Systems for replacement of the ends of bones with prostheses, and methods of using the systems for bone replacement. Electrons are transferred from the layer of graphene to the metal oxide film, forming a hole accumulation layer in the layer of graphene. The mounting cup is attachable to the rotating head of the bracket frame of a positively engaging tank holder usable with cylindrical tanks such as self-contained breathing apparatus primarily for facilitating adjustability of positioning of retaining of the tank with respect to the mounting bracket. The sensor is operable to transmit light along a plurality of wavelengths into the subject’s tissue, and produce signal data representative of the light sensed from the subject’s tissue.