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排序方式: 共有198条查询结果,搜索用时 203 毫秒
151.
Tada H Matsui H Shiota F Nomura M Ito S Yoshihara M Esumi K 《Chemical communications (Cambridge, England)》2002,(16):1678-1679
A heterosupramolecular photocatalyst consisting of TiO2 and a cationic surfactant bilayer formed on the surface has achieved a very high level of activity in the oxidation of 2-naphthol through the cooperation of the inorganic and organic components. 相似文献
152.
The fluorescence spectrum of dye molecules, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyron (DCM), dissolved in surfactant-free n-decane droplets (average diameters of approximately 300 and approximately 2000 nm) dispersed in water was measured by a confocal microscope. The fluorescence spectra for 300- and 2000-nm droplets are found to exhibit a peak at 640 and 625 nm, respectively, and the peak red shifts with a decrease in the droplet diameter (solvatochromic shift of DCM molecules). It is concluded that (1) DCM molecules are located in a polar surface region of n-decane droplets and (2) the polarity increases with decreasing the droplet diameter. 相似文献
153.
Qingren Zhu Fumitaka Horil Ryozo Kitamaru Hitoshi Yamaoka 《Journal of polymer science. Part A, Polymer chemistry》1990,28(10):2741-2751
H-type crosslinking and Y-type long-chain branching have been examined for linear polyethylene samples irradiate at different temperatures with 60Co gamma rays in vacuum by solution-state 13C-NMR spectroscopy. In this study, relatively low molecular weight samples were irradiated with doses less than a gel dose in both solid and molten states. Resonance lines associated with H-links and Y-branches have clearly been observed for each irradiated sample and their radiation yields significantly depend on the irradiation temperature and the morphology of the samples. In particular, the G-value for the production of Y-branches is higher than that for H-links at lower temperatures, while the latter is superior to the former at higher temperatures. This may be due to the decrease in the concentration of the primary radicals, which are formed by main-chain scissions and associated with the production of Y-branches, by the recombination with small fragments at higher temperatures. The radiation yields of methyl branches and double bonds are also briefly discussed. 相似文献
154.
Xiao Zhi Zhang Fumitaka Esaka Konomi T. EsakaMasaaki Magara Satoshi SakuraiShigekazu Usuda Kazuo Watanabe 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
The capability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of uranium isotope ratios in individual particles was determined. For this purpose, we developed an experimental procedure including single particle transfer with a manipulator, chemical dissolution and isotope ratio analysis, and applied to the analysis of individual uranium particles in certified reference materials (NBL CRM U050 and U350). As the result, the 235U/238U isotope ratio for the particle with the diameter between 0.5 and 3.9 μm was successfully determined with the deviation from the certified ratio within 1.8%. The relative standard deviation (R.S.D.) of the 235U/238U isotope ratio was within 4.2%. Although the analysis of 234U/238U and 236U/238U isotope ratios gave the results with inferior precision, the R.S.D. within 20% was possible for the measurement of the particle with the diameter more than 2.1 μm. The developed procedure was successfully applied to the analysis of a simulated environmental sample prepared from a mixture of indoor dust (NIST SRM 2583) and uranium particles (NBL CRM U050, U350 and U950a). From the results, the proposed procedure was found to be an alternative analytical tool for nuclear safeguards. 相似文献
155.
Fukuda Y Hayakawa T Inoue K Kasuga S Koshio Y Kumita T Matsumoto K Nakahata M Nakamura K Okumura K Sakai A Shiozawa M Suzuki J Suzuki Y Tomoeda T Totsuka Y Hirata KS Kihara K Oyama Y Koshiba M Nishijima K Horiuchi T Fujita K Hatakeyama S Koga M Maruyama T Suzuki A Mori M Kajimura T Suda T Suzuki AT Ishizuka T Miyano K Okazawa H Hara T Nagashima Y Takita M Yamaguchi T Hayato Y Kaneyuki K Suzuki T Takeuchi Y Tanimori T Tasaka S Ichihara E Miyamoto S Nishikawa K 《Physical review letters》1996,77(9):1683-1686
156.
Matsuo N Muto H Miyajima K Mafuné F 《Physical chemistry chemical physics : PCCP》2007,9(45):6027-6031
Gold nanoparticles with an average diameter of 11 nm (Au(39000)) were prepared in an SDS aqueous solution. A 80-microm liquid droplet (microdroplet) of the solution was ejected into the atmosphere from a microdroplet nozzle. Structural changes of the gold nanoparticles in the microdroplet, after they were irradiated with a focused single-nanosecond laser pulse at the wavelength of 532 nm, were studied by transmission electron microscopy (TEM) and optical absorption spectroscopy. It was revealed that the gold nanoparticles are fragmented into small particles and then the small fragments aggregate with each other. The aggregation was found to be terminated 100 micros after the laser-pulse excitation. 相似文献
157.
Shintani R Park S Shirozu F Murakami M Hayashi T 《Journal of the American Chemical Society》2008,130(48):16174-16175
A palladium-catalyzed asymmetric decarboxylative reaction of racemic gamma-methylidene-delta-valerolactones with aryl isocyanates has been developed to give enantioenriched 3,3-disubstituted 2-piperidones. High enantioselectivity has been achieved by tuning the ester group on substrate and the substituents of phosphoramidite ligand. 相似文献
158.
Watanabe S Kimura H Sato T Shibata H Sakamoto F Azumi R Sakai H Abe M Matsumoto M 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):8735-8741
We report a versatile method to confine metal thin films in micro- and nanopatterns using directed self-assembly on the templates fabricated from phase-separated mixed Langmuir-Blodgett (LB) films. The pattern of the mixed LB films can be tuned by adjusting intermolecular interaction between the film-forming molecules in the LB films and by varying the fabrication conditions of the films such as the mixing ratio, subphase temperature, and surface pressure. We use the patterned LB films for templates to confine metal in patterned regions, taking advantage of the difference between the surface free energy of the patterned regions and that of the self-assembled monolayer of the silane coupling agent. Au nanoparticles are confined onto the patterned films as a catalyst for the succeeding Cu electroless deposition. The atomic force microscopic images, Auger electron spectra, and scanning Auger electron maps of a Cu-deposited film show that Cu is selectively deposited on the patterns of phase separation of the original mixed LB films. 相似文献
159.
Satoshi Wakita Yasusato Sugahara Masayuki Nakamura Syunsuke Kobayashi Kazuhisa Matsuda Chinatsu Takasaki Masahiro Kimura Yuta Kida Maiko Uehara Eri Tabata Koji Hiraoka Shiro Seki Vaclav Matoska Peter O. Bauer Fumitaka Oyama 《Molecules (Basel, Switzerland)》2021,26(21)
Chitooligosaccharides exhibit several biomedical activities, such as inflammation and tumorigenesis reduction in mammals. The mechanism of the chitooligosaccharides’ formation in vivo has been, however, poorly understood. Here we report that mouse acidic chitinase (Chia), which is widely expressed in mouse tissues, can produce chitooligosaccharides from deacetylated chitin (chitosan) at pH levels corresponding to stomach and lung tissues. Chia degraded chitin to produce N-acetyl-d-glucosamine (GlcNAc) dimers. The block-type chitosan (heterogenous deacetylation) is soluble at pH 2.0 (optimal condition for mouse Chia) and was degraded into chitooligosaccharides with various sizes ranging from di- to nonamers. The random-type chitosan (homogenous deacetylation) is soluble in water that enables us to examine its degradation at pH 2.0, 5.0, and 7.0. Incubation of these substrates with Chia resulted in the more efficient production of chitooligosaccharides with more variable sizes was from random-type chitosan than from the block-type form of the molecule. The data presented here indicate that Chia digests chitosan acquired by homogenous deacetylation of chitin in vitro and in vivo. The degradation products may then influence different physiological or pathological processes. Our results also suggest that bioactive chitooligosaccharides can be obtained conveniently using homogenously deacetylated chitosan and Chia for various biomedical applications. 相似文献
160.
固体高分辨13C NMR研究γ线辐照对结晶聚乙稀聚集态结构的影响 总被引:1,自引:1,他引:1
结晶聚乙烯(PE)经60Coγ线辐照后,用固体高分辨13C NMR CP/DD MAS方法观测解析了辐射效果与具有片晶结构的结晶相,结晶-橡胶状无定形界面相以及橡胶状无定形相的聚集态结构的关系。考察了各相中的13C核自旋-晶格弛豫和自旋-自旋弛豫行为及辐照对其影响。得到辐照后产生交联,破坏,相转变及晶型变化等有意义的结果,对PE的辐照效应和机制的探讨提供了核磁共振的新实验证据。 相似文献