143 research outputs found
Weyl quantization of degree 2 symplectic graded manifolds
Let be a spinor bundle of a pseudo-Euclidean vector bundle
of even rank. We introduce a new filtration on the algebra
of differential operators on . As main property, the
associated graded algebra is isomorphic to the
algebra of functions on , where
is the symplectic graded manifold of degree canonically
associated to . Accordingly, we define the Weyl quantization on
as a map
, and prove
that satisfies all desired usual properties. As an
application, we obtain a bijection between Courant algebroid structures
, that are encoded by Hamiltonian generating
functions on , and skew-symmetric Dirac generating operators
. The operator gives a new invariant of
, which generalizes the square norm of the
Cartan -form of a quadratic Lie algebra. We study in detail the particular
case of being the double of a Lie bialgebroid .Comment: 41 page
Recherche, offres de formation et nouveaux métiers en matiÚre environnementale
International audienceDans le contexte de mutation technologique imposée par les nouvelles contraintes environnementales, le systÚme de formation et de recherche se trouve confronté à un paradoxe : d'un cÎté, au niveau de l'enseignement supérieur et de la recherche, il est le principal acteur dans la construction de nouveaux savoirs et de l'autre, au niveau des offres de formations professionnelles et des diplÎmes qui s'y rattachent, il traverse une période d'adaptation pour répondre en la matiÚre à la demande économique et sociale qui connaßt une progression rapide et importante
« InterprĂ©tation dâun conflit : retour sur les spĂ©cificitĂ©s de la mobilisation en France contre la loi Travail (2016) »
International audienceInterprĂ©tation d'un conflit : retour sur les spĂ©cificitĂ©s de la mobilisation en France contre la loi Travail (2016) Jean-Philippe MELCHIOR Les mobilisations sociales d'envergure nationale modifient souvent, Ă plus ou moins brĂšve Ă©chĂ©ance, le rapport des forces politiques. En France, le mouvement de grĂšve de novembre-dĂ©cembre 1995 a fragilisĂ© le gouvernement d'Alain JuppĂ© et a fait perdre Ă la droite les Ă©lections lĂ©gislatives anticipĂ©es du printemps 1997. Plus proche de nous, la longue mobilisation des salariĂ©s contre la rĂ©forme des retraites, imposĂ©e par Nicolas Sarkozy en 2010, a renforcĂ© le discrĂ©dit de ce dernier et favorisĂ© la victoire de François Hollande Ă l'Ă©lection prĂ©sidentielle de 2012. De mĂȘme, il est possible de relier la sĂ©vĂ©ritĂ© des dĂ©faites subies par le candidat socialiste BenoĂźt Hamon Ă la prĂ©sidentielle et par les candidats socialistes aux Ă©lections lĂ©gislatives du printemps 2017 Ă l'importante mobilisation sociale du printemps 2016 contre la loi El Khomri. Certes, avant mĂȘme que l'opposition au projet de la loi Travail 1 ne conduise Ă la premiĂšre journĂ©e d'action organisĂ©e par les syndicats du 9 mars 2016, la cote de popularitĂ© du prĂ©sident de la RĂ©publique François Hollande, Ă©tait dĂ©jĂ trĂšs basse 2. Cependant, en oeuvrant avec son Premier ministre Ă la remise en cause de plusieurs Ă©lĂ©ments essentiels du code du travail, un an avant la fin de son mandat, le chef de l'Ătat prit le risque de se couper dĂ©finitivement de pans entiers de son Ă©lectorat. Quant Ă ses liens avec sa majoritĂ©, ils s'Ă©taient tellement dĂ©gradĂ©s du fait de l'orientation nĂ©olibĂ©rale de ses choix Ă©conomiques qu'il fallut utiliser Ă plusieurs reprises la procĂ©dure du 49.3 pour faire adopter le texte, procĂ©dure pourtant dĂ©noncĂ©e avec vigueur par François Hollande quelques annĂ©es plus tĂŽt quand il Ă©tait dans l'opposition 3. Un tel constat oblige Ă comprendre ce qui s'est fondamentalement jouĂ© lors de ce conflit social. Dans un premier temps, il s'agira de caractĂ©riser le conflit et de le mettre en perspective avec d'autres mobilisations sociales plus anciennes. Les premiers Ă©lĂ©ments de diagnostic Ă©tant posĂ©s, il sera possible, dans un deuxiĂšme temps, d'analyser les raisons de la dĂ©faite et d'interroger les effets 1 L'intitulĂ© exact de ce texte est le suivant : « Loi relative au travail, Ă la modernisation du dialogue social et Ă la sĂ©curisation des parcours professionnels ». Par commoditĂ©, elle sera appelĂ©e « loi Travail » ou « loi El Khomri » dans ce chapitre. 2 En fĂ©vrier 2016, 80% des Français estimaient que François Hollande n'Ă©tait pas un bon prĂ©sident. L'impopularitĂ© a atteint 83% en mai et 86% en octobre. Sondages Odoxa-France Inter. 3 Lors du vote du Contrat PremiĂšre Embauche (CPE) en 2006, François Hollande avait dĂ©clarĂ© : « Le 49.3 est une brutalitĂ©, le 49.3 est un dĂ©ni de dĂ©mocratie, le 49.3 est une maniĂšre de freiner ou d'empĂȘcher le dĂ©bat parlementaire. » Ouest France, 10 mai 2016
Prevalence of Human African Trypanosomiasis in the Democratic Republic of the Congo
Human African Trypanosomiasis (HAT) is a major public health problem in the Democratic Republic of the Congo (DRC). Active and passive surveillance for HAT is conducted but may underestimate the true prevalence of the disease. We used ELISA to screen 7,769 leftover dried blood spots from a nationally representative population-based survey, the 2007 Demographic and Health Survey. 26 samples were positive by ELISA. Three of these were also positive by trypanolysis and/or PCR. From these data, we estimate that there were 18,592 people with HAT (95% confidence interval, 4,883â32,302) in the DRC in 2007, slightly more than twice as many as were reported
Variability and reproducibility of multi-echo T2 relaxometry: Insights from multi-site, multi-session and multi-subject MRI acquisitions
Quantitative magnetic resonance imaging (qMRI) can increase the specificity and sensitivity of conventional weighted MRI to underlying pathology by comparing meaningful physical or chemical parameters, measured in physical units, with normative values acquired in a healthy population. This study focuses on multi-echo T2 relaxometry, a qMRI technique that probes the complex tissue microstructure by differentiating compartment-specific T2 relaxation times. However, estimation methods are still limited by their sensitivity to the underlying noise. Moreover, estimating the model's parameters is challenging because the resulting inverse problem is ill-posed, requiring advanced numerical regularization techniques. As a result, the estimates from distinct regularization strategies are different. In this work, we aimed to investigate the variability and reproducibility of different techniques for estimating the transverse relaxation time of the intra- and extra-cellular space (T2IE) in gray (GM) and white matter (WM) tissue in a clinical setting, using a multi-site, multi-session, and multi-run T2 relaxometry dataset. To this end, we evaluated three different techniques for estimating the T2 spectra (two regularized non-negative least squares methods and a machine learning approach). Two independent analyses were performed to study the effect of using raw and denoised data. For both the GM and WM regions, and the raw and denoised data, our results suggest that the principal source of variance is the inter-subject variability, showing a higher coefficient of variation (CoV) than those estimated for the inter-site, inter-session, and inter-run, respectively. For all reconstruction methods studied, the CoV ranged between 0.32 and 1.64%. Interestingly, the inter-session variability was close to the inter-scanner variability with no statistical differences, suggesting that T2IE is a robust parameter that could be employed in multi-site neuroimaging studies. Furthermore, the three tested methods showed consistent results and similar intra-class correlation (ICC), with values superior to 0.7 for most regions. Results from raw data were slightly more reproducible than those from denoised data. The regularized non-negative least squares method based on the L-curve technique produced the best results, with ICC values ranging from 0.72 to 0.92
Modelling human choices: MADeM and decisionâmaking
Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
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