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 1844 for “"isotope"”.
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Iron Isotope Cosmochemistry
… of planetary formation and differentiation. Iron isotope ratios are robust process tracers used to understand the origin of the Solar System, planetary formation, and differentiation processes such as the moon-forming giant impact, core-mantle segregation, and crust formation. In this …
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Boron isotope geochemistry
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and Woods Hole Oceanographic Institution, 1986.
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Continental-scale isotope hydrology
… dissertation outlines several applications of isotope hydrology to address four previously unknown questions involving surface- and ground-water resources at regional- to continental-spatial scales over contemporary- to millennial-temporal scales. The four chapters in this dissertation …
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Thermochemical hydrogen-deuterium isotope effects
… deuterium containing compounds to yield isotope effects on heats of solution. These isotope effects were interpreted in terms of hydrogen bonding and an empirical equation for the prediction of enthalpies of formation of hydrogen bonds. It was concluded that for a given isotopic pair the …
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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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Magnetically activated and guided isotope separation
… experiment demonstrating a technique for stable isotope enrichment called Magnetically Activated and Guided Isotope Separation (MAGIS) (1). Over the past century a large number of enriched isotopes have become available, thanks largely to electromagnetic separators called calutrons that were …
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Carbon Isotope Effects: Malonic Acid Decarboxylation
Made available in DSpace on 2014-12-05T19:37:01Z (GMT). No. of bitstreams: 1 5900526.pdf: 3674148 bytes, checksum: 7b4988e9c0a6f505ce9e8dd72b26b4bd (MD5) Previous issue date: 1958
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Bayesian algorithms for automated isotope identification
Handheld radio-isotope identifiers (RIIDs) are widely used in the United States for nuclear security, but these detectors generally have poor performance in isotope identification. While much research is being conducted on alternative detector materials, there is much evidence that the primary …
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Isotope edited FT-IR of peptides
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1996.
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Hydrogen isotope fractionation in ammonia-oxidizing archaea
… years, the potential of the hydrogen stable isotope composition (δ2H) signature of isoprenoid glycerol dibiphytanyl glycerol tetraether (GDGT) membrane lipids of ammonia-oxidizing archaea (class Nitrososphaeria) as a novel palaeohydrological proxy has gained increasing attention. This PhD …
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Chlorine in ground water : stable isotope distribution
… measurements revealed no variation of the stable isotope ratio, 37C1/ 35C1 (with precision up to 1.0%.) in natural materials. This result is not surprising because chlorine occurs in relatively few compounds, has a strong affinity for the liquid phase, occurs mostly in the -1 oxidation state and …
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Numerical simulation of nuclear reactor isotope depletion
… isotopic concentrations, short-lived decay isotopes and their decay chains were identified and solved with a modified Bateman solution and then the long-lived isotopes concentrations were solved with matrix exponentiation. The flux was calculated to keep the heat output of the reactions …
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A generalized optimization methodology for isotope management
This research, funded by the Department of Energy's Advanced Fuel Cycle Initiative Fellowship, was focused on developing a new approach to studying the nuclear fuel cycle: instead of using the trial and error approach currently used in actinide management studies in which reactors are designed and …
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Evaluating mantle and crustal processes using isotope geochemistry
… of the mantle heterogeneities, and uses U-series isotope to constrain geodynamic parameters, such as the upwelling velocities and porosities of mantle plumes. The lower continental crust plays a pivotal role in understanding the composition and evolution of the continental crust and the …
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Stable isotope geochemistry of nitrogen in marine particulates
Isotope studies of nitrogen and carbon were undertaken to investigate the fate of particulate organic matter (POM) during its residence in the water column and after deposition on the seafloor. The processes focused on were water-column transformations and sedimentary diagenesis. Sampling sites …
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Stable isotope analysis: a new forensic science tool
… the development of the analytical technique isotope ratio mass spectrometry (IRMS) has increased the information obtainable regarding sample origin and history.<br/><br/>Investigations were carried out on white paint samples using Elemental Analysis Isotope Ratio Mass Spectrometry (EA-IRMS) …
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UNCERTAINTY CONTRIBUTIONS TO SPECIES SPECIFIC ISOTOPE DILUTION ANALYSIS
… mass spectrometry (ICP-MS) for species specific isotope dilution mass spectrometry (IDMS). 199Hg enriched methylmercurychloride has been synthesised and recovered in the solid form for use as a spike material. The stability of methylmercury during the IDMS procedure was investigated using 199Hg …
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The Mathematics behind Speciated Isotope Dilution Mass Spectrometry
Speciated Isotope Dilution Mass Spectrometry (SIDMS) allows researchers to measure the concentrations of species -- usually elemental -- in a sample by solving a system of non-linear equations. This thesis explores multiple mathematical methods to solve SIDMS equations, and compares the properties …
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