Disentangling the trajectories of alpha, beta and gamma plant diversity of North American boreal ecoregions since 15,500 years

Assessment of biodiversity in a changing world is a key issue and studies on the processes and factors influencing its history at relevant time scales are needed. In this study, we analyzed temporal trends of plant diversity using fossil pollen records from the North American boreal forest-taiga biome (NABT). We selected 205 pollen records spanning the last 15,500 years. Diversity was decomposed into α and γ richness, and β diversity, using Shannon entropy indices. We investigated temporal and spatial patterns of β diversity by decomposing it into independent turnover (variation in taxonomic composition due to species replacements) and nestedness (variation due to species loss) components. The palynological diversity of the NABT biome experienced major rearrangements during the Lateglacial and early Holocene in response to major climatic shifts. The β nestedness likely reflected plant immigration processes and generally peaked before the β turnover value, which mirrors spatial and temporal community sorting related to environmental conditions and specific habitat constraints. Palynological diversity was generally maximal during the Lateglacial and the early Holocene and decreased progressively during the Holocene. These results are discussed according to macro-ecological processes, such as immigration, disturbances, and environmental fluctuations, with climate most notably as the main ecological driver at millennial scales

Localisation à partir de données laser d'un robot naviguant autour d'un avion

National audienceThis article discusses the pose estimation of the mobile platform Air-Cobot relative to the aircraft around which it operates. Autonomous and collaborative, this robot inspects aircrafts. It is equipped with distance sensors laser scans. The presented localization methods have been successfully tested in a real environment.Cet article traite du calcul de la pose de la plateforme mobile Air-Cobot par rapport à l'avion autour duquel elle évolue. Autonome et collaboratif, ce robot inspecte des aéronefs. Il est équipé de capteurs de distance à balayage laser. Les méthodes de localisation présentées ont été testées avec succès en environnement réel

Sterilization of bacteria suspensions and identification of radicals deposited during plasma treatment

In this paper we will present results for plasma sterilization of planktonic samples of two reference strains of bacteria, Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212. We have used a plasma needle as a source of non-equilibrium atmospheric plasma in all treatments. This device is already well characterized by OES, derivative probes and mass spectrometry. It was shown that power delivered to the plasma is bellow 2 W and that it produces the main radical oxygen and nitrogen species believed to be responsible for the sterilization process. Here we will only present results obtained by electron paramagnetic resonance which was used to detect the OH, H and NO species. Treatment time and power delivered to the plasma were found to have the strongest influence on sterilization. In all cases we have observed a reduction of several orders of magnitude in the concentration of bacteria and for the longest treatment time complete eradication. A more efficient sterilization was achieved in the case of gram negative bacteria

Multiscale variation in drought controlled historical forest fire activity in the boreal forests of eastern Fennoscandia

Forest fires are a key disturbance in boreal forests, and characteristics of fire regimes are among the most important factors explaining the variation in forest structure and species composition. The occurrence of fire is connected with climate, but earlier, mostly local-scale studies in the northern European boreal forests have provided little insight into fire-climate relationship before the modern fire suppression period. Here, we compiled annually resolved fire history, temperature, and precipitation reconstructions from eastern Fennoscandia from the mid-16th century to the end of the 19th century, a period of strong human influence on fires. We used synchrony of fires over the network of 25 fire history reconstructions as a measure of climatic forcing on fires. We examined the relationship between fire occurrence and climate (summer temperature, precipitation, and a drought index summarizing the influence of variability in temperature and precipitation) across temporal scales, using a scale space multiresolution correlation approach and Bayesian inference that accounts for the annually varying uncertainties in climate reconstructions. At the annual scale, fires were synchronized during summers with low precipitation, and most clearly during drought summers. A scale-derivative analysis revealed that fire synchrony and climate varied at similar, roughly decadal scales. Climatic variables and fire synchrony showed varying correlation strength and credibility, depending on the climate variable and the time period. In particular, precipitation emerged as a credible determinant of fire synchrony also at these time scales, despite the large uncertainties in precipitation reconstruction. The findings explain why fire occurrence can be high during cold periods (such as from the mid-17th to early-18th century), and stresses the notion that future fire frequency will likely depend to a greater extent on changes in precipitation than temperature alone. We showed, for the first time, the importance of climate as a decadal-scale driver of forest fires in the European boreal forests, discernible even during a period of strong human influence on fire occurrence. The fire regime responded both to anomalously dry summers, but also to decadal-scale climate changes, demonstrating how climatic variability has shaped the disturbance regimes in the northern European boreal forests over various time scales.Peer reviewe

Sodium Selenide Toxicity Is Mediated by O2-Dependent DNA Breaks

Hydrogen selenide is a recurrent metabolite of selenium compounds. However, few experiments studied the direct link between this toxic agent and cell death. To address this question, we first screened a systematic collection of Saccharomyces cerevisiae haploid knockout strains for sensitivity to sodium selenide, a donor for hydrogen selenide (H2Se/HSe−/Se2−). Among the genes whose deletion caused hypresensitivity, homologous recombination and DNA damage checkpoint genes were over-represented, suggesting that DNA double-strand breaks are a dominant cause of hydrogen selenide toxicity. Consistent with this hypothesis, treatment of S. cerevisiae cells with sodium selenide triggered G2/M checkpoint activation and induced in vivo chromosome fragmentation. In vitro, sodium selenide directly induced DNA phosphodiester-bond breaks via an O2-dependent reaction. The reaction was inhibited by mannitol, a hydroxyl radical quencher, but not by superoxide dismutase or catalase, strongly suggesting the involvement of hydroxyl radicals and ruling out participations of superoxide anions or hydrogen peroxide. The •OH signature could indeed be detected by electron spin resonance upon exposure of a solution of sodium selenide to O2. Finally we showed that, in vivo, toxicity strictly depended on the presence of O2. Therefore, by combining genome-wide and biochemical approaches, we demonstrated that, in yeast cells, hydrogen selenide induces toxic DNA breaks through an O2-dependent radical-based mechanism

Vulnerability of mountain forests of the western Alps to changing fire regime

Les forêts d'altitude connaissent une émergence croissante des feux. Via une analyse rétrospective des feux et du climat des dernières décennies dans le sud-est de la France, cette thèse montre d'abord que l'augmentation de l'activité des feux a été largement restreinte aux zones de montagne, les politiques de lutte contraignant les feux au sein des paysages méditerranéens. Les attributs d'inflammabilité et de résistance des forêts Alpines qui gouvernent ses effets et sa réponse au feu ont ensuite été analysés au sein des niches environnementales des espèces dominantes. Les résultats obtenus montrent que l'abondance et les propriétés d'inflammabilité des litières, des strates herbacées et arbustives varient en fonction de l'ouverture de canopée et la saisonnalité des précipitations. Par ailleurs, les traits de résistance au feu des arbres varient entre espèces en lien avec l'inflammabilité des communautés, selon un compromis entre tolérance (écorce épaisse en climat sec) et évitement (houppier haut en climat humide), suggérant une coévolution entre espèces et feux. Ces gradients biotiques et abiotiques gouvernent ainsi les niches d'inflammabilité des espèces, depuis les forêts denses et humides peu inflammables des Alpes externes du nord aux forêts ouvertes inflammables périméditerranéennes des Alpes du sud et subalpines des Alpes internes. Ainsi, du fait des propriétés de leur niche et de leurs traits d'histoire de vie, les arbres Alpins ne sont pas tous égaux face à l'émergence des feux au sein de la diversité des conditions de végétation et de climat des montagnes du sud de l'Europe.Mountain forests are experiencing an increase in fire occurrence. Through a retrospective analysis over the past decades of fire and climate, this dissertation firstly shows that Mediterranean ecosystems have experienced a strong decrease in fire activity, emphasizing the strong efficiency of fire suppression policies, while fires have been more frequent and large in mountains like the southern Alps. I used vegetation and climate data to characterize the flammability and fire resistance traits of mountain forests of the western Alps that determine their effects and responses to fire. Then, assessing the vulnerability to fire of mountain ecosystems and tree species was carried out by simulating the behaviour of surface fires and their impacts (tree mortality) within the environmental niches of dominant tree species. Results show that tree cover and the seasonality of precipitation largely drive the amount and flammability properties of surface fuels (litter, grass and shrubs). Therefore, these environmental gradients govern the flammability niches of tree species, from the few flammable dense and moist forests of the northern Alps, to the open and highly flammable sub-Mediterranean and subalpine forests of the southern and inner Alps, respectively. Otherwise, fire resistance traits of trees vary according to community flammability through a trade-off between tolerance (thick bark in dry climates) and avoidance strategies (high crown in moist climates), suggesting a coevolution between species and surface fires. To conclude, the niche properties and the life history traits of Alpine trees make them unequally exposed to an increasing fire risk in southern European mountains

La communication non verbale chez l'enseignant de cycle 3

The teacher using of non-verbal and para-verbal in the classroom is necessary. Through his body, his voice, his gestures, the teacher continues to communicate to his pupils his feelings and intentions. These components nonverbal and para-verbal can be used by some teachers in a more or less effective depending on his experience, his personal representations and emotions. The question that concerns us is about the use of these items during a transition period with the following entry for all pupils in a didactic activity. Some non-verbal and para-verbal component will be more useful than others to bring these pupils in the know. By a clear observation of two teacher's body, facial expressions and voice, by a careful observation of the pupils' reactions following the use of non-verbal and para-verbal, we will try, taking into account three different phases to be involved in the activity, to verify the appropriateness of the use of certain elements.L'utilisation d'éléments non verbaux et para-verbaux de l'enseignant en situation de classe est inévitable. Par le biais de son corps, de sa voix, de ses mimiques, l'enseignant ne cesse de communiquer à ses élèves son ressenti et ses intentions. Ces composantes non verbales et para-verbales peuvent être utilisées par certains enseignants d'une manière plus ou moins efficace en fonction de son expérience, de ses représentations personnelles et de ses émotions. La question qui se pose ainsi concerne l'utilisation de ces éléments lors d'une situation de transition ayant pour suite l'entrée de tous les élèves dans une activité didactique. Certains éléments non verbaux et para-verbaux seront plus utiles que d'autres pour faire entrer ces élèves dans le savoir. Par une observation fine de la gestuelle, des mimiques et de la voix de deux enseignants de cycle 3, par une observation rigoureuse de la réaction des élèves suite à l'utilisation d'éléments non verbaux et para-verbaux, nous tenterons, en prenant en compte trois phases différentes pour entrer pleinement dans l'activité, de vérifier la pertinence de l'utilisation de certains éléments

Fast and scalable image auto-tagging

Inside Invenio, the web-based integrated system for handling digital libraries developed at CERN, there is a media module, enabling users to upload photos and videos. Especially in CDS, the Invenio instance used at CERN, people use this digital library to upload pictures of official events that took place at CERN. However, so far, there was no way of tagging what’s inside these photos. This project is meant to solve the problem of tagging persons in a photo in an easy and fast way. First, by implementing a complete tagging interface that allows the user to square parts of the photo, resize them, move them and give them a name. Second, by running face detection so that squares already appear on faces and the user just has to fill the title field. Finally, by running a face recognition system that learned from previous tags created by users. In this report, we will show how we implemented the tagging interface, how we improved the existing face detector to make it more efficient, which face detection methods we used and how we combined them to have a fully working framework. Finally, we will show the results we obtained and the study we did on the parameters to choose for the different algorithms