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Abstract  

The sulphur-containing proteinaceous amino acids l-cysteine, l-cystine and l-methionine were irradiated in the solid state to a dose of 3.2 MGy. This dose corresponds to that delivered by radionuclide decay in a timescale of 1.05 × 109 years to the organic matter buried at a depth >20 m in comets and asteroids. The purity of the sulphur-containing amino acids was studied by differential scanning calorimetry (DSC) before and after the solid state radiolysis and the preservation of the chirality after the radiolysis was studied by chirooptical methods (optical rotatory dispersion, ORD) and by FT-IR spectroscopy. Although the high radiation dose of 3.2 MGy delivered, all the amino acids studied show a high radiation resistance. The best radiation resistance was offered by l-cysteine. The radiolysis of l-cysteine leads to the formation of l-cystine. The radiation resistance of l-methionine is not at the level of l-cysteine but also l-methionine is able to survive the dose of 3.2 MGy. Furthermore in all cases examined the preservation of chirality after radiolysis was clearly observed by the ORD spectroscopy although a certain level of radioracemization was measured in all cases. The radioracemization is minimal in the case of l-cysteine and is more pronounced in the case of l-methionine. In conclusion, the study shows that the sulphur-containing amino acids can survive for 1.05 × 109 years and, after extrapolation of the data, even to the age of the Solar System i.e. to 4.6 × 109 years.

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. 5.2. Asteroid Mining Although the optimal methods to mine an asteroid has been studied and debated for decades and several technical challenges need to be solved, there is no question asteroid mining could one day become a booming

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Abstract  

The thermal properties are presented for a precious opal sourced from Coober Pedy, South Australia and a moldavite from Bohemia, Czech Republic whose origins differ significantly as opal is derived from the slow isothermal diagenesis of silica, while the tektites are specimens of vitreous silica formed from the terrestrial impact of asteroids. The differences between the two glassy silicates are presented through measurement of the TG–DSC, TMA and high-vacuum-hot-extraction DEGAS analysis.

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Abstract  

Gamma-rays emitted from the surfaces of atmosphere-free extraterrestrial bodies such as asteroids, planets, or moons, can be measured to determine their chemical surface composition. Gamma-rays are emitted from naturally radioactive elements and, in their majority, are induced by the interaction of the energetic galactic cosmic particle radiation. Neutrons of the secondary hadron cascade contribute considerably to the gamma-ray line surface fluxes via nonelastic scattering and neutron-capture reactions. In principle, planetary gamma-ray spectroscopy resembles laboratory applications of prompt activation techniques. However, the evaluation of an orbital gamma-ray spectrum of other bodies than the Moon is difficult, as comparisons to so-called ground truth values, which functioned as standards, are not possible. Future planetary exploration missions will require the evaluation of recorded gamma-ray spectra without such standards. Therefore, in an attempt to overcome some of these difficulties, prompt gamma-ray spectra of planetary constituents were measured in a set of laboratory experiments with neutron-generator and cyclotron produced neutrons of energies up to 78 MeV. The significance of neutron-capture and nonelastic scattering gamma-ray lines for the characterization of major elements were established, and the application of the results to planetary gamma-ray spectroscopy of asteroids is discussed.

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Abstract  

Molecular activation analysis (MAA) of iridium in geological samples, based on a combination of a newly-developed chemical sequential dissolution method and radiochemical and instrumental NAA, was described to study the distribution pattern and chemical species of iridium in various fractions (soluble carbonate, metal, sulfide, oxide, silicate and acid-insoluble residue) of geological boundary samples, meteorites, ultrabasic rock and volcanic lava. The correlations of Ir with Au, Os, siderophile, chalcophile and lithophile elements were discussed. In addition, the role of kerogen and noble-nugget in the Ir enrichment was scrutinized. The MAA results of Ir favors a mixed effect of asteroid impact, volcanic eruption and post-depositional redistribution to interpret the extant Ir anomaly at Cretaceous-Tertiary boundary layer.

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Abstract  

Thirty samples from a limestone stratum across the Pemian-Triassic (P-Tr) boundary layer in China were analyzed for 30 elements by instrumental neutron activation analysis, wavelength dispersive X-ray fluorescence and ICP-MS, and also for mineral compositions with a powder X-ray diffractometer. The depth profile was found to indicate a sudden change of elemental and mineral compositions across the P-Tr boundary. Also the profile showed severa peaks in elemental concentrations in the lower Permian layered samples as well as in the overlying Triassic strata, which are associated with the change of mineral compositions. Elemental profiles were found to be classified into 4 groups and to give some insights in the geochemical records. Ir is far less abundant (0.1 ppt) compared with that of the K-T boundaries (10 ppb), and the Ir/Co ratio is outside the K-T and Cl chondrite trends. This change of elementary profile is suggestive of the internal causes rather than the external ones such as an asteroid impact for the mass extinction at the P-Tr boundary.

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Central European Geology
Authors: Ildikó Gyollai, Ildikó Gyollai, Szaniszló Bérczi, Krisztián Fintor, Szabolcs Nagy, and Arnold Gucsik

2004 : Studies of thermal evolution of a chondritic asteroidal body: Synthesis from Antarctic meteorite thin section set of the National Institute of Polar Research, Tokyo . — Acta Mineralogica Petrographica 45/2 , pp. 55 – 60

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1071 1080 Nissen, S. E., Nicholls, S. J., Sipahi, I. és mtsai: ASTEROID Investigators. Effect of very high-intensity statin therapy on regression of coronary

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291 1071 1080 Nissen, S. E., Nicholls, S. J., Sipahi, I., et al., ASTEROID Investigators: Effect of very high-intensity statin therapy

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Nissen, S. E., Nicholls, S. J., Sipahi, I. és mtsai: Effect of very high-intensity statin therapy on regression of coronary atherosclerosis. The ASTEROID Trial. JAMA, 2006, 295 , 1556–1565. Sipahi I

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