It could also mean that a higher layer listens and ACTS upon events sent by a lower layer.

这还意味着，较高层将侦听较低层发出的事件，并据此进行操作。

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Typically it would mean that a higher layer can call a lower layer, but not the other way around.

这通常意味着较高层可以调用较低层，但是不能反过来调用。

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In the layered system, higher layers, such as application, can depend on any lower layer, such as util.

在分层系统中，上层(比如application)可以依赖于其下任何一层(比如util)。

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If I looked within the skin, one of the lower layers of your skin, the connective tissue layer, you'd find many fibroblasts there and they're just waiting in a more rounded shape than this, just waiting to do their job.

如果观察皮肤,更深处的一层细胞,结缔组织层,就能看到许多成纤维细胞,它们平时形状接近圆形,时刻准备着去完成自己的任务

耶鲁公开课 - 生物医学工程探索课程节选

But fewer ozone-eaters in the lower atmosphere mean that the ozone layer should eventually heal itself, perhaps by 2050 or so.

ECONOMIST: Phew, the ozone layer may be saved

To change your view layer in Apple Maps you have to tap the lower right corner (helpfully curled over as if it were physical paper) to reveal quite small traffic, satellite and hybrid views among four other options.

FORBES: Hands On With New Google Maps For iOS: Easier On The Eyes And Faster For The Fingers

The third layer uses TLC memory for capacity storage at a much lower price per bit.

FORBES: Explosive Growth in Flash Memory Enterprise Applications