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141.
Takeda T Kawai H Fujiwara K Suzuki T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(28):7915-7925
Isolation and low‐temperature X‐ray analyses of intramolecular triarylmethane–triarylmethylium complexes with a naphthalene‐1,8‐diyl‐type skeleton have been achieved. These bridged cations prefer a C? H localized structure both in solution and in the solid state. The bridging hydrogen undergoes a facile intramolecular 1,5‐hydride shift from one carbon to another in solution. The C? H delocalized geometry is suggested to be the transition‐state structure of the degenerate rearrangement. Charge‐transfer interaction from the triarylmethane to the triarylmethylium units is evident in the electronic spectra. This interaction stabilizes the present cations. Low reactivity toward Brønsted acids indicates that these species are not the reaction intermediates in the acid‐assisted long‐bond cleavage of 1,1,2,2‐tetraarylacenaphthene derivatives. 相似文献
142.
A 36-membered macrocyclic hexaoxime was quantitatively obtained by [3 + 3] condensation of dialdehyde 2 with diamine 3 using La3+ (core metal) and Zn2+ (shell metal) as a novel core/shell template, while the yield was very low in the absence of the metal ions. The high yield can be attributed to the efficient formation of a 3:3:1 complex of dialdehyde 2, Zn2+, and La3+, which readily gives the macrocycle keeping the Zn3La core/shell tetranuclear cluster structure. 相似文献
143.
Takanori Kiyokura Fumihiko MAEDA Yoshio Watanabe Yoshinori Iketaki Koumei Nagai Yoshiaki Horikawa Masaharu Oshima Eiji Shigemasa Akira Yagishita 《Optical Review》2000,7(6):576-578
The throughput of a Schwarzschild objective using undulator synchrotron radiation was measured. Conventionally, the throughput was estimated from the squared reflectivity of one multilayer mirror and from the obstruction ratio. However, we evaluated the transmission ratio from the input and output photon flux using a precisely calibrated monochromatic beam from an undulator light source. It was found that the objective has a maximum throughput of 8.5% at a wavelength of 13.9 nm. 相似文献
144.
Y. Endoh R. J. Birgeneau M. A. Kastner G. Shirane K. Yamada 《Physica B: Condensed Matter》2000,280(1-4):201-204
The discovery of the spin density wave (SDW) state defined as stripe in the doped Cu oxides becomes a central issue in the elucidation of the high-temperature superconducting mechanism. We present the coexistence of the stripe order and superconductivity, and the change of the stripe structure associated with the insultor–metal transition. Both static and dynamical SDW are robust of the high-temperature superconducting Cu oxides. 相似文献
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146.
Shigehisa Endoh Yoshikazu Kuga Hitoshi Ohya Chihiro Ikeda Hiroyuki Iwata 《Particle & Particle Systems Characterization》1998,15(3):145-149
This study was conducted to establish a simple method for evaluating the morphology of fine anisometric particles using size measurement techniques. The size distributions of mica particles and carbon fibers classified into narrower size ranges were measured by gravitational sedimentation and laser diffraction techniques. The ratio of mean diameters determined for flaky particles strongly depended on the aspect ratio, i.e. flatness. The relationship between particle shape and diameter is discussed theoretically. The experimental results were similar to those predicted. The flatness of fine particles can be evaluated by the ratio of the median diameter determined by laser diffraction to that determined by sedimentation. 相似文献
147.
Takanori Yamazaki Tadao Seguchi 《Journal of polymer science. Part A, Polymer chemistry》1997,35(2):279-284
The reaction mechanisms of thermal crosslinking of polyethylene with dicumyl peroxide (DCP) at high temperatures were investigated by electron spin resonance (ESR). The crosslinking reactions were induced by the alkyl radicals formed by the thermal decomposition of DCP above 120°C. The kinetics of the free radical reaction were followed during crosslinking reactions at temperatures between 145 and 180°C. © 1997 John Wiley & Sons, Inc. 相似文献
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150.
Itaru Sato Yohei Matsueda Kousuke Kadowaki Shigeru Yonekubo Takanori Shibata Kenso Soai 《Helvetica chimica acta》2002,85(10):3383-3387
1,3‐Disubstituted chiral allenes without any heteroatoms act as chiral initiators in the addition of (i‐Pr)2Zn to pyrimidine‐5‐carbaldehyde to afford, in combination with the subsequent asymmetric autocatalysis, chiral pyrimidin‐5‐yl alkanols with up to 98% ee. The absolute configuration of the pyrimidin‐5‐yl alkanol formed depend on that of the chiral allene. 相似文献