Polymerization with heterogeneous metalorganic catalysts. VI. Differences in polymerization activity of α-olefins and some kinetic results on butene-1 polymerization

Relative changes in polymerization activity of ethylene, propylene, and butene-1 in Ziegler-Natta polymerization were compared by use of TiCl₃ samples contaminated with O₂ and H₂O to various extents. Catalyst depletion varied for the three monomers which supported the existence of different active centers. In butene-1 polymerizations with the system Al(C₂H₅)₂Cl–TiCl₃, the formation of active centers involves an irreversible and a reversible (adsorption) reaction, the former pertaining to the formation of Al(C₂H₅)Cl₂ and dependent upon the purity of the TiCl₃. The kinetic treatment of the rate curves suggests a mixed order of catalyst deactivation and again points to the importance of Al(C₂H₅)Cl₂.     

The oxidation of carbon monoxide on polycrystalline rhodium under knudsen conditions: III. Simultaneous reaction with oxygen and nitrogen monoxide

The CO oxidation using mixtures of oxygen and nitrogen monoxide has been studied under stationary conditions. The measured selectivities could not always be foreseen from the results obtained in the binary systems CO/O₂ and CO/NO. At high temperatures the amount of NO reduced is directly proportional to its fraction in the oxidizing gas. At low temperatures, NO may be reduced with high selectivity even in the presence of high oxygen concentration.     

Homotopy forg functions and generalized retraction

Summary We introduce here a generalization of the usual concept of homotopy for continuous functions, because the traditional concept is not adequate to deal with some important geometrical situations. Entrata in Redazione il 2 settembre 1969.     

Generalized functions and Čech homology theory

Summary We study here conditions under which a homomorphism of Čech groups can be realized by generalized fonctions.     

On relations between usual continuous functions and generalized continuous functions

Summary I give here a theorem of realization of homomorphism in Cech homology theory, which improves some previous results of mine.     

Theory of transition probability saturation for photodissociation of Cs2 and photoionization of the 5D 5/2 product atoms

Transition probability saturation has been used as a means of investigation of cesium photoionization via photodissociative states of Cs₂ around 550 nm. We present here a theoretical interpretation of the data obtained with polarized light. It allows for dispersion of the cross-sections due to the multi-level structure of the dissociated molecules and of the 5D _5/2 product atoms. Thehfs in 5D _5/2 is also taken into account. From best data fits we obtain determinations of the averaged cross-sections, free of uncertainty due to Cs or Cs₂ densities. The 5D _5/2 ionization cross-section agrees with theoretical prediction.     

Cylindrical symmetry discrimination of magnetoelectric optical systematic effects in a pump-probe atomic parity violation experiment

A pump-probe atomic parity violation (APV) experiment performed in a longitudinal electric field , has the advantage of providing a signal which breaks mirror symmetry but preserves cylindrical symmetry of the set-up, i.e. this signal remains invariant when the pump and probe linear polarizations are simultaneously rotated about their common direction of propagation. The excited vapor acts on the probe beam as a linear dichroic amplifier, imprinting a very specific signature on the detected signal. Our differential polarimeter is oriented to yield a null result unless a chirality of some kind is acting on the excited atoms. Ideally, only the APV ( -odd) and the calibration ( -even) signals should participate in such a chiral atomic response, a situation highly favourable to sensitive detection of a tiny effect. In the present work, we give a thorough analysis of possible undesirable defects such as spurious transverse fields or misalignments, which may spoil the ideal configuration and generate a chiral response leading to possible systematics. We study a possible way to get rid of such defects by performing global rotations of the experiment by incremental angular steps , leaving both stray fields and misalignments unaltered. Our analysis shows that at least two defects are necessary for the -odd polarimeter output to be affected; a modulation in the global rotations reveals the transverse nature of the defects. The harmful systematic effects are those which subsist after we average over four configurations obtained by successive rotations of 45 . They require the presence of a stray transverse electric field. By doing auxiliary atomic measurements made in known, applied, magnetic fields which amplify the systematic effect, it is possible to measure the transverse E-field and to minimize it. Transverse magnetic fields must also be carefully compensated following a similar procedure. We discuss the feasibility of reducing the systematic uncertainty below the one percent level. We also propose statistical correlation tests as diagnoses of the aforementioned systematic effects.Received: 19 November 2003, Published online: 19 February 2004PACS: 32.80.Ys Weak-interaction effects in atoms - 32.60. + i Zeeman and Stark effects - 33.55.Fi Other magnetooptical and electrooptical effects - 42.25.Lc Birefringence