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排序方式: 共有391条查询结果,搜索用时 679 毫秒
191.
Seiichiro Nagayama Katsumi Katoh Eiko Higashi Katsuyuki Nakano Kosuke Kumagae Hiroto Habu Yuji Wada Mitsuru Arai 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1215-1219
Ammonium nitrate (AN) is an affordable oxidant; however, it undergoes crystal structure transformations accompanied by a change in volume at comparatively low temperatures (approx. 30, 80, and 125 °C) and exhibits high hygroscopicity. Both these properties are particularly problematic for the industrial application of AN. In a previous study, we prepared spray-dried particles comprising three components: AN, potassium nitrate (PN) as a phase stabilizer, and a polymer (e.g., polyvinyl alcohol, carboxymethylcellulose salt, and styrene-butadiene latex), which was confirmed to provide effective moisture proofing. In the present study, the crystal transformation behavior of AN/PN/Polymer particles is investigated by observing their thermal behavior by differential scanning calorimetry. The results reveal that phase-stabilized AN can be successfully prepared by the addition of PN. In addition, an intriguing possibility was identified in that carboxymethylcellulose ammonium salt and polyvinyl alcohol, which were both added as polymer components for moisture proofing, also acted as phase stabilizers for AN crystal transformation. 相似文献
192.
Treatment of N-aryl-N-methoxyamides with AlCl3 in EtSH (or Me2S) generates the corresponding N-aryl-N-hydroxyamides in high yields. 相似文献
193.
Yoshiaki Ueda Yusuke Tanigawa Prof. Chitoshi Kitamura Prof. Hiroshi Ikeda Yuichi Yoshimoto Mirai Tanaka Prof. Kazuhiko Mizuno Prof. Hiroyuki Kurata Prof. Takeshi Kawase 《化学:亚洲杂志》2013,8(2):392-399
A series of 17,17‐dialkyl‐3,14‐diaryltetrabenzofluorenes were efficiently prepared by using Suzuki–Miyaura cross‐coupling reactions of the corresponding 3,14‐dibromo derivatives. Studies of the unique fluorescence properties of these compounds showed that they display intense blue to yellow fluorescence with high quantum yields in the solution state and blue to orange fluorescence with moderate quantum yields in the solid state. In addition, the fluorescence wavelength of the bis(p‐nitrophenyl) derivative is remarkably solvent‐dependent in a manner that correlates with the solvent polarity parameter ET(30). The results of density function theory calculations suggest that the intramolecular charge‐transfer character of the HOMO–LUMO transition is responsible for the large solvent effect. Moreover, addition of water to a tetrahydrofuran (THF) solution of this compound leads to quenching of the yellow fluorescence owing to an increase in the solvent polarity. However, when the amount of water fraction exceeds 70 %, a new fluorescence band appears at the same orange‐red emission wavelength as that of the solid‐state fluorescence. This observation suggests the occurrence of a crystallization‐induced emission (CIE) phenomenon in highly aqueous THF. 相似文献
194.
Kenji Hotta Tomoko Kawase Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(7):961-975
Abstract A first total synthesis of a β-series ganglioside GQ1β (IV3Neu5Acα2, III6Neu5Acα2-Gg4Cer) is described. Regio- and stereoselective dimeric sialylation of the hydroxyl group at C-6 of the GalNAc residue in 2-(trimethylsilyl)ethyl O-(2-acetamido-2-deoxy-3-O-levulinyl-β-d-galactopyranosyl)-(1→4)-O-(2,3,6-tri-O-benzyl-β-d-galactopyranosyl)-(1→4)-O-2,3,6-tri-O-benzyl-β-d-glucopyranoside (3) with methyl [phenyl 5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1′,9-lactone)-4,7-di-O-acetyl-3,5-dideoxy-2-thio-d-glycero-d-galacto-2-nonulopyranosid]onate (4) using N-iodosuccinimide (NIS)-trifluoromethanesulfonic acid (TfOH) as a promoter gave the desired pentasaccharide 5 containing α-glycosidically-linked dimeric sialic acids. This was transformed into the acceptor 6 by removal of the levulinyl group. Condensation of methyl O-[methyl 5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1′,9-lactone)-4,7-di-O-acetyl-3,5-dideoxy-d-glycero-d-galacto-2-nonulopyranosylonate]-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-d-galactopyranoside (7) with 6, using dimethyl(methylthio)sulfonium triflate (DMTST) as a promoter, gave the desired octasaccharide derivative 8 in high yield. Compound 8 was converted into α-trichloroacetimidate 11, via reductive removal of the benzyl groups, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile, which, on coupling with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (12), gave the β-glycoside 13. Finally, 13 was transformed, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into the title ganglioside 15 in good yield. 相似文献
195.
Yukihiro Isogai Tomoko Kawase Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(8):1001-1023
ABSTRACT 3-O-Sulfo glucuronyl paragloboside derivatives (pentasaccharides) have been synthesized. The important intermediate designed for a facile sulfation in the last step and effective, stereocontrolled glycosidation, methyl (4-O-acetyl-2-O-benzoyl-3-O-levulinoyl-α-D-glucopyranosyl trichloroacetimidate)uronate (8) was prepared from methyl [2-(trimethylsilyl)ethyl β-D-glucopyranosid]uronate (3) via selective 4-O-acetylation, 2-O-benzoylation, 3-O-levulinoylation, removal of the 2-(trimethylsilyl)ethyl group and imidate formation. The glycosylation of 8 with 2-(trimethylsilyl)ethyl 2,4,6-tri-O-benzyl-β-D-galactopyranoside (9) using trimethylsilyl trifluoromethanesulfonate gave 2-(trimethylsilyl)ethyl O-(methyl 4-O-acetyl-2-O-benzoyl-3-O-levulinoyl-β-D-glucopyranosyluronate)-(1→3)-2,4,6-tri-O-benzyl-β-D-galactopyranoside (10), which was transformed via removal of the benzyl group, benzoylation, removal of the 2-(trimethylsilyl)ethyl group and imidate formation into the disaccharide donor 13. On the other hand, 2-(trimethylsilyl)ethyl O-(2-acetamido-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (20) as the acceptor was prepared from 2-(trimethylsilyl)ethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranoside (14) via O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, imidate formation, coupling with 2-(trimethylsilyl)ethyl O-(2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (18), removal of the O-acetyl and N-phthaloyl group followed by N-acetylation. Condensation of 13 with 20 using trimethylsilyl trifluoromethanesulfonate afforded the desired pentasaccharide 21, which was transformed by removal of the benzyl group, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group and imidate formation into the pentasaccharide donor 24. Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (25) with 24 gave the desired β-glycoside 26, which was transformed into the four target compounds, via reduction of the azido group, coupling with octadecanoic acid or tetracosanoic acid, selective removal of the levulinoyl group, O-sulfation, hydrolysis of the methyl ester group and O-deacylation. 相似文献
196.
Seiichiro Wakabayashi 《Annali dell'Universita di Ferrara》2006,52(2):471-482
Abstract In this article we shall introduce the results obtained in [16], i.e., we shall give a necessary and sufficient condition that the Cauchy problem for first order hyperbolic systems with constant
coefficient principal part is C∞ well-posed under the maximal rank condition (see the condition (R) below). We shall also give a simple sufficient condition
without any assumptions on the rank.
Keywords: Hyperbolic system, Cauchy problem, Constant coefficient principal part 相似文献
197.
Seiichiro Higashiya Thamarai Selvi Devarajan Manisha V. Rane‐Fondacaro Christopher Dangler Jeremy Snyder Pradeep Haldar 《Helvetica chimica acta》2009,92(8):1600-1609
Synthesis of ionic liquids (IL) based on oxygen‐containing spirobipyrrolidinium salts with BF4, BF3C2F5, and NTf2 as counterions was undertaken. Their physical and electrochemical properties were evaluated for suitability for Room Temperature Ionic Liquids (RTIL) application. Reduction in melting point occurred upon exchange of C(2) by an O‐atom of spirobipyrrolidinium, without sacrificing the electrochemical stability; while introduction of alkyl groups between the N‐ and O‐atoms led to incorporation of asymmetry, and hence reduced the melting points, and viscosity. 相似文献
198.
Self-assembled molecular aggregates of fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer can solubilize cytochrome c in organic media such as methanol, although the corresponding non-fluorinated polymer cannot solubilize cytochrome c in organic media. Interestingly, the resulting fluorinated oligomer-cytochrome c aggregate was found to act effectively as a new fluorinated biocatalyst for the oxidation of pinacyanol chloride with hydrogen peroxide in the non-aqueous methanol. 相似文献
199.
Low band gap dyad molecules were prepared that have absorption spectra matched well with the solar spectrum, and the construction of efficient charge transport pathways was observed. Under AM 1.5 illumination, the devices have achieved the highest J(SC) (4.79 mA cm(2)) and FF (0.46) in dyad-based organic solar cells to date. 相似文献
200.
Kawashima Y Nakano H Jung J Ten-no S 《Physical chemistry chemical physics : PCCP》2011,13(24):11731-11738
The generalized hybrid orbital (GHO) method is implemented at the second-order approximate coupled cluster singles and doubles (CC2) level for quantum mechanical (QM)/molecular mechanical (MM) electronic excited state calculations. The linear response function of CC2 in the GHO scheme is derived and implemented. The new implementation is applied to the first singlet excited states of three aromatic amino acids, phenylalanine, tyrosine, and tryptophan, and also bacteriorhodopsin for assessment. The results obtained for aromatic amino acids agreed well with the full QM CC2 calculations, while the calculated excitation energies of bacteriorhodopsin and its chromophore, all-trans retinal, reproduced the environmental shift of the experimental data. For the bacteriorhodopsin case, the environmental shift of GHO also showed good agreements with the experimental data. The contribution of the quantum effect of certain moieties in the excited states is elucidated by changing the partitioning of QM and MM regions. 相似文献