Questions de méthode

Conservateur responsable de l'Atelier de restauration et de conservation de la Ville de Paris (ARCP), Anne Cartier-Bresson a été chargée du commissariat d'une exposition itinérante de longue durée, intitulée "Paris sous l'objectif (1885-1994) ", susceptible d'être présentée pendant environ cinq ans dans différents pays à partir d'avril 1998, afin de produire un état des lieux des principales collections photographiques de la municipalité parisienne: Bibliothèque historique de la Ville..

La photographie contemporaine sous le regard de la conservation et de la restauration : le cas du « Plan couleur et impressions numériques » de la Ville de Paris

Bien qu’à l’origine de toute photographie, analogique ou numérique, il y ait l’empreinte de la lumière sur un support sensible, la « révolution numérique » a changé la manière d’appréhender ce médium.Dans ce contexte, l’Atelier de restauration et de conservation des photographies de la Ville de Paris (ARCP) a lancé, en 2006, un plan de conservation portant sur les photographies en couleurs photochimiques et les impressions numériques conservées dans les institutions municipales.Les différentes techniques recensées sont celles qui constituent majoritairement la production contemporaine, des tirages à développement chromogène aux impressions jet d’encre, en passant par les tirages argento-numériques.Mais au-delà de l’identification des procédés photographiques, cruciale pour la conservation des fonds, les problématiques de montage et de présentation spécifiques de la photographie contemporaine sont apparues tout aussi importantes.Ces dernières décennies, des avancées en matière de restauration et de montage ont été réalisées, en adaptant les pratiques aux nouveaux matériaux. Dans certains cas cependant, les collections ont encore recours au retirage des œuvres endommagées. Cette solution ne constitue pas une alternative définitive, notamment face à l’obsolescence des supports.Finalement, le numérique n’a pas fondamentalement modifié nos pratiques de conservation-restauration et son avenir résiderait, comme pour les procédés photochimiques, et davantage encore, dans la prévention.Although all photography, whether analogue or digital, begins with the impression of light on a sensitive support, the “digital revolution” has changed the way in which this medium is seen.In this context, in 2006, the Atelier de Restauration et de Conservation des Photographies de la Ville de Paris (ARCP) drew up a conservation plan for photochemical colour prints and digital prints now in municipal establishments.The majority of the different techniques listed in the inventory are those related to contemporary production, from chromogenic and ink-dot prints to digital silver imaging.But apart from the identification of photographic processes, which is crucial to the conservation of collections, the problems of mounting and displaying contemporary photography proved to be equally important.In the past few decades, much progress has been made in areas concerned with restoration and mounting by adapting familiar practices to new materials. In some cases, however, the collections have still resorted to reprinting damaged works. This solution does not constitute a definitive alternative, notably in the face of the obsolescence of supports.Lastly, digital photography has not modified our fundamental conservation-restoration practices and its future, like that of photochemical processes, if not more so, lies in preventive measures

Micromechanisms of fracture propagation in glassy polymers

While most glassy polymers are nominally brittle at macroscopic scales, they are known to exhibit plastic deformation in indentation, scratching, and microcutting when the loaded region is sufficiently small. The same applies to the micrometer size process zone at the tip of a propagating crack. While the presence and approximate size of this microscale plastic zone is well described by the Dugdale model, the prediction of the toughness of these materials is not possible without accounting for the details of the local large strain field and the work hardening behaviour of these polymers, which can be inferred from their response to compressive tests. Strain localization mechanisms such as crazing or shear banding should also be taken into account to properly model toughness. Finally, viscoplastic creep plays a major role in determining the dependence of the toughness on crack propagation velocity, as well as the important difference between the initiation and propagation toughness, which is responsible for the occurrence of a characteristic stick-slip propagation under some loading conditions. Please click Additional Files below to see the full abstract

XRCC1 is phosphorylated by DNA-dependent protein kinase in response to DNA damage

The two BRCT domains (BRCT1 and BRCT2) of XRCC1 mediate a network of protein–protein interactions with several key factors of the DNA single-strand breaks (SSBs) and base damage repair pathways. BRCT1 is required for the immediate poly(ADP–ribose)-dependent recruitment of XRCC1 to DNA breaks and is essential for survival after DNA damage. To better understand the biological role of XRCC1 in the processing of DNA ends, a search for the BRCT1 domain-associated proteins was performed by mass spectrometry of GST-BRCT1 pulled-down proteins from HeLa cell extracts. Here, we report that the double-strand break (DSB) repair heterotrimeric complex DNA-PK interacts with the BRCT1 domain of XRCC1 and phosphorylates this domain at serine 371 after ionizing irradiation. This caused XRCC1 dimer dissociation. The XRCC1 R399Q variant allele did not affect this phosphorylation. We also show that XRCC1 strongly stimulates the phosphorylation of p53-Ser15 by DNA-PK. The pseudo phosphorylated S371D mutant was a much weaker stimulator of DNA-PK activity whereas the non-phosphorylable mutant S371L endowed with a DNA-PK stimulating capacity failed to fully rescue the DSB repair defect of XRCC1-deficient EM9 rodent cells. The functional association between XRCC1 and DNA-PK in response to IR provides the first evidence for their involvement in a common DSB repair pathway

Socially Compliant Navigation in Dense Crowds

International audienceNavigating in complex and highly dynamic environments such as crowds is still a major challenge for autonomous vehicle such as autonomous wheelchairs or even autonomous cars. This article presents a new way of navigating in crowds by using behavioral clustering for the surrounding agents and representing the crowd as a set of moving polygons. Once the environment has been modelled in this way and the robot has all the information it needs, we then propose a navigation algorithm that is able to guide the vehicle through the scene. The key-points of this algorithm are that (1) it can avoid densely-populated areas in order to minimize the risk of being on a collision course with any of the surrounding dynamic obstacles, (2) it generates socially compliant trajectories

2D SLAM Correction Prediction in Large Scale Urban Environments

International audienceSimultaneous Localization And Mapping (SLAM) is one of the major bricks needed to build truly autonomous mobile robots. The probabilistic formulation of SLAM is based on two models: the motion model and the observation model. In practice, these models, together with the SLAM map representation, do not model perfectly the robot's real dynamics, the sensor measurement errors and the environment. Consequently, systematic errors affect SLAM estimations. In this paper, we propose two approaches to predict corrections to be applied to SLAM estimations. Both are based on the Ensemble Multilayer Perceptron model. The first approach uses successive estimated poses to predict the errors, with no assumptions on the underlying SLAM process or sensor used. The second method is specific to 2D likelihood SLAM approaches, thus, the likelihood distributions are used to predict the corrections, making this second approach independent of the sensor used. We also build a hybrid correction module based on successive estimated poses and the likelihood distributions. The validity of both approaches is evaluated through two experiments using different evaluation metrics and sensor configurations

PML-SLAM: a solution for localization in large-scale urban environments

International audienceLocalization is considered a key factor for autonomous cars. In this paper, we present a complete Simultaneous Localization And Mapping (SLAM) solution. This algorithm is based on probabilistic maximum likelihood framework using grid maps (the map is simply presented as a grid of occupancy probabilities). The solution mainly solve three renowned localization problems (1. localization in unknown environment, 2. localization in a pre-mapped environment and 3. recovering the localization of the vehicle). Memory issues caused by the open size of outdoor environment are solved using an optimized management strategy that we propose. This strategy allows us to navigate smoothly while saving and loading probabilities-grid submaps into/from a hard-disc in a transparent way. We present the results of our solution using our own experimental dataset as well as the KITTI dataset

Failure Detection for Laser-based SLAM in Urban and Peri-Urban Environments

International audienceSimultaneous Localization And Mapping (SLAM) is considered as one of the key solutions for making mobile robots truly autonomous. Based mainly on perceptive information, the SLAM concept is assumed to solve localization and provide a map of the surrounding environment simultaneously. In this paper, we study SLAM limitations and we propose an approach to detect a priori potential failure scenarios for 2D laser-based SLAM methods. Our approach makes use of raw sensor data, which makes it independent of the underlying SLAM implementation, to extract a relevant descriptors vector. This descriptors vector is then used together with a decision-making algorithm to detect failure scenarios. Our approach is evaluated using different decision algorithms through three realistic experiments

The Kasimir Project: Knowledge Management in Cancerology

Colloque avec actes et comité de lecture. internationale.International audienceThis paper describes the Kasimir project which aim is the knowledge management for the cancer treatment and which gathers researchers in computer science and in ergonomics, experts in cancerology and an association federating physicians from Lorraine involved in cancerology. For each cancer localisation, the treatment is based on a protocol. The system Kasimir-RBR implements this protocol. The system Kasimir-CBR will implement adaptations of the protocol for ``non-standard cases''. The third part of the project is to study how protocol adaptations can lead to evolutions of the protocol

Epigenetic changes in human model KMT2A leukemias highlight early events during leukemogenesis

Chromosomal translocations involving the KMT2A gene are among the most common genetic alterations found in pediatric acute myeloid leukemias although the molecular mechanisms that initiate the disease remain incompletely defined. To elucidate these initiating events we used a human model system of acute myeloid leukemia driven by the KMT2A-MLLT3 (KM3) fusion. More specifically, we investigated changes in DNA methylation, histone modifications, and chromatin accessibility at each stage of our model system and correlated these with expression changes. We observed the development of a pronounced hypomethyl - ation phenotype in the early stages of leukemic transformation after KM3 addition along with loss of expression of stem-cell-associated genes and skewed expression of other genes, such as S100A8/9, implicated in leukemogenesis. In addition, early increases in the expression of the lysine demethylase KDM4B was functionally linked to these expression changes as well as other key transcription factors. Remarkably, our ATAC-sequencing data showed that there were relatively few leukemia-specific changes and that the vast majority corresponded to open chromatin regions and transcription factor clusters previously observed in other cell types. Integration of the gene expression and epigenetic changes revealed that the adenylate cyclase gene ADCY9 is an essential gene in KM3-acute myeloid leukemia, and suggested the potential for autocrine signaling through the chemokine receptor CCR1 and CCL23 ligand. Collectively, our results suggest that KM3 induces subtle changes in the epigenome while co-opting the normal transcriptional machinery to drive leukemogenesis