7,296 research outputs found

    Hubble space telescope: Pointing error effects on nonlinear ball joints

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    The Hubble Space Telescope pointing error produced by optical benches mounted on free ball joints is examined. Spacecraft cable connections are assumed to produce translational and rotational damping and restoring forces which act through the optical bench center of mass. The nonlinear dynamics are modeled and then implemented using an existing computer program for simulating the vehicle dynamics and pointing control system algorithm. Results are presented for the test case which indicate acceptable performance

    On Carbon Burning in Super Asymptotic Giant Branch Stars

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    We explore the detailed and broad properties of carbon burning in Super Asymptotic Giant Branch (SAGB) stars with 2755 MESA stellar evolution models. The location of first carbon ignition, quenching location of the carbon burning flames and flashes, angular frequency of the carbon core, and carbon core mass are studied as a function of the ZAMS mass, initial rotation rate, and mixing parameters such as convective overshoot, semiconvection, thermohaline and angular momentum transport. In general terms, we find these properties of carbon burning in SAGB models are not a strong function of the initial rotation profile, but are a sensitive function of the overshoot parameter. We quasi-analytically derive an approximate ignition density, ρign2.1×106\rho_{ign} \approx 2.1 \times 10^6 g cm3^{-3}, to predict the location of first carbon ignition in models that ignite carbon off-center. We also find that overshoot moves the ZAMS mass boundaries where off-center carbon ignition occurs at a nearly uniform rate of ΔMZAMS\Delta M_{\rm ZAMS}/Δfov\Delta f_{\rm{ov}}\approx 1.6 MM_{\odot}. For zero overshoot, fovf_{\rm{ov}}=0.0, our models in the ZAMS mass range \approx 8.9 to 11 MM_{\odot} show off-center carbon ignition. For canonical amounts of overshooting, fovf_{\rm{ov}}=0.016, the off-center carbon ignition range shifts to \approx 7.2 to 8.8 MM_{\odot}. Only systems with fovf_{\rm{ov}} 0.01\geq 0.01 and ZAMS mass \approx 7.2-8.0 MM_{\odot} show carbon burning is quenched a significant distance from the center. These results suggest a careful assessment of overshoot modeling approximations on claims that carbon burning quenches an appreciable distance from the center of the carbon core.Comment: Accepted ApJ; 23 pages, 21 figures, 5 table

    Criminal law as a security project

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    This paper asks how criminal might be understood as a security project. Following Valverde’s lead, it does this not by trying to define the concept of security, but by looking at the operation of the temporal and spatial logics of the criminal law. It looks first at the basic logics of time and space in conceptions of criminal liability and jurisdiction, before reviewing some recent developments which challenge these practices and what these might mean for criminal law as a security project

    Mechanism-based strategies for the management of autoimmunity and immune dysregulation in primary immunodeficiencies

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    A broad spectrum of autoimmunity is now well described in patients with primary immunodeficiencies (PIDs). Management of autoimmune disease in the background of PID is particularly challenging given the seemingly discordant goals of immune support and immune suppression. Our growing ability to define the molecular underpinnings of immune dysregulation has facilitated novel targeted therapeutics. This review focuses on mechanism-based treatment strategies for the most common autoimmune and inflammatory complications of PID including autoimmune cytopenias, rheumatologic disease, and gastrointestinal disease. We aim to provide guidance regarding the rational use of these agents in the complex PID patient population

    Properties of Carbon-Oxygen White Dwarfs From Monte Carlo Stellar Models

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    We investigate properties of carbon-oxygen white dwarfs with respect to the composite uncertainties in the reaction rates using the stellar evolution toolkit, Modules for Experiments in Stellar Astrophysics (MESA) and the probability density functions in the reaction rate library STARLIB. These are the first Monte Carlo stellar evolution studies that use complete stellar models. Focusing on 3 M_{\odot} models evolved from the pre main-sequence to the first thermal pulse, we survey the remnant core mass, composition, and structure properties as a function of 26 STARLIB reaction rates covering hydrogen and helium burning using a Principal Component Analysis and Spearman Rank-Order Correlation. Relative to the arithmetic mean value, we find the width of the 95\% confidence interval to be ΔM1TP\Delta M_{{\rm 1TP}} \approx 0.019 M_{\odot} for the core mass at the first thermal pulse, Δ\Deltat1TPt_{\rm{1TP}} \approx 12.50 Myr for the age, Δlog(Tc/K)\Delta \log(T_{{\rm c}}/{\rm K}) \approx 0.013 for the central temperature, Δlog(ρc/g cm3)\Delta \log(\rho_{{\rm c}}/{\rm g \ cm}^{-3}) \approx 0.060 for the central density, ΔYe,c\Delta Y_{\rm{e,c}} \approx 2.6×\times105^{-5} for the central electron fraction, ΔXc(22Ne)\Delta X_{\rm c}(^{22}\rm{Ne}) \approx 5.8×\times104^{-4}, ΔXc(12C)\Delta X_{\rm c}(^{12}\rm{C}) \approx 0.392, and ΔXc(16O)\Delta X_{\rm c}(^{16}\rm{O}) \approx 0.392. Uncertainties in the experimental 12^{12}C(α,γ)16O\alpha,\gamma)^{16}\rm{O}, triple-α\alpha, and 14^{14}N(p,γ)15Op,\gamma)^{15}\rm{O} reaction rates dominate these variations. We also consider a grid of 1 to 6 M_{\odot} models evolved from the pre main-sequence to the final white dwarf to probe the sensitivity of the initial-final mass relation to experimental uncertainties in the hydrogen and helium reaction rates.Comment: Accepted for publication in The Astrophysical Journal; 19 Pages, 23 Figures, 5 Table

    Prediction of transonic flutter for a supercritical wing by modified strip analysis and comparison with experiment

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    Use of a supercritical airfoil can adversely affect wing flutter speeds in the transonic range. As adequate theories for three dimensional unsteady transonic flow are not yet available, the modified strip analysis was used to predict the transonic flutter boundary for the supercritical wing. The steady state spanwise distributions of section lift curve slope and aerodynamic center, required as input for the flutter calculations, were obtained from pressure distributions. The calculated flutter boundary is in agreement with experiment in the subsonic range. In the transonic range, a transonic bucket is calculated which closely resembles the experimental one with regard to both shape and depth, but it occurs at about 0.04 Mach number lower than the experimental one

    LTV beta-bremsstrahlung spectrometer for Gemini 12 Final report

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    Design and operation of combination bremsstrahlung spectrometer and data processor for radiation monitoring during Gemini 7 fligh

    Returning children home from care: What can be learned from local authority data?

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    International Human Rights and child rights conventions as well as U.K. wide legislation and guidance require that children in care should be returned home to one or both parents wherever possible. Reunification with parents is the most common route out of care, but rates of re‐entry are often higher than for other exit routes. This study used 8 years of administrative data (on 2,208 care entrants), collected by one large English local authority, to examine how many children were returned home and to explore factors associated with stable reunification (not re‐entering care for at least 2 years). One‐third of children (36%) had been reunified, with adolescent entrants being the most likely age group to return home. Three quarters (75%) of reunified children had a stable reunification. In a fully adjusted regression model, age at entry, being on a care order prior to return home, staying longer in care, being of minority ethnicity, and having fewer placements in care were all significant in predicting chances of stable reunification. The results underline the importance of properly resourcing reunification services. The methods demonstrate the value to local authorities of analysing their own data longitudinally to understand the care pathways for children they look after

    Economic Analysis of Children's Surgical Care in Low- and Middle-Income Countries: A Systematic Review and Analysis.

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    BackgroundUnderstanding the economic value of health interventions is essential for policy makers to make informed resource allocation decisions. The objective of this systematic review was to summarize available information on the economic impact of children's surgical care in low- and middle-income countries (LMICs).MethodsWe searched MEDLINE (Pubmed), Embase, and Web of Science for relevant articles published between Jan. 1996 and Jan. 2015. We summarized reported cost information for individual interventions by country, including all costs, disability weights, health outcome measurements (most commonly disability-adjusted life years [DALYs] averted) and cost-effectiveness ratios (CERs). We calculated median CER as well as societal economic benefits (using a human capital approach) by procedure group across all studies. The methodological quality of each article was assessed using the Drummond checklist and the overall quality of evidence was summarized using a scale adapted from the Agency for Healthcare Research and Quality.FindingsWe identified 86 articles that met inclusion criteria, spanning 36 groups of surgical interventions. The procedure group with the lowest median CER was inguinal hernia repair (15/DALY).Theproceduregroupwiththehighestmediansocietaleconomicbenefitwasneurosurgicalprocedures(15/DALY). The procedure group with the highest median societal economic benefit was neurosurgical procedures (58,977). We found a wide range of study quality, with only 35% of studies having a Drummond score ≥ 7.InterpretationOur findings show that many areas of children's surgical care are extremely cost-effective in LMICs, provide substantial societal benefits, and are an appropriate target for enhanced investment. Several areas, including inguinal hernia repair, trichiasis surgery, cleft lip and palate repair, circumcision, congenital heart surgery and orthopedic procedures, should be considered "Essential Pediatric Surgical Procedures" as they offer considerable economic value. However, there are major gaps in existing research quality and methodology which limit our current understanding of the economic value of surgical care
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