вот, с сайта посольства США в Москве:
U.S. Embassy Moscow's Consular Section wishes to remind applicants that additional administrative processing is often required for individuals involved in scientific or technical fields of work or study. We recommend that all applicants, particularly those involved in scientific or technical fields, apply for a visa as soon as they are aware of their travel plans to the U.S. We urge all applicants to apply no later than 30 days before the intended date of travel. Unfortunately, in most cases the possibility that your visa may be subject to additional processing will not be considered an emergency for the purpose of granting expedited appointments.
http://moscow.usembassy.gov/nivapplying.html
IT подпадает