紫外光直写杂化溶胶-凝胶SiO_2光波导器件

利用有机/无机杂化方法制备了光敏性溶胶-凝胶(sol-gel)SiO_2材料,在硅基片上旋涂成膜.研究了薄膜折射率和厚度随紫外曝光时间、后烘温度及时间等外界工艺条件的变化关系.利用紫外光直写技术,制作出1×2,1×4多模干涉(MMI)型分束器,并且观测到了分光效果较好的近场输出图像.

低温生长GaAs在Nd:YVO4激光器中调Q特性的研究

采用一种新型的被动调Q饱和吸收体,低温生长GaAs薄膜,实现了半导体抽运Nd:YVO4激光器的调Q运转.研究了激光器的调Q特性,调Q抽运阈值为2W.在抽运功率9.2 W时,获得的最短脉冲半峰全宽为15 ns,最大单脉冲能量为4.84 μJ,最高峰值功率为330 W,最大平均输出功率为1.16 W;脉冲重复频率在220 kHz到360 kHz之间.

科技期刊论文来源变化趋势探讨

在我国的科技创新体系中,科技期刊已成为知识经济时代传播知识的主要载体.近年来科技期刊收到的稿件量大幅度增加,其中来稿的质量及作者群也发生了一定的变化.以2005-2006年《生态学杂志》发表的稿件为统计源,对稿源进行了分析研究.结果表明:高等院校和研究院所的硕士生、博士生的稿件已成为科技期刊的主要稿源;在对研究生来稿存在的不足进行分析的基础上,提出了解决的方法.

植物抗旱的分子生物学机制研究进展

本文对当前植物抗旱的分子生物学研究成果进行了综述，特别是植物抗旱的转基因工程进展和代谢调控的分子生物学研究进展．这为我国干旱地区的植物改良、农业生产和生态建设提供重要参考．

双路易斯酸催化原位增容乙烯辛烯共聚物/聚苯乙烯的共混物

采用新型双路易斯酸,三甲基氯硅烷和三氯化铟为催化剂引发傅氏烷基化反应,实现了乙烯辛烯共聚物(POE)和聚苯乙烯(PS)共混物的原位增容。红外光谱的结果验证了接枝物的存在。用扫描电子显微镜观察了反应共混物和简单物理共混物的形态,前者分散相的尺寸小于1μm,后者分散相的尺寸一般为3～4μm。原位生成的接枝物(PS-g-POE)起到相容剂的作用,增容后材料的力学性能得到较明显的提升。如:当m(POE)∶m(PS)=40∶60时,与相同组成的物理共混物POE/PS相比,其悬臂梁冲击强度由1.9kJ/m2增加至9.7kJ/m2,断裂伸长率由3.4%提高至46.3%。增容后的共混物低频区的复数粘度升高,表明POE、PS间相互作用增加。

Conformation studies on sol-gel transition in triblock copolymer solutions

The gelation of physically associating triblock copolymers in a good solvent was investigated by means of the Monte Carlo simulation and a gelation process based on the conformation transition of the copolymer that was described in detail. In our simulative system, it has been found that the gelation is closely related with chain conformations, and there exist four types of chains defined as free, dangling, loop, and bridge conformations. The copolymer chains with different conformations contribute to the formation of gel in different ways. We proposed a conformational transition model, by which we evaluated the role of these four types of chains in sol-gel transition. It was concluded that the free chains keeping the conformation transition equilibrium and the dangling conformation being the hinge of conformation transition, while the chain with loop conformation enlarges the size of the congeries and the chain with bridge conformations binds the congeries consisted of the copolymer chains. In addition, the effects of temperature and concentration on the physical gelation, the association of the copolymer congeries, and the copolymer chain conformations' distribution were discussed.

Investigation of thermal unfolding process of cyanic adduct of horseradish peroxidase by Fourier transform infrared and circular dichroism spectrometry

Detailed circular dichroism(CD) and Fourier transform infrared (FTIR) studies have been carried out to monitor thermal unfolding of horseradish peroxidase isoenzyme C(HRP) inhibited by CN(HRP-CN). The results suggest that HRP-CN is quite different from native HRP with different spin states of Fe of heme and different coordinated states. Cyanide becomes the sixth ligand of Fe(I) of heme and the hydrogen-binding network is destroyed partly at the same time, which cause the drastic decrease of thermal stability of HRP. The FTIR and Soret-CD spectra analysis demonstrate that during the heating process there is an intermediate state(I') which has both partly destroyed secondary and tertiary structures of native HRP, then it is the appearance of protein aggregation state(A) after fully unfolding. The unfolding pathway thus can be shown as follows: I -->I'-->U -->A.