Abstract: In a wave energy apparatus vertical movement of a float suspended in a body of water drives a power generator. Motion of the float is controlled by taking advantage of the movement of water on the upper surface of the float body. The upper surface can be used to generate hydrodynamic forces acting downwardly against the upward forces acting on the lower surface of the float body, effectively damping its movement in the presence of waves that might otherwise provoke undesirably large vertical movement of the float. The movement of water onto the upper surface can be controlled by adjusting the depth at which the float is suspended.

Abstract: A dental tape is constituted by a length of incipiently fibrillatable plastics film. The tape may be made by extruding a polypropylene film in strip form onto chilled take-off rollers and then roll embossing the film by means of hardened steel rollers. After embossing, the film is oriented by means of draw rollers.In an alternative embodiment, the tape is made by partially fibrillating a plastics film by means of a spiked roller, followed by drawing to orient the film.The dental tape may be contained in a hand-held dispenser.