CoCl(2) inhibits neural differentiation of retinoic acid-treated embryoid bodies

The effects of CoCl(2) on retinoic acid (RA)-treated embryoid bodies (EBs) were investigated. Four-day EBs were treated with 5x10(-6) M of RA for 4 d, then subjected to attached culturing for 7 d in the presence of CoCl(2) at 0, 20, and 100 microM. Differentiation into MAP2- and GFAP-immunopositive cells was inhibited by CoCl(2) in a dose-dependent manner. Next, RA-treated EBs were dissociated into single cells and cultured for 7 d at an initial cell density of 1x10(3)/cm(2). The number of cells increased in a CoCl(2)-dose dependent fashion. In cultures with 100 microM of CoCl(2), more than 90% of the cells were immunopositive for nestin and nestin-immunopositive cells formed clusters, while there were few cells immunopositive for MAP2 or GFAP. These results suggest that CoCl(2) inhibits neural differentiation of RA-treated EB cells and promotes the proliferation of nestin-immunopositive cells, i.e., embryonic stem (ES)-derived neural stem-like cells.     

Effect of active oxygen species on the productivity of torularhodin by Rhodotorula glutinis No. 21

The effect of active oxygen species on the productivity of torularhodin, an effective antioxidant, by soil yeast, Rhodotorula glutinis no. 21, was examined. Methylene blue, methyviologen and AAPH [2,2'-azobis(2-amidinopropane) dihydrochloride] were used as generators of singlet oxygen, superoxide anion radicals and peroxy radicals, respectively. All of them indicated effectiveness at a dose of 1.0 x 10(-10) to 3.0 x 10(-6) M. Addition of these generators to the culture medium had almost no influence on the biosynthesis of beta-carotene, whereas it had marked enhancement on those of torulene and torularhodin. Production of uric acid by xanthineoxidase remained unchanged at a torularhodin concentration of up to 100 microM. This result suggests that torularhodin does not directly affect the productivity of superoxide anions. It has been proved that torularhodin has a more potent effect on the scavenging of peroxyl radicals and inhibits substrate degradation by singlet oxygen more effectively than beta-carotene does. Continuous addition of methylene blue enhanced the torularhodin accumulation more markedly than single addition.     

SiC－TiC陶瓷韧化机制探讨

采用ＣＶＤ法合成ＳｉＣ－ＴｉＣ陶资,探讨了ＴｉＣ含量与断裂韧性之间的关系。结果表明,当ＴｉＣ体积含量为４０％时,断裂韧性高达７．０ＭＰａ·ｍ１／２韧化效应归功于闭合效应以及弯曲效应。断裂韧性与体积含量之间存在ＫＩＣ＝［（ＫＩＣ０）＋Ｂｖｉ］　ＫＩＣ０＝（１＋Ａ）ＫＩＣｍ关系。建立的韧化模型与实验结果相一致。     

纤维层厚度对陶瓷复合靶板抗弹性的影响

用12.7mm穿燃弹对几种不同厚度玻纤布配置的陶瓷复合靶板进行垂直侵彻试验,以研究陶瓷复合靶板面基板间纤维层厚度对靶板抗枪弹性能的影响。试验以有效弹速下弹丸对靶板的总穿深作为靶板抗弹性能的衡量指标,作以比较。试验结果表明,随面基板间玻纤布的厚度增加靶板防护能力降低。从应力波、约束机制、背强效应等方面对其原因作了分析。     

Kinetic studies on lipase-catalyzed acetylation of 2-alkanol with vinyl acetate in organic solvent

Lipase-catalyzed acetylation of 2-alkanol with vinyl acetate has been studied kinetically using Burkholderia cepacia lipase (BCL), enantiomerically pure (R)- and (S)-2-alkanols and different organic solvents. The rate equation was derived by the steady state method for the simplified mechanism. The second order rate constants (k(R) and k(S)) for (R)- and (S)-2-alkanols were evaluated from the slopes of the double reciprocal plots, v(-1) vs. [2-alkanol](-1), where v is the initial rate of the reaction. The log k(R) value increased with the solvent hydrophobicity log P, where P is a partition coefficient of a given solvent between octanol and water. The log k(S) value also increased with log P except the bulky solvents such as 1,4-dioxane and cyclohexane, in which the rates were faster than those expected from the log k(S) vs. log P plot. The slope of log k(S) vs. log P plot was larger than that for (R)-2-alkanol. Thus, log E (E=k(R)/k(S): enantioselectivity) decreased with log P except the bulky solvents. The rate constants and the enantioselectivity were different depending on the structure (carbon number CN) of 2-alkanol. The log E vs. CN plot was minimized at CN=8 and 10 and the log k(S) vs. CN plot maximized at CN=8 and 10. In contrast the log k(R) vs. CN plot showed a different feature from the log E vs. CN plot. These facts suggest that dependence of E on CN is more strongly affected by the reactivity of (S)-2-alkanol than that of (R) isomer in this acetylation.     

夹层材料抗弹效益表征参量研究

对采用不同夹层材料的动态防护单元进行了抗弹性能试验研究,并对部分方案的射流出靶姿态拍摄了X光照片。试验结果表明,夹层材料的波阻抗(pc)是动态防护单元抗弹效益的表征參量。通过对试验结果分析,提出动态防护单元夹层材料的选用原则。     

离子注入改进陶瓷表面可焊性机理分析

进行了Ni+( 1 3 0keV)、Ti( 1 50keV)离子注入Al2 O3(质量分数为 85% ) -ZrO2 (质量分数为 1 5% )陶瓷表面改性试验 ,对改性陶瓷材料表面进行了X -光衍射谱物相分析、表面导电性分析以及与不锈钢材料的非活性钎焊性能分析。结果表明 ,注Ni+和注Ti+陶瓷表层导电性未发现明显变化 ,而注Ti+的陶瓷表层材料在注入剂量达到3× 1 0 17ions/cm2 时其导电性有明显的提高 ,这是由于在陶瓷材料表层生成的钛氧化物的导电性较高的原故。离子注入确实可以显著提高陶瓷材料的可焊性 ,但提高陶瓷材料表面导电性并不是提高其钎焊性能的主要因素。     

缩比件弹体侵彻混凝土过程相似律研究

在模拟实验条件下 ,研究了不同缩比件钨合金弹体侵彻混凝土过程的相似性。结果表明 ,钨合金弹体侵彻混凝土靶体时 ,在高速区侵彻深度与弹速间存在线性关系 ;弹体直径较大时 ,可以把不同直径弹体侵彻过程受到的平均压力看作相等 ,并且侵彻过程存在几何相似性     

晶粒尺寸对疲劳应力强度因子门坎值的影响

本文探讨了PCrNilMoVA及PCrNi3MoVA钢的晶粒尺寸和疲劳应力强度因子门坎值△K_(th)之间的关系。实验结果表明,随d增大,△K_(th)也相应地增大。 文中基于位错理论,提出疲劳应力强度因子门坎值△K_(th)由两部分组成,即:△K_(th)=△K_(th)~*+△K_(th)~d,△K_(th)~*与晶粒尺寸无关;△K_(th)~d表示使裂纹尖端激发出来的位错能够到达晶界的条件,它与√d呈正比关系。模型与实验结果相一致。