Inter-laboratory comparison of a WDS-EDS quantitative X-ray microanalysis of a metallic glass

We conducted an inter-laboratory study of a metallic glass whose main component is nickel. Two determinations of the mass fractions of the different elements present within the sample were asked to the participants: one at an acceleration voltage of 15 or 20 kV and another one at 5 kV. We compare the mass fractions obtained from wavelength dispersive (WDS) and energy dispersive spectrometries (EDS) and also try to find an influence of the kind of EDS detector and its entrance window, the background subtraction method, the use or not of standards as well as the quantification method. Both means of WDS and EDS mass fractions are close to the reference values. The dispersion of the results was larger at 5 kV than at 15-20 kV owing to the use of the L lines rather than K lines and to the lowest collected intensities. There is an exception with the case of boron because at the lowest voltage, the excitation condition is more favourable for the production of the K line. It appears that the dispersion of the results is larger with EDS than with WDS but it was not possible to find a correlation between the large dispersion and one of the considered experimental parameters and quantification factors. Thus, one can think that electron microprobes are inherently better for the determination of mass fractions or that the implementation of quantitative analysis must be optimized for some cases, especially in SEMs.Comment: Members of the GN-MEBA, SEMPA users group and Belgian laboratories coordinated by Universite Catholique de Louvain are thanked for their participation to this inter-laboratory stud

Introduction : Entretiens collectifs : Nouveaux usages ?

L’idée de consacrer un numéro de la Revue française de science politique à l’usage des entre- tiens collectifs (EC) part du constat que cette technique de recueil des données, totalement marginale il y a quelques années dans le champ de la science politique française, est de plus en plus souvent utilisée. En 2004, au moment de la publication du petit sur Les entretiens collectifs dans la collection « L’enquête et ses méthodes », les références de science politique signalées étaient rares. En 2009, une sorte de frémissement était perceptible puisque quelques thèses et des projets de recherche utilisant cette technique étaient disponibles. Ce mouvement nous a semblé justifier l’organisation d’une journée d’étude dans le cadre de l’Association française de science politique (AFSP). Nous nous étions donnés pour objectif de faire un état des lieux des objets ou des problématiques à travers lesquels la recherche fondamentale dans les sciences sociales du politique, mais également la recherche appliquée, en incluant le secteur des études marketing, avaient recours aux EC. Ce numéro est le prolongement de cette manifestation mais il ne rassemble que des contributions consacrées aux usages scientifiques. Depuis 2009, les choses semblent encore avoir évolué, puisqu’on trouve des indices supplémentaires d’une diffusion de la technique dans le milieu des politistes et au-delà. Ces recherches constituent, de par leur nombre mais aussi leur diversité, une masse critique permettant de tirer un premier bilan au moment où la nécessité de dynamiser le débat sur les méthodes en science politique est régulièrement mise en avant. L’inclusion d’un volet d’EC dans un projet de recherche est aujourd’hui une pratique de moins en moins exceptionnelle, même si, le plus souvent, ils font office de complément idéal dans la mise en place d’un dispositif « multiméthodes ». Ils s’inscrivent égale- ment parfois au sein d’enquêtes de type ethnographique, que leur recours soit programmé – quand il s’agit, par exemple, d’étudier le système d’influence entre proches ou plus impromptu, la dimension collective de l’entretien étant alors le résultat non prévu de la dynamique de terrain

Les enquêtés disent-ils toujours la même chose ? Concordances et discordances entre les réponses à un questionnaire et les interventions dans un entretien collectif

Cet article confronte les réponses à un questionnaire et les interventions dans des entretiens collectifs portant sur les attitudes à l’égard de l’intégration européenne réalisés en 2005-2006. Il compare également les positions sur l’Europe avec celles obtenues sur deux autres thèmes, l’État providence et l’immigration. Il soulève donc à la fois la question de la variabilité des opinions et celle de l’apport spécifique des entretiens collectifs. Il montre une certaine congruence des deux techniques d’enquête mais souligne également l’existence de subtils décalages. Ceux-ci ne sont pas imputables aux individus en tant que tels mais relèvent d’abord des thèmes et des contextes de discussion. Cette exploration fournit des premiers éléments de preuve confortant l’idée selon laquelle les entretiens collectifs sont particulièrement utiles pour saisir les positions des moins dotés socialement et politiquement parmi les citoyens.This article compares responses to questionnaires and contributions to focus groups carried out in 2005-2006 as part of research on attitudes toward European integration. It also compares the stances taken on Europe with those taken on two other issues, the welfare state and immigration. It therefore addresses questions about both the variability of opinions and the specific contribution of focus groups. It demonstrates a certain congruence between the two techniques as well as the existence of subtle shifts. These shifts are not attributable to individuals as such but to topics and to the contexts of discussion. This exploration provides evidence that focus groups are particularly useful to understand how citizens – and among them those with fewer social and political resource – are taking a stand

Merge-and-simplify operation for compact combinatorial pyramid definition

International audienceImage pyramids are employed for years in digital image processing. They permit to store and use different scales/levels of details of an image. To represent all the topological information of the different levels, combinatorial pyramids have proved having many interests. But, when using an explicit representation, one drawback of this structure is the memory space required to store such a pyramid. In this paper, this drawback is solved by defining a compact version of combinatorial pyramids. This definition is based on the definition of a new operation, called "merge-and-simplify", which simultaneously merges regions and simplifies their boundaries. Our experiments show that the memory space of our solution is much smaller than the one of the original version. Moreover, the computation time of our solution is faster, because there are less levels in our pyramid than in the original one

Entretiens collectifs : Nouveaux usages ?

Auparavant marginale, la méthodologie qualitative des entretiens collectifs est désormais d'un usage plus fréquent en science politique. En lui consacrant un dossier, où les auteurs rendent compte de leur expérience de recherches empiriques, la RFSP entend favoriser le débat sur les méthodes en science politique et s’interroger sur les usages que font les politistes des dispositifs « multiméthodes ». Une large partie des ouvrages socio-historiques traités dans la chronique bibliographique de ce numéro contribue également à cette réflexio

Ouaga 2007 : habiter, peupler, socialiser par les mobilités

Ce rapport dresse un panorama des mobilités et migrations qui traversent, forment et dynamisent Ouagadougou en 2007, date de l’enquête dont il présente les résultats. Il engage une observation des diverses mobilités formant la ville, observation qui sera actualisée en 2009 dans le cadre d’un projet plus large incluant d’autres capitales sahéliennes (Bamako, Niamey), avec la promesse de comparaisons instructives sur les évolutions urbaines de la sous-région. Dans cette étude, les migrations internationales sont centrales, mais elles sont replacées aux côtés des mouvements internes et des pratiques de multirésidence ou des migrations temporaires. En arrière-plan de l’analyse de ces mouvements, analyse déclinée selon l’âge, le sexe, l’éducation et le travail des individus, s’impose un questionnement sur les logiques de l’installation et du peuplement en ville. Dès lors, les migrations apparaissent comme une composante de la vulnérabilité urbaine, du caractère informel du travail. En effet, l’intensité des flux migratoires qui traversent et font la ville infléchit sa composition sociale et spatiale et ainsi son futur

Phylogenetic correlations can suffice to infer protein partners from sequences

International audienceDetermining which proteins interact together is crucial to a systems-level understanding of the cell. Recently, algorithms based on Direct Coupling Analysis (DCA) pairwise maximum-entropy models have allowed to identify interaction partners among paralogous proteins from sequence data. This success of DCA at predicting protein-protein interactions could be mainly based on its known ability to identify pairs of residues that are in contact in the three-dimensional structure of protein complexes and that coevolve to remain physicochemically complementary. However, interacting proteins possess similar evolutionary histories. What is the role of purely phylogenetic correlations in the performance of DCA-based methods to infer interaction partners? To address this question, we employ controlled synthetic data that only involve phylogeny and no interactions or contacts. We find that DCA accurately identifies the pairs of synthetic sequences that share evolutionary history. While phylogenetic correlations confound the identification of contacting residues by DCA, they are thus useful to predict interacting partners among paralogs. We find that DCA performs as well as phylogenetic methods to this end, and slightly better than them with large and accurate training sets. Employing DCA or phylogenetic methods within an Iterative Pairing Algorithm (IPA) allows to predict pairs of evolutionary partners without a training set. We further demonstrate the ability of these various methods to correctly predict pairings among real paralogous proteins with genome proximity but no known direct physical interaction, illustrating the importance of phylogenetic correlations in natural data. However, for physically interacting and strongly coevolving proteins, DCA and mutual information outperform phylogenetic methods. We finally discuss how to distinguish physically interacting proteins from proteins that only share a common evolutionary history

Abrasion of 6 dentifrices measured by vertical scanning interference microscopy

OBJECTIVES: The abrasion of dentifrices is well recognized to eliminate the dental plaque. The aims of this study were to characterize the abrasive powders of 6 dentifrices (3 toothpastes and 3 toothpowders) and to measure the abrasion on a test surface by Vertical Scanning Interference microscopy (VSI). MATERIAL AND METHODS: Bright field and polarization microscopy were used to identify the abrasive particles on the crude dentifrices and after prolonged washes. Scanning electron microscopy and microanalysis characterized the shape and nature of the particles. Standardized and polished blocks of poly(methylmethacrylate) were brushed with a commercial electric toothbrush with the dentifrices. VSI quantified the mean roughness (Ra) and illustrated in 3D the abraded areas. RESULTS: Toothpastes induced a limited abrasion. Toothpowders induced a significantly higher roughness linked to the size of the abrasive particles. One powder (Gencix® produced a high abrasion when used with a standard testing weight. However, the powder is based on pumice particles covered by a plant homogenate that readily dissolves in water. When used in the same volume, or after dispersion in water, Ra was markedly reduced. CONCLUSION: Light and electron microscopy characterize the abrasive particles and VSI is a new tool allowing the analysis of large surface of abraded materials

Towards a transparent deliberation protocol inspired from supply chain collaborative planning

International audienceIn this paper we propose a new deliberation process based on argumentation and bipolar decision making in a context of agreed common knowledge and priorities together with private preferences. This work is inspired from the supply chain management domain and more precisely by the "Collaborative Planning, Forecasting and Replenishment" model which aims at selecting a procurement plan in collaborative supply chains

Molecular Signature of Polyoxometalates in Electron Transport of Silicon-based Molecular Junctions

Polyoxometalates (POMs) are unconventional electro-active molecules with a great potential for applications in molecular memories, providing efficient processing steps onto electrodes are available. The synthesis of the organic-inorganic polyoxometalate hybrids [PM$_{11}$O$_{39}$(Sn(C$_6$H$_4$)C$\equiv$C(C$_6$H$_4$)N$_2$)]$^{3-}$ (M = Mo, W) endowed with a remote diazonium function is reported together with their covalent immobilization onto hydrogenated n-Si(100) substrates. Electron transport measurements through the resulting densely-packed monolayers contacted with a mercury drop as a top electrode confirms their homogeneity. Adjustment of the current-voltage curves with the Simmons equation gives a mean tunnel energy barrier of 1.8 eV and 1.6 eV, for the Silicon-Molecules-Metal (SMM) junctions based on the polyoxotungstates (M = W) and polyoxomolybdates (M = Mo), respectively. This follows the trend observed in the electrochemical properties of POMs in solution, the polyoxomolybdates being easier to reduce than the polyoxotungstates, in agreement with lowest unoccupied molecular orbitals (LUMOs) of lower energy. The molecular signature of the POMs is thus clearly identifiable in the solid-state electrical properties and the unmatched diversity of POM molecular and electronic structures should offer a great modularity