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排序方式: 共有1093条查询结果,搜索用时 62 毫秒
981.
Toru Takagishi Takeo Sugimoto Akiyo Hayashi Nobuhiko Kuroki 《Journal of polymer science. Part A, Polymer chemistry》1983,21(8):2311-2322
Polyethylenimine (PEI) was crosslinked with dichloroethane, glyoxal, or glutaraldehyde and polymers of various degrees of crosslinkage were made. The insoluble polymers obtained were examined for their ability to bind methyl orange and its homologs, methyl, ethyl, propyl, and butyl orange at 5, 15, 25, and 35°C, respectively, in an aqueous solution. PEI crosslinked with glutaraldehyde showed markedly increased binding affinity toward these cosolutes compared with the polymers crosslinked with dichloroethane or glyoxal. The extent of the binding increased with an increase in the degree of crosslinkage. These results suggest that the enhancement of the binding by the crosslinking is due mainly to a dual effect, introduction of hydrophobic moieties and proximity of neighboring polymer chains. The first binding constants and the thermodynamic parameters that accompanied the binding were calculated. The thermodynamic data show that the binding process is athermal and is stabilized entirely by the entropy term. Water-soluble PEI exhibited stronger cooperative interactions than the crosslinked polymer because the mobilities of the chains of the former are greater than those of the latter. 相似文献
982.
Wakihara T Sasaki Y Kato H Ikuhara Y Okubo T 《Physical chemistry chemical physics : PCCP》2005,7(19):3416-3418
The surface structure of zeolite A was investigated by FE-SEM, AFM, and HRTEM. First, it was shown by FE-SEM and AFM that the surface of zeolite A terminated with the same structure. Then, by combining the results with those of HRTEM, the terminal structure of zeolite A was identified as incomplete sodalite cages. 相似文献
983.
Toru KawakamiSaburo Aimoto 《Tetrahedron letters》2003,44(32):6059-6061
A photoremovable auxiliary for use in peptide synthesis via the native chemical ligation method is described. A 2-mercapto-1-(2-nitrophenyl)ethylamine (Mnpe-amine) moiety was attached to the N-terminus of a peptide via the periodate oxidation of a seryl peptide. The resulting peptide was then ligated to a peptide thioester, and UV (365 nm) irradiation resulted in the removal of the auxiliary from the peptide. 相似文献
984.
K. Shikano H. Yonezawa T. Shigematsu 《Journal of Radioanalytical and Nuclear Chemistry》1993,167(1):81-88
We have developed charged particle activation analysis to determine light elements at a sub-ppb level. This analytical method is characterized by sample bombardment with charged particles at a few tens of mA and substoichiometric separation for13N,11C and18F within two half-life times and with decontamination factors of more than 108. Nuclear reactor interference is also estimated with this method. This analytical method is confirmed to be useful for characterizing highly purified materials from analytical results for boron, carbon, nitrogen and oxygen in Nb refined by the floating zone melting method. 相似文献
985.
A new synthetic method of 3-acyltetronic acid derivatives from the corresponding 3-bromo compound via lithiation with n-BuLi followed either by acylation with acid chloride or better by first reacting with aldehyde and then subsequent oxidation with active MnO2 is described. A revised structure for aspertetronin A(gregatin A) was presented based on the synthesis of the proposed structure and spectral comparison of a model compound with the natural product. 相似文献
986.
Ichikawa J Kobayashi M Noda Y Yokota N Amano K Minami T 《The Journal of organic chemistry》1996,61(8):2763-2769
2,2-Difluorovinyl ketones 1 react with monosubstituted hydrazines to afford 5-fluoropyrazoles in a regioselective manner via replacement of the fluorine by the substituted nitrogen of the hydrazines and dehydration between the carbonyl group of 1 and the NH(2) end. The reactions are successfully effected for both aliphatic and aromatic hydrazines in aqueous ethanol under neutral conditions and in THF under basic conditions with butyllithium, respectively. A similar ring-forming reaction of 1 with hydrazine monohydrate is induced by the addition of trifluoroacetic acid to give N-unsubstituted 3-fluoropyrazoles, which in turn react with alkyl and aryl halides in the presence of sodium hydride, leading to a regiocontrolled synthesis of 3-fluoropyrazoles. 相似文献
987.
K. Shikano H. Yonezawa T. Shigematsu 《Journal of Radioanalytical and Nuclear Chemistry》1993,173(2):409-417
The charged particle activation analysis of ultra-trace carbon in boron-doped silicon with the12C(d,n)13N reaction has been developed. In order to apply13N substoichiometric separation to determine carbon in silicon, we studied the rapid dissolution of silicon using nitric acid as the13N carrier. Its amounts were as small and definite as possible and the nitrogen oxide gas produced during the dissolution was collected. Silicon was dissolved for 6 min in a mixture of hydrofluoric acid, acetic acid and phosphoric acid, which contained potassium nitrate as the13N carrier and nitrogen oxide was collected in the sodium hydroxide solution. In order to combine the dissolution method with13N substoichiometric separation, the conditions for steam distillation as pre-separation were also refined in relation to increases in the amount of carrier. Nitrogen-13 was separated substoichiometrically after silicon dissolution and steam distillation. This analytical procedure was used to determine carbon in boron-doped CZ–Si. Carbon at 0.7–12.7·1015 atoms/cm3 was determined with good reproducibility. It took less than 30 min to start the radioactivity measurement after the end of iradiation. The detection limit was 2·1013 atoms/cm3 (0.2 ppb). 相似文献
988.
Takeshi Toru Kenzo Watanabe Takeo Oba Toshio Tanaka Noriaki Okamura Kiyoshi Bannai Seizi Kurozumi 《Tetrahedron letters》1980,21(26):2539-2542
Several phenyl sulfides including stable 5- and 7-phenylthioprostacyclins were obtained by the reaction of the vinyl ether () and prostacyclin methyl ester () with PhSCl. 相似文献
989.
Shigenobu Funahashi Kimiyo Sengoku Toru Amari Motoharu Tanaka 《Journal of solution chemistry》1988,17(2):109-116
A convenient technique is described to determine reaction volumes by means of direct dilatometry. Reaction volumes were determined for the following complexation reactions: formation of monoamminenickel(II) in water (–0.1±0.5 cm3-mol–1); formation of the 1:1 nickel(II) complex with isoquinoline in methanol and ethanol (3.2±0.1 and 1.1±0.1 cm3-mol–1, respectively); formation of the 1:1 isothiocyanatoiron(III) complex in water, Me2SO, and DMF (8.9±0.2, 12.4±0.7, and 25.1±0.3 cm3-mol–1, respectively); formation of the 18-crown-6 potassium complex in water (10.9±0.2 cm3-mol–1). We discussed these values in terms of electrostriction and molecular size. 相似文献
990.
Kinoyama I Taniguchi N Yoden T Koutoku H Furutani T Kudoh M Okada M 《Chemical & pharmaceutical bulletin》2004,52(11):1330-1333
The search for novel antiandrogens by high-throughput screening (HTS) of the Yamanouchi chemical library led to the discovery of the lead compound (5), which possesses an arylmorpholine moiety. Through the optimization of the lead compound (5), we have found a series of novel arylpiperazine derivatives. Among them, 4-[4-cyano-(3-trifluoromethyl)phenyl]-N-(4-fluorophenyl)piperazine-1-carboxamide (22; YM-92088) exhibited a potent AR antagonistic activity with an IC(50) value of 0.47 microM in the reporter assay, which is more potent than bicalutamide (4) which has an IC(50) value of 0.89 microM. 相似文献