In {HEAD ~ an embodiment}, {TAIL ~ the barrier region} 38 is significantly less conductive than the regions 34 
In { HEAD ~ an embodiment } , { TAIL ~ the barrier region } 38 is significantly less conductive than the regions 34
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH