58,227 research outputs found
Asymmetric nuclear matter equation of state
No full textSystematic calculations of asymmetric nuclear matter have been performed in the framework of the Brueckner-Bethe-Goldstone approach in a wide range of both density and asymmetry parameter. The empirical parabolic law fulfilled by the binding energy per nucleon is confirmed by the present results in all the range of the asymmetry parameter values. The predominant role of the 3S1-3D1 component of the NN interaction is elucidated. A linear variation of the proton and neutron single-particle potentials is found as increasing the neutron excess; a deviation from the phenomenological potentials occurs for highly asymmetric matter as an effect of the self-consistency. The present calculations of the incompressibility predict a strong softening of the equation of state going from symmetric to asymmetric nuclear matter. The proton fraction in equilibrium with neutron matter has been determined from the beta-stability condition and its relevance to the superfluidity of neutron stars has been investigated
Complex Paleozoic magmatic and metamorphic evolution in the Argentera Massif (Western Alps) resolved with U-Pb dating
No full textThe timing of pre-Alpine magmatism and metamorphism in the Gesso-Stura Terrain (NW Argentera massif, External Crystalline Massifs) has been investigated by U-Pb dating. Conventional ID-TIMS analysis of zircons from an eclogite constrained the intrusion of the gabbroic protolith at 462 ± 6 Ma, in agreement with an ion microprobe age of 457 ± 6 Ma on the same sample. Regardless of their pristine magmatic zoning, the zircons from the eclogite suffered lead loss during one or more thermal events. A lower discordia intercept (323 ± 12 Ma) and the youngest zircon rim dated by ion-microprobe (330 ± 5 Ma) constrain the age of the last of these events, i.e. the Variscan amphibolite-facies metamorphism, to the Namurian. Zircon from a metadacite indicates that the acid magma crystallised during Late Ordovician at 443 ± 3 Ma. Ion microprobe dating of zircon from a monzonite affected by Variscan anatexis yielded an intrusion age of 332 ± 3 Ma. Our results help reconstructing the pre-Alpine evolution of the Gesso-Stura terrain of the Argentera basement, which records several magmatic and metamorphic events in the time span between Early Ordovician and Late Carboniferous. The zircon behaviour in the dated rocks bears some implications for U-Pb geochronolog
Giuseppe Lombardo Radice e la scuola attiva
No full textIl saggio analizza in maniera critica l'apporto personale di L. Radice all'educazione secondo il modello della scuola attiva e le principali critiche , alla luce della complessità del periodo storico. Riconosce tuttavia l'originalità del pensiero di Lombardo Radice nella criticità tra modello idealistico gentiliano e storico crociano
Nuclear Matter Superfluidity in the S-D channel
No full textThe neutron-proton superfluidity for nuclear matter in the S-3(1)-3D1 channel is studied within the BCS formalism. In agreement with previous calculations based on the T-matrix approach, a large energy pp is found if one adopts the bare nucleon-nucleon interaction in the gap equation. The dependence of the results on the single-particle spectrum and on the nucleon-nucleon interaction is analyzed and discussed. The relevance of the results for the structure of neutron stars, nuclear matter saturation and superfluidity in finite nuclei is briefly discussed
Asymmetric Nuclear Matter from extended Brueckner theory
No full textThe properties of isospin-asymmetric nuclear matter have been investigated in the framework of the extended Brueckner-Hartree-Fock approximation at zero temperature. Self-consistent calculations using the Argonne V-14 interaction are reported for several values of the asymmetry parameter beta = (N - Z)/A, ranging from symmetric nuclear matter to pure neutron matter. The binding energy per nucleon fulfills the beta(2) law in the whole asymmetry range. The symmetry energy is calculated for different densities and discussed in comparison with other predictions, At the saturation point it is in fairly good agreement with the empirical value. The present approximation, based on the Landau definition of quasiparticle energy, is investigated in terms of the Hugenholtz-Van Hove theorem, which is proved to be fulfilled with a good accuracy at various asymmetries. The isospin dependence of the single-particle properties is discussed, including mean field, effective mass, and mean free path of neutrons and protons. The isospin effects in nuclear physics and nuclear astrophysics are briefly discussed. [S0556-2813(99)03108-8]
L'esigenza di internalizzare la gestione dei sinistri: razionalizzazione del sistema organizzativo
No full textA Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
- …
