Very high-energy constraints on the infrared extragalactic background light

Context. Measurements of the Extragalactic Background Light (EBL) are a fundamental source of information on the collective emission of cosmic sources. Aims. At infrared wavelengths, however, these measurements are precluded by the overwhelming dominance from Interplanetary Dust emission and the Galactic infrared foreground. Only at $\lambda > 300 \ \mu$m, where the foregrounds are minimal, has the Infrared EBL (IR EBL) been inferred from analysis of the COBE maps. The present paper aims to assess the possibility of evaluating the IR EBL from a few $\mu$m up to the peak of the emission at >100 $\mu$m using an indirect method that avoids the foreground problem. Methods. To this purpose we exploit the effect of pair-production from gamma-gamma interaction by considering the highest energy photons emitted by extragalactic sources and their interaction with the IR EBL photons. We simulate observations of a variety of low redshift emitters with the forthcoming Imaging Atmospheric Cherenkov Telescope (IACT) arrays (CTA in particular) and water Cherenkov observatories (LHAASO, HAWC, SWGO) to assess their suitability to constrain the EBL at such long wavelengths. Results. We find that, even under the most extremely favorable conditions of huge emission flares, extremely high-energy emitting blazars are not very useful for our purpose because they are much too distant (>100 Mpc the nearest ones, MKN 501 and MKN 421). Observations of more local Very High Energy (VHE) emitting AGNs, like low-redshift radio galaxies (M87, IC 310, Centaurus A), are better suited and will potentially allow us to constrain the EBL up to $\lambda \simeq 100\ \mu$m

A Structured Approach to Insider Threat Monitoring for Offensive Security Teams

In many countries, government agencies resort to third parties to acquire security services of many kinds, including Red Team operations to test the effectiveness of own defenses mechanisms. Absolute trust is a key requirement, lest a potentially devastating finding be exploited by a treacherous Red Team against the same entity which commissioned the operation, or sold to its adversaries. In our endeavour as a joint private-academic initiative to address this peculiar market, we observed that a structured approach to this issue is much less common than we would have expected. In this work, we outline the process we are devising to offer customers a verified environment, but integrating it with an evidence-based proof of their correct behavior during the operation, striving to solve the “Quis custodiet ipsos custodes” struggle in an offensive setting

Constraining blazar distances with combined Fermi and TeV data: an empirical approach

We discuss a method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes. We assume that the VHE spectrum corrected for the absorption through the interaction with the Extragalactic Background Light can not be harder than the spectrum in the Fermi/LAT band. Starting from the observed VHE spectral data we derive the EBL-corrected spectra as a function of the redshift z and fit them with power laws to be compared with power law fits to the LAT data. We apply the method to all TeV blazars detected by LAT with known distance and derive an empirical law describing the relation between the upper limits and the true redshifts that can be used to estimate the distance of unknown redshift blazars. Using different EBL models leads to systematic changes in the derived upper limits. Finally, we use this relation to infer the distance of the unknown redshift blazar PKS 1424+240.Comment: 5 pages, 4 figures, accepted for publication in MNRAS, minor revisio

Alternative Linear Chiral Models for Nuclear Matter

The equation of state of a family of alternative linear chiral models in the mean field approximation is discussed. We investigate the analogy between some of these models with current models in the literature, and we show that it is possible to reproduce very well the saturation properties of nuclear matter.Comment: 11 pages in Latex, 4 ps figures include

In vitro evaluation of live attenuated vaccines against Salmonella enteritidis: humoral immune response

Salmonella enteritidis (SE) vaccination is one of the major tool to reduce the infection in commercial poultry. In this work, techniques, evaluating the presence of Ig-G and Ig-A in serum, tears and intestinal secretions, were studied to improve the knowledge of the humoral immune response following SE live attenuated vaccination. The Ig-G and Ig-A ELISA are important and easy tests to plan and optimize SE vaccination programs

MAGIC eyes to the extreme: testing the blazar emission models on EHBLs

Extreme high-energy peaked BL Lac objects (EHBLs) are blazars whose synchrotron emission peaks at exceptionally high energies, above few keV, in the hard X-ray regime. So far, only a handful of those objects has been detected at very high energy (VHE, E > 100 GeV) gamma rays by Imaging Atmospheric Cherenkov Telescopes. Very remarkably, VHE observations of some of these blazars (like 1ES 0229+200) have provided evidence of a VHE gamma-ray emission extending to several TeV, which is difficult to explain with standard, one-zone synchrotron self-Compton models usually applied to BL Lac objects. The MAGIC collaboration coordinated a multi-year, multi-wavelength observational campaign on ten targets. The MAGIC telescopes detected VHE gamma rays from four EHBLs. In this paper we focus on the source 1ES 1426+426 and its X-ray and VHE gamma-ray properties. The results of different models (synchrotron self-Compton, spine-layer, hadronic) reproducing the broadband spectral energy distribution are also presented.Comment: Proceedings of the 36th International Cosmic Ray Conference (ICRC2019), July 24th-August 1st, 2019. Madison, WI, U.S.

Progress in unveiling extreme particle acceleration in persistent astrophysical jets

International audienceExtreme blazars emitting teraelectronvolt photons are ideal targets to study particle acceleration processes. The growing number of such sources has been critical for γ-ray cosmology, studying intergalactic magnetic fields and putting constraints on exotic physics

Design of a SiPM-based cluster for the Large Size Telescope camera of CTA

A Silicon Photomultiplier (SiPM)-based photodetector is being built to demonstrate its feasibility for an alternative silicon-based camera design for the Large Size Telescope (LST) of the Cherenkov Telescope Array. It has been designed to match the size of the standard Photomultiplier Tube (PMT) cluster unit and to be compatible with mechanics, electronics and focal plane optics of the first LST camera. Here, we describe the overall SiPM cluster design along with the main differences with respect to the currently used PMT cluster unit. The fast electronics of the SiPM pixel and its layout are also presented. In order to derive the best working condition for the final unit, we measured the SiPM performances in terms of gain, photo-detection efficiency and cross-talk. One pixel, a unit of 14 SiPMs, has been built. We will discuss also some preliminary results regarding this device and we will highlight the future steps of this project.Comment: submitted to NIM

18FDG-PET and large vessel vasculitis: preliminary data on 25 patients

Objective: To evaluate the predictive value of clinical and biochemical features when compared to 18FDG-PET in the diagnostic work-up of large vessel vasculitis (LVV). Methods: Twenty-five patients underwent 18FDG-PET for the clinical suspect of LVV. All of them presented history of systemic symptoms lasting ≥6 months and laboratoristic evidence of persistently high markers of inflammation. The patients were stratified according with: i) clinical manifestations, defined as presence of one or more ACR criteria for the classification of LVV; ii) laboratory investigations: Erythrocyte Sedimentation Rate (ESR) higher or lower than 50 mm/h, C-Reactive Protein (CRP) higher or lower than 2 mg/dl; iii) prednisone dose in the 4 weeks preceding PET examination. Results: The total number of positive PET was higher in the group without clinical ACR criteria and in the group with inflammation markers under the established cut-off. The number of scans consistent with LVV was higher in the groups presenting one or more clinical criteria for LVV but in those with very high ESR and CRP. In all the cases differences between groups were not statistically significative. A clear cut negative correlation between steroid dose and number of scans suggestive for LVV has been observed. Conclusions: Diagnosis of LVV remains challenging, especially in patients presenting with a constellation of non-specific symptoms and laboratory findings. In this study, both clinical and biochemical features show low correlation with a vasculitic pattern of FDG uptake. In our experience 18FDG-PET represents an useful diagnostic tool in early stages of LVV and a powerful instrument to follow the treatment responses