An air void-forming agent, more particularly for cementitious systems, contains at least one air void-forming material with foaming effect, at least one air void-forming material with defoaming effect, and water. The workpiece is heated, causing a top portion of the metal layer to interact with the semiconductive material layer and causing a bottom portion of the metal layer to diffuse into the dielectric material layer. Thus, the file system reads a chunk from or writes a chunk to the storage device by reading or writing the sector having the chunk. An image sensor interface is connected to the processing circuitry and is configured to receive signals from an image sensor and to pass data representing the signals to the programmable processing circuitry. A preferred embodiment comprises a light beam generator including a housing, elongate members removably secured to the housing and complementing the rail for enabling the housing to be retainably slid along the rail, a transverse rail latching device removably secured to the housing, and a replaceable ambidextrous tail cap switch.