34,248 research outputs found

    Hulme: Ten years on

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    Non-BPS D8-branes and Dynamic Domain Walls in Massive IIA Supergravities

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    We study the D8-branes of the Romans massive IIA supergravity theory using the coupled supergravity and worldvolume actions. D8 branes can be regarded as domain walls with the jump in the extrinsic curvature at the brane given by the Israel matching conditions. We examine the restrictions that these conditions place on extreme and non-extreme solutions and find that they rule out some of the supersymmetric solutions given by Bergshoeff {\em et al}. We consider what happens when the dilaton varies on the worldvolume of the brane, which implies that the brane is no longer static. We obtain a family of D8-brane solutions parametrized by a non-extremality term on each side of the brane and the asymptotic values of the 10-form field. The non-extremality parameters can be related to the velocity of the brane. We also study 8-brane solutions of a massive IIA supergravity theory introduced by Howe, Lambert and West. This theory also admits a 10-form formulation, but the 10-form is not a R-R sector field and so these 8-branes are not D-branes.Comment: 23 pages REVTeX, 2 .eps figures. This paper completely replaces and extends an earlier paper (hep-th/9712112) by Chamblin and Perr

    New insights into the biomechanics of Legg-CalvĆ©-Perthesā€™ disease: The role of epiphyseal skeletal immaturity in vascular obstruction

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    ObjectivesLeggā€“CalvĆ©ā€“Perthesā€™ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition.MethodsFinite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.ResultsThe results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression.ConclusionThe findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease

    Putting the ā€˜digitalā€™ in Digital Intermediaries: the role of technical infrastructure in building business models

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    Digital Technology Innovation and Financial Business Practices The UK economy has a huge dependence on financial services, and this is increasingly based on digital platforms. Innovating new economic models around consumer financial services through the use of digital technologies is seen as increasingly important in developed economies. There are a number of drivers for this, ranging from national economic factors to the prosaic nature of enabling cheap, speedy and timely interactions for users. The potential for these new digital solutions is that they will allay an over-reliance on the traditional banking sector, which has proved itself to be unstable and risky, and we have seen a number of national policy moves to encourage growth in this sector. Partly as a result of the 2008 banking crisis, there has been an explosion in peer-to-peer financial services for non-professional consumers. These organisations act as intermediaries between users looking to trade goods or credit. However, building self-sustaining or profitable financial services within this novel space is itself fraught with commercial, regulatory, technical and social problems. This report addresses the mutual shaping of business models and innovations in digital technical infrastructure ā€“ both client-facing and administrative back-end ā€“ in two retail financial products currently in use in the United Kingdom: peer-to-peer consumer lending and a local digital/paper hybrid currency system. The two products and their issuing firms, Zopa Limited (Zopa) and The Bristol Pound Community Interest Company (the Bristol Pound), respectively, are established leaders in their respective product areas: Zopa was established in 2005 and the Bristol Pound in 2010. Each of these firms seeks to disrupt an established financial market through the application of digital technologies and processes: consumer lending for Zopa and retail payment for the Bristol Pound. Our research has involved teams from Lancaster University examining Zopa and Brunel University focusing on the Bristol Pound over approximately a one-year period from October 2013 to October 2014. Extensive interviews, document analysis, observation of user interactions, and other methods have been employed to develop the process analyses of the firms presented here. This report is comprised of three primary sections: descriptions of the business and technological processes of each of Zopa and the Bristol Pound, and a final analytical section drawing preliminary conclusions from the research presented.3DaRoC is funded by the UKā€™s Digital Economy ā€˜Research in the Wildā€™ initiative. It has a substantial research budget of over Ā£320K, with Ā£35K of additional industrial support

    ā€™Eyes freeā€™ in-car assistance: parent and child passenger collaboration during phone calls

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    This paper examines routine family car journeys, looking specifically at how passengers assist during a mobile telephone call while the drivers address the competing demands of handling the vehicle, interacting with various artefacts and controls in the cabin, and engage in co-located and remote conversations while navigating through busy city roads. Based on an analysis of video fragments, we see how drivers and child passengers form their conversations and requests around the call so as to be meaningful and paced to the demands, knowledge and abilities of their cooccupants, and how the conditions of the road and emergent traffic are oriented to and negotiated in the context of the social interaction that they exist alongside. The study provides implications for the design of car-based collaborative media and considers how hands- and eyesfree natural interfaces could be tailored to the complexity of activities in the car and on the road
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