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Title: Breaks in Connectedness? The Meaning and Experience of Response Delays in Mobile Communication
Creator: Gray, Rebecca Anne
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Individuals are communicating with one another to an increasing extent on mobile phones, which have enabled them to carry on conversations with others from nearly wherever they are and throughout whatever they are doing during the day. Maintaining connections with others through mobile phones contributes both to a need for synchrony in communication across mobile devices as well as to perceptions of increased accessibility to others - expectations that others are available to us as needed or...
Show moreIndividuals are communicating with one another to an increasing extent on mobile phones, which have enabled them to carry on conversations with others from nearly wherever they are and throughout whatever they are doing during the day. Maintaining connections with others through mobile phones contributes both to a need for synchrony in communication across mobile devices as well as to perceptions of increased accessibility to others - expectations that others are available to us as needed or desired. However, feelings of accessibility to others do not always signify true, uninterrupted access to others, as individuals may be unavailable to communicate for a number of reasons or unresponsive even when available. In order to understand the meaning of response delays in mobile interaction for individuals’ sense of connectedness to others, I interviewed emerging adults to engage in discussion with interviewees about their experiences of delayed responses from communication partners, unpacking the impact these delays may or may not have had on their sense of connectedness to them. I found that our cohort’s response time expectations were heavily informed by prior communication experience with communication partners and social norms, as posited by expectancy violation theory (Burgoon, 1988), which lays out a framework for predicting antecedents to nonverbal behavior expectancies and outcomes of violations to those expectancies. Perceived availability of communication partners was another recurring, important driver of responsiveness expectations. In close dyads, it appears that availability expectations may be even more precise than they would otherwise be with other communication partners given the increased access to information they have about others’ schedules as well as the more extensive prior communication experience. With these more precise availability expectations come potentially more severe or concerning reactions to expectancy-violating response delays.The lack of a shared environmental context in mobile communication can render it impossible to know another’s true availability to respond, no matter how “fine-tuned” or precise one’s expectations of availability are. This introduced a new layer of complexity in individuals’ interpretations of response delays, especially in cases where availability of a communication partner was presumed but a response was still not received. Reactions to response time violations included emotional reactions and compensation behaviors (such as modality switching) as predicted by the expectancy violation framework. We did not observe evidence that repeated response time violations hurt relationships with primary, typically close communication partners in any detectable way to the interviewees. Most response time violations with main communication partners that were discussed with participants were forgiven, described post-hoc as excusable instances of non-response based on later-realized circumstances.Based on these interviews and our findings, I recommend future work to continue to unpack the complexity of availability, seeking to better determine the impact of misconceived notions of availability on the evaluation of response delays. I also propose that future work dig more deeply into the role of communicator reward valence on the interpretation of and reaction to response delays in mobile communication.
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Title: Processing and properties of thermoplastic nanocomposite foams and porous polymer composite sheets
Creator: Lin, Xinting
Date: 2018
Collection: Electronic Theses & Dissertations
Description: The research work is divided into two parts. The first part is motivated by the need to produce recyclable lighter and thinner injection molded thermoplastic polyolefin (TPO) foam parts for automotive interiors by chemical foaming agent. This would require modifying the talc filled TPO compound with organoclay additive that can not only control the cell size to be smaller and more uniform, but also attain a smooth surface of the foamed parts. The objectives of this research were (1) to...
Show moreThe research work is divided into two parts. The first part is motivated by the need to produce recyclable lighter and thinner injection molded thermoplastic polyolefin (TPO) foam parts for automotive interiors by chemical foaming agent. This would require modifying the talc filled TPO compound with organoclay additive that can not only control the cell size to be smaller and more uniform, but also attain a smooth surface of the foamed parts. The objectives of this research were (1) to investigate the effect of different level of vapor phase silane coupling agent treatment on increasing the d-spacing of organoclay and the extent of dispersion in polypropylene; (2) to understand the relationship between melt rheology, surface appearance, foam morphology and mechanical properties of foam injection molded talc filled TPO and organoclay additive with optimized level of vapor phase silane pretreatment.TPO nanocomposites were prepared with organically modified montmorillonite, a silane coupling agent, maleic anhydride grafted polypropylene as compatibilizer and a commercial grade TPO with 23 wt% talc loading. The organoclay was treated with 0.8 wt% of the silane coupling agent under vapor phase process to improve the interaction between the clay and the TPO to reduce the usage of low viscosity compatiblizer. The rheology of the TPO and TPO nanocomposites was examined in shear and extensional flows and this was used to select the molding temperature profile. The effects of different molding parameters- extrusion back pressure and pack pressure on the uniformity of thickness, and cell structure were examined. Stronger shear thinning behavior was conducive to a smooth surface of molded parts, allowing an operating temperature profile close to that used for the base TPO and was crucial for both smooth surface and smaller cell size. The tensile strength, tensile modulus and flexural modulus were tested to be greater for the foam injection molded TPO nanocomposites. The second part of the research was motivated by the need to produce a thinner battery separator for nickel-metal hydride batteries (NiMH) that had higher tensile strength and puncture strength. This was achieved by solid phase die-drawing of talc-filled polypropylene to produce stronger and porous sheet with up to 40% void fraction. The objective of this research was to explore process limits and products obtained from two different composites with different talc particle size distributions. The limiting maximum linear draw ratio without breaking was higher for the composite with the smaller mean particle size; this may be attributed to the smaller transverse dimension of stacked voids obtained with this material. At the respective limiting linear draw ratios, the porosity level is the same for both composites but the composite with the smaller talc particle sizes and higher draw ratios led to drawn sheets with greater tensile strength; this may be attributed to greater crystalline rearrangement to fibrils in this composite at higher linear draw ratio.
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Title: AUTOMATED PET/CT REGISTRATION FOR ACCURATE RECONSTRUCTION OF PET IMAGES
Creator: Khurshid, Khawar
Date: 2018
Collection: Electronic Theses & Dissertations
Description: The use of a CT attenuation correction (CTAC) map for the reconstruction of PET image can introduce attenuation artifacts due to the potential misregistration between the PET and CT data. This misregistration is mainly caused by patient motion and physiological movement of organs during the acquisition of the PET and CT scans. In cardiac exams, the motion of the patient may not be significant but the diaphragm movement during the respiratory cycle can displace the heart by up to 2 cm along...
Show moreThe use of a CT attenuation correction (CTAC) map for the reconstruction of PET image can introduce attenuation artifacts due to the potential misregistration between the PET and CT data. This misregistration is mainly caused by patient motion and physiological movement of organs during the acquisition of the PET and CT scans. In cardiac exams, the motion of the patient may not be significant but the diaphragm movement during the respiratory cycle can displace the heart by up to 2 cm along the long axis of the body. This shift can project the PET heart onto the lungs in the CT image, thereby producing an underestimated value for the attenuation. In brain studies, patients undergoing a PET scan are often not able to follow instructions to keep their head in a still position, resulting in misregistered PET and CT image datasets. The head movement is quite significant in many cases despite the use of head restraints. This misaligns the PET and CT data, thus creating an erroneous CT attenuation correction map. In such cases, bone or air attenuation coefficients may be projected onto the brain which causes an overestimation or an underestimation of the resulting CTAC values. To avoid misregistration artifacts and potential diagnostic misinterpretation, automated software for PET/CT registration has been developed that works for both cardiac and brain datasets. This software segments the PET and CT data, extracts the brain or the heart surface information from both datasets, and compensates for the translational and rotational misalignment between the two scans. The PET data are reconstructed using the aligned CTAC, and the results are analyzed and compared with the original dataset. This procedure has been evaluated on 100 cardiac and brain PET/CT data sets, and the results show that the artifacts due to the misregistration between the two modalities are eliminated after the PET and CT images are aligned.
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Title: IL-27 MIMICS INTERFERON ACTIVATION OF MACROPHAGES TO CONTROL VIRAL, BUT NOT BACTERIAL, INFECTION
Creator: Andrews, Caroline
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Interleukin(IL)-27 is a heterodimeric type I cytokine in the IL-12 cytokine family with reported roles in cancer, infectious disease, and autoimmunity. However, the literature reports conflicting roles for IL-27 for either ameliorating or potentiating inflammatory conditions, especially within the gut. The majority of the literature describing the functions of IL-27 focuses on T cell biology, resulting in a paucity of knowledge on how IL-27 may act on its primary cellular source: myeloid...
Show moreInterleukin(IL)-27 is a heterodimeric type I cytokine in the IL-12 cytokine family with reported roles in cancer, infectious disease, and autoimmunity. However, the literature reports conflicting roles for IL-27 for either ameliorating or potentiating inflammatory conditions, especially within the gut. The majority of the literature describing the functions of IL-27 focuses on T cell biology, resulting in a paucity of knowledge on how IL-27 may act on its primary cellular source: myeloid cells such as macrophages. The objective of this study was to characterize the effect of IL-27 on murine macrophages and determine if macrophages may mediate any potential effects of IL-27 on the colon epithelium. Here we found that IL-27 activated murine macrophages in a manner similar to interferons (IFN). RNA sequencing followed by validation with real time RT-qPCR revealed that IL-27 induced the transcription of genes associated with interferon signaling and pathogen responses in macrophages. Using gene specific knockout mice, we demonstrated that this IL-27-induced gene expression was dependent on STAT1, independent of IL-27-induced IFN-γ, and selectively dependent on IL-27-induced type I interferons. IL-27 also increased macrophage secretion of TNF-α and IFN-γ, consistent with an activated phenotype. IL-27 increased surface expression of MHC II as determined by flow cytometry in a STAT1-dependent, IFN-independent manner. To determine the functional impact of the observed IL-27-induced gene and protein upregulation, we investigated the ability of IL-27 to promote viral or bacterial clearance in macrophages. IL-27 reduced vaccinia virus infection of macrophages and, in a separate experiment, also reduced the release of mouse cytomegalovirus by infected macrophages to subsequently decrease secondary viral infection of a susceptible cell line. In contrast, IL-27 was ineffective in reducing macrophage infection by Salmonella, likely due to a lack of nitric oxide production. Co-cultures of macrophages and colon epithelial organoids were used to evaluate the ability of macrophages to mediate the effects of IL-27 on murine colon epithelial cells, which do not respond directly to IL-27. RNA sequencing of colonoids co-cultured with IL-27-stimulated macrophages detected increased expression of gene pathways crucial for pathogen responses in colon epithelial organoids. In conclusion, our data provide novel mechanistic and functional insights into the shared and divergent effects of IL-27 and interferons on both non-activated resident and classically activated macrophages.
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Title: MANAGEMENT OF SOIL AND SEED BORNE DISEASES OF POTATO (SOLANUM TUBEROSUM)
Creator: Mambetova, Saltanat Kurmanbekovna
Date: 2018
Collection: Electronic Theses & Dissertations
Description: There are numerous important potato diseases that are annual production concerns for growers in Michigan. This study included three projects. The first project evaluated commercial cultivars and advanced breeding lines (ABL) with foliar resistance to late blight via tuber tests, and integrated disease management with foliar resistant varieties/ABLs in combination with fungicide seed treatments against four of genotypes of P. infestans. Commercial cultivars and ABLs showed differential...
Show moreThere are numerous important potato diseases that are annual production concerns for growers in Michigan. This study included three projects. The first project evaluated commercial cultivars and advanced breeding lines (ABL) with foliar resistance to late blight via tuber tests, and integrated disease management with foliar resistant varieties/ABLs in combination with fungicide seed treatments against four of genotypes of P. infestans. Commercial cultivars and ABLs showed differential responses to genotypes of P. infestans based on both experiments. Overall, ABLs and commercial cultivars in combination with seed treatments performed better based on plant stand compared to inoculated non-treated controls. A second project evaluated conventional and quantitative PCR primers for detection of Pectobacterium and Dickeya spp. to monitor the presence and spread of these bacteria in the field and in seed-lots for certification. In two consecutive years samples from the field had both Dickeya and Pectobacterium spp. Whereas, tubers from seed-lots from Michigan seed production did not test positive for Dickeya spp. and overall relatively low levels of Pectobacterium spp. within acceptable tolerance. Three conventional PCR primers were reliable and were able to differentiate Pectobacterium down to species. Finally, a third project characterized Streptomyces spp. recovered from potato and turnip phenotypically based on virulence, pathogenicity, and morphologically, and determined the diversity and phylogenetic relationships among species. This study identified morphological, molecular and phylogenetically differences among Streptomyces spp. isolated from turnip and potato.
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Title: Teacher’s Management of Classroom Interactions with English Language Learners : A Case Study of A Mainstream Teacher’s Practices and Beliefs
Creator: Teng, Yanjiang
Date: 2018
Collection: Electronic Theses & Dissertations
Description: In the past few decades, public schools in the United States have witnessed a fast-growing student population of English language learners (ELLs), who come from homes where a language other than English is dominant. The dual task of content and the English language learning has brought ELLs huge academic challenges, such as one-size-fit-all expectations, high-stakes tests, and unsatisfactory academic support, among many others. In addition, ELLs are often mainstreamed into content area...
Show moreIn the past few decades, public schools in the United States have witnessed a fast-growing student population of English language learners (ELLs), who come from homes where a language other than English is dominant. The dual task of content and the English language learning has brought ELLs huge academic challenges, such as one-size-fit-all expectations, high-stakes tests, and unsatisfactory academic support, among many others. In addition, ELLs are often mainstreamed into content area classes where teachers are underprepared to accommodate their learning needs. Thus, how mainstream teachers deal with ELLs for their content and English language learning merits further study. Educational scholars have paid increasing attention to the construct of teacher belief about teaching and learning. So far, studies on teachers’ beliefs suggest that the complex relationship between teacher beliefs and practice are not always static but rather emergent and likely to be moderated by contextual factors (e.g. Negueruela-Azarola, 2011). As Priestley, Biesta, and Robinson (2015) argued, examination of the issue should recognize the immediate situated context and focus on the beliefs-in-action to probe why the teacher makes decisions in that particular moment and for what purposes. Learning, from a sociocultural perspective, is achieved through the interactions between the teacher and students, as well as among the students themselves. In the classroom, teachers usually dominate the flow of the discourse and their beliefs on teaching and learning, to some extent, can shape the way of such teacher-student interaction and students’ learning. Classroom interaction is highly contextualized, spontaneous, and out of expectations. How the teacher manages this interactive practice and provides mediated support toward ELLs for both their content and language learning warrants further attention. This study draws upon a sociocultural perspective on learning, and a perspective that teachers’ decision-making is fluid, situated and context dependent. The present study examines how a mainstream teacher in a U.S. urban school manages her interaction with ELLs to scaffold their English and content learning and how these practices reflect her beliefs-in-action. This case study, using data generated from stimulated recall interviews, classroom videos, and observation notes, reports this teacher’s discursive practices with ELLs, along with her ongoing decision-making or her beliefs-in-action in this interactive process. The findings revealed that in this highly structured and teacher-dominated class, the interactive practice between the teacher and ELLs were limited. The teacher’s feedback on ELLs’ responses was not based on their learning needs but was impacted by some other contextual factors. The teacher’s strategies to scaffold ELLs’ learning were not as effective as she might expect: some are supportive of their learning, while others could impede their learning. Overall, the teacher’s challenges and dilemmas that arise from her interactive practice with ELLs were largely due to her lack of formal training in second language teaching. This study sheds light on the complexity of mainstream teachers’ beliefs and practices about ELLs. Furthermore, it advances our thinking on teachers’ practices and beliefs by bridging the link between teacher beliefs and classroom interaction in an interactive, moment-by-moment manner through the fine-grained analysis. In addition, it offers implications on better supporting and preparing mainstream teachers working with ELLs in a culturally and linguistically diverse environment.
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Title: Multiscale Gaussian-beam method for high-frequency wave propagation and inverse problems
Creator: Song, Chao
Date: 2018
Collection: Electronic Theses & Dissertations
Description: The existence of Gaussian beam solution to hyperbolic PDEs has been known to the pure mathematics community since sometime in the 1960s [3]. It enjoys popularity afterwards due to its ability to resolve the caustics problem and its efficiency [49, 28, 31]. In this thesis, we will focus on the extension of the multi-scale Gaussian beam method and its application to seismic wave modeling and inversion. In the first part of thesis, we discuss the application of the multi-scale Gaussian beam...
Show moreThe existence of Gaussian beam solution to hyperbolic PDEs has been known to the pure mathematics community since sometime in the 1960s [3]. It enjoys popularity afterwards due to its ability to resolve the caustics problem and its efficiency [49, 28, 31]. In this thesis, we will focus on the extension of the multi-scale Gaussian beam method and its application to seismic wave modeling and inversion. In the first part of thesis, we discuss the application of the multi-scale Gaussian beam method to the inverse problem. A new multi-scale Gaussian beam method is introduced for carrying out true-amplitude prestack migration of acoustic waves. After applying the Born approximation, the migration process is considered as shooting two beams simultaneously from the subsurface point which we want to image. The Multi-scale Gaussian Wavepacket transform provides an efficient and accurate way for both decomposing the perturbation field and initializing Gaussian beam solution. Moreover, we can prescribe both the region of imaging and the range of dipping angles by shooting beams from a subsurface point in the region of imaging. We prove the imaging condition equation rigorously and conduct error analysis. Some numerical approximations are derived to improve the efficiency further. Numerical results in the two-dimensional space demonstrate the performance of the proposed migration algorithm. In the second part of thesis, we propose a new multiscale Gaussian beam method with reinitialization to solve the elastic wave equation in the high frequency regime with different boundary conditions. A novel multiscale transform is proposed to decompose any arbitrary vector-valued function to multiple Gaussian wavepackets with various resolution. After the step of initializing, we derive various rules corresponding to different types of reflection cases. To improve the efficiency and accuracy, we develop a new reinitialization strategy based on the stationary phase approximation method to sharpen each single beam ansatz. This is especially useful and necessary in some reflection cases. Numerical examples with various parameters demonstrate the correctness and robustness of the whole method. There are two boundary conditions considered here, the periodic and the Dirichlet boundary condition. In the end, we show that the convergence rate of the proposed multiscale Gaussian beam method follows the convergence rate of the classical Gaussian beam solution.
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Title: Identification Of Deceased Border Crossers : Investigating Spatial And Skeletal Attributes Of Migrant Deaths
Creator: Vogelsberg, Caitlin Claire Madigan
Date: 2018
Collection: Electronic Theses & Dissertations
Description: International migration research has primarily focused on cultural, sociological, and economic components. Understanding geographic mortality patterns and the skeletal attributes among the deceased using a mixed-model framework can provide insight into route selection for irregular entrants via the Mexican border. This research investigates the spatial and skeletal properties of deceased undocumented border crossers (UBCs) recovered in the southern Arizona desert and the relationship between...
Show moreInternational migration research has primarily focused on cultural, sociological, and economic components. Understanding geographic mortality patterns and the skeletal attributes among the deceased using a mixed-model framework can provide insight into route selection for irregular entrants via the Mexican border. This research investigates the spatial and skeletal properties of deceased undocumented border crossers (UBCs) recovered in the southern Arizona desert and the relationship between recovery location and country of origin. Previous research investigating spatial patterns in the distribution of identified UBCs recovered in the jurisdiction of the Pima County Office of the Medical Examiner (PCOME) in Tucson, Arizona demonstrated positive spatial autocorrelation between individualizing attributes (such as biological sex and country of origin) and their recovery location (Vogelsberg 2018). Those results indicated several influencing factors, such as country of origin, on final recovery location. This research project combines spatial patterns and cranial skeletal indicators of geographic origin to improve country of origin prediction during the identification process.An optimized global linear model developed using craniometric and macromorphoscopic factors for a sample (n = 25) of identified Mexican and Guatemalan individuals analyzed at the PCOME was incorporated into several geographically weighted regression (GWR) platforms to predict country of origin. The best performing GWR analysis accounted for just over half of the variation in the data (R2= 0.540). This is an increase from the global model (R2 = 0.432) which did not incorporate recovery location and attributes of other individuals found nearby. Other indicators of model goodness-of-fit show more accurate country of origin predictions using the GWR method.Model testing on individuals with presumptive Mexican identifications (n = 8) resulted in the correct allocation for country of origin for two individuals and provided promising results for future application. Although sample sizes were small, the potential for applying mixed-model methods is clearly demonstrated. As more individuals are identified and added to the model reference sample, the utility of this predictive method will improve. Furthermore, the application of these techniques to situations in which the physical location of an individual might correlate with their personal attributes is demonstrated.This research provides the forensic and humanitarian community with supplemental information to aid in the investigation of undocumented border crossers recovered from the southern Arizona desert. Enhancements to the identification process by better directing missing persons searches may increase the number of identified individuals and the return of their remains to their families.
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Title: DETECTION OF COHERENT ENERGY TRANSFER PATHWAYS IN PHOTOSYNTHESIS WITH TWO-DIMENSIONAL ELECTRONIC SPECTROSCOPY
Creator: Roscioli, Jerome Daniel
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Light harvesting proteins in photosynthetic organisms contain highly ordered arrays of chromophores responsible for the collection of energy from solar photons. The organization of the chromophores may lead to collective excitations (excitons) that are delocalized over many molecules in the array. The delocalized excitations allow for coherent, or wavelike, energy transfer between the chromophores, rather than a particle-like, incoherent, energy transfer process. It has been proposed that...
Show moreLight harvesting proteins in photosynthetic organisms contain highly ordered arrays of chromophores responsible for the collection of energy from solar photons. The organization of the chromophores may lead to collective excitations (excitons) that are delocalized over many molecules in the array. The delocalized excitations allow for coherent, or wavelike, energy transfer between the chromophores, rather than a particle-like, incoherent, energy transfer process. It has been proposed that these collective excitations may direct the flow of energy along the most efficient pathway to enhance the fitness of photosynthetic organisms. Photosynthetic organisms may also favor closely packed chromophore arrays because the structure is compact whilst optimizing large optical cross sections for absorption. Control of the coupling between chromophores may lead to a photoregulatory mechanism, which could control the energy transfer rate as a function of ambient light intensity fluctuations. Broad-band two- dimensional electronic spectroscopy (2DES) can be used to elucidate donor–acceptor pathways and mechanisms for both coherent and incoherent excitation energy transfer (EET) in photosynthetic light-harvesting proteins. In this dissertation, 2DES is applied to determine how quantum coherent energy transfer occurs between carotenoids and chlorophylls (Chls) in the peridinin-chlorophyll protein (PCP), a mid-visible peripheral light-harvesting protein in marine dinoflagellates that delivers excitation energy to photosystem II. PCP is unique in that it uses a carotenoid, peridinin, as the main light harvesting chromophore and that it can be reconstituted with different chlorophylls to change the energy landscape without causing structural changes. Through 2DES experiments on native PCP with Chl a, we show that although the collective excitations of chromophores are very short lived, they lead to an enhanced quantum yield compared to that for conventional, incoherent energy transfer mechanisms. Replacing the native Chl a acceptor chromophores with Chl b slows energy transfer from peridinin to Chl despite narrowing the donor–acceptor energy gap. The formyl substituent on the Chl b macrocycle hastens decoherence by sensing the surrounding electrostatic noise, leading to lower EET efficiencies. This work is significant because it improves our understanding of the role of coherent energy transfer in photosynthetic light harvesting. This information may prove useful when designing materials featuring strongly interacting electronic chromophores for the collection of solar energy for the generation of fuels or for use in photocatalysis.
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Title: Effect of high-fat diet on sympathetic neurotransmission in mesenteric vasculature in dahl salt-sensitive hypertension
Creator: Alula, Kibrom Meles
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Obesity is a risk factor for cardiovascular and metabolic disorders. The prevalence of obesity-associated hypertension has been rising globally, and it is mainly linked to the increasing consumption of processed as well as fast foods. The current trend indicates that women are more likely to become obese than men; however, the onset of hypertension is delayed in obese women until they reach postmenopausal age. Several reasons have been given for such disparity, such as reproductive hormones...
Show moreObesity is a risk factor for cardiovascular and metabolic disorders. The prevalence of obesity-associated hypertension has been rising globally, and it is mainly linked to the increasing consumption of processed as well as fast foods. The current trend indicates that women are more likely to become obese than men; however, the onset of hypertension is delayed in obese women until they reach postmenopausal age. Several reasons have been given for such disparity, such as reproductive hormones and distribution of body fat. In addition, obesity-induced hypertension is indicated in the overdrive of sympathetic nerves centrally and peripherally. For example, sympathetic denervation in the kidneys and celiac ganglionic blockade have demonstrated the role of sympathetic nerves in hypertension. Nevertheless, there is little knowledge regards to the effect of obesity on the underlying mechanisms in the sympathetic neurotransmission in the mesenteric blood vessels. Therefore, we tested the hypothesis that high fat diet (HFD) compared to control diet (CD) results in greater sympathetic neurotransmission and nerve distribution in the Dahl salt-sensitive (Dahl ss) rat. HFD fed rats gained more body weight than rats on CD, and males became more obese than females. Mean arterial pressure (MAP) was greater in HFD versus CD at 17- and 24-wk in both sexes. Nevertheless, males and females became equally hypertensive on both diets. In mesenteric artery (MA), neurogenic constriction was higher in HFD versus CD at 17-wk in males; however, this observation was not supported by changes in vascular reactivity or nerve density at the same time point. ATP is co-released with norepinephrine (NE) from the presynaptic nerves and it mediates purinergic neurotransmission. Moreover, the purinergic nerves were low in count at this time point indicating minimal contribution to the higher neurogenic response in HFD at 17-wk in males. In mesenteric vein (MV), neurogenic response was greater in HFD versus CD at 17-wk in males (similar to MA). There was also a greater adrenergic venous reactivity (norepinephrine mediated) and higher tyrosine hydroxylase (TH; sympathetic nerve marker) nerve density in HFD versus CD at 17-wk in males. This suggests HFD-induced hypertension is partly driven by adrenergic nerves from MV at 17-wk in males. Finally, HFD increased in most cases the sympathetic vesicles in the nerve cell bodies in celiac ganglion (CG), and sympathetic nerve fibers in MA and MV. In addition, three distinct populations of sympathetic vesicles/nerves were identified in CG, MA, and MV, namely TH-immunoreactive (TH-ir), vesicular nucleotide transporter (VNUT-ir; ATP marker), and TH/VNUT colocalization. The distribution of adrenergic, purinergic, and colocalized vesicles in cell bodies at the CG was not necessarily reflected in the periarterial and perivenous nerves. Taken together, HFD-associated hypertension is not driven by changes in the sympathetic neurotransmission from the mesenteric vasculature in male and female Dahl ss rats.
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Title: Investigating the relationship between uv-b radiation exposure and racial disparities in preeclampsia : a medical geography study
Creator: Kutch, Libbey C.
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Preeclampsia is the leading cause of morbidity and mortality in the United States. Research had demonstrated that adequate levels of vitamin D can help to circumvent the risk of preeclampsia. Vitamin D plays a role in cardiovascular health and in maternal health, and cutaneous exposure to ultra-violet (UV)-B radiation is critical to maintaining healthy vitamin D levels. The majority of vitamin D in humans is produced when the skin is exposed to ultraviolet radiation. UV-B varies...
Show morePreeclampsia is the leading cause of morbidity and mortality in the United States. Research had demonstrated that adequate levels of vitamin D can help to circumvent the risk of preeclampsia. Vitamin D plays a role in cardiovascular health and in maternal health, and cutaneous exposure to ultra-violet (UV)-B radiation is critical to maintaining healthy vitamin D levels. The majority of vitamin D in humans is produced when the skin is exposed to ultraviolet radiation. UV-B varies geographically; therefore geography influences the availability of vitamin D and the potential risk for preeclampsia. However, research on the geographic relationship between UV-B and pregnancy induced hypertensive disorders, including preeclampsia has been relatively neglected. This research investigates the relationship between maternal UV-B exposure and preeclampsia for mothers giving birth in Michigan from 2008 to 2015 during 3 time periods, 1-pre-conception, 2-early pregnancy, and 3-late pregnancy. A medical geographic and human ecological framework conceptualizes the environmental, biological and behavioral factors influencing the UV-B and preeclampsia relationship. UV-B is estimated using the Erythemal Daily Dose calculated form OMI remote sensing data. Preeclampsia is measured using Michigan's Vital Statistics Birth Data 2008-2015. Multilevel models were estimated to study these relationships. This study found that slight increases in UV-B exposure prior to conception and later in pregnancy could reduce the odds of preeclampsia for white but not black mothers. Other important risk factors for preeclampsia were increasing BMI, chronic and gestational diabetes and living in urban areas. Receiving Medicaid was protective for preeclampsia for white mothers but not black mothers. Enrollment in WIC was highly protective for all mothers. This medical geography research demonstrates the importance of utilizing remote sensing to begin to understand UV-B exposure on an important pregnancy outcome from a population perspective. Future research should also focus on reevaluating the measurement of the Erythemal Daily Dose to reflect people with high melanin concentrations. Future research could also branch out to other highly prevalent conditions with low vitamin D susceptibility such as cancers and dementia and Alzheimer's.
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Title: A container-attachable inertial sensor for real-time hydration tracking
Creator: Griffith, Henry
Date: 2019
Collection: Electronic Theses & Dissertations
Description: The underconsumption of fluid is associated with multiple adverse health outcomes, including reduced cognitive function, obesity, and cancer. To aid individuals in maintaining adequate hydration, numerous sensing architectures for tracking fluid intake have been proposed. Amongst the various approaches considered, container-attachable inertial sensors offer a non-wearable solution capable of estimating aggregate consumption across multiple drinking containers. The research described herein...
Show moreThe underconsumption of fluid is associated with multiple adverse health outcomes, including reduced cognitive function, obesity, and cancer. To aid individuals in maintaining adequate hydration, numerous sensing architectures for tracking fluid intake have been proposed. Amongst the various approaches considered, container-attachable inertial sensors offer a non-wearable solution capable of estimating aggregate consumption across multiple drinking containers. The research described herein demonstrates techniques for improving the performance of these devices.A novel sip detection algorithm designed to accommodate the variable duration and sparse occurrence of drinking events is presented at the beginning of this dissertation. The proposed technique identifies drinks using a two-stage segmentation and classification framework. Segmentation is performed using a dynamic partitioning algorithm which spots the characteristic inclination pattern of the container during drinking. Candidate drinks are then distinguished from handling activities with similar motion patterns using a support vector machine classifier. The algorithm is demonstrated to improve true positive detection rate from 75.1% to 98.8% versus a benchmark approach employing static segmentation. Multiple strategies for improving drink volume estimation performance are demonstrated in the latter portion of this dissertation. Proposed techniques are verified through a large-scale data collection consisting of 1,908 drinks consumed by 84 individuals over 159 trials. Support vector machine regression models are shown to improve per-drink estimation accuracy versus the prior state-of-the-art for a single inertial sensor, with mean absolute percentage error reduced by 11.1%. Aggregate consumption accuracy is also improved versus previously reported results for a container-attachable device.An approach for computing aggregate consumption using fill level estimates is also demonstrated. Fill level estimates are shown to exhibit superior accuracy with reduced inter-subject variance versus volume models. A heuristic fusion technique for further improving these estimates is also introduced herein. Heuristic fusion is shown to reduce root mean square error versus direct estimates by over 30%. The dissertation concludes by demonstrating the ability of the sensor to operate across multiple containers.
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Title: The impact of bt crops on aflatoxin reduction
Creator: Yu, Jina
Date: 2019
Collection: Electronic Theses & Dissertations
Description: This dissertation is about how adoption of a genetically engineered plant works as a prevention method for aflatoxin, a carcinogen that commonly contaminates food crops such as corn and peanuts interacting with climate condition. First produced in the United States in 1996, Bt corn has become one of the most commonly grown transgenic crops worldwide. Aside from improving corn growers' yields, it has also resulted in an 11% decrease in insecticide use on US corn. Multiple experimental studies...
Show moreThis dissertation is about how adoption of a genetically engineered plant works as a prevention method for aflatoxin, a carcinogen that commonly contaminates food crops such as corn and peanuts interacting with climate condition. First produced in the United States in 1996, Bt corn has become one of the most commonly grown transgenic crops worldwide. Aside from improving corn growers' yields, it has also resulted in an 11% decrease in insecticide use on US corn. Multiple experimental studies found that the level of aflatoxin, a fungal toxin, can be mitigated by reducing the presence of insects because fungi colonize corn through kernel wounds from insect feeding. However, the relationship between Bt corn and aflatoxin has yet to be examined in field settings, wherein many environmental factors are at play. Given the higher environmental risks of temperature and drought, revealing the mechanism by which Bt corn reduces aflatoxin can inform farmers' decision-making on crop choices and seed choices.In the first essay, I developed a regression model that estimates causal relationships between aflatoxin-related insurance claims and Bt corn adoption rates, drought index, and climatic variables. From 2001-2016, a significant inverse correlation existed between Bt corn planting and aflatoxin-related insurance claims in the United States when controlling for temperature, drought, state, and year. Estimated benefits of Bt corn's aflatoxin reduction were about $120 million to $229 million per year in over 16 states on average. These results suggest that Bt corn is an important strategy with corresponding economic benefits for reducing aflatoxin risk in the United States. Climate change-typically increased temperature-may expand prevalence zones for aflatoxin because warm temperatures and dry conditions are associated with aflatoxin accumulation. The second essay's objectives were to predict both areas with high aflatoxin risks in 2031-2040 based on 16 climate models, as well as the extent of aflatoxin-related economic loss due climate change. To do so, growing season impacts on aflatoxin risk were modeled by allowing for the adjustment of planting season under different climate scenarios. It was found that more than 89% of corn planting areas are likely to experience increased aflatoxin risks in 2031-2040 when compared to aflatoxin risks from 2007-2016 in the United States. Ignoring health-related costs, aflatoxin-related economic loss was expected to amount to $36 million - $70 million per year.In the third essay, I examined an additional potential benefit of Bt crops (corn and cotton): a decrease in the incidence of aflatoxin in peanuts (non-Bt crops). Bt crops can help reduce aflatoxin levels by reducing insect damage, a key path of fungal infection. However, the effect of Bt crops should not be limited to the adopted crops, because insects controlled by Bt have a relationship with other crops and insects in the broader ecosystem. Furthermore, the sales of aflatoxin-contaminated peanuts are currently under regulation. As such, the negative relationship between Bt and aflatoxin in peanuts means that Bt crops can also provide a meaningful, unintended economic benefit to peanut farmers by reducing aflatoxin. In addition to the Bt crops, temperature and drought at key stages of peanut growth were included as potential confounding factors in aflatoxin-related insurance claims. The results indicate that a county with a higher Bt crops adoption rate was less likely to have aflatoxin-related insurance claims in peanuts. This means that, by reducing the incidence of aflatoxin, Bt crops adoption in the United States has saved losses of $0.45 million per year. Overall, my dissertation study increases current understandings of the unintended effects of Bt in protecting crops from aflatoxin damage in the broader ecosystem. It aims to shed light on the benefits of Bt crops in countries that suffer from aflatoxin-related damage and transgenic seed traits that are not planted. Additionally, this study contributes to improved knowledge about climate conditions that affect either aflatoxin levels or host plants (corn and peanut). As climate change is expected to increase temperature and dryness, it is likely to increase the risk of aflatoxin in the US. Bt crops and new biotechnology are thus expected to play an important role in protecting crops from aflatoxin damage.
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Title: Molecular dynamics and continuum simulations of fluid flows with slip boundary conditions
Creator: Niavaranikheiri, Anoosheh
Date: 2011
Collection: Electronic Theses & Dissertations
Description: Microfluidics is a rapidly developing field with applicationsranging from molecular biology, environmental monitoring, andclinical diagnostics. Microfluidic systems are characterized bylarge surface-to-volume ratios, and, therefore, fluid flows aresignificantly influenced by boundary conditions. The fundamentalassumption in fluid mechanics is the no-slip boundary condition,which states that the tangential fluid velocity is equal to theadjacent wall speed. Although this assumption is...
Show moreMicrofluidics is a rapidly developing field with applicationsranging from molecular biology, environmental monitoring, andclinical diagnostics. Microfluidic systems are characterized bylarge surface-to-volume ratios, and, therefore, fluid flows aresignificantly influenced by boundary conditions. The fundamentalassumption in fluid mechanics is the no-slip boundary condition,which states that the tangential fluid velocity is equal to theadjacent wall speed. Although this assumption is successful indescribing fluid flows on macroscopic length scales, recentexperimental and numerical studies have shown that it breaks down atmicroscopic scales due to the possibility of slip of the fluidrelative to the wall. The effect of slip is more pronounced forhighly viscous liquids like polymer melts or in the region near themoving contact line due to the large gradient in shear stress at theliquid/solid interface. The measure of slip is the so-called sliplength, which is defined as a distance between the real interfaceand imaginary plane where the extrapolated velocity profilevanishes. The slip length value is sensitive to several keyparameters, such as surface energy, surface roughness, fluidstructure, and shear rate.In this dissertation, the slip phenomena in thin liquid filmsconfined by either flat or structured surfaces are investigated bymolecular dynamics (MD) and continuum simulations. It is found thatfor flows of both monatomic and polymeric fluids over smoothsurfaces, the slip length depends nonlinearly on shear rate atsufficiently high rates. The laminar flow away from a curvedboundary is usually described by means of the effective slip length,which is defined with respect to the mean roughness height. MDsimulations show that for corrugated surfaces with wavelength largerthan the size of polymer chains, the effective slip length decreasesmonotonically with increasing corrugation amplitude. A detailedcomparison between the solution of the Navier-Stokes equation withthe local rate-dependent slip condition and results of MDsimulations indicates that there is excellent agreement between thevelocity profiles and the effective slip lengths at low shear rateand small-scale surface roughness. It was found that the main causeof the slight discrepancy between MD and continuum results at highshear rates is the reduction of the local slip length in the higherpressure regions where the boundary slope becomes relatively largewith respect to the mainstream flow. It was further shown that forthe Stokes flow with the local no-slip boundary condition, theeffective slip length decreases with increasing corrugationamplitude and a flow circulation is developed in sufficiently deepgrooves. Analysis of a numerical solution of the Navier-Stokesequation with the local slip condition shows that the inertialeffects promote the asymmetric vortex flow formation and reduce theeffective slip length.
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Title: Ecology and diversity of the lichen symbiosis : following established patterns, or an exception to the rule?
Creator: Scharnagl, Klara
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Few phenomena of biodiversity have perplexed researchers as much as the latitudinal diversity gradient. Though many taxa have been shown to follow this pattern of high species richness in the tropics and lower species richness towards the poles, no consensus has yet been reached regarding the drivers of this global pattern. Symbiosis, a long term and physically intimate interaction between two organisms, is a prevalent biotic interaction across the tree of life, yet few studies of the...
Show moreFew phenomena of biodiversity have perplexed researchers as much as the latitudinal diversity gradient. Though many taxa have been shown to follow this pattern of high species richness in the tropics and lower species richness towards the poles, no consensus has yet been reached regarding the drivers of this global pattern. Symbiosis, a long term and physically intimate interaction between two organisms, is a prevalent biotic interaction across the tree of life, yet few studies of the latitudinal diversity gradient have looked at symbiotic organisms. One example of symbiosis is the lichen symbiosis, an association between a filamentous fungal partner and a photosynthetic partner of green algae or cyanobacteria. Little is known about the latitudinal diversity gradient of lichens, yet their terrestrial ubiquity and symbiotic nature could provide insight into the drivers of this global pattern. To assess whether lichenized fungi follow a latitudinal diversity gradient, I compiled a dataset from three repositories for digitized herbarium specimen data: the Consortium for North American Lichen Herbaria, the Global Biodiversity Information Facility, and the Institutos Nacionais de Ciencia e Tecnologia. The fully compiled and quality-controlled dataset contained over 900,000 datapoints representing over 8,000 species. The raw species richness data revealed a peak in richness north of the equator outside of the tropics, however, this pattern mirrored the number of collections per latitudinal band. To correct for sampling effort biases in the digitized herbarium data, I rarefied species richness. I further corrected the rarefied species richness for land area, given the wide range of land area per latitudinal band in the Americas. This rarefied and land-area-corrected species richness data supports a latitudinal diversity gradient of lichenized fungi in the Americas. In a comparison to lichen checklist data at the country or state level, I revealed that tropical regions are underrepresented in the digitized herbarium data.To test the influence of sampling effort bias on the patterns revealed by the digitized herbarium data, I designed a field sampling approach directly targeted at the question of whether epiphytic lichens follow a latitudinal diversity gradient. This approach can help remove bias present in digitized herbarium data because they result from the compilation of many studies, each of which had its own taxonomic, regional, or ecological focus. To do so, I sampled from nine lowland forest sites across a 70-degree span of latitude in the Americas. At each site, I randomly chose ten plots, and sampled from ten trees within each plot for a total of nine hundred trees sampled. At each tree, I randomly chose a cardinal direction and placed a 20x40cm grid on the tree, collecting all lichens that fell within that grid. Thus, each site had the same amount of area surveyed for epiphytic lichen diversity. Lichens were identified to species in the lab. Data from systematic field sampling corroborate the latitudinal diversity gradient of (epiphytic) lichens. In a mixed effects model including tree and climate data, I found that this pattern is largely explained by host tree (substrate) diversity.With increasing land use change and impacts from climate change across the globe, it is increasingly important for us to set a baseline of patterns of diversity at large scales, as I did in my first two chapters, to then assess how these impacts are affecting the diversity of symbiotic organisms at different scales. For my third chapter, I applied my knowledge of lichen diversity to assess the impacts of three tropical forest restoration treatments on epiphytic lichens. The natural regeneration treatment had a small cohort of lichen species likely specialized to the high light and dry environment. The plantation and nucleation treatments had a mix of light and shade tolerant species and experienced higher competition from epiphytic bryophytes. The overall highest diversity of epiphytic lichens was found in the nucleation treatment, supporting this as the combination of the most cost-effective strategy that restores the greatest amount of tropical biodiversity.
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Title: Contemporary liberalism and the nation
Creator: Fram, Daniel
Date: 2019
Collection: Electronic Theses & Dissertations
Description: What is the status and legitimacy of the nation within the horizon of liberalism today? Surveying three representative, contrasting, recent works in contemporary political philosophy, I argue that the nation loses its status and legitimacy from every side. John Rawls's allegedly status-quo preserving theory in The Law of Peoples (Rawls 1999) defends only the shell of sovereignty and in fact points toward cosmopolitan aspirations. Cosmopolitan liberals, and conservative nationalists, therefore...
Show moreWhat is the status and legitimacy of the nation within the horizon of liberalism today? Surveying three representative, contrasting, recent works in contemporary political philosophy, I argue that the nation loses its status and legitimacy from every side. John Rawls's allegedly status-quo preserving theory in The Law of Peoples (Rawls 1999) defends only the shell of sovereignty and in fact points toward cosmopolitan aspirations. Cosmopolitan liberals, and conservative nationalists, therefore, claim with reason that liberalism is not capable of conferring status and legitimacy on the nation's "arbitrary" restrictions of individual autonomy (Nussbaum and Cohen 1996, MacIntyre 2003). But, in doing so, cosmopolitan liberalism creates a grave problem, for liberalism depends upon citizens to uphold freedom and upon limits to freedom to make freedoms meaningful. One would think to turn toward so-called liberal nationalist theories of liberalism, like David Miller's On Nationality (Miller 1995). But these, in turn, defend the nation only by depleting it of any content and rendering the very concept of the nation hollow. Neither of these two possible corrections of liberalism solves its problems with particularity and social unity; each only exacerbates them. My work as a whole therefore shows that contemporary liberalism tends to undermine the nation, on which it nevertheless relies. I demonstrate each part of the argument in separate chapters: two on Rawls's liberalism, one on Nussbaum's cosmopolitanism, and two on David Miller's liberal nationalism. These three perspectives represent a fairly complete spectrum of contemporary liberal thinking about the status of the nation.
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Title: Jesus People USA, the Christian Woodstock, and conflicting worlds : political, theological, and musical evolution, 1972-2010
Creator: Young, Shawn David
Date: 2011
Collection: Electronic Theses & Dissertations
Description: This study is an analysis of an evangelical commune located in Chicago's inner city. Self-described as an "intentional community," Jesus People USA (JPUSA) is one of the remaining collective expressions of the Jesus Movement, an American revival that occurred during the 1960s and 1970s. After considering the reasons for this commune's longevity, I make three core arguments. First, the study of communes in American history shows that in most cases, American communes are often short-lived....
Show moreThis study is an analysis of an evangelical commune located in Chicago's inner city. Self-described as an "intentional community," Jesus People USA (JPUSA) is one of the remaining collective expressions of the Jesus Movement, an American revival that occurred during the 1960s and 1970s. After considering the reasons for this commune's longevity, I make three core arguments. First, the study of communes in American history shows that in most cases, American communes are often short-lived. JPUSA has continued beyond its 1972 genesis due to various structural mechanisms and an ability to engage and evolve with American culture. The fact that JPUSA has survived to the present can be attributed to what sociologist Rosabeth Moss Kanter refers to as "commitment mechanisms." However, an analysis of commitment levels among second-generation communards demonstrates that these mechanisms are often problematic. Moreover, longevity will be determined by how the commune is perceived by the evangelical subculture as the commune evolves ideologically. Second, musical subgenres such as Christian heavy metal and punk rock would not have grown in influence if not for the Cornerstone Festival. Furthermore, JPUSA and their festival have challenged mainstream contemporary Christian music (CCM) and redefined the way evangelical popular music is commonly understood. In a sense, the commune and the festival have ruptured conventional understandings of "sacred" and "secular." Third, JPUSA's evolution demonstrates how a group committed to certain ideologies can change as a result of pluralism. Thus this community serves as one case-study in howAmerican evangelical groups must reinvent their collective ethos and re-categorize their cultural products if they are to remain relevant. In so doing, JPUSA's presence challenges "establishment evangelicalism" and problematizes conventional understandings of the classifier "evangelical." JPUSA's commitment to social justice and emphasis on humanizing the Christian gospel (without fully redefining conventional understandings of human salvation) places them in a category best understood as "Evangelical Left."
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Title: Correlation of point defects in lithium-rich layered cathode materials for lithium-ion battery applications
Creator: James, Christine Nicole
Date: 2019
Collection: Electronic Theses & Dissertations
Description: The limiting component of lithium-ion batteries continues to be the cathode component. Since the layered materials, such as LiCoO2, have observed capacities of roughly half of their theoretical capacities, advances have been made in attempts to improve their stability and thus capacity. One such attempt is adding Li2MnO3, thus creating Li2MnO3-LiMO2 materials, where M is typically a transition metal ion or combination of transition metals. These Li2MnO3 stabilized materials have been shown to...
Show moreThe limiting component of lithium-ion batteries continues to be the cathode component. Since the layered materials, such as LiCoO2, have observed capacities of roughly half of their theoretical capacities, advances have been made in attempts to improve their stability and thus capacity. One such attempt is adding Li2MnO3, thus creating Li2MnO3-LiMO2 materials, where M is typically a transition metal ion or combination of transition metals. These Li2MnO3 stabilized materials have been shown to be promising with >200mAh/g but still suffer from performance issues. The Li2MnO3 component is observed to lose oxygen during the first charge cycle and thus creates Li2-XMnO3-δ. These oxygen vacancies are related to some of the cathode performance issues. However, the amount of oxygen released and the role of the oxygen vacancies are still not very well understood. Therefore, this work takes an atomic level computational approach using density functional theory calculations to explore the impact of oxygen vacancies and the correlated effects on voltage, capacity, lithium diffusion, chemical strain, dopants and electrolyte decomposition. Despite the extensive computational work in the literature on lithium transition metal oxide cathode materials, little work has been devoted to the correlated effects of two vacancy types in these materials. Therefore, this work offers novel approaches to model both vacancy types and their impacts on each other. First, it was found that the oxygen vacancies can decrease the formation energy of lithium vacancies. Less hopping of lithium atoms is observed and the energy barrier for lithium hopping is increased when oxygen vacancies are present. The calculated diffusion coefficient decreases by ~5 order of magnitude from the perfect crystal structure. This suggests oxygen vacancies cause an increased capacity but at the expense of decreased rate capability of these materials. The chemical strain associated with both non-dilute lithium vacancies and dilute vacancies were analyzed with an anisotropic model. It was found that the oxygen vacancies and lithium vacancies are highly correlated causing the associated chemical expansion to not be a linear sum of the individual vacancy types. The predicted chemical strain due to a low energy VLi-VO-VLi¬ dumbbell structure can be correlated with the in situ experimentally measured stress. To investigate if the amount of oxygen vacancies can be controlled, the effects of Si and Al dopants were also studied. The silicon was shown to decrease the oxygen vacancy formation energy in neighboring octahedral to the silicon, thus suggested to activate the manganese and increase the capacity of the materials, consistent with experimental observations. Lastly, the impact of surface oxygen vacancies on adsorption and decomposition of an electrolyte component, ethylene carbonate (EC), on the Li¬2MnO3 surface was investigated. A two proton removal reaction from EC to Li2MnO3 (131) was discovered, suggesting some beneficial effect on the perfect Li2MnO3 surface. However, an EC appears to be repelled near a surface oxygen vacancy. The released oxygen can react with the EC molecule and trigger different decomposition reactions. Overall, the oxygen vacancies generated in the lithium-rich layered cathode materials are shown to have a very highly correlated impact on lithium, dopant and electrolyte-surface interactions which therefore can significantly impact battery performance and life.
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Title: Computational methods for understanding environmental processes and toxicity
Creator: Gao, Feng (Graduate of Michigan State University)
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Understanding environmental processes, risks and toxicities of persistent organic pollutants (POPs) are needed to protect human and ecosystem health. Usually the toxic effects of POPs on human health are assessed using a variety of time- and cost-intensive in vivo and in vitro experiments; in vivo evaluations utilizing animals and further complicated by ethical concerns. Computational models provide an alternative way to laboratory based experiments. Indeed, computational models have recently...
Show moreUnderstanding environmental processes, risks and toxicities of persistent organic pollutants (POPs) are needed to protect human and ecosystem health. Usually the toxic effects of POPs on human health are assessed using a variety of time- and cost-intensive in vivo and in vitro experiments; in vivo evaluations utilizing animals and further complicated by ethical concerns. Computational models provide an alternative way to laboratory based experiments. Indeed, computational models have recently become widely used to study reaction mechanisms, make predictions of chemical toxicity, and for risk assessment. In this dissertation, I study two computational methods that could potentially be used to advance remediation of dioxin and assess chemical toxicity: 1) molecular dynamics simulation of dioxin adsorption in activated carbon pores and 2) toxicity prediction with deep learning models, with a special focus on geometric scattering methods. Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) are ubiquitous environmental contaminants that resist chemical, biological and physical routes of dissipation. They are well known for their toxicity, including adverse effects on reproductive health, impairment of mammalian immunity, and carcinogenicity. Adding activated carbons (ACs) to soils or sediments has been suggested as a means to promote the sequestration of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) in forms with reduced bioavailability and hence toxicity to humans and other mammals. However, the mechanisms and adsorption processes of dioxin by ACs are not well understood. Thus, molecular dynamics simulations were used to study the mechanism of dioxin adsorption in AC pores, and to evaluate the effects of pore size on dioxin adsorption. The results showed that smaller pores created a comparatively more hydrophobic sub-aqueous environment that promoted the adsorption of dioxins. Deep learning has achieved great successes in image recognition, natural language processing and many other tasks. Recently, the application of deep learning methods for toxicity predictions of organic molecules has gained increasing interest. Molecules can be treated as graphs, where atoms are nodes and bonds are edges. However regular deep learning methods cannot be directly applied to data in a non-Euclidean space such as graphs. Therefore, geometric scattering methods that generalize regular scattering transforms to non-Euclidean spaces are proposed herein. Scattering transforms was used to provide mathematical understanding of convolutional networks. The results in this dissertation showed that geometric scattering methods achieved near state-of-art results on multiple standard graph classification tasks, and can be used for various explorations of biochemical data. Finally, geometric scattering was applied for toxicity prediction with real-world toxicity datasets. The results demonstrate that it has excellent potential as an alternative approach for toxicity predictions.
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Title: Weighting in multilevel models
Creator: Tong, Bing
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Large-scale survey programs usually use complex sampling designs such as unequal probabilities of selection, stratifications, and/or clustering to collect data to save time and money. This leads to the necessity to incorporate sampling weights into multilevel models in order to obtain accurate estimates and valid inferences. However, the weighted multilevel estimators have been lately developed and minimal guidance is left on how to use sampling weights in multilevel models and which...
Show moreLarge-scale survey programs usually use complex sampling designs such as unequal probabilities of selection, stratifications, and/or clustering to collect data to save time and money. This leads to the necessity to incorporate sampling weights into multilevel models in order to obtain accurate estimates and valid inferences. However, the weighted multilevel estimators have been lately developed and minimal guidance is left on how to use sampling weights in multilevel models and which estimator is most appropriate.The goal of this study is to examine the performance of multilevel pseudo maximum likelihood (MPML) estimation methods using different scaling techniques under the informative and non-informative condition in the context of a two-stage sampling design with unequal probabilities of selection. Monte Carlo simulation methods are used to evaluate the impact of three factors, including informativeness of the sampling design, intraclass correlation coefficient (ICC), and estimation methods. Simulation results indicate that including sampling weights in the model still produce biased estimates for the school-level variance. In general, the weighted methods outperform the unweighted method in estimating intercept and student-level variance while the unweighted method outperforms the weighted methods for school-level variance estimation in the informative condition. In general, the cluster scaling estimation method is recommended in the informative sampling design. Under the non-informative condition, the unweighted method can be considered a better choice than the weighted methods for all the parameter estimates. Besides, the ICC has obvious effects on school-level variance estimates in the informative condition, but in the noninformative condition, it also affects intercept estimates. An empirical study is included to illustrate the model.
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