Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Converse theorem for practical stability of nonlinear impulsive systems and applications

summary:The Lyapunov's second method is one of the most famous techniques for studying the stability properties of dynamic systems. This technique uses an auxiliary function, called Lyapunov function, which checks the stability properties of a specific system without the need to generate system solutions. An important question is about the reversibility or converse of Lyapunov's second method; i. e., given a specific stability property does there exist an appropriate Lyapunov function? The main result of this paper is a converse Lyapunov Theorem for practical asymptotic stable impulsive systems. Applying our converse Theorem, several criteria on practical asymptotic stability of the solution of perturbed impulsive systems and cascade impulsive systems are established. Finally, some examples are given to show the effectiveness of the derived results

Fractures network analysis and interpretation in carbonate rocks using a multi-criteria statistical approach. Case study of Jebal Chamsi and Jebal Belkhir, South-western part of Tunisia

International audienceThe quantitative analysis of fractures in carbonate rocks across termination folds is important for the understanding of the fractures network distribution and arrangement. In this study, we performed a quantitative analysis and interpretation of fracture network to identify the fracture networks type. For this reason, we used a multi-criteria statistical analysis. The distribution of directional families in all measured stations and their elemental distribution are firstly examined. Then we performed the analysis of directional criteria for each of the two and three neighbouring stations. Finally, the elemental analyses of fracture families crossing others were carried out. This methodology was applied to the folds of Jebal Chamsi and Jebal Belkhir areas located in south western Tunisia characterized by simple folds of carbonate geological formations. The application of the global and the elemental statistical analysis criteria of directional families show a random arrangement of fractures. However, elemental analysis of two and three neighbouring stations for families crossing one another shows a pseudo-organization of fracture arrangements

Urban land suitability analysis using geospatial techniques and combined weighting approach in Gabes zone, Southeastern Tunisia

International audienceUrban Land Suitability analysis is necessary in any development project in order to ensure rational urban planning and sustainable development. In this study, a novel approach based on GIS and Combined Weighting method were used to construct a reasonable assessment model and calculate the Urban Land SuitabilityIndex (ULSI) of Gabes area (Southeastern Tunisia). Seven conditional factors were selected: flooding susceptibility, Lithology,Topography, Seismotectonic, Water table depth, Swelling soils, Soils Aggressivity and the thematic layers were prepared in ArcMap_GIS. The resultant model following combination of the geo-spatial (GIS) and geostatistical (CRITIC-ANP) modeling show that this region is subdivided into four analyzed zones in terms of geo-hazard susceptibility and foundation excavation: flooding risk area; settlement risk zone; collapse risk area and subsidence risk zone. The ULSI is equal to 3.5. The accuracy degree of the achieved model was validated by ROC-AUC curve, it’s is around 78.4%. The ULS model developed enable assured a the assessed thorough and can well reflect an urban land suitability. The results achieved in this study assured planners, engineers, decision-makers and authorities assured a good risk prediction and management plan, could, thus, be facilitate decision-making and can serve as a guideline for all future urban planning projects in this region

Quantitative analysis of fractured carbonate reservoir and hydrodynamic implications: Case study of Horchane-Braga basin (central Tunisia)

International audienceFracture network properties in geological media are described and analyzed to evaluate the hydrodynamic functioning of fractured aquifer as well as permeability and transmissivity. In this paper, a concise approach for mapping and analyzing fracture properties in the outcrops was applied. The adopted methodology aims to explore the spatial distribution and properties of fractures to estimate the aquifer permeability. A detailed geological mapping was established to define the geometry and spatial extension of the fractured aquifer. A correlation between these data and the transmissivity values is discussed to evaluate groundwater flow in fractured aquifer. The Horchane basin was explored to investigate fracture distribution and their aperture, density and frequency. The fracture mapping at 1/1 scale was done over 42 stations containing 1000 fractures. Results of this investigation show that fracturing is the only parameter responsible for the circulation of water in the aquifer. Aperture and density of fractures have an important effect on permeability and water flow in the Horchane-Braga basin

Groundwater potentiality assessment in an arid zone using a statistical approach and multi-criteria evaluation, southwestern Tunisia

The aim of this paper is to assess the groundwater potentiality using statistical multi-criteria evaluation and AHP (analytic hierarchy process) as an additional method to the hydrogeological research in order to create a map that represents the groundwater potentiality. The extraction of this map is based on the study of multi-criteria input data, such as lineaments, land use, lithology, drainage, slope, soil, rainfall and geomorphology. Weights were assigned using the AHP method to all these multi-influencing factors according to their influence on groundwater potential. Sensitivity analysis was calculated to validate the AHP weights result. The presented methodology has been applied to the Bouhedma region in southwestern Tunisia, located in an arid climate. This technique revealed that very good, good, moderate and poor groundwater potential zones are spread over 382 km2 (26.9%), 437 km2 (30.7%), 552 km2 (38.8%) and 51 km2 (3.6%), respectively. Furthermore, the effect of each influencing factor on groundwater capacity was computed. The results provide significant information and found to be helpful in better planning and management of groundwater resources

GIS-based MCDM – AHP modeling for flood susceptibility mapping of arid areas, southeastern Tunisia

International audienceFloods are considered as a major natural disaster due to their devastating effects that lead to socio-economic losses. The present study is an attempt to prepare a flood hazard susceptibility map of the Gabes region using ‘multi-criteria decision making – analytical hierarchy process’ model in geographic information system environment. Eight factors have been used in the flood modeling: elevation, land use/land cover, lithology, rainfall intensity, drainage density, distance from the drainage network, slope, and groundwater depth. The impact of each factor contributing in the flood risk was examined by weights using analytical hierarchy process method. The results obtained shows that the most prominent flood occurrence factor is the elevation (22.5%), around 15% of the total area is flooded and the flood hazard index is equal 6.30. The validation of results by a susceptibility zones histogram showed that 74.51% of the observed flood areas are mainly concentrated in a moderate to very high susceptibility zone

Mapping groundwater recharge potential zones in arid region using GIS and Landsat approaches, southeast Tunisia

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Le Maghreb dans la Mondialisation

Le Maghreb occupe une place secondaire dans la polarisation de l’économie mondialisée à laquelle il est pourtant fortement arrimé mais dans un rapport asymétrique. Cette situation qui justifie la qualification de «Mondialisation subalterne», se traduit par une accentuation des déséquilibres régionaux au travers d’une valorisation différenciée et sélective des territoires. Elle se traduit également par l’irruption d’espaces marginaux directement connectés avec le système monde et de groupes sociaux censés, situés à la marge extrême des dynamiques de mondialisation et qui réussissent à intégrer celles-ci et à se les réapproprier y compris en mobilisant des référents sociaux traditionnels. Ces pratiques se développent dans une interpellation en miroir entre particularismes et mondialisation alors que l’entre-soi identitaire et national est largement fissuré par de multiples réseaux transnationaux y compris culturels, et virtuels