Abstract: A door drive for a motor vehicle door or motor vehicle flap, which is provided with an electromotive drive, a transmission downstream of the drive, and a force-transmission element. The force-transmission element is operatively connected to a leaf of the motor vehicle door or motor vehicle flap. An output element of the transmission and the force-transmission element are coupled by a toothing with compensation for play. According to the invention, the output element and/or the force-transmission element are not only designed to be moveable for play compensation, but can also be permanently fixed after the compensation for play.

Abstract: An apparatus (1) for the irradiation of solar cells (2) is described. The apparatus (1) contains at least 400 solid-state radiation sources in a matrix-like extensive arrangement for emitting monochromatic light in a spectral region of 880 nm, preferably for silicon cells.

Abstract: An apparatus (1) for converting solar energy into electrical energy and for radiating and/or receiving high frequency electromagnetic waves is described. The apparatus (1) includes at least one solar cell (2) provided with electrodes in the form of electrically conducting contacts, wherein at least one of the contacts of the solar cell at the same time forms an antenna element.