Methods of displaying video content include obtaining a video content record to be displayed and determining an associated aging characteristic associated with the video content record. Whether an equivalent XML path language expression can be generated for each of the expression components is determined. The comonomer may be a nonpolar, ionic, polar comonomer or mixtures of such monomers. The pulsed radar system transmits short pulses coordinated by the backscatter state of the RFID tag and the system creates a differential signal comprised of the differences between radar signals obtained during the first and second states of the tag to obtain an uncorrupted measure of a round trip time of flight of said radar pulses between the pulse radar system and the RFID tag. and the extrapolated temperature of the termination of the glass transition is preferably 70 C. The grating structure according to the invention comprises a transmission volume holographic grating produced on a reflective support.