C5b9 Deposition in Glomerular Capillaries Is Associated With Poor Kidney Allograft Survival in Antibody-Mediated Rejection

C4d deposition in peritubular capillaries (PTC) reflects complement activation in antibody-mediated rejection (ABMR) of kidney allograft. However, its association with allograft survival is controversial. We hypothesized that capillary deposition of C5b9—indicative of complement-mediated injury—is a severity marker of ABMR. This pilot study aimed to determine the frequency, location and prognostic impact of these deposits in ABMR. We retrospectively selected patients diagnosed with ABMR in two French transplantation centers from January 2005 to December 2014 and performed C4d and C5b9 staining by immunohistochemistry. Fifty-four patients were included. Median follow-up was 52.5 (34.25–73.5) months. Thirteen patients (24%) had C5b9 deposits along glomerular capillaries (GC). Among these, seven (54%) had a global and diffuse staining pattern. Twelve of the C5b9+ patients also had deposition of C4d in GC and PTC. C4d deposits along GC and PTC were not associated with death-censored allograft survival (p = 0.42 and 0.69, respectively). However, death-censored allograft survival was significantly lower in patients with global and diffuse deposition of C5b9 in GC than those with a segmental pattern or no deposition (median survival after ABMR diagnosis, 6 months, 40.5 months and 44 months, respectively; p = 0.015). Double contour of glomerular basement membrane was diagnosed earlier after transplantation in C5b9+ ABMR than in C5b9– ABMR (median time after transplantation, 28 vs. 85 months; p = 0.058). In conclusion, we identified a new pattern of C5b9+ ABMR, associated with early onset of glomerular basement membrane duplication and poor allograft survival. Complement inhibitors might be a therapeutic option for this subgroup of patients

Développement d'un modèle de suies pour la modélisation multidimentionnelle des polluants dans les moteurs diesel

ROUEN-INSA Madrillet (765752301) / SudocSudocFranceF

MODELISATION DES TRANSFERTS RADIATIFS EN MILIEU DIPHASIQUE, EMISSIF, ABSORBANT ET MULTIDIFFUSANT APPLICATION AUX PARTICULES DE SUIES FORMEES DANS LES FLAMMES LAMINAIRES

POUR DES MILIEUX EN COMBUSTION, LES PLUS IMPORTANTES SOURCES DE RAYONNEMENT THERMIQUE SONT LES PARTICULES PRESENTES DANS LES FLAMMES. LE BUT DE CE TRAVAIL CONSISTE A CREER UN OUTIL NUMERIQUE PERMETTANT DE QUALIFIER ET DE QUANTIFIER LES TRANSFERTS RADIATIFS DANS UN TEL MILIEU, C'EST-A-DIRE DANS UN MILIEU DIPHASIQUE COMPRENANT DES PARTICULES ET DES GAZ EMISSIFS ET ABSORBANTS, EN PRENANT EN COMPTE LA DIFFUSION MULTIPLE PAR LES PARTICULES. DEUX CODES DE CALCUL ONT ETE ELABORES : LE PREMIER BASE SUR UNE METHODE 4-FLUX MULTICOUCHE QUI PERMET DE MODELISER LES TRANSFERTS RADIATIFS D'UN MILIEU DIPHASIQUE MONODIMENSIONNEL, ET LE SECOND BASE SUR UNE METHODE STATISTIQUE DE MONTE CARLO QUI PERMET DE CALCULER LES TRANSFERTS RADIATIFS DANS UN MILIEU DIPHASIQUE DE GEOMETRIE TRIDIMENSIONNELLE QUELCONQUE. LES ETUDES REALISEES EN COMBUSTION (CODE RUN-1DL) ET EN SPECTROSCOPIE (METHODE DE LI) ONT PERMIS DE CARACTERISER CORRECTEMENT UNE FLAMME NON-PREMELANGEE LAMINAIRE A CONTRE-COURANT, QUI A SERVI DE CAS D'APPLICATION AUX DEUX CODES ELABORES. LA FLAMME CHOISIE ETAIT TROP PEU FULIGINEUSE POUR QUE LA PRESENCE DES PARTICULES AIT UN IMPACT CONSEQUENT SUR LES TRANSFERTS RADIATIFS. CEPENDANT, GRACE AUX ESSAIS REALISES, NOUS AVONS VERIFIE NUMERIQUEMENT LE PHENOMENE EMPIRIQUE BIEN CONNU DES SYSTEMES EN COMBUSTION : LA PRESENCE DES PARTICULES MODIFIE FORTEMENT LES TRANSFERTS D'ENERGIE VERS LE MILIEU EXTERIEUR. SUIVANT LEUR DENSITE, LES PARTICULES PEUVENT, CAS EXTREME, BLOQUER LES TRANSFERTS RADIATIFS JUSQU'A ETEINDRE LA FLAMME. UNE DES CONCLUSIONS IMPORTANTES DE CE TRAVAIL EST QUE LES CRITERES GENERALEMENT APPLIQUES AUX MILIEUX CHARGES EN PARTICULES (ALBEDO, EPAISSEUR OPTIQUE) NE PERMETTENT PAS DE SUPPOSER DU COMPORTEMENT RADIATIF DU MILIEU. CE RESULTAT SOULIGNE QUE LA MULTIDIFFUSION EST UN PHENOMENE PREPONDERANT POUR LES TRANSFERTS D'ENERGIE DANS UNE FLAMME.ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Applicability of the Homotopy Method to the determination of fixed points in chemical kinetics models

Reducing the complex chemical kinetics is an important challenge to implement chemical schemes in a turbulent combustion code. An important step in the reduction of chemical kinetics is to extract the fixed points of the set of differential equations associated with the chemical scheme since they are useful to determine the low manifolds which may be used to reduce kinetic mechanisms. This paper aims at testing a potentially powerful method, namely the Homotopy Method, for extracting fixed points from nonlinear dynamical systems. The method is tested on a 3D and a 7D model of the well-known Belousov-Zhabotinskii reaction. This study shows that the Homotopy Method has a significantly better efficiency than available Newton-Raphson algorithms but that the stiffness of the chemical kinetics equations still resists this method when the number of species increases

Etude par simulation numérique de l'influence de la diffusion multiple sur le rayonnement de milieux discrets émissifs

The focus of this research is to better understand the radiative heat transfer in combustion media with simultaneous absorption, multiple scattering, and emission. The work is mainly devoted to multiple scattering effects in participating media. A 3D Monte-Carlo model is developed, validated, then applied to non-optically thin media. A numerical simulation of two-color thermometry based on laser induced fluorescence (LIF) is presented for polydisperse sprays. The influence of several parameters on the spray emission spectrum is tested. Increasing droplets concentrations leads us to a known red-shift phenomenon, which is quantified. Then, the statistical approach is applied to soot particles in flames in the frame of the LII technique (Laser Induced Incandescence). Some diagnostics bias origins are emphasized.Ce travail de recherche a pour objectif une meilleure compréhension du transfert radiatif dans les milieux en combustion, en présence d'émission, d'absorption et de diffusion multiple. Il est axé sur les effets de la diffusion multiple dans les milieux discrets émissifs. Un modèle 3D de Monte-Carlo est développé, validé puis appliqué aux milieux non optiquement fins. Une simulation numérique de la thermométrie " deux couleurs ", fondée sur la fluorescence induite par laser (LIF) est présentée pour des sprays polydispersés. L'influence de plusieurs paramètres sur le spectre d'émission du spray a été testée. L'augmentation de la concentration de gouttes conduit à un phénomène connu de " décalage vers le rouge ", qui a été quantifié. L'approche statistique est ensuite appliquée aux particules de suie dans les flammes dans le cadre de l'Incandescence Induite par Laser (LII). Les origines de plusieurs biais de mesure sont soulignées.ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Experimental Study of Methane-Oxygen Flames Doped with Nitrogen Oxide or Ammonia. Comparison with Modeling

International audienceNH3 and NO have been added to low pressure, premixed laminar CH4-O2 flames of different equivalence ratios. The profiles of concentrations of major radicals and stable species have been obtained, using a molecular beam sampling technique coupled with a mass spectrometer. Laser-induced fluorescence has been used to measure CH radicals. Absorption spectroscopy has been applied to OH radical and temperature measurements. The behaviours of NO and HCN are mainly discussed, and the whole experimental result compared to complete flame structure computations. Using a recent reaction mechanism described by Miller, we notice that pollutants NO and HCN are generally underestimated by computations. Another mechanism, proposed by Bian et al., for nitrogen oxidation has been tested. Sensitivity and reaction path analysis made it possible to identify the reactions which would require modifications, according to a review of recently published kinetic values, in order to get a better fit between the experimental profiles and the computed ones

Mechanisms of formation and destruction of soot particles in a laminar methane-air diffusion flame

A laser light scattering/extinction method has been used to examine the evolution of soot particles in a cylindrical laminar diffusion flame of methane and air at atmospheric pressure. The soot particle characteristics (volume fraction, mean diameter, number density) were plotted versus time along the streamline trajectories, assuming a monodisperse distribution of particle-sizes. Different steps of soot evolution have been deduced: The soot formation phase consists of two steps, identical to those described by several authors in rich premixed flames: nucleation, then coagulation or aggregation; surface growth, which occurs simultaneously, is responsible for the main part of the total mass of soot. Three steps have been observed in the destruction phase: -In the first step, the mean diameter increases while the particles number decreses; this phenomenon may be considered as an aggregation process or as an effect of the change of particle size-distribution

Polycyclic aromatic hydrocarbons formation and destruction in a laminar diffusion flame

International audienceProfiles of Polycyclic Aromatic Hydrocarbons (PAH) concentrations in a well defined laminar diffusion flame of methane air have been obtained. Experimental techniques involved axial and radial sampling of flame products with an uncooled quartz microprobe. PAH accumulated in a sorbent trap have been analysed qualitatively and quantitatively using capillary gas chromatography and coupled gas-chromatography-mass spectrometry for selected samples. In addition, the intensity of the broadband fluorescence stimulated by the blue line of an argon-ion laser, as well as the elastically scattered light, were recorded at the same flame positions. When taking into account the difference in spatial resolution of the two techniques, a good correlation was obtained between fluorescence intensity and PAH concentration profiles, indicating that PAH are the fluorescing species

Comparison and Coupling of Homogeneous Reactor and Flamelet Library Soot Modeling Approaches for Diesel Combustion

International audienceSoot models applied to Diesel combustion can be grouped into two classes, one based on the flamelet concept and the other based on the homogeneous reactor concept. The first assumes that the laminar diffusion flame structure of the reaction zone, in the mixture fraction space, is preserved while convected and strained by the turbulent flow. The second assumes that the properties of the reaction zone are locally homogeneous. Thus the aerodynamic and chemical reaction interactions are modeled with opposing assumptions: the first assumes fast chemistry, the second fast mixing

Combustion of a droplet of coal-water mixture heated by laser beams

International audienceA heating system using a CW argon ion laser beam has been used simultaneously with a two color pyrometer and a high speed camara to study different steps occurring during the combustion of a coal water mixture (CWM) droplet, positioned around a microthermocouple junction. Experiments have been performed using by-products of coal processing (schlamms) from Freyming-France coal mixed with 38% water. Four distinct steps have been characterized including: water evaporation, devolatilization, volatile combustion and heterogeneous char combustion. A detailed parametric study has been made. The main results are as follows: the duration of heterogeneous combustion does not depend on the heating power, but surprisingly, this duration is increased when the particle size of droplet constitutive coal decreases. This is attributed either to ash effect or to porosity evolution. Ash does not influence the evaporation and total eterogeneous combustion durations. A computer model has been developed to describe the different steps. The water evaporation and fixed carbon combustion are assumed to be mass diffusion controlled, the combustion following a shrinking core model. Good agreement is obtained between computed and measured parameters