sentences:  Although dynamic memory is only specified and "guaranteed" to retain its contents when supplied with power and refreshed every short period of time (often ), the memory cell capacitors often retain their values for significantly longer time, particularly at low temperatures.Under some conditions most of the data in DRAM can be recovered even if it has not been refreshed for several minutes.This property can be used to circumvent security and recover data stored in the main memory that is assumed to be destroyed at power-down.