Search results

Title: EXPLORING THE REGULATORY MECHANISMS BEHIND CHLOROPLAST POPULATION MORPHOLOGY
Creator: Tallerday, Emily Jennings
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Eukaryotic cells tightly regulate their populations of endosymbiotically-derived organelles. Organelle populations can be described in terms of size, number, or coverage, the latter being the collective planar area taken up by the organellar population relative to that of the cell. As the photosynthetic organelle, chloroplasts are vital, and alterations to chloroplast population morphology can affect photosynthetic performance and biomass accumulation. However, how the cell perceives and...
Show moreEukaryotic cells tightly regulate their populations of endosymbiotically-derived organelles. Organelle populations can be described in terms of size, number, or coverage, the latter being the collective planar area taken up by the organellar population relative to that of the cell. As the photosynthetic organelle, chloroplasts are vital, and alterations to chloroplast population morphology can affect photosynthetic performance and biomass accumulation. However, how the cell perceives and regulates its chloroplast population remains a mystery. Division at the mid-plastid (binary fission) is the primary mechanism by which chloroplasts increase their population sizes. It has been well established that lower division rates result in a small population of enlarged chloroplasts, suggesting the existence of a compensatory mechanism ensuring that total chloroplast coverage within the cell is preserved through a tradeoff between chloroplast division and expansion. Most model plants keep a relatively large number of chloroplasts in their leaf cells (>50 per cell). In expanding leaf cells, multiple rounds of chloroplast division typically increase the number of chloroplasts per cell. However, a number of natural adaptive alterations to chloroplast morphology have been observed in several tropical plant species, primarily those native to low-light environments. The tropical plant genus Peperomia (Piperaceae) offers a unique opportunity for understanding the regulation of chloroplast population morphology, as some Peperomia spp. contain two to six giant chloroplasts in their palisade mesophyll cells at maturity, while most others have higher numbers of small chloroplasts in their mesophyll cells. I have characterized chloroplast population morphology in Peperomia, of which six species had not been studied previously, and shown that chloroplast division is inhibited in the palisade cells of Peperomia pellucida. Further, I have assembled and annotated the genome of Peperomia dahlstedtii, the first genome for this genus, and produced a novel transcriptome assembly for P. pellucida. Lastly, I have analyzed gene expression in these two species differing in palisade cell chloroplast population morphology and identified several candidate genes potentially underlying the differences in phenotype. For the first time, I also have described the expression of the chloroplast division genes in these two species. By characterizing variation in chloroplast population morphology in Peperomia, my work builds upon existing research on this trait over leaf development, provides the resources necessary for Peperomia to be used as a model, and identifies potential causes behind the large-chloroplast phenotype documented in several species.
Show less

Title: Red Cedar review. Volume 57 (2022) Page 80
Date: 2022
Collection: Red Cedar Review

Title: Red Cedar review. Volume 57 (2022) Page 119
Date: 2022
Collection: Red Cedar Review

Title: Red Cedar review. Volume 57 (2022) Page 50
Date: 2022
Collection: Red Cedar Review

Title: Red Cedar review. Volume 57 (2022) Page 10
Date: 2022
Collection: Red Cedar Review

Title: Red Cedar review. Volume 57 (2022) Page 37
Date: 2022
Collection: Red Cedar Review

Title: Red Cedar review. Volume 57 (2022) Page 120
Date: 2022
Collection: Red Cedar Review

Title: SOCIAL DETERMINANTS OF BREASTFEEDING : THE ROLE OF PRENATAL FOOD INSECURITY
Creator: Robinson, Chelsea
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Background: Relatively little work has quantified associations between prenatal food insecurity and breastfeeding practices; however, understanding the implications of prenatal food insecurity may support food insecurity screening recommendations during prenatal care. Therefore, the purpose of this study was to investigate associations between prenatal food insecurity and breastfeeding initiation and duration until 3 months postpartum. Method: This study utilized data from a prospective...
Show moreBackground: Relatively little work has quantified associations between prenatal food insecurity and breastfeeding practices; however, understanding the implications of prenatal food insecurity may support food insecurity screening recommendations during prenatal care. Therefore, the purpose of this study was to investigate associations between prenatal food insecurity and breastfeeding initiation and duration until 3 months postpartum. Method: This study utilized data from a prospective Michigan pregnancy cohort. Women were recruited during their first prenatal visit with planned follow-up through early childhood. Prenatal food insecurity was assessed during pregnancy, and breastfeeding initiation and duration were assessed at the 3-month postpartum visit. Multiple logistic regression models were used to evaluate associations between prenatal food insecurity and the two primary outcomes: breastfeeding initiation and breastfeeding status at 3-months postpartum. Cox proportional hazard ratios were used to assess differences in the risk of breastfeeding cessation until 3 months postpartum by food insecurity status. An adversity index was created to stratify women into higher- and lower-risk groups for not breastfeeding. Associations between food insecurity and breastfeeding at 3 months postpartum (yes/no) were assessed via Fisher’s Exact test within each group. Results: In the unadjusted models, women who reported food insecurity during pregnancy were less likely to initiate breastfeeding (OR = 0.39; 95% CI: 0.21-0.69) and continue breastfeeding until 3 months postpartum (OR = 0.35; 95% CI: 0.20-0.61) compared to food secure women, but the associations were no longer significant after adjustment for sociodemographic and health-related factors. Prenatal food insecurity was not associated with breastfeeding at 3 months postpartum in analyses stratified into high- and low-adversity groups. Conclusions: Prenatal food insecurity is a strong predictor of breastfeeding practices. Though not significantly associated with breastfeeding practices after adjustment, screening for prenatal food insecurity may help clinicians identify women who may need more supports to initiate and maintain breastfeeding.
Show less

Title: MIGRANT FARM WORK, COLLEGE, AND MONEY : A PARTICIPATORY ACTION RESEARCH STUDY WITH MIGRANT FARMWORKING COLLEGE STUDENTS
Creator: Flores, Amanda
Date: 2022
Collection: Electronic Theses & Dissertations
Description: College is the first time students have the opportunity to make independent financial decisions and employ financial practices. Research suggests that students pick up financial knowledge, habits, and practices from family, friends, and their broader community and that these practices can have long-term implications. Migrant farmworking college students are a small subset of college students who come from highly mobile families and whose source of income is dependent on agricultural seasons....
Show moreCollege is the first time students have the opportunity to make independent financial decisions and employ financial practices. Research suggests that students pick up financial knowledge, habits, and practices from family, friends, and their broader community and that these practices can have long-term implications. Migrant farmworking college students are a small subset of college students who come from highly mobile families and whose source of income is dependent on agricultural seasons. The migratory lifestyle influences how migrant farmworking families employ financial practices, which likely shapes how children in migrant farmworking families think about their finances and what kinds of financial practices they use. This study explores how the familial and cultural upbringing of migrant farmworking families influences the financial practices of migrant farmworking college students. Grounded in participatory action research methodology, I draw on funds of knowledge and consejos to elevate familial and cultural influences on the financial practices of 5 migrant farmworking college students. Ultimately, this study seeks to provide recommendations for advisors and other student-facing professionals to help meet the diverse needs of this distinct population of marginalized students.
Show less

Title: ENGINEERING STUDIES IN ADVANCED PLA MATERIALS – STEREOCHEMISTRY, STEREOCOMPLEXATION, AND THERMAL RECYCLING OF PLA
Creator: Alhaj, Mohammed A.
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Polylactide (PLA) polymers are the world’s foremost 100% biobased resin with both composting and recycling end-of-life options in harmony with Ellen MacArthur Foundation “Circularity Model.” It is commercially manufactured by converting lactic acid to lactide, which is then polymerized to PLA. These molecules present unique and intriguing stereochemistry that dictate manufacturing, performance properties, and processability. However, it is seldom discussed and not well understood in the role...
Show morePolylactide (PLA) polymers are the world’s foremost 100% biobased resin with both composting and recycling end-of-life options in harmony with Ellen MacArthur Foundation “Circularity Model.” It is commercially manufactured by converting lactic acid to lactide, which is then polymerized to PLA. These molecules present unique and intriguing stereochemistry that dictate manufacturing, performance properties, and processability. However, it is seldom discussed and not well understood in the role stereochemistry can play and impact product performance and use. In the current work, we critically review and discuss the stereochemical implications for PLA through studies on different PLA compositions.To-date, it is unclear the origin of D-content present in commercial grade PLA, although it is assumed to originate from D-lactide. In this work, we validate that manufacture of lactide monomer from (L)- lactic acid predominantly results in a mixture of L and meso (DL), not L- and D- lactide. Optical rotation and 1H NMR studies are used to elucidate this stereochemistry. Copolymers of L-lactide and meso-lactide and copolymers of L-lactide and D-lactide are synthesized via bulk polymerization at various compositions. The optical rotation, tacticity, crystallinity, and thermal properties of synthesized copolymers are characterized. The optical rotation of poly(meso-lactide) has also been reported for the first time in this text. Differential scanning calorimetry (DSC) and 1H NMR studies confirm that PLA transitions from a predominantly isotactic, semi-crystalline polymer to a predominantly atactic, amorphous polymer when one copolymerizes greater than 10% meso-lactide with L-lactide. The stereochemical composition, mechanical and rheological properties of commercial grade PLA are measured to elucidate the effect of stereochemistry on the tensile and rheological behavior of PLA. We conclude this section with studies on PLA stereochemistry and its influence on immune cellular response. Hydrolytic degradation of semi-crystalline and amorphous PLA is analyzed via molecular weight characterization and lactic acid abundance. Semi-crystalline and amorphous PLA are then studied as potential carriers for glycolytic inhibitors. The stereochemistry of PLA and its implication on performance properties are further explored in studies on stereocomplex PLA. A pilot-scale continuous manufacturing process of stereocomplex PLA is developed and optimized by melt-blending a 1:1 blend of high molecular weight poly(L-lactide) (PLLA) and high molecular weight poly(D-lactide) (PDLA) in a co-rotating twin screw extruder. Stereocomplexation is first characterized via DSC at different temperatures and times. The optimal reaction temperature and reaction time are found and used to process >95% stereocomplex PLA conversion (melting peak temperature Tpm = 240°C). Stereocomplex PLA is used as an additive to produce 70% PLLA/30% stereocomplex PLA composites. The crystallinity, thermal properties, and tensile properties of composites are then characterized. A study on stereocomplex PLA and its effect on the crystallization kinetics of PLLA is conducted. 5% stereocomplex PLA is blended with 95% PLLA to analyze its use as a nucleating agent. The final section discusses a pilot-scale end-of-life method for PLA via thermal recycling. This study continues previous studies on PLA thermodepolymerization by scaling up the reversible reaction in a pilot-scale batch reactor. PLA is run at various temperatures and times to elucidate the processing conditions that yield the highest lactide conversion. The chemical purity, optical purity, lactide yield and stereoisomeric composition of the final lactide product are characterized by DSC, optical rotation, mass balance, and 1H NMR, respectively.
Show less

Title: PLANNING FOR AUTONOMY AND ELECTRIFICATION IN FUTURE TRANSPORTATION SYSTEMS
Creator: Singh, Harprinderjot
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Autonomous vehicles (AVs) and electric vehicles (EVs) will improve safety, mobility, roadway capacity and provide efficient driving, efficient use of travel time, and reduced emissions. However, these technologies affect vehicle miles traveled (VMT), travel time, ownership cost, and electric grid network. Shared mobility systems can ameliorate the high price of these technologies. However, the shared mobility system poses additional problems such as users’ waiting time, inconvenience, and...
Show moreAutonomous vehicles (AVs) and electric vehicles (EVs) will improve safety, mobility, roadway capacity and provide efficient driving, efficient use of travel time, and reduced emissions. However, these technologies affect vehicle miles traveled (VMT), travel time, ownership cost, and electric grid network. Shared mobility systems can ameliorate the high price of these technologies. However, the shared mobility system poses additional problems such as users’ waiting time, inconvenience, and increased VMT. Further, the impact of these emerging technologies varies on different groups of users (different values of travel time (VOTT). Another hurdle to the adoption of EVs is the limited range and scarcity of charging infrastructure. A well-established network of charging infrastructure, especially the direct current fast chargers (DCFC), can alleviate this challenge. However, the widespread adoption of EVs and the growing network of DCFC stations will increase the electric energy demand affecting the electric grid stability, demand-supply imbalance, overloading, and degradation of the electric grid components. Distributed energy resources (DER) such as solar panels and energy storage systems (ESS) can support the EV demand and reduce the load on the electric grid. This study develops modeling frameworks for the optimal adoption of AVs and EVs, considering their effect on transportation systems, the environment, and the electric grid network. Further, it suggests different scenarios that would promote the adoption of these technologies and provide a sustainable and resilient system.This study proposes a multi-objective mathematical model to estimate the optimal fleet configuration in a system of private manual-driven vehicles (PMVs), private AVs (PAVs), and shared AVs (SAVs) while minimizing the purchase and operating costs, time (travel and waiting time), and emission production. SAVs can be the optimal solution with the efficient use of travel time or the purchase price below a certain relative threshold. PAVs can be the optimal solution only if the onboard amenities are improved, lifetime mileage is increased, AV technology is installed in luxurious cars, and adopted by people with high VOTT. The framework is extended to consider different combinations of EVs, AVs, and conventional human-driven vehicles in a private and shared mobility system. The metaheuristics based on genetic and simulated annealing algorithms are developed to solve the large-scale NP-hard nonlinear optimization problem. The model is implemented for the network of Ann Arbor, Michigan. The results suggest that EVs are optimal for the system due to low operating costs and zero tailpipe emissions. Shared autonomous electric vehicles (SAEVs) are the best option for users with low VOTT. Private autonomous electric vehicles (PAEVs) would favor the system if the travel time savings are at least 20% or the price of AV technology is less than one-third of the vehicle price. The study then investigates the optimum investment technology to support the rising energy demand at the DCFC stations and reduce the load on the electric grid network. The different investments include purchasing and installing various ESS (new batteries (NB), second-life batteries (SLB), flywheels), solar panels, electric grid upgrades, and the cost of buying/selling electricity from/to the electric grid. The model is implemented for the DCFC stations supporting the future needs of EV charging demand for urban trips in the major cities of Michigan in 2030. The combination of SLBs and solar panels provides maximum benefits. The total annual and electricity savings are $25,000-$165,000 and $40,000-$300,000 per city.
Show less