A rewriteable nonvolatile memory cell having two bits per cell is described. A movement in a direction parallel to the line of sight is determined from an average position, a relative distance and slopes of linear fittings for each point-component of the points in the two images. A gearbox selector is mounted for movement about an axis and in the direction of the axis. An additional aspect of the present invention relates to the synthesis of combinatorial libraries of the heterocyclic compounds, and the screening of those libraries for biological activity, e. Compositions which include these new proteins, recombinant cells, shuffling methods involving the new homologues, antibodies to the new homologues, and methods of using the homologues are also provided.