In all 17 species, the commonest kind of light receptors were "rod" cells, which are highly sensitive to light and allow night vision but cannot tell colors apart, they found.

在所有17种鲨鱼中，最常见的感光细胞是“杆状”细胞，这种细胞对光线非常敏感，可以使鲨鱼具有夜视能力，但这种细胞无法分辨颜色。

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Retinas use two main types of light-sensitive cells to allow animals to see: Rod cells help measure brightness, while various types of cone cells help distinguish colors.

动物主要借助网膜中的两类光感细胞获得视觉：视杆细胞帮助感知亮度，而种类众多的视锥细胞则帮助辨别颜色。

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It is shown that the resonant frequency of the composite system is sensitive to the alteration of the geometrical dimensions of tool rod with the wears in processing.

结果表明，随着加工过程中工具杆不断磨损，其长度和直径变化对系统共振频率影响明显。

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