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21.
[reaction: see text] Grubbs catalyst, Cl2(Cy3P)2Ru=CHPh, was found to catalyze the cross-metathesis of monosubstituted allenes to 1,3-disubstituted allenes in varying yields. 相似文献
22.
Barrett JC 《The Journal of chemical physics》2004,120(16):7636-7642
An expression for the free energy of a droplet composed of attracting hard spheres is found using a simple cell model. The hard-sphere repulsion is assumed to act only between molecules in the same cell, whereas attraction extends over many cells. A maximum term analysis gives rise to a mean-field free energy which includes terms proportional to the first and second power of the droplet radius R with coefficients which can be related to the planar surface tension and Tolman length. Certain Gaussian fluctuations about the maximum term are also considered, corresponding to droplet translation and capillary wave fluctuations. Inclusion of these fluctuations is necessary to ensure that the nucleation rate is proportional to the system volume. They also reduce the planar surface tension and introduce a logarithmic term, -4/3 ln R, into the free energy. The inclusion of other fluctuations and the relationship between these equations and those arising in density-functional theories of nucleation is discussed. 相似文献
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Efstathia G SakellariouAntonio Garrido Montalban Scott L BeallDavid Henderson Hubert G MeunierDavid Phillips Klaus SuhlingAnthony G.M Barrett Brian M Hoffman 《Tetrahedron》2003,59(46):9083-9090
Co-macrocyclizations of 2,3-dipropylmaleonitrile and 2,3-di-(4-(methoxycarbonyl)phenyl)maleonitrile, respectively, with N,N′-dibenzyl-N,N′-di-(11-tetrahydropyranyloxy-3,6,9-trioxo-undecyl))maleonitrile and N,N,N′,N′-tetramethylmaleonitrile were used to prepare derivatives of the 4,5-diamino-porphyrazine systems including the zinc(II) complexes. Subsequent oxidation of the macrocycles with potassium permanganate gave the corresponding seco-porphyrazines. These were shown to be efficient sensitizers for the production of singlet oxygen (ΦΔ=0.15-0.57) by the determination of their photophysical properties. 相似文献
25.
Wayne W. Barrett 《Journal of statistical physics》1977,16(4):371-394
A one-parameter family of partition functions is considered which for zero value of the parameter reduces to the spherical model of a ferromagnet. The model for > 0 is closer to the usual discrete lattice spin model of a ferromagnet than is the spherical model. The first four terms in of the limiting value of the partition function are calculated above and below the critical temperature for arbitrary interactions using the saddle point method to calculate certain correlation functions for the spherical model. These calculations indicate that the critical temperature is independent of for small and certain interactions.Part of this research appeared in the author's doctoral thesis.(3) 相似文献
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Amino acids were derivatised with 4-fluoro-7-nitrobenzo-2,1,3-oxadiazol (NBD-F), separated by micellar electrokinetic chromatography (MEKC), and detected by argon-ion (488 nm) laser-induced fluorescence. The optimised MEKC background electrolyte conditions were: 40 mM sodium cholate, 5 mM beta-cyclodextrin in 20 mM aqueous borate buffer, pH 9.1, with 7% v/v acetonitrile. Using these conditions, 19 amino acids were separated within 17 min. The limits of detection were in the range of 7.6-42.2 pmol/mL and limits of quantitation from 0.05-0.14 nmol/mL. The method was systematically validated for injection volume error, migration time variation, calibration linearity, accuracy, precision, and recovery. Nanolitre volume samples of phloem sap of individual sieve element cells from the plant Arabidopsis thaliana and honeydew from the aphid Myzus persicae were directly analysed with this method. Quantitative amino acid concentrations in these two biological matrices were profiled for the first time. This method is particularly important because it allows the complete profile of the amino acids obtained from individual phloem elements, allowing cell to cell and plant to plant variation to be quantified, which to date has not been possible with Arabidopsis thaliana. 相似文献
28.
James L. Kelley James B. Thompson Virgil L. Styles Francis E. Soroko Barrett R. Cooper 《Journal of heterocyclic chemistry》1995,32(5):1423-1428
The 3H-imidazo[4,5-c]pyridazine, 1H-imidazo[4,5-d]pyridazine, and 1H-benzimidazole analogues of the potent anticonvulsant purine 9-(2-fluorobenzyl)-6-methylamino-9H-purine (1, 78U79) were synthesized and tested for anticonvulsant activity. The 3H-imidazo[4,5-c]pyridazines 8 and 9 were prepared in five stages from 3,4,5-trichloropyridazine (2) . The 1H-imidazolo[4,5-d]pyridazine 15 was synthesized in four stages from 5-[(benzyloxy)methyl]-1,5-dihydro-4H-imidazo[4,5-d] pyridazin-4-one (10a) . The benz-imidazole analogues 18 and 20 were prepared from 2,6-dinitroaniline in three stages. These compounds were one-tenth or less as active as 1 in protecting rats against maximal electroshock-induced seizures. 相似文献
29.
The origins and properties of evaporation and condensation coefficients are described, and results of their measurement are surveyed for water and liquid metals. Contrasts are drawn as to whether their values are likely to limit practical transfer rates at plane surfaces and on aerosols, and between evaporation and condensation. Existing theories which express condensation and evaporation rates in terms of the coefficients are described. Their failure to satisfy energy and momentum conservation as well as mass conservation at the interface is remedied by constructing a new theory which also starts with vapor molecules in Maxwell-Boltzmann distributions. The resulting rates are shown to be close to those predicted by more accurate theories in which the Boltzmann transport equation is solved. 相似文献
30.