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排序方式: 共有148条查询结果,搜索用时 15 毫秒
1.
Tsuneaki Matsudaira Masashi Wada Naoki Kawashima Miyuki Takeuchi Daisaku Yokoe Takeharu Kato Masasuke Takata Satoshi Kitaoka 《Journal of the European Ceramic Society》2021,41(5):3150-3160
Mass transfer in polycrystalline Yb2SiO5 wafers with precise composition control was evaluated and analyzed by oxygen permeation experiments at high temperatures using an oxygen tracer. Oxygen permeation proceeded due to mutual grain boundary diffusion of oxide ions and Yb ions without synergistic effects such as acceleration or suppression. The oxygen shielding properties of Yb2SiO5 were compared with those of the other line compounds such as Yb2Si2O7 and Al2O3 based on the determined mass transfer parameters. It was found that the more preferentially an oxide ion diffuses in the grain boundary compared to the interior of the grain, the greater the effect of suppressing the movement of the oxide ion by applying an oxygen potential gradient becomes. 相似文献
2.
Gong-Liang Li Ishihara Tatsumi Moro-oka Yoshihiko Takita Yusaku 《Applied catalysis. B, Environmental》1996,9(1-4):239-249
The catalytic decomposition of CHClF2 was studied over various acidic metal oxides in a fixed-bed reactor. The Cr2O3ZrO2 exhibited the highest activity. The presence of water vapor in the reaction system suppresses the transformation of oxides to fluorides, progresses the formation of CO2, and it improves the catalysts life. 相似文献
3.
The hydrothermal treatment of two different wood biomass samples such as cherry (hard wood) and cypress (soft wood), whose composition is different i.e. lignin, cellulose and hemicellulose were performed at 280 °C for 15 min with aq. K2CO3 with different concentrations (0–1 M). The soft wood biomass contains higher lignin content than hard wood biomass. The cellulose rich cherry wood biomass produced higher proportion of acetic acid than cypress. The lignin rich cypress produced the hydrocarbons with major portion of phenolic hydrocarbons and derivatives than cherry. The total oil yields from both cherry and cypress wood biomass produced 50 wt% of liquid hydrocarbons at 280 °C for 15 min with 0.5 M K2CO3 solution. The volatility distribution of liquid hydrocarbons showed the characteristic features of soft and hard wood biomasses. 相似文献
4.
Villin 14T, a representative domain from the actin severing and bundling protein villin, binds calcium ions and actin monomers. To begin to understand the contributions of mobility to the villin-calcium and villin-actin interactions, relaxation rates for magnetization involving the amide nitrogens and protons have been measured for 15N-labeled villin 14T in solution. Although we have measured the complete set of rates required for a full spectral density map, difficulties in the accurate measurement of relaxation rates for antiphase coherence and two-spin order led us to consider a reduced mapping formalism. From the reduced spectral density map, a model-free analysis, or directly from the measured Nx,y relaxation rates, local variations in mobility along the backbone of villin 14T have been revealed. Fast motions are evident not only at the amino and carboxyl termini but also in the turn between strands beta 4 and beta 5 of the central beta-sheet and in the turn between helix alpha 3 and strand beta 7. Slower motions are suggested for the turn between strands beta 2 and beta 3. Motions on the microsecond to millisecond time scale have been probed directly by examining the dependence of the proton transverse relaxation rate on the spin-locking field strength. Leu11 shows a strong dependence on field strength, implying conformational exchange with a time constant of 125 +/- 69 microseconds. The backbone at the actin-binding interface appears to be rather rigid. 相似文献
5.
Hideaki Itoh Shigeharu Naka Tsuneaki Matsudaira Hiroshi Hamamoto 《Journal of Materials Science》1990,25(1):533-536
A sintered compact of titanium diboride (TiB2) was prepared by hot pressing of the synthesized TiB2 powder, which was obtained by a solid-state reaction between TiN and amorphous boron. Densification of the sintered compact occurred at 20 MPa and 1800° C for 5 to 60 min with the aid of a reaction sintering, including the TiB2 formation reaction between excess 20 at % amorphous boron in the as-synthesized powder (TiB2 + 0.2B) and intentionally added 10 at % titanium metal. A homogeneous sintered compact of a single phase of TiB2, which was prepared by hot pressing for 30 min from the starting powder composition [(TiB2 + 0.2B) + 0.1 Ti], had a fine-grained microstructure composed of TiB2 grains with diameters of 2 to 3 m. The bulk density was 4.47 g cm–3, i.e. 98% of the theoretical density. The microhardness, transverse rupture strength and fracture toughness of the TiB2 sintered compact were 2850 kg mm–2, 48 kg mm–2 and 2.4 MN m–3/2, respectively. The thermal expansion coefficient increased with increasing temperature up to 400° C and had a constant value of 8.8 x 10–6 deg–1 above 500° C. 相似文献
6.
Hideaki Itoh Tsuneaki Matsudaira Shigeharu Naka Hiroshi Hamamoto 《Journal of Materials Science》1989,24(2):420-424
TiB2 powder was synthesized by a controlled formation reaction from titanium metal and amorphous boron. Precursory TiB2 formed by the pretreatment of the mixed powder (mole ratio: B/Ti=2.0) at 600° C for 60 min in an argon stream. Hollow TiB2 powder with an average grain size of 15m was obtained by subsequent heat treatment above 900° C for more than 60 min in an argon stream. The formation reaction of TiB2 powder was further controlled by pretreatment of the mixed powder at 600° C for 60 min in a hydrogen and argon stream and subsequent heat treatment at 1000° C for 360 min in an argon stream, when hollow-free TiB2 powder was formed by a milder formation reaction between amorphous boron and the reformed titanium metal with hydrogen diffused lattice. 相似文献
7.
Zhaoxia Song Hiroyasu Nishiguchi Wei Liu Hiroshi Yamada Akihide Takami Kumiko Kudo Katsutoshi Nagaoka Yusaku Takita 《Catalysis Letters》2006,111(3-4):169-171
Redox properties of CeO2 and Pt-Rh/CeO2 were studied by temporal analysis of products (TAP) method using alternative pulses of CO and O2. A portion of pulsed CO was oxidized to CO2 and a portion of CO was adsorbed on the surface. Pulsing 18O2 onto the catalyst which has surface species derived from CO, evolved CO2 contained no 18O suggesting that the surface species will be carbonate ions. 相似文献
8.
Yusaku Takita Jun-ichi Moriyama Hiroyasu Nishiguchi Tatsumi Ishihara Fusakazu Hayano Tetsuo Nakajo 《Catalysis Today》2004,88(3-4):103-109
Activity for hydrolysis of CCl2F2 (CFC12) on various metal sulfate was investigated. Zr(SO4)2 was found to be the most active while FeSO4, Cr2(SO4)3, Al2(SO4)3, La2(SO4)3 and Ce2(SO4)3 had intermediate activity. MnSO4, CoSO4, and MgSO4 showed low activity and SrSO4, CaSO4, and BaSO4 had even less activity. The major carbon containing product was CO2 and small amount of CClF3 and CO were formed over several sulfates. The crystal structure of the sulfates was stable during decomposition of CCl2F2, and the conversion reached a steady state after initial decrease at 275 °C over Zr(SO4)2 catalyst. The concentration of surface hydroxyl was larger than that over AlPO4-based catalysts and a reaction mechanism similar to that over AlPO4-based catalysts was proposed. 相似文献
9.
10.
Salas-Solano O Schmalzing D Koutny L Buonocore S Adourian A Matsudaira P Ehrlich D 《Analytical chemistry》2000,72(14):3129-3137
We have examined the parametric performance of short microfabricated electrophoresis devices that operate with a replaceable linear poly(acrylamide) (LPA) solution for the application of DNA sequencing. A systematic study is presented of the dependence of selectivity, separation efficiency, and resolution of sequencing fragments on buffer composition, LPA concentration, LPA composition, microdevice temperature, electric field, and device length. A specific optimization is made for DNA sequencing on 11.5-cm devices. Using a separation matrix composed of 3.0% (w/w) 10 MDa plus 1.0% (w/w) 50 kDa LPA, elevated microdevice temperature (50 degrees C), and 200 V/cm, high-speed DNA sequencing of 580 bases on standard M13mp18 was obtained in only 18 min with a base-calling accuracy of 98.5%. Read lengths of 640 bases at 98.5% accuracy were achieved in approximately 30 min by reducing the electric field strength to 125 V/cm. We believe that this constitutes matrix-limited performance for microdevices of this length using LPA sieving matrix and this buffer chemistry. In addition, it was confirmed, that shorter devices are rather impractical for production sequencing applications when LPA is used as sieving matrix. 相似文献