A method of operating an internal combustion engine uses fuels having different reactivities obtained from the same fuel source. The optical lens includes a diverging surface and a cylindrical surface. The macromer bears acrylic end-groups and comprises a core Y defined by Formulas 2 to 9, that is linked by urethane, ester or anhydride bonds to the acrylic groups. The second portion of the nut is trapped between the first panel and the second panel.