Weakening the C – C bond: On the behavior of glyoxylic acid on Pt(111) and its vicinal surfaces

Adsorption and oxidation of glyoxylic acid (GA) on platinum single crystals were investigated by spectroelectrochemical techniques. Among basal planes, Pt(111) is taken as a model surface for reactivity studies in order to point out the Csingle bondC bond breaking. For a standard GA concentration (0.1 M), self-poisoning by adsorbed CO (COads) is the main process dominating the positive-going sweep. The presence of (110) steps on (111) terraces contribute in the Csingle bondC bond cleavage, leading to CO formation, while (100) steps do not show a significant effect. Poison stripping allows GA oxidation in a lower potential range in the negative-going sweep. By working with different GA concentrations (10− 5–0.1 M), surface blockage is hindered, pointing out an alternative reaction pathway, where GA is oxidized in a poison-free surface. Fourier transform infrared spectroscopy (FTIR) experiments allowed the identification of CO2, formic (FA) and oxalic acid (OA) as main products of GA oxidation. We highlight an activity peak at 0.01 M GA, concomitant to the presence of CO2 absorption bands at lower potentials (0.2 V). The formation of CO2 at potentials where CO cannot be oxidized suggests a change in the preferential reaction pathway, where GA is completely oxidized through an active intermediate distinct to COads.This work was carried out under financial support of MICINN (project no. CTQ2013-44083-P). R.M.H. acknowledges support from Generalitat Valenciana under Santiago Grisolia Program (GRISOLIA/2013/008)

Calidad de vida en pacientes trasplantados renales de una institución prestadora de servicios de salud en Medellín, Colombia

Introduction: Renal transplantation performed on patients with chronic renal disease (CRD) stage five, is an alternative treatment that prolongs survival, reduces morbidity, accelerate social and medical rehabilitation. However it is necessary to carry out studies to evaluate the quality of life of these patients. Objective: Establishing the socio-demographic, clinical and service characteristics of the health insurer that explain the life quality of kidney transplanted patients who consulted a health institution in Medellin in 2016. Materials and methods: Quantitative and transversal survey carried out in 228 patients to whom the SF-36 instrument were applied. There were calculated the statistical tests of Kolmogorov Smirnov for normality, U de Mann Whitney, Kruskal Wallis and the Spearman correlation coefficient. In the multivariate analysis the median regression model was selected. Results: 50% of the patients got 83.3 or less in its life quality score. The multivariate regression model shown significant differences in the time variables after transplantation and readmission to hospital in the last year; by each readmission to hospital, the values of life quality decreased in 3.82 points; according to the time after the transplantation, it was found that going from a state where the patient has a term between 7 and 36 months, to a state where the patient has a term over 36 months, shown a decrease of 12.03 points in life quality, adjusted by the other variables. Conclusions: The variables that best explained the life quality of the kidney transplanted patients who consulted a health institution were the time of transplantation and the number of readmissions to hospital

RUTAS DEL PACÍFICO: IDENTIDADES DIASPÓRICAS ASIÁTICAS EN EL CARIBE COLOMBIANO

Otros caribes: de las Antillas al continente (sudamérica, centroamérica y norteamérica

Exploring the interfacial neutral pH region of Pt(111) electrodes

The interfacial properties of Pt(111) single crystal electrodes have been investigated in the pH range 3 < pH < 5 in order to obtain information about the acidity of electrosorbed water. Proper experimental conditions are defined to avoid local pH changes while maintaining the absence of specifically adsorbed anions and preserving the cleanliness of the solution. For this purpose, buffer solutions resulting from mixtures of NaF and HClO4 are used. Total charge curves are obtained at different pHs from the integration of the voltammetric currents in combination with CO charge displacement experiments. Analysis of the composition of the interphase as a function of the pH provides information for the understanding of the notion of interfacial pH.Support from MINECO (Spain) through project CTQ2013-44083-P is greatly acknowledged. RMH thankfully acknowledges support from Generalitat Valenciana under the Santiago Grisolia Program (GRISOLIA/2013/008). PS thankfully acknowledges to the Generalitat Valenciana the award of a valid grand

Potential-induced acid-base chemistry of adsorbed species

The pKa of bicarbonate ion adsorbed on the surface of Pt(111), HCO3−(ads), in CO2 -saturated KClO4/HClO4 aqueous solutions has been determined by judicious application of a theoretical model originally proposed by Smith and White (Langmuir 1993, 9 (1), 1–3) to explain voltammetric features found for non-redox active alkyl chain monolayers bearing carboxylic moieties irreversibly bound to gold surfaces. The analysis herein presented relied on and coverages derived from in situ Fourier transform infrared spectroscopy measurements as a function of potential and pH reported by Martinez-Hincapie et al. (J. Phys. Chem. C 2016, 120 (29), 16191–16199), as input parameters, yielding a pKa for HCO3−(ads) of ca. 2.6 ± 0.2. This value is significantly smaller than that of HCO3−(aq) in bulk solutions, a phenomenon associated with the bonding of the species to the electrode surface, a factor that markedly modifies its acid base characteristics.This work was supported by a grant from the National Science Foundation (US) CHE 1808592

Simulación Monte Carlo del comportamiento ferroeléctrico de películas de PZT empleando un Hamiltoniano DIFFOUR dependiente de la presión

In this work the polarization and hysteresis response of Lead Zirconate Titanate (PZT) ferroelectric thin films was studied in relation to the variation on temperature, stress, electric field and the content of non-ferroelectric impurities by using a MontEn este trabajo, se estudió la respuesta de polarización e histéresis de las películas finas ferroeléctricas de titanato de zirconato de plomo (PZT) en relación con la variación de temperatura, tensión, campo eléctrico y el contenido de impurezas no ferr

Surface Acid–Base Properties of Anion-Adsorbed Species at Pt(111) Electrode Surfaces in Contact with CO2-Containing Perchloric Acid Solutions

Carbonate and bicarbonate adsorption on Pt(111) electrodes from CO2-saturated acidic solutions is investigated by cyclic voltammetry and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). Spectroscopic results show carbonate and bicarbonate adsorption even at pH = 1, where bulk concentration of these anions is negligible. Moreover, analysis of the potential dependence of band intensities corresponding to adsorbed carbonate and bicarbonate reveals an effect of the electrode potential on the surface acid–base equilibrium. In this regard, increasing potentials favor bicarbonate deprotonation, leading to carbonate formation. A tentative thermodynamic analysis is given to rationalize these trends.Support from MINECO (Spain) through project CTQ2013-44083-P is greatly acknowledged. RMH thankfully acknowledges support from Generalitat Valenciana under the Santiago Grisolía Program (GRISOLIA/2013/008)

Tratamiento de contaminantes orgánicos por foto fenton con luz artificial

El objetivo principal de la investigación que da lugar a este escrito fue minimizar el efecto contaminante de los residuos líquidos orgánicos solubles y medianamente solubles generados en los laboratorios del Centro de Laboratorios de la Universidad de Medellín (Medellín, Antioquia, Colombia), por medio de la fotodegradación sensibilizada (foto–fenton), usando luz artificial como fuente de radiación. Las concentraciones de hierro se variaron entre 5 y 50 mg/L y las de peróxido de hidrógeno entre 200 y 500 mg/L, y se encontró un valor óptimo para la remoción del Carbono Orgánico Total (COT) de 27.5 mg/L de Fe y 300 mg/L de H2O2, que corresponde a un 80% de mineralización, alcanzado en 150 minutos de irradiación