1,697 research outputs found
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 ?
LâidĂ©e de consacrer un numĂ©ro de la Revue française de science politique Ă lâusage des entre- tiens collectifs (EC) part du constat que cette technique de recueil des donnĂ©es, totalement marginale il y a quelques annĂ©es dans le champ de la science politique française, est de plus en plus souvent utilisĂ©e. En 2004, au moment de la publication du petit sur Les entretiens collectifsâŻdans la collection « LâenquĂȘte et ses mĂ©thodes », les rĂ©fĂ©rences de science politique signalĂ©es Ă©taient rares. En 2009, une sorte de frĂ©missement Ă©tait perceptible puisque quelques thĂšses et des projets de recherche utilisant cette technique Ă©taient disponibles. Ce mouvement nous a semblĂ© justifier lâorganisation dâune journĂ©e dâĂ©tude dans le cadre de lâAssociation française de science politique (AFSP). Nous nous Ă©tions donnĂ©s pour objectif de faire un Ă©tat des lieux des objets ou des problĂ©matiques Ă travers lesquels la recherche fondamentale dans les sciences sociales du politique, mais Ă©galement la recherche appliquĂ©e, en incluant le secteur des Ă©tudes marketing, avaient recours aux EC. Ce numĂ©ro est le prolongement de cette manifestation mais il ne rassemble que des contributions consacrĂ©es aux usages scientifiques. Depuis 2009, les choses semblent encore avoir Ă©voluĂ©, puisquâon trouve des indices supplĂ©mentaires dâune diffusion de la technique dans le milieu des politistes et au-delĂ . Ces recherches constituent, de par leur nombre mais aussi leur diversitĂ©, une masse critique permettant de tirer un premier bilan au moment oĂč la nĂ©cessitĂ© de dynamiser le dĂ©bat sur les mĂ©thodes en science politique est rĂ©guliĂšrement mise en avant. Lâinclusion dâun volet dâEC dans un projet de recherche est aujourdâhui une pratique de moins en moins exceptionnelle, mĂȘme si, le plus souvent, ils font office de complĂ©ment idĂ©al dans la mise en place dâun dispositif « multimĂ©thodes ». Ils sâinscrivent Ă©gale- ment parfois au sein dâenquĂȘtes de type ethnographique, que leur recours soit programmĂ© â quand il sâagit, par exemple, dâĂ©tudier le systĂšme dâinfluence entre proches ou plus impromptu, la dimension collective de lâentretien Ă©tant alors le rĂ©sultat non prĂ©vu de la dynamique de terrain
Les enquĂȘtĂ©s disent-ils toujours la mĂȘme chose ? Concordances et discordances entre les rĂ©ponses Ă un questionnaire et les interventions dans un entretien collectif
Cet article confronte les rĂ©ponses Ă un questionnaire et les interventions dans des entretiens collectifs portant sur les attitudes Ă lâĂ©gard de lâintĂ©gration europĂ©enne rĂ©alisĂ©s en 2005-2006. Il compare Ă©galement les positions sur lâEurope avec celles obtenues sur deux autres thĂšmes, lâĂtat providence et lâimmigration. Il soulĂšve donc Ă la fois la question de la variabilitĂ© des opinions et celle de lâapport spĂ©cifique des entretiens collectifs. Il montre une certaine congruence des deux techniques dâenquĂȘte mais souligne Ă©galement lâexistence de subtils dĂ©calages. Ceux-ci ne sont pas imputables aux individus en tant que tels mais relĂšvent dâabord des thĂšmes et des contextes de discussion. Cette exploration fournit des premiers Ă©lĂ©ments de preuve confortant lâidĂ©e selon laquelle les entretiens collectifs sont particuliĂšrement utiles pour saisir les positions des moins dotĂ©s 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 â and among them those with fewer social and political resource â 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 mĂ©thodologie qualitative des entretiens collectifs est dĂ©sormais d'un usage plus frĂ©quent en science politique. En lui consacrant un dossier, oĂč les auteurs rendent compte de leur expĂ©rience de recherches empiriques, la RFSP entend favoriser le dĂ©bat sur les mĂ©thodes en science politique et sâinterroger sur les usages que font les politistes des dispositifs « multimĂ©thodes ». Une large partie des ouvrages socio-historiques traitĂ©s dans la chronique bibliographique de ce numĂ©ro contribue Ă©galement Ă cette rĂ©flexio
Ouaga 2007 : habiter, peupler, socialiser par les mobilités
Ce rapport dresse un panorama des mobilitĂ©s et migrations qui traversent, forment et dynamisent Ouagadougou en 2007, date de lâenquĂȘte dont il prĂ©sente les rĂ©sultats. Il engage une observation des diverses mobilitĂ©s formant la ville, observation qui sera actualisĂ©e en 2009 dans le cadre dâun projet plus large incluant dâautres capitales sahĂ©liennes (Bamako, Niamey), avec la promesse de comparaisons instructives sur les Ă©volutions urbaines de la sous-rĂ©gion. Dans cette Ă©tude, les migrations internationales sont centrales, mais elles sont replacĂ©es aux cĂŽtĂ©s des mouvements internes et des pratiques de multirĂ©sidence ou des migrations temporaires. En arriĂšre-plan de lâanalyse de ces mouvements, analyse dĂ©clinĂ©e selon lâĂąge, le sexe, lâĂ©ducation et le travail des individus, sâimpose un questionnement sur les logiques de lâinstallation et du peuplement en ville. DĂšs lors, les migrations apparaissent comme une composante de la vulnĂ©rabilitĂ© urbaine, du caractĂšre informel du travail. En effet, lâintensitĂ© des flux migratoires qui traversent et font la ville inflĂ©chit 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 (GencixÂź 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
[PMO(Sn(CH)CC(CH)N)] (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
- âŠ