Entropy Dynamics of Community Alignment in the Italian Parliament Time-Dependent Network

Complex institutions are typically characterized by meso-scale structures which are fundamental for the successful coordination of multiple agents. Here we introduce a framework to study the temporal dynamics of the node-community relationship based on the concept of community alignment, a measure derived from the modularity matrix that defines the alignment of a node with respect to the core of its community. The framework is applied to the 16th legislature of the Italian Parliament to study the dynamic relationship in voting behavior between Members of the Parliament (MPs) and their political parties. As a novel contribution, we introduce two entropy-based measures that capture politically interesting dynamics: the group alignment entropy (over a single snapshot), and the node alignment entropy (over multiple snapshots). We show that significant meso-scale changes in the time-dependent network structures can be detected by a combination of the two measures. We observe a steady growth of the group alignment entropy after a major internal conflict in the ruling majority and a different distribution of nodes alignment entropy after the government transition

Spectroscopic techniques applied to the study of Italian painted Neolithic Potteries

In the field of cultural heritage, the study of the materials used by the artist is useful both for the knowledge of the artwork and for conservation and restoring interventions. In this communication, we present results of some decorations analysis obtained by the use of two complementary laser techniques: micro-LIBS and micro-Raman spectroscopy. With both techniques it is possible to operate in a practically nondestructive way on the artwork itself, without sampling or pretreatment. Micro-Raman spectroscopy gives information on the molecular structure of the pigments used, while micro-LIBS can give quantitative information about the elemental composition of the same materials. In this paper, qualitative results are reported obtained on the study of some Neolithic potteries coming from the archaeological site of Trasano (Matera); the fragments show decorations in different colors, red, black, and white. The aim of the study was detecting whether the colored decorations were made by using added pigments or came from the manufacturing process

A new line for laser-driven light ions acceleration and related TNSA studies

In this paper, we present the status of the line for laser-driven light ions acceleration (L3IA) currently under implementation at the Intense Laser Irradiation Laboratory (ILIL), and we provide an overview of the pilot experimental activity on laser-driven ion acceleration carried out in support of the design of the line. A description of the main components is given, including the laser, the beam transport line, the interaction chamber, and the diagnostics. A review of the main results obtained so far during the pilot experimental activity is also reported, including details of the laser-plasma interaction and ion beam characterization. A brief description of the preliminary results of a dedicated numerical modeling is also provided

Laser–Accelerated Plasma–Propulsion System

In this paper, the laser-accelerated plasma–propulsion system (LAPPS) for a spacecraft is revisited. Starting from the general properties of relativistic propellants, the relations between specific impulse, engine thrust and rocket dynamics have been obtained. The specific impulse is defined in terms of the relativistic velocity of the propellant using the Walter’s parameterization, which is a suitable and general formalism for closed–cycle engines. Finally, the laser-driven acceleration of light ions via Target Normal Sheath Acceleration (TNSA) is discussed as a thruster. We find that LAPPS is capable of an impressive specific impulse Isp in the 105 s range for a laser intensity I0≃1021W/cm2. The limit of Isp≲104 s, which characterizes most of the other plasma-based space electric propulsion systems, can be obtained with a relatively low laser intensity of I0≳1019W/cm2. Finally, at fixed laser energy, the engine thrust can be larger by a factor 102 with respect to previous estimates, making the LAPPS potentially capable of thrust-power ratios in the N/MW range

Enhanced laser-driven proton acceleration via improved fast electron heating in a controlled pre-plasma

The interaction of ultraintense laser pulses with solids is largely affected by the plasma gradient at the vacuum–solid interface, which modifies the absorption and ultimately, controls the energy distribution function of heated electrons. A micrometer scale-length plasma has been predicted to yield a significant enhancement of the energy and weight of the fast electron population and to play a major role in laser-driven proton acceleration with thin foils. We report on recent experimental results on proton acceleration from laser interaction with foil targets at ultra-relativistic intensities. We show a threefold increase of the proton cut-off energy when a micrometer scale-length pre-plasma is introduced by irradiation with a low energy femtosecond pre-pulse. Our realistic numerical simulations agree with the observed gain of the proton cut-off energy and confirm the role of stochastic heating of fast electrons in the enhancement of the accelerating sheath field

Multibeam Laser Plasma Interaction at Gekko XII laser facility in conditions relevant for Direct-Drive Inertial Confinement Fusion

International audienceLaser Plasma Interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive Inertial Confinement F usion. T he e xperiment h as b een carried out at Gekko XII laser facility in multibeam planar geometry at intensity ∼ 3 • 10 15 W/cm 2. Experimental data suggest that high-energy electrons, with temperature 20-50 keV and conversion efficiencies η < 1% , we re ma inly pr oduced by th e da mping of el ectron pl asma wa ves dr iven by Two Plasmon Decay. Stimulated Raman Scattering is observed in a near-threshold growth regime, producing a reflectivity o f ∼ 0 .01%, a nd i s w ell d escribed b y a n a nalytical m odel a ccounting for the convective growth in independent speckles. The experiment reveals that both TPD and SRS are collectively driven by multiple beams resulting in a more vigorous growth than that driven by single-beam laser intensity

Multibeam Laser Plasma Interaction at Gekko XII laser facility in conditions relevant for Direct-Drive Inertial Confinement Fusion

International audienceLaser Plasma Interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive Inertial Confinement F usion. T he e xperiment h as b een carried out at Gekko XII laser facility in multibeam planar geometry at intensity ∼ 3 • 10 15 W/cm 2. Experimental data suggest that high-energy electrons, with temperature 20-50 keV and conversion efficiencies η < 1% , we re ma inly pr oduced by th e da mping of el ectron pl asma wa ves dr iven by Two Plasmon Decay. Stimulated Raman Scattering is observed in a near-threshold growth regime, producing a reflectivity o f ∼ 0 .01%, a nd i s w ell d escribed b y a n a nalytical m odel a ccounting for the convective growth in independent speckles. The experiment reveals that both TPD and SRS are collectively driven by multiple beams resulting in a more vigorous growth than that driven by single-beam laser intensity