Science & Mathematics

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Interactions between surface waves and sea ice are thought to be an important, but poorly understood, physical process in the atmosphere-ice-ocean system. In this work, airborne scanning lidar was used to observe ocean waves propagating into the marginal ice zone (MIZ). These represent the first direct spatial measurements of the surface wavefield in the polar MIZ. Data were compared against two attenuation models, one based on viscous dissipation and one based on scattering. Both models were capable of reproducing the measured wave energy. The observed wavenumber dependence of attenuation was found to be consistent with viscous processes, while the spectral spreading of higher wavenumbers suggested a scattering mechanism. Both models reproduced a change in peak direction due to preferential directional filtering. Floe sizes were recorded using colocated visible imagery, and their distribution was found to be consistent with ice breakup by the wavefield.

The objective of this study was to compare the impact of six tree species on vegetation and soil. Eighty stands growing side by side, and of different dominant species, were selected in 26 locations. Within each location the stands had the same soil condition, landscape position and previous land-use history. Ground vegetation and soil were sampled in each stand. The tree species were: Norway spruce (Picea abies Karsten.), Scots pine (Pinus sylvestris L.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), silver fir (Abies alba Miller), European beech (Fagus sylvatica L.) and oaks (Quercus robur L., Quercus petraea (Matt.) Liebl.). The geographic and geological characteristics of sites influenced the vegetation and the soil chemistry more than the tree species did. Forest management influenced the ground flora more than the tree species did. Number of species and equitability differed little with tree species. The ground flora under Norway spruce included more mosses than under the other trees species except silver fir. The ground flora under Norway spruce was more typical of oligotrophic and acidic conditions than the flora under European beech. Soils under coniferous species, especially Norway spruce, were more acidic and had higher concentrations of aluminium than soils under hardwoods. The effect of tree species on soils was greatest in the topsoil (0-10 cm).

Effect of intensity of gravitational stimulus artificially induced on growth and tension wood formation in young shoots of poplar (P. euramericana cv 'Ghoy'). The formation of tension wood tissue is artificially induced by means of a gravitational stimulus obtained by inclining young shoots of poplar at different intensities, from 0 to 30°, during a growing season. At the end of the experiment, it appears that shoot elongation as well as the angle of tension wood arc are not affected by the stimulus intensity. In contrast, the upright reorientation of the axis, the amount of gelatinous fibres, the secondary growth over bark, the cross-section area of the stem and of the secondary xylem, the different rays, the diameter under bark and the pith eccentricity, react quantitatively to the lean intensity. The amount of tension wood is correlated with the upright reorientation, the secondary growth over bark and the radial growth under bark. Tension wood formation and eccentricity react to the gravitational stimulus but they are not causally linked. Finally, it exists a natural equilibrium position, different from the vertical, to which moved shoots try to return via the formation of a tension wood tissue.

Une méthode de calcul est proposée pour l’indexation des taureaux laitiers sur plusieurs lactations, considérées comme un seul caractère, quand le modèle d’analyse doit tenir compte des effets troupeau-année (HY), d’environnement autres que HY (ENV), vache et père. Après une présentation des équations conduisant aux estimations des différents effets et des méthodes de résolution, quelques améliorations sont proposées : 1) Une méthode est décrite pour l’absorption des équations vache. 2) Au lieu de recourir à l’absorption des équations HY, qui. serait trop longue, il est possible d’obtenir les solutions correspondantes aux effets HY, ENV et père par une procédure itérative. 3) En exprimant les performances antérieures en écart aux effets HY et ENV, à l’aide des solutions obtenues lors des calculs antérieurs on propose de combiner les données anciennes et récentes pour l’estimation de la valeur génétique des taureaux sans trop augmenter la complexité des calculs.

A study was established in 1993 to determine the response of four black spruce (Picea mariana) and white spruce (P. glauca) stock sizes on two sites located in Québec (Canada), each representing a different type of competing vegetation. At each site, a split-split-plot design with 15 to 17 replicates was used, in which the presence of competition (weedy and bare plots), seedling initial size, and spruce species were assigned respectively to the whole plot, the subplot, and the sub-subplot. Larger initial seedling size provided a greater competitive ability for light and had higher growth rates than the standard stock size for both species. Growth gains from combining plantation of large stock with vegetation control were multiplicative. Non-crop vegetation significantly lowered the seasonal profile of 10-cm depth soil temperature on both sites. This study shows that early release treatment is required on sites dominated by raspberry-hardwood competition complex and planting large spruce stock on such harsh competition sites will help reduce the need for repeated vegetation control.

Le trouble développemental du langage (TDL) affecte 3 à 7 % des enfants d’âge scolaire et compromet leurs apprentissages, leurs interactions sociales et leur qualité de vie. Face à ces enjeux, la lecture partagée représente une modalité d’intervention précoce prometteuse. Ce travail a visé à évaluer son efficacité spécifique auprès de jeunes enfants (3-6 ans) présentant un TDL, à travers une revue systématique. Une recherche documentaire a été conduite dans les bases PubMed et Scopus, selon les recommandations PRISMA. Les critères d’inclusion, les mots-clés et les équations de recherche ont été définis à partir de la question PICO. Douze études répondant aux critères ont été sélectionnées. Les enfants étaient âgés de 3 à 6 ans et présentaient un TDL objectivé. Les interventions comportaient une lecture partagée centrée sur l’interaction adulte-enfant. Les données ont été extraites, synthétisées et analysées, et la qualité méthodologique a été évaluée via les grilles d'évaluations CONSORT, RoB 2.0 et SCRIBE, selon le type de design. Les résultats ont montré des effets positifs sur le lexique, la morphosyntaxe, certaines compétences pragmatiques et, dans une moindre mesure, les habiletés associées à la littératie. L’intensité de l’intervention, le cadre de mise en œuvre et le rôle de l’adulte semblaient moduler les effets. Toutefois, la forte hétérogénéité des protocoles et les biais méthodologiques observés ont limité la portée généralisable des résultats. Cette revue a permis d’établir un premier état des lieux structuré des effets de la lecture partagée auprès d’enfants avec TDL, et a souligné la nécessité d’études complémentaires rigoureuses.

Introduction : le traumatisme crânien est une pathologie fréquente et grave. Or, il n’existe pas de recommandation des sociétés savantes après 24 heures de prise en charge. Notre étude a pour but d’observer le suivi médical de la cohorte NEURODATA par leur médecin traitant (MT) et secondairement par le CHU de Caen, dans l’année qui a suivi leur hospitalisation en réanimation. Matériel et méthode : les données ont été recueillies après appel du MT des patients et sur consultation de leur dossier médical au CHU de Caen. Les patients étaient groupés en bon et mauvais pronostic selon le Glasgow Outcome Scale Extended. Résultats : sur 99 patients inclus, 39 sont décédés, 47 ont eu une évaluation pronostique à 1 an, pour 31 des 47 patients (66%), les MT ont été contactés : 26 patients avaient un bon pronostic et 5 un mauvais. Les patients de bon pronostic ont été plus suivis par les MT (58%) que ceux de mauvais pronostics (p=0.007). Le suivi au CHU de Caen à 3 mois a été réalisé chez 61% des patients : ceux de bon pronostic étaient plus suivis que ceux de mauvais pronostics. Ils étaient également plus souvent adressés à des spécialistes par leur MT. Conclusion : les patients de bon pronostic à 1 an sont suivis par les médecins généralistes, contrairement à ceux de mauvais pronostics le plus souvent institutionnalisés avec un suivi spécialisé. Le MT cible une population de bon pronostic à 1 an avec pour mission de prévenir les complications secondaires des patients traumatisés crâniens passés en réanimation. Des consultations multidisciplinaires pourraient être instaurées pour aider les MT dans leur travail.

The effect of herbicide, fertilization and irrigation treatments on growth of planted Norway spruce seedlings were investigated in an experiment established in 1998 in southern Sweden. After three years, the amount of ground vegetation was about the same in fertilized, irrigated and fertilized + irrigated plots, but the amount was about double as in the control. Seedling growth was positively affected by the herbicide treatment. Fertilization increased growth when it was combined with herbicides. Irrigation did not have any significant effect on seedling growth. Results from this study indicate that competition for water between ground vegetation and planted Norway spruce seedlings is of little importance. However, this conclusion is restricted to seedling growth during years with at least normal precipitation. It was also indicated that increased nutrient availability is positive for seedling establishment and growth, but that the planted seedlings were not growing at their potential even when herbicide, irrigation and fertilization treatments were combined indicating establishment problems.

Magnetic fields are considered as a vital ingredient of contemporary star formation, and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations, and are subsequently amplified by the small-scale dynamo, leading to a strong tangled magnetic field. Here we explore how the magnetic field provided by the small-scale dynamo is further amplified via the $\alpha-\Omega$ dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop.~III star with $10$~M$_\odot$ and an accretion rate of $10^{-3}$~M$_\odot$~yr$^{-1}$, and a supermassive star with $10^5$~M$_\odot$ and an accretion rate of $10^{-1}$~M$_\odot$~yr$^{-1}$. For the $10$~M$_\odot$ Pop.~III star, we find that coherent magnetic fields can be produced on scales of at least $100$~AU, which are sufficient to drive a jet with a luminosity of $100$~L$_\odot$ and a mass outflow rate of $10^{-3.7}$~M$_\odot$~yr$^{-1}$. For the supermassive star, the dynamical timescales in its environment are even shorter, implying smaller orbital timescales and an efficient magnetization out to at least $1000$~AU. The jet luminosity corresponds to $\sim10^{6.0}$~L$_\odot$, and a mass outflow rate of $10^{-2.1}$~M$_\odot$~yr$^{-1}$. We expect that the feedback from the supermassive star can have a relevant impact on its host galaxy.

Extracellular-released vesicles (EVs), such as microvesicles (MV) and exosomes (Exo) provide a new type of inter-cellular communication, directly transferring a ready to use box of information, consisting of proteins, lipids and nucleic acids. In the nervous system, EVs participate to neuron-glial cross-talk, a bidirectional communication important to preserve brain homeostasis and, when dysfunctional, involved in several CNS diseases. We investigated whether microglia-derived EVs could be used to transfer a protective phenotype to dysfunctional microglia in the context of a brain tumor. When MV, isolated from microglia stimulated with LPS/IFNγ were brain injected in glioma-bearing mice, we observed a phenotype switch of tumor associated myeloid cells (TAMs) and a reduction of tumor size. Our findings indicate that the MV cargo, which contains upregulated transcripts for several inflammation-related genes, can transfer information in the brain of glioma bearing mice modifying microglial gene expression, reducing neuronal death and glioma invasion, thus promoting the recovery of brain homeostasis.

Dispersing 1D bands have been observed for the first time in an organic conductor by high resolution photoemission experiments on TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane). Their properties are extremely unusual: the bandwidth is much larger than traditional estimates, and the quasiparticle states are strongly renormalized, with no weight at the chemical potential. A deep pseudogap around the Fermi energy persists, and even increases, up to room temperature. We also report a direct determination of kF in this material, and the observation of the opening of a Peierls gap in the low-temperature charge density wave phase.