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Title: Assessing the involvement of altered neurotensin signaling in anorexia nervosa
Creator: Schroeder, Laura Elizabeth
Date: 2018
Collection: Electronic Theses & Dissertations
Description: ABSTRACTAssessing the Involvement of Altered Neurotensin Signaling inAnorexia NervosaByLaura Elizabeth SchroederAnorexia Nervosa (AN), characterized by a persistent and detrimental drive tolose weight via restriction of food intake and excessive exercise, is the psychiatricdisorder with the highest mortality rate. Very few options exist when consideringpharmacotherapies used to treat AN patients, and no drugs have been demonstrated tosignificantly improve weight gain. This highlights the need...
Show moreABSTRACTAssessing the Involvement of Altered Neurotensin Signaling inAnorexia NervosaByLaura Elizabeth SchroederAnorexia Nervosa (AN), characterized by a persistent and detrimental drive tolose weight via restriction of food intake and excessive exercise, is the psychiatricdisorder with the highest mortality rate. Very few options exist when consideringpharmacotherapies used to treat AN patients, and no drugs have been demonstrated tosignificantly improve weight gain. This highlights the need to not only find better drugbasedtherapies for AN but to also find druggable targets for this disorder. While AN isthought to be highly heritable, with heritability estimates ranging between 50-80%, it hasbeen challenging to identify significant genetic contributors. Thus, determining thegenetic risk factors of AN will first be required for development of better therapeutics.In an effort to better understand the genetic basis of AN, recent work has beenperformed to uncover rare genetic variants that confer high risk of disease development.Loss-of-function variants in Neurotensin (Nts) and Nts Receptor 1 (NtsR1) wereidentified in individuals with eating disorders. Nts is a neuropeptide known to regulateingestive and locomotor behavior. Nts modulates these behaviors centrally, and asubset of dopamine (DA) neurons with the ventral tegmental area (VTA) that coexpressNtsR1 are known to contribute to DA-mediated weight loss behaviors. Ablation of allNtsR1 VTA neurons was shown to promote excessive locomotor activity without asufficient increase in feeding, leading to low body weight. Finally, increased fiberdensities have been found within the lateral hypothalamic area (LHA) of individuals withAN, and the LHA is a region with a significant population of Nts neurons known tomodulate both feeding and activity. We therefore hypothesized that Nts populations infeeding centers, such as the LHA, receive altered input from structures associated withAN and that alterations and/or disruption of Nts signaling promotes AN-like behaviors.This hypothesis was explored via three different approaches. First, the locationand density of Nts populations within the brains of NtsCre; Floxed GFP mice weremapped, and this revealed the presence of Nts in regions implicated in regulation offeeding and AN. The next approach involved determining if disrupted Nts signalingincreases risk for development of AN-like behaviors. This was accomplished bycharacterizing NtsR1-deficient mice both at baseline and after exposure to anadolescent-stress model of AN. This study revealed that deficiency of NtsR1 is agenetic risk factor that, when interacting with risks of being female and exposure toadolescent stress, promotes aberrant feeding, excessive locomotor behaviors, andcompulsive anxiety behaviors analogous to those observed in AN. Finally, a rabiesvirus-based method was used to identify direct inputs to LHA Nts neurons, and thishighlighted the existence of afferents, and thus top-down control, from structuresimplicated in AN. In addition, densities of these inputs were determined in mousemodels of AN, and this demonstrated that afferent inputs to LHA Nts neurons areincreased from sites associated with AN.Altogether, the data presented in this thesis highlight the possible genetic andneurocircuitry alterations to the Nts-NtsR1 system that may promote and/or be the resultof development of AN. These data also indicate the need for future studies to betterunderstand the mechanism by which such alterations in Nts signaling promote thisdisease.
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Title: Mechanisms of southern grasshopper mouse (Onychomys torridus) muscle resistance to the paralytic and lethal toxins in Arizona bark scorpion (Centruroides sculpturatus) venom
Creator: Parigi, Abhijna A.
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Voltage-gated sodium ion channels (Nav¬¬¬¬¬¬) are transmembrane proteins responsible for initiating electrical signals in excitable cells. Because Nav channels play a crucial role in neuromuscular coordination, they are targeted by a diverse array of neurotoxins produced across the animal kingdom. Arizona bark scorpions (Centruroides sculpturatus) produce toxins that disrupt Nav channel function, causing pain, muscle paralysis and respiratory failure. Southern grasshopper mice (Onychomys...
Show moreVoltage-gated sodium ion channels (Nav¬¬¬¬¬¬) are transmembrane proteins responsible for initiating electrical signals in excitable cells. Because Nav channels play a crucial role in neuromuscular coordination, they are targeted by a diverse array of neurotoxins produced across the animal kingdom. Arizona bark scorpions (Centruroides sculpturatus) produce toxins that disrupt Nav channel function, causing pain, muscle paralysis and respiratory failure. Southern grasshopper mice (Onychomys torridus) hunt bark scorpions. In response to selection by scorpion venom, grasshopper mice have evolved physiological resistance to toxins that cause pain and death. Although previous work identified modifications in one grasshopper mouse Nav channel (Nav1.8) that provide resistance to venom pain, mechanisms underlying resistance to muscle paralysis remain unknown. In skeletal muscle, Nav1.4 channels regulate muscle contraction. Previous studies showed that toxins in C. elegans and C. vittatus venoms disrupt Nav1.4 gating mechanisms. Thus, I tested the hypothesis that C. sculpturatus venom contains toxins that target Nav1.4, and that grasshopper mice are resistant to the effects of these toxins via molecular changes to their Nav1.4. Using molecular and electrophysiological analyses, I compared the structural and functional properties of grasshopper mice Nav1.4 channels to those of house mice and rats (rodents that are both sensitive to scorpion venom) and found that grasshopper mice Nav1.4 has evolved reduced sensitivity to C. sculpturatus venom. Further, I identified amino acid changes in the grasshopper mice Nav1.4 protein that contribute to reduced toxin sensitivity. Finally, I show that the beta subunits (accessory proteins that modulate Nav1.4 channel gating kinetics) of grasshopper mice do not have species-specific effects on channel function in the presence or absence of venom. My results demonstrate that highly conserved proteins can be evolutionarily modified with minimal effects to their baseline functional properties.
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Title: " ... To do credit to my nation, wherever I go" : West Indian and Cape Verdean immigrants in Southeastern New England, 1890-1940
Creator: Edwards, Janelle Marlena
Date: 2018
Collection: Electronic Theses & Dissertations
Description: This work is a community study that centers the experiences of black immigrants as an overlapping diaspora in multi-ethnic and transnational African-American history. It argues that, through the operationalization of their familial networks, ethnic organizations, and neighborhood enclaves, black immigrants in New England depart from traditional histories of assimilation and acculturation. Though much scholarship has been dedicated to the politically charged organizations and black immigrant...
Show moreThis work is a community study that centers the experiences of black immigrants as an overlapping diaspora in multi-ethnic and transnational African-American history. It argues that, through the operationalization of their familial networks, ethnic organizations, and neighborhood enclaves, black immigrants in New England depart from traditional histories of assimilation and acculturation. Though much scholarship has been dedicated to the politically charged organizations and black immigrant participation in New York, this microhistory of Southeastern New England's port cities -- Providence and New Bedford--demonstrates the commonplace, quotidian lives of West Indians and Cape Verdeans as neighbors, friends, and relatives who experienced and adapted to their diaspora condition differently. While West Indians altered their community landscape and eventually assimilated into the African-American community, Cape Verdeans retained a Cape Verdean ethnic identity, bolstered by their transnational shipping fleet and the constant flow of people, goods, and ideas from the homeland.
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Title: Toward zero delay video streaming
Creator: Al-Qassab, Hothaifa Tariq
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Video streaming has been growing rapidly since the beginning of this century and it is expected to continue growing. With rapid growth of Internet traffic led by video traffic, the Internet busy hours on both mobile and fixed connection segments will double before the end of this decade. Meanwhile, transmission delay is a well-known problem in video streaming and it has been addressed by many prior works that demonstrated the feasibility of reducing packet delays over the Internet by...
Show moreVideo streaming has been growing rapidly since the beginning of this century and it is expected to continue growing. With rapid growth of Internet traffic led by video traffic, the Internet busy hours on both mobile and fixed connection segments will double before the end of this decade. Meanwhile, transmission delay is a well-known problem in video streaming and it has been addressed by many prior works that demonstrated the feasibility of reducing packet delays over the Internet by employing a variety of end-to-end techniques. This thesis consists of two parts that introduce new video streaming frameworks over the Internet and over connected-vehicle networks, respectively. Our objective in the first part of this thesis is to improve video streaming over the Internet. The emerging of new technology such as the HTTP-based Adaptive Streaming (HAS) approach has emerged as the dominant framework for video streaming mainly due to its simplicity, firewall friendliness, and ease of deployment. However, recent studies have shown that HAS solutions suffer from major shortcomings, including unfairness, significant bitrate oscillation under different conditions and significant delay. On the other hand, Quality-of-Service (QoS) based mechanisms, most notably multi-priority queue mechanisms such as DiffServ, can provide optimal video experience but at a major cost in complexity within the network. Our objective in this thesis is to design an efficient, low complexity and low delay video streaming framework.We call our proposed Internet streaming framework Erasable Packets within Internet Queues (EPIQ). Our proposed solution is based on a novel packetization of the video content in a way that exploits the inherent multi-priority nature of video. An important notion of our proposed framework is Partially Erasable Packet (PEP) that has two key attributes: (1) Each PEP packet carries multiple segments corresponding to multiple priority levels of the video content; and (2) High priority segments are placed next to the packet header while low-priority segments are placed toward the tail of the PEP packet. Furthermore, to evaluate our framework performance, we developed an analytical model for EPIQ that shows significant improvements when compared to the conventional and multi-priority queue video transmission models. Our proposed solution consists of a new Active Queue Management (AQM) that is similar to the RED algorithm. Under congestion, a best-effort AQM router can simply erase an arbitrary portion of a PEP packet starting from its tail where we denote this process as Partial Erasing (PE). To complement partial erasing in the AQM, a rate control protocol similar to TFRC is proposed to ensure fairness for video and non-video traffic. We demonstrate the viability of the proposed framework by simulating High Definition (HD) Video on Demand (VoD) streaming on the popular network simulator ns-2. Our results show that EPIQ provides improvements in video quality in terms of PSNR by at least 3dB over traditional video streaming formworks. In addition, packet loss ratio and delay jitter performance are comparable to the optimal video streaming mechanism that is offered by multi-priority systems such as DiffServ.The main objective of the second part of the thesis is to develop a vehicle active safety framework that utilizes video streaming and vehicle-to-vehicle (V2V) communication for driver warning. Most prior efforts for V2V safety applications have been limited to sharing vehicle status data between connected vehicles. On the other hand, video streaming has been mainly proposed for video contents sharing between vehicles or dashboard camera sharing.We propose a Cooperative Advanced Driver Assistance System (C-ADAS) where vehicles share visual information and fuse it with local visuals to improve the performance of driver assistance systems. In our proposed system, vehicles share detected objects (e.g., pedestrians, vehicles, cyclists, etc.) and important camera data using the DSRC technology. The vehicle receiving the data from an adjacent vehicle can then fuse the received visual data with its own camera views to create a much richer visual scene. The sharing of data is motivated by the fact that some critical visual views captured by one vehicle are not visible or captured by many other vehicles in the same environment. Sharing such data in real-time provides an invaluable new level of awareness that can significantly enhance a driver-assistance, connected vehicle, and/or autonomous vehicle’s safety-system. The experimental results showed that our proposed system performed as intended and was able to warn drivers ahead of time, and consequently, it could mitigate major accidents and safe lives.
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Title: Human in the loop : the role of individual and institutional behavior on predictive algorithms
Creator: Isaac, William
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Over the past decade, algorithmic decision systems (ADS)--applications of statistical or computational techniques designed to assist human-decision making processes--have moved from an obscure domain of statistics and computer science into the mainstream. The rapid decline in the cost of computer processing and ubiquity of digital data storage has created a dramatic rise in the adoption of ADS using applied machine learning algorithms, transforming various sectors of society from digital...
Show moreOver the past decade, algorithmic decision systems (ADS)--applications of statistical or computational techniques designed to assist human-decision making processes--have moved from an obscure domain of statistics and computer science into the mainstream. The rapid decline in the cost of computer processing and ubiquity of digital data storage has created a dramatic rise in the adoption of ADS using applied machine learning algorithms, transforming various sectors of society from digital advertising to political campaigns, risk modeling for the banking sector, healthcare and beyond. Many agencies and practitioners in the public sector turn to ADS as a means to stretch limited public resources amidst growing public demands for equity and accountability. However, recent research from multiple fields has found that social and institutional biases, often reflected by input data used to generate predictions. The potential of perpetuated discrimination via input data is a particular concern in fields such as criminal justice where historical biases against minorities have the potential to exacerbate existing racial inequalities. In a series of three essays, this dissertation seeks to outline how institutional norms often shape algorithmic predictions, examine how ADSs alter the incentive structures for agents using the tools, and ultimately its impact on human decision-making.
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Title: The effects of school choice on student achievement, school practices, and segregation : evidence from Seoul's School Choice Program
Creator: Kim, Young Ran (Graduate of Michigan State University)
Date: 2018
Collection: Electronic Theses & Dissertations
Description: This study seeks to understand how reforms driven by market principles, such as school choice, competition, and autonomy, affect student achievement, school administrative and curricular practices, and segregation by analyzing a school choice program in Seoul, South Korea (hereafter referred to as Korea). Korea provides a unique opportunity to examine the effects of market-based reforms because of a recent policy transition from strong governmental control to a universal school choice program...
Show moreThis study seeks to understand how reforms driven by market principles, such as school choice, competition, and autonomy, affect student achievement, school administrative and curricular practices, and segregation by analyzing a school choice program in Seoul, South Korea (hereafter referred to as Korea). Korea provides a unique opportunity to examine the effects of market-based reforms because of a recent policy transition from strong governmental control to a universal school choice program. In order to guarantee equal educational opportunities, the government adopted the Equalization Policy in 1974 to equalize many aspects of private and public schooling. Due to a high level of governmental control and limited school choice, market and educational consumers have exerted limited influence over the Korean education system. However, recently, the Seoul Local Education Authority (LEA) adopted a school choice program that significantly increased market influence by allowing school choice and by converting some of its high schools into autonomous schools that have greater flexibility in school curriculum and school operations.This study explores how these attempts have affected Seoul’s student achievement, school practices, and segregation. The effect of school choice on student achievement is identified using a comparative interrupted time series analysis (CITS) and Difference-in-Differences (DD) that rely on comparisons of test-score changes between Seoul and Incheon, a neighboring city that already had a school choice policy in place. Students’ scores in English and Korean on the College Scholastic Aptitude Test (CSAT) from 1994 to 2015 were utilized for these analyses. Study results indicate that the Seoul school choice policy has no significant effects on achievement in English and Korean.In addition, this study analyzes how market-based reforms affect school practices by examining how autonomous private high schools change their administrative and curricular practices when subjected to greater market influences. Specifically, this study uses seven-year panel data on school administration collected by the Korean Ministry of Education to examine the ways that autonomous private high schools changed their practices in expenditures, curriculum, and personnel. In order to isolate practice changes induced by the reform from those induced by other social and economic factors, we utilized a DD design that compares the changes within autonomous private high schools to the contemporaneous variation in traditional private high schools that are arguably less affected by the reform. This study found evidence suggesting that the reform significantly increased autonomous private schools’ per-pupil spending, expenditures for educational activities and after-school programs, and the number of after-school programs. In addition, results suggest that autonomous private schools allocated their instructional time away from social studies and toward Korean and math. Furthermore, this study found that autonomous private schools hired teachers with fewer years of teaching experience. Finally, this study explores how Seoul’ school choice policy affects student segregation by achievement and socioeconomic status across different types of schools and school districts. Results show that the policy significantly increased segregation across different types of schools without reducing segregation across districts.
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Title: Noradrenergic mechanisms of preclinical Alzheimer's disease
Creator: Kelly, Sarah Colette
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Noradrenergic locus coeruleus (LC) neuron loss is a feature of Alzheimer’s disease (AD). The LC is the primary source of norepinephrine (NE) in the forebrain, where it modulates attention and memory in vulnerable cognitive regions such as prefrontal cortex (PFC) and hippocampus. Furthermore, LC-mediated NE signaling is thought to play a role in blood-brain barrier (BBB) maintenance and neurovascular coupling, suggesting that LC degeneration may impact the high comorbidity of cerebrovascular...
Show moreNoradrenergic locus coeruleus (LC) neuron loss is a feature of Alzheimer’s disease (AD). The LC is the primary source of norepinephrine (NE) in the forebrain, where it modulates attention and memory in vulnerable cognitive regions such as prefrontal cortex (PFC) and hippocampus. Furthermore, LC-mediated NE signaling is thought to play a role in blood-brain barrier (BBB) maintenance and neurovascular coupling, suggesting that LC degeneration may impact the high comorbidity of cerebrovascular disease (CVD) and AD. However, the extent to which LC projection system degeneration occurs in the earliest stages of AD and the physiological consequences of this phenomenon is not fully characterized to date. To address these issues, we analyzed LC tissue samples from University of Kentucky AD Center (UKADC) subjects who died with a premortem diagnosis of no cognitive impairment (NCI) and Braak stages 0-II at autopsy, NCI subjects with Braak stages III-V thought to be in a preclinical AD (PCAD) stage, and subjects with mild cognitive impairment (MCI) or mild AD. Paraffin-embedded pontine tissue blocks containing the LC were cut at 20μm, immunostained with tyrosine hydroxylase (TH, a marker for NE synthesis), and analyzed to estimate total TH-positive LC neuron number. We measured a significant ~40-55% loss of LC neuron numbers in MCI and AD compared to NCI, whereas the mild ~25% LC neuron loss observed in PCAD did not reach significance. However, the topographical, rostrocaudal extent of LC cell loss in PCAD was significantly different from NCI and MCI. Moreover, LC cell loss correlated with premortem global cognition across the diagnostic groups. Studies were also performed to compare additional LC neuronal pathologies (phospho-tau and DNA/RNA oxidative damage markers) across the diagnostic groups. A significant ~15-30% increase in phospho-tau was observed in PCAD and MCI compared to NCI. DNA/RNA oxidative damage was significantly increased by ~25-40% in MCI and AD compared to NCI and PCAD. LC phospho-tau pathology correlated with Braak stage, whereas LC oxidative damage correlated with premortem global cognitive performance . Finally, while LC neuron number did not correlate with scores of global arteriosclerosis or microinfarcts, pontine arteriosclerosis severity was increased by two-fold in MCI and AD. To model the relationship between LC projection system degeneration and forebrain neuronal and vascular pathology in vivo, we stereotactically lesioned LC projection neurons innervating the PFC of the TgF344-19 rat model of AD (aged 6 months) using the noradrenergic immunotoxin, dopamine-β-hydroxylase IgG-saporin (DBH-sap), or an untargeted control IgG saporin (IgG-sap). DBH-sap lesioned animals performed significantly worse on the Barnes maze task and displayed increased amyloid and inflammatory pathology, as well as evidence for vessel remodeling and BBB leakage, compared to IgG-sap control animals. Taken together, these data compiled in my dissertation shed light on the multifactorial noradrenergic pathways contributing to neuronal and vascular pathologies during the onset of AD.
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Title: Essays in local public finance
Creator: Melnik, Walter Thomas
Date: 2018
Collection: Electronic Theses & Dissertations
Description: My dissertation studies how political factors, local labor demand shocks, and voting behavior affect state and local public goods provision. Following a brief introduction, I begin with “Legislative Redistricting, Party Politics, and the Spatial Distribution of Transportation Expenditure.” In this essay, I estimate how a state representative's political party affects road construction expenditure in areas that she represents. An extensive literature asks how a legislator's party affiliation...
Show moreMy dissertation studies how political factors, local labor demand shocks, and voting behavior affect state and local public goods provision. Following a brief introduction, I begin with “Legislative Redistricting, Party Politics, and the Spatial Distribution of Transportation Expenditure.” In this essay, I estimate how a state representative's political party affects road construction expenditure in areas that she represents. An extensive literature asks how a legislator's party affiliation affects public expenditure in the area the legislator represents. Unfortunately, almost all studies estimate this effect using party changes through election outcomes, which could be correlated with unobservable determinants of transportation expenditure. To overcome this issue, I identify my estimates using changes in party affiliation engendered by the 2012 state legislative redistricting in Ohio. In many cases, redistricting moved a geographic area into a district whose incumbent representative belonged to the opposing political party. This created variation in partisan alignment unrelated to election outcomes. From 2010-2017 the Republican party controlled the Ohio House of Representatives, the Ohio Senate, and the governorship. Using variation due to redistricting for identification, I find that areas moving from Republican to Democratic districts due to redistricting received $3.5 million (0.19 standard deviations) less annual highway construction funding than areas that remained in Republican districts. This funding decrease derives from a decline in the number of large construction projects in these areas. The estimated effects differ substantially when identified using variation through voting in non-redistricting years, perhaps due to selection issues concerning the type of districts changing parties through election outcomes. In addition, the expenditure change associated with a party change through election outcomes depends on whether the incumbent lost an election or retired, further evincing selection issues associated with this variation.In my next essay, “Municipal Government Reaction to Mass Layoffs in Ohio,” I study how municipal government finances respond to negative local employment shocks. Using data from 595 municipalities in Ohio, I estimate the change in municipal revenue after reported mass layoffs and plant closings, as well as the municipality's response: possible adjustments to tax rates, expenditure, and borrowing. I find that income tax revenue plummets in the year after a mass layoff, driven by a large decline in income tax base. Municipalities do not raise income or property tax rates to compensate for the income tax drop - rather, tax rates decline slightly. Property tax revenue also declines, while revenue from service charges and fees and intergovernmental revenue do not change significantly. Thus, total revenue drops substantially for several years after a mass layoff. In response, municipalities cut expenditure across several categories, including general government, public safety, leisure and community environment, and capital outlay. Cities also draw down their unreserved fund balance substantially, avoiding deeper cuts to expenditure by depleting their accumulated funds.In my last essay, “ Ballot Order and Ballot Roll-off: Evidence from Ohio,” coauthored with Mike Conlin and Paul Thompson, I study how an election item’s position on the ballot affects the probability that voters abstain from voting on that item (“roll-off”), and on the probability that voters choose to vote yes conditional on casting a ballot. Local tax referenda in Ohio rotate ballot position every year based on the level of local jurisdiction that placed the referendum on the ballot, providing a source of exogenous variation to test these propositions. Previous research suggests that voters are less likely to cast a vote for election items lower on the ballot, and more likely to choose the status quo. These findings support the idea of choice fatigue, suggesting that facing more decisions impairs voters’ decision making ability. Unlike previous papers, I am able to control for demographic characteristics (age and party affiliation) of voters who see each referendum. I find that voters tend to cast more yes votes for items lower on the ballot. I also find that older voters are much less likely, and partisan voters much more likely, to abstain from ballot items, showing the importance of controlling for these characteristics when estimating the effect of ballot position on roll-off.
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Title: Methodology towards accessing small molecule heterocycles for h20S and TB proteasome modulation
Creator: Bethel, Travis Kordero
Date: 2018
Collection: Electronic Theses & Dissertations
Description: "This dissertation focused on the development and advancement of methodology for accessing imidazoline scaffolds and other small heterocyclic molecules for biological evaluation. Past research within the Tepe group has correlated functionalized 2-imidazolines to proteasome modulation. Further diversification of the methodology for accessing these 2-imidazoline scaffolds, has allowed for the synthesis of a small library of analogs for SAR evaluation with the h20S proteasome. These finding were...
Show more"This dissertation focused on the development and advancement of methodology for accessing imidazoline scaffolds and other small heterocyclic molecules for biological evaluation. Past research within the Tepe group has correlated functionalized 2-imidazolines to proteasome modulation. Further diversification of the methodology for accessing these 2-imidazoline scaffolds, has allowed for the synthesis of a small library of analogs for SAR evaluation with the h20S proteasome. These finding were used to further experimentally model and synthesize more efficacious 2-imidazoline derivates for proteasome modulation. The proteasome is responsible for the degradation of polyubiquitinated proteins in the cell, producing amino acids that can then be used for alternative cellular functions. The introducition of small heterocyclic molecules like 2- imidazolines, bind to the proteasome and lower is efficacy for protein digestion through modulation of its activity."--Page ii.
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Title: Three Essays in the Economics of Education
Creator: Kho, Kevin
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Chapter 1: School Cellphone Bans and Student Substance Abuse: Evidence From California Public High SchoolsFollowing high profile school shootings and the September 11th terrorist attacks, public concern over school emergency preparedness prompted the California State Legislature in 2003 to overturn a statewide ban against student possession of cellphones on campuses. After the repeal of the prohibition, which had been established in 1988 to curb drug dealing, school districts were allowed...
Show moreChapter 1: School Cellphone Bans and Student Substance Abuse: Evidence From California Public High SchoolsFollowing high profile school shootings and the September 11th terrorist attacks, public concern over school emergency preparedness prompted the California State Legislature in 2003 to overturn a statewide ban against student possession of cellphones on campuses. After the repeal of the prohibition, which had been established in 1988 to curb drug dealing, school districts were allowed individually to either continue banning phones or modify their device policies; most opted over time to accommodate usage during certain hours of the day. Using fixed effects regression analysis clustered at the district level, I exploit variation in the timing of district policies to estimate the impact on substance abuse from lifting school cellphone bans. Results provide evidence that allowing students to use cellphones at school increases opportunities to obtain and abuse controlled substances; this effect is particularly pronounced in the incidence of marijuana smoking among 9th graders, who exhibit a 1.3 percentage point higher chance of reporting past-month marijuana use in the year a ban is lifted.Factors involved may include the capability that the technology provides to negotiate high risk interactions in private and to seek out and contact a relatively small number of drug suppliers; as is thus to be expected, no impact is found on the consumption of cigarettes, which can be obtained legally by a large proportion of high schoolers.Chapter 2: Impact of Internet Access on Student Learning in Peruvian Schools (with Leah Lakdawala and Eduardo Nakasone)We investigate the impacts of school-based internet access on pupil achievement in Peru, using a large panel of 5,903 public primary schools that gained internet connections during 2007-2014. We employ an event study approach and a trend break analysis that exploit variation in the timing of internet roll-out up to 5 years after installation. We find that internet access has a moderate, positive short-run impact on school-average standardized math scores, but importantly that this effect grows over time. We provide evidence that schools require time to adapt to internet access by hiring teachers with computer training and that this process is not immediate. These dynamics highlight the need for complementary investments to fully exploit new technological inputs and underscores the importance of using an extended evaluation window to allow the effects of school-based internet on learning to materialize.Chapter 3: Discretionary School Discipline Policies and Demographic DisparitiesIn 2014, California passed the law AB 420, becoming the first state to limit the use of school suspensions and expulsions as punishment for "willful defiance" - a subjectively determined offense thought by state lawmakers to lead to racial disparities in discipline. In this paper, I overview the state's recent (from 2012-2017) progress in reducing exclusionary discipline and note effects on disproportionality, here characterized as the difference between a given group's proportion of discipline and its proportion of enrollment. Using identification by treatment intensity, based on schools' pre AB 420 proportion of discipline attributable to willful defiance, I also attempt to gauge the effectiveness of reducing punishment of defiance in mitigating disproportionality. School level administrative data from elementary schools (spanning kindergarten through 5th grade) indicate that exclusionary discipline has considerably declined throughout the period. On the other hand, it does not appear that AB 420, along with lower willful defiance related discipline, has reduced disproportionality.
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Title: Constellating cultural rhetorics, first year writing, and service-learning : a story of teaching and learning
Creator: Prielipp, Sarah E.
Date: 2018
Collection: Electronic Theses & Dissertations
Description: This dissertation examines the relationships among cultural rhetorics theory and methods, first year writing, and service-learning by showing the ways these theories and pedagogies constellate, or build, new things from their intersections and relationality. The author argues that “story is theory is practice” and demonstrates how this can work in first year writing through a cultural rhetorics-informed service-learning pedagogy. The author explains that this story of teaching and learning –...
Show moreThis dissertation examines the relationships among cultural rhetorics theory and methods, first year writing, and service-learning by showing the ways these theories and pedagogies constellate, or build, new things from their intersections and relationality. The author argues that “story is theory is practice” and demonstrates how this can work in first year writing through a cultural rhetorics-informed service-learning pedagogy. The author explains that this story of teaching and learning – both hers and her students – builds theory through sharing their stories of practice in their writing classroom. This theory/story/practice shows us how relationality, accountability, and reciprocity help develop habits of mind that may transfer to other situations to become active, engaged citizens for social justice.Chapter one develops Wilson’s Indigenous research paradigm as a theoretical framework for the author’s teaching and research by explaining her research paradigm for this project and discussing the literature that she draws on throughout this project. Chapter two further explains how she defines and uses service-learning by providing two case studies from the FYW courses she taught at Michigan State University in the 2016-2017 academic year. Chapter three begins to constellate cultural rhetorics theory and methods, first year writing, and service-learning using Wilson’s Indigenous research paradigm as a framework. The “half” chapters are her students’ voices, their stories in their words; these student selections help to show how they are practicing habits of mind throughout the course in their writing.
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Title: Controlling the surface processes of X- and Z-type ligands to tailor the photophysics of II-VI semiconductor nanocrystals
Creator: Saniepay, Mersedeh
Date: 2018
Collection: Electronic Theses & Dissertations
Description: II−VI colloidal semiconductor nanocrystals (NCs), such as CdSe NCs, are often plagued by efficient nonradiative recombination processes that severely limit their use in energy-conversion schemes. While these processes are now well-known to occur at the surface, a full understanding of the exact nature of surface defects and of their role in deactivating the excited states of  NCs has yet to be established, which is partly due to challenges associated with the direct probing of the complex and...
Show moreII−VI colloidal semiconductor nanocrystals (NCs), such as CdSe NCs, are often plagued by efficient nonradiative recombination processes that severely limit their use in energy-conversion schemes. While these processes are now well-known to occur at the surface, a full understanding of the exact nature of surface defects and of their role in deactivating the excited states of  NCs has yet to be established, which is partly due to challenges associated with the direct probing of the complex and dynamic surface of colloidal NCs. In this dissertation, we report a detailed study of the surface of cadmium-rich zinc-blende CdSe NCs. The surfaces of these cadmium-richspecies are characterized by the presence of cadmium carboxylate complexes (CdX2) that act as Lewis acid (Z- type) ligands that passivate under-coordinated selenide surface species. The systematic displacement of CdX2 from the surface by N,N,N′,N′-tetramethylethylene-1,2-diamine (TMEDA) has been studied using a combination of 1H NMR and photoluminescence spectroscopies. We demonstrate the existence of two independent surface sites that differ strikingly in the binding affinity for CdX2 and that are under dynamic equilibrium with each other. A model involving coupled dual equilibria allows a full characterization of the thermodynamics of surface binding (free energy, as well as enthalpic and entropic terms), showing that entropic contributions are responsible for the difference between the two surface sites. Importantly, we demonstrate that cadmium vacancies only lead to important photoluminescence quenching when created on one of the two sites, allowing a complete picture of the surface composition to be drawn where each site is assigned to specific NC facet locale, with CdX2 binding affinity and nonradiative recombinationefficiencies that differ by up to two orders of magnitude.To understand the effect of steric hindrance and types of functional groups in different ligands on X-type ligand exchanges, using NMR, PL and UV-Vis absorption spectroscopy, we studied X-type exchanges on CdSe NCs capped with native carboxylates, with oleic acid, oleyl thiol, benzoic acid and benzenethiol ligands. We discussed the results and occurrence of undesired pathways including displacement of Z-type ligands, and suggested ligand exchange strategies that most likely lead to 100% X-type exchange.The structural complexity of surface of CdS NCs is also discussed in this dissertation. We demonstrate presence of two different sulfur surface defects on CdS NCs with ligand binding equilibrium constants that are two orders of magnitude apart and 20-60% smaller than those of selenium on similar size CdSe NCs. We also correlated the different surface defects to the PL quenching efficiency of CdS NCs.
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Title: A search for resonant Z' production in high-mass dielectron final states with the ATLAS detector in Run-2 of the Large Hadron Collider
Creator: Willis, Christopher G.
Date: 2018
Collection: Electronic Theses & Dissertations
Description: A search is performed for new resonant high-mass phenomena in the dielectron final state. The search uses 36.1 $\mathrm{fb}^{-1}$ of proton-proton collision data, collected at $\sqrt{s} = 13$ TeV by the ATLAS experiment at the Large Hadron Collider during its 2015 and 2016 data-taking runs. The dielectron invariant mass is used as the search variable. No significant deviations from the Standard Model prediction are observed. Upper limits at the 95\% credibility level are set on the cross...
Show moreA search is performed for new resonant high-mass phenomena in the dielectron final state. The search uses 36.1 $\mathrm{fb}^{-1}$ of proton-proton collision data, collected at $\sqrt{s} = 13$ TeV by the ATLAS experiment at the Large Hadron Collider during its 2015 and 2016 data-taking runs. The dielectron invariant mass is used as the search variable. No significant deviations from the Standard Model prediction are observed. Upper limits at the 95\% credibility level are set on the cross section times branching fraction to dielectron pairs for resonant $Z^{\prime}$ models considered in the search. Lower limits on the resonance pole mass are also presented. For the $Z^{\prime}_{\mathrm{SSM}}$, masses are excluded up to 4.5 TeV, while masses up to 4.1 TeV are excluded in the $E_{6}$-motivated $Z^{\prime}_{\chi}$ model. Limits are also derived in the Minimal $Z^{\prime}$ Model on the relative coupling strength $\gamma^{\prime}$. In addition, a series of studies are conducted in order to assess and reduce the dominant systematic uncertainty of this analysis, which arises from the imprecise knowledge of the Parton Distribution Functions in regions of very high parton $x$. While this uncertainty does not limit the discovery potential of the analysis presented here, it has the potential to do so in future searches. A novel approach is developed, and is shown to significantly reduce this systematic uncertainty in the high-mass search region of interest, thereby improving the discovery potential of future analyses.
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Title: "Flooding oil" : investigating poor health in vulnerable communities in the Niger Delta Region of Nigeria
Creator: Barry, Fatoumata Binta
Date: 2018
Collection: Electronic Theses & Dissertations
Description: The Niger Delta region in Nigeria has been exploited for decades due to extensive oil and gas deposits that have led to devastating livelihood and health consequences. In addition to oil and gas industry impacts, floods are intensifying in Niger Delta communities that have annual flooding during the rainy season (April to October). In 2012, Nigeria experienced a severe flooding event that damaged infrastructure and livelihoods with virtually no studies completed about the health consequences....
Show moreThe Niger Delta region in Nigeria has been exploited for decades due to extensive oil and gas deposits that have led to devastating livelihood and health consequences. In addition to oil and gas industry impacts, floods are intensifying in Niger Delta communities that have annual flooding during the rainy season (April to October). In 2012, Nigeria experienced a severe flooding event that damaged infrastructure and livelihoods with virtually no studies completed about the health consequences. This dissertation research study aims to fill this scholarly gap by disentangling the emerging health concerns in Niger Delta oil communities with particular attention to women and children as they are sensitive indicators of population health. It utilizes a mixed-methods approach with the inclusion of Eco-Syndemics and African womanism theoretical perspectives. It was found that the Niger Delta has multiple pre-existing vulnerabilities that put the population at more risk during flooding events. Also, through an evaluation of airborne concentrations of chemicals released by gas flares and a retrospective, cross-sectional comparison, women and children in Uzere (oil community) have greater exposure levels to toxic chemicals released and more health concerns than similar women and children in Aviara (non-oil community), even though both communities are located in flood-prone areas in the Niger Delta. Overall, this dissertation research advances our understanding of the complexity of health hazards in communities close to oil and gas activities in the midst of more severe flooding. It also enriches scholarly and policy debates by providing an initial assessment of the link between climate variability and health in vulnerable communities. -- Abstract.
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Title: The role of fetuin-A on adipose tissue lipid mobilization in dairy cows
Creator: Strieder-Barboza, Clarissa
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Adipose tissue (AT) is a major modulator of metabolic functions by regulating energy storage and acting as an endocrine organ. In periparturient dairy cows, increased AT mobilization of free fatty acids (FFA) is one a major adaptive mechanism to cope with higher energy demand for rapid fetal growth and the onset of lactation. As lactation progresses, lipolysis rates decrease, and lipogenesis replenishes triacylglycerol (TAG) stores in adipocytes. However, dysregulated metabolic responses,...
Show moreAdipose tissue (AT) is a major modulator of metabolic functions by regulating energy storage and acting as an endocrine organ. In periparturient dairy cows, increased AT mobilization of free fatty acids (FFA) is one a major adaptive mechanism to cope with higher energy demand for rapid fetal growth and the onset of lactation. As lactation progresses, lipolysis rates decrease, and lipogenesis replenishes triacylglycerol (TAG) stores in adipocytes. However, dysregulated metabolic responses, characterized by altered AT sensitivity to hormonal and endocrine changes around parturition, lead to a massive release of FFA into circulation and an increased susceptibility of cows to disease. These maladaptive responses are underlined by an altered secretory pattern of adipokines and a marked unbalance in lipolysis and lipogenesis rates, favoring TAG breakdown in adipocytes. Thus, identifying adipokines that modulate AT function in periparturient dairy cows can facilitate the development of novel management, nutritional, or pharmaceutical interventions to reduce disease incidence. Fetuin-A (FetA; alpha-2-Heremans-Schmid glycoprotein, AHSG) is an adipokine that functions as a carrier of FFA in plasma and is associated with insulin-mediated inhibition of lipolysis and stimulation of lipogenesis in humans. FetA increases the incorporation of fatty acids (FA) into intracellular lipids and enhances cellular TAG in human cells. However, the mechanisms by which FetA induces TAG synthesis are not defined. FetA has also anti-inflammatory properties by inhibiting the production of pro-inflammatory cytokines and acting as a negative acute-phase protein (APP) in acute inflammation. These findings suggest that FetA may also be involved in lipid mobilization and inflammation in AT of dairy cows. In our first in vivo study with periparturient dairy cows, we observed that serum and AT FetA expression decreased at the onset of lactation when lipogenesis was downregulated and plasma FFA was increased. FetA expression dynamics in AT were analogous to the patterns of lipogenic markers suggesting its link with lipid mobilization in AT of dairy cows. We also demonstrated that FetA is negative-APP locally in AT of dairy cows. These results suggest that FetA could support physiological adaptations to NEB in AT of periparturient dairy cows. To explore the potential roles of FetA on AT lipid mobilization of dairy cows, we developed an in vitro model for culturing bovine adipocytes that closely mimics the in vivo AT environment. For the first time, we reported an abundant expression and secretion of FetA by primary bovine adipocytes, thus suggesting a potential autocrine effect of FetA in AT of dairy cows. We observed that FetA attenuates lipolytic responses and enhances both, FA uptake and TAG accumulation in bovine adipocytes. Our results reveal that the upregulation of the expression and activity of 1-acylglycerol-3-phosphate acyltransferase (AGAPT2), a rate limiting lipogenic enzyme for TAG synthesis, may be a potential mechanism by which FetA enhances lipogenic function of bovine adipocytes. Overall, our results indicate that FetA is a lipogenic adipokine with anti-inflammatory function in the AT of dairy cows. Our findings provide evidence that FetA could buffer increased plasma FFA during negative energy balance by stimulating AGAPT2 activity and the use of excess FFA for TAG synthesis in AT of dairy cows. The genetic selection of cows by variations of the FetA coding gene associated with its anti-lipolytic and pro-lipogenic functions (already known in humans), the identification of dietary supplements (i.e. FA) that enhance FetA function, as well as the parenteral use of FetA to stimulate AGAPT2 activity, could serve as potential strategies to be tested and implemented in dairy cows.
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Title: Iridium catalyzed C-H activation borylations of fluorine bearing arenes and related studies
Creator: Jayasundara, Chathurika Ruwanthi Kumarihami
Date: 2018
Collection: Electronic Theses & Dissertations
Description: During the last two decades, iridium catalyzed aromatic borylation has emerged as one of the most convenient methodologies for functionalizing arenes and heteroarenes. The regioselectivity of Ir-catalyzed borylations are typically governed by sterics, therefore it complements the regioselectivity found in electrophilic aromatic substitution or directed ortho metalation. This unique regioselectivity and broad functional group tolerance (ester, amide, halogen, etc.) allows for synthesis of...
Show moreDuring the last two decades, iridium catalyzed aromatic borylation has emerged as one of the most convenient methodologies for functionalizing arenes and heteroarenes. The regioselectivity of Ir-catalyzed borylations are typically governed by sterics, therefore it complements the regioselectivity found in electrophilic aromatic substitution or directed ortho metalation. This unique regioselectivity and broad functional group tolerance (ester, amide, halogen, etc.) allows for synthesis of novel synthetic intermediates, many of which were previously either unknown or difficult to make. Since these reactions are mainly driven by sterics, it is possible to install boronic ester group (Bpin) next to small substituents like hydrogen, cyano, or fluorine. This feature is helpful but can also create challenges, specially in cases like borylation of fluoro arenes. These fluoro arenes tend give 1:1 mixture of steric (meta to fluorine) and electronic (ortho to fluorine) products. Therefore, to overcome this problem, we introduced a two-step Ir-catalyzed borylation/Pd-catalyzed dehalogenation sequence that allows one to synthesize fluoroarenes where the boronic ester is ortho to fluorine (electronic). Here, a halogen para to the fluorine is used as a sacrificial blocking group allowing the Ir-catalyzed borylation to favor the electronic product exclusively. Then the chemoselective Pd-catalyzed dehalogenation by KF activated polymethylhydrosiloxane (PMHS) is used to remove the halogen without compromising the Bpin group. Halosubstituted aryl boronates have the potential for orthogonal reactivity in cross-coupling reactions. We began exploring cross-coupling of triorganoindiums with these arylhalides bearing boronic esters in collaboration with Prof. P. Sestelo at University of da Coruña, Spain. We were able to synthesize borylated biaryls by merging Ir-catalyzed C–H borylations with Pd-catalyzed organoindium cross-couplings.As a part of the Dow–MSU-GOALI collaborations, we were able to synthesize a cobalt catalyst for C-H borylations of alkyl arenes and heteroarenes. This catalyst enables selective monoborylation of the benzylic position of alkyl arenes using pinacolborane (HBpin) as the boron source. In 2016, an internship opportunity led to the screening of ligands for C-H borylations at the Dow chemicals company in Midland, MI. From this internship opportunity, we discovered the first ligand controlled synthesis of 1,2-di and 1,2,3-tri borylated arenes. Also, I investigated a recyclable iridium heterogeneous catalyst for borylations during the internship. Finally, a bulky terphenyl incorporated bipyridine ligand is synthesized for selective iridium catalyzed para C–H borylations.
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Title: A multidimensional treatment integrity assessment of parent coaching in a telehealth parent training program for autism spectrum disorder
Creator: Tran, Shannon Quyen
Date: 2018
Collection: Electronic Theses & Dissertations
Description: An important principle of evidenced-based practice (EBP) is using interventions with strong empirical support for their effectiveness, commonly known as evidence-based interventions (EBIs). Evidence of an intervention’s effectiveness is strongest when supported by treatment integrity data. Treatment integrity refers to the degree to which an intervention is implemented as intended by the original design. The assessment’s purpose is to provide researchers and practitioners with data about the...
Show moreAn important principle of evidenced-based practice (EBP) is using interventions with strong empirical support for their effectiveness, commonly known as evidence-based interventions (EBIs). Evidence of an intervention’s effectiveness is strongest when supported by treatment integrity data. Treatment integrity refers to the degree to which an intervention is implemented as intended by the original design. The assessment’s purpose is to provide researchers and practitioners with data about the implementation process to enable valid conclusions to be drawn about an intervention’s effectiveness.The present study focused on the treatment integrity assessment of Project ImPACT (Improving Parents as Communication Teachers; Ingersoll & Dvortcsak, 2010), a parent training program that aims to improve parents’ competence in teaching social communication skills to children diagnosed with autism spectrum disorder (ASD). The parent coaching portion of the training program was the focus of this study. Treatment integrity assessment occurred at two stages: The coaching delivery and the treatment delivery.This study used videos of coaching sessions from two randomized controlled trial (RCT) studies that examined the effectiveness of delivering Project ImPACT via telehealth with and without parent coaching. Dane and Schneider’s (1998) treatment integrity conceptual framework was used to guide the assessment. For the coaching delivery, the assessment focused on the therapists’ adherence to the coaching procedure, provision of feedback, and quality of coaching delivery, and the parents’ responsiveness during the coaching session. For the treatment delivery, the assessment focused on the parents’ adherence to the intervention strategies and quality of the treatment delivery. Descriptive statistics provided a general overview of the therapists’ coaching performance and the parents’ teaching performance. Multilevel regression analysis determined which components of the coaching delivery best predicted how parents used the intervention techniques and structured the play session for their child during the coaching sessions.Overall, the therapists consistently completed the essential steps of the coaching process. They frequently provided comprehensive feedback, attention, and reassurance. They did not provide as many opportunities for the parents to engage in collaborative problem-solving or to reflect on their implementation progress. In turn, the parents fully participated in the coaching session and demonstrated sufficient capacity to implement the intervention techniques and structure a meaningful play session for their child.Results from a multilevel regression analysis indicated that none of the treatment integrity components of the coaching delivery significantly predicted the parents’ treatment adherence. The quality of coaching delivery did, however, significantly predict the parents’ structure of the play segment, albeit in a negative direction. The study’s results, along with its limitations, provided a platform for continuing the conversation about treatment integrity assessment in intervention studies. In particular, the study concluded with new questions about the conceptualization and operationalization of different parent coaching aspects for parent-implemented interventions. Seeking to understand the concept and improve the measurement of these parent coaching aspects can lead to a more accurate identification of the active ingredients of parent coaching in ASD parent-implemented interventions.
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Title: Fundamental studies and engineering modeling of hydrogen bonding
Creator: Bala Ahmed, Aseel Mohamed Ahmed
Date: 2018
Collection: Electronic Theses & Dissertations
Description: This project aims to enhance the engineering modeling of hydrogen bonding, or association, by blending ab initio quantum calculations, fundamental molecular level findings from experimental techniques, and thermodynamic models. Because of the ubiquity of hydrogen bonding, applications for an improved association model are extensive, ranging from drug design to plastics manufacturing. Therefore, a substantial amount of work has been aimed at improving traditional thermodynamic tools, which...
Show moreThis project aims to enhance the engineering modeling of hydrogen bonding, or association, by blending ab initio quantum calculations, fundamental molecular level findings from experimental techniques, and thermodynamic models. Because of the ubiquity of hydrogen bonding, applications for an improved association model are extensive, ranging from drug design to plastics manufacturing. Therefore, a substantial amount of work has been aimed at improving traditional thermodynamic tools, which often fail to capture the behavior of associating systems accurately. To guide models, spectroscopic techniques have been leveraged to gain insight into the interactions between molecules in the liquid phase, but interpretation is difficult. Moreover, with the advancement of computational chemistry technology, molecular dynamics (MD) and quantum mechanical (QM) calculations have also been utilized to understand the characteristics of hydrogen bonded clusters. However, few studies have combined all 3 techniques (the thermodynamic model, spectroscopy and ab initio calculations) in a rigorous way. To this end, an activity coefficient model for association is developed using Wertheim’s perturbation theory and its capabilities and limitations are explored with parameters from literature. Furthermore, a sequential MD and QM protocol is designed which facilitates the interpretation of the hydroxyl vibration in infrared spectroscopy and a method is developed to quantify the entire band. Finally, the methods are used to calculate the value of the association constant for an alcohol + alkane system.
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Title: Vicarious interaction with politicians by identifying with surrogates on social media : a social identification mechanism based on multiple salient social categories
Creator: Dai, Yue (College teacher)
Date: 2018
Collection: Electronic Theses & Dissertations
Description: New media platforms display politicians’ interactions with people from a variety of social categories. Previous research shows that observers could vicariously experience parasocial intimacy toward a public figure by identifying with a surrogate—an individual who directly interacts with the public figure and who is considered an ingroup member by the observer based on a salient social category (Dai & Walther, 2018). Developments in the social identity literature call for further examination...
Show moreNew media platforms display politicians’ interactions with people from a variety of social categories. Previous research shows that observers could vicariously experience parasocial intimacy toward a public figure by identifying with a surrogate—an individual who directly interacts with the public figure and who is considered an ingroup member by the observer based on a salient social category (Dai & Walther, 2018). Developments in the social identity literature call for further examination of this surrogacy effect in contexts where multiple social categories are activated as bases upon which observers identify with surrogates. Through two experiments involving a total sample of 1,068 participants, this research demonstrates that when a surrogate’s identity is presented as different combinations of political affiliation (democratic or republican) and social status (ordinary voter or politician), the more categories observers share in common with the surrogate, the more they identify with the surrogate, and thereby experiences greater parasocial intimacy toward a politician who is seen replying to the surrogate on Twitter. These findings extend previous findings on a social identification-based mechanism of the surrogacy effect and inform online impression management practices of politician.
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Title: Poly(ethylene glycol) tailored polymers : nanomicelles with tunable lower critical solution temperature behavior
Creator: Lien, Yu-Ling
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Propargyl and 1,1-dimethyl propargyl substituted poly(ethyleneoxides) (propargyl substituted = poly(PGE), 1,1ʹ-dimethyl propargyl substituted = poly(MGE)) have been prepared by ring-opening polymerization of epoxides, which were synthesized from epichlorohydrin and propargyl or 1,1-dimethyl propargyl alcohol via Williamson ether synthesis. The resulting polymers were modified by Cu-catalyzed azide alkyne cycloaddition (CuAAC) of the polymer propargyl groups and organic azides. When these...
Show morePropargyl and 1,1-dimethyl propargyl substituted poly(ethyleneoxides) (propargyl substituted = poly(PGE), 1,1ʹ-dimethyl propargyl substituted = poly(MGE)) have been prepared by ring-opening polymerization of epoxides, which were synthesized from epichlorohydrin and propargyl or 1,1-dimethyl propargyl alcohol via Williamson ether synthesis. The resulting polymers were modified by Cu-catalyzed azide alkyne cycloaddition (CuAAC) of the polymer propargyl groups and organic azides. When these reactions were carried out with mixtures of azides, the ratios of azides incorporated in the polymer side chains were equal to the molar ratios of the organic azides reactants (± 2%). Mixtures of hydrophobic (decyl azide) and hydrophilic (mDEG azide) azides result in amphiphilic polymers that exhibited a lower critical solution temperature (LCST) behavior. The polymer LCSTs scaled from 48 to 97 ± 2 °C (poly(PGE) derived amphiphiles) and 4 to 46 ± 1 °C (poly(MGE) derived amphiphiles) in a roughly linear fashion with the mole fraction of hydrophilic side chains in the polymer. When charged azides, COOH azide and aminium azide, were used, the physical property as well as the LCST behavior oh the polymers were changed. The LCSTs of polymers incorporating charged azides were increased and the LCSTs were decreased by adding salts in the solutions. The hydrodynamic radii (RH) obtained from DLS measurements indicate that polymers form unimolecular micelles in water (Mn = 52,000 g/mol, PDI = 1.19, RH = 6 ± 2 nm), and TEM data showed monodisperse domains (20 ± 4 nm, for Mn = 52,000) when water was evaporated at room temperature from solutions cast on TEM grids. This length scale is consistent with domains that consist of single polymer chains. When the TEM grid was heated during evaporation, the domain size increased to 74 ± 45 nm. In solution, the unimolecular micelles can solubilize hydrophobic small molecules, such as trans-azobenzene (trans-PhN=NPh) in water. DLS data suggested that polymer encapsulating trans-PhN=NPh (trans-PhN=NPh@poly(PGE) or poly(MGE)) derived amphiphiles) showed signs of aggregation in one case (RH = 12 ± 8 nm) and no signs of aggregation in another case (RH = 5 ± 2 nm). When the resulting solutions were raised above the polymer LCST the polymer and small molecule precipitated. When the mixture was cooled below the LCST, the polymer and hydrophobic small molecule re-dissolved. The unimolecular micelles were used to encapsulate a hydrophilic macromolecule, Subtilisin Carlsberg (SC), in aqueous solution and organic media. Poly(PGE) or poly(MGE) derived amphiphiles with COOH pendant group slowed down SC aggregation in aqueous environment. Also, the activity of SC@poly(MGE) derived amphiphiles with COOH pendant group was assayed and the half-life of SC was increased to 10 h from 2 h at 50 °C. Initial studies of SC@poly(PGE) or poly(MGE) derived amphiphiles in organic media showed enzymatic activity in toluene after 16 h at 37 °C.
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