A rotor for an electrical machine has a rotor body and permanent magnets arranged on the circumference of the rotor body, wherein those areas of the circumference of the rotor body which are covered by the permanent magnets have at least one recess andor that side of the permanent magnets which faces the circumference of the rotor body has at least one recess. In one example, the hydrocarbon trap includes an adsorber roll including an adsorbing material and a corrugate support, where the corrugate support is rolled with the adsorbing material to form a wound adsorber roll. The coupling facility includes a plurality of cache structures for catalogs of a cluster computing system.