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排序方式: 共有402条查询结果,搜索用时 156 毫秒
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Further Improvement in Mechanical Properties of Highly Anisotropic Silicon Nitride Ceramics 总被引:1,自引:0,他引:1
Hisayuki Imamura Kiyoshi Hirao Manuel E. Brito Motohiro Toriyama Shuzo Kanzaki 《Journal of the American Ceramic Society》2000,83(3):495-500
Si3 N4 ceramics were fabricated by tape casting of a raw-powder slurry seeded with three types of rodlike β-Si3 N4 particles. The effects of seed size on the microstructure and mechanical properties of the sintered specimens were investigated. All the seeded and tape-cast silicon nitrides presented an anisotropic microstructure, where the elongated grains grown from seeds were preferentially oriented parallel to the casting direction. The orientation degree of these grains, f 0 , was affected by seed size, and small-seed addition led to the highest f 0 value. This material exhibited high bending strength (∼1.4 GPa) and high fracture toughness (∼12 MPa. m1/2 ) in the direction normal to the grain alignment, which were attributed to the highly anisotropic and fine microstructure. 相似文献
76.
Constituents of Amomum tsao-ko and their radical scavenging and antioxidant activities 总被引:1,自引:0,他引:1
Teresita S. Martin Hiroe Kikuzaki Masashi Hisamoto Nobuji Nakatani 《Journal of the American Oil Chemists' Society》2000,77(6):667-673
Constituents of the fruit of Amomum tsao-ko were investigated following a preliminary screening of the antioxidant activity of several extracts of the fruit of this
plant that showed that the dichloromethane extract and the ethyl acetatesoluble and water-soluble fractions of the 70% aqueous
acetone extract had higher activity than α-tocopherol and butylated hydroxytoluene (BHT). Eleven compounds were isolated from
the ethyl acetate-soluble fraction, and their structures were elucidated as (+)-hannokinol (1), meso-hannokinol (2), (+)-epicatechin (3), (−)-catechin (4), β-sitosterol (5), β-sitosterol 3-O-glucoside (6), 2,6-dimethoxyphenol (7), protocatechualdehyde (8), protocatechuic acid (9), vanillic acid (10), and p-hydroxybenzoic acid (11) based on mass and various nuclear magnetic resonance (NMR) spectroscopic techniques. This is the first isolation of epicatechin
and catechin from the genus Amomum. The radical scavenging activity of the isolated compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and colorimetric
and electron spin resonance (ESR) analyses. The antioxidant activity of the compounds was also determined based on the oxidative
stability index (OSI). The catechins and catechol derivatives showed strong activities in both the DPPH radical scavenging
activity and antioxidant activity assays. 相似文献
77.
Yanbai Shen Zhifu Liu Dan Meng Toshio Kikuta Noriyuki Nakatani 《Thin solid films》2009,517(6):2069-3683
WO3 thin films having different effective surface areas were deposited under various discharge gas pressures at room temperature by using reactive magnetron sputtering. The microstructure of WO3 thin films was investigated by X-ray diffraction, scanning electron microscopy, and by the measurement of physical adsorption isotherms. The effective surface area and pore volume of WO3 thin films increase with increasing discharge gas pressure from 0.4 to 12 Pa. Gas sensors based on WO3 thin films show reversible response to NO2 gas and H2 gas at an operating temperature of 50-300 °C. The peak sensitivity is found at 200 °C for NO2 gas and the peak sensitivity appears at 300 °C for H2 gas. For both kinds of detected gases, the sensor sensitivity increases linearly with an increase of effective surface area of WO3 thin films. The results demonstrate the importance of achieving high effective surface area on improving the gas sensing performance. 相似文献
78.
Hiroto Kondo Hideko Yomo Susumu Furukubo Nobuyuki Fukui Kazuo Nakatani Yasutsugu Kawasaki 《Journal of the Institute of Brewing》1999,105(5):293-300
Proteinase A, excreted from yeast cells into beer during fermentation in the brewing process, has been shown to degrade foam-active proteins and to decrease foam stability. In order to improve the measurement of this enzyme in beer, a new fluorescent peptide, MOCAc-Ala-Pro-Ala-Lys-Phe-Phe-Arg-Leu-Lys (Dnp)-NH2, was synthesised and applied to the accurate and rapid estimation of proteinase A in commercial beer and fermenting wort. This novel substrate is several hundred times more sensitive to proteinase A than other previously reported synthetic substrates or native protein substrates. The concentration of proteinase A in beer is closely related to foam stability and proteinase A activity was found to increase gradually during fermentation. The concentration of proteinase A excreted from yeast cells is also closely related to the vitality of pitching yeast cells. This new method was successfully applied to the evaluation of yeast vitality and the development of optimum yeast handling procedures. 相似文献
79.
Incorporation of organic photochromes into magnetic systems not only provides new ways to photo‐control magnetic behavior but may also lead to interesting photochromic behavior. Cationic spiropyrans exhibit this type of behavior depending on whether the structure is open or closed (see Figure). These structures can also be incorporated into rigid layered MnPS3 materials where reversible photo‐switching of magnetic coercivity is observed. 相似文献
80.
Lobna A. Elsadek Dr. James H. Matthews Dr. Shinichi Nishimura Takahiro Nakatani Airi Ito Dr. Tongjun Gu Dr. Danmeng Luo Prof. Lilibeth A. Salvador-Reyes Dr. Valerie J. Paul Prof. Hideaki Kakeya Prof. Dr. Hendrik Luesch 《Chembiochem : a European journal of chemical biology》2021,22(10):1790-1799
Amantelide A, a polyhydroxylated macrolide isolated from a marine cyanobacterium, displays broad-spectrum activity against mammalian cells, bacterial pathogens, and marine fungi. We conducted comprehensive mechanistic studies to identify the molecular targets and pathways affected by amantelide A. Our investigations relied on chemical structure similarities with compounds of known mechanisms, yeast knockout mutants, yeast chemogenomic profiling, and direct biochemical and biophysical methods. We established that amantelide A exerts its antifungal action by binding to ergosterol-containing membranes followed by pore formation and cell death, a mechanism partially shared with polyene antifungals. Binding assays demonstrated that amantelide A also binds to membranes containing epicholesterol or mammalian cholesterol, thus suggesting that the cytotoxicity to mammalian cells might be due to its affinity to cholesterol-containing membranes. However, membrane interactions were not completely dependent on sterols. Yeast chemogenomic profiling suggested additional direct or indirect effects on actin. Accordingly, we performed actin polymerization assays, which suggested that amantelide A also promotes actin polymerization in cell-free systems. However, the C-33 acetoxy derivative amantelide B showed a similar effect on actin dynamics in vitro but no significant activity against yeast. Overall, these studies suggest that the membrane effects are the most functionally relevant for amantelide A mechanism of action. 相似文献