Impact of dissipative effects on the macroscopic evolution of a Vlasov system

Numerical diffusion is introduced by any numerical scheme as soon as small scales fluctuations, generated during the dynamical evolution of a collisionless plasma, become comparable to the grid size. Here we investigate the role of numerical dissipation in collisionless plasma simulations by studying the non linear regime of the two stream instability. We show that the long time evolution of the Vlasov - Poisson system can be affected by the used algorithm.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Propagation of finite amplitude electrostatic disturbances in an inhomogeneous magnetized plasma

A 1D2V open boundary Vlasov-Ampere code has been implemented with the aim of making a detailed investigation of the propagation of finite amplitude electromagnetic disturbances in an inhomogeneous magnetized plasma. The code is being applied to study the propagation of an externally driven electromagnetic signal, localized at one boundary of the integration interval, through a given equilibrium plasma configuration with inhomogeneous plasma density and magnetic field.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Non linear collisionless plasma dynamics

High temperature laboratory and rarefied space plasmas can be considered in many situations as collisionless and their dynamics as Hamiltonian. The capability of generating, during the time evolution, smaller and smaller scales in the velocity space is a characteristic of the majority of the processes developing in such plasmas. Since the non collisional dynamics, especially during the non linear regime, is often driven by kinetic effects, to describe theoretically its evolution a kinetic approach is necessary. The analytical model used for the study of small scales non collisional dynamics is based on the Vlasov equation coupled, in the electrostatic limit, to the Poisson equation. However, this is a non linear system of equations usually very difficult to solve analytically. For this reason, in this context numerical simulations are one of the most effective tools of investigation. However, the necessity of a numerical approach to discretize the equations on a numerical mesh introduces a strong limit. In fact, in Vlasov simulations, when a process develops scales so small to be comparable to the size of the numerical mesh, the algorithm becomes necessarily unable to describe correctly the plasma dynamics, with the consequent effect of introducing in the system numerical dissipation and dispersion and consequently of breaking the Hamiltonian character of the system. Here we have studied the problem of the role of small scales on the evolution of the non linear, collisionless plasma dynamics by considering several specific physical phenomena of basic interest in plasma physics described by the Vlasov Poisson mode

Il curricolo multiculturale e le competenze di comunicazione interculturale degli insegnanti: riflessioni a partire dal caso brasiliano

This article proposes a reflection on multicultural curriculum in Brazil and its implications in the relationship between education, identity and citizenship. From these considerations, the reflection continuies on the training of teachers working in multicultural contexts, with a specific focus on their intercultural communicative skills. The analysis relies, in particular, on the contributions of cultural and postcolonial pedagogical framework in which, from its origin in the Anglo-Saxon context, engage in unmask hegemonic tendencies of certain policies, models and educational practices, which for years have been prevailing in the contexts of formal education

Effects of endogenous morphine deprivation on memory retention of passive avoidance learning in mice

Memory and the processes of learning in mammals are well known to be affected by opioid agonists such as morphine, which has been proven to interfere and cause amnesia. The presence of endogenous morphine has been demonstrated in various tissues from mammals to invertebrates. In this study, we have investigated the effects caused by in-vivo immunodepletion of endogenous morphine on working memory under different experimental conditions. When mice were submitted to fasting, a stress condition, acquisition and consolidation of memory were significantly impaired compared to controls. This was demonstrated by a decrease in entry latency into the dark room in the retention session of the passive avoidance test. This effect was significantly reversed to baseline values when endogenous morphine was depleted from the extracellular brain space. These findings support a role for endogenous morphine in weakening memory processes under stress conditions

Protein Tyrosine Phosphatase Gamma (PTPγ) is a Novel Leukocyte Marker Highly Expressed by CD34+ Precursors

Protein Tyrosine Phosphatase gamma (PTPγ) is a receptor-like transmembrane protein belonging to the family of classical protein tyrosine phosphatases. PTPγ is known to regulate haematopoietic differentiation in a murine embryonic stem cells model. We have recently demonstrated that PTPγ mRNA is expressed in monocytes, tissue-localized myeloid dendritic cells and in both myeloid and plasmacytoid dendritic cells in peripheral blood. We now developed a PTPγ specific antibody that recognizes the protein by flow cytometry. PTPγ expression was detected in monocytes and both myeloid and plasmacytoid dendritic cells, while PMN showed a low but consistent staining in contrast with previous mRNA data. B cells were found to express the phosphatase while T cells were negative. In keeping with RNA data, PTPγ was detected in monocyte-derived dendritic cells and its expression rose upon LPS stimulation. Finally, we discovered that CD34+ haematopoietic precursors express high PTPγ level that drops during in vitro expansion induced by IL-3 and SCF growth factors. We therefore propose PTPγ as a new functionally regulated leukocyte marker whose role in normal and pathological context deserve further investigation