Abstract: A process for controlling the continuous gas-phase polymerization of one or more alpha-olefins in a fluidized and/or mechanically stirred bed reactor using a high activity catalyst based on a transition metal of groups IV, V or VI of the Periodic Table comprises introducing into the reactor, continuously and simultaneously, an activity retarder and an activator, in very small amounts, in a molar ratio and at flow rates which are varied with time in order to maintain substantially constant either the polymerization rate or the transition metal content of the polymer produced.

Abstract: The present invention relates to the application of a non aqueous fluid as heat transfer agent in cooling circuits or heat exchanger heating circuits, this application being characterized in that the non aqueous fluid comprising one or more alkleneglycol monoethers of the general formulaeR.sup.1 O(CH.sub.2 CHR.sup.2 O).sub.m Hin which m is an integer equal to 1 or 2, R.sup.1 is an alkyl radical comprising a number of carbon atoms from 4 to 8 where m=1 , or from 1 to 5 where m=2, and R.sup.2 is a hydrogen atom or a methyl radical. The present invention also relates to new compositions based essentially on alkyleneglycol monoether or monoethers, mixed with diols and/or other alkyleneglycol monoethers.