New insights on hadron acceleration at supernova remnant shocks

We outline the main features of nuclei acceleration at supernova remnant forward shocks, stressing the crucial role played by self-amplified magnetic fields in determining the energy spectrum observed in this class of sources. In particular, we show how the standard predictions of the non-linear theory of diffusive shock acceleration has to be completed with an additional ingredient, which we propose to be the enhanced velocity of the magnetic irregularities particles scatter against, to reconcile the theory of efficient particle acceleration with recent observations of gamma-ray bright supernova remnants.Comment: 7 pages, 2 figures. To apper in "Cosmic-ray induced phenomenology in star-forming environments: Proceedings of the 2nd Session of the Sant Cugat Forum of Astrophysics" (April 16-19, 2012), Olaf Reimer and Diego F. Torres (eds.

Strong evidences of hadron acceleration in Tycho's Supernova Remnant

Very recent gamma-ray observations of G120.1+1.4 (Tycho's) supernova remnant (SNR) by Fermi-LAT and VERITAS provided new fundamental pieces of information for understanding particle acceleration and non-thermal emission in SNRs. We want to outline a coherent description of Tycho's properties in terms of SNR evolution, shock hydrodynamics and multi-wavelength emission by accounting for particle acceleration at the forward shock via first order Fermi mechanism. We adopt here a quick and reliable semi-analytical approach to non-linear diffusive shock acceleration which includes magnetic field amplification due to resonant streaming instability and the dynamical backreaction on the shock of both cosmic rays (CRs) and self-generated magnetic turbulence. We find that Tycho's forward shock is accelerating protons up to at least 500 TeV, channelling into CRs about the 10 per cent of its kinetic energy. Moreover, the CR-induced streaming instability is consistent with all the observational evidences indicating a very efficient magnetic field amplification (up to ~300 micro Gauss). In such a strong magnetic field the velocity of the Alfv\'en waves scattering CRs in the upstream is expected to be enhanced and to make accelerated particles feel an effective compression factor lower than 4, in turn leading to an energy spectrum steeper than the standard prediction {\propto} E^-2. This latter effect is crucial to explain the GeV-to-TeV gamma-ray spectrum as due to the decay of neutral pions produced in nuclear collisions between accelerated nuclei and the background gas. The self-consistency of such an hadronic scenario, along with the fact that the concurrent leptonic mechanism cannot reproduce both the shape and the normalization of the detected the gamma-ray emission, represents the first clear and direct radiative evidence that hadron acceleration occurs efficiently in young Galactic SNRs.Comment: Minor changes. Accepted for publication in Astronomy & Astrophysic

Gamma Rays and Neutrinos from SNR RX J1713.7-3946

The supernova paradigm for the origin of galactic cosmic rays can be tested using multifrequency observations of both non-thermal and thermal emission from supernova remnants. The smoking gun of hadronic acceleration in these sources can, however, only be provided by the detection of a high energy neutrino signal. Here we apply the theory of non-linear particle acceleration at supernova shocks to the case of the supernova remnant RX J1713.7-3946, which is becoming the stereotypical example of a possible hadronic accelerator after the detection of high energy gamma rays by the HESS telescope. Our aim is twofold: on one hand we want to address the uncertainties in the discrimination between a hadronic and a leptonic interpretation of the gamma ray emission, mainly related to the possibility of a statistical uncertainty in the energy determination of the gamma ray photons in the TeV region. On the other we want to stress how a km cube neutrino telescope would break the degeneracy and provide evidence for efficient cosmic ray acceleration in RX J1713.7-3946. A 3 sigma evidence would require about two years of observation.Comment: 11 pages, 3 figures, accepted for publication in Astropaticle Physic

Antibiotic resistance patterns of faecal indicator organisms and occurrence of Salmonella spp. in wild boar (Sus scrofa scrofa) in Italy.

In order to monitor antibiotic resistance in faecal indicator organisms and evaluate the occurrence of Salmonella spp., faeces from 110 wild boars (Sus scrota scrota), killed during a demographic control program in two different regional parks in Bologna province, were collected from September 2002 to June 2003. A single isolate of Escherichia coli, Enterococcus faecalis and Enterococcus faecium from each sample was tested for antibiotic susceptibility using the agar diffusion method recommended by CLSI (formerly, NCCLS). A total of 110 E. coli, 48 E. faecium and 5 E. faecalis strains were isolated and submitted to antibiotic susceptibility tests. Antibiotic resistance patterns were similar in wild boar populations from both parks. Multiple antibiotic-resistance to ciprofloxacin, rifampin and erythromycin was found with h1gh frequency in Enterococcus spp strains. E. coli isolates showed a low antibiotic resistance level. Two Salmonella arizonae and one Salmonella spp. strains, isolated from wild boars of one park, didn\u27t show any resistance concerning the antibiotics tested

Discrimination of filter coffee extraction methods of a medium roasted specialty coffee based on volatile profiles and sensorial traits

An untargeted gas chromatography-mass spectrometry (GC-MS) approach combined with sensory analysis was used to present the effects of different extraction methods (i.e., Pure Brew, V60, AeroPress, and French Press) on specialty graded Coffea arabica from Kenya. Partial Least Square Discriminant analysis and hierarchical clustering were applied as multivariate statistical tools in data analysis. The results showed good discrimination and a clear clustering of the groups of samples based on their volatile profiles. Similarities were found related to the filter material and shape used for the extraction. Samples extracted with paper filters (V60 and AeroPress) resulted in higher percentages of caramel-, and flowery-related compounds, while from metal filter samples (Pure Brew and French Press), more fruity and roasted coffees were obtained. Discriminant analysis allowed the identification of eight compounds with a high VIP (variable important in projection) discriminant value (i.e., >1), with 2-furanmethanol being the main feature in discrimination. Sensorial analyses were carried out through an expert panel test. The main evaluations revealed the French Press system as the lowest-scored sample in all the evaluated parameters, except for acidity, where its score was similar to V60. In conclusion, the data obtained from GC-MS analyses were in line with the sensorial results, confirming that the extraction process plays a fundamental role in the flavor profile of filter coffee beverages

Gamma ray emission from SNR RX J1713.7-3946 and the origin of galactic cosmic rays

We calculate the flux of non-thermal radiations from the supernova remnant RX J1713.7-3946 in the context of the non-linear theory of particle acceleration at shocks, which allows us to take into account self-consistently the dynamical reaction of the accelerated particles, the generation of magnetic fields in the shock proximity and the dynamical reaction of the magnetic field on the plasma. When the fraction of particles which get accelerated is of order $\sim 10^{-4}$, we find that the strength of the magnetic field obtained as a result of streaming instability induced by cosmic rays is compatible with the interpretation of the X-ray emitting filaments being produced by strong synchrotron losses in $\sim 100 \mu G$ magnetic fields. If the X-ray filaments are explained in alternative ways, the constraint on the magnetic field downstream of the shock disappears and the HESS data can be marginally fit with ICS of relativistic electrons off a complex population of photons, tailored to comprise CMB and ambient IR/Optical photons. The fit, typically poor at the highest energies, requires a large density of target photons within the remnant; only a fraction of order $\sim 10^{-6}$ of the background particles gets accelerated; the local magnetic field is of order $\sim 20\mu G$ and the maximum energy of protons is much lower than the knee energy. Current HESS gamma ray observations combined with recent X-ray observations by Suzaku do not allow as yet to draw a definitive conclusion on whether RX J1713.7-3946 is an efficient cosmic ray accelerator, although at the present time a hadronic interpretation of HESS data seems more likely. We discuss the implications of our results for the GLAST gamma ray telescope, which should be able to discriminate the two scenarios discussed above.Comment: Accepted for Publication in MNRA

Short communication: Isolation of Shiga toxin-producing Escherichia coli in raw milk and mozzarella cheese in southern Italy

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