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41.
42.
Nigel T. Lucas Marie P. Cifuentes Lam T. Nguyen Mark G. Humphrey 《Journal of Cluster Science》2001,12(1):201-221
The new phosphines Ph2PC6H4-4-CCR [R=SiMe3 (1), H (2)] have been used to prepare Ru3(CO)9(Ph2PC6H4-4-CCSiMe3)3 (4) and Ru(CCC6H4-4-PPh2)(PPh3)2(-C5H5) (3), respectively, the latter with a pendent phosphine. Reaction of 4 with carbonate or fluoride affords Ru3(CO)9(Ph2PC6H4-4-CCH)3 (5) with pendent terminal alkynyl groups, the identity of which was confirmed by a structural study. Reaction of 5 with [Ru(NCMe)(PPh3)2(-C5H5)]PF6 or reaction of Ru3(CO)12 with 3 gives Ru3(CO)9{(Ph2PC6H4-4-CC)Ru(PPh3)2(-C5H5)}3 (6). Complexes 3–6 have been studied by cyclic voltammetry. Proceeding from Ru3(CO)12 to 4 or 5 shifts the cluster-centred reduction to more negative potential and affords facile cluster-centred oxidation. Proceeding from 4/5 and 3 to 6 results in similarly-located cluster-centred reduction and peripheral ruthenium-centred oxidation, but results in a lack of observable cluster-centred oxidation. Crystal data for 5·C6H14: space group P¯1, a=12.760(1) Å, b=17.077(1) Å, c=17.924(2) Å, =108.656(5)°, =96.344(5)°, =93.523(5)°, V=3658.4(6) Å3, Z=2, R=0.078, Rw=0.105 for 5008 reflections [I>2.00(I)]. 相似文献
43.
The cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)-cyclopentane-[PdCl(eta3-C3H5)]2 system catalyses the coupling of aryl halides with alkynes with very high ratios of substrates-catalyst in good yields; a turnover number of 2600000 can be obtained for the reaction of 4-trifluoromethylbromobenzene with phenylacetylene in the presence of this catalyst. 相似文献
44.
Anne Marie Torpe 《Journal of Functional Analysis》1985,61(1):15-71
The K-theory of the C1-algebra associated to C∞-foliations (V, F) of a manifold V in the simplest non-trivial case, i.e., dim V = 2, is studied. Since the case of the Kronecker foliation was settled by Pimsner and Voiculescu (J. Operator Theory4 (1980), 93–118), the remaining problem deals with foliations by Reeb components. The K-theory of for the Reeb foliation of S3 is also computed. In these cases the C1-algebra is obtained from simpler C1-algebras by means of pullback diagrams and short exact sequences. The K-groups are computed using the associated Mayer-Vietoris and six-term exact sequences. The results characterize the C1-algebra of the Reeb foliation of 2 uniquely as an extension of C(S1) by C(S1). For the foliations of 2 it is found that the K-groups count the number of Reeb components separated by stable compact leaves. A C∞-foliation of 2 such that K1(C1(2, F)) has infinite rank is also constructed. Finally it is proved, by explicit calculation using (M. Penington, “K-Theory and C1-Algebras of Lie Groups and Foliations,” D. Phil. thesis, Oxford, 1983), that the natural map is an isomorphism for foliations by Reeb components of 2 and S3. In particular this proves the Baum-Connes conjecture (P. Baum and A. Connes, Geometric K-theory for Lie groups, preprint, 1982; A. Connes, Proc. Symp. Pure Math.38 (1982), 521–628) when V = 2. 相似文献
45.
A number of 1-allylthio and 1-crotylthio 1-aminoalkenes derived from ketones and active methylene compounds has been prepared and rearranged to the corresponding thioamides (thio-Claisen rearrangement). Besides rearrangement products, small amounts of 1-alkyl-thio-N-alkyl-N-phenyl-1-aminoalkenes have also been isolated. When the ketene derivatives did possess a H-atom on nitrogen, cleavage of the formed thioamide produced phenyl isothiocyanate and substituted active methylene compounds. 相似文献
46.
G. J. Bengtsson U. Berzinsh J. Larsson S. Svanberg 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,23(1):29-32
We have measured radiative lifetimes for selenium and tellurium resonance levels by using short pulse laser excitation in differentially heated resonance cells. We obtained τ(3 S 1 Se I)=2.9(5) ns and τ(3 S 1 Te I)=3.1(5) ns, which together with branching ratio values given by Ubelis and Berzinsh yield the absorption oscillator strengthf abs(Se I, 196.0 nm)=0.074(16) andf abs(Te I, 214.3 nm)=0.098(17). 相似文献
47.
Quantification of phosphorylated sugar constituents of lipopolysaccharides has been performed by the following sequence: dephosphorylation by treatment with hydrofluoric acid, cleavage to monomeric constituents by methanolysis and analysis of the released sugars by capillary gas chromatography. Lipopolysaccharides of Salmonella minnesota Rd1P+, Bordetella pertussis NIH 114 and Vibrio cholerae, NAG and 95R strains, were used as model substances. Comparison of the chromatographic data obtained from hydrofluoric acid-treated and untreated lipopolysaccharide preparations indicated that all lipopolysaccharides examined contained one moiety of glucosamine bound to phosphate in a stable linkage. 2-Keto-3-deoxyoctonic acid appeared phosphorylated to a variable extent. Lipopolysaccharides of the two V. cholerae strains contained one moiety of fully phosphorylated 2-keto-3-deoxyoctonic acid, whereas in that of S. minnesota Rd1P+ only one of the three moieties was phosphorylated. Lipopolysaccharide of B. pertussis had one moiety of 2-keto-3-deoxyoctonic acid, ca. 70% phosphorylated. All four of the preparations examined contained L-glycero-D-manno-heptose in amounts varying from 2.6 to 5.2 moieties. In the lipopolysaccharides of B. pertussis and strain 95R of V. cholerae this sugar was unphosphorylated, whereas the two remaining strains contained one phosphorylated moiety of this sugar. Phosphorylated lipopolysaccharide constituents can be analysed by this approach on a 50-100 micrograms scale. 相似文献
48.
Issam SM Mohamed G Dominique LM Thierry M Farid L Nejib M 《Applied biochemistry and biotechnology》2004,112(2):63-78
The filamentous fungus Sclerotinia sclerotiorum, grown on a xylose medium, was found to excrete one beta-glucosidase (beta-glu x). The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, anion-exchange chromatography, and high-performance liquid chromatography (HPLC) gel filtration chromatography. Its molecular mass was estimated to be 130 kDa by HPLC gel filtration and 60 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis, suggesting that beta-glu x may be a homodimer. For p-nitrophenyl beta-d-glucopyranoside hydrolysis, apparent Km and Vmax values were found to be 0.09 mM and 193 U/mg, respectively, while optimum temperature and pH were 55-60 degrees C and pH 5.0, respectively. beta-Glu x was strongly inhibited by Fe2+ and activated about 35% by Ca2+. beta-Glu x possesses strong transglucosylation activity in comparison with commercially available beta-glucosidases. The production rate of total glucooligosaccharides (GOSs) from 30% cellobiose at 50 degrees C and pH 5.0 for 6 h with 0.6 U/mL of enzyme preparation was 80 g/L. It reached 105 g/L under the same conditions when using cellobiose at 350 g/L (1.023 M). Finally, GOS structure was determined by mass spectrometry and 3C nuclear magnetic resonance spectroscopy. 相似文献
49.
R. Zerne L. Caiyan J. Zhankui J. Larsson 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,37(3):259-261
The Landé g J factors in the 6snd 1,3 D 2 sequences as well as states from the perturbing configurations of neutral Ytterbium have been measured by timeresolved fluorescence spectroscopy. Strong singlet-triplet mixing effects were observed. The g J factors were measured using the Zeeman quantum-beat technique following step-wise laser excitation. The experiment provided new data for checking the Multi-channel Quantum Defect Theory (MQDT) used in energy-level and lifetime analysis. 相似文献
50.
Antonio Cnovas Jesús Fonrodona Juan-Julio Bonet Marie Claire Brians Jos Luis Brians 《Helvetica chimica acta》1980,63(8):2380-2389
The UV. irradiation of 17 β-hydroxy-2-aza-4-androsten-3-one (1) , N-methyl-17 β-hydroxy-2-aza-4-androsten-3-one (3) , 17 β-hydroxy-4-aza-5 β-androst-1-en-3-one (2) and N-methyl-17 β-hydroxy-4-aza-5 β-androst-1-en-3-one (4) , gives rise to 1,10-seco (from 1 and 3 ) and 5, 10-seco (from 2 and 4 ) steroids. 相似文献