How can large-scale twisted magnetic structures naturally emerge from buoyancy instabilities?

We consider the three-dimensional instability of a layer of horizontal magnetic field in a polytropic atmosphere where, contrary to previous studies, the field lines in the initial state are not unidirectional. We show that if the twist is initially concentrated inside the unstable layer, the modifications of the instability reported by several authors (see e.g. Cattaneo et al. (1990)) are only observed when the calculation is restricted to two dimensions. In three dimensions, the usual interchange instability occurs, in the direction fixed by the field lines at the interface between the layer and the field-free region. We therefore introduce a new configuration: the instability now develops in a weakly magnetised atmosphere where the direction of the field can vary with respect to the direction of the strong unstable field below, the twist being now concentrated at the upper interface. Both linear stability analysis and non-linear direct numerical simulations are used to study this configuration. We show that from the small-scale interchange instability, large-scale twisted coherent magnetic structures are spontaneously formed, with possible implications to the formation of active regions from a deep-seated solar magnetic field

Langual : un langage international pour la description structurée des aliments = Langual : an international language for the structured description of foods

L'article traite de l'organisation des nouvelles banques de données sur la composition des aliments en s'appuyant sur l'exemple de la banque française REGAL développée au CIQUAL. La codification des nutriments et les principes de standardisation des formules de calcul de certains nutriments sont évoqués. L'identification précise des aliments grâce à une description claire, complète, scientifique et se prêtant à des vérifications automatisées de similitude, est indispensable pour assurer de façon cohérente des transferts de données entre banques de différents pays. Langual, système international de codification descriptive des aliments permet une telle identification. Chaque aliment à coder est décrit par un ensemble des descripteurs standardisés, eux-mêmes regroupés en facettes. Chaque facette représente un sous-ensemble de caractéristiques comme l'origine biologique, les traitements technologiques, les méthodes de conservation et de cuisson, qui spécifient la qualité nutritionnelle et/ou hygiénique d'un aliment. (Résumé d'auteur

Validated data banks on food composition : concepts for modeling information

L'intérêt croissant pour la composition des aliments a conduit plusieurs pays à se doter de banque de données sur la composition des aliments. Ces banques sont des outils pour le contrôle de la qualité des aliments et pour la conduite des politiques alimentaires. L'article traite de la conception, de la structure, de la gestion et du fonctionnement de la banque de données française REGAL. Le système de description codifiée des aliments LANGUAL est, en particulier, présenté. Comme REGAL, les banques de données peuvent également prendre en compte la réglementation relative aux aliments ; il est aussi possible de leur incorporer des systèmes-experts. (Résumé d'auteur

Les lipides

L'exploitation d'une banque de données informatisées sur la composition des aliments permet de présenta la répartition des lipides sous différents aspects et selon divers modes : dispersion des teneurs en lipides au sein de chaque famille d'aliments, classement et regroupement des aliments en fonction de leurs teneurs ou de leurs densités en lipides, représentation de ces observations par différents types de tableaux, diagrammes et histogrammes. Ces mêmes modes d'exploitation permettent également d'étudier et de représenter la qualité nutritionnelle des lipides alimentaires en fonction de la proportion des divers acides gras : saturés, monoinsaturés, polyinsaturés, acides gras de configuration trans, acides gras à chaîne courte, moyenne ou longue. (Résumé d'auteur

Inverse cascade and symmetry breaking in rapidly-rotating Boussinesq convection

In this paper we present numerical simulations of rapidly-rotating Rayleigh-B\'enard convection in the Boussinesq approximation with stress-free boundary conditions. At moderately low Rossby number and large Rayleigh number, we show that a large-scale depth-invariant flow is formed, reminiscent of the condensate state observed in two-dimensional flows. We show that the large-scale circulation shares many similarities with the so-called vortex, or slow-mode, of forced rotating turbulence. Our investigations show that at a fixed rotation rate the large-scale vortex is only observed for a finite range of Rayleigh numbers, as the quasi-two-dimensional nature of the flow disappears at very high Rayleigh numbers. We observe slow vortex merging events and find a non-local inverse cascade of energy in addition to the regular direct cascade associated with fast small-scale turbulent motions. Finally, we show that cyclonic structures are dominant in the small-scale turbulent flow and this symmetry breaking persists in the large-scale vortex motion

Kinetic study of spiramycin removal from aqueous solution using heterogeneous photocatalysis

International audienceSpiramycin macrolide antibiotic (SPM) can be photocatalytically degraded on TiO2 (anatase variety). The experiments are done in a batch reactor and the effect of some key parameters is investigated under low energy of artificial UV light. The reaction rate is affected by varying TiO2 dose, pH and SPM concentration. Under optimized conditions, a photodegradation efficiency of 98% is achieved and the SPM photodegradation follows pseudo-first order kinetics. The Langmuir–Hinshelwood (L–H) model is successfully used to fit the experimental data, indicating the dependence of the reaction rate on the chemical reaction step. The L–H model led to the determination of both reaction kinetic and adsorption/desorption equilibrium constants. In order to give an overall estimate of the by-products, chemical oxygen demand, total organic carbon, and calculated average oxidation state monitor the photodegradation proces

Bioremediation: an overview on current practices, advances, and new perspectives in environmental pollution treatment

[Excerpt] Environmental pollution generated the need to search for new environmentally friendly, low-cost, and more efficient environmental clean-up techniques for its removal or reduction. Bioremediation, a branch of environmental biotechnology, is nowadays considered as one of the most promising alternatives. This technology uses the amazing ability of microorganisms or plants to accumulate, detoxify, degrade, or remove environmental contaminants. Bioremediation provides the transformation and/or even removal of organic and inorganic pollutants, even when they are present at low concentration. Continuous efforts are still made to understand the mechanisms by which microorganisms and plants remove or transform environmental pollutants. Thus, the purpose of this special issue was to explore different visions on bioremediation, while addressing recent advances and new ideas in the perspective of efficient process scale-up in view of application at larger scales. Authors’ contributions cover various topics with a range of papers including original research and review articles spanning studies in remediation of different environments which outline new findings in the biotechnology field. This special issue contains five papers including one review article and four original research articles. A brief description of these five manuscripts is detailed below. [...]We would like to extend our gratitude to all the authors who submitted their work for consideration in our special issue and to reviewers for their critical feedback. Contributions of Raluca Maria Hlihor and Maria Gavrilescu to this special issue were supported by a grant of the Romanian National Authority for Scientific Research,CNCS-UEFISCDI (Project no. PN-III-P4-ID-PCE-2016-0683, Contract no. 65/2017). Teresa Tavares’ contribution is supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the research project PTDC/AAG-TEC/5269/2014, the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of NORTE 2020 (Programa Operacional Regional do Norte).info:eu-repo/semantics/publishedVersio