1,721,079 research outputs found
Recursive combinatorial aspects of compactified moduli spaces
No full textIn recent years an interesting connection has been established between some moduli spaces of algebro-geometric objects (e.g. algebraic stable curves) and some modulispaces of polyhedral objects (e.g. tropical curves).In loose words, this connection expresses the Berkovich skeleton of a given algebrogeometric moduli space as the moduli space of the skeleta of the objects parametrizedby the given space; it has been proved to hold in two important cases: the modulispace of stable curves and the moduli space of admissible covers. Partial results areknown in other cases.This connection relies on the study of the boundary of the algebro-geometric moduli spaces and on its recursive, combinatorial properties, some of which have beenlong known and are now viewed from a new perspective
Tropical methods in the moduli theory of algebraic curves
No full textRecent results in tropical geometry and in non-Archimedean geometry are surveyed focussing on their impact on the classical theory of algebraic curves, Jacobian varieties, and their moduli theory
Ethylene as catalyst reactivator in the propene-styrene copolymerization
No full textAn experiment was conducted to show the presence of ethylene as catalyst reactivator in the propene-styrene copolymerization. The copolymerizations have been performed by bubbling the gaseous monomers at atmospheric pressure into a flask containing a styrene solution of the prototypical ansa-zirconocene complex rac-(ethylene)bis(1-indenyl)zirconium dichloride activated by methylalumoxane. In structure A one tertiary carbon atom bearing the phenyl ring is surrounded in both sides by sequences of two methylene groups while in structure B the junction is characterized by the presence of two tertiary carbon atoms bearing the phenyl ring separated by three methylene groups. By reducing the styrene content in the comonomer feed composition ([E]/[P]/[S] ) 1/135/65 in the liquid phase) a copolymer with a 6% styrene units is obtained. The results reported show that it is possible to introduce some styrene units in an isotactic polypropylene sequence by using a small amount of ethylene to reactivate the catalyst after the styrene insertion
Tropicalizing the moduli space of spin curves
No full textWe study the tropicalization of the moduli space of algebraic spin curves, S ̄ g,n. We exhibit its combinatorial stratification and prove that the strata are irreducible. We construct the moduli space of tropical spin curves S ̄g,ntrop, prove that is naturally isomorphic to the skeleton of the analytification, S ̄g,nan, of S ̄ g,n, and give a geometric interpretation of the retraction of S ̄g,nan onto its skeleton in terms of a tropicalization map S ̄g,nan→S ̄g,ntrop
Influenza della concentrazione di monomero sulla stereoselettività della reazione di polimerizzazione del propene promossa da sistemi Ziegler-Natta eterogenei
No full textMechanism of stereospecific polymerization of acrylates catalyzed by group 4 metallocenes
No full textInfluenza della concentrazione di monomero sulla stereoselettività della reazione di polimerizzazione del propene promossa da sistemi Ziegler-Natta eterogenei
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