53 research outputs found

    Evaluation of trace elements mobility from soils to sediments between the Iberian pyrite belt and the Atlantic Ocean

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    An environmental study was conducted in 193 stream sediments and 355 soil samples collected in the lower section of Guadiana River Basin to evaluate the trace elements transfer from one compartment into another. The objective was to evaluate the dispersion of Pb, Cu, Zn and other chemical elements resulting from upstream mines into the lower N-S sector of the Guadiana River Basin to the Atlantic Ocean. The area partly includes the Iberian Pyrite Belt, a known volcanogenic massive sulphide (VMS) province with important mining activity history. Median concentrations of the elements Cu, Pb, Zn, Al, As, Ba, Br, Ca, Mg, Mn and Na are generally higher in the studied sediments than in soils. Soils are normally acidic and mobility of elements is in these conditions higher. When the relations between upstream soils and downstream sediments were established, median values were higher in the upstream soils only for elements such as Co, Ni, K, Pb, Mn and Ti, probably the less mobile, and the Cu, Zn, Al, As, Ba, Br, Ca, Cr, Fe, Mg and Na have highest concentrations in the downstream sediments. Lead was considered the less mobile element and Zn the highly mobile of the base metals in the mining area of the lower Guadiana River. Dispersion of the metals, considering the studied soil and sediment samples is partially restricted to the mining areas or downstream sediments but close to the mine sources, where ore tailings and acid waters occur. Near the mouth, concentrations of As, Cu, Pb and Zn increase in relation with mining and other pollution sources. Interaction with salt water forces chemical elements precipitation from water and subsequent increase of their concentration in sediments. This may be the reason for the increase of those chemical elements concentrations in the sediment

    Quarkonium production in high energy proton-proton and proton-nucleus collisions

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    We present a brief overview of the most relevant current issues related to quarkonium production in high energy proton-proton and proton-nucleus collisions along with some perspectives. After reviewing recent experimental and theoretical results on quarkonium production in pp and pA collisions, we discuss the emerging field of polarisation studies. Thereafter, we report on issues related to heavy-quark production, both in pp and pA collisions, complemented by AA collisions. To put the work in a broader perspective, we emphasize the need for new observables to investigate quarkonium production mechanisms and reiterate the qualities that make quarkonia a unique tool for many investigations in particle and nuclear physics.Comment: Overview for the proceedings of QUARKONIUM 2010: Three Days Of Quarkonium Production in pp and pA Collisions, 29-31 July 2010, Palaiseau, France; 34 pages, 30 figures, Late

    Energy and system size dependence of \phi meson production in Cu+Cu and Au+Au collisions

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    We study the beam-energy and system-size dependence of \phi meson production (using the hadronic decay mode \phi -- K+K-) by comparing the new results from Cu+Cu collisions and previously reported Au+Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV measured in the STAR experiment at RHIC. Data presented are from mid-rapidity (|y|<0.5) for 0.4 < pT < 5 GeV/c. At a given beam energy, the transverse momentum distributions for \phi mesons are observed to be similar in yield and shape for Cu+Cu and Au+Au colliding systems with similar average numbers of participating nucleons. The \phi meson yields in nucleus-nucleus collisions, normalised by the average number of participating nucleons, are found to be enhanced relative to those from p+p collisions with a different trend compared to strange baryons. The enhancement for \phi mesons is observed to be higher at \sqrt{s_NN} = 200 GeV compared to 62.4 GeV. These observations for the produced \phi(s\bar{s}) mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.Comment: 20 pages and 5 figure

    System size dependence of associated yields in hadron-triggered jets

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    We present results on the system size dependence of high transverse momentum di-hadron correlations at sNN\sqrt{s_{NN}} = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation (Δϕ0\Delta\phi\sim0, Δη0\Delta\eta\sim0) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.Comment: 12 pages, 5 figure

    The trans-ancestral genomic architecture of glycemic traits

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    Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 x 10(-8)), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution.A trans-ancestry meta-analysis of GWAS of glycemic traits in up to 281,416 individuals identifies 99 novel loci, of which one quarter was found due to the multi-ancestry approach, which also improves fine-mapping of credible variant sets.Diabetes mellitus: pathophysiological changes and therap

    Direct numerical simulation from 3d imaging

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    In the last decade, the finite element method has shown to be a powerful and accurate computational tool to deal with material behavior and fluid-structure interaction simulations, with the increase on the computational power through the use of grids or cloud computing. On the other hand, numerical description of the researched objects with the improvement of imaging techniques, like X-Ray tomography (micro or nano) is very interesting, since it accesses the heterogeneity of the different phases with a definition and quality that may be very important. In the literature, the classical method to generate finite element meshes from images (2D or 3D) is based on a three-step processes: segmentation, for the identification of the different phases in the image; construction of a surface mesh for each phase, representing its boundary; construction of one or several volume meshes on which the specific properties of each phase can be defined. In this paper, we propose an efficient way to build directly the volume finite element representation of the multiphase domains using an “image immersion” method, by skipping the Marching Cubes’ step. Before mapping the image values in the mesh, we apply mathematical morphology treatments to the image, such as segmentation, distance to the interfaces function construction, and etc. Then, the treated image values are mapped in the coarse initial mesh by direct interpolation, providing the distance field distribution on the mesh. An appropriate error estimator built from this distance is used to compute a metrics field that our topological mesher will consider to adapt the mesh [1]. Finally, we have implemented a reinitialization procedure that, coupled to the automatic anisotropic mesh adaptation algorithm, allows the smoothing of the interpolated distance, but also the built-up of a smooth and regularized Heaviside function of this distance, which is actually a phase function. Meshes obtained using these techniques are well adapted for monolithic based methods (one mesh containing all the phases, each represented by an implicit - phase - function, like in classical diffuse interface methods). Furthermore, mesh adaptation provides nodal enrichment near phases “boundaries or interfaces”, which will allow results to converge towards a “sharp-interface” solution. Computations on such meshes will illustrate the relevance of our methodology. Firstly, we will show general cases of multiphase flows on common 2D pictures, all these 2D pictures can be taken from Paint, Camera, and even Smartphone. Secondly, for the 3D cases, the 3D images contain a huge number of fibers. Flows are calculated using a stabilized mixed finite element method, obtained through discretization of the Navier-Stokes equations and by imposing the rigid body motion
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