Many girls hear it when they are sleeping, but I was the only one who heard it awake.

许多女孩子睡觉的时候都听见它了，只有我醒着的时候听见它。

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Perhaps keeping one side of the brain awake allows a sleeping animal to surface occasionally to avoid drowning.

也许保持一侧大脑清醒可以让睡眠中的动物偶尔浮出水面，避免溺水。

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Birds that are literally half asleep—with one brain hemisphere alert and the other sleeping—control which side of the brain remains awake, according to a new study of sleeping ducks.

根据一项关于睡觉的鸭子的新研究来看，半睡半醒的鸟儿——大脑的一个半球处于警觉状态，另一个半球处于睡眠状态——控制着大脑的哪一边保持清醒。

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Finding our way down to camp would be the hardest part of the climb, crawling into our sleeping bags after being awake for 42 hours.

WSJ: El Capitan's Nose in a Day | By Michael J. Ybarra

Avoid sending any messages while most people are sleeping, even if you're wide awake.

CNN: Online dating and a formula for love

Gregg said he would have trouble sleeping after taking the pills, often remaining awake and alert into the early hours of the morning.

BBC: Gregg admits 'speed' use