Flow simulations with ultra-low Reynolds numbers over rigid and flexible airfoils subject to heaving and flapping motions

Numerical simulations of flow patterns at ultra-low Reynolds numbers over rigid and flexible airfoils and the influence of flexibility on main aerodynamic properties, are presented and discussed. Typical unsteady flights like heaving and flapping are, in terms of Reynolds and Strouhal numbers, reduced frequencies and FSI (Fluid Structure Interaction) factor, are valuated. It has been found that for some flexibility levels, the aerodynamic forces and propulsive efficiency are enhanced if compared with a rigid airfoil. The mathematical technical approach used to solve the laminar-incompressible flow equations coupled with structural algorithms, is described.Fil: Antonelli, Dino Paolo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Aeronáutica; ArgentinaFil: Sacco, Carlos Gustavo. Instituto Universitario Aeronautico; ArgentinaFil: Tamagno, Jose Pedro. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Aeronáutica; Argentin

SN 2003lw and GRB 031203: A Bright Supernova for a Faint Gamma-ray Burst

Optical and near-infrared observations of the gamma-ray burst GRB 031203, at z = 0.1055, are reported. A very faint afterglow is detected superimposed to the host galaxy in our first infrared JHK observations, carried out ~9 hours after the burst. Subsequently, a rebrightening is detected in all bands, peaking in the R band about 18 rest-frame days after the burst. The rebrightening closely resembles the light curve of a supernova like SN 1998bw, assuming that the GRB and the SN went off almost simultaneously, but with a somewhat slower evolution. Spectra taken close to the maximum of the rebrightening show extremely broad features as in SN 1998bw. The determination of the absolute magnitude of this SN (SN 2003lw) is difficult owing to the large and uncertain extinction, but likely this event was brighter than SN 1998bw by 0.5 mag in the VRI bands, reaching an absolute magnitude M_V = -19.75+-0.15.Comment: 6 pages, 4 figures. Accepted to ApJ Letters. Fig. 4 will not appear in the journal version due to space limitations. Typos fixed in Table 1 (thanks to Dr. Alexander Kann for pointing out the problem). No measurements change

The AGILE Mission

AGILE is an Italian Space Agency mission dedicated to observing the gamma-ray Universe. The AGILE's very innovative instrumentation for the first time combines a gamma-ray imager (sensitive in the energy range 30 MeV-50 GeV), a hard X-ray imager (sensitive in the range 18-60 keV), a calorimeter (sensitive in the range 350 keV-100 MeV), and an anticoincidence system. AGILE was successfully launched on 2007 April 23 from the Indian base of Sriharikota and was inserted in an equatorial orbit with very low particle background. Aims. AGILE provides crucial data for the study of active galactic nuclei, gamma-ray bursts, pulsars, unidentified gamma-ray sources, galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. Methods. An optimal sky angular positioning (reaching 0.1 degrees in gamma- rays and 1-2 arcmin in hard X-rays) and very large fields of view (2.5 sr and 1 sr, respectively) are obtained by the use of Silicon detectors integrated in a very compact instrument. Results. AGILE surveyed the gamma- ray sky and detected many Galactic and extragalactic sources during the first months of observations. Particular emphasis is given to multifrequency observation programs of extragalactic and galactic objects. Conclusions. AGILE is a successful high-energy gamma-ray mission that reached its nominal scientific performance. The AGILE Cycle-1 pointing program started on 2007 December 1, and is open to the international community through a Guest Observer Program

AGILE detection of intense gamma-ray activity from the blazar PKS 0537-441 in October 2008

We report the detection by the AGILE satellite of intense gamma-ray activity from the source 1AGL J0538-4424, associated with the low-energy-peaked BL Lac PKS 0537-441, during a target of opportunity (ToO) observation performed on 2008 October 10-17, triggered by a Fermi-LAT alert, together with REM and Swift observations. Aims. The quasi-simultaneous near-infrared, optical, UV, X-ray, and gamma-ray coverage allowed us to investigate the behaviour of the source in different energy bands and study the spectral energy distribution and a theoretical model that can describe the gamma-ray state observed in mid-October. Methods. AGILE observed the source with its two co-aligned imagers: the Gamma-Ray Imaging Detector (GRID) and the hard X-ray imager (SuperAGILE), sensitive in the 30 MeV-30 GeV and 18-60 keV ranges, respectively. During the AGILE observation, the source was monitored simultaneously in the UV and X-ray bands by the Swift satellite through 6 ToO observations carried out between 2008 October 8 and 17. Moreover, the source was observed in the near-infrared and optical bands by the REM telescope on 2008 October 7, 8, and 9. Results. During 2008 October 10-17, AGILE-GRID detected gamma-ray emission from PKS 0537-441 at a significance level of 5.3-sigma with an average flux of (42 +/- 11) x 10(-8) photons cm(-2) s(-1) for energies higher than 100 MeV. A significant increase in the gamma-ray activity was detected between the first and the second halves of the observing period. REM and Swift/XRT detected the source in near-infrared/optical and X-rays during a relatively low and intermediate activity state, respectively, with no signs of evident variability in the different observations. However, Swift/UVOT detected an increase between the first and the second parts of the observing period, smaller than in the gamma-rays. Conclusions. The average gamma-ray flux of PKS 0537-441 detected by AGILE is close to the average flux observed for this source by the EGRET and Fermi-LAT instruments, with an increase of a factor 3 throughout the observation period up to a flux level slightly lower than the highest flux observed by Fermi-LAT during the first 11 months of operation. The spectral energy distribution of PKS 0537-441 in mid-October 2008 seems to require two synchrotron self-Compton components to be modelled, to account for both the near-infrared/optical bump and the X-ray data, together with the information on the gamma-ray flux level observed by AGILE. An alternative model based on the external Compton radiation, which requires an accretion disk with a relatively high luminosity, is also proposed

Monitoring the hard X-ray sky with SuperAGILE

SuperAGILE is the hard X-ray monitor of the AGILE gamma ray mission, in orbit since 23 April 2007. It is an imaging experiment based on a set of four independent silicon strip detectors, equipped with one-dimensional coded masks, operating in the nominal energy range 18-60 keV. Aims. The main goal of SuperAGILE is the observation of cosmic sources simultaneously with the main gamma-ray AGILE experiment, the Gamma Ray Imaging Detector (GRID). Given its similar to steradian-wide field of view and its similar to 15 mCrab day-sensitivity, SuperAGILE is also well suited to the long-term monitoring of Galactic compact objects and the detection of bright transients. Methods. The SuperAGILE detector properties and design allow for a 6 arcmin angular resolution in each of the two independent orthogonal projections of the celestial coordinates. Photon by photon data are continuously available by means of experiment telemetry, and are used to derive images and fluxes of individual sources, with integration times depending on the source intensity and position in the field of view. Results. We report on the main scientific results achieved by SuperAGILE over its first two years in orbit, until April 2009. The scientific observations started in mid-July 2007, with the science verification phase, continuing during the complete AGILE Cycle 1 and the first similar to half of Cycle 2. Despite the largely non-uniform sky coverage, due to the pointing strategy of the AGILE mission, a few tens of Galactic sources were monitored, sometimes for unprecedently long continuous periods, leading to the detection also of several bursts and outbursts. Approximately one gamma ray burst per month was detected and localized, allowing for prompt multi-wavelength observations. A few extragalactic sources in bright states were occasionally detected as well. The light curves of sources measured by SuperAGILE are made publicly available on the web in almost real-time. To enable a proper scientific use of these, we provide the reader with the relevant scientific and technical background

AGILE detection of a rapid gamma-ray flare from the blazar PKS 1510-089 during the GASP-WEBT monitoring

We report the detection by the AGILE satellite of a rapid gamma-ray flare from the source 1AGL J1511-0908, associated with the powerful gamma-ray quasar PKS 1510-089, during a pointing centered on the Galactic center region from 1 March to 30 March 2008. This source has been continuosly monitored in the radio-to-optical bands by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). Moreover, the gamma-ray flaring episode triggered three ToO observations by the Swift satellite in three consecutive days, starting from 20 March 2008. The quasi-simultaneous radio-to-optical, UV, X-ray and gamma-ray coverage allows us to make a detailed study of the multifrequency time evolution, the spectral energy distribution of this source, and its theoretical interpretation based on the synchrotron and inverse Compton (IC) emission mechanisms. Methods. During the radio-to-optical monitoring provided by the GASP-WEBT, AGILE observed the source with its two co-aligned imagers, the gamma-ray imaging detector (GRID) and the hard X-ray imager (SuperAGILE), which are sensitive in the 30 MeV-30 GeV and 18-60 keV energy bands, respectively. Results. In the period 1-16 March 2008, AGILE detected gamma-ray emission from PKS 1510-089 at a significance level of 6.2-sigma with an average flux over the entire period of (84 +/- 17) x 10(-8) photons cm(-2) s(-1) for photon energies above 100 MeV. After a predefined satellite re-pointing, between 17 and 21 March 2008, AGILE detected the source at a significance level of 7.3-sigma, with an average flux (E > 100 MeV) of (134 +/- 29) x 10(-8) photons cm-2 s-1 and a peak level of (281 +/- 68) x 10(-8) photons cm(-2) s(-1) with daily integration. During the observing period January-April 2008, the source also showed an intense and variable optical activity, with several flaring episodes and a significant increase in the flux was observed at millimetric frequencies. Moreover, in the X-ray band, the Swift/XRT observations seem to show a harder-when-brighter behavior of the source spectrum. Conclusions. The flat spectrum radio quasar PKS 1510-089 showed strong activity between January and April 2008, with episodes of rapid variability from radio to gamma-ray energy bands, in particular with a rapid gamma-ray flaring episode. The spectral energy distribution of mid-March 2008 is modeled with a homogeneous one-zone synchrotron self Compton (SSC) emission plus contributions from inverse Compton scattering of external photons from both the accretion disk and the broad line region. Indeed, some features in the optical-UV spectrum seem to indicate Seyfert-like components such as the little and the big blue bumps

Cytomegalovirus infection management in solid organ transplant recipients across European centers in the time of molecular diagnostics: An ESGICH survey

Background: Scant information is available about how transplant centers are managing their use of quantitative molecular testing (QNAT) assays for active cytomegalovirus (CMV) infection monitoring in solid organ transplant (SOT) recipients. The current study was aimed at gathering information on current practices in the management of CMV infection across European centers in the era of molecular testing assays. Methods: A questionnaire-based cross-sectional survey study was conducted by the European Study Group of Infections in Immunocompromised Hosts (ESGICH) of the Society of Clinical Microbiology and Infectious Diseases (ESCMID). The invitation and a weekly reminder with a personal link to an Internet service provider (https://es.surveymonkey.com/) was sent to transplant physicians, transplant infectious diseases specialists, and clinical virologists working at 340 European transplant centers. Results: Of the 1181 specialists surveyed, a total of 173 responded (14.8%): 73 transplant physicians, 57 transplant infectious diseases specialists, and 43 virologists from 173 institutions located at 23 different countries. The majority of centers used QNAT assays for active CMV infection monitoring. Most centers preferred commercially available real-time polymerase chain reaction (RT-PCR) assays over laboratory-developed procedures for quantifying CMV DNA load in whole blood or plasma. Use of a wide variety of DNA extraction platforms and RT-PCR assays was reported. All programs used antiviral prophylaxis, preemptive therapy, or both, according to current guidelines. However, the centers used different criteria for starting preemptive antiviral treatment, for monitoring systemic CMV DNA load, and for requesting genotypic assays to detect emerging CMV-resistant variants. Conclusions: Significant variation in CMV infection management in SOT recipients still remains across European centers in the era of molecular testing. International multicenter studies are required to achieve commutability of CMV testing and antiviral management procedures