Abstract: A polyurethane foam and associated production process, in particular flexible to semi-hard block foams or soft molded foams, using polyesters or polyethers as polyols. A carbamate, or a mixture of carbamates, is used simultaneously as propellant and as catalyst, wherein the carbamate or the carbamates have the general Formula I wherein: R1 and R2 represent the same or different alkyl radicals, R3 and R4 represent the same or different radicals and denote hydrogen or alkyl radicals, R5 denotes hydrogen, an alkanol radical, a polyether monool radical or the alkyl radical, characterized by X and n represents 2 or 3.

Abstract: The invention pertains to metallocenes of formula (I), wherein M is a metal group of the group of Ti, Zr, Hf, V, Nb and Ta or an element from the group of lanthanides; X.sub.1 and X.sub.2 stand for an alkyl, alkoxy, aryl, aryloxy, alkenyl, arylalkyl, alkylaryl or arylalkenyl group, hydrogen or halogen; L.sub.1 and L.sub.2 stand for a hydrocarbon which can form a sandwich structure with M; R stands for C, Si, Ge or Sn; and A and B stand for a trimethylsilyl radical, B optionally for an alkyl or aryl radical.

Abstract: The invention relates to the use of cyclic organometallic compounds as components in coordination catalyst systems, to corresponding coordination catalyst systems and also to processes for the preparation of polymers by coordination polymerization and of unsaturated hydrocarbons by catalyzed metathesis of alkenes and alkynes using such coordination catalyst systems.

Abstract: The invention relates to the use of cyclic organometallic compounds as components in coordination catalyst systems, to corresponding coordination catalyst systems and also to processes for the preparation of polymers by coordination polymerization and of unsaturated hydrocarbons by catalyzed metathesis of alkenes and alkynes using such coordination catalyst systems.

Abstract: A Passive loudspeaker enclosure for a television receiver. Interference in the reproduced picture caused by magnetic stray fields from the enclosure occurs, in particular, with color television receivers with 33 inch picture tubes. The task is to reduce the magnetic stray fields by employing simple measures and without using additional components until the interference no longer appears in the picture. In particular, for a loudspeaker enclosure in a television receiver with a 33 inch picture tube.

Abstract: A membrane for a loudspeaker is designed so as to facilitate manufacture and to improve the tone of the loudspeaker. The membrane consists of a first plastic film (5a) which serves to retain the shape and a second plastic film (56) laminated to the first film which serves to damper partial oscillations. The membrane is particularly suitable as a conical membrane for a loudspeaker for a television receiver.

Abstract: Loudspeaker unit including a frame (FIG. 2) serving as sound guide to which the loudspeaker chassis (FIG. 1) is releasably fastened. According to the invention, form-locking cooperating detent means (4-6, 29-31) are provided on the frame and on the loudspeaker chassis. The loudspeaker chassis can be inserted into the frame by means of a relative translatory movement and can be removed by a rotational movement. Thus it becomes possible to install the loudspeaker in the frame and remove the loudspeaker from the frame by means of automatic machinery.

Abstract: In directly bonding a metal to ceramics, in accordance with the invention, that surface of a metal component which is to be bonded by heating to a ceramic substrate is provided with parallel-running grooves before the preoxidation. The grooves make it possible to optimize the quantity of oxygen available at the bonding location and provide good flow behavior of the melt. As a result, a bond with good adhesion is obtained. Moreover, there is no formation of a thicker oxide layer on the free smooth surface of the metal component.

Abstract: In an electromagnetic transducer including a member producing a magnetic field and presenting an air gap traversed by the field, a mass of magnetic liquid extending across the air gap, and a moving coil mounted on a moving coil carrier supported for movement through the air gap, the carrier is provided with at least one passage located to communicate with the magnetic liquid during at least part of the movement of the coil carrier through the air gap for permitting flow of magnetic liquid from one side to the other of the carrier in the direction of the air gap.

Abstract: A dynamic electroacoustic transducer comprising a magnetic pole case defining a magnetic air gap, a coil movably mounted in the air gap and spaced from the magnetic pole case with magnetic liquid extending between the coil and the case in the air gap. A diaphragm is connected to the coil and attached peripherally to the magnetic pole casing so that airtight spaces are defined above and below the coil which are in communication with each other. The airtight sealing of the spaces prevents the liquid portions of the magnetic liquid to evaporate which would result in deterioration of the characteristics of the dynamic electroacoustic transducer.

Abstract: A dynamic electroacoustic transducer includes a moving coil which is arranged in an air gap between a pole piece and a pole plate which is filled with a magnetic liquid. At least the outside of the coil has a smooth surface in contact with the magnetic liquid. The coil may also advantageously be wound on a carrier from a wire which is flat at least on one side so that this flat side is turned outwardly and presents a smooth continuous surface. The cross-section of such a wire may advantageously be rectangular. The coil may be coated on its outside surface with a foil of well-conducting material, such as aluminum, or the grooves between a cylindrical coil, for example, may be filled with a lacquer or the like.