I was accepted through email on 2/4, I did not get contact for any interviews.
I'm also waiting on Duke BME, Caltech CNS, and Berkeley EE, for phD fall 2013. Fairly sure Caltech and Berkeley have already made their decisions
I emailed Duke today, the director told me Duke doesn't have an ad-comm and the faculty does recruiting independently. The person handling recruiting at the lab I'm interested in at Duke told me that BME's about to send out interview invitations within the next week, as the person in charge of sending invitations has experienced some delays. Also, I was told that Duke only makes acceptance decisions after interviews.