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。

youdao

The middle region was composed of meristematic tissue whose cells had high proliferative activity (Plate Ib).

中层区是由增殖能力旺盛的分生组织细胞所构成；

youdao

Lastly, it is pointed out that the middle region with high gas content is a favourable target for exploration of coalbed methane.

最后指出中部高含气量区是最有利的煤层气勘探靶区。

youdao

"We support political and economic reform in the Middle East and North Africa that can meet the legitimate aspirations of ordinary people throughout the region.

VOA: special.2011.05.21

Administration officials say U.S.Middle East envoy George Mitchell, who was to have begun a trip to the region Monday, has postponed his departure because of the housing controversy.

VOA: standard.2010.03.16

U.S.Middle East envoy George Mitchell held six days of talks in the region last week trying to find a formula for resuming peace talks, but came up empty handed.

VOA: standard.2009.09.19

"In the Middle East region, there should be a negotiated settlement for peace, not a military settlement, " he said.

WSJ: Candidates Skirt a Political Circus

One of the most interesting aspects of marketing in the Middle East region is learning how to make campaigns work locally.

FORBES: Cross-Cultural Marketing: Can I Get a Camel With That?

She believes that one of the directors, presumably from the Middle East region on which she worked, had it in for her.

ECONOMIST: The World Bank's president will not go quietly