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