نتایج جستجو برای: isotopic
تعداد نتایج: 18280 فیلتر نتایج به سال:
Isotopic characterization of aerosol mineral particles (atmospheric dust) of varying sizes is essential in classifying source areas, and for determining the source of dust deposited over oceans and icesheets. However, the effect of atmospheric transport on radiogenic isotopic compositions is not well constrained, making provenance interpretation difficult. In order to investigate the isotopic v...
As a preliminary study of the utility of the natural stable-isotopic differentiation of batch samples produced by different synthetic pathways, multi-stable-isotopic analyses (delta(13)C, delta(15)N, delta(18)O, deltaD) of 53 samples of the antiepileptic drug, Topiramate, produced by three different synthetic pathways (designated "A," "B," "C") were performed. From the outset, we note that ther...
This paper presents a comprison of the isotopic values of eight pairings of hair keratin and bone collagen and 12 pairings of hair keratin and nail keratin taken from living humans resident in the U.K., with the aim of examining whether modern human isotopic data can be directly compared to archaeological isotopic data. Results showed that bone collagen was enriched relative to hair keratin fro...
Stable Ca isotopes are fractionated between bones, urine and blood of animals and between soils, roots and leaves of plants by >1000 ppm for the 44Ca/40Ca ratio. These isotopic variations have important implications to understand Ca transport and fluxes in living organisms; however, the mechanisms of isotopic fractionation are unclear. Here we present ab initio calculations for the isotopic fra...
Stable isotope data are useful for inferring foraging and niche variation in marine taxa but can be difficult to interpret, in part because different foraging patterns may result in similar isotopic values. Here, we integrate stable isotope analysis (δ13C and δ15N) with behavioral data to investigate the foraging ecology of loggerhead turtles Caretta caretta on a feeding ground in Shark Bay, We...
Isotope data from bulk carbonates, micrite, marine calcite cements, non-skeletal grains and brachiopods indicate deposition of a wide spectrum of warm to cold water carbonates during the Ordovician and the Jurassic. This isotopic interpretation is supported by warm to cold climatic models proposed for the Ordovician and the Jurassic. These carbonates formed during the Greenhouse mode (condition...
Introduction: Interplanetary dust particles (IDPs) are composed of a variety of primitive materials and are the repositories of various isotopic anomalies. They are well known to exhibit enrichments of deuterium (D) and N [e.g., 1-3], although the two types of isotopic anomalies do not appear to be directly correlated. The enrichments are generally thought to be carried by organic compounds [4-...
A range of isotopic methods (using radioactive and stable isotopes) have been used to investigate groundwater processes and to determine the sources and pathways for groundwater contamination. Methods using stable isotopes of nitrogen have been applied in a variety of Australian and international groundwater studies. Isotopic methods have involved either application of tracer isotopes or studyi...
The Mass Spectrometer Telescope (MAST) on SAMPEX is designed to provide high resolution measurements of the isotopic composition of energetic nuclei from He to Ni (Z = 2 to 28) over the energy range from -10 to several hundred MeV/nuc. During large solar flares MAST will measure the isotopic abundances of solar energetic particles to determine directly the composition of the solar corona, while...
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