Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 51 for “"stable isotope ratios"”.
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Inferring Extinct Reptilian Response To Global Warming: Insights From Modern Stable Isotope Ratios
… are disconnected from the taxon of interest. Stable isotope geochemistry, however, provides an independent test. I analyzed stable isotope ratios (δ¹⁸O, δ¹³C) from enamel, providing new data on the connection between morphology, diet, and environment. I find a trophic separation in δ¹³C, and …
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Composition of fine and ultra-fine particles and source identification by stable isotope ratios
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998.
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Selenium Stable Isotope Ratios in Wetlands: Insights Into Biogeochemical Cycling and How a Diffusive Barrier Affects the Measured Fractionation Factor
… via reduction, sorption, and assimilation. Isotope fractionation studies can potentially distinguish reduction from other removal processes, and possibly quantify the amount of reduction, assuming that the correct isotope fractionation factor, alpha, is applied. Typically, alpha is …
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STABLE ISOTOPE RATIOS AS A PROXY FOR HUMAN GEOGRAPHIC PROVENANCE: BIOGEOGRAPHICAL EVIDENCE FROM THE 2H, 18O, AND 13C SIGNATURES IN MODERN HUMAN TEETH
… personnel or do not yield immediate results. Stable isotope analysis of biogenic tissues such as tooth enamel and bone mineral has become a well‐recognized and increasingly important method for determining the provenance of human remains, and it has been used successfully in bioarchaeological …
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The use of stable isotope ratios of carbon and nitrogen to elucidate pelagic marine foodwebs of the Benguela and Agulhas Bank regions of South Africa
Isotope assessments of foodweb relationships amongst pelagic organisms may be influenced by their lipid content, since lipids are more depleted in ¹³C than other biochemical compounds. This is particularly important for plankton which show a greater decrease in δ¹³C caused by the failure to remove …
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Assessing the effect of feather wear on carbon and nitrogen stable isotope ratios, and the use of stable isotopes to determine predator diets in the Namibian Islands marine protected area
The stable isotope (SI) approach is widely used in ecological research to tackle problems such as delineating food web structure or tracing the migratory origins of various organisms. This thesis first tested the widely accepted assumption that SI ratios are fixed in an inert tissue, and then used …
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A multi-indicator approach to dietary assessments within Lake Michigan's nearshore area
… growth, development, and condition of predators. Stable isotope ratios have been used to infer community structure for decades, while fatty acid signatures have only recently been used in terrestrial and marine systems to explore dietary trends. Using a data set collected from Lake Michigan …
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Isotopic fractionation of chromium and uranium during abiotic and microbial Cr(VI) reduction and microbial U(VI) reduction
… These reduction reactions fractionate Cr isotopes and alter the Cr stable isotope ratios. Cr stable isotope ratios can be used to track the extent of this reduction and thus can be used as a redox-indicator. The magnitude of the isotopic fractionation must be determined to connect observed …
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Stable isotope and organic biomarker analysis of the late Proterozoic Coppercap formation in the MacKenzie Mountains
Sulfur and carbon stable isotope ratios and organic biomarker abundance were performed on drill core samples from the Coppercap Formation of the Coates Lake Group in the Windermere Supergroup of the MacKenzie Mountains to reconstruct an environmental condition proceeding the first Neoproterozoic …
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Mediterranean forest resilience to drought and climate change
… strong differences between pines and oaks in the stable isotope ratios of carbon, probably driven by underlying differences in water-use efficiency, and differences in the stable isotope ratios of nitrogen, probably driven by underlying differences in species’ investments in the photosynthetic …
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STABLE ISOTOPIC INSIGHTS INTO THE SUBSISTENCE PATTERNS OF PREHISTORIC DOGS (CANIS FAMILIARIS) AND THEIR HUMAN COUNTERPARTS IN NORTHEASTERN NORTH AMERICA
… in the Northeast region of North America using stable isotope analysis. The second goal of this study is to generate independent data concerning the presence or absence of C4 resources, such as maize, in the diets of dogs. Third, this study investigates the use of dog bone as a proxy for human …
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A heavy stable isotope approach to tracing mantle source and process
… part of this variability. Recently, heavy stable isotopes have been suggested as a new tool to complement existing tracers of mantle heterogeneity and lithology (e.g., major and trace elements, radiogenic isotopes), because mineral- and redox-specific equilibrium stable isotope …
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Oxygen isotopes as a tracer of biospheric CO2 gross fluxes : a local feasibility study
… Diurnal cycles of atmospheric CO2 and its stable isotope ratios, of the 18O/16O ratio of atmospheric water vapour, leaf and soil water were measured. The data sets were then quantitatively interpreted in a 222Radon-transport-calibrated 1-D canopy box model. On the basis of observations and …
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Eco-hydrological pathways inferred from stable isotopes in a Pinus ponderosa and Pinus monophylla woodland of the Sheep Range, southern Great Basin, USA
… or summer precipitation from the NAMS. Stable isotope ratios were used to examine seasonal plant water sources in two high-elevation tree species found in the southern Great Basin of Nevada- <italic>Pinus ponderosa</italic> and <italic>Pinus monophylla</italic>.Samples of xylem and leaf …
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The Trophic Ecology of Psammechinus miliaris in Scottish Sea Lochs
… state) with the fatty acid biochemistry and stable isotope ratios of Carbon and Nitrogen. These studies revealed high levels of spatial and temporal heterogeneity in the trophic interactions of P. miliaris and suggested that the populations<br/>exhibited significant levels of omnivory. The …
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A comprehensive chemical examination of methylamphetamine produced from pseudoephedrine extracted from cold medication
… of gas chromatography mass spectrometry (GCMS), isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry (ICPMS) to characterize methylamphetamine hydrochloride synthesised from precursors extracted from proprietary cold medication using three different extraction …
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Temporal Variations of delta 2 H, delta 18 O and Deuterium Excess in Atmospheric Moisture and Improvements in the CO 2 -H 2 O Equilibration Technique for 18 O/ 16 O Isotope Ratio Analysis
A continuous 18-year record (1981-2000) of the stable isotope ratios D/H and 18O/16O in atmospheric water vapour collected at the Central European site Heidelberg (49° 25’ N and 8° 41’ E) is analysed. Its basic features, such as seasonal variations of D/H and 18O/16O, are discussed and compared …
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The source of excess nutrients to Pine Draw, Turnbull National Wildlife Refuge
… for the duration of the sampling period. We used stable isotope ratios of oxygen and nitrogen in nitrate to determine that the source of nitrogen to Philleo drainage, groundwater and Pine Draw was a combination of ammonium fertilizer and soil nitrate varying seasonally based on water source.</p>
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Hyperspectral Reflectance and Stable Isotopic Nitrogen: Tools to Assess Forest Ecosystem Nitrogen Cycling
… between hyperspectral remote sensing, N stable isotope ratios ("15N) and growth response to nitrogenous fertilizer. In both species multiple linear regression models relating leaf-level reflectance to "15N showed strong predictive capabilities, with some models explaining more than 65% of …
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Stable Isotope Variability in the American Food Supply: Implications for Dietary Reconstruction Applications
Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) in human tissues, which reflect the stable isotope composition of the diet, offer numerous applications in the field of nutrition. One of the biggest contributors to uncertainty in stable isotope dietary reconstruction applications is …
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