一种基于形式概念分析的事件演化分析算法

针对传统基于内容相似度的事件关系计算方法不能分析出事件间的潜在关系的问题,提出了基于FCA的事件关系计算方法。该方法利用根据话题的三层结构模型,对话题中的事件进行属性提取,并依据特征频率因子进行属性选择。利用两个事件之间的属性关系建立形式背景,以此为基础形成概念格。用基于概念格的相似度分析发现事件之间潜在。实验证明了这种方法的有效性。     

Antibacterial characteristics and mechanisms of ɛ-poly-lysine against Escherichia coli and Staphylococcus aureus

The aim of this study was to investigate the antibacterial characteristics and antibacterial mechanisms of ɛ-poly-lysine against Escherichia coli and Staphylococcus aureus. The diameters of inhibition zones of E. coli (10 ± 0.5 mm) and S. aureus (12 ± 0.1 mm) treated by 200 μg/ml ɛ-poly-lysine were much larger than control (5 ± 0.3 mm) (p < 0.05). Minimum inhibition concentration of ɛ-poly-lysine against E. coli and S. aureus was 12.5 μg/ml. Scanning electron microscopy showed that ɛ-poly-lysine damaged the morphology of tested bacterial cells. The increase in electric conductivity of bacterial cells suspension indicated that the cytoplasmic membranes were broken by ɛ-poly-lysine, which caused leakage of ions in cells. SDS-PAGE of bacterial proteins demonstrated that ɛ-poly-lysine could damage bacterial cells through the destruction of cellular proteins. These results indicated that ɛ-poly-lysine has good potential to be as a natural food preservative.     

The antimicrobial effects and synergistic antibacterial mechanism of the combination of ε-Polylysine and nisin against Bacillus subtilis

The aim of the present study was to evaluate the combined effects of ε-Polylysine (ε-PL) and nisin and investigate the synergistic action of these compounds against Bacillus subtilis (B. subtilis).The combination of ε-PL and nisin showed synergistic anti-microbial activity against Escherichia coli (E. coli), B. subtilis and Staphylococcus aureus (S. aureus). SEM and TEM microscopy revealed that combined treatment with ε-PL and nisin synergistically damaged the morphology of tested bacterial cells. Propidium iodide (PI) infiltration experiments indicated that combined treatment with ε-PL and nisin synergistically enhanced the permeability of the bacterial cell membrane, likely reflecting the inhibition of both Na⁺K⁺- and Ca⁺⁺ Mg⁺⁺-ATPase activities through these compounds. The fluorescence spectrum showed an interaction between ε-PL and DNA, but not between nisin and DNA. The mode of ε-PL in binding with DNA was similar to that of ethidium bromide (EB). These results indicated that the uptake of ε-PL into cells was promoted through nisin, and subsequently, ε-PL interacted with the intracellular DNA achieving a synergistic effect.