A Genetic Algorithm for the Set Covering Problem

In this paper, the set covering problem (SCP) is considered. Several algorithms have been suggested in the literature for solving it. We propose a new algorithm for solving the SCP which is based on the genetic technique. This algorithm has been implemented and tested on various standard and randomly generated test problems. Preliminary results are encouraging, and are better than the existing heuristics for the problem.     

Photochemical [3 + 2] cycloaddition of α,β-acetylenic ketones with simple olefins

Irradiation of 3-pentyn-2-one (1) in the presence of tetramethylethylene, isobutylene, and cis- and trans -2-butene leads to vinyldihydrofurans 3,5,6, 8 and 9 (Table 1) in a novel [3 + 2] photochemical cycloaddition reaction. A related adduct 13 is formed between tetramethylethylene and 5,5-dimethyl-3-hexyn-2-one (2). A mechanism incorporating an initial biradical that closes to a carbene (eqn 3) is proposed to account for these reactions.     

Synthesis, 13C NMR and IR spectroscopic studies of gold(I) complexes of imidazolidine-2-thione and its derivatives

The gold(I) complexes of imidazolidine-2-thione and its derivatives were synthesized and their ¹³C NMR and IR spectroscopic studies were carried out. When gold(III) was reacted with the ligands using a 1:4 metal to ligand ratio, gold(III) was reduced to gold(I), the bis complexes of the general formula AuL_nX (where n = 2) were formed. However, when gold(III) was reduced to gold(I) by a reducing agent followed by an addition of the ligand to an aqueous or methanolic solution of gold(I), only mono complexes of the type AuLX were obtained. The structures of the reported complexes are proposed on the basis of their spectroscopic measurements.     

An unusual rearrangement in the iodination of some 1-allyl- and 1-benzylcyclopropenes

Iodination of selected 1-allyl- or 1-benzyl-cyclopropenes with electron-donating groups on the substituent leads to 2-iodo-1-iodomethyl-1 -vinyl or 1-arylcyclopropanes.     

Density of vapor deposited amorphous Ge films

The density of vapor-deposited amorphous Ge films (a-Ge) was determined by spectrophotometry combined with Rutherford backscattering spectroscopy. It was found to be 0.99±3% of the bulk value for crystalline Ge (c-Ge). This density is in agreement with the Lorentz-Lorenz law which, based upon the existing infrared data on the index of refraction of a-Ge, suggests that the density of a-Ge should be close (within 4%) to that of c-Ge.     

Trifluoroethylxanthate as an analytical reagent: Spectrophotometric determination of cobalt and copper as their trifluoroethylxanthates

Summary A direct spectrophotometric method has been developed for the micro-determination of Co(II) and Cu(II) as their trifluoroethylxanthates, by use of aqueous acetone medium. The reagent and methods have been found selective and sensitive for the determination of these metals in certain alloys.

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Trifluorethylxanthat als analytisches Reagens: Spektrophotometrische Bestimmung von Kobalt und Kupfer

Zusammenfassung Eine direkte spektrofluorimetrische Methode zur Mikrobestimmung von Co(II) und Cu(II) in Form ihrer Trifluorethylxanthate in wäßrigem Acetonmedium wurde ausgearbeitet. Reagens und Methode sind bei der Bestimmung der genannten Metalle in gewissen Legierungen selektiv und empfindlich.