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91.
J. Kobayashi 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):379-390
Classical molecular dynamics and Metropolis Monte Carlo simulations were carried out to investigate the thermal stability and melting behaviors of free-standing Pd-Pt bimetallic nanowires (NWs) with pentagonal multi-shell-type (PMS-type) structure in the whole composition range. Equilibrium configurations at 100 K are predicted in the semi-grand canonical ensemble. Pd-Pt PMS-type NWs are stable with a multishell structure of alternating Pd and Pt compositions and Pd segregating systematically to the surface. On thermal heating, an interesting composition-dependent structural transformation from the PMS-type to face-centred-cubic (FCC) by overcoming a high energy barrier is observed for Pd-Pt bimetallic NWs before the melting. Consequently, the system energy is decreased. The FCC structure is found more stable than PMS-type over the whole range of composition. The melting of Pd-Pt bimetallic NWs is also studied. It is found to start at the edges, then propagate over the whole surface, and next to the interior. It occurs in a composition-dependent range of temperature. 相似文献
92.
Yamamoto Y Terui N Tachiiri N Minakawa K Matsuo H Kameda T Hasegawa J Sambongi Y Uchiyama S Kobayashi Y Igarashi Y 《Journal of the American Chemical Society》2002,124(39):11574-11575
Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability. 相似文献
93.
Manabe K Iimura S Sun XM Kobayashi S 《Journal of the American Chemical Society》2002,124(40):11971-11978
Dehydration reactions in water have been realized by a surfactant-type catalyst, dodecylbenzenesulfonic acid (DBSA). These reactions include dehydrative esterification, etherification, thioetherification, and dithioacetalization. In these reactions, DBSA and substrates form emulsion droplets whose interior is hydrophobic enough to exclude water molecules generated during the reactions. Detailed studies on the esterification revealed that the yields of esters were affected by temperature, amounts of DBSA used, and the substrates. Esters were obtained in high yields for highly hydrophobic substrates. On the basis of the difference in hydrophobicity of the substrates, unique selective esterification and etherification in water were attained. Furthermore, chemospecific, three-component reactions under DBSA-catalyzed conditions were also found to proceed smoothly. This work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water. 相似文献
94.
Ito S Nomura A Morita N Kabuto C Kobayashi H Maejima S Fujimori K Yasunami M 《The Journal of organic chemistry》2002,67(21):7295-7302
The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement. 相似文献
95.
96.
Lembehsterols A and B,novel sulfated sterols inhibiting thymidine phosphorylase,from the marine sponge Petrosia strongylata 总被引:1,自引:0,他引:1
Aoki S Naka Y Itoh T Furukawa T Rachmat R Akiyama S Kobayashi M 《Chemical & pharmaceutical bulletin》2002,50(6):827-830
Lembehsterols A (1) and B (2), two novel sulfated sterols, were isolated from the marine sponge Petrosia strongylata. Both sterols showed inhibitory activity against thymidine phosphorylase, which is an enzyme related to angiogenesis in solid tumors. The structures of these sulfated sterols were established on the basis of chemical and physicochemical evidence. 相似文献
97.
To investigate influences of gravity on mobility of wheeled rovers for future lunar/planetary exploration missions, model experiments of a soil-wheel system were performed on an aircraft during variable gravity maneuvers. The experimental set-up consists of a single rigid wheel and a soil bed with two kinds of dry sands: lunar soil simulant and Toyoura sand. The experimental results revealed that a lower gravity environment yields higher wheel slippage in variable gravity conditions. In addition to the partial gravity experiments, the same experiments with variable wheel load levels were also performed on ground (1 g conditions). The on-ground experiments produced opposite results to those obtained in the partial gravity experiments, where a lower wheel load yields lower slippage in a constant gravity environment. In low gravity environments, fluidity (flowability) of soil increases due to the confining stress reduction in the soil, while the effect of the wheel load on sinkage decreases. As a result, both of these effects are canceled out, and gravity seemingly has no effect on the wheel sinkage. In the meantime, in addition to the effect of wheel load reduction, the increase of the soil flowability lessens the shear resistance to the wheel rotation, as a result of which the wheel is unable to hold sufficient traction in low gravity environments. This suggests that the mobility of the wheel is governed concurrently by two mechanisms: the bearing characteristics to the wheel load, and the shearing characteristics to the wheel rotation. It appears that, in low gravity, the wheel mobility deteriorates due to the relative decrease in the driving force while the wheel sinkage remains constant. Thus, it can be concluded that the lunar and/or Mars’ gravity environments will be unfavorable in terms of the mobility performance of wheels as compared to the earth’s gravity condition. 相似文献
98.
Akasaka T Maeda Y Wakahara T Mizushima T Ando W Walchli M Suzuki T Kobayashi K Nagase S Kako M Nakadaira Y Fujitsuka M Ito O Sasaki Y Yamamoto K Erata T 《Organic letters》2000,2(17):2671-2674
[reaction: see text]In the photochemical bis-germylation of C60 with 1,1,2,2-tetrakis(2,6-diethylphenyl)-1,2-digermirane (1), a cycloadduct (2) is obtained in high yield for the first time. Spectroscopic analysis and theoretical investigation confirm that 2 (which has C1 symmetry) results from 1,4-cycloaddition. Control experiments and laser flash photolysis experiments suggest that an exciplex intermediate is responsible for the formation of 2. The redox properties of 2 were examined by differential pulse voltammetry. 相似文献
99.
Jinhua Hong Shunsuke Kobayashi Akihide Kuwabara Yumi H. Ikuhara Yasuyuki Fujiwara Yuichi Ikuhara 《Molecules (Basel, Switzerland)》2021,26(12)
Solid electrolytes, such as perovskite Li3xLa2/1−xTiO3, LixLa(1−x)/3NbO3 and garnet Li7La3Zr2O12 ceramic oxides, have attracted extensive attention in lithium-ion battery research due to their good chemical stability and the improvability of their ionic conductivity with great potential in solid electrolyte battery applications. These solid oxides eliminate safety issues and cycling instability, which are common challenges in the current commercial lithium-ion batteries based on organic liquid electrolytes. However, in practical applications, structural disorders such as point defects and grain boundaries play a dominating role in the ionic transport of these solid electrolytes, where defect engineering to tailor or improve the ionic conductive property is still seldom reported. Here, we demonstrate a defect engineering approach to alter the ionic conductive channels in LixLa(1−x)/3NbO3 (x = 0.1~0.13) electrolytes based on the rearrangements of La sites through a quenching process. The changes in the occupancy and interstitial defects of La ions lead to anisotropic modulation of ionic conductivity with the increase in quenching temperatures. Our trial in this work on the defect engineering of quenched electrolytes will offer opportunities to optimize ionic conductivity and benefit the solid electrolyte battery applications. 相似文献
100.