Revisiting the redox transitions of Polyaniline. Semiquantitative interpretation of electrochemically induced IR bands

[EN] The redox transitions of PANI in acidic medium have been monitored by a combination of cyclic voltammetry, in situ conductance and in situ FTIR spectroscopy. The results of the semiquantitative analysis strongly suggest that the classical tetrameric model of PANI does not satisfactorily describe the actual structures of the polymer at different redox states. An octameric model is revisited, with the inclusion of essential resonant structures, to provide an appropriate prediction of the relative IR intensity changes of the aromatic Csingle bondC stretching (at around 1520 cm¿1) and the quinoid Cdouble bondC stretching (at around 1590 cm¿1) vibrations observed by FTIR, which are difficult to interpret by considering only 4 aniline rings. Particularly, it is found that the emeraldine state is better described as a resonance hybrid of the classical bipolaronic and semiquinoid (polaron lattice) structures, while most of the charge transferred at the onset of the second voltammetric peak comes from the additional oxidation of this hybrid, which becomes unstable in the electrochemical environment producing mineralization to CO2 and release of soluble quinones.This work was financed by the Spanish Ministerio de Ciencia e Innovacion (project PID2019-105923RB-I00) and by Generalitat Valenciana (Conselleria de Educacion, Investigacion, Cultura y Deporte through project PROMETEO/2018/087). The authors of this work are deeply grateful to Prof. Jose Luis Vazquez Pico (Pepe, nowadays retired) for his mentorship, which was the seed to develop this work. We appreciate the wise advice he gave us during our careers which served us to deepen the science contained in this article, as well as for the friendship with which he honored us over the years.Huerta, F.; Quijada, C.; Montilla, F.; Morallón, E. (2021). Revisiting the redox transitions of Polyaniline. Semiquantitative interpretation of electrochemically induced IR bands. Journal of Electroanalytical Chemistry. 897:1-11. https://doi.org/10.1016/j.jelechem.2021.115593S11189

Isolation of bovine β-lactoglobulin from complexes with chitosan

A simple, economical and non-toxic method is described for the solubilization of undenatured β-lactoglobulin (β-lg) from complexes with chitosan. The effect of pH (8-10), ionic strength (0.08-0.3 m) and volume ratio between sodium acetate solutions and whey on the dissociation of β-lg-chitosan complexes was evaluated. Following a single extraction step with the addition of 10 mL of 0.1 m sodium acetate solution at pH 9 to the β-lg-chitosan complexes obtained from 1 mL of cheese-whey, a recovery of 90% of β-lg with a protein purity of 95% was achieved, suggesting that electrostatic interactions play a key role in the complexation of β-lg with chitosan. The presence of free chitosan in solution was ruled out according to gas chromatography with flame-ionization detector analysis after acid hydrolysis. NMR spectroscopy showed that the recovered β-lg after further dialysis had structural features very similar to the native protein.This work was supported by the Comisión Interministerial de Ciencia y Tecnología (CICYT), Project Nos. AGL2004-07227-C02-02 and AGL2004-03322.Peer Reviewe

Osteocondritis disecante de rótula: A propósito de un caso

Presentamos un caso de Osteocondritis Disecante de inusual localización en rótula, con afectación bilateral y externa, tratado mediante perforaciones sin exéresis del fragmento, no descrito en la literatura previa para esta localización, consiguiendo un excelente resultado tras un seguimiento de 4 años.A case of osteochondritis dissecans at an unusual localization is presented. The lesion affected both patellae, and was externally located. Surgical treatment was indicated by means of bone perforations without removal of the fragment. An excellent result was observed at 4 years follow-up. To the best of our knowledge, this is the first time this method has been applied for the described location

Preparation of the catalyst support from the oil-shale processing by-product

5-methylresorcinol and the technical mixture of oil-shale phenolic compounds were applied for carbon aerogel preparation. Gels, which were prepared via base catalyzed polymerization were dried under supercritical conditions and subsequent pyrolysis of obtained dry aerogels led to carbon aerogels. Activation of carbon aerogel with CO2 and H2O was performed and porosity and the specific surface area of activated carbon aerogels were studied. Langmuir specific surface areas of well over 2000 m2/g were achieved and microporosity of carbon aerogel samples was tuneable ranging from below 50% until over 85%. Impregnation with the complex [Pd(C4HF6O)2] was carried out in supercritical CO2 using H2 for a quick reduction of Pd(II) to Pd(0). Eventually, highly porous material decorated with nanoparticles of black palladium was obtained having a homogeneous metal distribution

Sistema único de preservación para muestras geológicas : Nucleoteca La Concepción, Venezuela

El sistema único de preservación para muestras geológicas en Venezuela es el resultado de estudios y experiencias propias practicadas en los últimos 30 años en la toma, manejo, preservación, estudio, almacenamiento, administración y custodio de muestras geológicas tanto de superficie como del subsuelo en PDVSA Exploración, formando parte fundamental del patrimonio de estado en las nucleotecas a escala nacional. El sistema permitirá estandarizar y homologar entre las empresas del estado la preservación y transferir a las empresas estatales de Sur y Centro América un sistema de cajas plásticas en polietileno de alta densidad resistente en el tiempo para lograr una óptima preservación de la fauna, flora y estructuras sedimentarias con capacidad de garantizar la permanencia dentro de los testigos sin alteración externa. La diversidad actual en las nucleotecas de materiales de preservación tales como fibra de madera de densidad media (MDF), plástico polipropileno cargado con talco, bolsas de tela y plásticas generó a través de los años la degradación de los materiales y por ende, problemas de rotulación, estado físico y preservación general de las muestras. Ésto, aunado a los altos costos operacionales en la toma de testigos para descubrir nuevos yacimientos, hacen necesario mantener inalterable el estado natural de la litología presente, lo cual es garantizado por un sistema único y estándar en el custodio de las muestras geológicas.Sesiones libresFacultad de Ciencias Naturales y Muse

Valores antropométricos en niños con celiaquía diagnosticados precozmente

Peer Reviewe

Oil shale phenol-derived aerogels as supports for palladium nanoparticles

Palladium hexafluoroacetylacetonate [Pd(C4HF6O)2], which is both soluble and easily reducible in supercritical carbon dioxide, was used to impregnate the porous structure of carbon aerogels based on phenolic compounds from oil shale processing water. Metallic nanoparticles uniformly distributed on the surface of the carbon matrix enable it to be used as a catalyst. Through the study of various pyrolysis programs and physical activation with CO2 and H2O in the carbon aerogel preparation process, significant increases in the BET specific surface area of the carbon supports (achieving values of over 1600 m2/g) were achieved, and the possibility of tailoring the porosity of the samples (microporosity ranging from 40% up to over 90%) was realized

Load that maximizes power output in countermovement jump

Introduction: One of the main problems faced by strength and conditioning coaches is the issue of how to objectively quantify and monitor the actual training load undertaken by athletes in order to maximize performance. It is well known that performance of explosive sports activities is largely determined by mechanical power. Objective: This study analysed the height at which maximal power output is generated and the corresponding load with which is achieved in a group of male-trained track and field athletes in the test of countermovement jump (CMJ) with extra loads (CMJEL). Methods: Fifty national level male athletes in sprinting and jumping performed a CMJ test with increasing loads up to a height of 16 cm. The relative load that maximized the mechanical power output (Pmax) was determined using a force platform and lineal encoder synchronization and estimating the power by peak power, average power and flight time in CMJ. Results: The load at which the power output no longer existed was at a height of 19.9 ± 2.35, referring to a 99.1 ± 1% of the maximum power output. The load that maximizes power output in all cases has been the load with which an athlete jump a height of approximately 20 cm. Conclusion: These results highlight the importance of considering the height achieved in CMJ with extra load instead of power because maximum power is always attained with the same height. We advise for the preferential use of the height achieved in CMJEL test, since it seems to be a valid indicative of an individual's actual neuromuscular potential providing a valid information for coaches and trainers when assessing the performance status of our athletes and to quantify and monitor training loads, measuring only the height of the jump in the exercise of CMJEL.Actividad Física y Deport

Determinación espectrofotométrica de aldehídos furánicos previa formación de tiosemicarbazonas. I. – Estudio del furfural

A U.V. spectrophotometric study of furan-2-carboxaldehyde tiosemicarbazone was performed. It has an only maximum at 316 nm and is stable for secen days. Absorbance doesn't vary in a range of pH from 2 to 10. Lambert-Beer's law is obyed for furfural concentrations between 1.1O-5 M and5.1O-5 M. Molar absortivity is E316=29500 M-1 L cm-1.Se ha realizado un estudio espectrofotométrico en la región U.V. del furfural tiosemicarbazona. La disolución presenta un solo máximo a 316 nm y estable después de 7 días de su preparación. No presenta modificaciones en la absorbancia en un rango de pH comprendido entre 2 y 10. Cumple la Ley de Lambert-Beer para concentraciones de furfural 1.1O-5 M y  5.1O-5 M. La absortividad molar es E316= 29500 M-1 L cm-1