640 research outputs found

    The Einstein constraints: uniqueness and non-uniqueness in the conformal thin sandwich approach

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    We study the appearance of multiple solutions to certain decompositions of Einstein's constraint equations. Pfeiffer and York recently reported the existence of two branches of solutions for identical background data in the extended conformal thin-sandwich decomposition. We show that the Hamiltonian constraint alone, when expressed in a certain way, admits two branches of solutions with properties very similar to those found by Pfeiffer and York. We construct these two branches analytically for a constant-density star in spherical symmetry, but argue that this behavior is more general. In the case of the Hamiltonian constraint this non-uniqueness is well known to be related to the sign of one particular term, and we argue that the extended conformal thin-sandwich equations contain a similar term that causes the breakdown of uniqueness.Comment: 9 pages, 1 figur

    Improvement in Prediction of Coronary Heart Disease Risk over Conventional Risk Factors Using SNPs Identified in Genome-Wide Association Studies

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    We examined whether a panel of SNPs, systematically selected from genome-wide association studies (GWAS), could improve risk prediction of coronary heart disease (CHD), over-and-above conventional risk factors. These SNPs have already demonstrated reproducible associations with CHD; here we examined their use in long-term risk prediction.SNPs identified from meta-analyses of GWAS of CHD were tested in 840 men and women aged 55-75 from the Edinburgh Artery Study, a prospective, population-based study with 15 years of follow-up. Cox proportional hazards models were used to evaluate the addition of SNPs to conventional risk factors in prediction of CHD risk. CHD was classified as myocardial infarction (MI), coronary intervention (angioplasty, or coronary artery bypass surgery), angina and/or unspecified ischaemic heart disease as a cause of death; additional analyses were limited to MI or coronary intervention. Model performance was assessed by changes in discrimination and net reclassification improvement (NRI).There were significant improvements with addition of 27 SNPs to conventional risk factors for prediction of CHD (NRI of 54%, P<0.001; C-index 0.671 to 0.740, P = 0.001), as well as MI or coronary intervention, (NRI of 44%, P<0.001; C-index 0.717 to 0.750, P = 0.256). ROC curves showed that addition of SNPs better improved discrimination when the sensitivity of conventional risk factors was low for prediction of MI or coronary intervention.There was significant improvement in risk prediction of CHD over 15 years when SNPs identified from GWAS were added to conventional risk factors. This effect may be particularly useful for identifying individuals with a low prognostic index who are in fact at increased risk of disease than indicated by conventional risk factors alone

    Disease Status and Pubertal Stage Predict Improved Growth in Anti-TNF Therapy for Pediatric Inflammatory Bowel Disease

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    Background: Growth failure is well-recognised in pediatric Inflammatory Bowel Disease (PIBD; &lt;18 years). We aimed to examine whether anti-Tumor Necrosis Factor (TNF) therapy improves growth in a PIBD population-based cohort. Methods: A retrospective review of all Scottish children receiving anti-TNF (infliximab (IFX) and adalimumab (ADA)) from 2000-2012 was performed; height was collected at: 12 months before anti-TNF (T-12), start (T0) and 12 (T+12) months after anti-TNF. Results: 93/201 treated with IFX and 28/49 for ADA had satisfactory growth data; 66 had full pubertal data. Univariate analysis demonstrated early pubertal stages (Tanner 1-3 n = 44 vs. T4-5 n = 22), disease remission, disease duration &gt;=2 years and duration of IFX &gt;=12 months were associated with improved linear growth for IFX; for ADA only improvement was seen in Tanner 1-3. For IFX, Tanner 1-3 median [DELTA] ht SDS -0.3 (-0.7,0.2) at T0 changed to 0.04 (-0.5, 0.7) at T+12 (p &lt; 0.001) vs -0.01 (-0.5, 0.9) at T0 in T4-5 changed to -0.01 (-0.4, 0.2) at T+12 (p &gt; 0.05). For IFX disease duration &gt;=2 year, median [DELTA] ht SDS was -0.13 (-0.6, 0.3) at T0 then 0.07 (-0.3, 0.6) at T+12 (p &lt; 0.001). Remission improved [DELTA] ht SDS (median [DELTA] ht SDS -0.14 (-0.6, 0.3) at T0 to 0.17 (-0.2, 0.7) at T+12 (p &gt; 0.001)). Multiple regression analysis demonstrated corticosteroid usage at T0 predicted improved [DELTA] ht SDS at T+12 for IFX and ADA. Conclusions: Anti-TNF therapy is more likely to be associated with growth improvement when used at earlier stages of puberty with remission a key growth-promoting strategy in Paediatric Crohn's disease

    Results of search for magnetized quark-nugget dark matter from radial impacts on Earth

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    Magnetized Quark Nuggets (MQNs) are a recently proposed dark-matter candidate consistent with the Standard Model and with Tatsumi's theory of quark-nugget cores in magnetars. Previous publications have covered their formation in the early universe, aggregation into a broad mass distribution before they can decay by the weak force, interaction with normal matter through their magnetopause, and first observation consistent MQNs, i.e. a nearly tangential impact limiting their surface-magnetic-field parameter B_o from Tatsumi's values of 0.1 to 10.0 TT to new value of 1.65 TT +/- 21%. The MQN mass distribution and interaction cross section depend strongly on B_o. Their magnetopause is much larger than their geometric dimensions and can cause sufficient energy deposition to form non-meteorite craters, which are reported approximately annually. We report computer simulations of the MQN energy deposition in water-saturated peat, soft sediments, and granite and report results from excavating such a crater. Five points of agreement between observations and hydrodynamic simulations of an MQN impact support this second observation consistent with MQN dark matter and suggest a method for qualifying additional MQN events. The results also redundantly constrain B_o to greater than 0.4 TT.Comment: 30 pages, 13 figures, submitted to Univers

    Cost-effectiveness analyses for mirtazapine and sertraline in dementia: randomised controlled trial

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    BACKGROUND Depression is a common and costly comorbidity in dementia. There are very few data on the cost-effectiveness of antidepressants for depression in dementia and their effects on carer outcomes. AIMS To evaluate the cost-effectiveness of sertraline and mirtazapine compared with placebo for depression in dementia. METHOD A pragmatic, multicentre, randomised placebo-controlled trial with a parallel cost-effectiveness analysis (trial registration: ISRCTN88882979 and EudraCT 2006-000105-38). The primary cost-effectiveness analysis compared differences in treatment costs for patients receiving sertraline, mirtazapine or placebo with differences in effectiveness measured by the primary outcome, total Cornell Scale for Depression in Dementia (CSDD) score, over two time periods: 0-13 weeks and 0-39 weeks. The secondary evaluation was a cost-utility analysis using quality-adjusted life years (QALYs) computed from the Euro-Qual (EQ-5D) and societal weights over those same periods. RESULTS There were 339 participants randomised and 326 with costs data (111 placebo, 107 sertraline, 108 mirtazapine). For the primary outcome, decrease in depression, mirtazapine and sertraline were not cost-effective compared with placebo. However, examining secondary outcomes, the time spent by unpaid carers caring for participants in the mirtazapine group was almost half that for patients receiving placebo (6.74 v. 12.27 hours per week) or sertraline (6.74 v. 12.32 hours per week). Informal care costs over 39 weeks were £1510 and £1522 less for the mirtazapine group compared with placebo and sertraline respectively. CONCLUSIONS In terms of reducing depression, mirtazapine and sertraline were not cost-effective for treating depression in dementia. However, mirtazapine does appear likely to have been cost-effective if costing includes the impact on unpaid carers and with quality of life included in the outcome. Unpaid (family) carer costs were lower with mirtazapine than sertraline or placebo. This may have been mediated via the putative ability of mirtazapine to ameliorate sleep disturbances and anxiety. Given the priority and the potential value of supporting family carers of people with dementia, further research is warranted to investigate the potential of mirtazapine to help with behavioural and psychological symptoms in dementia and in supporting carers

    General Relativistic Models of Binary Neutron Stars in Quasiequilibrium

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    We perform fully relativistic calculations of binary neutron stars in corotating, circular orbit. While Newtonian gravity allows for a strict equilibrium, a relativistic binary system emits gravitational radiation, causing the system to lose energy and slowly spiral inwards. However, since inspiral occurs on a time scale much longer than the orbital period, we can treat the binary to be in quasiequilibrium. In this approximation, we integrate a subset of the Einstein equations coupled to the relativistic equation of hydrostatic equilibrium to solve the initial value problem for binaries of arbitrary separation. We adopt a polytropic equation of state to determine the structure and maximum mass of neutron stars in close binaries for polytropic indices n=1, 1.5 and 2. We construct sequences of constant rest-mass and locate turning points along energy equilibrium curves to identify the onset of orbital instability. In particular, we locate the innermost stable circular orbit (ISCO) and its angular velocity. We construct the first contact binary systems in full general relativity. These arise whenever the equation of state is sufficiently soft >= 1.5. A radial stability analysis reveals no tendency for neutron stars in close binaries to collapse to black holes prior to merger.Comment: 14 pages, 8 figures, RevTe
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