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Iwao Hashimoto Takatoshi Kawaji Florin D. Badea Tsuyoshi Sawada Shuntaro Mataka Masashi Tashiro Gouki Fukata 《Research on Chemical Intermediates》1996,22(9):855-869
The Friedel-Crafts acylations of various aromatic compounds with cyclic anhydrides such as 2-(p-substituted phenyl)butanedioic, 3-phenylpentanedioic and homophathlic anhydrides were carried out under various conditions in order to obtain informations about the regioselectivity of the ring opening of the cyclic anhydrides and about the possible reaction pathways in the acylations. 相似文献
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Naoki Yoneda Yukihiro Fukata Dr. Keisuke Asano Prof. Dr. Seijiro Matsubara 《Angewandte Chemie (International ed. in English)》2015,54(51):15497-15500
Chiral spiroketal skeletons are found as core structures in a range of bioactive compounds. These natural compounds and their analogues have attracted much attention in the field of drug discovery. However, methods for their enantioselective construction are limited, and easily available optically active spiroketals are rare. We demonstrate a novel catalytic asymmetric synthesis of spiroketal compounds that proceeds through an intramolecular hemiacetalization/oxy‐Michael addition cascade mediated by a bifunctional aminothiourea catalyst. This results in spiroketal structures through the relay formation of contiguous oxacycles, in which multipoint recognition by the catalyst through hydrogen bonding imparts high enantioselectivity. This method offers facile access to spiroketal frameworks bearing an alkyl group at the 2‐position, which are prevalent in insect pheromones. Optically active (2S,5S)‐chalcogran, a pheromone of the six‐spined spruce bark beetle, and an azide derivative could be readily synthesized from the bicyclic reaction product. 相似文献
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Yoshiaki Yasuno Shuichi Makita Takashi Endo Gouki Aoki Masahide Itoh Toyohiko Yatagai 《Optical and Quantum Electronics》2005,37(13-15):1157-1163
High speed complex full-range Fourier domain optical coherence tomography (FD-OCT) is demonstrated. This FD-OCT requires only a single A-scan for each single transversal position for full-range Fourier domain optical coherence tomography. The Fourier transform method is applied along the direction of the B-scan to reconstruct complex spectra, and the complex spectra compose a full-range OCT image. 相似文献
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Noriyuki Uchida Tsuyoshi Okami Hideo Tagami Naoki Fukata Masanori Mitome Yoshio Bando Kouichi Murakami 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):31
The effects of aluminum (Al-) doping in SiO2 film containing silicon-nanocrystal (nc-Si) dots were investigated by photoluminescence (PL) and electron spin resonance (ESR) measurements. The observed PL peak center showed a blueshift due to reduction of size of nc-Si dots as a result of the Al doping followed by annealing within a range of 600–800 °C. For the samples annealed at 1000 °C, the PL intensity showed increases with increasing concentration of Al atoms in the SiO2. The ESR results obtained from all the samples, however, revealed that the density of defects causing the PL quenching did not show decrease by the Al doping. Therefore, the enhancement of the PL intensity by the Al doping seemed to be caused probably by the increase in the density of nc-Si dots. 相似文献
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N. Fukata C. Li H. Morihiro K. Murakami M. Mitome Y. Bando 《Applied Physics A: Materials Science & Processing》2006,84(4):395-401
Significant enhancement of photoluminescence (PL) was attained for Er ions and Si nanocrystallites (nc-Si) in SiO2 films by two kinds of hydrogenation, using H2 molecules or H atoms. Er-doped SiO2 films containing Er impurities and a high density of nc-Si were fabricated by laser ablation of Er films deposited on Si substrate in an O2 gas atmosphere, followed by annealing at high temperatures in flowing Ar gas. Hydrogenation at 300–500 °C was found to effectively increase the PL intensity of Er ions as well as that of nc-Si. In particular, the hydrogen atom treatment dramatically shortens the hydrogenation time for the enhancement of Er PL compared to the hydrogen molecule treatment. Spectra of electron spin resonance showed a decrease in residual defects, namely, Pb-type defects located at the interfaces between nc-Si and SiO2 by hydrogenation. These results clearly show the effectiveness of hydrogen passivation for Si nanostructures; i.e., the increase in the Er PL and nc-Si PL due to hydrogen passivation of the nonradiative recombination centers located at the interfaces between nc-Si and SiO2. PACS 78.67.Bf; 71.20.Eh; 76.30.Mi; 81.15.Fg 相似文献
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N. Fukata S. Matsushita N. Okada J. Chen T. Sekiguchi N. Uchida K. Murakami 《Applied Physics A: Materials Science & Processing》2008,93(3):589-592
Boron (B) or phosphorus (P) doped silicon nanowires (SiNWs) were synthesized by laser ablation. Local vibrational modes of
B were observed in B-doped SiNWs by micro-Raman scattering measurements at room temperature. Fano broadening due to a coupling
between the discrete optical phonon and a continuum of interband hole excitations was also observed in the Si optical phonon
peak for B-doped SiNWs. An electron spin resonance signal due to conduction electrons was observed only for P-doped SiNWs.
These results prove that B and P atoms were doped in substitutional sites of the crystalline Si core of SiNWs during laser
ablation and electrically activated in the sites. 相似文献
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Shotaro Ito Haruhisa Akiyama Reiko Sekizawa Miyuki Mori Tamaki Fukata Masaru Yoshida Hideyuki Kihara 《Journal of polymer science. Part A, Polymer chemistry》2019,57(7):806-813
We previously reported that ABA‐type triblock copolymers with azobenzene‐containing terminal blocks can be utilized as a light‐induced reworkable adhesive that enables repeatable bonding and debonding on demand. The reworkability was based on the photoisomerization of the azobenzene moiety and concomitant softening and hardening of the azo blocks. Our aim in this study is to investigate the effect of the composition, molecular weight, and block copolymer architectures on the reworkable adhesive properties. For this purpose, we prepared AB diblock, ABA triblock, and 4‐arm (AB)4 star‐block copolymers consisting of polymethacrylates bearing an azobenzene moiety (A block) and 2‐ethylhexyl (B block) side chains and performed adhesion tests by using these block copolymers. As a result, among the ABA block copolymers with varied compositions and molecular weights, the ABA triblock copolymers with an azo block content of about 50 wt % and relatively low molecular weight could achieve an appropriate balance between high adhesion strength and low residual adhesion strength upon UV irradiation. Furthermore, the 4‐arm star‐block structure not only enhances the adhesion strength, but also maintains low residual adhesion strength when exposed to UV irradiation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 806–813 相似文献
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