A chrome-free acidic aqueous solution of sulfuric acid and one or more organic acids and manganese and ions is applied to an organic polymer surface to etch the surface. These systems and processes are accomplished by using a computer to intraoperatively obtain images of body parts and to register, navigate, and track surgical instruments. The beams may include openings to control mechanical properties while allowing edge to edge spacing between adjacent beams to be selected to provide desired electrical properties. Each primary call process comprises a primary call instance data table for storing call instance data used by the originating half-call model call application and the terminating half-call model application.