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- Title
- A comparison of two mediation analysis methods with sequential mediators
- Creator
- Bennett, Kyle
- Date
- 2019
- Collection
- Electronic Theses & Dissertations
- Description
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"Two methods for mediation analysis with sequential mediators were compared using multiple simulation scenarios. The performances of each method were assessed using three key metrics: relative bias, root mean square error, and coverage. The methods shared both similarities and key differences and some modification and adjustment were necessary to perform comparable simulations across the scenarios. Overall performance was assessed primarily using relative bias, where each simulated effect...
Show more"Two methods for mediation analysis with sequential mediators were compared using multiple simulation scenarios. The performances of each method were assessed using three key metrics: relative bias, root mean square error, and coverage. The methods shared both similarities and key differences and some modification and adjustment were necessary to perform comparable simulations across the scenarios. Overall performance was assessed primarily using relative bias, where each simulated effect estimate was compared to a "true" effect generated by simulating from a theoretical super population. Simulation scenarios included correctly specified models using both methods and various mis-specified estimation models by incorrectly specifying a critical parameter in the model to assess the performance and robustness of each mediation analysis method. The results of the simulations suggest that one method was particularly more resilient to mis-specification of the model over the other, and that proper specification of the marginal structural model is also critical to minimizing bias and maximizing coverage."--Page ii.
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- Title
- Variations in edible meat between purebred & crossbred roasting chickens
- Creator
- Pillar, Raymond
- Date
- 1941
- Collection
- Electronic Theses & Dissertations
- Title
- A multiport approach to modeling electromechanical systems
- Creator
- Moynes, John Francis
- Date
- 1976
- Collection
- Electronic Theses & Dissertations
- Title
- A study of types of magazine picture appeal and editors' ability to predict readers' picture-value judgment [sic]
- Creator
- Kao, Anne Li-an
- Date
- 1964
- Collection
- Electronic Theses & Dissertations
- Title
- An evaluation of market coordination in the Bolivian rice industry
- Creator
- Moran, Michael Joseph
- Date
- 1968
- Collection
- Electronic Theses & Dissertations
- Title
- A matrix of social and personality variables for the prediction of school achievement
- Creator
- Gigliotti, Richard Joseph, 1945-
- Date
- 1969
- Collection
- Electronic Theses & Dissertations
- Title
- Paper money and the Massachusetts Land Bank, 1740
- Creator
- Adams, Glenn Dallas
- Date
- 1950
- Collection
- Electronic Theses & Dissertations
- Title
- Improvements in fine-scale estimation and evaluation of geographic variables using climate data in East Africa
- Creator
- Hession, Sarah L.
- Date
- 2011
- Collection
- Electronic Theses & Dissertations
- Description
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Global environmental change has surfaced as a critical issue to both the scientific community and the general public. One aspect of particular concern involves climate change, which will exert impacts on ecosystems and economies, presenting considerable challenge to human adaptation. In Africa, a continent that is vulnerable due to multiple stressors and low adaptive capacity, climate change is expected to significantly affect both people and ecosystems. Adaptation strategies are being...
Show moreGlobal environmental change has surfaced as a critical issue to both the scientific community and the general public. One aspect of particular concern involves climate change, which will exert impacts on ecosystems and economies, presenting considerable challenge to human adaptation. In Africa, a continent that is vulnerable due to multiple stressors and low adaptive capacity, climate change is expected to significantly affect both people and ecosystems. Adaptation strategies are being developed using information from studies that evaluate the impacts of climate variability and climate change in Africa. Recommendations are made for local development of adaptation strategies due to the heterogeneity of climate change and its effects on East Africa's climate. However, global climate change models are coarse in scale and mask much of the local variation in regional climate, indicating the need for higher resolution climate data. This dissertation addresses this need by comparing spatially explicit statistical methods of interpolation and prediction, both theoretically and empirically; expanding upon the method of universal kriging by incorporating complex feedback relationships that may produce simultaneity between precipitation and its covariates; and evaluating precipitation patterns over space in East Africa through a case study. Mechanisms of precipitation have been considered in detail, expanding upon many other spatially explicit applications of prediction methods to date. Further, spatially explicit inferential regression models have been developed to better understand spatial patterns and variability in East African precipitation. Predicted maps of precipitation, generated at a resolution of 1 kilometer, accurately reflect the mesoscale influences of topography and the presence of large water bodies (i.e., Lake Victoria) as well as the seasonal influences of the passing of the intertropical convergence zone (ITCZ). In terms of prediction, the spatially explicit methods considered herein clearly outperformed a global data set (i.e., the CRU TS 3.1) in terms of error and ability to reflect local variability. The method of local ordinary kriging generally outperformed the multivariate kriging techniques, indicating that precipitation patterns in areas of high topographic variability, such as East Africa, may be modeled as well or better using local search neighborhoods in the kriging process rather than using complex multivariate regression models. However, additional work to improve the multivariate regression models and overall levels of correlation are expected to yield improved prediction results. Furthermore, the case study successfully demonstrated that the newly developed method of universal kriging with instrumental variables performs similarly to other standard methods of estimation, and perhaps better in the presence of significant measurable simultaneity.
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- Title
- The biology of Solierella plenoculoides plenoculoides
- Creator
- Boggs, Gordon Lee
- Date
- 1968
- Collection
- Electronic Theses & Dissertations
- Title
- The feasibility of establishing a feed analytical service for Michigan cattle feeders
- Creator
- Bortel, William Lee
- Date
- 1966
- Collection
- Electronic Theses & Dissertations
- Title
- A study of soil water movement as affected by drainage
- Creator
- Bornstein, Joseph
- Date
- 1949
- Collection
- Electronic Theses & Dissertations
- Title
- From synthesis to behavioral activity in streams : investigations of putative sea lamprey pheromone components
- Creator
- Brant, Cory Olaf
- Date
- 2011
- Collection
- Electronic Theses & Dissertations
- Description
-
The sea lamprey (Petromyzon marinus L.) has become a model species in the study of bile acid production and release into the environment where these compounds function as intraspecific chemical signals. Throughout the later stages of their life history, sea lampreys have been shown to rely upon pheromone communication to mediate reproduction. Laboratory and stream behavioral bioassays have implicated 3-keto petromyzonol sulfate (3kPZS) as a lamprey mating pheromone, but the full function of...
Show moreThe sea lamprey (Petromyzon marinus L.) has become a model species in the study of bile acid production and release into the environment where these compounds function as intraspecific chemical signals. Throughout the later stages of their life history, sea lampreys have been shown to rely upon pheromone communication to mediate reproduction. Laboratory and stream behavioral bioassays have implicated 3-keto petromyzonol sulfate (3kPZS) as a lamprey mating pheromone, but the full function of this bile alcohol derivative remains to be elucidated. Further, the biosynthesis, regulation, and release of 3kPZS and other putative components of the pheromone remain only partially characterized. In Chapter 1 of this thesis, I observed the behaviors of migratory females to the presence of 3kPZS in streams across a typical migratory season. In Chapter 2, the synthesis, transport, and release of several steroid-derived compounds in adult male sea lampreys were further examined using analytical chemistry and molecular biology-based approaches in adult males. The data presented here further characterize the male mating pheromone in sea lamprey, contribute to the understanding of pheromone communication in vertebrates, and provide implications for controlling the invasive species in the Laurentian Great Lakes.
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- Title
- Evaluating the impact of Gliricidia sepium on soil organic matter in maize-based cropping systems in southern Malawi
- Creator
- Beedy, Tracy L.
- Date
- 2009
- Collection
- Electronic Theses & Dissertations
- Title
- Effect of cyclic AMP in modulating cell differentiation and survival behaviors
- Creator
- Zhang, Linxia
- Date
- 2010
- Collection
- Electronic Theses & Dissertations
- Title
- Electronic structure and excited state dynamics of chromium(III) complexes
- Creator
- Schrauben, Joel Nicholas
- Date
- 2010
- Collection
- Electronic Theses & Dissertations
- Title
- How many fish are there and how many can we kill? : improving catch per effort indices of abundance and evaluating harvest control rules for lake whitefish in the Great Lakes
- Creator
- Deroba, Jonathan J.
- Date
- 2009
- Collection
- Electronic Theses & Dissertations
- Title
- The synthesis and reactions of dichloromethaneboronic esters
- Creator
- Wu, Show-jen Grace
- Date
- 1971
- Collection
- Electronic Theses & Dissertations
- 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
- The effect of kind and concentration of sugar on gluten formation and character
- Creator
- Meiske, Donna Poland
- Date
- 1957
- Collection
- Electronic Theses & Dissertations
- 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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