Abstract: A process for the stereospecific polymerization of olefins is described, wherein the selected monomer is homopolymerized, or the selected monomers are copolymerized, by reacting the selected monomer or monomers in the presence of a catalyst consisting of an uranium .pi. - allyl compound represented by one of the formulae: ##EQU1## in which R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5, the same or different, may be hydrogen atoms, alkyl radicals having from 1 to 10 carbon atoms, aryl radicals having from 6 to 10 carbon atoms, cycloalkyl radicals having from 4 to 10 carbon atoms, and alkylaryl radicals; the dotted line indicates the possible delocalization of the valence electrons; X is an anion selected from among Cl.sup.-, Br.sup.- and I.sup.-; and n is an integer ranging from 1 to 3; and, optionally, a co-catalyst which is a Lewis acid, or a complex thereof with an ether, a tertiary amine or a phosphine.

Abstract: A continuous bi-compound bulky yarn consisting of a pair of acrylic polymeric components differing from each other in some of their properties is prepared by spinning those components in solution to produce a spun yarn which is drawn and then, successively, passed through a first oven heated to a temperature in the range of 130.degree.-250.degree.C, subjected to a false twist by means of a rotating spindle, passed through a second oven heated to a temperature in the range of 120.degree.-240.degree.C, and wound on a holder.

Abstract: A process is described wherein prilled urea of low biuret content is prepared by crystallizing urea of low biuret content by melting from only 30 to 70 percent of the urea crystals through the application of heat thereto, and forming a heterogeneous mixture of the unmelted crystals in the melted urea. That mixture is then fed to conventional pelleting apparatus.

Abstract: An olefin or diolefin is polymerized, and mixtures thereof are copolymerized, in the presence of a catalyst system consisting of:A. a uranium compound consisting of U(OCH.sub.3).sub.4, U(OCH.sub.3).sub.3 Cl, U(OC.sub.4 H.sub.9).sub.4, U(OC.sub.8 H.sub.17).sub.4, U [N(C.sub.2 H.sub.5).sub.2 ].sub.4, U [N(C.sub.2 H.sub.5).sub.2 ].sub.3 Br, U(OCH.sub.3).sub.5, U(O-i-C.sub.4 H.sub.9).sub.5 ;b. a reducing compound of a metal belonging to the 2nd or 3rd group of the periodic system, selected from the hydrides, mixed hydrides and alkyl derivatives thereof;C. a Lewis acid selected from AlBr.sub.3, AlI.sub.3, AlCl.sub.3, AlCl.sub.3.OEt.sub.2, Al R Cl.sub.2, B Cl.sub.3 and TiCl.sub.4, wherein R is a hydrocarbon radical.