压下控制系统在冷轧酸轧机组的应用

主要介绍了新钢公司冷轧厂六辊CVC五机架压下系统（SDS）的主要功能、控制模式、信号的获取、压下校准顺序的控制、控制器输出的计算等。该系统采用的是德国西门子公司的SIMATIC TDC全数字分布式计算机控制系统,实际使用效果很好,为轧机的高效生产提供了保证。     

Cytoprotective effects of geraniin against peroxynitrite- and peroxyl radical-induced cell death via free radical scavenging activity

The role of natural antioxidants in combating the deleterious effects of free radicals has received much attention. In the present study, the cytoprotective effects and the free radical scavenging activity of geraniin, a hydrolysable ellagitannin from Nephelium lappaceum rind, were evaluated by using various approaches. Addition of geraniin to the culture media resulted in a profound cytoprotective effect against damages induced by the peroxynitrite generator 3-morpholinosydnonimine (SIN-1), and the peroxyl radical generator 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH). Geraniin exhibits more potent cytoprotective activity than that of 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). Geraniin exhibited potent antioxidant activity against reactive species, such as nitric oxide, superoxide anion, and chemically synthesized peroxynitrite. Kinetic analysis of reactivity against peroxyl radicals generated by AAPH revealed that geraniin possesses potent reactivity against peroxyl radicals with higher stoichiometric number than Trolox. The cytoprotective effect of geraniin was only observed when geraniin and these toxic compounds were co-existing, suggesting that geraninn exhibits cytoprotective effects via free radical scavenging activity in the extracellular fluid.     

Neriifolin S, a dimeric serine protease from Euphorbia neriifolia Linn.: Purification and biochemical characterisation

A dimeric serine protease Neriifolin S of molecular mass 94 kDa with milk clotting activity has been purified from the latex of Euphorbia neriifolia by anion exchange and size-exclusion chromatography. It hydrolyses peptidyl substrates l-Ala-pNA with highest affinity (K_m of 0.195 mM) and physiological efficiency (K_cat/K_m of 144.5 mM s). Enzyme belongs to the class of neutral proteases with pI value of 6.8, optimal proteolytic activity displayed at pH 9.5 and temperature 45 °C. Its proteolytic activity is strongly stimulated in the presence of Ca⁺² ions and exclusively inhibited by serine protease inhibitors. Enzyme is fairly stable toward chemical denaturants, pH and temperature. The apparent T_m, was found to be 65 °C. Thermal inactivation follow first order kinetics with activation energy (Ea), activation enthalpy (ΔH∗), free energy change (ΔG∗) and entropy (ΔS∗) of 27.54 kJ mol⁻¹, 24.89 kJ mol⁻¹, −82.34 kJ mol⁻¹ and 337.20 J mol⁻¹ K⁻¹.     

Possibilities of using near infrared reflectance/transmittance spectroscopy for determination of polymeric protein in wheat

Possibilities of using near‐infrared reflectance and near‐infrared transmittance (NIR/NIT) spectroscopic techniques for detecting differences in amount and size distribution of polymeric proteins in wheat were investigated. To evaluate whether differences in polymeric protein due to genetic or environmental variations were detectable by NIR/NIT techniques, wheat materials of different background were used. Size‐exclusion high‐performance liquid chromatography was applied to detect variation in polymeric protein. Partial least squares regression gave high R² values between many protein parameters and NIR/NIT spectra (particularly second‐derivative spectra of NIR 1100–2500 nm region) of flours, while no such relationship was found for whole wheat grains. Most and highest correlations were found for total amount of extractable and unextractable proteins and monomer/polymer protein ratio. Some positive relationships were found between percentage of total unextractable polymeric protein in the total polymeric protein and percentage of large unextractable polymeric protein in the total large polymeric protein and NIR/NIT spectra. Thus, it was possible to detect differences in polymeric proteins with NIR/NIT techniques. The highest amount of positive correlations between NIR/NIT spectra and protein parameters was found to be due to environmental influences. Some correlations were found for breeding lines with a broad variation in gluten strength and polymeric protein composition, while a more homogeneous sample showed less correlation. Thereby, detection of variation in amount and size distribution of polymeric protein due to cultivar differences with NIR/NIT methods might be difficult. Copyright © 2007 Society of Chemical Industry     

The Formation of Natural Gas Hydrate From SDS-Solutions and Decomposition By Microwave Heating in a Static Reactor

Gas mixture hydrates were quiescently produced from sodium dodecyl sulfate solutions of 20 ppm, 50 ppm, and 300 ppm to examine the potential for natural gas storage. Owing to the presence of C₂H₆ and C₃H₈, the concentration of 20 ppm is sufficient to promote the hydrate formation, although higher concentrations are better. The porous hydrate trapping more free water shows better microwave absorption and a higher decomposition rate. While conducting the work, pre-depressurization may weaken the water activity by forming ice.     

The Effect of Multi-walled Carbon Nanotubes on Solubility of Methane in Water

In this research, the effects of multi-walled carbon nanotubes (NTs) on dissolution of methane in water have been investigated. The tests were performed in a 370 CC vessel at pressures 3 and 5 bar and temperatures of 1–5°C. The solution volume was 300 CC. For any solution data of vessel pressure versus time and the total absorption capacity were collected. NTs were dispersed in water by using the sodium dodecyl sulfate (SDS) solution with a concentration of 1 wt% and applying ultrasonic agitation for 25 min. Utilization of 0.1 wt% SDS at a pressure of 3 bar reduced the dissolution capacity, while at the pressure of 5 bar a negligible increase was observed. Dissolution capacity increased up to 5.26% by using of NT along with SDS at the pressure of 5 bar and low temperatures. Utilization of SDS, NT, and their mixtures improved the pressure reduction slope of methane at low temperatures.     

Solubility of Methane in Water at the Presence of β-Cyclodextrin,SDS, and Multi Wall Carbon Nanotubes at Low Temperatures

In this research, the solubility of methane in water at presence of β-cyclodextrin (CD), sodium dodecyl sulfate (SDS), and multiwall carbon nanotubes (NTs) have been investigated. The tests were performed at the pressures 3 and 5 bars and temperatures of 1–3°C. For any solution, data of vessel pressure versus time and the total absorption capacity were collected. NTs were dispersed in water by using SDS solution with a concentration of 1 wt% and applying ultrasonic agitation for 25 min. Addition of 0.5 wt% cyclodextrin increased the capacity of methane absorption as much as 14.63% at temperature 1°C and primary pressure of 3 bar. Dissolution capacity increased up to 5.26% by using NT along with SDS at the pressure of 5 bar and low temperatures. Simultaneous usage of CD, SDS, and NT (the solution containing 1 wt% CD, 0.1 wt% SDS, and 1 wt% NT) had the highest effect on the increase of amount and rate of dissolution. The amount of dissolution increases for this solution was 14.63% at temperature 1°C and the primary pressure 3 bar. Utilization of CD, SDS, and NT and their mixture improved the initial dissolution rate of methane at low temperatures.     

从啤酒酿造酵母中提取蔗糖酶及酶的性质研究

采用SDS抽提法从啤酒酵母中提取蔗糖酶,通过正交实验对SDS浓度、提取时间、pH、提取温度等条件进行优化,确定了最佳提取工艺条件是：SDS浓度0.6mmol/L,温度50℃,时间10h,pH5.0。制得的粗酶经醇沉后,采用Q-琼脂糖凝胶FF阴离子交换层析方法得到纯化的酵母蔗糖酶,纯化倍数为16.8倍,并对蔗糖酶的酶性质进行了研究。