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231.
Futaba DN Hata K Namai T Yamada T Mizuno K Hayamizu Y Yumura M Iijima S 《The journal of physical chemistry. B》2006,110(15):8035-8038
We propose a statistical and macroscopic analysis to estimate the catalyst activity of water-assisted growth (super-growth) of single-walled nanotubes (SWNT) and to characterize SWNT forests. The catalyst activity was estimated to be 84% (+/-6%), the highest ever reported. The SWNT forest was found to be a very sparse material where SWNTs represent only 3.6% of the total volume. This structural sparseness is believed to play a critical role in achieving highly efficient growth. 相似文献
232.
Hexadecanaphthalenes (S,S,S,S,S,S,S,S,S,S,S,S,S,S,S)-4b and (S,S,S,S,S,S,S,R,S,S,S,S,S,S,S)-4b that possess two tetraphenylporphyrins (TPP) on the upper and lower naphthalene rings were synthesized. Long-range exciton-coupled CD in the Soret region of TPP (about 66 A) was observed. [structure: see text] 相似文献
233.
Sasaki T 《Chemical record (New York, N.Y.)》2006,6(1):43-51
This paper reviews our recent work on the photorefractive effect of ferroelectric liquid crystals (FLCs). The photorefractive effect is defined as the optical modulation of the refractive index of a medium as a result of a variety of processes. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon enables the creation of different types of photonic applications. FLCs exhibit fast electric field response, and the orientation of the molecular axis of FLCs changes its direction according to the change in direction of the spontaneous polarization (Ps). When two laser beams interfere in a photoconductive FLC, an orientational grating is formed. The mechanism of the formation of the grating is based on the response of the Ps to the photoinduced internal electric field. The time of formation of the refractive index grating is significantly shorter in FLC materials. 相似文献
234.
The purpose of this study was to examine the potential of diffusion-weighted (DW) three-dimensional (3D) MP-RAGE MRI for diffusion-tensor mapping of the rat brain in vivo. A DW-3D-MP-RAGE (3D-DWI) sequence was implemented at 2.0 T using six gradient orientations and a b value of 1000 s/mm2. In this sequence, the preparation sequence with a "90 degrees RF-motion proving gradient (MPG): MPG-180 degrees RF-MPG-90 degrees RF" pulse train (DW driven equilibrium Fourier transform) was used to sensitize the magnetization to diffusion. A centric k-space acquisition order was necessary to minimize saturation effects (T1 contamination) from tissues with short relaxation time. The image matrix was 128x128x128 (interpolated from 64x64x64 acquisitions), which resulted in small isotropic DW image data (voxel size: 0.273x0.273x0.273 mm3). Moreover, 3D-DWI-derived maps of the fractional anisotropy (FA), relative anisotropy (RA) and main-diffusion direction were completely free of susceptibility-induced signal losses and geometric distortions. Two well-known commissural fibers, the corpus callosum and anterior commissure, were indicated and shown to be in agreement with the locations of these known stereotaxic atlases. The experiment took 45 min, and shorter times should be possible in clinical application. The 3D-DWI sequence allows for in vivo 3D diffusion-tensor mapping of the rat brain without motion artifacts and susceptibility to distortion. 相似文献
235.
236.
Kohta Yamada Nobuaki Sato Takeo Fujino Choong G. Lee Isama Uchida Jan R. Selman 《Journal of Solid State Electrochemistry》1999,3(3):148-153
Syntheses of LiNiO2, LiCo0.5Ni0.5O2, and LiAl0.25Ni0.75O2 as thin films were carried out by electrostatic spray deposition (ESD) onto a gold substrate. Single-phase LiNiO2 film was obtained using a precursor solution of Li(OCOCH3)+Ni(OCOCH3)2/ethanol, and by heating the deposit at 700 °C under an oxygen stream. In the case of cobalt or aluminum doping, Co(NO3)2/ethanol or Al(NO3)3/ethanol were added to the precursor solution in a given ratio. X-ray diffractometry revealed that all films had a crystal
structure of space group R3ˉm; a=2.879, c=14.197 ? for LiNiO2; a=2.844, c=14.152 ? for LiCo0.5Ni0.5O2; a=2.855, c=14.148 ? for LiAl0.25Ni0.75O2 (in hexagonal setting). Although these products were highly porous, it was observed that the average film thickness of LiNiO2 increased almost proportionally with the deposition time. Electrochemical measurements (cyclic voltammetry, charge/discharge
measurement at a constant current) were carried out in organic solutions of LiClO4 (1 mol dm−3 LiClO4/propylene carbonate+ethylene carbonate). The results indicated that thin films fabricated by ESD were electrochemically active
for lithium ion extraction/insertion. The effect of cobalt or aluminum doping on the voltammograms is also described.
Received: 1 April 1998 / Accepted: 23 July 1998 相似文献
237.
In order to clarify the metering characteristics of the fluidic flowmeters employing selfsustained oscillation, the oscillating jets in a feedback oscillator and a target oscillator were visualized and the differential pressures across the jets were measured. 相似文献
238.
The copper(II) triflate- and hafnium(IV) triflate-catalyzed aminomethylation of indole (2) with an N-silyl-N,O-acetal 1 containing a trichloromethyl group provides the primary amine derivative (3a) in modest yield. When 1 equiv of trimethylchlorosilane (TMSCl) was added to the reaction mixture, the reaction proceeded smoothly, and the yield of 3a was dramatically improved (>90%). The use of this catalytic system permitted the introduction of an aminomethyl group onto indoles 2a-h bearing a variety of functional groups, which appears to deactivate the Lewis acid, in 52-92% yields. Hf(OTf)4-doped TMSCl catalyzed the successful aminomethylation of various electron-rich aromatic compounds 4a-j to produce 1-aryl-trichloroethylamine derivatives 5a-j. 相似文献
239.
The present article reviews our latest studies directed to improving gas sensing properties of semiconductor metal oxides, SnO2 and TiO2, by controlling their porous structure in the range of nano- to micro-meter size. Thermally stable mesoporous oxide powders and submicron-size porous thick films were fabricated by a templating method employing supramolecular surfactants or polymethylmethacrylate microspheres and also by a sol–gel process in a polyethylene glycol matrix. Advantages of these methods in improving the sensing properties are overviewed and then remaining problems are discussed. 相似文献
240.
Yoshiro Kobayashi Takeo Taguchi Norio Kanuma Nobuo Ikekawa Jun-ichi Oshida 《Tetrahedron letters》1981,22(43):4309-4312
Two new fluorinated 25-hydroxyvitamin D3 analogs, 26,26,26-trifluoro- 25-hydroxy () and 27-nor-26,26,26-trifluoro-25-hydroxyvitamin D3 (), were prepared from 24-phenylsulfonyl 25,26,27-triorcholest-5-en-3β-yl tetrahydropyranyl ether (). 相似文献