In high concentrations , qacs kill bacteria .

在较高浓度下，季铵盐化合物能杀灭细菌。

So do higher concentrations of the protein made by the gene .

由这种基因所产生的蛋白质的浓度也会增高。

As it happens , federal standards for fine-particle concentrations already exist .

巧的是，联邦政府对细微颗粒物浓度的标准早已有之。

Pills now in use contain much lower concentrations of estrogens than older preparations .

现在的避孕药所含的雌激素浓度要远低于过去的制剂。

Lower concentrations can damage engines without having an immediate effect on how well they work .

较低浓度的火山灰也能破坏引擎，但不会对其运行状态产生直接影响。