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Title: I. Determination of Absolute Configuration of Chiral 1,2-Diols. II. Progress Towards the Total Synthesis of Napyradiomycin A1.
Creator: Torabi Kohlbouni, Saeedeh
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation focuses on two parts. The first part introduces an operationally simple and microscale method for the absolute stereochemical determination of 1,2-diols. In situ derivatization of 1,2-diols with dinaphthyl borinic acid generates the induced helicity of the two naphthyl groups, which leads to an observable ECCD spectrum. The observed P or M helicity follows a predictable trend for S and R chiral 1,2-diols, respectively.The Second chapter is the progress towards the asymmetric...
Show moreThis dissertation focuses on two parts. The first part introduces an operationally simple and microscale method for the absolute stereochemical determination of 1,2-diols. In situ derivatization of 1,2-diols with dinaphthyl borinic acid generates the induced helicity of the two naphthyl groups, which leads to an observable ECCD spectrum. The observed P or M helicity follows a predictable trend for S and R chiral 1,2-diols, respectively.The Second chapter is the progress towards the asymmetric catalytic synthesis of napyardiomycin A1. The chapter is divided to three sections. The first section is installation of chlorine chiral center at C3. This goal is achieved using cinchona chiral catalyst, and DCDMH as chloronium source. The second section is the synthesis of the -lapachone core of napyradiomycin A1, was accomplished using Diels-Alder/aromatization cascade reaction. The last section shows our effort toward the attachment of geranyl side chain.
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Title: Molecular epidemiology, pangenomic diversity, and comparative genomics of Campylobacter jejuni
Creator: Rodrigues, Jose Alexandre
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Campylobacter jejuni, the leading cause of bacterial gastroenteritis in the United States, is often resistant to commonly used antibiotics and has been classified as a serious threat to public health. Through this work, we sought to evaluate infection trends, quantify resistance frequencies, identify epidemiological factors associated with infection, and use whole-genome sequencing (WGS) as well as comparative phylogenomic and pangenomic approaches to understand circulating C. jejuni...
Show moreCampylobacter jejuni, the leading cause of bacterial gastroenteritis in the United States, is often resistant to commonly used antibiotics and has been classified as a serious threat to public health. Through this work, we sought to evaluate infection trends, quantify resistance frequencies, identify epidemiological factors associated with infection, and use whole-genome sequencing (WGS) as well as comparative phylogenomic and pangenomic approaches to understand circulating C. jejuni populations in Michigan. C. jejuni isolates (n=214) were collected from patients via an active surveillance system at four metropolitan hospitals in Michigan between 2011 and 2014. Among the 214 C. jejuni isolates, 135 (63.1%) were resistant to at least one antibiotic. Resistance was observed for all nine antibiotics tested yielding 11 distinct resistance phenotypes. Tetracycline resistance predominated (n=120; 56.1%) followed by resistance to ciprofloxacin (n= 49; 22.9%), which increased from 15.6% in 2011 to 25.0% in 2014. Notably, patients with ciprofloxacin resistant infections were more likely to report traveling in the past month (Odds Ratio (OR): 3.0; 95% confidence interval (CI): 1.37, 6.68) and international travel (OR: 9.8; 95% CI: 3.69, 26.09). To further characterize these strains, we used WGS to examine the pangenome and investigate the genomic epidemiology of this set of C. jejuni strains recovered from Michigan patients. Among the 214 strains evaluated, 83 unique multilocus sequence types (STs) were identified that were classified as belonging to 19 previously defined clonal complexes (CCs). Core-gene phylogenetic reconstruction based on 615 genes identified three clades, with Clade I comprising six subclades (IA-IF) and predominating (83.2%) among the strains. Because specific cattle-associated STs, such as ST-982, predominated among strains from Michigan patients, we also examined a collection of 72 C. jejuni strains from cattle recovered during an overlapping time period by WGS. Several phylogenetic analyses demonstrated that most cattle strains clustered separately within the phylogeny, but a subset clustered together with human strains. Hence, we used high quality single nucleotide polymorphism (hqSNP) profiling to more comprehensively examine those cattle and human strains that clustered together to evaluate the likelihood of interspecies transmission. Notably, this method distinguished highly related strains and identified clusters comprising strains from both humans and cattle. For instance, 88 SNPs separated a cattle and human strain that were previously classified as ST-8, while the human and cattle derived ST-982 strains differed by >200 SNP differences. These findings demonstrate that highly similar strains were circulating among Michigan patients and cattle during the same time period and highlight the potential for interspecies transmission and diversification within each host. In all, the data presented illustrate that WGS and pangenomic analyses are important tools for enhancing our understanding of the distribution, dissemination, and evolution of specific pathogen populations. Combined with more traditional phenotypic and genotypic approaches, these tools can guide the development of public health prevention and mitigation strategies for C. jejuni and other foodborne pathogens.
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Title: PROBE EFFECTS DURING CONCENTRATION DETERMINATION IN SCANNING ELECTROCHEMICAL MICROSCOPY
Creator: Mirabal, Alex
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Efficient, sustainable chemical reactions will play a large role in addressing many growing issues, including alternative energy production, greenhouse gas conversion, and pharmaceuticals. Electrochemical reactions are attractive due to their relatively mild reaction conditions and direct use of electricity. The understanding and design of the local liquid-solid interface will guide future progress in electrocatalytic reactions.Over time, nature has evolved many highly efficient reactions...
Show moreEfficient, sustainable chemical reactions will play a large role in addressing many growing issues, including alternative energy production, greenhouse gas conversion, and pharmaceuticals. Electrochemical reactions are attractive due to their relatively mild reaction conditions and direct use of electricity. The understanding and design of the local liquid-solid interface will guide future progress in electrocatalytic reactions.Over time, nature has evolved many highly efficient reactions through enzymatic reactions. These long-studied catalysts provide complex reaction environments that: 1) enhance interaction with reactants, 2) protect intermediates from side reactions, 3) increase the rates of reactions, and 4) selectively react to a specific product. The overarching lesson to be learned is that the local reaction environment plays a large role in the catalyst’s reactivity, selectivity, and efficiency. One way to characterize the local environment is through scanning electrochemical microscopy (SECM), in which a small electrochemical probe is rastered over an interface. A quantitative correlation of the probe response to concentration provides a direct measurement of the local environment. The presence of the SECM probe itself can induce changes in the local environment. Comparing the changed local environment (in situ) to what it would be without the probe present (operando), shows large differences of up to 120% under specific operating conditions. A few physical parameters such as the surface site geometry are shown to have an impact on how significant the probe effects are. Additional parameters such as the tip geometry and tip-surface separation are also to have an impact. A finite element method (FEM) simulation informed by experiments is used to examine the above-mentioned tip effects. It is found that fitting responses to other frequently used electrochemical measurements, such as approach curves and CVs, to parameterize the model appropriately describes experimental SECM results. We first apply this method to study platinum nanoparticles, where a ~50 nm resolution is the highest resolution to our knowledge for AFM-SECM. Through statistical analysis of the surface, an isolated nanoparticle SECM response is correlated with a concentration profile. It is found that the concentration profile has minimal probe effects due to the use of a conical electrode. Applying a similar approach, we also study the probe effects in pH detection during hydrogen evolution and CO2 reduction. Where we match experimental results to parameterize the system. It shown that there is a pH difference of up to ~7 pH units underneath the probe due to hindered diffusion. However, even with these large differences, the probes are still able to reflect the trends seen without the probe present. Moreover, it is shown that the physical parameters have correlated responses, indicating that hindered diffusion is controlled by the insulation radius and tip-surface separation. Finally, the importance of the analyte is discussed with regard to its interaction with the tip. In addition to the concentration impact on the response signal, the compatibility with the tip need be considered. Degradation of the tip and/or the redox couple of choice will detrimentally affect the ability to examine the local interface. We show that, of the redox couples examined, ferrocene-based compounds appear to best satisfy the most crucial factors of stability and mild redox potentials. Overall, this work studies and removes the impact of the probe for local concentration detection using SECM. This work acts as a guide to quantitatively study the local environment of electrocatalyzed reactions. This is realized through a combined experimental-FEM approach in which the simulation is informed by experiments such that it’s representative of the experimental environment.
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Title: DEVELOPING LIGNIN-BASED EPOXY AND POLYURETHANE RESINS
Creator: Nikafshar, Saeid
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Lignin, the most abundant natural aromatic polymer, is currently produced as by-product during biorefinery and chemical pulping processes. Lignin is rich in hydroxyl functional groups (both phenolic and aliphatic OH), making it an excellent raw material for synthesizing epoxy and polyurethane resins. However, there are several challenges in utilizing unmodified lignins as feedstock for product development, including high polydispersity/heterogeneity, low reactivity, poor accessibility of...
Show moreLignin, the most abundant natural aromatic polymer, is currently produced as by-product during biorefinery and chemical pulping processes. Lignin is rich in hydroxyl functional groups (both phenolic and aliphatic OH), making it an excellent raw material for synthesizing epoxy and polyurethane resins. However, there are several challenges in utilizing unmodified lignins as feedstock for product development, including high polydispersity/heterogeneity, low reactivity, poor accessibility of hydroxyl groups for reaction with co-monomers low solubility in common organic solvents, and dark color. There are significant variations in lignin characteristics, depending on the source of biomass and isolation methods. Therefore, in-depth lignin characterization is needed to provide the basic knowledge of the structural, chemical, and thermal properties to facilitate lignin valorization.This study was focused on lignin characterization and development of lignin-based epoxy and polyurethane resins. First, a wide range of lignin samples was fully characterized by measuring their ash contents, elemental analyses, hydroxyl contents, chemical structures, molar mass distributions, and thermal properties. Next, a novel method was developed to measure the reactivity of thirteen different unmodified lignins toward biobased epichlorohydrin (ECH). A partial least square regression (PLS-R) model (with 92 % fitting accuracy and 90 % prediction ability) was created to study the correlation between lignin properties and epoxy content. The results showed that lignins with higher phenolic hydroxyl contents and lower molecular weights were more suitable for replacing 100 % of toxic bisphenol A (BPA) in the formulation of resin precursors. Additionally, two epoxidized lignin samples (with the highest epoxy contents) were cured using a biobased hardener (Cardolite from cashew nutshell), showed comparable thermomechanical performances and thermal stabilities to a petroleum-based epoxy system. Biobased waterborne polyurethane resins (PUDs) were also developed by entirely replacing the petroleum-based polyol and the internal emulsifier with either alkaline pre-extraction lignins or enzymatic hydrolysis lignins as well as tartaric acid (a biobased diacid). The formulated resins had zero VOC (volatile organic compound), which was achieved by replacing toxic n-methyl-2-pyrrolidone (NMP) with cyrene (a biobased solvent). To further improve the mechanical properties of our biobased PUD resins, 20 wt.% of lignin was substituted with low hydroxyl value soy-polyol, which increased their tensile strength and elongation at break to 87% and 68% of a commercial PUD resin. The results of this study demonstrated that it is imperative to fully characterize lignin and choose the right lignin for each specific application. This approach enabled us to entirely replace petroleum-based raw materials (BPA and polyol) with lignin and formulate biobased epoxy and polyurethane resins.
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Title: THE ORIGINATION AND IMPLEMENTATION OF THE NATIONAL WETLANDS POLICY OF UGANDA : ENVIRONMENT, KNOWLEDGE, AND POWER FROM THE LATE NINETEENTH CENTURY TO PRESENT
Creator: Doyle-Raso, John
Date: 2022
Collection: Electronic Theses & Dissertations
Description: In the 1980s, following widespread environmental and intellectual changes associated with “swamp reclamation” that in Uganda had started in the early twentieth century, proponents of the emerging science of “wetland conservation” sought to influence the practices and thinking of people across the country. To do so, they created a national wetlands policy based on decentralized “community-based” projects. Yet, farmers’ and investors’ engagements with reclamation have continued. Meanwhile, the...
Show moreIn the 1980s, following widespread environmental and intellectual changes associated with “swamp reclamation” that in Uganda had started in the early twentieth century, proponents of the emerging science of “wetland conservation” sought to influence the practices and thinking of people across the country. To do so, they created a national wetlands policy based on decentralized “community-based” projects. Yet, farmers’ and investors’ engagements with reclamation have continued. Meanwhile, the Ugandan wetlands policy became internationally influential for its groundbreaking approach to interdisciplinary questions about governance, emphasizing economic analyses based on concepts such as “ecosystem services” and “Environmental Economic Valuation.” Ugandan wetland conservationists have had more influence abroad than domestically, as in Uganda neoliberalization and recentralization have limited the power of the community-based groups who have worked through the national policy. Using a range of sources including but not limited to archives and interviews with conservationists, this dissertation historicizes the Ugandan wetlands conservation policy. It comprises two parts addressing overlapping time periods. The first three chapters consider the origination of this policy by analyzing environmental and intellectual changes in southeastern and southwestern Uganda, leading to the creation in the late-twentieth century of environmental regulations. The latter three chapters examine how conservationists have tried implementing the policy in rural and urban places, and in relation to the national emblem of Uganda – the Grey Crowned Crane. They have focused their efforts on community-based projects outside Protected Areas promoting indigenous knowledges and practices to obtain economic benefits from wetlands that conservationists. This approach was an early manifestation of connected trends in international developmentalist networks. Furthermore, the limitations on its implementation have become pivotal in the global histories of neoliberalization, decentralization, and recentralization. Historicizing Ugandan wetland conservationism contributes to four scholarly literatures. 1) Analyzing community-based projects outside “Protected Areas” advances the historiographies of conservation and watershed management in Africa by considering the significances of neoliberalization, decentralization, and recentralization beyond extraordinary legal cases. 2) Examining intellectual changes in this history – including an emphasis on community-based projects, use of the concept of ecosystem services, and the promotion of indigenous knowledges and sciences – reveals connections between changes in environmental science and global trends in developmentalism. 3) Focusing on these changes in Uganda builds on analyses of environmental management in political power there by identifying the importance of an underexamined resource in entrenched land conflicts, and by uncovering early institutional bases of recentralization. 4) Because Ugandan wetland conservationists were global leaders in policy creation, citizen science, and more changes in scientific thinking, researching their work reveals how African scientists have navigated tensions between their local, national, and international interlocutors to become internationally influential. Studying the history of Ugandan wetland conservationism reveals how different people’s engagements with changes in environmental thinking have reshaped environments and livelihoods, as well as influenced international scientific networks.
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Title: Development and application of hierarchical models for monitoring avian soundscapes, populations, and communities
Creator: Doser, Jeffrey W.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Climate change, land use change, and other anthropogenic pressures are increasing species extinctions, phenology shifts, and drastic population declines. Avian populations and communities are particularly vulnerable to global change given their mobile and migratory life history strategies. Avian abundance has drastically declined throughout North America over several decades, which is compounded by phenological shifts in breeding periods and migratory patterns. Informed management and...
Show moreClimate change, land use change, and other anthropogenic pressures are increasing species extinctions, phenology shifts, and drastic population declines. Avian populations and communities are particularly vulnerable to global change given their mobile and migratory life history strategies. Avian abundance has drastically declined throughout North America over several decades, which is compounded by phenological shifts in breeding periods and migratory patterns. Informed management and conservation of avian populations and communities requires large-scale monitoring programs, as well as associated inferential tools to provide statistically robust inference using multiple data sources. In this dissertation, I develop a suite of hierarchical modeling approaches to understand avian soundscapes, populations, and communities. I leverage a hierarchical Bayesian modeling framework, which is ideally suited for complex wildlife data with numerous types of observation error and dependencies among data points. In Chapter 1, I provide a brief overview of avian monitoring approaches and their associated statistical analysis frameworks. In Chapters 2 and 3, I develop hierarchical models for the analysis of complex avian soundscape data, and apply these approaches to two case studies. In Chapter 2, I apply a two-stage hierarchical beta regression model to quantify the relationship between anthropogenic and biological sounds in avian soundscapes in western New York. In Chapter 3, I use a multivariate linear mixed model to assess disturbance impacts of a shelterwood logging on avian soundscapes in northern Michigan. In Chapter 4, I develop a multi-region, multi-species abundance model to quantify trends of avian species and communities using point count data across a network of National Parks in the northeastern US. In Chapters 5 and 6, I use a model-based data integration approach to yield improved inference on avian population and communities. In Chapter 5, I integrate automated acoustic recording data with point count data to estimate avian abundance, which I apply to a case study on the Eastern Wood Pewee (Contopus virens) in a National Historical Park in Vermont. In Chapter 6, I develop an integrated community occupancy model that combines multiple types of detection-nondetection data for inference on species-specific and community level occurrence dynamics, which I use to assess occurrence dynamics of a foliage-gleaning bird community in New Hampshire. These results exhibit the value of hierarchical models to partition ecological data into distinct observation and ecological components for improved inference on avian population and community dynamics. Future work should continue to leverage complex data sources within hierarchical modeling frameworks to address pressing conservation and management questions on avian populations, communities, and the ecosystem services they provide.
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Title: LATE-GESTATION METABOLIC STRESS IN DAIRY CATTLE : ASSOCIATION WITH COLOSTRUM YIELD AND IMMUNOGLOBULIN CONTENT
Creator: May Rossi, Renato
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Despite improvements made in the dairy industry and advances on heifer management, calf morbidity and mortality are still high. Calves rely on colostrum ingestion for acquisition of passive immunity, and provision of insufficient quantity of colostrum may lead these animals to failure of transfer passive immunity, hence leading to higher risks of morbidity and mortality. Many farms do not have sufficient colostrum available at times to feed their calves. Synthesis of colostrum starts few...
Show moreDespite improvements made in the dairy industry and advances on heifer management, calf morbidity and mortality are still high. Calves rely on colostrum ingestion for acquisition of passive immunity, and provision of insufficient quantity of colostrum may lead these animals to failure of transfer passive immunity, hence leading to higher risks of morbidity and mortality. Many farms do not have sufficient colostrum available at times to feed their calves. Synthesis of colostrum starts few weeks before calving and it is at the time when cows are experiencing augmented metabolic adaptations due to increasing nutrient demands for fetal growth, colostrogenesis, and preparation for the onset of lactogenesis. The study described in Chapter 2 aimed to compare the metabolic status of dairy cows during the last 6 wk of gestation based on colostrum volume and Ig content across seasons during a year. The results in the latter study suggest that greater availability of antioxidants might support the production of higher volumes of colostrum. Therefore, the study reported in Chapter 3, aimed to evaluate whether administering a dietary antioxidant supplement during the last 3 weeks of gestation improves colostrum volume and immunoglobulin content. Our results showed that DATS increased colostrum volume. However, despite finding higher volume of colostrum in treatment group with statistical differences compared to control, the distribution of colostrum volume between groups are relatively the same, as well for IgG, IgM, and IgA.
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Title: MODELING THE JOINT IMPACTS OF SOCIAL NETWORK AND BUILT ENVIRONMENT ON ADOLESCENTS’ PHYSICAL ACTIVITY
Creator: Liu, Wei
Date: 2021
Collection: Electronic Theses & Dissertations
Description: This research stems from the worldwide public health problem of childhood obesity and insufficient physical activity (PA) among adolescents. Studies have shown that both social networks and the built environment could affect PA, but how do they jointly exert influence? Understanding the scale and mechanism of this joint impact could shed light on developing an effective intervention to promote PA. The goal of this dissertation is to try to disentangle the joint influence of social networks...
Show moreThis research stems from the worldwide public health problem of childhood obesity and insufficient physical activity (PA) among adolescents. Studies have shown that both social networks and the built environment could affect PA, but how do they jointly exert influence? Understanding the scale and mechanism of this joint impact could shed light on developing an effective intervention to promote PA. The goal of this dissertation is to try to disentangle the joint influence of social networks and the built environment on changes in PA through social network analysis and test a novel intervention based on the findings from the social network models. This study uses two waves of Add Health data from two sample schools. Chapter Two investigates how school-based friendship networks could influence Physical Education (PE) class enrollment. Chapter Three examines the influence of home location, neighborhood characteristics, as well as the demographic characteristics and change in PA of peers who were nominated as friends in the Add Health social survey on high school student’s friend selection and PA dynamics between two academic years. Chapter Four presents a spatial agent-based model that was derived from the social network model and integrates a location-based mobile game similar to Pokémon Go as a PA-promoting intervention to test different intervention scenarios. Through this research, I demonstrate that friends’ PE enrollment status has a weak influence on the change of individual’s PE enrollment in two consecutive years. Another observation is that student’s total PA change can affect their PA behaviors. Contrarily, the built environment of the neighborhood did not prove to exert significant influence. Due to social influence, students participating in an intervention program may cause a change in PA of non-participants, i.e., we can observe a spillover effect of the intervention program. This dissertation enriches the field of health geography by integrating social network analysis and spatial thinking to jointly investigate the influence of environmental and social spaces and to facilitate a more comprehensive understanding of the complex system of childhood obesity. It also extends existing models and provides a spatial agent-based model as an intervention exploration tool that can be calibrated for research and education by other scholars.
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Title: ANALYSIS OF ERWINIA AMYLOVORA POPULATION DYNAMICS AT FLOWER BLOOM AND FURTHER SYSTEMIC MOVEMENT OF THE PATHOGEN THROUGH HOST TISSUE
Creator: Slack, Suzanne M.
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Population dynamics of Erwinia amylovora have been utilized for many applications over the past 50 years. In this work, populations were tracked over the course of apple bloom under naturally occurring environmental conditions. Flower stigmas inoculated on the 1st day of being open can harbor large (107) populations after 3 or 5 days post inoculation, with 100-fold increases in E. amylovora stigma populations observed in atmospheric conditions with daily average temperatures near 14oC. These...
Show morePopulation dynamics of Erwinia amylovora have been utilized for many applications over the past 50 years. In this work, populations were tracked over the course of apple bloom under naturally occurring environmental conditions. Flower stigmas inoculated on the 1st day of being open can harbor large (107) populations after 3 or 5 days post inoculation, with 100-fold increases in E. amylovora stigma populations observed in atmospheric conditions with daily average temperatures near 14oC. These large 100-fold increases seem to occur at night, indicating that Erwinia amylovora is able to infect flowers in colder field temperatures than previously reported. In tandem, timing of antibiotic application relative to E. amylovora presence on flower stigmas had little impact on population dynamics, with streptomycin and kasugamycin consistently reducing populations while oxytetracycline was more variable. This study also led to the identification that Kasumin is prone to photodegradation. Culturable bacteria, yeast, and fungal populations were assessed over the course of bloom in relation to application of a biological control agent yeast (Aureobasidium pullulans) and a contact sterilant. Though populations fell rapidly directly after application, by 24 hours all populations returned to pre-spray levels. In regards to further systemic spread, a type three secretion system effector was indicted in blocking the abscission of infected flowers. The use of prohexadione calcium (Pro-ca) and acibenzolar-S-methyl (ASM) reduced internal E. amylovora spread in a seemingly synergistic manner on young trees, with rates of 28.3 g Pro-Ca + 28.3 g ASM or 56.6 g Pro-Ca + 28.3 g ASM. The sum of this work gives us a better understanding of E. amylovora population dynamics in field conditions as well as the population response to current treatment options.
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Title: THE COMMODIFICATION OF INTIMACY AND GENDER INEQUALITY WITHIN SOUTH KOREAN DATING RITUALS
Creator: Glayzer, Edward James
Date: 2021
Collection: Electronic Theses & Dissertations
Description: The economic boom of the 90’s promised increased gender equity for South Korean women through their new ability to “find employment off the land and outside of the family economy,” gaining some level of autonomy from their families. However, South Korea now has the widest gender income gap among OCED nations. I argue that, while women have gained the power to choose their own marriage partners, the hyper-commodification of dating rituals has left them as unequal partners in the negotiation of...
Show moreThe economic boom of the 90’s promised increased gender equity for South Korean women through their new ability to “find employment off the land and outside of the family economy,” gaining some level of autonomy from their families. However, South Korea now has the widest gender income gap among OCED nations. I argue that, while women have gained the power to choose their own marriage partners, the hyper-commodification of dating rituals has left them as unequal partners in the negotiation of romantic courtship. Additionally, the commodification of intimacy has also increased inequality between men and women within the South Korean sexual field, hardening class hierarchies. This has had negative effects on men’s ability to materially express their feelings of interest, love, and intimacy with their dating partners during a time of slow economic growth, concentration of wealth among elites, and high unemployment among South Korean youth. I found that a reversion to a reliance on South Korean singles’ parents class status and economic clout in the competitive South Korean sexual field has taken place despite tremendous economic development, and advances in women’s rights and education. While the democratizing effects of capitalism that have allowed South Korean women to choose their own marriage partners would seem to have increased gender equality, my study calls this assumption into question and asks how this shift instead creates new inequalities. I investigate how the development of a consumer economy has affected gender inequality through the commodification of intimate relationships within dating and marriage rituals. I use dating and courtship rituals in South Korea as a lens through which to examine how the commodification of intimacy has affected gender and class inequality. Unequal access to income between genders and classes unevenly effects the expression of intimate relationships that are heavily mediated by the hyper-consumption of commodities. I argue that inequity in the economic market creates analogous inequity in dating, marriage, and intimate markets with especially negative repercussions for those who do not fit what that market has deemed ideal feminine or masculine actors. Class inequalities within the sexual field are most apparent between men whose evaluations are based on breadwinner masculinity; strongly correlated with their incomes and the class background of their parents. Women too ascend or descend the hierarchy of the South Korean sexual field through their adherence to marketable ideals of femininity and a “good wife,” namely their education, docility, and erotica capital. The emancipatory power of new technologies of intimate consumption such as the internet are interrupted by both commodification and the threat of abuse by South Korean singles with the ability to weaponize their higher incomes within their intimate relationships. Online matchmaking agencies who perform such screening services are expensive and reintroduce economic inequalities and hegemonic male power back into intimate relationships. South Koreans exploit the internet to discover new social groups and extend the reach of their existing social networks through meetup groups and hobbies rather than deploying dating applications more directly to find a dating partner. However, I argue that the rise of online dating in South Korea and its intensive commodification has actually led to the retrenchment of existing gender norms and ideals rather than their subversion.
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Title: A nitrogen-responsive small peptide signaling mechanism modulates plant root system architecture
Creator: Lay-Pruitt, Katerina Sibala
Date: 2021
Collection: Electronic Theses & Dissertations
Description: The plant root system changes dynamically in response to environmental cues. Plants utilize their root system for uptake of essential mineral nutrients that are heterogeneously distributed in the soil environment. Nutrient-dependent modulation of root system architecture (RSA) traits such as primary root growth, lateral root emergence, and the angles at which these roots grow allows for optimization of nutrient acquisition. Among signaling pathways by which plants may sense the availability...
Show moreThe plant root system changes dynamically in response to environmental cues. Plants utilize their root system for uptake of essential mineral nutrients that are heterogeneously distributed in the soil environment. Nutrient-dependent modulation of root system architecture (RSA) traits such as primary root growth, lateral root emergence, and the angles at which these roots grow allows for optimization of nutrient acquisition. Among signaling pathways by which plants may sense the availability of nutrients from the environment, small signaling peptide (SSP) pathways play important roles in optimizing root functions. These SSP pathways may further regulate molecular processes underlying RSA, such as the biosynthesis and transport of the major plant growth hormone, auxin. Characterization of these nutrient-responsive SSP pathways is thus of great importance and critical for understanding plant development in nutrient-poor environments. For my dissertation, I have identified and characterized a nitrogen (N)-responsive SSP pathway modulating root gravitropic response and lateral root development. Co-regulation of these RSA components by this module is proposed to prevent root outgrowth into N-poor regions and drive deeper root growth towards mobile nitrate (NO3-) resources stratified deeper in the soil profile. First, I show that a signaling pathway involving the CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) family of peptides and the CLAVATA1 (CLV1) receptor kinase, which is involved in N-dependent repression of lateral root emergence, also enhances root gravitropic response under N-limited conditions. Transcriptomic profiling of a clv1 mutant and CLE3 overexpressing lines identified Arabidopsis thaliana CENTRORADIALIS (ATC), a mobile protein previously characterized for its role in flowering regulation, as a downstream target of CLE-CLV1 signaling. Loss of ATC function significantly weakens root gravitropic response and has a moderate impact on lateral root emergence under low NO3- availability. ATC promoter activity and protein localization are also detected throughout the phloem and in the root columella cells, which are major centers for gravity sensing. Second, I demonstrate the relevance of ATC function on the molecular processes underlying root gravitropic response. While mutation in ATC does not impact gravity sensing via amyloplast sedimentation, it does inhibit the asymmetric transport of auxin needed for gravitropic bending. I determine that this occurs via the significant reduction of the PIN3 auxin efflux transporter in the vasculature and root tip of atc mutant lines. Lastly, I examine how the known roles of ATC in floral development could be implicated in root developmental processes. ATC binds to phosphatidic acid and phosphatidylserine, which is contrary to the binding capacity of its homolog FLOWERING LOCUS T (FT) to phosphatidylcholine and may contribute to its activity in N-limited environments. I also investigate the interaction of ATC and the transcription factor FD in the transcriptional regulation of PIN3. Although FD appears to have an impact on root gravitropic response, FD inhibits the expression of PIN3, suggesting potentially complex control of this gene via floral regulatory components. Taken together, the results presented in this dissertation contribute greatly to our understanding of how plant root architecture alters in response to N. These results can be further utilized in plant engineering strategies to regulate root growth in nutrient-limited soils.
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Title: THE ORIGINS OF SUPEROXIDE AND HYDROGEN PEROXIDE PRODUCTION BY THE MAMMALIAN MITOCHONDRIAL ELECTRON TRANSPORT CHAIN : A COMPUTATIONAL AND EXPERIMENTAL APPROACH
Creator: Duong, Quynh Van
Date: 2021
Collection: Electronic Theses & Dissertations
Description: The mitochondrial electron transport chain (ETC) produces reactive oxygen species (ROS) as by-products of cellular respiration. Certain pathological conditions including ischemia-reperfusion (IR) injury disrupts mitochondrial ROS homeostasis, causing oxidative stress which can lead to cell death. Despite research efforts in the past few decades, an incomplete understanding of how mitochondria orchestrate ROS production and elimination prevails and hinders the development of efficacious...
Show moreThe mitochondrial electron transport chain (ETC) produces reactive oxygen species (ROS) as by-products of cellular respiration. Certain pathological conditions including ischemia-reperfusion (IR) injury disrupts mitochondrial ROS homeostasis, causing oxidative stress which can lead to cell death. Despite research efforts in the past few decades, an incomplete understanding of how mitochondria orchestrate ROS production and elimination prevails and hinders the development of efficacious therapeutic measures against oxidative stress. A major impediment is the lack of a quantitative framework capable of identifying site-specific sources of mitochondrial ROS production. Many mathematical models of mitochondria have been developed to tackle this challenge. Unfortunately, none is comprehensive and able to quantitatively reproduce a variety of bioenergetic data.The work presented in this dissertation culminates in a mathematical model of ROS production by the ETC complexes coupled with substrate metabolism. First, a variety of bioenergetic data are generated in-house using isolated mitochondria. Generating in-house data permits precise control over experimental conditions, which minimizes hidden variables in model simulations. Second, a biophysically detailed model of the ETC complex II is developed. Finally, the complex II model is integrated with the models developed by Beard and colleagues. These include the bioenergetic model, the kinetic model of complex I and the functional bc1 dimer model. The integrated model is biophysically detailed, mass-and-charge balanced and thermodynamically consistent. The modelling process involves an iterative process of model calibration and validation to ensure the quality of model predictions. Using this model, the flavin mononucleotide of complex I is identified as the primary source of superoxide and hydrogen peroxide in forward electron transport. The model predicts that, under conditions that favor highly reduced quinol and NADH pools in uninhibited mitochondria, both sites IF and IQ produce significant amounts of ROS. The model also reveals that hydrogen peroxide (H2O2) production by site IF underlies the substrate-specific monotonic dependence between net ROS production and oxygen concentrations. When electron flux is perturbed such as in the presence of an inhibitor, the topology of ROS production is altered. Thus, the model can be used to quantify the effects of changes to mitochondrial environment on ROS production, an application that, today, is experimentally limited. The model also highlights the importance of furthering our understanding of the scavenging system under different conditions to establish a complete picture of mitochondrial ROS homeostasis.
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Title: Face Anti-Spoofing : Detection, Generalization, and Visualization
Creator: Liu, Yaojie
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Face anti-spoofing is the process of distinguishing genuine faces and face presentation attacks: attackers presenting spoofing faces (e.g. photograph, digital screen, and mask) to the face recognition system and attempting to be authenticated as the genuine user. In recent years, face anti-spoofing has brought increasing attention to the vision community as it is a crucial step to prevent face recognition systems from a security breach. Previous approaches formulate face anti-spoofing as a...
Show moreFace anti-spoofing is the process of distinguishing genuine faces and face presentation attacks: attackers presenting spoofing faces (e.g. photograph, digital screen, and mask) to the face recognition system and attempting to be authenticated as the genuine user. In recent years, face anti-spoofing has brought increasing attention to the vision community as it is a crucial step to prevent face recognition systems from a security breach. Previous approaches formulate face anti-spoofing as a binary classification problem, and many of them struggle to generalize to different conditions(such as pose, lighting, expressions, camera sensors, and unknown spoof types). Moreover, those methods work as a black box and cannot provide interpretation or visualization to their decision. To address those challenges, we investigate face anti-spoofing in 3 stages: detection, generalization and visualization. In the detection stage, we learn a CNN-RNN model to estimate auxiliary tasks of face depth and rPPG signals estimation, which can bring additional knowledge for the spoof detection. In the generalization stage, we investigate the detection of unknown spoof attacks and propose a novel Deep Tree Network (DTN) to well represent the unknown spoof attacks. In the visualization stage, we find “spoof trace, the subtle image pattern in spoof faces (e.g., color distortion, 3D mask edge, and Moire pattern), is effective to explain why a spoof is a spoof. We provide a proper physical modeling of the spoof traces and design a generative model to disentangle the spoof traces from input faces. In addition, we also show that a proper physical modeling can benefit other face problems, such as face shadow detection and removal. A proper shadow modeling can not only detect the shadow region effectively, but also remove the shadow in a visually plausible manner.
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Title: THEORETICAL MODELING OF ULTRAFAST OPTICAL-FIELD INDUCED PHOTOELECTRON EMISSION FROM BIASED METAL SURFACES
Creator: Luo, Yi
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Laser-induced electron emission from nanostructures offers a platform to coherently control electron dynamics in ultrashort spatiotemporal scales, making it important to both fundamental research and a broad range of applications, such as to ultrafast electron microscopy, diffraction, attosecond electronics, strong-field nano-optics, tabletop particle accelerators, free electron lasers, and novel nanoscale vacuum devices. This thesis analytically studies nonlinear ultrafast photoelectron...
Show moreLaser-induced electron emission from nanostructures offers a platform to coherently control electron dynamics in ultrashort spatiotemporal scales, making it important to both fundamental research and a broad range of applications, such as to ultrafast electron microscopy, diffraction, attosecond electronics, strong-field nano-optics, tabletop particle accelerators, free electron lasers, and novel nanoscale vacuum devices. This thesis analytically studies nonlinear ultrafast photoelectron emission from biased metal surfaces, by solving the time-dependent Schrödinger equation exactly. Our study provides better understanding of the ultrafast control of electrons and offers useful guidance for the future design of ultrafast nanoelectronics. First, we present an analytical model for photoemission driven by two-color laser fields. We study the electron energy spectra and emission current modulation under various laser intensities, frequencies, and relative phase between the two lasers. We find strong modulation for both the energy spectra and emission current (with a modulation depth up to 99%) due to the interference effect of the two-color lasers. Using the same input parameter, our theoretical prediction for the photoemission current modulation depth (93.9%) is almost identical to the experimental measurement (94%). Next, to investigate the role of dc field, we construct an analytical model for two-color laser induced photoemission from dc biased metal surfaces. We systematically examine the combined effects of a dc electric field and two-color laser fields. We find the strong modulation in two-color photoemission persists even with a strong dc electric field. In addition, the dc field opens up more tunneling emission channels and thus increases the total emission current. Application of our model to time-resolved photoelectron spectroscopy is also demonstrated, showing the dynamics of the n-photon excited states depends strongly on the applied dc field. We then propose to utilize two lasers of the same frequency to achieve the interference modulation of photoemission by their relative phase. This is motivated by the easier access to single-frequency laser pairs than two-color lasers in experiments. We find a strong current modulation (> 90%) can be achieved with a moderate ratio of the laser fields (< 0.4) even under a strong dc bias. Our study demonstrates the capability of measuring the time-resolved photoelectron energy spectra using single-frequency laser pairs. We further extend our exact analytic model to photoelectron emission induced by few-cycle laser pulses. The single formulation is valid from photon-driven electron emission in low intensity optical fields to field-driven emission in high intensity optical fields, and is valid for arbitrary pulse length from sub-cycle to CW excitation, and for arbitrary pulse repetition rate. We find the emitted charge per pulse oscillatorily increases with pulse repetition rate, due to varying coherent interaction of neighboring laser pulses. For a well-separated single pulse, our results recover the experimentally observed vanishing carrier-envelope phase sensitivity in the optical-field regime. We also find that applying a large dc field to the photoemitter is able to greatly enhance the photoemission current and in the meantime substantially shorten the current pulse. Finally, we construct analytical models for nonlinear photoelectron emission in a nanoscale metal-vacuum-metal gap. Our results reveal the energy redistribution of photoelectrons across the two interfaces between the gap and the metals. Additionally, we find that decreasing the gap distance tends to extend the multiphoton regime to higher laser intensity. The effect of dc bias is also studied in detail.
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Title: AN INTEGRATED OF CONTROL AND PROTECTION SCHEME FOR AC MICROGRIDS
Creator: AlZahrani, Saad Atitullah
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Numerous advances have occurred in the area of microgrids (MGs) in the last two decades. Protection is one of the most significant challenges facing the deployment of MGs. With the utilization of renewable energy resources (RES) to reduce emissions and costs, short circuit levels have drooped in comparison to those produced by conventional generating sources. Therefore, traditional protection schemes that apply to distribution system are no longer effective in protecting the microgrid against...
Show moreNumerous advances have occurred in the area of microgrids (MGs) in the last two decades. Protection is one of the most significant challenges facing the deployment of MGs. With the utilization of renewable energy resources (RES) to reduce emissions and costs, short circuit levels have drooped in comparison to those produced by conventional generating sources. Therefore, traditional protection schemes that apply to distribution system are no longer effective in protecting the microgrid against fault currents, either in grid–connected or islanded mode. In microgrid framework, distributed generation (DG) based RES require an interface of power electronic converters to regulate their output voltage, current, and frequency as well as to share the generated power properly. Mitigation the impacts of fault currents in microgrid system is an important aspect of restricting the output current of converters from exceeding their rated value, preventing power discontinuity, enhancing reliability of protection system and improving the stability of the network.For microgrid control and protection challenges, several approaches have been proposed in the last decade. However, the need for efficient and reliable protection schemes of islanded microgrid system still exists. This research thesis develops and synthesizes an adaptive integration of control and protection framework for MGs. The proposed strategy is based on detecting the faults and limiting the fault currents for short periods until the protection devices make a proper decision. A single state observer has been developed to detect the faults that occur within protection zones. Moreover, fault current limiter (FCL) devices have been utilized to achieve rapid switching with instant reduction of fault current contribution. The adaptive integrated protection proposed in this research is achievable using either centralized or decentralized control in MGs. The proposed framework has been applied to islanded microgrid configuration and is demonstrated to be an effective means to protect the system and maintain the voltage and frequency within acceptable range with the capability of power continuity during both transient and persistent faults.
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Title: Insurgent Stratego : How Rebels Influence the Public During Civil Conflict
Creator: Lucas, Caleb
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Rebel groups rely on civilians to achieve victory in civil conflict. The public's attitudes determine their ability to realize key aims, such as extracting vital information, coercing support, and mobilizing new fighters. However, numerous strategic considerations encourage rebels to use violence against civilians. More so, rebel groups also face battlefield losses and political setbacks that can damage their reputation among non-combatants. I explore how rebels navigate the tension that...
Show moreRebel groups rely on civilians to achieve victory in civil conflict. The public's attitudes determine their ability to realize key aims, such as extracting vital information, coercing support, and mobilizing new fighters. However, numerous strategic considerations encourage rebels to use violence against civilians. More so, rebel groups also face battlefield losses and political setbacks that can damage their reputation among non-combatants. I explore how rebels navigate the tension that results from these dynamics in this dissertation. Overall, I argue that rebels influence the public's attitudes using intentional messaging and violence. My theory suggests rebel media can effectively shape how the public perceives an organization and be used to distract from bad behavior or losses to the government. It can also justify and contextualize attacks that might otherwise be considered offensive. However, I argue that tactical considerations still restrain rebel behavior and that they generally attempt to conduct violence when the payoffs are high and the costs are relatively low. I argue in the first empirical chapter that civilians partly rely on rebel propaganda to inform their beliefs about a conflict. This is because credible information about a conflict's warring parties and their attributes is difficult for civilians to obtain, as misinformation, rumors, and selective news coverage are common in civil conflicts. Rebels understand this and provide ostensible evidence that indicates their organization is strong relative to the government in their media outlets. I expect civilians to update their beliefs partly based on this information due to their information disadvantage. I estimate a difference-in-differences model that exploits the sudden introduction of a rebel group's radio station between two representative survey waves and demonstrate that exposure to rebel media can increase perceptions of a group's strength. I explore the functional use of propaganda in the second empirical chapter. Specifically, I argue that rebels use media to distract their supporters from tactical setbacks and to refute narratives of the conflict that are unfavorable to them. By deploying messaging approximate to events that could cause reputational harm, rebels attempt to reshape public perceptions of their organization. Consistent with this, I show that rebel groups in Syria respond to battlefield losses by publishing more propaganda. Additionally, I demonstrate through two case studies that rebels provide evidence of military strength while losing territory to the government and information about their governance activities when targeting civilians. The third empirical chapter examines the logic that rebel groups employ when deciding whether to conduct violence. I specifically examine the use of terrorism during religious holidays. I argue multiple incentives exist that encourage violence on these days. For example, attacks on holy days allow terrorists to signal their religiosity and impose extra terror on their targets. Rebels can decrease possible blowback from their own supporters for violating these days by framing their violence as divinely inspired in official propaganda. Governments understand these days are triggers for violence though and increase security surrounding them. However, their ability to do this is limited by the length of the holiday due to resource constraints and practical concerns. I demonstrate that the probability of an attack occurring on holidays that last a few days or less is lower than on non-holidays and provide evidence this is because state security is at its peak. I also show that holidays that last weeks have a higher likelihood of witnessing a terror attack than non-holidays, which I argue is because they are more difficult to protect and still provide payoffs to terror groups. This dissertation consequently broadly investigates how rebel groups attempt to influence the public during civil conflict through both propaganda and violence. I argue throughout that rebels are calculating actors that seek to maximize their ability to use violence while minimizing possible sanctions for that behavior. In doing so, I demonstrate propaganda meaningfully affects civilian attitudes. More so, I provide evidence that rebels understand the benefits of propaganda and attempt to use it to their advantage. However, I also show that tactical choices made by the government can limit the behavior of rebel groups, influencing their ability to benefit from propaganda.
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Title: Theoretical and Experimental Investigations of Arterial Pulse Wave Velocity (PWV)
Creator: Yavarimanesh, Mohammad
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Pulse transit time (PTT) is the time delay for the energy wave to travel between two sites in the arteries. (The energy wave can be visualized as acute dilation of the arterial wall and usually moves much faster than blood.) PTT in the form of pulse wave velocity (PWV = D/PTT, where D is the distance between the two sites) has proven to be a marker of arterial stiffness and a major cardiovascular risk factor based on a large body of epidemiological data. The Bramwell-Hill (BH) equation...
Show morePulse transit time (PTT) is the time delay for the energy wave to travel between two sites in the arteries. (The energy wave can be visualized as acute dilation of the arterial wall and usually moves much faster than blood.) PTT in the form of pulse wave velocity (PWV = D/PTT, where D is the distance between the two sites) has proven to be a marker of arterial stiffness and a major cardiovascular risk factor based on a large body of epidemiological data. The Bramwell-Hill (BH) equation relates arterial stiffness and radius to PWV. Arterial stiffness positively relates to blood pressure (BP); thus, many have pursued BP monitoring via PWV. We investigated PWV from theoretical, experimental, and application prospective.In the first theory study, we investigated the 100-year Bramwell-Hill equation, which relates PWV to BP and thus represents a basis for cuff-less BP monitoring. However, it has long been known that this equation underestimates PWV in a BP-dependent manner. We developed a new equation that accounts for spatial changes in arterial cross-sectional area. This new equation largely corrected this well-known underestimation and predicted PWV better based on experimental data in the literature. In the second experimental study, we examined the most popular PTT (finger PTT). We hypothesize that whole body PTT could be better than finger PTT due to less smooth muscle contraction. We collected data from 32 participants in a near supine position. We placed sensors including electrodes on the chest for an ECG waveform, clips on the ear, finger, and toe for photo-plethysmography (PPG) waveforms, and a cuff on the arm for auscultation BP. We recorded the waveforms and referenced BP before and after mental arithmetic, a cold pressor test, slow breathing, and nitroglycerin. Conventional PTTs were assessed as markers of BP in human subjects undergoing a battery of interventions to change BP. This experimental study concludes that PTTs through the whole body rather than the arm show the best BP change tracking ability. Thirdly, we repeated the previous study for seven subjects in three sessions one year apart to see how much PTTs and other PPG waveform feature models change after one year. While it is known that the PTTs calibration models must be updated periodically to account for aging effects, data on the time period required for these “cuff re-calibrations” are scant. Our experimental finding suggests that the PTTs model through the whole body could hold up after one year, and calibration may occur every year, which is reasonably practical. Finally, because of the inverse relation of PWV and arterial radius in the BH equation, we investigated innovative applications for PTT and other physiology-inspired features of carotid and femoral waveform for screening and surveillance of aortic abdominal aneurysm diameter. We hypothesized that arterial waveform features such as PTT constitute a non-imaging solution for the aneurysm size of the aorta. The features detected AAA with 72-80% accuracy. In conclusion, from a theoretical standpoint, we improved the 100-year PWV equation by relaxing its main assumption. From an experimental perspective, we showed the best body location for measuring PWV in the sense of BP prediction and robustness after one year. Lastly, we found that PWV could be used as markers of the abdominal aortic aneurysm from an application standpoint.
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Title: “This story was inside me this whole time, just waiting” : Coming to Blackgirl storying
Creator: Johnson, Lauren Elizabeth Reine
Date: 2021
Collection: Electronic Theses & Dissertations
Description: This dissertation project explores the various ways Blackgirls (Hill, 2016) from across a New Orleans came together in a collective space to engage in discussions of Blackgirlhood, wherein they shared and developed insights into their individual and collective understandings of self and community. Collective members’ multimodal storying, discussions, and reflections, are centered in this dissertation in response to an urgent need for more expansive presentations of Blackgirls. Informed by...
Show moreThis dissertation project explores the various ways Blackgirls (Hill, 2016) from across a New Orleans came together in a collective space to engage in discussions of Blackgirlhood, wherein they shared and developed insights into their individual and collective understandings of self and community. Collective members’ multimodal storying, discussions, and reflections, are centered in this dissertation in response to an urgent need for more expansive presentations of Blackgirls. Informed by theories, methodologies, and pedagogies, including: Black feminisms and Black Girlhood Studies (e.g., Collins, 2000; Dillard, 2016; Hill, 2016; hooks, 1996; Owens et al., 2017), Indigenous storywork (Archibald, 2008), sociocultural perspectives of literacies (e.g., Street, 1984), and culturally responsive/sustaining humanizing pedagogies (e.g., Ladson-Billings, 1995; Paris & Alim, 2017; Paris & Winn, 2014), this study also builds with the works and examples as put forth by other Blackgirls and Black women, such as Toni Cade Bambara’s (1996) “The Education of a Storyteller” to inquire into how centering Blackgirls and their narratives may move us towards what I conceptualize as “Blackgirl storying,” a medium that we used to critically name and honor our lives and the plurality of Blackgirlhood.
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Title: USING FRAGARIA AS A MODEL SYSTEM FOR THE STUDY OF SUBGENOME DOMINANCE AND ADAPTATION IN CROPS
Creator: Alger, Elizabeth
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Polyploidy, or the presence of three or more complete genomes in a single organism, has occurred frequently in plants, especially in the angiosperm lineage. Allopolyploids, or polyploids resulting from the merging of different genomes in an interspecific hybrid, have often been shown to experience subgenome dominance. Subgenome dominance is the phenomenon where there is bias in the gene loss and expression between the different genomes in a polyploid, known as subgenomes. Despite the...
Show morePolyploidy, or the presence of three or more complete genomes in a single organism, has occurred frequently in plants, especially in the angiosperm lineage. Allopolyploids, or polyploids resulting from the merging of different genomes in an interspecific hybrid, have often been shown to experience subgenome dominance. Subgenome dominance is the phenomenon where there is bias in the gene loss and expression between the different genomes in a polyploid, known as subgenomes. Despite the prevalence of polyploids and subgenome dominance, little is known about the factors and mechanisms that influence this process. Strawberry (Fragaria sp.) is emerging as a powerful model system to investigate polyploid subgenome dominance evolution due to the recent identification of the four extant diploid progenitor species of the cultivated octoploid strawberry (Fragaria x ananassa). Having the diploid progenitors in hand allows us to identify differences between the dominant subgenome, F. vesca, and the other three progenitors that may have an impact of subgenome dominance. One possible factor is transposable element (TE) abundance, as low TE density has been consistently associated with the dominant subgenome in allopolyploids. Epigenetic silencing of TEs by DNA methylation to suppress TE activity has been shown to result in decreased expression of neighboring genes and this lowered gene expression may affect the establishment of subgenome dominance. F. vesca will be used as a diploid model for the study of subgenome dominance in strawberry where I can examine how TE abundance and other factors influence gene expression in a single accession and in hybrid crosses between different accessions. Tracking changes in gene expression in the hybrids will allow us to examine how genomes with difference sizes and genomic factors interact. The results and insights observed from this study can then be applied to subgenome dominance research in octoploid strawberry. In addition to the germplasm and genomic resources, strawberries are also a high value crop and the loss of their production due to (a)biotic stressors results in the loss of millions of United States dollars annually. Using a population of octoploid strawberries segregating for salt tolerance, I will identify candidate genes related to salt tolerance. Together this work will identify factors and mechanisms related to subgenome dominance and use genotypic data in a practical breeding context.
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Title: INVESTIGATING UGANDA’S HIGH HIV INCIDENCE AMONG YOUNG WOMEN IN AN ERA OF WIDESPREAD GAINS IN HIV PREVENTION AND TREATMENT
Creator: Namanya, Judith
Date: 2021
Collection: Electronic Theses & Dissertations
Description: This dissertation examines the factors driving risky sexual behavior associated with reported high numbers of new HIV infections among young women in Uganda, using Mbarara District as a case study. Using the modified Social Ecological Model for Young Women’s Vulnerability to HIV Infection, the study investigates the contextual and broader structural factors, their interactions within and across multiple levels, and how they influence the sexual behaviors of individual young women in ways that...
Show moreThis dissertation examines the factors driving risky sexual behavior associated with reported high numbers of new HIV infections among young women in Uganda, using Mbarara District as a case study. Using the modified Social Ecological Model for Young Women’s Vulnerability to HIV Infection, the study investigates the contextual and broader structural factors, their interactions within and across multiple levels, and how they influence the sexual behaviors of individual young women in ways that increase their vulnerability to contracting HIV. The objectives of the study are: 1) Evaluate individual-level factors associated with sexual risk-taking behavior, specifically having unprotected sex, among young women ages 15-35 years; 2) Describe contextual and broader structural factors that make young women vulnerable to HIV-related risky sexual behaviors, and assess how these contextual factors interact with individual-level factors in ways that perpetuate high levels of HIV infection; and 3) Re-examine the connection between poverty and other economic factors to risky sexual behavior and vulnerability in the context of high HIV transmission among young women. The study used mixed qualitative and quantitative methods, combining household surveys, focus group discussions, key informant interviews, and in-depth interviews. Household survey results show that risky sexual behavior i.e., having sex without a condom, is still high (over 48%) among the unmarried young women ages 15-35 years. Engagement in unprotected sex increased by age, with young adults reporting more unprotected sex encounters than adolescent girls. Those with primary or some secondary education were at an increased risk of having unprotected sex. Surprisingly, women with tertiary education were at higher risk of engaging in unprotected sex than those who had completed secondary education. Negative binomial regression analyses show that women with no employment and those with part-time employment were at an increased risk for unprotected sex compared to those with low paying but stable employment. These findings on education and HIV risk call for a careful reexamination of the link between higher education and HIV vulnerability to inform policy. Education policies and interventions need to focus on curricula that incorporate entrepreneurial skills at different educational levels from primary to college. Keeping girls in school under the protective eye of parents, guardians and teachers is key in reducing exposure to unprotected sex among young girls. Findings from the qualitative analysis revealed that sociocultural and structural factors, including social norms (premarital sex as taboo, early marriage pressures, subornation of girls and women), youth unfriendly HIV services (e.g., long waiting times, rude and unprofessional clinic staff), high unemployment rates, sexual harassment, exploitation by male employers, and discrimination were key factors perceived to drive risky sexual behavior in relation to HIV contraction among young women. The findings show that while many young women, especially those with children, engaged in risky transactional sexual behavior to meet basic needs, many younger women, including college-level ones, did so to meet materialistic wants and to fit-in with peers. Widespread availability of antiretroviral drugs (ARVs) caused complacency among young people. HIV was no longer perceived as life threatening due to ARVs, which prevent progression into full-blown AIDS, morbidity and death. In fact, some young women were more scared of getting pregnant than contracting HIV. We suggest that efforts to reduce new HIV infections among young women and young men should target individual risk perception, and balance HIV treatment and prevention messages. Findings reveal a complex mix of dynamic and interacting factors operating at different levels that create context specific sexual behavioral risk socioscapes that sustain or accentuate the high rates of new HIV infections among the young women. Using a Social Ecological Model for Young Women’s Vulnerability to HIV as a guiding framework, we contend that efforts for addressing the high HIV infections among young women, including sexual behavioral change interventions, economic empowerment programs, should not only aim at individual women but also target factors operating at the sociocultural and structural levels.
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