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1.
KS Atia AI El‐Batal 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(7):805-811
Glucose oxidase (EC 1.1.3.4) was immobilized on different polymeric materials using different immobilization techniques (entrapping by γ‐irradiation, and covalent binding using epichlorohydrin). Studies were carried out to increase the thermal stability of glucose oxidase (GOD) for different applications. The activity and stability of the resulting biopolymers have been compared with those of free GOD. The effect of different polyvinyl alcohol/polyacrylamide (PVA/PAAm) compositions of the copolymer carrier on the enzymatic activity of the immobilized GOD was studied. The maximum enzymatic activity was obtained with the composition ratio of PVA/PAAm of 60:40. The behaviour of the free and immobilized enzyme was analysed as a function of pH. A broadening in the pH profile (5.5–8) was observed for immobilized preparations. The activity and stability of the resulting biopolymers produced by immobilization of GOD onto different carriers have been compared, in both aqueous and organic media, with those of the free GOD. The enzyme's tolerance toward both heat and organic solvent was enhanced by immobilization onto polymers. The addition of different concentrations of organic solvents (10–50%, v/v) to the enzyme at higher temperature (60 °C) was found to stabilize the enzyme molecule. The strongest stabilizing effect on the enzymatic activity was achieved at a concentration of 10%. Copyright © 2005 Society of Chemical Industry 相似文献
2.
含羧基的聚乙烯醇胺肟螯合纤维吸附钯的研究 总被引:4,自引:0,他引:4
研究了含羧基的聚乙烯醇胺肟(PVAAO-AAc)螯合纤维对钯的吸附,讨论了pH、温度、浓度、吸附时间对吸附率及回收率的影响。确定了最佳吸附条件,吸附钯的纤维用5%硫脲+0.10mol/L硝酸溶液可以解吸。 相似文献
3.
丙烯酸酯有较大的反应活性,能与聚氯乙烯发生接技共聚反应。本文中,我们着重研究不同结构丙烯酸酯单体对聚乙烯基密封胶粘剂的改性作用。以PVC为100份,分别加入甲基丙烯酸一缩二乙二醇双脂(DEGDMA),甲基丙烯酸乙二醇双酯(EGDMA)和丙烯酸一缩二乙二醇双酯(DEGDA)各为10份、20份、30份的试验结果看出,随着丙烯酸酯单体添加量的增加,PVC片基的硬度增大,拉伸强度提高,而伸长率降低。不同的单体其影响也不同。就硬度和拉伸强度有EGDMA>DEGDA>DEGDMA的规律伸长率的降低则为DEGDMA>DEGDA>EGDMA。就丙烯酸… 相似文献
4.
5.
Nicholas HOENICH 《Hemodialysis international. International Symposium on Home Hemodialysis》2007,11(Z1):S26-S31
The extracorporeal circuit in hemodialysis and related therapies facilitates passage of blood to and from the patient and forms an integral link with the safety systems of the proportioning system. Historically, elements of the circuit were subject to problems such as spallation introduced by the blood pump and plasticizer from the tubing sets leaching into the blood. Many of these early issues have been largely resolved, although there is still potential for further improvement and innovation. The introduction of such improvements and innovations into clinical practice is critically dependent upon their cost and benefit to patient and renal unit staff. 相似文献
6.
织物-树脂复合材料层压板的准静态侵彻机理 总被引:4,自引:1,他引:3
本文利用MTS得到了芳纶和高强维纶织物复合材料层压板受尖头侵彻体穿孔的准静态侵彻曲线 ,比较和分析了不同类型纤维集合体与热固性树脂和热塑性树脂复合材料的破坏模式 ,并考察了芳纶织物复合材料层压板侵彻的逐步破坏过程 ,揭示了复合材料层压板的准静态侵彻机理。 相似文献
7.
Fractionation of partly hydrolysed polyvinyl acetate (PVA) was performed by warming of its aqueous solutions. The following properties of the obtained fractions were determined: viscosity, molecular weight and molecular weight distribution, surface tension, and absorbance in the IR range. The blockiness of the polymer molecules, characterized by their behaviour towards iodine-containing systems such as I2,-H3BO3 and I2,-KI, was estimated. Fractionation of the aqueous solutions of PVA by warming is based mainly on the different internal molecular structure of the separated products, i.e. on the length of the vinyl acetate blocks in the PVA molecules and, to a lesser extent, on the degree of hydrolysis and the degree of polymerization. The more blocklike are the PVA molecules, the less compatible are the polymers in the PVA-hydroxypropyl methylcellulose (HPMC)-water system. At phase separation in this sytem the PVA molecules which are not compatible with HPMC are, in the first place, those of the highest blockiness. 相似文献
8.
聚乙烯醇膜的阻醇及导电性能(Ⅱ)戊二醛交联聚乙烯醇膜 总被引:3,自引:0,他引:3
为提高直接甲醇燃料电池(DMFC)用膜的阻醇性能,采用在渗透蒸发领域广泛使用且具有良好分离效果的聚乙烯醇(PVA)为主要材料,制备了戊二醛(GA)交联PVA膜,考察了此类膜的阻醇及质子导电能力。PVA(GA)膜的阻醇效果较目前在DMFC中广泛使用的Nation膜有显著提高,但其自身不具有质子导电能力,需外加电解质溶液以提高其电导率。 相似文献
9.
用差热、热重法对原丝的热性能及由不同预处理方法所引起的PVA纤维的热行为变化进行了研究;并通过模拟脱水条件,用不同升温速率,求出了经不同预处理纤维的脱水反应活化能。结果表明,PVA原丝在230℃有一软化点,三种预处理都不同程度地影响了原丝的热效应变化;纤维在180~340℃主要为脱水反应;原丝及经脱水剂、O_3和O_3综合脱水剂处理的纤维,其脱水反应的表观活化能分别为:164.3kJ/mol,92.9kJ/mol,130.5kJ/mol和117.6kJ/mol。 相似文献
10.
Hamdy F. M. Mohamed 《应用聚合物科学杂志》2008,108(2):1307-1313
Coincidence Doppler broadening of annihilation radiation (CDBAR) and Vickers hardness techniques were performed to study pure Al2O3, pure polyvinyl chloride (PVC), and doped PVC with different concentrations of Al2O3 (10–50%). The CDBAR ratio curves with respect to pure PVC were presented and reflect the momentum distribution of all the samples. The peak around 14.5 ×10?3 moC in the CDBAR ratio curves suggests a large contribution of positron annihilation with the Al2O3. There is a linear correlation between the height of this peak and the Al2O3 concentration. The S‐ and W‐parameters were extracted from the CDBAR spectra and increase with increasing the Al2O3 concentration showing discontinuity at 30% of Al2O3 concentration on PVC. The present data confirmed that there is no positronium formation in pure Al2O3 as a result of smaller S‐parameter. The Vickers hardness increases with increasing the Al2O3 concentration in PVC showing a linear dependence with two different slopes depend on the Al2O3 concentration range. A correlation between the Vickers hardness (macroscopic data) and the W‐parameter (microscopic data) was observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献