نتایج جستجو برای: isotopic
تعداد نتایج: 18280 فیلتر نتایج به سال:
Isotopic studies of palaeoecological and ecological questions often use bone collagen or bioapatite as substrates, but rarely both. Substantial new information can be gained from the incorporation of isotopic values from both the organic and inorganic fractions of bone. Here we show that combining isotopic data from both substrates provides valuable and unique insights into (1) trophic relation...
UNLABELLED Mass spectrometry (MS) is widely used for isotopic labeling studies of metabolism and other biological processes. Quantitative applications-e.g. metabolic flux analysis-require tools to correct the raw MS data for the contribution of all naturally abundant isotopes. IsoCor is a software that allows such correction to be applied to any chemical species. Hence it can be used to exploit...
Introduction: Whole rocks, chondrules and matrix from the same chondrite group typically have the same or very similar oxygen-isotopic compositions [e.g., 1]. Among the three major clans of chondrites, enstatite chondrites (ECs) have the most uniform oxygen isotopic compositions (Fig. 1). In order to study oxygen-isotopic heterogeneity of ECs in microscale, we carried out SIMS measurements on c...
A procedure was developed that allows precise determination of Fe isotopic composition. Purification of Fe was achieved by ion chromatography on AG1-X8 strongly basic anion-exchange resin. No isotopic fractionation is associated with column chemistry within 0.02 per thousand /amu at 2sigma. The isotopic composition was measured with a Micromass IsoProbe multicollection inductively coupled plasm...
The isotopic composition of an element records information about its history. Given a fossil, it is possible to analyse the isotopic composition of the elements in the fossil and to use this to reconstruct the diet that the animal consumed. The process of dietary reconstruction, however, is far from simple. Biological systems are quite complex and can themselves introduce isotopic fractionation...
Lead isotopic ratios of cassiterite, the dominant tin ore, evolve after crystallization through decay of uranium and thorium to lead. We show that the lead isotopic ratios of smelted tin at Rooiberg, South Africa, form an isochron that matches the known geological age of the Rooiberg cassiterite deposits. Since the lead isotopic ratios of several prehistoric tin and bronze artifacts throughout ...
Isotopic analyses of subglacially precipitated calcite from near a modern temperate glacier show that the delta(18)O (= (18)O/(16)O relative to standard mean ocean water) of the calcite records the delta(18)O of the ice from that glacier. It may therefore be possible to determine the delta(18)O of Pleistocene ice sheets on the basis of isotopic analyses of calcite formed under that ancient ice....
Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 I...
Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except...
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