EARLY DEVELOPMENT OF SYNCHRONY IN CORTICAL ACTIVATIONS IN THE HUMAN

Peer reviewe

RSAT: regulatory sequence analysis tools

The regulatory sequence analysis tools (RSAT, http://rsat.ulb.ac.be/rsat/) is a software suite that integrates a wide collection of modular tools for the detection of cis-regulatory elements in genome sequences. The suite includes programs for sequence retrieval, pattern discovery, phylogenetic footprint detection, pattern matching, genome scanning and feature map drawing. Random controls can be performed with random gene selections or by generating random sequences according to a variety of background models (Bernoulli, Markov). Beyond the original word-based pattern-discovery tools (oligo-analysis and dyad-analysis), we recently added a battery of tools for matrix-based detection of cis-acting elements, with some original features (adaptive background models, Markov-chain estimation of P-values) that do not exist in other matrix-based scanning tools. The web server offers an intuitive interface, where each program can be accessed either separately or connected to the other tools. In addition, the tools are now available as web services, enabling their integration in programmatic workflows. Genomes are regularly updated from various genome repositories (NCBI and EnsEMBL) and 682 organisms are currently supported. Since 1998, the tools have been used by several hundreds of researchers from all over the world. Several predictions made with RSAT were validated experimentally and published

Automated EEG background analysis to identify neonates with hypoxic-ischemic encephalopathy treated with hypothermia at risk for adverse outcome: A pilot study

Background: To improve the objective assessment of continuous video-EEG (cEEG) monitoring of neonatal brain function, the aim was to relate automated derived amplitude and duration parameters of the suppressed periods in the EEG background (dynamic Interburst Interval= dIBIs) after neonatal hypoxic-ischemic encephalopathy (HIE) to favourable or adverse neurodevelopmental outcome. Methods: Nineteen neonates (gestational age 36-41 weeks) with HIE underwent therapeutic hypothermia and had cEEG-monitoring. EEGs were retrospectively analyzed with a previously developed algorithm to detect the dynamic Interburst Intervals. Median duration and amplitude of the dIBIs were calculated at 1h-intervals. Sensitivity and specificity of automated EEG background grading for favorable and adverse outcomes were assessed at 6h-intervals. Results: Dynamic IBI values reached the best prognostic value between 18 and 24h (AUC of 0.93). EEGs with dIBI amplitude ≥15 μV and duration 10s were specific for adverse outcome (89-100%) at 18-24h (n = 10). Extremely low voltage and invariant EEG patterns were indicative of adverse outcome at all time points. Conclusions: Automated analysis of the suppressed periods in EEG of neonates with HIE undergoing TH provides objective and early prognostic information. This objective tool can be used in a multimodal strategy for outcome assessment. Implementation of this method can facilitate clinical practice, improve risk stratification and aid therapeutic decision-making. A multicenter trial with a quantifiable outcome measure is warranted to confirm the predictive value of this method in a more heterogeneous dataset

Large eddy simulation of forced ignition of an annular bluff-body burner

International audienc

From Large-Eddy Simulation to Direct Numerical Simulation of a lean premixed swirl flame: Filtered laminar flame-PDF modeling

International audienceLarge-Eddy Simulations (LES) and Direct Numerical Simulation (DNS) are applied to the analysis of a swirl burner operated with a lean methane–air mixture and experimentally studied by Meier et al. [19]. LES is performed for various mesh refinements, to study unsteady and coherent large-scale behavior and to validate the simulation tool from measurements, while DNS enables to gain insight into the flame structure and dynamics. The DNS features a 2.6 billion cells unstructured-mesh and a resolution of less than 100 microns, which is sufficient to capture all the turbulent scales and the major species of the flame brush; the unresolved species are taken into account thanks to a tabulated chemistry approach. In a second part of the paper, the DNS is filtered at several filter widths to estimate the prediction capabilities of modeling based on premixed flamelet and presumed probability density functions. The similarities and differences between spatially-filtered laminar and turbulent flames are discussed and a new sub-grid scale closure for premixed turbulent combustion is proposed, which preserves spectral properties of sub-filter flame length scales. All these simulations are performed with a solver specifically tailored for large-scale computations on massively parallel machines

Heat release effects on mixing scales of non-premixed turbulent wall-jets: A direct numerical simulation study

International audienc

A massively parallel solution strategy for efficient thermal radiation simulation

International audienceA novel and efficient methodology to solve the Radiative Transfer Equations (RTE) in thermal radiation is discussed. The BiCGStab(2) iterative solution method, as designed for the non-symmetric linear equation systems, is used to solve the discretized RTE. The numerical upwind and central schemes are blended to provide a stable numerical scheme (MUCS) for interpolation of the cell facial radiation intensities in finite volume formulation. The combination of the BiCGStab(2) and MUCS methods proved to be very efficient when coupling with the DOM approach to solve the RTE. A cost-effective tabulation technique for the gaseous radiative property model SNB-FSCK using 7-point Gauss-Labatto quadrature scheme is also introduced. The whole methodology is implemented into a massively parallel unstructured CFD code where the radiative and fluid flow solutions share the same domain decomposition, which is the bottleneck in current radiative solvers. The dual mesh decomposition at the cell groups level and processors level is adopted to optimize the CFD code for massively parallel computing. The whole method is applied to simulate the radiation heat-transfer in a 3D rectangular enclosure containing non-isothermal CO2 and H2O mixtures. Two test cases are studied for homogeneous and inhomogeneous distributions of CO2 and H2O in the enclosure. The result is reported for the heat flux and radiation energy source and the comparison is also made between the present methodology BiCGStab(2)/MUCS/tabulated SNB-FSCK, the benchmark method SNB-CK (implemented at 25cm−1 narrow-band) and some other methods available in the literature. The present method (BiCGStab(2)/MUCS/tabulated SNB-FSCK) yields more accurate predictions particularly for the radiation source term. When comparing with the benchmark solution, the relative error of the radiation source term is remarkably reduced to less than 4% and the CPU time is drastically diminished

Composition-space premixed flamelet solution with differential diffusion for in situ flamelet-generated manifolds

International audienceCanonical flame problems have been widely used in the combustion literature to tabulate detailed chemistry. Prior to three-dimensional flame simulations, reference laminar premixed flames are usually solved in physical-space, and, diffusion flames in either physical, or, mixture fraction space. Composition-space solutions would be convenient for premixed flame also, because all the points are relevant for chemistry, as a result of the zoom inside the flame zone; however, differential diffusion is not always easy to introduce with accuracy in these moving-frame coordinate systems, parameterized by their physical-space gradients (or scalar dissipation rates). A projection is discussed in this paper that ensures that differential diffusion is properly accounted for, in any composition-space coordinates, thus allowing for perfect matching between physical- and composition-space solutions, even for premixed flames. Both a diffusion velocity correction, which is necessary to properly conserve mass with Fick’s law, and a differential diffusion effect between the composition-space moving with the flow and fast diffusing species, are introduced. A procedure for rapidly building converged composition-space solutions for premixed flamelets is then proposed and tested. It provides the framework for an efficient in situ calculation of complex chemistry with differential diffusion, to be applied to three-dimensional unsteady flame simulations. The objective is to avoid building a priori look-up tables, whose range of validity is strongly limited by their boundary conditions, which are fixed once for all, therefore lacking of generic character, specifically when pressure, composition and enthalpy of fresh gases are varying in space and time