Oxydation du phenol sur un catalyseur à base de Fer supporté sur une argile marocaine

L'objectif du présent travail est l'étude de l'oxydation par voie humide du phénol en catalyse hétérogène, en présence de peroxyde d'hydrogène. Les catalyseurs choisis sont à base de fer et de cuivre; l'oxydation est effectuée dans des conditions normales de température et de pression. Les résultats expérimentaux montrent une oxydation complète du phénol et une diminution significative de la demande chimique en oxygène DCO. D'autre part ces catalyseurs manifestent une grande stabilité; on peut donc les utiliser sans causer des problèmes de pollution métallique.Mots-clés : Phénol, peroxyde d'hydrogène, catalyse hétérogène, Fe-argile, oxydation

Preparation and characterization of electrolytic alumina deposit on austenitic stainless steel

Conversion coating modified by alumina has been studied as a way for improving the resistance to thermal oxidation of an austenitic stainless steel. Conversion coating, characterized by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. The influence of the current density and treatment time on alumina deposit was studied using statistical experimental designs like Doehlert uniform shell design. After heating, coatings present a continuous composition gradient with refractory compounds at the surface. The behavior at high temperature (1000 8C) of the alumina coating was investigated. The presence of alumina increases the oxidation resistance of an austenitic stainless steel at 1000 8C. The morphology and the chemical composition of the deposit are analyzed. Results on the thermal stability of coating on austenitic stainless steel are presented

Beneficial Effects of Pomegranate Fruit Consumption in Cardiovascular Diseases Prevention

Oxidative stress, dyslipidemia, hypercoagulability, endothelial dysfunction and inflammation are key elements in the development of atherosclerosis. Oxidative stress has been implicated as well in most of the key steps in the pathophysiology of atherosclerosis and the consequential clinical manifestations of cardiovascular diseases. In addition to the formation of atherosclerosis, oxidative stress acute thrombotic events, including dyslipidemia, the oxidation of low-density lipoproteins (LDLs) and plaque rupture leading to atherothrombosis and myocardial infarction. In the last decades, multiple experimental studies and clinical trials have demonstrated that diet plays a central role in the prevention of atherosclerosis. Pomegranate (Punica granatum L.) is one of nature's most concentrated sources of antioxidants. It contains some very potent antioxidants (i.e. tannins, anthocyanins and flavonoids), which provide a wide spectrum of action against free radicals and are considered to be potent anti-atherogenic products. These properties make pomegranate a healthy fruit with a high potential in preventing cardiovascular diseases. In this review, we give an overview on the newest insights in the role of pomegranate in therapy of vascular diseases

A New Approach of Total Least Square Algorithm for Parameter Extraction of a Photovoltaic Panel: A Comparison Study

The degradation of the photovoltaic panels due to their long outdoor exposure leads to a variation in their internal parameters. The function describing the I-V characteristic of the photovoltaic cell is known to be non-linear and implicit, with five unknown parameters. To identify these photovoltaic parameters, the cost function used for optimization is the Total Least Square function (TLS), defined as a sum of quadratic terms representing the quantification of the errors between a mathematical model and a measured set of experimental data, which is usually accompanied by measurement uncertainties (measuring current and voltage). However, the studies that have been done so far to extract the photovoltaic parameters work with the Ordinary Least Square (OLS) function defined as the sum of quadratic terms representing the quantification of the errors between a mathematical model and a measured set of experimental data of one variable (current only), because it is facile to apply, especially in the case of nonlinear models. Nether less, taking into account both differences in measurement uncertainties accompanying both variables will help to achieve more efficient optimization and more precise results. This work presents a new iterative, simple to implement algorithm that can calculate the value of the Total Least Square function at each step of the optimization process. The results are then compared with the ones obtained by applying the OLS function

Étude de la dégradation d’une canalisation de conduite d’eau en béton armé

Dans ce travail nous nous sommes intéressés à l’étude des causes de dégradation d’une canalisation en béton armé dans la région de l’oriental au Maroc. Cet ouvrage est utilisé pour transporter de l’eau potable. L’altération de l’ouvrage n’a été constatée et de manière sévère que sur un tronçon bien situé. Dans ce cadre on a procédé à la détermination des causes de dégradation. Pour cela nous avons effectué un prélèvement d’échantillons du tronçon dégradé et de part et d’autre. Des échantillons témoins ont été réalisés à l’usine de fabrication des canalisations.Nous avons effectué le dosage de la teneur en chlorure et en ciment, étudié l’impact de la carbonatation et déterminé les pourcentages en silice et carbonates. Nous avons aussi mis au point la présence des ionschlorures en pourcentage assez important pouvant être responsable de la corrosion des aciers de frettage des tuyaux en béton précontraint et par conséquent des dégradations affectant ces tuyaux. La présence d’unenvironnement humide aurait favorisé la dégradation. Par ailleurs, la détermination de la teneur en chlorures par rapport à la masse de ciment a nécessité la détermination du pourcentage de ciment contenu dans le béton. Nous avons utilisé la méthode dite des inertes. La détermination de la teneur en anhydre carbonique CO2 a été réalisée par calcimétrie. Les résultats obtenus montrent que nous sommes en présence d’un béton ayant subi une légère carbonatation et contenant à la fois des teneurs en chlorures dépassant largement le seuil d’amorçage de la corrosion.Mots-clés : dégradation, canalisation, béton armé, corrosion, carbonatation

Chemical and mineralogical characterization and ceramic suitability of raw feldspathic materials from Dschang (Cameroon)

The chemical and mineralogical characterization of raw feldspathic materials from Dschang (Cameroon) was realized by means of X-ray diffraction, differential thermal analyses, optical and scanning electron microscopies, and analytical techniques. It was found that these materials consist of albite (43 ± 3 wt.%), microcline (41 and 26 wt.%), quartz (14.5 ± 1.5 wt.%), plagioclase (oligoclase type) (6 and 12 wt.%) and a minor content of biotite. The amount of fluxing oxides is about 12 wt.% and those of pigments are quasi-null. The ceramic suitability of these materials was assessed in the light of the obtained chemical data and physical characteristics (fusibility, viscosity, colour). The results showed that these raw materials are convenient, as fluxing compounds, for manufacturing white ceramic.KEY WORDS: Raw feldspathic materials, Mineralogy, Chemical composition, Ceramic suitability, Cameroon   Bull. Chem. Soc. Ethiop. 2010, 24(1), 39-46