SOFIA/HAWC + observations of the Crab Nebula: dust properties from polarized emission

Supernova remnants (SNRs) are well-recognized dust producers, but their net dust production rate remains elusive due to uncertainties in grain properties that propagate into observed dust mass uncertainties, and determine how efficiently these grains are processed by reverse shocks. In this paper, we present a detection of polarized dust emission in the Crab pulsar wind nebula, the second SNR with confirmed polarized dust emission after Cassiopeia A. We constrain the bulk composition of the dust with new SOFIA/HAWC+ polarimetric data in band C 89 mu m and band D 154 mu m. After correcting for synchrotron polarization, we report dust polarization fractions ranging between 3.7-9.6 per cent and 2.7-7.6 per cent in three individual dusty filaments at 89 and 154 mu m, respectively. The detected polarized signal suggests the presence of large (greater than or similar to 0.05-0.1 mu m) grains in the Crab Nebula. With the observed polarization, and polarized and total fluxes, we constrain the temperatures and masses of carbonaceous and silicate grains. We find that the carbon-rich grain mass fraction varies between 12 and 70 per cent, demonstrating that carbonaceous and silicate grains co-exist in this SNR. Temperatures range from similar to 40 to similar to 70 K and from similar to 30 to similar to 50 K for carbonaceous and silicate grains, respectively. Dust masses range from similar to 10(-4) to similar to 10(-2) M-circle dot for carbonaceous grains and to similar to 10(-1) M-circle dot for silicate grains, in three individual regions.European Research Council (ERC) European Commission 851622MCIN/AEI PID2020114414GB-100National Aeronautics & Space Administration (NASA) NNA17BF53CDeutsches SOFIA Institut (DSI) under DLR 50 OK 0901 URF\R1\21132

Behaviour and damage of injected carbon-fibre-reinforced polyether ether ketone: From process to modelling

International audienceShort-carbon-fibre-reinforced polyether ether ketones are materials of great interest for the aeronautical industry. In this study, a design of experiment was carried out to understand the effect of process parameters on micro- and macro-scale properties of injection-moulded short-carbon-fibre-reinforced polyether ether ketone (90HMF40). Mould temperature was found to be the most significant parameter; it had a positive effect, essentially on failure stress and strain. Once the damage and plasticity scenarios were understood, a micromechanical model based on Mori-Tanaka homogenization theory was developed, featuring micro-damage and coupling with macro-plasticity. This model gave good predictions for quasi-static tensile tests

Evaluation of impact of artificial reefs on artisanal fisheries: need for complementary approaches

Dentro do atual contexto de redução nos estoques de peixes ligados à sobrepesca, e também à outros fenômenos tais como as mudanças climáticas, é indispensável implementar um plano de gestão durável para os recursos pesqueiros, conciliando sua exploração e conservação. Os recifes artificiais (RAs) tem surgido nos dias atuais como uma importante ferramenta de gestão, freqüentemente combinada à cotas de pesca ou áreas marinhas protegidas. Com a finalidade de avaliar a eficiência dos recifes artificiais, utilizou-se os seguintes métodos: i) censo visual direto através de mergulho autônomo com escafandro (na escala dos recifes artificiais); ii) monitoramento dos desembarques da pesca artesanal (na escala espacial local); e iii) marcações externas (em escala regional). As contagens realizadas através de mergulho mostraram que densidade e riqueza são significativamente mais elevadas nos recifes artificiais do que na área controle. A abundância, biomassa e os DPUE (Desembarques por unidade de esforço) provenientes do monitoramento dos desembarques da pesca artesanal, não foram significativamente diferentes entre as zonas de pesca do entorno dos recifes artificiais e as outras zonas de pesca da costa catalã francesa. Os resultados dos experimentos de marcação do sargo, Diplodus sargus, sugerem que a conectividade das populações de peixes demersais devem ser consideradas para avaliação das zonas de influência dos recifes artificiais e de seus impactos indiretos sobre a pesca artesanal. O presente estudo evidencia a oportunidade em combinar métodos que cubram diferentes escalas espaciais, a fim de avaliar os impactos diretos e indiretos dos RAs sobre a pesca artesanal. Os métodos para avaliar a eficiência dos recifes artificiais são também discutidos.In a general context of fisheries decline due to overfishing and to other phenomena such as climate change, it appears to be crucial to implement a sustainable management of natural resources by finding a balance between conservation and exploitation purposes. Artificial reefs (ARs) have recently become one of the existing management tools, often in combination with fishing quotas or marine protected areas. To evaluate the effectiveness of the studied ARs, different methods have been used: (i) visual census by SCUBA diving (AR scale), (ii) fisheries landings survey (local scale) and (iii) external fish tagging (regional scale). Underwater visual census (UVC) showed a significantly higher species richness and density in ARs than in the control site. Abundance, biomass and LPUE data (Landings Per Unit Effort) issued from artisanal fisheries landings survey were not significantly different around the AR system from other fishing grounds of the French Catalan coast. The tagging experiments on Diplodus sargus suggested that the connectivity of demersal fish populations must be taken into account to evaluate the influence area of ARs and thus their indirect impacts on artisanal fisheries. The present study highlights the interest of combining methods covering different spatial scales in order to evaluate direct and indirect impacts of ARs on artisanal fisheries. Methods for the evaluation of AR efficiency are discussed

Development of chiral phosphoric acids based on ferrocene-bridged paracyclophane frameworks

International audienceThis work deals with the development of a new family of planar chiral phosphoric acids, based on a ferrocenophane/paracyclophane scaffold. The synthetic approach has been improved by taking advantage of a chiral phosphorylating agent to access enantiomerically enriched acids via diastereomers separation. These phosphoric acids have been used as catalysts for the enantioselective H-transfer reduction of alpha-substituted quinolines with Hantzsch esters. Optimization of both the catalyst and the Hantzsch reductant allowed ee in the range 82-92% to be attained starting from alpha-arylquinolines

Rôle des enrochements côtiers artificiels dans la connectivité des populations, cas du sar commun (Diplodus sargus, Linné, 1758) en Méditerranée nord-occidentale

Habitat destruction is a major cause of its fragmentation. Since the 1960's, human pressure on seashores, especially along the Gulf of Lion has induced lots of fragmented habitats. Destruction is not the predominant factor for this fragmentation, but the large-scale installation of coastal artificial rocks which creates new habitats. This study investigated on the role of these structures compared to natural areas (lagoons, rocky shores) to maintain fish populations more south, on the rocky coast. The white seabream, infeodated to these rocky areas, is the biological model used. Scuba diving visual census of adults and juveniles, direct tagging and otolith microchemistry were performed to better understand these dynamics.Coastal artificial habitats have to be considered as important nursery areas. Depending on the year, densities of juveniles are 30 to 109 times higher than those observed on natural habitats, either on the rocky coast or in the lagoon. Such differences could be explained by the presence of only two main groups of adults along the French Catalan coast. The first would supply the coastal artificial rocks and be located at cap Leucate. The second, in the reserve of Cerbère-Banyuls, would export juveniles to the Spanish coast following the dominant north-south current. Moreover, the lagoon has lost its nursery function to the benefit of the artificial coastal habitats.Our results also show the connectivity during the adult phase between these coastal structures and the natural rocky areas. 20% of white seabreams which had settled on the artificial habitats, left for the rocky coast, mainly in spring and autumn. We also presume that one third of the seabreams living there are those that had settled on the artificial habitats of the sandy coast.This study underlies the importance presumably of major role played by these artificial habitats to the maintenance and expansion of populations of white seabream in the Catalan coast. The results are possibly a snapshot of the population dynamics in the Gulf of Lion. Habitat fragmentation has a positive effect in this case. It could be the origin of emergence of new species on the coast of Languedoc-Roussillon like the zebra seabream, Diplodus cervinus and the common dentex, Dentex dentex.La destruction d'une partie des habitats est souvent la cause principale de leur fragmentation. Or, depuis les années 1960-1970, l'anthropisation du littoral du golfe du Lion a engendré la création d'habitats fragmentés, non pas par une destruction, mais bien par un apport nouveau via l'installation massive d'enrochements côtiers artificiels. Cette étude a eu pour but principal de comprendre le rôle de ces structures en comparaison à des zones naturelles (lagunes, zone rocheuse) dans le maintien des populations de poissons de la côte rocheuse située plus au sud. Le sar commun, poisson caractéristique des zones rocheuses, a été utilisé comme modèle. Des comptages d'adultes et de juvéniles en plongée subaquatique, des marquages directs mais aussi l'utilisation de la microanalyse chimique des otolithes ont été utilisés afin de répondre à ces interrogations.Les aménagements littoraux jouent un rôle de nourricerie non négligeable. Selon les années, les densités de juvéniles sont de 30 à 109 fois supérieures à celles observées sur les habitats naturels, que ce soit sur la côte rocheuse ou dans la lagune. La présence de seulement deux groupes principaux de géniteurs sur la côte catalane française pourrait expliquer de telles différences. Un des deux alimenterait les enrochements côtiers artificiels, il serait situé au cap Leucate. Le second, dans la réserve de Cerbère-Banyuls exporterait des juvéniles vers la côte espagnole suivant un courant dominant nord-sud. De plus, la lagune aurait perdu son rôle de nourricerie au profit des aménagements littoraux.Nos résultats montrent aussi qu'il existe une connectivité lors de la phase adulte entre ces structures côtières et les zones rocheuses naturelles. Elle a lieu principalement au printemps et en automne. 20 % des sars ayant fait leur installation sur les aménagements littoraux les quittent pour la côte rocheuse. Sur cette côte un tiers des sars sont issus d'une installation sur des habitats artificiels de la côte sableuse.Cette étude souligne le rôle majeur que peuvent avoir ces habitats artificiels dans le maintien, voire l'extension des populations de sars communs au niveau de la côte catalane, mais aussi de l'ensemble du golfe du Lion. La fragmentation de l'habitat est dans ce cas positive. Elle pourrait être à l'origine de l'apparition de nouvelles espèces sur la côte du Languedoc-Roussillon comme le sar tambour, Diplodus cervinus et le denti, Dentex dentex

Rôle des enrochements côtiers artificiels dans la connectivité des populations, cas du sar commun (Diplodus sargus, Linné, 1758) en Méditerranée nord-occidentale

Cette étude montre que les aménagements littoraux jouent un rôle de nourricerie non négligeable. Selon les années, les densités de juvéniles sont de 30 à 109 fois supérieures à celles observées sur les habitats naturels, que ce soit sur la côte rocheuse ou dans la lagune. La présence de seulement deux groupes principaux de géniteurs sur la côte catalane française pourrait expliquer de telles différences. Un des deux alimenterait les enrochements côtiers artificiels, il serait situé au cap Leucate. Le second, dans la réserve de Cerbère-Banyuls exporterait des juvéniles vers la côte espagnole suivant un courant dominant nord-sud. De plus, la lagune aurait perdu son rôle de nourricerie au profit des aménagements littoraux.Nos résultats montrent aussi qu il existe une connectivité lors de la phase adulte entre ces structures côtières et les zones rocheuses naturelles. Elle a lieu principalement au printemps et en automne. 20 % des sars ayant fait leur installation sur les aménagements littoraux les quittent pour la côte rocheuse. Sur cette côte un tiers des sars sont issus d une installation sur des habitats artificiels de la côte sableuse.Cette étude souligne le rôle majeur que peuvent avoir ces habitats artificiels dans le maintien, voire l extension des populations de sars communs au niveau de la côte catalane, mais aussi de l ensemble du golfe du Lion. La fragmentation de l habitat est dans ce cas positive. Elle pourrait être à l origine de l apparition de nouvelles espèces sur la côte du Languedoc-Roussillon comme le sar tambour, Diplodus cervinus et le denti, Dentex dentexCoastal artificial habitats have to be considered as important nursery areas. Depending on the year, densities of juveniles are 30 to 109 times higher than those observed on natural habitats, either on the rocky coast or in the lagoon. Such differences could be explained by the presence of only two main groups of adults along the French Catalan coast. The first would supply the coastal artificial rocks and be located at cap Leucate. The second, in the reserve of Cerbère-Banyuls, would export juveniles to the Spanish coast following the dominant north-south current. Moreover, the lagoon has lost its nursery function to the benefit of the artificial coastal habitats.Our results also show the connectivity during the adult phase between these coastal structures and the natural rocky areas. 20% of white seabreams which had settled on the artificial habitats, left for the rocky coast, mainly in spring and autumn. We also presume that one third of the seabreams living there are those that had settled on the artificial habitats of the sandy coast.This study underlies the importance presumably of major role played by these artificial habitats to the maintenance and expansion of populations of white seabream in the Catalan coast. The results are possibly a snapshot of the population dynamics in the Gulf of Lion. Habitat fragmentation has a positive effect in this case. It could be the origin of emergence of new species on the coast of Languedoc-Roussillon like the zebra seabream, Diplodus cervinus and the common dentex, Dentex dentexPERPIGNAN-BU Lettres-Sc.humaines (661362102) / SudocPARIS-Museum-Bib. d'ichtyologie (751052306) / SudocSudocFranceF

Coastal man-made habitats: Potential nurseries for an exploited fish species, Diplodus sargus (Linnaeus, 1758)

Human pressure on seashores has induced the installation of many seawalls. Artificial coastal defence structures may be providential for the juveniles of fish species exploited by artisanal fisheries. Focusing on Diplodus sargus, the number of settling juveniles was estimated on artificial structures and on natural rocky shores. The aim is to know if these artificial areas can have a nursery function. Densities of juveniles are from 30 to 109 times greater than those in natural habitats. Artificial coastal defence structures can be regarded as artificial nurseries. However, in the studied case, they also cause the loss of the nursery function of the nearby lagoon. The artificial seawalls at the entrance to the lagoon receive almost all the larvae that would normally enter the lagoon. This study underlines the important role of these artificial habitats in the life cycle of white seabream. They may have a positive impact on maintaining other species exploited by artisanal fisheries

Experiment and modelling of injected carbon-fibre-reinforced-peek behaviour under tensile loading

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Etude de l'influence des paramètres d'injection sur le comportement de PEEK renforcé de fibres de carbone par thermographie infrarouge

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