The most troubling of the short-lived HFCs were invented to replace chlorofluorocarbons, refrigerants that were thinning the ozone layer in the upper atmosphere, and were also a major warming agent.

其中最短命的氢氟碳化合物，被发明取代氯氟烃，制冷剂可以稀释高层空气中的臭氧层，同时也是主要的升温剂。

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So is that not troubling that he got through that first layer?

WHITEHOUSE: Press Briefing

Troubling for more traditional regional banks a layer or two down from the very biggest U.S. banks are rules that may force them to raise capital and, bankers argue, restrict lending.

FORBES: Dodd-Frank Bill Complete, Bankers React

More troubling are security issues, since most safeguards work in a different layer of a network from the data-hauling Ethernet layer of 802.11.

FORBES: Mr. and Mrs. Network