An unexpectedly rapid decline in the X-ray afterglow emission of long gamma-ray bursts

'Long' gamma-ray bursts (GRBs) are commonly accepted to originate in the explosion of particularly massive stars, which give rise to highly relativistic jets. Inhomogeneities in the expanding flow result in internal shock waves that are believed to produce the gamma-rays we see. As the jet travels further outward into the surrounding circumstellar medium, 'external' shocks create the afterglow emission seen in the X-ray, optical and radio bands. Here we report observations of the early phases of the X-ray emission of five GRBs. Their X-ray light curves are characterised by a surprisingly rapid fall-off for the first few hundred seconds, followed by a less rapid decline lasting several hours. This steep decline, together with detailed spectral properties of two particular bursts, shows that violent shock interactions take place in the early jet outflows.     

An Holistic Approach to the Management of Information Systems Development—A View Using a Soft Systems Approach and Multiple Viewpoints

This paper argues that only a systems-based approach to information systems development is likely to cover all the recognized problem issues reported in the literature. It is then shown that software development can be characterized by the structure of the Soft Systems Methodology, so that this methodology acts as a metaphor for the process of information systems development. The structure of this methodology can be seen at lower levels of the development process, and so the model generated here is seen as recursive. Further, information systems development is seen as an unstructured business problem that can be characterized by the Multiple Viewpoint approach. The connections between this approach and the methodology are identified. Finally, the unifying link between these approaches and all forms of action research is identified.     

Interaction between peripheral blood leucocytes and X-irradiated cells from lymphoid cell lines

Résumé Une interaction stimulante très marquée s'observe dans les cultures de lymphocytes frais du sang humain merlées à des cellules lymphoïdes de plusieurs lignées continues exposées aux rayons X.

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We thank Dr. R. M.Flinn (Department of Anatomy) for the use of his computer programme for the calculation of radioactivity and Mrs. J.Wallin for her excellent technical help. D.A.H. gratefully acknowledges a studentship from the Wellcome Trust. This work was financed, in part, by grants from the Wellcome Trust and the Medical Research Council.     

Monocyte chemoattractant protein-1 and the blood–brain barrier

The blood–brain barrier (BBB) is a dynamic structure that maintains the homeostasis of the brain and thus proper neurological functions. BBB compromise has been found in many pathological conditions, including neuroinflammation. Monocyte chemoattractant protein-1 (MCP1), a chemokine that is transiently and significantly up-regulated during inflammation, is able to disrupt the integrity of BBB and modulate the progression of various diseases, including excitotoxic injury and hemorrhage. In this review, we first introduce the biochemistry and biology of MCP1, and then summarize the effects of MCP1 on BBB integrity as well as individual BBB components.     

R-spondin1 is essential in sex determination, skin differentiation and malignancy

R-spondins are a recently characterized small family of growth factors. Here we show that human R-spondin1 (RSPO1) is the gene disrupted in a recessive syndrome characterized by XX sex reversal, palmoplantar hyperkeratosis and predisposition to squamous cell carcinoma of the skin. Our data show, for the first time, that disruption of a single gene can lead to complete female-to-male sex reversal in the absence of the testis-determining gene, SRY.