On-chip fabrication of magnetic alginate hydrogel microfibers by multilayered pneumatic microvalves

Alginate hydrogel has widespread applications in tissue engineering, cancer therapy, wound management and drug/cell/growth factor delivery due to its biocompatibility, hydrated environment and desirable viscoelastic properties. However, the lack of controllability is still an obstacle for utilizing it in the fabrication of 3D tissue constructs and accurate targeting in mass delivery. Here, we proposed a new method for achieving magnetic alginate hydrogel microfibers by dispersing magnetic nanoparticles in alginate solution and solidifying the magnetic alginate into hydrogel fiber inside microfluidic devices. The microfluidic devices have multilayered pneumatic microvalves with hemicylindrical channels to fully stop the fluids. In the experiments, the magnetic nanoparticles and the alginate solution were mixed and formed a uniform suspension. No aggregation of magnetic nanoparticles was found, which is crucial for flow control inside microfluidic devices. By regulating the flow rates of different solutions with the microvalves inside the microfluidic device, magnetic hydrogel fibers and nonmagnetic hydrogel fibers were fabricated with controlled sizes. The proposed method for fabricating magnetic hydrogel fiber holds great potential for engineering 3D tissue constructs with complex architectures and active drug release.     

A reanalysis method for local modification and the application in large-scale problems

A novel reanalysis method, named independent coefficients (IC) method is suggested in this study. This method is proposed to reanalyze structures with local modification which leads to a low-rank change in the stiffness matrix. IC method requires only initial solution as input, and can determine the independent coefficients for each degree of freedoms (DOFs) influenced by structural modifications. Since any extra operations such as decomposition of the initial stiffness matrix is not involved in computation procedure, the IC is a “cheap” algorithm and can be an alternative choice for reanalysis. In order to verify the performance of IC method, several large scale numerical examples are tested. The results demonstrate that the IC method has high accuracy as well as efficiency when the modification is local. The cases involving beyond 1,500,000 DOFs and 3,000,000 DOFs show that IC method has low demands on computer storage, and large scale problems can be easily reanalyzed by this method.     

Solute diffusion through degradable semicrystalline polyethylene glycol/poly(l-lactide) copolymers

Summary The diffusion of C.I. direct orange 34(MW=299) and benzoic acid(MW=122) through degraded semicrystalline polyethylene glycol(PEG)/poly(L-lactide)(PLLA) block copolymers with various PEG contents and PEG segment lengths at 37°C was studied by UV-visible spectroscopy, differential scanning calorimetry(DSC), wide angle X-ray diffractometer (WAXS) and scanning electron microscopy(SEM). The influences of the PEG contents, PEG segment lengths and hydrolytic degradation of PEG/PLLA copolymers on the solute diffusion coefficient and mode for transport were investigated. It is concluded that the diffusion rate increases with the increase of PEG contents and PEG segment lengths in PEG/PLLA copolymers. This is understandable that the increase of PEG content and PEG segment length both make the degree of crystallinity decrease. The steady state of mass flux could not be reached at the diffusion times up to 1000 h, because the copolymers underwent hydrolysis reaction during this period. Furthermore, it is understood that the characteristic time of diffusion as defined by the square of film thickness at an instant of time over the diffusion coefficient of solute through polymer decreases with the increasing diffusion time.     

无患子表面活性物及其复配体系的性质研究

对天然植物原料无患子提取物中的表面活性物的性质（临界胶束浓度、表面张力和起泡性能）及其影响因素（温度、pH、水硬度和盐度等）进行了系统的研究，结果表明无患子表面活性物具有很低的cmc和γcmc，且在一定范围内受一些因素的影响也不大，是一种理想的香波原料；同时也研究了无患子活性物与其他温和型的阴离子表面活性剂的复配体系，表明具有明显的协同增效效果。     

微波烧结Al2O3-TiC复合材料的研究

以纳米级TiC、Al2 O3 为原料 ,用微波烧结制备Al2 O3 -TiC复合材料 ,并与常规烧结比较。分析了两种烧结方法对制备试样的力学性能的影响 ,并探讨了添加剂对Al2 O3 -TiC复合材料烧结性能的影响     

我国合成树脂市场分析及预测

分析了我国合成树脂的生产、消费及进出口情况。近几年我国合成树脂工业发展很快,2002年合成树脂总产量达到1366.5万t,其中聚乙烯、聚丙烯、聚氯乙烯、聚苯乙烯和丙烯睛-丁二烯-苯乙烯(ABS)树脂的总生产能力为1479.6万t/a.产量为1289.2,表观消费量为2528.6万t。预计2000～2005年我国五大合成树脂需求的年均增长率为11.4％,2005年需求量将达到3267万t。     

抗冲聚丙烯结构与性能研究

对部分国内外抗冲聚丙烯(PP)产品进行了微观形态和结构分析，研究其对材料宏观力学性能的影响。实验结果表明：抗冲PP是一个含有PP均聚物、丙烯与乙烯-丙烯两嵌段共聚物、乙丙橡胶(EPR)、聚乙烯均聚物等的多相体系。EPR的分子序列结构对聚合物抗冲击性能起主要作用。在序列结构中，丙烯、乙烯单体在分子链上的位置交换越频繁，抗冲击性能越得到提高。丙烯序列平均长度的增大对抗冲击性能有一定的削弱作用。     

离子膜片碱装置的国产化改造

介绍了对离子膜片碱装置部分设备如F-1A片碱机转鼓、降膜浓缩器、碱液预热器等国产化改造的过程及运行效果。     

电化学消毒法的消毒效果试验

本研究主要是采用自行设计的电化学消毒器对河水及不同含盐量的配水进行了系统的消毒试验，试验结果表明电化学消毒器的消毒效果良好，耗电很低，杀菌率随电流、停留时间和盐度的增加而提高。     

通信用片式介质陶瓷双工器的设计与制作

介绍了通信用介质陶瓷双工器的设计方法和制作过程。该双工器是由接收滤波器和发射滤波器组成的。每种滤波器是由一块高介电常数、高Q值和接近零温度系数的介质陶瓷块制成的。这个陶瓷块上包含两个四分之一波长同轴谐振腔、输入及输出电极和耦合装置,并且输入及输出电极在陶瓷块的同一侧面上,因此滤波器具有体积小巧,结构稳定和安装方便的特点。采用介电常数为90的陶瓷材料制作了中心频率分别为903MHz和927MHz的接收和发射滤波器,经网络分析仪测试,各项技术指标满足设计要求。