17,331 research outputs found

    Flame Instability and Transition to Detonation in Supersonic Reactive Flows

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    Multidimensional numerical simulations of a homogeneous, chemically reactive gas were used to study ignition, flame stability, and deflagration-to-detonation transition (DDT) in a supersonic combustor. The configuration studied was a rectangular channel with a supersonic inflow of stoichiometric ethylene-oxygen and a transimissive outflow boundary. The calculation is initialized with a velocity in the computational domain equal to that of the inflow, which is held constant for the duration of the calculation. The compressible reactive Navier-Stokes equations were solved by a high-order numerical algorithm on an adapting mesh. This paper describes two calculations, one with a Mach 3 inflow and one with Mach 5.25. In the Mach 3 case, the fuel-oxidizer mixture does not ignite and the flow reaches a steady-state oblique shock train structure. In the Mach 5.25 case, ignition occurs in the boundary layers and the flame front becomes unstable due to a Rayleigh-Taylor instability at the interface between the burned and unburned gas. Growth of the reaction front and expansion of the burned gas compress and preheat the unburned gas. DDT occurs in several locations, initiating both at the flame front and in the unburned gas, due to an energy-focusing mechanism. The growth of the flame instability that leads to DDT is analyzed using the Atwood number parameter

    Managing for change: May 3, 1989

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    Bi-weekly newsletter of University Hospital's Change Project, provided to managers at the hospital

    The association of criminal justice supervision setting with overdose mortality: a longitudinal cohort study.

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    Background and aimsDespite the high prevalence of substance use among people in the US criminal justice system, little is known about the incidence of overdose mortality by use patterns, drug convictions and supervision setting. We examined the associations between these characteristics and overdose mortality.DesignRetrospective cohort study.Setting and participantsIndividuals sentenced to prison, jail, probation or jail plus probation for a felony conviction in Michigan, USA from 2003 to 2006.MeasurementsUsing the National Death Index, we assessed overdose mortality to December 2012. We calculated overdose mortality rates by pre-sentence opioid use, drug convictions and supervision setting. Multivariable analyses were conducted using competing risks regression with time-varying covariates.FindingsAmong 140 266 individuals followed over a mean of 7.84 years [standard deviation (SD) = 1.52], 14.9% of the 1131 deaths were due to overdose (102.8 per 100 000 person-years). Over the follow-up, more than half of overdose deaths occurred in the community (57.7%), nearly a third (28.8%) on probation and 12.8% on parole. The adjusted risk of overdose death was lower on probation [hazard ratio (HR) = 0.71, 95% confidence interval (CI) = 0.60, 0.85] than in the community without probation or parole (HR = 1.00) but not significantly different on parole (HR = 1.13, 95% CI = 0.87, 1.47). Pre-sentence daily opioid use (HR = 3.54, 95% CI = 3.24, 3.87) was associated with an increased risk. Drug possession (HR = 1.11, 95% CI = 0.93, 1.31) and delivery convictions (HR = 0.92, 95% CI = 0.77, 1.09) were not significantly associated with overdose mortality.ConclusionsBased on the absolute or relative risk, parole, probation and community settings are appropriate settings for enhanced overdose prevention interventions. Ensuring that individuals with pre-sentence opioid use have access to harm reduction and drug treatment services may help to prevent overdose among people involved with the criminal justice system

    A profiling analysis of contributions of cigarette smoking, dietary calcium intakes, and physical activity to fragility fracture in the elderly

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    Fragility fracture and bone mineral density (BMD) are influenced by common and modifiable lifestyle factors. In this study, we sought to define the contribution of lifestyle factors to fracture risk by using a profiling approach. The study involved 1683 women and 1010 men (50+ years old, followed up for up to 20 years). The incidence of new fractures was ascertained by X-ray reports. A “lifestyle risk score” (LRS) was derived as the weighted sum of effects of dietary calcium intake, physical activity index, and cigarette smoking. Each individual had a unique LRS, with higher scores being associated with a healthier lifestyle. Baseline values of lifestyle factors were assessed. In either men or women, individuals with a fracture had a significantly lower age-adjusted LRS than those without a fracture. In men, each unit lower in LRS was associated with a 66% increase in the risk of total fracture (non-adjusted hazard ratio [HR] 1.66; 95% CI, 1.26 to 2.20) and still significant after adjusting for age, weight or BMD. However, in women, the association was uncertain (HR 1.30; 95% CI, 1.11 to 1.53). These data suggest that unhealthy lifestyle habits are associated with an increased risk of fracture in men, but not in women, and that the association is mediated by BMD

    Study of excited nucleon states at EBAC: status and plans

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    We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N* pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.Comment: Plenary talk given at Workshop on the Physics of Excited Nucleon -- NSTAR2009, Beijing, April 19-22, 2009. 8 pages, 8 figure

    Blue harvest: inland fisheries as an ecosystem service

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    Global food production has increased greatly in recent years and rural livelihoods are much improved in many regions. Yet, despite this clear progress rural poverty and food insecurity remain deeply entrenched in many areas, especially in South Asia and sub-Saharan Africa. In response the international community has renewed calls for increased commitment to meeting the needs of the world's poor. This report, commissioned as a contribution to the 10th Conference of the Parties to the Convention on Biological Diversity taking place in Nagoya, Japan, not only underlines the value of freshwater fisheries but provides guidance on how the ecosystem approach can be applied in order to sustain future harvests.Inland fisheries, Nutrition, Food security, Sustainability, Ecosystems

    A selected bibliography on tilapia (Pisces: Cichlidae): a list of documents available in the WorldFish Center Library

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    Research by the WorldFish Center and its partners on tilapia began in the late 1970s and focused on key issues that affect their production and conservation. WorldFish Center library as part of its effort to serve the information needs of the Center staff, partners and other external users worldwide, has been acquiring documentation on the subject. Such documentation ranges from published/unpublished documents, theses, journal articles, to reports and conference papers. This bibliography covers all publications available in the WorldFish library on tilapia and is a revision of Tilapia: A Selected Bibliography published by the Center in 2001. This volume covers a total of 1977 references.Tilapia, Bibliographies, WorldFish Center
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