Professor Cook says the tree-ring records show periods of wet and dry weather.

VOA: special.2010.05.25

And then they found that they could freeze-dry this preparation of virus, and freeze-drying to lower the temperature, freeze it, then extract out all the water, so you're left with a powder, basically a powdered form of the virus, that could be shipped all over the world, and then reconstituted by adding water to it.

研究者们发现可以冷冻干燥这些病毒制剂,冷冻干燥就是就是降低温度,冷冻病毒,然后提取出所有水份,然后就剩下一些粉末,这主要是粉末状的病毒,这样就能将它运往全世界,并可以通过加水来恢复病毒的活性

耶鲁公开课 - 生物医学工程探索课程节选

Slowly the area became what visitors see today -- a dry land of high flat mesa tops and deep canyons formed through thousands of years by flowing rivers.

VOA: special.2010.07.05

Abshir Ahmed,52, has lived all his life along a stretch of the desert near the town of Docol, Scratching the bone-dry earth with his bare,calloused feet, Ahmed says the devastation that he and others are experiencing now is worse than anything they have ever been through before.

VOA: standard.2009.10.06