37 research outputs found

    Civil service management in developing countries: what works?: evidence from a survey with 23,000 civil servants in Africa, Asia, Eastn Europe and Latin America

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    Civil servants are central to effective governance in developing countries. They deliver essential services to citizens, commission infrastructure, regulate economic activity and engage in diplomacy with foreign countries – to name just a few tasks. This puts a premium on understanding how to manage civil servants in developing countries effectively. Yet, to-date, there are scarcely any quantitative studies which deliver robust findings across developing countries – let alone regions – on what works in civil service management. To address this gap, this report draws on data from an original survey of 23,000 civil servants in ten countries in Africa, Asia, Eastern Europe and Latin America – the, to our knowledge, largest original cross-country survey of civil servants ever conducted in the developing world

    Riemannian geometry of irrotational vortex acoustics

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    We consider acoustic propagation in an irrotational vortex, using the technical machinery of differential geometry to investigate the ``acoustic geometry'' that is probed by the sound waves. The acoustic space-time curvature of a constant circulation hydrodynamical vortex leads to deflection of phonons at appreciable distances from the vortex core. The scattering angle for phonon rays is shown to be quadratic in the small quantity Γ/(2πcb)\Gamma/(2\pi cb), where Γ\Gamma is the vortex circulation, cc the speed of sound, and bb the impact parameter.Comment: 4 pages, 2 figures, RevTex4. Discussion of focal length added; to appear in Physical Review Letter

    Superposition of macroscopic numbers of atoms and molecules

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    We theoretically examine photoassociation of a non-ideal Bose-Einstein condensate, focusing on evidence for a macroscopic superposition of atoms and molecules. This problem raises an interest because, rather than two states of a given object, an atom-molecule system is a seemingly impossible macroscopic superposition of different objects. Nevertheless, photoassociation enables coherent intraparticle conversion, and we thereby propose a viable scheme for creating a superposition of a macroscopic number of atoms with a macroscopic number of molecules.Comment: 4 pages, 2 figs, to appear in Phys. Rev. Let

    Constraints on Star Forming Galaxies at z> 6.5 from HAWK-I Y-band Imaging of GOODS-South

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    We present the results of our search for high-redshift Lyman-break galaxies over the GOODS-South field. We use HST-ACS data in B, V, i' & z', VLT-ISAAC J and Ks, Spitzer-IRAC 3.6, 4.5, 5.8 and 8.0 micron data in conjunction with the new HAWK-I Y-band science verification data to search for dropout galaxies in the redshift range 6<z<9. We survey ~119 arcmin^2 to Y_AB=25.7 (5sigma), of which 37.5 arcmin^2 reaches Y_AB=25.9. Candidate z' and Y drop-outs were selected on the basis of a colour cut of (Y-J)_{AB}>0.75 mag and (z'-Y)_{AB}>1.0 mag respectively. We find no robust Y-drops (z~9) brighter than J_{AB}<25.4. In our search for z'-band dropouts (z~6.5-7.5), we identify four possible candidates, two with z'-drop colours and clear Spitzer-IRAC detections and two less likely candidates. We also identify two previously-known Galactic T-dwarf stellar contaminants with these colours, and two likely transient objects seen in the Y-band data. The implications if all or none of our candidates are real on the Ultra-Violet galaxy luminosity functions at z>6.5 are explored. We find our number of z'-drop candidates to be insufficient based on the expected number of z' drops in a simple no-evolution scenario from the z=3 Lyman-break galaxy luminosity function but we are consistent with the observed luminosity function at z~6 (if all our candidates are real). However, if one or both of our best z'-drop candidates are not z>6.5 galaxies, this would demand evolution of the luminosity function at early epochs. We show that the future surveys to be conducted with the ESO VISTA telescope over the next five years will be able to measure the bulk of the luminosity function for both z' and Y drop-outs.Comment: 14 pages, 15 figure. Accepted for publication in MNRA

    The Evolution of K* and the Halo Occupation Distribution since z=1.5: Observations vs. Simulations

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    We study the evolution of the K-band luminosity function (LF) and the Halo Occupation Distribution (HOD) using Subaru observations of 15 X-ray clusters at z=0.8-1.5 and compare the results with mock clusters (0<z<1.3) extracted from the Millennium Simulation and populated with galaxies using the semi-analytic model (SAM) of Bower et al., matched in mass to our observed sample. We find that the characteristic luminosity K* defined by a Shechter LF is consistent with SAM predictions, which mimic well the evolution of K* in z>1 rich clusters. However, we cannot distinguish between this model and a simple stellar population synthesis model invoking passive evolution with a formation redshift z~5 - consistent with the presence of an old red galaxy population ubiquitous in rich clusters at z=1.5. We also see a small difference (\Delta K*~0.5) between our clusters and studies of the field population at similar redshifts, suggesting only a weak dependence of the luminous (L>L*) part of the LF on environment. Turning to our HOD study, we find that within R_{500}, high-z clusters tend to host smaller numbers of galaxies to a magnitude K*+2 compared to their low-z counterparts. This behavior is also seen in the mock samples and is relatively insensitive to the average mass of the cluster haloes. In particular, we find significant correlations of the observed number of member cluster galaxies (N) with both z and cluster mass: N(M,z)=(53±1)(1+z)0.610.20+0.18(M/1014.3)0.86±0.05N(M,z)=(53\pm1)(1+z)^{-0.61^{+0.18}_{-0.20}}(M/10^{14.3})^{0.86\pm0.05}. Finally, we examine the spatial distribution of galaxies and provide a new estimate of the concentration parameter for clusters at high z (cg=2.80.8+1.0c_{g}=2.8^{+1.0}_{-0.8}). Our result is consistent with predictions from both our SAM mock clusters and literature's predictions for dark matter haloes. The mock sample predictions rise slowly with decreasing redshift reaching cg=6.30.36+0.39c_{g}=6.3^{+0.39}_{-0.36} at z=0.Comment: 17 pages, 3 tables, 12 Figures. Accepted for publications in MNRAS. Version 2: modified Figs. 4, 8 and 1

    Mouth magnetoencephalography: A unique perspective on the human hippocampus

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    Traditional magnetoencephalographic (MEG) brain imaging scanners consist of a rigid sensor array surrounding the head; this means that they are maximally sensitive to superficial brain structures. New technology based on optical pumping means that we can now consider more flexible and creative sensor placement. Here we explored the magnetic fields generated by a model of the human hippocampus not only across scalp but also at the roof of the mouth. We found that simulated hippocampal sources gave rise to dipolar field patterns with one scalp surface field extremum at the temporal lobe and a corresponding maximum or minimum at the roof of the mouth. We then constructed a fitted dental mould to accommodate an Optically Pumped Magnetometer (OPM). We collected data using a previously validated hippocampal-dependant task to test the empirical utility of a mouth-based sensor, with an accompanying array of left and right temporal lobe OPMs. We found that the mouth sensor showed the greatest task-related theta power change. We found that this sensor had a mild effect on the reconstructed power in the hippocampus (~10% change) but that coherence images between the mouth sensor and reconstructed source images showed a global maximum in the right hippocampus. We conclude that augmenting a scalp-based MEG array with sensors in the mouth shows unique promise for both basic scientists and clinicians interested in interrogating the hippocampus

    Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

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    A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

    Whole-genome sequencing reveals host factors underlying critical COVID-19

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    Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2–4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

    Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

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    BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)

    Whole-genome sequencing reveals host factors underlying critical COVID-19

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    Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease
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