992 resultados para Vi - marquèting


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El palacio conocido con el nombre de Qasr ibn Wardan se encuentra hoy día en el interior de la zona esteparia siria. Aunque nosotros nos vamos a centrar en el palacio en sí, en realidad es un complejo de edificios que también incluye una iglesia y un posible cuartel. Aparte del alto grado de conservación, su importancia radica en ser uno de los pocos ejemplos de arquitectura civil de época justinianea en todo Oriente Próximo. Redescubierto a finales del siglo xix, el palacio ha sido estudiado parcialmente desde entonces. Gracias a los trabajos de restauración llevados a cabo entre las décadas de 1970 y 1990, se pudieron volver a estudiar los restos, destacando en ello la obra de F. De’Maffei publicada en 1995. Nuestro trabajo pretende retomar el estudio de este edificio, ofrecer una restitución en 3D para una mejor comprensión de sus fases edilicias y plantear nuevas hipótesis acerca de las motivaciones que llevaron a su construcción a partir del año 561.

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Digitoitu 24. 4. 2008.

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Invocatio: [hepreaa].

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Invocatio: Q.D.B.V.

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This work describes the liquid-liquid extraction of uranium after digestion of colofanite (a fluoroapatite) from Itataia with sulfuric acid. The experiments were run at room temperature in one stage. Among the solutions tested the highest distribution coefficient (D > 60) was found for 40%vol. DEHPA (di(2-ethyl-hexyl)phosphoric acid) + 20% vol. TOPO (trioctylphosphine oxide) in kerosene. Thorium in the raffinate was quantitatively extracted by TOPO (0.1% vol.) in cyclohexane. Uranium stripping and separation from iron was possible using 1.5 mol L-1 ammonium or sodium carbonate (room temperature, one stage). However, pH control is essential for a good separation.

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Invocatio: I.N.J.A.

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Painovuosi nimekkeestä.

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Arkit: A-C4.

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Invocatio: I.N.J.

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The synthesis and characterization of crosslinked chitosan microbeads and their application in the removal of Cr(VI) are described. New kinetic and thermodynamic parameters of Cr(VI) adsorptions processes were found using continuous isothermal calorimetry. All adsorption processes are exothermic in nature. However, a multivariate statistical analysis have pointed out that adsorption enthalpies were affected by important binary interactions of the initial Cr(VI) in solution and temperature. The adsorption energetic data were well fitted to a kinetic exponential model, which have indicated fractionary adsorption kinetic orders.

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A spectrophotometric method for the indirect determination of captopril (CP) in pharmaceutical formulations is proposed. The proposed procedure is based on the oxidation of captopril by potassium dichromate and the determination excess oxidant on the basis of its reaction with diphenylcarbazide (DPC). Under the optimum conditions, a good linear relationship (r = 0.9997) was obtained in the range of 0.08-3.5 µg mL-1. The assay limits of detection and quantitation were 0.024 and 0.08 µg mL-1, respectively. The results obtained for captopril determination in pharmaceuticals using the proposed method and those obtained with the US Pharmacopoeia method were in good agreement at the 95% confidence level.

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In this work, hydrotalcite, a layered double hydroxide, had its ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe 500. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. Removal of chromium (VI) from aqueous solutions using HT-Fe 500 was achieved using batch adsorption experiments. The adsorption capacity, calculated with the Langmuir-Freundlich model showed to be dependent on temperature, reaching values of 25.93 and 48.31 mg g-1, respectively, for temperatures of 25 and 30 ºC.

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In this study, a method for determination of hexavalent chromium in aqueous samples using liquid-liquid microextraction (LLME) and detection by Flame Atomic Absorption Spectrometry (F AAS) was developed. The LLME procedure was based on the extraction of Cr (VI) by acetone at a sample pH of 1.2. The use of saturated ammonium sulphate solution allowed effective separation of the aqueous and organic phases and acetone extracted chromium. The sample pH, acetone volume and stirring time were optimized by a full factorial design.

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Effluents containing toxic metals are dangerous and more economical, efficient and environmentally friendly treatments must be studied, with the biosorption process with microbial biomass constituting an efficient solution. Thus, the ability of Spirulina platensis biomass for removing chromium (VI) using passive and active biosorption was evaluated. Inactive microalgae biomass and synthetic solution containing chromium (VI) were used to evaluate important factors in the process and biomass biosorption ability. Results of the experiments showed that microalgae have potential for biosorption of chromium (VI), attaining removal of 100.39 mg g-1, and that pH was the variable with the greatest influence on the process.

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In this study, electric arc furnace dust (EAFD) was thermally modified at different temperatures under H2 flow or charcoal in order to obtain reduced iron phases (Fe3O4, FeO and Fe0). The formation of these phases was confirmed by powder X-ray diffraction. The tests performed for reducing Cr (VI) using resultant materials obtained after thermal treatment of the EAFD showed excellent results, with PAE600H (EAFD reduced at 600 ºC under H2 flow) decreasing around 100% of the Cr (VI) in only 10 minutes of reaction. These results indicate the possibility of adding value to the residue, obtaining materials that offer great potential for environmental applications.