La fouille de textes au service de la documentation

Article de vulgarisation scientifiqueNational audienceLes masses de données textuelles aujourd'hui disponibles engendrent un problème spécifique lié à leur traitement automatique. Des méthodes de fouille de textes et de traitement automatique du langage peuvent en partie répondre à cette difficulté. Approche des procédés et des nouveaux défis à relever présentés par deux chercheurs du Cirad, centre de recherche français qui répond, avec les pays du Sud, aux enjeux internationaux de l'agriculture et du développement

Total synthesis of cyclotheonamide C using a tandem backbone-extension-coupling methodology

International audienceNo abstrac

New Histone Incorporation Marks Sites of UV Repair in Human Cells

SummaryChromatin organization is compromised during the repair of DNA damage. It remains unknown how and to what extent epigenetic information is preserved in vivo. A central question is whether chromatin reorganization involves recycling of parental histones or new histone incorporation. Here, we devise an approach to follow new histone deposition upon UV irradiation in human cells. We show that new H3.1 histones get incorporated in vivo at repair sites. Remarkably we find that H3.1, which is deposited during S phase, is also incorporated outside of S phase. Histone deposition is dependent on nucleotide excision repair (NER), indicating that it occurs at a postrepair stage. The histone chaperone chromatin assembly factor 1 (CAF-1) is directly involved in the histone deposition process in vivo. We conclude that chromatin restoration after damage cannot rely simply on histone recycling. New histone incorporation at repair sites both challenges epigenetic stability and possibly contributes to damage memory

Extraction automatique des mots-clés à partir de publications scientifiques pour l’indexation et l’ouverture des données en agronomie

National audienceWith the large amounts of textual data related to agriculture now available, indexing becomes a crucial issue for research organizations. One way to index documents consists in extracting terminology. This paper investigates the use and combination of text mining methodologies to highlight and publish the most appropriate terms from documents in open data systems. Experiments conducted on CIRAD data, show the validity of the approach used to extract new and relevant terms.Dans le contexte des masses de données textuelles liées à l’agriculture aujourd’hui disponibles, leur indexation devient un enjeu crucial pour les organismes de recherche. Une manière d’indexer au mieux les documents consiste à en extraire la terminologie. Cet article explore l’utilisation et la combinaison de méthodologies de fouille de textes afin de mettre en exergue, puis de publier dans des systèmes d’open data, les termes les plus adaptés issus de documents. Des expérimentations menées sur des données du CIRAD (Centre de coopération internationale en recherche agronomique pour le développement), montrent le bien-fondé de la démarche qui a permis d’extraire des termes à la fois nouveaux et pertinents

Control of the repeatability of high frequency multibeam echosounder backscatter by using natural reference areas

The increased use of backscatter measurements in time series for environmental monitoring necessitates the comparability of individual results. With the current lack of pre-calibrated multibeam echosounder systems for absolute backscatter measurement, a pragmatic solution is the use of natural reference areas for ensuring regular assessment of the backscatter measurement repeatability. This method mainly relies on the assumption of a sufficiently stable reference area regarding its backscatter signature. The aptitude of a natural area to provide a stable and uniform backscatter response must be carefully considered and demonstrated by a sufficiently long time-series of measurements. Furthermore, this approach requires a strict control of the acquisition and processing parameters. If all these conditions are met, stability check and relative calibration of a system are possible by comparison with the averaged backscatter values for the area. Based on a common multibeam echosounder and sampling campaign completed by available bathymetric and backscatter time series, the suitability as a backscatter reference area of three different candidates was evaluated. Two among them, Carré Renard and Kwinte, prove to be excellent choices, while the third one, Western Solent, lacks sufficient data over time, but remains a valuable candidate. The case studies and the available backscatter data on these areas prove the applicability of this method. The expansion of the number of commonly used reference areas and the growth of the number of multibeam echosounder controlled thereon could greatly contribute to the further development of quantitative applications based on multibeam echosounder backscatter measurements

Microscopic structural study of collagen aging in isolated fibrils using polarized second harmonic generation

International audiencePolarization resolved second harmonic generation (PSHG) is developed to study, at the microscopic scale, the impact of aging on the structure of type I collagen fibrils in two-dimensional coatings. A ribose-glycated collagen is also used to mimic tissue glycation usually described as an indicator of aging. PSHG images are analyzed using a generic approach of the molecular disorder information in collagen fibrils, revealing significant changes upon aging, with a direct correlation between molecular disorder and fibril diameters

Total synthesis of cyclotheonamide C by use of an alpha-keto cyanophosphorane methodology for peptide assembly

International audienceThe total synthesis of cyclotheonamide C (3), a macrocyclic pentapeptide incorporating an alpha-keto homoarginine (k-Arg) and a vinylogous dehydrotyrosine (V-deltaTyr) unit, has been achieved. For comparison of macrocyclisation feasibility, two linear pentapeptides bearing free ketone functions at the k-Arg units were prepared, by use of tandem oxidation/coupling reactions on alpha-keto cyanophosphorane precursors as the key processes for pentapeptide elaboration. Successful activation and coupling at the pentapeptide V-deltaTyr C terminus led to the target molecule core, and thus provided a short total synthesis of the target compoun