On the Formation of Massive Primordial Stars

We investigate the formation by accretion of massive primordial protostars in the range 10 to 300 M _⊙. The high accretion rate used in the models (M _⊙ = 4.4 x 10^-3 M_⊙ yr^-1) causes the structure and evolution to differ significantly from those of both present-day protostars and primordial zero-age main sequence stars. The stellar surface is not visible throughout most of the main accretion phase, since a photosphere is formed in the in falling envelope. Significant nuclear burning does not take place until a protostellar mass of about 80 M _⊙. As the interior luminosity approaches the Eddington luminosity, the protostellar radius rapidly expands owing to the radiation pressure. Eventually, a final swelling occurs when the stellar mass reaches about 300 M _⊙. This expansion is likely to signal the end of the main accretion phase, thus setting an upper limit to the protostellar mass formed in these conditions. This revised version was published online in September 2006 with corrections to the Cover Date.     

Intergalactic shock acceleration and the cosmic gamma-ray background

We investigate numerically the contribution to the cosmic gamma-ray background from cosmic-ray ions and electrons accelerated at intergalactic shocks associated with cosmological structure formation. We show that the kinetic energy of accretion flows in the low-redshift intergalactic medium is thermalized primarily through moderately strong shocks, which allow for an efficient conversion of shock ram pressure into cosmic-ray pressure. Cosmic rays accelerated at these shocks produce a diffuse gamma-ray flux which is dominated by inverse Compton emission from electrons scattering off cosmic microwave background photons. Decay of neutral π mesons generated in p–p inelastic collisions of the ionic cosmic-ray component with the thermal gas contribute about 30 per cent of the computed emission. Based on experimental upper limits on the photon flux above 100 MeV from nearby clusters we constrain the efficiency of conversion of shock ram pressure into relativistic CR electrons to  ≲1 per cent  . Thus, we find that cosmic rays of cosmological origin can generate an overall significant fraction of order 20 per cent and no more than 30 per cent of the measured gamma-ray background.     

Long‐term demographic and reproductive trends in Ciona intestinalis sp. A

Ciona intestinalis sp. A (Tunicata, Ascidiacea) is a marine invertebrate with a widespread distribution and high invasive potential, yet little is known about its ecology. Here, the macrodynamics of demographic and reproductive trends were first determined using archive data covering 2002–2012. Species abundance in the central Tyrrhenian Sea (Campania, Italy ‐ NW Mediterranean) displayed Poisson distribution across 2002–2008, massive die‐off in 2009/2010 and population recovery in 2011/2012. We defined the seasonal ranges of sea surface temperature in which sampling size, animal size and reproductive status reached their highest values. In 2003/2004, self and non‐self fertilization appeared to follow reverse trends across the year. The long‐term recording run here on Ciona intestinalis sp. A provides novel insights into its population biology and ecology, and represents a valuable tool for sampling management and research planning.     

Weathering processes affecting granitoid profiles of Capo Vaticano (Calabria,southern Italy) based on petrographic,mineralogic and reaction path modelling approaches

This work focuses on developing multidisciplinary research on weathering profiles of granitoid rocks related to the tectonic and landscape evolution of the Capo Vaticano area, Calabria, southern Italy. During the Pleistocene, the Mediterranean climate plays, on the already decomposed plutonic rocks, important processes of alteration, on both the highest and inland areas and the coastal areas of the Calabrian region, such as the studied area. Field observations coupled to chemical, minero‐petrographical features and geochemical modelling are used to characterize the weathering processes affecting the granitoid complex. The granitoid cut slopes show a generally simple weathering profile characterized by a progressive increase in weathering towards the top of the slopes. The completely weathered rocks (class V) and residual soil (class VI) contain a high percentage of altered minerals, microfractures, and voids. The main mineralogical changes are the partial transformation of biotite and the partial destruction of feldspars (mainly plagioclase) that are associated with the neoformation of secondary clay minerals and ferruginous products during the most advanced stage of weathering. These transformations produce a substitution of the original rock fabric. Geochemical modelling showing the precipitation of kaolinite, illite, vermiculite, ferrihydrite and calcite. These secondary solid phases are similar to those found in this natural system. Thus, the final results of the weathering process is a soil‐like material mainly characterized by mostly a sand to gravel grain‐size fractions related to microfabric changes and mineralogical and chemical variations. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrological regimes in different slope environments and implications on rainfall thresholds triggering shallow landslides

Natural Hazards - Assessing hazard of rainfall-induced shallow landslides represents a challenge for the risk management of urbanized areas for which the setting up of early warning systems, based...