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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 125 for “"oxygen isotope"”.
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Oxygen isotope systematics of nitrification
During nitrification there is an exchange of oxygen atoms between water and nitrite, causing the [delta]¹⁸O of nitrate produced by nitrification to be closer to the [delta]¹⁸O of water than expected. A series of lab and field experiments were set up in order to quantify the exchange, and then …
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Oxygen isotope composition of megacrysts from the Monastery kimberlite
Kimberlite megacrysts are large (>1 cm diameter) crystals that are thought to have crystallized from sub lithospheric proto-kimberlite melts near the base of the subcontinental lithospheric mantle (SCLM) during complex melt-SCLM interactions. Thus, these megacrysts represent an excellent …
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Triple oxygen isotope measurements in chert: insights into the Snowball Earth glaciations
… for the trajectory of life, atmospheric oxygen, and planetary habitability. There remains a myriad of questions about the dynamics of these global glaciations, especially regarding the relationship between the cryosphere and hydrosphere during this time. This study analyzes silica …
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An inverse approach to understanding benthic oxygen isotope records from the last deglaciation
… a gradual warming and a decrease of the seawater oxygen isotope ratio 18O (a signature of melting land ice sheets). These changes do not occur uniformly in the ocean, but propagate like plumes of dye over hundreds and thousands of years, the aggregate results of turbulent advective and diffusive …
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An inverse approach to understanding benthic oxygen isotope records from the last deglaciation
… a gradual warming and a decrease of the seawater oxygen isotope ratio 5180 (a signature of melting land ice sheets). These changes do not occur uniformly in the ocean, but propagate like plumes of dye over hundreds and thousands of years, the aggregate results of turbulent advective and diffusive …
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Investigation of the Oxygen Isotope Exchange Between Carbon Dioxide and O3 via O(1D)
… shows an increasing enrichment in the heavy oxygen isotopes with altitude which preferential enrichment for 17O according to d17O =1.7 d18O. This is contrary to tropospheric CO2 where d17O ~ 0.5d18O. These isotope enrichments are transferred from O3 into CO2, but details of the mechanism are …
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The oxygen isotope composition of the country rock of the Koegel Fontein igneous complex
… and Harris, 2018). This thesis investigates the oxygen isotope composition of the country rock of the Koegel Fontein Complex, which consists of Namaqua-Natal Belt granulite facies rock and minor remnants of overlying Gariep Supergroup metasedimentary rock. The Brak Fontein Shear Zone (BFSZ) is …
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Coccoliths and oxygen isotope observations from the sediment surface of the southwest Indian Ocean
… resistant microfossils below this depth. Stable oxygen isotope ratios in a planktonic foraminifera and percent abundances of E. huxleyi reveal that apart from cores taken in the Agulhas Passage, most of the core-top samples are probably less than 85,000 yrs. BP. Lightest isotope ratios of -1.5 to …
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Stable oxygen isotope variability in seawater: Insights into past and present ocean circulation and hydroclimate
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-02-04 without embargo terms
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Triple oxygen isotope measurements by tunable infrared laser direct absorption spectroscopy, and applications to ratite eggshell
… for highprecision measurement of the three oxygen isotopes directly in CO2 samples using Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS). After the introduction and optimization of both the sample preparation and analytical systems, it is applied to fossil ratite eggshell …
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Application of Hydrogen and Oxygen Isotope Ratios of Water to the Study of Evaporation, Palaeoclimate, and Ancient Marine Conditions
Triple-oxygen and hydrogen isotopes of water are critical to aid our understanding of the hydrological cycle on the modern and ancient Earth. As such, this thesis presents advancements in techniques and in the understanding of the isotopic behaviour of water that undergoes evaporation in different …
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Childhood diet and mobility at medieval (1240s AD) Solt-Tetelhegy, Hungary as reconstructed from stable carbon, nitrogen, and oxygen isotope analysis
… of Solt-Tételhegy. Stable carbon and nitrogen isotope analyses were conducted on dental enamel and dentin from 24 individuals to examine their childhood diet. Although previous stable isotopic research has described the diet of medieval European peoples, this is the first such study on a …
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A detailed petrographic and oxygen isotope study of metamorphic rocks and archean basement complex Gneisses from the Vredefort dome, South Africa
Metamorphism observed in the Vredefort structure increases in grade on a regional scale from lower greenschist facies in the outer perimeter of the Potchefstroom syncline, throughupper greenschist and amphibolite grades within rocks of the Witwatersrand Supergroupand Dominion Group in the collar of …
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Water balance and productivity of a Mediterranean oak woodland : Quantifying understory vegetation impacts by development of a stable oxygen isotope partitioning approach
… technique were combined with a novel stable oxygen isotope partitioning approach. Stable oxygen isotopes are valuable tracers for water movements within the ecosystem, but due to methodological restrictions in the past, it was necessary to validate modeling approaches and derive field …
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Stable carbon and oxygen isotope investigation of Pleistocene growing-season paleoclimate using tree-ring cellulose from the Missinaibi Formation, Adam Creek, James Bay Lowland, Canada
… and temperature. We analyzed stable isotopes of carbon (δ13Ccellulose) and oxygen (δ18Ocellulose) in early-wood and late-wood of five conifer sub-fossil wood samples from the Missinaibi Formation, which likely grew during the peak of Marine Isotope Substage (MIS) 5a (~82 kya) at Adam …
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Sedentism among the Archaic fisher-folk of northern Chile: A malacological perspective
Oxygen isotope analysis of shell material from the Camarones West Shell Midden and from the site of Quiani has revealed that year-round collection of shellfish for food by the people of the Chinchorro Culture was not practiced. Additional shell demographics from the site of Quiani further support …
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A 20,000 year flowstone record of Gulf of Mexico sourced moisture in Texas
… As part of this effort, speleothem-based oxygen isotope records have been used to hypothesize the contribution of either Gulf of Mexico (GoM) or Pacific Ocean sourced moisture since the Last Glacial Maximum (LGM) at cave sites across the Southwest. In this study, a new oxygen isotope time …
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Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction
… suite, are consistent with the attainment of isotope equilibrium and largely closed system conditions. The majority of the temperatures calculated by conventional mineral-pair thermometers are spurious, as a result of oxygen isotope diffusion during slow cooling. Closure temperatures for …
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