A computer readable medium, method and user device for a user interface functionality for SMS and SMS-like message conversations is provided. The techniques allow for an increase in the optical thickness of the photocathode device, while simultaneously allowing for an increase in the probability of electron escape into the vacuum of the device. Here, the signed, digital certificate is signed with a group private key that is associated with a certification authority for the group. The error correcting method further includes writing the parity information into one of the physical pages of the first physical block following the data and correcting the data in the first physical block according to the parity information. Turning the threaded stud positions the bushings to expand the inner sleeve, whereby the crank axle portions of the two tubular members are secured within the inner sleeve and the outer sleeve by the expanding inner sleeve.