83,889 research outputs found

    The basic parameters of gamma-ray-loud blazars

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    We determined the basic parameters, such as the central black hole mass (MM), the boosting factor (or Doppler factor) (δ\delta), the propagation angle (Φ\Phi) and the distance along the axis to the site of γ\gamma-ray production (dd) for 23 γ\gamma-ray-loud blazars using their available variability timescales. In this method, the absorption effect depends on the γ\gamma-ray energy, emission size and property of the accretion disk. Using the intrinsic γ\gamma-ray luminosity as a fraction λ\lambda of the Eddington luminosity, Lγin=λLLedd.L^{in}_{\gamma}=\lambda L_{Ledd.} and the optical depth equal to unity, we can determine the upper limit of the central black hole masses. We found that the black hole masses range between 107M10^{7}M_{\odot} and 109M10^{9}M_{\odot} when λ\lambda = 0.1 and 1.0 are adopted. Since this method is based on gamma-ray emissions and the short time-scale of the sources, it can also be used for central black hole mass determination of high redshift gamma-ray sources. In the case of the upper limit of black hole mass there is no clear difference between BLs and FSRQs, which suggests that the central black hole masses do not play an important role in the evolutionary sequence of blazars.Comment: 8 pages, 3 figures, 1 table, Accepted by A&

    Environmental modelling of the Chief Information Officer

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    Since the introduction of the term in the 1980’s, the role of the Chief Information Officer (CIO) has been widely researched. Various perceptions and dimensions of the role have been explored and debated. However, the explosion in data proliferation (and the inevitable resulting information fuelled change) further complicates organisational expectations of the CIOs role. If organisations are to competitively exploit the digital trend, then those charged with recruiting and developing CIOs now need to be more effective in determining (and shaping) CIO traits and attributes, within the context of their own organisational circumstances and in line with stakeholder expectations. CIOs also need to determine their own suitability and progression within their chosen organisation if they are to remain motivated and effective. Before modelling the role of the future CIO, it is necessary to synthesise our current knowledge (and the lessons learnt) about the CIO. This paper, therefore, aims to identify and summate the spectrum of key researched ‘themes’ pertaining to the role of the CIO. Summating previous research, themes are modelled around four key CIO ‘dimensions’, namely (1) Impacting factors, (2) Controlling factors (3) Responses and (4) CIO ‘attributes’. Having modelled the CIOs current environment, and recognising the evolving IT enabled information landscape, the authors call for further research to inform the recruitment and development of the future CIO in terms of personal attributes and the measurable impact such attributes will have on their respective organisation