SAN'A, Yemen – Yemeni police arrested a woman on suspicion of mailing a pair of bombs powerful enough to take down airplanes, officials said Saturday as details emerged about a terrorist plot aimed at the U.S. that exploited security gaps in the worldwide shipping system. Investigators were hunting Yemen for more suspects tied to al-Qaida and several U.S. officials identified the terrorist group's top explosives expert in Yemen as the most likely bombmaker.The explosives, addressed to Chicago-area synagogues, were pulled off airplanes in England and the United Arab Emirates early Friday morning, touching off a tense search for other devices....