A two-zone approach to neutrino production in gamma-ray bursts

Context. Gamma-ray bursts (GRB) are the most powerful events in the universe. They are capable of accelerating particles to very high energies, so are strong candidates as sources of detectable astrophysical neutrinos. Aims. We study the effects of particle acceleration and escape by implementing a two-zone model in order to assess the production of high-energy neutrinos in GRBs associated with their prompt emission. Methods. Both primary relativistic electrons and protons are injected in a zone where an acceleration mechanism operates and dominates over the losses. The escaping particles are re-injected in a cooling zone that propagates downstream. The synchrotron photons emitted by the accelerated electrons are taken as targets for pγ interactions, which generate pions along with the pp collisions with cold protons in the flow. The distribution of these secondary pions and the decaying muons are also computed in both zones, from which the neutrino output is obtained. Results. We find that for escape rates lower than the acceleration rate, the synchrotron emission from electrons in the acceleration zone can account for the GRB emission, and the production of neutrinos via pγ interactions in this zone becomes dominant for Eν > 105 GeV. For illustration, we compute the corresponding diffuse neutrino flux under different assumptions and show that it can reach the level of the signal recently detected by IceCube. © 2014 ESO

About the Earth density and the neutrino interaction

We visit again the problem to extract information about the mass distribution of the Earth using neutrino collisions with the Earth matter. The topic was addressed in several opportunities using different observable related with the neutrino flux arriving to a neutrino telescope like IceCube. In the present work we have used an observable that is weakly dependent of the initial flux. We check the homogeneity hypothesis and fit a simplified Earth model consistent with the observational value of the Earth mass and the inertia moment

Fusarium species (section liseola) occurrence and natural incidence of beauvericin, fusaproliferinand fumonisins in maize hybrids harvested in mexico

Fusarium species can produce fumonisins (FBs), fusaric acid, beauvericin (BEA), fusaproliferin (FUS) and moniliformin. Data on the natural occurrence of FBs have been widely reported, but information on BEA and FUS in maize is limited. The aims of this study were to establish the occurrence of Fusarium species in different maize hybrids in Mexico, to determine the ability of Fusarium spp. isolates to produce BEA, FUS and FBs and their natural occurrence in maize. Twenty-eight samples corresponding to seven different maize hybrids were analyzed for mycobiota and natural mycotoxin contamination by LC. Fusarium verticillioides was the dominant species (44-80%) followed by F. subglutinans (13-37%) and F. proliferatum (2-16%). Beauvericin was detected in three different hybrids with levels ranging from 300 to 400 ng g-1, while only one hybrid was contaminated with FUS (200 ng g-1). All samples were positive for FB1 and FB2 contamination showing levels up to 606 and 277 ng g-1, respectively. All F. verticillioides isolates were able to produce FB1 (13.8-4,860 μg g-1) and some also produced FB2 and FUS. Beauvericin, FUS, FB1 and FB2 were produced by several isolates including F. proliferatum and F. subglutinans and co-production was observed. This is the first report on the co-occurrence of these toxins in maize samples from Mexico. The analysis of the presence of multiple mycotoxins in this substrate is necessary to understand the significance of these compounds in the human and animal food chains. © Society for Mycotoxin Research and Springer 2011

Relativistic Jets in Active Galactic Nuclei and Microquasars

Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly understood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravitational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by (Formula presented.)-ray emission observed from many jet sources) and the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially blazars) and microquasars, and then presents a comparative discussion of similarities and differences between them.Fil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; ArgentinaFil: Boettcher, Markus. North-West University; SudáfricaFil: Markoff, Sera. University of Amsterdam; Países BajosFil: Tavecchio, Fabrizio. Osservatorio Astronomico Di Brera; Itali