I completed my masters and have an admit for a phd. I have come back home for a semester break and will be going back in august to start my phd. My first F1 visa is still valid and will expire in 2012. After completing my masters i applied for my opt extension but cancelled my opt in one month and came home. Since i will be chaning universities and my phd would take more than 2 years to complete can i reapply for a F1 visa with my new i20?