Early interest in selenium by nutritionists was first identified in the 1930 s as a toxic element, nowadays it is known to be important in livestock and human diet. Its poisonous nature arouses the curiosity of researchers to investigate the impact of this element in human and animal metabolism. However, selenium has become the center of attention due to its physiological functions explained on the basis of its role as an active component of the enzyme glutathione peroxidase (GSH-PX), which is responsible for the animal antioxidant defense by destruction of hydrogen peroxide and lipid peroxides. Selenium metabolism and toxicity has been consistently studied in different species but data investigations on camelidae species are very limited. Our current study is configured to investigate the selenium intolerance in dromedary camel and carry out the symptoms related to continuous selenium supplementation. Investigations showed that camel is potentially sensitive to selenium excess. Several symptoms revealed by their different intensity from 3 batches, resumed in alopecia - abnormal movement and posture, breathing difficulties, prostration, diarrhea, lost of weight and nervous alteration. (Résumé d'auteur)

In four regions of Kazakhstan (Atyrau, Aralsk, Shymkent and Almaty), a survey on camel farms was achieved in order to study the variability of the physico-chemical composition of camel milk both in dromedary (Camelus dromedarius) and Bactrian (Camelus bactrianus) camel as well as their hybrids. As the whole, 163 milk samples were analyzed for calcium, phosphorus and iron determination. In order to maximize the variance, the samples were done in four different seasons which expressed the feeding change and the physiological stage changes as the calving season was concentrated in few months. The mean values were respectively 1.232 ± 0.292 g/l, 1.003 ± 0.217 g/l and 2.02 ± 1.24 mg/l for calcium, phosphorus and iron. No species, season or region effect was observed on iron content in the milk. Calcium and phosphorus change significantly according to season and species, but only phosphorus was linked to region effect. Especially phosphorus content is high in Aralsk region (1.156 ± 0.279 g/l). Globally, it is noticeable to observe the high level of phosphorus in the camel milk of Kazakhstan compared to the literature's results. (Résumé d'auteur)

Reactivity of nanopar8cles represents a central issue for many laboratories around the world. Among many supported efforts the control of the morphology of nanopar8cles is mo8vated by the fact that morphology strongly influence the proper8es of the final products. Among the vast family of available nanopar8cles, imogolite is a clay nanotube for which perfect control of the diameter is possible. Imogolites were first observed in volcanic soils[1]. They are natural aluminosilicate nanotubes having the general formula (OH)3Al2O3SiOH with a 2 nm external diameter and up to micrometers in length. The impressive monodispersity in imogolite nanotube diameter has mo8vated research on their forma8on mechanism. Synthesis protocols to produce imogolite were quickly developed. Farmer et al. were the first to obtain synthe8c imogolite using low concentra8ons of AlCl3 and SiO 2 monomers as star8ng materials (millimolar concentra8ons of the reagents) [2]. However, the produc8on of large amount of imogolite or imogolite type materials remained challenging for long 8me. We will present our most recent results concerning the possibility to produce imogolite type materials from highly concentrated stock solu8ons. We will also detail the possibility to form double wall Al- Ge nanotubes and the different stages of their forma8on [3-7]. We will then detail the surface reac8vity of these nanotubes toward metals at he lab scale as well as in natural soil. (Résumé d'auteur)

La quantification de la répartition de l'eau dans le sol et des flux hydriques est essentielle pour comprendre les relations sol eau plante. Pour les plantations d'Eucalyptus de la région de Pointe-Noire (Congo) installées sur des sols sableux très filtrants, une bonne connaissance du comportement de l'eau dans les couches supérieures de sols apparaît comme capitale pour une gestion durable des plantations d'Eucalyptus, mais aussi pour mesurer l'impact de ces plantations sur les ressources en eau de la région. L'objectif de cette étude est de paramétrer un modèle de transfert hydrique dans le sol sous trois plantations d'eucalyptus à l'aide d'un logiciel spécifique HYDRUS 1D et à des expériences de drainage interne in situ afin (i) de comparer ces trois parcelles quant à leur fonctionnement hydrique, et (ii) d'établir le bilan hydrique de peuplements d'Eucalyptus à différents stades de développement. Les résultats montrent des caractéristiques hydriques différentes pour les parcelles imputables à la géométrie et à la morphologie de l'espace poral et au passé cultural des sols. Les bilans hydriques pour les quatre stades de développement des plantations sont présentés et l'implication de ces résultats est discutée. (Résumé d'auteur)