نتایج جستجو برای: fractionation
تعداد نتایج: 19571 فیلتر نتایج به سال:
Isotope fractionations associated with high temperature evaporation provide important constraints on the physicochemical processes that affected planetary materials at the birth of the solar system. Previous evaporation experiments have focused on isotopic fractionation of moderately to highly volatile elements. Here, we investigate the isotope fractionation behavior of two highly refractory el...
The iron isotopic fractionation factor between magnetite and fayalite was measured at high temperature in a piston–cylinder apparatus. For the first time, the three-isotope method [Matsuhisa, J., Goldsmith, J. R., and Clayton, R. N., 1978. Mechanisms of hydrothermal crystallisation of quartz at 250 °C and 15 kbar. Geochim. Cosmochim. Acta 42, 173–182.] has been used to determine equilibrium fra...
MOTIVATION Fractionation is arguably the greatest cause of gene order disruption following whole genome duplication, causing severe biases in chromosome rearrangement-based estimates of evolutionary divergence. RESULTS We show how to correct for this bias almost entirely by means of a 'consolidation' algorithm for detecting and suitably transforming identifiable regions of fractionation. We c...
The fractionation of sulfur isotopes by the thermophilic chemolithoautotrophic Thermodesulfatator indicus was explored during sulfate reduction under excess and reduced hydrogen supply, and the full temperature range of growth (40–80 C). Fractionation of sulfur isotopes measured under reduced H2 conditions in a fed-batch culture revealed high fractionations (24–37&) compared to fractionations p...
All terrestrial higher plants preferentially assimilate CO 2 relative to CO 2 during photosynthesis as a result of physical and biological isotope fractionation processes, with much larger overall C fractionation by plants using the C 3 photosynthetic pathway (approximate range of 14–27‰) compared to plants using the C 4 pathway (approximate range of 3–6‰). Fractionation against CO 2 in both C ...
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...
Evaporative fractionation of petroleum by gas injection over oil was established by Thompson. In this process he could fractionate reservoir petroleum to paraffin rich condensate in the shallow reservoir and aromatic rich residual oil in the original reservoir. In the present work attempt has been made to test fractionation by heating crude oil in a closed system to build up adequate vapour pre...
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