聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物薄膜表面原位原子力显微镜相图

采用原位原子力显微镜在线跟踪方法,研究了聚甲基丙烯酸甲酯/苯乙烯 丙烯腈无规共聚物共混体系表面相分离行为,得到了具有下临界共溶温度（临界温度约为175 ℃）原位相图。 与文献报道的用离位方法所得结果的主要差别是原位的临界相分离温度稍有提高,以及离位结果中存在的组成对称性。 这些差别主要来源于离位和原位实验方法上的差别,薄膜厚度减小导致的相容性,热力学历史的变化以及基底效应的加剧。     

并联机器人刚度与静力学研究现状与进展

并联机器人的刚度与静力学分析, 对于机构力学性能研究具有重要的理论价值和意义. 本文围绕杆支撑、绳牵引和钢带传动 3 种结构形式, 详细阐述了国内外并联机构刚度和静力学分析的研究现状. 着重从有限元、解析模型和性能分析 3 方面分析了杆支撑并联机构的刚度研究进展. 讨论了有关绳牵引并联机构中绳拉力、动载荷频率、绳牵引预紧力与刚度、静力学之间关系的研究成果. 根据钢带并联机器人结构的特殊性, 对钢带并联机构的刚度与静力学分析中可能遇到的失稳与振动问题进行了探讨. 最后, 对并联机器人技术发展情况进行总结与展望, 指出随着刚度分析与静力学分析的不断深入, 并联机器人的力学理论将会日趋成熟和完善, 为并联机器人机构优化设计提供更深入、系统的理论依据.      

金属离子与腺嘌呤异构体复合物的稳定性

在B3LYP/6-311++G**//6-31+G*基组水平上结合PCM模型系统的优化了气相和液相环境中14种腺嘌呤异构体与四种金属离子(Na+,K+,Mg2+,Ca2+)形成的132个稳定复合物。通过能量对比,得到了所有复合物异构体在气液两相中的稳定性顺序及不同金属离子与同一异构体形成的复合物的能量排序,首次给出了液相中这些不同金属离子复合物的最稳定结构。结果发现溶剂效应导致了液相中的复合物稳定性顺序与气相中的相比发生了很大变化;同一异构体与不同金属离子形成的复合物其稳定性在排序中也变化很大。对于这些变化,本文分别从金属离子与腺嘌呤的复合物在气相中的结合能(EBE)及在液相中的溶质溶剂相互作用能(Epol)能等方面进行了系统的阐述     

NORMAL GRID RULE FOR HYPERSONIC HEAT FLUX NUMERICAL SIMULATION

采用数值求解雷诺平均Navier-Stokes 方程方法对高超声速钝双锥模型进行了计算,比较了不同法向网格尺度对热流计算的影响,并在此基础上提出了一种适于热流计算的网格准则. 研究表明:在实际外形的热流计算中,使用过密或过粗的法向网格均不利于得到准确的热流数据;采用该文提出的基于当地温度梯度的法向网格尺度准则可以在保证热流计算精度的同时实现较高的收敛速度.     

1H,89Y HMQC and further NMR spectroscopic and X-ray diffraction investigations on yttrium-containing complexes exhibiting various nuclearities

2D (1)H,(89)Y heteronuclear shift correlation through scalar coupling has been applied to the chemical-shift determination of a set of yttrium complexes with various nuclearities. This method allowed the determination of (89)Y NMR data in a short period of time. Multinuclear NMR spectroscopy as function of temperature, PGSE NMR-diffusion experiments, heteronuclear NOE measurements, and X-ray crystallography were applied to determine the structures of [Y(5)(OH)(5)(L-Val)(4)(Ph(2)acac)(6)] (1) (Ph(2)acac=dibenzoylmethanide, L-Val=L-valine), [Y(2)(OTf)(3)] (3), and [Y(2)(4)(OTf)(5)] (5) (2: [(S)P{N(Me)N=C(H)Py}(3)], 4: [B{N(Me)N=C(H)Py}(4)](-)) in solution and in the solid state. The structures found in the solid state are retained in solution, where averaged structures were observed. NMR diffusion measurements helped us to understand the nuclearity of compounds 3 and 5 in solution. (1)H,(19)F HOESY and (19)F,(19)F EXSY data revealed that the anions are specifically located in particular regions of space, which nicely correlated with the geometries found in the X-ray structures.     

2.2]Paracyclophane derived bisphosphines for the activation of hydrogen by FLPs: application in domino hydrosilylation/hydrogenation of enones

The heterolytic splitting of hydrogen by two types of [2.2]paracyclophane derived bisphosphines (1, 2a and 2b) in combination with tris(pentafluorophenyl)borane (3) at room temperature is described. The corresponding frustrated Lewis pairs (FLPs) exhibit different behavior in the activation of hydrogen. This results from diverse steric and electronic properties of the bisphosphines. The reactivity of the frustrated Lewis pairs was exploited in the first diastereoselective domino hydrosilylation/hydrogenation reaction catalyzed by FLPs.     

液相色谱-串联质谱法测定蜂蜜和鱼肉中烟曲霉素残留量

提出了液相色谱串联质谱测定蜂蜜和鱼肉中烟曲霉素残留量的分析方法。蜂蜜样品和鱼肉样品分别用磷酸盐缓冲液和乙腈提取,经Oasis MAX固相萃取柱净化后,在Kinetex C18(2.6μm×2.1 mm×100 mm)反相色谱柱上以乙腈-0.1%甲酸酸水溶液(70+30)为流动相色谱分离,采用电喷雾正离子扫描、多反应监测模式(ESI+-MRM)进行质谱检测,外标法定量。方法的测定下限(10S/N)蜂蜜为2μg/kg,鱼肉为5μg/kg。在2～100μg/L的浓度范围内呈良好线性,线性相关系数>0.9997。方法在3个水平的添加回收率在75.4%～79.6%之间,相对标准偏差在6.4%～8.4%之间。方法适用于蜂产品和鱼肉中烟曲霉素残留的定量及确证检测。     

Effects of electron-vibration coupling in transport through single molecules

Using scanning tunneling spectroscopy, we study the transport of electrons through C(60)?molecules on different metal surfaces. When electrons tunnel through a molecule, they may excite molecular vibrations. A fingerprint of these processes is a characteristic sub-structure in the differential conductance spectra of the molecular junction reflecting the onset of vibrational excitation. Although the intensity of these processes is generally weak, they become more important as the resonant character of the transport mechanism increases. The detection of single vibrational levels crucially depends on the energy level alignment and lifetimes of excited states. In the limit of large current densities, resonant electron-vibration coupling leads to an energy accumulation in the molecule, which eventually leads to its decomposition. With our experiments on C(60)?we are able to depict a molecular scale picture of how electrons interact with the vibrational degrees of freedom of single molecules in different transport regimes. This understanding helps in the development of stable molecular devices, which may also carry a switchable functionality.     

Pareto-Geometric分布

本文提出了一种具有单调失效率的新型寿命分布, 即由Pareto分布和Geometric分布生成的两参数的Pareto-Geometric分布, 研究了该分布的各种性质和参数极大似然估计的存在唯一性, 并应用 EM 算法得到了参数的极大似然估计值和相应的渐近方差、协方差.     

Alkynyl-functionalised and linked bicyclo[1.1.1]pentanes of group 14

We report the synthesis and properties of alkynyl-functionalised and -bridged bicyclo[1.1.1]pentane derivatives consisting of the heavier group 14 elements silicon and tin.