Effects of Chronic Exposure to Silver Nanoparticles on <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> Gills Using Biochemical Markers

Nanoparticles are among the particular materials produced by industrial activities; the release of these nanoparticles in natural ecosystems interacts with living organisms. Aquatic environment is the most common estuary waste medium for industrial and all human activities, the consequences may be highly effective on sea food species. Moreover, the potential in situ reduction of metallic ions by preexistent agents leads to nanoparticles which may cause hazardous effects. Many organisms become at risk especially those that use gills during respiration process such as bivalves. The study undertaken investigates the potential effect of silver nanoparticles obtained by green synthesis method on the gills of Ruditapes decussatus as a model. Nanoparticles have been synthesized using Ceratonia siliqua fruit extract as a reducing agent. The organisms have been chronically exposed to silver nanoparticles and the effects were biochemically evaluated. The tests performed show a typical behavior of catalase, glutathione reductase, and glutathione S-transferase activities that give information about the oxidative stress-induced malondialdehyde quantification, which reveals a possible membranous deterioration of the gills. Acetylcholinesterase expression has been qualified to be at a safe rate which implies the capacity of the animal to protect the cholinergic system.     

Surface Morphology Investigation of Tunisian Dromedary Hair

In raw materials of dromedary hair, there are two distinct fibre populations： The fine one is of textile relevance and the coarse one is rather worthless and must be as a rule separated prior to spinning and subsequent processing. The fibre surface morphology and fibre fineness of Tunisian dromedary hair has been investigated by means of scanning electron microscope （SEM）. SEM microscopic method provides the fibre diameter, the scale shape, the scale frequency and scale height. The results show that dehaired dromedary fibre presents a relatively low mean fibre diameter （≈ 17 μm） with a high coefficient of variation （CV ≈ 25%）. The scales of the dromedary fibre are on average extremely long and quite visible, they tend not to protrude from the fibre, appear almost convex, and provide a wavy appearance in profile of the relatively coarse fibre. On counting the scale frequency, that is, the number of scale margins within a determined fibre length of 100 μm on the surface of a fine （diameter 〈 30 μm） and coarse （diameter 〉 30 μm） dromedary fibre, comes out roughly five at eight and eight at twelve scale margins, respectively. The mean height of the cuticle scale is 0.12μm and 0.24 μm, respectively, for fine and coarse dromedary fibre. These explain why dromedary fibres present a soft touch due to the prominence of the scale edges. This aspect of the surface structure has a high correlation with the felting capacity of the matter, and contributes to the concepts of handle and gloss.     

Morphological and crystalline characterization of NaOH and NaOCl treated Agave americana L. fiber

This study investigates the effect of NaOH and NaOCl treatments on chemical composition, morphology and crystalline structure of Agave americana L. fibers. These fibers have been subjected to NaOCl and NaOH alkali treatments at different concentrations.The percentages of lignin and hemicellulose show a decrease with alkaline treatments which, in turn, induces a modification of both morphological and crystalline structures.Unit cell dimensions and crystallite size were more affected with NaOH treatment than NaOCl one. This may result from the mercerisation process which occurs with caustic soda treatment.The observed defibrillization on the treated fiber surface proves the dissolution of the non-cellulosic components present in the fiber cell wall by NaOH and NaOCl treatments. These morphological changes may improve the interaction between matrix and fiber in composites.