886 resultados para decaimento do carbono lábil
Resumo:
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Resumo:
A diferença entre fontes alimentares da ordem de 14 , originárias de plantas com ciclos fotossintéticos Carbono-3 (C3) e Carbono-4 (C4) e seus subprodutos, abre novas perspectivas para o estudo do metabolismo do carbono em aves e animais de pequeno porte. Os autores propõem um modelo teórico e experimental capaz de exprimir os resultados de enriquecimento relativo, delta per mil (delta ) da razão 13C/12C versus tempo em diferentes tecidos. Utilizou-se a equação y(t) = (y0 -- q/k) e-kt + q/k onde, y(t) é a concentração isotópica no tempo desejado, y0 a concentração isotópica inicial existente no tecido, k é uma constante de troca isotópica com unidade 1/tempo, t é unidade de tempo e q é a taxa de entrada de metabólitos que contém carbono, com valores de delta /tempo. Para fígado de galinhas que tiveram a ração de ciclo fotossintético C4 substituída por dieta C3 obteve-se a equação delta13C = -24,74 + 12,37 e-0.237(nT), com meia-vida (T) de 2,9 dias. O patamar de equilíbrio de substituição do carbono foi alcançado em --24,48 , de modo que praticamente 98,4% do conteúdo isotópico do C4 no fígado foi substituído por C3 após 5,6 meias-vidas. O modelo foi adequado para determinar o tempo de reciclagem total ou parcial da concentração de carbono nos tecidos em estudo.
Resumo:
Organic carbon is a major component of soil organic matter and its stock is influenced by the management system adopted. This study aimed to examine the effects of cropping systems and nutrient sources (mineral and organic) on the concentrations and storage of soil organic carbon in no-tillage system. The experiment was carried out in Mercedes, Parana, Brazil, in an Nitossolo Vermelho (Alfisol) from October 2007 to September 2009. The treatments consisted of four crop succession systems: (1) soybean/wheat/corn/wheat; (2) soybean/black oat/corn/black oat, (3) soybean/radish/corn/radish and (4) soybean/common vetch/corn/common vetch and by two sources of nutrients (mineral and organic), arranged in a to split plot randomized block design with four replications. Soil samples were collected in layers of 0.0-0.05, 0.05-0.10, 0.10-0.20 and 0.20 to 0.40 m deep in the first and the second years of cultivation. Different cropping systems does not affect the content and the stock of soil organic carbon in the first two years of adoption of the systems. The organic fertilization with manure increased soil organic carbon stock, with an annual contribution of C, layer 0.0 to 0.20 m, 1.15 Mg ha(-1) yr(-1). Cropping systems fertilized with mineral fertilizers provide the greatest losses of soil organic carbon, resulting in negative balance of C in soil.
Resumo:
The aim of this study is to determine the natural abundance of carbon stable isotope (13C) of some food components and determine its contribution to the pintado juvenile growth, in laboratory conditions. 150 fishes were used with average weight of 1.39 g, and stocked in two net ponds with 125L each, during 60 days. Every 10 days a water sample was collected to analyse phytoplakton and zooplankton. Clacocera was dominant in the analysis of the stomach contents, following Chironomidae and Copepoda. A fish sample was collected in the beginning, and at the end of the experiment to analyses the isotopic signal. An average value of -20.94; -15.36 and -18.81 δ13C%o was obtained for phytoplankton, Cladocera and Chironomidae, respectively. Cladocera was the main carbon source and contribution with carbon average 89.24% in feeding this species, while the Chironomid contribution was 10.76%. The δ13C was effective as carbon tracer in food chain, because the consumer reflects its diet isotopicly.
Resumo:
This paper discusses the formation of microstructures with different volume fractions, as an outcome of a specific heat treatment, with the following phases: ferrite, martensite, bainite and retained austenite. For the microstructure characterization it is developed a chemical etching that allows to distinguish the phases by optical microscopy. The evaluation of the mechanical properties is done based on the results of tensile and fatigue tests. The experimental results show that appropriate heat treatments can contribute to a significant improvement in the mechanical properties of the steel. In this process it is essential to control the fraction volume, morphology of the phases, and grain size.
Resumo:
Incluye Bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye bibliografía
Resumo:
Incluye Bibliografía
Resumo:
Incluye bibliografía
