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排序方式: 共有272条查询结果,搜索用时 15 毫秒
131.
Hidetsura Cho Yoshio Nishimura Hiroshi Ikeda Mitsuhiro Asakura Shinji Toyota 《Tetrahedron》2018,74(20):2405-2413
Experimental and theoretical studies on the thermodynamics and properties of 2-substituted 6(4)-methyl-1,4(1,6)-dihydropyrimidine-5-carboxylates were undertaken by 1H NMR measurements and DFT (density functional theory) calculations. The ratios of tautomers a/b of dihydropyrimidines (DPs) 1, 2, and 3 were determined under various conditions to reveal the effects of temperature, solvent, and concentration on the thermodynamic data. The observed results, the free energy differences (ΔG), enthalpy differences (ΔH), and entropy differences (ΔS), are discussed in terms of the molecular structures, dipole moments (DM), and the electrostatic potential maps calculated by the DFT to clarify the nature of the DPs. 相似文献
132.
Dispersion Theory of Liquids Containing Optically Linear and Nonlinear Maxwell Garnett Nanoparticles 总被引:2,自引:0,他引:2
Kai-Erik Peiponen Martti O. A. M#xE;kinen Jarkko J. Saarinen Toshimitsu Asakura 《Optical Review》2001,8(1):9-17
Kramers-Kronig relations and sum rules for effective linear permittivity of the Maxwell Garnett liquid-nanosphere system were obtained using complex analysis and general expression of the effective permittivity. When reflectance from optically linear and nonlinear Maxwell Garnett nanoparticles was calculated it was observed that the reflectance, in the case of attenuated total reflection, depends on the fill fraction of the nanospheres and their nonlinear susceptibility. According to simulations a good sensitivity of the nonlinear contribution on the reflectance can be obtained by using a probe wavelength corresponding to the resonance frequency of the nanosphere system. In Kretchmann#x0027;s configuration it was observed that the surface-plasmon-resonance angle depends on the fill fraction and on the intensity of the incident light. By using reflectance, it is possible to detect optically nonlinear nanospheres in liquids. 相似文献
133.
Kenji Nozaki Jun-Ichi Asakura Masakuni Yoshihara Toshihisa Maeshima 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11-12):1405-1409
Optical rotation values of the polymers of N-vinylcarbazole (VCZ) obtained by a (+)-D-camphor-10-sulfonic acid (DCS) catalyst were found to increase linearly with an increase in the donor numbers of such solvents as 1,2-dichloroethane, dioxane, and tetrahydro-furan and such additives as N,N-dimethylformamide and tetra-methylurea. Asymmetric induction is considered to be caused by a stereoselective fixation of the growing VCZ cation with the optically active DCS anion, and fixation is assisted by nucleophilic solvation. No optically active VCZ polymer was obtained by using p-toluenesulfonic acid as the catalyst and (2s)-N,N′-carbonyl-N-cyclohexyl-aminomethyl pyrolizine as the additive. 相似文献
134.
135.
Reduction kinetics of Pu(IV) by N,N-dimethylhydrazine (NNDMH) were studied by spectrophotometry, and the reduction rate equation
in 3M (mol/dm3) nitric acid was obtained. The reduction properties of NNDMH for U(VI), Np(VI), and Pu(IV) was studied in the mixture solution
of trin-butylphosphate diluted to 30 vol.% by n-dodecane (30% TBP) and 3M nitric acid. It was confirmed that NNDMH selectively
reduce Np(VI) to Np(V) without affecting the valences of U(VI) and Pu(IV) in a few minutes. Numerical simulation indicated
that 99.9% of Np was separated from U and Pu applying NNDMH for a mixer-settler. 相似文献
136.
137.
138.
Fabrication of nanorattles with passive shell 总被引:1,自引:0,他引:1
Chen HM Liu RS Asakura K Lee JF Jang LY Hu SF 《The journal of physical chemistry. B》2006,110(39):19162-19167
This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with Au(core)Ag(shell) nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS). 相似文献
139.
Donghui Guo Yuta Nakagawa Hiroko Ariga Shushi Suzuki Kumiko Kinoshita Takeshi Miyamoto Satoru Takakusagi Kiyotaka Asakura Shigeki Otani S.Ted Oyama 《Surface science》2010,604(17-18):1347-1352
The surface structure of Ni2P (101?0), a model for highly active hydrodesulfurization catalysts, was studied using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) in order to understand the reconstruction of the surface layers. Annealing at 573 K revealed a (1 × 1) LEED pattern which changed to a c(2 × 4) arrangement by further heating to 723 K. Atomic scale STM images were obtained for both the (1 × 1) and c(2 × 4) structures. Bright spots observed in the STM images were interpreted to be due to surface phosphorus atoms and this was supported by a density functional theory (DFT) simulation. Several possible models for the c(2 × 4) reconstructed structures were proposed including a P-dimer defect model, a missing-row model and a missing-row + added-row model. The last model gave the best explanation for the c(2 × 4)structure. The mechanism for the c(2 × 4) reconstruction on the Ni2P (101?0) surface is discussed. 相似文献
140.
Yunzhu Wang Shinya Furukawa Song Song Qian He Hiroyuki Asakura Ning Yan 《Angewandte Chemie (International ed. in English)》2020,59(6):2289-2293
Chemical synthesis of amino acids directly from biomass feedstock is rare. Reported here is a one‐step protocol to convert crude glycerol, from the biodiesel industry, into 43 % alanine over a Ru1Ni7/MgO catalyst. The multifunctional catalytic system promotes glycerol conversion into lactic acid, and then into alanine. X‐ray absorption spectroscopy and scanning transmission electron microscopy revealed the existence of bimetallic RuNi species, whereas density‐functional theory calculations suggested Ni‐doped Ru substantially decreased the Ea of C?H bond dissociation of lactate alkoxide to form pyruvate, which is the rate‐determining step. The catalytic route established in this work creates new opportunities for glycerol utilization and enriches the substrate scope of renewable feedstock to access value‐added amino acids. 相似文献