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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 21 for “"Isotopic enrichment"”.
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Studies towards the Organocatalytic ‘Dialled In’ Synthesis of Chiral, Non-Racemic Aziridines, and Amino Acids, Containing Multiple Isotopic Labels
… the first part of the thesis, enantio- and isotopically enriched cis- N-aryl 3-aryl-aziridine-2-carboxylates have been synthesised in a regioselective manner; with deuterium selectively introduced at the C2, and/or C3 positions of the aziridine ring with generally >90 % isotopic enrichment. …
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Organocatalytic synthesis of chiral non-racemic aziridines, labelled with 2H, 15N, 13C stable isotopes
… introduced within an aziridine ring with > 95% isotopic enrichment. The desired compounds were generated in yields of up to 81% and up to 87% e.e. Furthermore optically active β-bromo-α-amino acid derivatives were generated via aziridine ring-opening methodology without loss of the isotopic …
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Isotope hydrology of Lehman and Baker creeks drainages, Great Basin National Park, Nevada
… and creek discharges and also to determine the isotopic behavior of the alpine lakes, as well as groundwater exchange with the lakes; Winter snow is the major contributor to groundwater and makes up about 80% of groundwater recharge while summer rains contribute about 20%; The isotopic …
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Production and separation of medically relevant terbium-161 for radiopharmaceutical applications and recycling of target materials
… and [160Gd]Gd2O3 targets (98.2-99.96% isotopic enrichment) were irradiated at the University of Missouri Research Reactor (MURR) at thermal neutron fluxes of 1.76 × 1014 - 3.30 × 1014 n·cm-2·sec-1, producing 161Tb at the end of irradiation. For research-scale production, a …
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Caracterização geoquímica e paleoambiental do cretáceo inferior da Bacia de Camamu, Bahia
… hydrogen indices, together with the strong ¹³C isotopic depletion reflect a medium to low primary productivity and a intense recycling of carbon through the degradation of organic matter by anaerobic bacteria. Aratu and Buracica sediments were deposited in a broad and shalower lake with fresh to …
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Estimating warhead design properties from multiple resonances in physical cryptographic warhead verification
… measurements to verify a candidate warhead's isotopic and geometric characteristics. To conceal sensitive design information, the NRF signal from the warhead is not directly measured, but is first convolved with that of an encrypting foil containing relevant warhead isotopes in quantities …
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Ice core methane and carbon monoxide as tracers of the terrestrial biosphere since the pre-industrial
… 1941 to 1994 CE that suggests a greater rate of isotopic enrichment than previously reported. Mass balance calculations support previous top- down studies which indicate that historical anthropogenic fossil fuel emissions have been largely underestimated by bottom-up approaches. Then, to explain …
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Regional hyrdrologic controls on acid-sensitivity of lakes in boreal Canada : an isotopic perspective
… derived from river gauging stations. Regional isotopic variations measured for components of the water cycle indicated a wide range of hydrologic conditions prevail, from throughflow, high water-yield lakes (186 mm.yr-1) to evaporative, low water-yield systems (23 mm•yr-1). Notably, hydrology …
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Investigations of hexagonal boron nitride: bulk crystals and atomically-thin two dimensional layers
… crystals from the flux in situ. (3) Growth of isotopically pure hBN crystals was undertaken. By modifying the crucible material for solution growth, enrichment of hBN crystals over 90% was accomplished. (4) Exfoliation of hBN has many potential applications, specifically as graphene-hBN …
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Split gate tunnel barriers in double top gated silicon metal-oxide-semiconductor nanostructures
… ability to eliminate background nuclear spins by isotopic enrichment. One way spin qubits can be realized in silicon is by using donor-bound electron spins. Individual donor atoms intentionally implanted into tunnel barriers of silicon have been examined using transport measurements. However, …
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Purification of Argon via Distillation with Aria and Purity Monitoring for Dark Matter Searches
… search. Moreover, Aria will be used for the isotopic enrichment of germanium for future expansion of LEGEND-1000, as well as the production of isotopes with various applications in different fields, such as 13C, 18O, 17O, 15N.
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Development and Application of 19F NMR of Proteins
… into calmodulin. In the first approach, isotopic enrichment facilitated two-dimensional heteronuclear experiments based on INEPT and COSY magnetization transfer schemes to correlate the fluorine nucleus to sidechain and backbone 1H, 13C, and 15N atoms, providing complete spectral …
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In-situ measurement of denitrification in the Elk Valley aquifer
… in the remaining NO₃¯-N from 2.4 to 43.5‰ and an isotopic enrichment factor of -20.4‰ also provide evidence of denitrification. An increase of 1.70 mmol/L in sulfate identifies pyrite as the electron donor for 61% of the observed denitrification with the remaining 39% attributed to heterotrophic …
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A Solid State NMR Investigation of Poly (ADP-ribose) and Its Involvement in Tissue Calcification
… points and chain ends. Moreover, careful isotopic enrichment of cells and matrix with sugars or key amino acid residues help us define novel hypotheses about the interactions between collagen fibrils and PAR at a molecular level, and the involvement of the latter in the mineralisation of …
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Groundwater of the North-Western Kalahari, Namibia
… recharge areas showing almost no or only little isotopic enrichment by evaporation. Soil water balance modelling confirmed that direct groundwater recharge in hard-rock environments tends to be much higher than in areas covered with thick Kalahari sediments. According to the water balance model …
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Nitrogen isotopes in chlorophyll and the origin of Eastern Mediterranean sapropels
… and δl3C as proxies for the nitrogen and carbon isotopic composition of marine phytoplankton; and (3) to use chlorophyll nitrogen isotopic ratios to understand the origin of Late Quaternary Eastern Mediterranean sapropels. Techniques are presented for the determination of chlorin nitrogen and …
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Elucidating Structure and Dynamics of Extracellular Matrix Collagen Using Solid-State NMR
… of $^13$C, $^15$N-labelled amino acid enrichment of in-vitro or in-vivo materials with two-dimensional solid-state NMR spectroscopy potentially provides a more detailed understanding of the complex collagen structure and dynamics at atomic resolution. Furthermore, our knowledge of …
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Geochemical tools and paleoclimate clues : multi-molecular and isotopic investigations of tropical marine sediments and alpine ice
… Through the use of organic molecular isotopic techniques and multi-molecular stratigraphy, a great deal can be learned about communities of marine organisms and terrestrial plants that existed in the past and the environments in which they lived. Vascular plant leaf wax carbon and …
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A study of the remineralization of organic carbon in nearshore sediments using carbon isotopes
… were not at steady-state concentrations. The isotopic signature of ΣCO2 was used as an indicator of the processes affecting ΣCO2 in pore water. During every month, the oxidation of organic carbon to CO2 provided over half of the carbon added to the ΣCO2 pool. However, in every month, the δ13C …
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A study of the remineralization of organic carbon in nearshore sediments using carbon isotopes
… were not at steady-state concentrations. The isotopic signature of 2C02 was used as an indicator of the processes affecting IC02 in pore water. During every month, the oxidation of organic carbon to C02 provided over half of the carbon added to the IC02 pool. However, in every month, the 6'"C …
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