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991.
Sota Akiyama Koji Kubota Malte S. Mikus Paulo H. S. Paioti Filippo Romiti Qinghe Liu Yuebiao Zhou Amir H. Hoveyda Hajime Ito 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12126-12131
The first catalytic method for diastereo‐ and enantioselective synthesis of allylic boronates bearing a Z‐trisubstituted alkenyl fluoride is disclosed. Boryl substitution is performed with either a Z‐ or E‐allyldifluoride and is catalyzed by bisphosphine/Cu complexes, affording products in up to 99 % yield with >98:2 Z/E selectivity and 99:1 enantiomeric ratio. A variety of subsequent modifications are feasible, and notable examples are diastereoselective additions to aldehydes/aldimines to access homoallylic alcohols/amines containing a fluorosubstituted stereogenic quaternary center. 相似文献
992.
Katsuhisa Tanaka Koji Fujita Hajime Hojo 《Journal of magnetism and magnetic materials》2009,321(7):818-821
We have synthesized thin films of disordered zinc ferrite (ZnFe2O4) and ilmenite-hematite (FeTiO3-Fe2O3) solid solution, the former and the latter of which are interesting from the viewpoints of magnetooptics and spintronics, respectively, by utilizing sputtering and pulsed laser deposition methods, and have explored their magnetic, magnetooptical, and electrical properties. Although ZnFe2O4 possesses a normal spinel structure as its stable phase, some of the Fe3+ ions occupy the tetrahedral as well as the octahedral sites in ZnFe2O4 of which the sputtered thin film is composed. Consequently, the as-deposited thin film manifests large magnetization even at room temperature although the magnetic phase transition temperature of the stable phase of ZnFe2O4 is as low as 10 K. Also, the thin film exhibits a cluster spin glass transition at a temperature as high as 325 K. Furthermore, the ZnFe2O4 thin films exhibit large Faraday effects at a wavelength of 400 nm or so. The ilmenite-hematite solid solution is one of the ferrimagnetic semiconductors. Most of the compositions possess Curie temperatures higher than room temperature, and the type of carrier can be tuned only by changing the composition. We have succeeded in synthesizing solid-solution thin films of various compositions grown epitaxially on sapphire substrates with a (0 0 0 1) plane, and have shown that the thin films are ferrimagnetic semiconductors. 相似文献
993.
Bin Chen Jun Chen Takashi Sekiguchi Takasumi Ohyanagi Hirofumi Matsuhata Akimasa Kinoshita Hajime Okumura Filippo Fabbri 《Superlattices and Microstructures》2009,45(4-5):295-300
The electrical activities of stacking faults (SFs) and partial dislocations in 4H-SiC homoepitaxial films were investigated by using the electron-beam-induced current (EBIC) technique. The basal plane dislocation was dissociated into Si(g) 30° and C(g) 30° partials under electron-beam irradiation, with a SF formed in between. The SF shows bright contrast at RT and dark contrast at 50 K in EBIC images. The reasons were discussed according to the quantum-well state of SF. C(g) 30° partial is always more electrically active than Si(g) 30° partial at each specific accelerating voltage. The EBIC contrasts of those two partials were discussed with the number of recombination centers. 相似文献
994.
Yoshiaki Nakajima Hajime Inaba Atsushi Onae Takao Kobayashi Hirokazu Matsumoto 《Optics Communications》2008,281(17):4484-4487
We report a method for optimizing the amplification of femtosecond optical pulses by using dispersion management. The amount of dispersion provided to the seed optical pulse of an erbium-doped fiber (EBF) has an optimal region that enhances the output power of an amplifier. The power enhancement is accompanied by spectral broadening, which originates from adiabatic narrowing in the erbium-doped fiber. The amplified optical pulses can be used to generate an octave-spanning optical frequency comb (OFC) by employing a highly nonlinear fiber (HNLF). 相似文献
995.
Toyoda M Kugo H Shimizu T Takahashi D 《The Journal of the Acoustical Society of America》2008,123(2):825-831
Many studies on the sound transmission through a single plate have been carried out theoretically and experimentally. The transmission-loss characteristics, in general, follow mass law. Therefore, increasing mass of a plate is a fundamental measure to improve the insulation performance. This method, however, has limitations and might not be a reasonable alternative in current standards. Furthermore, the transmission loss at the critical frequency of coincidence is deteriorated significantly even if the mass is rather large. In this paper, the effect of the air-layer-subdivision technique is studied in detail from the viewpoint of the sound transmission problem of a single plate. An analytical model of an infinite single plate with a subdivided layer is considered and the improvement of the transmission loss is estimated. The limitations of the technique are clarified with some parametric studies. In order to validate the predictions, an experiment was carried out. The transmission loss of a glass board with the air layer subdivided by acryl partitions was measured in the experiment. They were in good agreement with the theoretical ones near and above the coincidence. 相似文献
996.
The one-pot Robinson annelation from 2-methyl-cyclohexane-1,3-dione with 3-buten-2-one can be achieved in high yield (95%) and high selectivity (95%) by pressure and temperature manipulation using supercritical carbon dioxide in the presence of MgO catalyst, whose method could be applied for various ketones to synthesize fused polycyclic compounds. 相似文献
997.
Kazuo Kamigaki Masatoshi Shono Hajime Yoshida Shunya Abe Takejiro Kaneko 《Journal of magnetism and magnetic materials》1987,70(1-3):218-220
Magnetic susceptibility and crystal structure were studied on CrSb1−xAs0.6, structural transformation occurs between MnP-type and NiAs-type at 270 K, the Néel temperature is 300 K. Paramagnetic moments of the system are 2.45−2.7μB/Cr, considerably larger than antiferromagnetic moments. 相似文献
998.
The constructive functional calculus for a sequence of commuting selfadjoint operators on a separable Hilbert space is shown to be independent of the orthonormal basis used in its construction. The proof requires a constructive criterion for the absolute continuity of two positive measures in terms of test functions. Mathematics Subject Classification: 03F60, 46S30, 47S30. 相似文献
999.
H Inagawa F Saitoh M Iguchi T Nishizawa T Okutomi A Morikawa G I Soma D Mizuno 《Chemical & pharmaceutical bulletin》1992,40(4):998-1000
Protective effect of lipopolysaccharide (LPS) from various sources on gastric ulcer has been examined in mice using parenteral as well as oral route. Ulcer is induced by indomethacin, stress or alcohol. LPS was prepared from 6 species of bacteria (Escherichia coli, Pantoea agglomerans, Serratia ficaria, Enterobacter cloacae, Bordetella pertussis, Alcaligenes faecalis) and from wheat flour. When administered intravenously, LPS of Pantoea agglomerans was the most effective among other LPS examined. Lipopolysaccharide of wheat flour (LPSw) showed a significantly protective effect by the oral route, especially when given ad libitum in drinking water to mice. 相似文献
1000.