Typically, the animal's daily internally generated cycle of activity continues without change.

通常情况下，动物每天内部产生的活动循环继续保持不变。

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Recently, it showed signs of picking up as the Sun enters a new cycle of activity, although recent research raises the possibility of a new lull.

尽管最近的研究也提出来太阳可能还会归于平静，但是由于太阳又进入了新一轮活动期，所以它的活动又呈现加剧的趋势。

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Virtually all species in nature, from single-cell organisms to mammals, including humans, exhibit a daily cycle of activity called circadian rhythm.

几乎自然界中所有的物种，从单细胞生物到哺乳动物(包括人类)，都具有一种日常活动周期，称为昼夜节律。

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We need to help families break the cycle of welfare benefits and criminal activity.

BBC: Nottingham

Climate scientists have already looked at changes related to Sun spot activity - a cycle of approximately 11 years - and long-term changes in the Sun's brightness, which has a cycle that lasts for centuries.

BBC: Viewpoint: The Sun and climate change

Sunspot activity waxes and wanes on the sun in a 11-year cycle, and we are approaching the peak of sunspot activity, probably reaching it in 2013, according to Hesse.

FORBES: Huge Solar Flares Could Spell Catastrophe for Earth