Abstract: In an embodiment a semiconductor emitter includes a semiconductor layer sequence having a plurality of active zones, each active zone including at least one quantum well layer and at least two barrier layers between which the at least one quantum well layer is embedded, and at least one tunnel diode located along a growth direction of the semiconductor layer sequence between adjacent active zones, wherein a thickness of the at least one tunnel diode is at most 40 nm, and wherein a distance between adjacent barrier layers of adjacent active zones, facing the at least one tunnel diode, is at most 50 nm.

Abstract: An improved process for working-up crude liquid vinyl acetate which contains vinyl acetate, acetic acid, water, and ethyl acetate, possibly together with small amounts of other impurities, by distillation is disclosed, wherein a mixture essentially containing vinyl acetate and water is obtained as the top product and essentially acetic acid is obtained as the bottom product, and a sidestream, in which ethyl acetate is concentrated is removed. According to the process the top product is condensed and, after phase separation, a portion of the vinyl acetate phase is recycled as reflux into the distillation. The improved process involves the introduction of water above the point of introduction of the crude vinyl acetate. Preferably, the water is introduced in an amount which is not greater than the amount required to achieve a maximum water content in the vapors leaving the distillation at the top.

Abstract: A new catalyst which can be prepared from certain aluminosilicates and certain clay minerals, a process for its preparation and a process for the skeletal isomerization of n-alkenes to iso-alkenes which is carried out in the presence of this catalyst.

Abstract: Producton of cyclopentene by splitting of dicyclopentadiene to produce cyclopentadiene and hydrogenating the cyclopentadiene to produce the cyclopentene in crude form, and distilling the crude cyclopentene to separate low boilers and high boilers therefrom and provide the cyclopentene product. The high boilers are recycled to the dicyclopentadiene splitting stage and serve to reduce resin formation in that stage. The process is particularly effective where the dicyclopentadiene has a low content of the so-called "codimers" which, if present in sufficient amount, would reduce resin formation.