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排序方式: 共有273条查询结果,搜索用时 15 毫秒
91.
The structure of an Al–Rh–Cu decagonal quasicrystal formed with two quasiperiodic planes along the periodic axis in an Al63Rh18.5Cu18.5 alloy has been studied by spherical aberration (Cs)-corrected high-angle annular detector dark-field (HAADF)- and annular bright-field (ABF)-scanning transmission electron microscopy (STEM). Heavy atoms of Rh and mixed sites (MSs) of Al and Cu atoms projected along the periodic axis can be clearly represented as separate bright dots in observed HAADF-STEM images, and consequently arrangements of Rh atoms and MSs on the two quasiperiodic planes can be directly determined from those of bright dots in the observed HAADF-STEM image. The Rh atoms are arranged in pentagonal tiling formed with pentagonal and star-shaped pentagonal tiles with an edge-length of 0.76 nm, and also MSs with a pentagonal arrangement are located in the pentagonal tiles with definite orientations. The star-shaped pentagonal tiles in the pentagonal tiling are arranged in τ2(τ: golden ratio)-inflated pentagonal tiling with a bond-length of 2 nm. From arrangements of Rh atoms placed in pentagonal tilings with a bond-length of 2 nm, which are generated by the projection of a five-dimensional hyper-cubic lattice, occupation domains in the perpendicular space are derived. Al atoms as well as Rh atoms and MSs are represented as dark dots in an observed ABF-STEM image, and arrangements of Al atoms in well-symmetric regions are discussed. 相似文献
92.
A Combined Experimental and Computational Study on the Cycloisomerization of 2‐Ethynylbiaryls Catalyzed by Dicationic Arene Ruthenium Complexes 下载免费PDF全文
Prof. Dr. Yoshihiko Yamamoto Kazuma Matsui Dr. Masatoshi Shibuya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7245-7255
Ruthenium‐catalyzed cycloisomerization of 2‐ethynylbiaryls was investigated to identify an optimal ruthenium catalyst system. A combination of [η6‐(p‐cymene)RuCl2(PR3)] and two equivalents of AgPF6 effectively converted 2‐ethynylbiphenyls into phenanthrenes in chlorobenzene at 120 °C over 20 h. Moreover, 2‐ethynylheterobiaryls were found to be favorable substrates for this ruthenium catalysis, thus achieving the cycloisomerization of previously unused heterocyclic substrates. Moreover, several control experiments and DFT calculations of model complexes were performed to propose a plausible reaction mechanism. 相似文献
93.
Shock wave attenuation in polyurethane foams is investigated experimentally and numerically. This study is a part of research project regarding shock propagation in polyurethane foams with high-porosities
= 0.951 ~ 0.977 and low densities of ρc = 27.6 ~55.8 kg/m3. Sixty Millimeter long cylindrical foams with various cell numbers and foam insertion condition were installed in a horizontal shock tube of 50 mm i.d. and 5.4 mm in length. Results of pressure measurements in air/foam combination are compared with CFD simulation solving the one-dimensional Euler equations. In the case of a foam B fixed on shock tube wall, pressures at the shock tube end wall increases relatively slowly comparing to non-fixed foam, free to move and a foam A fixed on shock tube wall. This implies that elastic inertia hardly contributes to pressure build up. Pressures behind a foam C fixed on shock tube wall decrease indicating that shock wave is degenerated into compression wave. Dimensionless impulse and attenuation factor decrease as the initial cell number increases. The momentum loss varies depending on cell structure and cell number. 相似文献
94.
One-dimensional interaction between a planar shock wave and a rubber or low-porosity foam is investigated experimentally and
numerically. The considered polyurethane foam is of high density (ρ
c=290 kg/m3) and lowporosity (ϕ=0.76), and this corresponds to an intermediate condition between rubber and high-porosity foam. Stress-strain
relations for the low-porosity foam are investigated by machine tests, which show larger deformation against compressive force
and higher non-linearity in stress-strain curve as compared with rubber. Also the low-porosity foam shows a hysteresis cycle.
Experiments on shock wave-foam interactions are conducted by using a shock tube. Experimental time history of the surface
stress of the foam at the end of the shock tube does not show shock type stress increase, but continuous excessive stress
rise can be seen, and then dumping vibration approaching to gas dynamic pressure of the reflected shock wave is followed,
and the highest stress amounts about 3∼4 times of the pressure after the reflected gas dynamic shock wave. Interactive motions
of gas and the low-porosity foam are analyzed using the Lagrangean coordinates system. An elastic model for a low-porosity
foam is assumed to be a single elastic material with the measured stress-strain relation. Results of numerical simulations
are compared with the shock tube experiments, which show essentially same stress variations with experimental results. 相似文献
95.
Ken Hosoya Mari Sakamoto Kunihiko Akai Tomoko Mori Takuya Kubo Kunimitsu Kaya Kazuma Okada Norio Tsujioka Nobuo Tanaka 《Analytical sciences》2008,24(1):149-154
This report describes the development of novel wired chip devices for mu-HPLC analyses. The monolithic capillary column to be wired was prepared using a tri-functional epoxy monomer, tris(2,3-epoxypropyl)isocyanurate with a diamine, 4-[(4-aminocyclohexyl)methyl]cyclohexylamine. The prepared column was evaluated by SEM observation of the sectional structure of column and micro-HPLC. In addition, the reproducibility in the preparation of long capillary columns having nearly 1 m length was extensively examined for applications of novel wired chip devices. The authors demonstrated that the monolithic structure of the prepared long capillary could be finely controlled under the strictly maintained operational conditions and thus the relative standard deviation (RSD) of the column properties such as the number of theoretical plates, retention factor, and permeability could be well controlled to become less than 10%. Furthermore, the wired chip device column showed that its high performance was kept even after chip preparation. 相似文献
96.
A theory of electron correlations giving self-consistently the compressibility and spin susceptibility is formulated within the generalized random-phase approximation. 相似文献
97.
Yousuke Yamaoka Motoki Ueda Tohru Yamashita Kazuma Shimoda Ken-ichi Yamada Kiyosei Takasu 《Tetrahedron letters》2017,58(30):2944-2947
Cyclic ketene silyl acetals were utilized for [2 + 2] cycloaddition with propiolates to prevent an undesired electrocyclic ring opening reaction. Trimethylaluminum catalyzed this cycloaddition to afford the cyclobutene derivatives in high yields. The advantage of this reaction was highlighted by the successful application of β-substituted propiolates to afford the multi-substituted cyclobutenes. Furthermore, we applied this methodology to the late stage functionalization of natural product artemisinin. 相似文献
98.
An optical scanning probe microscope, based on surface plasmon resonance (SPR) in the attenuated total reflection geometry, is shown to successfully image the polarization structures in self-assembled monolayers of hemicyanine adsorbed on a gold surface. Application of an ac field to the tip gives rise to the linear electro-optic effect in the monolayer just below the tip and the local change in the refractive index of the monolayer was detected via the ac component of the reflected light intensity, in which SPR-based detection intensifies the ac component. Polarization structures in a monolayer can be clearly imaged by this technique. 相似文献
99.
Kobayashi K Nishimura Y Gao F Gotoh K Nishihara Y Takagi K 《The Journal of organic chemistry》2011,76(6):1949-1952
Carbonylative homocoupling of arylzinc compounds 1 using 1 atm of CO and 1,2-dibromoethane as an oxidant was achieved in the presence of Rh-dppf catalyst, affording symmetrical diaryl ketones in good yields. Under similar conditions, Pd or Ni catalysts induced oxidative homocoupling of 1 to yield biaryls instead. The beneficial catalysis by Rh in the carbonylation was presumed to stem from the facility by which the migration of the aryl ligand to CO at the Rh(3+) intermediate occurred. 相似文献
100.
Muktar MR Osman N Awang K Hazni H Qureshi AK Hadi AH Zaima K Morita H Litaudon M 《Molecules (Basel, Switzerland)》2011,17(1):267-274
A new indole alkaloid; neonaucline (1), along with six known compounds-Cadamine (2), naucledine (3), harmane, benzamide, cinnamide and blumenol A-were isolated from the leaves of Ochreinauclea maingayii (Rubiaceae). In addition to that of compound 1, (13)C-NMR data of cadamine (2) and naucledine (3) were also reported. Structural elucidations of these alkaloids were performed using spectroscopic methods especially 1D- and 2D-NMR, IR, UV and LCMS-IT-TOF. The excellent vasorelaxant activity on isolated rat aorta was observed for the alkaloids 1-3 after injection of each sample at 1 × 10(-5) M. 相似文献