In certain embodiments, multiple portions of {HEAD ~ surface} 501 are sequentially exposed to {TAIL ~ electromagnetic radiation} 
In certain embodiments , multiple portions of { HEAD ~ surface } 501 are sequentially exposed to { TAIL ~ electromagnetic radiation }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL