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91.
Hideo Nemoto Mitsuo Nagai Keiichiro Fukumoto Tetsuji Kametani 《Tetrahedron letters》1985,26(38):4613-4616
A stereoselective total synthesis of 19-nor-Δ9(10)-progesterone (14) was achieved through des-A B-aromatic steroid (3) which was obtained by an intramolecular cycloaddition of the -quinodimethane generated from the thermolysis of 3-isopropenyl-5-(4-metho-xybenzocyclobutenyl)pentan-2-one-2-ethylene ketal (2), and the compound (14) thus obtained was further converted into Δ9-progesterone (18). 相似文献
92.
The effects of the volume fraction and length of natural fibers on flexural properties of biodegradable composites were investigated. Kenaf and bagasse were mixed with corn-starch biodegradable resin, and composite flexural specimens were fabricated by press forming. Cox's model that incorporates the effect of fiber compression in the cross section was applied to calculate the flexural modulus. Bagasse was found to be more compressible than kenaf due to the difference structure in the cross section. For up to 60% volume fraction kenaf and 66% bagasse composites, the flexural modulus increased with increase in fiber volume fraction, and these results were in good agreement with the calculated values. However, above 60% fiber volume fraction kenaf and 66% bagasse, the flexural modulus decreased due to insufficient resin. Moreover, the decrease of the flexural modulus occurred at fiber lengths 2.8 mm kenaf and 3.2 mm bagasse. Above these fiber lengths, there was no change in the flexural modulus of the composite specimens. This trend was also identified by the calculation. 相似文献
93.
An efficient synthesis of 3β-hydroxy-5-cholanic acid (8) and 3β-hydroxy-Δ5-cholanic acid (16) was carried out starting from 5-dihydropregnenolene (1) and pregnenolone (9). The monoacetates (3 and 11), prepared by Grignard reaction of 1 and 9 with 3,3-ethylenedioxypropylmagnesium bromide followed by acetylation, were dehydrated selectively to give the Δ20(22)-compounds (4 and 12) which on hydrogenation followed by acid treatment and Jones oxidation yielded 8 and 16, respectively. 相似文献
94.
95.
Tadashi Kawai Keiichiro Shiga Takehiko Suzuki Tomokazu Iyoda 《Journal of molecular catalysis. A, Chemical》1999,140(3):15-292
Tetravinylsilane and divinylsilanes have been successfully metathesized for the first time over Re2O7/Al2O3 catalyst promoted with tetrabutyltin under mild reaction conditions. All of the products were acyclic oligomers via intermolecular metathesis; the cyclic products via intramolecular metathesis were not formed. 相似文献
96.
Shinichi Aoki Shinya Ohara Keiichiro Kimura Hirotaka Mizuguchi Yasuro Fuse Etsu Yamada 《Analytical sciences》2008,24(3):389-394
The contribution of dissolved organic matter (DOM) released from phytoplankton (Microcystis aeruginosa) during cultivation and biodegradation was examined to clarify the causes of the organic pollution of Lake Biwa. Two peaks, peak 2 (retention time (RT) = 32 min) and peak 3 (RT = 35 min), were detected in the algal DOM released from Microcystis aeruginosa during cultivation and biodegradation by gel chromatography with a fluorescence detector (Ex = 340 nm, Em = 435 nm). As these peaks correspond with the peaks detected in the surface water of Lake Biwa, one can conclude that the algal DOM released from Microcystis aeruginosa during cultivation and biodegradation makes a considerable contribution to the refractory organic matter in Lake Biwa. Three fluorescence maxima were observed in the cultivation of Microcystis aeruginosa: a fulvic-like fluorescence peak (peak A) with Ex/Em values of 320/430 nm, a protein-like fluorescence peak (peak C) with Ex/Em values of 280/360 nm, and another peak with Ex/Em values of 240/370 nm. The fluorescence material of peak C has a larger MW than that of peak A. The algal-derived DOM from Microcystis aeruginosa has similar fluorescence to fulvic acid of soil origin but exhibits mainly hydrophilic characteristics. In the biodegradation of Microcystis aeruginosa, a fulvic-like fluorescence peak (peak B) with Ex/Em values of 250/440 nm and a peak with Ex/Em values of 320/380 nm were observed. 相似文献
97.
Hideo Nemoto Hiroshi Kurobe Masataka Ihara Keiichiro Fukumoto Tetsuji Kametani 《Tetrahedron letters》1984,25(29):3095-3098
A convergent and stereoselective synthesis of vitamin D3 was achieved via 3,5-cyclovitamins D3 (20) which were prepared from the chiral aldehyde (2) and the vinyl bromide (12) derived from Grundmann's ketone. 相似文献
98.
In this paper, we introduce a 6-dimensional example of non-compact complete Einstein non-K?hler almost-K?hler manifold G with negative scalar curvature which was constructed by Apostolov-Drăghici- Moroianu ([5]) and discuss the geometric structures.
相似文献
99.
Akikazu Matsumoto Keiichi Shimizu Keiichiro Mizuta Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1994,32(10):1957-1968
Radical polymerization of several alkyl crotonates (RCr) was carried out in bulk or in benzene in the presence of radical initiators. Homopolymerization of RCr bearing bulky ester alkyl groups, e.g. tert-butyl (tBCr), 1-adamantyl (AdCr), and 3,5-dimethyl-1-adamantyl crotonate (DMAdCr) proceeded to give a polymer with molecular weight of several thousands despite of the steric hindrance and chain transfer by the presence of the β-methyl group, while the methyl and ethyl esters gave no polymer. The kinetics of the polymerization was examined in detail and absolute rate constants were evaluated by means of electron spin resonance spectroscopy. The propagation rate constants of RCr were 0.41–1.0 L/mol s, being much smaller than those of the corresponding methacrylates (530–570 L/mol s). The termination rate constants were also determined from the analyses of steady state and non-steady state polymerizations. Radical copolymerizations of AdCr (M2) with several vinyl monomers (M1) were carried out in bulk at 60°C and the rate constants for cross propagations were calculated to examine reactivities of the monomer and its polymer radical. The structure and thermal properties of the resulting poly (AdCr) were also investigated. Onset temperature of decomposition and glass transition temperature of poly(AdCr) were revealed to be much high as 302 and 234°C, respectively. © 1994 John Wiley & Sons, Inc. 相似文献
100.
Mitsuru Toishi Tomiji Tanaka Atsushi Fukumoto Mikio Sugiki Kenjiro Watanabe 《Optics Communications》2007,270(1):17-24
In this paper, we evaluate photopolymer media using a polycarbonate (PC) substrate. In holographic data storage medium, substrates that sandwich the photopolymer material are needed to protect the photopolymer material against exogenous shock and open air. An optical glass such as BK-7 is normally used as a substrate, but a PC substrate has a cost advantage and is easy to fabricate compared with optical glass. For holographic recording and reading, however, the high birefringence and high thermal expansion of a PC substrate are significant problems. First, we analyze the degree of degradation of output power by the polarization change and estimate the threshold value of birefringence to record hologram normally. Next, we estimate the temperature tolerance of hologram readout with polycarbonate substrate hologram medium. These analyses results indicate the possible usage of the PC substrate as holographic recording media. 相似文献