N_2O和CO_2在N+Fe/TiO_2(101)面吸附的第一性原理研究

基于周期性密度泛函理论,研究了N2O和CO2气体在N/Fe共掺杂锐钛矿TiO2(101)面最稳定结构的吸附,并与其在洁净TiO2(101)面的结果进行了对比.详细比较了三原子气体不同吸附位、不同吸附端在Fe位及N位吸附的吸附能、键长和键角的变化.结果表明:N2O在Fe位吸附较清洁表面强,为化学吸附;CO2在改性表面的吸附较清洁表面弱.     

两种六元瓜环与钆(Ⅲ)离子的超分子自组装

本文利用X射线单晶衍射方法测定了六元瓜环(Q[6])和对称四甲基取代六元瓜环(TMeQ[6])与钆(Ⅲ)离子形成的配合物的结构。结果表明,Q[6]-Gd(Ⅲ)离子和TMeQ[6]-Gd(Ⅲ)离子都形成1∶2的配合物,配合物通过氢键网络形成超分子链。     

一氧化氮生成反应的课堂讨论和课外实践

通过“问题-探索-分析-结论”教学模式,引发学生的求知欲和探索未知的好奇心,激发学生主动学习的热情并牢固掌握所学的内容.结构化学教学中,氧气和氮气化合生成一氧化氮引起了学生的兴趣.为了加深学生对前线轨道的理解,课堂教学中讨论了该反应发生的条件.课外实践中,学生利用分子轨道理论计算验证了反应的机理,得出了一些有趣的结论.这次教学实践活动加深了学生对前线轨道理论的理解,同时增加了对分子轨道理论的认识和利用该理论探索化学现象的兴趣.     

基于有限元方法的涡轮分子泵转子系统模态分析

以FB-1500型涡轮分子泵为分析原型,依据分子泵转子系统形状、尺寸、材料、支承形式以及质量分布,建立了分子泵转子系统几何模型.采用有限元方法对转子系统进行模态分析,获得了转子系统的临界转速和振型.模态分析结果表明:泵运行在5~6阶固有频率之间,但未完全满足柔性转子安全设计要求,仍然存在安全隐患.提出改进转轴惯性矩、轴承支撑位置来提高转子系统的固有频率,以确保分子泵的安全运行.获得的转子系统模态,对涡轮分子泵启动加速和停车减速过程控制策略制定、减弱或回避共振带来的安全隐患、提高分子泵使用寿命具有参考价值.     

中华按蚊的分子鉴定标准

中华按蚊（Anopheles sinensis）是重要的传疟媒介之一,广泛分布于中国和东南亚,它的形态特征和赫坎按蚊种团（Anopheles hyrcanus Group）其他蚊种十分近似,建立中华按蚊的分子鉴定标准十分重要。本研究从实验室中华按蚊品系的一个个体测序了线粒体DNA COI和COII基因,以及核糖体DNA D2、D3和ITS2位点,测序片段长度分别为658、663、551、365、556 bp。这些序列和近缘蚊种对应序列分别用最大似然法构建系统发育树,结果表明中华按蚊的序列均聚合为同一支。将测序的中华按蚊COII序列和已知蚊种的对应序列比对发现其中的保守位点分别是第133位点C,321位点C,382位点C,435位点T,516位点A和651位点C,线粒体DNA COI和COII基因序列的碱基组成具有AT偏向性,分别占69.15%和74.96%。提交了5条序列到NCBI数据库,其中核糖体DNA D2位点序列是首次在中华按蚊中公开报道。     

三聚氰胺分子印迹聚合物的合成与识别机理研究

为了制备三聚氰胺分子印迹聚合物用于分离富集等目的,以三聚氰胺为模板分子,优化选择溶剂和致孔剂为甲醇,功能单体为丙烯酰胺,采用沉淀聚合法和本体聚合法制备对应的MIP和NIP,沉淀聚合法的MIP与NIP平均产率分别为57.48%和58.85%,本体聚合法的MIP与NIP分别为91.35%和92.71%.从制备分子印迹聚合物的操作过程简便性考虑,沉淀聚合法为较优的合成方法.三聚氰胺与功能单体的结合实验表明:三聚氰胺与丙烯酰胺之间主要以氢键形成1∶3型结合物,产生特异性的选择性分子识别,结合常数K达到4.93×105,表明分子印迹聚合物结构稳定.     

Retarding and manipulating of DNA molecules translocation through nanopores

Nanopores are emerging sensitive sensors that can detect and analyze single charged molecule. Nanopores present a promising approach for sequencing human gen- ome below US$1,000 because of its superior performance, such as high throughput and low cost. However, a dominant bottleneck, that is, the high translocation speed of DNA molecules, has to be overcome. This property decreases accuracy of nanopore sensors to the single-base level. In this review, we mainly introduce the recent research works of retarding and manipulating of DNA motion through nanopores by actively control of three forces, which are the driving force, interaction force between nanopore and molecule, and exterior drag force. Lastly, conclusion and further outlook are presented pore-based DNA sequencing on future directions of nano- technology.     

Finite element models and molecular dynamic simulations for studying the response of mast cell under mechanical activation

In micropipette aspiration experiment, increasing mechanical stress applied to cell membrane induced degranulation of mast cell as well as a current that could be inhibited by an inhibitor, which is specific for the transient receptor potential vanilloid （TRPVs） channels. To determine the sensitivity of TRPVs to membrane strain and tension, and to gain new insights into the activation mechanism of TRPVs, finite element models of mast cell and molecular dynamic simulations of human aquaporin-1 are presented. During the finite element simulations, the cell membrane sustained to micropipette aspiration was simulated, and the strain distribution along membrane thickness direction was obtained. Besides, combining the finite element models of osteoblast aspirated into micro- pipette and other compared models, we examined the relationship between cell mechanical stimulations and mechanical attributes and presented a new perspective to determine the cell equivalent elastic modulus. Consid- ering the indetermination of TRPV crystal structure, human aquaporin-1, one kind of the channel membrane proteins, substituting for TRPV, has been studied with molecular dynamic （MD） simulations, under different external lateral tensions which have been obtained in mast cell finite ele- ment simulations, to investigate the mechanical stimulation effects on the membrane channels. The simulations show that human aquaporin-1 undergoes significant conforma- tional change and expands in accordance with lateraltension, which not only confirms the tendency of the pre- vious electrophysiological experiments but also leads us to a better understanding of TRPVs. The multi-scale study combining finite element simulation and MD simulation is a significant breakthrough in the field of mechanical mechanism in cell system.     

Comparison of the accuracy of powder and single-crystal X-ray diffraction techniques in determining organic crystal structure

This study demonstrates the accuracy of pow- der X-ray diffraction （PXRD） in determining the crystal structures of four organic molecules by comparing the structural information obtained from both single-crystal X-ray diffraction （SXRD） and PXRD techniques. Results showed that the PXRD technique had approximately the same precision as the SXRD technique. The majority of the relative deviations from PXRD-derived lattice parameters were within 4-0.2 % of the correct values （average of the SXRD data）, whereas the relative deviations in bond lengths and angles are within 4-1,0 %, All of the relative deviations were subjected to normal statistical distributions （# = 0） and coincided with the SXRD data. As an auxiliary implement of SXRD, PXRD is clearly an effective and powerful technique in establishing an accurate character- ization of organic molecules.     

Laser intensity induced transparency in atom-molecular transition process

We propose a new transparency mechanism, which is based on photoassociation （PA） laser intensity induced transitional frequency shift for ultracold cesium molecules formed in PA scheme. The PA laser intensity is supposed to change before the atommolecule resonance. Thus, a remarkable transparent effect for PA laser is expected to appear in the vicinity of original resonant transitional line, where the variation of PA laser intensity induces the shift of the excited molecular levels. The mechanism is different from electromagnetically induced transparency effect and interesting for further research on the scattering length for cesium atomic condensate.