Contribution à l’étude de la salinisation de la nappe côtière de sahel El Haouzia région d’El Jadida au Maroc

La nappe côtière du Sahel d’El Haouzia circulent soit dans les calcaires fissurés du Cénomanien (partie amont), soit dans les formations détritiques du Plioquaternaire (partie avale). Ce sont des formations perméables favorisant le transit des eaux d’infiltration à forte charge saline, vers la nappe d’eau souterraine, circulant généralement à de faibles de la surface. La conductivité électrique moyenne des eaux souterraines étudiées montre des variations importantes, de 1,7 mS/cm (zone interne) à 7 mS/cm. En effet, elle accuse des valeurs de plus en plus importantes en direction de la mer, avec un gradient d’augmentation important dans les premiers kilomètres du rivage. La minéralisation totale est déterminée principalement par les ions chlorures et sodium qui montrent une corrélation positive avec la conductivité électrique. La combinaison des outils, géologiques, hydrogéologiques, piézométriques et hydrochimiques a montré que les fortes salinités des eaux souterraines sont liées au phénomène d’intrusion marine (dans les premiers kilomètres de la côte), à celui du lessivage de la roche réservoir et de l’infiltration des eaux de retour. Ces méthodes d’étude ont montré une meilleure adaptation avec notre système aquifère côtier.Mots-clés : Nappe côtière, salinité, intrusion marine, hydrochimie, Sahel ElHaouzia, Maroc

Influence of design parameters on the unsteady flow in a centrifugal fan

ABSTRACT The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental study has been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these fans. The effects on the unsteady flow behavior related to irregular blade spacing, blade number and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using Computational Fluid Dynamics tools (CFD) based on Unsteady Reynolds Averaged Navier Stokes approach (URANS). The sliding mesh technique has been applied at the interfaces between the rotating and stationary zones in order to model the blades' motion relative to the volute casing. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations (pressure and velocity fluctuations acquired upon the surfaces of the rotating blades) have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). Using this model, the acoustic pressure has been computed at the fan exit duct. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 [1] standard. In addition to this, pressure microphones have been flush-mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found

Recipe adaptation and new recipe development for high temperature heat treatment of North American wood species

The thermal treatment of wood at high temperatures is an environment friendly and commercially viable alternative wood modification technology. In this process, wood is heated to temperatures above 200ºC. This modifies the structure of wood and improves its hardness, dimensional stability, and resistance to biological attacks compared to those of the untreated wood. Its color also becomes darker and more attractive. However, this treatment may cause a decrease in wood elasticity. Therefore, optimization of the treatment parameters is necessary for a quality product. In addition, the high temperature heat-treatment processes for wood were first developed in Europe, and the recipes used for the European species were not necessarily applicable to the North American species. Thus, adaptation of the technologies to the latter species was necessary. The industrialists in the Saguenay-Lac-St-Jean region of Quebec brought two heat treatment technologies (Bois Perdure from France and Thermowood from Finland) to Canada. The adaptation of the technology is a very costly procedure at industrial scale. The Research Group on the Thermotransformation of Wood (GRTB – Groupe de recherche sur la thermotransformation du bois) at the University of Quebec at Chicoutimi (UQAC) which works closely with these industries developed a method for adapting the existing recipes to the North American species as well as for developing new ones for other species. UQAC is the first North American university which has such a unique research structure to carry out this type of research. The recipe development starts in a laboratory scale furnace. The high temperature heat-treatment experiments are carried out in a thermogravimetric system under different conditions until a promising set of conditions is identified for the properties sought by the industry. Consequently, the trends are identified for a given species. To determine the properties, various characterization tests (bending, dimensional stability, screw withdrawal, etc.) are done. Then, the heat treatment trials in a prototype furnace are carried out to finalize the recipe. This is followed by trials in an industrial-scale furnace for validation of the results

Observational signatures of disk and jet misalignment in images of accreting black holes

Black hole accretion is one of nature's most efficient energy extraction processes. When gas falls in, a significant fraction of its gravitational binding energy is either converted into radiation or flows outwards in the form of black hole-driven jets and disk-driven winds. Recently, the Event Horizon Telescope (EHT), an Earth-size sub-millimetre radio interferometer, captured the first images of M87's black hole. These images were analysed and interpreted using general-relativistic magnetohydrodynamics (GRMHD) models of accretion disks with rotation axes aligned with the black hole spin axis. However, since infalling gas is often insensitive to the black hole spin direction, misalignment between accretion disk and black hole spin may be a common occurrence in nature. In this work, we use the general-relativistic radiative transfer (GRRT) code \texttt{BHOSS} to calculate the first synthetic radio images of (highly) tilted disk/jet models generated by our GPU-accelerated GRMHD code \texttt{HAMR}. While the tilt does not have a noticeable effect on the system dynamics beyond a few tens of gravitational radii from the black hole, the warping of the disk and jet can imprint observable signatures in EHT images on smaller scales. Comparing the images from our GRMHD models to the 43 GHz and 230 GHz EHT images of M87, we find that M87 may feature a tilted disk/jet system. Further, tilted disks and jets display significant time variability in the 230 GHz flux that can be further tested by longer-duration EHT observations of M87

Modelling of high temperature heat treatment of wood using thermowood technology

Heat treatment of wood at relatively high temperatures (in the range of 180–240°C) is an effective method to improve the dimensional stability and to increase the biological durability of wood. During the heat treatment process, the heat and mass transfer takes place between the solid and the drying medium, and the moisture evaporation occurs within the solid due to the capillarity action and diffusion. In this article, a coupling method is presented for high temperature heat treatment of wood based on ThermoWood technology. A three-dimensional mathematical model considering the simultaneous unsteady heat and moisture transfer between a gas phase and a solid phase during heat treatment has been developed. The conservation equations for the wood part are obtained using the diffusion equation with variable diffusion coefficients, and the 3-dimensional incompressible Reynolds-averaged NavierStokes equations have been solved for the flow field. The coupling between the two parts is achieved by expressing the continuity of the state variables and their respective fluxes through the interface. A detailed discussion of the computational model and the solution algorithm is given

General relativistic MHD simulations of non-thermal flaring in Sagittarius A*

Sgr A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this variability is still ambiguous since both inverse Compton and synchrotron emission are possible radiative mechanisms. The underlying particle distributions are also not well constrained, particularly the non-thermal contribution. In this work, we employ the GPU-accelerated general relativistic magnetohydrodynamics code H-AMR to perform a study of flare flux distributions, including the effect of particle acceleration for the first time in high-resolution 3D simulations of Sgr A*. For the particle acceleration, we use the general relativistic ray-tracing code bhoss to perform the radiative transfer, assuming a hybrid thermal+non-thermal electron energy distribution. We extract ∼60 h light curves in the sub-millimetre, NIR and X-ray wavebands, and compare the power spectra and the cumulative flux distributions of the light curves to statistical descriptions for Sgr A* flares. Our results indicate that non-thermal populations of electrons arising from turbulence-driven reconnection in weakly magnetized accretion flows lead to moderate NIR and X-ray flares and reasonably describe the X-ray flux distribution while fulfilling multiwavelength flux constraints. These models exhibit high rms per cent amplitudes, ≳150 per cent both in the NIR and the X-rays, with changes in the accretion rate driving the 230 GHz flux variability, in agreement with Sgr A* observations

General relativistic radiative transfer: formulation and emission from structured tori around black holes

We construct a general relativistic radiative transfer (RT) formulation, applicable to particles with or without mass in astrophysical settings. Derived from first principles, the formulation is manifestly covariant. Absorption and emission, as well as relativistic, geometrical and optical depth effects are treated self-consistently. The RT formulation can handle 3D geometrical settings and structured objects with variations and gradients in the optical depths across the objects and along the line-of-sight. The presence of mass causes the intensity variation along the particle bundle ray to be reduced by an aberration factor. We apply the formulation and demonstrate RT calculations for emission from accretion tori around rotating black holes, considering two cases: idealised optically thick tori that have a sharply defined emission boundary surface, and structured tori that allow variations in the absorption coefficient and emissivity within the tori. Intensity images and emission spectra of these tori are calculated. Geometrical effects, such as lensing-induced self-occulation and multiple-image contribution are far more significant in accretion tori than geometrically thin accretion disks. Optically thin accretion tori emission line profiles are distinguishable from the profiles of lines from optically thick accretion tori and optically thick geometrically thin accretion disks. Line profiles of optically thin accretion tori have a weaker dependence on viewing inclination angle than those of the optically thick accretion tori or accretion disks, especially at high viewing inclination angles. Limb effects are present in accretion tori with finite optical depths. Finally, in accretion flows onto relativistic compact objects, gravitationally induced line resonance can occur. This resonance occurs easily in 3D flows, but not in 2D flows, such as a thin accretion disk around a black hole.Comment: 13 pages, 10 figures, Accepted for publication in Astronomy and Astrophysic

Fine-Scale Phylogeographic Structure of Borrelia lusitaniae Revealed by Multilocus Sequence Typing

Borrelia lusitaniae is an Old World species of the Lyme borreliosis (LB) group of tick-borne spirochetes and prevails mainly in countries around the Mediterranean Basin. Lizards of the family Lacertidae have been identified as reservoir hosts of B. lusitaniae. These reptiles are highly structured geographically, indicating limited migration. In order to examine whether host geographic structure shapes the evolution and epidemiology of B. lusitaniae, we analyzed the phylogeographic population structure of this tick-borne bacterium using a recently developed multilocus sequence typing (MLST) scheme based on chromosomal housekeeping genes. A total of 2,099 questing nymphal and adult Ixodes ricinus ticks were collected in two climatically different regions of Portugal, being ∼130 km apart. All ticks were screened for spirochetes by direct PCR. Attempts to isolate strains yielded 16 cultures of B. lusitaniae in total. Uncontaminated cultures as well as infected ticks were included in this study. The results using MLST show that the regional B. lusitaniae populations constitute genetically distinct populations. In contrast, no clear phylogeographic signals were detected in sequences of the commonly used molecular markers ospA and ospC. The pronounced population structure of B. lusitaniae over a short geographic distance as captured by MLST of the housekeeping genes suggests that the migration rates of B. lusitaniae are rather low, most likely because the distribution of mediterranean lizard populations is highly parapatric. The study underlines the importance of vertebrate hosts in the geographic spread of tick-borne microparasites

Compensatory-reserve-weighted intracranial pressure versus intracranial pressure for outcome association in adult traumatic brain injury: a CENTER-TBI validation study

Background: Compensatory-reserve-weighted intracranial pressure (wICP) has recently been suggested as a supplementary measure of intracranial pressure (ICP) in adult traumatic brain injury (TBI), with a single-center study suggesting an association with mortality at 6 months. No multi-center studies exist to validate this relationship. The goal was to compare wICP to ICP for association with outcome in a multi-center TBI cohort. Methods: Using the Collaborative European Neuro Trauma Effectiveness Research in TBI (CENTER-TBI) high-resolution intensive care unit (ICU) cohort, we derived ICP and wICP (calculated as wICP = (1 12 RAP) 7 ICP; where RAP is the compensatory reserve index derived from the moving correlation between pulse amplitude of ICP and ICP). Various univariate logistic regression models were created comparing ICP and wICP to dichotomized outcome at 6 to 12 months, based on Glasgow Outcome Score\u2014Extended (GOSE) (alive/dead\u2014GOSE 65 2/GOSE = 1; favorable/unfavorable\u2014GOSE 5 to 8/GOSE 1 to 4, respectively). Models were compared using area under the receiver operating curves (AUC) and p values. Results: wICP displayed higher AUC compared to ICP on univariate regression for alive/dead outcome compared to mean ICP (AUC 0.712, 95% CI 0.615\u20130.810, p = 0.0002, and AUC 0.642, 95% CI 0.538\u2013746, p < 0.0001, respectively; no significant difference on Delong\u2019s test), and for favorable/unfavorable outcome (AUC 0.627, 95% CI 0.548\u20130.705, p = 0.015, and AUC 0.495, 95% CI 0.413\u20130.577, p = 0.059; significantly different using Delong\u2019s test p = 0.002), with lower wICP values associated with improved outcomes (p < 0.05 for both). These relationships on univariate analysis held true even when comparing the wICP models with those containing both ICP and RAP integrated area under the curve over time (p < 0.05 for all via Delong\u2019s test). Conclusions: Compensatory-reserve-weighted ICP displays superior outcome association for both alive/dead and favorable/unfavorable dichotomized outcomes in adult TBI, through univariate analysis. Lower wICP is associated with better global outcomes. The results of this study provide multi-center validation of those seen in a previous single-center study