Electrical and mechanical properties of ZrO2(2Y)/TiN composites and laminates made from these materials

High density composites with the compositions of ZrO₂(2Y):TiN=40:60 and 70:30 mol% have been fabricated by hot isostatic pressing for 2 h at 1500°C and 196 MPa. The electrical resistivities (ρ) of the two composites are very different; showing metallic behaviour in the first case and insulating behaviour in the latter case. These properties are highly dependent on the sample texture. Laminated materials with compositions of ZrO₂(2Y)/TiN=(40:60)/(70:30)/(40:60) mol% have been prepared by hot isostatic pressing. The electrical resistivities in the perpendicular and parallel to the interface directions have been determined to be ρ⊥≈1×109 and ρ∥≈ 1×10^-6 Ωm, respectively. A residual stress of as much as ≈ 150 MPa is induced in the interfaces. The fracture toughness is greatly affected by the residual stress. This revised version was published online in November 2006 with corrections to the Cover Date.     

Crystallization and Transformation of Distorted Tetragonal YNbO4

Distorted tetragonal YNbO₄ crystallizes from an amorphous material prepared by the simultaneous hydrolysis of yttrium and niobium alkoxides. It can be preserved at room temperature by quenching and has a unit cell with α=0.5164 nm and c= I,0864 nm. The structure contains tetrahedral NbO⁴ groups.     

X-Ray Photoelectron Spectroscopy Analysis of Antiwear Tribofilms Produced on Boundary-Lubricated Steel Surfaces from Sulfur- and Phosphorus-Containing Additives and Metal Deactivator Additive

X-ray photoelectron spectroscopy (XPS) was performed on AISI 52100 steel surfaces subjected to sliding in the boundary lubrication regime at 32 and 100°C. The specimens were lubricated with base oil blended with individual additives containing sulfur (S), phosphorus (P), or metal deactivator, as well as base oil with all the previous additives in the same amounts as in the single blends. XPS spectra were analyzed to confirm the formation and determine the chemical composition of the antiwear tribofilms produced on the steel surfaces during sliding. The use of S- and P-containing additives on the tested disk surfaces revealed that tribochemical reactions resulted in the formation of antiwear tribofilms containing S- and P-rich components. Results for the multi-additive blend provided evidence for two components in the produced tribofilm, appearing to consist primarily of sulfide and phosphate. This investigation provides new insight into the competing roles of these compounds on the tribological properties of the antiwear tribofilms. The significance of the sulfide components is demonstrated by the more pronounced antiwear effect of the S-containing additive in the multi-additive formulation.     

Visible light responsive photocatalysts developed by substitution with metal cations aiming at artificial photosynthesis

To solve resource, energy, and environmental issues, development of sustainable clean energy system is strongly required. In recent years, hydrogen has been paid much attention to as a clean energy. Solar hydrogen production by water splitting using a photocatalyst as artificial photosynthesis is a promising method to solve these issues. Efficient utilization of visible light comprised of solar light is essential for practical use. Three strategies, i.e., doping, control of valence band, and formation of solid solution are often utilized as the useful methods to develop visible light responsive photocatalysts. This mini-review introduces the recent work on visible-light-driven photocatalysts developed by substitution with metal cations of those strategies.     

Ordering Mechanisms in Li Ferrites

This paper describes the ordering mechanisms observed in Li ferrite powder samples with different particle sizes and aggregation states, as well as in sintered pellets. Measurement of ordering rates in the powder samples and observation of chemically etched surfaces of partially ordered pellets indicate that the ordering proceeds by a nucleation-growth mechanism and that the ordering initiates at grain boundaries and prevails into the inner part of the grains. In powder samples, surfaces as well as grain boundaries contribute to the initiation of ordering but their temperature dependences are different. The activation energy of the ordering is calculated to be 192 kj/mol.     

Determination of Tetrodotoxin by Capillary Isotachophoresis

A method is described for the quantification of tetrodotoxin (TTX) in crude extracts of puffer fish by capillary isotachophoresis. Conditions for isotachophoresis consisted of a leading electrolyte of 5 mM potassium acetate, pH 6.0, containing 0.2% Triton X-100 and 0.5 vol of dioxane, and a terminating electrolyte of 10 mM β-alanine adjusted to pH 4.5 with acetic acid. It was possible to quantify the TTX content of crude unfractionated puffer extracts, and obtain values similar to those obtained by mouse bioassays which are time consume.     

Determination of Hypoxanthine in Fish Meat with an Enzyme Sensor

An enzyme sensor specific for hypoxanthine (Hx) was developed using immobilized xanthine oxidase-membrane and an oxygen probe. Xanthine oxidase (E.C. 1.2.3.2.) was covalently immobilized on a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane, and glutaraldehyde. Hx is oxidized to uric acid by the immobilized enzyme, the output current of the oxygen probe decreasing due to oxygen consumption. A linear relationship was obtained between current decrease and Hx concentration in the range 0.06–1.5 mM. The enzyme sensor could be used for more than 100 assays without decrease of output current After 30-day-storage at 5°C, no remarkable decrease of output current was observed. The enzyme sensor system was applicable to the simple, rapid, and economical determination of Hx in several fish meats including sea bass, saurel, mackerel, yellowfish, and flounder.     

基于自然对流PCR与毛细管电泳技术的牙周病原菌检测

细菌种类的快速识别在牙病防治中具有重要的应用价值。以牙周病原菌为研究对象,建立了DNA快速扩增的自然对流聚合酶链式反应(PCR)方法及毛细管电泳荧光光学检测系统。研究表明,当毛细管有效长度为8cm、电场强度为100V/cm时,50bp DNA ladder在筛分介质为0.5%HEC(羟乙基纤维素)(1 300K)中的分离效果最佳。毛细管电泳结果表明,采用自然对流法可以在25min内在圆柱腔体中实现牙周病原菌的快速PCR。     

可见光固化树脂的研究

本文介绍了一种新型的可见光固化(VLC)树脂,通过与一般过氧化物固化的乙烯基酯树脂的机械性能和耐腐蚀性能比较可以看出,两者性能相当。但使用可见光,而非对人体有害的紫外光,安全环保,应用广泛;快速固化,苯乙烯挥发极少,操作简便,无需繁琐的添加促进剂及固化剂和脱泡过程。提高生产效率的同时,大幅度降低施工成本。     

PURIFICATION AND CHARACTERIZATION OF ENDOPROTEASES FROM FRUIT BODY OF 'SHIMEJI'MUSHROOM, Lyophyllum aggregatum

Two proteolytic enzymes, L.a. protease I and II, were purified from the fruit body of 'shimeji'mushroom, Lyophyllum aggregatum, by ammonium sulfate precipitation, gel filtration, hydrophobic chromatography and ion-exchange chromatography. The enzymes were assayed using t-butyloxycarbonyl-Ala-Ala-Pro-Phe p-nitroanilide as a substrate. Each of the final enzyme preparations was homogeneous on polyacrylamide gel electrophoresis. The molecular weights of the enzymes were estimated as 44,000 and 46,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzymes had the same optimal pH range of 7–8. Protease I preferentially hydrolyzed peptide bonds of the carboxyl-terminal sides of phenylalanine and leucine, and slowly hydrolyzed the peptide bonds of alanine, threonine and asparagine. On the other hand, protease II showed broader substrate specificity. Both enzymes were almost completely inactivated by diisopropyl phosphofluoridate, and partially inhibited by chymostatin. Protease I was also inhibited weakly by o-phenanthroline. These unusual proteases may have potential for specific food treatment applications.