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排序方式: 共有311条查询结果,搜索用时 15 毫秒
221.
Mark A. Olson Adam B. Braunschweig Dr. Lei Fang Taichi Ikeda Dr. Rafal Klajn Ali Trabolsi Dr. Paul J. Wesson Diego Benítez Dr. Chad A. Mirkin Prof. Bartosz A. Grzybowski Prof. J. Fraser Stoddart Prof. 《Angewandte Chemie (International ed. in English)》2009,48(10):1792-1797
Side‐chain poly[2]catenanes at the click of a switch! A bistable side‐chain poly[2]catenane has been synthesized and found to form hierarchical self‐assembled hollow superstructures of nanoscale dimensions in solution. Molecular electromechanical switching (see picture) of the material is demonstrated, and the ground‐state equilibrium thermodynamics and switching kinetics are examined as the initial steps towards processible molecular‐based electronic devices and nanoelectromechanical systems.
222.
Hirotomo Nishihara Dr. Hiroyuki Itoi Taichi Kogure Peng‐Xiang Hou Dr. Hidekazu Touhara Prof. Fujio Okino Prof. Takashi Kyotani Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(21):5355-5363
Ordered microporous carbon : The mechanism of an electrical double‐layer capacitor containing zeolite‐templated carbons as model microporous materials was investigated in detail (see figure). Its three‐dimensionally ordered and connected micropores were found to greatly reduce ion‐transfer resistance and, therefore, exhibited a high rate performance.
223.
Makoto Yanaga Kazutoyo Endo Hiromichi Nakahara Shigeru Ikuta Taichi Miura Masashi Takahashi Masuo Takeda 《Hyperfine Interactions》1989,52(2):147-151
The121Sb Mössbauer spectra of rapidly frozen solutions of antimony compounds were observed. The isomer shifts were compared with the electron density at the antimony nucleus calculated with the ab initio molecular orbital method. A value ΔR/R=?(11±2)×10?4 was derived for the 37.15 keV M1 transition of121Sb. 相似文献
224.
Machida K Takano M Kakuda R Yaoita Y Kikuchi M 《Chemical & pharmaceutical bulletin》2002,50(5):669-671
A new lignan glycoside, (-)-massoniresinol 4'-O-beta-D-glucopyranoside (4), was isolated, together with six known ones (1-3, 5-7), from the leaves of Sambucus sieboldiana. Their structures were established on the basis of chemical and spectral data. 相似文献
225.
Hayashi H Zhang SL Nakaizumi T Shimura K Yamaguchi M Inoue K Sarsenbaev K Ito M Honda G 《Chemical & pharmaceutical bulletin》2003,51(10):1147-1152
A new prenylated flavanone, licoleafol, and a new prenylated dihydrostilbene, uralstilbene, together with four known compounds, 8-dimethylallyleriodictyol, sophoraflavanone B, gancaonin R, and 6-dimethylallyleriodictyol, were isolated from the leaves of Glycyrrhiza uralensis collected in Kazakhstan. HPLC analysis of the leaves of Glycyrrhiza plants collected in Kazakhstan showed that both G. uralensis-specific and Glycyrrhiza glabra-specific compounds were detected in the leaves of the morphologically intermediate-type plants, suggesting that the intermediate-type plant is a hybrid of G. glabra and G. uralensis. In addition, HPLC profiles of leaf extracts from offspring of intermediate-type plants were divided into the three types: the G. uralensis type, G. glabra type, and the intermediate type. From these results, it appears likely that the intermediate-type plant back-crosses with G. glabra and G. uralensis to generate a G. glabra-type plant and a G. uralensis-type plant, respectively. 相似文献
226.
Fumio Hama Yoshiteru Sakata Soichi Misumi Misako Aida Chikayoshi Nagata 《Tetrahedron letters》1982,23(30):3061-3064
The structure of the title compound 1a was determined to be a cross-stacking form with an interplanar distance of ca. 3.3 Å by X-ray analysis. On the basis of this structure, the hypochromicity of 1a was calculated by the ASMO SCF CI method. 相似文献
227.
Ikeda T Asakawa M Goto M Miyake K Ishida T Shimizu T 《Langmuir : the ACS journal of surfaces and colloids》2004,20(13):5454-5459
Alkyl-chain-assisted self-assembled monolayers of pyridine-coordinated porphyrin rhodium chlorides were observed at the solid-liquid interface by scanning tunneling microscopy (STM). The resolved images at a molecular level were obtainable in the pure solution of pyridine-coordinated porphyrin rhodium chloride with four triacontyl groups [Rh(C300PP)(Cl)(Py)]. In the case of pyridine-coordinated porphyrin rhodium chloride with four octadecyl groups [Rh(C18OPP)(Cl)(Py)], the STM images were not obtainable in the pure solution of Rh(C18OPP)(Cl)(Py) but obtainable in the mixture containing Rh(C18OPP)(Cl)(Py) and free porphyrin C18OPP. On the basis of the mixed self-assembled monolayer analysis, the apparent difference in the adsorption free energy between Rh(CnOPP)(Cl)(Py) and CnOPP (deltaGapp) was calculated. The calculated deltaGapp values for C18OPP and C30OPP mixed systems were quite different. The disadvantage of the adsorption free energy of Rh(C18OPP)(Cl)(Py) makes it difficult to obtain molecularly resolved images of Rh(C18OPP)(Cl)(Py), and the large adsorption energy due to the long alkyl chains enabled us to obtain molecularly resolved images of Rh(C30OPP)(Cl)(Py). 相似文献
228.
Masakatsu Matsumoto Taichi Akimoto Yuki Matsumoto Nobuko Watanabe 《Tetrahedron letters》2005,46(36):6075-6078
Four bicyclic dioxetanes bearing a 4-(benzothiazol-2-yl)-3-hydroxyphenyl or 4-(benzoxazol-2-yl)-3-hydroxyphenyl group were synthesized. These dioxetanes underwent base-induced decomposition with accompanying emission of light with high efficiency in NaOH/H2O as well as in tetrabutyl ammonium fluoride (TBAF)/acetonitrile. Among them, benzothiazol-analogs decomposed faster in the aqueous solution than in acetonitrile. 相似文献
229.
Wasaburo Kawai Masaji Ogawa Taichi Ichihashi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(6):1599-1604
Methyl methacrylate was polymerized by triethylaluminum—cuprous chloride catalyst. A study of the polymerization kinetics indicated that the overall rate was represented by the equation, Rp = K[AlEt3] [CuCl]½ [M]2. The overall activation energy was 16.5 kcal/mole. From ESR measurement and the results of copolymerization of methyl methacrylate with styrene, it was suggested that the catalytic system has the character of a radical initiator. A polymerization scheme was also proposed. 相似文献
230.
Kitazawa M Ishitsuka Y Kobayashi M Nakano T Iwasaki K Sakamoto K Arakane K Suzuki T Kligman LH 《Photochemistry and photobiology》2005,81(4):970-974
The generation of reactive oxygen species (ROS) by ultraviolet radiation (UVR) accelerates skin aging, which is known as photoaging. Because cutaneous iron catalyzes ROS generation, sequestering iron by chelating agents is thought to be an effective approach toward preventing photoaging. Previously, N-(4-pyridoxylmethylene)-l-serine (PYSer) was designed as an antioxidant to suppress iron-catalyzed ROS generation by its iron-sequestering activity. In this study, PYSer showed protective effects against skin damage in hairless mice irradiated with ultraviolet B (UV-B). Topical application of PYSer to the skin significantly delayed and/or decreased the visible wrinkle formation induced by chronic UV-B irradiation. A histological study indicated that UV-B-induced epidermal hypertrophy and lymphocytic infiltration were suppressed by PYSer. Moreover, PYSer showed suppressive activity against the UV-B-induced increase in glycosaminoglycans (GAG). These results indicate that PYSer is a promising antioxidant for the prevention of chronic skin photoaging by its iron-sequestering activity. 相似文献