 23, 2024

In these minutes: PEAK Implementation Update; FY 2025 Budget Variables and Levers; Committee DiscussionUniversity of Minnesota: Senate Committee on Finance and Planning. (2024). Minutes: Senate Committee on Finance and Planning: January 23, 2024. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/261608

Embedded Plate Anchorage Strength in Precast Hollowcore Slabs

University of Minnesota M.S. thesis. June 2024. Major: Civil Engineering. Advisor: Brock Hedegaard. 1 computer file (PDF); vi, 82 pages.In current practice, hollowcore slabs are connected to supporting elements bycasting a headed stud embedment plate in the hollowcore. This provides an area that can be welded to the supporting elements. When the supporting elements consist of foundation retaining walls or exterior walls, load is applied to the supporting element and is transferred to the hollowcore in the form of shear force. The capacity of anchors cast-in concrete can be calculated using design codes for structural concrete; however, these design procedures were developed using experimental data on solid concrete slabs. Due to the longitudinal voids in hollowcore slabs, it is uncertain if the design procedures developed for solid concrete apply to hollowcore. This research aimed to determine the applicability of the current design procedures to hollowcore and provide insight into the anchorage strength of the embedded plate in hollowcore slabs. Experimental testing was performed on hollowcore slabs to establish the anchorage strength in three directions. The results indicated that for the out-of-plane suction direction the headed stud nearest the slab edge may not be effective and the anchorage capacity should be designed using only the headed stud further from the slab edge. Additionally, the breakout strength in this direction should be calculated using a projected failure area that accounts for the longitudinal voids. The predicted failure mode matched the experimental failure mode for most tests, but the experimental capacity varied in comparison to the predicted capacity for the tests.Entinger, Justin. (2024). Embedded Plate Anchorage Strength in Precast Hollowcore Slabs. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/265091

Geomorphological and Archaeoastronomical Analysis of a Neolithic Landscape, Cranborne Chase, Southern Britain

University of Minnesota Ph.D. dissertation. January 2024. Major: Earth Sciences. Advisor: Howard Mooers. 1 computer file (PDF); xii, 221 pages.Cranborne Chase in southwest England is a well-known area of Neolithic archaeology where a nexus of population growth, cultural evolution and resource extraction during the 4th millennium led to development of one of the highest densities of earthen monuments, including numerous long barrows, the largest and longest cursus in Britain, and many other structures. Natural physiographic characteristics of the study area in tandem with anthropomorphic modification of local vegetation patterns on the downs since the Mesolithic provided a distinctive setting where the Early- to Middle-Neolithic cultural landscape developed. However, reasons for siting monuments at certain locations within the complex chalkland landscape, the purpose of specific and unique architectural forms and features of the earthen structures, and spatial relationships between the pattern of monuments and elements of the surrounding environment as a whole remain largely enigmatic. Are there special features of the natural landscape that the Neolithic population valued for earthen monument development, and why was such a high density of earthen monuments developed there? This thesis describes geological and paleo-environmental characteristics and cultural features of the study area c. 4th millennium, evaluates similarities and differences associated with Neolithic and Bronze Age earthen and chambered burial sites located across Britain, and presents methods and results of an astrometric analysis of topographic position, monument orientation, and viewscape from earthen monuments at Cranborne Chase. Results of this study demonstrate that spatial and temporal relationships between the earthen structures and elements of the surrounding landscape, seascape, and skyscape are key to recognizing and understanding the symbolism and signification expressed by the monumental architecture. The cultural landscape – including the pattern of both natural features and earthen monuments at Cranborne Chase, the South Hampshire Lowlands, and surrounding region – expresses spatial and temporal unification by alignment between Earth and sky, and the living and the dead. In that way, the cultural landscape is related to a Neolithic cosmology emphasizing features of the landscape and skyscape.Burley, Paul. (2024). Geomorphological and Archaeoastronomical Analysis of a Neolithic Landscape, Cranborne Chase, Southern Britain. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/262882

Cloverchat Episode 27: California 4-H

Runtime 26:47 minutesMinnesota 4-H State Ambassador Ebrahim, Lacey, Hallee and Hannah interview California 4-H State Ambassadors Sanjana, Michaela, and Tejas. They chat about what is unique about 4-H in California and what their State Ambassador team is like.Minnesota 4-H State Ambassadors; University of Minnesota Extension. (2024). Cloverchat Episode 27: California 4-H. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/265028

Effects of oxygen availability on metabolic enzyme abundances in Leptomonas pyrrhocoris

This item is a University Honors Capstone.Trypanosomes are parasitic protozoans. Trypanosomes have a unique membrane-bound metabolic organelle called the glycosome, which contains the first seven steps of glycolysis. It is thought the glycosome formed to facilitate enzymatic overhauls that were cellular responses to altered environmental conditions. Environmental changes are more apparent for dual-host trypanosomes, but the glycosome is still found in single-host species. This led to the research question: In single-host trypanosomes, what environmental condition could potentially cause glycosomal protein abundance changes? We hypothesized that a dramatic change in oxygen levels is responsible for the overhaul of glycosomal enzymes in the single-host trypanosome species Leptomonas pyrrhocoris. Additionally, this overhaul would not be seen in metabolic enzymes located outside the glycosome. To test the hypothesis, Leptomonas pyrrhocoris cells were placed in hypoxia and normoxia conditions. Cell counting and protein collection occurred on days two, three, and six. The abundances of five glycosomal enzymes and one cytoplasmic enzyme were measured via western blotting. Significance was determined through an unpaired two-tailed t-test. Trends observed in all enzymes showed that by day three enzymatic abundance was greater in hypoxia. This trend was either maintained or amplified through day six in all but one enzyme. However, because this trend was also observed in the cytosolic enzyme, the hypothesis was rejected. The trend seen in all enzymes suggests that while a change in oxygen level does cause an enzymatic overhaul, it is not one related to the glycosome.Tangen, Madelyn R. (2024). Effects of oxygen availability on metabolic enzyme abundances in Leptomonas pyrrhocoris. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/262680

The PRRSV-2 Saga: Evolutionary and Epidemiological Dynamics of Porcine Reproductive and Respiratory Syndrome Virus 2 in the United States

University of Minnesota Ph.D. dissertation. 2024. Major: Veterinary Medicine. Advisor: Kimberly VanderWaal. 1 computer file (PDF); 188 pages.Porcine reproductive and respiratory syndrome (PRRS) has inflicted substantial economic losses on the US swine industry over the past three decades, driven by the main etiological agent, PRRSV-2, which continuously evolves and spreads despite control efforts. Enhancing disease control measures necessitates an understanding of evolutionary dynamics of PRRSV. By leveraging virus genetic data and bioinformatics tools, this dissertation aims to unravel how PRRSV-2 has adapted, persisted, and disseminated within the U.S. Chapter 1 provides a background of the disease, the virus itself, and the existing knowledge gaps. Chapter 2 employs nationwide PRRSV-2 genetic and geographic data to uncover the patterns of disease spread and the dynamics of the virus population within the U.S. In Chapter 3, we conduct an in-depth investigation into between-farm transmission of an emerging PRRSV-2 sub-lineage within a specific, swine-dense region, using genetic and animal movement data. Chapter 4 utilizes data from the largest active PRRS monitoring program in the U.S. to forecast the potential emerging variants. Finally, in Chapter 5, we pinpoint the origin of a novel PRRSV-2 variant through an advanced analysis of whole-genome sequences.Chapter 2 revealed a cyclical pattern of sub-lineages contributing to the overall PRRSV-2 population and a shift across time in major hotspots for inter-regional spread. In Chapter 3, we narrow our focus to intra-regional spread by applying molecular epidemiological tools to construct farm-to-farm transmission networks for an emerging PRRSV-2 sub-lineage. These networks allowed us to examine factors contributing to between-farm spread and highlighted the significance of live animal movement, while recognizing that most transmission events remained unexplained. Both Chapters 2 and 3 characterize the periodic emergence of novel genetic variants of PRRSV-2, and anticipating such emergence events could aid in more strategic disease control. Chapter 4 demonstrated the utility of phylogenetic branching patterns and putative antigenic differences as early indicators of variant emergence. Finally, in Chapter 5, we expand the discussion of variant emergence from the ORF5 gene to the whole genome perspective. Analysis of whole-genome sequences unveiled a recombinant ancestor for an emerging variant of concern and emphasized the role of genomic recombination in PRRSV-2 evolution. Ultimately, our findings address novel insights into PRRSV-2 evolution and epidemiology at various geographic scales, providing beneficial guidance for targeted and early-response PRRS mitigation strategies in the U.S.Pamornchainavakul, Nakarin. (2024). The PRRSV-2 Saga: Evolutionary and Epidemiological Dynamics of Porcine Reproductive and Respiratory Syndrome Virus 2 in the United States. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/262879

How is one university doing in regards to teaching sex, gender, and reproduction topics inclusively? LGBTQ+ students respond.

Faculty Advisor: A. Kelly LaneCompared to their peers, LGBTQ+ students have lower persistence in STEM majors. This issue is, in part, due to exposure to topics that do not align with LGBTQ+ students’ lived experiences, reinforcing the theory of gender essentialism: the thought that gender and gender roles are natural and biologically driven based on sex. These topics are especially prevalent in biology courses where, commonly, sex is defined as binary, sex and gender are incorrectly conflated, and only heterosexual sex is presented making LGBTQ+ students feel erased. We investigate how LGBTQ+ students would alter the way sex and gender topics are addressed in their biology courses at one university. We investigated the following research question: How are biology lessons on sex and gender viewed as inclusive or exclusive by LGBTQ+ students? To conduct this research, we conducted focus group interviews with students who identify as LGBTQ+ and took undergraduate biology classes at one university. We followed focus group best practices. To analyze the focus group interviews, three researchers used iterative directed content analysis to create themes, coming to consensus. Participants were generally impressed with the inclusive teaching approaches in their biology classes, however, students noted potential areas of improvement, including creating safe spaces to use pronouns, providing disclaimers for potentially exclusive terminology (e.g., male and female), and managing the intricacies of active learning practices, such as negative student peer interactions in group work. We suggest several recommendations for instructors to establish a higher standard for inclusivity for LGBTQ+ students, including respecting students' pronouns, implementing a no-tolerance policy for discrimination, and using disclaimers to explain their language choices. Incorporating these recommendations into instruction has the potential to address LGBTQ+ student attrition in STEM majors, increasing persistence through the creation of more inclusive environments.This project was approved by the University of Minnesota IRB (Study #00017850. This work was funded by the CBS Microgrant.Hammerstrom, Emma M.; Kivett, Abbi; Driessen, Emily P.; Malmquist, Sarah. (2024). How is one university doing in regards to teaching sex, gender, and reproduction topics inclusively? LGBTQ+ students respond.. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/262608