A sliding subframe mounted to the derriere-supporting section of an adjustable bed is adapted to translate the rotational axis of the torso-supporting section of the bed toward the head end as the torso-supporting section is raised to an inclined position, and back toward the foot end as the torso-supporting section is lowered to a level position. In an example, a system effective to form graphene may include a source of carbon atoms and a reaction chamber configured in communication with the source of carbon atoms. When the U-shaped end portions clear the bottom wall of the tub, they resiliently spring inward into supporting positions under the bottom wall. The first granularity may be finer than the second granularity.