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91.
Ab initio molecular orbital theory and density functional theory calculations have been carried out on the reactions of the trifluoromethyl radical with the hydroxyl and the hydrogen radicals. These reactions are key reactions that underlie a new fire extinguishing mechanism of non-bromine-containing halon replacements. The activation energies calculated by the MP2 and QCISD methods are in good agreement with the experimental values. The B3LYP, as well as MP2 and QCISD, give good results for the calculations of the heats of reactions. The GAUSSIAN-1 and GAUSSIAN-2 theory calculations present the most acxcurate results on both the activation energies and the heats of reactions. The effects of the scaling factors on the activation energies and the heats of reactions are also evaluated. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 277–289, 1998 相似文献
92.
Katsuhiko Kishi Taizo Ishimaru Masayoshi Ozono Ikuyoshi Tomita Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(1):35-42
A new thermal latent hydrosilylation catalyst on the basis of H2PtCl6 and polystyrene derivatives having propargyl moieties is described. The polystyrene derivatives having various propargyl moieties were obtained by the reaction of propargyl alcohols with poly(p‐chloromethylstyrene) or its copolymer with styrene. The polymer‐supported platinum catalysts were prepared by aging H2PtCl6 with these polymers in tetrahydrofuran at 30 °C for 12 h. In the presence of the polymers, the hydrosilylation activity of H2PtCl6 was found to be controlled thermally in the model reaction of trimethylsilane and triethylvinylsilane. Effective control of the crosslinking reaction of silicone resin was also achieved by using these latent catalyst systems. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 35–42, 2000 相似文献
93.
Masao Ichida Yumie Kiyohara Yasumitsu Miyata Hiromichi Kataura 《Journal of luminescence》2009,129(12):1794-1797
We have investigated third-order nonlinear optical properties of bundled and isolated semiconducting single-walled carbon nanotubes (SWNTs) by means of Z-scan method, pump-probe method, and two-beam time-resolved degenerate four-wave mixing (DFWM) method. The figures of merit Im χ(3)/α in both bundled and isolated SWNTs samples were found to be enhanced with increasing tube diameter. The measured Im χ(3)/α value in the bundled SWNTs was an order of magnitude smaller than that in the isolated SWNTs. Both population relaxation time T1 and phase-relaxation time T2 for bundled samples were smaller than those in the isolated samples. These experimental results can be explained by an increase in nonradiative recombination rate and phase-relaxation rate in the bundled sample. The phase-relaxation time T2 is considered to have a significant role in the enhancement of Im χ(3)/α. 相似文献
94.
Hidetaka Kasai Taizo Kawauchi Xiao-Wei Zhang Takumi Kikegawa Tatsuo Okano 《Applied Surface Science》2009,256(4):984-986
We applied the time-domain analysis of nuclear resonant scattering (NRS) of X-rays for the study of the hydrogen-induced enhancement of atomic diffusion. The time-domain analysis of NRS is a powerful technique for studying diffusion processes on an atomic scale. The NRS measurement combined with high-pressure technique enables the direct measurement of self-diffusion processes under high hydrogen pressures. In this preliminary experiment, self-diffusion in 4 μm thick 57Fe foils at 0.8 GPa was investigated. The samples of the 57Fe were encapsulated with MgO or NaCl. Faster decays caused by diffusion of Fe atoms were observed in the time spectra of NRS at high temperatures. This enhancement of diffusion is believed to be the hydrogen-induced effect. In the present experiment, hydrogen should have been supplied to the samples by reaction with water originally adsorbed on NaCl/MgO powder particles. It was concluded that the diffusion of 57Fe atoms under high pressure can be studied by nuclear resonant scattering of X-rays using a compact cubic-anvil press. The NRS method can also be extended to the study of atomic diffusion in the subsurface region by doping 57Fe layer(s) at known depths. 相似文献
95.
We consider the dimer problem on a planar non-bipartite graph G, where there are two types of dimers one of which we regard as impurities. Computer simulations reveal a reminiscence of
the Cheerios effect, that is, impurities are attracted to the boundary, which is the motivation to study this particular graph.
Our main theorem is a variant of the Temperley bijection: a bijection between the set of dimer coverings and the set of spanning
forests with certain conditions. We further discuss some implications of this theorem: (1) the local move connectedness yielding
an ergodic Markov chain on the set of all possible dimer coverings, and (2) a rough bound for the number of dimer coverings
and that for the probability of finding an impurity at a given edge, which is an extension of a result in (Nakano and Sadahiro
in ). 相似文献
96.
We give an upper bound for the alternation number of a torus knot which is of either 3-, 4-, or 5-braid or of other special types. Using the inequality relating the alternation number, signature, and Rasmussen s-invariant, discovered by Abe, we determine the alternation numbers of the torus knots T(3,l), , and T(4,5). Also, for any positive integer k we construct infinitely many 3-braid knots with alternation number k. 相似文献
97.
Pentafluorophenylation of perfluoroarenes with C6F5Si(CH3)3 was investigated by using NMR and MALDI-TOF-MS techniques. Successive multiple pentafluorophenylation easily occurred not only on the para-position but also on the ortho-positions to provide perfluorinated p-phenylene and m-phenylene compounds. The perfluoroarenes having electron-withdrawing substituents provided oligo- to poly-(phenylene)s depending on the added amounts of C6F5Si(CH3)3, while the perfluoroarenes having electron-donor substituents gave H(C6F4)nF polymers produced from C6F5H, which was the decomposed product of C6F5Si(CH3)3. 相似文献
98.
Masao Ichida Shingo Saito Ye Feng Kazuhiro Yanagi Hiroaki Ando 《Solid State Communications》2011,151(22):1696-1699
Absorption spectra of high purity metallic and semiconducting single-walled carbon nanotubes separated by the density-gradient ultracentrifugation method have been measured in the wide energy region from 1 meV to 5 eV. In the high purity metallic nanotube sample, a strong and broad absorption band has been observed at 0.06 eV. This observation suggests that the optical properties of even high purity metallic nanotube bundles cannot be explained by the simple Drude conduction model. We discuss the origin of these absorption bands for metallic and semiconducting nanotube samples by considering the existence of a small energy gap in metallic nanotube bundles and plasmon resonance. 相似文献
99.
Taizo Hatta Muneob Kawano Hironori Maeda Otohiko Tsuge 《Journal of heterocyclic chemistry》1997,34(2):579-583
The reaction of 5-bromomethyl-3-(p-bromomethylphenyl)isoxazole with o-, m-, and p-bis(mercap-tomethyl)benzenes gave the corresponding dithia- and/or tetrathiaisoxazolophanes, whose relative yields strongly depended upon the nature of the mercaptomethyl compound. The above isoxazole dibromide reacted with the bis(mercaptomethyl)isoxazole to afford a mixture of two isomeric dithiaisoxazolophanes. 相似文献
100.
Masao Ichida Satoshi Sakoda Yumie Kiyohara Singo Saito Yasumitsu Miyata Hiromichi Kataura Ken-ichi Mizuno Hiroaki Ando 《Journal of luminescence》2008,128(5-6):952-955
We have studied 1D exciton relaxation dynamics in semiconducting single-walled carbon nanotubes (SWNTs) by femtosecond pump–probe experiments. The time evolution of change in transmittance ΔT/T induced by photo-excitation varies depending on the tube diameter. The decay time decreases with a decrease in the tube diameter. Pressure measurements have been conducted to explore the relaxation mechanism. The deformation potential estimated from the pressure dependence of photoluminescence spectra increases with decreasing tube diameter. This means that the exciton–phonon interaction becomes stronger in the smaller diameter tubes. The diameter dependences of decay time and deformation potential suggest that the exciton–phonon interaction plays an important role in exciton nonradiative relaxation process in semiconducting SWNTs. 相似文献