pH-responsive poly（2-diethylaminoethyl methacrylate）-functionalized multiwalled carbon nanotubes

Poly（2-diethylaminoethyl methacrylate） （PDEAEMA）-coated multiwalled carbon nanotubes （MWNT-PDEAEMA） were successfully prepared by MWNT-surface initiated atom transfer radical polymerization （ATRP）. The obtained MWNT-PDEAEMA nanocylinders have a core of MWNT and a shell of PDEAEMA and this core-shell structure was confirmed by TEM observations. The UV-Vis and AFM measurements showed that the MWNT-PDEAEMA exhibited obvious pH sensitivity. The solubility of PDEAEMA-coated MWNT dramatically decreased when pH increased to ca. 7.0. Because of the giant molecular weight of the molecular hybrids and local high density of polymeric grafts linked onto MWNTs, the resulting MWNT-PDEAEMA nanocomposites are easier to aggregate, or more sensitive to pH, as compared with the neat PDEAEMA.     

Behavior of MC3T3-E1 Osteoblast Cultured on Chitosan Modified with Polyvinylpyrrolidone

The physical and chemical properties of four kinds of modified chitosan materials made by blending chitosan with polyvinylpyrrolidone （PVP） were investigated. All four of these modified chitosan materials were hydrophilic with water contact angles ranging from 59°to 69°. Fourier transform-infrared spectra of the modified materials showed a new band at 1288 cm^-1, implying formation of a surface physical interpenetrating network structure. Enzyme linked immunosorbent assay results indicated that much less fibronectin was adsorbed on the modified materials than on only chitosan. The viability of MC3T3-E1 osteoblasts cultured on the materials was assessed by 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl- 2H-tetrazolium bromide assay. The results show that adding PVP10000 into the chitosan promotes adhesion of MC3T3-E1 osteoblasts on the modified materials, but has no effect on cell growth and proliferation; while adding PVP40000 reduces cell adhesion, growth, and proliferation. The results suggest that the increased hydrophilicity of the material surface does not always improve its biocompatibility, which will influence the selection and design of biomaterials.     

Study on molecular interaction between NifA and NifL of Pseudomonas stutzeri A1501 by using the yeast two-hybrid system

Pseudomonas stutzeri AI501 (formerly Alcaligenes faecalis A1501), which was isolated from rice paddies in South China in 1980, can colonize tightly on rhizoplane of the host plants or invade the roots of plants for growth and nitrogen fixation. But A1501 can fix nitrogen only under the micro-aerobic and nitrogen-free conditions. The oxygen concentration and the availability of fixed nitrogen are therefore important factors in the regulation of nitrogenase biosynthesis of associative nitrogen-fixing bacteria.     

Functional identification of gene cluster for the aniline metabolic pathway mediated by transposable element

A convenient and widely applicable method has been developed to clone aniline metabolic gene cluster in this study. Three positive recombinant plasmids pDA1, pDB2 and pDB11 were cloned from genomic library of aniline degradation strain AD9. The result of aniline dioxygenase （AD） activity and catechol 2,3-oxygenase （C230） activity assay showed that pDA1 and pDB11 contain aniline dioxygenase genes and catechol 2,3-dioxygenase genes, respectively. The sequence analysis of the total 24.7-kb region revealed that this region contains 25 ORFs, of which 17 genes involve metabolism of aniline. In the gene cluster, the first five genes （tadQTA1A2B） and the subsequent gene （tadR1） were predicted to encode a multi-component aniline dioxygenase and a LysR-type regulator, respectively, while the others （tadD1C1D2C2EFGIJKL） were expected to encode metacleavage pathway enzymes for catechol degradation. The gene cluster was surrounded by two IS1071 sequences.     

模糊层次分析法在地基处理方案优选中的应用

简要介绍了模糊层次分析法的基本原理和分析问题的步骤。基于模糊层次分析法的软土地基处理方案优选，结果表明选择结果与实际相符合。     

流媒体技术及其教育应用

在流格式媒体出现之前,人们若想从网络上观看影片或收听音乐,必须先将影音档案下载至计算机储存后,才可以点选播放,不但浪费下载时间、硬盘空间,也无法满足消费者使用方便及确切的需要。Streaming Media(流媒体)的发展,克服了这些不足。本文介绍了市面上较为流行的三种流媒体技术及其在学校教育中应用。     

膛内燃烧与力学环境物理仿真技术研究

该文研制了发射装药膛内燃烧与力学物理环境仿真装置及其测试系统。用“探棒”测试获得了径向不同位置火药气体压力，解决了药室内同截面不同径向压力测试问题，用光纤测试获得了火焰膛内的传播过程，用弹底压力传感器获得了弹底药床被点燃前药床所处力学环境。多次试验再现并测试获得了膛内燃烧与力学环境。为发射药床膛内燃烧与力学环境和发射装药发射安全性定量研究提供了新方法。     

P2P软件中UPnP功能的实现

主要研究UPnP在P2P软件中的应用及UPnP功能实现的原理和步骤.因为现在互联网有一部分机器是工作在内网,而UPnP应用于P2P软件中可以将软件性能提高30%左右,利用UPnP实现端口映射对P2P软件性能提高有大?篌帮助.     

具有时滞的捕食者-食饵系统的正周期解

讨论了一类具有功能性反应的具有时滞的捕食者-食饵系统,利用重合度理论中的延拓定理,得到了该系统正周期解的存在性判据.