Concentrations of positively charged particles develop at the top and bottom of the cloud, but the middle region becomes negatively charged.

带正电荷的粒子集中在云团的顶部和底部，但中间区域形成的是带负电荷的粒子。

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The wing of Xenicibis (top) compared with that of a typical ibis Eudocimus (middle) and the extinct, flightless ibis Apteribis (bottom).

始祖鸟的翅膀(顶部)与典型鹮类(中部)和已灭绝不飞行的鹮类(底部)样本对比。

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The new column has a header cell at the top, a data cell in the middle, and a footer cell at the bottom.

新列在顶部拥有一个头单元，中部的一个数据单元，以及底部的一个底单元。

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Nelson's injuries destroyed all three main skin layers - the epidermis, dermis and hypodermis (the top, middle and bottom), in some places right down to the periosteum, the membrane overlying the bone.

BBC: US Army seeks new ways to treat facial skin injuries

Whether it's the gap between the top tenth and the bottom tenth, or between the middle and the bottom - they all got smaller in 2010-11.

BBC: Britain's recession: Harsh but fair?

On the right, the top and bottom buttons scroll up and down and the middle button selects.

WSJ: Watch Keeps Alerts From a Phone at Arm's Length