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排序方式: 共有233条查询结果,搜索用时 15 毫秒
101.
Terao J Watanabe H Ikumi A Kuniyasu H Kambe N 《Journal of the American Chemical Society》2002,124(16):4222-4223
A new method for the cross-coupling reaction of Grignard reagents with alkyl chlorides, bromides, and tosylates has been developed by the use of a nickel catalyst in the presence of a diene as an additive. This reaction proceeds efficiently at 0-25 degrees C in THF using primary and secondary alkyl and aryl Grignard reagents. Nickel complexes bearing no phosphine ligands, such as NiCl2, Ni(acac)2, and Ni(COD)2, afford the coupling products in good yields, whereas NiCl2(PPh3)2 and NiCl2(dppp) were less effective. 1,3-Butadiene shows the highest activity as an additive for the present coupling reaction. A plausible reaction pathway was proposed. 相似文献
102.
Yoshio Imai Kazuo Itoya Masami Kanamaru Masa‐Aki Kakimoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(11):1790-1795
New phenolic hydroxyl‐pendant aromatic polyimides were synthesized with the N‐silylated diamine method in two steps: the ring‐opening polyaddition of tetrakis(trimethylsilyl)‐substituted 4,4′‐diamino‐3,3′‐dihydroxybiphenyl to various aromatic tetracarboxylic dianhydrides, giving trimethylsiloxy‐pendant poly(amic acid) trimethylsilyl esters, and thermal imidization. The hydroxyl‐bearing polyimides were amorphous but insoluble in organic solvents. They had glass‐transition temperatures greater than 370 °C and temperatures of 10% weight loss greater than 415 °C in nitrogen. The hydroxyl‐pendant polypyromellitimide film had a high tensile strength and a high modulus of 310 MPa and 10 GPa, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1790–1795, 2002 相似文献
103.
Sigeo Aki 《Annals of the Institute of Statistical Mathematics》1981,33(1):1-14
Summary In this paper we investigate the effect of estimating the center of symmetry on a Cramér-von Mises type statistic for testing
the symmetry of a distribution function. The test statistic is defined by
whereF
n is the empirical distribution function andS[F
n] is an estimator of the center ofF which is consistent with the ordern
1/2 and has von Mises derivative. The asymptotic distribution ofnT
0[Fn] under the null hypothesis is obtained. The distribution depends on the distributionF and on the estimatorS[F
n].
The Institute of Statistical Mathematics 相似文献
104.
The insertion reaction of isocyanide into a C-S bond of dithioacetals is catalyzed by GaCl3 or TiCl4 to afford thioimidates containing an alpha-alkylthio group. Balanced thiophilicity of these Lewis acids is critical for efficient catalysis. 相似文献
105.
Shimada Y Goto T Kawamoto S Kiso T Katayama A Yamanaka Y Aki T Chiang KC Nakano T Goto S Chen CL Ohmori N Ono K Sato S 《Biomedical chromatography : BMC》2008,22(1):13-19
In organ transplantation, the development of a novel immunosuppressant free of the need for permanent administration and any serious side effects has eagerly been awaited. We have previously reported that an anti-histone H1 polyclonal antibody has immunosuppressant activity. Here we prepared an anti-histone H1 monoclonal antibody as an analytical tool to elucidate its mechanism of immunosuppression. The isotype of this monoclonal antibody was immunoglobulin M. A monoclonal antibody prepared for administration to organ transplantation model animals should not contain any allogenic proteins and should have high purity. Therefore, we conducted a two-step chromatography procedure, consisting of strong anion-exchange chromatography and gel filtration chromatography, to purify an anti-histone H1 monoclonal immunoglobulin M antibody from the serum-free culture supernatant of hybridomas. Consequently, we successfully purified the monoclonal antibody at 96%, a purification rate at which its administration to organ transplantation model animals is possible. 相似文献
106.
7-Acylaminocephalosporanic acid derivatives (1) were converted into 7-acylamino-3-methylenecepham-4-carboxylic acids (2) by treatment with chromium(II) salts in aqueous media. The esters (4a or 4b) of 7-acylamino-3-methylenecepham compounds were readily isomerized to the 3-methyl-3-cephem compounds (5a or 5b) under basic conditions. The reaction mechanism is discussed. 相似文献
107.
108.
109.
Sueli M. Tanaka Aki Sandra M.S. de Godoy 《Nonlinear Analysis: Real World Applications》2009,10(1):172-184
The paper studies a class of a system of linear retarded differential difference equations with several parameters. It presents some sufficient conditions under which no stability changes for an equilibrium point occurs. Application of these results is given. 相似文献
110.
H. Aki T. Niiya Y. Iwase M. Yamamoto 《Journal of Thermal Analysis and Calorimetry》2001,64(2):713-719
Two different types (structures) of inclusion complexes with a 1:1 stoichiometry between barbiturates and 2-hydroxypropyl-β-cyclodextrin
(HPCyD) were realized in aqueous solution using isothermal titration calorimetry and molecular dynamics simulation. The first
type of complex with a higher association constant was entropy driven and the substituent R
2 was inserted into the HPCyD cavity by hydrophobic interaction. The barbituric acid ring contributed to the second type of
complex, which was characterized by large negative values of ΔH and small positive ΔS reflecting van der Waals interaction and/or hydrogen bonding formation between the hetero atoms in the barbituric acid ring
and the secondary hydroxyl groups of HPCyD.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献