VOA常速英语:US Alert for Terrorist Threats Following bin Laden's Death

短语讲解：

1. While the U.S. Department of Homeland Security has not issued specific terror warnings, law enforcement agencies have heightened security around the country to guard against attacks by al-Qaida-affiliated groups or by terrorists acting on their own.

act on奉行; 按照…而行动
例句：The police are acting on the information received.
警方正根据获得的情报采取行动。

2. Law enforcement agencies across the United States have stepped up patrols at travel hubs and government facilities, following warnings that Osama bin Laden's death might inspire home-grown extremists.

step up (使)增加, (使)提高
例句：The firm must step up production this year.
这个公司今年必须提高生产。

3. "You're not going to have 19 hijackers taking down aircraft, but kids trying to find AK-47s or buy handguns or buy hand grenades on the street and go do something at a commercial facility like a mall or a 7-11 [convenience store]," said Philip Mudd, a former CIA officer and FBI counterterrorism agent.

take down 拆卸
例句：They are taking down the old building.
他们正在拆毁旧建筑物。
convenience store 便利店

4. Just a year year ago, a Pakistani-born U.S. citizen - Faisal Shahzad - tried to set off a car bomb in New York's Times Square.

set off点燃, 爆炸
例句：The children are setting fireworks off in the garden.
孩子们在花园里燃放烟火。

5. James Carafano, a national security expert with The Heritage Foundation in Washington, says security officials are keeping a close eye on al-Qaida-affiliated groups.

keep a close eye on 密切关注
例句：We should keep a close eye on new technology. 
我们应该密切新技术。 

6. "The U.S. has always been concerned about al-Shabab, that is a group based in Somalia," he said.

be concerned about 关心,挂念
例句：More and more people begin to be concerned about our natural environment.
越来越多的人开始关心我们的自然环境。

7. The group is linked to radical cleric Anwar al-Alawki, an American believed to have ties to the failed 2009 Christmas Day plot to blow up a U.S.-bound jetliner, and a scheme to plant parcel bombs on U.S. cargo flights last November.

have ties to 与…有联系
例句：The military says the militants have ties to al-Qaeda. 
军方称武装分子和基地组织有联。
blow up (使)爆炸, 将…炸毁, 毁掉
例句：The terrorists blew up the police station.
恐怖分子炸毁了警察局。

8. They definitely have a tendency to go back to the targets that they know.

have a tendency to有…趋势
例句：You have a tendency to romanticize your life.
你有把生活浪漫化的倾向。

9. You don't have to have a lot of sophisticated efforts to go after them."

go after追逐, 追求
例句：The dogs went after the wounded deer.
猎狗追捕受伤的鹿。