Abstract: A sealing system for large-surface thin parts to be interconnected, used for the mutual sealing of separating plates, in particular of bipolar plates with interposed ion-exchange membrane units (MEA) in fuel cells. The system uses sealing elements made of polymer material, in which the individual sealing elements, injected into recesses, form an integral unit with the respective associated bipolar plate. Provision is made between the side walls of the sealing elements and the adjacent walls of the recesses for free spaces or gaps to accommodate the elastic sealing material which spreads during the compression. The sealing elements only partially fill the recesses or gaps and the height (H) of the sealing elements are greater than the depth (T) of the recess or gaps before the compression.

Abstract: The device for feeding gaseous substances into liquid media comprises a number of hollow membrane bodies which are permeable to gas and contain the liquid media. These membranes are arranged with a distance between them in such a way that they can be reached by the gaseous substances. Such a device lends itself particularly to air purification. Gaseous substances such as nitrogen oxides can be converted with the aid of this device. According to the invention the device can also be used for pure or mixed cultures of various microorganisms whereby, above all, information about the toxicity of individual substances can be obtained.

Abstract: The invention relates to a process for producing an aqueous suspension of nitrifying bacteria using a growth medium containing ammonia or nitrite, in which the bacteria remain metabolically and physiologically active by induction of the specific nitrification enzyme systems, in which the bacteria can be kept for long periods and can be finally used, as well as a device for carrying out the process.