In this paper we propose a new probabilistic Fair Exchange Protocol which requires no central Trusted Third Party. Instead, it relies on a virtually distributed and decentralized Trusted Third Party which is formalized as a Guardian Angel: a kind of Observer e.g. a tamper proof security device. We thus introduce a network model with Pirates and Guardian Angels which is well suited for Ad Hoc ne...

We analyze the funding of start-up companies across financing rounds, focusing on dynamic interactions between angel investors and venture capitalists. Using unique data from British Columbia, Canada, we show that angels capitalists are substitutes. This substitutes pattern applies performance range companies. It is less pronounced for serial angels. An instrumental variable analysis, based ava...

STATEMENT OF THE PROBLEM The diagnosis of vertical root fracture (VRF) is a challenging task. PURPOSE This in vitro study compared cone beam computed tomography (CBCT) imaging with digital periapical radiography (DPR) made by three different horizontal angels (20°mesial, 0° and 20° distal) for accurate diagnosis of VRF. MATERIALS AND METHOD Among 120 posterior teeth included in this study, ...