A structural flotation device formed of two elongated shear panels embodied as substantially planar sheets of high-density polyethylene that are spaced apart by two or more substantially parallel and spaced apart heavy-gauge HDPE buoyancy tubes. Generally speaking, the systems assume multiple configurations to facilitate both use and storage of the dumbbell assemblies. An arterial probe is inserted into an artery in the forearm of the patient and is coupled into the control and display module and provides an electrical output signal representing the dissolved oxygen in the arterial blood. The thus obtained integrated substrate is cut into individual semiconductor light emitting device bodies. In one embodiment, the assistance signals include Doppler frequencies for the satellites.