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Title: Greatest common divisors near S-units, applications, and conjectures on arithmetic abelian surfaces
Creator: Xiao, Zheng
Date: 2022
Collection: Electronic Theses & Dissertations
Description: We bound the greatest common divisor of two coprime multivariable polynomials evaluated at algebraic numbers, generalizing the work of Levin by thickening the finitely generated group to allow non-finitely generated elements. Going towards conjectured inequalities of Silverman and Vojta, an immediate corollary shows a similar inequality without a normal crossing assumption. The proofs rely on Schmidt's Subspace Theorem.As an application, we prove results on the greatest common divisors of...
Show moreWe bound the greatest common divisor of two coprime multivariable polynomials evaluated at algebraic numbers, generalizing the work of Levin by thickening the finitely generated group to allow non-finitely generated elements. Going towards conjectured inequalities of Silverman and Vojta, an immediate corollary shows a similar inequality without a normal crossing assumption. The proofs rely on Schmidt's Subspace Theorem.As an application, we prove results on the greatest common divisors of terms from two general linear recurrence sequences, extending the results of Levin, who considered the case where the linear recurrences are simple. The exceptional set is not as good as finitely many linear relations as in the simple case, but within the control of a logarithmic region, improving recent results of Grieve and Wang. An example shows that the logarithmic region is necessary.On abelian surfaces which come from the jacobians of hyperelliptic curves, we establish the connection between the GCD conjecture and the conjecture on arithmetic discriminant. It predicts, under particular situations, stronger inequality than Vojta's theorem of the arithmetic discriminant. We give some examples of extreme values of the arithmetic discriminant.
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Title: ESSAYS ON FIRMS, CLIMATE CHANGE AND FOOD SYSTEMS TRANSFORMATION
Creator: Nuhu, Ahmed Salim
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation broadly examines how climate change, and the rapidly transforming agrifood value chains are impacting firms, workers, and farmers in developing countries. Chapter 1 examines the effect of ignoring adaptation when estimating the short-run impacts of temperature shocks on workers and firms in developing regions. To do this, we first obtain naïve estimates of the short-run impacts of extreme temperatures (shocks) on workers’ wages and firm output in Sub-Saharan Africa using the...
Show moreThis dissertation broadly examines how climate change, and the rapidly transforming agrifood value chains are impacting firms, workers, and farmers in developing countries. Chapter 1 examines the effect of ignoring adaptation when estimating the short-run impacts of temperature shocks on workers and firms in developing regions. To do this, we first obtain naïve estimates of the short-run impacts of extreme temperatures (shocks) on workers’ wages and firm output in Sub-Saharan Africa using the standard panel fixed effects approach. We then obtain the pure short-run effects by adjusting the naïve estimates by conditioning the effects of the temperature shocks on the historical local temperature information held by firms and workers prior to the occurrence of the temperature shocks. The difference between the naïve and the pure short-run estimates provide evidence of adaptation. We find evidence of temperature shock effects on wages and output that similar to other studies from our naïve estimates. However, the estimated effects are much higher when we condition on firms’ prior knowledge of the local temperature. This finding indicates the importance of accounting for firms and workers’ knowledge of local temperature patterns (when estimating the impacts of temperature shocks) and provides evidence of incomplete adaptation (of up to 50% of the original effects). Evidence of incomplete adaptation suggests the presence of barriers to adaptation that need to be addressed to prevent a locking-in of vulnerability to climate change impacts. In a further application to the United States in Chapter 2, we find that accounting for the historical local temperature information is less relevant in the presence of more complete adaptation that may be aided by established institutional capacity for dealing with extreme weather. Taken together, these findings reveal (1) the importance of accounting for adaptation in estimating the impacts of short-term temperature shocks in developing regions with more barriers to adaptation and (2) that policies aimed at adaptation should not ignore local institutional and environmental contexts in which adaptation occurs. Chapter 3 examines the effects of the recent rise of numerous midstream agri-food firms and their authorized agents on smallholder soybean farmers in Zambia. Specifically, I examine the implications of non-contractual sale of soybean output to midstream firms and processors for the welfare of smallholder farmers. Using fixed effects and instrumental variables estimation techniques to address the endogeneity of the smallholder decision to sell to large-scale firms, I find significant positive crop income effects of selling to soybean large-scale firms on all smallholders. However, the observed effects only translate into higher total household incomes and poverty reduction for medium-scale smallholders (operating 5 ha- 20 ha) but not for small-scale smallholders operating less than five hectares. The positive crop income effects are mainly driven by the opportunity to sell more although small-scale smallholders also receive a price premium from selling to large buyers. These results suggest that the recent rise in purchasing activity by firms in the soybean industry in Zambia is benefiting smallholder farmers but not necessarily enough to move the smallest of these farmers out of poverty.
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Title: FACULTY BELIEFS OF CURRICULUM AND THE CONTEXTS IN WHICH THEY ENACT THOSE BELIEFS IN PRACTICE
Creator: Lopez , Kari Schueller
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Curriculum, and the teaching and learning that stem from it, is at the heart of each higher education institution. Faculty have the responsibility for developing curriculum in higher education contexts, yet little is known about the beliefs faculty hold of curriculum that underpin how they engage in the curriculum development process. Using qualitative methodology and Grundy’s (1987) theory of curriculum as product, curriculum as practice, and curriculum as praxis as a conceptual framework,...
Show moreCurriculum, and the teaching and learning that stem from it, is at the heart of each higher education institution. Faculty have the responsibility for developing curriculum in higher education contexts, yet little is known about the beliefs faculty hold of curriculum that underpin how they engage in the curriculum development process. Using qualitative methodology and Grundy’s (1987) theory of curriculum as product, curriculum as practice, and curriculum as praxis as a conceptual framework, this study explored the following research question with eleven faculty participants: What are faculty beliefs of curriculum and in what contexts do they act on those beliefs?Findings reveal faculty hold a myriad of deeply held beliefs about curriculum. They associate curriculum with their own courses, as well as with their academic programs or majors. Faculty beliefs center on the process of teaching and learning and the transformative possibility of the curriculum for students. They outlined both philosophical and practical goals for student learning, including preparing students for their lives as critical thinkers and engaged citizens, while also instilling applied skills to use in the workplace. Faculty enacted their beliefs when engaging in individual and/or group curriculum development work, and through pedagogy, teaching, and assessment. Faculty also discussed challenges to enacting curriculum and outlined administrative barriers, access to large-scale curriculum processes, tensions between teaching, research, and service responsibilities, and department culture. The discussion addresses these themes and includes recommendations for future research to examine the relationship between faculty beliefs of curriculum and accreditation bodies, the impact of department culture, faculty appointment type, and the COVID-19 pandemic on how faculty enact their beliefs of curriculum. Suggestions for practice include more training for faculty to engage in curriculum development work, more self-reflection opportunities, and recognition of curriculum-related work in the reappointment, promotion, and tenure process.
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Title: DEORPHANIZATION AND CHARACTERIZATION OF SEA LAMPREY OLFACTORY TRACE AMINE-ASSOCIATED RECEPTORS
Creator: JIA, LIANG
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The sense of smell plays an important role in mediating diverse behaviors in the animal kingdom. Odor detection in the sea lamprey is mediated by a limited number of odorant receptors (ORs) and trace amine-associated receptors (TAARs). Upon binding with odorants, the receptors are activated and subsequently activate the downstream neuronal signaling cascade that transforms the chemical information into electrophysiological signals. Odorous biogenic amines, when enriched in biological...
Show moreThe sense of smell plays an important role in mediating diverse behaviors in the animal kingdom. Odor detection in the sea lamprey is mediated by a limited number of odorant receptors (ORs) and trace amine-associated receptors (TAARs). Upon binding with odorants, the receptors are activated and subsequently activate the downstream neuronal signaling cascade that transforms the chemical information into electrophysiological signals. Odorous biogenic amines, when enriched in biological excretions, stimulate TAARs of the main olfactory epithelium and evoke innate behaviors in animals. I hypothesized that these biogenic amines are potent ligands for lamprey TAARs, and characterized the structural basis for amine recognition in these receptors. Chapter 1 describes discovery that spermine, an odorous polyamine in semen, serves as a sex pheromone in sea lamprey. Spermine potently stimulates the lamprey olfactory system, activates TAAR348 receptor, and attracts ovulated females. A novel antagonist to this receptor inhibits olfactory and female behavioral responses to spermine. This discovery elucidates a mechanism that male animals recruit mates through the release of chemical cues in ejaculates. In chapter 2, I demonstrated that two clades of independently evolved TAARs, represented by sea lamprey TAAR365 (sTAAR365) and mouse TAAR9 (mTAAR9), share a similar response profile. The results suggest a conserved mechanism whereby independently evolved TAAR receptors utilize convergent structural bases to detect various biogenic polyamines. In chapter 3, I found that a cadaverine-responsive sea lamprey TAAR receptor, TAAR346a, exhibits high basal activity when heterologously expressed in HEK293T cells. Triethylamine serves as an inverse agonist for TAAR346a that can specifically attenuate its high basal activity. These data support a model in which the inverse agonist recognizes only one of the two orthosteric sites used by the agonist as it elicits its inhibitory effect on the basal activity of the receptor. Further evidence was provided to highlight the importance of interhelical interactions in modulating ligand-independent activation of TAAR346a. Thus, this thesis contributes to a better understanding of sea lamprey olfaction and the structural basis of TAARs for amine recognition in vertebrate animals.
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Title: PARTNERSHIP AND PREDATION IN PLANT-BIOTIC INTERACTIONS : THEORY, METHODS, AND EVIDENCE
Creator: Rowe, Shawna L.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As sessile organisms, plants face an endless series of encounters with other living organisms in their environment. Ranging from the beneficial to the harmful, the pressures of these biotic interactions force plants to rapidly adapt to survive and thrive. This dissertation is aimed at addressing questions about the metabolism of plant interactions with herbivores and nutritional symbionts in legumes. Despite spanning different systems and methods, these questions reflect my interest in...
Show moreAs sessile organisms, plants face an endless series of encounters with other living organisms in their environment. Ranging from the beneficial to the harmful, the pressures of these biotic interactions force plants to rapidly adapt to survive and thrive. This dissertation is aimed at addressing questions about the metabolism of plant interactions with herbivores and nutritional symbionts in legumes. Despite spanning different systems and methods, these questions reflect my interest in understanding the biochemistry underlying ecological and evolutionary function and my desire to develop tools that enable the investigation of such questions. To this end, the work in this dissertation is aimed at building conceptual and methodological tools to enable more thorough investigations of plant symbioses and, more broadly, plant-biotic interactions across levels of biological organization.First, I present a framework for making predictions on evolutionary trajectories and origins of plant--microbe communication systems. By highlighting the prevalence of coercive interactions in plant--microbe interactions, I demonstrate the plausibility of such interactions types to be an evolutionary precursor to seemingly stable signaling mechanisms. This work aims to provide useful evolutionary context for investigations concerning the evolutionary stability and exploitation of signaling mechanisms in established biological relationships. Second, I present collaborative work in which we developed and applied a cost-effective, high-throughput protocol for quantifying multiple biochemical defense responses from small quantities of plant tissue using spectrophotometric techniques. This protocol was then applied on two distinct populations of the legume Medicago polymorpha to investigate how changes defensive traits in responses to altered selective pressures have manifested over the course of novel range expansion. Our work demonstrated the feasibility and potential of assessing defense responses across plant populations. Further, the work documents a shift in herbivore preference of plants from familiar and unfamiliar ranges by demonstrating a herbivore preference for plant tissues with pre-induced defenses over uninduced tissues from an unfamiliar geographic range. Finally, I demonstrate the creation, construction, and validity of a novel microcosm system for assessing nutrient exchange in the symbiotic mutualism between plants and arbuscular mycorrhizal fungi (AMF). The novel system is reliable, biologically-relevant, durable, and sufficiently simple and cost-effective to deploy. I demonstrate the validity of the microcosm system and discuss in-progress work which demonstrates its potential to rigorously investigate unknown aspects of the plant-AMF mutualism. Taken together, these developments and suggestions contribute to the growing set of methods and frameworks developed for improving our understanding a various plant-biotic interactions.
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Title: CLICKABLE POLY(PROPARGYL METHACRYLATE) PREPARED BY ATOM TRANSFER RADICAL POLYMERIZATION AND ITS DERIVATIVES AS ENZYME STABILIZERS
Creator: Hsiao, Po-Jen
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Enzymes are nearly perfect catalysts with excellent selectivity and high turnover frequencies. A long-standing goal has been enabling enzymes to operate ex vivo in non-aqueous solvents, but the structures of native enzymes are typically compromised under these conditions. Polymer-enzyme bioconjugates have shown some promise—albeit limited—in this regard. The clickable poly(propargyl methacrylate) (PPMA) was proposed as a platform to enhance different polymer structures versus the residual...
Show moreEnzymes are nearly perfect catalysts with excellent selectivity and high turnover frequencies. A long-standing goal has been enabling enzymes to operate ex vivo in non-aqueous solvents, but the structures of native enzymes are typically compromised under these conditions. Polymer-enzyme bioconjugates have shown some promise—albeit limited—in this regard. The clickable poly(propargyl methacrylate) (PPMA) was proposed as a platform to enhance different polymer structures versus the residual enzymatic activities. The degree of polymerization and polydispersity are two factors that affect the polymer properties and can affect the enzymatic activities of the polymer-enzyme bioconjugates. The literature examples of PPMA with degree of polymerization greater than 200 are limited. In the atom transfer radical polymerization (ATRP) conditions we discovered, the degree of polymerization and the polydispersity of poly(trimethylsilylpropargyl methacrylate) (PTMSPMA) can be precisely adjusted by the initiator and monomer ratio, the copper catalyst loading, and the reducing agent loading (copper wire). After deprotection, PPMA is further reacted with different mole fraction compositions of hydrophilic triethylene glycol monomethyl ether (mDEG) azide and hydrophobic dodecyl azide to prepare amphiphilic polymers as enzyme stabilizers. The activities of the model enzyme, Subtilisin Carlsberg (SC), and polymer-SC bioconjugates were determined by 4-nitrophenolate and 4-thiopyridone assays, and the polymer-enzyme bioconjugate SC@82%mDEG-PPMA was found to be more active than SC alone in toluene. The SC@82%mDEG-PPMA is also more active than SC@100%mDEG-PPMA in 4-nitrophenolate assay, proving that the side chain structure of the polymer micelles can affect the polymer-enzyme bioconjugates. The micelle 80%mDEG-PPMA may isolate the enzyme from the bulk toluene better than 100%mDEG-PPMA. Deprotonated amino acid salts are great alternatives to the synthesized alkylamines as post-combustion CO2 absorbents due to their non-toxic and low volatile nature. For CO2 capture, gas uptake was measured when solutions of monodeprotonated amino acids were sparged with CO2. The speciation between dissolved CO32–, HCO3– , and CO2(aq), and CO2 captured as carbamates of the deprotonated amino acids, was quantified by 13C{1H} and 1H NMR spectroscopy. Less hindered amino acids like glycine tend to have faster CO2 absorption kinetic and higher carbamate concentrations due to the formation of relatively stable carbamates. One equivalent of carbamate forms requires one equivalent of amino acid as sacrificial base. Therefore, the formation of carbamate decreases the total CO2 absorption capacity and is an unfavorable pathway for CO2 capture. While the amino acids containing substituents at the α carbon atom adjacent to the amino group, like alanine and proline, destabilize their carbamates by unfavorable steric interaction and lead to carbamate hydrolysis to CO32–/HCO3– and enhance the CO2 capture capacity. Therefore, mixing different amino acids can have the fast absorption kinetics and higher absorption capacity. Based on the results, the mixture amino acid solutions were observed to have higher CO2 absorption capacity than the single amino acid counterparts.
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Title: UNDERSTANDING THE GENETIC BASIS OF HUMAN DISEASES BY COMPUTATIONALLY MODELING THE LARGE-SCALE GENE REGULATORY NETWORKS
Creator: Wang, Hao
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Many severe diseases are known to be caused by the genetic disorder of the human genome, including breast cancer and Alzheimer's disease. Understanding the genetic basis of human diseases plays a vital role in personalized medicine and precision therapy. However, the pervasive spatial correlations between the disease-associated SNPs have hindered the ability of traditional GWAS studies to discover causal SNPs and obscured the underlying mechanisms of disease-associated SNPs. Recently, diverse...
Show moreMany severe diseases are known to be caused by the genetic disorder of the human genome, including breast cancer and Alzheimer's disease. Understanding the genetic basis of human diseases plays a vital role in personalized medicine and precision therapy. However, the pervasive spatial correlations between the disease-associated SNPs have hindered the ability of traditional GWAS studies to discover causal SNPs and obscured the underlying mechanisms of disease-associated SNPs. Recently, diverse biological datasets generated by large data consortia provide a unique opportunity to fill the gap between genotypes and phenotypes using biological networks, representing the complex interplay between genes, enhancers, and transcription factors (TF) in the 3D space. The comprehensive delineation of the regulatory landscape calls for highly scalable computational algorithms to reconstruct the 3D chromosome structures and mechanistically predict the enhancer-gene links. In this dissertation, I first developed two algorithms, FLAMINGO and tFLAMINGO, to reconstruct the high-resolution 3D chromosome structures. The algorithmic advancements of FLAMINGO and tFLAMINGO lead to the reconstruction of the 3D chromosome structures in an unprecedented resolution from the highly sparse chromatin contact maps. I further developed two integrative algorithms, ComMUTE and ProTECT, to mechanistically predict the long-range enhancer-gene links by modeling the TF profiles. Based on the extensive evaluations, these two algorithms demonstrate superior performance in predicting enhancer-gene links and decoding TF regulatory grammars over existing algorithms. The successful application of ComMUTE and ProTECT in 127 cell types not only provide a rich resource of gene regulatory networks but also shed light on the mechanistic understanding of QTLs, disease-associated genetic variants, and high-order chromatin interactions.
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Title: RECREATIONAL CANNABIS LEGALIZATION : PREDICTING LOCAL POLICY ADOPTION AND ESTIMATING THE ASSOCIATED EFFECTS ON POPULATION CANNABIS USE
Creator: Montgomery, Barrett Wallace
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Cannabis is undergoing a remarkable transformation from a regulated drug to a recreationally legal one in the United States (U.S.). Yet, in states that have legalized recreational cannabis, there is substantial geographic variability in actual cannabis policies and the effects of cannabis legalization are still being debated. This dissertation addresses these modern scientific issues of the recreational cannabis landscape. The population under study primarily includes non-institutionalized U...
Show moreCannabis is undergoing a remarkable transformation from a regulated drug to a recreationally legal one in the United States (U.S.). Yet, in states that have legalized recreational cannabis, there is substantial geographic variability in actual cannabis policies and the effects of cannabis legalization are still being debated. This dissertation addresses these modern scientific issues of the recreational cannabis landscape. The population under study primarily includes non-institutionalized U.S. civilian residents, sampled and assessed in successive waves of the National Survey on Drug Use and Health (NSDUH) starting in 2008 through 2019. Estimates on drug use and mental illness prevalences are aggregated to the county level for the first aim, and to the state level for the second and third aims. In the first aim, the county-level data are linked to several other publicly available sources of information on all 3,142 U.S. counties including the 2010 Census, 2012 presidential election, and recreational cannabis sales policies. I then used these data to train a machine learning algorithm to predict which counties allowed for the recreational sale of cannabis in 2014. In the second aim, I used state-level estimates of cannabis incidence in an event study model to estimate the effects of legalizing recreational cannabis on cannabis use onsets for persons under and over the legal minimum age of 21. The final aim focuses specifically on 21 year-olds to better understand the implications for setting a legal minimum age drug policy on age-specific patterns of incidence and proposes a theoretical framework that may help understand these findings. For the first aim, the model-averaging predictions classified almost 94% of the U.S. counties correctly. The main factors associated with county-level recreational cannabis laws were the prevalences of past-month cannabis use and past-year cocaine use. In the second aim, I found that for those who were legally able to purchase cannabis (21 and older), cannabis legalization did not appear to affect incidence in the first year following legalization. Even so, between two and four years after legalization, the difference in differences modeling disclosed statistically robust increases of 0.6% for this sub-population of adults. After four years, the estimated increase is 1.3%. The corresponding estimates for underage persons who were ineligible to legally purchase cannabis show no appreciable differences in the occurrence in past-year cannabis use incidence. Finally, the age-specific incidence estimates for 21-year-olds show a rise after the passage of recreational cannabis laws (RCL) and are suggestive of the arrival of a new pattern of age-specific incidence. Taken together, the work and results of this dissertation point toward four potential conclusions. First, cannabis legalization might depend on a predictable process driven in part by prior drug use in each jurisdiction. Second, once implemented, recreational cannabis legalization might not have effects on adolescent onset newly incident cannabis use. Third, for adults permitted to buy cannabis without penalty, the occurrence of newly incident cannabis use might increase. Fourth, a tentative conclusion is that legalization of retail sales to adults removes a barrier for adults who had been interested in trying cannabis, but did not do so, perhaps due to concerns about legal or social consequences faced before legalization.
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Title: The Geography and Recent Activity of Lake Michigan’s Coastal Sand Dunes
Creator: McKeehan, Kevin G.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation attempts to fill a gap in knowledge regarding conditions amongst the dunefields of Lake Michigan’s eastern shore. Much is now known about the evolution and geochronology of these unique freshwater dune systems. The region’s coastal dunes began forming during the Nipissing high stand phase (~5.5ka) of ancestral Lake Michigan. Since then, according to the chronology constructed from several studies, the coastal dunes then underwent several periods of stability and instability...
Show moreThis dissertation attempts to fill a gap in knowledge regarding conditions amongst the dunefields of Lake Michigan’s eastern shore. Much is now known about the evolution and geochronology of these unique freshwater dune systems. The region’s coastal dunes began forming during the Nipissing high stand phase (~5.5ka) of ancestral Lake Michigan. Since then, according to the chronology constructed from several studies, the coastal dunes then underwent several periods of stability and instability along the entire shoreline. However, questions remain regarding dune conditions and variability since ~1900. The goal of this dissertation was to determine if changes have occurred to the region’s coastal dune systems in the last ~120 years and what might be driving those changes. Given that dune systems are sensitive to biotic and abiotic variables, examining the last ~120 years of dune behavior could potentially reveal how Lake Michigan coastal dunes are responding to anthropogenic climate change and human development.Three studies, each comprising a dissertation chapter (Chapters 2-4), were conducted to help close this knowledge gap. Each chapter is broadly linked through an ecogeomorphic lens, particularly through the relationship between dunes and vegetation, which are interconnected in important ways. In Chapter 2, changes in dunefield vegetation and morphology were determined at several locations along the eastern Lake Michigan shoreline through the use of ground-level repeat photography. The second dissertation study – Chapter 3 – concerns the spatiotemporal analysis of historical changes of blowouts, which are important indicators of significant disturbance in the dunes. In this chapter, blowouts were mapped from aerial images at three timestamps – 1938, 1986-8, and 2018 – and the changes quantified. Chapter 4, the final dissertation study, explores the relationship between terrain ruggedness and vegetation in a coastal dunefield along Lake Michigan by calculating two terrain indices – Riley’s Terrain Ruggedness Index (TRI) and Sappington’s Vector Ruggedness Measure (VRM) – and the Soil-Adjusted Vegetation Index (SAVI). Through a land systems framework, the results were compared to determine if any correlation exists between the ruggedness of dunes and vegetation.In the first two dissertation studies, the results show a clear expansion of vegetation at the expense of previously bare sand. In the final study, the values from TRI and VRM and the values from the Soil-Adjusted Vegetation Index (SAVI) were not correlated overall, especially where one type of vegetation was dominant. However, within one land system – the dune barrens -- a moderate-to-strong negative correlation existed between terrain ruggedness and vegetation. Moreover, evidence suggests that vegetation has transformed the dune barrens land system area within the modern period. Overall, the results of these three studies demonstrate that vegetation is expanding over previously bare surfaces in coastal dunes along the eastern shore of Lake Michigan and has a considerable influence on regional dune conditions. While the precise driver(s) of this transformation is unclear, the regional-scale nature of these results suggests a uniform control is affecting these changes. As described in this dissertation, it is possible that an increase in precipitation since the 1930s, elevated atmospheric CO2 and N concentrations, a reduction in wind power, some other change in climate drivers, or a combination of many factors is responsible for the expansion in vegetation. It is also possible the trend in vegetation growth in Lake Michigan’s coastal dunes is a lagged response to an earlier climate event.
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Title: The water-energy-food nexus assessments of carbon neutral efforts
Creator: Xie, Yachen
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Efforts toward carbon neutrality are crucial for humans' well-being and the environment. Currently, two main ongoing carbon mitigation efforts are enhancing carbon sequestration and reducing carbon emissions. However, there are debates regarding the tradeoffs of these two efforts' related policies and action plans. This dissertation investigates and assesses the tradeoffs of carbon neutral efforts from a WEF nexus perspective. Three typical efforts were selected as assessment targets to...
Show moreEfforts toward carbon neutrality are crucial for humans' well-being and the environment. Currently, two main ongoing carbon mitigation efforts are enhancing carbon sequestration and reducing carbon emissions. However, there are debates regarding the tradeoffs of these two efforts' related policies and action plans. This dissertation investigates and assesses the tradeoffs of carbon neutral efforts from a WEF nexus perspective. Three typical efforts were selected as assessment targets to answer the overarching question of how carbon neutral efforts would affect the water-energy-food (WEF) nexus. The Chinese conversion of cropland to forestland program (CCFP) is representative of carbon sequestration. The hydropower development in MRB is an example of the energy transition to reduce emissions. The coal power industry is the coupling effort of energy transition and carbon capture, utilization, and storage (CCUS) applications in reducing carbon emissions. This dissertation consists of three main chapters, each corresponding to a journal article to address the three assessment targets. In Chapter 2, I evaluated the accomplishment of CCFP in China and its WEF nexus tradeoffs by applying remote sensing images from 2001 to 2019. The WEF assessment includes the transition matrix generation and the water yield calculation of the converted cropland and irrigation land. Indices related to WEF systems are also considered. In Chapter 3, a diagnostic approach with ten indicators was developed to assess the unilateral change's impacts on the WEF nexus. Using the diagnostic method, I provided statistical evidence of the benefits and tradeoffs of water, energy, food, economic prosperity, and the environment surrounding hydro dams in the Mekong River Basin. In Chapter 4, a scenario-based, life cycle coal power production assessment tool was proposed. By evaluating three portfolios or scenarios, the tradeoffs between reducing coal power production and CCUS application were revealed. This dissertation has successfully assessed the primary tradeoffs of carbon mitigation efforts from the WEF nexus perspective. The three studies can be wrapped up and come to three major conclusions: 1) The cons of major carbon mitigation efforts on WEF nexus and local sustainability exist, but not as speculated, especially for the CCFP and the hydropower dam construction. 2) The carbon neutral policies in China can accomplish their goals if adequately implemented. 3) The adaptive equilibrium between the CCUS application and coal power production reduction in China is crucial and needs to be better planned. The dissertation can enrich the carbon neutrality debate and fill gaps in the current literature on WEF nexus tradeoff studies on carbon mitigation by providing a remote-sensing approach and detailed coal modeling tools. The assessment tools proposed in Chapters 3 and 4 can be widely used by policymakers to understand better the tradeoffs regarding sustainability and WEF nexus in carbon neutral efforts.
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Title: CRANIAL METRIC AND NONMETRIC VARITION IN SOUTHEAST MEXICO AND GUATEMALA : IMPLICATIONS FOR POPULATION AFFINITY ASSESSMENT IN THE UNITED STATES
Creator: Kamnikar, Kelly Rae
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The scientific identification of unknown human skeletal remains in forensic contexts relies heavily on the estimation of demographic parameters (i.e., sex, age, stature, and population affinity). Population affinity, or the likelihood of group relatedness to a defined population of a decedent, can be estimated using measurements and observations from the cranial and postcranial skeleton. These estimations may be less accurate among populations which have been pooled together based on...
Show moreThe scientific identification of unknown human skeletal remains in forensic contexts relies heavily on the estimation of demographic parameters (i.e., sex, age, stature, and population affinity). Population affinity, or the likelihood of group relatedness to a defined population of a decedent, can be estimated using measurements and observations from the cranial and postcranial skeleton. These estimations may be less accurate among populations which have been pooled together based on convention. Latin American individuals—with geographic origins widely distributed throughout Central and South America—are broadly pooled together under the blanket term Hispanic with little regard for the immense cultural and biological diversity represented by these groups. Consequently, forensic anthropologists may be unintentionally disregarding genetic diversity, population structure, and population history and their impact on the formation and morphology of these groups. The purpose of this dissertation is to investigate variation in craniofacial morphology and develop population affinity models for Latin American groups using cranial metric and nonmetric data. The intent is to move beyond a single classification level (i.e., Hispanic) to more refined levels based on geographic origins (e.g., Guatemala, Southeast Mexico). The broad category of Hispanic was adopted by forensic anthropologists in large part because it is still used in medicolegal death investigations in the U.S. to describe individuals with familial origins in Latin America, Spain, and the Caribbean (U.S. Census Bureau 2021). Since the term Hispanic does not narrow down the region of origin for unidentified human remains, it is uninformative for identification and repatriation purposes, particularly regarding forensic investigations along the southern U.S. border. In this context, population affinity estimation benefits from refinement of a broad category to a more focused, population-level group. Craniometric and cranial macromorphoscopic (MMS) data are collected from samples in Guatemala City, Guatemala and Mérida, Mexico—with strong support from the forensic anthropologists in these countries—to capture aspects of skeletal variation associated with these regions. Biological distance and population affinity models are assessed and comparative data from other Latin American and U.S. populations are used to assess how well these model skeletal variation. Biological distance analysis demonstrates that Latin American populations, including the Meridian and Guatemala sample are distinct. Classification models obtain varying accuracy rates; the combined craniometric and cranial MMS model had the highest classification accuracy (70.7%). This study provides further support for the refinement of this broad category and is important for future investigations involved in identification efforts along the U.S.-Mexico border.
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Title: Circuit-Specific Inhibition of Dopaminergic Signaling Associated with Phantom Gustatory Sensations in Disrupted-in-Schizophrenia-1 Mice
Creator: Fry, Benjamin R.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Schizophrenia is a severe neuropsychiatric disorder characterized by a suite of symptoms occurring across cognitive (delayed processing, paraphasia, attentional deficits), negative (anhedonia, blunted affect, catatonia), and positive (hallucinations, delusions) domains. Antipsychotics are the most commonly prescribed medication to treat positive symptoms, however their use is complicated by substantial side-effects and inadequate efficacy. This reflects a lack of progress in understanding the...
Show moreSchizophrenia is a severe neuropsychiatric disorder characterized by a suite of symptoms occurring across cognitive (delayed processing, paraphasia, attentional deficits), negative (anhedonia, blunted affect, catatonia), and positive (hallucinations, delusions) domains. Antipsychotics are the most commonly prescribed medication to treat positive symptoms, however their use is complicated by substantial side-effects and inadequate efficacy. This reflects a lack of progress in understanding the precise neurobiological mechanisms underlying these symptoms, due in part to a lack of appropriate preclinical animal models. Here, I used an animal model of genetic vulnerability for neuropsychiatric illness known as Disrupted-in-schizophrenia-1 (DISC-1) to examine impaired reality testing, which reflects an aberrant internal representation of an absent event. In mice, this can be observed by an associatively evoked perception of an absent sweet taste. This effect is dopaminergically-dependent and associated with elevated activity in the insular cortex (IC). By combining sophisticated Pavlovian behavioral procedures with chemogenetic inhibition of dopamine neurons projecting from the ventral tegmental area (VTA) to the IC, I show that inactivation of the VTA --> IC dopaminergic circuitry leads to impaired reality testing in wild-type mice, and that DISC-1 mice have significantly less dopamine neurons which send projections to the IC, specifically. These data yield new insights with regard to the neurobiology underlying reality testing and the functional anatomical outcomes following perturbations of the DISC-1 genetic locus. My studies also suggest potential targets for the development of novel pharmacological treatments in humans with schizophrenia.
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Title: EXPRESSION AND ROLES OF BLASTOCYST LINEAGE-DETERMING GENES DURING SOMATIC CELL REPROGRAMMING
Creator: Moauro, Alexandra
Date: 2022
Collection: Electronic Theses & Dissertations
Description: In order to properly use stem cells, it is important that we first understand how these cells are establish and maintained. One of the most widely used stem cells are induced pluripotent stem cells (iPSCs) which provide great therapeutic promise and a novel source of ethical stem cells for research models. iPSCs are created by overexpression Oct4, Sox2, Klf4 and c-Myc (OSKM) in a somatic cell. As studies have sought to improve reprogramming efficiency and develop the most embryonically...
Show moreIn order to properly use stem cells, it is important that we first understand how these cells are establish and maintained. One of the most widely used stem cells are induced pluripotent stem cells (iPSCs) which provide great therapeutic promise and a novel source of ethical stem cells for research models. iPSCs are created by overexpression Oct4, Sox2, Klf4 and c-Myc (OSKM) in a somatic cell. As studies have sought to improve reprogramming efficiency and develop the most embryonically identical stem cells, our lab has uncovered that OSKM is not a specific cocktail for pluripotency formation. Instead OSKM induces additional cell fates including the formation of a multipotent stem cell termed induced extraembryonic endoderm stem (iXEN) cells. This raises the question as to how two distinct stem cell types arise in parallel. Interestingly, in embryo development we observe the same pluripotent and multipotent extraembryonic endoderm lineages form in parallel. Using our knowledge of normal embryo development, I set out to identify what blastocyst lineage markers can help us identify early iPSC and iXEN colonies as they start to form and mature. Of these markers, we observed that endogenous OCT4 is expressed in both iXEN and iPSC colonies. Based on the expression pattern of the key embryonic transcription factor, OCT4, we further focused on how this transcription factor may have a dual role in establishing iPSC and iXEN fates. Lastly, we altered the reprogramming cocktail using additional embryonic transcription factors to determine how these factors affect the propensity for pluripotency or extraembryonic endoderm fate.
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Title: Deterministic and Semi-Stochastic CC(P;Q) Approaches : New Developments and Applications to Spectroscopy and Photochemistry
Creator: Yuwono, Stephen Haniel
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The development of electronic structure methods that can accurately describe ground and excited states of molecular systems with manageable computational costs and in a systematically improvable manner continues to be the central theme of quantum chemistry. This dissertation focuses on some of the recent developments in the coupled-cluster (CC) theory and its equation-of-motion (EOM) extension to excited electronic states. One of the key challenges in the development of the CC and EOMCC...
Show moreThe development of electronic structure methods that can accurately describe ground and excited states of molecular systems with manageable computational costs and in a systematically improvable manner continues to be the central theme of quantum chemistry. This dissertation focuses on some of the recent developments in the coupled-cluster (CC) theory and its equation-of-motion (EOM) extension to excited electronic states. One of the key challenges in the development of the CC and EOMCC methodologies is the incorporation of many-electron correlation effects due to higher-rank components of the cluster and EOM excitation operators without incurring significant increase in the computational costs, while avoiding failures of perturbative methods of the CCSD(T) type in multireference situations, such as bond breaking and excited states dominated by two-electron transitions, and in certain weakly bound systems. Among the best ways to address these issues is the CC(P;Q) framework, which provides robust and computationally affordable noniterative energy corrections to lower-order CC/EOMCC calculations. In this dissertation, we discuss the different CC(P;Q) variants relying on both the conventional and unconventional truncations in the cluster and EOM excitation operators. The advantages of the CC(P;Q) hierarchy are illustrated using a few examples ranging from small molecule spectroscopy to photochemistry of large organic species in solution. In particular, we discuss the computational investigations of the novel super photobase FR0-SB, which exhibits a drastic increase in basicity upon photoexcitation, including the energetics and properties of its excited states, the steric effects governing the excited-state proton transfer involving FR0-SB and alcohols, and the enhanced photoreactivity of FR0-SB resulting from two-photon excitations, where the δ-CR-EOMCC(2,3) approach that belongs to the CC(P;Q) hierarchy played a key role. Furthermore, we demonstrate that the relatively inexpensive CC(t;3) and CC(q;4) approaches derived from the CC(P;Q) framework are as accurate in describing the challenging weakly bound magnesium dimer, including its ground-state potential and vibrational levels supported by it, as the much more demanding CCSDT and CCSDTQ parent theories. We also show how the highly accurate ground- and excited-state ab initio potentials obtained in the state-of-the-art CCSDT, CR-EOMCCSD(T), and full configuration interaction (CI) computations allowed us to resolve the existing laser-induced fluorescence and photoabsorption spectra of the magnesium dimer and find the missing high-lying vibrational states of Mg2 that have eluded scientists for half a century. Last, but not least, we discuss our recent extension of the semi-stochastic CC(P;Q) framework, which combines the deterministic CC(P;Q) theory with stochastic CI quantum Monte Carlo (QMC), to excited electronic states, providing rapid convergence to the parent high-level EOMCC methods, such as EOMCCSDT, out of the early stages of QMC propagations. The advantages of the semi-stochastic CC(P;Q) approach targeting EOMCCSDT are illustrated by examining vertical excitations in CH+ and adiabatic excitations in the CH and CNC species.
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Title: Three Essays on Panel Data Models with Interactive and Unobserved Effects
Creator: Brown, Nicholas Lynn
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Chapter 1: More Efficient Estimation of Multiplicative Panel Data Models in the Presence of Serial Correlation (with Jeffrey Wooldridge)We provide a systematic approach in obtaining an estimator asymptotically more efficient than the popular fixed effects Poisson (FEP) estimator for panel data models with multiplicative heterogeneity in the conditional mean. In particular, we derive the optimal instrumental variables under appealing `working' second moment assumptions that allow...
Show moreChapter 1: More Efficient Estimation of Multiplicative Panel Data Models in the Presence of Serial Correlation (with Jeffrey Wooldridge)We provide a systematic approach in obtaining an estimator asymptotically more efficient than the popular fixed effects Poisson (FEP) estimator for panel data models with multiplicative heterogeneity in the conditional mean. In particular, we derive the optimal instrumental variables under appealing `working' second moment assumptions that allow underdispersion, overdispersion, and general patterns of serial correlation. Because parameters in the optimal instruments must be estimated, we argue for combining our new moment conditions with those that define the FEP estimator to obtain a generalized method of moments (GMM) estimator no less efficient than the FEP estimator and the estimator using the new instruments. A simulation study shows that the GMM estimator behaves well in terms of bias, and it often delivers nontrivial efficiency gains -- even when the working second-moment assumptions fail.Chapter 2: Information equivalence among transformations of semiparametric nonlinear panel data modelsI consider transformations of nonlinear semiparametric mean functions which yield moment conditions for estimation. Such transformations are said to be information equivalent if they yield the same asymptotic efficiency bound. I first derive a unified theory of algebraic equivalence for moment conditions created by a given linear transformation. The main equivalence result states that under standard regularity conditions, transformations which create conditional moment restrictions in a given empirical setting need only to have an equal rank to reach the same efficiency bound. Example applications are considered, including nonlinear models with multiplicative heterogeneity and linear models with arbitrary unobserved factor structures.Chapter 3: Moment-based Estimation of Linear Panel Data Models with Factor-augmented ErrorsI consider linear panel data models with unobserved factor structures when the number of time periods is small relative to the number of cross-sectional units. I examine two popular methods of estimation: the first eliminates the factors with a parameterized quasi-long-differencing (QLD) transformation. The other, referred to as common correlated effects (CCE), uses the cross-sectional averages of the independent and response variables to project out the space spanned by the factors. I show that the classical CCE assumptions imply unused moment conditions which can be exploited by the QLD transformation to derive new linear estimators which weaken identifying assumptions and have desirable theoretical properties. I prove asymptotic normality of the linear QLD estimators under a heterogeneous slope model which allows for a tradeoff between identifying conditions. These estimators do not require the number of cross-sectional variables to be less than T-1, a strong restriction in fixed-$T$ CCE analysis. Finally, I investigate the effects of per-student expenditure on standardized test performance using data from the state of Michigan.
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Title: Subgenome dominance and genome evolution in allopolyploids
Creator: Bird, Kevin Andrew
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The merger of divergent genomes, via hybridization or allopolyploidization, frequently results in a ‘genomic shock’ that induces a series of rapid genetic and epigenetic modifications as a result of conflicts between parental genomes. This conflict among the subgenomes routinely leads one subgenome to become dominant over the other subgenome(s), resulting in subgenome biases in gene content and expression. Recent advances in methods to analyze hybrid and polyploid genomes with comparisons to...
Show moreThe merger of divergent genomes, via hybridization or allopolyploidization, frequently results in a ‘genomic shock’ that induces a series of rapid genetic and epigenetic modifications as a result of conflicts between parental genomes. This conflict among the subgenomes routinely leads one subgenome to become dominant over the other subgenome(s), resulting in subgenome biases in gene content and expression. Recent advances in methods to analyze hybrid and polyploid genomes with comparisons to extant parental progenitors have allowed for major strides in understanding the mechanistic basis for subgenome dominance. In particular, our understanding of the role that homoeologous exchange might play in subgenome dominance and genome evolution is quickly growing. Here I present novel work in several polyploid species investigating the biological and evolution impact of polyploidy and the evolution of these polyploid species. The first chapter introduces concepts like whole-genome duplication and describes advances in genomic sequencing technology that have accelerated the study of polyploid genomes. The second chapter reviews subgenome dominance and recent breakthroughs in understanding its causes and implications for genome evolution. The third chapter explores the repeatability of subgenome dominance in independently resynthesized Brassica napus. The fourth chapter investigates the extent to which genomic rearrangements from chromosomal duplications and deletions and homoeologous exchange can bias the analysis of subgenome expression dominance from RNAseq data. The fifth chapter explores the prevalence and impact of homoeologous exchange on independently resynthesized Brassica napus, providing novel evidence that gene dosage changes from homoeologous exchange are constrained by the need to maintain dosage balance of gene products. The sixth chapter explores the origins and admixture of wild octoploid strawberries Fragaria virgniana and Fragaria chiloensis with newly generated genomic resources applied to global collections.
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Title: DISRUPTIONS IN HEPATIC ONE CARBON METABOLISM AND THE GUT MICROBIOME DURING THE PROGRESSION OF NON-ALCOHOLIC FATTY LIVER DISEASE
Creator: Fling, Russell Ryan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The etiology of non-alcoholic fatty liver disease is complex, with multiple contributing factors including dietary, environmental, gut microbiome and genetic mechanisms. Accumulating evidence suggests exposure to polychlorinated dibenzo-p-dioxins and similar compounds may increases risk for NAFLD development. These environmentally persistent dioxin-like compounds bind and activate the aryl hydrocarbon receptor, a transcription factor that regulates intestinal homeostasis, xenobiotic and...
Show moreThe etiology of non-alcoholic fatty liver disease is complex, with multiple contributing factors including dietary, environmental, gut microbiome and genetic mechanisms. Accumulating evidence suggests exposure to polychlorinated dibenzo-p-dioxins and similar compounds may increases risk for NAFLD development. These environmentally persistent dioxin-like compounds bind and activate the aryl hydrocarbon receptor, a transcription factor that regulates intestinal homeostasis, xenobiotic and central metabolism. In a AhR-dependent manner, mice orally gavaged with 2,3,7,8-tetracholordibenzo-p-dioxin (TCDD) exhibit steatosis progressing to steatohepatitis with fibrosis akin to NAFLD progression. NAFLD and hepatocellular carcinoma (HCC) is also closely correlated with dysregulation of central metabolism e.g., hepatic one carbon metabolism (OCM), and gut dysbiosis contributing to NAFLD progression and worsening prognosis. This report investigates mechanisms involved in the dysregulation of the gut microbiome and OCM associated pathways relevant to NAFLD progression through comparisons of molecular analyses of TCDD-treated mice to human NAFLD and HCC. OCM describes the biosynthesis, homeostasis, and utilization of the cell’s main methyl donor, S-adenosylmethionine (SAM) including high flux anabolic biosynthesis of polyamines, phosphatidylcholine and creatine. In later stages of NAFLD, OCM is dysregulated with altered OCM gene expression as well as SAM and s-adenosylhomocysteine (SAH) levels. To assess TCDD-elicited effects on OCM, mice were orally gavaged with TCDD every 4 days for 28 days. Serum and livers collected at early (8 days) and late (28 days) time points were subjected to metabolomic analyses with integration of chromatin immunoprecipitation sequencing, transcriptomics and protein levels. Results from these studies suggest AhR-mediated repression of OCM required prolonged repeated TCDD-treatment and indirect effects elicited by AhR activation e.g., oxidative stress. Gut dysbiosis with disrupted enterohepatic bile acid metabolism is commonly associated with NAFLD and recapitulated in TCDD-treated mice. Similar to NAFLD, TCDD also increases systematic levels of secondary bile acids. These microbial transformed secondary bile acids are involved in modulation of host bile acid signaling pathways relevant to NAFLD. To investigate the effects of TCDD on the gut microbiota, the cecum contents of TCDD-treated mice were subjected to shotgun metagenomic sequencing. Taxonomic analysis identified dose-dependent increases in Lactobacillus species, notably Lactobacillus reuteri. Top enriched species were also associated with increased abundances of bile salt hydrolase sequences, responsible for the initial deconjugation reaction in secondary bile acid metabolism. L. reuteri levels were also attributed to enrichment of mevalonate-dependent isopentenyl diphosphate (IPP) biosynthesis genes, a pathway that was also elevated in cirrhosis patients. These results extend the role of Lactobacilli in the AhR/intestinal axis and NAFLD progression as well as highlight the similarities between TCDD-elicited phenotypes in mice to human NAFLD. Collectively, these studies evaluated TCDD-elicited mechanisms involved in disruptions in host and microbial metabolism, highlighting the AhR’s role in NAFLD progression.
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Title: ASSURING THE ROBUSTNESS AND RESILIENCY OF LEARNING-ENABLED AUTONOMOUS SYSTEMS
Creator: Langford, Michael Austin
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As Learning-Enabled Systems (LESs) have become more prevalent in safety-critical applications, addressing the assurance of LESs has become increasingly important. Because machine learning models in LESs are not explicitly programmed like traditional software, developers typically have less direct control over the inferences learned by LESs, relying instead on semantically valid and complete patterns to be extracted from the system’s exposure to the environment. As such, the behavior of an LES...
Show moreAs Learning-Enabled Systems (LESs) have become more prevalent in safety-critical applications, addressing the assurance of LESs has become increasingly important. Because machine learning models in LESs are not explicitly programmed like traditional software, developers typically have less direct control over the inferences learned by LESs, relying instead on semantically valid and complete patterns to be extracted from the system’s exposure to the environment. As such, the behavior of an LES is strongly dependent on the quality of its training experience. However, run-time environments are often noisy or not well-defined. Uncertainty in the behavior of an LES can arise when there is inadequate coverage of relevant training/test cases (e.g., corner cases). It is challenging to assure safety-critical LESs will perform as expected when exposed to run-time conditions that have never been experienced during training or validation. This doctoral research contributes automated methods to improve the robustness and resilience of an LES. For this work, a robust LES is less sensitive to noise in the environment, and a resilient LES is able to self-adapt to adverse run-time contexts in order to mitigate system failure. The proposed methods harness diversity-driven evolution-based methods, machine learning, and software assurance cases to train robust LESs, uncover robust system configurations, and foster resiliency through self-adaptation and predictive behavior modeling. This doctoral work demonstrates these capabilities by applying the proposed framework to deep learning and autonomous cyber-physical systems.
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Title: Interactions Between Plasma and Material Surfaces for Sterilization and Impurity Adsorption
Creator: Mackinder, Madeline Ann
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As the worldwide population increases, maintaining a standard of public health becomes more critical. Two major concerns in this area are nosocomial infections (NI) and water contamination. Current processes in sterilization and water treatment have limitations that could be overcome using plasma techniques. The unique characteristics of plasma make it a promising alternative for energy-intensive processes. This work investigated the characteristics of plasma that have the greatest impact on...
Show moreAs the worldwide population increases, maintaining a standard of public health becomes more critical. Two major concerns in this area are nosocomial infections (NI) and water contamination. Current processes in sterilization and water treatment have limitations that could be overcome using plasma techniques. The unique characteristics of plasma make it a promising alternative for energy-intensive processes. This work investigated the characteristics of plasma that have the greatest impact on sterilization and the reactivation of activated carbon. Previous studies have researched the physical and chemical surface properties of biochar but have not been able to establish an efficient process to activate biochar with desired characteristics. Plasma treatment would offer a way to etch the surface of biochar and specifically functionalize the surface. Successfully activating biochar would increase its adsorption ability and enable its use for water treatment. This project aims to harness these plasma properties and use plasmas to address three important topics related to public health: sterilization of surfaces, modulating commercial activated carbon (AC), and activations of biochar.Cold plasma sterilization offers an efficient way to sterilize medical components and instruments without the risk of deformation to heat-sensitive materials. This paper reports the use of magnetized plasma to realize low-temperature sterilization. A radio frequency dielectric barrier discharge was created in a quartz tube using a mixture of argon and oxygen gas. Glass slides inoculated with a uniform amount of Escherichia coli were exposed to the plasma afterglow at different pressures with and without a magnetic field. A global model was developed to evaluate the magnetically enhanced dielectric barrier discharges and predict species densities. Optical emission spectroscopy identified the plasma species present and validated the model. The magnetic field significantly promoted the intensity of the plasma and the sterilization efficiency. A process gas pressure of 100 mTorr presented the most effective treatment with a sterilization time less than one minute and sample temperature below 32 °C. The effects of O2 plasma on the adsorption capacity of activated carbon (AC) was investigated by varying treatment times. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Zeta potential were used to characterize the surface properties of the AC. The carbon was then applied to remove methylene blue (MB) from an aqueous solution. The adsorption kinetics and isotherm were also studied. Results showed that pseudo-second-order kinetics was the most suitable model for describing the adsorption of MB onto AC. Equilibrium data were well fitted to the Freundlich and Langmuir isotherm models. The highest adsorption capacity resulted from 4 minutes of O2 plasma treatment. This work shows that activation of AC by plasma can open the micropore and increase the effectiveness of chemical removal.Biochar was activated using a combination of O2 plasma and KOH. The adsorption capacity was investigated for different O2 plasma treatment times, KOH concentrations, and treatment temperatures. The adsorption capacity of methylene blue (MB) by the plasma activated biochar was evaluated. The adsorption kinetics and isotherm were also investigated. Results showed that pseudo-second-order kinetics was the most suitable model for describing the adsorption of MB onto biochar. Both the Freundlich and Langmuir isotherm models fit the equilibrium data. The highest adsorption capacity resulted from 10\% KOH + 300 °C for 5 minutes. This work shows that activation of biochar by plasma can improve adsorption capacity. The plasma treated AC and the plasma activated biochar were applied to the removal of PFOA. It was demonstrated that plasma treatment can improve PFOA adsorption. The negative surface charge was shown to negatively impact PFOA adsorption which aligns with the hypothesis that PFOA would preferentially adsorb onto more positive surfaces due to its anionic state in water.
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Title: Food Access, Insecurity, and Health : The Experience of International Students
Creator: Khandelwal, Shruti
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Food insecurity is rising among college students and minority groups in the United States. This is closely associated with poor health outcomes, including chronic health risks and poor mental health outcomes. Two key parameters, namely physical access and affordability have been commonly employed for assessing food insecurity by various institutions and researchers. While the food security is assessed for US populations and hinged upon measuring access to healthy and nutritious foods, food...
Show moreFood insecurity is rising among college students and minority groups in the United States. This is closely associated with poor health outcomes, including chronic health risks and poor mental health outcomes. Two key parameters, namely physical access and affordability have been commonly employed for assessing food insecurity by various institutions and researchers. While the food security is assessed for US populations and hinged upon measuring access to healthy and nutritious foods, food security among international students is difficult to comprehend. Moreover, perceptions and experiences of food access for international students does not encompass access to healthy and culturally appropriate foods. Therefore, if international students cannot access healthy and culturally appropriate foods, they are more likely to be food insecure and therefore, suffer from poor health and behavioral outcomes. The aim of this study is to explore perceived access to healthy and culturally appropriate foods for South Asian students that mitigate their food related health risk. The main research question examines if international students experience poor health and behavioral outcomes due to food inaccessibility than domestic students. Three hypotheses were tested to investigate the main research question. The first hypothesis is that international students perceive greater food inaccessibility than domestic students. The second hypothesis is that international students perceive greater food insecurity due to food inaccessibility than domestic students. The third hypothesis is that international students perceive poor health and behavior outcomes due to food insecurity than domestic students. Using mixed-methods research approach, quantitative assessment (n=427) was supplemented with qualitative – thematic coding to understand the perceptions of accessing healthy and culturally appropriate foods for Indian students (n=88) which formed the majority of the sample population (77%). Additionally, to comprehend the local-level access to foods, built area analysis (n=53) was conducted for one university in the Midwest (with the maximum responses) to explore the experiences of accessing healthy and culturally appropriate foods and the parameters of the modes of transit (mode of transportation, frequency of trips, travel time).The quantitative assessment utilized chi-square test for hypothesis one and two and logistic regression for the third hypothesis. The affirmation of all three hypotheses showed that access is a critical aspect in assessing food security/insecurity and in turn, good health and behavior outcomes for international students studying in the US universities. The qualitative assessment was based on interviews (n=88) and food journal responses (n=87). This method illustrates two important factors. First, the key definition for culturally appropriate foods emerged from interviews and second, acceptability to healthy and culturally appropriate foods was most preferred among interviewees. However, it was ranked lower in all other dimensions of access, i.e., accessibility, accommodation, availability, and affordability. The built area analysis (n=53) helped in understanding the local level assessment of the food environment of one university. The study concludes with recommendations on improving access to healthy and culturally appropriate foods through interventions at local planning level in three area- zoning, mobility, and governance.
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