Novel mechanisms to enhance the capacitance beyond the classical limits in capacitors with free-electron-like electrodes

The so-called negative electron compressibility refers to the lowering of the chemical potential of a metallic system when the carrier density increases. This effect has often been invoked in the past to explain the enhancement of the capacitance beyond the classical limits in capacitors with two-dimensional electron gases as electrodes. Based on experiments on strongly confined semiconductor quantum wells (QWs), it has been traditionally ascribed to the electron exchange energy as the main driving force. Recent research, however, has revealed that analogous effects can occur in other classes of materials systems, such as polar oxide interfaces, whose characteristics drastically depart from those of the previously considered cases. To rationalize these new results, it is necessary to revisit the established theory of confined electron gases, and test whether its conclusions are valid beyond the specifics of semiconductor-based QWs. Here we find, based on first-principles calculations of jellium slabs, that one must indeed be very careful when extrapolating existing results to other realistic physical systems. In particular, we identify a number of additional, previously overlooked mechanisms (e.g., related to the displacement of the electronic cloud and to the multiband structure of the delocalized gas), that enter into play and become new sources of negative capacitance in the weak-confinement regime. Our detailed analysis of these emerging contributions, supported by analytic models and multiple test cases, will provide a useful guidance in the ongoing quest for nanometric capacitors with enhanced performance.Comment: 24 pages, 19 figure

El Brexit: causas, consecuencias y alternativas futuras

La historia reciente y en particular en estos últimos dos años ha sido caracterizada por multitud de desafíos al orden internacional establecido, desde la votación por la independencia de Escocia, a la proclamación de Donald Trump como presidente de los Estados Unidos. El Brexit ha sido uno de estos fenómenos y amenaza con reconfigurar la concepción actual que se tenía hasta ahora de la Unión Europea. Esto podría ser el inicio del desmantelamiento de esta unión de países o al menos la fragmentación de Europa tal y como la conocemos. Lo que aún queda por decidir es en qué derivarán estas pretensiones soberanistas y si se materializaran en una ruptura total o en la aplicación de un modelo intermedio de membresía para Reino Unido en la UE. Esto hace relevante reunir las distintas opciones que tendrán los británicos en el futuro y comprender sus implicaciones.The recent history and, in particular the last two years have been characterised by a series of challenges to the stablished global order, from Scotland’s independence referendum to Donald Trump’s winning the United States elections for president. Brexit has been one of these phenomena and threats to reconfigure the idea we used to have of the European Union. This could be the beginning of the dismantling of this union of countries or at least the fragmentation of Europe as we know it. What hasn’t been decided yet is the result of these sovereign claims and whether they will result in a total breakup or in the establishment of an intermediate model of membership in the EU. These aspects make it vital to bring together the different options the UK could have in the future and to understand their implications.Universidad de Sevilla. Grado en Administración y Dirección de Empresa

Interplay of couplings between antiferrodistortive, ferroelectric, and strain degrees of freedom in monodomain PbTiO3_{3}/SrTiO3_{3} superlattices

We report first-principles calculations on the coupling between epitaxial strain, polarization, and oxygen octahedra rotations in monodomain (PbTiO$_{3}$)$_{n}$/(SrTiO$_{3}$)$_{n}$ superlattices. We show how the interplay between (i) the epitaxial strain and (ii) the electrostatic conditions, can be used to control the orientation of the main axis of the system. The electrostatic constrains at the interface facilitate the rotation of the polarization and, as a consequence, we predict large piezoelectric responses at epitaxial strains smaller than those that would be required considering only strain effects. In addition, ferroelectric (FE) and antiferrodistortive (AFD) modes are strongly coupled. Usual steric arguments cannot explain this coupling and a covalent model is proposed to account for it. The energy gain due to the FE-AFD coupling decreases with the periodicity of the superlattice, becoming negligible for $n \ge 3$.Comment: 5 pages, 4 figure

Data-Analytics Modeling of Electrical Impedance Measurements for Cell Culture Monitoring

High-throughput data analysis challenges in laboratory automation and lab-on-a-chip devices’ applications are continuously increasing. In cell culture monitoring, specifically, the electrical cell-substrate impedance sensing technique (ECIS), has been extensively used for a wide variety of applications. One of the main drawbacks of ECIS is the need for implementing complex electrical models to decode the electrical performance of the full system composed by the electrodes, medium, and cells. In this work we present a new approach for the analysis of data and the prediction of a specific biological parameter, the fill-factor of a cell culture, based on a polynomial regression, data-analytic model. The method was successfully applied to a specific ECIS circuit and two different cell cultures, N2A (a mouse neuroblastoma cell line) and myoblasts. The data-analytic modeling approach can be used in the decoding of electrical impedance measurements of different cell lines, provided a representative volume of data from the cell culture growth is available, sorting out the difficulties traditionally found in the implementation of electrical models. This can be of particular importance for the design of control algorithms for cell cultures in tissue engineering protocols, and labs-on-a-chip and wearable devices applicationsEspaña, Ministerio de Ciencia e Innovación y Universidades project RTI2018-093512-B-C2

Editorial

Editorial Monográfico "Economía, gestión y márketing en organizaciones deportivas

Special Issue: Research in economics and sport management

El deporte supone actualmente uno de los fenómenos sociales de mayor arraigo, el cualb además cuenta con una elevada capacidad de movilización. Además posee una gran importancia social así como una importante dimensión económica que si bien son difíciles de cuantificar, se consideran un motor de desarrollo, que implican indirectamente a un gran número de diferentes actividades entre las que se incluyen otras industrias relacionadas con el sector, en las que el deporte constituye un eje vertebrador fundamental. En este contexto, la Revista Intangible Capital lanza este monográfico en el que se incluye la investigación de la economía del deporte desde diversas perspectivas, destacando así la importancia y el impacto que pueden llegar a tener en diferentes áreas. Por lo tanto, el objetivo de este trabajo es avanzar en el estudio de la economía del deporte a partir de la sinergia de recopilar artículos que traten esta temática

Modelling and Analysing Highly-Configurable Services

Since the emergence of XaaS and Cloud Computing paradigms, the number and complexity of available services have been increasing enormously. These services usually o er a plethora of con guration options, which can even include additional services provided as a bundled o er. In this scenario, usual tasks, such as description, discovery and selection, become increasingly complex due to the variability of the decision space. The notion of Highly-Con gurable Service (HCS) has been coined to identify such group of services that can be con gured and bundled together to perform demanding computing tasks. In this paper we characterize HCSs by means of an abstract model and a text-based, human-readable notation named SYNOPSIS that facilitates the execution of various service tasks. In particular, we validate the usefulness of our model when checking the validity of HCSs descriptions in SYNOPSIS, as well as selecting the optimal con guration with regards to user requirements and preferences by providing a prototype implementation.Junta de Andalucía P12-TIC-1867Ministerio de Economía y Competitividad TIN2015-70560-RScience Foundation Ireland Research. Centre grant 13/RC/2094ERC Advanced Grant no. 29165

Lattice screening of the polar catastrophe and hidden in-plane polarization in KNbO3/BaTiO3 interfaces

We have carried out first-principles simulations, based on density functional theory, to obtain the atomic and electronic structure of (001) BaTiO3/KNbO3 interfaces in an isolated slab geometry. We tried different types of structures including symmetric and asymmetric configurations and variations in the thickness of the constituent materials. The spontaneous polarization of the layer-by-layer non-neutral material (KNbO3) in these interfaces cancels out almost exactly the “built-in” polarization responsible for the electronic reconstruction. As a consequence, the so-called polar catastrophe is quenched and all the simulated interfaces are insulating. A model, based on the modern theory of polarization and basic electrostatics, allows an estimation of the critical thickness for the formation of the two-dimensional electron gas between 33 and 36 KNbO3 unit cells. We also demonstrate the presence of an unexpected in-plane polarization in BaTiO3 localized at the p-type TiO2/KO interface, even under in-plane compressive strains. We expect this in-plane polarization to remain hidden due to angular averaging during quantum fluctuations unless the symmetry is broken with small electric fields