"In the tropics, a lot of tree species don't even form rings that we can see.

VOA: standard.2010.04.05

It wouldn't be the same if I turned it upside down because the carbons - the rings here, the pentose's would all be turned over, the chemistry would look different and the sequence of bases would look different.

记住单链倒过来,就和原来不一样了,这是因为碳原子和糖环结构,戊糖会翻转,使得这个化学结构看起来不一样了,碱基的顺序也不一样了

耶鲁公开课 - 生物医学工程探索课程节选

Buckley isn't an archaeologist. He studies tree rings, which record the growth history of trees that can be hundreds of years old, or even older.

VOA: standard.2010.04.05

"If they fail to do that and something else comes up, the rings won't be tarnished, they'll be broken, " he said.

CNN: ASIANOW - TIME Asia

They knew that stiff o-rings didn't provide a secure seal.

NPR: Challenger: Reporting a Disaster's Cold, Hard Facts

It's the trinkets - the branded mugs, T-shirts and key-rings given away as promotional gifts.

BBC: Quiz of the week's news