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Amperometric sensor for determination of oxygen permeability of polymer membranes: applications in the field of contact lenses and food wrapping films.
No full textTHE REDUCTION PROCESS OF COPPER-ZINC OXIDE-(ALUMINA) METHANOL CATALYSTS
No full textCuO-ZnO-Al2O3 catalysts at different copper and zinc contents were obtained by thermal decomposition of hydroxycarbonate precursors at 350°C in air. They were characterized by using X-ray diffraction, diffuse reflectance spectroscopy and surface area determination. We find disticnt CuO and ZnO phases whose particle sizes, determined by XRD line broadening, are in the range 65-90 Å for CuO and around 100 Å for ZnO in the binary CuO/ZnO systems. For pure CuO the particle dimensions are higher (D~140 A ̊). For the three component oxide, CuO|ZnO|Al2O3=60|30|10, the particle sizes of both CuO and ZnO phases are around 60 Å. The BET surface areas are around 70 m2/g for the two components oxides, ~40 for pure CuO and for the three component systems. The reduction of the copper oxide (CuO) has been studied by in situ XRD. The reduction to metallic copper proceeds through the formation of intermediate Cu2O which is present together with metallic copper even at relatively high extents of reduction. It has also been observed that the reduction process is much slower in the three component system than for pure CuO or the two component, CuO-ZnO, system. The presence of alumina in intimate contact with CuO and ZnO (due to the preparation conditions of the precursors) thus seems to hinder the reduction of the Cu2+ species (to Cu+ or Cuo) and to prevent the nucleation of both cuprous oxide and metallic copper partcles. © 1989
Tyrosinase inhibition organic phase biosensor for triazinic and benzotriazinic pesticide analysis (part two)
No full textSeveral triazine pesticides, such as atrazine, are much more soluble in several organic solvents, such as chloroform, than in water. Our recent research was aimed at analyzing this class of pesticides using tyrosinase OPEE (organic phase enzyme electrodes), exploiting their inhibiting action on the tyrosinase enzyme when operating in water-saturated chloroform medium. In this work we studied the response of a tyrosinase inhibition enzyme sensor to several triazinic (simazine, propazine, terbuthylazine) and benzotriazinic (azinphos-ethyl and azinphos-methyl) pesticides (LOD=0.5x10(-9) mol l(-1)). Recovery trials were also performed in vegetal matrixes (corn, barley, lentils). Lastly, the effect of the solvent (chloroform or water) on the inhibition process was investigated via Hill's equation and the diffusion of analyte from the solvent to the enzyme membrane
Study of toxicity and variation in polyphenol and hydroperoxide content of food oils subjected to thermal stress or used for frying foodstuffs
No full textAn investigation was made of variations over time in the toxicity of extra-virgin olive oil and peanut oil subjected to thermal stress (160-180degreesC) or used to fry potatoes at 160degreesC. In parallel, variations in polyphenol concentration and in that of hydroperoxides were monitored. Measurements were carried out using a suitable toxicity measuring device consisting of an oxygen sensor + yeast cells or enzymatic biosensors, for the phenols and hydroperoxides, respectively
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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