现代浓度测量技术及其应用

介绍了两种先进的浓度测量控制技术及其在纸浆稀释控制中的应用,该技术可更有效地对纸机纵向和横向进行质量控制.     

Evaluation of Biodegradation of Pineapple Leaf Fiber Reinforced PVA Composites

Composites of polyvinyl alcohol (PVA) reinforced with different weight percentages of pineapple leaf fibers (PALF) were fabricated and evaluated for biodegradation by soil burial test and plate test. FTIR analysis indicated the existence of a chemical interaction between PVA and PALF. The water uptake study showed that the composites with higher fiber content displayed high tensile strength and brittleness but possessed lower water uptake potential. In the soil burial test, the composites with low matrix to filler ratios exhibited higher rates of degradation as evident by the associated decrease in molecular weights. Plate test performed using Pseudomonas putida showed that the composites were susceptible for degradation by bacteria. The results of this study indicated that PALF-reinforced PVA composites were completely biodegradable and could find potential applications in industries such as agriculture and packaging and safely disposed after use without causing environmental damage.     

考马司亮蓝G-250染色法测定羊毛酶减量

文章研究了考马司亮蓝G-250染色法测定羊毛酶减量的可行性,分析了羊毛织物经过木瓜蛋白酶、savinase、woolase 3种酶单独处理、经过3种不同氧化前处理后,再经过同种酶处理和不同种酶处理的织物减量率与工作残液中析出的蛋白质浓度的线性关系.实验表明,不同的处理工艺不会影响这种线性相关性,同时也充分证明了考马司亮蓝G-250染色法测定羊毛酶减量的稳定性.     

Inhibition of Bacillus cereus spore outgrowth and multiplication by chitosan

Bacillus cereus is an endospore-forming bacterium able to cause food-associated illness. Different treatment processes are used in the food industry to reduce the number of spores and thereby the potential of foodborne disease. Chitosan is a polysaccharide with well-documented antibacterial activity towards vegetative cells. The activity against bacterial spores, spore germination and subsequent outgrowth and growth (the latter two events hereafter denoted (out)growth), however, is poorly documented. By using six different chitosans with defined macromolecular properties, we evaluated the effect of chitosan on Bacillus cereus spore germination and (out)growth using optical density assays and a dipicolinic acid release assay. (Out)growth was inhibited by chitosan, but germination was not. The action of chitosan was found to be concentration-dependent and also closely related to weight average molecular weight (M_w) and fraction of acetylation (F_A) of the biopolymer. Chitosans of low acetylation (F_A = 0.01 or 0.16) inhibited (out)growth more effectively than higher acetylated chitosans (F_A = 0.48). For the F_A = 0.16 chitosans with medium (56.8 kDa) and higher M_w (98.3 kDa), a better (out)growth inhibition was observed compared to low M_w (10.6 kDa) chitosan. The same trend was not evident with chitosans of 0.48 acetylation, where the difference in activity between the low (19.6 kDa) and high M_w (163.0 kDa) chitosans was only minor. In a spore test concentration corresponding to 10²-10³ CFU/ml (spore numbers relevant to food), less chitosan was needed to suppress (out)growth compared to higher spore numbers (equivalent to 10⁸ CFU/ml), as expected. No major differences in chitosan susceptibility between three different strains of B. cereus were detected. Our results contribute to a better understanding of chitosan activity towards bacterial spore germination and (out)growth.     

基于巴特沃思滤波器的纸张定量信号处理

针对纸张定量在线检测信号受“温漂”噪声影响稳定性差、补偿效果不理想的问题,从定量检测原理出发对噪声干扰源及主要耦合通道进行了时-频域分析和研究,并根据定量信号和噪声不同的频谱分布规律,构造了相应的巴特沃思滤波器处理定量信号。     

Content of low molecular weight carbohydrates in vining peas (Pisum sativum) after blanching and freezing: effect of cultivar and cultivation conditions

The content of low molecular weight carbohydrates (LMWC, glucose, fructose, sucrose, raffinose, stachyose and verbascose) was investigated in 29 cultivars of vining peas after blanching and freezing. The peas were harvested at about the same degree of ripeness. There was a positive correlation between the amount of raffinose, stachyose and sorbitol, while a high content of verbascose only could be seen when there was a low content of these sugars. High concentrations of sucrose were generally associated with high concentrations of glucose and fructose. Samples from 1999 had a significantly (p < 0.001) higher content of raffinose, stachyose and sorbitol and lower of verbascose, probably because of the drier and warmer summer that year compared with 1998. Furthermore, medium and late maturing cultivars contained larger amounts of raffinose, stachyose and sorbitol than early cultivars, possibly due to the fact that these cultivars, to a greater extent, were exposed to a higher temperature and more intense sunlight for a longer time. Considerable differences in the content of LMWC could be seen both between the different cultivars and the various trials. Glucose and sucrose were generally similarly affected by cultivar and cultivation conditions, while cultivation conditions had a greater influence on the content of sorbitol and the raffinose family oligosaccharides (RFO; raffinose, stachyose, verbascose) in late‐maturing groups. It is concluded that many factors affect the content of LMWC in peas. However, as the content of RFO is comparatively small in vining peas, any nutritional significance of these sugars in the human colon is probably rather small. Copyright © 2004 Society of Chemical Industry     

大麻/黄麻交织物的焦磷酸钠与复合酶联合处理工艺

针对当前大麻/黄麻交织物粗糙刚硬,刺痒感明显及碱煮氯漂过程污染环境等问题,采用焦磷酸钠和复合酶(漆酶/酸性木聚糖酶复配)联合工艺对大麻/黄麻交织物进行处理,以织物质量减少率、织物断裂强力(经向)、弯曲长度、芯吸高度为指标进行单因子和正交优化试验,并进行了方差分析。得出最佳处理工艺方案:焦磷酸钠质量浓度为9 g/L,处理时间为90 min,处理温度为80 ℃,漆酶质量浓度为7.5 g/L,酸性木聚糖酶质量浓度为6.0 g/L,处理时间90 min,处理液pH值5.0。此时织物质量减少率为18.26%,织物断裂强力(经向)为780 N,织物弯曲长度较未经处理下降了24.82%,芯吸高度提高了46.4%,该工艺可达到碱煮氯漂(或碱氧一浴)效果,生态环保。     

Comparison of stunning methods in the dissemination of central nervous system tissue on the beef carcass surface

Beef carcasses were examined to explore the effects of stunning methods on central nervous system tissue (CNST) dissemination on the surface during the slaughtering process. The frequency of occurrence of CNST contamination on four defined parts, each on the interior and exterior surfaces of the split carcass, and their level of the contamination were measured by an ELISA test. The effect of hot carcass weight was also examined. The results showed that the frequency of contamination occurrence was not affected by the stunning method. However, the penetrating captive bolt stunning method resulted in a higher level of CNST contamination than non-penetrating sledge-hammer stunning (P < 0.001). The higher level of contamination occurred on the interior surface of carcasses along the vertebral area. Therefore, the dissemination of CNST on carcasses seemed to be affected by the stunning method, carcass splitting, and carcass washing. The carcass weight significantly affected the level of CNST contamination on the carcass (P < 0.01) but there was no interaction with the stunning method.     

基于结构熵权法的电力ICT通信网可靠性的评估方法

电力信息与通信技术网络是电力系统运营的重要支撑网络之一,是电网运营智能化、电网管理手段信息化和保障电力调度自动化方面的重要基础。提出了一种基于结构熵权法评估电力ICT通信网可靠性的方法,根据专家库的专家对电力ICT通信网各个环节单元的评价,利用结构熵权法对这些评价结果进行权重计算,综合所得各个环节单元的权重结果得出ICT电力通信网可靠性的综合评估指数。通过这一评估方法可以获知电力通信网的可靠性发展趋势,为电力通信网的发展规划提供指导信息。     

共轭亚油酸降脂及分子机理研究进展

共轭亚油酸是一类具有两个共轭双键的十八碳多不饱和脂肪酸混合物的总称,具有确切的减肥降脂活性与可验证的临床安全性,使其成为国际减肥市场的宠儿。简要回顾了共轭亚油酸减肥降脂的研究成果,并从调控能量代谢、脂代谢、骨骼肌代谢和糖代谢,介导脂肪细胞的分化与凋亡以及调节肠道微生物群6个方面总结了共轭亚油酸减肥降脂的作用机制,同时对其存在问题及发展机会做了分析与讨论。共轭亚油酸作为减肥降脂的天然产物,具有更大、更广阔的发展潜力。