Isotope Ratio
Mostrando 13-24 de 111 artigos, teses e dissertações.
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13. Cadmium phytoavailability in soils and evaluation of extractant effectiveness using an isotope technique
Large areas of land are nowadays contaminated by heavy metals and, it is therefore, important to monitor their levels in soils. Vegetables act as transfer mechanisms of such contaminants from soils to higher levels in the food chain. In this study, we aimed to evaluate the effectiveness of chemical extractants by the L-value method for Cd phytoavailability u
Sci. agric. (Piracicaba, Braz.). Publicado em: 2014-10
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14. DEPLOYMENT OF METHOD FOR ANALYSIS OF STABLE CARBON ISOTOPES (N-ALKANES C1-C5) IN GAS SAMPLES AT LOW CONCENTRATIONS / IMPLANTAÇÃO DE MÉTODO PARA ANÁLISE DE ISÓTOPOS ESTÁVEIS DE CARBONO (N-ALCANOS C1-C5) EM GASES A BAIXAS CONCENTRAÇÕES
The concentration and isotopic composition of n-alkanes C1-C5 has revealed as a powerful tool for interpretation of interesting processes in the oil exploration industry, studies of global climate change, oil biodegradation and carbon cycle elucidation. In this context, studies about methane analysis have been distinguished and multiplied due to the importan
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 06/10/2011
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15. 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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16. Physiological aspects of coffee growth and production / Aspectos fisiológicos do crescimento e da produção do cafeeiro
In this work, changes in vegetative growth, crop production, branch die-back, gas exchange, carbohydrate metabolism, nitrogen and pigment concentration were investigated in leaves and branch segments in coffee trees grown (north-south orientation) under field conditions along two years. Samplings and measurements were conducted using outer leaves from the up
Publicado em: 2009
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17. Gênese, distribuição e caracterização dos espongilitos do noroeste de Minas Gerais
This study relates to the spongillites deposits that occurs in shallow ponds on a karstic planation surface developed on rocks of the Neoproterozoic São Francisco Supergroup. Cenozoic siliciclastics sediments are related to this surface and Mesozoic Areado Group rocks occur adjacent to the deposits. Field studies associated with the analysis of multispectra
Publicado em: 2009
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18. Otimização da análise isotópica de UF6 utilizando-se a técnica de espectrometria de massas por quadrupolo
A procedure for determining of the isotope ratio 235U/238U in UF6 samples was established using a quadrupole mass spectrometer with ionization by electron impact. The following items were optimized in the spectrometer: the parameters in the ion source that provided the most intense peak, with good shape, for the most abundant isotope; the resolution that red
Química Nova. Publicado em: 2008
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19. Determinação da composição isotópica de estrôncio em águas naturais: exemplos de sua aplicação em águas subsuperficiais da zona costeira na região Bragantina-PA
Analytical procedures used for determining the concentrations and isotope composition of strontium in subsurface waters, by mass spectrometry, are described. Sampling was performed in coastal plateaus, salt marsh and mangrove environments in the coastal region of Pará. Coastal plateau waters have delta87Sr between 1.51 and 6.26‰ and Sr concentration bello
Química Nova. Publicado em: 2007-08
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20. Isotopic composition of respired CO2 and seasonal variability in the Amazon tropical Forest / A composição isotópica do CO2 respirado e sua variabilidade sazonal na Amazônia Oriental
This study was conducted in 2003 and 2004 at the km 67 old growth forest in the Tapajós National Forest (2 ° 51'S 54 ° 58'W). The objective was measure the carbon isotope ratio (13C/12C) of respired CO2 from the entire ecosystem and isotope composition of organic components leaves, soil, litter and dead wood. The Keeling plot technique and
Publicado em: 2007
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21. "Boro em mamoneira: Aspectos morfológicos e fisiológicos relacionados à deficiência e toxicidade" / Boron in castor bean plants: Morphologic and physiologic aspects related to the deficiency and toxicity
The castor bean production has highlighted as one of the most promising crops in cerrado and semi-arid farmlands, as the castor oil, besides being used in several industries, presents potential for biodiesel production. This work is based in the following hypotheses: a) the production of seeds and castor oil is related with appropriate supply of boron (B), a
Publicado em: 2007
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22. 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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23. PREPARATION, CARACTERIZATION AND CERTIFICATION OF URANIUM ISOTOPE REFERENCE MATERIALS / "Preparação, caracterização e certificação de materiais de referência isotópicos de urânio"
This work describes the preparation, characterization and certification of a set of uranium isotope reference materials ranging from 0.5 to 20.0 % of 235U in mass. The most important concepts of metrology in chemical measurements were applied so that the certified quantities in these materials could be directly traceable to the International System of Units
Publicado em: 2006
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24. Caracterização dos vinhos Merlot e Cabernet Sauvignon da serra gaúcha através de determinação das razões isotópicas 13C/12C e 18O/16O
In this work, wines provided by micro-winemakings of the variety Merlot and Cabernet Sauvignon of the sub-regions of Pinto Bandeira, Vale dos Vinhedos, Nova Pádua and Monte Belo do Sul in the 2005 and 2006 harvest have been studied. It has been established the isotopic ratios 13C/12C of the ethanol and 18O/16O of the water and ethanol, seeking for a possibl
Publicado em: 2006