The mixing set with divisible capacities: A simple approach

We give a simple algorithm for linear optimization over the mixing set with divisible capacities, and derive a compact extended formulation from such an algorithm. The main idea is to apply a suitable unimodular transformation to obtain an equivalent problem that is easier to analyze.     

Simplicial Persistence of Financial Markets: Filtering,Generative Processes and Structural Risk

We introduce simplicial persistence, a measure of time evolution of motifs in networks obtained from correlation filtering. We observe long memory in the evolution of structures, with a two power law decay regimes in the number of persistent simplicial complexes. Null models of the underlying time series are tested to investigate properties of the generative process and its evolutional constraints. Networks are generated with both a topological embedding network filtering technique called TMFG and by thresholding, showing that the TMFG method identifies high order structures throughout the market sample, where thresholding methods fail. The decay exponents of these long memory processes are used to characterise financial markets based on their efficiency and liquidity. We find that more liquid markets tend to have a slower persistence decay. This appears to be in contrast with the common understanding that efficient markets are more random. We argue that they are indeed less predictable for what concerns the dynamics of each single variable but they are more predictable for what concerns the collective evolution of the variables. This could imply higher fragility to systemic shocks.     

Syndiotactic-specific polymerization of propene with a Ni-based catalyst

Polymerization of propene at −78°C in the presence of a homogeneous catalytic system based on a Ni(II) diimine derivative and methylaluminoxane affords prevailingly syndiotactic crystalline poly(propylene) (rr triad content ≈80%). ¹³C NMR analysis of the polymer microstructure indicates that the stereochemistry of the monomer insertion is controlled by the configuration of the methine carbon of the growing chain end (unlike-1,3 asymmetric induction). This is the first example of stereospecific homopolymerization of propene promoted by a late transition metal catalyst.     

New Ni(II) based catalysts active in the polymerization of olefins

Polymerization of ethylene in the presence of Cp₂Ni (Cp: cyclopentadienyl) and methylaluminoxane affords polyethylene of high molecular weight and with high melting point. The same catalyst is active in the polymerization of styrene and 1,3-butadiene to give partially isotactic polystyrene and 1,4-cis-polybutadiene, respectively.     

Polymerization of propene by post-metallocene catalysts

In the last few years several non-metallocene catalysts have been disclosed as efficient catalysts for the stereospecific polymerization of propene. In this paper we summarize some recent literature data and some new results concerning the stereochemical mechanism of propene polymerization promoted by late transition metal systems and group 4 metal bis(phenoxyimine) systems. NMR analysis of the fine structure of the polymers obtained, in some cases using isotopically enriched reagents, provides valuable information on the regiochemistry and stereochemistry of the polymerization.