No description available.

This study is the geochemical examination of mineral weathering and its path from hinterland, through sediment deposition and pedogenesis, to its dissolution and eventual uptake into plants or precipitation as carbonate minerals. The three papers examine the rate and character of carbonate and silicate mineral weathering over a wide range of climatic and tectonic regimes, time periods, and lithologies, and focus on very different questions. Examination of the 87Sr/86Sr ratios of architectural ponderosa pine in Chaco Canyon, New Mexico confirms a societally complex style of timber procurement from the 10th to the 12th centuries. In El Malpais National Monument, New Mexico, we measured the 87Sr/86Sr ratios in local bedrock and soils and compared them to the leaf/wood cellulose of four conifers (Pinus ponderosa, Pinus edulis, Juniperus monosperma, Juniperus scopulorum), a deciduous tree (Populus tremuloides), three shrubs (Chrysothamus nauseosus, Fallugia paradoxa, Rhus trilobata), and an annual grass (Bouteloua gracilis) and a lichen (Xanthoparmelia lineola). We found that plant 87Sr/86Sr ratios covaried with variations in plant physiognomy, life history, and rooting depth. In addition, the proportion of atmospheric dust and bedrock mineral contributions to soil water 87Sr/86Sr ratios varied predictably with landscape age and bedrock lithology. On the Himalayan floodplain, soils and paleosol silicate weathering intensities were measured along a climatic transect and through time. Overall, carbonate weathering dominates floodplain weathering. But, periods of more intense silicate weathering between 9 - 2 Ma, identified in soil profile and in the 87Sr/86Sr ratios of pedogenic carbonates, appear to be driven by changes in tectonic, rather than climatic, regime. All three papers are good examples of how 87Sr/86Sr isotopic tracer studies can shed light on pedogenic formation rates and internal processes. The complexity of each system warns against generalizations based on just one locale, one species or lithology, or a few isotopic ratios.

Years of habitat loss, hatchery production and water regulation in the Puntledge River have potentially compromised diversity in coho salmon. Diversity was interpreted from age and early rearing history of mature coho that returned to spawn in 2009 (n=28). Life history groups were interpreted through a visual analysis of the micro-chemistry profiles in the otoliths. There were 2 age classes and 9 life history groups detected. Group differences in Sr:Ca, Ba:Ca and Mn:Ca were significant (p<0.0001) between groups with >2 members (n=6). Cluster analysis using Sr:Ca and Ba:Ca resulted in similar groups. Sr:Ca profiles indicate different rearing habitats, coho that reared in both freshwater and the estuary, and a Jack that reared entirely in the estuary. Results support the need for further studies on the extent of diversity in Puntledge coho, and management actions that identify, restore and protect important rearing habitats.

No description available.

No description available.

More than one million people worldwide receive some kind of bone graft each year. Grafts are often needed following bone tumour removal or traumatic fractures to fill voids in the bone and to aid in the healing process. The most common method involves bone transplantation, in which bone tissue is taken from one site to fill the defect in another site. The procedure thus involves two surgeries, which leads to an increased risk of complications. New, synthetic graft materials that can be used to fill defects and minimise the complications associated with bone tissue harvesting are therefore necessary. The synthetic materials available today lack the inherent biological factors of bone that stimulate the bone regeneration process. Much of today’s research concerning synthetic bone graft materials aims to solve this issue and researchers have suggested several different strategies. The purpose of this thesis is to improve the performance of acidic calcium phosphate cements, which are materials used as synthetic bone grafts. By combining these cements with drugs or ion additives, local delivery could be achieved with the potential to stimulate bone formation. Two different combinations were attempted in this thesis: cement in combination with simvastatin, or cement in combination with strontium halide salts. Both simvastatin and strontium are known to positively affect bone formation. The efficacy of the cements with the additives was evaluated using different bone cell cultures. The results regarding simvastatin showed that the cement’s mechanical property was not affected upon drug loading, and that the drug was released by a diffusion-controlled mechanism. Moreover, results showed that simvastatin stimulated the bone-forming cells (osteoblasts) to produce more bone tissue, while it inhibited bone-degrading cells (osteoclasts) from degrading the cement. These findings suggest that simvastatin could aid in the bone regeneration process in the local area surrounding the cement. The main purpose of the study using strontium halide salts was to increase the cement’s X-ray contrast, which is a property used to monitor cement during injection. In addition, strontium is believed to positively affect bone cells. The X-ray contrast did increase after the addition of 10 wt% strontium bromide or strontium iodide, while the cell study results did not indicate any significant effects on the bone-forming cells. In the last section of this thesis, zebrafish were used as a model to evaluate bone formation upon treatment with degradation products from synthetic bone grafts. The zebrafish is a small organism with 70 % gene homology to humans; due to its transparency, fast development and ease of handling, it is an interesting model for high-throughput studies. Silicate, which is an ionic degradation product of many different bone substitute materials, was used as a proof-of-concept to visualise bone formation in these fish. The results showed an increased bone formation upon treatment with 0.625 μM silicate ions. The results suggest that this model could be used as a complement to bone cell culture studies in pre-clinical evaluations of the degradation products of bone substitute materials, thus helping researchers to design materials with degradation products that could stimulate bone formation.

The collection and analysis of a large number of belemnites and oysters with excellent biostratigraphic and diagenetic control has resulted in a highly detailed determination of the seawater Sr-isotope curve through the Jurassic and Early Cretaceous. The new data confirm the broad trends established by previous work, but the much sharper resolution of the new data allows the application of Sr-isotope stratigraphy with an optimal stratigraphic resolution of ± 1 to 4 ammonite subzones (± 0.5 to 2 Ma). The data show a general decline from the Hettangian (Early Jurassic) to a minimum in the Callovian and Oxfordian (Middle/Late Jurassic). This is followed by an increase through the Kimmeridgian (Late Jurassic) to a plateau reached in the Barremian (Early Cretaceous). In addition, there are major negative excursions in the Pliensbachian/Toarcian (Early Jurassic) and Aptian/Albian (Early Cretaceous). Stable isotope data collected from belemnites and oysters have resulted in the most extensive Jurassic δ¹³C and δ¹⁸O database to date. While both the carbon and oxygen data appear to give reasonable marine signals, the scatter in the data suggests that future research must document possible biological fractionation effects and develop better indicators for the diagenetic alteration of 613C and 6i 8O. The final chapter documents an unexpected correlation between sudden shifts in the Sr-isotope curve, the occurrence of positive 513C excursions, and the eruption of flood basalts. In the Jurassic and Cretaceous there is a correlation in time between sudden downward shifts in the Sr-isotope curve (Pliensbachian, Aptian, Cenomanian/Turonian), the occurance of positive 613C excursions, and the eruption of flood basalts. Each of these major downward shifts in the Sr-isotope curve is followed by a sudden upward shift, which although associated with a positive 613C excursion is not associated with an episode of flood basalt volcanism. In the Cenozoic the Sr-isotope curve no longer displays downward shifts, but the correlation continues between the occurrence of flood basalts and positive 513C excursions. Several lines of evidence suggest that the eruption of flood basalts is associated with pulses of hydrothermal activity, and that this hydrothermal activity brings about the conditions necessary for the genesis of carbon-burial events.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 39-42). Also available on the World Wide Web.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Douglas J. Buttrey, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 194-209).