Pulsar Wind Nebulae as a source of the observed electron and positron excess at high energy: the case of Vela-X

We investigate, in terms of production from pulsars and their nebulae, the cosmic ray positron and electron fluxes above $\sim10$ GeV, observed by the AMS-02 experiment up to 1 TeV. We concentrate on the Vela-X case. Starting from the gamma-ray photon spectrum of the source, generated via synchrotron and inverse Compton processes, we estimated the electron and positron injection spectra. Several features are fixed from observations of Vela-X and unknown parameters are borrowed from the Crab nebula. The particle spectra produced in the pulsar wind nebula are then propagated up to the Solar System, using a diffusion model. Differently from previous works, the omnidirectional intensity excess for electrons and positrons is obtained as a difference between the AMS-02 data and the corresponding local interstellar spectrum. An equal amount of electron and positron excess is observed and we interpreted this excess (above $\sim$100 GeV in the AMS-02 data) as a supply coming from Vela-X. The particle contribution is consistent with models predicting the gamma-ray emission at the source. The input of a few more young pulsars is also allowed, while below $\sim$100 GeV more aged pulsars could be the main contributors.Comment: Accepted for publication in Journal of High Energy Astrophysics (2015

The cool core state of Planck SZ-selected clusters versus X-ray selected samples: evidence for cool core bias

We characterized the population of galaxy clusters detected with the SZ effect with Planck, by measuring the cool core state of the objects in a well-defined subsample of the Planck catalogue. We used as indicator the concentration parameter Santos et al. (2008). The fraction of cool core clusters is $29 \pm 4 \%$ and does not show significant indications of evolution in the redshift range covered by our sample. We compare the distribution of the concentration parameter in the Planck sample with the one of the X-ray selected sample MACS (Mann & Ebeling, 2011): the distributions are significantly different and the cool core fraction in MACS is much higher ($59 \pm 5 \%$). Since X-ray selected samples are known to be biased towards cool cores due to the presence of their prominent surface brightness peak, we simulated the impact of the "cool core bias" following Eckert et al. (2011). We found that it plays a large role in the difference between the fractions of cool cores in the two samples. We examined other selection effects that could in principle bias SZ-surveys against cool cores but we found that their impact is not sufficient to explain the difference between Planck and MACS. The population of X-ray under-luminous objects, which are found in SZ-surveys but missing in X-ray samples (Planck Collaboration 2016), could possibly contribute to the difference, as we found most of them to be non cool cores, but this hypothesis deserves further investigation.Comment: Accepted for publication in MNRA

CFD characterization of flow regimes inside open cell foam substrates

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.In this work a combination of micro-CT, image-based modeling and CFD has been applied to investigate the pressure drop in open-cell foams. The analysis covers a range of flow regimes and is aimed at determining the effects of important morphological parameters on the pressure drop. The adoption of micro-CT technology along with detailed CFD modeling allows the investigation of phenomena occurring in real foam micro-structures. Moreover, by means of image processing tools, the geometry can be artificially modified in order to investigate the effects of mathematical transformation of the geometrical parameters of a real foam, one parameter at a time, e.g. varying pore size without affecting the porosity. Non-dimensional coefficients have been defined for the analysis of the results, with the purpose of describing the pressure drop as a function of the Reynolds number. The proposed formulation allows us to relate the permeability properties of an open-cell foam to its morphology alone, without any dependence on the properties of the fluid adopted or on the effective characteristic dimension of the foam micro-structure (pore or cell size). Comparison with experimental results available in the literature is also provided for one of the cases studied

Molecular evidence of incipient speciation within Anopheles gambiae s.s. in West Africa

We karyotyped and identified by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis Anopheles gambiae s.s. samples collected in several African countries. The data show the existence of two non-panmictic molecular forms, named S and M, whose distribution extended from forest to savannahs, Mosquitoes of the S and M forms are homosequential standard for chromosome-2 inversions in forest areas. In dry savannahs, S is characterized mainly by inversion polymorphisms typical of Savanna and Bamako chromosomal forms, while M shows chromosome-2 arrangements typical of Mopti and/or Savanna and/or Bissau, depending on its geographical origin. Chromosome-2 inversions therefore seem to be involved in ecotypic adaptation rather than in mate-recognition systems. Strong support for the reproductive isolation of S and M in Ivory Coast comes from the observation that the kdr allele is found at high frequencies in S specimens and not at all in chromosomal identical M specimens. However, the kdr allele does not segregate with molecular forms in Benin

Reconstructing the Emergent Organization of Information Flows in International Stock Markets: A Computational Complex Systems Approach

In this paper we study the interdependences between the dynamics of the stock market indexes of 30 different stock markets across 29 different countries to analyze the nonlinear dynamics of their information flows. We find that the system exhibits complex dynamic properties that go beyond what has been generally found in the previous literature, suggesting that the structure of information flows is regulated by subtle homeostatic forces that cause the roles of the single markets in the whole network to evolve in unexpected ways. We present a toolkit of ANN-based methods that can be systematically deployed to analyze different aspects of such dynamics

Antiproton modulation in the Heliosphere and AMS-02 antiproton over proton ratio prediction

We implemented a quasi time-dependent 2D stochastic model of solar modulation describing the transport of cosmic rays (CR) in the heliosphere. Our code can modulate the Local Interstellar Spectrum (LIS) of a generic charged particle (light cosmic ions and electrons), calculating the spectrum at 1AU. Several measurements of CR antiparticles have been performed. Here we focused our attention on the CR antiproton component and the antiproton over proton ratio. We show that our model, using the same heliospheric parameters for both particles, fit the observed anti-p/p ratio. We show a good agreement with BESS-97 and PAMELA data and make a prediction for the AMS-02 experiment