A model for bifurcation regions of the human tracheo-bronchial tree was developed. Equations for the surfaces are given to enable calculations of doses from alpha-particles emitted in these regions. It has been found that a bifurcation region is well approximated by a quasi-ellipsoid. The absorbed fractions of alpha-particles emitted in bifurcation regions were calculated by the Monte Carlo met...

Context. Aims. Intrinsic absorption is a fundamental physical property to understand the evolution of active galactic nuclei (AGN). Here a sample of 1290 AGN, selected in the 2–10 keV band from different flux-limited surveys with very high optical identification completeness is studied. Methods. The AGN are grouped into two classes, unabsorbed (type-1) and absorbed (type-2), depending on their ...

We present an analysis of the X-ray properties of sources detected in the 13H XMM-Newton deep (200ks) field. In order to constrain the absorbed AGN population, we use extensive Monte Carlo simulations to directly compare the X-ray colours of observed sources with those predicted by several model distributions. In particular, we have carried out our comparisons over the entire 0.2–10 keV energy ...