Abstract: This process for preparing L .alpha.-amino-acid is characterized in that the corresponding racemic .alpha.-amino-acid is hydrolysed in liquid phase in a free form or in the form of a salt, by an agent containing an L-stereospecific amidase and in that the L .alpha.-amino-acid obtained is separated from the D .alpha.-amino-amid unhydrolysed. This process is appropriate for the preparation of optically active natural amino-acids.

Abstract: Electron multiplier tube, comprising along the principal axis an electron-emitting surface, several dynode stages with distributed structure, capable of reflux secondary electron emission, and an electron-receiving surface, as well as means producing an electron-accelerating electric field generally oriented along the principal axis, from the electron-emitting surface to the electron-receiving surface. With it is associated coil means producing a magnetic field generally oriented along the principal axis of the tube.Particular example is a photomultiplier with high spatial resolution.