Material enrichment

Complex ( + )-(FeS)-3 is obtained by extraction of the diastereomeric mixture with 50 mL of pentane in portions at r.t. The specific rotation of the solid product obtained from the first fraction is [a]jJ6 +50 (o = 0.001. benzene). The rotation of the remaining mixture becomes more negative as the (+)-isomer is removed. After concentration of the combined fractions, the resulting material, enriched in the ( + )-isomcr, is further purified by extraction with 10 mL of pentane in portions. Repetition of the pentane extraction procedure affords ( + )-(FeS)-3 yield-. 750 mg (30%) mp 120"C (dee) [a] +72 (c = 0.001, benzene). The residue, enriched in (—)-(FeR)-3 is extracted for 1 h with boiling pentane. After separation from the extraction liquor, a yellow-orange solid is obtained yield I -35 g (50%) mp 120°C (dec) — 120... 

Since most (if not all) low-metallicity objects that are currently observed in the halo are not in the AGB phase, material enriched in carbon and the s-process elements is assumed to have accreted from the companion AGB stars, which have already evolved to faint white dwarfs, to the surface of the surviving companion. This scenario is the same as that applied to classical CH stars [4], Unfortunately, long-term radial velocity monitoring has been obtained for only a limited number of objects a clear binarity signature has been established for six objects in our sample to date. However, there exists additional support for the mass-accretion scenario for the Ba-rich CEMP stars. Fig. lb shows [C/H] as a function of luminosity roughly estimated from the effective temperature... 

It was formerly believed that coniferous woods contain a mannan. However, before the polysaccharide containing the mannose residues was isolated in a state of purity, Leech d and Anthis> were able to show that it was a glucomannan, by the isolation of disaccharides containing both glucose and mannose from a hydrolysate of polysaccharide material enriched in the mannose-containing material. This observation was later confirmed by the isolation of pure glucomannans from these woods. - ... 

Fuel Recycle Requirements. We asstime that the final product returned for fuel fabrication and recycle is a mixed uranium-plutonium dioxide material, partially decontaminated from fission products. The questions of fissile material enrichment, radiation levels, and required handling facilities are not addressed. 

Figure 2. Mossbauer spectra. Top solid monoferric phytate, 212 mg at 80 K. Center wheat seeds, 1.54 g at room temperature. Bottom dissected wheat bran, 9.5 mg at 80 K. All materials enriched in 17Fe. (Reprinted from Ref. 8. Copyright 1980, American Chemical Society.)...

Separation. — Krypton tins never been obtained except from the atmosphere, A convenient method of separation consists in passing a slow stream of dry oxygen, which has I men materially enriched by fractionation in a liquid air plant, through a tube cooled with liquid air, In this way krypton and xenon together with a little argon condense ns a liquid or solid. 

In general, material enrichment is conducted by physical separation processes such as density separation, magnetic separation, electrical assortment, and flotation. With complex or poorer ores where physical separation is neither possible nor economically feasible, a wet-chemical process such as leaching, precipitation or extraction is often used. Generally, the wet-chemical processing of the ore preparation is also a substantial part of the hydrometallurgical... 

The process of combustion of materials enriched with yttrium seems to be a risk factor as a source of flammable dusts. Yttrium oxide, yttrium chloride, yttrium citrate, and certain other yttrium compounds may cause chronic pathological effects in different parts of the mammalian respiratory system, according to the results of experimental studies carried out in rats, mice, guinea pigs, and rabbits. Therefore, a higher risk for human health may be... 

The isolation and characterization of D2 Synmictrical Cyg in 1991 [1] led to important conclusions It was shown that pure fuUerenes with more than 70 carbon atoms could be isolated in macroscopic quantities from soot produced by the Kratschmer-Huffrnan method [2] and that the vaporization of achiral graphite was able to generate chiral carbon cages. Mass spectrometric evidence for the presence of higher fullerenes - that is, carbon molecules (n > 70) - in crude fullerene soot extract had been obtained shortly before, and optimization of the fullerene purification protocol soon afforded milligram samples of material enriched in higher fullerenes [3]. 

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