Even caffeine, which is generally known only for its stimulatory effects, displays this property, depressing mouse locomotion at very low concentrations and stimulating it at higher ones.

就连人们通常觉得有刺激作用的咖啡因，也表现出了这种特性，它在浓度极低的情况下会抑制老鼠的运动，而在浓度较高的情况下则会刺激老鼠。

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The scientists at Rutgers University in New Jersey say a low to moderate intake of caffeine combined with exercise can be good for health and prevent damage caused by the Sun's ultra violet rays.

新泽西的科学家们称，适当的摄入少量咖啡因，同时保持运动，对健康是有好处的，可预防紫外线引起的皮肤伤。

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Instead, they found high caffeine levels near Carl Washburne State Park and Cape Lookout, two areas not near the potential pollution sources, and low levels of caffeine near large population centers such as Astoria, Warrenton and Coos Bay.

CNN: Researchers find caffeine in waters off Oregon

Alternatively, it might be that people with low moods chose not to drink coffee because it contained caffeine, point out the researchers.

BBC: Coffee may prevent depression, scientists say