Novel near-infrared fluorescent liquid crystal: Bodipy bearing multiple alkyl chains with columnar mesophase

By the typical Knoevenagel condensation of Bodipy with aldehyde derivatives, two novel Bodipy derivatives 3 and 6 with symmetric three and six alkyl chains were designed and prepared. The Bodipy derivative 3 with three alkyl chains showed no mesophase but the Bodipy derivative 6 with six alkyl chains possessed the orderly hexagonal columnar mesophase at room temperature. Both samples 3 and 6 exhibited the near-infrared fluorescence with high fluorescence quantum yields and larger Stokes shifts than their Bodipy precursors. Sample 6 was the first near-infrared fluorescent columnar liquid crystal with Bodipy core. This research presented a good strategy on constructing the near-infrared columnar Bodipy liquid crystal.     

奎宁-冠醚组合型手性固定相直接拆分氨基酸的机理

合成了一种新型奎宁-冠醚组合型手性固定相(QN-CR CSP)并用于氨基酸手性对映体的直接拆分,该固定相对12种氨基酸对映体有良好的手性拆分能力。基于氨基酸手性识别中离子交换和络合的协同作用,建立了一种新型的等温吸附模型。通过迎头特殊点洗脱法(FACP)测定色氨酸(Trp)在不同金属离子添加剂条件下的等温吸附线,验证了模型的合理性。流动相中的Li⁺、Na⁺、K⁺等金属离子与氨基酸竞争固定相中的冠醚络合位点,随着金属离子与冠醚的络合作用力和络合吸附平衡常数增大,固定相对Trp的手性拆分能力下降。该模型的建立对理解氨基酸在此类固定相中的手性保留行为以及固定相结构的进一步优化具有重要意义。     

Dynamic behavior of bridge-erecting machine subjected to moving mass suspended by wire ropes

The dynamic behavior of a bridge-erecting machine, carrying a moving mass suspended by a wire rope, is investigated. The bridge-erecting machine is modelled by a simply supported uniform beam, and a massless equivalent “spring-damper” system with an effective spring constant and an effective damping coefficient is used to model the moving mass suspended by the wire rope. The suddenly applied load is represented by a unitary Dirac Delta function. With the expansion method, a simple closed-form solution for the equation of motion with the replaced spring-damper-mass system is formulated. The characters of the rope are included in the derivation of the differential equation of motion for the system. The numerical examples show that the effects of the damping coefficient and the spring constant of the rope on the deflection have significant variations with the loading frequency. The effects of the damping coefficient and the spring constant under different beam lengths are also examined. The obtained results validate the presented approach, and provide significant references in the design process of bridgeerecting machines.     

锂离子电池硅基复合物负极材料*

作为颇有前途的锂离子电池负极材料,硅基材料的研究日益受到重视。硅基负极材料在充放电循环中体积变化过大导致的循环性能差、首次库仑效率低等始终是阻碍其商业化的主要问题。纳米化、合金化和碳包覆是有效的解决措施。本文详细论述了TiB2、TiN、TiC作为基质的硅-化合物复合物,Fe-Si、Cu-Si、Ni-Si体系的硅-金属复合物和硅-碳复合物的研究进展。在硅-碳复合物的研究上,综述了分别采用热解法、球磨法、球磨-热解法、化学聚合法合成,以聚吡咯、聚氯乙烯、聚丙烯腈、间苯二酚-甲醛、柠檬酸、环氧树脂等为碳源的研究进展,同时也综述了Si/碳纳米管复合电极材料的研究情况。     

6-烷氨(氧)基-3-甲硫基-1H-吡唑并[3,4-d]嘧啶-4(5H)-酮衍生物的合成与生物活性

用六氯乙烷、三苯基膦和5-氨基吡唑衍生物一锅法合成关键中间体膦亚胺。 再利用串联aza-Wittig反应,加入对氯苯基异氰酸酯,进一步和烷基胺或取代酚反应合成了11个未见文献报道的6-烷氨（氧）基-3-甲硫基1H-吡唑并[3,4-d]嘧啶-4(5H)-酮衍生物。 通过1H NMR、EI-MS、IR和元素分析等方法对所合成的化合物进行了结构表征,并测试了它们的杀菌和除草活性。 测试结果表明,部分化合物对稗草(barnyard grass)和油菜(Rape)均表现出了较好的抑制活性。     

解线性互补问题的预处理加速模Gauss-Seidel迭代方法

本文提出了解线性互补问题的预处理加速模系Gauss-Seidel迭代方法,当线性互补问题的系统矩阵是M-矩阵时证明了方法的收敛性,并给出了该预处理方法关于原方法的一个比较定理.数值实验显示该预处理迭代方法明显加速了原方法的收敛.     

Selective determination of melamine in milk samples using 3-mercapto-1-propanesulfonate-modified gold nanoparticles as colorimetric probe

A novel and sensitive colorimetric method for determination of melamine in milk samples was developed by a 3-mercapto-1-propanesulfonate-modified gold nanoparticles (MPS-GNPs) probe. Melamine molecule has multiple -NH₂ groups. These functional groups can interact with MPS to form strong hydrogen bonding and induce the aggregation of the MPS-GNPs, resulting in a dramatic color change from red to blue. Therefore, the concentration of melamine in milk samples can be quantitatively detected by the naked eyes or a UV-vis spectrometer. Moreover, investigations have revealed that the sensitivity of the detection could be clearly improved by adding NaCl to the modified GNPs solution, which leads to a more rapid color change in the NaCl-optimized GNPs system. It is worth noting that the absorption ratio (A₆₅₀/A₅₂₀) of the modified GNPs in the NaCl-optimized system exhibited a linear correlation with melamine concentration and the limit of detection is 8 nM, well below the safety limit (1 ppm for infant formula in China).     

An analysis of the radial flow in the heterogeneous porous media based on fractal and constructal tree networks

In this paper, an analysis of the radial flow in the heterogeneous porous media based on fractal and constructal tree networks is presented. A dual-domain model is applied to simulate the heterogeneous porous media embedded with a constructal tree network based on the fractal distribution of pore space and tortuosity nature of flow paths. The analytical expressions for seepage velocity, pressure drop, local and global permeability of the network and binary system are derived, and the transport properties for the optimal branching structure are discussed. Notable is that the global permeability (K_n) of the network and the volume fraction (f_n) occupied by the network exhibit linear scaling law with the fractal dimension (D_p) of channel diameter bylogK_n∼0.46D_p and logf_n∼1.03D_p, respectively. Our analytical results are in good agreement with the available numerical results for steady-state soil vapor extraction and indicate that the fractal dimension for pore space has significant effect on the permeable properties of the media. The proposed dual-domain model may capture the characteristics of heterogeneous porous media and help understanding the transport mechanisms of the radial flow in the media.     

基于Tolman长度的Lucas-Washburn渗吸模型改进及数值模拟

经典的Lucas-Washburn(L-W)渗吸模型用Young-Laplace方程计算毛管压力, 但该方程在管径细小情形得出的毛管压力值与真实值存在较大偏差。本文运用Tolman长度改进Young-Laplace方程, 提出一种改进的L-W渗吸模型, 并将等截面圆管扩展至任意变化截面圆管, 得到变截面圆管中润湿流体注入长度随时间变化的数学模型。该模型为二阶非线性常微分方程, 无法求出解析解, 为此提出一种数值解法。选取截面变化的毛细管道, 通过数值模拟计算出润湿液体注入长度与时间的对应关系, 对Tolman长度的改进效果进行检验和分析。结果表明: 在研究范围内Tolman长度对L-W渗吸模型的改进效果表现出毛细管道半径越小, 效果越明显的规律。圆管局部缩小能改变渗吸水运动状态, 依次呈现出三种运动模式; 圆管局部扩大会缓慢改变渗吸水运动状态, 只呈现单一运动模式。     

不同边界条件下的渗吸驱动因素

建立不同边界条件下的渗吸数学模型, 分别研究在单一边界(OEO边界条件)和混合边界条件(TEO-OW边界条件)下重力和毛管压力对渗吸作用的驱动。结果表明: OEO边界条件下, 只存在逆向渗吸, 并且当开启端面在下端时, 重力抑制渗吸进行; 当开启端面在上端时, 重力促进渗吸进行; TEO-OW边界条件下, 同时存在逆向渗吸和同向渗吸, 对于逆向渗吸, 重力是阻力, 对于同向渗吸, 重力是动力, 当Bond数倒数较小时, 重力在渗吸作用中占主导地位, 当Bond数倒数较大时, 毛管力占主导地位。对比OEO开启端面在上端时和TEO-OW边界条件下重力和毛管力对渗吸作用的大小。结果显示, 在相同Bond数倒数下, OEO边界条件下重力作用的渗吸排油比例要高于TEO-OW边界条件下重力作用的渗吸排油比例。对比不同Bond数倒数下OEO和TEO-OW渗吸速度发现, 当Bond数倒数较小时, 重力起主导作用, OEO边界渗吸速度更快; 当Bond数倒数较大时, 毛管力起主导作用, TEO-OW边界条件渗吸速度更快。