The purpose of {TAIL ~ the activation mechanism} is to stiffen the leaflets to {HEAD ~ the same level} as in the passive version, i.e., to provide the stiffness necessary to resist flow until the desired threshold pressure level is reached 
The purpose of { TAIL ~ the activation mechanism } is to stiffen the leaflets to { HEAD ~ the same level } as in the passive version , i.e. , to provide the stiffness necessary to resist flow until the desired threshold pressure level is reached
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH