一个就是视网膜中央凹，一个用来看颜色并察觉出细节的中间地带。

One is the fovea, a central area used to see colors and pick out details such as fine print.

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目的：研究不同种源厚朴的化学特征，有效鉴别厚朴、凹叶厚朴及中间类型，建立新的厚朴药材的质量标准。

Objective: to study the chemical characteristic, to identify the different forms and to establish the new standard for the quality control of Cortex Magnoliae Officinalis.

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一项来自瑞典的研究表明长方形、中间有下凹的颈枕能增加睡眠质量，同时减少颈部酸痛。

One Swedish study found that neck pillows, which resemble a rectangle with a depression in the middle, can actually enhance the quality of your sleep as well as reduce neck pain.

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