Toward a Better Understanding and Optimization of the Electrochemical Activity of Na-Ion TiO2 Anatase Anodes Using Uniform Nanostructures and Ionic Liquid Electrolytes.

TiO2 anatase has emerged as a promising anode for Na-ion batteries (SIBs). However, widespread use of this anode is severely limited by a series of factors that need to be identified and understood to further improve their electrochemical response. Here, we have taken benefit from the versatility of a self-assembly seeding-assisted method to obtain a variety of uniform high-surface-area undoped TiO2 anatase nanostructures. Electrodes built from these uniform nanostructures in combination with a safe ionic liquid electrolyte have allowed a systematic study on some of the factors that determine the electrochemical activity of Na-ion anatase anodes. Interestingly, the inherent low penetrability of the ionic liquid electrolyte has resulted in an unexpected asset to clarify large differences in Na+ uptake by different nanostructures. Basically, solid electrolyte interface (SEI) effects were maximized and therefore clearly separated from electrochemical reactions strictly associated with the anatase anode. Thus, for electrodes built from nanostructures that preserved their initial conformation after cycling, the first discharge showed Na+ uptakes well-beyond those of the Ti4+/Ti3+ redox couple. This large uptake has been associated with an apparent reversible reaction that operates below ca. 0.5-0.7 V and an irreversible mechanism that operates at lower voltages (ca. 0.3 V). However, for electrodes built from nanostructures that favored SEI formation, the irreversible reaction associated with the plateau at ca. 0.3 V was not observed during the first discharge. In accordance, the total Na+ uptake did not reach values beyond those of the corresponding Ti4+/Ti3+ redox couple. Irreversibility, in this case, is associated with SEI formation. Our results also establish the strong effect that size at different scale levels has in the electrochemical response of anatase anodes for SIBs (changes from ca. 6 to 11 nm in crystal sizes and from 50 to 80 in nanostructure sizes led to pronounced differences). This result emphasizes that any conclusions on mechanistic studies other than size effects must be done under strict control on size at various scales (size as a strict control variable at crystal level and nanostructure or in more general terms aggregate scale levels). Finally, we have found that at 30 and 60 °C the performance of the best of the electrodes, with the low-flammable and low-volatile ionic liquid electrolyte, is comparable to that of similar nanostructures immersed in their Li-ion electrolyte counterparts. This result is promising, as in stationary applications where SIBs could replace Li-ion batteries, large accumulation of storage components imposes more strict safety criteria. Basically, power criteria can be relaxed in response to more strict safety criteria.

Chemical vs. electrochemical extraction of lithium from the Li-excess Li(1.10)Mn(1.90)O4 spinel followed by NMR and DRX techniques.

Lithium extraction from the Li-excess Li1.10Mn1.90O4 spinel has been performed by chemical and electrochemical methods in aqueous and in organic media, respectively. De-lithiated samples have been investigated by XRD, SEM, TG, (7)Li and (1)H MAS-NMR techniques. The comparative study has allowed demonstrating that the intermediate de-intercalated samples prepared during the chemical extraction by acid titration are similar to those prepared by the electrochemical way in a non-aqueous electrolyte. LiMn2O4 based spinel with a tailored de-lithiation degree can be prepared as a single phase by controlling the pH used in chemical extraction. (7)Li MAS-NMR spectroscopy has been used to follow the influence of the manganese oxidation state on tetra and octahedral Li-signals detected in Li-extracted samples. The oxidation of Mn(III) ions goes parallel to the partial dissolution of the spinel, following Hunter's mechanism. Based on this mechanism, a generalized chemical reaction has been proposed to explain the formation of intermediate Li(+) de-intercalated samples during acid treatment in aqueous media. By the (1)H MAS NMR study, no evidence of Li-H topotactic exchange in the bulk of the acid treated material was found.

Importancia de las redes interpersonales en la toma de decisiones vinculadas a la salud sexual y reproductiva en ámbitos rurales / Importance of interpersonal networks in decision-making related to sexual and reproductive health in rural areas

INTRODUCCIÓN La salud sexual y reproductiva (SSyR) es una prioridad entre las políticas públicas de salud en Argentina. Es necesario estudiar los procesos locales de implementación del Programa Nacional de Salud Sexual y Procreación Responsable (PNSSyPR) y su impacto en una población cuyas especificidades en materia de SSyR han sido poco abordadas: la de los adolescentes de zonas rurales. OBJETIVOS Estudiar la implementación del PNSSyPR en el sistema local de salud y las redes personales de adolescentes y jóvenes (AyJ) rurales, por medio de las cuales comparten y sostienen los conocimientos que guían la toma de decisiones sobre la SSyR. MÉTODOS Se utilizó un método comparativo cuali-cuantitativo de cuatro estudios de caso situados en localidades rurales del norte argentino. El muestreo fue intencional. Se administraron, en total, 53 entrevistas semiestructuradas a agentes del sistema público de salud y AyJ de 13 a 25 años residentes en zonas rurales. A estos últimos se les administró un módulo de mapeo de redes personales. RESULTADOS Se constató que las implementaciones territoriales del PNSSyPR se centran en la entrega de anticonceptivos y en el asesoramiento sobre su uso, y que a las estrategias de transferencia de información empleadas subyace una mirada estereotipada de los adolescentes y simplista de los problemas vinculados con la SSyR. Los AyJ ensayan estrategias de resolución acudiendo a sus redes personales, que están compuestas mayormente por amigos y familiares, y tienden a la homofilia con respecto al sexo y la edad. DISCUSIÓN Se proponen líneas estratégicas para el diseño e implementación de programas sobre SSyR referidas a aspectos organizativos, a la articulación con instituciones locales, a la capacitación de los padres y a la formación de los agentes del sistema de salud y de orientadores locales, para facilitar el acceso de ambos sexos a los beneficios del programa.

Radiculalgia asociada a hipopotasemia / Hypopotassemia-linked radiculalgia

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