In {HEAD ~ certain embodiments}, surface 501 is exposed to overlapping {TAIL ~ fields} of electromagnetic radiation 
In { HEAD ~ certain embodiments } , surface 501 is exposed to overlapping { TAIL ~ fields } of electromagnetic radiation
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH