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A multivariate statistical method (factor analysis of mixed data and hierarchical classification) was used to classify the environmental settings where sorted patterned ground develops in a wet oceanic periglacial area (Skagafjorður, Northern Iceland). A total of 750 periglacial features, distributed over 75 sites, were studied. Nine explanatory variables were assessed by fieldwork and using a digital elevation model, the variables were subdivided into three groups (latitude, topography and soil characteristics) and then integrated into a geographical information system. Furthermore, a correlation between the environmental variables and an intrinsic variable (patterned ground mesh diameter) was determined by a bivariate test. The results show that sorted patterned ground are spread over three homogenous areas, mostly differentiated by altitude, insolation, grain size characteristics and type of drift. In addition, feature diameters differ significantly from one group to another. Finally, it appears that patterned ground diameters are positively correlated with (i) the proportion of clay to medium silt content (r=0.35), (ii) altitude (r=0.51), and especially with (iii) clast length (r=0.97). This strong relationship with clast length is observed in each homogenous patterned ground area at both site and feature scales.

International audience; During the 1970s, the development of direct marketing lead to the formation of sociability circles between women, especially within the framework of Tupperware meetings. These meetings contributed to the spread of certain ideas and feminist practices. They had an effect on the social trajectories of women from the middle and popular classes. Sharing experiences about feminine and conjugal submission as well as the confrontation with models of professionalized women, the demonstrators allowed certain women to develop greater awareness and self confidence which allowed them to achieve a relative autonomy.; Au cours des années 1970, le développement de la vente directe à domicile a donné lieu à la formation de cercles de sociabilité entre femmes dans le cadre des réunions Tupperware. Ces rencontres ont contribué à diffuser par capillarité nombre d’idées et pratiques féministes. Elles n’ont pas été sans incidence sur le déroulement de certaines trajectoires de femmes des classes moyennes et populaires. Le partage d’expériences de la soumission féminine, conjugale, et la confrontation aux modèles de femmes professionnalisées, les démonstratrices, ont ainsi parfois ouvert à la prise de conscience du sentiment de soi et permis d’accéder à une certaine autonomie.

International audience; One of the fundamental ideas of structural analysis is that in order to understand social structures, one must begin with relations. Yet where do relations come from? A survey of personal networks in the Toulouse area (France) allows us to demonstrate the importance of social circles in the genesis of dyadic relations.

International audience; One of the fundamental ideas of structural analysis is that in order to understand social structures, one must begin with relations. Yet where do relations come from? A survey of personal networks in the Toulouse area (France) allows us to demonstrate the importance of social circles in the genesis of dyadic relations.

International audience; One of the fundamental ideas of structural analysis is that in order to understand social structures, one must begin with relations. Yet where do relations come from? A survey of personal networks in the Toulouse area (France) allows us to demonstrate the importance of social circles in the genesis of dyadic relations.

International audience; The existing O(n log n) algorithms for finding the convex hulls of circles and the lower envelope of parabolas follow the divide-and-conquer paradigm. The difficulty with developing incremental algorithms for these problems is that the introduction of a new circle or parabola can cause Theta(n) structural changes, leading to Theta(n^2) total structural changes during the running of the algorithm. In this note we examine the geometry of these problems and show that, if the circles or parabolas are first sorted by appropriate parameters before constructing the convex hull or lower envelope incrementally, then each new addition may cause at most 3 changes in an amortized sense. These observations are then used to develop O(n log n) incremental algorithms for these problems.