Microstructure and interfacial adhesion of high velocity oxy‐fuel‐sprayed MoB–CoCr alloy coating on 316L stainless steel

In this article, a newly developed MoB–CoCr alloy coating was deposited on 316L stainless steel substrate by high velocity oxy‐fuel thermal spraying process. The microstructures and interfacial adhesion of the alloy coating were determined by scanning electron microscopy, X‐ray diffraction and three‐point bending. The results show that the coating consisted of ternary transition metal boride matrix phases (CoMo₂B₂, CoMoB) and a little amount of binary borides (MoB and CrB), the former composed of partially amorphous phase. The formation of the amorphous phase was attributed to the high cooling rates of molten droplets and the proper powder compositions. In the interfacial adhesion measurement, the delamination of the coating is induced during the three‐point bending test, and the interfacial fracture toughness is analyzed using a finite element analysis model. The critical load is determined by comparing the load versus deflection curves obtained by finite element analysis under assumed no crack conditions with the experimental data, and other inputs are determined by test. Copyright © 2009 John Wiley & Sons, Ltd.     

Folding behaviors of apocytochrome b5 and its mutants: Insights from high temperature molecular dynamics simulations

Apocytochrome b₅ (apocyt b₅) with heme removal from the heme-binding core 1, and its mutants with amino acid replaced in the hydrophobic core 2, namely apocyt b₅ Y7P, P81A and H15R/S20E, have been subjected to molecular dynamics (MD) simulation at high temperature (500 K) for elucidating their folding behaviors. The early events upon thermal induced unfolding were found to be in good agreement with available experimental results, and the lowest stability of Y7P was predicted among the four apoproteins. The influences of these key residues on protein folding behavior were compared directly at an atomic level. At the same time, the influences of non-native interactions of hydrogen bonds and salt-bridges on protein stabilities were analyzed in detail. The insights from current MD simulations are valuable for understanding the apoprotein folding and the holoprotein formation in terms of heme proteins.     

多壁碳纳米管表面过氧化苯甲酰印迹复合材料的制备及固相萃取应用

以过氧化苯甲酰(BOP)为模板分子,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,采用热聚合法在多壁碳纳米管(MWNTs)表面制备印迹聚合物(MWNTs-MIPs)。采用红外和热重分析等技术对聚合物结构进行表征。采用液相色谱考察该分子印迹聚合物对过氧化苯甲酰的吸附特性。结果表明该印迹聚合物对过氧化苯甲酰表现出特异性吸附,该印迹聚合物对模板分子存在一种结合位点,其最大表观结合量为56.20 µmol/g。该印迹聚合物成功应用于固相萃取富集面粉中微量过氧化苯甲酰,浓度富集因子为526。     

Second-order two-scale computational method for ageing linear viscoelastic problem in composite materials with periodic structure

The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elastic case. However, the correspondence principle becomes invalid when the materials exhibit ageing. To deal with this problem, a second-order two-scale (SOTS) computational method in the time domain is presented to predict the ageing linear viscoelastic performance of composite materials with a periodic structure. First, in the time domain, the SOTS formulation for calculating the effective relaxation modulus and displacement approximate solutions of the ageing viscoelastic problem is formally derived. Error estimates of the displacement approximate solutions for SOTS method are then given. Numerical results obtained by the SOTS method are shown and compared with those by the finite element method in a very fine mesh. Both the analytical and numerical results show that the SOTS computational method is feasible and efficient to predict the ageing linear viscoelastic performance of composite materials with a periodic structure.     

受限空间下的烯烃聚合研究

近些年来,随着纳米技术的发展,出现了很多微纳米反应器,该反应器能够提供具有纳米尺寸的反应环境,使得在该环境下进行的反应受到纳米空间的影响,生成具有纳米效应或特殊结构的产物。在聚烯烃催化聚合中,也出现很多具有受限空间的微纳米反应器载体,这些载体不仅能够负载烯烃催化剂,还能为烯烃聚合反应提供受限空间环境。在纳米尺度效应的影响下,催化烯烃聚合进程发生变化,可以得到一些具有特殊结构与性能(比如高熔点、超高分子量、纤维状)的聚烯烃产物。本文总结现阶段受限空间下烯烃聚合研究的最新成果,主要根据聚合物的不同结构进行分类,分别介绍了受限空间对聚烯烃产物的形貌、反应动力学及活性、初级结构、二级结构和凝聚态结构及性能的影响,并对受限聚合研究的发展趋势进行了展望。     

利用纳米球提高红外波长上转换探测器效率

在红外波长上转换探测器氮化硅(SiN_x)钝化层制作单层六角密排的二氧化硅(SiO_2)纳米球阵列,以提高红外波长上转换探测器的整体效率.采用自组装的方法在器件钝化层上制备了直径分别约为300,450,750和1000 nm的SiO_2纳米球,并与无表面微纳结构器件进行对比测试.结果表明:钝化层附着SiO_2纳米球能有效地提高红外波长上转换器的光提取效率;当SiO_2纳米球直径为750 nm时的光提取效率最优,是无表面微纳结构器件的2.6倍,可实现低成本制作高效率红外波长上转换探测器.     

镍铁水滑石/还原氧化石墨烯的制备及电催化水氧化性能

首先制备了不同镍/铁比的镍铁水滑石, 并通过液相剥离法得到水滑石纳米薄片溶胶, 随后将其与还原氧化石墨烯复合, 并对其进行了电催化水氧化的性能测试. 结果表明, 镍铁水滑石的剥离可以大幅度提高其电催化性能, 起峰电位为1.47 V, 电流密度为10 mA/cm² 时, 电位仅为1.53 V; 与还原氧化石墨烯复合后, 其催化活性得到了进一步提高, 在10 mA/cm²时电位降为 1.515 V.     

基于酪氨酸磷酸酶(PTP1B)的Ⅱ型糖尿病药物设计、合成和体外活性及毒性的初步评价

酪氨酸磷酸酶PTP1B已被公认为治疗Ⅱ型糖尿病药物的理想靶标蛋白.通过重组表达制备PTP1B蛋白及其蛋白质晶体,并尝试将其与768种小分子片段进行以结构为基础的筛选,得到了数个与PTP1B结合的小分子片段及其化学结构.在此基础上利用计算机辅助药物设计方法设计与优化出一种新型PTP1B抑制剂,并经13步反应合成了该目标分子.体外药理活性和毒性的初步评价的结果表明,其对体外重组人源PTP1B的酪氨酸磷酸酶活性半数抑制浓度IC50值达到(3.4±1.2) μmol/L,优于阳性对照;在HepG2细胞胰岛素抵抗模型中,该化合物能有效改善胰岛素抵抗细胞对葡萄糖的利用能力,其改善效果与阳性药匹格列酮相当.初步的斑马鱼毒性检测表明,目标该化合物在浓度为500μmol/L时未对幼鱼产生明显毒性.新化合物的发现为新型PTP1B抑制剂的后续开发开辟了新基础.     

新型B(C6F5)3/有机胺盐酸盐催化体系的反应研究

近年来, 受限路易斯酸碱对(FLPs: Frustrated Lewis Pairs)在小分子的活化以及在催化还原等方面所表现出的独特反应特性, 使得有关FLPs化学的研究受到了国内外广泛的关注. 设计了一种新型的FLPs催化体系, 该体系以三(五氟苯基)硼(BCF)为路易斯酸, 以多种不同取代的有机胺盐酸盐替代常规FLPs中的路易斯碱有机胺. 发现利用该体系与氢化硅烷反应, 不仅可以高产率地制备分离得到相应的伯、仲、叔硼氢化胺盐; 而且还可以这一体系作为催化剂, 以氢化硅烷作为还原剂, 在常温常压下可高选择性地部分或彻底还原大部分含羰基官能团醛酮等有机化合物. 由BCF/2,2,6,6-四甲基哌啶(TMP)盐酸盐组成的催化体系在对CO₂催化还原为甲烷的反应中, 亦较相应的BCF/TMP体系显示更高的活性. 还通过核磁共振详细地对比研究了原料有机胺盐酸盐、中间体氯代硼胺盐以及产物氢化硼胺盐中, 胺基氮上质子的核磁共振谱信息, 发现不仅胺基上取代基的位阻效应会影响到具有电四极矩性的¹⁴N磁性核的弛豫效应, 而且阴离子基团的配位强弱对胺基氮上质子的化学位移也会产生较大的影响.     

Ga对新型远红外Te基硫系玻璃光学性能的影响

用传统熔融淬冷法制备了新型远红外Te基硫系玻璃(100-x)(GeTe₄)-xGa (x=0, 5, 10 mol%).利用差热分析(DTA)、可见/近红外吸收光谱、红外透射光谱等技术,在GeTe₄玻璃的基础上,通过引入较高配位金属Ga, 研究其对玻璃组成、结构和性能的影响,利用经典的Tauc方程计算了样品光学带隙允许的直接跃迁、允许的间接跃迁及Urbach能量.分析结果表明:在GeTe₄玻璃中引入 关键词： 光学材料 硫系玻璃 光学带隙 红外光谱