Abstract: Method for purifying antibiotic compounds of the dalbaheptide family by means of isoelectric focusing (IEF) in a multicompartinent electrolyzer with immobiline membranes, in particular zwitterionic membranes. A further object of the invention are pure antibiotic compounds obtainable according to the present process, in particular the pure 6.sup.B -decarboxy-6.sup.B -(hydroxymethyl)-N.sup.63 -3-(dimethylamino) propyl amide derivatives of antibiotic A40926.

Abstract: A sound-attenuating ventilation louver is provided for location in an aperture of a wall which separates a chamber containing a source of noise from the external environment, the purpose of the louver being to allow gaseous flows to pass into and out of the chamber while minimizing the noise passing out through the louver from the noise source. The louver includes a plurality of profiled slats each in the form of an aerodynamically-shaped blade. Each slat includes a solid portion made of a sound-absorbent material and a hollow portion defined by a thin wall of rigid material; in use of the louver the sound-absorbent solid portion of each slat is disposed towards the chamber containing the noise source while the hollow portion is disposed towards the external environment. The hollow portion of each slat is subdivided into a plurality of chambers communicating with the atmosphere through ports and acting as resonators.

Abstract: An exhaust silencer for an agricultural tractor having a diesel engine with a cylinder capacity 2.5 to 4 liters and developing a power of 50 to 75 HP has a cylindrical body of elliptical cross-section which is closed at each end by an end-wall and is subdivided internally into two resonance chambers and two gas expansion chambers by three dished baffle-plates, the third baffle-plate having two tubular ducts. To optimize the acoustic performance specific dimensions of the chambers, of the ducts, of a perforated induction pipe and of an outlet pipe are prescribed.

Abstract: An exhaust silencer for a railway locomotive with a supercharged, six-cylinder diesel engine developing a power of about 200-250 HP has a cylindrical body closed at each end by an end wall and subdivided into three resonance chambers and three gas expansion chambers by five dished baffle-plates, the fourth and fifth baffle-plates each having four tube sections. To optimize the acoustic performance specific dimensions of the chambers, of the tube sections, of a perforated induction pipe and of an outlet pipe are prescribed.