Monoalkyl,chiral-at-metal 'constrained geometry' complexes as efficient alpha-olefin and methyl methacrylate polymerisation catalysts

A new class of monoalkyl or monochloro constrained geometry group 4 complexes has been synthesized; upon activation with aluminium activators they serve as efficient catalysts for olefin polymerisation and for polymerisation of methyl methacrylate.     

Theoretical vibrational analysis of monohalogenated phenols

Harmonic vibrational frequencies of a representative series of X-phenols (X = F, Cl, Br) in ortho, meta and para positions are determined using density functional theory (B3LYP) in conjunction with 6-311 + + G(d,p), 6-311 + + G(2d,2p), and 6-311 + + G(2df,2p) basis sets. Their complete and clear-cut vibrational assignment based on the concept of the potential energy distribution is carried out. Such assignment allows to resolve a number of uncertainties appeared in the previous studies and to propose a new explanation of frequency alterations of particular vibrational modes in this series.     

Multiple scattering in random media

The paper is an application of a general microscopic approach to the theory of the average scattering matrix for a particle interacting with random scatterers. We present a detailed treatment for the case of uncorrelated positions of the scatterers. First, the general two-body additive approximation is used to truncate the hierarchy of correlation functions for fluctuations. It is shown that the self-energy is accurate through the fourth power of the individual scattering amplitude. Second, the hierarchy is terminated at the next stage. The self-energy is correct to the sixth power of the scattering amplitude.Work supported in part by the National Science Foundation under Contract No. NSF DMR 79-23213.     

Homotopy groups of -contact toric manifolds

Contact toric manifolds of Reeb type are a subclass of contact toric manifolds which have the property that they are classified by the images of the associated moment maps. We compute their first and second homotopy group terms of the images of the moment map. We also explain why they are -contact.