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Title: THE PERSISTENT AND MULTIDIMENSIONAL MICROGLIAL RESPONSE TO PATHOLOGICAL ALPHA-SYNUCLEIN AGGREGATION
Creator: Stoll, Anna C.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Parkinson’s Disease, the second most common neurodegenerative disease, affects approximately 1 million people in the USA with 60,000 newly diagnosed people each year. Pathologically, PD is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies) and the progressive loss of the nigrostriatal dopamine (DA) neurons. While the exact cause of PD remains unknown, mounting evidence has suggested that neuroinflammation may play a significant role in PD...
Show moreParkinson’s Disease, the second most common neurodegenerative disease, affects approximately 1 million people in the USA with 60,000 newly diagnosed people each year. Pathologically, PD is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies) and the progressive loss of the nigrostriatal dopamine (DA) neurons. While the exact cause of PD remains unknown, mounting evidence has suggested that neuroinflammation may play a significant role in PD progression. The pathological features of PD can be recapitulated in vivo using the α-syn preformed fibril (PFF) model of synucleinopathy in rats. Specifically, in association with accumulation of phosphorylated α-syn (pSyn) inclusions in the SNpc, microglia increase soma size and MHC-II expression. This microglial response parallels pSyn inclusion formation, peaking at 2 months following intrastriatal PFF injection, months prior to the SNpc degeneration observed in the model. The overarching question of this dissertation is: does the microglial response to pathological α-syn accumulation contribute to degeneration? In Aim 1 of this dissertation an inhibitor of colony stimulating factor 1 receptor (CSF1R) was used to partially deplete microglia within the context of the α-syn PFF rat model in order to determine whether degeneration of the nigrostriatal system can be attenuated. Despite significant microglial depletion, increased soma size and expression of major-histocompatibility complex-II (MHC-II) on microglia within the α-syn inclusion bearing substantia nigra pars compacta (SNpc) was maintained. Further, partial microglia depletion did not impact degeneration of dopaminergic neurons in the SNpc. Paradoxically, long term partial microglial depletion increased the soma size of remaining microglia in both control and PFF rats was associated with widespread MHC-IIir expression in extranigral regions. These results suggest that partial microglial depletion is not a promising anti-inflammatory therapeutic strategy for PD and that this approach may induce a heightened proinflammatory state in remaining microglia. Aim 2 of this dissertation built on a previous study RNA-Seq dataset that identified multiple upregulated innate and adaptive immune transcripts in the inclusion bearing SNpc in the PFF model. Complementary approaches of fluorescent in situ hybridization (FISH) and droplet digital PCR (ddPCR) were used. FISH results identified an a-syn aggregate associated microglial (a-SAM) phenotype that is characterized by upregulation of CD74, CXCl10, RT1-A2, GRN, CSF1R, Tyrobp, C3, C1qa and Fcer1g. ddPCR results identified additional neuroinflammatory genes, Cd4, Stat1, Casp 1, Axl and IL18, that are significantly upregulated in inclusion bearing nigral tissue. Collectively these findings implicate that the deposition of pathological α-syn inclusions in the SNpc is associated with perturbations in immune functions related to complement, inflammasome and T cell activation, phagocytosis, and interferon gamma signaling. Collectively, the findings of these dissertation experiments demonstrate that the microglial response to pathological α-syn aggregation is persistent and multifaceted. This comprehensive understanding of the multidimensional response of microglia to pathological α-syn aggregates may help to uncover novel therapeutic targets that could facilitate future anti-inflammatory, disease-modifying strategies for PD.
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Title: LITHOSPHERIC MODIFICATION OF FLOOD BASALT MAGMAS : A CHEMO STRATIGRAPHIC ANALYSIS OF THE EOCENE TO EARLY OLIGOCENE FLOOD BASALT PROVINCE IN EAST AFRICA
Creator: Steiner, Ronald Alexander
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Continental large igneous provinces are among the largest magmatic events on Earth, characteristically manifesting at the surface as stacks of monotonous flood basalt lavas that form through a dynamic pattern of eruptive pulses separated by hiatuses. Mantle plumes are typically considered responsible for generating the large volume of magma required, however, the geometry of these upwellings is poorly constrained. Two distinct flood basalt episodes are evident in East Africa – an Eocene...
Show moreContinental large igneous provinces are among the largest magmatic events on Earth, characteristically manifesting at the surface as stacks of monotonous flood basalt lavas that form through a dynamic pattern of eruptive pulses separated by hiatuses. Mantle plumes are typically considered responsible for generating the large volume of magma required, however, the geometry of these upwellings is poorly constrained. Two distinct flood basalt episodes are evident in East Africa – an Eocene Initial Phase and an Oligocene Traps Phase – both considered related to the African Large Low Shear Velocity Province. The initial interaction between material rising from the African Large Low Shear Velocity Province and the African lithosphere manifests as the Eocene Initial Phase, centered on southern Ethiopia and northern Kenya. In chapter 2 we present a geographically well-distributed geochemical dataset comprising the flood basalt lavas of the Eocene Initial Phase to refine the regional volcano-stratigraphy into three distinct magmatic units: (1) the highly-alkaline small-volume Akobo Basalts (49.4 -46.6 Ma), representing the initial phase of flood basalt volcanism derived from the melting of lithospheric-mantle metasomes, (2) the primitive and spatially restricted Amaro Basalts (45.2-39.58 Ma) representing the early main phase of flood basalt volcanism derived from the melting of the upwelling thermochemical anomaly, and (3) the spatially extensive Gamo-Makonnen magmatic unit (38-28 Ma) representing the mature main phase of flood basalt volcanism that has undergone significant processing within the lithosphere resulting in relatively homogeneous compositions. The focused intrusion of these main phase magmas over 10 m.y. preconditioned the African lithosphere for the localization of strain during subsequent episodes of lithospheric stretching. The focusing of strain into the region occupied by this continental LIP may have contributed to the initial extension in SW Ethiopia associated with the East African Rift. Chapter 3 presents a stratigraphically well-constrained series of 54 flood basalt flows from the Eocene Initial Phase of magmatic activity in East Africa. These flows, and more importantly, their crystal cargo, permit temporal insight into the development of one the youngest and best-preserved continental large igneous provinces. The stratiform mafic lavas exposed in northern Kenya consist of alternating aphyric and plagioclase-rich lava packages consistent with periods of eruption punctuated by volcanic hiatus, where magmas stall and crystallize plagioclase at medium to shallow crustal levels. Plagioclase compositions (n=545) exhibit little intra-crystal or intra-sample compositional diversity. Intra-crystal equilibrium calculations for Sr and Ti indicate internal chemical equilibrium, requiring storage at high temperature over a prolonged time interval (10,000-100,000 years). Using a series of seven interlinked partial crystal fractionation under equilibrium conditions models, we replicate the observed stratigraphic patterns in plagioclase composition. We find that the balance between recharge and evacuation, and diffusive equilibration within a shallow magmatic system, controls the composition of plagioclase in these flood basalts. We conclude that the shallow fractionation system modulates eruptive cycles and thus constitutes a critical component in studies of continental large igneous provinces. Chapter 4 presents the first chemo-stratigraphic section of the continuous series of flood basalts from the Eocene Initial Phase. Building upon the petro-stratigraphic framework developed in chapter 3, we explore how magma flux influences erupted lava compositions at Lokitaung in northern Kenya. We find that the geochemical variability within the lava flows parallels the existing petro-stratigraphic framework – stratigraphic trends in lava compositions have inflection points at the boundaries between petro-stratigraphic units. Incompatible trace element profiles of Lokitaung lavas show a common pattern consistent with a common parental magma composition, suggesting the observed geochemical heterogeneity between flows is a function of magma differentiation within the continental lithosphere. We interpret the variability in lava compositions as reflecting open-system magma differentiation processes and use the mass balance equations to construct numerical models to resolve the petro- and chemo-stratigraphic variability the lava compositions at Lokitaung. We find that the three volcano-stratigraphic units differ in terms of magma recharge: the Lower Basalts represent the initiation of the system (first 200m of stratigraphy) and are the period of highest magma recharge; the Middle Basalts, though the main phase of flood basalt activity (500m thickness), are a period of lower magma recharge; the Upper Basalts represent the termination of flood basalt activity (uppermost 64m), and are the period of the least magma recharge. This cycle of activity parallels similar petrographic observations from the Oligocene Traps Phase of the NW Ethiopian Plateau therefore illustrating a similar progression in the development of a continental flood basalt magma plumbing system at both locales.
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Title: Factor analyses and clinical discriminant validity of the Gilliam Autism Rating Scale – 3rd Edition (GARS-3) using special education staff ratings in samples with autism spectrum disorder and other developmental disabilities
Creator: Isbell, Nicole Bergamo
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Based on Center for Disease Control and Prevention (CDC) surveillance reports, the prevalence of autism spectrum disorder (ASD) continues to increase (Maenner et al., 2021). As such, assessment tools that are efficient, cost-effective, and psychometrically sound are key to effective screening, accurate diagnosis, and clarification of intervention needs (Kuriakose & Shalev, 2016; Zwaigenbaum & Penner, 2018). The Gilliam Autism Rating Scale – Third Edition (GARS-3; Gilliam, 2013), a substantial...
Show moreBased on Center for Disease Control and Prevention (CDC) surveillance reports, the prevalence of autism spectrum disorder (ASD) continues to increase (Maenner et al., 2021). As such, assessment tools that are efficient, cost-effective, and psychometrically sound are key to effective screening, accurate diagnosis, and clarification of intervention needs (Kuriakose & Shalev, 2016; Zwaigenbaum & Penner, 2018). The Gilliam Autism Rating Scale – Third Edition (GARS-3; Gilliam, 2013), a substantial revision from earlier editions, is a rating scale used to gather information from parents, caregivers, or teachers for screening or as part of a more comprehensive ASD assessment. Across editions, the GARS is considered a popular assessment tool among school psychologists (e.g., Aiello et al., 2017; Benson et al., 2019). However, despite the strong psychometric characteristics reported in the test manuals with standardization samples, prior editions were criticized for their screening performance in independent research samples, and factor analyses suggested problems with the test author’s proposed subscales (e.g., Lecavalier, 2005; Pandolfi et al., 2010; South et al., 2002; Volker et al., 2016; Volker et al., 2022). To date, there has been little to no research focused on the psychometric properties of the current version of the GARS beyond what is reported in the test manual. Of critical importance, there have been no published independent factor analyses conducted in ASD or broader developmental disability samples and no independent estimates of screening effectiveness or clinical discriminant validity of the GARS-3. Therefore, the present project seeks to add to the limited research regarding the GARS-3 using program evaluation data from a large special education agency in Western New York state. The project consisted of three different studies that addressed aspects of GARS-3 internal structure validity and clinical discriminant validity. Study one involved an exploratory factor analysis (EFA) of the GARS-3 items with an ASD sample (n = 204) rated by special education teaching staff. Study two, confirmatory factor analyses (CFA) using a second ASD and non-ASD developmental disabilities (DDs) sample (n = 200), were used to examine the model fit of the published GARS-3 model and the factor model derived from the study one EFA, and assess which of the two models better fit the sample covariance matrix. Finally, aspects of the GARS-3's clinical discriminant validity were assessed using unique ASD cases from studies one and two (ASD sample n = 226) and an additional non-ASD developmental disabilities sample (non-ASD DDs sample n = 64) from the same special education agency. Clinical discriminant validity was examined via between-group comparisons, classification accuracy of a predetermined cut score, and exploration of other possible cut scores using receiver operator characteristic (ROC) curve analyses. The EFA resulted in a six-factor solution that was very similar in structure to the GARS-3 published six-factor model – differing only in the placement of one item. The CFAs indicated that the GARS-3 published model and the EFA-derived model both fit the data well and did not substantively differ. However, when cross-loadings were added, based on EFA results, CFA model fit significantly improved. ROC curve analyses indicated that, when using the suggested cut score of 70, sensitivity and specificity were lower than predicted. Lower cut scores yielded good sensitivity but poorer specificity, while higher cut scores showed the opposite pattern. Discussion and recommendations pertained to examining items and subscales based on cross-loadings and inter-factor correlations in addition to clinical implications of sensitivity and specificity findings.
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Title: IMPROVING ANTIMICROBIAL STEWARDSHIP FOR CONTROL OF MASTITIS IN DAIRY HERDS
Creator: Leite de Campos, Juliana
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Implementation of better management practices that promote antimicrobial stewardship on farms is needed due to increased concerns with the impact of antimicrobial usage (AMU) on development and transmission of antimicrobial resistance from animals to humans. Interventions to reduce AMU can be applied by monitoring antimicrobial treatments at farm-level and identifying diseases that contribute to AMU. Mastitis is the most frequent bacterial disease occurring on dairy farms (USDA–APHIS–VS–CEAH,...
Show moreImplementation of better management practices that promote antimicrobial stewardship on farms is needed due to increased concerns with the impact of antimicrobial usage (AMU) on development and transmission of antimicrobial resistance from animals to humans. Interventions to reduce AMU can be applied by monitoring antimicrobial treatments at farm-level and identifying diseases that contribute to AMU. Mastitis is the most frequent bacterial disease occurring on dairy farms (USDA–APHIS–VS–CEAH, 2008), and it is well known that the occurrence of mastitis results in major economic losses for dairy farmers (Ruegg, 2005). Intramammary administration is the major route of AMU on dairy farms when using a dose-based metric to calculate AMU. (Pol and Ruegg, 2007; Saini et al., 2012a; Stevens et al., 2016) Dry cow therapy typically accounts for 31 to 70% of intramammary treatments (Pol and Ruegg, 2007; Saini et al., 2012a; Stevens et al., 2016; Schrag et al., 2020b). The overall hypotheses of this dissertation is: 1)the greatest quantity of AMU on large dairy farms is for treatment and control of mastitis, and 2) that AMU and costs on farm can be reduced by reducing the days of treatment for clinical mastitis during lactation or implementing selective treatments at dry-off. The aims of this dissertation are to: 1) quantify AMU on large dairy farms and contrast total AMU by route and active ingredients using both dose-based and mass-based metrics. With these results, we will demonstrate how antimicrobial treatments related to udder health impact on total AMU on large dairy farms. 2) Estimate direct costs of treated and non-treated clinical mastitis using data obtained from commercial dairy farms and contrast variation in treatment costs among herds. 3) Estimate direct costs at dry-off and potential saving if selective dry cow therapy was used. And 4), evaluate a method to potentially decrease AMU at dry-off by performing a clinical trial to determine if use of an alternative dosing schedule for an immune stimulant (pegbovigrastim) reduces the need for administration of antimicrobials at dry-off.
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Title: SPARSE GRID DISCONTINUOUS GALERKIN METHODS FOR NONLINEAR OPTICS AND MATHEMATICAL MODELING OF ASYNCHRONOUS DATA FLOW IN PARALLEL COMPUTERS
Creator: Huang, Kai
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This thesis consists of two parts: the first part discusses the Sparse Grid Discontinuous Galerkin (SGDG) method and its adaptive version, and their applications in Maxwell equations in nonlinear optical media [1, 2]; the second part discusses a Hamilton-Jacobi model of asynchronous data flow in parallel computers, and corresponding numerical simulation using Weighted Essentially Non-Oscillatory (WENO) method.SGDG method and its adaptive version were developed in recent years [3, 4, 5, 6, 7],...
Show moreThis thesis consists of two parts: the first part discusses the Sparse Grid Discontinuous Galerkin (SGDG) method and its adaptive version, and their applications in Maxwell equations in nonlinear optical media [1, 2]; the second part discusses a Hamilton-Jacobi model of asynchronous data flow in parallel computers, and corresponding numerical simulation using Weighted Essentially Non-Oscillatory (WENO) method.SGDG method and its adaptive version were developed in recent years [3, 4, 5, 6, 7], to numerically solve different linear or nonlinear PDE problems, reducing degrees of freedom and computational cost. Compared to the previous works, this thesis mainly focuses on fully implicit SGDG method of nonlinear equations, which broadens the applications of the method. To achieve this goal, the existing SGDG package [8] is coupled with nonlinear solvers in PETSc [9]. Numerical simulations of several model equations and physical relevant problems are presented to demonstrate accuracy and robustness of the method.Presented in second part of the thesis are models of data flow on processors in a high performance computing framework involving computations necessitating inter-processor communications [10]. First comes an ordinary differential model, and its asymptotic limit results in a model which treats the computer as a continuum of processors and data flow as an Eulerian fluid governed by a conservation law. We derive a Hamilton-Jacobi equation associated with this conservation law for which the existence and uniqueness of solutions can be proved. High order WENO interpolation [11, 12], together with strong stability preserving (SSP) method for time discretization, is applied to simulation of the Hamilton-Jacobi model. We then present the results of numerical experiments for both discrete and continuum models; these show a qualitative agreement between the two and the effect of variations in the computing environment’s processing capabilities on the progress of the modeled computation.
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Title: Family Matters : Adult Involvement and Early Childhood Outcomes Across Low- and Middle-Income Countries
Creator: Grover, Vanika
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Nourishing care through caregiver involvement helps children grow and thrive to their full potential. Caregiver involvement develops different aspects of children’s development, such as their motor, cognitive, and socio-emotional skills. Extensive research establishes that early childhood care and education (ECCE) is closely linked to children’s environments, involving their caregivers and immediate surroundings, and also their socio-cultural interactions, overarching identities, values, and...
Show moreNourishing care through caregiver involvement helps children grow and thrive to their full potential. Caregiver involvement develops different aspects of children’s development, such as their motor, cognitive, and socio-emotional skills. Extensive research establishes that early childhood care and education (ECCE) is closely linked to children’s environments, involving their caregivers and immediate surroundings, and also their socio-cultural interactions, overarching identities, values, and cultures in which children are embedded. Yet, the bulk of the existing literature on caregiver involvement in ECCE is based on Western countries. I address this gap in the research through three studies based in low- and middle-income countries (LMICs). Through a literature review, the first study analyzes the conceptualization and measurement of parental involvement in ECCE in LMICs. This study reveals crucial gaps in the conceptualization and measurement of parental involvement. There is an urgent need for comprehensive frameworks and valid, reliable measures that are better aligned to understand caregiver involvement in ECCE embedded in their local contexts in LMICs. The second study quantitatively analyzes home-based parental and adult involvement in ECCE across Ghana, The Gambia, and Zimbabwe. Using UNICEF’s Multiple Indicator Cluster Surveys (MICS) data for the three countries, I conduct descriptive and multi-variate regression analysis. I examine variation in parental and adult involvement, child and household factors that influence involvement, and associations between involvement and early childhood development outcomes. The primary contribution of this study is the careful exposition of the important role other household members apart from parents, play in children’s literacy and numeracy development, executive functioning, and overall development. The third study analyzes parental perceptions of early childhood education (ECE) in the context of increased global recognition of the need for responsive parental involvement. Through qualitative interviews with eighteen parents living in a low-income urban settlement in Delhi, India, I analyze parental perceptions, beliefs, and expectations of ECE. I find a dissonance between international and national policies on ECE, and local parental perceptions of children’s early education. Although the international community and national policies push for a child-centered, developmentally-appropriate curriculum at the ECE level, parents prefer a cognitively focused education that develops reading, writing, and numeracy skills early on. As part of the conclusion of my dissertation, I present a conceptual framework that brings together findings from the three studies. This framework builds on existing theories and evidence yet expands the understanding of adult involvement particularly for LMIC contexts. My dissertation provides a breadth and depth of analysis on caregiver involvement while paying attention to variations in local contexts, environments, and socio-cultural settings. In doing so, this current research has highly pertinent implications for policy programs and future research. An increased understanding of parental and adult involvement patterns in relation to early childhood outcomes will facilitate better-informed policy programs for children and communities, addressing social inequalities in the long run.
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Title: CROP BIOTECHNOLOGY : ECONOMICS, ENVIRONMENT, AND POLICY
Creator: Ye, Ziwei
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Crop biotechnology has been one of the most prominent technological advances in agriculture in recent decades. The first generation of biotech crops since the mid-1990s has protected plants from biotic stresses such as insects (insect-resistant crops) and weeds (herbicide-tolerant crops), while the newly emerged second-generation aims to protect crops from abiotic stress like drought, and improves quality, among other things. A central theme of this dissertation is the economic and...
Show moreCrop biotechnology has been one of the most prominent technological advances in agriculture in recent decades. The first generation of biotech crops since the mid-1990s has protected plants from biotic stresses such as insects (insect-resistant crops) and weeds (herbicide-tolerant crops), while the newly emerged second-generation aims to protect crops from abiotic stress like drought, and improves quality, among other things. A central theme of this dissertation is the economic and environmental implications of crop biotechnology, whether direct or indirect through associated markets, as well as the role of policy in balancing the benefits and risks to effectively accommodate these innovations. The dissertation comprises three essays on three representative biotech crops in maize production in the United States: (the herbicide glyphosate complementary to) the glyphosate-tolerant (GT) crop, the rootworm-resistant Bt crop, and the drought-tolerant (DT) crop. The first essay investigates the economic and environmental consequences of legislation restricting the use of glyphosate, the most commonly used herbicide in U.S. corn production because of its complementarity with glyphosate-tolerant crops. A monetary framework compris-ing economic, human health, and environmental welfare analysis is developed to examine the welfare consequence of a hypothetical glyphosate tax, given the currently available alternative herbicides. The results suggest substantial economic loss with only minor gains in human health and environmental welfare. The second essay evaluates the regulatory needs for balancing short-term rootworm con-trol benefits with long-term costs of lost pest susceptibility in rootworm-Bt corn planting. Changes in Bt efficacy are related to historical Bt planting to determine the empirical long-term cost, which is then incorporated into a dynamic game of Bt planting to align it with current pest damage and risk of Bt efficacy erosion and propose counterfactual changes for sustainable use to benefit producers. Our findings indicate the necessity for region-specific regulation strategies, with the East significantly lowering rootworm Bt planting and the West adopting a more inte-grated management strategy. The third essay assesses the climate adaptation value of drought-tolerant corn in the con-text of crop insurance. Using a county-level panel dataset in the Corn Belt of the United States, we found that yield implications of DT crops differ by region: drought-related yield risks, measured using insurance claims data, are found to be lower with higher DT planting rates for Western Corn Belt but not the Eastern counties. Further quantile analysis and simulations for the rainfed Western Corn Belt counties suggest that insurance premiums need to be reduced to reflect the yield protection value of DT innovation and be actuarially fair.
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Title: THE VASCULAR EFFECTS OF CLOPIDOGREL
Creator: Kuszynski, Dawn Shirley
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Dual antiplatelet therapy using aspirin with a purinergic receptor 2Y12 (P2Y12) antagonist is the most common preventative method for arterial thrombosis. The favored P2Y12 antagonist clopidogrel is a prodrug that is absorbed in the intestine and then converted into the active metabolite by cytochrome P450 enzymes (CYP450s). However, only about 5% of clopidogrel is converted into this active metabolite. The remainder is converted into more than 15 additional metabolites to which the effects...
Show moreDual antiplatelet therapy using aspirin with a purinergic receptor 2Y12 (P2Y12) antagonist is the most common preventative method for arterial thrombosis. The favored P2Y12 antagonist clopidogrel is a prodrug that is absorbed in the intestine and then converted into the active metabolite by cytochrome P450 enzymes (CYP450s). However, only about 5% of clopidogrel is converted into this active metabolite. The remainder is converted into more than 15 additional metabolites to which the effects have been previously thought inactive. Antiplatelet agents, such as clopidogrel, cause an increased risk of developing cerebral microbleeds and intracerebral hemorrhage. Cerebral blood flow regulation is essential in maintaining blood-brain barrier homeostasis. Larger arteries, like the middle cerebral artery and posterior cerebral artery, generate myogenic tone to regulate cerebral blood flow. Myogenic tone is the contraction of vascular smooth muscle cells in response to increasing pressure. Tone generation protects the capillary bed from changes in pressure that could lead to cerebral microbleeds and intracerebral hemorrhage. When pressure increases in cerebral arteries, these vessels constrict to decrease blood flow. Arteries also undergo active contraction when damaged to reduce blood flow. Both acute vasoconstriction (myogenic tone) and chronic vasoconstriction (in response to injury) are crucial in the prevention and protection of arteries from major bleeds. P2Y1, P2Y2, P2Y4, and P2Y6 are expressed in the endothelium of cerebral arteries, while P2Y2, P2Y4, and P2Y6 are expressed in the smooth muscle. P2Y4 and P2Y6 in the smooth muscle are key regulators of myogenic tone. Due to the structural similarity between purinergic receptors, additional clopidogrel metabolites might modulate P2Y1, P2Y2, P2Y4, or P2Y6 on the vasculature. A major focus of the work described in this dissertation was to identify which receptor(s) clopidogrel or its metabolites inhibit. My studies tested the hypothesis that clopidogrel metabolites modulate P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, and/or P2Y14 signaling in the vasculature which results in increased bleeding side effects. I addressed this hypothesis using pharmacological and genetic approaches. My studies show that clopidogrel inhibits ADP-induced platelet aggregation, but this effect does not correlate with the increase in adverse bleeding. Additionally, my studies demonstrate endothelial P2Y2-mediated vasoconstriction is inhibited in clopidogrel-treated rabbits. Furthermore, the prodrug clopidogrel, the M1 metabolite, and the M2 metabolite are not responsible for inhibiting P2Y2 signaling. Lastly, I discovered both P2Y12-/- mice and clopidogrel-treated mice have decreased distensibility and increased arterial stiffness. My studies could have wide implications for the development of new antiplatelet agents. The finding of P2Y2 inhibition by clopidogrel allowed us to better define the mechanism to which clopidogrel causes adverse bleeding. This provides a basis for what to avoid in the development of improved antiplatelet therapies.
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Title: The Status of Complex Instruction : Making Up Students
Creator: Jackson, Brent Eugene
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Complex Instruction (Cohen & Lotan, 2014) is a groupwork pedagogy aimed at making classrooms equitable. The notion of status is at the core of this pedagogy and guides how teachers ought to respond to inequitable groupwork. In this dissertation study, I consider how the concept of status (from Expectation States Theory) is applied within mathematics education. In doing so I consider how status is used in the mathematics education research and teacher-practitioner literature, as well as how...
Show moreComplex Instruction (Cohen & Lotan, 2014) is a groupwork pedagogy aimed at making classrooms equitable. The notion of status is at the core of this pedagogy and guides how teachers ought to respond to inequitable groupwork. In this dissertation study, I consider how the concept of status (from Expectation States Theory) is applied within mathematics education. In doing so I consider how status is used in the mathematics education research and teacher-practitioner literature, as well as how prospective secondary mathematics teachers’ used the notion of status to make sense of small groupwork in their student teaching placements. This study was guided by the following research questions: (a) How has status become an object that explains groupwork processes? and (b) How do prospective teachers use status to make sense of groupwork?To answer these questions, I developed a theoretical framework that explains how kinds of people are made up. Hacking’s (1986) notion of human kinds plays a central role to understand the social construction of low status and high status students. I also draw on Foucault’s (1980) notion of power/knowledge discourses to explain how systems of thinking, such as Complex Instruction, can be legitimized by institutions such as teacher preparation; and how scientific discourses contribute to the recognition of certain kinds of individuals. These ideas are complemented with Goffman’s (1967) notion of interaction rituals to explain how being recognized as a certain kind influences individuals’ interactions in certain settings. I generated data from a methods course for secondary mathematics teachers. As a course assignment, the prospective teachers implemented aspects of Complex Instruction in their student teaching placement and then participated in reflective conversations with their student-teaching peers. I analyzed the framing (Goffman, 1974) of the stories that were told by the prospective teachers. The analysis revealed that Complex Instruction acted as an authoritative discourse which created a system of reasoning where status was recognized as a way of being (rather than as a function of the group members’ interactions). More specifically, I demonstrate how the notion of the notion of status was coordinated with students’ characteristics and mathematically histories to explain students’ interactions. Overall, I argue that the discourses of Complex Instruction may undermine its own equity-oriented goals. I discuss the implications of thinking about low status and high status kinds of students in which students are once again ranked among social and mathematical dimensions. I discuss implications for mathematics teacher educators when teaching about Complex Instruction.
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Title: Managing Biological Resistance in Agriculture : Investigating the Roles of Information and Data Analysis in Decision Making
Creator: Jia, Yanan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Damage control tactics have been widely applied to control organisms that are detrimental to agriculture. Due to natural selection, the targeted organisms will inevitably become less susceptible and in time develop resistance to these control tactics. Resistance development is a widespread problem and has had large adverse consequences for agricultural productivity and even for human health. My dissertation investigates damage control input decisions in agricultural production which have...
Show moreDamage control tactics have been widely applied to control organisms that are detrimental to agriculture. Due to natural selection, the targeted organisms will inevitably become less susceptible and in time develop resistance to these control tactics. Resistance development is a widespread problem and has had large adverse consequences for agricultural productivity and even for human health. My dissertation investigates damage control input decisions in agricultural production which have important implications for biological resistance management. The dissertation consists of three essays on the consequences of and management approaches to decisions regarding an infection control input in livestock and a pest control input in crop production. Essay One presents a decision model of a farmer's disease management decision problem under uncertainty. In response to the concerns about antibiotic resistance development, prescriptions are now re quired in the USA for medically important antibiotic use in animals. We investigate determinants of farmers' demand for tests, veterinary services, and antibiotics and how they will change in light of increasing oversight. We show that although the prescription requirement (PR) may reduce farmer therapeutic antibiotic use it may not achieve the social optimum. PR may cause knock on distortions in test and service markets such as excessive demand for veterinary services. Essay Two develops on the work in Essay One. PR places stewardship of antibiotics susceptibility largely into the hands of veterinarians. We investigate how effectively veterinarians manage information when making diagnostic and antibiotic treatment decisions. In a survey sent to veterinarian veterinarians in practice across the United States, we asked for probabilistic assessments in stylized s in practice across the United States, we asked for probabilistic assessments in stylized disease diagnosis settings. Combining the findings that information management biases exist in disease diagnosis settings. Combining the findings that information management biases exist in diagnosis decisions and that diagnosis affects treatment choices, we cdiagnosis decisions and that diagnosis affects treatment choices, we conclude that the veterinary onclude that the veterinary oversight requirement as an approach to relying on veterinarians for promoting judicious antibiotic oversight requirement as an approach to relying on veterinarians for promoting judicious antibiotic use may fail to manage onuse may fail to manage on--farm antibiotic consumption efficiently. Training programs for farm antibiotic consumption efficiently. Training programs for veterinarians to improve their informatveterinarians to improve their information management capabilities may complement the ion management capabilities may complement the veterinary oversight requirement.veterinary oversight requirement. Essay Three investigates the impact of Bt corn adoption on substituting out applied insecticide use as well as the seed trait's environmental and health implications in the Uninsecticide use as well as the seed trait's environmental and health implications in the United ited States. Bt resistance management policies have expanded across countries over years, aiming at States. Bt resistance management policies have expanded across countries over years, aiming at conserving the effectiveness of Bt crops. However, optimal regulation of Bt crops should also conserving the effectiveness of Bt crops. However, optimal regulation of Bt crops should also consider the external benefits of Bt crops when compared to otconsider the external benefits of Bt crops when compared to other control tactics. Therefore it is her control tactics. Therefore it is important to justify and evaluate externalities associated with Bt crops. Using a panel dataset, we important to justify and evaluate externalities associated with Bt crops. Using a panel dataset, we investigate how Bt corn can affect insecticide use by adopters and noninvestigate how Bt corn can affect insecticide use by adopters and non--adopters over years in a adopters over years in a generalized differencegeneralized difference--inin--difference framework. We found insecticide use reduction among both difference framework. We found insecticide use reduction among both adopters and nonadopters and non--adopters as a result of Bt adoption.adopters as a result of Bt adoption.
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Title: EXAMINING THE RELATIONSHIP BETWEEN DRIVER DISTRACTION, CRASH, AND NEAR-CRASH RISK USING NATURALISTIC DRIVING DATA
Creator: Bamney, Anshu
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Distracted driving is among the leading causes of motor vehicle crashes worldwide, though the magnitude of this problem is difficult to quantify given the limitations of police-reported crash data. A more promising approach is to evaluate the impacts of distraction in real-world driving events. To that end, this study leverages data from the second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS) to gain important insights into the risks posed by driver distraction...
Show moreDistracted driving is among the leading causes of motor vehicle crashes worldwide, though the magnitude of this problem is difficult to quantify given the limitations of police-reported crash data. A more promising approach is to evaluate the impacts of distraction in real-world driving events. To that end, this study leverages data from the second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS) to gain important insights into the risks posed by driver distraction. The objectives of this study are to assess the risk of crash and near-crash events under different contextual environments based upon whether the driver was engaged in any secondary (i.e., non-driving related) tasks. The research also compares speed profiles of distracted drivers in low-speed and high-speed environments, providing important insights into how driver behavior changes based upon the type and intensity of distraction. The first analysis uses the standard SHRP 2 data to compare the differences between near-crash risks on limited access freeways and two-lane highways. Mixed-effects logistic regression models were estimated to discern how the risks of near-crash events varied by distraction type while controlling for the effects of driver, roadway, and traffic characteristics. In general, the risks were more pronounced for those distractions that were a combination of cognitive, visual, and manual distractions (for e.g., cell phone texting). While the same factors tended to increase near-crash risk on both types of facilities, the impacts of several factors tended to be more pronounced on two-lane highways where interaction with other vehicles occurred more frequently. The second analysis uses a subset of the NDS data that were focused on naturalistic engagement in secondary tasks (NEST). The NEST data were used to assess how the type and duration of distraction impacted the likelihood of crash and near-crash events. Separate comparisons were made between crashes and near-crashes with “normal” baseline driving events. The results show the duration of distraction to be a strong predictor of both crash and near-crash risk and were found to have similar relationships with crashes and near-crashes. The risks were highest for those secondary tasks that introduce a combination of visual and manual distractions that provides evidence that distractions requiring higher levels of engagement have more pronounced impacts on safety. The third and final analysis uses NEST data to analyze how driver speed selection varies based upon the types of secondary tasks that a driver is engaged in. Comparisons are made as to differences between high-speed and low-speed environments. Two-way random effects linear regression models were estimated for both speed regimes while controlling for driver, roadway, and traffic characteristics. In general, engagement in all tasks was found to decrease speeds in high-speed environments, while the effects were mixed in low-speed settings. These changes in speeds are much pronounced for secondary tasks that include a combination of visual, manual, and cognitive distractions, such as cell phone use. Among all secondary tasks, handheld cellphone talking was associated with highest speed changes in both environments followed by reaching/manipulating an object and holding an object. Ultimately, the results of this study provides further motivation for more aggressive legislation and enforcement against distracted driving. This can be achieved by enforcing strict laws and fines, graduated licensing process, public campaigns, modified infrastructure (rumble strips and tactile lane marking), and other such measures.
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Title: Statistical Methods for Single Cell Gene Expression : Differential Expression, Curve Estimation and Graphical Modelling
Creator: Saha, Satabdi
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation elucidates a set of statistical methods developed for analysis of single cellgene expression datasets. Gene expression profiling of single cells has led to unprecedented progress in understanding normal physiology, disease progression and developmental pro- cesses. However, despite many improvements in high throughput sequencing, various tech- nical factors including cell-cycle heterogeneity, library size differences, amplification bias, and low RNA capture per cell lead to...
Show moreThis dissertation elucidates a set of statistical methods developed for analysis of single cellgene expression datasets. Gene expression profiling of single cells has led to unprecedented progress in understanding normal physiology, disease progression and developmental pro- cesses. However, despite many improvements in high throughput sequencing, various tech- nical factors including cell-cycle heterogeneity, library size differences, amplification bias, and low RNA capture per cell lead to high noise in scRNA-seq experiments. A primary characteristic of these datasets is the presence of high number of zeroes which represents the undetectable level of expression for a transcript. Statistical methods capable of modelling novel single cell experiments are developed and new estimation strategies are proposed and validated using simulated and real data experiments. In Chapter 1, the motivation and underlying philosophies of single cell gene expression is reviewed. Methods for analysis of dose response experiments and gene co-expression networks are reviewed and novel statistical hypothesis to be investigated using single cell experiments are discussed. In Chapter 2, I analyze a unique in vivo dose response hepatic scRNAseq dataset con- sisting of 9 dose groups with 3 biological replicates for 11 distinct liver cell types for greater than 100K cells. A Hurdle model for multiple group data is proposed, which models the bimodality of single cell gene expression within multiple groups. Based on the model assumptions, I derive a fit for purpose Bayesian test for simultaneously testing the differences in mean gene expression and zero proportions for multiple dose groups. For comparison the counterpart likelihood-ratio test for differential expression that incorporates testing for both components is also derived. This chapter was originally published in [1]. In Chapter 3, dose response curve estimation for single cell experiments is studied. Cur- rent protocols for genomic dose response modelling are only capable of modelling bulk and microarray datasets. A semiparametric regression model for joint dose response curve estimation for multiple cell-types while accounting for confounding covariates is proposed. A novel, scalable and efficient optimization algorithm using the MM phi- losophy is proposed for the estimation of both monotone and non-monotone curves. Two relevant tests of hypothesis are discussed and the proposed methods are validated using several simulated datasets. In Chapter 4, co-expression network estimation is studied using graph signal processing. A kernelized signed graph learning approach is developed for learning single cell gene co-expression networks, based on the assumption of smoothness of gene expressions over activating edges. Performance is assessed using real human and mouse embryonic datasets. This chapter was originally published in [2].
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Title: Assessment of Operational and Safety Impacts of Various Traffic Control Devices
Creator: Megat Johari, Megat Usamah Bin
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Fatal crashes have been increasing, both in Michigan and across the United States, despite continuing improvements in roadway design, vehicle safety, and other areas. Various factors may have contributed to this trend, including increased in-vehicle distractions, higher speed limits, legalization of marijuana, and other factors. Studies have suggested that driver error is a critical reason associated with more than 90 percent of all traffic crashes. Driver behavior can be improved by several...
Show moreFatal crashes have been increasing, both in Michigan and across the United States, despite continuing improvements in roadway design, vehicle safety, and other areas. Various factors may have contributed to this trend, including increased in-vehicle distractions, higher speed limits, legalization of marijuana, and other factors. Studies have suggested that driver error is a critical reason associated with more than 90 percent of all traffic crashes. Driver behavior can be improved by several engineering strategies, such as the use of better and more efficient traffic control devices, such as signs, signals, and pavement markings. To that end, this research assesses the operational and safety impacts of a series of traffic control devices.The use of dynamic message signs (DMS) as a medium to display safety messages to drivers has become popular among transportation agencies. Despite their widespread use, evaluations as to the resultant impacts on traffic crashes have been very limited. This study addresses this gap in the extant literature and assesses the relationship between traffic crashes and the frequency with which various types of safety messages are displayed. A series of count models are estimated to examine total, speeding-related, and nighttime crashes based upon historical messaging data while controlling for other site-specific factors. Ultimately the results provide important insights regarding messaging strategies for transportation agencies. This research also evaluates driver response to advisory speed signs. Posted speed limit signs are used to inform drivers of the legal maximum allowable speed. In contrast, advisory speed signs provide recommendations to drivers as to safe travel speeds at specific roadway locations. Various studies have investigated the safety impacts of speed limit changes, particularly on high-speed rural highways. One area of particular concern on such roadways is the approach to exit ramps that require substantive speed reductions, such as loop ramps. To date, there has been limited research examining the safety impact of the differential between the mainline speed limit and the lower exit ramp advisory speeds. This study addresses this gap through the estimation of a series of safety performance functions. The findings from this study show the safety of these locations is related to speed differential, as well as other factors such as the length of the upstream deceleration lane. These factors should be considered when considering speed limit policy impacts in the vicinity of full and partial cloverleaf interchanges.Lastly, this study assesses the use of dynamic speed feedback sign (DSFS) as a means to reduce vehicle speeds in speed transition zones, where speeds are reduced as drivers enter rural communities. DSFS have been evaluated in several settings, including high-speed exit ramps and horizontal curves. However, research is limited as to the effectiveness of this sign for other purposes, such as these high-speed transition areas. This is particularly important as the limits on some of these roadways have recently been increased, making speed control a particular concern. This study addresses this gap through a before-and-after evaluation of DSFS at five different sites in northern Michigan. A series of speed models were estimated, which provide insights on the effectiveness of DSFS.
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Title: AN EXAMINATION OF EMPATHY AND SOCIAL OUTCOMES FOR INDIVIDUALS WITH INTELLECTUAL AND DEVELOPMENTAL DISABILITIES
Creator: Josol, Cynde Katherine
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Empathy is generally described as a multidimensional construct, consisting of cognitive and affective components. Researchers demonstrate that a better ability to understand and express empathy toward others is associated with positive social outcomes such as strong communication skills and meaningful social relationships. For individuals with intellectual and developmental disabilities (IDD), the understanding and expression of empathy and its various components can be challenging. However,...
Show moreEmpathy is generally described as a multidimensional construct, consisting of cognitive and affective components. Researchers demonstrate that a better ability to understand and express empathy toward others is associated with positive social outcomes such as strong communication skills and meaningful social relationships. For individuals with intellectual and developmental disabilities (IDD), the understanding and expression of empathy and its various components can be challenging. However, different etiologies can elucidate various strengths and weaknesses related to empathy. Given empathy’s critical role in various social domains and potential differences in empathy skills and social outcomes across different IDD groups, the purpose of this dissertation is to expand the current literature on empathy for three distinct and unique IDD groups to better inform current and future interventions.This dissertation consists of three independent, but related manuscripts presented in journal submission format. The first study was a systematic literature review of 169 studies conducted to identify the current research on empathy skills and social outcomes for individuals with autism spectrum disorder (ASD), Williams syndrome (WS), and Down syndrome (DS). Overall, the results of the systematic literature review indicate that individuals with ASD experience poorer empathy skills and these deficits relate to poor social skills. Further, there is a lack of research on empathy for other IDD conditions (e.g., WS and DS) and in relation to other social domains (e.g., social skills). As such, the second study examined the specific relationship of empathy and social skills for individuals with ASD, WS, and DS and examined for differences across groups and compared to a typically developing (TD) control group. The final sample (N = 120) included 30 students diagnosed with ASD (mean age = 10.73 years) and their caregivers, 30 students diagnosed with WS (mean age = 12.07 years) and their caregivers, 30 students with DS (mean age = 11.53 years) and their caregivers, and 30 TD students (mean age = 10.90 years) and their caregivers. Results demonstrate that, according to parent reports, students with ASD present with lower empathy skills compared to students with WS and DS and to students without disabilities. Differences between groups were also demonstrated regarding the relationship between empathy skills and social skills. More specifically, for students with WS, lower empathy skills were not significantly correlated with social motivation. The results of Chapter 3 highlight that differences in empathy and social skills should be accounted for in empathy-related interventions and underscore the importance of developing etiology-specific interventions. In response to the importance of developing interventions that account for the student’s disability, the third manuscript was written to guide special educators in addressing empathy skills for students with ASD. When assessing empathy skills, it is crucial that special educators obtain accounts from multiple informants including parent- and teacher-reports. The use of multiple sources will provide both a general picture of a student’s empathy skills along with information for specific areas of concern. Other general considerations for empathy assessment and intervention include incorporating elements of cognitive and affective empathy during assessment, adopting a developmental framework to guide both short term and long-term goals, and identifying additional social skills deficits to target prior to or during the empathy intervention, if applicable.
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Title: EXAMINING THE IMPACT OF SHAREHOLDER ACTIVISM ON THE TARGETED FIRMS’ TEMPORAL ORIENTATION AND RESOURCE DECISIONS
Creator: Lee, Jennifer
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Prior research on shareholder activism has expanded our knowledge on how activism affects firms, especially with respect to the types and magnitudes of activist-impelled changes. However, it remains unanswered how deeply activist intervention morphs the targeted firms and how long such changes persist. Focusing on the firm temporal orientation, I develop theory on how activism influences the targeted firm’s time horizon, both when attacked by activists and when activists leave the firm. I...
Show morePrior research on shareholder activism has expanded our knowledge on how activism affects firms, especially with respect to the types and magnitudes of activist-impelled changes. However, it remains unanswered how deeply activist intervention morphs the targeted firms and how long such changes persist. Focusing on the firm temporal orientation, I develop theory on how activism influences the targeted firm’s time horizon, both when attacked by activists and when activists leave the firm. I open the dissertation by reviewing the rapidly evolving research in shareholder activism. In my first empirical study, I examine how activist intervention shortens the targeted firm’s time horizon, and how the degree of shortening is contingent on the relative motivation and capability of activist investors vis-à-vis managers. In the second study, I propose that targeted firms shift their course of strategy once activist investors leave the firm, specifically by increasing their resource-consuming investments. Yet, because of the inherent temporal tradeoff such investments present, I posit that the degree of shift is likely affected by leader attributes and situational factors. Specifically, I argue that the CEOs who are high in their future temporal focus and who have a high level of prospective wealth will increase their resource-consuming investments to a greater degree. In addition to testing hypotheses, the empirical data revealed an unexpected insight into the time horizon changes in non-targeted firms. With my dissertation, I aim to contribute to streams of research on shareholder activism, firm temporal orientation, and corporate governance.
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Title: EVALUATION OF DRIVER RESPONSE TO SAFETY MESSAGES ON DYNAMIC MESSAGE SIGNS
Creator: Megat Johari, Nusayba Binti
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Between 2010 and 2020, many transportation agencies began displaying safety messages and crash facts to the traveling public using roadside dynamic message signs (DMS). The content of these messages varies from annual crash and fatality statistics to more detailed messages regarding specific driving behaviors or risk factors. Despite the widespread use of DMS for safety messaging purposes, evaluations of potential impacts on driver behavior and resultant impacts on traffic safety have been...
Show moreBetween 2010 and 2020, many transportation agencies began displaying safety messages and crash facts to the traveling public using roadside dynamic message signs (DMS). The content of these messages varies from annual crash and fatality statistics to more detailed messages regarding specific driving behaviors or risk factors. Despite the widespread use of DMS for safety messaging purposes, evaluations of potential impacts on driver behavior and resultant impacts on traffic safety have been limited. This research addresses this gap through a series of investigations to determine the degree to which the use of DMS for safety messages impacts various aspects of driver behavior. Driver behavior was examined in response to different DMS messages while considering critical contextual factors, such as the type of messages displayed, traffic flow conditions, and roadway geometric characteristics. The first set of field evaluations examined driver behavior as vehicles approached in-service emergency and MDOT service vehicles parked on the roadway shoulder in consideration of the state’s move-over law. Compliance was measured in terms of speed reduction and lane selection and comparisons were made based upon a series of targeted messages displayed on upstream DMS. Logistic regression models were estimated to assess driver compliance with the law while considering important contextual factors, such as the type of vehicle on the shoulder and the message displayed on the DMS. The results indicate that drivers were more likely to move over or reduce their speeds when a police car was parked on the shoulder as compared to a transportation agency pickup truck. In general, the type of message displayed had minimal impact on driver behavior. The one exception showed that drivers were less likely to exceed the speed limit when targeted move over messages were shown as compared to standard travel time messages. For all message types, both speed and lane compliance were improved if the roadside vehicle was a police car. The second study examined cell phone use rates in consideration of enforcement activities that were conducted in conjunction with the display of targeted safety messages on roadside DMS. The results showed that cell phone use rates were lower during and, particularly, after the enforcement activities were conducted. Use rates were also found to vary based on age, gender, and race, allowing for the identification of target groups for public awareness and outreach campaigns. Cell phone use rates were also lower at freeway exit ramps compared to signalized and stop-controlled surface street intersections. Furthermore, cell phone-specific safety messages were associated with lower use rates than other message types.Ultimately, the findings largely reinforce federal guidance on the use of DMS for secondary purposes, which include displaying road safety messages. As a stand-alone measure, DMS provide marginal impacts on driver behavior. Such messaging strategies are likely to be more effective when used as a part of active safety campaigns with a limited duration as compared to more frequent and continuous display of generic message types. The outcome of the field investigations also shows that combining targeted messaging with the presence of enforcement results in the most substantive improvements in driver behavior.
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Title: FIELD AND EXPERIMENTAL STUDIES FIND VARIATION IN LEVELS OF LARVAL LAKE STURGEON PREDATION IS ASSOCIATED WITH BEHAVIOR AND ENVIRONMENTAL CONDITIONS
Creator: Riedy, Joseph Jerry
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Species are vulnerable to predation during early in life stages, especially those who provide little or no parental care. Predation risk is further elevated during periods of migration when individuals are exposed to a greater abundance and diversity of predators. Levels of predation during migration are often variable and can be heavily influenced by environmental conditions and changes in behavior. It is important to understand how these factors influence predation rates of threatened and...
Show moreSpecies are vulnerable to predation during early in life stages, especially those who provide little or no parental care. Predation risk is further elevated during periods of migration when individuals are exposed to a greater abundance and diversity of predators. Levels of predation during migration are often variable and can be heavily influenced by environmental conditions and changes in behavior. It is important to understand how these factors influence predation rates of threatened and endangered species. Lake sturgeon are an imperiled species native to the Great Lakes, Mississippi River, and Hudson Bay drainages that undergo a downstream from spawning grounds to nursery habitat at the beginning of the larval stage. This migration begins at night and larvae are exposed to several known predator species as they migrate the length of the spawning river in event. In this dissertation, I examine influences of ecological factors and behavior on levels of predation during the downstream migration. In Chapters 1 and 2, I used mesocosm experiments to determine the effects of night light level, rearing temperature, and prey abundance on survival during migration. Survival is highest during the environmental conditions present early in the season: new moon light levels, colder rearing conditions, and when prey abundance is high. In Chapters 3 and 4, I returned to the mesocosms to examine the survival implications of the behavioral responses to alarm cues during the larval stage. Lake sturgeon larvae exposed to a predator species odor and lake sturgeon alarm cue have higher survival rates when later exposed to the predator species. Additionally, lake sturgeon can use alarm cues from unrelated allopatric and sympatric species as kairomones similarly to conspecific alarm cues. In Chapter 5, I collected lake sturgeon larvae and predator diets from a natural lake sturgeon spawning stream to estimate nightly mortality rates, identify the predatory species that consumed, and determine the environmental factors that influence lake sturgeon mortality in a wild population. Survival rates varied greatly, but on average, approximately one third of lake sturgeon larvae survived the section of the river sampled. Additionally, roughly one third of all potential predator diets sampled contained lake sturgeon. Similar to previous chapters, light level and the abundance of prey had the greatest influence on the survival rates of lake sturgeon and the probability of detecting lake sturgeon in the diets of potential predators. Results indicate the timing of lake sturgeon spawning influences larval survival by determining the ecological conditions present during offspring development and downstream migration. Work presented here identifies the factors with the strongest influence on larval lake sturgeon survival. Though variation in larval lake sturgeon mortality is high, managers may begin to use these factors to forecast larval lake sturgeon survival rates in populations. It will be important to monitor changes to these ecological variables, such as fluctuations in co-distributed fish and invertebrate populations, and variation in water temperatures during development, because these factors have strong and predictable influences lake sturgeon recruitment rates.
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Title: THE EFFECT OF SALES TAXES ON LOCATION DECISIONS AND CAPITAL MARKET OUTCOMES : EVIDENCE FROM WAYFAIR
Creator: Shaw, Joanna
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This study examines how investors, analysts, and firms respond to changes in sales tax obligations for e-commerce firms. Previous research finds that e-retailers have a competitive advantage over their brick-and-mortar counterparts due to their ability to avoid collecting sales taxes. Using the Supreme Court of the United States (The Court) decision in South Dakota v. Wayfair, Inc., 585 U.S.__ (2011) (Wayfair) as a setting, I examine investor and analyst reactions to, and corporate location...
Show moreThis study examines how investors, analysts, and firms respond to changes in sales tax obligations for e-commerce firms. Previous research finds that e-retailers have a competitive advantage over their brick-and-mortar counterparts due to their ability to avoid collecting sales taxes. Using the Supreme Court of the United States (The Court) decision in South Dakota v. Wayfair, Inc., 585 U.S.__ (2011) (Wayfair) as a setting, I examine investor and analyst reactions to, and corporate location decisions following, the broadening of state nexus rules for interstate commerce. I find that investors and analysts responded negatively to the announcement that The Court would hear the Wayfair case and to the release of the ruling, as evidenced by negative mean cumulative abnormal returns and downward revenue forecast revisions, respectively. These results are consistent with capital market participants perceiving increased sales tax obligations as being detrimental to e-commerce firms. Next, I investigate how e-commerce firms respond to increased sales tax obligations by examining their location decision-making in the wake of Wayfair. I find that e-commerce firms are more likely to establish locations in new states with sales taxes after Wayfair. In cross-sectional analysis, I find that my results are primarily driven by retail, wholesale, and service firms. I also find evidence that e-commerce firms are more likely to establish locations in states with high populations after Wayfair.
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Title: BUSINESS RESPONSES TO SUPPLY CHAIN DYNAMICS : IMPLICATIONS FOR SOURCING AND PUBLIC POLICY
Creator: Yan, Zhenzhen
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation studies drivers and consequences of firms' policy decisions from a supply chain perspective. Policy decisions can be both internal and external to the firms and carry substantial implications for firms’ performance outcomes. Both internal and external aspects of policy engagement are critical since they help further disciplinary understanding of not only how policy decisions influence the performance of products firms manufacture, but also the fact that firms can reshape...
Show moreThis dissertation studies drivers and consequences of firms' policy decisions from a supply chain perspective. Policy decisions can be both internal and external to the firms and carry substantial implications for firms’ performance outcomes. Both internal and external aspects of policy engagement are critical since they help further disciplinary understanding of not only how policy decisions influence the performance of products firms manufacture, but also the fact that firms can reshape their environmental conditions through adopting policy decisions to engage with regulators and impact their own business practices. Specifically, I investigate firms' sourcing policies and their product performance implications – an internal policy set by firms. Within the context of external policy engagement, my research investigates firms' policy responses to external conditions, such as climate change public policies.The first essay focuses on manufacturing localization, an internal policy set by automakers to relocate manufacturing activities closer to their target market. I apply a causal estimation method to 23-year panel data of the automotive industry complied from diverse data sources including Wards, National Highway and Traffic Safety Authority (NHTSA) recall data to investigate the quality implications of manufacturing localization. The results show an immediate quality decline for localized vehicles, indicated by an increase of 68.203% in the number of recalls (equivalent to 0.552 more recall campaigns) and an increase of customer complaints by 56.831% (equivalent to 9.997 more complaints) in the three years after the manufacturing localization. The increased number of recalls can lead to an extra expense of $2.76 million for a localized vehicle based on conservative estimations. A cautionary note is thus issued for automakers to adjust their planned budgets to account for warranty claims before the localization. This study provides guidance for firms considering the relocation of their manufacturing activities and for regulators that seek to reduce vehicle recalls. The second and third essays of my dissertation investigate firms’ engagement in influencing climate change policies (EICCP), which refers to firms’ strategic actions to influence climate change policymaking processes, aiming at reshaping policies or promoting policy changes in favor of their interests. In the second essay, I conceptualize EICCP and propose a taxonomy for EICCP strategies considering firms’ perceptions of external conditions and internal resources. I also create measures for EICCP to empirically validate this taxonomy by performing text analytics with machine-learning techniques on firms’ self-disclosure in CDP Climate Change data. Building on the second essay, I undertake a large-scale empirical analysis to investigate antecedents of EICCP in the third essay. Specifically, I examine the regulatory risks associated with climate change and firms’ supply network complexity as critical and interrelated factors for firms’ EICCP. The latter two essays contribute to the growing literature on climate change and firm responses. Overall, my thesis responds to the call for policy-related studies in the supply chain field and provides insights for policy decision-makers.
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Title: Evaluation of Operational and Safety Impacts of Part-Time Use of The Inside Shoulder
Creator: Cai, Qiuqi
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The Michigan Department of Transportation (MDOT) introduced its first application of dynamic part-time shoulder use (D-PTSU) on the US-23 corridor in November 2017 to mitigate recurring congestion. This project referred to as the Flex route involved widening the left shoulder, which now serves as a temporary travel lane during between M-14 and M-36 during periods of heavy congestion. As the application of D-PTSU is relatively novel in the United States, especially the use of the left shoulder...
Show moreThe Michigan Department of Transportation (MDOT) introduced its first application of dynamic part-time shoulder use (D-PTSU) on the US-23 corridor in November 2017 to mitigate recurring congestion. This project referred to as the Flex route involved widening the left shoulder, which now serves as a temporary travel lane during between M-14 and M-36 during periods of heavy congestion. As the application of D-PTSU is relatively novel in the United States, especially the use of the left shoulder, this study evaluates the operational and safety performance of the US-23 Flex route and provides guidance for future implementation of similar facilities in Michigan and elsewhere. The evaluation assessed various metrics, including average travel time, travel time reliability, driver compliance, and incident clearance times. The findings show that operations of the US-23 Flex route have improved significantly, especially in the southbound direction. While the northbound direction also showed better performance after the Flex lane opened in general, some of the prior congestion has shifted to the end of the Flex route in the northbound direction due to a bottleneck that was introduced at the end terminal. Fortunately, this problem is expected to be alleviated by the planned extension of the Flex lane to I-96 in 2024. The operational analyses also showed improved operations when special events occurred, such as football games and holidays. Incident clearance times largely decreased after the Flex route was opened. Part-time shoulder running also provided an additional travel lane during peak periods, such as University of Michigan home football games, reducing such non-recurrent congestion. Crash data were compared for a period of five years (i.e., 2012 to 2016) before the construction of the Flex route, and two years (i.e., 2018 and 2019) after its completion. After considering increases in traffic volume, crashes were reduced by 17 percent when considering all times of day, including 34 percent in the southbound direction. During the peak operational periods, reductions of approximately 50 percent were experienced in the southbound direction. In contrast, total crashes were comparable in the northbound direction and actually increased by approximately 24 percent during the peak traffic periods. However, much of this increase is attributable to the lane drop that occurs at the northern terminus of the Flex route. The planned extension to I-96 should remedy the existing safety issues.
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