250 research outputs found
Adaptive evolution and segregating load contribute to the genomic landscape of divergence in two tree species connected by episodic gene flow
Speciation often involves repeated episodes of genetic contact between divergent populations before reproductive isolation (RI) is complete. Whole-genome sequencing (WGS) holds great promise for unravelling the genomic bases of speciation. We have studied two ecologically divergent, hybridizing species of the âmodel treeâ genus Populus (poplars, aspens, cottonwoods), Populus alba and P. tremula, using >8.6 million single nucleotide polymorphisms (SNPs) from WGS of population pools. We used the genomic data to (i) scan these speciesâ genomes for regions of elevated and reduced divergence, (ii) assess key aspects of their joint demographic history based on genomewide site frequency spectra (SFS) and (iii) infer the potential roles of adaptive and deleterious coding mutations in shaping the genomic landscape of divergence. We identified numerous small, unevenly distributed genome regions without fixed polymorphisms despite high overall genomic differentiation. The joint SFS was best explained by ancient and repeated gene flow and allowed pinpointing candidate interspecific migrant tracts. The direction of selection (DoS) differed between genes in putative migrant tracts and the remainder of the genome, thus indicating the potential roles of adaptive divergence and segregating deleterious mutations on the evolution and breakdown of RI. Genes affected by positive selection during divergence were enriched for several functionally interesting groups, including well-known candidate âspeciation genesâ involved in plant innate immunity. Our results suggest that adaptive divergence affects RI in these hybridizing species mainly through intrinsic and demographic processes. Integrating genomic with molecular data holds great promise for revealing the effects of particular genetic pathways on speciation
Inter-Comparison of the Spatial Distribution of Methane in the Water Column From Seafloor Emissions at Two Sites in the Western Black Sea Using a Multi-Technique Approach
Understanding the dynamics and fate of methane (CH 4 ) release from oceanic seepages on margins and shelves into the water column, and quantifying the budget of its total discharge at different spatial and temporal scales, currently represents a major scientific undertaking. Previous works on the fate of methane escaping from the seafloor underlined the challenge in both, estimating its concentration distribution and identifying gradients. In April 2019, the Envri Methane Cruise has been conducted onboard the R/V Mare Nigrum in the Western Black Sea to investigate two shallow methane seep sites at âŒ120 m and âŒ55 m water depth. Dissolved CH 4 measurements were conducted with two continuous in-situ sensors: a membrane inlet laser spectrometer (MILS) and a commercial methane sensor (METS) from Franatech GmbH. Additionally, discrete water samples were collected from CTD-Rosette deployment and standard laboratory methane analysis was performed by gas chromatography coupled with either purge-and-trap or headspace techniques. The resulting vertical profiles (from both in situ and discrete water sample measurements) of dissolved methane concentration follow an expected exponential dissolution function at both sites. At the deeper site, high dissolved methane concentrations are detected up to âŒ45 m from the seabed, while at the sea surface dissolved methane was in equilibrium with the atmospheric concentration. At the shallower site, sea surface CH 4 concentrations were four times higher than the expected equilibrium value. Our results seem to support that methane may be transferred from the sea to the atmosphere, depending on local water depths. In accordance with previous studies, the shallower the water, the more likely is a sea-to-atmosphere transport of methane. High spatial resolution surface data also support this hypothesis. Well localized methane enriched waters were found near the surface at both sites, but their locations appear to be decoupled with the ones of the seafloor seepages. This highlights the need of better understanding the processes responsible for the transport and transformation of the dissolved methane in the water column, especially in stratified water masses like in the Black Sea
Altimetry for the future: Building on 25 years of progress
In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ââGreenâ Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instrumentsâ development and satellite missionsâ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion
Lagrangian ocean analysis: fundamentals and practices
Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. The overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing
Altimetry for the future: building on 25 years of progress
In 2018 we celebrated 25âŻyears of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology.
The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the âGreenâ Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instrumentsâ development and satellite missionsâ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion
Voyage d'exploration de HuĂȘ en Cochinchine par la route mandarine; avec 6 cartes en couleur et 12 gravures
Evaluation du risque cancérogÚne dans le secteur industriel papetier (observation dans trois papeteries lorraines)
L'Ă©valuation et la gestion du risque cancĂ©rogĂšne en milieu professionnel est prioritaire en raison de sa gravitĂ©. Le secteur industriel papetier a fait l'objet d'Ă©tudes Ă©pidĂ©miologiques qui indiquent un excĂšs de mortalitĂ© pour certains types de cancers, mais les donnĂ©es ne sont pas toutes concordantes : en raison de ces contradictions, ce secteur n'a pu ĂȘtre classĂ© du point de vue de sa cancĂ©rogĂ©nicitĂ©.Aujourd'hui la dĂ©marche d'Ă©valuation du risque cancĂ©rogĂšne est en Ćuvre dans les entreprises. Cependant, en l'absence d'une mĂ©thode d'Ă©valuation spĂ©cifique, elle s'intĂšgre dans l'Ă©valuation gĂ©nĂ©rale de l'exposition aux toxiques et ne permet pas de hiĂ©rarchiser les prioritĂ©s d'action entre plusieurs cancĂ©rogĂšnes. De plus, la nature mĂȘme du risque complique l'Ă©laboration de rĂ©fĂ©rences cohĂ©rentes en matiĂšre de surveillance mĂ©dicale, rendant la gestion du risque difficile pour les professionnels de santĂ© au travail. Une mĂ©thodologie est Ă©laborĂ©e puis validĂ©e dans trois papeteries lorraines, afin de proposer des outils d'aide au repĂ©rage et Ă la gestion technique et mĂ©dicale du risque cancĂ©rogĂšne. Les rĂ©sultats mettent en Ă©vidence la diversitĂ© des procĂ©dĂ©s papetiers, liĂ©e Ă la grande variĂ©tĂ© du papier, l'utilisation de multiples produits chimiques et l'exposition des personnels Ă plusieurs substances cancĂ©rogĂšnes certaines ou suspectĂ©es. La tendance est Ă la substitution mais persistent encore des situations pour lesquelles elle n'est pas possible. La gestion mĂ©dicale du risque rĂ©siduel, pour les cancĂ©rogĂšnes non substituĂ©s, nĂ©cessite une Ă©valuation du risque sanitaire en intĂ©grant les donnĂ©es de la relation dose-effet.NANCY1-SCD Medecine (545472101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
L' Enfant et le cabinet dentaire (une approche comportementale)
MONTROUGE-BUFR Odontol.PARIS5 (920492101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
Thermochromic Luminescent Materials and Multi-Emission Bands in d10 Clusters
International audienc
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