低温制备微晶硅薄膜生长机制的研究

采用热丝化学气相沉积技术制备了一系列处于不同生长阶段的薄膜样品,用原子力显微镜系统地研究生长在单晶硅衬底和玻璃衬底上薄膜表面形貌的演化.按照分形理论分析得到:在玻璃衬底上的硅薄膜以零扩散随机生长模式生长;而在单晶硅衬底上,薄膜早期以有限扩散生长模式生长,当膜厚超过某一临界厚度时转变为零扩散随机生长模式.岛面密度与膜厚的依赖关系表明,在临界厚度时硅衬底和玻璃衬底上的岛面密度均出现了极大值.Raman谱的测量证实,玻璃衬底上薄膜临界厚度与非晶/微晶相变之间存在密切的关系.不同的衬底材料直接影响反应基元的表面扩散能力,从而造成薄膜早期生长模式的差异.

微重力细胞生物学实验地面模拟技术研究

<正>微重力对细胞的影响是空间生命科学研究的重要环节,(哺乳动物)细胞感受重力变化的机制是其中的一个基本问题。由于空间实验机会稀少且成本昂贵,必须辅助以相关的地面微重力效应模拟方法。旋转培养器在微重力细胞生物学实验中一直是模拟微重力效应的主要手段,其前提假设是,旋转可以"迷惑"细胞对固定重力方向的感知,并且重力方向改变的速度快于细胞对重力方向感知的响应时间阈值。严格上说旋

Injection by hydrostatic pressure in conjunction with electrokinetic force on a microfluidic chip

A simple method was developed for injecting a sample on a cross-form microfluidic chip by means of hydrostatic pressure combined with electrokinetic forces. The hydrostatic pressure was generated simply by adjusting the liquid level in different reservoirs without any additional driven equipment such as a pump. Two dispensing strategies using a floating injection and a gated injection, coupled with hydrostatic pressure loading, were tested. The fluorescence observation verified the feasibility of hydrostatic pressure loading in the separation of a mixture of fluorescein sodium salt and fluorescein isothiocyanate. This method was proved to be effective in leading cells to a separation channel for single cell analysis.

塔叶苔属(SchiffneriaSteph.)(Hepaticae)的研究

塔叶苔属(Schiffneria Steph.)建立于1894年。作者在研究中国标本时,发现一新种———Schiffneria yunnanensis C.Gao& W.Li sp.nov.。塔叶苔属的配子体为叶状体,生殖枝具茎叶返祖现象,应置于叶苔亚纲的叶状体无组织分化类群———带叶苔目(Pallaviciniales)之中。

遮阴对黄波罗幼苗的光合特性及光能利用效率的影响

一直以来黄波罗(Phellodendron amurense)被认为是不耐阴树种,然而引入美国纽约后,发现它具有一定的耐阴性,在全光和林下均能更新,在纽约已经成为生物入侵种。为了探讨黄波罗的耐阴性问题,通过设置自然光与遮阴(15%自然光)两种光环境,观测了三年生黄波罗幼苗(遮阴1a后)光合生理参数、光能利用效率、叶绿素和比叶重的变化。结果表明,与自然光处理相比,遮阴处理的黄波罗幼苗最大光合速率、表观量子效率和暗呼吸速率略有下降,但差异不显著(p>0.05),光补偿点下降显著(p<0.05);同时,单位面积叶绿素含量无显著差异(p>0.05),而单位干重叶绿素含量显著升高,比叶重显著下降,叶面积显著增大(p<0.05)。上述结果说明:遮阴的黄波罗幼苗通过降低光补偿点和暗呼吸速率利用环境中的弱光,同时通过减小比叶重、增大叶面积和提高叶绿素b相对含量来增强对光的捕获,使其在弱光时的光能利用效率提高。由此推断,黄波罗幼苗能适应一定程度的遮阴。

基于县域要素的三江源地区旅游扶贫模式探讨

随着我国旅游业的兴起,人们越来越认识到旅游在消除贫困上的潜力和能力,然而,要让旅游真正朝着有利于消除贫困的方向发展,必须对旅游的发展方式加以调整,因地制宜地选择旅游扶贫的模式。本文构建了三江源地区各县贫困程度和旅游资源禀赋评价指标体系,定量测度了各评价区的贫困度和旅游资源禀赋综合得分,并采用四象限法划分出资高贫低、双高、双低、资低贫高4种旅游扶贫类型区,在此基础上,提出适用于整个三江源地区的旅游扶贫基本模式为政府主导模式,以及各类型区的旅游扶贫辅助模式,即资高贫低区的政企合作模式,双高区的项目推动模式,双

The influence of arrangement of St in MBS on the properties of PVC/MBS blends

Three series of MBS core-shell impact modifiers were prepared by grafting styrene and methyl methacrylate onto PB or SBR seed latex in emulsion polymerization. All the MBS modifiers were designed to have the same total chemical composition, and MMA/Bd/St equals 30/42/28, which is a prerequisite for producing transparent blends with PVC. Under this composition, there were three different ways of arrangement for styrene in MBS, which led to the different structure of MBS modifier. The concentration of MBS in PVC/MBS blends was kept at a constant value of 20 wt.%. The effects of arrangement of St in MBS on the mechanical and optical properties of PVC/MBS blends were studied. The notched Izod impact test results showed that the MBS with a PB homopolymer core grafted with St had a lowest brittle-ductile transition (BDT) temperature and BDT temperature increased with the amount of St copolymerized with Bd in the core of MBS. The transparency of blends also increased with the amount of St copolymerized with Bd in the core. TEM results showed that the arrangement of St in MBS influenced the deformation behavior. Two deformation modes were observed in the blends: cavitation and shear yielding.