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 :

Bibliothèques d’atelier

À la fin du XVIIIe et au début du XIXe siècle, si l’architecture était considérée comme un art d’imitation, sa vocation essentielle était de reproduire les édifices du passé, et notamment ceux de l’Antiquité gréco-romaine. Outre ce caractère autoréférentiel, elle était soumise à des difficultés matérielles d’exécution ou à des réalités financières qui faisaient que ses inventions les plus brillantes en restaient souvent au stade du projet. Ce qui explique l’intérêt et l’importance que cette discipline a toujours accordés aux livres. Libérés des contraintes économiques et des lois de la gravité, les ateliers où les élèves s’exerçaient en vue de prendre part aux concours académiques étaient les laboratoires de l’architecte de demain. Mais les modèles qu’on y étudiait attentivement, pour les reproduire dans des œuvres nouvelles, n’étaient pas des modèles vivants, plutôt des schémas reproduisant les travaux des aînés. Ces gravures formaient les recueils conservés dans les bibliothèques d’atelier. Parmi les pièces uniques appartenant aux collections de la bibliothèque Jacques Doucet, se trouvent deux exemplaires aquarellés du premier recueil des prix, qui reproduit les dessins des années 1780 ; ce recueil assura ainsi le relais entre les dernières années fécondes de l’Ancien Régime et les débuts de l’École des beaux-arts. Autour de ces volumes souvent remarquables, l’exposition réunit une série d’ouvrages qui ont tous joué un rôle majeur dans l’enseignement de l’architecture, et des dessins qui s’y rattachent, soit parce qu’ils y sont reproduits, soit parce qu’ils s’en inspirent. Associant un point de vue qui relève de l’histoire du livre d’architecture et des préoccupations qui touchent à l’histoire de son enseignement, cette exposition croise les programmes de recherche documentaire que l’INHA consacre à la bibliographie du livre d’architecture français et aux élèves architectes de l’École des beaux-arts ; une première partie des résultats, mise en ligne sur AGORHA, est désormais accessible au public. Antoinette Le Normand-Romain, Directeur général de l’INHA

The European Registered Toxicologist (ERT) : Current status and prospects for advancement

Acknowledgements We would like to thank the participants of the five workshops in which the issues presented in this paper were discussed and the revised guidelines prepared, as well as the EUROTOX Executive Committee and the societies of toxicology of Sweden, the Netherlands, Switzerland, Austria and France for their support which allowed the workshops to take place.Peer reviewedPostprin

Etude in vitro et in planta de l’activité antifongique de différents lipopeptides de Bacillus sp. contre Venturia inaequalis

editorial reviewedLa tavelure du pommier (Venturia inaequalis) est une maladie redoutable, combattue classiquement par des fongicides chimiques dont la substitution par des alternatives plus respectueuses de l’environnement est recherchée. Dans cette étude l’activité antifongique de biofongicides d’origine bactérienne a été évaluée contre une souche de V. inaequalis. Il s’agit de métabolites de type lipopeptides produits par différentes espèces de bactéries appartenant au genre Bacillus sp. Les CI50 des lipopeptides seuls (fengycine, mycosubtiline, iturine A, surfactine, pumilacidine et lichénysine) et de leurs mélanges binaires (fengycine/surfactine ou iturine A ou pumilacidine ou lichénysine) ont été déterminées et comparées à celles du tébuconazole et du tétraconazole (fongicides chimiques). La fengycine, la mycosubtiline, l’iturine A et la surfactine ainsi que les quatre mélanges binaires présentent une activité antifongique significative. La fengycine seule est la plus active (CI50 = 0,024 mg.L-1 [0,016-0,034]) avec un niveau d’activité proche du tébuconazole (CI50 = 0,012 mg.L-1 [0,008-0,017]) et du tétraconazole (CI50 = 0,009 mg.L-1 [0,006-0,013]). Deux mélanges de lipopeptides (fengycine/surfactine et mycosubtiline/surfactine) ont également été testés en vergers et présentent une diminution de 70% de l’incidence de la maladie pour les deux mélanges. Leur utilisation en tant que produit de biocontrôle semble donc prometteuse

Experimental Comparative Study between Conventional and Green Parking Lots: Analysis of Subsurface Thermal Behavior under Warm and Dry Summer Conditions

Green infrastructure has a role to play in climate change adaptation strategies in cities. Alternative urban spaces should be designed considering new requirements in terms of urban microclimate and thermal comfort. Pervious pavements such as green parking lots can contribute to this goal through solar evaporative cooling. However, the cooling benefits of such systems remain under debate during dry and warm periods. The aim of this study was to compare experimentally the thermal behavior of different parking lot types (PLTs) with vegetated urban soil. Four parking lots were instrumented, with temperature probes buried at different depths. Underground temperatures were measured during summer 2019, and the hottest days of the period were analyzed. Results show that the less mineral used in the surface coating, the less it warms up. The temperature difference at the upper layer can reach 10 °C between mineral and non-mineral PLTs. PLTs can be grouped into three types: (i) high surface temperature during daytime and nighttime, important heat transfer toward the sublayers, and low time shift (asphalt system); (ii) high (resp. low) surface temperature during daytime (resp. nighttime), weak heat transfer toward the sublayers, and important time shift (paved stone system); and (iii) low surface temperature during daytime and nighttime, weak heat transfer toward the sublayers, and important time shift (vegetation and substrate system, wood chips system, vegetated urban soil). The results of this study underline that pervious pavements demonstrate thermal benefits under warm and dry summer conditions compared to conventional parking lot solutions. The results also indicate that the hygrothermal properties of urban materials are crucial for urban heat island mitigation

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

L’Orientalisme architectural entre imaginaires et savoirs

Regroupement des recherches des meilleurs spécialistes, actes du colloque international « Les orientalismes en architecture à l’épreuve des savoirs. Europe et monde extra-européen, XIXe et XXe siècles » (Paris, Institut national d’histoire de l’art, 4-5 mai 2006), ce livre fait le point sur les savoirs et la vision de l’Orient transmis aux architectes au cours des XIXe et XXe siècles par les récits de voyageurs, les publications savantes sur l’architecture, ou encore les cours dispensés à l’École des beaux-arts, et la manière dont ceux-ci ont adapté leurs connaissances à leurs projets réalisés ou non. Quand certains proposent des compilations d’éléments orientaux, d’autres mettent en avant un style « national » reprenant des motifs architectoniques perçus par les Occidentaux comme orientaux. Ces différentes approches montrent combien l’idée d’orientalisme est multiple, en Orient comme en Occident. De nombreux dessins d’architectes, des gravures et des photos anciennes qui permettent de mieux comprendre le contexte de la transmission des savoirs sont reproduits en couleurs