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81.
Kenji Hara Keiji Iwahashi Satoru Takakusagi Kohei Uosaki Masaya Sawamura 《Surface science》2007,601(22):5127-5132
Functionalization of self-assembled monolayer (SAM) of alkanethiolate with metal containing unit is one of the versatile methods to obtain functional surfaces such as heterogeneous catalysts. However, organic molecules that strongly bind to transition metals at SAM terminal are limited. Recently N-heterocyclic carbenes (NHCs) such as cyclic diaminocarbenes have emerged as strongly σ-donating ligands forming a robust bond with broad spectrum of transition metals. In the present study, for the purpose of establishment of a new robust basement for heterogeneous metal catalysts, a SAM of the alkanethiolate terminated with NHC-rhodium(I) complex moiety was prepared by utilizing a newly designed disulfide molecule bearing NHC-metal complex terminals. X-ray photoelectron spectroscopy (XPS) analysis and angle resolved XPS measurement revealed successful formation of the Rh-complex-terminated SAM on a gold substrate. Infrared reflection absorption spectroscopy (IRRAS) analysis suggested that the linker methylene chains connecting the rhodium complex moiety and the gold surface are in a loosely packed structure. This unique chemical species, NHC, would be a promising candidate as a basement for the construction of functional surface. 相似文献
82.
Yasuaki KohamaDaiki Motegi 《Experimental Thermal and Fluid Science》1994,8(4):273-278
Boundary layers that develop over a body in fluid flow are in most cases three-dimensional owing to the spin, yaw, or surface curvature of the body. Therefore, the study of three-dimensional (3D) boundary-layer transition is essential to work in practical aerodynamics. The present investigation is concerned with the problem of 3D boundary layers over a yawed body. A yawed cylinder model that represents the leading edge portion of a swept wing and the mechanism of crossflow instability are investigated in detail using hot-wire velocimetry and a flow visualization technique. As a result, traveling disturbances having frequencies f1 and f2, which differ by about one order of magnitude, are detected in the transition region. The phase velocities and directions of travel of those disturbances are measured. Results for the low-frequency disturbance f1 show qualitative coincidence with results numerically predicted for a crossflow unsteady disturbance. Nameley, F1 travels nearly spanwise to the yawed cylinder and very close to the cylinder wall. The results for the high-frequency disturbance f2 good agreement with the existing experimental results. The 2 disturbance is found to be the high-frequency inflectional secondary instability that appears in 3D boundary layer transition in general. A two-stage transition process, where stationary crossflow vortices appear as the primary instability and a traveling inflectional disturbance is generated as a secondary instability, was observed. Secondary instability seems to play a major role in turbulent transition. 相似文献
83.
Daiki Fujise Kiyomi Tsuji Naoko Fukushima Kohei Kawai Ken-ichi Harada 《Journal of chromatography. A》2010,1217(39):6122-6125
In order to fully understand the role of volatile organic compounds (VOCs) under natural conditions, an adaptable analytical method was developed as the first step. β-Ionone, β-cyclocitral, 2-methyl-1-butanol and 3-methyl-1-butanol were simultaneously analyzed in addition to geosmin and 2-MIB using GC/MS with SPME. The slight modification of a known method allowed the simultaneous detection and quantification of these VOCs. The SIM of the 3-methyl-1-butanol was always accompanied by a shoulder peak, suggesting the presence of two compounds. In order to separate both compounds, the GC/MS conditions were optimized, and the additional peak was identified as 2-methyl-1-butanol by direct comparison of the authentic compound, indicating that the Microcystis strain always produces a mixture of 2-methyl-1-butanol and 3-methyl-1-butanol. Furthermore, it was found that 2-methyl-1-butanol and 3-methyl-1-butanol were predominant in the dissolved fractions. β-Cyclocitral was easily oxidized to provide the oxidation product, 2,6,6-trimethylcyclohexene-1-carboxylic acid, which causes the blue color formation of cyanobacteria as a consequence of acid stress. The intact acid could be satisfactorily analyzed using the usual GC/MS without derivatization. 相似文献
84.
Magneto-optical properties of semimagnetic semiconductors with nanometer-scale structures (nanostructures) are described. Superlattices of the CdTe/Cd1 − xMnxTe and Cd1 − xMnxTe/ZnTe systems and microcrystals of Cd1 − xMnxSe were grown by epitaxy and sputtering methods. These semimagnetic semiconductor nanostructures show remarkably enhanced magneto-optical responses in the optical absorption, the luminescence and the dynamics of the confined excitons. The results are interpreted by the quantum-confined excitonic states interacting with the magnetic ion spins involved in the nanostructures. 相似文献
85.
Daisuke Adachi Kohei Takei Toshihiko Toyama Hiroaki Okamoto 《Applied Surface Science》2007,254(1):299-302
Effects of ZnS:Mn/AlN multilayer structure on luminescent properties of nanostructured (NS) thin-film electroluminescent (TFEL) device of which emission layer is a multilayer composed with ZnS:Mn layers and 0.7-nm-thick AlN interlayers were studied. The bandgap widening and the increased PL efficiency of Mn2+ 3d-3d transitions with a decrease in the ZnS:Mn single-layer thickness down to 5 nm were observed, which is ascribed to quantum confinement effects. Meanwhile, the multilayer with 2-nm-thick ZnS:Mn single-layers shows a drop of PL efficiency, indicating the presence of defective region just on AlN. The tendency of the luminous efficiency of the NS-TFEL device against the ZnS:Mn single-layer thickness is similar to the tendency found in the PL efficiency, indicating the importance of the ZnS:Mn/AlN interface for the device performance. 相似文献
86.
Takako Yamaguchi Kohei Hasegawa Shinichiro Kamino Kanako Miyachi Hiroshi Tominaga Yoshikazu Fujita 《Analytical sciences》2007,23(2):223-226
A simple and highly sensitive spectrophotometric method for the determination of uric acid (UA) was established based on fading of the o-hydroxyhydroquinonephthalein-palladium(II)-hexadecyltrimethylammonium complex. In the determination of UA, Beer's law is obeyed in the range of 0.01-0.20 microg ml(-1), with an effective molar absorptivity at 635 nm, the relative standard deviation being 6.5 x 10(5) dm(3) mol(-1) cm(-1) and 1.5% (n = 5). This method is about 20-times more sensitive than the conventional methods. The method was successfully applied to the assay of UA in human urine. 相似文献
87.
Dr. Shinichiro Fuse Ayako Ikebe Kazuya Oosumi Tomoya Karasawa Keisuke Matsumura Dr. Miho Izumikawa Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Kazuo Shin‐ya Prof. Takayuki Doi Prof. Takashi Takahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9454-9460
An asymmetric total synthesis of ent‐pyripyropene A was achieved by a convergent synthetic route. We used our originally developed TiIII‐catalyzed radical cyclization to construct an AB‐ring portion that consisted of a trans‐decalin skeleton with five contiguous stereogenic centers. The coupling between the AB‐ring and the DE‐ring portions, and a subsequent C‐ring cyclization, led to the total synthesis of ent‐pyripyropene A. An evaluation of the insecticidal activity of ent‐pyripyropene A against two aphid species revealed that ent‐pyripyropene A was 35–175 times less active than naturally occurring pyripyropene A. This result indicated that the biological target of pyripyropene A recognizes the absolute configuration of pyripyropene A. 相似文献
88.
Directing/Protecting‐Group‐Free Synthesis of Tetraaryl‐Substituted Pyrazoles through Four Direct Arylations on an Unsubstituted Pyrazole Scaffold 下载免费PDF全文
Dr. Shinichiro Fuse Taiki Morita Dr. Kohei Johmoto Dr. Hidehiro Uekusa Dr. Hiroshi Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14370-14375
A directing/protecting‐group‐free synthesis of 1,3,4,5‐tetraaryl‐substituted pyrazoles was achieved through four transition metal‐catalyzed direct arylations. Various pyrazoles with four different aryl rings were obtained using readily available reagents from an unsubstituted pyrazole. Two aryl‐substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf=0.68, 0.64), and large Stokes shifts (19000, 15200 cm?1). 相似文献
89.
The effect of boric acid on the vapour liquid equilibrium of aqueous potassium carbonate 总被引:1,自引:0,他引:1
Kohei EndoQue S. Nguyen Sandra E. KentishGeoffrey W. Stevens 《Fluid Phase Equilibria》2011,309(2):109-113
Aqueous potassium carbonate has seen renewed interest as a viable solvent for pre and post combustion carbon capture and storage. However, slow reaction kinetics may require the addition of a rate promoter such as boric acid to improve efficiency. The vapour liquid equilibrium of 30 weight percent potassium carbonate with 0, 3 and 5 weight percent boric acid was investigated at 50 and 70 °C using a dynamic inert gas stripping method. By estimating the boric acid reactions an Electrolyte-NRTL model was able to fit this data and literature results very closely. 相似文献
90.
A cationic Ir(I)-tolBINAP complex catalyzed an enantioselective C-C bond formation initiated by secondary sp(3) C-H bond cleavage adjacent to a nitrogen atom. The reaction of 2-(alkylamino)pyridines with various alkenes gave chiral amines in good yields with high enantiomeric excesses. 相似文献