Abstract: A piston of an internal combustion engine includes a piston head including a ring belt having a firing land and a plurality of ring grooves for receiving piston rings. A first ring groove of the plurality of ring grooves that is arranged directly adjacent to the firing land has a ring groove axis that runs coaxially to a piston axis of the piston. The first ring groove has an upper groove flank and a lower groove flank arranged away from the firing land relative to the upper groove flank. At least the lower groove flank of at least the first ring groove is inclined by an inclination angle with respect to an orthogonal plane relative to the piston axis, and the inclination angle of at least the lower groove flank varies in a circumferential direction of the piston axis.

Abstract: A downhole apparatus is described comprising a body and a sealing arrangement located on the body. The body has a longitudinal axis and the sealing arrangement comprises at least one elongated sealing member with an axis of elongation extending around the longitudinal axis. The sealing member comprises a material selected to expand on exposure to at least one predetermined fluid, such as a hydrocarbon or aqueous fluid encountered in a wellbore. A method of forming the apparatus and methods of use are described. Embodiments of the invention relate to wellbore packers.