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71.
The concise synthesis of Amaryllidaceae alkaloids, such as anhydrolycorinone, anhydrolycorin-7-one, assoanine, and oxoassoanine, which have a pyrrolophenanthridine skeleton, was achieved in moderate yield using the Pd-mediated biaryl coupling reaction of 1-(2-halobenzyl)-2,3-dihydroindole, which applied the regioselective C-H activation method with intramolecular coordination of the benzylamino group to Pd. 相似文献
72.
Eietsu Hasegawa Shinya Takizawa Akira Yamaguchi Naoki Chiba Hiroshi Ikeda 《Tetrahedron》2006,62(27):6581-6588
Photoinduced electron-transfer reactions of several ketone substrates were studied to evaluate the utilities of 1,6-bis(dimethylamino)pyrene (BDMAP), 1,6-dimethoxypyrene (DMP), 9,10-bis(dimethylamino)anthracene (BDMAA), and 9,10-dimethoxyanthracene (DMA) as electron-donating sensitizers cooperating with 2-aryl-1,3-dimethylbenzimidazolines. BDMAP and DMP generally led higher conversion of ketones and better yield of reduction products compared to BDMAA and DMA. 相似文献
73.
74.
This paper is concerned with the comparison between mechanical properties of polymer composite system and those of each individual constituent. The comparison is mainly performed with respect to the viscoelastic Young's modulus and the relaxation Young's modulus. These mechanical constants may be obtained from the correspondence principle by applying the Laplace transform to the constitutive equation. The calculated results exhibit that the mechanical property of polymer composite system strongly depends on that of matrix with respect to frequency- and time-dependences. That is, as for the vibration and dynamic response in the steady state, the frequency-dependence of peak position about imaginary part of dynamic modulus of composite system is similar to that of matrix, while the magnitude of dynamic modulus depends on volume fraction of dispersed particles to total volume. As for the stress relaxation, the time-dependence of the relaxation Young's modulus of composite system resemble that of matrix each other, while the magnitude depends on the volume fraction of dispersed particles to total volume. This is due to the calculating condition that particle is assumed to be very rigid in comparison with matrix in this paper. 相似文献
75.
Sodium poly(styrenesulfonate)(polySSNa)-grafted polymer nanoparticles were synthesized by core-cross-linking of block copolymer micelles and subsequent chemical transformation. Block copolymers, poly(p-((1-methyl)silacyclobutyl)styrene-block-poly(neopentyl p-styrenesulfonate)s, polySBS-b-polySSPen, were synthesized by nitroxy-mediated living radical polymerization. The block copolymers formed micelles (Rh=15-23 nm, where Rh represents the hydrodynamic radius) with a polySBS core and polySSPen shell in acetone. The micelle core was cross-linked by ring-opening polymerization of silacyclobutyl groups in polySBS. Hydrolysis of the neopentyl groups provided polySSNa-grafted nanoparticles. The Rh of the particles before the hydrolysis ranged from 12 to 21 nm in acetone, while they varied to the range from 50 to 110 nm in water after the hydrolysis. 相似文献
76.
77.
Photoluminescence enhancement of PEG-modified YAG:Ce3+ nanocrystal phosphor prepared by glycothermal method 总被引:1,自引:0,他引:1
Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement. 相似文献
78.
Hirakawa Y Suzuto M Ohnishi H Shingaki T Eyring EM Tokunaga M Masujima T 《The Analyst》2003,128(6):676-680
The nano-kinetic movement of a single DNA molecule was observed and analyzed by a newly developed video-microscope system with an optical fiber, called a pin-fiber video scope. A single lambda-DNA molecule was put in focus using fiber-illumination, and the stretching and shrinking motion was measured. The molecule's kinetics were analyzed by numerical calculations and are discussed. A photocleavage phenomenon of DNA molecules was also visualized by the pin-fiber video scope. The new video-microscope system has the potential to observe and analyze the nano-kinetics of a single molecule. 相似文献
79.
Hitoshi Kubota Yukitaka Murata Yoshitaka Ogiwara 《Journal of polymer science. Part A, Polymer chemistry》1973,11(2):485-492
The effects of swelling of the sample and polymerization solvents were studied for photo-induced graft copolymerization of vinyl monomers on cellulose. The graft copolymerization of methyl methacrylate (MMA) was activated by swelling of the sample or organic solvent-water solutions within a certain range of their concentrations. Though each organic solvent gave a maximum in per cent grafting and the number of grafts at about 25 vol-% concentration, the initiation reaction scarcely took place at 100% concentration; thus, the solvent itself is considered to have a negative effect. The solvents used in the experiments were all hydrophilic, such as methanol, acetone, and dioxane. The average molecular weight of the grafted PMMA differed in each solvent, indicating a different characteristic effect of solvent on the growing grafted polymer radicals. The presence of ferric ion as a sensitizer stimulated further the contributions of the sample swelling and the organic solvents to the copolymerization reaction. A similar effect was observed for styrene as for MMA, but not for acrylic acid and methacrylic acid. 相似文献
80.
Hitoshi Takeshita Hiroaki Mametsuka Hideshi Motomura 《Journal of heterocyclic chemistry》1986,23(4):1211-1214
Upon heating at ca. 160°, 2-(2-thienylmethoxy)tropone afforded 3- and 5(2-thienylmethyl)tropolones. Formation of 3,5-bis(2-thienylmethyl)tropolone and unsubstituted tropolone indicated a radical chain mechanism for the thermolysis. 相似文献