Cross-Products LASSO

Negative co-occurrence is a common phenomenon in many signal processing applications. In some cases the signals involved are sparse, and this information can be exploited to recover them. In this paper, we present a sparse learning approach that explicitly takes into account negative co-occurrence. This is achieved by adding a novel penalty term to the LASSO cost function based on the cross-products between the reconstruction coefficients. Although the resulting optimization problem is non-convex, we develop a new and efficient method for solving it based on successive convex approximations. Results on synthetic data, for both complete and overcomplete dictionaries, are provided to validate the proposed approach

Blind analysis of atrial fibrillation electrograms: A sparsity-aware formulation

The problem of blind sparse analysis of electrogram (EGM) signals under atrial fibrillation (AF) conditions is considered in this paper. A mathematical model for the observed signals that takes into account the multiple foci typically appearing inside the heart during AF is firstly introduced. Then, a reconstruction model based on a fixed dictionary is developed and several alternatives for choosing the dictionary are discussed. In order to obtain a sparse solution, which takes into account the biological restrictions of the problem at the same time, the paper proposes using a Least Absolute Shrinkage and Selection Operator (LASSO) regularization followed by a post-processing stage that removes low amplitude coefficients violating the refractory period characteristic of cardiac cells. Finally, spectral analysis is performed on the clean activation sequence obtained from the sparse learning stage in order to estimate the number of latent foci and their frequencies. Simulations on synthetic signals and applications on real data are provided to validate the proposed approach.This work has been partly financed by the Spanish government through the CONSOLIDER-INGENIO 2010 program (COMONSENS project, ref. CSD2008-00010), as well as projects COSIMA (TEC2010-19545-C04-03), ALCIT (TEC2012 38800- C03-01), COMPREHENSION (TEC2012-38883-C02-01) and DISSECT (TEC2012-38058-C03-01)

Sparse spectral analysis of atrial fibrillation electrograms

Atrial fibrillation (AF) is a common heart disorder. One of the most prominent hypothesis about its initiation and maintenance considers multiple uncoordinated activation foci inside the atrium. However, the implicit assumption behind all the signal processing techniques used for AF, such as dominant frequency and organization analysis, is the existence of a single regular component in the observed signals. In this paper we take into account the existence of multiple foci, performing a spectral analysis to detect their number and frequencies. In order to obtain a cleaner signal on which the spectral analysis can be performed, we introduce sparsity-aware learning techniques to infer the spike trains corresponding to the activations. The good performance of the proposed algorithm is demonstrated both on synthetic and real data. RESUMEN. Algoritmo basado en técnicas de regresión dispersa para la extracción de las señales cardiacas en pacientes con fibrilación atrial (AF)

L'imaginaire urbain dans les régions ouvrières en reconversion: Le bassin stéphanois et le bassin minier du Nord Pas de Calais

Cette recherche est une recherche sociologique et anthropologique coordonnée par Michel Rautenberg rassemblant le Centre Max Weber de Saint-Étienne, le Centre Lillois d'études et de recherches sociologiques et économiques (sous la responsabilité du professeur Licia Valladarès) et l' Université de Sofia (sous la responsabilité du professeur Ivaylo Ditchev). Démarrée en décembre 2007 elle s'est terminée en avril 2011 et a bénéficié d'une aide de l'ANR de 180 k€ pour un montant global de 250 k€ de subventions publiques (non comprise une allocation de recherche).The general hypothesis at the origin of this research is that urban transformations do not go without social representations and the field of the imagination. It is essential for each image, word or story to be related to concrete situations that the researcher can describe. The choice of cities is thus not negligible. In this research programme, it has focussed on cities which have a had a difficult economic history characterised by brutal de-industrialization - more in people's minds than by its suddenness. This has left a traumatic effect on individual and collective memories, an urban landscape of industrial wasteland and 3 decades later it continues to strongly influence urban renovation policies. The first issue of this research, which in its second phase was extended to include Bulgarian cities thanks to the support of the Ministry for Foreign Affairs, was to establish a method making it possible to describe this imagination. So researchers agreed to work on imagination "operators", that is to say means (administrative, artistic or social) used by socially identified actors : artists, associations, inhabitants, former miners, municipal authorities. The second issue was to favour the imagination of cites which cannot be measured against communication strategies but which considers the "popular" social imagination which is sufficiently autonomous to exist outside municipal institutions - without asserting that it is completely independent. The third issue was to find common features in the comparison between situations close enough in their history to justify a pertinent comparison.L'hypothèse générale à l'origine de cette recherche est que les transformations urbaines ne font pas l'économie des représentations et des imaginaires sociaux. Il est donc nécessaire que chaque image, parole ou récit recueilli soit rapporté à des situations concrètes que le chercheur peut décrire. Le choix des villes n'est alors pas anodin. Dans ce programme de recherche, il s'est porté sur des villes qui ont eu une histoire économique difficile caractérisée par une désindustrialisation brutale -dans les esprits peut-être plus que par sa soudaineté. Celle ci a laissé des traumatismes dans les mémoires individuelles et collectives, un paysage urbain de friches industrielles, et continue après 3 décennies d'influencer fortement sur les politiques de rénovation urbaine

Entre figure du mineur et évocation de l’ouvrier contemporain. Mise en scène d’un mort-vivant par la compagnie Hendrick Van der Zee

National audienc

« Une institution culturelle et son territoire : Culture commune, scène nationale du bassin minier du Nord-Pas de Calais, ou l'art de "transfigurer" la mémoire ouvrière »

International audienc

L'imaginaire ouvrier dans les constructions mémorielles et patrimoniales des villes industrielles. L'exemple stéphanois

Avec Sandra Trigano et Michel Rautenber

Saint-Etienne ville imaginée. Mineurs, artistes et habitants. Saint-Etienne, PUSE, collection Sociologie Matières à penser

International audienc