Simulation of the carbon dioxide hydrate-water interfacial energy

Hypothesis: Carbon dioxide hydrates are ice-like nonstoichiometric inclusion solid compounds with importance to global climate change, and gas transportation and storage. The thermodynamic and kinetic mechanisms that control carbon dioxide nucleation critically depend on hydrate-water interfacial free energy. Only two independent indirect experiments are available in the literature. Interfacial energies show large uncertainties due to the conditions at which experiments are performed. Under these circumstances, we hypothesize that accurate molecular models for water and carbon dioxide combined with computer simulation tools can offer an alternative but complementary way to estimate interfacial energies at coexistence conditions from a molecular perspective. Calculations: We have evaluated the interfacial free energy of carbon dioxide hydrates at coexistence conditions (three-phase equilibrium or dissociation line) implementing advanced computational methodologies, including the novel Mold Integration methodology. Our calculations are based on the definition of the interfacial free energy, standard statistical thermodynamic techniques, and the use of the most reliable and used molecular models for water (TIP4P/Ice) and carbon dioxide (TraPPE) available in the literature. Findings: We find that simulations provide an interfacial energy value, at coexistence conditions, consistent with the experiments from its thermodynamic definition. Our calculations are reliable since are based on the use of two molecular models that accurately predict: (1) The ice-water interfacial free energy; and (2) the dissociation line of carbon dioxide hydrates. Computer simulation predictions provide alternative but reliable estimates of the carbon dioxide interfacial energy. Our pioneering work demonstrates that is possible to predict interfacial energies of hydrates from a truly computational molecular perspective and opens a new door to the determination of free energies of hydrates.We thank Pedro J. Pérez for the critical reading of the manuscript. We also acknowledge Centro de Supercomputación de Galicia (CESGA, Santiago de Compostela, Spain) and MCIA (Mésocentre de Calcul Intensif Aquitain) of the Universités de Bordeaux and Pau et Pays de l’Adour (France) for providing access to computing facilities. We thank financial support from the Ministerio de Economía, Industria y Competitividad (FIS2017- 89361-C3-1-P), Junta de Andalucía (P20-00363), and Universidad de Huelva (P.O. FEDER UHU-1255522), all three cofinanced by EU FEDER funds. J.A. acknowledges Contrato Predoctoral de Investigación from XIX Plan Propio de Investigación de la Universidad de Huelva and a FPU Grant (Ref. FPU15/03754) from Ministerio de Educación, Cultura y Deporte. J. A., J. M. M., and F. J. B. thankfully acknowledge the computer resources at Magerit and the technical support provided by the Spanish Supercomputing Network (RES) (Project QCM- 2018–2- 0042). Funding for open access charge: Universidad de Huelva / CBU

Requisitos de seguridad y salud en los proyectos de rehabilitación de edificios en España y Portugal: estudio comparativo de los requisitos de seguridad y salud en los proyectos de rehabilitación en España y Portugal

Las malas condiciones de trabajo y la elevada siniestralidad son una lacra para el sector de la construcción que, en estos aspectos, le hace destacar tristemente de entre el resto de sectores productivos en cualquier país. La nefasta situación descrita nos obliga a todos los implicados en el proceso constructivo a aportar un esfuerzo adicional en nuestras responsabilidades para luchar contra la elevada accidentalidad. La Directiva Marco 89/391/CEE sobre seguridad y salud en el trabajo, desarrollada para el sector de la construcción por la Directiva 92/57/CEE relativa a las disposiciones mínimas de seguridad y salud que deben aplicarse en las obras de construcción temporales o móviles y el resultado de estudios de investigación multitud desarrollados por universidades y por multitud de organismos técnicos nacionales e internacionales, obligan y demuestran que el camino para la mejora de las condiciones de seguridad y salud en el trabajo, y por lo tanto de la disminución de la siniestralidad en el sector, comienza por la implementación de técnicas, métodos y herramientas diseñadas para la neutralización y el control de los riesgos durante la elaboración del proyecto. En este trabajo vamos a analizar los requisitos de seguridad y salud que deben aplicarse a los proyectos de rehabilitación de edificios en España y Portugal, posteriormente compararemos los resultados obtenidos y obtendremos conclusiones sobre las fortalezas y las debilidades de cada modelo

Soil physical conditions limit palm and tree basal area in Amazonian forests

Background: Trees and arborescent palms adopt different rooting strategies and responses to physical limitations imposed by soil structure, depth and anoxia. However, the implications of these differences for understanding variation in the relative abundance of these groups have not been explored. Aims: We analysed the relationship between soil physical constraints and tree and palm basal area to understand how the physical properties of soil are directly or indirectly related to the structure and physiognomy of lowland Amazonian forests. Methods: We analysed inventory data from 74 forest plots across Amazonia, from the RAINFOR and PPBio networks for which basal area, stand turnover rates and soil data were available. We related patterns of basal area to environmental variables in ordinary least squares and quantile regression models. Results: Soil physical properties predicted the upper limit for basal area of both trees and palms. This relationship was direct for palms but mediated by forest turnover rates for trees. Soil physical constraints alone explained up to 24% of palm basal area and, together with rainfall, up to 18% of tree basal area. Tree basal area was greatest in forests with lower turnover rates on well-structured soils, while palm basal area was high in weakly structured soils. Conclusions: Our results show that palms and trees are associated with different soil physical conditions. We suggest that adaptations of these life-forms drive their responses to soil structure, and thus shape the overall forest physiognomy of Amazonian forest vegetation. © 2014 Copyright 2013 Botanical Society of Scotland and Taylor & Francis

Range-wide factors shaping space use and movements by the Neotropic’s flagship predator: the jaguar

The range-wide management of the jaguar (Panthera onca) depends upon maintaining core populations connected through multi-national, transboundary cooperation, which is dependent upon understanding the movement ecology and space use of jaguars throughout their range. Using 117 telemetry trajectories from 12 ecoregions, we examined the landscape-level environmental and anthropogenic factors related to jaguar home range size and movement parameters. Range-wide and at the ecoregional scale home range size decreased with increasing net productivity and increased with increasing road density. Also, range-wide, home range size decreased with increasing forest cover and decreasing human population density. Movement within home ranges was best explained by a different set of environmental covariates. Range-wide predictions of home range size were consistent with expectations based upon density estimates. Our findings provide a mechanism to evaluate range-wide habitat quality for jaguars and an inferential modeling framework that can be adapted to the conservation of other large terrestrial carnivores