Activation Energy of Hydrogen Adsorption on Pt(111) in Alkaline Media: An Impedance Spectroscopy Study at Variable Temperatures

The hydrogen evolution reaction is one of the most studied processes in electrochemistry, and platinum is by far the best catalyst for this reaction. Despite the importance of this reaction on platinum, detailed and accurate kinetic measurements of the steps that lead to the main reaction are still lacking, particularly because of the fast rate of the reaction. Hydrogen adsorption on Pt(111) has been taken as a benchmark system in a large number of computational studies, but reliable experimental data to compare with the computational studies is very scarce. To gain further knowledge on this matter, a temperature study of the hydrogen adsorption reaction has been carried out to obtain kinetic information for this process on Pt(111) in alkaline solution. This was achieved by measuring electrochemical impedance spectra and cyclic voltammograms in the range of 278 ≤ T ≤ 318 (K) to obtain the corresponding surface coverage by adsorbed species and the faradaic charge transfer resistance. From this data, the standard rate constant has been extracted with a kinetic model assuming a Frumkin-type isotherm, resulting in values of 2.60 × 10–7 ≤ k0 ≤ 1.68 × 10–6 (s–1). The Arrehnius plot gives an activation energy of 32 kJ mol–1. Comparisons are made with values calculated by computational methods and reported values for the overall HER, giving a reference frame to support future studies on hydrogen catalysis.This work was financially supported by the MINECO (Spain) project no. CTQ2016-76221-P. L.E.B. thanks the Generalitat Valenciana for funding from the Santiago Grisolia Program (no. GRISOLIAP/2017/181)

Medical Students’ Perception Towards the COVID-19 Pandemic in Mexico: Distance Learning, Assisting Hospitals, and Vaccination

Background: Mexico has been one of the most affected countries by the COVID-19 pandemic. Its health workers are playing a substantial role, but they are suffering from a high mortality rate, which highlights the need of vaccinating them before any other population. Medical interns have reduced their practices, some continue to assist clinical rotations without the protective equipment, and they are not being considered for vaccination. We wanted to determine the attitude of medical students and interns towards distance learning, assisting hospitals, and vaccination. Methods: We conducted a paired survey of a cohort of medical students who were evaluated twice, in June 2020 and in December 2020, using an online survey (32-online questions) to assess their perception of the pandemic. Results: We collected the response of 384 students in the summer period and 331 in the winter period; the majority were women from non-clinical semesters, and the median age of response was 21 years old (IQR 19 – 22). We found that the percentage of acceptance for vaccination was 95.6% in the summer and 93.7% in the winter, a remarkable acceptance in both periods. The percentage of students who manifested having someone close to them with symptoms suggestive of COVID-19 was 38.5% in the summer, showing an increase to 77.6% in the winter. Conclusion: We observed that medical students had a positive attitude towards vaccination and that the probable COVID-19 cases among them have increased in just a few months

Three-dimensional nucleation with diffusion controlled growth: a comparative study of electrochemical phase formation from aqueous and deep eutectic solvents

The nucleation of Ag onto vitreous carbon from aqueous 3 M NaCl or 0.6 M NaClO4 and deep eutectic solvent (DES) 1:2 M mixture of choline chloride:urea solutions containing Ag+, has been studied analyzing the chronoamperometric response to single potential steps. From the coordinates of the maxima observed in the current responses, the nucleation frequencies A (s(-1)) and number densities of nucleation sites N-0 (cm(-2)) were obtained from the standard model of nucleation with diffusion-controlled three-dimensional growth. Analysis of the overpotential dependence of nucleation frequencies using the classical electrochemical nucleation theory allowed to calculate the Gibbs free energy of nucleation Delta(G) over tilde (n(c)) and critical nucleus size n(c) as well as the exchange current density j(o), transfer coefficient alpha and surface tension sigma of silver nuclei. The kinetics of Ag+ reduction is two orders of magnitude slower in DES compared to both aqueous systems studied, and values of alpha << 0.5 where found in both aqueous and DES media, indicating either that the intermediate state for metal ion reduction is located close to the initial state, i.e., the solvated or complexed metal ion in solution, or that the metal ion is specifically adsorbed on the surface and the symmetry factor involved requires an alternative electron transfer formalism. The low Delta(G) over tilde (n(c)) and n(c) values observed indicate that the discharge of a single Ag ion on the surface already becomes a supercritical nucleus, involving a very low Gibbs energy barrier, characteristic of a non-activated process. (C) 2016 Elsevier B.V. All rights reserved

Maternal dietary patterns and acute leukemia in infants: results from a case control study in Mexico

BackgroundChildhood cancer is the leading cause of disease-related mortality among children aged 5–14 years in Mexico, with acute leukemia being the most common cancer among infants. Examining the overall dietary patterns allows for a comprehensive assessment of food and nutrient consumption, providing a more predictive measure of disease risk than individual foods or nutrients. This study aims to evaluate the association between maternal dietary patterns during pregnancy and the risk of acute leukemia in Mexican infants.MethodsA hospital-based case–control study was conducted, comparing 109 confirmed acute leukemia cases with 152 age-matched controls. All participants (≤24 months) were identified at hospitals in Mexico City between 2010 and 2019. Data on a posteriori dietary patterns and other relevant variables were collected through structured interviews and dietary questionnaires. Multivariate logistic regression was employed to estimate the association between maternal dietary patterns during pregnancy and the risk of acute leukemia in infants.ResultsThe “Balanced &amp; Vegetable-Rich” pattern, characterized by a balanced consumption of various food groups and higher vegetable intake, exhibited a negative association with acute leukemia when compared to the “High Dairy &amp; Cereals” Pattern (adjusted odds ratio [OR] = 0.51; 95% confidence interval [CI]: 0.29, 0.90). We observed that mothers who gave birth to girls and adhered to a healthy dietary pattern during pregnancy exhibited significantly lower odds of their children developing AL compared to those who gave birth to boys [OR = 0.32 (95% CI 0.11, 0.97)]. Our results underscore the significance of maternal nutrition as a modifiable factor in disease prevention and the importance of prenatal health education

Three-dimensional nucleation with diffusion controlled growth: a comparative study of electrochemical phase formation from aqueous and deep eutectic solvents

The nucleation of Ag onto vitreous carbon from aqueous 3 M NaCl or 0.6 M NaClO4 and deep eutectic solvent (DES) 1:2 M mixture of choline chloride:urea solutions containing Ag+, has been studied analyzing the chronoamperometric response to single potential steps. From the coordinates of the maxima observed in the current responses, the nucleation frequencies A (s(-1)) and number densities of nucleation sites N-0 (cm(-2)) were obtained from the standard model of nucleation with diffusion-controlled three-dimensional growth. Analysis of the overpotential dependence of nucleation frequencies using the classical electrochemical nucleation theory allowed to calculate the Gibbs free energy of nucleation Delta(G) over tilde (n(c)) and critical nucleus size n(c) as well as the exchange current density j(o), transfer coefficient alpha and surface tension sigma of silver nuclei. The kinetics of Ag+ reduction is two orders of magnitude slower in DES compared to both aqueous systems studied, and values of alpha << 0.5 where found in both aqueous and DES media, indicating either that the intermediate state for metal ion reduction is located close to the initial state, i.e., the solvated or complexed metal ion in solution, or that the metal ion is specifically adsorbed on the surface and the symmetry factor involved requires an alternative electron transfer formalism. The low Delta(G) over tilde (n(c)) and n(c) values observed indicate that the discharge of a single Ag ion on the surface already becomes a supercritical nucleus, involving a very low Gibbs energy barrier, characteristic of a non-activated process. (C) 2016 Elsevier B.V. All rights reserved

Calidad del agua: un enfoque multidisciplinario

El concepto integral de calidad del agua está aún muy poco desarrollado en México. Así, el objetivo de este libro es que especialistas en los diversos aspectos de la calidad del agua, compartan sus conocimientos y experiencias, con el fin de disponer de un enfoque multidisciplinario sobre las causas y consecuencias de la contaminación del agua, así como con soluciones para mejorar la calidad del agua en el país. Libro de texto de naturaleza multidisciplinaria para el nivel superior, con lenguaje técnico pero con explicaciones y definiciones que lo hacen comprensible sin pérdida del rigor académico.Índice: INTRODUCCIÓN Conceptos de calidad del agua: un enfoque multidisciplinario PROBLEMÁTICA 1. Calidad, una limitante más para la disponibilidad del agua 2. La contaminación del agua subterránea en México 3. La contaminación de las costas mexicanas 4. La contaminación difusa 5. Las especies exóticas como contaminación biológica del agua SOLUCIONES 6. Soluciones tecnológicas a la contaminación del agua 7. Soluciones ecológicas a la contaminación del agua 8. Soluciones de la teoría económica para la contaminación del agua GOBERNANZA Y CALIDAD DEL AGUA 9. Aspectos sociales sobre la calidad del agua y los ecosistemas acuáticos: un análisis de conflictos y controversias en torno al agua 10. El marco jurídico e institucional para la gestión de la calidad del agua en México CONCLUSIONES Calidad del agua: un enfoque multidisciplinari