Abstract: The invention relates to a photochemical cell (1) and to a method for the solar-driven decomposition of a starting material, in particular water or carbon dioxide, into a product gas bound therein, in particular hydrogen or carbon monoxide, comprising a supply line (7) for the starting material, a discharge line (9) for the obtained product gas, a first electrode (2) made of a photoelectrically active material and exposed to solar radiation (3?, 3?) during operation, and a second electrode (5), wherein the electrodes (2, 5) are connected to each other in a closed circuit by means of an electron conductor (4) for transporting electrons excited by the solar radiation (3?, 3?) in the first electrode (2) and an ion conductor (6) for transporting ions produced in the decomposition of the starting material, wherein an electrolyte made of a heat-resistant solid material and arranged between the electrodes (2, 5) is provided as the ion conductor (6).

Abstract: The invention relates to a drying cylinder for drying a paper, cardboard, tissue or other fibrous web in a machine for manufacturing and/or finishing the former, which is heated from inside with a gaseous heat transfer medium, the inner side of the roll shell having elevations which protrude out of the condensation of the heat transfer medium which collects on the inner side. Here, the heat transfer is to be improved by the fact that the elevations are at least 1.2 times higher than the mean condensation height and/or the cross section of the elevations is reduced inwards.