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991.
Yoshiaki Hidaka Kazuyuki Kawanami Hiroyuki Kawano Masao Suga 《Chemical physics letters》1984,103(5):393-396
CF3ClH2 mixtures highly diluted with Ar were heated to 1400–1600 K behind reflected shock waves. The HCl emission was followed in order to determine the rate constant (k1) of the reaction, CF3Cl + M CF3 + Cl + M, and k1 = 2.1 × 1017 exp(?75000/RT) cm3 mol?1 s?1 was computed. 相似文献
992.
A basic study of the mechanisms of necking and ductile failure of polymer melts in uniaxial elongational flow has been carried out. A linear stability analysis was carried out using a White—Metzner convected Maxwell model with a deformation-rate-dependent relaxation time, which varies according to τ = τo/(1 + aτo[2trd2]). It was shown that filament stability and elongation to break depend upon τoE, where E is the elongation rate, and a. At fixed τoE, filament stability decreases with increasing a. At small a, stability increases with increasing τoE while for a > , stability decreases with increasing τoE. For a material with small a, ductile failure can occur for small τoE, but cohesive fracture should be the cause of failure at larger τoE. For a material with large a, however, ductile failure always dominates the failure mode. These results are used to interpret failure in elongational flow of low density and high density polyethylene and polypropylene melts and describe how the latter two melts exhibit ductile failure. 相似文献
993.
Yoshiaki Inaki Yo Sakuma Yasuo Suda Kiichi Takemoto 《Journal of polymer science. Part A, Polymer chemistry》1982,20(7):1917-1933
A series of oligomer models of polyethyleneimine derivatives having pendant thymine bases were prepared by the reaction of carboxyethyl derivatives of thymine with oligomer amines using an activated-ester method. It was found that the hypochromicity values obtained from UV spectra and pKa values obtained from spectrophotometric titrations depend on the chain length of the oligomers and the thymine content of the polymers. 相似文献
994.
The soliton physics for the propagation of waves is represented by a stochastic model in which the particles of the wave can jump ahead according to some probability distribution. We demonstrate the presence of a steady state (stationary distribution) for the wavelength. It is shown that the stationary distribution is a convolution of geometric random variables. Approximations to the stationary distribution are investigated for a large number of particles. The model is rich and includes Gaussian cases as limit distribution for the wavelength (when suitably normalized). A sufficient Lindeberg‐like condition identifies a class of solitons with normal behavior. Our general model includes, among many other reasonable alternatives, an exponential aging soliton, of which the uniform soliton is one special subcase (with Gumbel's stationary distribution). With the proper interpretation, our model also includes the deterministic model proposed in Takahashi and Satsuma [A soliton cellular automaton, J Phys Soc Japan 59 (1990), 3514–3519]. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 2004 相似文献
995.
木根黄芩中-新黄酮的光谱特征 总被引:1,自引:0,他引:1
从木根黄芩(Scutellaria planipes Nakai et Kitag.)中分离得到一新黄酮类化合物. 该化合物被鉴定为5,7,3′,6′-tetrahydroxy-6,8,2′-trimethoxyflavone. 它有很强的抑制5-酯氧合酶活性. 由于该化合物的A环全部被取代,因此,应用一般的光谱技术很难准确归属各碳的化学位移. 我们应用13C-13C相关谱和酰化位移方法,明确归属了各碳的信号,并订正了文献中对部分信号的错误归属. 相似文献
996.
1-Butyne diluted with Ar was heated behind reflected shock waves over the temperature range of 1100–1600 K and the total density range of 1.36 × 10?5?1.75 × 10?5 mol/cm3. Reaction products were analyzed by gas-chromatography. The progress of the reaction was followed by IR laser kinetic absorption spectroscopy. The products were CH4, C2H2, C2H4, C2H6, allene, propyne, C4H2, vinylacetyiene, 1,2- butadiene, 1,3-butadiene, and benzene. The present data were successfully modeled with a 80 reaction mechanism. 1-Butyne was found to isomerize to 1,2-butadiene. The initial decomposition was dominated by 1-butyne → C3H3 + CH3 under these conditions. Rate constant expressions were derived for the decomposition to be k7 = 3.0 × 1015 exp(?75800 cal/RT) s?1 and for the isomerization to be k4 = 2.5 × 1013 exp(?65000 cal/RT) s?1. The activation energy 75.8 kcal/mol was cited from literature value and the activation energy 65 kcal/mol was assumed. These rate constant expressions are applicable under the present experimental conditions, 1100–1600 K and 1.23–2.30 atm. © 1995 John Wiley & Sons, Inc. 相似文献
997.
Yoshiaki Sasada Yuzuru Niide Mitsuru Takano Takeshi Satoh 《Journal of Molecular Spectroscopy》1977,66(3):421-427
The microwave spectra of 3-iodopropene were measured in the frequency region 12–18 GHz. The a-type R-branch and the b-type Q-branch rotational transitions of one conformer, skew, have been assigned and the rotational constants of the ground state have been obtained: A = 17 644.34, B = 1588.12, and C = 1538.64 MHz. The second-order quadrupole effects give rise to anomalous hyperfine splittings and are analyzed by taking into account χab of the quadrupole coupling tensor. The nuclear quadrupole coupling constants have been determined to be χaa = ?1337, χbb = 387, χcc = 950, and ∥χab∥ = 1081 MHz. 相似文献
998.
999.
Acoustic fluxes constituting an acoustic domain in a piezoelectric semiconducting n-CdS were analyzed by Brillouin scattering method. Obtained results were as follows: 0.8 GHz and 2.0 GHz acoustic fluxes were faster than the sound velocity 1.75 × 105 cm/s. The observed profile of the 2.0 GHz flux agreed fairly well with the simulated one performed numerically by KdV equation. The faster positions of the acoustic domain were formed by lower frequency acoustic fluxes and the slower positions understood by acoustic fluxes around maximum gain frequency generated first in a small signal regime. 相似文献
1000.
Application of the Pummerer reaction to Biotin sulfoxides gives a good access to the corresponding thiolactol and thiolactone, which are key-compounds for the synthesis of new functionalized Biotin derivatives. 相似文献