掺杂对γ－Fe_2O_3气敏元件灵敏度及其它特性的影响

本文着重研究了稀土氧化物及其它某些化合物对γ－Ｆｅ＿２Ｏ＿３气敏元件灵敏度、选择性、工作温度和使用寿命的影响，并对加粘土在γ－Ｆｅ＿２Ｏ＿３气敏元件中的作用做了详细研究，为制备优异的γ－Ｆｅ＿２Ｏ＿３气敏元件提供了实验依据。     

新型水煤浆添加剂的开发前景

介绍了水煤浆技术的特点及其主要特性参数 ,分析了我国水煤浆技术的现状和存在的不足 ,提出发展我国水煤浆技术的长远策略主要应该是 :通过开展对某些非离子型分散剂的研究 ,开发出新一代的水煤浆添加剂 ,以便进一步提高水煤浆质量 ,降低水煤浆成本     

Survey of residual solvents in natural food additives by standard addition head-space GC

Residual levels of 12 solvents in 87 natural food additives (66 samples of food colours, 19 samples of natural antioxidants and two natural preservatives) collected between 1997 and 1999 were determined by automated head-space GC using FID, with a porouspolymer (PLOT) column. Calibration curves were prepared by the method of standard addition. Confirmation was by manually injected head-space GC using mass spectrometric detection. 1,2-Dichloroethane was found in turmeric colour (natural food colour) collected in 1997 at the concentrations of 8.6 μg g^-1, but was not found in samples collected in 1998 and 1999. Hexane was found in three samples of dunaliella carotene (11, 72 and 75 μg g^-1), and in chlorophyll at 93 μg g^-1 (both natural food colours). Acetone was found in turmeric colour, annatto colour, dunaliella carotene, kaoliang colour, cacao colour at a concentration between 8.7 and 42 μg g^-1 (all natural food colours).     

减水剂对建筑石膏作用效果影响因素的研究

为了提高建筑石膏中减水剂的使用效率，试验研究了建筑石膏比表面积、减水剂掺法、pH值等因素对建筑石膏分散性和强度的影响，并对其影响规律进行了分析。结果表明适当增加建筑石膏细度可提高减水剂的使用效率；不同掺法的减水剂作用效果存在较大差异，先掺法效果最好；pH值对减水剂分散效果有一定影响，在弱碱性条件下减水剂分散效果最好。     

聚落的再现——对伍重、西扎的比较阅读

本文从设计方法的角度,以聚落研究为基础,对当代建筑师伍重、西扎的作品进行比较阅读。在某种程度上伍重和西扎都从聚落中获得了启示,但最终两位建筑师的作品分别以宏大叙事和小叙事的角度再现了聚落的场景。     

Montgomery方法及其在伪随机数发生器中的应用

文章在Montgomery算法的基础上作了一些改进使之适合于硬件实现,并将修改后的Montgomery算法用于计算一种类Blum－Micali伪随机数发生器的计算,从而在很大程度上提高了该发生器的速度。该伪随机数发生器的安全性是基于离散对数的难题,如果素数q的位数很高（如512－bit）,则伪随机数发生器是很安全的。     

基于随机加法链的高级加密标准抗侧信道攻击对策

侧信道攻击已经对高级加密标准(AES)的硬件安全造成严重威胁,如何抵御侧信道攻击成为目前亟待解决的问题。字节替换操作作为AES算法中唯一的非线性操作,提高其安全性对整个加密算法有重要意义。该文提出一种基于随机加法链的AES抗侧信道攻击对策,该对策用随机加法链代替之前固定的加法链来实现有限域GF(2⁸)上的乘法求逆操作,在此基础上研究随机加法链对算法安全性和有效性方面的影响。实验表明,所提随机加法链算法比之前固定的加法链算法在抵御侧信道攻击上更加安全、有效。

     

Organocatalytic Activation of Pyruvates Toward Michael Addition to Nitroalkenes: Synthesis of γ-Aminobutyric Acid (GABA) Derivatives

Despite the significant role of pyruvic acid in biotransformations, the utilization of pyruvates in the field of catalytic asymmetric synthesis has been unexpectedly limited. This statement also applies to enamine catalysis, in which pyruvates seem to be challenging substrates. Recently, the first illustration of the asymmetric addition of pyruvic acid to β-nitrostyrenes, catalyzed by a NahE enzyme using the enamine mechanism, has appeared in the literature. Now, we demonstrate pyrrolidine-based catalyst can mimick enamine mechanism used by this enzyme to activate pyruvates in the asymmetric addition to structurally diverse nitroalkenes to produce highly enantioenriched Michael adducts without the limitations in substrate structures associated with biocatalysts. In addition to confirming that optically pure pyrrolidines can serve as ultimately small organic catalysts in pyruvate activation, we present an exceedingly simple and versatile method for the synthesis of optically pure γ-nitro acids, which are precursors for well-known active pharmaceutical ingredients namely GABA derivatives     

高频板制作关键技术探讨

高频板涉及的技术相对较高，相关制作、检测设备和技术人员都是企业在跨越的一道难题，所以应充分考虑市场和技术、设备能力等方面的因素尤为重要。通讯基站应用的高频板市场方面，在中国及另一些发展中国家市场需求相对旺盛，值得关注。文章重点介绍高频板内层-压合层间控制和钻孔-电镀孔粗控制两个方式制作关键点，以供参考和建议。     

Antioxidative activities of tocotrienols on phospholipid liposomes

Antioxidative activity of tocotrienol (Toc3) was studied in the oxidation of dilinoleoylphosphatidylcholine (DLPC) liposomes. The objective was to measure the differences in the antioxidative activities betweenα-Toc3 andα-tocopherol (α-Toc), and betweenγ-Toc3 andγ-Toc. When each antioxidant was added to the already prepared DLPC liposome solution, the antioxidative activity of Toc3 was larger than that of Toc. However, when incorporated into the liposomal membrane, the antioxidative activities of Toc3 and Toc were the same and were intermediate between those of the added Toc3 and Toc. When added to the liposome solution, the consumption of Toc3 during the induction period was larger than that of Toc. When incorporated into the liposomal membrane, the consumptions of Toc3 and Toc were the same and were intermediate between those of the added Toc3 and Toc. These results suggest that the reactions of Toc3 and Toc with phospholipid peroxide within the membrane are inhibited to a different degree depending on the dosing manner of Toc3 and Toc. Namely, the degree of inhibition decreases in the following order: Toc(added)> Toc(incorporated)= Toc3(incorporated)> Toc3(added).