Gamma-ray Bursts - A Puzzle Being Resolved

For a few seconds a gamma-ray burst (GRB) becomes the brightest object in the Universe, over-shining the rest of the Universe combined! Clearly this reflects extreme conditions that are fascinating and worth exploring. The recent discovery of GRB afterglow have demonstrated that we are on the right track towards the resolution of this long standing puzzle. These observations have confirmed the relativistic fireball model (more specifically the internal-external shocks model). The prompt optical emission seen in GRB 990123 have demonstrated that GRBs involve ultra-relativistic motion. The breaks in the light curves of GRB 990123 and GRB 990510 and the peculiar light curves of GRB 980519 and GRB 980326 disclosed that these GRBs are beamed. I examine these recent developments and discuss their implications to the models of the source. I argue that the current understanding implies that GRBs signal the birth of stellar mass black holes.Comment: A 28 pages review of recent developments in GRB physics. An update to astro-ph/9810256 (Physics Reports 1999 314 575). To appear in related froms in the Dave Schramm memorial volume, in the proceedings of the Gr\"aft{\aa}vallen workshop `Gamma Ray Bursts: The First Three Minutes' (Ed. Juri Poutanen), and in the proceedins of the VIII International Workshop on "Neutrino Telescopes" (Ed. Milla Baldo Ceolin

The problem of unilateralism in agency theory: towards a bilateral formulation

Some business ethicists view agency theory as a cautionary tale – a proof that it is impossible to carry out successful economic interactions in the absence of ethical behaviour. The cautionary-tale view presents a nuanced normative characterisation of agency, but its unilateral focus betrays a limited understanding of the structure of social interaction. This article moves beyond unilateralism by presenting a descriptive and normative argument for a bilateral cautionary-tale view. Specifically, we discuss hat swaps and role dualism in asymmetric-information principal-agent relationships and argue that the norm of reciprocity can function as a moral solution to agency risks in adverse-selection and moral-hazard problems. Our novel bilateral cautionary-tale formulation extends the normative boundaries of the asymmetric-information stream of agency theory, while leaving the fundamental economic assumptions of agency theory intact

Spitzer 24 um Excesses for Bright Galactic Stars in Bootes and First Look Survey Fields

Optically bright Galactic stars (V 1 mJy are identified in Spitzer mid-infrared surveys within 8.2 square degrees for the Bootes field of the NOAO Deep Wide-Field Survey and within 5.5 square degrees for the First Look Survey (FLS). 128 stars are identified in Bootes and 140 in the FLS, and their photometry is given. (K-[24]) colors are determined using K magnitudes from the 2MASS survey for all stars in order to search for excess 24 um luminosity compared to that arising from the stellar photosphere. Of the combined sample of 268 stars, 141 are of spectral types F, G, or K, and 17 of these 141 stars have 24 um excesses with (K-[24]) > 0.2 mag. Using limits on absolute magnitude derived from proper motions, at least 8 of the FGK stars with excesses are main sequence stars, and estimates derived from the distribution of apparent magnitudes indicate that all 17 are main sequence stars. These estimates lead to the conclusion that between 9% and 17% of the main sequence FGK field stars in these samples have 24 um infrared excesses. This result is statistically similar to the fraction of stars with debris disks found among previous Spitzer targeted observations of much brighter, main sequence field stars.Comment: Accepted for publication in The Astronomical Journa

Trading in Strategic Resources: Necessary Conditions, Transaction Cost Problems, and Choice of Exchange Structure

This is the author's final draft. The publisher's official version is available from: http://dx.doi.org/10.1002/smj.4250150403The paper develops a theoretical framework for analyzing the exchange structure in the trading of imperfectly imitable and imperfectly mobile firm resources. It first explores the conditions for such resources to be gainfully traded between firms and then investigates the interconnections between barriers to imitation and impediments to trading. A major part of the paper is devoted to developing an integrative and yet parsimonious model for assessing the exchange structure between firms that are involved in the trading of strategic resources in the face of significant transaction cost problems. The model is applied in the last part of the paper to the analysis of the choice between acquisitions and collaborative ventures

The determinants of IPO firm prospectus length in Africa

This paper studies the differential impact on IPO firm listing prospectus length from increasing proportions of foreign directors from civil as opposed to common law societies and social elites. Using a unique hand-collected and comprehensive sample of 165 IPO firms from across 18 African countries the evidence suggests that increasing proportions of directors from civil code law countries is associated with shorter prospectuses while the opposite is true for their common law counterparts. Furthermore increasing proportions of directors drawn from elevated social positions in indigenous society is related to increasing prospectus length in North Africa while being insignificant in SSA

R&D managers’ adaptation of firms’ HRM practices

The heads of R&D departments are those most responsible for the adaptation of firms’ human resource management (HRM) practices to the idiosyncrasies of their departments. From their description, this paper analyzes the HRM practices in R&D departments and the adaptation achieved in four different firms. The data suggest that the main adaptations are produced primarily in recruiting and organizing the work of R&D personnel. In contrast to suggestions in the specialized literature, less adaptation is found in other HRM practices analyzed (managerial support and degree of delegation, compensation and career plans). Psychological theories of procedural justice and social comparison can improve our understanding of such results. The organizational structure affects the reference group for such comparisons and, consequently, the R&D managers’ capacity to adapt such practices. Based on these arguments, the delegation of HRM practices to R&D departments will enhance the degree of adaptation of such policiesPublicad