نتایج جستجو برای: isotopic
تعداد نتایج: 18280 فیلتر نتایج به سال:
Isotopic chirality influences sensitively the enantiomeric outcome of the Soai asymmetric autocatalysis. Therefore magnitude and eventual effects of isotopic chirality caused by natural abundance isotopic substitution (H, C, O, Zn) in the reagents of the Soai reaction were analyzed by combinatorics and probability calculations. Expectable enantiomeric excesses were calculated by the Pars–Mills ...
Introduction: Presolar graphite was isolated from the Murchison meteorite [1] only 3 years after the discovery of presolar SiC [2]. Yet it has not been studied as extensively as SiC. One of the reasons is that trace element concentrations in graphite grains are, in general, not high enough to perform isotopic analysis with sufficient precision. A new type of ion microprobe, the NanoSIMS, has re...
Measurements of ratios of stable isotopes are used in such diverse fields as petroleum prospecting, medical diagnostics, and planetary exploration. The narrow emission linewidth available from tunable diode lasers permits high-resolution infrared absorption measurements of closely spaced isotopic rovibrational lines. Our dual beam spectrometer uses the sweep integration technique in a spectral ...
Naphthalene and 2-naphthol are two naphthalene derivatives, which play important roles in the chemical and pharmaceutical industries. The aim of this study was to evaluate the impact of biofield energy treatment on the isotopic abundance of 13 C/ 12 C or 2 H/ 1 H and 18 O/ 16 O in naphthalene and 2-naphthol using gas chromatography-mass spectrometry (GCMS). Naphthalene and 2-naphthol samples we...
The U/U isotopic composition of uranium in seawater can provide important insights into the modern U budget of the oceans. Using the double spike technique and a new data reduction method, we analyzed an array of seawater samples and 41 geostandards covering a broad range of geological settings relevant to low and high temperature geochemistry. Analyses of 18 seawater samples from geographicall...
Introduction: Interplanetary dust particles (IDPs) have been shown to preserve isotopic anomalies, particularly in nitrogen and hydrogen associated with molecular cloud organic material [1-3]. Furthermore, with the heightened capabilities of the NanoSIMS ion microprobe, submicrometer-sized presolar silicate grains have been identified in IDPs [3-6]. Recently, four IDPs collected during the 2003...
Introduction: Carbonaceous chondrites play a key role in determining the history of the early Solar System; a knowledge of the oxygen isotope variation within these materials will not only help in our understanding of the origin and evolution of those meteorites, but also the early Solar System reservoirs from which they formed [1]. However, several problems present themselves when trying to in...
The Lalezar granitoids crop out within volcanic successions of the Urumieh-Dokhtar Magmatic Assemblage (UDMA). These granitoids have a range from gabbro-diorites to granites in composition. The mineral compositions of the most felsic rocks are characterized by the abundances of Na-plagioclase, quartz, alkali feldspar, biotite and hornblende. In the gabbro-diorite rocks, plagioclase (Ca-rich), h...
the darreh-zar porphyry copper deposit, located in the urumieh – dokhtar magmatic belt, lies about 10 km southeast of sar-cheshmeh porphyry copper deposit. the ore body with hydrothermally altered zones including potassic, chlorite-sericite, sericite, argillic and propylitic all related to the darreh-zar porphyry stock intruded the eocene volcanic rocks. pyrite, chalcopyrite, molybdenite, with ...
Lead hazard control measures to reduce children's exposure to household lead sources often result in only limited reductions in blood lead levels. This may be due to incomplete remediation of lead sources and/or to the remobilization of lead stores from bone, which may act as an endogenous lead source that buffers reductions in blood lead levels. Here we present a noninvasive isotopic approach ...
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