La conductivité électro-magnétique : application au suivi de la salinité des sols des périmètres irrigués de Tunisie

Le but de la mission était de présenter une méthode d'évaluation de la salinité des sols par conductivimétrie électromagnétique et de tester dans les conditions de la Tunisie son application à la cartographie de la salure des périmètres irrigués du territoire. La présentation de l'appareillage a d'abord fait l'objet d'un séminaire à Sidi Thabet, organisé par la Direction des Sols. Puis quatre études de cas représentatifs ont été réalisées sur le terrain avec la collaboration des ingénieurs des laboratoires d'arrondissements de la Direction des Sols : périmètre de Sidi Saad (Kairouan), périmètre de Zelba (Mahdia), périmètre de Hazeg (Sfax), périmètre de Sebala ben Amar (Tunis). Au total plus de 700 mesures ont été réalisées au cours de la tournée soit sur la totalité de chaque périmètre, soit sur des parcelles représentatives (cf rapport technique). La facilité de mise en oeuvre de l'appareillage par rapport aux mesures habituelles avec prélèvements, la rapidité de la mesure qui est immédiate, la sensibilité de l'appareil même aux faibles salinités, l'appréhension d'une salinité globale permettant de s'affranchir du problème de variabilité spatiale, font de cette méthodologie une technique bien adaptée au suivi simultané d'un grand nombre de périmètres irrigués dans le cadre d'un réseau national de surveillance de la salinité des sols. (Résumé d'auteur

Effect of soil moisture on trace elements concentrations using portable x-ray fluorescence spectrometer

Portable X-ray fluorescence (PXRF) technology can offer rapid and cost-effective determination of the trace elements concentrations in soils. The aim of this study was to assess the influence of soil moisture content under different condition on PXRF measurement quality. For this purpose, PXRF was used to evaluate the soil elemental concentrations for Ca, Mg, Cd, Cr, Cu, Ni, Zn, P, Fe, Mn and Pb in 60 samples in a perimeter irrigated with treated wastewater (Cebala Borj Touil, North-east Tunisia). Scanning was conducted under four moisture conditions: in-situ, dried soil at 105°C, 40% moisture content soil and saturated soil. All were then compared relatively to dried sample scans. As expected, the relationship between dried vs both in-situ and 40% moisture content elements concentrations were linear. However, PXRF readings from saturated samples were significantly underestimated compared to the measurements on dry samples. Furthermore, soil moisture content caused a significant under-reporting of elemental concentrations compared to the scanning on dry samples. PXRF acted differently for each element following the moisture content of soil. In fact, attenuation coefficient σ of Cr, Fe and Mn were the most affected by saturation of soil samples, whilst Ca, Mg and Ni were more affected for 40% moisture content while Cd, Pb, Zn, Cu and P were affected for in-situ measurements. Correction equations enhanced the error produced by the water influence moisture content and corrected PXRF measurements.Keywords: PXRF analysis; Soil; moisture content; trace elements

Energetic and Thermodynamic Analysis of Adsorption Isotherm Type VI of Xenon on Graphite Nanotubes

New theoretical expressions for the modeling of adsorption isotherms of Xenon on Graphite at 110 K have been established. The establishment of these new expressions is based on statistical physics formalism and some working assumptions. This method allowed estimation of physico-chemical parameters in the theoretical model. The parameters intervening in the adsorption process have been deduced directly from experimental adsorption isotherm by numerical simulation. The proposed models allow a good correlation to Type VI experimental isotherms. We mainly introduce three parameters affecting the adsorption process, namely, the density of Xenon receptor sites NM, the number of molecules per site n and the Xenon adsorption energy. Then we apply the model to calculate thermodynamics functions which govern the adsorption mechanism such as entropy, free enthalpy and internal energy

Assessment of aortic stiffness by cardiovascular magnetic resonance following the treatment of severe aortic stenosis by TAVI and surgical AVR

Aortic stiffness is increasingly used as an independent predictor of adverse cardiovascular outcomes. We sought to compare the impact of transcatheter aortic valve implantation (TAVI) and surgical aortic valve replacement (SAVR) upon aortic vascular function using cardiovascular magnetic resonance (CMR) measurements of aortic distensibility and pulse wave velocity (PWV).A 1.5 T CMR scan was performed pre-operatively and at 6 m post-intervention in 72 patients (32 TAVI, 40 SAVR; age 76 ± 8 years) with high-risk symptomatic severe aortic stenosis. Distensibility of the ascending and descending thoracic aorta and aortic pulse wave velocity were determined at both time points. TAVI and SAVR patients were comparable for gender, blood pressure and left ventricular ejection fraction. The TAVI group were older (81 ± 6.3 vs. 72.8 ± 7.0 years, p < 0.05) with a higher EuroSCORE II (5.7 ± 5.6 vs. 1.5 ± 1.0 %, p < 0.05). At 6 m, SAVR was associated with a significant decrease in distensibility of the ascending aorta (1.95 ± 1.15 vs. 1.57 ± 0.68 × 10(-3)mmHg(-1), p = 0.044) and of the descending thoracic aorta (3.05 ± 1.12 vs. 2.66 ± 1.00 × 10(-3)mmHg(-1), p = 0.018), with a significant increase in PWV (6.38 ± 4.47 vs. 11.01 ± 5.75 ms(-1), p = 0.001). Following TAVI, there was no change in distensibility of the ascending aorta (1.96 ± 1.51 vs. 1.72 ± 0.78 × 10(-3)mmHg(-1), p = 0.380), descending thoracic aorta (2.69 ± 1.79 vs. 2.21 ± 0.79 × 10(-3)mmHg(-1), p = 0.181) nor in PWV (8.69 ± 6.76 vs. 10.23 ± 7.88 ms(-1), p = 0.301) at 6 m.Treatment of symptomatic severe aortic stenosis by SAVR but not TAVI was associated with an increase in aortic stiffness at 6 months. Future work should focus on the prognostic implication of these findings to determine whether improved patient selection and outcomes can be achieved

Dust Effect on Solar Energy Systems and Mitigation Methods

Received: 2 February 2023. Accepted: 29 March 2023.Solar energy systems present a potential solution to global challenges in energy production and addressing environmental issues. However, such systems' performance could deteriorate in harsh weather conditions, which may lead to short- and long-term degradation. Particular attention should be paid to dust accumulation affecting both types of solar systems: Photovoltaic (PV) and Concentrated Solar Power systems (CSP). This review discusses the influencing factors affecting dust accumulation and the dust impact on solar systems. The comparison of dust accumulation effect on both technologies is then assessed. The reported dust accumulation studies showed more performance deterioration in CSP systems than in PV systems. In both cases, dust accumulation leads to a drop in optical characteristics resulting in a loss of energy yield. Potential mitigation methods and their advantages and disadvantages are also reviewed. It is concluded and recommended from the review analysis that dust accumulated on solar systems should be considered in the design and operation phases to define appropriate cleaning methods and frequencies.The authors would like to thank the University of Sharjah, Project #20020406150, for its financial support

Les cellulites cervico-faciales d’origine dentaire: a propos de 150 cas

Les cellulites cervico-faciales d’origine dentaire sont des infections des tissus cellulo-adipeux, de la face et du cou, ayant des potentialités extensives pouvant parfois être graves et engager le pronostic vital. Le but de ce travail est d’étudier le profil épidémioclinique et paraclinique de nos patients, d’évaluer leur prise en charge thérapeutique et leur évolution. Notre étude est rétrospective et a porté sur 150 cas de cellulites cervico-faciales d’origine dentaire colligés sur 10 ans entre 1997 et 2006. La prise en charge thérapeutique était médico-hirurgicale. Les cellulites cervico-faciales d’origine dentaire sont une pathologie potentiellement grave dont la prise en charge est coûteuse et les répercussions socio-professionnelles et économiques sont lourdes d’où l’intérêt d’une politique de prévention efficace et ciblée visant à réduire la morbidité liée à ces infections.Mots clés : cellulites cervicale et faciale, infections dentaire, prévention