Nigerian Information Minister Dora Akunyili told reporters a range of measures have been introduced to boost security at airports in response to the failed attack.

VOA: standard.2009.12.28

You have to inject it multiple times because the first blip that you get in immune response is not very high, you have to boost and often you have to boost again in order to get a high enough response to be protected.

你必须得进行多次注射,因为第一次注射,无法使免疫系统产生强烈反应,你得要增强免疫,通常还得再增强一次,以使反应足够强烈,从而起到保护作用

耶鲁公开课 - 生物医学工程探索课程节选

Earlier this year, the president challenged the private sector to join with government in a nationwide effort to boost student achievement in science and mathematics.

VOA: standard.2009.11.24

On broader themes, Mr.Obama announced a U.S.initiative to boost lending and spur economic growth and recovery in the Americas, and proposed a hemispheric partnership to tackle energy and climate challenges.

VOA: standard.2009.04.17

President Obama got the most applause from opposition Republicans when he said the number-one focus in the coming year would be on creating jobs and giving a boost to small businesses.

VOA: standard.2010.01.28