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751.
Kazuo Itoya Michitoshi Arata Masa-Aki Kakimoto Yoshio Imai Jouji Maeda Toshikazu Kurosaki 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):817-826
Abstract A series of aliphatic polybenzoxazoles of high molecular weights was prepared in three steps by the low-temperature solution polycondensation of tetrakis(trimethylsilyl)-substituted 4,4′-diamino-3,3′-dihydroxy-biphenyl with aliphatic diacid chlorides with 7 to 12 methylene units yielding trimethylsilyl-substituted poly(o-hydroxysamide) precursor polymers, which were subjected to desilylation with methanol giving the poly(o-hydroxyamide)s, followed by thermal cyclodehydration. The aliphatic polybenzoxazoles had melting points in the 172 to 246 °C range with glass transition temperatures of 55-97°C. They were stable in the melt state up to 400 °C in nitrogen. These polybenzoxazoles and the corresponding bisbenzoxazole model compounds exhibited no liquid crystallinity. 相似文献
752.
Hideki Ohtsuki Kanna Kamei Takuya Nagata Tatsuyuki Yamamoto Yoshihisa Matsui 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(1-2):25-30
Binding constants for -cyclodextrin ( -CD) complexes with 1- alkanols and 1- alkanoate ions were determined by analyzing changes ( ) in chemical shifts of guest 13C NMR signals with -CD concentration. The guests gave well-separated 13C NMR signals. The curve-fitting analyses of for individual carbons upon assumption of a simple 1:1 complexation gave virtually the same binding constants (K1) in the cases of guests with relatively short alkyl chains, such as 1-propanol, 1-butanol, 1- pentanol , 1- butanoate , 1- pentanoate , and 1-hexanoate. However, thus obtained individual K1 values were significantly different from one another, when the guests had relatively long alkyl chains such as 1- hexanol , 1- heptanol , and 1-octanoate. In these guests, satisfactorily consistent K1 values were obtained by the curve-fitting analyses of for individual carbons upon an assumption that not only 1:1 but also 2:1 (host:guest) complexation occurs. 相似文献
753.
Qiang Wang Zhang Rong Jie Teng Yoshihisa Takaishi Hong Quan Duan 《中国化学快报》2008,19(2):187-189
Two new diterpenes, 15-ethyl-18-methyl pinifolate (1) and 18-hydroxy-labda-8(17), 13E-dien-15-acetate (2), were isolated from the needles of Pinus sylvestris. Their structures were elucidated by spectroscopic methods, including 2D-NMR spectra. Compound 1 exhibited the significant cytotoxic activity against the human carcinoma cell lines Hela, SK-N-SH and BEL-7402 in vitro. 相似文献
754.
Sumiyoshi T Nishimura K Nakano M Handa T Miwa Y Tomioka K 《Journal of the American Chemical Society》2003,125(40):12137-12142
A series of 10 didodecanoylamides of alpha,omega-alkylidenediamines bridged by a straight carbon chain varying in length from 0 to 9 carbons was examined as possible gelator molecules of organic liquids to gain information on the relationships between the spacial arrangement of two amide groups in a molecule and their effects on the microscopic structures of the gel. The structural characteristics of these amides are parallel and antiparallel arrangements of two amide carbonyl groups, which depend on the even and odd numbers of a bridging zigzag carbon chain. The linear alkyl chain moieties and a center carbon chain of diamides intermolecularly interact with each other within the van der Waals contact. Two amide moieties of an even number carbon chain diamide intermolecularly interact with each other by using two pairs of hydrogen bonds with two other molecules in a plane, which formed ribbonlike self-complementarily assembled aggregates. On the other hand, a diamide of an odd number carbon chain forms four independent hydrogen bonds with four other molecules not in a plane, which assembled into woven aggregates. Asymmetric introduction of a methyl group at the alpha-position of the amide groups successfully twists the two side chain van der Waals cores of the chiral diamides in the fixed direction, giving helically twisted ribbon and coiled coil aggregates. The helically twisted ribbon and coiled coil aggregates of these chiral diamides were directly observed by CD, SEM, and TEM, providing a basis for the design of a sophisticated small molecular gelator of a tailor-made shape. 相似文献
755.
Yoshihisa Kurasawa Mari Okiyama Yumiko Kamigaki Megumi Kanoh Atsushi Takada Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1988,25(4):1259-1262
The reactions of the 3-substituted 4-amino-8-ethoxycarbonyl[5,1-c][1,2,4]triazines 1 and 2 with o-amino-phenol hydrochloride gave the pyrazolo[1′,5′:3,4][1,2,4]triazino[5,6-b][1,5]benzoxazepines 5 and 8 . The alkylation of 5 with methyl iodide and isopropyl iodide afforded the 6-alkoxylpyrazolo[1′,5′:3,4][1,2,4]triazino-[5,6-b][1,5]benzoxazepines 6a and 6b , respectively. Refluxing of 5, 6a, 6b and 8 in hydrochloric acid/acetic acid resulted in ring transformation to produce the spiro[benzoxazole-2′(3′H),4(1H)pyrazolo[5,1-c][1,2,4]-triazines] 7a, 7b and 9 . The screening data of the above compounds was described. 相似文献
756.
The reaction of diphenylketene with terminal acetylenes catalyzed by tetrakis-(triphenylphosphine)palladium gave disubstituted acetylenes in high yields. 相似文献
757.
Takeshi Yagi Naofumi Kuboki Yoshihisa Suzuki Naotaka Uchino Kazunori Nakamura Kazuaki Yoshida 《Optical Review》1997,4(5):596-600
A new fiber-optic ammonia sensor utilizing rectangular-cladding eccentric-core fiber and a sensitive film containing an indicator dye is demonstrated. The sensitive film is a SiO2-GeO2 gel film including an indicator dye of bromocresol purple or bromocresol green, which is dip-coated by a sol-gel technique. The attenuation of this sensor changes depending on the concentration of ammonia at the wavelength range of 500–700 nm. This sensor can detect several ppm of gaseous ammonia. Various factors determining the sensitivity to detect the ammonia gas and time response of the sensor are also studied. 相似文献
758.
Langrock C Diamanti E Roussev RV Yamamoto Y Fejer MM Takesue H 《Optics letters》2005,30(13):1725-1727
Conventional single-photon detectors at communication wavelengths suffer from low quantum efficiencies and large dark counts. We present a single-photon detection system, operating at communication wavelengths, based on guided-wave frequency upconversion in a nonlinear crystal with an overall system detection efficiency (upconversion + detection) exceeding 46% at 1.56 microm. This system consists of a fiber-pigtailed reverse-proton-exchanged periodically poled LiNbO3 waveguide device in conjunction with a silicon-based single-photon counting module. 相似文献
759.
Rika Nishikiori Shotaro Morimoto Yoshihisa Fujiwara Yoshifumi Tanimoto 《Applied magnetic resonance》2011,41(2-4):221-227
The magnetic field effect (0?C0.47?T) on cathodic potential oscillation of a zinc cathode in an alkaline solution was studied. By applying a magnetic field, the oscillation interval increased. The oscillation was quenched at 0.47?T. In situ bore-scope observation of the cathode during electrolysis in magnetic fields revealed that the solution convection induced by the Lorentz force causes the observed effect. 相似文献
760.
Martí X Park BG Wunderlich J Reichlová H Kurosaki Y Yamada M Yamamoto H Nishide A Hayakawa J Takahashi H Jungwirth T 《Physical review letters》2012,108(1):017201
We employ antiferromagnetic tunneling anisotropic magnetoresistance to study the behavior of antiferromagnetically ordered moments in IrMn exchange coupled to NiFe. Experiments performed by common laboratory tools for magnetization and electrical transport measurements allow us to directly link the broadening of the NiFe hysteresis loop and its shift (exchange bias) to the rotation and pinning of antiferromagnetic moments in IrMn. At higher temperatures, the broadened loops show zero shift, which correlates with the observation of fully rotating antiferromagnetic moments inside the IrMn film. The onset of exchange bias at lower temperatures is linked to a partial rotation between distinct metastable states and pinning of the IrMn antiferromagnetic moments in these states. The observation complements common pictures of exchange bias and reveals an electrically measurable memory effect in an antiferromagnet. 相似文献