Undergraduate Honors Theses

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    How Global Change Shapes Our World: Nitrogen and Salt Addition Affect Phytoplankton Morphology in a Small Freshwater Lake
    (2024) Rodgers, Amanda;
    Global environmental change has accelerated the deposition of nitrogen and salt into freshwaters. These changes affect the morphology of freshwater microbes, especially phytoplankton, which serve as primary producers for these ecosystems. Morphology reflects a microbe’s response to energy demands, selection, and environmental disturbance. In this pilot experiment, a handmade suspension device held samples from Cedar Bog Lake (East Bethel, MN) in three nitrogen conditions (17.6 mM NaNO3, 9 mM NaNO3, 0 mM NaNO3) crossed with two salt conditions (10 mM of NaCl or 0 mM of NaCl) plus a DI water control for BG11 media in triplicate on the surface of the lake for three weeks. I used flow cytometry to quantify community-level within-sample morphology using circle fit, area-based diameter (ABD) volume, aspect ratio, elongation, ABD area, compactness, particles/mL, and perimeter. A principal components analysis (PCA) revealed trait correlations between ABD area and ABD volume, and between circle fit, elongation, and compactness. A two-way analysis of variance (ANOVA) on the first three principal components (highly significant, accounting for 94.89% of the total variance) revealed a significant effect of nitrogen and a marginally significant effect of salt on principal component three, but no effect of treatment on the first two principal components. Nitrogen had a significant effect on particles/mL but treatment did not affect any of the other morphological traits individually. These results indicate that climate change has a complicated effect on freshwater microbial morphology at the community level. Future studies should focus on long-term changes in morphology in the field, focusing on the effects of nitrogen.
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    When States Kill Their Own Citizens: Protest Repression Under Occupation in Kashmir
    (2024) Rehman, Aleena;
    The following study provides an analysis of the conditions under which a state chooses to repress protestors in the context of Indian-administered Kashmir. Three hypotheses were tested, all of which were informed by the theory that democratic states are more likely to repress their citizens when they are not seen as part of the central polity. I examined five different instances of protest in Kashmir, controlling for size and relative location, and for each I determined whether or not expressions of religion, ethnonationalism, or separatism were present in the protests, as well as the extent of repression or lack thereof. I then used statements made by government and security officials in order to analyze the impact of these three expressions on the extent of repression faced by the protestors. The case studies demonstrated that all three types of expressions are correlated with increased state repression, but separatism has the most support as a causal factor in increased protest repression. Government and security officials are inclined to justify repression against separatist protestors by citing the integrity and sovereignty of the state, while also placing an emphasis on the importance of Indian nationalism. Their statements also indicated a lack of tolerance for any expressions of nationalism that extend beyond Indian nationalism, while also deeming certain sentiments expressed in protests to be more acceptable than others.
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    Abstract Syntax Contextualization Framework for Debugging Attribute Grammar Specifications
    (2024) Feraru, Matthew;
    In this thesis, we explore an aspect of debugging attribute grammar (AG) specifications. AG frameworks in themselves are high-level languages that allow a programmer to specify the syntax rules and semantics of a new programming language. The debugging of AG specifications is often done by interactively traversing abstract syntax trees (ASTs) that represent a parsed program in a metaprogram. The goal of such debugging is to find AG specifications with semantic rules that observe correct inputs but incorrect outputs—the possible bugs of AG specifications we consider. For large programs, ASTs may be difficult to understand by a programmer; graphically rendering ASTs in a debugging interface is challenging and still does not make it straightforwardly easy to understand ASTs relative to source code. Resultantly, we propose a textual way to use source and source-like syntax to represent the location of a navigated-to AST node relative to its position in an entire AST and highlight any notable features of the tree, such as the application of rewrite rules. This contextualization framework of abstract syntax tree nodes has been prototyped to work on Silver [1] specifications, but it is applicable to any AG framework since it only relies on the core features of the AG paradigm itself.
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    Dynamic Modelling and Control of Exoskeleton Gantry Robot
    (2024) Hajare, Eesha;
    This thesis presents the development and analysis of dynamic model of an exoskeleton gantry used to perform brain studies in freely moving mice for neuroscience experiments. The dynamic of model of the exoskeleton gantry comprised of X and Y stages is developed, and relevant system characteristics like bandwidth and stability are studied using theoretical model to predict the system behavior. The predicted bandwidth of the open loop system is found to be 1.9Hz and 3.8Hz for the Stage X and Y respectively using the theoretical model. The open loop system was further verified experimentally using LABVIEW and an experimental model was generated using computer software. According to the experimental results, the open-loop bandwidth of the X and Y stages was found to be 2.3 Hz and 2.76 Hz respectively. Furthermore, the open loop system is also used to gauge the stability of the closed-loop and the gain and phase margin are studied for the same purpose. According to theoretical studies, it is expected that the bandwidth of the open and closed loop system is expected to increase with a decrease in payload. The gain margin and phase margin are predicted theoretically and verified experimentally are well above the determined threshold of 2dB for gain margin and 450 for phase margin, this ensures the stability of the closed loop exoskeleton system. Moreover, the closed-loop bandwidth of the system is predicted using the theoretical model and an admittance control framework is proposed. The predicted closed-loop bandwidth for the exoskeleton gantry is found to be 19.2Hz and 16.4Hz for X and Y stages respectively. Furthermore, preliminary experimentation of the gantry with admittance control implementation suggests a closed loop bandwidth of 46Hz for Stage X.
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    Human Facial Perception of Primates Through ERP Measurement
    (2024-05-06) West, Abigail;
    Several studies, some using electrophysiological methods, have examined the capacity of humans to perceive primate faces. Through subsequent data, humans are confirmed to be far more adept at recognizing human faces, and less skilled at recognizing non-human primate faces. However, comparative perceptual research utilizing non-human primate species as stimuli is limited. In this study, I utilized EEG technology to compare the amplitude and latency of the P1 and N170 components in adults when exposed to chimp, macaque, and human faces. I determined that chimpanzee faces result in a significantly higher P1 amplitude, as well as a faster N170 latency. Human faces, meanwhile, showed a significantly higher N170 amplitude. Macaque faces demonstrated a faster P1 latency. These findings support non-evolutionary mechanisms for facial processing. In addition, the results from the chimpanzee face trials align with previous literature regarding human perception of threatening faces. Overall, through the measurement of the P1 and N170 components, more insight could be gained in regards to human perception of different primate species.
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    Redshift Dependence of Stochastic Gravitational Wave Background and Galaxy Overdensity Cross-Correlation
    (2023) Feist, Noelle;
    Following [1], the cross-correlation between the stochastic gravitational wave background (SGWB) due to binary black hole mergers and the sky distribution of galaxies was computed. The SGWB anisotropies are obtained from the third observing run (O3) of Advanced LIGO, and the galaxy distribution was taken from the Sloan Digital Sky Survey (SDSS) spectroscopic catalogue. The angular power of the cross-correlation in 10Hz wide GW frequency bins and 0.1 wide redshift bins was found to be noise-dominated. The resulting angular cross-rcross-correlation power spectra were used to find the maximum likelihood estimates for parameters to a simplified astrophysical kernel with amplitude Amax and redshift center zc. No constraints were able to be placed on the redshift, but a 95% confidence upper-limit was found for Amax = 8.3 × 10−33erg/cm3s1/3. This analysis was limited by the redshift range of the catalogue and GW sensitivity. As data sensitivity grows, better estimates for the bound of the astrophysical kernel will be found.
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    Analyzing U.S. Media Discussion of Political Polarization
    (2023) Dunk, Brandon;
    How does the media cover political polarization in the United States, and with what effects? The effects of media coverage of political polarization vary based on the type of political polarization presented. Does political polarization manifest as issue position or affective polarization? Are elites or the mass public becoming politically polarized? Is political polarization beneficial or harmful? Depending on how the media answers these questions in coverage of political polarization, perceived polarization may have different effects. This paper provides the first accurate measure of the media coverage of different types of political polarization through a rigorous examination of media coverage of political polarization by the top five U.S. newspapers over a 27-year period. Using keyword sets to identify coverage, I find that media coverage of political polarization has been severely underestimated by past studies and that it is a major component of media coverage today. Since 2016, coverage has increased across all types of political polarization at a rapid pace. This may have a major impact on perceived polarization, resulting in strengthened effects. I additionally discuss the impact to those opposed to further political polarization and those looking to benefit from it.
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    Echoes of Identity: Reflections of Medea in Euripides' Bacchae
    (2023) Tallarini, Amelia;
    In Euripides’ Medea, one of his earliest surviving plays, we are faced with an unusual titular character. Medea is an extraordinarily powerful woman. Before her marriage to Jason, she had enabled him to reach heroic status through obtaining the Golden Fleece by her ruthless use of magical force. Despite this help which he received from her, Jason decides to divorce Medea, a barbarian woman, in favor of the princess of Corinth. The action of the play opens with Medea deciding what to do given this situation. As the plot unfolds, Medea takes on multiple roles. She starts as a victim of Jason’s abandonment. She then begins plotting vengeance upon him, and her initial plan includes murdering his future bride to get herself even with Jason. When she adds filicide into her revenge plot, Medea transgresses ordinary human boundaries and becomes a fiend. At the same time, however, she once again becomes a victim, but this time Medea is a victim of herself rather than of another. Medea’s personality is thus split, and her character contains contradictory elements both sequentially and simultaneously.
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    Busted: Executive Misconduct and Its Implications for a Firm's Tax Avoidance
    (2023) Manna, Jackson;
    The title of ‘CEO’ confers upon an individual considerable influence over his or her organization, from corporate culture to financial reporting. Prior research has documented that the individual acting as CEO has a significant impact on a firm’s tax planning activities – the degree to which tax is avoided and the aggressiveness of tax positions taken. With such power comes substantial responsibility – particularly in recent years, corporate CEOs have faced heightened scrutiny and accusations regarding personal behaviors outside of work. This thesis analyzes whether an accusation of personal misconduct against a CEO has a significant impact on the tax planning activities of his or her firm. Tax avoidance is an appropriate means through which to measure the impact that personal misconduct allegations against the CEO have on the business-related aspects of a company. In the context of ethical misconduct and the allegations that follow, tax avoidance is unique from other financial metrics in that it has strong ethical considerations. It may follow, therefore, that decisions made by a firm in light of alleged ethical violations by the CEO will be reflected in the firm’s tax planning. I hypothesize that perceived scrutiny against a CEO for personal misconduct will motivate the firm to perform less aggressive tax avoidance in the years that follow. I examine this hypothesis through a multi-year event study which compares the change in tax avoidance for firms that experienced a CEO “violation event” against firms that did not. Through correlation and regression analyses, my results do not show significant evidence that personal misconduct allegations against a CEO influence a firm’s level of tax avoidance. However, there still exists strong motivation for further research.
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    FIST-nD: A tool for n-dimensional spatial transcriptomics data imputation via graph-regularized tensor completion
    (2023) Atkins, Thomas K;
    Functional interpretation of spatial transcriptomics data usually requires non-trivial preprocessing steps and other supporting data in the analysis due to the high sparsity and incompleteness of spatial RNA profiling, especially in 3D constructions. As a solution, we present a new software tool FIST-nD, Fast Imputation of Spatially-resolved transcriptomes by graph-regularized Tensor completion in n-Dimensions for imputing 3D as well as 2D spatial transcriptomics data. FIST-nD is implemented based on a novel graph-regularized tensor decomposition method, which imputes spatial gene expression data using 4-way high-order tensor structure and relations in spatial and gene functional graphs. The implementation, accelerated by GPU or multicore parallel computing, can efficiently impute high-resolution 3D spatial transcriptomics data within a few minutes. The experiments on three 3D Spatial Transcriptomics datasets and one 3D high-resolution Stereo-seq dataset confirm the high accuracy of the imputation by FIST-nD and demonstrate that the imputed spatial transcriptomes provide a more complete gene expression landscape for downstream analyses such as spatial gene expression clustering and visualizations.
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    Urban Production of Fruits and Vegetables: Current Estimates and Opportunities for Growth in Ramsey County, Minnesota
    (2023) Schulz, Laura;
    Population growth and the progression of climate change will require a more sustainable, resilient, and equitable food system. A more sustainable food system may include shifting where food is grown, such as growing more perishable and intensive crops (fruits and vegetables) closer to large population centers. Production of fruits and vegetables near urban centers has the potential to offer a wide array of benefits, including increasing access to healthy food and reducing food waste. This project used USDA data to quantify the current production of fruits and vegetables in Ramsey County, Minnesota and estimate potential production capacity if fruits and vegetables were to be grown on farmland currently used to grow grains or raise animals, on land currently used for parking lots, and with rooftop gardens. These estimates were compared to the quantity required to meet the population of Ramsey County’s needs based on the Dietary Guidelines for Americans to illustrate potential pathways to meeting the nutritional needs of urban areas with an equitable, low-carbon food system. Current (2017) production of fruits and vegetables in Ramsey County meets its population’s needs for just under 4 days per year, while the potential production methods considered were estimated to add an additional 32.4 days of meeting the population’s needs. These low current and potential production figures emphasize the continued importance of rural areas as the primary producers of food for urban populations, while also illustrating the potential to significantly increase food production in urban areas and improve food system resiliency through diversifying where and how crops are grown.
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    Experimental investigation of hybrid hydraulic fiber-reinforced actuators incorporating shape memory alloy
    (2023) Brinkert, Kate;
    The emerging field of soft robotics aims to offer solutions to many of the limiting factors present in traditional, “hard” robotics, such as complexity, material rigidity, and a lack of compliance. Fiber-reinforced elastomeric enclosure (FREE) actuators, including the well-researched McKibben pneumatic artificial muscle, are some of the most prevalent applications of this field due to their high power density and ability to actuate an entire structure with many degrees of freedom from a single pressure source. The kinematic behavior of these actuators is governed by the wrap architecture of the inextensible reinforcing fibers, and tailored motions can be achieved by simply adjusting the number of fiber families and their respective wrap angles. In this experimental investigation, eight hybrid hydraulic FREE prototypes are developed to explore the kinematic effects of incorporating a single wire of shape memory alloy (SMA) into various wrap geometries, including asymmetric configurations, which are previously unexplored. Changes in actuator length and rotation for each prototype are analyzed using discrete marker tracking as functions of the control variables of volumetric input and applied current, and kinematic behaviors are compared over various parameters of wrap geometry. Trends are established for the effects of wrap angles and their relationships to a generalized kinematic design space for FREES on the actuation potential of an incorporated fiber of SMA. Promising results are described for two additional proof of concept prototypes in an initial exploration of incorporating more than one SMA fiber into a hybrid actuator and expanding to more complex wrap configurations. This research demonstrates the capability of SMA to both augment passive actuator behavior and produce new forms of multimodal motion, providing a stepping stone towards more tailored applications of hybrid soft actuators.
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    Opinions on the Peruvian Executive: A Study on Presidential Transitions and Approval
    (2023) Llerena, Gabriela;
    This paper explores the various presidential transitions in Peru, their relationship with Congress and corruption, and the impact of Alberto Fujimori’s decade-long presidency. I build upon existing literature investigating Peruvian opinion and draw from nationally conducted Peruvian polls to investigate individual presidents' role in the public’s perceptions of corruption, support for democracy, tolerance of the president closing Congress, and confidence in elections, Congress, and the president. To supplement these public opinion surveys, I conducted qualitative interviews with Peruvians in the U.S. and Peru, providing a deeper look at what has impacted their opinion towards the government. I analyze how the rapid presidential turnover after 2016 influences public opinion and why the public looks more favorably upon the president than Congress. Since 2016, Peru has had six presidents, three of whom Congress impeached. Almost all Peruvian presidents have been involved in corrupt practices, yet the public views the president as more favorable than Congress. I find that Fujimori’s strong-handed presidency, differences in accountability of Congress and the president to the public, and heightened divisions between the two branches offer an explanation for public opinion. This study is important for exploring the ongoing presidential transitions and whether Peru hopes to regain governmental stability in the future.
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    Media Consolidation's Relationship to Voter Turnout in Elections
    (2022) Mazzetta, Marissa;
    Media consolidation is on the rise especially when it comes to local news. This study aims to find if media consolidation affects citizens’ civic engagement, specifically voter turnout in non-presidential and presidential elections. Understanding what factors lead to higher voter turnout can be helpful in creating a more civically engaged country leading to progress that reflects the needs and wants of a more accurate majority. Consumption of local news has been tied to better civic engagement in the past. While media consolidation has been known to diminish the local news environment it has taken control over. Due to these two notions, it could be expected that there would be a connection between media consolidation and voter turnout. Through data analysis of voter turnout data of 24 Texas counties from the years 1990 to 2020 it was found through ANOVA tests that there were no significant changes in voter turnout between elections. These results lead to the belief that media consolidation alone does not have a significant impact on voter turnout. This opens up further understanding into the relationship between journalism and election turnout, and the reasons for fluctuation in voter turnout between elections.
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    Survival Analysis of Associations Between Health Insurance Status, Race, Yearly Household Income and Diabetes Incidence
    (2022) Bastian, Lauren;
    Objective We examined the effects of health insurance status, race, and income, on diabetes incidence in a racially and socioeconomically diverse sample of middle-aged American women. Methods Using Kaplan-Meier survival curves and stratified Cox proportional hazards models, we evaluated the associations between insurance status, race, income, and diabetes incidence in a sample of 2,686 middle-aged women who participated in the Study of Women’s Health Across the Nation between the years of 1994 and 2008. Models were adjusted for covariates and stratified by age upon study entry. Results Women with lower incomes tend to have higher risk for incident diabetes after adjusting for health insurance status, race, household income, BMI, and age upon study entry. Black/African American and Hispanic women may be at especially high risk for incident diabetes after adjusting for other covariates. Uninsured women were at significantly higher risk for diabetes incidence after adjusting for race, BMI, and age upon study entry, but insurance status is not found to affect diabetes incidence after additionally adjusting for household income. Discussion Results for yearly household income and race reinforce findings from existing literature, and suggest the need for additional investigation of diabetes incidence among Hispanic women. Women without health insurance were at higher risk for diabetes when adjusted only for race, BMI, and age upon study entry. After adjusting the model additionally for household income, the association between insurance status and diabetes risk was non-significant, possibly due to confounding between household income and insurance status. Insurance status may be indicative of and confounded by several other socioeconomic, cultural, and environmental factors not explored in this study.
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    Renewable Energy Development by Electric Cooperatives: Indirect Uses of Federal Energy Tax Credits
    (2022-12-22) Gutenkauf, Gabriella;
    In this thesis, I look to understand how electric cooperatives develop renewable energy in a cost-effective manner, despite the inability to use popular financing methods such as the production tax credit and the investment tax credit. I also analyze how their current practices may be impacted by the addition of direct pay as a policy tool in the Inflation Reduction Act. Electric cooperatives provide energy to 56% of the nation’s landmass, specifically to rural communities that investor-owned utilities do not reach. The national push for decarbonization of the energy industry has put requirements such as renewable portfolio standards on utilities, demanding certain percentages of their portfolio to come from renewable energy. Electric cooperatives struggle with this development of renewable energy because their status as not-for-profit entities prevents them from utilizing federal investment and production tax credits. I conducted four interviews with the electric cooperatives Dairyland Power, Great River Energy, Hoosier Energy, and Old Dominion Electric Cooperative to understand their decision-making process in the development of renewable energy. I identified five key factors impacting this decision making: providing low-cost energy to members, size of staff and resources, membership in the National Renewables Cooperative Organization, project size, and interconnection concerns. I also found that cooperatives had mixed opinions on whether they were hoping to quickly begin using direct pay options once it was available. These findings show that it will be very important that any future policy tool, including direct pay, will need to ensure it still allows cooperatives to achieve their goal of providing the lowest cost of energy.
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    Examining the Effects of Serotonin on Medium Spiny Neurons (MSNs)
    (2022-06-01) Belhe, Aishwarya;
    Serotonin is the key hormone in stabilizing our mood and feelings of well-being. The relationship between alterations in the levels of serotonin in the central nervous system and depression has been well-established. The most common antidepressants prescribed to alleviate the symptoms of depression are selective serotonin reuptake inhibitors (SSRIs), which increase the levels of serotonin in the brain. Although these drugs are prescribed to pregnant women with chronic depression, how the SSRI-induced increase in the level of serotonin affects fetal brain development has been only minimally investigated. In this study, we investigated the effects of serotonin on the development of a particular type of neuron called medium spiny neurons (MSNs). These neurons are the major type of neurons present in the striatum, a brain region whose circuits have been implicated in depression. MSNs are known to have distinct morphological traits of cell body size, dendritic branching pattern and high density of dendritic spines. Although many studies have focused on the role of serotonin in regulating the function of the mature striatum, an exhaustive literature review identified no studies that have specifically examined the role of serotonin on MSN development. Our study hints towards a trend that an increase in serotonin might lead to an increase in dendritic branching of MSNs. These results indicate a need for caution about the consumption of SSRIs by pregnant women.
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    Connecting to the Cold-blooded: Impacts of Educational Messaging on Audience Attitudes Towards Rattlesnakes
    (2022) Bachhuber, Owen;
    As some of the most feared and misunderstood animals in North America, rattlesnakes are threatened by human persecution. Zoos, wildlife managers, and other conservation organizations seek to increase public acceptance of rattlesnakes through educational programming. This thesis addresses two key questions: 1) What is the effect of a rattlesnake exhibit on the attitudes of zoo guests, and 2) What is the effect of social complexity messaging on student attitudes towards rattlesnakes. I formulated a survey to quantify attitudes towards rattlesnakes using a seven-point Likert scale and administered it to visitors before and after walking through the Desert Dome of Omaha’s Henry Doorly Zoo and Aquarium. The same survey was given to zoology students at the University of Minnesota before and after learning about rattlesnake social complexity during a reptile diversity lab. I measured the impacts of the two learning environments using a two-tailed t-test to compare the incoming and outgoing attitudes of participants. No statistically significant changes in attitudes towards rattlesnakes were detected in guests after viewing the Desert Dome exhibits. Zoology students reported a significantly more positive view towards rattlesnakes after learning about rattlesnake social complexity, including increased utilitarian and ecologistic attitudes. Whereas public education programs have historically cited the ecological and biomedical contributions of rattlesnakes, this study suggests that the emerging field of reptile sociality has the potential to humanize rattlesnakes and increase audience acceptance of them.
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    Impact of Air Gap Length and Waveguide Refractive Index on Luminescent Solar Concentrator Optical Behavior
    (2022) Hoernemann, Diana;
    The optical properties of luminescent solar concentrators (LSCs) containing CdSe/CdS core/shell nanocrystal luminophores in a matrix with a high index of refraction were characterized using UV-Vis spectroscopy, photoluminescence (PL), and PL lifetime measurements. The high refractive index matrix was realized by spin-coating solutions containing polyvinylpyrrolidone (PVP), titania, butanol, and luminophores onto glass substrates. The proportion of titania in the solutions was varied in order to change the refractive indices of the resulting samples. The transmission and reflection spectra of the samples showed evidence of thin film oscillations, known as Fabry-Perot modes, that increased in magnitude with the amount of titania in the sample, suggesting that increasing the amount of titania in the matrix of a sample likely increased its refractive index. The PL peaks of the luminophore blue-shifted from 630 to 627 nm as the concentration of titania increased. The PL lifetime of these samples was found to be 1.8-2.7 ns, with an outlier of 0.5 ns for one sample. Complementary Monte Carlo ray tracing simulations were used to explore the impact of a variable thickness air gap on the optical efficiency of an LSC system. It was found that an air gap of 0.05 mm reduced the peak optical efficiency by 14.6% as compared to a system with no air gap. This decrease is attributed to escape cone loss pathway as photons couple out the air gap as opposed to another loss pathway. Therefore, it is suggested the thickness of an adhesive layer between the waveguide and solar cells should be no greater than 0.05 mm to preserve the optical performance of the device.
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    Individual Investors' Values in Times of Crisis: Evaluating the Relationship Between Individuals' Investments and ESG Scores
    (2022) Schaffer, Sarah;
    Investor preferences have long been analyzed to improve both portfolio management and company investor relations. The entry of new individuals investing combined with the economic uncertainty brought by COVID-19 is likely to show new investor preferences. This thesis examines the relationship between individual investors ownership and companies’ ESG scores to see if there is a heighten ESG preference for this class of investors. Results suggest that while ESG is a component of individual investors preference, it does not fully explain their trading decisions. Key Words: ESG, individual investors preferences, e-trading, COVID-19