A Case Study of Sedimentation of Charged Colloids: The Primitive Model and the Effective One-Component Approach

Sedimentation-diffusion equilibrium density profiles of suspensions of charge-stabilized colloids are calculated theoretically and by Monte Carlo simulation, both for a one-component model of colloidal particles interacting through pairwise screened-Coulomb repulsions and for a three-component model of colloids, cations, and anions with unscreened-Coulomb interactions. We focus on a state point for which experimental measurements are available [C.P. Royall et al., J. Phys.: Cond. Matt. {\bf 17}, 2315 (2005)]. Despite the apparently different picture that emerges from the one- and three-component model (repelling colloids pushing each other to high altitude in the former, versus a self-generated electric field that pushes the colloids up in the latter), we find similar colloidal density profiles for both models from theory as well as simulation, thereby suggesting that these pictures represent different view points of the same phenomenon. The sedimentation profiles obtained from an effective one-component model by MC simulations and theory, together with MC simulations of the multi-component primitive model are consistent among themselves, but differ quantitatively from the results of a theoretical multi-component description at the Poisson-Boltzmann level. We find that for small and moderate colloid charge the Poisson-Boltzmann theory gives profiles in excellent agreement with the effective one-component theory if a smaller effective charge is used. We attribute this discrepancy to the poor treatment of correlations in the Poisson-Boltzmann theory.Comment: 9 pages, 7 figure

Uncertainty propagation in neuronal dynamical systems

One of the most notorious characteristics of neuronal electrical activity is its variability, whose origin is not just instrumentation noise, but mainly the intrinsically stochastic nature of neural computations. Neuronal models based on deterministic differential equations cannot account for such variability, but they can be extended to do so by incorporating random components. However, the computational cost of this strategy and the storage requirements grow exponentially with the number of stochastic parameters, quickly exceeding the capacities of current supercomputers. This issue is critical in Neurodynamics, where mechanistic interpretation of large, complex, nonlinear systems is essential. In this paper we present accurate and computationally efficient methods to introduce and analyse variability in neurodynamic models depending on multiple uncertain parameters. Their use is illustrated with relevant example

Identification of Main Causes of Student Dropout at Universidad Libre: Design of a Predictive Model.

Este estudio se centra en la problemática de la deserción estudiantil en las instituciones de educación superior y busca abordar la falta de herramientas eficaces para identificar a tiempo desertores. Para ello, se utilizó la analítica de datos para desarrollar un modelo predictivo que permita identificar tempranamente a los estudiantes que probablemente no finalicen sus estudios universitarios en la facultad de ingeniería de la Universidad Libre y determinar las variables que conllevan a la deserción. Apoyado en la metodología CRISP-DM como guía para llevar a cabo el proceso, se recopilaron datos de los sistemas de información de la universidad con los cuales se entrenaron tres algoritmos de aprendizaje supervisado. El algoritmo Support Vector Machine (SVM) obtuvo la mejor puntuación en la métrica seleccionada para medir la pertinencia de cada modelo. Los resultados sugieren que variables como el rendimiento académico, la situación económica tanto personal como familiar, el nivel de escolaridad de los padres y aspectos psicológicos son factores importantes en la deserción estudiantil en la facultad de ingeniería. En conclusión, este estudio demuestra que la analítica de datos es una herramienta valiosa para la identificación temprana de posibles desertores y puede ayudar a la institución a tomar decisiones para prevenir la deserción y permitir que los estudiantes completen sus estudios universitarios.Universidad Libre -- Facultad de Ingenierías -- Maestría en Ingeniería con Énfasis en Analítica de DatosThis study focuses on the problem of student dropout in institutions of higher education and seeks to address the lack of effective tools to identify potential dropouts in a timely manner. To this end, data analytics was used to develop a predictive model that allows for the early identification of students who are likely not to complete their university studies in the Faculty of Engineering at Universidad Libre and to determine the variables that contribute to dropout. Supported by the CRISP-DM methodology as a guide to carry out the process, data were collected from the university's information systems and used to train three supervised learning algorithms. The Support Vector Machine (SVM) algorithm obtained the highest score in the metric selected to measure the relevance of each model. The results suggest that variables such as academic performance, personal and family economic situation, parents' level of education, and psychological aspects are important factors in student dropout in the Faculty of Engineering. In conclusion, this study demonstrates that data analytics is a valuable tool for the early identification of potential dropouts and can help the institution make decisions to prevent dropout and enable students to complete their university studies

The polydisperse cell model: Non-linear screening and charge renormalization in colloidal mixtures

We propose a model for the calculation of renormalized charges and osmotic properties of mixtures of highly charged colloidal particles. The model is a generalization of the cell model and the notion of charge renormalization as introduced by Alexander and his collaborators (J. Chem. Phys. 80, 5776 (1984)). The total solution is partitioned into as many different cells as components in the mixture. The radii of these cells are determined self-consistently for a given set of parameters from the solution of the non-linear Poisson-Boltzmann equation with appropriate boundary conditions. This generalizes Alexanders's model where the (unique) Wigner-Seitz cell radius is fixed solely by the colloids packing fraction. We illustrate the technique by considering a binary mixture of colloids with the same sign of charge. The present model can be used to calculate thermodynamic properties of highly charged colloidal mixtures at the level of linear theories, while taking the effect of non-linear screening into account

Aproximaciones teóricas sobre el desarrollo del pensamiento numérico en educación primaria

El artículo aborda la relación y representación de números racionales (fraccionarios y decimales), como contenido fundamental en la práctica didáctica de la educación primaria en el área de Matemáticas. Describe los aportes teóricos de la pedagogía, la sociología, la ontología, la semiótica y la didáctica; así como algunas reflexiones sobre el pensamiento numérico dentro del contexto de Escuela Nueva, obtenidas a partir del desarrollo de una investigación que se desarrolla con un grupo de estudiantes de los grados cuarto y quinto de Básica Primaria en la Institución Educativa Técnica Ramón Ignacio Avella, acerca de la representación decimal y fraccionaria de números racionales. Finalmente, se describe un ejemplo sobre la aplicación de una actividad desarrollada en una secuencia didáctica

Identificación de las áreas aptas para la agricultura extensiva en el municipio del Espinal-Tolima

En la escuela de ciencias agrícolas, pecuarias y del medio ambiente, en el programa de agronomía de la universidad nacional abierta y a distancia UNAD en ejecución con el diplomado de sistemas de información geográfica para el ordenamiento agroambiental del territorio, se realizó varias actividades para el modelamiento y desarrollo territorial de tipo agrícola, ambiental y climático, empleando el análisis de datos y técnicas de modelamiento para proyectar un mapa con una finalidad que es el análisis de varios aspectos técnicos como las coberturas del territorio, la proyección geográfica,atributos. Recopilando a la información necesaria y empleando las herramientas que senecesitan para el diseño de un modelo de datos preciso y que se pueda interpretar, con la finalidad de identificar esas áreas que sean aptas para la agricultura extensiva ya que es una de las principales fuentes de trabajo y economía del municipio del Espinal.In the school of agricultural, livestock and environmental sciences, in the agronomy program of the national open and distance university UNAD in execution with the diploma in geographic information systems for the agro-environmental planning of the territory, several activities were carried out for modeling and territorial development of an agricultural, environmental and climatic type, using data analysis and modeling techniques to project a map with a purpose that is the analysis of various technical aspects such as territory coverage, geographic projection, attributes. Gathering the necessary information and using the tools needed to design an accurate and interpretable data model, with the aim of identifying those areas that are suitable for extensive agriculture since it is one of the main sources of work. and economy of the municipality of Espinal

XVI International Congress of Control Electronics and Telecommunications: "Techno-scientific considerations for a post-pandemic world intensive in knowledge, innovation and sustainable local development"

Este título, sugestivo por los impactos durante la situación de la Covid 19 en el mundo, y que en Colombia lastimosamente han sido muy críticos, permiten asumir la obligada superación de tensiones sociales, políticas, y económicas; pero sobre todo científicas y tecnológicas. Inicialmente, esto supone la existencia de una capacidad de la sociedad colombiana por recuperar su estado inicial después de que haya cesado la perturbación a la que fue sometida por la catastrófica pandemia, y superar ese anterior estado de cosas ya que se encontraban -y aún se encuentran- muchos problemas locales mal resueltos, medianamente resueltos, y muchos sin resolver: es decir, habrá que rediseñar y fortalecer una probada resiliencia social existente - producto del prolongado conflicto social colombiano superado parcialmente por un proceso de paz exitoso - desde la tecnociencia local; como lo indicaba Markus Brunnermeier - economista alemán y catedrático de economía de la Universidad de Princeton- en su libro The Resilient Society…La cuestión no es preveerlo todo sino poder reaccionar…aprender a recuperarse rápido.This title, suggestive of the impacts during the Covid 19 situation in the world, and which have unfortunately been very critical in Colombia, allows us to assume the obligatory overcoming of social, political, and economic tensions; but above all scientific and technological. Initially, this supposes the existence of a capacity of Colombian society to recover its initial state after the disturbance to which it was subjected by the catastrophic pandemic has ceased, and to overcome that previous state of affairs since it was found -and still is find - many local problems poorly resolved, moderately resolved, and many unresolved: that is, an existing social resilience test will have to be redesigned and strengthened - product of the prolonged Colombian social conflict partially overcome by a successful peace process - from local technoscience; As Markus Brunnermeier - German economist and professor of economics at Princeton University - indicates in his book The Resilient Society...The question is not to foresee everything but to be able to react...learn to recover quickly.Bogot

Sine-Gordon field theory for the calculatión of universal finite size corrections in the free energy of Coulomb systems at the Debye-Hückel regime

Magíster en FísicaMaestrí