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排序方式: 共有286条查询结果,搜索用时 15 毫秒
191.
S. Sato S. Horii J. Shimoyama H. Ogino K. Kishio 《Physica C: Superconductivity and its Applications》2010
Superconducting properties have been systematically studied for oxygen content controlled Y2Ba4O7O15?δ (Y247) polycrystalline bulks sintered under various conditions, 940–975 °C and P(O2) = 4–16 atm. Tc of oxygen annealed Y247 samples at 400 °C varied largely depending on the sintering conditions from ~60 to ~90 K. Samples sintered under higher P(O2) exhibited lower Tc, whereas they were confirmed to be of Y247 single phase by powder X-ray analyses. Strong relationship between orthorhombicity defined as 1000(b ? a)/(a + b) and Tc was found in Y247 as in the cases of REBa2Cu3O7?δ with light rare-earth elements, such as La, Nd, Sm, Eu and Gd. In addition, Tc‘s of samples with nominal compositions of Y2+xBa4?xO7O15?δ systematically decreased with an increase of x. These results indicated that partial substitution of Y for Ba occurred in the Y247 compounds possibly due to high occupancy ratio of oxygen at the Cu–O1-δ chain during the sintering process. 相似文献
192.
R. Kita N. Hosoya N. Otawa S. Kawabata T. Nakamura O. Miura M. Mukaida K. Yamada A. Ichinose K. Matsumoto M.S. Horii Y. Yoshida 《Physica C: Superconductivity and its Applications》2009,469(15-20):1157-1160
We investigated the effects of added Tm2O3, Sc2O3, and Yb2O3 on the superconducting properties of sintered Er123 samples. Tm2O3 addition caused the least Tc degradation, exhibiting a Tc above 90 K even for 17 vol% addition. Samples with added Sc2O3 maintained a Tc at above 90 K up to an addition of 7.2 vol%, while Yb2O3-containing samples showed a monotonic decrease in Tc with increased vol% of added Yb2O3. Tm2O3-containing samples exhibited a slight increase in Jc(0.1 T)/Jc(0) and had constant Jc values even for 17 vol% addition. XRD and SEM results indicate that the Tm2O3 is very stable in the superconducting matrix. 相似文献
193.
Keine Nishiyama Koki Hoshikawa Masatoshi Maeki Akihiko Ishida Hirofumi Tani Manabu Tokeshi 《Electroanalysis》2019,31(9):1736-1743
A concentric ring array electrode that amplifies the current signal without redox cycling has been developed for highly sensitive electrochemical detection at a single potential in a microfluidic platform. Herein, the effect of ring‐electrode width on the current and current density was examined. A ring‐array electrode with widths that decrease from the inner to the outer ring was shown to exhibit the highest sensitivity. This electrode delivered a current density that was approximately 50 % higher than that of a conventionally used disc electrode. We used numerical simulations to further optimize this type of array electrode, which led to a limit of detection for catechol of 6.2 nmol/L. This ring array electrode has great potential for use in a variety of applications because it can be used to detect irreversible targets with a simple apparatus at a single potential and requires no electrode modification to achieve high sensitivity. 相似文献
194.
Saburo Yuasa Kou Sakoda Shinri Aizawa Koki Kitagawa 《Proceedings of the Combustion Institute》2007,31(2):2037-2044
An experimental study was performed on the combustion characteristics of a jet diffusion flame of Mg vapor injected through a small nozzle into CO2 atmospheres at low pressures from 8 to 48 kPa with a view to using Mg as fuel for a CO2-breathing turbojet engine in the Mars atmosphere. The Mg vapor jet produced three types of the flame. At lower pressures and higher injection velocities, a red-heated jet flame formed, in which the injected Mg vapor was heated by spontaneous reactions, turning red. At medium pressures and injection velocities, a stable luminous lifted-like flame developed above the rim of the chimney, a tube-like combustion product for the Mg vapor passage that grew on the nozzle during combustion. The flame had similar flame length properties to laminar jet diffusion flames of gaseous fuels. At higher pressures and lower injection velocities, a stable luminous attached flame developed at the rim of the chimney. The same reactions, producing MgO(g), CO and MgO(c), proceeded preferentially for all flames and chimneys. Carbon was only subordinately generated. Burning behavior of Mg vapor jets in a CO2 atmosphere has been represented, including the homogeneous reaction of Mg vapor with CO2, the diffusion of CO2, and the condensation and deposit of MgO. The injection velocity of Mg vapor at the rim of the chimney and the exothermic reactions with diffused CO2 that occur there play a crucial role in the attachment and development of the flames. The flame structure may be explained in terms of the relatively low gas-phase reaction rate of Mg with CO2. 相似文献
195.
196.
Kimura T Yamamoto N Suzuki Y Kawano K Norimine Y Ito K Nagato S Iimura Y Yonaga M 《The Journal of organic chemistry》2002,67(17):6228-6231
An asymmetric synthesis of (2S)-2-(2-isopropyl)-5-hydroxy-2-phenylpentanenitrile (emopamil left hand, 2) has been completed by use of the MAD (methyl aluminum bis(4-methyl-2,6-di-tert-butylphenoxide)-induced rearrangement of a chiral epoxyalcohol as the key reaction. The stereochemistry of the chiral quaternary center was confirmed by transformation of 2 to (S)-noremopamil. This method requires minimal purification procedures and affords high chemical and optical yields. Acid-catalyzed isomerization of an allylaldehyde and retro-aldol type racemization at the quaternary carbon of a nitrile-alcohol were encountered. 相似文献
197.
198.
Yoshiaki Kimura Akira Ikegami Koki Ohno Satoshi Saigo Yasuaki Takeuchi 《Photochemistry and photobiology》1981,33(4):435-439
Abstract— Suspensions of purple membranes were exposed to reversing rectangular pulses of relatively low electric field (less than 100V/cm) at various frequencies. Orientation of the membranes was estimated by measuring linear dichroism at 565nm. In the electric field of frequency lower than about 10Hz the purple membranes tended to align perpendicular to the electric field. This orientation was induced mostly by permanent dipole which was perpendicular to the membrane surface. The value of permanent dipole moment was determined to be 140D per protein at pH 7.0, 25°C, in the presence of 5m M phosphate buffer.
In an electric field of frequency more than 100Hz the membrane tended to align parallel to the electric field. Electric polarizability parallel to the membrane surface was estimated to be 1 ± 10−12 cm3 under the same conditions.
Electric dichroism of light-adapted and dark-adapted purple membranes was found to coincide with each other at high frequency. From this result the angle of retinal to the membrane surface was concluded to be the same between light-adapted and dark-adapted bacteriorhodopsins. 相似文献
In an electric field of frequency more than 100Hz the membrane tended to align parallel to the electric field. Electric polarizability parallel to the membrane surface was estimated to be 1 ± 10
Electric dichroism of light-adapted and dark-adapted purple membranes was found to coincide with each other at high frequency. From this result the angle of retinal to the membrane surface was concluded to be the same between light-adapted and dark-adapted bacteriorhodopsins. 相似文献
199.
Hiroyuki Akita Akiya Furuichi Hiroko Koshiji Koki Horikoshi Takeshi Oishi 《Tetrahedron letters》1982,23(39):4051-4054
Four functionalized chiral synthons – having high optical purity were prepared by microbiological asymmetric reduction. 相似文献
200.