Sulphur abundance

Abstract. We present here the results of the measurement of the sulphur abundance in very metal-poor stars. Our sample covers the [-4 -2] range of metallicity, and thus allows us to constraint the chemical evolution models and also to put some key constraints... 

Sulphur is generally considered as an a/p/ia-element. Thus we expect the sulphur over iron ratio to behave as do other [a/Fe] ratios, that is to say that this ratio reaches a plateau when metallicity goes beyond -1.0. But unfortunately, measuring sulphur abundance can be quite tricky. We can measure S abundance using two different line systems one system lies around 800nm and the other is around 920 nm. The first system has very weak lines, and the second is blended by atmospheric lines. Thus, the S abundance is difficult to derive from EW measurement. 

We have used the infra-red triplet (921.286 nm, 922.809 nm and 923.754 nm) to determine the sulphur abundance in the 32 giants from ESO s Large Program Galaxy Formation, Early Nucleosynthesis, and First Stars . 

Figure 9.32 illustrates the isotopic enrichment of SFe following irradiation with a pulsed CO2 laser in the 3g vibrational band, at 945 cm, of SFe, V3 being a strongly infrared active bending vibration. The natural abundances of the isotopes of sulphur are (95.0 per cent), (4.24 per cent), (0.74 per cent) and (0.017 per cent). The figure shows that depletion of SFg has been achieved to such an extent that equal quantities of SFg and SFa remain. 

Thus it will be necessary to exploit other more abundant resources of hydrocarbons. In the United Kingdom there are large reserves of coal which could satisfy demand for at least two hundred and fifty years. The National Coal Board currently mines approximately 120 million tons of coal per annum of which 65% is used for generating electricity (JO. (Combustion of the low sulphur British coals does not result in excessive atmospheric pollution.) To satisfy the increased demand for coal the National Coal Board has undertaken an investment programme which includes the development of a mining complex at Selby in Yorkshire which, it is estimated, will produce in excess of 10-million tons when full production is reached in 1988. 

The surface of Venus is hidden under an unbroken layer of clouds 45-60 km above it. Recently, the planet has been subjected to a complete cartography by radar satellites. Its atmosphere contains 96% CO2 by volume, the remainder consisting of N2, SO2, sulphur particles, H2SO4 droplets, various reaction products and a trace of water vapour. The water is probably subject to photolytic decomposition. Noble gases are more abundant than on Earth 36Ar by a factor of 500, neon by a factor of 2,700, and D (deuterium) by a factor of 400. 

We measured the IR triplet of the sulphur, that is to say the following lines 9212.863, 9228.093 and 9237.538. The abundance determination leads to the confirmation that sulphur behaves like an a element, and we can confirm that the [S/Fe] ratio reaches a plateau when the metallicity decreases and becomes lower than —2. The value of this plateau is close to 0,4 dex. 

Damped Ly-a absorbers are well suited to abundance analysis because the large column density ensures that O and N are essentially all in their neutral state while sulphur and metals are essentially all singly ionized, with column densities leading to readily measurable spectral features. Also, the degree of depletion from the gas phase by the formation of dust is lower than in the local ISM. Some typical metallicities (based on zinc which is not seriously depleted even in the local... 

The elements whose isotopes are routinely measured with gas inlet mass spectrometers are carbon (12C and 13C, but not 14C), oxygen (160, 170, l80), hydrogen ( H, 2H, but not 3H), nitrogen (14N and 1SN) and sulphur (32S, 33S, 34). Stable isotopes of H, C, N, O, and S occur naturally throughout atmosphere, hydrosphere, lithosphere, and biosphere. They are atoms of the same elements with a different mass. Each element has a dominant light isotope with the nominal atomic weight (I2C, 160,14N, 32S, and H) and one or two heavy isotopes (l3C, nO, 180, 15N, 33S, 34S, and, 2H) with a natural abundance of a few percent or less Table 1). 

The analysis of organosulphur compounds has been greatly facilitated by the flame photometric detector [2], Volatile compounds can be separated by a glass capillary chromatographic column and the effluent split to a flame ionization detector and a flame photometric detector. The flame photometric detector response is proportional to [S2] [3-6]. The selectivity and enhanced sensitivity of the flame photometric detector for sulphur permits quantitation of organosulphur compounds at relatively low concentrations in complex organic mixtures. The flame ionization detector trace allows the organosulphur compounds to be referenced to the more abundant aliphatic and/or polynuclear aromatic hydrocarbons. 

Wesley and Wall (4 ) and Brown and coworkers (18) collected dust samples at five cotton gins with high volume air samplers at three locations in the gin. The dust was removed from the filters in the seime manner as the weave room dusts discussed above. The average ash content was 32.9%. X-ray fluorescence analyses showed that silicon was the most abundant element detected (7.69%), followed by potassium (1.82%), aluminum (1.46%), calcium (1.15%), magnesium (1.05%), phosphorous (0.52%), iron (0.45%), sulphur (0.33%) and chlorine (0.16%). The total dust was separated into a "respirable fraction" (28) by the sonic sifting procedure and analyzed as above. The ash content of the respirable fraction of gin dusts increased to 46.0%. Only the... 

Ferredoxins (Fds) are widespread in the three domains of life and an abundance of sequence data and structural information are available for Fds isolated from several sources. In particular, the bacterial type Fds are small electron-transfer proteins that posses cubane xFe-yS clusters attached to the protein matrix by Fe ligation of Cys via a conserved consensus ligating sequence. The archaeal type ferredoxins are water-soluble electron acceptors for the acyl-coenzyme A forming 2-oxoacid/ferredoxin oxidoreductase, a key enzyme involved in the central archaeal metabolic pathways. Fds have been distinguished according to the number of iron and inorganic sulphur atoms, 2Fe-2S, 4Fe-4S/3Fe-4S (Fig. Ib-d) and Zn-containing Fds. 

We also know that a considerable enrichment of prebiotic moieties may have come from submarine vents and other hydrothermal sources (see, for example, Miller and Bada, 1988 Holm and Andersson, 1998 Stetter, 1998). Let s start with the 1979 discovery of deep-sea vents with black smokers, which are associated with an extraordinary abundance of the most phylogenetically primitive organisms on Earth. This ecosystem is sulphur based, and is distinct from the more familiar, photosynthetically-based ecosystem that dominates Earth s surface. Corliss et al. (1981) were struck by the richness of the vent biota, based on chemosynthesis, and proposed that these were the origin of life. 

Conditions that are conducive to the accumulation and decay of plant residues, and therefore conducive to the formation of coal, are typically associated with water-saturated and reducing environments. Consequently, a large portion of the trace elements associated with the mineral fraction of coal are expected to occur in reduced forms, primarily as sulphides or carbonates. However, because of its abundance compared to sulphur, it is unlikely that the complete reduction of iron oxides to iron sulphide would ever occur. Therefore, the presence of Fe oxides, and trace... 

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