The purpose of the activation mechanism is to stiffen {HEAD ~ the leaflets} to {TAIL ~ 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 
to
The purpose of the activation mechanism is to stiffen { HEAD ~ the leaflets } to { TAIL ~ 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 OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH