Consensus theories: an oriented survey

This article surveys seven directions of consensus theories: Arrowian results, federation consensus rules, metric consensus rules, tournament solutions, restricted domains, abstract consensus theories, algorithmic and complexity issues. This survey is oriented in the sense that it is mainly – but not exclusively – concentrated on the most significant results obtained, sometimes with other searchers, by a team of French searchers who are or were full or associate members of the Centre d'Analyse et de Mathématique Sociale (CAMS).Consensus theories ; Arrowian results ; aggregation rules ; metric consensus rules ; median ; tournament solutions ; restricted domains ; lower valuations ; median semilattice ; complexity

Rétractions, corétractions et enveloppe injective d'une algèbre de transitions

AbstractThe notions of retraction and injectivity have been useful in the study of many categories (category of modules over a ring, category of posets, category of metric spaces over an Heyting albegra ...).In this article the category of Σ-transition algebras is considered, and in this frame, answers are given to the key questions related to these notions. For instance it is shown:—how to construct all the retraction types of a given Σ-transition algebra.—that the category of Σ-transition algebras has enough injective objects and an injective cogenerator.—that every Σ-transition algebras has an injective envelope.These allow to obtain results concerning the structure and the decomposition of a Σ-transition algebra

Aristotle on Non-Contradiction: Philosophers vs. Non-Philosophers

Aristotle’s principle of non-contradiction (PNC) has been interpreted by Łukasiewicz through three distinct formulations, namely ontological, logical, and psychological. Many have criticized Łukasiewicz’s position, but they still maintain that Aristotle defends distinct formulations. In contrast, this paper shows that Aristotle suggests only one formulation of the PNC. This unique formulation belongs to philosophy as the first science, so that the philosophers think of the PNC as a necessarily true principle, owing to their meta-physical cognition of the nature of things. Yet, there is another way to understand this formulation. Indeed, the non-philosophers believe in the PNC, without being able to understand its necessary truth, due to their ignorance of philosophy. Thus, Aristotle has to convince them that the PNC is the most certain opinion of all, and his dialectical justifications are purposely weak, as they are only concerned with the defense of a common opinion

Gaze following, gaze reading, and word learning in children at-risk for autism

We investigated gaze following abilities as a prerequisite for word learning, in a population expected to manifest a wide range of individual variability – children with a family history of autism. Three-year-olds with or without a family history of autism took part in a word-learning task that required following gaze to find the correct referent of a novel word. Using an eye-tracker to monitor children’s gaze behavior we show that the ability to follow an adult’s gaze was necessary but not sufficient for successful word learning. Those children that had poor social and communicative skills could follow gaze to the correct object, but did not then learn the word associated with that object. These findings shed light on the conditions that lead to successful or less successful word learning in typical and atypical populations

Consensus theories: an oriented survey

URL des Documents de travail : http://ces.univ-paris1.fr/cesdp/cesdp2010.htmlDocuments de travail du Centre d'Economie de la Sorbonne 2010.57 - ISSN : 1955-611XThis article surveys seven directions of consensus theories: Arrowian results, federation consensus rules, metric consensus rules, tournament solutions, restricted domains, abstract consensus theories, algorithmic and complexity issues. This survey is oriented in the sense that it is mainly – but not exclusively – concentrated on the most significant results obtained, sometimes with other searchers, by a team of French searchers who are or were full or associate members of the Centre d'Analyse et de Mathématique Sociale (CAMS).Cet article présente une vue d'ensemble de sept directions de recherche en théorie du consensus : résultats arrowiens, règles d'agrégation définies au moyen de fédérations, règles définies au moyen de distances, solutions de tournoi, domaines restreints, théories abstraites du consensus, questions de complexité et d'algorithmique. Ce panorama est orienté dans la mesure où il présente principalement – mais non exclusivement – les travaux les plus significatifs obtenus – quelquefois avec d'autres chercheurs – par une équipe de chercheurs français qui sont – ou ont été – membres pléniers ou associés du Centre d'Analyse et de Mathématique Sociale (CAMS)

Optimal clustering of multipartite graphs

AbstractGiven a graph G=(X,U), the problem dealt within this paper consists in partitioning X into a disjoint union of cliques by adding or removing a minimum number z(G) of edges (Zahn's problem). While the computation of z(G) is NP-hard in general, we show that its computation can be done in polynomial time when G is bipartite, by relating it to a maximum matching problem. When G is a complete multipartite graph, we give an explicit formula specifying z(G) with respect to some structural features of G. In both cases, we give also the structure of all the optimal clusterings of G

The sexual identity of adult intestinal stem cells controls organ size and plasticity

Sex differences in physiology and disease susceptibility are commonly attributed to developmental and/or hormonal factors, but there is increasing realization that cell-intrinsic mechanisms play important and persistent roles. Here we use the Drosophila melanogaster intestine to investigate the nature and importance of cellular sex in an adult somatic organ in vivo. We find that the adult intestinal epithelium is a cellular mosaic of different sex differentiation pathways, and displays extensive sex differences in expression of genes with roles in growth and metabolism. Cell-specific reversals of the sexual identity of adult intestinal stem cells uncovers the key role this identity has in controlling organ size, reproductive plasticity and response to genetically induced tumours. Unlike previous examples of sexually dimorphic somatic stem cell activity, the sex differences in intestinal stem cell behaviour arise from intrinsic mechanisms that control cell cycle duration and involve a new doublesex- and fruitless-independent branch of the sex differentiation pathway downstream of transformer. Together, our findings indicate that the plasticity of an adult somatic organ is reversibly controlled by its sexual identity, imparted by a new mechanism that may be active in more tissues than previously recognized

The Modified-Classroom Observation Schedule to Measure Intentional Communication (M-COSMIC): Evaluation of reliability and validity

The Modified – Classroom Observation Schedule to Measure Intentional Communication (M-COSMIC) was developed as an ecologically valid measure of social-communication behaviour, delineating forms, functions, and intended partners of children’s spontaneous communication acts. Forty one children with autism spectrum disorder (ASD) aged 48 to 73 months were filmed within small-group settings at school. Communication behaviours during a five-minute teacher-led activity and a 10-minute free play session were coded from video-tape. Inter-rater reliability was high. Many M-COSMIC codes were significantly associated as predicted with Social and Communication domain scores on the Autism Diagnostic Observation Schedule (ADOS) and with scores on standardised language assessments. Agreement was more variable, however, at the level of individual M-COSMIC codes and ADOS items. Higher rates of responding, compliance behaviours and following pointing gestures and gaze occurred during the more structured teacher-led activity, compared to the free play. Results demonstrate preliminary construct validity of the M-COSMIC, showing its potential to describe and evaluate spontaneous social-communication skills in young children with ASD for research and applied purposes