Solubility of gases in fluoroorganic alcohols. Part III. Solubilities of several non-polar gases in water¿+¿1, 1, 1, 3, 3, 3-hexafluoropropan-2-ol at 298.15¿K and 101.33¿kPa

Solubilities of the non-polar gases H2, N2, O2, CH4, C2H6, C2H4, CF4, SF6, and CO2 in the mixture (water + 1, 1, 1, 3, 3, 3-hexafluoropropan-2-ol) at the temperature of 298.15 K and 101.33 kPa partial pressure of gas are reported. A polynomial dependence of the solubilities on the molar fraction of the binary liquid mixture is found. The Henry''s constants at the vapor pressure of water, the standard changes in the Gibbs energy for the solution process and for the solvation process, and the so-called excess Henry''s constant are calculated. The results have been compared with those obtained by Scaled Particle Theory (SPT). A method to compare the solubility of a gas in different liquids is proposed and applied to 2, 2, 2-trifluoroethanol and 1, 1, 1, 3, 3, 3-hexafluoropropan-2-ol

Thermophysical and volumetric study of mixtures {p-cymene¿+¿propan-1-ol} at several temperatures and atmospheric pressure. Modeling with COSMO-RS

Experimental isobaric molar heat capacities at atmospheric pressure have been determined for the mixture {p-cymene + propan-1-ol} every 10 K in the temperature interval (298.8–328.5) K and over the entire composition range with a Calvet type calorimeter. Densities, necessary for calculating heat capacities, have been also measured in similar conditions. Excess molar volumes have been calculated from densities. They are positive at (318.15 and 328.15) K and sigmoidal at (298.15 and 308.15) K with negative values in the zone very rich in propan-1-ol. Excess molar heat capacities have been calculated from the molar heat capacities and show positive values. Both excess molar properties increase as the temperature rises at a given molar fraction. Excess properties are discussed in terms of intermolecular interactions. The solvation model COSMO-RS has been applied to predict the excess molar heat capacities, being the quantitative predictions rather poor

Solubilities of gases in cycloethers. The solubility of 13 nonpolar gases in 2, 5-dimethyltetrahydrofuran at 273.15 to 303.15¿K and 101.32¿kPa

The solubilities of gases in liquids are interesting, not only from a practical point of view, but also because they provide a rigorous touchstone to test the structural models on the liquid state. In this work the solubilities of 13 nonpolar gases, He, Ne, Ar, Kr, Xe, H2, D2, N2, CH4, C2H4, C2H6, CF4, and SF6, in 2, 5-dimethyltetrahydrofuran at five temperatures between (273.15 and 303.15) K and 101.32 kPa partial pressure of gas were measured and the associated thermodynamic functions were calculated. Correlation of data has been made and the capacity of prediction of several typical molecular models of liquids, namely, SPT model, perturbation theory, UNIFAC and COSMO-RS, specifically applied to gas solubilities, has been checked

Effects of the insecticide fipronil in freshwater model organisms and microbial and periphyton communities

Fipronil is a broad-spectrum insecticide whose release in the environment damages many non-target organisms. This study evaluated the toxicity of fipronil at two biological levels using in vivo conditions and environmentally relevant concentrations: the first based on two model organisms (aquatic invertebrate Daphnia magna and the unicellular freshwater alga Chlamydomonas reinhardtii) and a second based on three natural communities (river periphyton and freshwater and soil microbial communities). The physicochemical properties of fipronil make it apparently unstable in the environment, so its behaviour was followed with high performance liquid chromatography (HPLC) under the different test conditions. The most sensitive organism to fipronil was D. magna, with median lethal dose (LC50) values from 0.07 to 0.38 mg/L (immobilisation test). Toxicity was not affected by the media used (MOPS or river water), but it increased with temperature. Fipronil produced effects on the photosynthetic activity of C. reinhardtii at 20 °C in MOPS (EC50 = 2.44 mg/L). The freshwater periphyton presented higher sensitivity to fipronil (photosynthetic yield EC50 of 0.74 mg/L) in MOPS and there was a time-dependent effect (toxicity increased with time). Toxicity was less evident when periphyton and C. reinhardtii tests were performed in river water, where the solubility of fipronil is poor. Finally, the assessment of the metabolic profiles using Biolog EcoPlates showed that bacteria communities were minimally affected by fipronil. The genetic identification of these communities based on 16S rRNA gene sequencing revealed that many of the taxa are specialists in degrading high molecular weight compounds, including pesticides. This work allows us to better understand the impact of fipronil on the environment at different levels of the food chain and in different environmental conditions, a necessary point given its presence in the environment and the complex behaviour of this compound

Molar heat capacities of the mixture {1, 8-cineole + ethanol} at several temperatures and atmospheric pressure

Molar heat capacities at atmospheric pressure have been determined every 5 K for the mixture {1, 8-cineole (1) + ethanol (2)} in the temperature interval (304.7 to 324.5) K and the whole composition range with a Calvet type calorimeter Setaram C80. From the molar heat capacities, excess molar heat capacities have been calculated, their values being positive and increasing as the temperature rises. The solvation model COSMO-RS has been applied to predict the excess molar heat capacities. The model overestimates the values of the excess heat capacities but predicts well the trend of variation of the excess molar heat capacity with the temperature

Supercritical Extraction and Separation of Antioxidants from Residues of the Wine Industry

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Brucellosis in Sub-Saharan Africa:Current challenges for management, diagnosis and control

Brucellosis is a highly contagious zoonosis caused by bacteria of the genus Brucella and affecting domestic and wild mammals. In this paper, the bacteriological and serological evidence of brucellosis in Sub-Saharan Africa (SSA) and its epidemiological characteristics are discussed. The tools available for the diagnosis and treatment of human brucellosis and for the diagnosis and control of animal brucellosis and their applicability in the context of SSA are presented and gaps identified. These gaps concern mostly the need for simpler and more affordable antimicrobial treatments against human brucellosis, the development of a B. melitensis vaccine that could circumvent the drawbacks of the currently available Rev 1 vaccine, and the investigation of serological diagnostic tests for camel brucellosis and wildlife. Strategies for the implementation of animal vaccination are also discussed.Publishe

Formación de conceptos : estrategias y niveles al finalizar el preescolar

Desde el modelo piagetiano el estudio ha intentado definir los modelos utilizados por los niños para conceptualizar, lo que denominamos estrategias de conceptualización. 244 niños de cinco años y medio de 30 centros escolares de Aragón. Variables: sexo, tipo de centro y medio social, empleo de técnicas gráficas y entrevista clínica para estudiar la variable 'nivel de abstracción'. Los datos se han obtenido por medio de dos pruebas complementarias: la primera gráfica (dibujo de una mano, la lluvia y el colegio) y la segunda verbal (definición de cada uno de los conceptos y comparación con otros dibujos). Tablas de convergencia, Test de Chi cuadrado, Test Cramer y T de Student. En algunos casos se ha utilizado análisis de varianza. El estudio se ha realizado con el paquete SPSS. En la fase totalmente espontánea de la prueba el niño se mantiene en el nivel de conceptualización puramente externo -figural- en las áreas de experiencia personal -manos-, natural -lluvia- y social -colegio-. El grupo urbano de la muestra trabaja a un nivel de abstracción funcional y por tanto más abstracto que los subgrupos rural y semiurbano. Asimismo, el grupo urbano pone de manifiesto un conocimiento semánticamente más rico que los otros dos grupos de la muestra en los conceptos objeto de la investigación. Se ha comprobado que en la medida en que se domina más ampliamente el nivel de abstracción inferior se favorece el conocimiento de niveles superiores, así, se comprende los atributos 'funcionales' en la medida en que se demuestra dominar los 'figurales' -externos-. Se ha intentado proponer las bases necesarias para que los profesores puedan planificar con fundamentación realista sus programaciones escolares, tanto en el nivel preescolar como en el ciclo inicial.AragónES

Supercritical extraction and supercritical antisolvent fractionation of natural products from plant material: Comparative results on Persea indica

Supercritical fluids (SCFs) are alternative solvents in the field of Green Chemistry that are being developed as advanced separation techniques due to their combined properties such as the penetrability of a gas and the solvent power of a liquid. These characteristics are used in the supercritical fluid extraction (SFE), where compounds of interest can be extracted after mixing a SCF as a solvent with a matrix in a pressurized vessel. Supercritical antisolvent fractionation (SAF) uses the SCF as antisolvent, allowing for the precipitation of insoluble compounds in the SCF-organic solution mixture. An updated overview of SFE and SAF of natural products is presented in this article. Additionally we compare the results of SFE, SAF and organic soxhlet extraction (OSE) of Persea indica, a Macaronesian paleoendemism with strong insecticidal components. The composition of the extracts was analyzed by HPLC-MS, showing in the SFE extracts as major components ryanodol, cinnzeylanol and alkyl-γ-lactones, with their abundance varying with the extraction conditions. On the other hand, the SAF allowed for the fractionation of a liquid solution to give a ryanodol enriched extract (31 % more ryanodol than the initial ethanolic solution). The antifeedant and postingestive effects of these extracts on Spodoptera littoralis showed that the SAF extracts were the most active followed by SFE and OSE and their different effects can be partially explained by their composition.This work has been supported by grant MICINN-FEDER CTQ2009-14629-C01-02 and Departamento de Medio Ambiente del Cabildo de Tenerife and Gobierno de Aragon-Fondo Social Europeo (group E52). L. Martín acknowledges a FPU grant and V. Vallejo a JAE-CSIC grant