Methods and systems for processing a body of reference material to generate a directory for accessing information from a database. The first electronic camera picks up an image from an opening of each of the test tubes, and the second electronic camera picks up an image from a side thereof. When an overload condition is detected, the usage rate of at least one of these users is changed, at least in part according to the user’s set of persistence vectors. The front support structure pivots the seat assembly between a generally horizontal seating position and a generally upright tumbled position.