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The initial stage of cubic silicon carbide (3C-SiC) growth on a Si(0 0 1) surface using dimethylsilane (DMS) as a source gas was observed using scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED). It was found that the dimer vacancies initially existing on the Si(0 0 1)-(2 × 1) surface were repaired by the Si atoms in DMS molecules, during the formation of the c(4 × 4) surface. From the STM measurement, nucleation of SiC was found to start when the Si surface was covered with the c(4 × 4) structure but before the appearance of SiC spots in the RHEED pattern. The growth mechanism of SiC islands was also discussed based on the results of RHEED, STM and temperature-programmed desorption (TPD). 相似文献
4.
D. Kaneko T. Narita J. P. Gong Y. Osada J. Ando K. Yamamoto S. Ohnishi V. V. Yaminsky 《Journal of Polymer Science.Polymer Physics》2003,41(22):2808-2815
The effect of the shear flow on the thickness change of a polyelectrolyte membrane grafted onto a glass substrate was directly investigated with a flow cell combined with a confocal laser scanning microscope. The membrane thickness decreased proportionally to an increase in the shear stress of the flow when the shear rate exceeded a critical value of 1 s?1. The higher the ionic strength was of the fluid, the greater the thinning effect was. The correlation between the critical shear rate and the relaxation of the polymer in the gel membrane was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2808–2815, 2003 相似文献
5.
Oishi S Kamano T Niida A Odagaki Y Hamanaka N Yamamoto M Ajito K Tamamura H Otaka A Fujii N 《The Journal of organic chemistry》2002,67(17):6162-6173
Diastereoselective synthesis of new psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type alkene dipeptide isosteres corresponding to dipeptides having one N-methylamino acid, and application to bioactive peptides, are described. In a key reaction introducing the chiral alpha-alkyl group of the isosteres, organocopper-mediated alkylation of syn-beta-methylated gamma-mesyloxy-alpha,beta-enoate 26a afforded E- and Z-isomers of anti-S(N)2' products in a solvent-dependent manner. The resulting two isosteres, D-Phe-psi[(E)-CH=CMe]-L-Val 27a and D-Phe-psi[(Z)-CH=CMe]-L-Val 28b, which corresponded to trans- and cis-conformers of D-Phe-L-MeVal, respectively, were utilized in a structure-activity relationship study on cyclic RGD peptides 1 and 2, in company with a psi[(E)-CH=CH]-type alkene dipeptide isostere, D-Phe-psi[(E)-CH=CH]-L-Val. The cyclic isostere-containing pseudopeptides 3, 4, and 40 were synthesized and biological activity against integrin alpha(V)beta(3) and alpha(IIb)beta(3) receptors were also evaluated. 相似文献
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T Tatee K Narita S Kurashige S Ito H Miyazaki H Yamanaka M Mizugaki T Sakamoto H Fukuda 《Chemical & pharmaceutical bulletin》1986,34(4):1643-1655
7.
Masatoshi Oue Akira Ishigaki Keiichi Kimura Yousuke Matsui Toshiyuki Shono 《Journal of polymer science. Part A, Polymer chemistry》1985,23(7):2033-2042
Poly- and bis(thiacrown ether) derivatives in which some oxygen atoms of benzocrown ether moiety are replaced by sulfur atoms have been synthesized. Their cation-binding abilities were investigated by using the solvent extraction method. The poly- and bis(benzothiacrown ether)s showed great affinity for silver ion, being more excellent in the affinity than the corresponding monocyclic analogs. They, however, possess very poor cation-binding ability for alkali and alkaline-earth metal ions. The poly- and bis(thiacrown ether)s also bind mercuric ions effectively, whereas the corresponding monomeric analogs do not at all. 相似文献
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Susumu Narita Takeshi Hamakawa Tetsuo Morikawa Tai-ichi Shibuya 《Monatshefte für Chemie / Chemical Monthly》2002,133(7):987-990
Summary. The generalized Pauling bond order was enumerated in the C60 fullerene cage molecule (truncated icosahedral symmetry). This index measures chemical similarity in fullerene derivatives
such as dihydrofullerene (C60H2), anionized monohydrofullerene (C60H−), N-substituted monohydrofullerene (C59NH), the fullerene dimer ((C60)2), and the dianionic fullerene dimer ((C60)2
2−). It is also useful in judging the chemical stability of isomers.
Received October 9, 2001. Accepted November 9, 2001 相似文献
10.
Nishimoto A Narita K Ohmoto S Takahashi Y Yoshizumi S Yoshida T Kado N Okezaki E Kato H 《Chemical & pharmaceutical bulletin》2001,49(9):1120-1127
A series of erythromycin A 9-O-substituted oxime ether derivatives have been synthesized and evaluated for antibacterial activity against Mycobacterium avium complex (MAC) and Staphylococcus aureus. These compounds possessed stronger in vitro activity against MAC including macrolide-resistant strains than clarithromycin (2), although in vitro antibacterial activities of these compounds were less than that of 2 against Staphylococcus aureus. Our studies found that several factors contribute to the antibacterial activity against MAC. The length and spatial orientation of the substituent at 9-position were found to significantly influenced the anti-MAC activity, especially against macrolide-resistant strains. Of all the compounds prepared, erythromycin A 9-[O-(4-phenylbutyl)oxime] (12q) and erythromycin A 9-[O-(3-phenoxypropyl)oxime] (12t) possessed 16 times stronger antibacterial activity than 2 against clarithromycin-resistant strains. Surprisingly, the minimum inhibitory concentrations (MICs) of 12q and 12t against the resistant strains were almost same as those against the susceptible strains. These results suggest that the erythromycin A 9-O-substituted oxime ether derivatives would be promising macrolide antibiotics. 相似文献