A graded-refractive-index optical plastic material composed of an amorphous fluoropolymer and at least one material which differs from the polymer in refractive index by at least 0. A primer having a 3-hydroxyl group at one end and having a sequence of nucleotides sufficiently homologous with an identifying sequence of nucleotides in the target DNA is selected. The front and side rails are respectively attached to the tops of the front and side walls of the bed. The result is an aspherical lens whose measured cross-sectional profile has only small errors from an ideal curve. An elongate slot is formed in each of the arms for engaging an edge of the wall of the panel about the hole in the panel. Recording an event may include recording a result of the attempt.