A cement additive comprising a polycarboxylic acid type copolymer andor a salt thereof and a polyalkylene glycol derivative, wherein said polycarboxylic acid type copolymer contains one or more species of copolymers composed of at least an unsaturated polyalkylene glycol type monomer and an unsaturated mono- or dicarboxylic acid type monomer as their monomer components. In one form, one spectrophotometer of a plurality that may be present in an image rendering system is treated as \u201cprimary\u201d. The PDLC material offers all of the features of holographic photopolymers with the added advantage that the hologram can be switched on and off with the application of an electric field. Then, the host-handling processor turns off a SW of a host IF and the disk processor writes, to an HDD, data that have been written to a cache memory. Only the data blocks affected by the modification are duplicated. The methods comprise the step of administering to the patient a composition comprising a therapeutically effective amount of an extract from pomegranate.