Abundance of metals

Abstract. The chemical composition of B 12, a Be star in the SMC cluster NGC 330, is analysed using high-resolution UVES/VLT spectra and the non-LTE model atmosphere code TLUSTY. A differential analysis relative to a SMC standard star AV 304 revealed (1) a general under-abundance of metals compared with that expected for the SMC, and (2) the lack of nitrogen enhancement. The former is attributed to the presence of a disk, and its contribution to the overall emission is estimated. Possible explanations for the lack of rotational mixing in the apparently rapidly rotating star are discussed. 

Studies of chemical abundances of metal rich samples are still not numerous due to the paucity of stars in the super-solar metallicity range. Nevertheless, some recent works have succeeded to delineate the chemical evolution pattern of important elements, showing interesting behaviors for such domain (e.g. [2], [6]). In the present work we report preliminary abundances for super-solar metallicity bulge-like stars. 

Abstract. We have performed the chemical analysis of extragalactic carbon stars from VLT/UVES spectra. The derived individual abundances of metals and s-elements as well as the well known distance of the selected stars in the Small Magellanic Cloud and the Sagittarius dwarf galaxies permit us to test current models of stellar evolution and nucleosynthesis during the Asymptotic Giant Branch phase in low metallicity environments. 

The selected extragalactic carbon stars have been observed with the VLT/UVES instrument in service mode. The spectral resolution was around 40000 over the domains 420-500 nm and 670-900 nm. We used carbon-rich MARCS model atmospheres and specific linelists in order to derive the abundances of metals,... 

In a closed box, the star formation rate can only decrease with time. Thus the timing of a collision is irrelevant for the metallicity history of such a galaxy the final abundance of metals will always increase relative to the moment of stripping. In contrast, in an open system, the global star formation rate can recover due to infall of externally or internally supplied diffuse gas and clouds. The metallicity history then becomes sensitive to the timing and frequency of such events. The final star formation rate may resemble an anemic systems. 

Moon J, Davison AJ, Smith TJ, et al. 1988. Correlation clusters in the accumulation of metals in human scalp hair Effects of age, community of residence and abundances of metals in air and water supplies. Sci Total Environ 72 87-112. 

Figure 9.49 Comparison of isotope abundances of metallic Os and natural highly enriched 187Os samples (a) results of isotope analysis on metallic osmium (lohnson Matthey Chemicals) (b) isotope analysis on natural 187Os enriched samples due to /3 decay of 187Re.108...

The fact that there is such a paucity of metal formyl complexes is both interesting and significant because of the proposed intermediacy of coordinated formyl in CO reduction, and the sharply contrasting abundance of metal acyl complexes. Since many of the acyl complexes are known to form by migratory insertion of CO in an alkyl carbonyl complex (20, 20a, 22), the lack of formyl complexes from hydride carbonyls relates to the thermodynamic difference in the equilibrium (5) when Y is alkyl and when it is hydride. 

Rhenium is an element known for its abundance of metal hydride complexes spanning a variety of oxidation states, for example, from Re(I), Re(CO)sH to Re(VII), ReH92 . However, despite the recent interest in light-driven H2 formation from different substrates (such as water) there are few recent photochemical studies of Re hydride complexes. 

Apart from necessities of efficient coupling of different metal-catalyzed biochemical pathways, e.g. in photosynthesis, there is highly positive correlation among most of these elements yet, holding for abundances of metals and non-metals in various plants alike (also cp. Fig. 1.3). Apart from this, biochemically relevant ligands will control resorption, retention and transport of metals according to Eqs. 2.1 0,2.11 (below, section 2.2.5) all the way from rhizosphere upward to... 

Abundances of metals with respect to hydrogen are mostly derived using the intensity ratio of collisionally excited lines with H/3. It is instructive to understand the dependence of such emission line ratios with metallicity. Let us consider the [O III] A5007/H/ line ratio and follow its behaviour as n(0)/n(H) decreases (from now on the notation n(0)/n(H) will be replaced by O/H). The temperature dependence of the [O III] A5007 and H/3 lines implies that ... 

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