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排序方式: 共有235条查询结果,搜索用时 15 毫秒
91.
Tanabe A Tsuchida Y Ibaraki T Kawata K Yasuhara A Shibamoto T 《Journal of chromatography. A》2005,1066(1-2):159-164
River water collected from 27 sites in 21 rivers, groundwater from 66 sites in 34 cities, and 2 sewage plants in the Niigata Prefecture, Japan (total 301 samples) were analyzed for methyl tert-butyl ether (MTBE) using an improved purge-and-trap-GC-MS method. The amount of MTBE found in water samples from the 27 river sites ranged from 0.003 to 5.3 microg l(-1). MTBE was found in all 27 sites during winter but it was found at only 9 sites and 14 sites, respectively, during the summer. MTBE was found most frequently (in 21 sites) at levels ranging from 0.003 to 0.009 microg l(-1) during February. The highest levels of MTBE were always found in the samples collected from the same site. The amount of MTBE found in sewage water samples ranged from <0.003 to 0.025 microgl(-1). No significant differences were observed between the amounts of MTBE recovered from inflow and outflow waters. Relatively high levels (0.02-0.034 microg l(-1) ) of MTBE were found in January at two sites, which were located on the upper course of the Shinano River. MTBE levels ranged from 0.004 to 0.035 microgl(-l) and from 0.005 to 0.041 microgl(-1) at the mouths of the Shinano River and Agano River, respectively. The levels of MTBE in groundwater collected from 66 sites in 34 cities in Niigata Prefecture ranged from <0.003 to 5.9 microg l(-1). 相似文献
92.
Takehito Kodzasa Toshihide Kamata Hiro Matsuda Toshio Fukaya Fujio Mizukami Jun Matsunami Yuji Nagai Kazuko Matsumoto 《Journal of Sol-Gel Science and Technology》1997,8(1-3):1029-1033
The preparation of transparent films consisting of one-dimensional tetranuclear platinum complex and an alumina gel was attempted. Characterization of the composite films obtained was performed by UV-Vis-NIR spectroscopy. From the redox behavior of the complex in films, it was confirmed that the complex maintains the tetranuclear structure in the alumina gel, when the content of the complex is low. However, it seems to turn into another complex with a longer platinum chain, as the content of complex in the gel increases. The third-order nonlinear susceptibility (3) values of composite films was estimated from the third harmonic generation (THG) Maker-fringe measurements of this preliminary study. 相似文献
93.
Cascade Synthesis of Five‐Membered Lactones using Biomass‐Derived Sugars as Carbon Nucleophiles 下载免费PDF全文
Dr. Sho Yamaguchi Takeaki Matsuo Dr. Ken Motokura Dr. Akimitsu Miyaji Prof. Toshihide Baba 《化学:亚洲杂志》2016,11(11):1731-1737
We report the cascade synthesis of five‐membered lactones from a biomass‐derived triose sugar, 1,3‐dihydroxyacetone, and various aldehydes. This achievement provides a new synthetic strategy to generate a wide range of valuable compounds from a single biomass‐derived sugar. Among several examined Lewis acid catalysts, homogeneous tin chloride catalysts exhibited the best performance to form carbon–carbon bonds. The scope and limitations of the synthesis of five‐membered lactones using aldehyde compounds are investigated. The cascade reaction led to high product selectivity as well as diastereoselectivity, and the mechanism leading to the diastereoselectivity was discussed based on isomerization experiments and density functional theory (DFT) calculations. The present results are expected to support new approaches for the efficient utilization of biomass‐derived sugars. 相似文献
94.
95.
Toshihide Matsuno Sachie Horii Takanobu Sato Yoshiki Matsumiya Motoki Kubo 《Applied biochemistry and biotechnology》2013,169(3):795-809
Accumulations of inorganic nitrogen (NH4 +, NO2 ?, and NO3 ?) were analyzed to evaluate the nitrogen circulation activity in 76 agricultural soils. Accumulation of NH4 + was observed, and the reaction of NH4 +?→?NO2 ? appeared to be slower than that of NO2 ??→?NO3 ? in agricultural soil. Two autotrophic and five heterotrophic ammonia-oxidizing bacteria (AOB) were isolated and identified from the soils, and the ammonia-oxidizing activities of the autotrophic AOB were 1.0?×?103–1.0?×?106 times higher than those of heterotrophic AOB. The relationship between AOB number, soil bacterial number, and ammonia-oxidizing activity was investigated with 30 agricultural soils. The ratio of autotrophic AOB number was 0.00032–0.26 % of the total soil bacterial number. The soil samples rich in autotrophic AOB (>1.0?×?104 cells/g soil) had a high nitrogen circulation activity, and additionally, the nitrogen circulation in the agricultural soil was improved by controlling the autotrophic AOBs. 相似文献
96.
Yamasaki T Ito Y Mito F Kitagawa K Matsuoka Y Yamato M Yamada K 《The Journal of organic chemistry》2011,76(10):4144-4148
Nitroxides have antioxidative activities toward lipid peroxidation, but the influence of steric factors is not known. We synthesized alkyl-substituted nitroxides at the α-position of the N-O moiety to enhance lipophilicity and the bulk effect. There was good correlation between the IC(50) and lipophilicity (log P(o/w)) of nitroxides with use of the thiobarbituric acid-reactive substances (TBARS) assay. Furthermore, an inhibitory effect on the TBARS assay was dependent upon the number and length of alkyl groups, though nitroxides had almost identical lipophilicity. 相似文献
97.
Toshihide Maki Dr. Shinya Iikawa Gen Mogami Hitomi Harasawa Yoshihiro Matsumura Prof. Dr. Osamu Onomura Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(21):5364-5370
Get selective! A selective oxidation of 1,2‐diols to α‐hydroxyketones catalyzed by organotin compounds has been developed (see scheme). Invaluable chemo‐ and stereoselectivity were found in the reaction. The catalytic system has been achieved by electrochemical and chemical oxidation.
98.
Toshihide Baba 《Catalysis Surveys from Japan》2000,4(1):17-29
This review describes the preparation, characterization and application of KNH2 loaded on alumina and KF loaded on alumina. These strong solid bases catalyze a variety of organic reactions in a very selective manner. The reactions include isomerizations of alkenes and alkynes, dimerization of alkynes, Tishchenko reaction, and the reaction of silanes to form of Si–C, Si–N and Si–O bonds. 相似文献
99.
Yoshitaka Shimizu Yoko Ohte Xinnu Bao Satoko Otsuka Yuko Kitamaki Keiichiro Ishikawa Toshihide Ihara Kenji Kato 《Accreditation and quality assurance》2008,13(7):389-396
For accurate measurement of concentrations of substances by instrumental analysis, reliable calibration standards are needed.
In Japan, national reference materials are supplied under the national standards dissemination system named the Japan Calibration
Service System (JCSS). In JCSS, calibration standards for the analysis of environmental pollutants are supplied. For the traceability
to the SI of reference materials for calibration in JCSS, the National Metrology Institute of Japan (NMIJ) is developing high-purity
reference materials of volatile organic compounds (VOCs) as NMIJ CRMs. The freezing-point depression method, which has potential
as a primary method of measurement, is employed for the determination of property value. In this paper, a development scheme
of certified reference materials of high-purity VOCs is described.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
100.
Toshihide Maki 《Tetrahedron letters》2009,50(13):1466-375
A catalytic monoalkylation of 1,2-diols by using a weak base has been developed. Copper(II) dichloride and boronic acids are effective catalysts for activating 1,2-diols in the presence of potassium carbonate as a base. Various 1,2-diols were selectively monoalkylated with allyl-, benzyl- and alkyl- halides in DMF by choosing a suitable catalyst for each 1,2-diols. 相似文献