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排序方式: 共有1413条查询结果,搜索用时 15 毫秒
191.
Masaru Matsuo Hiroshi Hattori Shunji Nomura Hiromichi Kawai 《Journal of Polymer Science.Polymer Physics》1976,14(2):223-238
A model relating crystal orientation to the deformation of nylon-6 spherulites under uniaxial stretching is discussed in terms of the orientation distribution functions of reciprocal lattice vectors of crystal planes, such as the (002) and (200) planes. The distribution functions calculated from the model are compared with those obtained from x-ray diffraction experiments. It is found that the crystal a axis and, consequently, the direction of hydrogen bonds within the crystal (α modification) orient parallel to the lamellar axis in the undeformed state, and that the crystal orientation behavior of nylon-6 is much different from that of low-density polyethylene, being characterized by much smaller values of the reorientation parameters of crystallites within orienting lamellae. Moreover, small-angle light scattering for Hv and Vv polarization is also calculated on the basis of the spherulite deformation model by taking the nylon-6 crystal as having orthogonal–biaxial symmetry in optical anisotropy. It is concluded that the Hv scattering can be realized in terms of the proposed model for spherulite deformation by taking into account a considerable contribution of hydrogen bonds to the molecular polarizability, so as to make the polarizability along the crystal a axis larger than that along the b axis. In other words, this conclusion suggests positively birefringent spherulites in the nylon-6 samples studied. 相似文献
192.
Hidetoshi Iwamoto Takaaki Sonoda Hiroshi Kobayashi 《Journal of fluorine chemistry》1984,26(4):535-537
Anion-catalyzed phase-transfer catalysis was successfully applied to diazotization of pentafluoroaniline in a dichloromethane-aqueous sulfuric acid two-phase system. The resulting diazonium group was coupled with anisole, 1-methoxynaphthalene, and mesitylene, and replaced with bromo, hydryl, and phenyl substituents under a two-phase condition. 相似文献
193.
194.
M. Yamaguchi S. Nomura D. Sato T. Akazaki H. Tamura H. Takayanagi 《Surface science》2005,583(1):94-99
We measured the photoluminescence (PL) spectra of a two-dimensional electron system induced in a Be-δ-doped GaAs/AlGaAs quantum well (QW) with a back gate. The electron density is controlled by means of the back-gate voltage. We estimated the electron density using the magneto-optical method and the PL linewidth, and also by undertaking transport measurements. We show that a uniform 2DES as large as 1 mm2 is induced by the back-gate operation from 2.5 × 1010 cm−2. This experiment indicates that optical measurement with a back-gated QW is advantageous for studying the low-density 2DES. 相似文献
195.
Yoshinori Asakawa Tsunematsu Takemoto Masao Toyota Takaaki Aratani 《Tetrahedron letters》1977,18(16):1407-1410
The stereostructures of the two new exceptional diterpene dialdehydes from the liverwort, Trichocoleopsis sacculata: sacculatal (1), responsible for the characteristic pungent taste, and isosacculatal (2) have been determined by the spectral evidence and by comparison with polygodial (3), isopolygodial (4), and drimanediol (6) of known relative configurations. 相似文献
196.
197.
Maeda H Yamamoto K Nomura Y Kohno I Hafsi L Ueda N Yoshida S Fukuda M Fukuyasu Y Yamauchi Y Itoh N 《Journal of the American Chemical Society》2005,127(1):68-69
Fluorometric detection of O2-* is performed based on desulfonylation of 3 to the corresponding fluoresceins 4 through nucleophilic substitution, and this fluorescing process is quite specific toward O2-* over H2O2, t-BuOOH, NaOCl, 1O2, HO*, NO*, and ONOO-. Furthermore, effects of glutathione, cytochrome P450 reductase/NADPH, and diaphorase/NADH are relatively small on the fluorescing process of probe 3 with X = Y = F, which is useful to detect O2-* released from neutrophils stimulated by phorbol myristate acetate with satisfactory sensitivity. 相似文献
198.
Matsuo Maeda Sadao Hibi Fumihiro Itoh Shunji Nomura Tatsuro Kawaguchi Hiromichi Kawai 《Journal of Polymer Science.Polymer Physics》1970,8(8):1303-1322
A mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single-phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two-phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements. 相似文献
199.
The method of measuring f(I) values is proposed as a measure of the adsorption capacity of adsorbents. The f(I) value, a characteristic figure for a particular system, can be obtained chromatogiaphically by measuring the progression rate of zone and the degree of packing of the column. For a system involving a unit concentration of trasns-p-methoxyazobenzene in benzene as standard solution and alumina as adsorbent, optimum conditions for the measurement of f(I) were established. The effects of day-light, pretreatment of column, temperature, flow rate of solution, amount of adsorbent and degree and mode of packing were studied Under optimum conditions, the value of f(I) was reproducible within ±2%. 相似文献
200.
Relative cross sections for residual nuclei following fusion reactions were measured by γ-ray spectroscopy in the reactions 52Cr+ 12C at 56.00 MeV and 48Ti+ 16O at 57.74 MeV, in which the common “compound nucleus” 64Zn was excited at the same energies and the relative distributions of the entrance spins were nearly identical. It is shown that ratios of the measured cross sections in both entrance channels can be precisely determined experimentally and are insensitive to small changes of the parameters in calculations based on the evaporation model. Using these particular quantities, we have shown that the evaporation process is not the sole mechanism producing the observed residues, especially those resulting from α-particle emission. The assumption of preequilibrium α-particle emission at high channel spins is shown to reproduce the present data fairly well. 相似文献