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

New ideas for understanding the structure and magnetism in AgF₂: prediction of ferroelasticity

In the search for new high-temperature superconductors, it has been proposed that there are strong similarities between the fluoroargentate AgF₂ and the cuprate La₂CuO₄. We explored the origin of the possible layered structure of AgF₂ by studying its parent high-symmetry phase and comparing these results with those of a seemingly analogous cuprate, CuF₂. Our findings first stress the large differences between CuF₂ and AgF₂. Indeed, the parent structure of AgF₂ is found to be cubic, naturally devoid of any layering, even though Ag²⁺ ions occupy trigonal sites that, nevertheless, allow the existence of a Jahn-Teller effect. The observed Pbca orthorhombic phase is found when the system is cooperatively distorted by a local E⊗e trigonal Jahn-Teller effect around the silver sites that creates both geometrical and magnetic layering. While the distortion implies that two Ag²⁺ -F⁻ bonds increase their distance by 15% and become softer, our simulations indicate that covalent bonding and interlayer electron hopping is strong, unlike the situation in cuprate superconductors, and that, in fact, exfoliation of individual planes might be a harder task than previously suggested. As a salient feature, these results prove that the actual magnetic structure in AgF₂ is a direct consequence of vibronic contributions involved in the Jahn-Teller effect. Finally, our findings show that, due to the multiple minima intrinsic to the Jahn-Teller energy surface, the system is ferroelastic, a property that is strongly coupled to magnetism in this argentate.The support by the Spanish Ministerio de Ciencia, Innovación y Universidades under Project PGC2018-096955-B-C41 and the European Union and the University of Cantabria under FEDER project EQC2019-006136-P is acknowledged

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

Strain-induced ferromagnetic to antiferromagnetic crossover in d⁹-Ion (Cu²+ and Ag²+)-layered perovskites

A characteristic aspect of undoped high-temperature layered copper oxide superconductors is their strong in-plane antiferromagnetic coupling. This state is markedly different from that found in other chemically similar copper- or silver-layered fluorides, which display a ferromagnetic ground state. The latter has been connected in the literature with the presence of an orthorhombic deformation of the lattice that shifts the intermediate ligand between two metal ions to be closer to one and further from the other. This distortion is completely absent in the oxides, which are essentially tetragonal. However, no quantitative information exists about how this distortion influences the antiferromagnetic state and its relative stability with respect to the ferromagnetic state. Here, we carry out first-principles simulations to show that the fluorides in the parent tetragonal phase are also antiferromagnetic and that the antiferromagnetic-to-ferromagnetic transition is only triggered for a large enough distortion, with a typical ligand shift of 0.1 Å. Moreover, we employ a valence-bond model and second-principles simulations to show that the factor in superexchange that favors the antiferromagnetic state reduces as the ligand moves away from the symmetric metal–metal position. Importantly, we find that this distortion is sensitive to the application of an epitaxial strain which, in turn, allows controlling the difference of energy between ferromagnetic and antiferromagnetic states and thus the Curie or Néel temperatures. In fact, for compressive strains larger than 5.1%, this piezomagnetic effect makes K₂CuF₄ and Cs₂AgF₄ antiferromagnetic, making these two lattices close chemical analogs of oxide superconductors.We acknowledge financial support from Grant No. PGC2018-096955-B-C41 funded by MCIN/AEI/10.13039/501100011033. I.S.M. acknowledges financial support from grant BDNS:589170 (Gobierno de Cantabria-Universidad de Cantabria)

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

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

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