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21.
An optically active helical poly(phenylacetylene) was synthesized by the copolymerization of phenylacetylenes bearing optically active hydroxy or ester groups obtained by the kinetic resolution of a racemic phenylacetylene with lipase; the helix-sense was inverted from one helix to another by the further chemical modification of the hydroxy groups with achiral bulky isocyanates or an acid chloride. 相似文献
22.
Kenji Yoshii Yasuhiro Yoneda Ignace Jarrige Tatsuo Fukuda Yasuo Nishihata Chikashi Suzuki Yoshiaki Ito Takahito Terashima Shinzo Yoshikado Sei Fukushima 《Journal of Physics and Chemistry of Solids》2014
We have studied the electronic properties of the ferroelectric barium titanate BaTiO3 using two complementary bulk-sensitive spectroscopic probes, resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L3 and Ti-K absorption edges. Contrary to a previous study, we found no fine structure in the pre-edge area of the PFY-XAS spectrum at the Ba-L3 edge, and no temperature-induced spectral change was observed between room temperature and 150 °C. This result is not supportive of the possible presence of the displacement around Ba2+ at the Curie temperature. RXES spectra were measured at the Ti-K edge for BaTiO3, along with SrTiO3 and La-doped metallic SrTiO3. The photon energy of the emission peak is found to be nearly constant throughout the absorption edge for all three compounds. We deduce the Ti 3d states to have a delocalized character, in contrast with the Ba 5d states, a property which is consistent with the proposed scenario of the formation of electric dipoles in BaTiO3. 相似文献
23.
Shinzo Watanabe 《Acta Appl Math》2000,63(1-3):441-464
We study asymptotic winding properties of Brownian motion paths on Riemann surfaces by obtaining limit laws for stochastic line integrals along Brownian paths of meromorphic differential 1-forms (Abelian differentials). 相似文献
24.
Shinzo Kano Tsutomu Yokomatsu Hajime Nemoto Shiroshi Shibuya 《Tetrahedron letters》1985,26(12):1531-1534
A high diastereoselective synthesis of 6-hydroxy-4a-aryl--decahydroisoquinoline derivatives was achieved by an application of N-acyliminium ion-induced polyene cyclization procedure. 相似文献
25.
Yuko Ikeda Kazutoshi Kodama Kanji Kajiwara Shinzo Kohjiya 《Journal of Polymer Science.Polymer Physics》1995,33(3):387-394
Poly(ethylene oxide)-grafted butyl rubbers (IIR-g-PEOs), which were synthesized from potassium salt of polyethylene glycol monomethyl ether (PEGM) and chlorinated butyl rubber, were found to behave like thermoplastic elastomers. The poly(ethylene oxide) (PEO) content of these amphiphilic polymers was ca. 10 wt %, and their PEO lengths were 750, 2000, and 5000, respectively. The grafted segments of PEO in butyl rubber (IIR) aggregated to form the PEO domains in IIR matrix. At constant PEO content, the longer the PEO segment length, the larger the size and the crystallinity of PEO domains became. This PEO domain worked as a cross-linking site and a reinforcing filler. The degree of swelling in water of IIR-g-PEO film that was prepared from PEGM-5000 was largest, but its emulsification ability was smallest among them. © 1995 John Wiley & Sons, Inc. 相似文献
26.
The effect of the different cooling processes on the disorder of flourine ions and ionic conductivity in β-PbF2 has been studied by X-ray method and ionic conductivity measurements on single crystals below the transition temperature Tc. The spike-like diffuse scattering was observed along the <111>1 directions around the Bragg reflections. The activation energies for the conduction process are 0.40 eV for the sample quenched from 970 K and 0.54 eV for the one from 720 K. The higher the quenching temperature is, the higher the conductivity and the lower the activation energy become. The dependence of conductivity on the different cooling processes is more evident in single crystals than in polycrystalline samples. The contribution of the different cooling processes to ionic conductivity can be quantitatively explained by the extent of ordering of mobile fluorine ions. Time dependence of ionic conductivity has not been observed. 相似文献
27.
28.
Fumio Yamakawa Shinzo Yamakawa 《Journal of polymer science. Part A, Polymer chemistry》1980,18(7):2257-2265
A detailed kinetic study of the γ-ray-induced surface grafting of methyl acrylate (MA) onto polyethylene (PE) has been investigated by using quartz helix microbalances. Under typical graft conditions, the grafting rate increases, levels off, and then accelerates with irradiation time; i.e., the typical growth process of the surface grafting consists of an initial stage having an increasing rate of grafting, an intermediate stage having a constant rate, and an advanced stage having an accelerated rate. A homopolymer layer (consisting only of an MA component) begins to be formed on the inner graft copolymer layer (consisting both of MA and PE components) at the transition zone in grafting rate after a duration of a constant rate of grafting. Therefore, the increasing rate in increasing rate in the intial stage of grafting reflects the graft copolymerization in the graft copolymer layer (inside the PE sheet), and the increasing rate in the advanced stage reflects the growth of the homopolymer layer. Under grafting reflects the graft tage reflects the growth of the homopolymer layer. Under grafting conditions by which the homolymer layer is not formed throughout the whole grafting process, the surface grafting remains remains in the initial stage. On the order hand, under grafting conditions by which the homopolymer layer begins to be formed from an early stage of grafting, the surface grafting proceeds rapidly from the initial stage to the advanced stage and thus skips the intermediate stage. 相似文献
29.
30.
Fumio Yamamoto Shinzo Yamakawa Yoshinori Kato 《Journal of polymer science. Part A, Polymer chemistry》1978,16(8):1883-1895
Mutual irradiation of polyethylene (PE) in methyl acrylate vapor easily forms a poly(methyl acrylate) (PMA) homopolymer layer on the inner graft copolymer layer consisting of both PE and PMA components as a result of the rapidly increasing surface-graft composition. This growth process of surface grafting has been found to provide some specific kinetic features different from those in other surface-grafting systems. With formation of the surface homopolymer layer, low- and highdensity PE sheets give the same grafting rate, whereas both sheets give different rates in grafting stages or conditions in which the homopolymer layer is not formed. This result indicates that most monomers, penetrating across the surface, are entrapped or consumed in the surface homopolymer layer; accordingly the rate becomes independent of the type of PE sheets that have significantly different diffusion coefficients. The thickness of the inner graft copolymer layer, which is kept constant after homopolymer-layer formation, increases with decreasing dose rate and with increasing monomer vapor pressure and temperature. This behavior can be qualitatively explained according to an equation for the initial steady-state grafting depth. 相似文献