Design of novel adsorption processes for the removal of arsenic from polluted groundwater employing functionalized magnetic nanoparticles

For many developing countries, groundwater is the main source for water consumption in rural and urban areas. The occurrence of arsenic in groundwater is an environmental problem due to its high toxicity. Although the removal of arsenic by different technologies has been proven, adsorption is one of the best alternatives due to its simplicity and low cost. In particular, nanoadsorbents incorporating magnetic properties are promising separation agents because of their advantageous and efficient potential recovery in a magnetic field, characteristic that is very attractive and of utmost relevance in the development of low cost technologies to provide drinking water in developing countries. In this work, Fe3O4 and Fe3O4/SiO2 magnetic nanoparticles functionalized by amino derivatives coordinated with Fe3+ were synthesized and characterized and further evaluated as adsorbents to remove arsenate from groundwater. The adsorption equilibrium of As5+ was satisfactorily described at 298 K by the Langmuir model with the following parameters: a) Fe3O4: qm=20.4±0.3 mg g-1 and KL=0.373±0.003 L mg-1 and b) Fe3O4/SiO2: qm=121±4.1 mg g-1 and KL=0.383±0.066 L mg-1. At low arsenate concentrations, 50-1000 µg L-1, the adsorption equilibrium As5+-Fe3O4/SiO2 was described by linear isotherms with equilibrium parameters KH=278.8 L g-1 in monocomponent systems and KH=1.80 L g-1 in the presence of competing ions, being carbonate and especially phosphate the main species affecting the process with contributions to the loss of efficacy around 70%. Finally, the material reuse after regeneration with NaOH 10-3 mol L-1 d was assessed under several composition scenarios reaching adsorption yields similar to those obtained with fresh materials.Financial support from the Spanish Ministry of Economy and Competitiveness under the project CTQ2012-31639 (FEDER 2007-2013) is gratefully acknowledged

Toward fluorinated aminoglycosides: Structural studies of phenylhydrazine condensation with carbohydrate derivatives

The reaction of phenylhydrazine with a sugar dialdehyde in water, as a key step for the synthesis of the 3-amino-3-deoxy-d-glucose moiety contained in kanamycin, has been revisited. Structural studies (IR and NMR as well as a simple theoretical model based on energy-minimization calculations and MD calculations) reported herein support the observed stereo- and regioselectivity. Efforts to improve the reproducibility and viability of the process as part of a convenient approach towards fluorinated kanamycin are also now presented.Agencia Española de Cooperación Internacional para el Desarrollo A/023577/09 A/030422/10Junta de Andalucía FQM 142 P09-AGR-459

A novel approach to the synthesis of N-substituted 1-C-aminomethyl glycofuranosides

Reductive amination of formyl C-glycofuranosides, easily available from hexose-derived equatorial-2-OH-glycopyranosides by DAST-promoted ring contraction, afforded N-substituted 1-C-aminomethyl glycofuranosides in most cases in high yield.European Commission, Directorate General for Science and Development FP6-508430Junta de Andalucía FQM14

Estrategias pedagógicas para propiciar ambientes de aprendizaje que promuevan la indagación como competencia científica en estudiantes de grado segundo.

La investigación surge de la necesidad de dar una mirada a los ambientes de aprendizaje áulicos que perturban a los estudiantes del grado 2-1 de la institución Juan María Céspedes de Tuluá, sede Jorge Eliecer Gaitán, no solo desde lo físico, sino también desde lo pedagógico, ya que es una problemática que afecta el proceso educativo, tanto desde lo comunicativo como del aprendizaje de las ciencias y la relación con el entorno. Lo anterior conlleva, a considerar la competencia indagatoria, con el fin de que los estudiantes desarrollen su capacidad de análisis, sentido crítico y mejoren su capacidad de escucha y actitud frente a como les afecta el ambiente áulico. Para tal fin, se plantea una metodología cualitativa, con enfoque Investigación Acción, la cual nos permite una mirada reflexiva de la acción pedagógica, desde la propuesta de María Elena Chan (2004). Luego con la observación constante y la sistematización en los diarios de campo las maestras investigadoras, diseñaron e implementaron estrategias pedagógicas que permitieron caracterizar que la presencia del ruido es un factor distractor que afecta el ambiente de aprendizaje en el aula. Finalmente, mediante la triangulación de fuentes se caracterizan e identifican cuáles estrategias son las más indicadas para propiciar ambientes positivos de aprendizajes y a su vez promover la capacidad de indagación en los niños.MaestríaMAGISTER EN EDUCACIÓN ÉNFASIS EN EDUCACIÓN MATEMÁTICAS Y CIENCIAS EXPERIMENTALES (TULUÁ

Estudio de mercado para la comercialización de las marcas de harinas de HARINISA en el departamento de Carazo.

Presenta los resultados de un investigación de mercado para la comercialización de las marcas de harinas de HARINISA en el departamento de Carazo, abarca el análisis del entorno atingente a la inversión, condiciones actuales de funcionamientos del mercado en el sector de panaderías y características de los consumidores

Easy Access to Configurationally Controlled C-Glycofuranoside-Based Building Blocks by Means of Formyl C-Glycofuranosides

A general approach to enantiopure C-glycofuranoside-based hybridα/β-amino acids and nitrones, among other valuable building blocks, has been established via formyl C-glycofuranosides, easily available from hexose-derived equatorial-2-OH-glycopyranosides by DAST-promoted ring contraction. © Georg Thieme Verlag Stuttgart New York.European Commission. Directorate General for Science and Development FP6-508430Junta de Andalucía FQM14

Innermost stable circular orbits around magnetized rotating massive stars

In 1998, Shibata and Sasaki [Phys. Rev. D 58, 104011 (1998)] presented an approximate analytical formula for the radius of the innermost stable circular orbit (ISCO) of a neutral test particle around a massive, rotating and deformed source. In the present paper, we generalize their expression by including the magnetic dipole moment. We show that our approximate analytical formulas are accurate enough by comparing them with the six-parametric exact solution calculated by Pach\'on et. al. [Phys. Rev. D 73, 104038 (2006)] along with the numerical data presented by Berti and Stergioulas [MNRAS 350, 1416 (2004)] for realistic neutron stars. As a main result, we find that in general, the radius at ISCO exhibits a decreasing behavior with increasing magnetic field. However, for magnetic fields below 100GT the variation of the radius at ISCO is negligible and hence the non-magnetized approximate expression can be used. In addition, we derive approximate analytical formulas for angular velocity, energy and angular momentum of the test particle at ISCO.Comment: 8 pages, 3 figure

Computational modeling and fluorescence microscopy characterization of a two-phase magnetophoretic microsystem for continuous-flow blood detoxification

Magnetic beads can be functionalized to capture and separate target pathogens from blood for extracorporeal detoxification. The beads can be magnetically separated from a blood stream and collected into a coflowing buffer solution using a two-phase liquid-liquid continuous-flow microfluidic device in the presence of an external field. However, device design and process optimization, i.e. high bead recovery with minimum blood loss or dilution remain a substantial technological challenge. We introduce a CFD-based Eulerian-Lagrangian computational model that enables the rational design and optimization of such systems. The model takes into account dominant magnetic and hydrodynamic forces on the beads as well as coupled bead-fluid interactions. Fluid flow (Navier-Stokes equations) and mass transfer (Fick's law) between the coflowing fluids are solved numerically, while the magnetic force on the beads is predicted using analytical methods. The model is demonstrated via application to a prototype device and used to predict key performance metrics; degree of bead separation, flow patterns, and mass transfer, i.e. blood diffusion to the buffer phase. The impact of different process variables and parameters-flow rates, bead and magnet dimensions and fluid viscosities-on both bead recovery and blood loss or dilution is quantified for the first time. The performance of the prototype device is characterized using fluorescence microscopy and the experimental results are found to match theoretical predictions within an absolute error of 15%. While the model is demonstrated here for analysis of a detoxification device, it can be readily adapted to a broad range of magnetically-enabled microfluidic applications, e.g. bioseparation, sorting and sensing