نتایج جستجو برای: stable isotopes
تعداد نتایج: 276152 فیلتر نتایج به سال:
Introduction Conclusions References
We use chronologies of stable isotopes measured from elephant (Loxodonta africana) hair to determine migration patterns and seasonal diet changes in elephants in and near Samburu National Reserve in northern Kenya. Stable carbon isotopes record diet changes, principally enabling differentiation between browse and tropical grasses, which use the C3 and C4 photosynthetic pathways, respectively; s...
The use of stable isotopes to solve biogeochemical problems in ecosystem analysis is increasing rapidly because stable isotope data can contribute both source-sink (tracer) and process information: The elements C, N, S, H, and all have more than one isotope, and isotopic compositions of natural materials can be measured with great precision with a mass spectrometer. Isotopic compositions change...
The use of stable isotopes in studies of carotenoid biosynthesis is reviewed, beginning with early work with l8 which defined the origin of oxygen in a range of xanthophylls. A series of experiments from our own laboratory is then described, in which 2H and 13C have been used to investigate the stereochemistry of cyclization to form C40 and C50 and i-ring carotenoids. Novel procedures involving...
To document the evolution of the early cryosphere, stable isotope analyses were conducted on the planktonic and benthic foraminifers from Ocean Drilling Program Site 1218. We generated two parallel 54m-long records at 10-cm resolution and thus produced a standard Pacific stable isotope reference curve for the 26.4to 30.0-Ma interval within the Oligocene. These data are necessary to document the...
Divergent selection and adaptive divergence can increase phenotypic diversification amongst populations and lineages. Yet adaptive divergence between different environments, habitats or niches does not occur in all lineages. For example, the colonization of freshwater environments by ancestral marine species has triggered adaptive radiation and phenotypic diversification in some taxa but not in...
Understanding the composition of paleodiets is crucially important for the archaeological investigation of lifeways and subsistence practices within ancient societies. Among the numerous research methods capable of investigating various elements of paleodiets, the use of stable isotope analysis has become increasingly popular. Advantages of this research technique include its ability to recogni...
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