5,091 research outputs found

    Analysis of GeV-band gamma-ray emission from SNR RX J1713.7-3946

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    RX J1713.7-3946 is the brightest shell-type Supernova remnant (SNR) of the TeV gamma-ray sky. Earlier Fermi-LAT results on low-energy gamma-ray emission suggested that, despite large uncertainties in the background determination, the spectrum is inconsistent with a hadronic origin. We update the GeV-band spectra using improved estimates for the diffuse galactic gamma-ray emission and more than doubled data volume. We further investigate the viability of hadronic emission models for RX J1713.7-3946. We produced a high-resolution map of the diffuse Galactic gamma-ray background corrected for HI self-absorption and used it in the analysis of more than 5~years worth of Fermi-LAT data. We used hydrodynamic scaling relations and a kinetic transport equation to calculate the acceleration and propagation of cosmic-rays in SNR. We then determined spectra of hadronic gamma-ray emission from RX J1713.7-3946, separately for the SNR interior and the cosmic-ray precursor region of the forward shock, and computed flux variations that would allow to test the model with observations. We find that RX J1713.7-3946 is now detected by Fermi-LAT with very high statistical significance, and the source morphology is best described by that seen in the TeV band. The measured spectrum of RX J1713.7-3946 is hard with index gamma=1.53 +/- 0.07, and the integral flux above 500 MeV is F = (5.5 +/- 1.1)e-9 photons/cm^2/s. We demonstrate that scenarios based on hadronic emission from the cosmic-ray precursor region are acceptable for RX J1713.7-3946, and we predict a secular flux increase at a few hundred GeV at the level of around 15% over 10 years, which may be detectable with the upcoming CTA observatory.Comment: 9 pages, accepted for publication in Astronomy & Astrophysic

    The extended structure of the remote cluster B514 in M31. Detection of extra-tidal stars

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    We present a study of the density profile of the remote M31 globular cluster B514, obtained from HST/ACS observations. Coupling the analysis of the distribution of the integrated light with star counts we can reliably follow the profile of the cluster out to r~35", corresponding to ~130pc. The profile is well fitted, out to ~15 core radii, by a King Model having C=1.65. With an estimated core radius r_c=0.38", this corresponds to a tidal radius of r_t~17" (~65pc). We find that both the light and the star counts profiles show a departure from the best fit King model for r>~8" - as a surface brightness excess at large radii, and the star counts profile shows a clear break in correspondence of the estimated tidal radius. Both features are interpreted as the signature of the presence of extratidal stars around the cluster. We also show that B514 has a half-light radius significantly larger than ordinary globular clusters of the same luminosity. In the M_V vs. log r_h plane, B514 lies in a region inhabited by peculiar clusters, like Omega Cen, G1, NGC2419 and others, as well as by the nuclei of dwarf elliptical galaxies.Comment: 9 pages, 6 figures. Accepted for publication in Astronomy & Astrophysic

    Design of Wireless Sensor Nodes for Structural Health Monitoring applications

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    Enabling low-cost distributed monitoring, wireless sensor networks represents an interesting solution for the implementation of structural health monitoring systems. This work deals with the design of wireless sensor networks for health monitoring of civil structures, specifically focusing on node design in relation to the requirements of different structural monitoring application classes. Design problems are analysed with specific reference to a large-scale experimental setup (the long-term structural monitoring of the Basilica S. Maria di Collemaggio, L’Aquila, Italy). Main limitations emerged are highlighted, and adopted solution strategies are outlined, both in the case of commercial sensing platform and of full custom solutions

    The Crossover beteween Aslamazov-Larkin and Short Wavelength Fluctuations Regimes in HTS Conductivity Experiments

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    We present paraconductivity (AL) measurements in three different high temperature superconductors: a melt textured YBa2Cu3O7YBa_2Cu_3O_7 sample, a Bi2Sr2CaCu2O8Bi_2Sr_2CaCu_2O_8 epitaxial thin film and a highly textured Bi2Sr2Ca2Cu3O10Bi_2Sr_2Ca_2Cu_3O_{10} tape. The crossovers between different temperature regimes in excess conductivity have been analysed. The Lawrence-Doniach (LD) crossover, which separates the 2D and 3D regimes, shifts from lower to higher temperatures as the compound anisotropy decreases. Once the LD crossover is overcome, the fluctuation conductivity of the three compounds shows the same universal behaviour: for ŌĶ=ln‚Ā°T/Tc>0.23\epsilon =\ln T/T_c > 0.23 all the curves bend down according to the 1/ŌĶ31/\epsilon^3 law. This asymptotic behaviour was theoretically predicted previously for the high temperature region where the short wavelength fluctuations (SWF) become important.Comment: 4 pages, Revtex, 1 PostScript figure available upon request ([email protected]); submitted to Physical Review B rapid communication

    Do we need research on reporting on diabetes research?

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    Response of Autonomic Nervous System to Body Positions: Fourier and Wavelet Analysis

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    Two mathematical methods, the Fourier and wavelet transforms, were used to study the short term cardiovascular control system. Time series, picked from electrocardiogram and arterial blood pressure lasting 6 minutes, were analyzed in supine position (SUP), during the first (HD1), and the second parts (HD2) of 90‚ąė90^{\circ} head down tilt and during recovery (REC). The wavelet transform was performed using the Haar function of period T=2jT=2^j (% j=1,2,...... ,6) to obtain wavelet coefficients. Power spectra components were analyzed within three bands, VLF (0.003-0.04), LF (0.04-0.15) and HF (0.15-0.4) with the frequency unit cycle/interval. Wavelet transform demonstrated a higher discrimination among all analyzed periods than the Fourier transform. For the Fourier analysis, the LF of R-R intervals and VLF of systolic blood pressure show more evident difference for different body positions. For the wavelet analysis, the systolic blood pressures show much more evident difference than the R-R intervals. This study suggests a difference in the response of the vessels and the heart to different body positions. The partial dissociation between VLF and LF results is a physiologically relevant finding of this work.Comment: RevTex,8 figure
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