Oxygen Isotope Ratio 18o
Mostrando 1-9 de 9 artigos, teses e dissertações.
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1. Avaliação da aplicação associada dos dados de δ18O e da razão Mg/Ca de foraminíferos como uma ferramenta paleoceanográfica / Evalution of the associated applicability of ?18O and Mg/Ca ratio data in foraminifera as a paleoceanographic tool
O objetivo do presente estudo é avaliar o uso associado dos proxies ?18O e Mg/Ca obtidos em testas de foraminíferos. Para alcançar tal objetivo foram realizadas análises de ?18O e Elemento/Ca em amostras de foraminíferos planctônicos (G. ruber e G. sacculifer) e bentônicos (Cibicidoides spp., C. corpulentus, Uvigerina spp. e H. elegans) de dois testem
Publicado em: 2011
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2. Hydrothermal alteration of the Cerro La Mina gold prospect, Los Menucos, Patagonia Argentina : geology, remote sensing and stable isotopes / Alteração hidrotermal do prospecto aurifero Cerro La Mina, Los Menucos, Patagonia Argentina : geologia , sensoriamento remoto e isotopos estaveis
The epithermal Cerro La Mina prospect, located in the Los Menucos region, Patagonia Argentina, is currently being explored for epithermal precious-metal mineralization. Triassic hydrothermal activity produced intense alteration of rhyolites, andesites, ignimbrites, and tuffs of the Middle- to Late Triassic Los Menucos Group, in the Somún Curá massif. The u
Publicado em: 2007
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3. Microbe forensics: Oxygen and hydrogen stable isotope ratios in Bacillus subtilis cells and spores
Bacillus subtilis, a Gram-positive, endospore-forming soil bacterium, was grown in media made with water of varying oxygen (δ18O) and hydrogen (δD) stable isotope ratios. Logarithmically growing cells and spores were each harvested from the cultures and their δ18O and δD values determined. Oxygen and hydrogen stable isotope ratios of organic matter were
The National Academy of Sciences.
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4. Kinetic isotope effects in Ras-catalyzed GTP hydrolysis: Evidence for a loose transition state
A remote labeling method has been developed to determine 18O kinetic isotope effects (KIEs) in Ras-catalyzed GTP hydrolysis. Substrate mixtures consist of 13C-depleted GTP and [18O,13C]GTP that contains 18O at phosphoryl positions of mechanistic interest and 13C at all carbon positions of the guanosine moiety. Isotope ratios of the nonvolatile substrates and
National Academy of Sciences.
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5. Oxygen isotope ratios of PO4: An inorganic indicator of enzymatic activity and P metabolism and a new biomarker in the search for life
The distinctive relations between biological activity and isotopic effect recorded in biomarkers (e.g., carbon and sulfur isotope ratios) have allowed scientists to suggest that life originated on this planet nearly 3.8 billion years ago. The existence of life on other planets may be similarly identified by geochemical biomarkers, including the oxygen i
The National Academy of Sciences.
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6. Water Relations Link Carbon and Oxygen Isotope Discrimination to Phloem Sap Sugar Concentration in Eucalyptus globulus
A strong correlation was previously observed between carbon isotope discrimination (Δ13C) of phloem sap sugars and phloem sap sugar concentration in the phloem-bleeding tree Eucalyptus globulus Labill. (J. Pate, E. Shedley, D. Arthur, M. Adams [1998] Oecologia 117: 312–322). We hypothesized that correspondence between these two parameters results from cov
American Society of Plant Biologists.
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7. Variation in the Oxygen Isotope Ratio of Phloem Sap Sucrose from Castor Bean. Evidence in Support of the Péclet Effect1
Theory suggests that the level of enrichment of 18O above source water in plant organic material (Δ) may provide an integrative indicator of control of water loss. However, there are still gaps in our understanding of the processes affecting Δ. One such gap is the observed discrepancy between modeled enrichment of water at the sites of evaporation within t
American Society of Plant Physiologists.
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8. Mechanism for antibody catalysis of the oxidation of water by singlet dioxygen
Wentworth et al. [Wentworth, P., Jones, L. H., Wentworth, A. D., Zhu, X. Y., Larsen, N. A., Wilson, I. A., Xu, X., Goddard, W. A., Janda, K. D., Eschenmoser, A. & Lerner, R. A. (2001) Science 293, 1806–1811] recently reported the surprising result that antibodies and T cell receptors efficiently catalyze the conversion of molecular singlet oxygen (1O2) plu
The National Academy of Sciences.
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9. The gas phase reaction of singlet dioxygen with water: A water-catalyzed mechanism
Stimulated by the recent surprising results from Wentworth et al. [Wentworth, A. D., Jones, L. H., Wentworth, P., Janda, K. D. & Lerner, R. A. (2000) Proc. Natl. Acad. Sci. USA 97, 10930–10935] that Abs efficiently catalyze the conversion of molecular singlet oxygen (1O2) plus water to hydrogen peroxide (HOOH), we used quantum chemical methods (B3LYP densi
The National Academy of Sciences.