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排序方式: 共有258条查询结果,搜索用时 15 毫秒
1.
Hidehiro Yoshida Masayasu Kodo Kohei Soga Takahisa Yamamoto 《Journal of the European Ceramic Society》2012,32(12):3103-3114
The sintering behavior of Y2O3 doped with 1 mol% of a trivalent or tetravalent cation was investigated by pressureless sintering in air. Ga3+ or Ge4+-doped Y2O3 bodies exhibited higher relative densities than the undoped Y2O3, while the La3+ or Zr4+-doping suppressed the densification of Y2O3. An interdiffusion experiment was performed on the diffusion couples of polycrystalline Er2O3 and Y2O3 doped with Ni2+ or Zr4+, which are some of the most effective and least effective dopants for the improvement of the sinterability, respectively. The lattice and grain boundary diffusion coefficients of the Er3+ cation in Y2O3 were increased by the Ni2+-doping, but were decreased by the Zr4+-doping. High-resolution transmission electron microscopy observations and nano-probe X-ray energy dispersive spectroscopy analyses confirmed that the dopant cations segregate along the grain boundaries without forming an amorphous phase. The doping effect on the sinterability of Y2O3 must result from the change in the diffusivity in Y2O3. 相似文献
2.
Synthesis of Succinic Gemini Surfactants and the Effect of Stereochemistry on Their Monolayer Behaviors 下载免费PDF全文
Tokuzo Kawase Maiko Kagawa-Ohara Tsunetomo Aisaka Tatsuo Oida 《Journal of surfactants and detergents》2015,18(4):615-627
In this work, succinic gemini surfactants, dl‐ and meso‐2,3‐bis(alkyl)succinic acids (alkyl: C6H13–C13H27), were successfully synthesized by oxidative coupling of enolates of fatty acid tert‐butyl esters with copper(II) bromide followed by treatment with CF3COOH. Focusing on the influence of stereochemistry (dl‐ and meso‐) of succinic geminis, their monolayer behaviors at the air–water interface were explored using surface pressure–area (Π–A) isotherms, the compression modulus of monolayers (εs), and Brewster angle microscope (BAM) analysis. meso‐2,3‐Bis(undecyl)succinic acid showed a unique isotherm where the surface pressure drastically decreased at A = ~0.56 nm2 (Π = 21.9 mN m?1) regardless of compression rates and subphase temperatures, while dl‐isomer showed the common isotherm of gas → liquid‐expanded → liquid‐condensed phase transitions. BAM analysis on meso‐2,3‐bis(undecyl)succinic acid films at the air–water interface showed that small islands of aggregates appear just after the maximum pressure (A = ~0.56 nm2), and on further compression needle‐shaped assemblies appear that can grow in size. It was reasonably concluded that hydrophobic interactions can operate more effectively in meso‐isomers than in dl‐isomers, and that meso‐molecules can “jump up” to cause a transition from monolayer to bilayer. This is the first finding of the “jumping‐up” phenomenon of gemini surfactants having meso‐stereochemistry. 相似文献
3.
Tomoyuki Kawase Kazuhiro Okuda Hiroyuki Kogami Hitoshi Nakayama Masaki Nagata Hiromasa Yoshie 《Journal of materials science. Materials in medicine》2010,21(2):731-739
Our animal implantation studies have demonstrated that, after osteogenic processing, cultured human periosteal sheets form
osteoid tissue ectopically without the aid of conventional scaffolding materials. To improve the osteogenic activity of these
periosteal sheets, we have tested the effects of including a scaffold made of salmon collagen-coated ePTFE mesh. Periosteal
sheets were produced with minimal manipulation without enzymatic digestion. Outgrown cells penetrated into the coated mesh
fiber networks to form complex multicellular layers and increased expression of alkaline phosphatase activity in response
to the osteoinduction. In vitro mineralization was notably enhanced in the original tissue segment regions, but numerous micro-mineral
deposits were also formed on the coated-fiber networks. When implanted subcutaneously into nude mice, periosteal sheets efficiently
form osteoid around the mineral deposits. These findings suggest that the intricate three-dimensional mesh composed of collagen-coated
fibers substantially augmented the osteogenic activity of human periosteal sheets both in vitro and in vivo. 相似文献
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6.
M Kawase M Fujimura Y Morita-Fujimura PH Chan 《Canadian Metallurgical Quarterly》1999,30(2):441-8; discussion 449
BACKGROUND AND PURPOSE: To clarify the relationship between apurinic/apyrimidinic endonuclease (APE/Ref-1), a multifunctional protein in the DNA base excision repair pathway, and delayed neuronal cell death associated with apoptosis, we examined the expression of APE/Ref-1 before and after transient global ischemia in rats. METHODS: Global ischemia was induced by bilateral common carotid artery occlusion and hypotension. Expression of the APE/Ref-1 protein was evaluated by Western blot and immunohistochemical analyses. Apoptosis after global ischemia was observed by DNA electrophoresis and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) staining. RESULTS: Immunohistochemistry showed the nuclear expression of APE/Ref-1 in the control brains. Nuclear immunoreactivity of APE/Ref-1 was significantly decreased 2 days after 10 minutes of ischemia in the hippocampal CA1 subregion. Western blot analysis of a sample from the normal brains showed a characteristic 37-kDa band, which was reduced in the hippocampal CA1 subregion after ischemia. A significant amount of DNA fragmentation was observed at 3 days but not at 1 day after ischemia. Double staining with APE/Ref-1 and TUNEL clearly showed that the neurons that lost APE/Ref-1 immunoreactivity became TUNEL positive. CONCLUSIONS: Our data provide evidence that APE/Ref-1 decreased in hippocampal CA1 neurons after transient global ischemia and that this reduction precedes DNA fragmentation, which is destined to cause apoptosis. Our results suggest the possibility that a decrease of APE/Ref-1 activity and the failure of DNA repair may underlie the mechanism of apoptosis after transient focal ischemia. 相似文献
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8.
Anup K. Ghosh Y. Kawase J.J. Ulbrecht 《International Communications in Heat and Mass Transfer》1985,12(6):687-696
A simple analytical technique for turbulent natural convection heat transfer from an isothermal vertical plate to a power-law fluid is developed. The model is based on the assumption that the turbulent heat transfer rate is controlled by the flow characteristic near the surface in the limit of large Prandtl numbers. The formulation proposed in this work agrees well with the correlations available in the literature. 相似文献
9.
Y. Kawase 《Chemical Engineering Communications》1990,93(1):245-255
A new model for turbulent natural convection heat transfer from an isothermal vertical plate is developed. It is based on a unified energy dissipation rate concept originally proposed by Calderbank and Moo-Young (Chem. Eng. Sci., 16, 39-54 (1961)). The proposed model is developed to include non-Newtonian flow behaviors. The predictions of the model are compared with published experimental and theoretical results. Satisfactory agreement is found and therefore the applicability of the energy dissipation rate concept to natural convection is confirmed. 相似文献
10.
Mass transfer in a slurry bubble column reactor was examined. A theoretical correlation for liquid-phase mass transfer coefficient was developed using a combination of Higbie's penetration theory and the Einstein-Li periodic viscous sublayer model. The proposed correlation predicts that the liquid-phase mass transfer coefficient decreases with an increase of the yield stress of slurries. The measurement of mass transfer rates was conducted in a 40-L bubble column reactor. The slurries containing low-density particles were simulated by aqueous carboxypolmethylene solutions. Satisfactory agreement was found between the proposed correlation and the experimental data. 相似文献