Deuterium abundance of natural waters
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An analyzing method is introduced for accurate measurement of deuterium abundance in the hydrogen-deuterium system by low resolution MAT253 mass spectrometer.The calibration coefficient is determined based on building up an equipment for laboratory-scale preparation of secondary standard gases and considering the sensitivity difference between hydrogen isotopes.The results show that measure value is believable in the relative error range of 0.5% for gas samples of different deuterium abundance.
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New formulae for calculating isotope abundance ratios of oxygen enriched with 17O and 18O are derived without assuming any contribution to be negligible.
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Oxygen-18
Isotopic ratio
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By a high-field 2 Hmr study of deuteriated 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ones (fenchones), we have established that the geminal deuterium isotope effects on the exo-6-, endo-6-, and methyl deuterons are 1.46 ± 0.06 Hz (0.019 ppm), 1.61 ± 0.06 Hz (0.021 ppm), and 1.46 ± 0.06 Hz (0.019 ppm), respectively. From this study it is clear that high-field 2 Hmr has the potential of providing directly all the information on the degree of deuterium substitution at carbon previously obtained indirectly by 13 Cmr, while retaining the ability to identify chemically nonequivalent deuterons.
Geminal
Kinetic isotope effect
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Methods for the determination of 2H KIEs at natural abundance of deuterium have not been widely used due to the requirement for very long NMR times or large reaction scale. We previously reported a simple methodology for reducing these restrictions by the addition of a small amount of deuterated substrate. Herein, we evaluate the deuterium loadings that give the lowest errors in the determination of 2H KIEs. Our simulations indicate that our approach leads to a 4000-fold reduction in NMR time over natural abundance methods.
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Kinetic isotope effect
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The challenge in astrobiology and planetary research in the near future is to realize space missions to study the habitability of Mars and the icy moons of the Jovian and Saturnian systems. Mars is an interesting object to search for habitable environments and for fossilized (and potentially present) life because of its past water driven wet history. On the other hand the Jovian moon Europa and the Saturnian moon Enceladus are promising candidates, where liquid water oceans beneath the surface are expected. These oceans can be habitable environments and the next challenge is to search there for present life. Some examples on potential biospheres and their biosignatures in Mars-like environments and in environmental conditions with reference to the icy moons will be given, which might exist in such kind of icy environments.
Habitability
Icy moon
Enceladus
Planetary habitability
Liquid water
Extraterrestrial Life
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Relative standard deviation
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Using 4 years of data from the Mass Time-of-Flight and Proton Monitor, two CELIAS sensors on board SOHO, we report the sulfur abundances in comparison to magnesium and calcium (two low first ionization potential elements) for the slow solar wind, and for the first time we measure the sulfur isotopic abundance ratio. For the period in which the proton velocity was 380 ± 2 km s-1 we obtain [S]/[Mg] = 0.26 ± 0.03, [S]/[Ca] = 4.7 ± 0.5, and [34S]/[S] = 0.043 ± 0.009. We compare these measurements with the available measurements reported in the literature, and we check the quality of the results by using the magnesium isotopic ratio and the calcium-to-magnesium abundance ratio as a control. Finally, as a further result we also obtain the absolute abundance of the previous elements. In astronomical notation we have AS = 7.44 ± 0.04, AMg = 8.03 ± 0.05, and ACa = 6.77 ± 0.04.
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