Electrical Conduction in Co1-χMgχO

Electrical conductivity and thermoelectric power were measured on Co_1-χMg_χO (0.16χ 0.87) at 900° to 1200°C. Electrical conductivity σ decreased and the activation energy increased with increasing MgO content. Seebeck coefficient α appeared to be positive for all χ. The difference in temperature dependence of σ and α was 0.2 to 0.5 eV and the hole mobility decreased with increasing MgO content. The results were interpreted as showing that electron holes were localized to cation clusters and their thermally activated hopping conduction was operative in the solid solution. The dominant lattice defect changed from singly to doubly ionized cobalt vacancy with increasing MgO content.     

PHYTOCYSTATINS AND THEIR TARGET ENZYMES: FROM MOLECULAR BIOLOGY TO PRACTICAL APPLICATION: A REVIEW

Cystatins are protein inhibitors of cysteine proteinases. Oryzacystatin I (OC-I) has been cloned and is apparently the first well-defined cystatin of plant origin (phytocystatin). Besides OC-I, various other phytocystatins occur in rice, corn, wheat and soybean. Phytocystatins have endogenous target enzymes whose expression is induced by gibberellin, and also exogenous target enzymes from viruses and insects. It is thus likely that phytocystatins are involved in the regulation of intracellular protein catabolism as well as in the defense from infection. Better understanding of this phenomenon and cloning of appropriate genes will facilitate the creation of transgenic crops with enhanced resistance to viruses and insects.     

用ESCA分析等离子体处理了的氟树脂表面

用微波炉产生的微波对氟树脂进行等离子体处理,用ESCA作了表面分析。处理后的试样在533eV处出现O_(1S)的一大峰,在292eV～285eV间出现C_(1S)的连续宽谱带。氧的导入量随着处理时容器内气压(P)的降低而增大,可见随着P的降低处理的效果增大。为了得到深度方向的分布,采用了氩离子剥蚀法和掠射法。随着剥蚀的进行,由等离子体处理所导入的氧急剧减少。用掠射法测定了刚经过处理的FEP和处理后放置了70小时后的FEP的深度分布。刚处理后的试样,氧量随出射角(θ)的减少(即随分析深度的减小)而增大,氟量则减小。相反,处理后放置70小时,在15°<θ<60°的范围内,氟量增加,氧量减少。这是因为低表面自由能的含氟键段移动到表面上所致。由深度方向的分布的结果可以推断,等离子体处理的效果达到了ESCA在θ=90°的分析深度的一半左右。     

Abalone (Hariltis discus): Seasonal Variations in Chemical Composition and Textural Properties

Seasonal changes in adenosine 5′-triphosphate, total free amino acids, and total oligopeptides in abalone meat were analyzed. Levels were higher in summer and lower in winter. In both seasons, the most abundant free amino acid was taurine followed by arginine, glycine, glutamine, and glutamic acid. The largest peptide-bond amino acid was glutamic acid + glutamine. The collagen content decreased in summer and increased in winter. The breaking stress values of the meat were low in summer and high in winter, indicating that summer abalone would be more tender. Scanning electron microscopy revealed the collagen network was more compact in winter.     

Evaluation of Fracture Toughness for Ceramic Materials by a Single-Edge-Precracked-Beam Method

As a substitute for the fatigue-cracked-beam method prescribed in ASTM E399 A2, a recently devised precracking method was applied to the evaluation of fracture toughness of ceramic materials. Straight-through precracks proved to be easily introduced into rectangular beams of several ceramic materials. This method gives K_ic values almost identical with those of the fatigue-cracked-beam method. The K_ic values are almost constant over wide ranges of the pop-in precrack length and the loading rate of the three-point bend test. The test can be easily performed even at elevated temperatures although its validity should be further examined.     

猫与四季流转的生活诗

春的樱花,夏的萤火,秋的落叶,冬的飘雪。四季的景致在平凡琐碎的生活中悄然划过。时间流转之中的细微美感也在快速厚重的现代化包裹之中渐渐磨失不见。或许大多数的我们选择接受这种方式、调整自己适合如此的生活,但也有人最终还是逆势去找寻内心最渴望的回归。     

OCCURRENCE OF RUPTURES ON THE SURFACE OF FOODS DURING FRYING

An attempt was made to clarify the mechanism of ruptures on the surface of foods occurring during frying. Two different products were fried in a corn oil bath at a temperature of 160C or 180C. One of the products was ellipsoidal croquettes coated by the crust with different thicknesses ranging from 1 mm to 4 mm, while the other was ring doughnuts consisting of the three different compositions of a fixed size. The type of ruptures on the crust of croquette samples could roughly be divided into two categories according to the results obtained by the precise observations during the process of frying, i.e., a small hole and a crack. The small hole, like a pinhole, occurred in the crust of the croquette with 1 mm thickness early in the procedure, while the cracks could be observed with the crusts of croquettes more than 2 mm thicknesses after 120 s or more of frying time. The cracks also occurred on the curved surface of all the doughnut samples tested, although the location of cracks on the three surfaces, i.e., upper, outer and inner, was much influenced by the composition of the samples. A variety of measurements were made to obtain information on the changes in mechanical properties of the core region and crusted surfaces of the samples in the frying process so as to confirm generalized simple considerations assumed for the occurrence of ruptures.     

Kinetics of Hydration of Monocaldum Aluminate

Hydration of CaAl₂O₄ (CA) was studied by calorimetry, analysis of the liquid phase, measurement of the combined water, and electron microscopy. During the induction period, the solution remains almost unchanged and is equilibrated temporarily with both superficially intrusion-hydrated CA particles and Al(OH)₃ gel formed by dissociation of Al(OH)₄^– ions, the solubility of the Al(OH)₃ gel being 10^–4.24 molkg^–1 at 25°C, while the intrusion-hydrated layer on the CA particles grows following a nearly linear law to reach a critical thickness (∼3 nm at 10° to 20°C, or 12 nm at 30°C). At this point destruction of the layer occurs, nuclei of hydrous compounds are generated, and the induction period terminates. Subsequent reaction proceeds in accordance with the rate equation of Schiller based on the dissolution-crystallization mechanism.     

纳米Pt膜的晶粒尺寸及其对热导率的影响

采用电子束-物理气相沉积法（EB-PVD）制备了6个厚度为15-62nm的铂薄膜,研究了纳米薄膜的晶粒尺寸及其对热导率的影响规律．当薄膜厚度小于30nm时,晶粒平均尺寸接近于薄膜的厚度;晶粒尺寸随着薄膜厚度的增加而增大并趋于定值;当薄膜厚度大于30nm时,晶粒尺寸约为20nm．受薄膜的表面和内部晶界的综合影响,铂纳米薄膜的热导率大大低于体材料的值,并且纳米薄膜的热导率随着薄膜厚度的增加而增大并趋于一个低于体材料热导率的值．