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991.
Toshihiro Nishiyama Tetsuya Kajimoto Swapnil S. Mohile Noboru Hayama Teppei Otsuda Minoru Ozeki Manabu Node 《Tetrahedron: Asymmetry》2009,20(2):230-234
The first enantioselective synthesis of protected imino-digitoxose (?)-16 was attained starting with a synthetic intermediate of polyoxin C prepared by the l-threonine aldolase-catalyzed aldol condensation of (2S,3S)-2,3-O-isopropyriden-4-penten-1-al 8 and glycine. The strategy took advantage of an intramolecular nucleophilic attack by a Cbz-protected amino group on the hemiacetal carbon, a side reaction in the synthesis of natural products, for the formation of the piperidine ring of the imino-sugar. Imino-deoxydigitoxose (+)-18 was also synthesized from (?)-16 by reduction and acid hydrolysis. 相似文献
992.
Yoshihiko Togawa Ken Harada Tetsuya Akashi Hiroto Kasai Tsuyoshi Matsuda Atsutaka Maeda Akira Tonomura 《Pramana》2006,66(1):279-287
We have investigated the vortex dynamics for the ‘ratchet’ operation in a niobium superconductor via a direct imaging of Lorentz
microscopy. We directly observe one-directional selective motion of field-gradient-driven vortices along fabricated channels.
This results from the rectification of vortices in a spatially asymmetric potential under the oscillating magnetic field in
a temporally symmetric manner. Based on the observation of the individual motion of vortices, we clarify the elementary process
involved in this rectification. 相似文献
993.
We construct a one-parameter family of self-repelling processes on the Sierpiński gasket, by taking continuum limits of self-repelling
walks on the pre-Sierpiński gaskets. We prove that our model interpolates between the Brownian motion and the self-avoiding
process on the Sierpiński gasket. Namely, we prove that the process is continuous in the parameter in the sense of convergence
in law, and that the order of H?lder continuity of the sample paths is also continuous in the parameter. We also establish
a law of the iterated logarithm for the self-repelling process. Finally we show that this approach yields a new class of one-dimensional
self-repelling processes.
Received: 8 March 2001 / Revised version: 30 May 2001 / Published online: 22 August 2002 相似文献
994.
995.
A waveguide optical isolator with a CeY2Fe5O12 guiding layer employing a nonreciprocal phase shift was studied.The isolation ratio of more than 12.2 dB was achieved at a wavelength of 1.55 μm. 相似文献
996.
Reduction of Fringe Noise in Wavelength Modulation Spectroscopy Using a One-Dimensional Focal Plane Array 总被引:1,自引:0,他引:1
Shang-Qian Wu Tetsuya Kimishima Yotsumi Yoshii Hiroaki Kuze Nobuo Takeuchi 《Optical Review》2002,9(5):189-192
In wavelength modulation spectroscopy using diode lasers, detection limit of molecular absorption is often imposed by spurious fringe noises that arise from slight reflections among optical components. In an attempt to reduce this fringe effect, we propose and demonstrate the use of a one-dimensional focal plane array. With the help of a multiplexer, a single lock-in amplifier is employed to obtain multiple-channel signals from wavelength-modulated output of an array detector. It is found that the intensity change of the molecular absorption signal is nearly proportional to the transversal beam intensity distribution, whereas that of fringe noise is much less conspicuous. These features, as well as the phase difference among the channels, contribute to separate the signal and fringe noise components from the multiplexed spectra, leading to the overall improvement in the signal-to-noise ratio. 相似文献
997.
Ken Takaki Kentaro Sonoda Takeshi Kousaka Go Koshoji Tetsuya Shishido Katsuomi Takehira 《Tetrahedron letters》2001,42(52):9211-9214
Divalent lanthanide–imine complexes and a related species catalyzed the hydrosilylation of olefins with phenyl- and diphenylsilane. On the other hand, conjugated dienes were converted to 1,4-bissilyl-2-butenes and 3-silacyclopentenes, accompanied with hydrogen evolution, under similar conditions. 相似文献
998.
This paper considers a class of stationary batch-arrival, bulk-service queues with generalized vacations. The system consists of a single server and a waiting room of infinite capacity. Arrivals of customers follow a batch Markovian arrival process. The server is unavailable for occasional intervals of time called vacations, and when it is available, customers are served in groups of fixed size B. For this class of queues, we show that the vector probability generating function of the stationary queue length distribution is factored into two terms, one of which is the vector probability generating function of the conditional queue length distribution given that the server is on vacation. The special case of batch Poisson arrivals is carefully examined, and a new stochastic decomposition formula is derived for the stationary queue length distribution.AMS subject classification: 60K25, 90B22, 60K37 相似文献
999.
Yu Yao Tetsuya Tsuda Tsukasa Torimoto Susumu Kuwabata 《Chemical record (New York, N.Y.)》2023,23(8):e202200274
Metal nanoparticle-based electrocatalysts are widely used in electronic devices, which serve for electrochemical reactions like oxygen reduction reaction, alcohol oxidation and CO2 reduction reaction. These catalyst-dependent reactions are the key of the emerging clean energy systems. Catalyst design and synthesis therefore have received keen attention in past decades. We are motivated to study synthesis approaches of metal nanoparticle-based electrocatalysts using ionic liquids (ILs), which are promising solvents for the nanoparticle preparation because of their unique physicochemical properties. In this personal account, we review our previous and present works on nanoparticle preparation in IL and utilization of the obtained nanoparticles as electrocatalysts. 相似文献
1000.
Takao Tsuneda Hiroki Sumitomo Masatoshi Hasebe Takuro Tsutsumi Tetsuya Taketsugu 《Journal of computational chemistry》2023,44(2):93-104
It is established that the reactive orbital energy theory (ROET) theoretically reproduces the rule-based electronic theory diagrams of organic chemistry by a comparative study on the charge transfer natures of typical organic carbon–carbon and carbon–heteroatom bond formation reactions: aldol, Mannich, α-aminooxylation, and isogyric reactions. The ROET, which is an expansion of the reaction electronic theories (e.g., the frontier orbital theory) in terms of orbital energies, elucidates the reactive orbitals driving reactions and the charge transferability indices of the reactions. Performing the ROET analyses of these reactions shows that the charge transfer directions given in the rule-based diagrams of the electronic theory are reproduced even for the functional groups of charge transfer destinations in all but only two processes for 38 reaction processes. The ROET analyses also make clear the detailed orbital-based pictures of these bond formation reactions: that is, the use of the out-of-plane antibonding π orbitals in acidic conditions (enol-mode) and in-plane antibonding π orbitals in basic conditions (enolate-mode), which explain the experimentally assumed mechanisms such as the π-bond formations in acidic conditions and σ-bond formations at α-carbons in basic conditions. Furthermore, the ROET analyses explicate that the methyl group initially accepts electrons and then donates them to the bond formations in the target reactions. It is, consequently, suggested that the ROET serves a theoretical foundation for the electronic theory of organic chemistry. 相似文献