Silicon recovery from silicon-iron alloys by electrorefining in molten fluorides

Electrorefining of a silicon-iron material (Si-4.7at%Fe) in molten NaF-KF at 850°C has been investigated in view of recovering pure Si, using electrochemical techniques, SEM-EDS and ICP-AES analyses. The selective electrochemical dissolution of Si was evidenced. Electrorefining runs led to a maximum Si recovery of 80% of the initial Si contained in the material, in the form of a dense deposit at the cathode, with very high current efficiencies. The Si purity has been examined and no Fe was detected by ICP-AES analysis: the recovered Si purity is thus assumed to be higher than 99.99%

Fluoroacidity evaluation in molten salts

The fluoroacidity of several alkaline fluoride media was studied by monitoring the concentration of electroactive species which is decreasing versus time due to a gas species release, such as silicon fluorides, as indicated by the reaction: SiF(4+x)x- = SiF4(g) + x F- This article relates the Si(IV) reaction study to define a relative fluoroacidity scale by studying the silicon ions stability in different melts. Electrochemical techniques allow the measurement of SiF4+xx- concentration evolution and thus the reaction rate constant to be calculated at different temperatures and for several fluoride media. The article shows that the free F- content depends on the fluoride mixture and that the rate values are correlated with the fluoroacidity allowing a qualitative estimation. Then a fluoride solvents fluoroacidity scale was proposed, scaling the different eutectic melts from basic melt to acidic one: NaF-KF < LiF-KF < NaF-MgF2 < NaF-CaF2 < LiF-NaF < LiF < LiF-CaF2

Silicon electrodeposition in molten fluorides

Silicon nucleation process was investigated in molten NaF-KF (40-60 mol%) on silver electrodes in the 820-950°C temperature range in order to optimize silicon coating operating conditions. Chronoamperometric measurements evidenced that silicon electrodeposition process involved an instantaneous nucleation with diffusion-controlled nuclei growth whatever temperature and Si(IV) ions concentration in the mixture. The overpotential and temperature influence on nucleation sites number was also studied. Silicon deposits were obtained using the same temperature range as nucleation study, for different current densities on substrates: Ni, Ag, Cgraphite and Cvitreous. A sensitive influence of the cathodic substrate on the deposit adherence and roughness was observed and discussed

Aide à la communication informatisée dans les TED

National audienceAprès avoir rappelé les symptômes de l'autisme comme pathologie neuro-développementale qui appartient aux Troubles Envahissants du Développement (TED), nous étudions les principes et les caractéristiques des supports visuels (classeurs traditionnels et tablettes électroniques) destinés aux enfants autistes afin qu'ils puissent communiquer avec leur entourage (famille et personnes chargées du suivi thérapeutique, éducatif ou pédagogique). Nous présentons les fonctionnalités d'un prototype innovant fonctionnant sur tablette électronique que nous avons développé (paramétrage des utilisateurs, du lexique, de la syntaxe des messages, mémorisation d'un journal des interactions, ...). Nous exposons les modalités de l'expérience que nous allons mener auprès de jeunes enfants autistes de moins de 6 ans dans le cadre de leur accueil au CATTP ISATIS (CH St-Jean-de Dieu) et dans leur cadre familial

Selecting answers to questions from Web documents by a robust validation process

International audienceQuestion answering (QA) systems aim at finding answers to question posed in natural language using a collection of documents. When the collection is extracted from the Web, the structure and style of the texts are quite different from those of newspaper articles. We developed a QA system based on an answer validation process able to handle Web specificity. A large number of candidate answers are extracted from short passages in order to be validated according to question and passages characteristics. The validation module is based on a machine learning approach. It takes into account criteria characterizing both the passage and answer relevance at the surface, lexical, syntactic and semantic levels to deal with different types of texts. We present and compare results obtained for factual questions posed on a Web and on a newspaper collection. We show that our system outperforms a baseline by up to 48% in MRR

Construction of a dairy microbial genome catalog opens new perspectives for the metagenomic analysis of dairy fermented products

Microbial communities of traditional cheeses are complex and insufficiently characterized. The origin, safety and functional role in cheese making of these microbial communities are still not well understood. Metagenomic analysis of these communities by high throughput shotgun sequencing is a promising approach to characterize their genomic and functional profiles. Such analyses, however, critically depend on the availability of appropriate reference genome databases against which the sequencing reads can be aligned. We built a reference genome catalog suitable for short read metagenomic analysis using a low-cost sequencing strategy. We selected 142 bacteria isolated from dairy products belonging to 137 different species and 67 genera, and succeeded to reconstruct the draft genome of 117 of them at a standard or high quality level, including isolates from the genera Kluyvera, Luteococcus and Marinilactibacillus, still missing from public database. To demonstrate the potential of this catalog, we analysed the microbial composition of the surface of two smear cheeses and one blue-veined cheese, and showed that a significant part of the microbiota of these traditional cheeses was composed of microorganisms newly sequenced in our study. Our study provides data, which combined with publicly available genome references, represents the most expansive catalog to date of cheese-associated bacteria. Using this extended dairy catalog, we revealed the presence in traditional cheese of dominant microorganisms not deliberately inoculated, mainly Gram-negative genera such as Pseudoalteromonas haloplanktis or Psychrobacter immobilis, that may contribute to the characteristics of cheese produced through traditional methods.https://doi.org/10.1186/1471-2164-15-110

What is really social about social insect cognition?

It is often assumed that social life imposes specific cognitive demands for animals to communicate, cooperate and compete, ultimately requiring larger brains. The “social brain” hypothesis is supported by data in primates and some other vertebrates, but doubts have been raised over its applicability to other taxa, and in particular insects. Here, we review recent advances in insect cognition research and ask whether we can identify cognitive capacities that are specific to social species. One difficulty involved in testing the social brain hypothesis in insects is that many of the model species used in cognition studies are highly social (eusocial), and comparatively little work has been done in insects that live in less integrated social structures or that are solitary. As more species are studied, it is becoming clear that insects share a rich cognitive repertoire and that these abilities are not directly related to their level of social complexity. Moreover, some of the cognitive mechanisms involved in many social interactions may not differ from those involved in non-social behaviors. We discuss the need for a more comparative and neurobiologically grounded research agenda to better understand the evolution of insect brains and cognition

Isoselective Ring-Opening Polymerization of rac-Lactide From Chiral Takemoto’s Organocatalysts:Elucidation of Stereocontrol

Despite significant advances in organocatalysis, stereoselective polymerization reactions utilizing chiral organocatalysts have received very little attention, and much about the underlying mechanisms remains unknown. Here, we report that both commercially available (R,R)- and (S,S)-enantiomers of chiral thiourea-amine Takemoto’s organocatalysts promote efficient control and high isoselectivity at room temperature of the ring-opening polymerization (ROP) of racemic lactide by kinetic resolution, yielding highly isotactic, semicrystalline and metal-free polylactide (PLA). Kinetic investigations and combined analyses of the resulting PLAs have allowed the stereocontrol mechanism, which eventually involves both enantiomorphic site control and chain-end control, to be determined. Moreover, epimerization of rac-LA to meso-LA is identified as being responsible for the introduction of some stereoerrors during the ROP process

Isoselective ring-opening polymerization of rac-lactide from chiral takemoto's organocatalysts : elucidation of stereocontrol

peer reviewe

A recruitment maneuver increases oxygenation after intubation of hypoxemic intensive care unit patients: a randomized controlled study

International audienc