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