There are two models of protein folding that are currently being confirmed: 1  The diffusion collision model, in which a nucleus is formed, then the secondary structure is formed, and finally these secondary structures are collided together and pack tightly together.
ATT Validity Dates. 1  Each ATT is valid for a period of time specified by the BON/RB (the average length of an ATT is 90 days). 2  Once the BON/RB has declared you eligible to test and you receive your ATT, you must test within the validity dates on the ATT.
If you need to test outside the U.S., please e-mail militaryexaminee@nbcc.org.â¢ To reschedule your exam, contact Pearson Vue at least 24 hours prior to your scheduled appointment. There is a $25 fee to reschedule within seven days of your appointment. You cannot reschedule less than 24 hours prior to your appointment.