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排序方式: 共有861条查询结果,搜索用时 46 毫秒
61.
Masahiro Yamashita Daisuke Kawakami Satoshi Matsunaga Yoshio Nakayama Mari Sasaki Shinya Takaishi Fumiyasu Iwahori Hitoshi Miyasaka Ken‐ichi Sugiura Yoshiki Wada Hiroshi Miyamae Hiroyuki Matsuzaki Hiroshi Okamoto Hisaaki Tanaka Kazuhiro Marumoto Shin‐ichi Kuroda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2004,116(36):4867-4871
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An evaluation of the feasibility of liquid chromatography-mass spectrometry (LC-MS) with atmospheric pressure ionization was made for quantitation of four diarrhetic shellfish poisoning toxins, okadaic acid, dinophysistoxin-1, pectenotoxin-6 and yessotoxin in scallops. When LC-MS was applied to the analysis of scallop extracts, large signal suppressions were observed due to coeluting substances from the column. To compensate for these matrix signal suppressions, the standard addition method was applied. First, the sample was analyzed and then the sample involving the addition of calibration standards is analyzed. Although this method requires two LC-MS runs per analysis, effective correction of quantitative errors was found. 相似文献
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Sugita M Yamaguchi A Yamagiwa N Handa S Matsunaga S Shibasaki M 《Organic letters》2005,7(23):5339-5342
[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield). 相似文献
66.
Komoto A Maenosono S Yamaguchi Y 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8916-8923
Fluorescence oscillation is observed in an ensemble of colloidal CdSe/ZnS core/shell quantum dots (QDs) dispersed in nonpolar solvent under continuous irradiation. The QDs dispersed in toluene gradually aggregate and change their fluorescence intensity, even in the dark. During the aggregation, the QD/toluene suspension is unstable, that is, overdispersed. The fluorescence oscillation is found only in this unstable state before the system reaches steady state. In addition, the aggregation rate is promoted by irradiation and strongly correlates with the oscillation amplitude. Our experimental results indicate that the dispersion instability plays an important role in both linear and nonlinear dynamics of the fluorescence. It is inferred from the experimental results and previous studies that the complex time evolution of fluorescence in the QD/toluene dispersion is possibly due to adsorption and desorption of surface ligand molecules over the course of QD aggregation. 相似文献
67.
Shinya Harusawa 《Tetrahedron》2004,60(51):11911-11922
A novel measuring method (electroimmunoassay) of 17β-estradiol (E2) in urine or blood was proposed on the basis of a competition between E2 and a labeled E2 against an immobilizing antibody. To evaluate the principle, 3-{4-[17β-hydroxy-1,3,5(10)-estratrien-3-yloxy]butyldisulfanyl}-N-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxabenzocyclopentadecen-2-yl) succinamic acid (1) was designed and synthesized as a novel aminobenzo-15-crown-5-containing E2 tethered with disulfide linkage. Two thiol-intermediates 5b and 19c were efficiently synthesized from mercaptosuccinic acid 7 and 4,4′-dithiodibutyric acid 12, respectively. Formations of disulfide linkages from less reactive thiols were examined and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) could be employed for the formation of an unsymmetrical disulfide 20c from 5b and 19c. Then, removal of TMS- and allyl-protecting groups in 20c successfully afforded the crown ether-containing E21. 相似文献
68.
Morimoto Y Kohyama S Nakai K Matsuo H Karasawa F Kikuchi M 《Photochemistry and photobiology》2003,78(4):372-376
Several studies have shown that UV irradiation may be effective for preventing vascular restenosis or vasopasm. However, the long-term effects of UV light on the physiological properties of vessels such as arterial tension have not been elucidated. We therefore studied the long-term effects of UV using rat carotid arteries treated with UV-B light (wavelength = 313 nm, total energy = 14 mJ/mm2). The animals were sacrificed at 1, 7 and 14 days after UV light exposure, and the carotid arteries were studied by light microscopy and the contractile responses of isolated arterial rings were recorded under isometric tension. UV treatment had induced a substantial loss of smooth muscle cells (SMC) along the entire circumference of the media on days 7 and 14, whereas loss of SMC on day 1 was negligible. Contractile responses of arteries that had been exposed to UV light were significantly reduced on days, 1, 7 and 14. The susceptibility of UV-treated arteries to phenylephrine and prostaglandin F2 alpha was significantly decreased on days 1 and 7, but decreased susceptibility was not seen on day 14. Acetylcholine-induced relaxations were not altered by UV treatment. These results suggest that the long-term effect of UV light is an attenuation of smooth muscle contractility without impairment of endothelial function. 相似文献
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70.
Byungchan Bae Shinya Kawamura Kenji Miyatake Masahiro Watanabe 《Journal of polymer science. Part A, Polymer chemistry》2011,49(17):3863-3873
Random and multiblock sulfonated poly(arylene ether sulfone)s (SPEs) containing various azole groups such as oxadiazole and triazole were synthesized and characterized for fuel cell application. Successful preparation of SPE membranes depended on the structure of azole groups, which affected solubility of precursors and the resulting SPEs. Although oxadiazole groups were incorporated into hydrophobic component, they were found to be hydrophilic to give higher proton conductivity. Introduction of oxadiazole groups into random SPE gave comparable proton conductivity to that of Nafion NRE at >60% relative humidity at 80 °C. Block copolymer structure further increased the proton diffusion coefficient without increasing ion exchange capacity. Hydrolytic and oxidative stability of the SPE membranes was affected by both hydrophilic and hydrophobic components. Oxadiazole groups gave negative impact on hydrolytic and mechanical stability to the SPE membranes. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献