Stable variable selection for right censored data: comparison of methods

The instability in the selection of models is a major concern with data sets containing a large number of covariates. This paper deals with variable selection methodology in the case of high-dimensional problems where the response variable can be right censored. We focuse on new stable variable selection methods based on bootstrap for two methodologies: the Cox proportional hazard model and survival trees. As far as the Cox model is concerned, we investigate the bootstrapping applied to two variable selection techniques: the stepwise algorithm based on the AIC criterion and the L1-penalization of Lasso. Regarding survival trees, we review two methodologies: the bootstrap node-level stabilization and random survival forests. We apply these different approaches to two real data sets. We compare the methods on the prediction error rate based on the Harrell concordance index and the relevance of the interpretation of the corresponding selected models. The aim is to find a compromise between a good prediction performance and ease to interpretation for clinicians. Results suggest that in the case of a small number of individuals, a bootstrapping adapted to L1-penalization in the Cox model or a bootstrap node-level stabilization in survival trees give a good alternative to the random survival forest methodology, known to give the smallest prediction error rate but difficult to interprete by non-statisticians. In a clinical perspective, the complementarity between the methods based on the Cox model and those based on survival trees would permit to built reliable models easy to interprete by the clinician.Comment: nombre de pages : 29 nombre de tableaux : 2 nombre de figures :

De la psychogènese à l’appropriation de la langue française ecrite

Inexistent

Copper supply during the Final Neolithic at the Saint-Blaise/Bains des Dames site (Neuchâtel, Switzerland)

The Saint-Blaise/Bains des Dames stratified site in Neuchâtel, Switzerland, contains several occupations that span the Late through Final Neolithic, including the Horgen, Lüscherz, and Auvernier-Cordé periods. As part of a study on prehistoric metallurgy in western Switzerland, we compare the lead isotope ratios (multicollector inductively coupled plasma mass spectrometer) and elemental compositions (instrumental neutron activation analysis) of the site's numerous copper finds to a database of corresponding measurements for copper ores throughout Europe. The results show a considerable variation in copper compositions present at the site, suggesting complex economic relationships and multiple chaînes opératoires during the time in question. Specifically, during the Final Neolithic, we distinguished ten coherent clusters, confirmed by both the elemental compositions and lead isotope ratios. When compared to the Europe-wide database of copper ores, we observed significant changes in the provenance of the copper through time that reflect equally significant changes in social, cultural, and economic interactions

L’Influence de l’Education dans la Construction Sociale des Valeurs

Cet article traite du rapport existant entre le développement moral et l’échec scolaire. Il s’agit d’une étude basée sur les travaux de Piaget et d’autres constructivistes. Dans une recherche sur les effets de la remédiation cognitive pour les enfants qui présentent un obstacle d’apprentissage lié au développement moral, un entretien avec les parents des enfants a eu lieu pendant lequel un questionnaire a été rempli. Une des questions de ce questionnaire demandait aux parents de hiérarchiser certains valeurs. Le but envisagé était de vérifier s’il y a une relation entre ce que chaque parent a priorisé dans son ordre d’importance des valeurs à encourager chez les enfants et ce qu’a montré l’enfant pendant les évaluations. Cette recherche a eu lieu dans trois écoles de la ville de Lyon – France

“Crochetage” (Notch) on R wave in inferior limb leads: A new independent electrocardiographic sign of atrial septal defect

AbstractObjectives. This study sought to determine the clinical significance of a “crochetage” pattern—a notch near the apex of the R wave in electrocardiographic (ECG) inferior limb leads—in secundum atrial septal defect.Background. Atrial septal defect is often overdiagnosed on the basis of classical clinical features. Thus, more specific signs on the ECG for screening are needed.Methods. We searched for a crochetage pattern in 1,560 older children and adults: 532 with secundum atrial septal defect, 266 with ventricular septal defect, 146 with pulmonary stenosis, 110 with mitral stenosis, 47 with cor pulmonale and 459 normal subjects.Results. This pattern was observed respectively in 73.1%, 35.7%, 23.3%, 6.4%, 10.6% and 7.4% of these groups (p < 0.001). In atrial septal defect, its incidence increased with larger anatomic defect (p < 0.0001) or greater left-to-right shunt (p < 0.0001), even in the presence of pulmonary hypertension. By multiple regression analysis, only shunt size (p < 0.0006) and defect location (p < 0.0001) were the determinants of its presence. In all groups, the specificity of this sign for the diagnosis was remarkably high when present in all three inferior limb leads (≥92%), even when comparison was limited to patients with an incomplete right bundle branch block (≥95.2%). Early disappearance of this pattern was observed in 35.1% of the operated-on patients although the right bundle branch block pattern persisted.Conclusions. A crochetage pattern of the R wave in inferior limb leads is frequent in patients with atrial septal defect, correlates with shunt severity and is independent of the right bundle branch block pattern. Sensitivity and specificity of this sign are remarkably high when it is associated with an incomplete right bundle branch block or present in all inferior limb leads

Session E9: Cumulated Mortalities of Salmon and Eel in the Turbines of the Loire-Brittany District

Abstract: The effect of dams on mortality during downstream migration was simulated using distribution and mortality models in the whole Loire-Brittany water district (155 000 Km2). A combination of models was used: (1) juvenile habitats for smolts, (2) productivity of juvenile salmon habitats, (3) production of silver eels (EDA model), The models (1)*(2) and (3) were used to predict the number of downstream migrants in the current conditions and with a transparent upstream migration. (4) Turbine mortality was calculated from either the characteristics of the turbine (diameter, rotation speed, height ...) or by extrapolation from the average mortality when information was missing to run the model. (5) Mortalities at the dam level were then derived from the nominal flow of each turbine and from the flow of the spill under 5 flow scenarios. A similar overall production of about 100 000 smolts per year was found in the Loire and Britany and the current production of eels was evaluated at 306 700, 314 900 and 124 400 silver eels for Brittany, the Loire and Vendée coastal streams respectively. The average mortality calculated at 387 dams and 578 turbines was estimated at 16.9% in Kaplan, 19.6% in Francis turbines, for smolts, and 45.8% and 88.5% for eels. For salmon, the number of kills was evaluated as N=26 900 (ie 27% of the Loire’s smolt production), and N=1 636 (ie 2%) in Brittany. For eel, the number of kills was evaluated as N=9 800 (ie 3.1%) of the silver eel production in the Loire, N=9 400 (ie 3.3%) in Brittany and N=2 700 (ie 2.2%) in Vendée. The results will allow to prioritize actions and provide a first estimate of the level of mortality affecting eel and salmon in the Loire-Britany basin

Illettrisme, évaluation et formation : réflexions sur une approche européenne

Le PsyEF, équipe de recherche à l’université Lyon 2, a participé à trois projets européens de formation d’adultes. Après la construction des projets et leur intérêt pour l’équipe, le présent article détaille le partenariat et aborde les contraintes d’une recherche conduite dans des pays aux cultures et aux langues différentes. Sont exposés également les avantages d’une dynamique de coopération, les adaptations nécessaires et les exigences de la diffusion sur internet. Compte tenu de l’évolution et de l’internationalisation des pratiques de formation, il semble utile de maintenir des recherches au niveau européen ; à cet égard, les travaux des trois projets représentent une avancée pour la réflexion sur les compétences des personnes en difficulté et sur les profils de formateurs.The PsyEF, a research team at the University Lyon 2, took part in three European projects for adult education. After detailing the development of the projects and their interest for the team, this article describes the partnership and discusses the difficulties of research conducted in countries with different cultures and languages. The benefits of a dynamic cooperation, the necessary adjustments and the requirements of the webcasting are explained. Given the evolution and internationalization of practices in training programs, it appears helpful to maintain researches at European level and in this respect, the work of the three projects represents a headway for the thought about the skills of people with learning difficulties and the profiles of trainers

De l’arolle ou du chêne ? Mobilité verticale et exploitation des ressources végétales au Néolithique dans les Alpes occidentales

Au Néolithique, les montagnes sont exploitées pour leurs ressources minérales, cynégétiques et pastorales. À partir de 5 500 ans avant notre ère, les premières communautés agropastorales atteignent les Alpes depuis le nord de l’Italie et la vallée du Rhône et s’établissent dans les massifs subalpins comme dans les Alpes internes. Les études archéobotaniques (analyse des macrorestes végétaux, principalement des graines, des fruits et des charbons de bois) permettent de comprendre l’économie végétale de ces communautés néolithiques : quelles espèces, sauvages ou cultivées, étaient récoltées pour le fourrage, pour construire, se nourrir, se soigner, se chauffer ? Les données de cinq sites néolithiques nous indiquent les différentes façons dont ces populations ont exploité leur territoire en tirant profit des ressources de divers biotopes, de l’étage collinéen à l’étage alpin, contribuant ainsi à mieux comprendre la mobilité verticale au Néolithique en contexte alpin.During the Neolithic, mountains were exploited for their mineral, hunting and pastoral resources. The first agro-pastoral communities reached the Alps from Northern Italy and the Rhone valley and settled in the subalpine massifs and in the internal Alps. Archeobotanical studies (plant macroremains and charcoal analysis) conducted at five sites allow us to understand the plant economy of these Neolithic communities: they determine which crops were cultivated, used as fodder, or gathered for consumption, medicine or other purpose, such as firewood. In the present paper, we support that the use of plant resources and the exploitation of territory are very different for the same period from one region to another, depending on the activities carried out at each site but also on cultural backgrounds. Archeobotanical data indicate how these people took resources from various plant associations growing from the colline to the subalpine level, and thus contribute to the understanding of vertical mobility in alpine contexts