In related embodiments of the invention, {TAIL ~ at least one recessed region} is positioned at {HEAD ~ a magnetic pole} 
In related embodiments of the invention , { TAIL ~ at least one recessed region } is positioned at { HEAD ~ a magnetic pole }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD