对氦气介质阻挡放电等离子体和氦气毛细管介质阻挡放电冷等离子体射流失活酵母菌的效率和机制进行了比较研究.分析比较了两种等离子体处理的菌液存活曲线和pH值的变化情况;利用扫描电子显微镜观察了菌体表面超微结构的变化.结果显示两种等离子体对酵母菌均有较强的杀灭作用,介质阻挡放电等离子体处理5 m in后可使其减少约7个数量级,而毛细管介质阻挡放电冷等离子体射流处理后可使其减少约8个数量级;同时经过两种等离子体处理后的pH值均明显下降,且毛细管介质阻挡放电冷等离子体射流处理菌液的pH下降幅度大于介质阻挡放电等离子体处理的菌液;从扫描电子显微镜的照片可以看到两种等离子体处理后的菌体均已破裂.实验结果表明毛细管介质阻挡放电冷等离子体射流失活酵母菌的效率要高于介质阻挡放电等离子体,并且杀菌机理应该与细胞破裂及pH值的变化有关.
A self-consistent analysis of a pulsed direct-current (DC) N2 glow discharge is presented. The model is based on a numerical solution of the continuity equations for electron and ions coupled with Poisson's equation. The spatial-temporal variations of ionic and electronic densities and electric field are obtained. The electric field structure exhibits all the characteristic regions of a typical glow discharge (the cathode fall, the negative glow, and the positive column). Current-voltage characteristics of the discharge can be obtained from the model. The calculated current-voltage results using a constant secondary electron emission coefficient for the gas pressure 133.32 Pa are in reasonable agreement with experiment.
In this paper, the mechanism of yeast inactivation in low temperature atmospheric pressure helium, nitrogen and air plasmas generated by dielectric barrier discharge is analysed and compared. The results show that all the three gas plasmas have a high germicidal efficiency. The morphology of the yeast is observed by scanning electron microscopy, which reveals that the yeast treated in helium plasma is ruptured completely but there are only some flaws on the cell walls in the nitrogen and air plasma treated samples. Also, the flaws on the cell walls treated by air plasma are more significant than that by nitrogen treatment. Simultaneously, the pH values of the samples after 5 rain nitrogen and air plasma treatment have no remarkable change either, while the sample treated with helium plasma descends below 4.0, which is beyond the optimum one for the yeast＇s living environment. The difference in pH values may be caused by the treatment effect and the degree of the cell＇s rupture when the gas discharge plasma treatment is applied.
