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 23 for “"Elemental abundances"”.
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Photoionization of Se Ions for the Determination of Elemental Abundances in Astrophysical Nebulae
Absolute single photoionization cross section measurements are presented for Se+ ,Se2+, Se3+ and Se5+. These measurements were performed at undulator beamline 10.0.1 of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the merged-beams technique. All ions except Se5+ …
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Coronal properties of pre-main sequence stars in the Orion Trapezium Cluster
… peculiarities, specifically with respect to abundances and accretion signatures. We analyzed the high resolution X-ray spectra of six young stars in Orion using data from the Chandra X-Ray Observatory. We fit plasma models to the spectra, calculated temperature-insensitive elemental …
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On understanding the lives of dead stars : Supernova Remnant N103B, radio pulsar B1951+32, and the Rabbit
… Mg, Ne, and O emission lines. Due to the elemental abundances, we are able to tentatively reject suggestions that N103B arose from a Type Ia supernova, in favor of the massive progenitor, core-collapse hypothesis indicated by earlier radio and optical studies, and by some recent X-ray …
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Geochemical characerization of endmember mantle components
… and radiogenic isotope tracers to define elemental abundances in reservoirs of the Earth's mantle, including EM2 (the Enriched Mantle 2), as seen in the Samoan hotspot track, and DMM (the depleted upper mantle), which is sampled at mid-ocean ridges. Together these components comprise up to …
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A pipeline for the analysis of stellar spectra
… into tables of stellar parameters and chemical abundances in far less time than if they were analysed by hand. The results from these surveys open new windows on to the history of our galaxy and other disk galaxies. In this thesis, we present the development of a new pipeline, the STellAR …
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Geochemical characterization of endmember mantle components
… and radiogenic isotope tracers to define elemental abundances in reservoirs of the Earth's mantle, including EM2 (the Enriched Mantle 2), as seen in the Samoan hotspot track, and DMM (the depleted upper mantle), which is sampled at mid-ocean ridges. Together these components comprise up to …
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Geochemistry of Tl and selected elements in four Carlin-Type Gold deposits
… the enrichment of iodine over reported average elemental abundances in rocks using a revised spectrophotometric method. The Carlin-type gold deposits studied include Carlin, Jerritt Canyon, Alligator Ridge, and Mercur. The rhyolite hosted Rawhide deposit was studied as a comparison. The …
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Chemical composition study of Galactic stellar substructures /
… this dissertation work we investigate detailed elemental abundances in stars belonging to two of the newly identified GCS kinematic groups. The main aim of the study is to perform a high-resolution spectroscopic analysis of the kinematic groups stars and to compare the results with Galactic …
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Effects of convection and non-equilibrium radiation transfer in stellar atmospheres /
… is assessed by analyzing differences in the elemental abundances obtained by using 3D hydrodynamical and 1D hydrostatic stellar model atmospheres of MSTO and RGB stars, within the framework of spectral line formation under the assumption of local thermodynamic equilibrium (LTE). We find that …
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A frequency analysis of the rapidly oscillating Ap star HD 101065
… They may also provide information on the elemental abundances and mixing and indicate the presence of low-mass companions. In asteroseismological studies, the primary data are the frequencies of the normal modes present in the object of interest. This thesis describes an attempt to perform …
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X-Ray Fluorescence Analysis of Tuscaloosa Marine Shale Cuttings from Horizontally Drilled Wells
… chemostratigraphy of the TMS, to characterize elemental changes along well paths and to evaluate the effect of basic sample clean on XRF results. The data available for this study were geophysical logs and well cuttings from two lateral wells (B-NEZ 43H 001 and B-NEZ 43H 002) from Little Silver …
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A New Library of Stellar Model Atmospheres and Spectra
… with theoretical predictions. The relative abundances of elements within the Sun provide the baseline against which the elemental abundances of all other stars, galaxies and the interstellar medium are based upon. Libraries of model atmospheres and stellar spectra have been previously …
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Geochemical Insights into Crustal Melting in the Bhutan Himalaya
… the Lesser Himalayan Series (LHS). Multiple elemental and isotopic techniques provide insight into leucogranite source and petrogenesis in central Bhutan (eastern Himalaya). Whole-rock major and trace elemental abundances confirm that all studied leucogranites are the product of muscovite …
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Exogeology as Revealed by Polluted White Dwarfs
… (or mantle) material. However, given a set of elemental abundances, identifying the physical processes which best explain the data is a highly non-trivial exercise. Bayesian modelling is a powerful method to disentangle the most likely explanation from the myriad of possibilities. This approach …
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Mechanical design, calibration, and environmental protection of the REXIS DAM
… on the imaging array. A spatial map of selected elemental abundances on Bennu is constructed by cross-correlating the mask pattern with the collected data. The CCDs are integrated into a Detector Assembly Mount (DAM) that serves three critical functions: Mechanical alignment, calibration and …
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Chemodynamical Adaptive Mesh Refinement Simulations of Disk Galaxies
… ramses-ch. Under the new scheme, energetic and elemental feedback is contributed by stars throughout their lifetime rather than (as previously) in a single burst. This relaxation of the ‘instantaneous feedback approximation’ in ramses-ch opens up the opportunity for studying chemical evolution …
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Extreme Ultraviolet Spectroscopy of the Solar Corona
… the temperature distribution, densities and elemental abundances in the solar plasma. A differential emission measure (DEM) diagnostic technique has been used to infer the temperature structure and the element abundances. The importance of including DEM effects in the element abundance …
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Exoplanetary Atmospheric Retrievals with Transit Spectroscopy in the JWST Era
… new aerosol model, I constrain the atmospheric elemental abundances of O, C and S, finding them to be largely consistent with the inferred C abundance of Saturn. I subsequently present VIRA, a new atmospheric retrieval framework designed to make the most of JWST observations. VIRA implements …
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Organic and inorganic geochemical characterization of the Juana Lopez and Montezuma Valley members of the lower Mancos Shale, Piceance Basin, Colorado
… profile and the use of established elemental proxies to better understand paleoconditions, and (4) the use of petrophysical analysis to better define this interval throughout the Piceance Basin to aid future exploration. The Frontier Member is a known producing interval in the …
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Hydroclimate variability in Central America during the Holocene inferred from lacustrine sediments in Lake Izabal, eastern Guatemala
"Holocene hydroclimate reconstructions have contributed to our understanding of the mechanisms controlling precipitation in Central America. Recent hydroclimate proxy records from the region, however, have revealed considerable spatiotemporal complexity in precipitation variability. This complexity …
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