Charge distribution model in cubic perovskite-type compounds

A non-zero electric field gradient tensor, detected by probes that occupy sites with cubic point group symmetry, was observed in many ABO3 perovskite-type compounds. This breakdown of local cubic symmetry is commonly associated with the presence of oxygen vacancies around the probe. This effect in BaTixHf1-xO3 with x = 0.7, 0.5, 0.3, 0.1, 0.05 and 0.01 is studied in this work. The cell parameters were obtained at laboratory temperature using XRD spectroscopy. The hyperfine parameters were measured at a 181Ta probe in the B site using Perturbed Angular Correlations (PAC) spectroscopy as a function of both temperature and composition. As a common trend, a static asymmetric and distributed quadrupolar interaction, strongly dependent on composition has been observed. The results, together with those corresponding to 1 > x ≥ 0.75, are analyzed using the point-charge model in terms of polarized oxygen vacancies, different covalence of the Ti-O and Hf-O bonds with computational simulation for the lattice positions of cations and oxygen vacancies.Facultad de Ciencias Exacta

Charge distribution model in cubic perovskite-type compounds

A non-zero electric field gradient tensor, detected by probes that occupy sites with cubic point group symmetry, was observed in many ABO3 perovskite-type compounds. This breakdown of local cubic symmetry is commonly associated with the presence of oxygen vacancies around the probe. This effect in BaTixHf1-xO3 with x = 0.7, 0.5, 0.3, 0.1, 0.05 and 0.01 is studied in this work. The cell parameters were obtained at laboratory temperature using XRD spectroscopy. The hyperfine parameters were measured at a 181Ta probe in the B site using Perturbed Angular Correlations (PAC) spectroscopy as a function of both temperature and composition. As a common trend, a static asymmetric and distributed quadrupolar interaction, strongly dependent on composition has been observed. The results, together with those corresponding to 1 > x ≥ 0.75, are analyzed using the point-charge model in terms of polarized oxygen vacancies, different covalence of the Ti-O and Hf-O bonds with computational simulation for the lattice positions of cations and oxygen vacancies.Facultad de Ciencias Exacta

Charge distribution model in cubic perovskite-type compounds

A non-zero electric field gradient tensor, detected by probes that occupy sites with cubic point group symmetry, was observed in many ABO3 perovskite-type compounds. This breakdown of local cubic symmetry is commonly associated with the presence of oxygen vacancies around the probe. This effect in BaTixHf1-xO3 with x = 0.7, 0.5, 0.3, 0.1, 0.05 and 0.01 is studied in this work. The cell parameters were obtained at laboratory temperature using XRD spectroscopy. The hyperfine parameters were measured at a 181Ta probe in the B site using Perturbed Angular Correlations (PAC) spectroscopy as a function of both temperature and composition. As a common trend, a static asymmetric and distributed quadrupolar interaction, strongly dependent on composition has been observed. The results, together with those corresponding to 1 > x ≥ 0.75, are analyzed using the point-charge model in terms of polarized oxygen vacancies, different covalence of the Ti-O and Hf-O bonds with computational simulation for the lattice positions of cations and oxygen vacancies.Facultad de Ciencias Exacta

Acute effects of small changes in bicycle saddle height on gross efficiency and lower limb kinematics

P. 784-791El objetivo del presente estudio fue evaluar los efectos agudos de pequeños cambios en la altura del sillín de bicicleta sobre la eficiencia bruta y cinemática de las extremidades inferiores. Ciclistas bien entrenados (n = 14) realizaron una prueba de pedaleo sub-máximo (~ 70-75% del VO2max) a cadencia constante (90 rpm). Consistió en tres series aleatorias de 6 minutos con la altura de sillín preferida, 2% más alta y 2% más baja. La eficiencia bruta (GE) fue significativamente menor y el consumo de oxígeno (VO2) fue significativamente mayor levantando el sillín (GE = 19.9 ± 1.5%; VO2 = 43.8 ml.kg-1.min-1) que al bajarlo (GE = 20.4 ± 1.3%; VO2 = 42.8 ml.kg-1.min-1). Adicionalmente, un cambio de 0.8% en GE (20.6 ± 1.6 a 19.8 ± 1.6%, p < 0.05) se observó al comparar las posiciones donde se obtuvieron los mejores y peores GE. También se observó un efecto significativo en la cinemática de las extremidades inferiores (p <0.05) al efectuar pequeños cambios en la altura del sillín. Las diferencias entre las posiciones de silla de montar más bajas y más altas, en las articulaciones de cadera, rodilla y tobillo fueron un aumento de la extensión (~ 4, 7 y 8º, respectivamente), una disminución de la flexión (~3, 4 y 4º respectivamente) y, en consecuencia, un aumento del rango de movimiento (~1, 3 y 4º respectivamente). Los resultados del presente estudio indican que pequeños cambios en la altura del sillín afectaron a GE y a la cinemática de las extremidades inferiores. Los cambios observados en la cinemática de las extremidades inferiores podrían justificar, en parte, los cambios de GES

Upregulated proteasome subunits in COVID-19 patients: a link with hypoxemia, lymphopenia and inflammation

Severe COVID-19 disease leads to hypoxemia, inflammation and lymphopenia. Viral infection induces cellular stress and causes the activation of the innate immune response. The ubiquitin-proteasome system (UPS) is highly implicated in viral immune response regulation. The main function of the proteasome is protein degradation in its active form, which recognises and binds to ubiquitylated proteins. Some proteasome subunits have been reported to be upregulated under hypoxic and hyperinflammatory conditions. Here, we conducted a prospective cohort study of COVID-19 patients (n = 44) and age-and sex-matched controls (n = 20). In this study, we suggested that hypoxia could induce the overexpression of certain genes encoding for subunits from the α and β core of the 20S proteasome and from regulatory particles (19S and 11S) in COVID-19 patients. Furthermore, the gene expression of proteasome subunits was associated with lymphocyte count reduction and positively correlated with inflammatory molecular and clinical markers. Given the importance of the proteasome in maintaining cellular homeostasis, including the regulation of the apoptotic and pyroptotic pathways, these results provide a potential link between COVID-19 complications and proteasome gene expressionThis research was funded by Health Research Fund (Fondo de Investigación Sanitario [FIS])-European Regional Development Fund (FEDER), Spain through PI19/01612 (F.G.-R.) and COV20/00207 and PI19-01363 (C.C.-Z.) and ISCIII (CP18/00028), co-funded by ESF, “Investing in your future

Dielectric behaviour of Hf-doped CaCu3Ti4O12 ceramics obtained by conventional synthesis and reactive sintering

CaCu3(Ti4xHfx)O12 ceramics (JC = 0.04, 0.1 and 0.2) were prepared by conventional synthesis (CS) and through reactive sintering (RS), in which synthesis and sintering of the material take place in one single step. The microstructure and the dielectric properties of Hf-doped CCTO (CCTOHf) have been studied by XRD, FE-SEM, AFM, Raman and impedance spectroscopy (IS) in order to correlate the structure, microstructure and the electrical properties. Samples prepared by reactive sintering show slightly higher dielectric constant than those prepared by conventional synthesis in the same way than the pure CCTO. Dielectric constant and dielectric losses decrease slightly increasing Hf content. For CCTOHf ceramics with x> 0.04 for CS and x> 0.1 for RS, a secondary phase HfTi04 appears. As expected, the reactive sintering processing method allows a higher incorporation of Hf in the CCTO lattice than the conventional synthesis one

High-resolution TDPAC measurement in K₂ZrF₆

A time resolution of 2τ=0.75 ns, achieved with a conventional TDPAC setup with FCs detectors, allowed a determination of the very high electric field gradient at Hf impurity sites in K2ZrF6. Simple theoretical calculations seem to indicate that nearest neighbours are responsible for the interaction observed.Departamento de Físic

Temperature defendence of the hyperfine interaction in (NH4)2ZrF6

The thermal evolution of the hyperfine quadrupole interaction in (NH4)2ZrF6 has been investigated via TDPAC from 14 to 400 K. A phase transition is detected near 370 K. The low-temperature phase exhibits two sites equally populated for181Ta probes. The associated electric field gradients are described by both high asymmetry parameters and high interaction frequencies. On the other hand, the high-temperature phase corresponds to an unique axially symmetric and more intense electric field gradient.Facultad de Ciencias Exacta

Circonia finamente molida y circonia dopada con MgO: aparición de una nueva estructura común

Muestras de badeleyita (ZrO, monoclínica) molidas finamente durante diferentes tiempos y cerámicas de circonia estabilizadas fabricadas por adición de 6, 14 y 20 % molar de MgO fueron caracterizadas por difractometría de rayos X y espectrometría Raman (Er). Posteriormente se determinó la abundancia de fases presentes mediante el método hiperfino de las Correlaciones Angulares Perturbadas Diferenciales en Tiempo (CAPDT). Tanto la molienda más prolongada que llevó a un tamaño de cristalito de 145 Á como la adición del óxido dopante condujeron a la aparición de una fase desordenada que pudo ser caracterizadas como una nueva estructura tetragonal de la circonia, metaestable, no transformable por enfriamiento y con alto contenido de defectos, similar a la encontrada en circonias dopadas con óxido de ytrio.Facultad de Ciencias ExactasCentro de Tecnología de Recursos Minerales y Cerámic

Controlling a Mouse Pointer with a Single-Channel EEG Sensor

Goals: The purpose of this study was to analyze the feasibility of using the information obtained from a one-channel electro-encephalography (EEG) signal to control a mouse pointer. We used a low-cost headset, with one dry sensor placed at the FP1 position, to steer a mouse pointer and make selections through a combination of the user’s attention level with the detection of voluntary blinks. There are two types of cursor movements: spinning and linear displacement. A sequence of blinks allows for switching between these movement types, while the attention level modulates the cursor’s speed. The influence of the attention level on performance was studied. Additionally, Fitts’ model and the evolution of the emotional states of participants, among other trajectory indicators, were analyzed. (2) Methods: Twenty participants distributed into two groups (Attention and No-Attention) performed three runs, on different days, in which 40 targets had to be reached and selected. Target positions and distances from the cursor’s initial position were chosen, providing eight different indices of difficulty (IDs). A self-assessment manikin (SAM) test and a final survey provided information about the system’s usability and the emotions of participants during the experiment. (3) Results: The performance was similar to some brain–computer interface (BCI) solutions found in the literature, with an averaged information transfer rate (ITR) of 7 bits/min. Concerning the cursor navigation, some trajectory indicators showed our proposed approach to be as good as common pointing devices, such as joysticks, trackballs, and so on. Only one of the 20 participants reported difficulty in managing the cursor and, according to the tests, most of them assessed the experience positively. Movement times and hit rates were significantly better for participants belonging to the attention group. (4) Conclusions: The proposed approach is a feasible low-cost solution to manage a mouse pointe