According to one embodiment of the invention, the pockets are defined by upstanding walls in {TAIL ~ the movable element} adjacent the surface exposed to {HEAD ~ gases} of combustion 
According to one embodiment of the invention , the pockets are defined by upstanding walls in { TAIL ~ the movable element } adjacent the surface exposed to { HEAD ~ gases } of combustion
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH