La funcionalidad de los esquemas gráficos durante el aprendizaje de la Física para carreras de Ingeniería

El interés de esta investigación es describir los esquemas gráficos construidos por estudiantes de primer año de ingeniería, y explorar sus funciones didácticas. Los datos obtenidos durante catorce cuatrimestres corresponden a una actividad de apertura de un curso de Física, a partir de la lectura de una selección de textos de física y epistemología. Para su análisis se integran elementos filosóficos, científicos, históricos, estéticos y psicológicos. El estudio es etnográfico, cualitativo y émico. Los resultados permiten caracterizar, perceptual y conceptualmente, los esquemas gráficos construidos por los estudiantes de ingeniería sobre áreas canónicas de la física. Didácticamente las representaciones analizadas parecen funcionar como esquemas organizadores e integradores de sistemas conceptuales, estilos perceptuales y pautas sociocognitivas previas

Intermolecular interactions of substituted benzenes on multi-walled carbon nanotubes grafted on HPLC silica microspheres and interaction study through artificial neural networks

Purified multi-walled carbon nanotubes (MWCNTs) grafted onto silica microspheres by gamma-radiation were applied as a HPLC stationary phase for investigating the intermolecular interactions between MWCNTs and substituted benzenes. The synthetic route, simple and not requiring CNTs derivatization, involved no alteration of the nanotube original morphology and physical–chemical properties. The affinity of a set of substituted benzenes for the MWCNTs was studied by correlating the capacity factor (k′) of each probe to its physico-chemical characteristics (calculated by Density Functional Theory). The correlation was found through a theoretical approach based on feedforward neural networks. This strategy was adopted because today these calculations are easily affordable for small molecules (like the analytes), and many critical parameters needed are not known. This might increase the applicability of the proposed method to other cases of study. Moreover, it was seen that the normal linear fit does not provide a good model. The interaction on the MWCNT phase was compared to that of an octadecyl (C18) reversed phase, under the same elution conditions. Results from trained neural networks indicated that the main role in the interactions between the analytes and the stationary phases is due to dipole moment, polarizability and LUMO energy. As expected for the C18 stationary phase correlation, is due to dipole moment and polarizability, while for the MWCNT stationary phase primarily to LUMO energy followed by polarizability, evidence for a specific interaction between MWCNTs and analytes. The CNT-based hybrid material proved to be not only a chromatographic phase but also a useful tool to investigate the MWCNT-molecular interactions with variously substituted benzenes

La funcionalidad de los esquemas gráficos durante el aprendizaje de la Física para carreras de Ingeniería

El interés de esta investigación es describir los esquemas gráficos construidos por estudiantes de primer año de ingeniería, y explorar sus funciones didácticas. Los datos obtenidos durante catorce cuatrimestres corresponden a una actividad de apertura de un curso de Física, a partir de la lectura de una selección de textos de física y epistemología. Para su análisis se integran elementos filosóficos, científicos, históricos, estéticos y psicológicos. El estudio es etnográfico, cualitativo y émico. Los resultados permiten caracterizar, perceptual y conceptualmente, los esquemas gráficos construidos por los estudiantes de ingeniería sobre áreas canónicas de la física. Didácticamente las representaciones analizadas parecen funcionar como esquemas organizadores e integradores de sistemas conceptuales, estilos perceptuales y pautas sociocognitivas previas

Air- and water-stable and photocatalytically active germanium-based 2D perovskites by organic spacer engineering

There is increasing interest in the role of metal halide perovskites for heterogeneous catalysis. Here, we report a Ge-based 2D perovskite material that shows intrinsic water stability realized through organic cation engineering. Incorporating 4-phenylbenzilammonium (PhBz) we demonstrate, by means of extended experimental and computational results, that PhBz2GeBr4 and PhBz2GeI4 can achieve relevant air and water stability. The creation of composites embedding graphitic carbon nitride (g-C3N4) allows a proof of concept for light-induced hydrogen evolution in an aqueous environment by 2D Ge-based perovskites thanks to the effective charge transfer at the heterojunction between the two semiconductors

Reaction Mechanism of Hydrogen Generation and Nitrogen Fixation at Carbon Nitride/Double Perovskite Heterojunctions

Photocatalytically active heterojunctions based on metal halide perovskites (MHPs) are drawing significant interest for their chameleon ability to foster several redox reactions. The lack of mechanistic insights into their performance, however, limits the ability of engineering novel and optimized materials. Herein, a report is made on a composite system including a double perovskite, Cs2AgBiCl6/g-C3N4, used in parallel for solar-driven hydrogen generation and nitrogen reduction, quantified by a rigorous analytical approach. The composite efficiently promotes the two reactions, but its activity strongly depends on the perovskite/carbon nitride relative amounts. Through advanced spectroscopic investigation and density function theory (DFT) modeling the H2 and NH3 production reaction mechanisms are studied, finding perovskite halide vacancies as the primary reactive sites for hydrogen generation together with a positive contribution of low loaded g-C3N4 in reducing carrier recombination. For nitrogen reduction, instead, the active sites are g-C3N4 nitrogen vacancies, and the heterojunction best performs at low perovskites loadings where the composites maximize light absorption and reduce carrier losses. It is believed that these insights are important add-ons toward universal exploitation of MHPs in contemporary photocatalysis

Occurrence, Distribution, and Ecological Risk of Fluoroquinolones in Rivers and Wastewaters

The use of fluoroquinolones for the treatment of infections in humans and animals has increased in Argentina, and they can be found in large amounts in water bodies. The present study investigated the occurrence and associated ecological risk of 5 fluoroquinolones in rivers and farm wastewaters of San Luis, Santa Fe, Córdoba, Entre Ríos, and Buenos Aires provinces of Argentina by high-performance liquid chromatography coupled to fast-scanning fluorescence detection and ultra–high-performance liquid chromatography coupled to triple quadrupole mass spectrometry detection. The maximum concentrations of ciprofloxacin, enrofloxacin, ofloxacin, enoxacin, and difloxacin found in wastewater were 1.14, 11.9, 1.78, 22.1, and 14.2 μg L–1, respectively. In the case of river samples, only enrofloxacin was found, at a concentration of 0.97 μg L–1. The individual risk of aquatic organisms associated with water pollution due to fluoroquinolones was higher in bacteria, cyanobacteria, algae, plants, and anurans than in crustaceae and fish, with, in some cases, risk quotients >1. The proportion of samples classified as high risk was 87.5% for ofloxacin, 63.5% for enrofloxacin, 57.1% for ciprofloxacin, and 25% for enoxacin. Our results suggest that the prevalence of fluoroquinolones in water could be potentially risky for the aquatic ecosystem, and harmful to biodiversity.Fil: Teglia, Carla Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Desarrollo Analítico y Quimiometría; ArgentinaFil: Perez, Florencia Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Desarrollo Analítico y Quimiometría; ArgentinaFil: Michlig, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Investigación y Análisis de Residuos y Contaminantes Químicos; ArgentinaFil: Repetti, María Rosa. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Investigación y Análisis de Residuos y Contaminantes Químicos; ArgentinaFil: Goicoechea, Hector Casimiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Desarrollo Analítico y Quimiometría; ArgentinaFil: Culzoni, Maria Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Desarrollo Analítico y Quimiometría; Argentin

Allaitement, corps et contamination: notes sur les racines multiples de la connaissance sociale

Dans cet article on pr\ue9sente la contribution de l'oeuvre et de la pens\ue9e de Denise Jodelet \ue0 un certain nombre de recherches conduites \ue0 l'Universit\ue9 de Bologna. En particulier on discute sur les r\ue9sultats de plusieurs \ue9tudes sur un des th\ue8mes privil\ue9gi\ue9s par Denise Jodelet: les repr\ue9sentations de l'allaitement, sujet qui se pose au carrefour entre nature et culture, entre tradition et modernit\ue9. Les recherches ont \ue9t\ue9 conduites sur des \ue9chantillons diff\ue9rents et plus ou moins concern\ue9s par le th\ue8me en question: m\ue8re allaitantes, p\ue8res de b\ue9b\ue9s, saches-femmes, \ue9tudiants universitaires, adultes sans enfants. Un des \ue9l\ue9ments qui ont \ue9t\ue9 mis en evidence par ces recherches est le concept de contamination qui a une longue histoire dans les diff\ue9rentes cultures et que, en partant des r\ue9sultats obtenus, garde une permanence chez des populations modernes et de haut niveau culturel