Influence of magnetic ordering on structural instabilities in insulating perovskites

We propose a general model, based on Anderson superexchange and the pseudo Jahn-Teller effect, to explain why ferroelectric and octahedral tilting distortions are favored by ferromagnetic ordering when compared to antiferromagnetic tilting distortions in ABX3 (A = alkali, alkaline-earth ion, f-filling rare earth; B = magnetic transition-metal ion; X = O2−, F−) perovskite crystals. Ab initio calculations are used to check the model under a wide range of pressures for oxides and fluorides, with the latter displaying an enhancement of the ferroelectric distortion when pressure is increased.The support by the Spanish Ministerio de Ciencia y Tecnología under Project FIS2009-07083 and computational time in both the Altamira Supercomputing node and Calderon HPC cluster in Universidad de Cantabria is acknowledged. We would like to thank J. Junquera and M.T. Barriuso for valuable discussions

Enfermedad inflamatoria intestinal: depresión y estrategias de afrontamiento

Los objetivos de esta investigación fueron evaluar las estrategias de afrontamiento del estrés que utilizan los enfermos de Crohn y Colitis Ulcerosa una vez diagnosticada las enfermedad y relacionar estas estrategias con el estado de ánimo (depresivo - no depresivo), con el fin de determinar qué estrategias de afrontamiento son las que más están influyendo en el estado de ánimo del enfermo. La muestra estuvo formada por 40 pacientes, a los que se les administró un cuestionario demográfico, el Inventario de Depresión de Beck y el Cuestionario de Estrategias de Afrontamiento de Lazarus y Folkman. Los datos de este estudio reflejan que un alto porcentaje de enfermos de Crohn y Colitis Ulcerosa (45%) se encuentra deprimido, y que las diferencias en cuanto al sexo y la situación laboral son estadísticamente significativas, siendo las mujeres y aquellos pacientes que se encuentran desempleados, jubilados o que se dedican a sus labores los que mayor puntuación en depresión obtienen. Asimismo, la estrategia de afrontamiento que mejor predice un estado de ánimo depresivo es la de huida.The objectives of this research were to evaluate the stress coping strategies that Crohn and Ulcerative Colitis patients use once the illness is diagnosed and to relate these strategies with the mood (depressive - not depressive), with the aim of determining which coping strategies are influencing more in the patient mood. The sample was formed by 40 patients. They completed a demographic questionnaire, the Beck Depression Inventory and the Coping Strategies Questionnaire by Lazarus and Folkman. The data of this study reflect that a high percentage of Crohn and Ulcerative Colitis patients (45%) are depressed, and differences relating the sex and employed situation are statistically significant, being women and unemployed, retired or housewife patients who got a higher score in depression. Likewise, the coping strategy that better predicts the mood depression state is the avoidance

Prefrontal gray matter and motivation for treatment in cocaine dependent individuals with and without personality disorders

Addiction treatment is a long-term goal and therefore prefrontal–striatal regions regulating goal-directed behavior are to be associated with individual differences on treatment motivation. We aimed at examining the association between gray matter volumes in prefrontal cortices and striatum and readiness to change at treatment onset in cocaine users with and without personality disorders. Participants included 17 cocaine users without psychiatric comorbidities, 17 cocaine users with Cluster B disorders, and 12 cocaine users with Cluster C disorders. They completed the University of Rhode Island Change Assessment Scale, which measures four stages of treatment change (precontemplation, contemplation, action, and maintenance) and overall readiness to change, and were scanned in a 3 T MRI scanner. We defined three regions of interest (ROIs): the ventromedial prefrontal cortex (including medial orbitofrontal cortex and subgenual and rostral anterior cingulate cortex), the dorsomedial prefrontal cortex (i.e., superior medial frontal cortex), and the neostriatum (caudate and putamen). We found that readiness to change correlated with different aspects of ventromedial prefrontal gray matter as a function of diagnosis. In cocaine users with Cluster C comorbidities, readiness to change positively correlated with gyrus rectus gray matter, whereas in cocaine users without comorbidities it negatively correlated with rostral anterior cingulate cortex gray matter. Moreover, maintenance scores positively correlated with dorsomedial prefrontal gray matter in cocaine users with Cluster C comorbidities, but negatively correlated with this region in cocaine users with Cluster B and cocaine users without comorbidities. Maintenance scores also negatively correlated with dorsal striatum gray matter in cocaine users with Cluster C comorbidities. We conclude that the link between prefrontal–striatal gray matter and treatment motivation is modulated by co-existence of personality disorders

Prefrontal gray matter and motivation for treatment in cocaine-dependent individuals with and without personality disorders

Addiction treatment is a long-term goal and therefore prefrontal–striatal regions regulating goal-directed behavior are to be associated with individual differences on treatment motivation. We aimed at examining the association between gray matter volumes in prefrontal cortices and striatum and readiness to change at treatment onset in cocaine users with and without personality disorders. Participants included 17 cocaine users without psychiatric comorbidities, 17 cocaine users with Cluster B disorders, and 12 cocaine users with Cluster C disorders. They completed the University of Rhode Island Change Assessment Scale, which measures four stages of treatment change (precontemplation, contemplation, action, and maintenance) and overall readiness to change, and were scanned in a 3T MRI scanner. We defined three regions of interest (ROIs): the ventromedial prefrontal cortex (including medial orbitofrontal cortex and subgenual and rostral anterior cingulate cortex), the dorsomedial prefrontal cortex (i.e., superior medial frontal cortex), and the neostriatum (caudate and putamen). We found that readiness to change correlated with different aspects of ventromedial prefrontal gray matter as a function of diagnosis. In cocaine users with Cluster C comorbidities, readiness to change positively correlated with gyrus rectus gray matter, whereas in cocaine users without comorbidities it negatively correlated with rostral anterior cingulate cortex gray matter. Moreover, maintenance scores positively correlated with dorsomedial prefrontal gray matter in cocaine users with Cluster C comorbidities, but negatively correlated with this region in cocaine users with Cluster B and cocaine users without comorbidities. Maintenance scores also negatively correlated with dorsal striatum gray matter in cocaine users with Cluster C comorbidities. We conclude that the link between prefrontal–striatal gray matter and treatment motivation is modulated by co-existence of personality disorders

El papel del piping en la espeleogénesis del sistema endokárstico de Seso (Pirineo central,Huesca)

[ES] El sistema endokárstico de Seso (Boltaña, Huesca), localizado en el sector central surpirenaico, presenta una espeleogénesis singular. La excavación mecánica en condiciones vadosas de material margoso fácilmente erosionable (procesos de piping) constituye el principal mecanismo espeleogenético. La disposición espacial del sistema endokárstico respecto a las terrazas datadas del río Ara permite situar la formación de la cavidad en el Pleistoceno superior, probablemente coincidiendo con fases húmedas del MIS 4[EN] The Seso Cave system (Boltaña, Huesca province) in the Southcentral Pyrenees presents a singular speleogenesis. Vadose mechanical entrenchment of highly erosive and dispersive marls (piping processes) is the main espeleogenetic mechanism. Geometric relationship between the endokarstic system and a terrace of the Ara River chronologically controlled allows dating the cave formation in the Upper Pleistocene, probably during stages of the MIS 4 with high water availabilityEste trabajo es una contribución del Proyecto CGL2009-10455/BTE (Ministerio de Ciencia e Innovación y Fondos Europeos) y de los Grupos de Investigación Geomorfología y Cambio Global y Paleoambientes del Quaternario del Gobierno de Aragón.Agradecemos la ayuda económica del Geoparque del Sobrarbe y la colaboración de Enrique Oliver en el trabajo de laboratorio. Los autores agradecen los comentarios realizados por Juan José Durán, Jerónimo López- Martínez y un revisor anónimo.Peer reviewe

Tunneling splitting of Jahn-Teller ions in oxides

The magnitude of tunneling splitting, 3?, that governs decoherence in quantum systems under symmetric potentials, is frequently unknown. Using first-principles calculations, we have obtained 3? for a number of E?e Jahn-Teller impurities in solids. Calculated values span 6 orders of magnitude on passing from KCl?Ag2+ to MgO?Cu2+. Values associated with Cu2+- and Ag2+-doped MgO are 2 orders of magnitude larger than those previously assumed and consistent with the existence of a dynamic Jahn-Teller effect. The origin and enhancement with pressure of these high 3? values is discussed in detail.The support by the Spanish Ministerio de Ciencia y Tecnología under Projects FIS2006-02261 and FIS2009- 07083 is acknowledged

Investigación, desarrollo e innovación en materia de energías renovables: la urgencia de Europa por ser energéticamente independiente

[ES] El repunte del consumo de energía que se ha producido tras la fase aguda de la pandemia COVID-19 ha supuesto, a lo largo de 2021, un incremento en los precios de la energía que, tras la invasión rusa de Ucrania, han alcanzado importantes picos no previstos por los analistas. La incertidumbre en torno a la seguridad del suministro de gas natural que necesita Europa para acometer la transición energética, ha conducido a un replanteamiento de la estrategia de descarbonización que los representantes europeos se plantearon durante la COP21 de París. En este artículo analizamos el comportamiento y tendencias del mercado del gas natural, con especial enfoque en la situación en Europa, y analizaremos las consecuencias que está teniendo la actual crisis energética y económica generada por el previsible incumplimiento ruso de los acuerdos de suministro de gas natural a Europa tras la condena europea de la invasión rusa de Ucrania.[EN] The spike in energy consumption following the acute phase of the COVID-19 pandemic has led, throughout 2021, to an increase in energy prices which, following the Russian invasion of Ukraine, have reached significant peaks not foreseen by analysts. The uncertainty surrounding the security of natural gas supply that Europe needs to undertake the energy transition has led to a reassessment of the decarbonisation strategy that European representatives proposed during the COP21 in Paris. In this article we analyse the behaviour and trends in the natural gas market, with a special focus on the situation in Europe, and we will analyse the consequences that the current energy and economic crisis generated by the predictable Russian non-compliance with the agreements to supply natural gas to Europe after the European condemnation of the Russian invasion of Ukraine.Moreno Mas, MA.; Estellés Miguel, S.; Poza Plaza, EDL. (2023). Investigación, desarrollo e innovación en materia de energías renovables: la urgencia de Europa por ser energéticamente independiente. Editorial Universitat Politècnica de València. 435-442. https://doi.org/10.4995/INN2022.2022.1587443544

Internal electric fields and color shift in Cr3+-based gemstones

Seeking to better understand the origin of the different colors of emerald and ruby, both ab initio periodic and cluster calculations have been carried out. The calculations reproduce the interatomic distances measured for pure Be3Si6Al2O18 and Al2O3 as well as the Cr3+?O2? distances in emerald and ruby. The mean Cr3+?O2? distance for Be3Si6Al2O18:Cr3+ and Al2O3:Cr3+ is found to be practically equal to 1.97 Å, in agreement with recent experimental values. The present calculations confirm that the variations of optical properties due to Cr3+ impurities along the series of ionic oxides can be understood merely through the CrO69? unit but subject to the electric field due to the rest of the lattice ions. As a salient feature it is proved that changes in electronic density and covalency due to the internal field are not the cause of the color shift. Therefore, the red color of ruby is not due to the polarization of the electronic cloud around chromium as a result of the C3 local symmetry. The present study also demonstrates that the variation of the ligand field splitting parameter, 10Dq, induced by the internal electric field comes mainly from the contributions of first shells of ions around the CrO69? unit. As a consequence, 10Dq in emerald is not influenced by the internal field, as the contribution from Be2+ first neighbors is practically compensated by that of Si4+ second neighbors. In contrast, in ruby the t2g levels are shifted by the internal field 0.24 eV more than the eg ones, so explaining the color shift in this gemstone in comparison with emerald. This result is shown to arise partially from the asymmetric form of the internal electrostatic potential along the C3 axis in Al2O3.Support from the Spanish Ministerio de Ciencia y Tecnología under Project No. FIS2009-07083 is acknowledge

Impurities bound to vacancies in insulators: electronic relaxation and physical properties of the Cr 3 + − V M model center in K M F 3 ( M = Mg, Zn)

This work is aimed at gaining a better insight into the influence of a close vacancy, V, on the properties of impurities in insulating materials. To achieve this goal the Cr3+−VM model center formed in KMF3 (M = Mg, Zn) fluoroperovskites has been explored in detail by means of ab initio calculations on clusters involving up to 87 ions. It is shown that the presence of the M2+ vacancy, VM, induces a significant structural relaxation on the CrF3−6 cubic complex which cannot be fully understood assuming that ions were rigid spheres that could not be polarized. Thus, although VM forces all the ligands to move away, the Cr3+−F− distance corresponding to the furthest ligand, Ffar, is found to be slightly higher than that for the closer equatorial ions. This unexpected fact is shown to be due to the electronic relaxation also induced by VM on the CrF3−6 complex, causing a charge of 0.2e to be transferred from the closest ligand to VM, Fnext, mainly to Ffar, and, to a lesser extent, to any equatorial ligand. This transfer of charge is mainly accomplished through orbitals lying in planes containing the C4 axis. In spite of these changes due to the vacancy, the 4A2g→4T2g optical transition is found to be weakly altered, a fact that concurs with available experimental data and whose origin is discussed. In contrast, electron paramagnetic resonance parameters such as gyromagnetic or superhyperfine tensors, which do depend on the electronic density around a point of the CrF3−6 complex, are shown to be particularly sensitive to the electronic relaxation induced by VM. In particular, the present study explains that the dominant component of the superhyperfine tensor for the Fnext ligand is clearly higher than that for Ffar, in agreement with experimental data. The relevance of the present results for understanding the electronic properties of other systems involving vacancies is also discussed. Some results on the Cr3+−Li+ center formed in KMgF3 are also discussed for comparison.The support by the Spanish Ministerio de Ciencia y Tecnología under Project FIS2009-07083 is acknowledge

Insulators containing CuCl4X22? (X = H2O, NH3) units: Origin of the orthorhombic distortion observed only for CuCl4(H2O)2 2?

The origin of the difference in structure between compounds containing CuCl4X22? (X=H2O, NH3) units is analyzed by means of first-principles calculations. While NH3-containing compounds display tetragonal symmetry, H2O-containing ones display an orthorhombic distortion at low temperature where the equatorial Cl? ions are no longer equivalent. Our simulations of optical and vibrational transitions show good agreement with all available experimental optical absorption and Raman data. As a salient feature, the value of the force constant for the B1g mode, K(B1g), driving the orthorhombic distortion in the CuCl4(H2O)22? unit is found to be four times smaller than that calculated for CuCl4(NH3)22?, stressing that CuCl4(H2O)22? is in the verge of the D4h?D2h instability. The analysis of results obtained for different values of the distortion coordinate, Q(B1g), clearly shows that the softening undergone by K(B1g) in CuCl4(H2O)22? comes mainly from the vibronic admixture of the antibonding a?1g(?3z2-r2) orbital with the bb1g bonding (or charge transfer) level. This mechanism is thus similar to that responsible for distortions observed in some fluoroperovskites and oxoperovskites. The present results, quantifying the importance of vibronic effects in structural instabilities, clearly demonstrate that, contrary to what was suggested by several authors, the instability in CuCl4(H2O)22? is not related to the Jahn-Teller effect and that the orthorhombic distortion observed in the pure compound Rb2CuCl4(H2O)2 has a local origin.The support by the Spanish Ministerio de Ciencia y Tecnología under Project No. FIS2009-07083 is acknowledged