Equilibrium states for a plane incompressible perfect fluid

We associate to the plane incompressible Euler equation with periodic conditions the corresponding Hopf equation, as an equation for measures on the space of solenoidal distributions. We define equilibrium states as the solutions of the stationary Hopf equation. We find a class of equilibrium states which corresponds to a class of infinitely divisible distributions, and investigate the properties of gaussian and poissonian states. Equilibrium dynamics for a class of poissonian states is constructed by means of the Onsager vortex equations.Research partially supported by C.N.R., G.N.F.M.     

On the mechanical modelling of masonry structures using the F.E. technique

A non-linear finite element for the mechanical modelling of masonry structures is presented. Both material and geometrical non-linearities are introduced, developing the expression of the potential strain energy through appropriate average functions. The characteristics of the numerical model are explained and the approximations introduced in the analysis are discussed.

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Sommario Viene sviluppata la formulazione di un nuovo elemento finito per la modellazione meccanica di strutture murarie in campo non lineare. Vengono prese in esame sia non-linearita' geometriche che materiali, sviluppando l'espressione dell'energia potenziale elastica del solido murario attraverso l'introduzione di opportune funzioni medie sulle deformazioni. Vengono discusse le caratteristiche del modello numerico e le approssimazioni introdotte nell'analisi.

     

Time behaviour of non-linear stochastic processes in the presence of multiplicative noise: From Kramers' to Suzuki's decay

The diffusional regime of a Brownian particle in a double-well potential in the presence of both additive and multiplicative noise is explored. As a relevant effect of the multiplicative noise, the escape rate from a well is shown to change from the small value of the Kramers theory into the large relaxation rate of the Suzuki regime. It is shown, furthermore, that the time required to get equilibrium in a well after sudden application of multiplicative noise (the activation time) is very much shorter than the Kramers relaxation time. We envisage therefore an operational scheme making available multiplicative noise for a short interval of time (for example using a light pulse) as an efficient tool to get a fast process of escape from a well. These results are obtained by using a continued-fraction algorithm which makes it possible even to successfully deal with the decay of an unstable state at the critical point.     

The palladium-catalyzed reaction of aryl iodides with mono and disubstituted acetylenes: a new synthesis of trisubstituted alkenes.

Mono and disubstituted acetylenes react with aryl iodides containing a variety of functional groups in the presence of palladium catalyst, formic acid and a tertiary amine to give trisubstituted alkenes.     

Palladium-catalyzed carbonylation of enol triflates. A novel method for one-carbon homologation of ketones to α,β-unsaturated carboxylic acid derivatives

Ketones can be homologated to α,gb-unsaturated esters or amides via their enol triflates by a palladium-catalyzed reaction with carbon monoxide and alcohols or amines.     

Casimir-lifshitz force out of thermal equilibrium and asymptotic nonadditivity

We investigate the force acting between two parallel plates held at different temperatures. The force reproduces, as limiting cases, the well-known Casimir-Lifshitz surface-surface force at thermal equilibrium and the surface-atom force out of thermal equilibrium recently derived by M. Antezza et al., Phys. Rev. Lett. 95, 113202 (2005)10.1103/PhysRevLett.95.113202. The asymptotic behavior of the force at large distances is explicitly discussed. In particular when one of the two bodies is a rarefied gas the force is not additive, being proportional to the square root of the density. Nontrivial crossover regions at large distances are also identified.     

The variability of composition of the volatile fraction of olive oil

Aroma of olive oil is a very complex mixture of components. Analysis of head space of a series of virgin olive oil samples indicate a great variability of volatile substances composition in olives and these data probably should be related to the story of olives after collecting.