A suitable parametrization to simulate slug flows with the Volume-Of-Fluid method

Diffuse–interface methods, such as the Volume-Of-Fluid method, are often used to simulate complex multiphase flows even if they require significant computation time. Moreover, it can be difficult to simulate some particular two-phase flows such as slug flows with thin liquid films. Suitable parametrization is necessary to provide accuracy and computation speed. Based on a numerical study of slug flows in capillary tubes, we show that it is not trivial to optimize the parametrization of these methods. Some simulation problems described in the literature are directly related to a poor model parametrization, such as an unsuitable discretization scheme or too large time steps. The weak influence of the mesh irregularity is also highlighted. It is shown how to capture accurately thin liquid films with reasonably low computation times

N-acetylcysteine for the prevention of stricture after circumferential endoscopic submucosal dissection of the esophagus: a randomized trial in a porcine model

BACKGROUND: Circumferential endoscopic submucosal dissection (CESD) of the esophagus would allow for both the eradication of Barrett’s esophagus and its related complications, such as advanced neoplasia. However, such procedures generally induce inflammatory repair resulting in a fibrotic stricture. N-acetylcysteine (NAC) is an antioxidant that has shown some efficacy against pulmonary and hepatic fibrosis. The aim of our study was to evaluate the benefit of NAC in the prevention of esophageal cicatricial stricture after CESD in a swine model. ANIMALS AND METHODS: Two groups of six pigs each were subjected to general anesthesia and CESD: after randomization, a first group received an oral NAC treatment regimen of 100 mg/kg/day, initiated one week before the procedure, whereas a second group was followed without any prophylactic treatment. Follow-up endoscopies took place seven, fourteen, twenty-one, and twenty-eight days after CESD. Necropsy, histological assessment of esophageal inflammation, and fibrosis were performed on day 28. RESULTS: The median esophageal lumen diameter on day 21 (main judgment criterion) was 4 mm (range 2 to 5) in group 1 and 3 mm (range 1 to 7) in group 2 (P = 0.95). No significant difference was observed between the two groups regarding clinical evaluation (time before onset of clinically significant esophageal obstruction), number of dilations, esophageal inflammation and fibrosis, or oxidative stress damage on immunohistochemistry. CONCLUSIONS: Despite its antioxidant effect, systemic administration of NAC did not show significant benefit on esophageal fibrosis in our animal model of esophageal wound healing within the experimental conditions of this study. Since the administered doses were relatively high, it seems unlikely that NAC might be a valuable option for the prevention of post-endoscopic esophageal stricture

Experimental and numerical study of two-phase flows in arrays of cylinders

In this paper we study the spreading of a liquid jet in a periodic array of cylinders with a characteristic size of the passages between solid obstacles equal to 1.5 mm, close to the capillary length. An important outcome of our study is to show that this configuration allows most of the two phase flow regimes described in the literature about trickle beds to be observed, even with no gas injection. Different aspects of the flow phenomenology have been studied, such as bubble creation and transport. As direct numerical methods for tracking interfaces would require too much computation time, especially in three-dimensional cases, we propose to simulate the two-phase flows observed experimentally with two-dimensional simulations corresponding to the spreading of a liquid jet in an array of disks. We show that this numerical approach allows the phenomenology observed experimentally to be reproduced satisfactorily. Hence, numerical simulations can be used subsequently to study the effects of specific parameters without setting up a new experimental procedure. As an example, the stabilizing effect of gas injection on the flow pattern is studied numerically

Ecclésiologie et hérésiologie (Moyen Âge, Temps modernes)

Dans quelle mesure l’institution ecclésiale génère-t-elle par nécessité propre les dissidences, « ses » dissidences ? Le père Yves Congar, auquel l’une des journées du cycle les « Nouveaux horizons de l’ecclésiologie » a été consacrée en janvier 2009, a, en bonne partie, fondé son histoire de l’ecclésiologie sur le couple ecclésiologie/hérésiologie, notant le fait avéré que les grands tournants ecclésiologiques sont, au Moyen Âge, le plus souvent concomitants de graves crises internes – par e..

Recovery of succinic acid in fermentation broth via reactive LL extraction: effect of chemical kinetics and solvent choice

In this paper, a study of kinetics effects on the reactive liquid-liquid extraction column is proposed. In a first part, design parameters of reactive liquid-liquid extraction column are derived from a method proposed by Mizzi (2016). In a second part, using a kinetic model, the performances of the column are studied with different configuration and design parameters. This study allows a comparison of the performances of the column in terms of conversion rate, recovery rate and purity. For the chosen examples, the kinetic limitation is very strong. So the unit operations of reactive liquid-liquid extraction with a high retention capacity will be privileged: a cascade of decanter mixers. In conclusion, this article shows that the choice of solvent and the parameters of the column as the solvent flowrate, the number of theoretical stage, liquid hold up or kinetics of the reaction have an important influence on the performances of the column and sometimes on the feasibility of the separation

L’ours des cavernes de Font-de-Gaume III

Le niveau 4-5 (fouilles Prat) de la grotte de Font-de-Gaume est riche en ossements d’Ours des cavernes. Quelques artefacts lithiques y ont également été trouvés. Parmi eux, signalons la présence de deux pointes de Châtelperron. La reprise de ce matériel a permis de découvrir des traces de découpe sur des restes d’Ours.Layer 4-5 (Prat excavation) of Font-de-Gaume cave is reach in cave bear remains. This layer also includes a few lithic artefacts, including two châtelperron points. A recent analysis of this material shows that cutmarks are present on some of the cave bear bones

Pore-network modeling of trickle bed reactors: Pressure drop analysis

A pore network model (PNM) has been developed to simulate gas–liquid trickle flows inside fixed beds of spherical particles. The geometry has been previously built from X-ray micro-tomography experiments, and the flow in the throats between pores is modeled as a pure viscous Poiseuille two-phase flow. The flow distribution between pores and throats is obtained by solving mass and momentum balance equations. As a first application of this simple but powerful meso-scale model, a focus is proposed on the ability of PNM to estimate pressure drop and liquid saturation in co-current gas–liquid flows. PNM results are compared to the classical 1D pressure drop models of Attou et al. (1999), Holub et al. (1992) and Larachi et al. (1991). Agreement and discrepancies are discussed, and, finally, it has been found that the actual PNM approach produces realistic pressure drops as far as inertial contributions to friction are negligible. Concerning liquid saturation, the PNM only estimates its value in the throats between pores. As a consequence, liquid saturations are overestimated, but they can be easily corrected by an ad hoc empirical model

Pancreatic Metastasis from Prostate Cancer

The pancreas is an unusual location for metastases from other primary cancers. Rarely, pancreatic metastases from kidney or colorectal cancers have been reported. However, a variety of other cancers may also spread to the pancreas. We report an exceptional case of pancreatic metastasis from prostate cancer. Differences in management between primary and secondary pancreatic tumors make recognition of metastases to the pancreas an objective of first importance. Knowledge of unusual locations for metastatic spread will reduce diagnostic delay and lead to a timely delivery of an appropriate treatment

General design methodology for reactive liquid–liquid extraction: application to dicarboxylic acid recovery in fermentation broth

A general design methodology for reactive liquid–liquid extraction is introduced in this paper. It is composed of three different steps: feasibility analysis, pre-design determination and simulation validation. This paper is focused on the first and the second step. This methodology leads to the design specifications of the units from the information concerning the physico-chemical behaviour of the studied system, exploiting the equilibrium and material balance equations. The results of this methodology are a good starting point for an optimization study or for an investment calculation process. This methodology has been applied to different case studies: two different strategies of extraction and several solvents to recover succinic acid in fermentation broth