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991.
The absolute configuration of dechlorogilmaniellin ( 2 ) could be determined from its chiroptical data by applying coupled-oscillator theory to the CD couplet around 272 nm and from the sign of its n →π* Cotton effect. Gilmaniellin ( 1 ) has the same absolute configuration. 相似文献
992.
Ag5GeO4, the First Subvalent Ternary Silver Oxide Applying high oxygen pressure the first subvalent ternary silver oxide Ag5GeO4 was obtained (for crystallographic data c.f. “Inhaltsübersicht”). Ag5GeO4 contains tetrahedral GeO44?-ions besides [Ag6]4+ clusters, which have not been observed in ternary silver oxides, so far. The electrical and magnetical properties prove the localisation of two paired electrons in each silver octahedron. The thermal decomposition occurs in two steps at 432.7 °C and 524.5°C. 相似文献
993.
994.
Andrea Konnert Sabine Arends Stefan Schubert Christoph Berding Cas Weykamp Carla Siebelder 《Accreditation and quality assurance》2006,11(7):319-328
Within the last decade, the IFCC HbA1c standardization network has established the metrologically highest reference measurement procedure for HbA1c testing. Based on this procedure, reference calibrators are produced which in turn provide the starting point for the standardization of the manufactures routine HbA1c assays. According to the IVD directive, the uncertainty of the reference calibrators must be calculated and reported together with their assigned values. Within this article, we elaborate the uncertainty calculation according to GUM (guide to the expression of uncertainty in measurement) in detail. Finally, the results are validated by a simulation study. 相似文献
995.
Amthor S Lambert C Graser B Leusser D Selinka C Stalke D 《Organic & biomolecular chemistry》2004,2(20):2897-2901
Thianthrenophane 1 has a cavity which offers enough room to potentially enable endohedral coordination to small ions or molecules. For the complexation of silver(I) perchlorate the complex stability constants of 1 logK1=5.45 +/- 0.13 and of thianthrene logK2=9.16 +/- 0.10 were determined by UV/Vis titration. Single competition transport experiments with ten metal salts demonstrate a very high selectivity of 1 as a carrier for silver(I) and a distinctly higher transport rate compared to carriers such as thianthrene and 1,4,8,11-tetrathiacyclotetradecane (14-ane-S4). Although the X-ray crystal structure analysis of the polymeric [Ag(1)]ClO4.(dioxane)7 complex shows an exohedral coordination to silver(I) we suggest that the formation of an endohedral [Ag(1)]+ complex is the explanation for the unusual carrier selectivity of silver(I) by 1 in bulk liquid membrane. 相似文献
996.
Site-specific solvation has been determined by intermolecular NOE measurements between solvent and solute. The experimental effect is shown on the four compounds 2-butanol, L-alanyl-L-tryptophan (Ala-Trp), adenosine and the disodium salt of adenosine 5'-monophosphate (5'-AMP) in the two solvents water and dimethyl sulfoxide (DMSO). The strength of NOE transfer correlates with the average distribution of solvent molecules around the corresponding solvation sites represented by the number of solvent molecules in a first solvation sphere, which can be obtained from molecular dynamics simulations in water. Saturation transfer between exchanging protons explains some deviations from this correlation. The NOE transfer measurements provide information on specific solute-solvent interactions and contribute to a better understanding of solvation phenomena. On the basis of a distinct relationship between steric solvation hindrance and the strength of NOE transfer, the application of such measurements for conformational analysis has been demonstrated for the first time. 相似文献
997.
998.
999.
Remo Gamboni Peter Mohr Nada Waespe-Šarčevic̀ Christoph Tamm 《Tetrahedron letters》1985,26(2):203-206
3-Phenylpropionates of chiral alcohols derived from (+)-camphor are oxidized by Mo05· Py·HMPT (MoOPH) with high diastereoselectivity. 相似文献
1000.
The molecular and electronic structures of the V2O4+/0/- species are examined by multireference averaged coupled-pair functional (MR-ACPF) and density functional B3LYP calculations. For all three species, new conformers have been found. Shallow potential energy curves imply high mobility of the oxygen atoms in the neutral and anionic species for which antiferromagnetic coupling of the weakly interacting 3dV electrons is found. Good agreement between the MR-ACPF and B3LYP results for the molecular structures and the relative energies of states with different spin multiplicity, as well as for the ionization energy and electron affinity, is observed. For the computation of the height of the transition barriers between different conformers elaborated MR-ACPF calculations are required. 相似文献