AFRP20: New P-Wavespeed Model for the African Mantle Reveals Two Whole-Mantle Plumes Below East Africa and Neoproterozoic Modification of the Tanzania Craton

Africa’s Cenozoic tectonism is often attributed to mantle plumes, particularly below East Africa, but their morphology, number, location, and impact on the African lithosphere are debated. The broad slow wavespeed African Superplume, ubiquitous in large-scale tomographic models, originates below South Africa, reaching the surface somewhere below East Africa. However, whether the diverse East African mantle geochemistry is best reconciled with one heterogeneous upwelling, or current tomographic models lack the resolution to image multiple distinct plumes, remains enigmatic. S-wavespeed tomographic images of Africa are legion, but higher-frequency P-wavespeed whole-mantle models possessing complementary diagnostic capabilities are comparatively lacking. This hinders attempts to disentangle the effects of Cenozoic hotspot tectonism and Pan African (and older) tectonic events on the East African lithosphere. Here we develop a continental-scale P-wave tomographic model capable of resolving structure from upper-to-lower mantle depths using a recently-developed technique to extract absolute arrival-times from noisy, temporary African seismograph deployments. Shallow-mantle wavespeeds are δVP ≈–4% below Ethiopia, but less anomalous (δVP ≥–2%) below other volcanic provinces. The heterogeneous African Superplume reaches the upper mantle below the Kenyan plateau. Below Ethiopia/Afar we image a second sub-vertical slow wavespeed anomaly rooted near the core-mantle boundary outside the African LLVP, meaning multiple disparately sourced whole-mantle plumes may influence East African magmatism. In contrast to other African cratons, wavespeeds below Tanzania are only fast to 90–135km depth. When interpreted alongside Lower Eocene on-craton kimberlites, our results support pervasive metasomatic lithospheric modification caused by subduction during the Neoproterozoic Pan-African orogeny.A. B. and S. C. are funded by the Natural Environment Research Council (NERC) Grant number NE/R010862/1 from PI Cottaar in Cambridge. A. B. was previously funded by the NERC Doctoral Training Partnership: Science and Solutions for a Changing Planet - Grant number NE/L002515/1 at Imperial College. I. B is funded by Natural Environment Research Council Grant number NE/S014136/1

Improving Network-on-Chip-based Turbo Decoder Architectures

In this work novel results concerning Networkon- Chip-based turbo decoder architectures are presented. Stemming from previous publications, this work concentrates first on improving the throughput by exploiting adaptive-bandwidth-reduction techniques. This technique shows in the best case an improvement of more than 60 Mb/s. Moreover, it is known that double-binary turbo decoders require higher area than binary ones. This characteristic has the negative effect of increasing the data width of the network nodes. Thus, the second contribution of this work is to reduce the network complexity to support doublebinary codes, by exploiting bit-level and pseudo-floatingpoint representation of the extrinsic information. These two techniques allow for an area reduction of up to more than the 40 % with a performance degradation of about 0.2 d

AFRP20: New P-Wavespeed Model for the African Mantle Reveals Two Whole-Mantle Plumes Below East Africa and Neoproterozoic Modification of the Tanzania Craton

Africa’s Cenozoic tectonism is often attributed to mantle plumes, particularly below East Africa, but their morphology, number, location, and impact on the African lithosphere are debated. The broad slow wavespeed African Superplume, ubiquitous in large-scale tomographic models, originates below South Africa, reaching the surface somewhere below East Africa. However, whether the diverse East African mantle geochemistry is best reconciled with one heterogeneous upwelling, or current tomographic models lack the resolution to image multiple distinct plumes, remains enigmatic. S-wavespeed tomographic images of Africa are legion, but higher-frequency P-wavespeed whole-mantle models possessing complementary diagnostic capabilities are comparatively lacking. This hinders attempts to disentangle the effects of Cenozoic hotspot tectonism and Pan African (and older) tectonic events on the East African lithosphere. Here we develop a continental-scale P-wave tomographic model capable of resolving structure from upper-to-lower mantle depths using a recently-developed technique to extract absolute arrival-times from noisy, temporary African seismograph deployments. Shallow-mantle wavespeeds are δVP ≈–4% below Ethiopia, but less anomalous (δVP ≥–2%) below other volcanic provinces. The heterogeneous African Superplume reaches the upper mantle below the Kenyan plateau. Below Ethiopia/Afar we image a second sub-vertical slow wavespeed anomaly rooted near the core-mantle boundary outside the African LLVP, meaning multiple disparately sourced whole-mantle plumes may influence East African magmatism. In contrast to other African cratons, wavespeeds below Tanzania are only fast to 90–135km depth. When interpreted alongside Lower Eocene on-craton kimberlites, our results support pervasive metasomatic lithospheric modification caused by subduction during the Neoproterozoic Pan-African orogeny.A. B. and S. C. are funded by the Natural Environment Research Council (NERC) Grant number NE/R010862/1 from PI Cottaar in Cambridge. A. B. was previously funded by the NERC Doctoral Training Partnership: Science and Solutions for a Changing Planet - Grant number NE/L002515/1 at Imperial College. I. B is funded by Natural Environment Research Council Grant number NE/S014136/1

Effets de l’allaitement maternel sur l’âge du début de la maladie cæliaque

L'âge de début des symptômes et le type de présentation clinique de la maladie cæliaque ont souvent été reliés it l'âge de l'introduction du gluten dans l'alimentation. Il a aussi été montré que l'allaitement maternel retarde le début de la maladie. Patients et méthodes. - Dans cette étude rétrospective portant sur 169 cas de maladie cæliaque, nous analysons la contribution respective de ces deux paramètres dans la détermination de l'âge de début des symptômes. Résultats. - Dans notre population, la durée moyenne de l'allaitement maternel a été de 9,6 mois (± 8,9) et l'âge moyen à l'introduction du gluten de 5,6 mois (± 3,2). L'âge moyen de début de la maladie était de 15 mois (± 8,7) et le dé1ai moyen séparant l'introduction du gluten et le début de 9,5 mois (± 7,8). Les deux variables gluten et allaitement maternel étaient fortement corrélées à l'âge de début (r = 0,47 et 0,40, respectivement). Seule la variable allaitement maternel était corrélée à la variable dé1ai (r = 0,33). L'analyse de régression multiple montre que ces deux variables influençaient de manière indépendante l'âge de début, avec des coefficients de régression de 0,90 ± 0,2 et 0,26 ± 0,07. En revanche, seule la variable allaitement maternel influençait la variable délai, avec un coefficient de régression de 0,26 ± 0,07. Discussion. - Notre étude confirme l'effet indépendant de I'allaitement matemel dans la detérmination de l'âge de début. L'allaitement maternel joue un rôle protecteur indirect en retardant l'introduction du gluten et un rôle protecteur direct en augmentant le délai entre l'introduction du gluten et le début de la maladie cæliaque. Conclusion. - Un allaitement maternel prolongé, au moins jusqu'à la fin du 6e mois, et l'introduction retardée du gluten, au moins à partir du 5e mois, retardent de manière significative le début de la maladie. L'introduction du gluten doit être progressive et sous protection de l'allaitement maternel. L'introduction du gluten 2 mois avant le sevrage retarde de manière significative l'âge de debut de la maladie

AFRP20: New P-wavespeed Model for the African Mantle Reveals Two Whole-Mantle Plumes Below East Africa and Neoproterozoic Modification of the Tanzania Craton

Africa’s Cenozoic tectonism is often attributed to mantle plumes, particularly below East Africa, but their morphology, number, location, and impact on the African lithosphere are debated. The broad slow wavespeed African Superplume, ubiquitous in large-scale tomographic models, originates below South Africa, reaching the surface somewhere below East Africa. However, whether the diverse East African mantle geochemistry is best reconciled with one heterogeneous upwelling, or current tomographic models lack the resolution to image multiple distinct plumes, remains enigmatic. S-wavespeed tomographic images of Africa are legion, but higher-frequency P-wavespeed whole-mantle models possessing complementary diagnostic capabilities are comparatively lacking. This hinders attempts to disentangle the effects of Cenozoic hotspot tectonism and Pan African (and older) tectonic events on the East African lithosphere. Here we develop a continental-scale P-wave tomographic model capable of resolving structure from upper-to-lower mantle depths using a recently-developed technique to extract absolute arrival-times from noisy, temporary African seismograph deployments. Shallow-mantle wavespeeds are δVP ≈–4% below Ethiopia, but less anomalous (δVP ≥–2%) below other volcanic provinces. The heterogeneous African Superplume reaches the upper mantle below the Kenyan plateau. Below Ethiopia/Afar we image a second sub-vertical slow wavespeed anomaly rooted near the core-mantle boundary outside the African LLVP, meaning multiple disparately sourced whole-mantle plumes may influence East African magmatism. In contrast to other African cratons, wavespeeds below Tanzania are only fast to 90–135km depth. When interpreted alongside Lower Eocene on-craton kimberlites, our results support pervasive metasomatic lithospheric modification caused by subduction during the Neoproterozoic Pan-African orogeny

Réponses écophysiologiques d'Ostreopsis en fonction de la température: Etude de cas d'une espèce responsable d'efflorescence algale nuisible face au réchauffement des océans

International audienceReports of the benthic dinoflagellate Ostreopsis spp. have been increasing in the last decades, especially in temperate areas. In a context of global warming, evidences of the effects of increasing sea temperatures on its physiology and its distribution are still lacking and need to be investigated. In this study, the influence of temperature on growth, ecophysiology and toxicity was assessed for several strains of O. cf. siamensis from the Bay of Biscay (NE Atlantic) and O. cf. ovata from NW Mediterranean Sea. Cultures were acclimated to temperatures ranging from 14.5 ◦C to 32 ◦C in order to study the whole range of each strain-specific thermal niche. Acclimation was successful for temperatures ranging from 14.5 ◦C to 25 ◦C for O. cf. siamensis and from 19 ◦C to 32 ◦C for O. cf. ovata, with the highest growth rates measured at 22 ◦C (0.54–1.06 d-1) and 28 ◦C (0.52–0.75 d-1), respectively. The analysis of cellular content of pigments and lipids revealed some aspects of thermal acclimation processes in Ostreopsis cells. Specific capacities of O. cf. siamensis to cope with stress of cold temperatures were linked with the activation of a xanthophyll cycle based on diadinoxanthin. Lipids (neutral reserve lipids and polar ones) also revealed species-specific variations, with increases in cellular content noted under extreme temperature conditions. Variations in toxicity were assessed through the Artemia franciscana bioassay. For both species, a decrease in toxicity was observed when temperature dropped under the optimal temperature for growth. No PLTX-like compounds were detected in O. cf. siamensis strains. Thus, the main part of the lethal effect observed on A. franciscana was dependent on currently unknown compounds. From a multiclonal approach, this work allowed for defining specificities in the thermal niche and acclimation strategies of O. cf. siamensis and O. cf. ovata towards temperature. Potential impacts of climate change on the toxic risk associated with Ostreopsis blooms in both NW Mediterranean Sea and NE Atlantic coast is further discussed, taking into account variations in the geographic distribution, growth abilities and toxicity of each species