Screening of Antagonistic Bacteria against Phytophthora infestans and Its Inhibition Effect

[ Objective ] The paper was to screen bacterial strain with significant antagonistic effect against Phytophthora infestans, so as to provide basis for further development and utilization of antagonistic bacteria to inhibit P. infestans and control potato late bright. [ Method] Plate dual culture and filter paper method were used to determine the inhibition effect of strains in vivo, fermentation broth and bacterial liquid of 61 strains against P. infestans and the resistance-induction effect of SR13-2 strain. [ Result] The inhibition rate of 24 strains among 61 tested strains against mycelial growth of P. infestans was greater than 60%, and the inhibi- tion effect of HT-6 strain was the strongest with the inhibition rate of 89.92%. However, fermentation broth of all tested strains had no significant inhibition effect against P. infestans, while the inhibition effect of bacterial liquid of most strains was significantly higher than strain in vivo; the inhibition effect of $34-1 strain was the strongest with inhibition rate of 91.50%. The bacterial liquid of SR13-2 strain was found to have significant resistance-induction effect with protective rate of 60%. [ Conclusion] The inhibition effect of strains in vivo and fermentation broth of antagonistic strains S34-1 and SR13-2 had no relationship with each other, while bacterial liquid had great application potential in controlling potato late bright.

电阻电感非线性RLC电路弹簧耦合系统3次超谐共振

研究电阻和电感非线性RLC(resistance-inductance-capacitance)电路弹簧耦合系统的非线性振动,应用拉格朗日-麦克斯韦方程,建立受简谐激励的具有电阻和电感非线性RLC电路弹簧耦合系统的数学模型。根据非线性振动的多尺度法,得到系统满足3次超谐共振条件的一次近似解以及对应的定常解。对其进行数值计算,分析系统不同参数对响应曲线的影响。增大激励电压、极板面积和非线性电阻系数,响应曲线振幅和共振区变大。增大极板间距、线性电感系数和线性电阻系数,响应曲线振幅和共振区变小。系统的固有频率随极板间距增大而增大,随极板面积和线性电感系数的增大而减小。