Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 110-120). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 110-120). Also available on the Internet.

Lithium-ion (Li-ion) batteries are critically important for portable electronics, electric vehicles, and grid-level energy storage. The development of next-generation Li-ion batteries requires high-capacity electrodes with a long cycle life. However, the high capacity of Li storage is usually accompanied by large volume changes, dramatic morphological evolution, and mechanical failures in the electrodes during charge and discharge cycling. To understand the degradation of electrodes and resulting loss of capacity, this thesis aims to develop mechanistic-based models for predicting the chemo-mechanical processes of lithiation and delithiation in high-capacity electrode materials. To this end, we develop both continuum and atomistic models that simulate mass transport, interface reaction, phase and microstructural evolution, stress generation and damage accumulation through crack or void formation in the electrodes. The modeling studies are tightly coupled with in-situ transmission electron microscopy (TEM) experiments to gain unprecedented mechanistic insights into electrochemically-driven structural evolution and damage processes in high-capacity electrodes. Our models are successfully applied to the study of the two-phase lithiation and associated stress generation in both crystalline and amorphous silicon anodes, which have the highest known theoretical charge capacity, as well as the lithiation/sodiation-induced structural changes and mechanical failures in silicon-based multilayer electrodes. The modeling studies have uncovered unexpected electrochemical reaction mechanisms and revealed novel failure modes in silicon-based nanostructured anodes. Our modeling research provides insights into how to mitigate electrode degradation and enhance capacity retention in Li-ion batteries. More broadly, our work has implications for the design of nanostructured electrodes in next-generation energy storage systems.

The ability of an asphalt mix to heal is an important property that influences the overall fatigue performance of the mix in the field. Micro damage healing in an asphalt mix is a function of several factors such as the physical and chemical properties of the binder, properties of the mixture, level of damage prior to the rest period during which healing occurs, duration of the rest period, temperature, and pressure. This thesis presents details from a two-part study that addresses the following aspects. In the first part of this study, a DSR based test method was developed to measure inherent healing in asphalt binder and a modified form of the Avrami equation was used to model it. In the second part of this study, an experimental and analytical method based on viscoelastic continuum damage theory was developed to characterize the healing in an asphalt composite (fine aggregate matrix) as a function of the level of damage prior to the rest period and the duration of the rest period. The intrinsic healing of three different asphalt binders was measured at three different temperatures and two aging conditions and it was further demonstrated to be the sum of two components: instantaneous strength gain immediately upon wetting and time dependent strength gain. The intrinsic healing results obtained from the DSR tests were demonstrated to be in agreement with the hypothesis that time dependent intrinsic healing increases with an increase in temperature and decreases with aging of the asphalt binder. The overall healing was measured in four different fine aggregate matrix (FAM) asphalt mixes and various tests were performed to quantify overall healing at isothermal and short term aged test conditions. Additionally two different verification tests were also conducted to demonstrate that the percentage healing measured using the proposed method are independent of the sequence of loading or rest periods. Finally, the overall healing results were demonstrated to support the hypothesis that the healing characteristics determined using the proposed test method can be treated as a characteristic material property. / text

Evapotranspiration dominates the water budget in drylands, exerting important controls not only on the dynamics of water, but also on the amount and distribution of vegetation on a landscape. The spatial and temporal variability of vegetation cover imposes constraints on key ecohydrological processes that feedback to the dynamics of evapotranspiration and, most importantly, its partitioning between direct evaporation and transpiration from plants, one of the most significant ecohydrological challenges. Yet, lacking are systematic evaluations of how variations in woody plant cover--a fundamental vegetation attribute of landscapes that can vary spatially with amount of cover and temporally with leaf phenology-- influence the dynamics of soil microclimate and ultimately the partitioning of evapotranspiration into its components. This study presents the results of field experiments that systematically evaluated the effects of amount of canopy cover and its seasonality in both surface microclimate and soil evaporation. These field observations are complemented by controlled experiments that directly evaluate the relationship between amount of canopy cover and the partitioning of evapotranspiration, with an assessment of its larger-scale implications using a regional land surface-atmosphere model. Finally, this study presents a classroom-adaptation of the evapotranspiration partitioning experiment that was used to effectively translate new scientific concepts and information into k-12 classrooms. Overall, the results from this study provide a comprehensive understanding about the interactive ways in which canopy cover, canopy structure attributes and plant phenology influence soil surface microclimate--characterized by near-ground solar radiation and soil temperature--and soil evaporation. More specifically, the results illustrate how the main control of deciduous-woody vegetation on soil evaporation is the addition of litter to the surface. However, in absence of litter, attributes of woody cover influence soil evaporation variably with season and phenology. Further, The results from this study illustrate how the partitioning of evapotranspiration exhibits a non-linear response to amount of woody canopy cover. Notably, when incorporated into a regional surface-atmosphere model, this non-linearity strongly affects water fluxes, highlighting the potential implications for ecological, hydrological, and atmospheric processes associated with the partitioning of evapotranspiration, providing important insights for natural resource management.

Animals appear in many guises in Charles Dickens’s novels, as wild animals, domestic animals, animals used in the service of humans, and, not least, as images and symbols. Based on a close reading of all of Dickens’s major novels, this thesis centres on the symbolic use of (both metaphorical and actual) animals in the depiction of human characters, the chief aim being to explore a phenomenon that Dickens frequently resorts to, namely, the animalisation of human characters. Certain Dickensian characters are in fact more or less consistently compared to animals – to animals in general, or to specific animals. On occasion, not only individual characters but also groups of characters are animalised, and sometimes to the point of dehumanisation. By and large, being animalised equals being portrayed in a negative light, as if what Dickens himself at one point termed “the divine spark” – the special light accorded to the human brain as opposed to the animal brain – has been extinguished or has at least become almost imperceptible. Furthermore, in conjunction with the investigation of Dickens’s animalisation of human characters, the thesis discusses his implicit attitude to the human-animal divide and argues that, though largely anthropocentric and hierarchical, it also points to a view of human and nonhuman animals as part of a continuum, with no fixed boundaries. A number of different approaches inform the discussion, but theoretical frameworks such as ecocriticism and, above all, contemporary theory on the significance of Darwin’s ideas in the Victorian era, are foregrounded.

The most widely accepted approach to long-term storage of nuclear waste is to design and construct a deep geological repository, where the geological environment acts as a natural barrier to radio nuclide migration. Sedimentary rocks, particularly argillaceous formations, are being investigated by many countries because of favorable isolating qualities (laterally continuous and low permeability) and the ability of self-sealing of fractures. Underground construction creates a damage zone around the excavation. The depth away from the excavation surface of the damage zone depends on the rock mass properties, the stress field, and the construction method. This research investigates the fracture development process in sedimentary rocks and evaluates continuum modelling methods to predict the damage zone dimensions. At the laboratory scale, a complete classification system for samples of carbonate and siliciclastic rocks has been developed, with geotechnical considerations, which when applied narrows the variability of the mechanical properties. Using this system, crack initiation (CI) shows the most uniform range in each class, particularly for mud rocks. Tensile strength was found to be higher for the Brazilian method than Direct method of testing. Brazilian reduction to Direct values was found to be rock type dependent. Laboratory testing results are also influenced by the orientation of bedding. Bedding and other structures were also found to influence the excavation behaviour as observed at the Niagara Tunnel Project in a mudstone and in excavations in the Quintner limestone of Switzerland. The conceptual stages of damage development and the potential fracture networks in sedimentary rocks are used to summarize the understanding of excavation damage developed in this thesis. Using a continuum based modelling approach, a set of predictive damage depth curves were developed for the different excavation damage zones. This approach was found to be most sensitive to the tensile strength used as an input. Back analysis of the Niagara Tunnel Project and forward prediction of the excavation damage around a shaft in the Queenston Formation are used to illustrate the importance of this research. The prediction methods were also applied to cut-off design analysis. This research has enhanced the understanding of excavation damage development in sedimentary rocks and provided a methodology to predict the dimensions of the excavation damage zones using a continuum based approach. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2014-01-29 16:08:58.022

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No description available.

Sterols have been identified as major components of membrane lipids that are part of specialized membrane domains necessary for organizing events such as polar protein targeting and signal transduction in plants, fungi and animals. However a common modification of sterols is the addition of sugar moieties via glycosylation abundantly found in plants. An exact physiological role for such diversification of sterols in plants is still unknown. Using reverse genetics and transcriptomics we show that UDP-glucose: sterol glucosyltransferase encoded by UGT80B1 is necessary for correct epidermal patterning in Arabidopsis root. Patterning of hair cells (trichoblasts) and non-hair cells (atrichoblasts) in the epidermis of the Arabidopsis root involves signaling through SCRAMBLED (SCM), a plasma membrane localized LRR-RL kinase. Feedback regulation via the transcriptional regulatory complex containing R2R3-MYB transcription factor WEREWOLF (WER) represses SCM and activates the homeodomain-leucine-zipper protein GLABRA2 (GL2) in atrichoblasts. Evidence suggests symplastic connections between cells, known as plasmodesmata, establish passage ways for single-repeat R3-MYB transcription factors to activate SCM expression in trichoblasts. Mutations in UGT80B1 cause atypical localization patterns of GL2, WER, and SCM in the root epidermis. The ugt80B1 formed fewer trichoblasts in comparison to wild-type. A translational fusion of UGT80B1 to GFP localizes to the ER, plasma membrane and to sites that appear to be plasmodesmata-associated desmotubules. Ultrastructural analysis revealed abnormalities in plasmodesmata formation and morphology in ugt80B1 mutants. Steryl glucoside profiling indicated deficiencies in specific glycosylated sterol compounds in roots. This study identifies UGT80B1 as a novel membrane component that is critical for plasmodesmata morphogenesis and cell-fate determination in the root epidermis. A model is proposed in which UGT80B1 activity provides spatially discreet sterol and steryl glucoside architecture within the plasma membrane to anchor the SCM receptor and within plasmosdesmata to facilitate intercellular movement of R3-MYB regulatory proteins underlying proper differentiation of trichoblasts versus atrichoblasts. Moreover, evidence from reverse genetics, proteomics and live cell imaging point to a actin dependent localization of UGT80B1 at the vesicle rich zone of root hair tip. This localization actively supports root hair elongation via tip growth, possibly by membrane modifications required for vesicle trafficking.