No estequiometria y estabilidad en agua de SrCeO3 no dopado

[EN] Strontium cerate is the parent phase of an important class of proton-conducting perovskites with various potential technological applications. Phase formation and structure of SrCeO3 with Sr:Ce nonstoichiometry have been investigated for the series, Sr1±xCeO3±δ (0.98 ≤ x ≤ 1.04). Analyses by EPMA (electron probe micro analysis) and X-ray diffraction (XRD) indicate that, for samples sintered at 1350°C, the main phase is Sr-rich for all x. The accommodation of excess SrO in the bulk phase and/or intergranular regions is discussed. The stability of nominally stoichiometric SrCeO3 was examined in an atmosphere of high water vapour partial pressure (pH2O) for 2 hours, degrading to Sr(OH)2.H2O and CeO2 for pH2O ≥ 3.6atm.[ES] La fase SrCeO3 da origen a una importante familia de perovskitas conductoras protónicas con potenciales aplicaciones tecnológicas. En este trabajo se estudia la formación de la fase y la estructura de SrCeO3 con la relación Sr:Ce no estequiométrica para la serie Sr1±xCeO3±δ (0.98 ≤ x ≤ 1.04). Los análisis por microsonda (EPMA) y difracción de rayos X (DRX) indican que en las muestras sinterizadas a 1350°C, la fase principal es rica en estroncio para todo valor de x. Se discute la posible ubicación del exceso de SrO tanto en la región intergranular como en el propio grano. También se examina la estabilidad de la composición con estequiometría nominal SrCeO3 en una atmosfera con una alta presión de vapor de agua (pH2O), observándose que la degradación a Sr(OH)2.H2O y CeO2 ocurre a pH2O ≥ 3.6atm (expuesto durante 2 horas).One of the authors (GCM) is sponsored by the EU RTN programme High Temperature Proton Conductors (HiTP) “Investigation of high temperature solid proton conductors of relevance to fuel processing and energy conversion applications”.Peer reviewe

Relationship between band structure and Physical properties in transition metal ceramic oxides with perovskite structure: (II) Magnetic and electrocatalytic properties

[ES] Se revisan los principales modelos teóricos y parámetros presentes en la literatura, que pretenden dar una explicación sobre las propiedades magnéticas y electrocatalíticas de óxidos cerámicos con estructura perovsquita, en los que en la posición B se encuentran los metales de transición (Fe, Co, Ni, Mn), en relación con su estructura de bandas y el carácter de sus electrones más externos. Se pretende integrar y dar una visión global clara a dichos modelos inconexos.[EN] Theoretical models present in literature and developed for the explanation of magnetic and electrocatalytic properties in transition metal (Fe, Co, Ni, Mn) ceramic oxides with perovskite structure in relation with their band diagram and outer electron nature have been revised. It is proposed to give an integrated and global idea about of several theoretical models that have not been yet connected.Peer reviewe

Eletrodo, eletrólito, célula a combustível óxido sólido e processo de produção de energia

Universidade Federal do Rio Grande do SulEngenhariaDepositad

Mixed electrical conduction of calcium aluminates synthesized by polymeric precursors

A study of the electrical transport properties of calcium aluminate (CA) with coexisting C3A and C12A7 phases was carried out. In this work, powders resulting from synthesis based on the polymer precursor method. The resulting product was characterized by means of XRD, Raman, and UV-visible analysis to obtain the optical BG and by EIS. From the XRD and Raman analyses, the presence and coexistence of the two self-modified phases were confirmed. In this biphasic composition, celite phase was estimated to be the major phase. An optical BG of 5.69 eV at room temperature was calculated, and under the condition of a reducing atmosphere in the temperature range of 750-950 ºC, an activation energy for conduction of 2.98 eV was determined by EIS measurements. Further, in this biphasic sample, the electronic conduction transport might be governed by the mayenite minor phase due to its large defect nature and concentration compared to celite. In oxidizing conditions, the activation energy for electrical conduction was 1.42 eV, which is somewhat higher than that observed by other authors in mayenite single phase; this result was explained by taking into account the coexistence of biphasic material and an actual chemical defect scenario in SMCM is discussed

In situ drug release measuring in α-TCP cement by electrochemical impedance spectroscopy

The use of drug delivery systems is a good technique to leave the right quantity of medicine in the patient’s body in a suitable dose, because the drug application is delivered directly to the affected region. The current techniques such as HPLC and UV–Vis for the drug delivery calculation has some disadvantages, as the accuracy and the loss of the sample after characterization. With the aim of reducing the amount of material used during the characterization and have a nondestructive test with instantaneous results, the present paper shows the possibility of using electrochemical impedance spectroscopy (EIS) to have a drug delivery measurement during the release phenomena for a calcium phosphate cement (CFC) delivery system with gentamicin sulfate (GS) and lidocaine hydrochloride (LH), at a ratio of 1% and 2%, respectively. The equivalent circuit and the chemical mechanism involved during the measurements have been proposed as a tool to determine the drug delivery profile. The method has been compared with the UV–Vis technique. XRD was realized to verify conditions, before and after release. It was possible to verify the potential for using EIS as an instant technique to quantify drug delivery

A Bayesian cost-effectiveness analysis of a telemedicine-based strategy for the management of sleep apnoea: a multicentre randomised controlled trial

BACKGROUND: Compliance with continuous positive airway pressure (CPAP) therapy is essential in patients with obstructive sleep apnoea (OSA), but adequate control is not always possible. This is clinically important because CPAP can reverse the morbidity and mortality associated with OSA. Telemedicine, with support provided via a web platform and video conferences, could represent a cost-effective alternative to standard care management. AIM: To assess the telemedicine impact on treatment compliance, cost-effectiveness and improvement in quality of life (QoL) when compared with traditional face-to-face follow-up. METHODS: A randomised controlled trial was performed to compare a telemedicine-based CPAP follow-up strategy with standard face-to-face management. Consecutive OSA patients requiring CPAP treatment, with sufficient internet skills and who agreed to participate, were enrolled. They were followed-up at 1, 3 and 6 months and answered surveys about sleep, CPAP side effects and lifestyle. We compared CPAP compliance, cost-effectiveness and QoL between the beginning and the end of the study. A Bayesian cost-effectiveness analysis with non-informative priors was performed. RESULTS: We randomised 139 patients. At 6 months, we found similar levels of CPAP compliance, and improved daytime sleepiness, QoL, side effects and degree of satisfaction in both groups. Despite requiring more visits, the telemedicine group was more cost-effective: costs were lower and differences in effectiveness were not relevant. CONCLUSIONS: A telemedicine-based strategy for the follow-up of CPAP treatment in patients with OSA was as effective as standard hospital-based care in terms of CPAP compliance and symptom improvement, with comparable side effects and satisfaction rates. The telemedicine-based strategy had lower total costs due to savings on transport and less lost productivity (indirect costs)

Alternativas de bajo coste a la captura fotovoltaica

18 pp.-- Comunicación presentada en el Seminario "Soluciones para el cambio climático mediante una edificación eficiente. Gestión integral de la energía en la construcción", organizado por el Instituto de Automática Industrial (IAI-CSIC) y la Fundación Terrasol, que se celebró el día 21 de marzo de 2007 en el salón de Actos del Edificio Central del CSIC

Band structure and physical properties relationship in transition metal ceramic oxides with perovskite structure (I): Electronic conduction properties

[ES] En este artículo se revisa los principales modelos teóricos, que pretenden dar una explicación sobre las propiedades de conducción electrónica de óxidos cerámicos con estructura perovskita, que incluyen en la posición B metales de transición del primer período (Fe, Co, Ni, Mn), en conexión con su estructura de bandas y el carácter de sus electrones más externos, así como las transiciones metal aislante. Una continuación de este trabajo (Parte II), tratará lo referente a propiedades magnéticas y electrocatalíticas intentando integrar los trabajos llevados a cabo en la literatura sobre los campos citados.[EN] Theoretical models present in the literature and developed for the explanation of electronic conduction properties in transition metal (Fe, Co, Ni, Mn) ceramic oxides with perovskite structure in relation with their band diagram and outer electron nature, as well as metal insulator transitions have been revised. The second part of this work will be involved with magnetic and electrocatalytic properties.Peer reviewe

Influencia de la adición de TÍO2 sobre la sinterización microestructura y propiedades de Ce-TZP

Se han preparado materiales cerámicos policristalinos de circona tetragonal (TZP) con composiciones de 1 a 10 moles % de TÍO2 y 10 a 12 moles % de Ce02 usando mezclas de circona monoclínica, dióxido de titanio y oxalato de cerio como materias primas. Se consiguieron piezas totalmente densificadas en el rango de temperatura de 1400 °C a 1600 °C para composiciones ternarias conteniendo 10 moles % de Ce02. En el caso de las composiciones con 12 moles % de Ce02 la densidad decrece con el contenido de TÍO2. ^^ ^^^ muestras con alto contenido de TÍO2 se encontraron los compuestos ZrTiO^ y (CCQ 73ZrQ 25)02- Puesto que la relación c/a era extremadamente alta, todas las muestras tenían simetría tetragonal a temperatura ambiente. La tenacidad a la fractura decrece con el contenido de TÍO2 en las muestras 12Ce-TZP/TÍO2 y se encontró un máximo en el valor de Kj^- para las muestras 10Ce-TZP/TiO2 con un contenido de 3 moles % de TÍO2. De las medidas de impedancia compleja en aire hasta 1000 °C se deduce que el incremento del contenido de TÍO2 da lugar a un aumento de la resistividad.Peer reviewe

Una revisión del uso del TiO2 en terapias e ingeniería tisular

El óxido de titanio es considerado un biomaterial multifuncional con una experimentada aplicación en el reemplazo óseo. Sin embargo, gracias a sus propiedades, en los últimos años se ha demostrado la viabilidad de este óxido en nuevas áreas de la biomedicina, como es la ingeniería de tejidos. En esta revisión se pretenden exponer nuevas aportaciones del TiO2-x en su interacción con diferentes tipos celulares, revisando aquellas características físico-químicas del material que pueden explicar la naturaleza de su elevada biocompatibilidad. Se demuestra la idoneidad del TiO2-x como sustrato para el crecimiento de células hepáticas, endoteliales vasculares o neuronales.Peer reviewe