Experimental study of linear and nonlinear regimes of density-driven instabilities induced by CO2 dissolution in water

Density driven instabilities produced by CO2 (gas) dissolution in water containing a color indicator were studied in a Hele Shaw cell. The images were analyzed and instability patterns were characterized by mixing zone temporal evolution, dispersion curves, and the growth rate for different CO2 pressures and different color indicator concentrations. The results obtained from an exhaustive analysis of experimental data show that this system has a different behaviour in the linear regime of the instabilities (when the growth rate has a linear dependence with time), from the nonlinear regime at longer times. At short times using a color indicator to see the evolution of the pattern, the images show that the effects of both the color indicator and CO2 pressure are of the same order of magnitude: The growth rates are similar and the wave numbers are in the same range (0?30 cm-1) when the system is unstable. Although in the linear regime the dynamics is affected similarly by the presence of the indicator and CO2 pressure, in the nonlinear regime, the influence of the latter is clearly more pronounced than the effects of the color indicator.Fil: Outeda, Mabel Noemi. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: El Hasi, Claudio Daniel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: D'onofrio, Alejandro Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; ArgentinaFil: Zalts, Anita. Universidad Nacional de General Sarmiento. Instituto de Ciencias. Área de Química; Argentin

The association between medical students\u27 motivation with learning environment, perceived academic rank, and burnout

Objectives: To assess the correlations between extrinsic and intrinsic motivation, personal growth and quality of life with learning environment perceptions, perceived academic rank and burnout among medical students. Methods: Cross-sectional questionnaires were administered to medical students at three medical schools in Israel, Malaysia, and China, at the end of one academic year. Surveys included demographic data, students\u27 perceived academic rank, two learning environment perceptions scales, and scales for personal growth, goal orientation, burnout and quality of life. Comparative analyses were made to determine the significance of relationships between the outcome measures and control variables, using a series of t-tests. Pearson correlation coefficients were used to test the hypothesis. Results: Sixty-four percent (400/622) of the students responded. Significant correlations were found between: intrinsic motivation (r(398) =.37, p\u3c.001); personal growth (r(398)=.62, p\u3c.001); and quality of life (r(398)= .48, p \u3c.001) with higher learning environment perceptions, intrinsic motivation (r(398)= .21, p\u3c.001); personal growth (r(398) =.21, p\u3c .001); and quality of life (r(398)=.18, p\u3c.001) with perceived academic rank, and negative correlation between personal growth (r(398) =-.38, p\u3c.001); and quality of life (r(398) =-.42, p\u3c.001) with burnout. Conclusions: Intrinsic motivation, personal growth and quality of life are correlated with higher learning environment perceptions and perceived academic rank. Burnout is influenced by personal growth and quality of life. We suggest focusing on motivation profiles before acceptance to medical school and during studies

Environmental pesticide distribution in horticultural and floricultural periurban production units

The environmental pesticide distribution on non-target systems (soil, drift and agricultural plastics) during the application stage in small periurban production units (open field and greenhouses), was studied for various crops (tomato, lettuce, broccoli, strawberry and flowers) using different pesticides (endosulfan, procymidone, chlorothalonil, chlorpyrifos and deltamethrin). In all cases, soil was the most exposed non-target system. For greenhouses, a general pesticide distribution was found of approximately 2/3 for crop, 1/4 for soil and 1/20 for plastic, of the total amount applied. In horticultural open fields, although the distribution was very dependent on the crop size and type, soil was also the most exposed non-target subsystem. Pesticide drift seems not to be significant in these production units, whilst pesticide accumulation on agricultural plastics reached up to 45% of the total applied, for polyethylene mulching in strawberry fields.Fil: Querejeta, Giselle Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Ramos, Laura Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Flores, Andrea Pamela. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Hughes, Enrique Alejandro. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Zalts, Anita. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Montserrat, Javier Marcelo. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin

Remoción de compuestos fenólicos de aguas superficiales y efluentes.

Capítulo de libroEn los últimos años, se ha llamado la atención sobre una serie de compuestos de origen antropogénico –ya sean residuos urbanos, efluentes industriales o agrícolas– que llegan a los cursos de agua superficiales, denominados contaminantes emergentes. Entre los residuos urbanos, un grupo muy importante son los provenientes de productos de cuidado personal, principalmente cosméticos y farmacéuticos.Fil: Beiguel, Érica. ICI-UNGS, Los Polvorines, Argentina. Email: [email protected]: Hughes, Enrique. ICI-UNGS, Los Polvorines, Argentina.Fil: Zalts, Anita. ICI-UNGS, Los Polvorines, Argentina.Fil: Montserrat, Javier. ICI-UNGS, Los Polvorines/CONICET, Argentina

Active Role of a Color Indicator in Buoyancy-Driven Instabilities of Chemical Fronts

Chemical reactions are able to trigger hydrodynamic flows by changing the density of the solutions across reactive interfaces. In this work, an experimental study of the buoyancy-driven hydrodynamic instabilities that can occur when two miscible reactive solutions of an acid−base system are put in contact in the gravity field shows that the patterns observed and the instabilities taking place strongly depend on the presence of a color indicator. A reaction−diffusion−convection model explains how the color indicator can modify the instability scenarios by affecting the density of the solutions and allows one to numerically recover the observed experimental patterns. The present work clearly demonstrates that color indicators should therefore be used with caution in experimental works devoted to analyze reaction−diffusion−convection patterns and instabilities.Fil: Almarcha, C.. Université Libre de Bruxelles; BélgicaFil: Trevelyan, P. M. J.. Université Libre de Bruxelles; BélgicaFil: Riolfo, L. A.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; ArgentinaFil: Zalts, Anita. Universidad Nacional de General Sarmiento. Instituto de Ciencias. Área de Química; ArgentinaFil: El Hasi, Claudio Daniel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: D'onofrio, Alejandro Gustavo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: De Wit, A.. Université Libre de Bruxelles; Bélgic

Differential diffusion effects on buoyancy-driven instabilities of acid-base fronts: The case of a color indicator

Buoyancy-driven hydrodynamic instabilities of acid-base fronts are studied both experimentally and theoretically in the case where an aqueous solution of a strong acid is put above a denser aqueous solution of a color indicator in the gravity field. The neutralization reaction between the acid and the color indicator as well as their differential diffusion modifies the initially stable density profile in the system and can trigger convective motions both above and below the initial contact line. The type of patterns observed as well as their wavelength and the speed of the reaction front are shown to depend on the value of the initial concentrations of the acid and of the color indicator and on their ratio. A reaction-diffusion model based on charge balances and ion pair mobility explains how the instability scenarios change when the concentration of the reactants are varied.Fil: Kuster, S.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; ArgentinaFil: Riolfo, L. A.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; ArgentinaFil: Zalts, Anita. Universidad Nacional de General Sarmiento; ArgentinaFil: El Hasi, C.. Universidad Nacional de General Sarmiento; ArgentinaFil: Almarcha, C.. Université Libre de Bruxelles; BélgicaFil: Trevelyan, P.M.J.. Université Libre de Bruxelles; BélgicaFil: De Wit, A.. Université Libre de Bruxelles; BélgicaFil: D'onofrio, Alejandro Gustavo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Grupo de Medios Porosos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin