4,061 research outputs found

    Open and hidden charm in proton-nucleus and heavy-ion collisions

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    We review the collectivity and the suppression pattern of charmed mesons - produced in proton-nucleus and nucleus-nucleus collisions at SPS (158 AGeV) and RHIC energies (21 ATeV) - in comparison to dynamical and thermal models. In particular, we examine the charmonium `melting' and the `comover dissociation' scenarios - implemented in a microscopic transport approach - in comparison to the available data from the SPS and RHIC. The analysis shows that the dynamics of c, c-bar quarks at RHIC are dominated by partonic or `pre-hadronic' interactions in the strongly coupled plasma stage. Both the `charmonium melting' and the hadronic `comover absorption and recreation model' are found, however, to be compatible with the experimental observation at SPS energies; the experimental ratio of Psi'/J/Psi versus centrality clearly favors the `hadronic comover' scenario. We find that the collective flow of charm in the purely hadronic Hadron-String Dynamics (HSD) transport appears compatible with the data at SPS energies, but substantially underestimates the data at top RHIC energies. Thus, the large elliptic flow v2 of D-mesons and the low R_AA(p_T) of J/Psi seen experimentally have to be attributed to early interactions of non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic interactions are mandatory in order to describe the narrowing of the J/Psi rapidity distribution from pp to central Au+Au collisions at the top RHIC energy. We demonstrate additionally that the strong quenching of low-pT J/Psi's in central Au+Au collisions indicates that a large fraction of final J/Psi mesons is created by a coalescence mechanism close to the phase boundary. Throughout this review we, furthermore, provide predictions for charm observables from Au+Au collisions at FAIR energies of 25-35 AGeV.Comment: review for Int. J. Mod. Phys. E, 75 pages, 50 figure

    Biogeochemical cycle in a coccolithophorid bloom

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    The biogeochemical properties of an extensive bloom of the coccolithophore, Emiliania huxleyi, at the shelf break in the northern Gulf of Biscay was investigated in June 2006. Total Alkalinity (TA) values in the water column showed strong non-conservative behaviour indicative of the impact of calcification, with the highest TA anomalies (up to 26μmol.kg-1) in the high reflectance coccolith patch. Partial pressure of CO2 (pCO2) values ranged from 250 to 338μatm and the area was found to act as a sink for atmospheric CO2.Overall, pCO2@13°C (pCO2 normalized at a constant temperature of 13°C) in the water column was negatively related to TA anomalies in agreement with an overall production of CO2 related to calcification. Hence, the calcifying phase of the E. huxleyi bloom decreased the sink of atmospheric pCO2, but did not reverse the direction of the flux. Rates of pelagic respiration up to 5.5mmol O2.m-3.d-1 suggested a close coupling between primary production and respiration and/or between organic carbon content and respiration. Benthic respiration rates were quite low and varied between 2 and 9mmol O2.m-3.d-1, in agreement with the fact that the study area consists of sandy sediments with low organic matter content. Benthic respiration was well correlated to the chlorophyll a content of the top 1cm of the sediment cores. Evidence was found for dissolution of CaCO3 due to the acidification of superficial sediments in relation to the production of CO2 and the oxidation of H2S in the oxic layers

    An attempt to observe economy globalization: the cross correlation distance evolution of the top 19 GDP's

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    Economy correlations between the 19 richest countries are investigated through their Gross Domestic Product increments. A distance is defined between increment correlation matrix elements and their evolution studied as a function of time and time window size. Unidirectional and Bidirectional Minimal Length Paths are generated and analyzed for different time windows. A sort of critical correlation time window is found indicating a transition for best observations. The mean length path decreases with time, indicating stronger correlations. A new method for estimating a realistic minimal time window to observe correlations and deduce macroeconomy conclusions from such features is thus suggested.Comment: to be published in the Dyses05 proceedings, in Int. J. Mod Phys C 15 pages, 5 figures, 1 tabl

    Desempenho econômico do cultivo de mandioca consorciado com feijão-caupi no sistema de preparo de área com corte e trituração.

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    O projeto SHIFT-Capoeira foi iniciado no ano de 1991, dentro do programa SHIFT (Studies of Human Impact on Forest and Floodplains in the Tropics). A iniciativa consistiu no estudo da importância da capoeira nos sistemas agrícolas familiares do Nordeste Paraense. Com os resultados obtidos foi proposto um sistema de cultivo baseado no corte e trituração da capoeira como forma de reduzir as perdas de nutrientes e manter o solo protegido, permitindo o cultivo da mandioca por até dois ciclos devido à cobertura formada pelo material triturado manter a umidade do solo e disponibilizar os nutrientes gradativamente por meio da decomposição. Este preparo de área atualmente é adotado por 42 unidades de produção familiar nos municípios de Igarapé-Açu e Marapanim/PA. Para observar o desempenho do sistema de cultivo adotado pelos agricultores, foram identificados os custos e rendimentos do cultivo de mandioca consorciada com feijão-caupi implantados no sistema de preparo de área com corte e trituração. Informações referentes aos coeficientes e demais fatores de produção foram coletados para determinar o preço do insumo e da comercialização do produto, relativos a uma área referencial de um hectare. Os dados obtidos foram analisados através do Valor Presente Líquido (VPL) e da Taxa Interna de Retorno (TIR). Através dos resultados foi observado que o sistema de produção de mandioca consorciado com feijão-caupi em sistemas agroflorestais seqüenciais com preparo de área através de corte e trituração da capoeira é viável economicamente.Editores técnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa

    Uncertainty-aware multi-resolution whole-body MR to CT synthesis

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    Synthesising computed tomography (CT) images from magnetic resonance images (MRI) plays an important role in the field of medical image analysis, both for quantification and diagnostic purposes. Especially for brain applications, convolutional neural networks (CNNs) have proven to be a valuable tool in this image translation task, achieving state-of-the-art results. Full body image synthesis, however, remains largely uncharted territory, bearing many challenges including a limited field of view and large image size, complex spatial context and anatomical differences between time-elapsing image acquisitions. We propose a novel multi-resolution cascade 3D network for end-to-end full-body MR to CT synthesis. We show that our method outperforms popular CNNs like U-Net in 2D and 3D. We further propose to include uncertainty in our network as a measure of safety and to account for intrinsic noise and misalignment in the data

    A Multi-Channel Uncertainty-Aware Multi-Resolution Network for MR to CT Synthesis

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    Synthesising computed tomography (CT) images from magnetic resonance images (MRI) plays an important role in the field of medical image analysis, both for quantification and diagnostic purposes. Convolutional neural networks (CNNs) have achieved state-of-the-art results in image-to-image translation for brain applications. However, synthesising whole-body images remains largely uncharted territory, involving many challenges, including large image size and limited field of view, complex spatial context, and anatomical differences between images acquired at different times. We propose the use of an uncertainty-aware multi-channel multi-resolution 3D cascade network specifically aiming for whole-body MR to CT synthesis. The Mean Absolute Error on the synthetic CT generated with the MultiResunc network (73.90 HU) is compared to multiple baseline CNNs like 3D U-Net (92.89 HU), HighRes3DNet (89.05 HU) and deep boosted regression (77.58 HU) and shows superior synthesis performance. We ultimately exploit the extrapolation properties of the MultiRes networks on sub-regions of the body
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