Modeling electrowinning process in an expanded bed electrode

In this paper, the photocatalytic degradation of methamidophos, an organophosphorous pesticide, was investigated in aqueous solution by using TiO(2) as a photocatalyst. The degradation was studied under different conditions such as the amount of the photocatalyst, illumination time, pH of the system, reaction temperature, initial concentration, electron acceptors, metal ions and presence of anions. The results showed that the photocatalytic degradation of methamidophos was strongly influenced by these parameters. The best conditions for the photocatalytic degradation of methamidophos were obtained. The optimum amount of the photocatalyst used is 12.0g/L. The photodegradation efficiency of methamidophos increases with the increase of the illumination time. Alkaline media are favorable for the photocatalytic degradation of methamidophos. The degradation efficiency is enhanced by increasing reaction temperature, and the photodegradation efficiency decreases with the increase in the initial concentration of methamidophos. The photodegradation efficiency of methamidophos is accelerated by adding a small amount of H(2)O(2), K(2)S(2)O(8), KBrO(3), Fe(3+) or Cu(2+). There are no obvious effects on the reactions with the addition of a small amount of Na(+), K(+), Mg(2+), Ca(2+), Zn(2+), Co(2+) and Ni(2+) or adding trace amount of SO(4)(2-), Cl(-), Br(-). The possible roles of the additives on the reactions and the possible mechanisms of effect were also discussed.     

Sonolytic degradation of dimethoate: kinetics, mechanisms and toxic intermediates controlling

The sonolytic degradation of aqueous solutions of dimethoate, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl]dithiophosphate, was examined. Optimal degradation rates were obtained at 619 kHz for continuous sonolysis and 406 kHz for pulse sonolysis. The primary pathways for degradation include hydroxyl radical oxidation, hydrolysis and pyrolysis on collapsing cavitation bubble interfaces. Reaction mechanisms coupled with the corresponding kinetic models are proposed to reproduce the observed concentration versus time profiles for dimethoate, omethoate and N-(methyl) mercaptoacetamide during sonolysis. The oxidation and hydrolysis of dimethoate and omethoate occurred at the water-bubble interface was the rate-determining step for sonolytic overall degradation of dimethoate. More than 90% toxicity of dimethoate was reduced within 45 min ultrasonic irradiation. Ferrous ion at micro molar level can significantly enhance the sonolytic degradation of dimethoate and effectively reduce the yields of toxic intermediate omethoate.     

发酵肉制品中生物活性肽的研究进展

发酵肉制品营养丰富、风味独特,深受广大消费者的喜爱。肉制品在发酵过程中受组织内源酶和微生物共同作用会发生一系列复杂的生物化学变化,其中最重要的是蛋白质降解。蛋白质降解既可以增加肉制品风味物质的种类,又提高了蛋白质的消化率,提升了产品的营养价值,并且蛋白质降解生成的部分肽类物质具有一定的生物活性及生理功能,如抗氧化、抗菌、降血压、提高人体免疫力等,因此对生物活性肽的制备与功能研究具有重要的理论与应用价值。发酵肉制品是生物活性肽的一个良好来源,本文主要综述发酵肉制品中蛋白质降解生成生物活性肽的种类、分离纯化方法及生物活性肽的功能利用,旨在为功能性发酵肉制品的研发和生产提供理论支持。     

Decay of material properties of degraded MEA caused by repeated cold starts under subzero conditions in polymer electrolyte fuel cells

This study investigated the characteristics of cell performance degradation, decline of component performance, and changes in the properties of membrane electrode assembly materials caused by repeated cold starts under a subzero condition of ?30 °C. It was made clear that functional decay appeared mainly at the cathode due to increased proton conductive impedance and reduction of reactivity of the electrode catalyst. Among the cathode components, an increase in proton conductive impedance in the cathode electrolyte was dominant. Furthermore, the application of ion chromatography and a newly developed proton‐induced gamma‐ray emission method to measure fluorine in the off‐gas drain revealed that decomposition of the electrolyte was dominant in the cathode catalyst layer. A decrease in fluorine in the cathode electrolyte measured by fluorine‐19 nuclear magnetic resonance confirmed this decomposition. A hypothesis is also presented concerning the cause of the performance degradation. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20394     

Products from Lignocellulosic Materials via Degradation Processes

Abstract

Products from lignicellulosic materials by degradation processes are reviewed based on the results of some investigations. Biomass provides a potential source of added value chemicals, such as reducing sugars, furfural, ethanol and other products by using biochemical or chemical and thermochemical. The initial degradation reactions include depolymerization, hydrolysis, oxidation, dehydration, and decarboxylation. The gas phase of pyrolitic degradation products contain mostly carbon monoxide and carbon dioxide, and minor proportions of hydrogen, methane, ethane, and propane. The liquid fraction consists mainly of water, with small proportions of acetaldehyde, propion aldehyde, butiraldehyde, acrolein, croton-aldehyde, furan, acetone, butanedione, and methanol. There are many studies on biomass conversion methods because of energy problems and environmental pollution. Ethanol is an alcohol and is fermented from sugars, starches or from lignocellulosic biomass. In order to produce bioethanol from lignocellulosic biomass, a pretreatment process is used to reduce the sample size, degrade the hemicelluloses to sugars, and open up the structure of the cellulose component. The cellulose portion is hydrolyzed by acids or enzymes into glucose sugar that is fermented to bioethanol. The sugars from the hemicelluloses are also fermented to bioethanol.     

秀丽隐杆线虫模型在食品营养评价中的应用研究进展

食品营养一直是食品领域研究的重点和热点,近些年消费者对功能性食品的消费量逐年增加,而对食品的功能性评价需要模式生物来完成。秀丽隐杆线虫作为模式生物,具有信号通路同人类相似的优点,且成本低、易于培养。本文综述了秀丽隐杆线虫与人类信号通路的同源性,对食品中活性因子的营养功能进行分类评价,并且对秀丽隐杆线虫在食品营养评价中的研究进展进行总结,为食品营养研究以及功能性食品的研发提供参考。     

玉米赤霉烯酮毒素降解酶基因的克隆及在毕赤酵母中的高效表达

以粉红黏帚霉菌株总RNA为模板,采用RT-PCR技术克隆得到玉米赤霉烯酮降解酶基因cD-NA序列,插入pPIC9K载体后,转化毕赤酵母。经MD板筛选,得到His+型重组子,进行甲醇诱导表达,并进行了降解玉米赤霉烯酮能力测定。克隆得到的cDNA序列全长795 bp,连续编码编码264个氨基酸;阳性克隆子在甲醇诱导培养3~5 d后,HPLC检测证实,经表达后的酶液能完全降解液体中玉米赤霉烯酮(ZEN)。     

Effect of hot drawing on properties of wet‐spun poly(L,D‐lactide) copolymer multifilament fibers

Polylactide stereocopolymer multifilament fibers were prepared by wet spinning and subsequent hot drawing. The stereocopolymers were poly‐(L,D ‐lactide) [P(L,D )LA], L/D ratio 96/4, and poly‐(L,DL ‐lactide) [P(L,DL )LA], L/DL ratio 70/30. They were dissolved in dichloromethane and coagulated in a spin bath containing ethanol. The hot‐drawing temperature was 65°C. The draw ratios (DR) were upto 4.5 to the P(L,D )LA 96/4 filaments and upto 3 to the P(L,DL )LA 70/30 filaments. Wet spinning decreased crystallinities of both copolymers. Hot drawing increased the crystallinity of the P(L,D )LA 96/4 filament but not to the level of the original copolymer, whereas the as‐spun and the hot‐drawn P(L,DL )LA 70/30 filaments were amorphous. The filament diameter, tenacity, Young's modulus, and elongation at break were dependent on the DR. The maximum tenacity (285 MPa) and Young's modulus (2.0 GPa) were achieved with the P(L,D )LA 96/4 filament at the DR of 4.5. Respectively, the maximum tenacity of the hot‐drawn P(L,DL )LA 70/30 filament was 175 MPa and Young's modulus 1.3 GPa at the DR of 3. Hot drawing slowed down in vitro degradation rate of both stereocopolymer filaments. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

氟硼酸重氮盐裂解反应条件的探讨

讨论了以重氮化法合成4,4’-二氟二苯甲酮路线中的关键工艺——重氮盐裂解的各种影响因素。研究发现,通过加入Fe粉末作催化剂,将干燥的氟硼酸重氮盐分批次缓慢加入到m（重氮盐）：m（甲苯）=1：2．6的甲苯溶剂中裂解,反应可以十分平稳、温和地进行,并且其收率可以稳定在85％左右,含量达94％以上（气相色谱）。     

Kinetic study on the first stage during thermal degradation of polystyrene

The kinetic parameters of the first stage of polystyrene degradation have been investigated to elucidate the reaction mechanisms using the flow reactor system. The decrease in molecular weight of polystyrene was recorded at minute intervals over the temperature range 310°–390°C. Generally, the first and second stages were observed by thermogravimetric analysis (t.g.a.), however in the early stage of the degradation volatile yields of at least 5% occurred. Therefore, using t.g.a. analysis it is difficult to detect this earlier stage. It became evident that the first stage in the earlier part of the reaction could be detected by g.p.c. analysis. We have observed the hidden kinetic parameters of the nature of the first stage of the polystyrene degradation. The results indicate that the main chains were degraded randomly with the small quantitative volatile groups in the first stage and the rates of decrease in molecular weight in the first stage against reaction temperatures were evaluated as log k_s = 12.0 ? 41300/RT.