NPR's Vicky O'Hara reports people of Chinese descent in the United States, both citizens and non-citizens, have been alarmed by the recent arrests of academics by Chinese authorities. At least six U.S. citizens have been taken into Chinese custody since December, and an unknown number of non-U.S. citizens. Some of those who were detained and released have signed statements promising to keep their ordeals secret. Specialists in sociology and mass communication seem especially vulnerable to arrest. Some Chinese in this country are canceling plans to visit relatives back home.