An apparatus for cleaning an animal’s paw broadly comprises an elongated rigid cylindrical sidewall having an end wall and an open rim which substantially seals to an animal’s paw as the paw is withdrawn from the apparatus. A photocathode is formed on the inner side of the faceplate. This technique has been used to identify peptide ligands that foster the growth of human stem cells, which otherwise require an extracellular matrix in order to grow in an undifferentiated state. For each iteration of the recursive processing, a modal interval linear interpolation operation is executed. The system also includes a power source controller configured to select from a plurality of power sources based on availability of one or more power sources and time so as to maximize the economic efficiency of operating the system. The catalyst composition is prepared by:.