Researchers have found an "anxiety gene" which when switched on not only causes stress but increases our craving for sweets and comfort food.

科学家们业已发现“焦虑基因”，它一旦发作，不仅会令我们备受压力煎熬，而且还使得我们更加想吃糖果或安慰食品【1】。

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The design incorporates a channel thin enough to become entirely devoid of carriers (ie, free electrons or holes) when switched off, thus acting as a valve, yet full of them when switched on.

这一设计包含了一条足够细的隧道，当它关闭时，里面完全没有载流子(电子或空穴)，当它打开时，里面便充满了载流子，起到了阀门的作用。

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The block becomes magnetic when the current is switched on.

一通上电流，这块板就会有磁性。

《牛津词典》

There are 100 of these molecules, when a receptor gets activated a kinase activity gets activated, the kinase acts on the protein, the protein gets switched on, something new starts to happen inside the cell.

有一百个这样的分子,当受体被激活,激酶被激活后,激酶作用于蛋白,使蛋白活化,细胞中就会发生一些新变化

耶鲁公开课 - 生物医学工程探索课程节选

Norway has just emerged to say the air conditioning is switched off in the room because it makes too much noise when the recording equipment is switched on.

BBC: In a bedroom with Madonna

An historic fort in Kent is to be bathed in light when feature illuminations are switched on.

BBC: Lights switch-on at Chatham's historic fort

In Chlamydomonas, the gene only gets switched on when environmental conditions are poor for instance, when sunlight or nutrients are scarce.

ECONOMIST: How to become multicellular