在低浓度时，酶活性急剧下降，随着毒物浓度的增加逐渐趋于平缓。
At low concentrations, enzyme activity declined sharply, leveled off gradually with the increasing of toxic concentration.
她说，对于铜来说，半数致死浓度lc50(一定时间内受试动物半数死亡的毒物浓度)随温度减弱-这就意味着毒性增加。
For copper, she said, the LC50 (the concentration lethal to half of any given species over a certain time) decreases with temperature - meaning that toxicity increases.
如果希望某种技术在商业利用方面切实可行，首先在物料的预处理方面要求所得到的中间产品必须是容易发酵的糖份，产量高，浓度也较高，而且技术的实施成本还不能过高，还有生产过程中更不能使用有毒物质，不可以耗费太多能源，最后，所生产出来的草料油在价格方面必须能够与传统汽油一争高下。
They should not use toxic materials or require too much energy input to work. They must also be able to produce grassoline at a price that can compete with gasoline.
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