MICROSPRAY SIMULATION OF DENSE GAS DISPERSION IN COMPLEX TERRAIN

An extended validation of the new Lagrangian particle model MicroSpray version for dense gas simulation is proposed. MicroSpray simulates the dense gas dispersion in situations characterized by the presence of buildings, other obstacles, complex terrain, and possible occurrence of low wind speed conditions. Its performances are compared to a chlorine railway accident (Macdona), to a field experiment (Kit Fox) and to an atmospheric CFD model

Effects of in vitro contamination by Brucella Abortus on mice and cows embryos

On a cultivé in vitro des embryons de souris et de vache, à zone pellucide intacte, dans des milieux contenant 101 à 105 brucella par mi pour tester la viabilité et les risques de contamination de ces embryons après contact prolongé de 24 h et 48 h. Il en ressort que : — pour de faibles concentrations en brucella (101 à 102 b/ml), la viabilité des embryons est peu modifiée par rapport aux témoins ; — dans nos conditions expérimentales, aucun embryon n’a été conta miné après 48 heures de contact quelle que soit la concentration en brucella et en particulier celles-ci ne sont pas adsorbées sur la zone pellucide ; — dix lavages successifs des embryons contaminés, même à des concentrations elevées sont suffisants pour éliminer les brucella du milieu de transfert (effet dilution) à condition de respecter le protocole proposé. En conclusion, il paraît possible d'utiliser des vaches brucelliques de haute valeur génétique comme donneuses d’embryons, sans risque de transmission de cette maladie aux receveuses et aux futurs produits.In vitro cultures of mice (as a model) and cows embryos with intact zona pellucida have been performed in media containing 101 to 105 brucella per ml. This was aimed at evaluating both viability and risks of contamination of these embryos after 24 or 48 h of such cultures. It was found : (1) with low concentrations of brucella (101 - 10- b./ml, embryo viability was not affected when compared to that of controls ; (2) in our experimental conditions, no embryo was found to be contaminated after 48 h whatever was the brucella concentration in the culture medium ; in particular, brucella were not adsorbed on the zona pellucida ; (3) ten consecutive washings of the embryos initially inserted in a brucella-infected medium (at any of the concentrations studied) are definitely sufficient to eliminate all brucella from the transfer medium under strict conditions defined in the present paper. In conclusion, embryos from cows with high breeding values but unfortunately affected with brucellosis may be transferred with no risk of contamination neither to the embryo nor to the recipient

Transfert embryonnaire chez les bovins avec référence particulière à l'interaction embryons-agents pathogènes

International audienc

New lagrangian approach for wet plume modelling

International audienceA new version of the lagrangian dispersion modelling system Micro-SWIFT-SPRAY (MSS developed by ARIA Technologies and ARIANET) has been developed in order to allow simulation of wet plume, microorganisms, insecticide or pesticide dispersion. For all these applications, it is necessary to take into account both gas and liquid phase evolution including mass and heat transfer. In the particular case of microorganisms distinct behaviors potentially occur when transported by the liquid and/or the gas phase. Following the MSS lagrangian approach, it is easy to define a mass quantity of vapor and a large number of droplets of the same diameter by a virtual particle. Hence a spectrum of different size of droplets can be model using several virtual particles. The development of the new module consists of modelling the physical phenomenon of evaporation and condensation inside a wet plume taking into account temperature and humidity of ambient atmosphere. Microphysics of droplet is solved using the classical laws of evaporation/condensation processes in the surrounding atmosphere. The calculated evaporation rate allows to estimate the diameter evolution and the temperature inside the droplet. The difficulty consists in characterizing the surrounding atmosphere. The interaction between droplets and ambient humidity has been performed on an eulerian frame. Two methods of two way coupling have been tested on academic cases (0D). The proposed paper will present the two approaches and the obtained results

Acceleration of simulations by application of a kernel method in a high-resolution Lagrangian Particle Dispersion model.

The role of microscale atmospheric dispersion modelling is becoming increasingly important in air quality assessment, especially in residential areas, for regulatory purposes and to project pollution control strategies. Consequently, the use of these models in long-term studies and forecasting systems is growing. However, this modelling can be challenging because of the amount of time and CPU required for the simulations, especially if the computational domain has a significant extension. This article describes the application of a concentration calculation methodology to reduce the computational time needed by microscale Lagrangian Particle Dispersion Models (LPDMs). These models normally estimate the concentration with the box counting method: a 3D mesh is set, and the density is computed counting particles in each box. An alternative method based on the use of the statistical technique of kernel density estimation is proposed to determine the concentration from the particles’ position. The kernel method allows for a reduction of computational particles emitted during the simulation, guaranteeing a similar accuracy to that of box counting method. It enables therefore to optimize the overall simulation time and the required CPUs in order to improve time and cost, enhancing the efficiency of models and widening their application fields. The use of the kernel method to perform high-resolution simulations took the first steps with an application inside the LPDM of PMSS (Parallel-Micro-SWIFT-SPRAY) system to evaluate road traffic gases emissions in urban areas, enabling an 80% simulation time reduction. In this article, additional features of this method are developed within the Micro-SPRAY model and validated against two new test cases. The test cases consider microscale simulations of industrial sources emitting gases and particles, evaluated both inside a domain divided in tiles and inside a nested domains configuration. The existing kernel method is enhanced in order to estimate the pollutant concentrations of point sources and to compute also the corresponding deposition at building-resolving scale and in nested domains with different horizontal resolution

Effets de la contamination expérimentale in vitro des embryons de souris et de brebis par Campylobacter fetus

Effects of Campylobacter fetus in vitro experimental infection of mice and ewes embryos. A total of 350 ZP-I, days 3-5 mice embryos were collected and subdivided as follows : 184 were exposed to C. fetus ss fetus compared to 46 controls (non contaminated) and 182 exposed to C. fetus ss venerealis compared to 48 controls. In addition, 164 ZP-I, day 6 sheep embryos were collected and contaminated with C. fetus ss fetus compared to 51 control embryos. The mice embryos were submitted for 48 hours at 37°C to a range of 0.01-100 IDso and the sheep embryos to a range of 0.1-100 ID50. After 48 hours, the non-degenerated embryos were washed, homogeneized and then cultured simultaneously to the washing fluids for search of Campylobacter fetus. After 48 hours, a dose-effect on the survival rate of the embryos (p < 0.001) and a duration-effect (p < 0.01) of the contamination are shown both for mice and sheep embryos for the two species of Campylobacter fetus. No Campylobacter fetus either in mice or sheep were isolated in the last washing mediums nor in the homogeneized embryos.Un ensemble de 460 embryons de souris de 3 à 5 jours, à zone pellucide intacte, ont été collectés et exposés à une contamination expérimentale in vitro par C. fetus ss fetus (n = 184, 1 lot témoin = 46 embryons) et par C. fetus ss venerealis (n = 182, 1 lot témoin = 48 embryons). Semblablement, 164 embryons de brebis ont été parallèlement exposés dans les mêmes conditions à C. fetus ss fetus, et SI embryons ont servi de témoins. Les embryons ont été exposés pendant 48 heures à 37 °C, à des doses variant entre 0,01 et 100 DIES50 pour les embryons de souris et entre 0,1 et 100 DIES50 pour les embryons de brebis. Après l’épreuve infectante, les embryons vivants ont été lavés, broyés et mis en culture, ainsi que les liquides de lavage, en vue de la recherche de C. fetus. Après 48 heures d’incubation, on constate un effet de la durée de l’énreuve infectante (p < 0.01) et un effet de la dose (p < 0.001) sur la survie embryonnaire pour tous les embryons et pour les deux espèces bactériennes testées. Après lavage et broyage, aucun embryon n’était contaminé par Campylobacter fetus.Guérin Bernard, Builly J. P., Humblot P., Nibart M., Thibier Michel. Effets de la contamination expérimentale in vitro des embryons de souris et de brebis par Campylobacter fetus. In: Bulletin de l'Académie Vétérinaire de France tome 141 n°1, 1988. pp. 63-78

Nuclear transfer from sexed parent embryos in cattle: efficiency and birth of offspring

International audienc