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71.
72.
73.
L.V. Natarajan Fredrick M. Stein Robert E. Blankenship Raymond Chang 《Chemical physics letters》1983,95(6):525-528
A study of the linear diehroism and fluorescence polarization of diphenylpolyenes (C6H5—(CH=CH)n—C6H5) with n = 1,2,3,4,6,8 in stretched polyethylene films shows that the polyenes orient in the anisotropic matrix with their transition dipole (emission and absorption, π → π*) aligned with the direction of stretch. The maximum dichroic ratio is observed for 1,6-diphenyl-1,3,5-hexatriene (DPH), with n = 3, whereas the values are substantially lower for n < 3 or n > 3. The high orientation of DPH and poor alignment of the higher polyenes may be accounted for in terms of the growing flexibility of the polyene chains with increasing chain length. The results justify the use of DPH as a convenient fluorescence probe for biological and synthetic membranes. 相似文献
74.
T. C. Chang 《中国化学会会志》1979,26(4):133-139
The difficulties of the SCF and MCSCF calculations on excited states have been reviewed. Three constraint variational methods are then developed which can perform the SCF and MCSCF calculations on excited states in the scheme of the generalized Brillouin theorem method. The proper constraints and the ways to incorporate the constraints into the variational calculations on excited states have been studied and the comparison with other approaches have been accessed. 相似文献
75.
[reaction: see text] It has been demonstrated for the first time that conjugated enynes can be employed as a facile substrate in olefin metathesis with the use of a bispyridine-substituted ruthenium benzylidene catalyst. Cross-metathesis of the enynes with alkenes turns out to proceed with preferential formation of (Z)-isomers over (E)-isomers up to >25:1 in moderate to good yields. The intramolecular version of conjugated enynes affords novel butadienyl cycloalkenes, which are a highly useful synthetic building blocks, in acceptable yields. 相似文献
76.
H. Bruchertseifer Choi Valsek K. A. Gavrilov M. Schwarzenberg 《Journal of Radioanalytical and Nuclear Chemistry》1983,77(1):97-104
The electrolytic deposition of the hydroxides of rare earth and transplutonium elements on nickel holders from α-hydroxyisobutyrate
solutions of 10−5 M to 5·10−1 M concentrations has been investigated in the presence of ammonium chloride. It is shown that at total concentrations of
≥10−12 M of rare earth and transplutonium elements, their electrodeposition proceeds with a 90% yield. 相似文献
77.
Shu-Pei Chang Thomas K. Miwa William H. Tallent 《Journal of polymer science. Part A, Polymer chemistry》1969,7(2):471-477
A computerized version of the Fineman-Ross linearization procedure was used to determine reactivity ratios for copolymerization of vinyl chloride (monomer 1) and 2-methylpentyl vinyl brassylate (monomer 2). From differential refractometry data for the products of low-conversion copolymerization, the procedure gave r1 = 1.06 and r2 = 0.234. The ratios computed from chlorine contents of the same products were r1 = 1.10 and r2 = 0.239. The polarity factor (e2) and general monomer reactivity (Q2) calculated for monomer 2 from these ratios were, respectively, ?0.95 to ?0.98 and 0.032–0.033. The interquartile range for the copolymerization of a mixture of 60% monomer 1 and 40% monomer 2 was 1.4%. These values suggest that from suitable proportions of reactants, sufficiently homogeneous distribution of monomers can be achieved in copolymers of vinyl chloride and 2-methylpentyl vinyl brassylate to offer the possibility of effective internal plasticization. 相似文献
78.
From petroleum ether extracts of the bark of M. azedarach four novel tetracyclic triterpenoids have been isolated and characterized to be C30 compounds of the euphane (20R) series. Previously known triterpenoids from Meliaceae have all been 20S compounds. Kulinone 1 is the first known euphane or tirucallane (20S) derivative oxygenated in the D ring; kulactone 2, kulolactone 3 and methyl kulonate 4 are additionally oxygenated in the side chain. Compounds 2 and 3 have a 2-oxa-trans-bicyclo[3,3,0]-octanone structure. 相似文献
79.
Chang Gon Lee 《Tetrahedron letters》2004,45(40):7409-7413
We developed an efficient synthetic method for indenoquinoline skeletons from Baylis-Hillman adducts. 4b,5,10a,11-Tetrahydroindeno[1,2-b]quinolin-10-ones and 7H-indeno[2,1-c]quinolines were prepared from Baylis-Hillman adducts in polyphosphoric acid. 相似文献
80.
Injection-molded, short-glass-fiber-reinforced high-impact polystyrene was investigated under uniaxial tension with special attention to the effects of fiber and rubber concentration on fracture behavior. According to a fracture morphology study performed by polarized optical and scanning electron microscopy, crazes were consecutively initiated from rubber-styrene composite particles and from fiber ends. The rubber particles exhibited an intra-particle failure mode which resulted from the failure manner of the matrix becoming of a more brittle character with increasing fiber fraction. Fibers were surrounded by neigh boring growing crazes. Failure at the fiber-matrix interfaces proceeded with an increase in the number of crazes. With increasing concentration of the fibers, crazing at rubber particles appeared to be suppressed and crazing occurred more preferentially at the fiber ends, which accelerated a macroscopic fracture.Dedicated to Prof. H. H. Kausch on the occasion of his 60th birthday. 相似文献