45,484 research outputs found

    Is the Graviton a goldstone boson /ques/

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    Elementary particle theory for describing gravitation - Lorentz invariance - Graviton as boso

    Supporting research and development in ambulance services: research for better healthcare in prehospital settings

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    Background This paper discusses recent developments in research support for ambulance trusts in England and Wales and how this could be designed to lead to better implementation, collaboration in and initiation of high-quality research to support a truly evidence-based service. Method The National Ambulance Research Steering Group was set up in 2007 to establish the strategic direction for involvement of regional ambulance services in developing relevant and well-designed research for improving the quality of services to patients. Results Ambulance services have been working together and with academic partners to implement research and to participate, collaborate and lead the design of research that is relevant for patients and ambulance services. Conclusion New structures to support the strategic development of ambulance and prehospital research will help address gaps in the evidence for health interventions and service delivery in prehospital and ambulance care and ensure that ambulance services can increase their capacity and capability for high-quality research

    Creation of entangled states in coupled quantum dots via adiabatic rapid passage

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    Quantum state preparation through external control is fundamental to established methods in quantum information processing and in studies of dynamics. In this respect, excitons in semiconductor quantum dots (QDs) are of particular interest since their coupling to light allows them to be driven into a specified state using the coherent interaction with a tuned optical field such as an external laser pulse. We propose a protocol, based on adiabatic rapid passage, for the creation of entangled states in an ensemble of pairwise coupled two-level systems, such as an ensemble of QD molecules. We show by quantitative analysis using realistic parameters for semiconductor QDs that this method is feasible where other approaches are unavailable. Furthermore, this scheme can be generically transferred to some other physical systems including circuit QED, nuclear and electron spins in solid-state environments, and photonic coupled cavities.Comment: 10 pages, 2 figures. Added reference, minor changes. Discussion, results and conclusions unchange

    Computer-aided space shuttle orbiter wing design study

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    An analytical and experimental investigation has been made to provide a space shuttle orbiter wing design that met the guideline requirements of landing performance, stability, and hypersonic trim for a specified center-of-gravity envelope. The analytical study was facilitated by the use of the Optimal Design Integration system (ODIN) and the experimental part of the investigation was conducted in the Langley low-turbulence pressure tunnel and the Langley continuous-flow hypersonic tunnel

    Curvature Constraints from the Causal Entropic Principle

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    Current cosmological observations indicate a preference for a cosmological constant that is drastically smaller than what can be explained by conventional particle physics. The Causal Entropic Principle (Bousso, {\it et al}.) provides an alternative approach to anthropic attempts to predict our observed value of the cosmological constant by calculating the entropy created within a causal diamond. We have extended this work to use the Causal Entropic Principle to predict the preferred curvature within the "multiverse". We have found that values larger than ρk=40ρm\rho_k = 40\rho_m are disfavored by more than 99.99% and a peak value at ρΛ=7.9×10123\rho_{\Lambda} = 7.9 \times 10^{-123} and ρk=4.3ρm\rho_k =4.3 \rho_m for open universes. For universes that allow only positive curvature or both positive and negative curvature, we find a correlation between curvature and dark energy that leads to an extended region of preferred values. Our universe is found to be disfavored to an extent depending the priors on curvature. We also provide a comparison to previous anthropic constraints on open universes and discuss future directions for this work.Comment: 5 pages, 3 Figure

    Long-shore transport of sediment during August and September on the Terengganu coast

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    Mengabang Telipot is a slough about 10 km north of Kuala-Terengganu on the east coast of Peninsular Malaysia. Its mouth is normally closed to free exchange of sea water by a sand "wash-over" bar. On 16 August, 1984 the mouth was opened artificially, the slough became tidal, and a delta of sand was formed. The mouth remained open until the end of September. The long-shore current averaged 13 cm/sec toward the north-west. This modified the delta, and eventually led to the closing of the slough mouth. Deposition on the south-east side of the delta made it possible to estimate a volume of long-shore sand transport of250 cu m/day. This is in agreement with other estimates

    Quantum condensation from a tailored exciton population in a microcavity

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    An experiment is proposed, on the coherent quantum dynamics of a semiconductor microcavity containing quantum dots. Modeling the experiment using a generalized Dicke model, we show that a tailored excitation pulse can create an energy-dependent population of excitons, which subsequently evolves to a quantum condensate of excitons and photons. The population is created by a generalization of adiabatic rapid passage, and then condenses due to a dynamical analog of the BCS instability.Comment: 5 pages, 3 figures. Version 2 is extensively rewritten, and incorporates some new results in further support of our claim

    Orthotic management of cerebral palsy : recommendations from a consensus conference

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    An international multidisciplinary group of healthcare professionals and researchers participated in a consensus conference on the management of cerebral palsy, convened by the International Society for Prosthetics and Orthotics. Participants reviewed the evidence and considered contemporary thinking on a range of treatment options including physical and occupational therapy, and medical, surgical and orthotic interventions. The quality of many of the reviewed papers was compromised by inadequate reporting and lack of transparency, in particular regarding the types of patients and the design of the interventions being evaluated. Substantial evidence suggests that ankle-foot orthoses (AFOs) that control the foot and ankle in stance and swing phases can improve gait efficiency in ambulant children (GMFCS levels I-III). By contrast, little high quality evidence exists to support the use of orthoses for the hip, spine or upper limb. Where the evidence for orthosis use was not compelling consensus was reached on recommendations for orthotic intervention. Subsequent group discussions identified recommendations for future research. The evidence to support using orthoses is generally limited by the brevity of follow-up periods in research studies; hence the extent to which orthoses may prevent deformities developing over time remains unclear. The full report of the conference can be accessed free of charge at www.ispoint.org

    Method of forming a wick for a heat pipe

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    A method of forming a tubular wick for a heat pipe is presented. The method is characterized by the steps of forming a wick blank of a predetermined thickness comprising a plurality of superimposed layers of stainless steel mesh screen, wet rolling the blank for reducing the thickness, wrapping the blank about an inner mandrel, compressing the blank into a rigid tubular structure, removing the tubular structure from the mandrel and sintering the tubular structure
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