Iron ratio

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. 

The kinetics of iron(III) dissociation from a series of dihydrox-amate siderophores and siderophore mimics, including rhodo-torulic acid (3) and alcalagin, have been investigated (52,127,128, 177,178). ESI-MS studies show that these systems form multiple species as a function of pH and siderophore/iron ratio (128). The lability of these systems and the resultant multiple species leads to several parallel paths to iron(III) dissociation (177). Both the distribution of structures and kinetics of dissociation were shown to be dependent on the length of the spacer chain between the dihydroxamate donor groups (52,127). 

Fig. 8.8. Element iron ratios measured in Galactic disk stars, after Edvardsson et al (1993). Courtesy Johannes Andersen.

Fig. 8.9. Even-numbered element iron ratios measured in ultra-metal-deficient Galactic halo stars, after Cayrel et al. (2004). 

Fig. 8.27. Fits of the model to element-to-iron ratios measured by Edvardsson et al. (1993) for disk stars and by various authors for Population II stars which include a significant component from the metal-weak thick disk. The model curve is for coA = 0.4. After Pagel and Tautvaisiene (1995).

Fig. 8.28. Europium and thorium to iron ratios plotted against metallicity [Fe/H], Curves represent the model predictions as in Table 8.2 and the symbols represent observational results by different authors. After Pagel and Tautvaisiene (1995).

Fig. 8.29. Europium to iron ratios plotted against metallicity [Fe/H] according to the model of supernova-induced star formation, after Tsujimoto, Shigeyama and Yoshii (1999). Grey scales represent predicted stellar surface densities in the ([Fe/H],[Eu/Fe]) plane convolved with a Gaussian with o = 0.2dex for Eu/Fe and 0.15 dex for Fe/H, and symbols show observational data from various authors. The inset shows the unconvolved predictions.

Fig. 8.30. Main s-process element to iron ratios plotted against metallicity [Fe/H] according to the analytical model by Pagel and Tautvaisiene (1995), compared to observational data. The s-process begins to contribute, superimposed on a pure r-process contribution, already at [Fe/H] = —2.5 ( >A = 0.01 A 0.3 Gyr), followed by a more delayed s-process that sets in at [Fe/H] = -0.65 ( >A = 0.8 A 2 Gyr, compared to 1 Gyr for iron). The large scatter displayed by strontium is probably real. After Pagel and Tautvaisiene (1997).

Figure 11.5 shows the a-element to iron ratios in the LMC and in the anomalous halo stars of Nissen and Schuster (1997). The trend with metallicity is much reduced compared to the disk and the majority of halo stars in the Galaxy, which is attributed to the longer timescale for star formation in the Clouds see Fig. 8.7. However, below [Fe/H] = -1.3, there are similar plateaux to those in the Milky Way,...

For example, consider the sample specified in the top line of Table 1.1, with an oxygen iron ratio of 1.058, a measured density of 5728 kg m-3 and a cubic lattice parameter, a, of 0.4301 nm. 

In Table II, it can be seen that decomposition at low temperatures left a CO/Fe ratio on the surface of between 0.8 and 1.3. A reasonable explanation for the high CO to iron ratios on the surfaces, given the fact that Mossbauer spectroscopy studies show that a large fraction of the iron is oxidized, is that iron subcarbonyl species are stable on the surface at 383 K. This is true since CO does not adsorb strongly on iron oxides (35). 

Even nuclei, and in particular the class of a nuclei (oxygen, magnesium, silicon, calcium), are the basic products of nucleosynthesis in high-mass stars. They are abundantly present in the ashes of SNll events, where the cx/iron ratio is about three times the solar value. The amounts of even elements ejected by explosion of a high-mass star are, to the first approximation, independent of the star s initial metallicity. 

M.G. (1984) Estimating relative ages from iron-oxide/total-iron ratios of soils in the Western Po Valley, Italy. Geoderma 33 39-52 Artman, J.O. Murphy, J.C. Foner, S. (1965) Magnetic anisotropy in antiferromagnetic corundum type sesquioxides. Phys. Rev. 138 A912-917... 

Zinc Iron Brown. Variation of the zinc to iron ratio in red-brown iron spinel (ZnFe204), or replacement of some of the iron ions by aluminum and titanium ions, gives light to medium brown pigments. Inclusion of a small proportion of lithium ions considerably improves stability towards reducing agents, e.g., when the pigments are used to color plastics [3.87]. The partial replacement of iron ions by chromium(III) ions yields dark brown products [3.88]. 

Roth, C.B., Jackson, M.L. and Syers, J.K., 1969. Deferration effect on structural ferrous-ferric iron ratio and C.E.C. of vermiculites and soils. Clays Clay Miner., 17 253-264. 

A method for converting 1,3-butadiene into polybutadiene having at least an 88.4% vinyl content using iron isooctanoate, triisobutylaluminum, and ethyl phosphite is described. The optimum weight ratio of reagents of aluminum/iron was 5 100 with a phosphite/iron ratio of 1 20, respectively. 

It is now widely agreed that both copper and iron are essential components 52-56). The metal content (11 nmoles/mg protein) and the iron to copper ratio (1.0) are well established for the bovine enzyme, whereas in yeast the reported metal contents are higher and more variable (5-15 nmoles of iron per milligram of protein) and the copper to iron ratio is greater than unity ( 1.5) (Table II) (44-4 > 48-52, 57-59). The iron is present as the unusual heme, heme A, with an apparently unique structure (Fig. 2) 60). The coordination environment of copper is far less clear, but the easy reducibility of copper seems to require a ligand envi-... 

About the manganese-to-iron ratio in the solutions produced by deep-sea weathering of basalt or from deep-sea hydrothermal solutions we do not know very much. The deep-sea precipitates which are evidently hydrothermal can cover the wide scale of compositions from nearly pure iron hydroxide to nearly pure manganese hydroxide. 

Cohen and Ng (C21) described a process of improving the chrome-iron ratio of reduced pelletized chromite concentrate by acid leaching of iron without significant loss of chromium. A 5% sulfuric acid solution was used to quench and leach the fired pellets from 400 C to room temperature. 

In addition to appearance, EP products offer other advantages such as an extremely smooth surface which minimizes the adherence of debris, an increased chromium to iron ratio which improves corrosion resistance, the creation of a passive layer that is free from iron contamination, improved ability to visually detect surface defects, and improved mechanical property performance through the minimization of stress risers. 

Some of the most recognized tests to detect, measure, and quantitate the chrome/iron ratio and to ensure that a passive layer has been established are the Ferroxyl Test for Free Iron, X-Ray Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA), and Auger Electron Spectroscopy (AES). 

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