Side-chain cholesteric liquid crystalline elastomers containing isosorbide as chiral agent – synthesis and characterisation

In this work the new-style nematic monomer M₁ , chiral crosslinking reagent M_C and a series of new side-chain cholesteric liquid crystalline elastomers derived from M₁ and M_C were prepared. The effect of the content of the chiral crosslinking unit on phase behaviour of the elastomers has been discussed. Polymer P₁ showed nematic phase, P₂ –P₇ showed cholesteric phase, P₃ formed Grandjean texture in the heating cycle and turned out a blue Grandjean texture in the cooling cycle, P₂ –P₃ with less than 6 mol% of chiral crosslinking agent gave rise to selective reflection. The elastomers containing less than 15 mol% of the crosslinking units displayed elasticity, reversible phase transition and high thermal stability. Experimental results demonstrated that the glass transition temperatures reduced first and then increased, and the isotropisation temperatures and the mesophase temperature ranges decreased with increasing content of crosslinking unit.     

用非饱和三相孔弹模型研究浅层土壤中地震波的传播特性

研究浅层土壤中声波耦合的地震波的传播特性, 用于声波探雷技术的机理分析. 根据浅层土壤具有孔隙度和可压缩性的特点, 利用非饱和三相孔隙介质中的地震波模型, 研究了土壤孔隙度、含水饱和度等参数对地震波传播特性的影响. 计算结果显示: 在给定的参数条件下, 地震波的传播速度和衰减系数均随频率的增加而增加; 纵波的传播速度随孔隙度的增加而减小, 横波的传播速度随孔隙度的增加而增加; 地震波的传播特性随含水饱和度的增加变化比较复杂. 通过对计算结果与已发表实验结果的比较分析, 讨论了解析方法的可行性, 为声-地震耦合机理及其在声波探雷研究中的应用提供了一定的理论基础. 关键词： 声-地震耦合 地震波 孔隙度 声波探雷     

Hydrothermal Synthesis and Crystal Structure of One 3D Coordination Polymer of Nickel(Ⅱ) Achieved from 5-Iodo-isophthalic Acid Ligand

A new coordination polymer [Ni(L)(m-bix)(H2O)]n(1, H2L = 5-iodo-isophthalic acid, m-bix = 1,3-bis(imidazol-1-ylmethyl)-benzene) has been synthesized by the hydrothermal method and characterized by IR, elemental analysis, powder XRD and single-crystal X-ray analysis. The crystal is of triclinic, space group P1 with a = 9.1638(3), b = 10.2319(3), c = 13.2463(4) ?, α = 80.1710(10), β = 83.671(2), γ = 70.3790(10)o, C22H19NiIN4O5, Mr = 605.02, V = 1150.85(6) ?3, Dc = 1.746 g/cm3, F(000) = 600, μ = 2.225 mm-1, S = 1.045 and Z = 2. The final R = 0.0388 and wR = 0.1257 for 5089 observed reflections with I 2σ(I). In the title complex, the M and P layers are arranged alternately to give a double-layer structure by the symmetry related hydrogen bonds, and these double-layers are further joined together to achieve a 2D supramolecular architecture through I···π interaction involving iodine atoms and imidazole rings. The thermal stability of the title complex was studied by thermal gravimetric(TG) and differential thermal analysis(DTA).     

Cloning,Overexpression, and Characterization of a High Enantioselective Nitrilase from Sphingomonas wittichii RW1 for Asymmetric Synthesis of (R)-Phenylglycine

In this study, a high (R)-enantioselective nitrilase gene from Sphingomonas wittichii RW1 was cloned and overexpressed in Escherichia coli BL21 (DE3). The recombinant nitrilase was purified to homogeneity with a molecular weight of 40 kDa. The pH and temperature optima were shown to be pH 8.0 and 40 °C, respectively. The purified nitrilase was most active toward succinonitrile, approximately 30-fold higher than that for phenylglycinonitrile. Using the E. coli BL21/ReSWRW1 whole cells as biocatalysts, the kinetic resolution for asymmetric synthesis of (R)-phenylglycine was investigated at pH 6.0. A yield of 46 % was obtained with 95 % enantiomeric excess (ee), which made it a promising biocatalyst for synthesis of (R)-phenylglycine.     

金纳米颗粒可视化传感器在生物分子分析中的研究进展

基于金纳米颗粒的可视化传感器具有灵敏度高、选择性好、肉眼可见、无需大型仪器等优点,是一种具有应用潜力的分析检测方法。生物分子分析检测与人体健康息息相关。本文综述了近几年基于金纳米颗粒的可视化传感器在生物分子分析中的应用研究。     

Suzuki-Miyaura cross-couplings of arenediazonium tetrafluoroborate salts with arylboronic acids catalyzed by aluminium hydroxide-supported palladium nanoparticles

Suzuki-Miyaura cross-couplings of arenediazonium salts with arylboronic acids catalyzed by highly active aluminium hydroxide-supported palladium nanoparticles catalyst have been investigated for the first time. The reactions are performed at 25 °C in MeOH without any base and ligand to afford biaryls in good to excellent yields under non-anhydrous and non-degassed conditions.     

Controllable synthesis of a non-interpenetrating microporous metal-organic framework based on octahedral cage-like building units for highly efficient reversible adsorption of iodine

A novel non-interpenetrating metal-organic framework was successfully constructed based on octahedral cage-like building units and its outstanding performance in reversible adsorption of iodine was investigated.     

Tuning of redox potentials by introducing a cyclometalated bond to bis-tridentate ruthenium(II) complexes bearing bis(N-methylbenzimidazolyl)benzene or -pyridine ligands

A series of asymmetrical bis-tridentate cyclometalated complexes including [Ru(Mebib)(Mebip)](+), [Ru(Mebip)(dpb)](+), [Ru(Mebip)(Medpb)](+), and [Ru(Mebib)(tpy)](+) and two bis-tridentate noncyclometalated complexes [Ru(Mebip)(2)](2+) and [Ru(Mebip)(tpy)](2+) were prepared and characterized, where Mebib is bis(N-methylbenzimidazolyl)benzene, Mebip is bis(N-methylbenzimidazolyl)pyridine, dpb is 1,3-di-2-pyridylbenzene, Medpb is 4,6-dimethyl-1,3-di-2-pyridylbenzene, and tpy is 2,2':6',2″-terpyridine. The solid-state structure of [Ru(Mebip)(Medpb)](+) is studied by X-ray crystallographic analysis. The electrochemical and spectroscopic properties of these ruthenium complexes were studied and compared with those of known complexes [Ru(tpy)(dpb)](+) and [Ru(tpy)(2)](2+). The change of the supporting ligands and coordination environment allows progressive modulation of the metal-associated redox potentials (Ru(II/III)) from +0.26 to +1.32 V vs Ag/AgCl. The introduction of a ruthenium cyclometalated bond in these complexes results in a significant negative potential shift. The Ru(II/III) potentials of these complexes were analyzed on the basis of Lever's electrochemical parameters (E(L)). Density functional theory (DFT) and time-dependent DFT calculations were carried out to elucidate the electronic structures and spectroscopic spectra of complexes with Mebib or Mebip ligands.     

流体泵在放射性危险流体输送中的应用

流体泵是一类利用压缩空气为动力的管道式输送装置,通过气液换能装置,依靠不同的流体元件组合实现流动换向控制,达到流体输送目的。由于该类装置不含运动部件,具备固有安全性和免维修性,故特别适于核后处理中乏燃料的输送。在核电规模高速发展的今天,必须尽快展开对该项技术的研究。本文综述了国外与流体技术相关各类流体泵装置应用型式,对英、美等核电发达国家的流体泵工业化进程进行了介绍,对各国流体泵学者主要研究成果进行了综述,对今后我国流体泵技术研究方向和工业化应用装置的发展趋势进行了展望。     

冷却用弯掠轴流风机气动噪声预测与试验分析

采用Navier-Stokes方程和标准k-ε湍流模型,对五种不同结构的弯掠轴流风机A/B/C/D/E进行稳态数值模拟,结合给定的性能要求筛选出B/E风机。以稳态流场为基础,采用大涡模拟(LES)与基于Lighthill声类比的FW-H模型相结合的方法对B/E风机进行非定常计算和气动噪声预测,并将预测结果与试验数据进行了对比验证。分析了以叶轮表面作为噪声源时B/E风机的涡流噪声频谱特性,研究了风机三维非定常内部流场中旋涡分布特性,并探讨了风机旋转区域内部声压级的分布规律。