In some embodiments, the invention involves using a dedicated service processor with out-of-band capabilities to enable a secure boot using biometric data to authenticate the user. When the fallen pulse signal is detected, the sampling unit directs the signal state discriminating unit to obtain the state of the pulse signal at a time point, which is output as the pulse duration of the pulse signal. The polarity of the heating element can be switched upon the occurrence of a predetermined event such as between read or write events or upon activating deactivating the disk drive device or could be performed at regular, predetermined time intervals. Statistical information derived from the inverted index of each sub-collection is collected by a global collection custodian and compiled into a global index. The cross-linking agent is one or more monomers used to lower the viscosity and promote cross-linking, and include acrylate esters of mono-, di-, tri-, or tetrafunctional alcohols.