Kinetics of polycyclotrimerization of aromatic dicyanates

Polycyclotrimerization of 4,4′-thiodiphenylcyanate (TDPC) and bisphenol-A dicyanate (BADC) were studied and compared by means of differential scanning calorimetry. Samples of different impurity levels (most likely residual moisture) or different catalyst loadings (n-nonylphenol) were studied. Moisture absorbed may indeed function as a catalyst. In the absence of residual phenols or added catalyst, the polycyclotrimerization of identical species shared the same apparent activation energy and all followed an autocatalyzed first-order rate expression. The autocatalytic effect was justified by the cure behavior of partially cured monofunctional cyanate (p-diphenyl cyanate). The rate expression obtained by the dynamic method is still available for the isothermal method. In the presence of an externally added catalyst (n-nonylphenol, NP), the polycyclotrimerization proceeded at obviously lower temperature as compared with the uncatalyzed case. In addition to the expected lowering of activation energy (independent of the catalyst concentration), the cure reaction exhibited an autocatalyzed higher order kinetics (second order for TDPC system and 1.7-th power for BADC system). These kinetic observations were explained in terms of proposed mechanistic scheme in which the competition between hydroxyl-catalyzed and autocatalytic paths is considered. In particular, formation of NP aggregates ((NP)_m, where m = 7 for TDPC system and m = 5 for BADC system, respectively) is proposed to explain the less-than-additive catalytic capacity with increasing added NP level.     

贫营养原位生物接触氧化法对微污染水源水的脱氮试验研究

在水库水源水质为NH+4-N、NO-2-N,NO-3-N、TN质量浓度分别为0.246.0.009、1.730、1.989mg·L-1,UV254为0.099cm-1和CODmn5.5mg·L-1的条件下,采用新型悬浮填料.贫营养原位生物接触氧化法对微污染原水进行脱氮处理.结果表明,在Do质量浓度为3.0～4.0 mg·L-1,水温为25℃左右时,系统对水中的NIL+4-N、NO-3-N、TN及CODMo均有较好的处理效果,最大去除率分别可达到73%,80%、77%和28%.系统稳定运行时的脱氮效果可满足地表水环境III类水体的质量标准.同时还探讨了在生物脱氮过程中贫营养微生物及生物膜系统的净水机理.     

Effects of various post-treatments on carbon nanotube films for reliable field emission

In this report, the FE characteristics of carbon nanotubes (CNTs) treated using both thermal annealing and mechanical coatings on the as-grown CNTs systematically studied. It was found that in the high temperature annealed samples, CNTs were attacked at its root during annealing due to a small amount of oxygen, and were pulled out of the substrate in places after FE measurements because of the contact resistance. However, for the mechanically coated samples both with spin on glass (SOG) and polymethyl methacrylate (PMMA), CNTs were found to be nearly intact after FE measurements and showed reliable FE characteristics over repeatable voltage scan. The reliability of CNTs during FE could be owing to the strong adhesion of CNTs to the substrate both by SOG and PMMA coatings.     

Colorless polyimides from 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) and various aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of organosoluble and light-colored polyimides (III) was prepared from 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) with various fluorinated aromatic bis(ether amine)s via two-step method with thermal or chemical imidization of poly(amic acid)s yielded polyimides. The III series had inherent viscosity of 0.74-1.01 dl/g and showed excellent solubility in a variety of organic solvents. They were soluble in the amide polar solvent, ether-type solvent, and chlorinated solvent. These polyimide films also showed a high optical transparency and less color intensity, with an ultraviolet-visible absorption edge of 369-382 nm and low b^* values (a yellowness index) of 5.0-11.7. Glass-transition temperature of the III series was recorded at 244-319 °C and higher than the isomeric polyimides V series. Compared with the nonfluorinated polyimides IV, the III series showed lighter-colored and lower dielectric constants and moisture absorptions. The good tensile properties and excellent thermal properties of the III series were also observed.     

Event‐specific analytical methods for biotech maize MIR 604 and DAS‐59122‐7

BACKGROUND: It is very important to develop analytical methods for genetically modified organism (GMO) labelling systems and living modified organism (LMO) management. The polymerase chain reaction (PCR) is the most efficient DNA‐based analytical method for identifying and quantifying biotech crops. Qualitative PCR methods have been developed to detect the presence of biotech crops, while quantitative PCR methods have been developed to analyse the content of biotech crops. Analytical methods are now required for new biotech maize events, MIR 604 and DAS‐59122‐7. RESULTS: The event‐specific primers and probes were developed for qualitative and quantitative analysis of biotech maize MIR 604 and DAS‐59122‐7 based on the 3′ flanking regions. As a reference molecule, single standard plasmid was developed. The specificity of the qualitative primers was confirmed by the single PCR product, with limits of detection (sensitivity) of 0.01 and 0.05% respectively. In‐house validation of the quantitative methods was performed using six levels of mixing samples (0.1–10% w/w). As a result, the biases from the true value and the relative standard deviations were within the range of ± 30%. The limits of quantitation of the quantitative methods were all 0.1% for real time PCRs of MIR 604 and DAS‐59122‐7. CONCLUSION: In this study, event‐specific analytical methods were developed and applied to the qualitative and quantitative analysis of biotech maize MIR 604 and DAS‐59122‐7. Copyright © 2009 Society of Chemical Industry     

曲酸对常见食品污染菌的抑制作用

分别采用分光光度法、菌体量法以及滤纸圆片法系统比较了曲酸对5种细菌、2种酵母、2种丝状真菌的生长抑制作用。实验结果表明,虽然0 5 %曲酸基本上不影响霉菌的生长,但对于食品中其他常见污染菌有较好的抑制效果,尤其是对于革兰氏阴性细菌的抑菌效果显著。而且由于曲酸的热稳定性好,经12 1℃、30min热处理仍有良好的抑菌效果,并且在中性条件下抑制供试细菌和酵母菌的能力强于苯甲酸钠。     

XDL型淀粉过滤机的开发与使用

介绍了过滤机的工作原理，结构特征及使用情况。     

Lactococcal 936-species phage attachment to surface of Lactococcus lactis

The interactions of the 936-species phages sk1, jj50, and 64 with the cell surface of Lactococcus lactis LM0230 were analyzed. Cell envelopes (walls + plasma membrane), cell wall, or plasma membrane from L. lactis ssp. lactis LM0230 each inactivated the phages in vitro. However, other 936-species phages kh and P008, which do not infect strain LM0230, were not inactivated by any of the subcellular fractions. Treating cell walls or plasma membrane with the cell wall hydrolase mutanolysin eliminated inactivation of phage sk1. This suggested that intact cell wall fragments were required for inactivation. A role for plasma membrane in phage sk1 inactivation was further investigated. Boiling, washing in 2 M KCl, 8 M urea, or 0.1 M Na(2)CO(3)/pH 11, or treating the plasma membrane with proteases did not reduce adsorption or inactivation of phage. Adding lipoteichoic acid or antibodies to lipoteichoic acid did not reduce inactivation of phage in a mixture with membrane, suggesting that lipoteichoic acid was not involved. Inactivation by envelopes or cell wall correlated with ejection of DNA from the phage sk1 capsid. Although calcium is required for plaque formation, it was not required for adsorption, inactivation, or ejection of phage DNA by envelopes or cell wall. The results suggest that at least for phages sk1, jj50, and 64, adsorption and phage DNA injection into the host does not require a host membrane protein or lipoteichoic acid, and that cell wall components are sufficient for these initial steps of phage infection.     

Outlast粘胶纤维的吸放湿性能研究

研究Outlast粘胶纤维的吸放湿性能。在标准大气条件下对Outlast粘胶纤维进行了吸放湿性能试验,由此建立了该纤维的吸湿和放湿回归曲线以及吸湿和放湿速率回归曲线,并与普通粘胶纤维进行了对比。结果表明,Outlast粘胶纤维的吸放湿能力低于普通粘胶纤维;其吸湿速率随时间呈指数形式衰减并在2 h后达到吸湿平衡;其放湿速率亦随时间呈指数形式衰减并在18 h后达到放湿平衡。     

乳酸菌在食品工业中的应用

乳酸菌是应用于食品工业的重要菌种,阐述了乳酸菌的基本特征和分类,综述了其在乳制品、植物蛋白饮料、蔬菜深加工、肉制品生产、食品防腐及保鲜方面的应用,并对乳酸菌的应用前景进行了展望。