A platen roller is provided for conveying a thermally active adhesive sheet having a recordable surface formed on one side of a sheet-like substrate and a thermally active adhesive layer formed on the other side of the sheet-like substrate. The present invention uses two U-shaped port plate supporters of high rigidity to respectively join with drive devices such as lead screws, shaft bearings, and a lead device, and then join with components such as a port plate, a port door, and a base. Libraries of compounds based on a peptide motif and compounds identified by the methods of the invention are also disclosed. If the first switching field is substantially higher than the second switching field, the first MTJ may be a reference element for the second MTJ.