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Title: EXPLORING THE REGULATORY MECHANISMS BEHIND CHLOROPLAST POPULATION MORPHOLOGY
Creator: Tallerday, Emily Jennings
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Eukaryotic cells tightly regulate their populations of endosymbiotically-derived organelles. Organelle populations can be described in terms of size, number, or coverage, the latter being the collective planar area taken up by the organellar population relative to that of the cell. As the photosynthetic organelle, chloroplasts are vital, and alterations to chloroplast population morphology can affect photosynthetic performance and biomass accumulation. However, how the cell perceives and...
Show moreEukaryotic cells tightly regulate their populations of endosymbiotically-derived organelles. Organelle populations can be described in terms of size, number, or coverage, the latter being the collective planar area taken up by the organellar population relative to that of the cell. As the photosynthetic organelle, chloroplasts are vital, and alterations to chloroplast population morphology can affect photosynthetic performance and biomass accumulation. However, how the cell perceives and regulates its chloroplast population remains a mystery. Division at the mid-plastid (binary fission) is the primary mechanism by which chloroplasts increase their population sizes. It has been well established that lower division rates result in a small population of enlarged chloroplasts, suggesting the existence of a compensatory mechanism ensuring that total chloroplast coverage within the cell is preserved through a tradeoff between chloroplast division and expansion. Most model plants keep a relatively large number of chloroplasts in their leaf cells (>50 per cell). In expanding leaf cells, multiple rounds of chloroplast division typically increase the number of chloroplasts per cell. However, a number of natural adaptive alterations to chloroplast morphology have been observed in several tropical plant species, primarily those native to low-light environments. The tropical plant genus Peperomia (Piperaceae) offers a unique opportunity for understanding the regulation of chloroplast population morphology, as some Peperomia spp. contain two to six giant chloroplasts in their palisade mesophyll cells at maturity, while most others have higher numbers of small chloroplasts in their mesophyll cells. I have characterized chloroplast population morphology in Peperomia, of which six species had not been studied previously, and shown that chloroplast division is inhibited in the palisade cells of Peperomia pellucida. Further, I have assembled and annotated the genome of Peperomia dahlstedtii, the first genome for this genus, and produced a novel transcriptome assembly for P. pellucida. Lastly, I have analyzed gene expression in these two species differing in palisade cell chloroplast population morphology and identified several candidate genes potentially underlying the differences in phenotype. For the first time, I also have described the expression of the chloroplast division genes in these two species. By characterizing variation in chloroplast population morphology in Peperomia, my work builds upon existing research on this trait over leaf development, provides the resources necessary for Peperomia to be used as a model, and identifies potential causes behind the large-chloroplast phenotype documented in several species.
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Title: MIGRANT FARM WORK, COLLEGE, AND MONEY : A PARTICIPATORY ACTION RESEARCH STUDY WITH MIGRANT FARMWORKING COLLEGE STUDENTS
Creator: Flores, Amanda
Date: 2022
Collection: Electronic Theses & Dissertations
Description: College is the first time students have the opportunity to make independent financial decisions and employ financial practices. Research suggests that students pick up financial knowledge, habits, and practices from family, friends, and their broader community and that these practices can have long-term implications. Migrant farmworking college students are a small subset of college students who come from highly mobile families and whose source of income is dependent on agricultural seasons....
Show moreCollege is the first time students have the opportunity to make independent financial decisions and employ financial practices. Research suggests that students pick up financial knowledge, habits, and practices from family, friends, and their broader community and that these practices can have long-term implications. Migrant farmworking college students are a small subset of college students who come from highly mobile families and whose source of income is dependent on agricultural seasons. The migratory lifestyle influences how migrant farmworking families employ financial practices, which likely shapes how children in migrant farmworking families think about their finances and what kinds of financial practices they use. This study explores how the familial and cultural upbringing of migrant farmworking families influences the financial practices of migrant farmworking college students. Grounded in participatory action research methodology, I draw on funds of knowledge and consejos to elevate familial and cultural influences on the financial practices of 5 migrant farmworking college students. Ultimately, this study seeks to provide recommendations for advisors and other student-facing professionals to help meet the diverse needs of this distinct population of marginalized students.
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Title: ENGINEERING STUDIES IN ADVANCED PLA MATERIALS – STEREOCHEMISTRY, STEREOCOMPLEXATION, AND THERMAL RECYCLING OF PLA
Creator: Alhaj, Mohammed A.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Polylactide (PLA) polymers are the world’s foremost 100% biobased resin with both composting and recycling end-of-life options in harmony with Ellen MacArthur Foundation “Circularity Model.” It is commercially manufactured by converting lactic acid to lactide, which is then polymerized to PLA. These molecules present unique and intriguing stereochemistry that dictate manufacturing, performance properties, and processability. However, it is seldom discussed and not well understood in the role...
Show morePolylactide (PLA) polymers are the world’s foremost 100% biobased resin with both composting and recycling end-of-life options in harmony with Ellen MacArthur Foundation “Circularity Model.” It is commercially manufactured by converting lactic acid to lactide, which is then polymerized to PLA. These molecules present unique and intriguing stereochemistry that dictate manufacturing, performance properties, and processability. However, it is seldom discussed and not well understood in the role stereochemistry can play and impact product performance and use. In the current work, we critically review and discuss the stereochemical implications for PLA through studies on different PLA compositions.To-date, it is unclear the origin of D-content present in commercial grade PLA, although it is assumed to originate from D-lactide. In this work, we validate that manufacture of lactide monomer from (L)- lactic acid predominantly results in a mixture of L and meso (DL), not L- and D- lactide. Optical rotation and 1H NMR studies are used to elucidate this stereochemistry. Copolymers of L-lactide and meso-lactide and copolymers of L-lactide and D-lactide are synthesized via bulk polymerization at various compositions. The optical rotation, tacticity, crystallinity, and thermal properties of synthesized copolymers are characterized. The optical rotation of poly(meso-lactide) has also been reported for the first time in this text. Differential scanning calorimetry (DSC) and 1H NMR studies confirm that PLA transitions from a predominantly isotactic, semi-crystalline polymer to a predominantly atactic, amorphous polymer when one copolymerizes greater than 10% meso-lactide with L-lactide. The stereochemical composition, mechanical and rheological properties of commercial grade PLA are measured to elucidate the effect of stereochemistry on the tensile and rheological behavior of PLA. We conclude this section with studies on PLA stereochemistry and its influence on immune cellular response. Hydrolytic degradation of semi-crystalline and amorphous PLA is analyzed via molecular weight characterization and lactic acid abundance. Semi-crystalline and amorphous PLA are then studied as potential carriers for glycolytic inhibitors. The stereochemistry of PLA and its implication on performance properties are further explored in studies on stereocomplex PLA. A pilot-scale continuous manufacturing process of stereocomplex PLA is developed and optimized by melt-blending a 1:1 blend of high molecular weight poly(L-lactide) (PLLA) and high molecular weight poly(D-lactide) (PDLA) in a co-rotating twin screw extruder. Stereocomplexation is first characterized via DSC at different temperatures and times. The optimal reaction temperature and reaction time are found and used to process >95% stereocomplex PLA conversion (melting peak temperature Tpm = 240°C). Stereocomplex PLA is used as an additive to produce 70% PLLA/30% stereocomplex PLA composites. The crystallinity, thermal properties, and tensile properties of composites are then characterized. A study on stereocomplex PLA and its effect on the crystallization kinetics of PLLA is conducted. 5% stereocomplex PLA is blended with 95% PLLA to analyze its use as a nucleating agent. The final section discusses a pilot-scale end-of-life method for PLA via thermal recycling. This study continues previous studies on PLA thermodepolymerization by scaling up the reversible reaction in a pilot-scale batch reactor. PLA is run at various temperatures and times to elucidate the processing conditions that yield the highest lactide conversion. The chemical purity, optical purity, lactide yield and stereoisomeric composition of the final lactide product are characterized by DSC, optical rotation, mass balance, and 1H NMR, respectively.
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Title: PLANNING FOR AUTONOMY AND ELECTRIFICATION IN FUTURE TRANSPORTATION SYSTEMS
Creator: Singh, Harprinderjot
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Autonomous vehicles (AVs) and electric vehicles (EVs) will improve safety, mobility, roadway capacity and provide efficient driving, efficient use of travel time, and reduced emissions. However, these technologies affect vehicle miles traveled (VMT), travel time, ownership cost, and electric grid network. Shared mobility systems can ameliorate the high price of these technologies. However, the shared mobility system poses additional problems such as users’ waiting time, inconvenience, and...
Show moreAutonomous vehicles (AVs) and electric vehicles (EVs) will improve safety, mobility, roadway capacity and provide efficient driving, efficient use of travel time, and reduced emissions. However, these technologies affect vehicle miles traveled (VMT), travel time, ownership cost, and electric grid network. Shared mobility systems can ameliorate the high price of these technologies. However, the shared mobility system poses additional problems such as users’ waiting time, inconvenience, and increased VMT. Further, the impact of these emerging technologies varies on different groups of users (different values of travel time (VOTT). Another hurdle to the adoption of EVs is the limited range and scarcity of charging infrastructure. A well-established network of charging infrastructure, especially the direct current fast chargers (DCFC), can alleviate this challenge. However, the widespread adoption of EVs and the growing network of DCFC stations will increase the electric energy demand affecting the electric grid stability, demand-supply imbalance, overloading, and degradation of the electric grid components. Distributed energy resources (DER) such as solar panels and energy storage systems (ESS) can support the EV demand and reduce the load on the electric grid. This study develops modeling frameworks for the optimal adoption of AVs and EVs, considering their effect on transportation systems, the environment, and the electric grid network. Further, it suggests different scenarios that would promote the adoption of these technologies and provide a sustainable and resilient system.This study proposes a multi-objective mathematical model to estimate the optimal fleet configuration in a system of private manual-driven vehicles (PMVs), private AVs (PAVs), and shared AVs (SAVs) while minimizing the purchase and operating costs, time (travel and waiting time), and emission production. SAVs can be the optimal solution with the efficient use of travel time or the purchase price below a certain relative threshold. PAVs can be the optimal solution only if the onboard amenities are improved, lifetime mileage is increased, AV technology is installed in luxurious cars, and adopted by people with high VOTT. The framework is extended to consider different combinations of EVs, AVs, and conventional human-driven vehicles in a private and shared mobility system. The metaheuristics based on genetic and simulated annealing algorithms are developed to solve the large-scale NP-hard nonlinear optimization problem. The model is implemented for the network of Ann Arbor, Michigan. The results suggest that EVs are optimal for the system due to low operating costs and zero tailpipe emissions. Shared autonomous electric vehicles (SAEVs) are the best option for users with low VOTT. Private autonomous electric vehicles (PAEVs) would favor the system if the travel time savings are at least 20% or the price of AV technology is less than one-third of the vehicle price. The study then investigates the optimum investment technology to support the rising energy demand at the DCFC stations and reduce the load on the electric grid network. The different investments include purchasing and installing various ESS (new batteries (NB), second-life batteries (SLB), flywheels), solar panels, electric grid upgrades, and the cost of buying/selling electricity from/to the electric grid. The model is implemented for the DCFC stations supporting the future needs of EV charging demand for urban trips in the major cities of Michigan in 2030. The combination of SLBs and solar panels provides maximum benefits. The total annual and electricity savings are $25,000-$165,000 and $40,000-$300,000 per city.
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Title: ESSAYS ON COMMUNITY FOCUSED SUPPLY CHAINS
Creator: Cole, Dustin
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Businesses are increasingly being called upon to improve their Environment, Social and Governance (ESG) performance. The need to tackle a range of concerns, both environmentally and socially, can be seen in the United Nations’ 17 development goals set forth in 2015. Beyond governments and regulators, businesses themselves are increasingly aware of the importance of addressing such issues. Two hundred of the top CEOs of the country have emphasized the importance of the role that businesses...
Show moreBusinesses are increasingly being called upon to improve their Environment, Social and Governance (ESG) performance. The need to tackle a range of concerns, both environmentally and socially, can be seen in the United Nations’ 17 development goals set forth in 2015. Beyond governments and regulators, businesses themselves are increasingly aware of the importance of addressing such issues. Two hundred of the top CEOs of the country have emphasized the importance of the role that businesses play in confronting community-related issues and Diversity, Equity and Inclusion (DEI) (Murray 2019). In a series of three essays, this dissertation focuses on the social and environmental sustainability aspects of ESG, thus contributing substantially to the overall domain of sustainability. The first essay examines the impact of leader-worker disability status similarity on front-line manufacturing worker productivity using micro-data gathered from a real-world organization in Michigan. It contributes to the nascent field of inclusive operations and explores how organizations can both be profitable and inclusive of traditionally marginalized workers. The essay focuses on the moderating influence of direct supervisors with a disability on workgroup productivity as the number of workers with disabilities increases. Results suggest that a direct supervisor with a disability does indeed benefit the productivity of workers with disabilities. This benefit, however, is the mitigation of potential productivity declines as the number of workers with a disability increases in the workgroup. A follow-up qualitative study is performed to understand the mechanisms of the productivity benefit by interviewing 50 workers and supervisors with and without disabilities across three organizations. The second and third essays focus on the issue of water, a resource that is increasingly important as an environmental concern. As a resource shared between communities and firms, water is an essential component of building sustainable cities and communities.The second essay examines trade-offs and synergies experienced by organizations when reducing water use and carbon emissions using secondary panel data of large firms. Previous research has found differing results of organizations trading off carbon emissions and water. Some have found reducing one comes at the expense of the other, while other research has found organizations can reduce these two concerns jointly. This past research, though, has generally been qualitative and at the facility level, without quantitative analysis at the firm level. This research fills this gap by providing a firm-level examination of such potential trade-offs using a combination of Data Envelopment Analysis and econometric methods.The third essay uses a vignette experiment with real-world procurement professionals to examine how buyers weigh the competing environmental concerns of carbon emissions and water use reductions in the supply chain against supplier location (local vs. offshore suppliers). The results show an overwhelming preference for local suppliers with lower carbon emissions, to the extent that a supplier with a superior overall environmental performance may be passed over in pursuit of local suppliers with marginally lower carbon emissions.
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Title: ENHANCING CORPORATE CRIME ENFORCEMENT WITH MACHINE LEARNING—A MULTIDISCIPLINARY RISK FACTOR APPROACH
Creator: Chan, Fiona
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Despite its severe and lasting social and financial ramifications, corporate financial crime remains one of the most understudied crime types, as it is often hindered by two challenges. First, its multidisciplinary nature requires both financial and criminological expertise among others to conduct proper investigations. Second, corporate crime data is fraught with constraints such as high dimensionality, complex interactions, and nonlinear functional forms that are ill-suited for classical...
Show moreDespite its severe and lasting social and financial ramifications, corporate financial crime remains one of the most understudied crime types, as it is often hindered by two challenges. First, its multidisciplinary nature requires both financial and criminological expertise among others to conduct proper investigations. Second, corporate crime data is fraught with constraints such as high dimensionality, complex interactions, and nonlinear functional forms that are ill-suited for classical statistical modeling. The lack of research coupled with the limited resources in corporate crime enforcement represent a great impediment to the advancement of fraud interventions. This dissertation seeks to overcome these specific challenges by unifying cross-disciplinary financial fraud research under a risk factor framework, and by leveraging recent advancements in artificial intelligence. The goal is to examine whether two machine learning algorithms—random forest and neural network—can be used to enhance corporate fraud risk detection/prediction beyond more commonly employed analytical techniques. Findings from the analysis showed that the random forest algorithm outperformed logistic regression and a naïve classifier in a 1:1 matched sample. The neural network performed better than a naïve classifier but slightly worse than logistic regression. Feature selection improved the algorithms’ predictive accuracy and ability to distinguish between classes even further. Despite promising results from the 1:1 matched sample, both machine learning algorithms struggled with a heavily imbalanced 1: many dataset, which represents a more realistic setting. With the implementation of an oversampling strategy and feature selection, the algorithms improved substantially in identifying the rare fraud cases, and showed promise of improvement with further research on imbalanced classification. Feature importance from the random forest classifier identified risk factors that are consistent with findings from prior studies. Measures of financial distress ranked lower in importance than measures of financial health, suggesting future research can build on prior findings on corporate strain to examine specific mechanisms. The analysis also identified auditor independence as a key concept of guardianship and opportunity structure that warrants further study. Findings from this research also have important methodological implications for corporate crime studies—namely, the need to improve measurements of organizational-level fraud risk factors.
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Title: GENDER EQUITY IN COMMUNITY SUSTAINABILITY : BREASTFEEDING AND INTIMATE PARTNER ABUSE
Creator: Bomsta, Heather D.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: We live within a web, connected to our family, friends, communities, societies, nations and ultimately, the greater biome of the Earth. Healthy, thriving women and children benefit their communities; healthy women work to contribute to and help care for their families and friends, and healthy children are able to learn well at school and are best positioned to develop into healthy, able citizens. Unfortunately, the presence of intimate partner abuse (IPA) negatively impacts maternal and child...
Show moreWe live within a web, connected to our family, friends, communities, societies, nations and ultimately, the greater biome of the Earth. Healthy, thriving women and children benefit their communities; healthy women work to contribute to and help care for their families and friends, and healthy children are able to learn well at school and are best positioned to develop into healthy, able citizens. Unfortunately, the presence of intimate partner abuse (IPA) negatively impacts maternal and child health, resulting in lost productivity, missed schooling, increased healthcare costs, and in some cases the deaths of women and infants. IPA is a critical issue in community well-being and sustainability. This dissertation presents three studies focusing on better understanding dynamics around IPA that impact women and their children. The first two studies focus on how abuse impacts breastfeeding. Providing human milk for an infant has benefits for infants, lowering all causes of infant mortality and resulting in increased IQ and lifelong health benefits (Victora et al., 2016). Nursing an infant also benefits mothers by reducing postpartum hemorrhage, lowering the risk of postpartum depression and their lifetime risks of nine different types of cancer (Stuebe, 2009). These benefits accumulate across individuals, resulting in healthier mothers and children, better able to contribute to their families and communities. The first study uses a nationwide dataset from the Centers for Disease Control, the Pregnancy Risk Assessment and Monitoring survey (PRAMS), to quantitatively explore the relationship between reported physical abuse and breastfeeding initiation. The relationship between IPA and breastfeeding initiation is complex and the literature is not yet settled. This study contributes to the literature by using an alternate approach that is not definitive, but points toward new areas for future research. Working to resolve this question can help healthcare providers, IPA advocates and policy makers with better information to begin to shape interventions to support mothers coping with abuse. Breastfeeding matters to these mothers for health reasons, but also because it is one of the first major decisions they make for an infant and if they do not meet their breastfeeding goals, they often experience guilt, question their value as mothers (Jackson, DePascalis, Harrold & Fallon, 2020) and face a higher risk of postpartum depression (Gregory, Butz, Ghazarian, Gross & Johnson, 2015; Borra, Iacovou & Sevilla, 2015). The first hypothesis explored is that mothers reporting physical abuse will initiate breastfeeding at a lower rate than mothers reporting no physical abuse. Logistic regression confirmed mothers reporting physical violence initiate breastfeeding at a lower rate than their unabused counterparts. The relationship remains significant when controlling for race and maternal education, but marital status reverses the effect. Subsequent subgroup analyses show married women’s decisions around breastfeeding initiation to be significantly impacted by physical abuse, while unmarried abused mothers initiated breastfeeding at roughly the same rate as unmarried mothers reporting no physical violence. The second hypothesis focuses only on mothers reporting physical abuse and explores whether a ‘dose’ effect exists. Logistical regression again shows mothers who report physical abuse at two time points initiate breastfeeding at a lower rate than mothers reporting physical abuse at only one time point. This finding remained significant even when controlling for maternal education, race/ethnicity, and marital status. The second study is a qualitative exploration of mothers’ experience of living with an abusive partner while breastfeeding. While quantitative studies can estimate the size and direction of a phenomenon it does not tell us what is happening in the day-to-day life of people experiencing it. Qualitative research can raise the voices of women coping with abuse during the breastfeeding phase, who are the experts on their situations. It is also essential for those working to end abuse to understand how mothers and their decisions are constrained by abuse and how they use their agency to resist and survive. This study uses semi-structured interviews with thirteen mothers with infants under one year of age who lived with an abusive partner for some amount of time while breastfeeding/pumping. Using thematic content analysis, themes emerged around mothers using gender performativity, successfully and unsuccessfully, to attempt to stem the violence and chaos in their relationships. Mothers attempted to fulfill traditional female roles to appease abusive partners, used breastfeeding to protect themselves and their infants, and drew strength from family, friends, and medical/support professionals by fulfilling the ‘good mother’ role through breastfeeding. The third study examines organizational resilience for nonprofits, which often function as a key part of the social safety net by providing services to vulnerable populations and strengthening communities. Despite their essential nature, organizational resilience (OR) among nonprofits is not well studied. Finding no models specific to nonprofits, a model of OR from the for-profit sector was adapted and extended. The model adaptation focuses on financial resources, technical resources and social resources and expands each category to cover unique aspects of nonprofits that the for-profit OR model does not contain. The gap between OR and social-ecological resilience (SER) was also examined, and several SER concepts were added to enhance our nonprofit OR model. The adapted model is then illustrated through a case study of intimate partner abuse (IPA) agencies. Managers and frontline staff from eight IPA nonprofits in a Midwestern state were interviewed during the COVID-19 pandemic. The adapted model can be used by researchers and practitioners to better understand and evaluate OR not only in IPA agencies, but all nonprofits.
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Title: ASSESSMENT OF WATER TREATMENT TECHNOLOGIES FOR PER-AND POLYFLUOROALKYL SUBSTANCES (PFAS) IN MULTIPLE MATRICES
Creator: Maldonado , Vanessa
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The ubiquitous presence of per-and polyfluoroalkyl substances (PFAS) in the environment resulted in extensive water contamination that poses a significant risk to human health and biota. Continuous research efforts aim to develop efficient treatment technologies to treat PFAS in water, break the PFAS accumulation cycle in the environment, and improve the efficiency of emerging technologies. In this thesis work, selected treatment technologies including electrochemical oxidation and...
Show moreThe ubiquitous presence of per-and polyfluoroalkyl substances (PFAS) in the environment resulted in extensive water contamination that poses a significant risk to human health and biota. Continuous research efforts aim to develop efficient treatment technologies to treat PFAS in water, break the PFAS accumulation cycle in the environment, and improve the efficiency of emerging technologies. In this thesis work, selected treatment technologies including electrochemical oxidation and dielectrophoresis-enhanced adsorption were used to assess and advance the state-of-the-art for PFAS remediation in multiple matrices, not previously addressed. A boron-doped diamond (BDD) flow-through cell was used to evaluate the electrochemical oxidation of perfluoroalkyl acids (PFAAs) in landfill leachates. Multiple leachates with a concentration of individual PFAAs in the range of 10^2 -10^4 ng/L were treated. The effect of current density and variability of the composition of leachates was investigated. Non-detect levels and >90% removal of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were reached for all leachates tested after electrochemical treatment. Although high removal efficiencies for long-chain PFAAs were obtained, high concentrations of short-chain PFAAs were generated and associated with the transformation of perfluoroalkyl acid (PFAA) precursor compounds.In the second part of this thesis research, the oxidative transformation of PFAA-precursors typically present in leachates was addressed for the first time. Target and suspect PFAS were identified in a landfill leachate and their concentrations during electrochemical treatment were quantified over time. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF) measurements of the leachate identified 53 PFAS compounds and 19 PFAS classes. Multiple PFAS were reported for the first time in landfill leachates. The evaluation of the intermediate and final products generated during the electrochemical treatment showed evidence of known electrochemical degradation pathways.Coupling destructive technologies (e.g., electrochemical oxidation) with concentration technologies (e.g., ion exchange (IX), adsorption) in a treatment train approach could reduce the treatment cost of destructive technologies and increase their feasibility. Therefore, in the next part of this work, electrochemical oxidation of PFAAs from the concentrated waste of IX still bottoms was assessed at laboratory and semi-pilot scales. The concentrated waste resulted from the treatment of PFAAs-impacted groundwater with IX resins. Multiple current densities were evaluated at laboratory scale and the optimum current density was used at the semi-pilot scale. The results at the laboratory and semi-pilot scales allowed for >99% and >94% removal of total PFAAs with 50 mA/cm^2, respectively. Defluorination values, energy consumption, and implications were discussed.The third matrix addressed for PFAS remediation was drinking water. Dielectrophoresis-enhanced adsorption was used for the removal of low concentrations of PFOA. This study introduced a coaxial-electrode cell (CEC) that allowed for the generation of a non-uniform electric field to enhance the adsorption of PFOA. Experiments were performed in batch and continuous-flow modes. The dielectrophoretic-enhanced adsorption in batch mode resulted in a 4, 7, and 8-fold increase in the removal of PFOA with 5, 25, and 50 V when compared to adsorption only. The performance of the CEC in continuous-flow mode allowed for an increase of up to 2.4-fold in the PFOA removal with 25 V. The results highlighted the benefits of using a dielectrophoresis-enhanced adsorption process for the removal of PFOA from water. Overall, results from this thesis contribute to the understanding of the electrochemical degradation of PFAS in multiple matrices and introduce an alternative process to enhance the widely used adsorption technology for PFAS removal. Treatment implications of each matrix are discussed and provide a clear baseline for future research, development, and scale-up of treatment technologies for PFAS remediation.
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Title: REACTIVE ION ENHANCED MAGNETRON SPUTTERING OF NITRIDE THIN FILMS
Creator: Talukder, Al-Ahsan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Magnetron sputtering is a popular vacuum plasma coating technique used for depositing metals, dielectrics, semiconductors, alloys, and compounds onto a wide range of substrates. In this work, we present two popular types of magnetron sputtering, i.e., pulsed DC and RF magnetron sputtering, for depositing piezoelectric aluminum nitride (AlN) thin films with high Young’s modulus. The effects of important process parameters on the plasma I-V characteristics, deposition rate, and the properties...
Show moreMagnetron sputtering is a popular vacuum plasma coating technique used for depositing metals, dielectrics, semiconductors, alloys, and compounds onto a wide range of substrates. In this work, we present two popular types of magnetron sputtering, i.e., pulsed DC and RF magnetron sputtering, for depositing piezoelectric aluminum nitride (AlN) thin films with high Young’s modulus. The effects of important process parameters on the plasma I-V characteristics, deposition rate, and the properties of the deposited AlN films, are studied comprehensively. The effects of these process parameters on Young’s modulus of the deposited films are also presented. Scanning electron microscope imaging revealed a c-axis oriented columnar growth of AlN. Performance of surface acoustic devices, utilizing the AlN films deposited by magnetron sputtering, are also presented, which confirms the differences in qualities and microstructures of the pulsed DC and RF sputtered films. The RF sputtered AlN films showed a denser microstructure with smaller grains and a smoother surface than the pulsed DC sputtered films. However, the deposition rate of RF sputtering is about half of the pulsed DC sputtering process. We also present a novel ion source enhanced pulsed DC magnetron sputtering for depositing high-quality nitrogen-doped zinc telluride (ZnTe:N) thin films. This ion source enhanced magnetron sputtering provides an increased deposition rate, efficient N-doping, and improved electrical, structural, and optical properties than the traditional magnetron sputtering. Ion source enhanced deposition leads to ZnTe:N films with smaller lattice spacing and wider X-ray diffraction peak, which indicates denser films with smaller crystallites embedded in an amorphous matrix.
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Title: STUDIES ON DIVERSITY OF ALTERNARIA ALTERNATA ASSOCIATED WITH ALTERNARIA LEAF SPOT IN SUGAR BEET
Creator: Jayawardana, Malini Anudya
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Alternaria leaf spot (ALS) is one of the foliar diseases that can impact sugar beet. Recently, ALS has been an increasing issue in fields from several states in the United States including Michigan. One of the most common causative agents of ALS is Alternaria alternata. This same organism has been reported as a pathogen not only in sugar beet, but also in a number of other crops. Michigan is the second most agriculturally diverse state in the United States and a wide range of crops are grown...
Show moreAlternaria leaf spot (ALS) is one of the foliar diseases that can impact sugar beet. Recently, ALS has been an increasing issue in fields from several states in the United States including Michigan. One of the most common causative agents of ALS is Alternaria alternata. This same organism has been reported as a pathogen not only in sugar beet, but also in a number of other crops. Michigan is the second most agriculturally diverse state in the United States and a wide range of crops are grown in the state. Since A. alternata is a pathogen on a number of crops currently grown and associated with sugar beet crop rotation in Michigan, it is important to learn about the interactions between A. alternata and its hosts. Therefore, the current projects were carried out to examine some of the host-pathogen interactions in A. alternata with a focus on ALS in sugar beet. The first project addressed developing effective inoculation methods for ALS in the laboratory, greenhouse or in the field. An effective inoculation method for ALS in sugar beet is important for assessing potential management tools for ALS such as screening for resistance and for fungicide efficacy. A detached leaf assay and a greenhouse inoculation with the inoculum in 0.2% malt extract as an outside nutrient source indicated a significant difference between susceptible and resistant varieties for the disease. Field results showed a significant effect of inoculation in three out of four years but showed issues with other pathogens and still need further testing. However, preliminary evidence for a consistent inoculation was observed in 2021, where the inoculum in an outside nutrient source, similar to what we used in the greenhouse, gave higher disease severity than a non-inoculated control or water-suspended inoculum. The diversity of A. alternata was observed in the second and third projects. Aspects of the host range of A. alternata were examined by isolating the pathogen from four crops growing in Michigan and cross-inoculating each isolate across four hosts. All the A. alternata strains caused lesions on all four host crops tested regardless of the crop from which they originally were isolated. Therefore, the results supported a wide host range of A. alternata. Furthermore, genetic diversity of A. alternata was examined in the third project. A total of 48 A. alternata isolates, collected from four hosts in Michigan, and in-silico data for an additional 15 A. alternata isolates from different hosts in other geographic areas, were used in a genetic analysis using three loci. The phylogenetic tree in this study agreed with previous reports of a high level of genetic diversity for A. alternata. This was the first study to examine diversity on beet and indicated similar diversity to what has been observed on other crops like potato and apple. No clear separation was observed between A. alternata strains related to the host from which they were originally collected. This further supports a lack of host specialization of A. alternata among the diverse hosts examined. Therefore, care should be taken when including these crops in a crop rotation system. If these crops are grown in rotation, the potential for disease development needs to be considered for appropriate management. The pathogen diversity also has implications for screening for host resistance.
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Title: Supervised Dimension Reduction Techniques for High-Dimensional Data
Creator: Molho, Dylan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The data sets arising in modern science and engineering are often extremely large, befitting the era of big data. But these data sets are not only large in the number of samples they have, they may also have a large number of features, placing each data point in a high-dimensional space.However, unique problems arise when the dimension of the data has the same or even greater order than the sample size. This scenario in statistics is known as the High Dimension, Low Sample Size problem (HDLSS...
Show moreThe data sets arising in modern science and engineering are often extremely large, befitting the era of big data. But these data sets are not only large in the number of samples they have, they may also have a large number of features, placing each data point in a high-dimensional space.However, unique problems arise when the dimension of the data has the same or even greater order than the sample size. This scenario in statistics is known as the High Dimension, Low Sample Size problem (HDLSS). In this paradigm, many standard statistical estimators are shown to perform sub-optimally and in some cases can not be computed at all. To overcome the barriers found in HDLSS scenarios, one must make additional assumptions on the data, either with explicit formulations or with implicit beliefs about the behavior of the data. The first type of research leads to structural assumptions placed on the probability model that generates the data, which allow for alterations to classical methods to yield theoretically optimal estimators for the chosen well-defined tasks. The second type of research, in contrast, makes general assumptions usually based on the the causal nature of chosen real-world data application, where the data is assumed to have dependencies between the parameters.This dissertation develops two novel algorithms that successfully operate in the paradigm of HDLSS. We first propose the Generalized Eigenvalue (GEV) estimator, a unified sparse projection regression framework for estimating generalized eigenvector problems.Unlike existing work, we reformulate a sequence of computationally intractable non-convex generalized Rayleigh quotient optimization problems into a computationally efficient simultaneous linear regression problem, padded with a sparse penalty to deal with high-dimensional predictors. We showcase the applications of our method by considering three iconic problems in statistics: the sliced inverse regression (SIR), linear discriminant analysis (LDA), and canonical correlation analysis (CCA). We show the reformulated linear regression problem is able to recover the same projection space obtained by the original generalized eigenvalue problem. Statistically, we establish the nonasymptotic error bounds for the proposed estimator in the applications of SIR and LDA, and prove these rates are minimax optimal. We present how the GEV is applied to the CCA problem, and adapt the method for a robust Huber-loss based formulation for noisy data. We test our framework on both synthetic and real datasets and demonstrate its superior performance compared with other state-of-the-art methods in high dimensional statistics. The second algorithm is the scJEGNN, a graphical neural network (GNN) tailored to the task of data integration for HDLSS single-cell sequencing data.We show that with its unique model, the GNN is able to leverage structural information of the biological data relations in order to perform a joint embedding of multiple modalities of single-cell gene expression data. The model is applied to data from the NeurIPS 2021 competition for Open Problems in Single-Cell Analysis, and we demonstrate that our model is able to outperform top teams from the joint embedding task.
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Title: THE IMPACT OF THE AFFORDABLE CARE ACT ON UNINTENDED PREGNANCY
Creator: MacCallum-Bridges, Colleen Lynn
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Background & Objectives: Nearly half of all pregnancies in the United States (US) are unintended (i.e., mis-timed or unwanted), and roughly 5% of US women experience an unintended pregnancy each year, suggesting the population-level need for contraceptives is not being met. Further, these pregnancies are experienced disproportionately by women who are younger, women of color, and women of lower socioeconomic status – indicating these groups are particularly underserved. The Patient Protection...
Show moreBackground & Objectives: Nearly half of all pregnancies in the United States (US) are unintended (i.e., mis-timed or unwanted), and roughly 5% of US women experience an unintended pregnancy each year, suggesting the population-level need for contraceptives is not being met. Further, these pregnancies are experienced disproportionately by women who are younger, women of color, and women of lower socioeconomic status – indicating these groups are particularly underserved. The Patient Protection and Affordable Care Act (ACA) had the potential to improve our ability to meet this population-level need by increasing access to and affordability of contraceptive products and services. There is evidence that the ACA increased health insurance coverage and is associated with an increase in the use of highly effective long-acting reversible contraceptives, but it is unclear whether these effects translated into fewer unintended pregnancies. Further, it is unknown whether these effects were equitably distributed across race and ethnicity. Thus, the objectives of this dissertation are to: 1) estimate the overall impact of the ACA on unintended pregnancy, and if evidence of an impact exists, describe the timing of this impact, 2) explore three mechanisms of the ACA by investigating the impact of three major provisions (i.e., the dependent coverage provision, Marketplace subsidies, and ACA insurance expansions), and 3) assess the impact of the ACA on racial/ethnic disparities in unintended pregnancy. Methods: Data from multiple cross-sectional cycles of the National Survey of Family Growth (NSFG) were used. NSFG uses a multistage probabilistic sampling methodology to survey non-institutionalized civilian men and women regarding family planning, marriage, divorce, and both general and reproductive health. I included sexually active female respondents aged 18-44 interviewed between 2006 and 2019 (n=25,426). To address objectives (1) and (2) I used a difference-in-differences approach to compare trends in unintended pregnancy between women who were eligible to benefit from the intervention (the overall ACA or one of the listed components), to that of women who were ineligible to benefit. Eligibility was determined by respondent age and income. To address objective (3), I used a pre/post analysis to explore how racial/ethnic disparities in unintended pregnancy differed prior to and following enactment of the overall ACA and its components. Results: There was evidence that: 1) the overall ACA was associated with a 2.1 percentage point (ppt) decrease in unintended pregnancy among eligible women, and this decrease was fairly consistent during and following the ACA’s implementation period, 2) the dependent coverage provision was associated with a large (8.2 ppt) decrease in unintended pregnancy among lower income young women, and 3) the disparities in unintended pregnancy between Hispanic and non-Hispanic (NH) White women and between NH Black and NH White women decreased by 2.9 ppt and 4.1 ppt, respectively, among eligible women following full implementation of the ACA. There was insufficient evidence that the Marketplace subsidies or insurance expansions were associated with unintended pregnancy, or that the dependent coverage provision, Marketplace subsidies, or insurance expansions were associated with racial/ethnic disparities in unintended pregnancy. Conclusions: The overall ACA and the dependent coverage provision may be associated with reductions in unintended pregnancy, and the magnitude of these associations appear to differ across sociodemographic subgroups (i.e., income, race/ethnicity) – holding implications for health equity. These findings provide insight regarding how the ACA works to influence reproductive health, and for whom – which is critical information for both researchers and public policy makers who seek to improve reproductive health and health equity.
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Title: "I want to be a better person and a better teacher" : Exploring the constructs of race and ability in a music educator collaborative teacher study group
Creator: Knapp, Erika
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The way teachers engage with dis/ability and race in their classrooms links to theirunderlying belief systems (Heroux, 2013; Ryan, 2020). Unfortunately, substantial evidence connects teacher beliefs and perceptions to the reification of hegemonic norms, which upholds barriers for students in educational settings (Annamma, 2015b; Heroux, 2013; Ryan, 2020). The purpose of this study was to examine a music educator collaborative teacher study group (CTSG) focused on exploring and unpacking...
Show moreThe way teachers engage with dis/ability and race in their classrooms links to theirunderlying belief systems (Heroux, 2013; Ryan, 2020). Unfortunately, substantial evidence connects teacher beliefs and perceptions to the reification of hegemonic norms, which upholds barriers for students in educational settings (Annamma, 2015b; Heroux, 2013; Ryan, 2020). The purpose of this study was to examine a music educator collaborative teacher study group (CTSG) focused on exploring and unpacking narratives of race and dis/ability in music education. Research questions were: 1) How do teachers conceptualize issues of race and ability in both their belief systems and stated classroom practices? 2) How, if at all, did participants’ beliefs about race and ability change as a result of participating in the CTSG? 3) What conditions facilitated changes in mindset and behavior for participants? I designed and completed a descriptive, collective case study (Stake, 1995; Yin 2018) that examined the experiences of eight music educators across the U.S. Participants were public school music educators who varied in age, teaching experience and assignment, personal identity characteristics and geographic location. As the researcher and facilitator, I served as the ninth member of the CTSG. Participants met via Zoom eleven times (every other week from July 27 to December 14, 2021) to share stories, discuss assigned readings/videos, participate in activities, and collaborate on lesson plans. Throughout the study, participants completed three individual interviews (beginning, midpoint, end), took turns leading the group sessions, contributed to a private social media page, and wrote in their online journal. In addition to my analytic memos, I used transcripts of interviews, planning meetings, CTSG meetings, conversations on Facebook and reflections in journals as data. I utilized two frameworks, Dis/ability Critical Race Theory (DisCrit) (Annamma et al., 2013) and Transformative Learning Processes (TLP) (Salvador et al., 2020a) to frame the study, design the CTSG, and analyze the data. Initially participants varied in their stated beliefs and described classroom practices. Further, participants displayed a continuum of prior experiences and stated goals, as well as a broad spectrum of agreements and dissonances between their words (stated beliefs and goals) and actions (conversations in the CTSG and descriptions of their teaching practice). By the end of the study, participants described and demonstrated several changes resulting from participation in the CTSG. Participants reported becoming more aware of the ways that racism and ableism operated in schools and in their personal lives. Furthermore, they reported that participation in the CTSG had lit a spark for continued discovery, reflection, and action. Many ended the CTSG by setting personal and professional goals, such as building allyship in their classroom or redesigning their curriculum through an equity-focused lens. Several conditions proved salient in creating an environment conducive to change. Primary factors that contributed to change were participants building connections with other music teachers, experiencing emotional intensity, having the space and time to grapple with difficult materials, as well as the structures put in place during the CTSG. Based on these themes, I offered several recommendations for practice and policy, including the importance of preservice and continuing education to work with diverse learners, and the necessity of highlighting voices of minoritized students in music education.
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Title: TWO PARTITIONS : POSTCOLONIAL CULTURE AND NATION IN BANGLADESHI AND SOUTH ASIAN ANGLOPHONE LITERATURES
Creator: Iqbal, Asif
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As a comparative and interdisciplinary study of South Asian literatures, this project traces the fracturing of the subcontinent in 1947, and the subsequent emergence of Bangladesh in 1971. I analyze Global Anglophone, diasporic and Bengali novels from 1956-2014 as a prism through which I interrogate Bangladesh’s birth through specific historic transformations: the 1947 Partition, the entity East Pakistan (1947-1970) and the 1971 War. My analysis methodologically deploys historiographical...
Show moreAs a comparative and interdisciplinary study of South Asian literatures, this project traces the fracturing of the subcontinent in 1947, and the subsequent emergence of Bangladesh in 1971. I analyze Global Anglophone, diasporic and Bengali novels from 1956-2014 as a prism through which I interrogate Bangladesh’s birth through specific historic transformations: the 1947 Partition, the entity East Pakistan (1947-1970) and the 1971 War. My analysis methodologically deploys historiographical concepts and postcolonial theory to illuminate Bangladesh in its multiplicity, including the nation’s peasant identities, religious minorities and their insecurity, gendered hypermasculinist nationalism and related diasporic perspectives. My readings at the intersections of literary works and historical documents recasts the 1947 Partition and its legacy in South Asia, pointing to interconnections between East Pakistan’s proto-national character leading up to the 1971 war and the postwar formation of Bangladesh, responsible for the country’s ongoing religious and ethnic fragmentations. In Chapter 1, “Counter-Imaginations of Partition: East Bengal and Peasant Identities in Adwaita Mallabarman’s A River Called Titash (1956) and Shaukat Osman’s Janani (1961),” I invoke the short-lived idea of a United Bengal just before the 1947 Partition to interrogate Partition-era nationalism’s adverse influence on the Hindu and Muslim peasantry in Bengal’s countryside. Chapter 2, “‘Looking-glass Border’ Novels: Reading East Pakistan’s Hindu Minority in Amitav Ghosh’s The Shadow Lines (1988) and the Unified Bengali Identity During the 1971 War in Dilruba Z. Ara’s Blame (2015),” analyzes the antagonizing of the Hindu minority during the 1965 war between India and Pakistan and the subsequent policy of Hindu extermination during the 1971 war. The third chapter, “Fracturing Pakistan, Forming Bangladesh: Class and Gender Insurgencies in the Time of ‘Passive Revolution’ in Akhteruzzaman Elias’ The Sepoy in the Attic (Chilekothar Sepai 1987) and the Many ‘Birangona’ Stories in Shaheen Akhtar’s The Search (2004),” simultaneously considers the Mass Revolution of 1969 and the 1971 war to trace the patriarchal underside of Bengali nationalism, which was an ideological force against the repressive Pakistan state. In the final chapter, “‘Us’ Beside ‘Them,’ Not ‘Us’ Versus ‘Them’: Cosmopolitan Imagination and Familial Reckoning of 1971 in Zia Haider Rahman’s In the Light of What We Know (2014) and Kamila Shamsie’s Kartography (2002),” I problematize the nationalized war narratives in present day Bangladesh and Pakistan. The chapter argues that the intricate network of South Asian kinships and diasporic belongings can create a cosmopolitan understanding of the 1971 war. Two Partitions, therefore, argues that Bangladesh’s historic emergence is intertwined with the Bengali Muslim adoption of two-nation theory during their participation in the Pakistan Movement before 1947, and their subsequent jettisoning of the idea of Pakistan in support of Bengali ethno-linguistic nationalism in postcolonial East Pakistan (1947-1970). Subsequently, the two visions continue to inform the complex postcolonial identity of the citizens of Bangladesh, this project contends.
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Title: High-precision and Personalized Wearable Sensing Systems for Healthcare Applications
Creator: Tu, Linlin
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The cyber-physical system (CPS) has been discussed and studied extensively since 2010. It provides various solutions for monitoring the user's physical and psychological health states, enhancing the user's experience, and improving the lifestyle. A variety of mobile internet devices with built-in sensors, such as accelerators, cameras, PPG sensors, pressure sensors, and the microphone, can be leveraged to build mobile cyber-physical applications that collected sensing data from the real world...
Show moreThe cyber-physical system (CPS) has been discussed and studied extensively since 2010. It provides various solutions for monitoring the user's physical and psychological health states, enhancing the user's experience, and improving the lifestyle. A variety of mobile internet devices with built-in sensors, such as accelerators, cameras, PPG sensors, pressure sensors, and the microphone, can be leveraged to build mobile cyber-physical applications that collected sensing data from the real world, had data processed, communicated to the internet services and transformed into behavioral and physiological models. The detected results can be used as feedback to help the user understand his/her behavior, improve the lifestyle, or avoid danger. They can also be delivered to therapists to facilitate their diagnose. Designing CPS for health monitoring is challenging due to multiple factors. First of all, high estimation accuracy is necessary for health monitoring. However, some systems suffer irregular noise. For example, PPG sensors for cardiac health state monitoring are extremely vulnerable to motion noise. Second, to include human in the loop, health monitoring systems are required to be user-friendly. However, some systems involve cumbersome equipment for a long time of data collection, which is not feasible for daily monitoring. Most importantly, large-scale high-level health-related monitoring systems, such as the systems for human activity recognition, require high accuracy and communication efficiency. However, with users' raw data uploading to the server, centralized learning fails to protect users' private information and is communication-inefficient. The research introduced in this dissertation addressed the above three significant challenges in developing health-related monitoring systems. We build a lightweight system for accurate heart rate measurement during exercise, design a smart in-home breathing training system with bio-Feedback via virtual reality (VR) game, and propose federated learning via dynamic layer sharing for human activity recognition.
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Title: IT’S LIKE LOOKING IN A MIRROR, ONLY NOT : THE INFLUENCE OF ACQUIRER-TARGET SIMILARITY ON CORPORATE ACQUISITIONS
Creator: Wuorinen, Stefan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: With the recent explosion of behavioral acquisition research, the collective knowledge in respect to acquisition behavior and outcomes has advanced tremendously. Despite these advancements, due to the rapid growth in this literature, various shortcomings have also developed. One such shortcoming is that the vast majority of this literature has examined acquisition influences emanating from the acquirer or the target but has rarely investigated the joint effects of these two entities. As such,...
Show moreWith the recent explosion of behavioral acquisition research, the collective knowledge in respect to acquisition behavior and outcomes has advanced tremendously. Despite these advancements, due to the rapid growth in this literature, various shortcomings have also developed. One such shortcoming is that the vast majority of this literature has examined acquisition influences emanating from the acquirer or the target but has rarely investigated the joint effects of these two entities. As such, in an attempt to contribute to the growing wealth of acquisition knowledge, the aim of this dissertation is to extend this research by examining how the degree of similarity between the acquirer and target can contribute to the outcomes of acquisition decisions. Specifically, this dissertation first investigates the implications for post-acquisition innovation due to pre-acquisition authority structure similarity, while also introducing and testing the arguments of Structural Adaptation Theory to the macro-organizational level and acquisition literature. Second, the influence of CEO regulatory fit between acquirer and target executives and the degree to which their respective orientations align with each manager’s negotiation roles within an acquisition are argued to influence acquisition premium and market reactions. Collectively, these studies begin to illuminate the joint affects that acquirers and targets have on distinct acquisition outcomes.
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Title: UNDERSTANDING DRIVERS OF PLANT MICROBIOME IN MICHIGAN AGRICULTURE : STUDIES OF THE APPLE ROOT ZONE AND COMMON BEAN SEEDS
Creator: Bintarti, Ari Fina
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Plant-associated microbial communities are crucial for plant health and fitness, and may enhance plant tolerance to various environmental stresses. As global climate change threatens crop production and increases demands on sustainable agriculture, harnessing the plant microbiome has become one potential strategy to address these issues. Thus, it is fundamental to understand the relative contributions of both the host plant as well as the environment in shaping the plant microbiome. Moreover,...
Show morePlant-associated microbial communities are crucial for plant health and fitness, and may enhance plant tolerance to various environmental stresses. As global climate change threatens crop production and increases demands on sustainable agriculture, harnessing the plant microbiome has become one potential strategy to address these issues. Thus, it is fundamental to understand the relative contributions of both the host plant as well as the environment in shaping the plant microbiome. Moreover, the response of plant microbiomes to stress and any consequences of microbiome stress responses for the host plants are poorly understood, though this information is critical to achieve a basis of knowledge for plant microbiome engineering. My research aimed to contribute to this knowledge by investigating the factors that structure root- and seed-associated microbial communities of two valuable crops for Michigan’s agricultural economy: apple and common bean. The first chapter of my dissertation aimed to assess the biogeography of bacterial, archaeal, fungal, and nematode communities in the root zone of apple trees, and to determine their relationships with each other and their changes over natural abiotic gradients across orchards. I also assessed the influence of plant cultivar on microbiome structure in the root zone. I found that root zone microbiome community structure was strongly affected by geographic location and edaphic properties of soil. The next chapter of my dissertation investigated the variability of seed endophyte community of common bean (Phaseolus vulgaris L.). My results showed that plant-to-plant variability under controlled growth conditions exceeded within-plant variability among seeds from different pods. My study developed protocols and added insights to the growing toolkit of approaches to understand the plant-microbiome engagements that support the health of agricultural and environmental ecosystems. The last chapter assessed the responses of common bean seed endophytes to drought stress in the field across two growing locations and four genotypes of common bean. To summarize, this work advances foundational knowledge of the seed microbiome as a critical component of the plant microbiome, and in the context of two key crops for Michigan agriculture.
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Title: Metamodeling in Evolutionary Multi-Objective Optimization for constrained and unconstrained Problems
Creator: Hussein, Rayan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: One of the main difficulties in applying an optimization algorithm to a practical problem is that the evaluation of objectives and constraints often involve computationally expensive procedures. To handle such problems, a metamodel (or surrogate model, or response surface approximations) is first formed from a few exact (high-fidelity) solution evaluations, and then optimized by an algorithm in a progressive manner. However, there has been lukewarm interest in finding multiple trade-off...
Show moreOne of the main difficulties in applying an optimization algorithm to a practical problem is that the evaluation of objectives and constraints often involve computationally expensive procedures. To handle such problems, a metamodel (or surrogate model, or response surface approximations) is first formed from a few exact (high-fidelity) solution evaluations, and then optimized by an algorithm in a progressive manner. However, there has been lukewarm interest in finding multiple trade-off solutions for multi-objective optimization problems using surrogate models. The literature on surrogate modeling for constrained optimization problems is also rare. The difficulty lies in the requirement ofbuilding and solving multiple surrogate models, one for each Pareto-optimal solution. In this study, we propose a taxonomy of different possible metamodeling frameworks for multi-objective optimization and provide a comparative study by discussing advantages and disadvantages of each framework. Also, we argue that it is more efficient to use different metamodeling frameworks at different stages of the optimization process. Thereafter, we propose a novel adaptive method for switching among different metamodeling frameworks. Moreover, we observe the convergence behavior of the proposed approaches is better with a trust regions method applied within the metamodeling frameworks. The results presented in this study are obtained using the well-known Kriging metamodeling approach. Based on our extensive simulation studies on proposed frameworks, we report new and interesting observations about the behavior of each metamodeling framework, which may provide salient guidelines for further studies in this emerging area within evolutionary multi-objective optimization. Results of this study clearly show the efficacy and efficiency of the proposed adaptive switching approach compared to three recently-proposed other metamodeling algorithms on challenging multi-objective optimization problems using a limited budget of high-fidelity evaluations.
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Title: ECOPHYSIOLOGY OF (PERI)ORAL BACTERIA AND IMPACT OF OTIC COLONIZATION
Creator: Jacob, Kristin Marie
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The middle ear is typically assumed to be sterile in health due to its secluded location, closed off from external forces by the tympanic membrane (ear drum) and from the naso/oropharynx by a collapsed Eustachian tube. However, the periodic opening of the Eustachian tube to the naso/oropharyngeal space, which releases pressure across the eardrum and drains otic fluids, could introduce bacteria. Previous studies have tested for the presence of bacteria in the uninfected otic cavity using...
Show moreThe middle ear is typically assumed to be sterile in health due to its secluded location, closed off from external forces by the tympanic membrane (ear drum) and from the naso/oropharynx by a collapsed Eustachian tube. However, the periodic opening of the Eustachian tube to the naso/oropharyngeal space, which releases pressure across the eardrum and drains otic fluids, could introduce bacteria. Previous studies have tested for the presence of bacteria in the uninfected otic cavity using samples collected via invasive surgeries (through or around the eardrum). Findings from these studies are controversial due to contradictory results between studies, lack of critical experimental controls, and sampling of participants with underlying ailments (i.e., cochlear implant surgery) that could impact the microbiology of the otic mucosa. The studies reported herein bypass these limitations by using samples of otic secretions collectively non-invasively (through the mouth) in a cohort of healthy young adults. This dissertation describes cultivation-dependent methods to investigate the microbiology of the middle ear in health. The study used an IRB-approved protocol (#17-502) to collect otic secretions in order to 1) sequence their microbiome (contribution by Dr. Joo-Young Lee) and 2) recover in pure culture otic bacteria for further characterization (my contribution). As controls, we also collected buccal (top palate and inside of cheeks) and oropharyngeal swabs from each participant. Of the collected secretions, samples from 19 individuals were used for culture independent studies, while samples from the remaining 3 participants were subjected to culture dependent studies. 16S rRNA-V4 sequencing detected a diverse and distinct microbiome in otic secretions comprised primarily of strictly anaerobic bacteria belonging to the phyla Bacteroidetes, Firmicutes and Fusobacteria, and to a lesser extent facultative anaerobes (Streptococcus). I recovered from the otic, oropharyngeal, and buccal secretions 39 isolates of predominantly facultative anaerobes belonging to Firmicutes (Streptococcus and Staphylococcus), Actinobacteria (Micrococcus and Corynebacterium), and Proteobacteria (Neisseria) phyla, and used partial 16S rRNA amplicon sequences to demonstrate the distinct phylogenetic placement of otic streptococci compared to the oral ancestors (Chapter 2). This finding is consistent with the ecological diversification of oral streptococci once in the middle ear microenvironment. The recovery of streptococci and transient migrants (Staphylococcus, Neisseria, Micrococcus and Corynebacterium) from otic secretions prompted us to study the adaptive responses that give the streptococcal migrants a competitive advantage during the colonization of the middle ear (Chapter 3). For these studies, I sequenced and partially assembled the genomes of the otic isolates and used the full length 16S rRNA sequences for taxonomic demarcation at the species levels. Phylogenetic analyses demonstrated the oral ancestry of the otic streptococci, which retained from the otic adaptive traits critical for growth and reproduction in the middle ear mucosa (biofilm formation, mucolytic and proteolytic activity, robust growth under redox fluctuations, and fermentative production of lactate, a key metabolic intermediate in the otic trophic webs). These adaptive traits give oral streptococci a colonization advantage over competing (peri)oral migrants such as Staphylococcus. Furthermore, the otic streptococci inhibited the growth of otopathogens, including Staphylococcus aureus. These antagonistic interactions give streptococci a competitive advantage during the colonization of the middle ear and suggest a role for these commensals in promoting mucosal health. The ability of staphylococcal migrants to breach the middle ear mucosal barrier and cause infections prompted us to study the environmental factors that facilitate the spreading of staphylococci from the nasal to the middle ear mucosa. Allergies, respiratory maladies (cold, flu), or (peri)oral bacterial infections (sinus, adenoids, tonsils, etc.) lead to inflammation of the Eustachian tube and changes in the rheological properties of the otic mucus that increase the risk of infections. Thus, we examined the spreading of staphylococci on mucus-like viscous surfaces (semisolid agar plates). In Chapter 4, I show that mucins, the mucosal glycoproteins that control the viscosity and wettability of the mucus layer, induce the rapid spreading and dendritic expansion of clinical isolates closely related to S. aureus and Staphylococcus epidermidis but not of Staphylococcus hominis. Mucin glycosylation controlled the hydration of the mucoid surface and the ability of the cells to spread rapidly, in a process that was dependent on the secretion of surfactant-active, phenol-soluble modulins via the agr-quorum sensing two-component system. These results provide a plausible explanation for the rapid spreading of staphylococcal otopathogens from the nasopharynx to the middle ear through a swollen, and mucin-rich Eustachian tube. The work described in this dissertation provides much needed understanding of the adaptive responses that allow (peri)oral bacteria to colonize the middle ear. The studies add to the accumulating evidence that the middle ear mucosa is not sterile but rather harbors a commensal microbiota in health. These commensal community shares many metabolic similarities with ancestors in oral biofilms and retain adaptive traits critical for growth in the otic mucosa and inhibition of otopathogens. Additionally, this work identifies environmental factors that could contribute to staphylococcal virulence, broadening the understanding of newly identified motility phenotypes in the genus that could provide novel pharmaceutical targets.
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Title: CIRCADIAN RHYTHMS IN LATE PREGNANCY : A ROLE IN THE REPRODUCTIVE AXIS, UTERINE CONTRACTIONS AND PRETERM LABOR
Creator: Duong, Thu Van Quynh
Date: 2022
Collection: Electronic Theses & Dissertations
Description: What drives labor onset remains largely unknown. Understanding the molecular mechanisms defining pregnancy duration and preparing the uterus for labor onset can help improve current treatment strategies to promote or halt labor. Biological processes with a ~24-hour cycle called circadian rhythms are generated by endogenous “clock” transcription factors referred to as the molecular clock, which drives daily changes in cellular functions. To understand the role of circadian rhythms in pregnancy...
Show moreWhat drives labor onset remains largely unknown. Understanding the molecular mechanisms defining pregnancy duration and preparing the uterus for labor onset can help improve current treatment strategies to promote or halt labor. Biological processes with a ~24-hour cycle called circadian rhythms are generated by endogenous “clock” transcription factors referred to as the molecular clock, which drives daily changes in cellular functions. To understand the role of circadian rhythms in pregnancy, we first characterized how the molecular clock of the reproductive axis adapts to pregnancy and found the molecular clock is upregulated. Next, to understand if the molecular clock helps define pregnancy duration, we analyzed gene expression data from pregnant women. We found that low maternal levels of two clock genes increased the risk of preterm birth 5 fold. As preterm birth is driven by a premature increase in uterine contractions, we then asked how time of day impacted uterine contractile response to oxytocin, a hormone that increases uterine contractions and is widely used to induce labor. As model for human pregnancy, mice presented with daily time windows of increased uterine sensitivity to oxytocin. To determine if the molecular clock drives this daily change in sensitivity to oxytocin, we used conditional knockout mice which had the molecular clock ablated in uterine smooth muscle. These mice lost the daily change in sensitivity to oxytocin-induced contractions and presented stronger spontaneous uterine contractions than controls. In conclusion, we show that circadian rhythms have an important role in regulating pregnancy duration and uterine function, where the uterine molecular clock defines daily time windows of enhanced uterine sensitivity to oxytocin.
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