{HEAD ~ An annular seal} between {TAIL ~ the two barrier layers} is formed by pressing the layers together while applying ultrasonic vibrations to them 
between
{ HEAD ~ An annular seal } between { TAIL ~ the two barrier layers } is formed by pressing the layers together while applying ultrasonic vibrations to them
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH