A semiparametric extension of the stochastic block model for longitudinal networks

To model recurrent interaction events in continuous time, an extension of the stochastic block model is proposed where every individual belongs to a latent group and interactions between two individuals follow a conditional inhomogeneous Poisson process with intensity driven by the individuals' latent groups. The model is shown to be identifiable and its estimation is based on a semiparametric variational expectation-maximization algorithm. Two versions of the method are developed, using either a nonparametric histogram approach (with an adaptive choice of the partition size) or kernel intensity estimators. The number of latent groups can be selected by an integrated classification likelihood criterion. Finally, we demonstrate the performance of our procedure on synthetic experiments, analyse two datasets to illustrate the utility of our approach and comment on competing methods

Exact calculations for false discovery proportion with application to least favorable configurations

In a context of multiple hypothesis testing, we provide several new exact calculations related to the false discovery proportion (FDP) of step-up and step-down procedures. For step-up procedures, we show that the number of erroneous rejections conditionally on the rejection number is simply a binomial variable, which leads to explicit computations of the c.d.f., the {$s$-th} moment and the mean of the FDP, the latter corresponding to the false discovery rate (FDR). For step-down procedures, we derive what is to our knowledge the first explicit formula for the FDR valid for any alternative c.d.f. of the $p$-values. We also derive explicit computations of the power for both step-up and step-down procedures. These formulas are "explicit" in the sense that they only involve the parameters of the model and the c.d.f. of the order statistics of i.i.d. uniform variables. The $p$-values are assumed either independent or coming from an equicorrelated multivariate normal model and an additional mixture model for the true/false hypotheses is used. This new approach is used to investigate new results which are of interest in their own right, related to least/most favorable configurations for the FDR and the variance of the FDP

Entre injonctions contradictoires et bricolages identitaires : quelles identifications pour les descendants d’immigrés marocains en Belgique ?

Cet article propose une grille d’analyse des processus identitaires qui se jouent chez les descendants d’immigrés marocains en Belgique, en regard des familles immigrées et du cadre social. Les descendants d’immigrés marocains se trouvent privés de l’identification pleine aux parents ainsi que de l’héritage d’une mémoire familiale et collective. Soumis à une injonction contradictoire de la part de leurs parents et de la société (« Réussissez, mais restez fidèles aux traditions »; « Intégrez-vous, mais vous serez toujours considérés comme des immigrés »), ils échappent difficilement aux processus sociaux d’assignation à une altérité identitaire dévalorisée et sont contraints de bricoler de nouvelles formes identitaires. Cette problématique identitaire est située dans le cadre plus large du déclin du mode traditionnel d’hériter et de la transmission généalogique dans la modernité. Mais le hiatus profond entre le contexte de socialisation des parents immigrés et celui de leurs enfants et l’impact de la domination sociale sont tels que les processus d’identification dans l’immigration marocaine sont particulièrement complexes.This article provides an analytic framework for understanding the identity processes, with respect to immigrant families and the social situation, that are at play among descendants of Moroccan immigrants in Belgium. They are deprived of the possibility of fully identifying with their parents and of inheriting a familial and collective memory. Receiving contradictory instructions from their parents and from society (“be successful but be faithful to our traditions”; “be integrated but remember you are an immigrant”), they find it difficult to escape from social processes that assign them a devalued identity of difference and they are obliged to construct new forms of identity. Such issues about identity are common to the decline of modernity’s traditional modes of inheritance and genealogical transmission. However, the huge gap between the socialisation context of immigrant parents and that of their children as well as the impact of social domination are such that the processes of identity formation among Moroccan immigrants are particularly complicated

How Geometry Controls the Tearing of Adhesive Thin Films on Curved Surfaces

Flaps can be detached from a thin film glued on a solid substrate by tearing and peeling. For flat substrates, it has been shown that these flaps spontaneously narrow and collapse in pointy triangular shapes. Here we show that various shapes, triangular, elliptic, acuminate or spatulate, can be observed for the tears by adjusting the curvature of the substrate. From combined experiments and theoretical models, we show that the flap morphology is governed by simple geometric rules.Comment: 6 pages, 5 figure

Online Peer Feedback in Beginners’ Writing Tasks: Lessons Learned

This study contributes to the body of research that aims to understandthe relationship between online communication and foreign language(FL) learning, in particular when teachers seek to provide authenticopportunities for interaction for their learners. The study wasmotivated by efforts made in the New Zealand context to overcome thegeographic limitations of interaction between FL learners and nativespeakers. We report on the findings of an exploratory study into anonline reciprocal peer tutoring program established to enhance the FLlearning of a group of beginner eleven-year old students of Spanish,with particular focus on the benefits of written corrective feedback. Theproject aimed to examine the processes by which students tutored eachother in the online environment as they responded to each other’s texts.The analysis of the students’ messages focused on (1) the aspects oflanguage corrected by the tutors, (2) the frequency with which tutorsaccurately identified and provided input on errors, (3) the types offeedback provided by the tutors, and (4) what the learners did with thecorrections and feedback. The findings indicate that the students werewilling to contribute to peer correction and used different strategiesand correction techniques to foster attention to linguistic form,although they were not always capable of providing accurate feedbackor metalinguistic explanations