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用农药残毒速测仪和气相色谱 火焰光度检测器(GC FPD)2种方法对拉萨市周边4个温室蔬菜基地抽样采集的26个蔬菜样品测定其农药残留量.结果,用速测仪检测出7个蔬菜样品中有农药残留存在.为进一步验证其结果,参考国家农业标准NY/T 761-2008,建立了气相色谱火焰光度(GC-FPD)检测蔬菜样品中敌敌畏、氧化乐果、二嗪农、乐果、甲基对硫磷、马拉硫磷、对硫磷、水胺硫磷、喹硫磷9种有机磷农药残留的分析方法,建立的气相色谱分析方法:检出限为0.039 7~0.182 0 μg·mL-1、回收率为51.64%~91.04%、方法的精密度为1.61%~10.80%.用该方法对农药残留超标的蔬菜样品进行分析,结果未检测到上述9种有机磷农药的残留.实验结果为从事农药残留检测工作者在分析方法的选择和评价拉萨市蔬菜农药残留状况提供参考. 相似文献
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在Eigen的单峰适应面模型基础上,提出了生物体的适应值为高斯分布的随机适应面模型。 利用系综平均的方法, 计算了在单峰高斯分布适应面上准物种的浓度分布和误差阈。 结果表明, 对于小的适应面涨落, 准物种分布和误差阈与确定情形相比变化极小,误差阈对于小的涨落是稳定的。 然而, 当适应值涨落较大时,从准物种到误差灾变的转变不再明显。 误差阈变宽, 并且在涨落增加时向大的突变率方向移动。 Based on the Eigen model with a single peak fitness landscape, the fitness values of all sequence types are assumed to be random with Gaussian distribution. By ensemble average method, the concentration distribution and error threshold of quasispecies on single peak Gaussian distributed fitness landscapes were evaluated. It is shown that the concentration distribution and error threshold change little in comparing with deterministic case for small fluctuations, which implies that the error threshold is stable against small perturbation. However, as the fluctuation increases, the situation is quite different. The transition from quasi species to error catastrophe is no longer sharp. The error threshold becomes a narrow band which broadens and shifts toward large values of error rate with increasing fluctuation. 相似文献
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