Influencia de la estructura electrohidrodinámica de la interfase sólido-líquido en la viscosidad de suspensiones coloidales diluidas

Tesis Univ. Granada

Electrothermoplasmonic flow in gold nanoparticles suspensions: nonlinear dependence of flow velocity on aggregate concentration

Efficient mixing and pumping of liquids at the microscale is a technology that is still to be optimized. The combination of an AC electric field with a small temperature gradient leads to a strong electrothermal flow that can be used for multiple purposes. Combining simulations and experiments, an analysis of the performance of electrothermal flow is provided when the temperature gradient is generated by illuminating plasmonic nanoparticles in suspension with a near-resonance laser. Fluid flow is measured by tracking the velocity of fluorescent tracer microparticles in suspension as a function of the electric field, laser power, and concentration of plasmonic particles. Among other results, a non-linear relationship is found between the velocity of the fluid and particle concentration, which is justified in terms of multiple scattering-absorption events, involving aggregates of nanoparticles, that lead to enhanced absorption when the concentration is raised. Simulations provide a description of the phenomenon that is compatible with experiments and constitute a way to understand and estimate the absorption and scattering cross-sections of both dispersed particles and/or aggregates. A comparison of experiments and simulations suggests that there is some aggregation of the gold nanoparticles by forming clusters of about 2–7 particles, but no information about their structure can be obtained without further theoretical and experimental developments. This nonlinear behavior could be useful to get very high ETP velocities by inducing some controlled aggregation of the particles.This research has been supported by Consejería de Universidad, Investigación e Innovación de la Junta de Andalucía and FEDER, “Una manera de hacer Europa”/Projects P18-FR-3583 and FQM-410-UGR18, Ministerio de Ciencia, Innovación y Universidades through Project EQC2018-004693-P, and Grant PID2021-127427NB-I00/ MCIN/AEI/10.13039/501100011033/FEDER,UE. Funding for open access charge: Universidad de Málaga/CBUA

Optical performance analysis of the Copenhagen solar cooker with COMSOL Multiphysics

The Copenhagen solar cooker is a compact, panel-type design with four flexible reflective panels to redirect solar radiation onto a cooking pot. The geometric configuration of the panels is adjustable, depending on the sun elevation angle. Despite the simplicity of the concept, the resulting curved reflector geometries do not align with any analytical surface, posing a modeling challenge. This work introduces an innovative approach: COMSOL Multiphysics structural mechanics simulation is used to emulate the manual folding process of the reflector panels, in order to create accurate geometric models of the two most used configurations: Ninety and Flower. Then, the COMSOL ray optics module is used to characterize the optical performance of the generated Copenhagen solar cooker models. A large number of studies are presented, of interest both to the practical user who wants to optimize the use of their Copenhagen cooker and to the designer looking for future optimizations. This is the first work in scientific literature that analyzes the optical system of the Copenhagen solar cooker

ESTUDIO QUÍMICO DE LA CORTEZA DE Remijia peruviana “Cascarilla”

En el presente trabajo se realizó el análisis cualitativo de los metabolitos secundarios y la cuantificación e identificación de los alcaloides presentes en la corteza de Remijia peruviana, la cual forma parte de la familia Rubiaceae, caracterizada por sintetizar mayoritariamente alcaloides. Se ha aislado y determinado la estructura química de cinco alcaloides quinolínicos: tres nuevos derivados, Quinina acetato (1), Quinina alcohol (2) y N-Etil Quinina (3); y dos reportados anteriormente en la literatura: Quinina (4) y Cinchonina (5). La estructura de los nuevos alcaloides fueron elucidados por análisis básicos de espectroscopía RMN, incluyendo correlaciones homonuclear y heteronuclear (COSY, NOESY, HMBC y HSQC)

General electrokinetic model for concentrated suspensions in aqueous electrolyte solutions: electrophoretic mobility and electrical conductivity in static electric fields

In recent years different electrokinetic cell models for concentrated colloidal suspensions in aqueous electrolyte solutions have been developed. They share some of its premises with the standard electrokinetic model for dilute colloidal suspensions, in particular, neglecting both the specific role of the so-called added counterions (i.e., those released by the particles to the solution as they get charged), and the realistic chemistry of the aqueous solution on such electrokinetic phenomena as electrophoresis and electrical conductivity. These assumptions, while having been accepted for dilute conditions (volume fractions of solids well below 1 %, say), are now questioned when dealing with concentrated suspensions. In this work, we present a general electrokinetic cell model for such kind of systems, including the mentioned effects, and we also carry out a comparative study with the standard treatment (the standard solution only contains the ions that one purposely adds, without ionic contributions from particle charging or water chemistry). We also consider an intermediate model that neglects the realistic aqueous chemistry of the solution but accounts for the correct contribution of the added counterions. The results show the limits of applicability of the classical assumptions and allow one to better understand the relative role of the added counterions and ions stemming from the electrolyte in a realistic aqueous solution, on electrokinetic properties. For example, at low salt concentrations the realistic effects of the aqueous solution are the dominant ones, while as salt concentration is increased, it is this that progressively takes the control of the electrokinetic response for low to moderate volume fractions. As expected, if the solids concentration is high enough the added counterions will play the dominant role (more important the higher the particle surface charge), no matter the salt concentration if it is not too high. We hope this work can help in setting up the real limits of applicability of the standard cell model for concentrated suspensions by a quantitative analysis of the different effects that have been classically disregarded, showing that in many cases they can be determinant to get rigorous predictions.Financial supports for this work by MICINN, Spain (projects FIS2010- 18972, FIS2013-47666-C3-1R, 2R, 3R) and Junta de Andalucía, Spain (project P2012-FQM-694), co-financed with FEDER (European Fund for Regional Development) funds by the EU

Use of dietary supplements by pregnant women in Colombia

Background: During pregnancy, the need for certain nutrients increases. This study assessed the prevalence and socio-demographic factors associated with dietary supplement use in a representative sample of pregnant women in Colombia. Method: Data for this study were obtained from a cross-sectional, nationally representative survey (ENSIN, 2010). A total of 1856 pregnant women, 13–49 years of age, were recruited. The use of prenatal dietary supplements (Vitamins A, C or E) was treated as a binary outcome (used at some time or never sued during pregnancy when prescribed by a doctor) in multinomial analyses. Sociodemographic data and associated factors were assessed by computer-assisted personal interview technology. Results: Of the sample, 1123 women (68.6%) reported taking prenatal dietary supplements at some stage during their pregnancy. Most users had a high socioeconomic level (79.5%), were in their third trimester of pregnancy (79.5%), were 30–49 years of age (74.0%), and lived in the central region of Colombia (73.8%). The multivariate logistic regression showed that third trimester of pregnancy (OR 6.2;95% CI 4.0 to 9.3), high educational level (OR 2.3; 95% CI 1.5 to 3.4), high socioeconomic level -SISBEN IV or more- (OR 2.0; 95% CI 1.4 to 2.8), residence in the Atlantic region (north) (OR 2.6; 95% CI 1.7 to 3.6), Eastern region (OR 2.0; 95% CI 1.3 to 3.1), central region (OR 2.6; 95% CI 1.7 to 3.9), Pacific region (west) (OR 1.5; 95% CI 1.0 to 2.3), and belonging to the mestizo (others) ethnic group (OR 1.2; 95% CI 1.0 to 2.6), were all associated with a higher probability of dietary supplement intake. Conclusion: The prevalence of prenatal dietary supplements in pregnant women in Colombia was found to be substantial. The variables significantly associated with their use were educational level, socioeconomic level, trimester of pregnancy, geographic level and ethnic group. These results indicate the necessity of implementing new health policies that guarantee uniform access to nutritional supplements for all population sectors, especially in countries, such as Colombia, who are currently undergoing a process of nutritional transition.The ENSIN was funded by the Colombian Institute of Family Welfare (ICBF, for its initials in Spanish) and was conducted during the years 2008–2010. The funding had no role in the study design, in the collection, analysis, and interpretation of data, in the writing of the manuscript, or in the decision to submit the manuscript for publication

Ion size effects on the electrokinetics of salt-free concentrated suspensions in ac fields

We analyze the influence of finite ion size effects in the response of a salt-free concentrated suspension of spherical particles to an oscillating electric field. Salt-free suspensions are just composed of charged colloidal particles and the added counterions released by the particles to the solution, that counterbalance their surface charge. In the frequency domain, we study the dynamic electrophoretic mobility of the particles and the dielectric response of the suspension. We find that the Maxwell-Wagner-O'Konski process associated with the counterions condensation layer, is enhanced for moderate to high particle charges, yielding an increment of the mobility for such frequencies. We also find that the increment of the mobility grows with ion size and particle charge. All these facts show the importance of including ion size effects in any extension attempting to improve standard electrokinetic models.Comment: J. Colloid Interface Sci., in press, 13 pages, 9 figure

Metodologías Activas para los “Cuidados de enfermería en el adulto con problemas en la eliminación urinaria y digestiva” de la asignatura Enfermería del Adulto III. Realidad Virtual para el marcaje del estoma

Dentro de la asignatura Enfermería de Adulto III hay un contenido denominado “Cuidados de enfermería en el adulto con problemas en la eliminación urinaria y digestiva”. El cuidado del estoma digestivo es una intervención principalmente de enfermería, por lo tanto, su formación y capacitación en este campo es imprescindible para garantizar la autonomía en los pacientes con estoma digestivo. Así pues, se hace necesaria la búsqueda y el establecimiento de las mejores prácticas pedagógicas para mejorar el aprendizaje y potenciar la formación de los alumnos de Grado en Enfermería para un desempeño autónomo y pertinente a las demandas sociales vinculadas al autocuidado de los pacientes con estoma digestivo. Por esta razón se elabora el presente proyecto, cuyo objetivo principal consiste en implementar las metodologías activas (MA) como estrategia didáctica para mejorar el nivel de enseñanza/aprendizaje en los estudiantes de Grado en Enfermería en el abordaje de las personas con estoma digestivo y analizar si estas metodologías mejoran su aprendizaje. Dentro de la gran variedad de métodos de aprendizaje activo, se ha seleccionado el Flipped Classroom (aula invertida), la Gamificación y la Realidad Virtual. El interés en estas MA se debe a su carácter innovador y por estar en pleno apogeo didáctico, además de los resultados relevantes mostrados en diferentes acciones formativas y los múltiples beneficios para el desarrollo del aprendizaje del alumno. Para alcanzar los objetivos propuestos, se organizará un seminario que se impartirá en los Campus Universitarios de Ceuta, Melilla y Granada. En una primera sesión se presentará el proyecto a los docentes encargados de la asignatura y se tendrá una primera toma de contacto con los alumnos, explicándoles cómo se va a desarrollar la acción formativa, así como la posibilidad de otorgar o no su consentimiento de participación. Tras finalizar la experiencia se llevará a cabo la evaluación de los resultados obtenidos, así como el impacto que han tenido las sesiones en los estudiantes a través de una encuesta de satisfacción