A novel ligand that binds the Elk subfamily of Eph receptors is identified, and methods for making the soluble Elf-6 ligand in biologically active form is described. The method provides catalyst temperature regulation while reducing fuel consumption. A pair of arcuately shaped guide rails are conjoined to the central frame and extend over and around the end bars. At such point, the stored data can be progressively migrated from the first virtualizer to the second virtualizer. The semiconductor nanowire has a P-type semiconductor portion and an N-type semiconductor portion, and one of the P-type semiconductor portion and the N-type semiconductor portion is a common structural element of both the first and second regions.