Phagocytosis is the main CR3-mediated function affected by the lupus-associated variant of CD11b in human myeloid cells.

The CD11b/CD18 integrin (complement receptor 3, CR3) is a surface receptor on monocytes, neutrophils, macrophages and dendritic cells that plays a crucial role in several immunological processes including leukocyte extravasation and phagocytosis. The minor allele of a non-synonymous CR3 polymorphism (rs1143679, conversation of arginine to histidine at position 77: R77H) represents one of the strongest genetic risk factor in human systemic lupus erythematosus, with heterozygosity (77R/H) being the most common disease associated genotype. Homozygosity for the 77H allele has been reported to reduce adhesion and phagocytosis in human monocytes and monocyte-derived macrophages, respectively, without affecting surface expression of CD11b. Herein we comprehensively assessed the influence of R77H on different CR3-mediated activities in monocytes, neutrophils, macrophages and dendritic cells. R77H did not alter surface expression of CD11b including its active form in any of these cell types. Using two different iC3b-coated targets we found that the uptake by heterozygous 77R/H macrophages, monocytes and neutrophils was significantly reduced compared to 77R/R cells. Allele-specific transduced immortalized macrophage cell lines demonstrated that the minor allele, 77H, was responsible for the impaired phagocytosis. R77H did not affect neutrophil adhesion, neutrophil transmigration in vivo or Toll-like receptor 7/8-mediated cytokine release by monocytes or dendritic cells with or without CR3 pre-engagement by iC3b-coated targets. Our findings demonstrate that the reduction in CR3-mediated phagocytosis associated with the 77H CD11b variant is not macrophage-restricted but demonstrable in other CR3-expressing professional phagocytic cells. The association between 77H and susceptibility to systemic lupus erythematosus most likely relates to impaired waste disposal, a key component of lupus pathogenesis

Transfer function estimation with SMC method for combined heat transfer: insensitivity to detail refinement of complex geometries: CHT-21 ICHMT - International Symposium on Advances in Computational Heat Transfer, Aug 2021, Rio de Janeiro (online), Brazil.

The optimization of heat transfers in engineering systems such as heat exchangers requires the analysis of the influence of heat sources on the temperature at different positions of interest in the system under study. In order to solve the coupled heat transfers in these systems, their complex couplings and 3D geometries must be taken into account with great accuracy. Recent developments in probabilistic formulations in the context of coupled heat transfers (linear conduction-radiation-convection) have opened a new way to solve such problems with Monte Carlo (MC) algorithms, using numerical computations libraries from image synthesis to handle complex geometries. To estimate the temperature at a probe position of interest, random paths are generated from the probe position and propagate through the geometry until a known temperature is reached. From a single MC calculation to sample the path statistics, the Symbolic Monte Carlo (SMC) method is used to express the probe temperature as a linear function of the sources. This function can then be used to estimate the probe temperature for any source value, this avoids the need to repeat Monte Carlo simulations for each change in source value, greatly reducing the computational time. This approach is applied to the case of an open cavity porous medium and the insensitivity of the computation time to the complexity and refinement of the geometry is demonstrated.At the CHT-21 international conference in August 2021 on advances in numerical heat transfer, this work was presented orally and is the subject of this video. Following this presentation, this research work has been published in the conference proceedings (https://hal-mines-albi.archives-ouvertes.fr/hal-03374353)L’optimisation des transferts thermiques dans les systèmes d’ingénieurs tels que les échangeurs de chaleur nécessite l’analyse de l’influence des sources de chaleur sur la température à différentes positions d’intérêt dans le système étudié. Afin de résoudre les transferts de chaleurs couplés dans ces systèmes, leurs couplages et géométries 3D complexes doivent être prise en compte avec une grande précision. Les développements récents des formulations probabilistes dans le contexte des transferts de chaleur couplés (conduction-radiation-convection linéaires) ont ouvert une nouvelle voie pour résoudre de tels problèmes avec des algorithmes de Monte Carlo (MC), en utilisant des librairies de calculs numériques issues de la synthèse d’image pour traiter des géométries complexes. Pour estimer la température en une position d’intérêt de la sonde, des chemins aléatoires sont générés à partir de la position sonde et se propagent dans la géométrie jusqu’à ce qu’une température connue soit atteinte. À partir d’un unique calcul MC pour échantillonner les statistiques de chemins, la méthode de Monte Carlo Symbolique (SMC) est utilisée pour exprimer la température de la sonde comme une fonction linéaire des sources. Cette fonction peut ensuite être utilisée pour estimer la température de la sonde pour n’importe quelle valeur de source, ceci évite le fait de devoir répéter les simulations de Monte-Carlo pour chaque changement de valeur de source, réduisant considérablement le temps de calcul. Cette approche est appliquée au cas d’un milieu poreux à cavité ouverte et l’insensibilité du temps de calcul à la complexité et au raffinement de la géométrie est démontrée.Lors de la conférence internationale CHT-21, en août 2021, portant sur les avancées dans le domaine du calcul numérique des transferts de chaleur, ces travaux ont été présentés à l'oral et font l'objet de cette vidéo. Suite à cette présentation, ces travaux de recherche ont été publiés dans les proceedings de la conférence (https://hal-mines-albi.archives-ouvertes.fr/hal-03374353

Toward the use of Symbolic Monte Carlo for Conduction-Radiation Coupling in Complex Geometries

International audienceWe address the interest of using Symbolic Monte Carlo to obtain a reduced model for conduction-radiation coupling in complex geometries. Symbolic Monte Carlo was successfully used for radiative transfer in a decoupled manner, but no attempt has yet been reported to extend its use to radiation coupled with other modes. Here we show that from a unique Monte Carlo simulation of radiation coupled with conduction in a semi-transparent solid surrounded by a convective flow, it is possible to build a formulation of the local temperature as function of the convective heat trans- fer coefficient, for instance, including the evaluation of uncertainty. This reduced model (a transfer function) enables to decrease the computation time when the function needs to be evaluated plenty of times for different values of the parameters as in optimization or control algorithms

Integral formulation of null-collision Monte Carlo algorithms

International audienceAt the kinetic level, the meaning of null-collisions is straightforward: they correspond to pure-forward scattering events. We here discuss their technical significance in integral terms. We first consider a most standard null-collision Monte Carlo algorithm and show how it can be rigorously justified starting from a Fredholm equivalent to the radiative transfer equation. Doing so, we also prove that null-collision algorithms can be slightly modified so that they deal with unexpected occurrences of negative values of the null-collision coefficient (when the upper bound of the heterogeneous extinction coefficient is nonstrict). We then describe technically, in full details, the resulting algorithm, when applied to the evaluation of the local net-power density within a bounded, heterogeneous, multiple scattering and emitting/absorbing medium. The corresponding integral formulation is then explored theoretically in order to distinguish the statistical significance of introducing null-collisions from that of the integral-structure underlying modification

Synthèse d'images infrarouges sans calcul préalable du champ de température

International audienceNous presentons un ensemble d’algorithmes statistiques permettant d’effectuer le rendu d’une image thermique, en régime instationnaire, dans une scène quelconque. Simuler le signal reçu par chaque pixel de la camera consiste à propager les sources thermiques (conditions aux limites et initiales) par les phenomènes de conduction, convection et rayonnement. La technique ne nécessite pas un calcul préalable du champ de température en tout point de la scène et en tout temps. Un exemple en geométrie complexe est présenté, et qualitativement comparé à une prise de vue