The source of an unusual crunching sound heard by the crew of the international space station earlier this week remains unexplained, but it does not appear to have come from an impact with space debris, a NASA spokesman said Friday.

A nanoscale transistor that self-assembles instead of having to be painstakingly put together molecule by molecule has been developed with DNA proteins by scientists from the Technion Israel Institute of Technology in Haifa.

The Federal Bureau of Investigation has been collecting information on the tactics, training and organization of antiwar demonstrators, The New York Times reported in Sunday editions.

In a report sourced to several interviews as well as a confidential bureau memorandum, the Times said that the law enforcement agency has also advised local officials that they should report to counterterrorism squads any suspicious activity at protests.