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121.
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
122.
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
123.
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
124.
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
125.
126.
Ito F Ikoma T Akiyama K Kobori Y Tero-Kubota S 《Journal of the American Chemical Society》2003,125(16):4722-4723
Magnetic field effects on the charge-transfer (CT) fluorescence of a 1,2,4,5-tetracyanobenzene-doped poly(N-vinylcarbazole) thin film were investigated to clarify the primary process in photoconductive organic amorphous solid. The CT fluorescence increased with increasing magnetic field until 10 mT, and then it showed the dip around 40-50 mT. The hyperfine coupling mechanism observed in the low field and the level-crossing mechanism observed around 46 mT clearly indicate that the spin-conservative stepwise hole hops take place in the films. The boundary distance determined from the simulation based on the stepwise hopping model almost agreed with the interionic separation estimated within the Onsager analysis. 相似文献
127.
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
128.
H. Nakahara K. Sueki W. Sato K. Akiyama 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(1):169-179
Radiochemical techniques have been applied in various ways to the study of fullerenes and metallofullerenes for the past several years, and they have provided invaluable information pertaining to the stability, structures, and formation of the novel carbon material. This paper reviews those experimental results that have fully shown the usefulness and uniqueness of radionuclides demonstrated in the field of fullerene science. 相似文献
129.
Mitsuhisa Narukawa Shinya KoideHideto Miyake Kazumasa Hiramatsu 《Journal of Crystal Growth》2009,311(10):2970-2972
Undoped and Zn-doped GaN nanowires were synthesized by chemical vapor deposition (CVD), and the effects of substrates, catalysts and precursors were studied. A high density of GaN nanowires was obtained. The diameter of GaN nanowires ranged from 20 nm to several hundreds of nm, and their length was about several tens of μm. The growth mechanism of GaN nanowires was discussed using a vapor–liquid–solid (VLS) model. Furthermore, room-temperature cathodoluminescence spectra of undoped and Zn-doped GaN nanowires showed emission peaks at 364 and 420 nm, respectively. 相似文献
130.