Communication: Improving the density functional theoryU description of CeO 2 by including the contribution of the O 2p electrons

Density functional theory (DFT) based approaches within the local-density approximation or generalized gradient approximation frameworks fail to predict the correct electron localization in strongly correlated systems due to the lack of cancellation of the Coulomb self-interaction. This problem might be circumvented either by using hybrid functionals or by introducing a Hubbard-like term to account for the on site interactions. This latter DFTU approach is less expensive and therefore more practical for extensive calculations in solid-state computational simulations. By and large, the U term only affects the metal electrons, in our case the Ce 4f ones. In the present work, we report a systematic analysis of the effect of adding such a U term also to the oxygen 2p electrons. We find that using a set of U f 5 eV and U p 5eV effective terms leads to improved description of the lattice parameters, band gaps, and formation and reduction energies of CeO

Agroecological Traditional Peasant Knowledge in Mexico

The aim of the paper is to present an application of a theoretical and methodological model for the systematization of peasant knowledge about a traditional agriculture practice of family orchards. It is a proposal that involves social participation, community organization and environmental education at three rural localities in the State of Mexico. The methodology applied includes participatory workshops, for obtaining ecological knowledge from farmers related to family orchards and agroecosystems management. The collected information was analyzed to identify aspects related to origin, application, transformation and transmission of traditional knowledge. The last step for knowledge systematization consisted of an important reflection that includes confrontation of the empirical experience with current theoretical approaches. The importance of this research, related to knowledge associated with family orchards, is due to their function of providing products for family subsistence. Because they allow “in situ” germplasm conservation, they favor family integration, foster community relationships, and bring environmental goods and services. Their management is based on vernacular and rational experience of using available natural resources, and represents an alternative for sustainable local development. However, these systems are subject to a disappearance process caused by urban growth, social migration, loss of traditional knowledge about orchard management, and lack of maintenance activities, among other problems that lead to abandonment. The study is based on the theoretical framework of agroecology, environmental education and knowledge systematization

Conocimiento tradicional del huerto familiar en el Altiplano Central Mexicano

Los agroecosistemas son una estrategia implementada para el manejo de recursos naturales (Altieri, 2009: 71), donde realizan prácticas de producción y conservación (Garnatje et al., 2011: 73; Montañez et al., 2014: 102). Su funcionamiento se sustenta en el conocimiento tradicional, estrechamente relacionado con la cosmogonía de las comunidades, su finalidad es fortalecer el manejo de plantas, semillas, animales y formas de organización (Toledo et al., 2008: 350; Calvet- Mir et al., 2014: 2). Por esta razón, el conocimiento tradicional favorece que el sistema de producción promueva la diversidad y se acumule conocimiento acerca del ambiente, la biodiversidad, así como el contexto local. Algunos ejemplos de estos agroecosistemas son el huerto familiar, la milpa y el cultivo de café bajo sombra (Colín et al., 2012: 13; Cahuich et al., 2014: 157; Montañez et al., 2014: 104; Santana et al., 2015: 407). En el caso particular de los huertos familiares, son una práctica desarrollada por generaciones, en estos agroecosistemas ocurren procesos sociales, culturales, ecológicos y agronómicos (Rivas, 2014: 4). En México son llamados traspatios, solares y huertos caseros. Se caracterizan por estar cerca de la casa (Rivas y Rodríguez, 2013: 7), su composición florística, arreglo espacial, así como el aprovechamiento de las especies dependen de las características del terreno, circunstancias de vida y necesidades de las personas (García et al., 2016a: 31; García et al., 2016b: 624). En los huertos se cultivan una amplia diversidad de árboles, arbustos y herbáceas, su importancia ecológica es la conservación de agrobiodiversidad in situ (Van der Wal et al., 2011: 5). Debido a que las actividades humanas influyen en las plantas cultivadas que existe en el huerto familiar, propician el desarrollo de especies silvestres por medio de su siembra fomentada o tolerada (Calvet-Mir et al. 2014: 6). Por lo general, las mujeres definen lo que se cultiva en los huertos, puesto que en muchas sociedades son las principales responsables de la alimentación y de la salud familiar. Esto propicia la adaptación de las especies al contexto local, a las condiciones ambientales, así como a las técnicas de cultivo. Los productos obtenidos de origen vegetal como animal satisfacen necesidades básicas de alimentación familiar (Montañez et al., 2014: 101; Salazar et al., 2015: 2). En este sentido, son fuente de alimentos e ingresos durante todo el año, aún sin hacer uso de insumos agrícolas sofisticados (FAO, 2015: 30; Toledo, 2005: 17). Por lo tanto son importantes para las familias de escasos recursos económicos (Mariaca, 2012: 10; White et al., 2013: 175; Juan et al., 2013: 18). En los municipios de Malinalco, Tenancingo y Villa Guerrero, Estado de México se presentan los Agroecosistemas con Huerto Familiar (AEHF), sin embargo, el proceso de urbanización, el crecimiento de la familia, la división del terreno para construcción, el abandono por causa de la migración, la pérdida de conocimientos para el manejo del huerto, la falta de mecanismos de transmisión pone en riesgo su continuidad (Chablé et al., 2015: 35; García et al., 2016b: 639). El objetivo principal fue analizar el conocimiento tradicional acerca de los huertos familiares que poseen los habitantes de las localidades rurales de Colonia Juárez (Malinalco), El Carmen (Tenancingo) y Progreso Hidalgo (Villa Guerrero)

Analysis of nonlinear noisy integrate & fire neuron models: blow-up and steady states

Nonlinear Noisy Leaky Integrate and Fire (NNLIF) models for neurons networks can be written as Fokker-Planck-Kolmogorov equations on the probability density of neurons, the main parameters in the model being the connectivity of the network and the noise. We analyse several aspects of the NNLIF model: the number of steady states, a priori estimates, blow-up issues and convergence toward equilibrium in the linear case. In particular, for excitatory networks, blow-up always occurs for initial data concentrated close to the firing potential. These results show how critical is the balance between noise and excitatory/inhibitory interactions to the connectivity parameter

A numerical solver for a nonlinear Fokker-Planck equation representation of neuronal network dynamics

To describe the collective behavior of large ensembles of neurons in neuronal network, a kinetic theory description was developed in [13, 12], where a macroscopic representation of the network dynamics was directly derived from the microscopic dynamics of individual neurons, which are modeled by conductance-based, linear, integrate-and-fire point neurons. A diffusion approximation then led to a nonlinear Fokker-Planck equation for the probability density function of neuronal membrane potentials and synaptic conductances. In this work, we propose a deterministic numerical scheme for a Fokker-Planck model of an excitatory-only network. Our numerical solver allows us to obtain the time evolution of probability distribution functions, and thus, the evolution of all possible macroscopic quantities that are given by suitable moments of the probability density function. We show that this deterministic scheme is capable of capturing the bistability of stationary states observed in Monte Carlo simulations. Moreover, the transient behavior of the firing rates computed from the Fokker-Planck equation is analyzed in this bistable situation, where a bifurcation scenario, of asynchronous convergence towards stationary states, periodic synchronous solutions or damped oscillatory convergence towards stationary states, can be uncovered by increasing the strength of the excitatory coupling. Finally, the computation of moments of the probability distribution allows us to validate the applicability of a moment closure assumption used in [13] to further simplify the kinetic theory

High-throughput screening of the thermoelastic properties of ultrahigh-temperature ceramics

Ultrahigh-temperature ceramics (UHTCs) are a group of materials with high technological interest because of their applications in extreme environments. However, their characterization at high temperatures represents the main obstacle for their fast development. Obstacles are found from an experimental point of view, where only few laboratories around the world have the resources to test these materials under extreme conditions, and also from a theoretical point of view, where actual methods are expensive and difficult to apply to large sets of materials. Here, a new theoretical high-throughput framework for the prediction of the thermoelastic properties of materials is introduced. This approach can be systematically applied to any kind of crystalline material, drastically reducing the computational cost of previous methodologies up to 80% approximately. This new approach combines Taylor expansion and density functional theory calculations to predict the vibrational free energy of any arbitrary strained configuration, which represents the bottleneck in other methods. Using this framework, elastic constants for UHTCs have been calculated in a wide range of temperatures with excellent agreement with experimental values, when available. Using the elastic constants as the starting point, other mechanical properties such a bulk modulus, shear modulus, or Poisson ratio have been also explored, including upper and lower limits for polycrystalline materials. Finally, this work goes beyond the isotropic mechanical properties and represents one of the most comprehensive and exhaustive studies of some of the most important UHTCs, charting their anisotropy and thermal and thermodynamical properties.Ministerio de Ciencia e Innovación PID2019-106871GB-I00European Union 752608Red Española de Supercomputación QS-2019-2-0006, QS-2019-3-0021, QS-2020-2-003

Contractions in the 2-wasserstein lenght space and thermalization of granular media

An algebraic decay rate is derived which bounds the time required for velocities to equilibrate in a spatially homogeneous flowthrough model representing the continuum limit of a gas of particles interacting through slightly inelastic collisions. This rate is obtained by reformulating the dynamical problem as the gradient flow of a convex energy on an infinite-dimensional manifold. An abstract theory is developed for gradient flows in length spaces, which shows how degenerate convexity (or even non-convexity) - if uniformly controlled - will quantify contractivity (limit expansivity) of the flow

Ruptura del septum ventricular como complicación de un evento coronario agudo

ResumenLa ruptura del septum ventricular (RSV) es una complicación mecánica infrecuente del infarto agudo de miocardio (IAM). Los principales factores de riesgo descritos son la edad avanzada, el género femenino, un primer episodio de IAM y la presencia de enfermedad coronaria. Se sospecha de esta patología cuando clínicamente se evidencia un deterioro inexplicable del estado hemodinámico posterior al infarto. Los estudios imagenológicos (ecocardiograma y Doppler color) ayudan a confirmar el diagnóstico de RSV. Respecto al manejo, la corrección quirúrgica continúa siendo el pilar del tratamiento, ya que posee menor mortalidad en comparación con el abordaje médico no quirúrgico. Se presentan dos casos de ruptura del septum ventricular; el primero corresponde a una paciente femenina adulta mayor, con múltiples comorbilidades, quien desarrolló un síndrome coronario agudo tipo infarto agudo de miocardio con elevación del segmento ST a nivel anteroseptal. Se le realizó angioplastia primaria con evidencia de ruptura del septum ventricular, que fue corregida mediante cirugía de forma temprana. Pasadas veinticuatro horas, presentó ruptura de la pared libre del ventrículo izquierdo, hecho que precipitó su deceso. El segundo caso es una paciente femenina adulta mayor, quien presentó síndrome coronario agudo tipo infarto agudo de miocardio sin elevación del ST en cara lateral. Siete días después se documentó la existencia de la ruptura del septum ventricular, la cual fue corregida de manera tardía, en el día octavo, sin complicaciones asociadas.AbstractVentricular septal rupture (VSR) is a rare mechanical complication of acute myocardial infarction (AMI). The main risk factors described are advanced age, female gender, a first episode of AMI and presence of coronary disease. There is suspicion for this condition when clinical evidence shows unexplained deterioration of hemodynamic status following infarction. Imaging studies (echocardiogram and colour Doppler) help confirm the diagnosis of ventricular septal rupture. Regarding management, surgical correction continues to be the mainstay of treatment, as it poses lower mortality in comparison to nonsurgical medical approach. Two cases of VSR are presented, the first one is a female adult patient with multiple comorbidities who developed an acute coronary syndrome of a acute myocardial infarction with an anteroseptal ST segment elevation. Primary angioplasty was performed that evidenced ventricular septal rupture, which was surgically corrected at an early stage. After 24hours, patient showed left ventricular free wall rupture, which precipitated her death. Second case is a female old patient who presented acute acute coronary syndrome of a acute myocardial infarction without lateral ST segment elevation. Seven days later a ventricular septal rupture was documented, which was corrected at a later stage on the eighth day without associated complications

Nature of the mixed-oxide interface in ceria-titania catalysts: Clusters, chains, and nanoparticles

The ceria-titania mixed metal oxide is an important component of catalysts active for the production of hydrogen through the water-gas shift reaction (CO + H2O → H2 + CO2) and the photocatalytic splitting of water (H2O + hv → H2 + 0.5O 2). We have found that ceria-titania catalysts prepared through wet chemical methods have a unique hierarchal architecture. Atomic resolution imaging by high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) reveals that ceria supported on titania exhibits a range of morphologies. One can clearly identify ceria structures involving clusters, chains, and nanoparticles, which are distributed inhomogeneously on the titania support. These structures are often below the sensitivity limit of techniques such as X-ray diffraction (XRD), which in this case identifies the average particle size of the ceria and titania nanoparticles (via the Debye-Scherer equation) to be 7.5 and 36 nm, respectively. The fluorite-structured ceria grows epitaxially on the anatase-structured titania, and this epitaxial growth influences the morphology of the nanoparticles. The presence of defects in the ceria - such as dislocations and surface steps - was routinely observed in HAADF STEM. Density functional theory (DFT) calculations indicate an energetic preference for the formation of O vacancies and the corresponding Ce 3+ sites at the ceria-titania interface. Experimental corroboration by soft X-ray absorption spectroscopy (SXAS) does suggest the presence of Ce3+ sites at the interface. © 2013 American Chemical Society.The research carried out at the Center for Functional Nanomaterials and the Chemistry Department of Brookhaven National Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. The theoretical studies were funded by the Ministry of Economy and Competitiveness (Spain, grants MAT2012-31526 and CSD2008-0023) and EU FEDER. Computational resources were provided by the Barcelona Supercomputing Center/Centro Nacional de Supercomputación (Spain).Peer Reviewe