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排序方式: 共有177条查询结果,搜索用时 15 毫秒
81.
Uyama H Kuwabara M Tsujimoto T Nakano M Usuki A Kobayashi S 《Macromolecular bioscience》2004,4(3):354-360
This study deals with the preparation and properties of a new class of organic-inorganic hybrids from renewable resources. The hybrids were synthesized by an acid-catalyzed curing of epoxidized triglycerides in the presence of an organophilic montmorillonite (a modified clay). The mechanical properties were improved by the incorporation of clay in the oil-based polymer matrix. The reinforcement effect due to the addition of clay was confirmed by dynamic viscoelasticity analysis. The hybrids showed relatively high thermal stability. The co-curing of epoxidized soybean and linseed oils in the presence of clay produced hybrids with controlled mechanical and coating properties. The barrier property of the hybrid towards water vapor was superior to that of the oil polymer. The development of the present hybrids consisting of inexpensive renewable resources, triglyceride and clay is expected to contribute to global sustainability. 相似文献
82.
Li Y Kuwabara H Gong YK Takaki Y Nakashima K 《Journal of photochemistry and photobiology. B, Biology》2003,70(3):171-176
Resonance energy transfer from dibucaine (DC) to acriflavine (AF) has been investigated both in homogeneous aqueous solutions and in polystyrene latex dispersions. The energy transfer reaction is observed by monitoring fluorescence quenching of DC as well as sensitized emission of AF. It is found that the energy transfer from DC to AF is remarkably enhanced on going from the aqueous homogeneous solution to the latex dispersion. This is mainly attributed to the fact that both the donor and acceptor are effectively adsorbed onto the latex particles, as evidenced by the measurement of adsorption isotherms. From the adsorption experiments, it is also elucidated that electrostatic interaction is significant at low DC concentration, while hydrophobic interaction dominates at the higher concentration especially at higher pH. 相似文献
83.
Suzumura K Yoshinari K Tanaka Y Takagi Y Kasai Y Warashina M Kuwabara T Orita M Taira K 《Journal of the American Chemical Society》2002,124(28):8230-8236
It has been generally accepted, on the basis of kinetic studies with phosphorothioate-containing substrates and analyses by NMR spectroscopy, that a divalent metal ion interacts directly with the pro-Rp oxygen at the cleavage site in reactions catalyzed by hammerhead ribozymes. However, results of our recent kinetic studies (Zhou, D.-M.; Kumar, P. K. R.; Zhang. L. H.; Taira, K. J. Am. Chem. Soc. 1996, 118, 8969-8970. Yoshinari, K.; Taira, K. Nucleic Acids Res. 2000, 28, 1730-1742) demonstrated that a Cd(2+) ion does not interact with the sulfur atom at the Rp position of the scissile phosphate (P1.1) in the ground state or in the transition state. Therefore, in the present study, we attempted to determine by (31)P NMR spectroscopy whether a Cd(2+) ion binds to the P1.1 phosphorothioate at the cleavage site in solution. In the case of the R32-S11S (ribozyme-substrate) complex, neither the Rp- nor the Sp-phosphorothioate signal from the S11S substrate at the cleavage site was perturbed (the change was less than 0.1 ppm) upon the addition of Cd(2+) ions (19 equiv) at pH 5.9 and 8.5. By contrast, we detected the significant perturbation of the P9 phosphorothioate signal from another known metal-binding site (the A9/G10.1 metal-binding motif). The Rp-phosphorothioate signal from A9/G10.1 was shifted by about 10 ppm in the higher field direction upon the addition of Cd(2+) ions. These observations support the results of our kinetic analysis and indicate that a Cd(2+) ion interacts with the sulfur atom of the phosphorothioate at the A9/G10.1 site (P9) but that a Cd(2+) ion does not interact with the sulfur atom at the Rp- or at the Sp-position of the scissile phosphate (P1.1) in the ground state. 相似文献
84.
S. Yu. Tolmachyov J. Kuwabara H. Noguchi 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(1):125-131
A method based on flow injection extraction chromatography coupled to on-line ICP-MS (FI-EXC-ICPMS) has been developed and
validated for simultaneous thorium and uranium determination in human body fluids. By using extraction chromatography, the
limits of detection achieved for 232Th, 235U and 238U were 0.06 ng.l-1, 0.0014 ng.l-1 and 0.05 ng.l-1, respectively. The accuracy of the FI-EXC-ICPMS method was 102.4% and 101.5% with overall precision (RSDmax at 95% CI) of 5.3% and 4.9% for 232Th and 238U, respectively. The 235U/238U atom ratio is measured with 1.8% precision. The technique was employed for simultaneous thorium and uranium analyses in
human urine and blood samples after microwave digestion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
85.
Koji Ishizu Shojiro Kuwabara Hui Chen Hirohide Mizuno Takashi Fukutomi 《Journal of polymer science. Part A, Polymer chemistry》1986,24(8):1735-1746
Soluble microgels with several pendant vinyl groups were synthesized by radical copolymerization of methyl methacrylate (MMA) with p-divinyl benzene (p-DVB). The polymerization conditions used for intramolecular crosslinking of microgels were chosen from gel permeation chromatograph (GPC) measurements of the reaction products. The rate constant of intramolecular crosslinking (kpi) was estimated from the changes in the concentration of pendant vinyl groups of microgel by using photometrical measurements at 30°C assuming a unimolecular termination mechanism of polymer radicals. As a result, kpi showed larger values than kp of styrene and depended strongly on the internal structure of the microgels. 相似文献
86.
H. Abe K. Ikebuchi S. J. Wagner M. Kuwabara N. Kamo S. Sekiguchi 《Photochemistry and photobiology》1997,66(2):204-208
We have investigated the mechanism of virus photoinactivation with methylene blue (MB) by conducting deuterium oxide (D2O), azide ion (N3-) and oxygen-dependent, studies. Inactivation of M13 bacteriophage and singlet oxygen (1O2) generation by MB photosensitization were irradiation dose dependent. Inactivation of M13 was enhanced by D2O and inhibited by N3-, suggesting that 1O2 participates in M13 inactivation by MB photosensitization. However, N3- did not inhibit M13 inactivation completely. On the other hand, deoxygenating the reaction solution still caused 52-67% of M13 inactivation observed in the presence of oxygen. These results suggest that 102-mediated (Type II) and sensitizer-mediated (Type I) reactions may both play roles in M13 inactivation by MB photosensitization. 相似文献
87.
J. Kuwabara M. Yamamoto H. Nagai K. Komura K. Ueno D. J. Assinder 《Journal of Radioanalytical and Nuclear Chemistry》1995,197(2):369-385
Depth profiles and inventories of237Np in sediment cores from the Ribble Estuary in the Irish Sea have been studied along with those of Pu isotopes,241Am and137Cs, to allow a more detailed look of anomalously high237Np content observed in this estuary previously. The comprehensive data obtained showed that the depth profiles of both237Np contents and237Np/239,240Pu activity ratios were clearly different from those of239,240Pu,241Am, and137Cs and their activity ratios. As much as 80–90% of237Np inventories (0.32–1.06 kBq/m2), found in three cores, were estimated to be derived from a source other than Sellafield, on the basis of comparison of the237Np/239,240Pu inventory ratio (0.65–1.74%) found in the Ribble Estuary cores with those (0.10–0.16%) in the Ravenglass Estuary cores. 相似文献
88.
89.
Synthesis of bithiazole‐based crystalline polymers via palladium‐catalyzed direct CH arylation
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Wei Lu Junpei Kuwabara Masahiro Kuramochi Takaki Kanbara 《Journal of polymer science. Part A, Polymer chemistry》2015,53(11):1396-1402
Palladium‐catalyzed direct arylation polycondensation afforded a bithiazole‐based homopolymer and donor–acceptor (D–A)‐type copolymers where the bithiazole unit served as an acceptor unit. The results of polymerization strongly depended on the solubility of the polymers; long alkyl chain substituents were required for the formation of high‐molecular‐weight polymers in high yields owing to low solubility of the bithiazole‐based polymers. X‐ray diffraction studies revealed that the obtained polymers were highly crystalline. In particular, a well‐ordered lamellar structure was observed in the D–A‐type copolymer with flexible alkyl chains after thermal annealing, presumably owing to the combination of interchain interactions between the bithiazole units and the electrostatic D–A interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1396–1402 相似文献
90.