Molecularly imprinted poly(MAA‐co‐AM) composite membranes for selective recognition of nicosulfuron herbicide

Molecularly imprinted membranes with different ratio of acrylamide (AM) versus methacrylic acid (MAA) were prepared by photocopolymerization on commercial filter paper using nicosulfuron as the template. The structures, the thermal stability, and the morphology of membranes were characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. Static equilibrium binding and competitive recognition properties of the membranes to nicosulfuron and its analogs (pyrazosulfuron ethyl and bensulfuron methyl) were tested. The results showed that nicosulfuron‐imprinted membranes had the best recognition capacity to nicosulfuron compared with its analogs. The biggest selectivity factors of ${\rm \alpha }_{{\rm N}_{\rm 1} /{\rm P}_{\rm 2} }$ and ${\rm \alpha }_{{\rm N}_{\rm 1} /{\rm B}_{\rm 3} }$ were 1.28 and 1.83 and the imprinted factor reached to 2.34. The results of this study implied that the molecularly imprinted composite membranes could be used as separation membranes for nicosulfuron enrichment. The Scatchard plot revealed that one class of binding sites was mainly produced in the imprinted composite membrane in the studied concentration range of nicosulfuron. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of high‐molecular‐weight poly(l‐lactic acid) by chain‐extending reaction with phosphites

Poly(l ‐lactic acid) (PLLA) of high molecular weight was prepared by a chain‐extending reaction in a microcompounder. Phosphites were used as chain extenders to increase the molecular weight of the PLLA prepolymer, which was prepared by the bulk polycondensation of l‐lactic acid. The effects of the amount of phosphite, the temperature, and the screw speed on the torque of the PLLA melt were studied. Under the optimal conditions, the molecular weight of PLLA increased from 62,100 to 126,000 g/mol. The chemical structure and crystallinity of PLLA were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR and ¹³C‐NMR, differential scanning calorimetry, and X‐ray diffraction. The mechanical properties of PLLA were measured. The results indicate that triphenyl phosphite (TPPi) was an effective chain extender for PLLA. The role of the TPPi in chain extending is suggested to be an esterification‐promotion agent. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of oxygen substitution by nitrogen on magnetic and transport properties in Sr2FeMoO6 compound

The result of Fullprof_suite refinement shows that the structure of Sr₂FeMo(O_0.889N_0.111)₆ is assigned to tetragonal system with space group I4/m and its cell parameters are a = 0.559250(8) nm and c = 0.789842(19) nm. The M-T curve demonstrates the magnetic transition temperature being over 300 K. Isothermal magnetization shows that the saturation and spontaneous magnetization are 1.29 and 0.87 μ_B/fu at 300 K, respectively. The sample shows a large magnoresistance in a 0.5 T magnetic field. The electrical transport behavior in the temperature range from 108 to 274 K is dominated by electron-phonon scattering under a zero magnetic field. However, under a magnetic field of 0.5 T the electron-electron and electron-magnon scattering control electrical transport behavior in the temperature range from 145 to 267 K and electrical transport property is governed by electron-phonon scattering in the temperature region of 97-130 K.     

聚乳酸阻燃改性研究进展

综述了近年来国内外聚乳酸( PLA)阻燃改性的研究进展,对磷系、氮系、硅系、膨胀型阻燃体系,无机及纳米粉体等各种环保型阻燃体系在PLA中的应用情况进行探讨,并对未来的发展趋势进行了展望.     

吡唑衍生物的合成与细胞毒性研究

设计合成了七个吡唑类化合物,通过1H NMR和质谱分析对所合成的化合物进行了结构表征,并且用四甲基偶氮唑蓝(MTT)染色法测试了它们对Bel-7402(人肝癌细胞)、KB(口腔表皮样癌细胞)、HL-60(白血病细胞)和BGC-823(胃腺癌细胞)四类癌细胞株的细胞毒性,测试结果表明,4f对Bel-7402和BGC-823细胞株有较高的细胞毒性。     

多遇地震下填充墙侧向刚度对RC框架结构抗震性能的影响

目前,我国RC框架结构抗震设计通常采用纯框架模型:将填充墙作为非结构构件,不考虑其抗侧力作用仅将墙体重量当作外荷载加到计算模型上,通过减小结构自振周期考虑填充墙对结构整体刚度增大作用。然而,多遇地震下填充墙具有一定的抗侧刚度,在其影响下纯框架计算模型是否合理有待商榷。针对该问题,建立考虑填充墙布置的RC框架结构计算模型,并进行线性动力时程分析。对计算结果进行分析表明:当填充墙均匀布置时,从框架部分承担水平地震作用力方面考虑纯框架模型是合理的,而从框架柱轴压力方面考虑又是不合理的;当填充墙不均匀布置时,结构抗震性能的各个指标均有很大的不同,纯框架模型是不合理的。     

基于FPGA的DDS基本信号发生器的设计

本设计基于DDS原理和FPGA技术按照顺序存储方式,将对正弦波、方波、三角波、锯齿波四种波形的取样数据依次全部存储在ROM波形表里,通过外接设备拨扭开关和键盘控制所需波形信号的输出,最终将波形信息显示在LCD液晶显示屏上。各硬件模块之间的协调工作通过嵌入式软核处理器NiosⅡ用编程实现控制。本设计所搭建的LCD12864控制器是通过编程实现的IP核。     

辉光放电光谱仪用高稳定度高压恒流源的研制

直流辉光放电等离子体激发光源工作时需要0.5～1.5 kV的高电压以及5～100 mA恒定可控的电流。放电电流的稳定性对辉光放电光源的稳定工作至关重要,为此,研制了一种用于辉光放电光谱仪的高稳定度高压恒流源。该恒流源用于驱动Grimm型辉光放电光源对样品进行溅射和光谱激发,恒流源采用绝缘栅双极型晶体管(IGBT)和高精度低漂移运算放大器,结合电路图介绍了其工作原理及过压、过流、过热保护措施。经实验验证,恒流源输出开路电压为1.1 kV,输出电流为0～100 mA连续可调,该恒流源的输出电流稳定性高,保证了辉光放电光谱仪样品成分分析的精密度,其负载调整率和输入电压调整率均0.05%;此恒流源驱动Grimm型辉光放电等离子体激发光源对金属样品溅射效果良好,给出了溅射坑表面形貌图以及显微照片、溅射速率。对GBSA6800x不锈钢标样中的Cr、Cu、Al、W元素测试结果相对标准偏差(RSD)2.5%。     

一种高稳定数控恒流源的设计

设计了一种高稳定的数控直流恒流源。以单片机为控制核心,采用模拟比较器反馈控制和A/D、D/A转换器的数字反馈控制,提高了输出电流的稳定性和精度。经实际测试,该恒流源纹波电流小、步进调整功能可靠。恒流值给定和测试精度、变负载恒流稳定性均基本达到0.1%水平。