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排序方式: 共有192条查询结果,搜索用时 31 毫秒
71.
Masaki Hasegawa Tadashi Yurugi Satoru Namiki Takatoshi Shiobara Hachiro Nakanishi Fusae Nakanishi 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1291-1299
The photopolymerization behavior of p-phenylene diacrylic acid dimethyl ester (p-PDA Me) crystal and the thermal behavior of the resultant poly-p-PDA Me were investigated. From the kinetic study of polymerization at various temperatures a topochemical process via a stepwise mechanism was observed. Continuous change from monomer to polymer crystals was demonstrated by x-ray diffraction pattern and DSC analysis. Crystallinity of the reacting phase was maintained at an extremely high degree during the polymerization process in support of monomer crystal lattice control. Thermal study on as-polymerized poly-p-PDA Me crystal confirmed that the thermal reaction was a polymer crystal lattice-controlled depolymerization, which was followed by miscellaneous processes that involved vaporization, sublimation, and deterioration of the oligomeric or monomeric units of p-PDA Me. Thermal stability was dependent on the molecular weight. All the results are compared with those of four-center-type photopolymerization in the crystalline state. 相似文献
72.
Ryoji Takahashi Satoshi Sato Toshiaki Sodesawa Takatoshi Azuma 《Journal of Sol-Gel Science and Technology》2004,31(1-3):373-376
The comparison of bimodal pore structures between silica gels prepared from silicon alkoxide and from water glass was performed based on the results of phase separation tendency, mesopore formation, and atomic scale observation using 29Si NMR. Macropore structure could be controlled for both the raw material systems by inducing phase separation. Although the gelation in the water glass system is much faster than that in the silicon alkoxide system, there is little difference in the atomic scale structure, mesopore evolution during processing, and phase separation tendency. The results suggest that the obtained bimodal porous silica from water glass is essentially the same as that from silicon alkoxide. Because of the low cost of water glass, water-glass-derived bimodal porous silica is applicable to industrial use. 相似文献
73.
Grinding a mixture of hydrous amorphous chromium oxide (Cr2O3·nH2O), vanadium oxide (V2O5) and antimony oxide (Sb2O5) was conducted by using a planetary ball mill, to investigate their mechanochemical reactions to form chromium vanadium oxide (CrVO4) and chromium antimony oxide (CrSbO4). The synthesis reactions proceed with an increase in grinding periods of time. The ground samples consist of agglomerates with particle size of about ten nanometers. The synthesized CrVO4 sample exhibits a rutile-type tetragonal crystal structure, which is a high pressure phase. Additionally, solid solutions, CrV1−xSbxO4 (x=0∼1, Δx=0.25), have been synthesized mechanochemically from the mixtures of Cr2O3·nH2O, V2O5 and Sb2O5. 相似文献
74.
Yoshihiro Saito Kei Watanabe Kaname Hashizaki Hiroyuki Taguchi Naotake Ogawa Takatoshi Sato Haruhisa Ueda 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):445-452
The stability constants for the inclusion of alkanols with-cyclodextrin (-CD) in aqueous solutionhave been determined using the surface tension method. Dataanalyses assuming 1 : 1 stoichiometry were appliedto estimate the stability constants of thesecomplexes. The stability constants obtained using this methodwere in reasonable agreement with the corresponding values inthe literature. Chemically modified -CDs could not beused in this method because those CDs themselves have surfaceactivity. In addition, the relation between the stability constantsand the carbon number of alkanols is discussed. 相似文献
75.
Yoshiharu Tsujita Ryoko Ojika Akira Takizawa Takatoshi Kinoshita 《Journal of polymer science. Part A, Polymer chemistry》1990,28(6):1341-1351
Copoly(γ-stearyl L-glutamate-γ-methyl L-glutamate)s with various compositions were synthesized by ester exchange of poly(γ-methyl L-glutamate) with stearyl alcohol. The temperature dependence of the volume and helical spacing of the copolyglutamates thus prepared was examined from 0 to 100°C, observing the melting and crystallization of the long alkyl side chain attached to the polypeptide backbone. The melting temperature of the long side chain increased with increasing stearyl L-glutamate content. With increasing temperature, the α helical spacing decreased, especially with the melting of the side chain. On the other hand, the volume increased with increasing temperature and a marked increase was observed on melting. The above two phenomena were elucidated according to the structural model of the long side chain of the copolyglutamates proposed here. The transport properties, permeability coefficients were found to be considerably affected by the side-chain structure of the copolyglutamate and by the melting or crystallization of the side chain. The permeability coefficient of the copolyglutamate with 67% degree of stearylation, varied as much as two orders of magnitude before and after melting or crystallization. It was also confirmed that the permeability coefficient is controllable by the side-chain structural change of polypeptides. 相似文献
76.
Takatoshi Kawaji Kikue Hayashi Taisuke Matsumoto Shuntaro Mataka 《Tetrahedron letters》2005,46(32):5277-5279
SmI2/HMPA-mediated double reductive coupling of N,N′-(m-xylylidene)dianiline affords 1,2,9,10-tetrakis(N-phenylamino)[2.2]metacyclophane in good yield. 相似文献
77.
A microbial chip was fabricated by filling the micropores on a glass substrate with collagen-embedded Escherichia coli(E. coli) cells, and characterized by scanning electrochemical microscopy (SECM) in a solution containing ferricyanide. The activity of the E. coli cells in the collagen gel microstructure was imaged and characterized with SECM by mapping the localized concentration of ferrocyanide produced by the respiration of the cells. The SECM-based activity measurement detected as low as approximately 100 E. coli cells. Furthermore, the optical-microscopic observation indicated that the E. coli cells on the chip proliferated during the incubation. The sequential SECM measurements were performed for the same E. coli chip to obtain the microbial growth curve for a small number of microorganisms. 相似文献
78.
Fukaminato T Sasaki T Kawai T Tamai N Irie M 《Journal of the American Chemical Society》2004,126(45):14843-14849
Photochromic reactions of diarylethene derivatives were detected at a single-molecule level by using a fluorescence technique. Fluorescent photoswitching molecules in which photochromic diarylethene and fluorescent bis(phenylethynyl)anthracene units are linked through an adamantyl spacer were synthesized, and switching of fluorescence upon irradiation with UV and visible light was followed in solution as well as on polymer films at the single-molecule level. Although in solution the fluorescence intensity gradually changed upon irradiation with UV and visible light, digital on/off switching between two discrete states was observed at the single-molecule level. The "on"- and "off"-times were dependent on the power of UV and visible light. When the power of UV and visible light was increased, the average on- and off-times became short in proportion to the reciprocal power of the light. The response-times were found to show distribution. The distribution of the on- and off-times is considered to reflect the difference in the micro-environment as well as conformation of the molecules. 相似文献
79.
Gianola AJ Ichino T Hoenigman RL Kato S Bierbaum VM Lineberger WC 《The journal of physical chemistry. A》2005,109(50):11504-11514
The 351.1 nm photoelectron spectrum of imidazolide anion has been measured. The electron affinity (EA) of the imidazolyl radical is determined to be 2.613 +/- 0.006 eV. Vibrational frequencies of 955 +/- 15 and 1365 +/- 20 cm(-1) are observed in the spectrum of the (2)B1 ground state of the imidazolyl radical. The main features in the spectrum are well-reproduced by Franck-Condon simulation based on the optimized geometries and the normal modes obtained at the B3LYP/6-311++G(d,p) level of density functional theory. The two vibrational frequencies are assigned to totally symmetric modes with C-C and N-C stretching motions. Overtone peaks of an in-plane nontotally symmetric mode are observed in the spectrum and attributed to Fermi resonance. Also observed is the photoelectron spectrum of the anion formed by deprotonation of imidazole at the C5 position. The EA of the corresponding radical, 5-imidazolyl, is 1.992 +/- 0.010 eV. The gas phase acidity of imidazole has been determined using a flowing afterglow-selected ion tube; delta(acid)G298 = 342.6 +/- 0.4 and delta(acid)H298 = 349.7 +/- 0.5 kcal mol(-1). From the EA of imidazolyl radical and gas phase acidity of imidazole, the bond dissociation energy for the N-H bond in imidazole is determined to be 95.1 +/- 0.5 kcal mol(-1). These thermodynamic parameters for imidazole and imidazolyl radical are compared with those for pyrrole and pyrrolyl radical, and the effects of the additional N atom in the five-membered ring are discussed. 相似文献
80.
Yogo T Urano Y Ishitsuka Y Maniwa F Nagano T 《Journal of the American Chemical Society》2005,127(35):12162-12163
Photosensitizers are reagents that produce reactive oxygen species upon light illumination and are commonly used to study oxidative stress or for photodynamic therapy. There are many available photosensitizers, but most have limitations, such as low photostability, structural instability, or a limited usable range of solvent conditions. Here, we describe a novel photosensitizer scaffold (2I-BDP) based on the unique characteristics of the BODIPY chromophore (i.e., high extinction coefficient, high photostability, and insensitivity to solvent environment). 2I-BDP shows stronger near-infrared singlet oxygen luminescence emission and higher photostability than the well-known photosensitizer, Rose Bengal. Unlike other photosensitizers, this scaffold is widely applicable under various conditions, including lipophilic and aqueous environments. HeLa cells loaded with 2I-BDP could be photosensitized by light illumination, demonstrating that 2I-BDP is potentially useful as a reagent for cell photosensitization, oxidative stress studies, or PDT. 相似文献