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21.
Masayuki Yamane 《Journal of Sol-Gel Science and Technology》1997,8(1-3):483-487
A thick silica gel film, corresponding to the glass film of 10–20 micron in thickness, has been formed at the interface between
two immiscible liquids, hexane and water, using E-40, a partially polymerized silicon alkoxide, as the precursor. The film
formation was possible using both acid- and base-catalyzed water, but was greatly dependent on the type of catalyst. Only
the trace of a film was observed for the system catalyzed with a strong electrolyte such as HCl, HNO3 or NaOH, while a gel film, corresponding to the glass film of several to 10 micron in thickness was formed with a weak electrolyte
such as ammonia, organic acid like acetic acid, citric acid, etc., of similar pH value. The direct introduction of organic
base catalyst like triethylamine in hexane was much more effective than the use of ammonia water, suggesting that the polymerization
of E-40 to form a gel film takes place in the organic phase, where water molecules, as well as undissociated ammonia or organic
acids, can diffuse in. 相似文献
22.
Merrilactone A (1) has been shown to possess neurotrophic activity and thus is expected to hold therapeutic potential in the treatment of neurodegeneration diseases. In this paper, we report the total synthesis of (+/-)-1, employing, as key steps, a novel desymmetrization protocol of meso-diketone to construct the core cis-bicyclo[3.3.0]octyl system of 1 (3 --> 2) and a radical cyclization to install the highly congested C9-quaternary carbon (16 --> 17). 相似文献
23.
Sm2+-doped glasses in the system of Al2O3-SiO2 were prepared by sol-gel processing of metal alkoxides and reacting with H2 gas at 800°C. The hole burning properties of these glasses were investigated. The holes were burned in the 7F0 5D0 line of the Sm2+ ions using a DCM dye laser at 77 K. The hole depth increased with increasing the laser irradiation time, reaching up to 15% of the total intensity within a few hundred seconds. The hole width was 3 cm–1 full width at half maximum. Fluorescence line narrowing spectra of the 5D0 7 F1 transition were analyzed to study the local structure surrounding the Sm2+ ion. It is concluded that the Sm2+ ions are closely coordinated with nine oxygens of the AlO6 group in aluminosilicate glasses and that the addition of Al3+ ions into glass induces an increase in the coordination number of the Sm2+. 相似文献
24.
Masayuki Kuzuya Tohru Kawaguchi Yasukichi Yanagihara Sachihiko Nakai Takachiyo Okuda 《Journal of polymer science. Part A, Polymer chemistry》1986,24(4):707-713
To provide a satisfactory basic understanding of the solvent effect of plasma-initiated polymerization, we have carried out several kinds of polymerizations of various water-soluble vinyl monomers. It has been shown that aqueous solution of such vinyl monomers underwent the polymerizations induced by methyl isobutyrate (MIB) plasma-exposed glass surface. The invisible ultrathin polymer film trapping an active radical species deposited on the plasma-exposed glass surface apparently induced the polymerizations. The efficiency, however, was largely dependent on the solvent used: the solvent can be considered to act as “an initiation-activator” for the lifelike postpolymerization. The nature of the solvent effect was ascribed to the physicomechanical property such as swelling ability and/or solubility toward the ultrathin film formed on the glass surface. Thus it has been suggested that the choice of good-balanced combination between the structural feature of the plasma-induced ultrathin polymer film and the solvent as an initiation-activator is important to achieve activity of a desired solution polymerization. 相似文献
25.
Kimura T Yoshino M Yamane T Yamato M Tobita M 《Langmuir : the ACS journal of surfaces and colloids》2004,20(14):5669-5672
A diamagnetic particle with magnetic susceptibilities chi3 < chi2 = chi1 < 0 was subjected to a rotating magnetic field to obtain an alignment of the chi3 axis (the smallest susceptibility axis) in the direction perpendicular to the plane of the rotating magnetic field. A polymer short fiber, whose fiber axis coincides with the chi3 axis, was suspended in a fluid with the same density, and then a rotating magnetic field generated by a rotation of a pair of permanent magnets was applied. The fiber axis, rotating following the applied field, finally ended up with an alignment perpendicular to the plane of the rotating magnetic field. The experimental data on the time course of the alignment was in good agreement with the numerical calculation based on the equation of rotation. 相似文献
26.
Toshio Morikawa Osama Bashir Abdel-Halim Hisashi Matsuda Osamu Muraoka Masayuki Yoshikawa 《Tetrahedron》2006,62(26):6435-6442
Three new pseudoguaiane-type sesquiterpenes, dichrocepholides A-C, and two new pseudoguaiane-type sesquiterpene dimers, dichrocepholides D and E, were isolated from the aerial part of Dichrocephala integrifolia. Their stereostructures were determined on the basis of chemical and physicochemical evidence. In addition, the extract and its principal sesquiterpene constituent, parthenin, showed an inhibitory activity on nitric oxide (NO) production and on induction of inducible NO synthase. 相似文献
27.
Highly efficient methods for synthesizing metacyclophanes such as 2,6-bridged pyrones and pyridines are described. 4-Hydroxy-2-pyrone derivative 3 bridged at the 3 and 6-positions is readily available. This compound was transformed into 2,6-bridged 4-pyrone 4 on heating in ethanol or in hydrochloric acid. Heating 4 with ammonia or methylamine afforded the corresponding 2,6-bridged 4-pyrone 7 or 8. These pyridones were synthesized directly from 3 by treatment with ammonia or methylamine. These methods have a wide applicability to the bridge length of metacyclophane; compounds with a short bridge (n=8) as well as long bridge (n=18) are synthesized in satisfactory yields. 相似文献
28.
Masayuki Ito 《Physica D: Nonlinear Phenomena》1984,14(1):1-28
This paper is concerned with the competitive-diffusive systems , with homogeneous Dirichlet boundary conditions. From a global bifurcation view point, the dependency of steady-states on the parameters ai, bi, ci and di (i = 1, 2) is investigated. In particular, bifurcation of coexist ence solutions amd their stabilities are our main interests. 相似文献
29.
Hiromi Matsushita Ritsuko Nagao Masayuki Nogami Toshihiro Kasuga Tomokatsu Hayakawa 《Journal of Sol-Gel Science and Technology》2000,19(1-3):559-562
High proton-conducting P2O5-SiO2 glass was applied to the electrolyte of the hydrogen concentration cell for hydrogen gas sensing. 5P2O5·95SiO2 glass was prepared using the sol-gel method and its electrical conductivity and electromotive force were measured at 50°C as a function of both the ambient humidity and hydrogen gas concentration. The electrical conductivities increased with increasing humidity and reached 10–2 S/cm at 90% relative humidity. The electromotive force of the hydrogen concentration cell, where the glass was used as a membrane, showed good Nernstian response to hydrogen pressure in the high relative humidity region. 相似文献
30.
Nakano S Uotani Y Uenishi K Fujii M Sugimoto N 《Journal of the American Chemical Society》2005,127(2):518-519
We have synthesized the deoxyadenosine derivative tethering a phenyl group (X), which mimics the Watson-Crick A/T base pair. The RNA/DNA hybrid duplexes containing X in the middle of the DNA sequence showed a similar thermal stability regardless of the ribonucleotide species (A, G, C, or U) opposite to X, probably because of the phenyl group stacking inside of the duplex accompanied by the opposite ribonucleotide base flipped in an extrahelical position. The RNA strand hybridized with the DNA strand bearing X was cleaved on the 3'-side of the ribonucleotide opposite to X in the presence of MgCl2, and the RNA sequence to be cleaved was not restricted. The site-specific RNA hydrolysis suggests that the DNA strand bearing X has the advantage of the site-selective base flipping in the target sequence and the development of a "universal deoxyribozyme" to exclusively cleave a target RNA sequence. 相似文献