Determination of the total concentration of casein and β-lactoglobulin by indirect competitive ELISA in milk and dairy products

The main purpose of this work was to develop an assay as a means of quality control in milk and dairy products. As specific and high abundant proteins in milk and diary products, casein and β-lactoglobulin were chosen as the targets, and an indirect competitive enzyme-linked immunosorbent assay （ELISA） was developed for determination of the total concentration of casein and β-lactoglobulin. The detection limit of the assay was 79.07 ng/mL, and a working range of the calibration curve was from 140.6 to 36,000 ng/mL. The intrassay and inter-assay coefficients of variations were 4.7 % and 6.5 %, respectively. The recoveries ranged from 94.1% to 106.6 %. The developed ELISA assay was used to detect the total con- centration of casein and β-lactoglobulin in liquid milk and milk powder. The results indicated that the developed assay was very specific, and the addition of nonprotein nitrogen （such as melamine, cyanuric acid, and urea） and vegetable protein did not affect the detection. The good performance of the assay makes it suitable for use in the quality control of milk and dairy products.     

论有线电视工程验收在有线电视稳定可靠发展建设中的作用

文章详细介绍了有线电视工程验收的几个方面,阐述了如何通过工程验收来保证有线电视可靠稳定发展.     

The effect of water content in crude oil on the tribological behavior of screw pump’s stator rubber

It is worthy of studying the effect of water content in crude oil on tribological behavior of stator rubber, because the different water content would affect the swelling and wear of rubber. Compatibility of dewatered crude oil and water was observed after mixture of dewatered crude oil and water （called oilwater mixture） was mechanical stirred and statically placed. Static etching experiment of samples in oil-water mixture was performed using hanging patch test. Wetting contact angle of oil- water mixture on rubber surface was measured by contact angle meter. Tribological behavior of samples in mixture was measured using a ringonblock tester. The result shows that when the water content is less than 15 %, water can blend with dewatered crude oil, and oil-water separation happens when water content was more than 15 %. With the increasing of water content in crude oil, Wettability of mixture and swelling increment of samples decrease. The wear loss of sample increases after treated by swelling experiment, and FKM owns better wear resistance than NBR.     

对潞安集团公司人力资源管理工作现状的建议

人力资源管理理论起源于美国,20世纪80年代引入中国。经过多年的实践探索,潞安集团逐渐形成适合企业发展战略总体要求的运行模式,为企业可持续发展提供了强大的智力支持和人才保障。文章针对潞安人力资源管理系统自身能力建设、员工培训及人力资源信息系统构建3个环节,提出一些简单的建议和想法。     

多功能电能表与智能电能表的异同

以多功能电能表与智能电能表的不同及相同之处分析了今后国家电网的电能表发展方向.     

数字化无线温度传感器与无线数据采集系统的设计

目前,大型场所对环境温度的检测需求越来越大,而现有的温度测量系统显然不能满足检测需求,设计数字化无线温度传感器有着积极的意义.     

民族地区高等院校学生信息素养现状与对策研究

针对民族地区高等院校学生信息素养教育存在的问题,通过问卷调查的方法,以云南高校为例,从信息素养的四个核心要素以及影响信息素养教育的主要因素等方面入手,研究分析民族地区高等院校学生信息素养的现状,探讨进一步加强培养学生信息素养、提高学生信息素养能力的举措,以适应信息化社会和西部跨越式发展的需要.     

湍流射流中示踪粒子的跟随性数值模拟分析

为了探究聚苯乙烯颗粒在射流场中的跟踪效果,采用大涡模拟(LES)方法求解射流流场,并与实验结果进行对比,以验证流场模型.定义了密度与水相同的5种不同粒径的虚拟颗粒,采用离散相模型(DPM)计算其运动轨迹,将其响应时间的理论分析结果与数值模拟结果进行对比,验证了DPM模型的准确性.随后对粒径范围为1~400μm的11种不同粒径的聚苯乙烯颗粒在一定雷诺数射流流场中的跟随特性进行了模拟计算,并与初始时刻相同位置的质点运动轨迹进行对比分析.结果表明,流场的复杂变化对颗粒的跟随性有很大影响,这表现在即使颗粒粒径很小时,颗粒与流场的速度依然存在一定偏差.在所研究工况下,粒径小于200μm的聚苯乙烯颗粒与水的速度偏差大部分在20%以内.     

重组葡萄糖脱氢酶的表达及辅酶再生应用研究

为解决异源表达酮还原酶域EryKR1的重组大肠杆菌Escherichia coli BL21(pET28a-eryKR1)催化环己酮还原时消耗的氢供体NADPH再生的问题,构建了克隆枯草芽孢杆菌葡萄糖脱氢酶基因gdh的重组菌E.coli BL21(pET28a-gdh),其中的gdh基因经Nucleotide BLAST功能分析显示与枯草芽孢杆菌9902的gdh基因序列(登录号为EF626962.1)的一致性达到100%。SDS-PAGE检测显示该重组菌经IPTG诱导后可以高效表达出葡萄糖脱氢酶(GDH),其表达量占全菌可溶性蛋白质的64%。GDH粗酶液的比酶活为137.90U/mg。通过气相色谱检测添加了E.coli BL21(pET28a-gdh)的E.coli BL21(pET28a-eryKR1)环己酮还原反应体系中的环己醇含量,结果显示加入重组GDH的双重组菌耦合反应体系中环己醇的产率为82.21%,是未添加GDH的反应体系对应值的3.23倍,表明重组GDH可以为EryKR1还原环己酮系统解决辅酶再生问题。     

沥青路面在半正弦荷载下的力学响应

研究轮胎/路面的接触印迹特征及随机荷载作用特点,采用ABAQUS软件构建路面结构三维有限元模型,对半正弦荷载作用下的沥青路面力学响应进行分析。结果表明,半正弦荷载作用下沥青路面的上面层和中面层出现应力应变集中,应力应变值随路面深度的增加而逐渐减小;沥青路面的竖向、横向及纵向应力最大值均出现在上面层,且竖向应力最大,横向应力次之,纵向应力最小;竖向、横向应变最大值出现在上面层,纵向应变最大值出现在上-中面层,且路面结构内部出现反复的纵向拉-压变形,这很可能是沥青路面轮迹带附近材料产生疲劳损坏的根本原因。另外,荷载作用时间和路面温度对沥青路面应变的影响要大于其对应力的影响,路面温度的升高导致应变增大且延迟了残余应变的恢复时间。