Testing the performance of state-of-the-art dust emission schemes using DO4Models field data

Within the framework of the Dust Observations for Models (DO4Models) project, the performance of three commonly used dust emission schemes is investigated in this paper using a box model environment. We constrain the model with field data (surface and dust particle properties as well as meteorological parameters) obtained from a dry lake bed with a crusted surface in Botswana during a 3 month period in 2011. Our box model results suggest that all schemes fail to reproduce the observed horizontal dust flux. They overestimate the magnitude of the flux by several orders of magnitude. The discrepancy is much smaller for the vertical dust emission flux, albeit still overestimated by up to an order of magnitude. The key parameter for this mismatch is the surface crusting which limits the availability of erosive material, even at higher wind speeds. The second-most important parameter is the soil size distribution. Direct dust entrainment was inferred to be important for several dust events, which explains the smaller gap between modelled and measured vertical dust fluxes. We conclude that both features, crusted surfaces and direct entrainment, need to be incorporated into dust emission schemes in order to represent the entire spectra of source processes. We also conclude that soil moisture exerts a key control on the threshold shear velocity and hence the emission threshold of dust in the model. In the field, the state of the crust is the controlling mechanism for dust emission. Although the crust is related to the soil moisture content to some extent, we are not as yet able to deduce a robust correlation between state of crust and soil moisture

Cell Cycle Phase-Specific Surface Expression of Nerve Growth Factor Receptors TrkA and p75NTR

[EN]Expression of the nerve growth factor (NGF) receptors TrkA and p75NTR was found to vary at the surface of PC12 cells in a cell cycle phase-specific manner. This was evidenced by using flow cytometric and microscopic analysis of cell populations labeled with antibodies to the extracellular domains of both receptors. Differential expression of these receptors also was evidenced by biotinylation of surface proteins and Western analysis, using antibodies specific for the extracellular domains of TrkA and p75NTR. TrkA is expressed most strongly at the cell surface in M and early G1 phases, whereas p75NTR is expressed mainly in late G1, S, and G2 phases. This expression reflects the molecular and cellular responses to NGF in specific phases of the cell cycle; in the G1 phase NGF elicits both the anti-mitogenic effect, i.e., inhibition of the G1 to S transition, and the differentiation response whereas a survival effect is provoked elsewhere in the cell cycle. A model is proposed relating these responses to the surface expression of the two receptors. These observations open the way for novel approaches to the investigation of the mechanism of NGF signal transduction

Exploration naturaliste sous-marine des petits fonds rocheux du Cap Santa Clara au Cap Esterias, Province de l’Estuaire, Gabon: les poissons marins

Bien que située à moins de vingt kilomètres du centre de la capitale Libreville, la zone marine comprise entre le Cap Santa Clara et le Cap Esterias n’avait fait l’objet que de travaux scientifiques limités, essentiellement orientés vers les tortues marines, emblématiques des efforts de conservation du milieu marin au Gabon. Aucun véritable inventaire de la faune spécifique aux estrans et aux petits fonds rocheux n’avait été entrepris, et l’évidence d’une mission d’exploration s’imposait, renforcée par la probabilité de découvrir de nouvelles espèces, pour le Gabon, voire peut-être même pour la Science.info:eu-repo/semantics/publishedVersio

Operational Dust Prediction

Over the last few years, numerical prediction of dust aerosol concentration has become prominent at several research and operational weather centres due to growing interest from diverse stakeholders, such as solar energy plant managers, health professionals, aviation and military authorities and policymakers. Dust prediction in numerical weather prediction-type models faces a number of challenges owing to the complexity of the system. At the centre of the problem is the vast range of scales required to fully account for all of the physical processes related to dust. Another limiting factor is the paucity of suitable dust observations available for model, evaluation and assimilation. This chapter discusses in detail numerical prediction of dust with examples from systems that are currently providing dust forecasts in near real-time or are part of international efforts to establish daily provision of dust forecasts based on multi-model ensembles. The various models are introduced and described along with an overview on the importance of dust prediction activities and a historical perspective. Assimilation and evaluation aspects in dust prediction are also discussed

La compensation écologique fonctionnelle : innover pour mieux traiter les impacts résiduels des projets d’aménagements sur la biodiversité

Face aux impacts résiduels d’un projet d’aménagement, les mesures compensatoires doivent permettre de rétablir la qualité et la biodiversité des milieux naturels impactés à un niveau au moins équivalent de l'état initial. Véritable défi technique et organisationnel, la conception et la mise en œuvre de ces mesures nécessitent d'évaluer l’équivalence écologique en mettant en miroir les pertes engendrées par les projets et les gains attendus des mesures compensatoires, pour les intégrer ensuite dans le territoire aménagé. Cet article présente ici une méthode spécifique et novatrice appliquée dans le cadre du projet de contournement ferroviaire Nîmes-Montpellier

Acaricidal activity of essential oils from five endemic conifers of New Caledonia on the cattle tick Rhipicephalus (Boophilus) microplus

International audienceThe aim of the present study was to demonstrate acaricidal activity on the cattle tick Rhipicephalus (Boophilus) microplus of essential oils from endemic conifers of New Caledonia in the context of the development of natural alternatives. Acaricidal activity of essential oils extracted from resin and heartwood of five endemic conifers of New Caledonia (Araucaria columnaris, Agathis moorei, Agathis ovata, Callitris sulcata, and Neocallitropsis pancheri) was evaluated on 14- to 21-day-old Rhipicephalus microplus tick larvae using the Larval Packal Test bioassay. A first screening with 5 % dilute solution was carried out and the oils with 100 % of mortality at this rate were diluted until no activity was shown. The heartwood oils of the two Cupressaceae were the most active with LC50 value of 0.65 % for C. sulcata and 0.55 % for N. pancheri while resin oil of A. columnaris (LC50=1.62 %) was the most active of the Araucariaceae family. Negative control (ethanol) was not toxic to the larvae. The chemical composition of essential oil from resin of A. columnaris was analyzed by gas chromatography-mass spectrometry. The essential oil was characterized by high level of sesquiterpene hydrocarbons and oxygenated sesquiterpenes and was composed mainly of aromadendrene (23.1 %) and bicyclogermacrene (16.0 %). In order to compare different plant resources in a sustainable program of natural acaricide, an "essential oil efficiency EOE" can be measured as the ratio between the yield of extraction and LC50 value. This study shows that A. columnaris (EOE=2.36) and N. pancheri (EOE=3.51) could provide valuable and effective natural acaricides for control of the cattle tick R. microplus

Chemical composition and antimicrobial activity of the essential oils of leaves, roots and bark of Glossocalyx staudtii

International audienc