Fluorescent Ly-alpha emission from the high-redshift intergalactic medium

We combine a high-resolution hydro-simulation of the LambdaCDM cosmology with two radiative transfer schemes (for continuum and line radiation) to predict the properties, spectra and spatial distribution of fluorescent Ly-alpha emission at z~3. We focus on line radiation produced by recombinations in the dense intergalactic medium ionized by UV photons. In particular, we consider both a uniform background and the case where gas clouds are illuminated by a nearby quasar. We find that the emission from optically thick regions is substantially less than predicted from the widely used static, plane-parallel model. The effects induced by a realistic velocity field and by the complex geometric structure of the emitting regions are discussed in detail. We make predictions for the expected brightness and size distributions of the fluorescent sources.Our results account for recent null detections and can be used to plan new observational campaigns both in the field (to measure the intensity of the diffuse UV background) and in the proximity of bright quasars (to understand the origin of high colum-density absorbers).Comment: 15 pages, 12 figures, accepted for publication in Ap

Deeper Chandra Follow-up of Cygnus TeV Source Perpetuates Mystery

A 50 ksec Chandra observation of the unidentified TeV source in Cygnus reported by the HEGRA collaboration reveals no obvious diffuse X-ray counterpart. However, 240 Pointlike X-ray sources are detected within or nearby the extended TeV J2032+4130 source region, of which at least 36 are massive stars and 2 may be radio emitters. That the HEGRA source is a composite, having as counterpart the multiple point-like X-ray sources we observe, cannot be ruled out. Indeed, the distribution of point-like X-ray sources appears non-uniform and concentrated broadly within the extent of the TeV source region. We offer a hypothesis for the origin of the very high energy gamma-ray emission in Cyg OB2 based on the local acceleration of TeV range cosmic rays and the differential distribution of OB vs. less massive stars in this association.Comment: Substantially revised version; incorporates referee suggestions & expanded discussio

Careggi Smart Hospital: A mobile app for patients, citizens and healthcare staff

This paper presents a mobile app called “Careggi Smart Hospital” which has been developed for the Careggi Polyclinic in Florence. The application is designed for Android smartphones and tablets and it is freely downloadable from the Google Play Store. It provides various useful tools to the hospital's users such as personnel and structures finding, way-finding and the possibility to access personal medical records collected on regional electronic health record

Accretion Shocks in Clusters of Galaxies and their SZ Signature from Cosmological Simulations

Cold dark matter (CDM) hierarchical structure formation models predict the existence of large-scale accretion shocks between the virial and turnaround radii of clusters of galaxies. Kocsis et al. (2005) suggest that the Sunyaev-Zel'dovich (SZ) signal associated with such shocks might be observable with the next generation radio interferometer, ALMA. We study the three--dimensional distribution of accretion shocks around individual clusters of galaxies drawn from adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) simulations of LCDM (dark energy dominated CDM) models. In relaxed clusters, we find two distinct sets of shocks. One set ("virial shocks"), with Mach numbers of 2.5-4, is located at radii 0.9-1.3 Rvir, where Rvir is the spherical infall estimate of the virial radius, covering about 40-50% of the total surface area around clusters at these radii. Another set of stronger shocks ("external shocks") is located farther out, at about 3 Rvir, with large Mach numbers (~100), covering about 40-60% of the surface area. We simulate SZ surface brightness maps of relaxed massive galaxy clusters drawn from high resolution AMR runs, and conclude that ALMA should be capable of detecting the virial shocks in massive clusters of galaxies. More simulations are needed to improve estimates of astrophysical noise and to determine optimal observational strategies.Comment: 41 pages including 11 figures and 2 tables; ApJ, in pres

UHECR Acceleration in Dark Matter Filaments of Cosmological Structure Formation

A mechanism for proton acceleration to ~10^21eV is suggested. It may operate in accretion flows onto thin dark matter filaments of cosmic structure formation. The flow compresses the ambient magnetic field to strongly increase and align it with the filament. Particles begin the acceleration by the ExB drift with the accretion flow. The energy gain in the drift regime is limited by the conservation of the adiabatic invariant p_perp^2/B. Upon approaching the filament, the drift turns into the gyro-motion around the filament so that the particle moves parallel to the azimuthal electric field. In this 'betatron' regime the acceleration speeds up to rapidly reach the electrodynamic limit $cp_{max}=eBR$ for an accelerator with magnetic field $B$ and the orbit radius $R$ (Larmor radius). The periodic orbit becomes unstable and the particle slings out of the filament to the region of a weak (uncompressed) magnetic field, which terminates the acceleration. The mechanism requires pre-acceleration that is likely to occur in structure formation shocks upstream or nearby the filament accretion flow. Previous studies identify such shocks as efficient proton accelerators to a firm upper limit ~10^19.5 eV placed by the catastrophic photo-pion losses. The present mechanism combines explosive energy gain in its final (betatron) phase with prompt particle release from the region of strong magnetic field. It is this combination that allows protons to overcome both the photo-pion and the synchrotron-Compton losses and therefore attain energy 10^21 eV. A requirement on accelerator to reach a given E_max placed by the accelerator energy dissipation \propto E_{max}^{2}/Z_0 due to the finite vacuum impedance Z_0 is circumvented by the cyclic operation of the accelerator.Comment: 34 pages, 10 figures, to be published in JCA

Energy Dissipation in Interstellar Cloud Collisions

We present a study of the kinetic energy dissipation in interstellar cloud collisions. The main aim is to understand the dependence of the elasticity (defined as the ratio of the final to the initial kinetic energy of the clouds) on the velocity and mass ratio of the colliding clouds, magnetic field strength, and gas metallicity for head-on collisions. The problem has been studied both analytically and via numerical simulations. We have derived handy analytical relationships that well approximate the analogous numerical results. The main findings of this work are: (i) the kinetic energy dissipation in cloud collisions is minimum (i.e. the collision elasticity is maximum) for a cloud relative velocity $v_r \simeq 30 km s^{-1}$; (ii) the above minimum value is proportional $Z L_c^2$, where $Z$ is the metallicity and $L_c$ is the cloud size: the larger is $Z L_c^2$ the more dissipative (i.e. inelastic) the collision will be; (iii) in general, we find that the energy dissipation decreases when the magnetic field strength, and mass ratio of the clouds are increased and the metallicity is decreased, respectively. We briefly discuss the relevance of this study to the global structure of the interstellar medium and to galaxy formation and evolution.Comment: 16 pages, aasms LaTeX, 7 figures. ApJ, accepte

Integrated HTA and FMECA methodology for the evaluation of robotic surgery

Robotic surgery has been strongly improved since the beginning of the twenty-first century and chased important level of technical and clinical performances. Within the robotic area, the most worldwide used surgical robot is the da Vinci® system made by Intuitive Surgical Inc. The aim of this study was to evaluate at the hospital scale the robotic surgery (Hospital –Based Health Technology Assessment) in comparison to the open and laparoscopic procedures yet combining a FMECA analysis to accurately assess all those aspects involving patient and staff safety. The total number of robotic procedures directly observed by the surgical department and reported in the following study was 44, including 28 urology interventions and 16 general surgeries. The study confirmed clinical benefits carried out with the robot but bigger complexity in managing the whole surgical system in terms of structural needs, staff and technology. For the future, further steps regard the necessity to dispose of a wider number of robotic procedures in order to strength the analysis reliability and complete the socio-economic assessment with medium and long terms observation. Finally a new FMECA application will be essential to monitor the real effects of the suggested actions on the evaluated risks according to the already known and new failure modes