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排序方式: 共有282条查询结果,搜索用时 15 毫秒
1.
2.
Xinjiang Chen Goh Matsuo Bunsho Ohtani Kaoru Tsujii 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4891-4900
A racemic amphiphilic monomer, n‐dodecyl glyceryl itaconate (DGI), forms bilayer membranes in water in the presence of small amount of ionic cosurfactant and shows iridescent color. A chiral DGI, S‐DGI, also shows an iridescent property, but with a rather red shift in the color, which can be ascribed to the increased packing density of the monomer in the bilayer membranes. Chrial DGI has a more compact packing density than racemic one owing to closer distance between the monomer molecules; the conversion rate, however, is slower than that of racemic one when H2O2 is used as an initiator. When the initiator is changed to an amphiphilic one, 4‐(2‐hydroxyethoxy) phenyl‐(2‐hydroxy‐2‐propyl) ketone (Irgacure 2959), the chiral DGI shows even a little faster conversion rate than that of racemic one. The NMR chemical shift results of protons in benzene ring show that the molecules of Irgacure 2959 insert into the bilayer membranes. The molecular weights of the corresponding polymers prove that the initiation by H2O2 is restricted compared to that by Irgacure 2959. It is concluded that the decelerated polymerization behavior of chiral DGI initiated by H2O2 is a result of limited diffusion of the initiator into the lamellar bilayer structures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4891–4900, 2007 相似文献
3.
The double-bond conversion of UV-cured resins prepared from pentaerythritol triacrylate (PETA) was determined by pyrolysis-gas chromatography in the presence of an organic alkali, tetramethylammonium hydroxide (TMAH). The pyrogram of the uncured prepolymer compound, consisting of PETA and a photoinitiator, 2,2-dimethoxy-2-phenylacetophenone, contained specific products reflecting the original acrylate structure, such as methyl acrylate (MA) and methyl ethers of pentaerithritol. Meanwhile, in pyrograms of the UV-cured PETA, the yields of MA considerably decreased. The double-bond conversions of the cured resins, irradiated with various UV dosages, were calculated based on the relative yields of MA among specific products in the pyrograms. The conversions determined by this approach were analyzed by comparing them with those estimated by Fourier-transform infrared spectroscopy. 相似文献
4.
Solid sampling technique for direct detection of condensed tannins in bark by matrix-assisted laser desorption/ionization mass spectrometry 总被引:2,自引:0,他引:2
Ishida Y Kitagawa K Goto K Ohtani H 《Rapid communications in mass spectrometry : RCM》2005,19(5):706-710
A novel method for the direct analysis of condensed tannin components in bark was developed on the basis of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with a simple solid sampling technique. The MALDI mass spectra obtained from the wood (bark) powder sample clearly showed a series of peaks corresponding to the sodium ion adducts of condensed tannin oligomers up to around m/z 3000. The results indicate that the condensed tannins in the bark sample used in this work mostly consist of combinations of flavan-3-ol units such as profisetinidin (PF), prorobinetinidin (PR) and prodelphinidin (PD), at least up to 10-mers (m/z approximately 3000). 相似文献
5.
Shigeharu KittakaSachie Nishida T. IwashitaTsukio Ohtani 《Journal of solid state chemistry》2002,164(1):144-149
Formation and chemical properties of amorphous AgVO3, which was prepared by mechanochemical treatment of an Ag2O-V2O5 mixture, and crystalline AgVO3 were studied in relation to AgVO3 polymorphs. A ball-milled sample of the mixture was assigned as a highly deformed β-AgVO3 rather than the low density phase α-AgVO3. Crystalline α-AgVO3 and β-AgVO3 were converted into deformed β-AgVO3 by ball milling, which produced a clear change. δ-AgVO3 is resistant to mechanical treatment and its structure was not markedly affected. The dissolved chemical species from the ball-milled sample precipitates to form α-AgVO3 without a seeding crystal, but other polymorphs deposit if they are present; i.e., β-AgVO3 and δ-AgVO3 grow on the seeding crystal. 相似文献
6.
Photoirradiation at >300 nm of aqueous suspensions of several natural crystal specimens and synthesized crystallites of mercury(II) sulfide (HgS) induced deaminocyclization of optically active or racemic lysine into pipecolinic acid (PCA) under deaerated conditions. This is the first example, to the best of our knowledge, of photoinduced chemical reactions of natural biological compounds over natural minerals. It was found that the natural HgS crystals had activity higher than those of synthesized ones but lower than those of other sulfides of transition metals, e.g., CdS and ZnS, belonging to the same II-IV chalcogenides. In almost all of the photoreactions, decompostion of HgS occurred to liberate hydrogen sulfide (H(2)S) and Hg(2+), and the latter seemed to have undergone in-situ reductive deposition on HgS as Hg(0) after a certain induction period (24-70 h) during the photoirradiation, as indicated by the darkened color of the suspensions. The formation of PCA, presumably through combination of oxidation of lysine and reduction of an intermediate, cyclic Schiff base, could also be seen after a certain induction time of the Hg(0) formation. This was supported by the fact that the addition of small amount of Hg(2+) (0.5 wt % of HgS) increased the PCA yield by almost 2-fold. We also tried to elucidate certain aspects of the plausible stereochemical reactions in relation to the chiral crystal structure of HgS. Although, in some experiments, slight enantiomeric excess of the product PCA was observed, the excess was below or equal to the experimental error and no other supporting analytical data could not be obtained; we cannot conclude the enantiomeric photoproduction of PCA by the natural chiral HgS specimen. 相似文献
7.
8.
Y. Ogata Y. Sakuma N. Ohtani M. Kotaka 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):539-541
A tritium separation from heavy water by electrolysis using a solid polymer electrode layer was specified. The cathode was made of stainless steel or nickel. The electrolysis was performed for 1 hour at 5, 10, 20, and 30 °C. Using a palladium catalyst, generated hydrogen and oxygen gases were recombined, which was collected with a cold trap. The activities of the samples were measured by a liquid scintillation counter. The apparent tritium separation factors of the heavy and light water at 20 °C were 2 and 12, respectively. 相似文献
9.
The ternary phase diagram of the TlVS system was investigated using samples quenched from 400°C, especially in the neighborhood of TlV6S8 and TlV5S8 phases. The TlV6S8 phase (TlxV6Sy) exists between 0.75 < x < 1.00 and 7.55 < y < 7.90, and the TlV5S8 phase (Tlx′V5Sy′) between 0.70 < x′ < 1.00 and 7.54 < y′ < 7.98. A new ternary phase with the nominal composition of TlV2S4 was found in addition to the three known ternary phases. The entirely deintercalated V6S7.8 with the framework structure was obtained by using 1 N AlCl3 + 0.01 N FeCl3 aqueous solution, while the lower phase limit of the TlV5S8 phase was Tl0.33V5S8 consistent with the earlier work. The electrical resistivity and the magnetic susceptibility measurements show that these compounds are expected to be weakly magnetic itinerant-electron systems. 相似文献
10.
Ozeki H Nomoto A Ogawa K Kobuke Y Murakami M Hosoda K Ohtani M Nakashima S Miyasaka H Okada T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(24):6393-6401
We synthesized special-pair/electron-acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl-substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole pi system of the dimer. Time-resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special-pair arrangement for efficient charge separation in photosynthesis. 相似文献