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71.
The cationic ruthenium catalyst (Cp*RuCl2)2/AgOTf/Ligand promotes the addition reaction of carboxylic acids across olefins without beta-hydride elimination. 相似文献
72.
Takao Fukui 《General Relativity and Gravitation》2003,35(1):121-127
An accelerating flat universe with a variable cosmological term is obtained in the Robertson-Walker metric. The variable cosmological term is defined by the correction terms of the metric tensor field. Simple solutions of the scale factor and the cosmological term are shown. In this model of the universe, the magnitude-redshift relation is analytically studied to see if the model reproduces the tendency of the present observational data. The equation of state parameter is touched. 相似文献
73.
The observation of slow-wave sustained (SW) discharge in a whistler- or helicon-wave range of frequency is made using high-frequency and very-high-frequency bands of rf. The SW discharge occurs at an extremely low rf power and plasma density, which are lower than a capacitive-coupling discharge region. 相似文献
74.
Yamamoto Y Arakawa T Ogawa R Itoh K 《Journal of the American Chemical Society》2003,125(40):12143-12160
In the presence of a catalytic amount of Cp*RuCl(cod), 1,6-diynes chemoselectively reacted with monoalkynes at ambient temperature to afford the desired bicyclic benzene derivatives in good yields. A wide variety of diynes and monoynes containing functional groups such as ester, ketone, nitrile, amine, alcohol, sulfide, etc. can be used for the present ruthenium catalysis. The most significant advantage of this protocol is that the cycloaddition of unsymmetrical 1,6-diynes with one internal alkyne moiety regioselectively gave rise to meta-substituted products with excellent regioselectivity. Completely intramolecular alkyne cyclotrimerization was also accomplished using triyne substrates to obtain tricyclic aromatic compounds fused with 5-7-membered rings. A ruthenabicycle complex relevant to these cyclotrimerizations was synthesized from Cp*RuCl(cod) and a 1,6-diyne possessing phenyl terminal groups, and its structure was unambiguously determined by X-ray analysis. The intermediary of such a ruthenacycle intermediate was further confirmed by its reaction with acetylene, giving rise to the expected cycloadduct. The density functional study on the cyclotrimerization mechanism elucidated that the cyclotrimerization proceeds via oxidative cyclization, producing a ruthenacycle intermediate and subsequent alkyne insertion initiated by the formal [2 + 2] cycloaddition of the resultant ruthenacycle with an alkyne. 相似文献
75.
We propose the novel preparation method, Self-seeding Process, based on the following concept for low temperature crystallization of oxide films. Introduction of desirable inhomogeneity should give lowering of a crystallization temperature through heterogeneous nucleation accompanied with reduced activation energy. We carried out inspection of the above concept through use of PZT films. PZT gel films with the desirable inhomogeneity of microstructure were prepared, and their crystallization behaviors was examined. The PZT film was successfully crystallized at 500°C by the self-seeding process. The single phase (001) oriented PZT film with 0.55 m in thickness was obtained at 550°C for 5 min. The self-seeding process by microstructure control is efficient for the low temperature process of the oxide thin film. 相似文献
76.
Okamura H Kawahara J Nanba T Kimura S Soda K Mizutani U Nishino Y Kato M Shimoyama I Miura H Fukui K Nakagawa K Nakagawa H Kinoshita T 《Physical review letters》2000,84(16):3674-3677
Optical conductivity data of the intermetallic compounds (Fe1-xVx)3Al ( 0=x=0.33) reveal that their density of states around the Fermi energy ( E(F)) is strongly reduced as x is increased. In particular, Fe2VAl ( x = 0.33) has a deep, well-developed pseudogap of 0.1-0.2 eV at E(F) and a small density ( approximately 5x10(20) cm(-3)) of carriers, which is highly unusual for intermetallic compounds. It is shown that the pseudogap results from the band structure of Fe2VAl, rather than from temperature-dependent correlation effects. Based on the present results, we propose a simple model that consistently explains both the semiconductorlike transport and the metallic photoemission results previously observed for Fe2VAl. 相似文献
77.
The interaction of gaussian evanescent light with a single dielectric sphere or ordered dielectric spheres in an attenuated total reflection (ATR) geometry was analyzed by the finite-difference time-domain method. Various aspects of this interaction were investigated in terms of spatial visualizations of light intensity, reflectance vs. wavelength characteristics, the transient behavior of reflectances, and so forth. In the case of a single sphere, it was evident that the whispering gallery mode can be excited in ATR geometries, but such excitation cannot be easily confirmed only through the observation of wavelength-scanned ATR spectra. In the case of a closely packed two-dimensional array of dielectric spheres, it was found that an easy axis and also a difficult axis for light propagation exist.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Phisics and Mombusho Grantin Aid for Scientific Research on Priority Areas “Near-field Nano-optics” Project, sponsored by Japan Society for the Promotion of Science. 相似文献
78.
Yohei Uchiyama Shohei Iwasaki Chiaki Ueoka Takashi Fukui Kenzo Okamoto Masayuki Yamaguchi 《Journal of Polymer Science.Polymer Physics》2009,47(4):424-433
Effect of mixing and processing conditions at T‐die extrusion on the structure and mechanical properties is studied for isotactic polypropylene (PP) containing a small amount of β‐form nucleating agent, N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide. It is found that trigonal β crystals are predominantly formed in the extruded samples containing the nucleating agent irrespective of the mixing and processing conditions, leading to the marked mechanical toughness. On the contrary, the molecular orientation is significantly affected by the mixing and processing conditions. In particular, it should be noted that PP molecules in the extruded sheet which was mixed at high temperature (260 °C) and extruded at low temperature (200 °C) orient perpendicular to the applied flow direction. As a result, the sheet shows anomalous mechanical anisotropy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 424–433, 2009 相似文献
79.
Tatsuya Kubokawa Yoshihiko Konno 《Annals of the Institute of Statistical Mathematics》1990,42(2):331-343
For estimating the power of a generalized variance under a multivariate normal distribution with unknown means, the inadmissibility of the best affine equivariant estimator relative to the symmetric loss is shown, and a class of improved estimators is given. The problem of estimating the covariance matrix is also discussed. 相似文献
80.
Prof. Dr. Yoshihiko Yamamoto Kei-ichiro Nishimura Dr. Shota Mori Dr. Masatoshi Shibuya 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(20):5586-5589
In the presence of a cationic Ru catalyst, 1,6-diynes bearing a terminal styryl moiety underwent [2+2+2] cyclization to produce dehydrobiphenylenes fused with a five-membered ring. Although the cycloadducts were unstable toward purification, their one-pot iodine-mediated ring expansion successfully afforded unprecedented bridged ketone products containing a benzo-fused bicyclo[3.2.1] framework. 相似文献