A cover structure for a scan device comprises a cover mounted on a housing of the scan device and an angle-positioning mechanism disposed between the housing and the cover. The method includes steps of retrieving traffic information for roadways included in a predictive travel zone, including traffic incidents. A drive link permits the rotating portion of the valve to be optionally coupled directly to the motor of the drill string. A first capacitor dielectric layer isolates the capacitor storage node from the buried plate. In use, the application program communicates information relating to the application data to the scanning subsystem to facilitate the scanning by the scanning subsystem. The novel structural forms of T cell costimulatory molecules can be used to identify agents which stimulate the expression of alternative forms of costimulatory molecules and to identify components of the signal transduction pathway which results in costimulation of T cells.