The present invention provides a system and method for reserving space to guarantee file writability in a file system supporting PCPIs. The lighting device comprises a light emitter thermally connected to a heat sink. Moreover the invention describes an appropriate method for generating audio-visual summaries for audio-visual program content. Depending on the types of contaminants for which the sample is tested, it is possible to detect whether explosives, biological or chemical agents, andor narcotics residues are present on or in the item being screened. The projecting portions have a substantially trapezoidal cross section.