Imaging the lithospheric structure and plumbing system below the Mayotte volcanic zone

Teleseismic receiver-functions and Rayleigh-wave dispersion curves are jointly inverted for quantifying $S$-wave velocity profiles beneath the active volcanic zone off Mayotte. We show that the lithosphere in the east-northeast quadrant is composed of four main layers, interpreted as the volcanic edifice, the crust with underplating, the lithospheric mantle, and the asthenosphere, the latter two presenting a main low-velocity zone. The depths of the old (10–11 km) and new Moho (28–31 km) coincide with the two magma reservoirs evidenced by recent seismological and petrological methods. We propose that the main magma reservoir composed of mush with an increasing amount of liquid extends down to 54 km depth. This magma storage develops from a rheological contrast between the ductile lower and brittle upper lithospheric mantle and accounts for most of the volcanic eruption-related seismicity. Finally, the abnormally small thickness of the lithospheric mantle (33 km) is likely a result of a thermal thinning since the onset of Cenozoic magmatism

Seeking treatment for symptomatic malaria in Papua New Guinea

Background: Malaria places a significant burden on the limited resources of many low income countries. Knowing more about why and where people seek treatment will enable policy makers to better allocate the limited resources. This study aims to better understand what influences treatment-seeking behaviour for malaria in one such low-income country context, Papua New Guinea (PNG). Methods: Two culturally, linguistically and demographically different regions in PNG were selected as study sites. A cross sectional household survey was undertaken in both sites resulting in the collection of data on 928 individuals who reported suffering from malaria in the previous four weeks. A probit model was then used to identify the factors determining whether or not people sought treatment for presumptive malaria. Multinomial logit models also assisted in identifying the factors that determined where people sought treatments. Results: Results in this study build upon findings from other studies. For example, while distance in PNG has previously been seen as the primary factor in influencing whether any sort of treatment will be sought, in this study cultural influences and whether it was the first, second or even third treatment for a particular episode of malaria were also important. In addition, although formal health care facilities were the most popular treatment sources, it was also found that traditional healers were a common choice. In turn, the reasons why participants chose a particular type of treatment differed according to the whether they were seeking an initial or subsequent treatments. Conclusions: Simply bringing health services closer to where people live may not always result in a greater use of formal health care facilities. Policy makers in PNG need to consider within-country variation in treatment-seeking behaviour, the important role of traditional healers and also ensure that the community fully understands the potential implications of not seeking treatment for illnesses such as malaria at a formal health care facility.Carol P Davy, Elisa Sicuri, Maria Ome, Ellie Lawrence-Wood, Peter Siba, Gordon Warvi, Ivo Mueller and Lesong Conte

Lithospheric structure below the currently active Mayotte volcanic area from joint inversion of receiver function and surface wave dispersion data

International audienc

Imaging the lithospheric structure and plumbing system below the Mayotte volcanic zone

International audienceTeleseismic receiver-functions and Rayleigh-wave dispersion curves are jointly inverted for quantifying S-wave velocity profiles beneath the active volcanic zone off Mayotte. We show that the lithosphere in the east-northeast quadrant is composed of four main layers, interpreted as the volcanic edifice, the crust with underplating, the lithospheric mantle, and the asthenosphere, the latter two presenting a main low-velocity zone. The depths of the old (10-11 km) and new Moho (28-31 km) coincide with the two magma reservoirs evidenced by recent seismological and petrological methods. We propose that the main magma reservoir composed of mush with an increasing amount of liquid extends down to 54 km depth. This magma storage develops from a rheological contrast between the ductile lower and brittle upper lithospheric mantle and accounts for most of the volcanic eruptionrelated seismicity. Finally, the abnormally small thickness of the lithospheric mantle (33 km) is likely a result of a thermal thinning since the onset of Cenozoic magmatism

Imaging the lithospheric structure and plumbing system below the Mayotte volcanic zone

International audienceTeleseismic receiver-functions and Rayleigh-wave dispersion curves are jointly inverted for quantifying S-wave velocity profiles beneath the active volcanic zone off Mayotte. We show that the lithosphere in the east-northeast quadrant is composed of four main layers, interpreted as the volcanic edifice, the crust with underplating, the lithospheric mantle, and the asthenosphere, the latter two presenting a main low-velocity zone. The depths of the old (10-11 km) and new Moho (28-31 km) coincide with the two magma reservoirs evidenced by recent seismological and petrological methods. We propose that the main magma reservoir composed of mush with an increasing amount of liquid extends down to 54 km depth. This magma storage develops from a rheological contrast between the ductile lower and brittle upper lithospheric mantle and accounts for most of the volcanic eruptionrelated seismicity. Finally, the abnormally small thickness of the lithospheric mantle (33 km) is likely a result of a thermal thinning since the onset of Cenozoic magmatism

Analysis of Plasmodium falciparum diversity in natural infections by deep sequencing.

Malaria elimination strategies require surveillance of the parasite population for genetic changes that demand a public health response, such as new forms of drug resistance. Here we describe methods for the large-scale analysis of genetic variation in Plasmodium falciparum by deep sequencing of parasite DNA obtained from the blood of patients with malaria, either directly or after short-term culture. Analysis of 86,158 exonic single nucleotide polymorphisms that passed genotyping quality control in 227 samples from Africa, Asia and Oceania provides genome-wide estimates of allele frequency distribution, population structure and linkage disequilibrium. By comparing the genetic diversity of individual infections with that of the local parasite population, we derive a metric of within-host diversity that is related to the level of inbreeding in the population. An open-access web application has been established for the exploration of regional differences in allele frequency and of highly differentiated loci in the P. falciparum genome

La résilience des villes portuaires européennes

L’histoire des ports peut être renouvelée à travers l’usage du concept de résilience. Il désigne la capacité d’un système social à s’adapter de manière proactive et à se remettre de perturbations majeures. Face à la nécessité vitale de maîtriser des flux ou des ressources, de se faire une place dans les échanges, le port s’insère dans un environnement juridique et technique dicté par des facteurs exogènes, des enjeux géostratégiques, des politiques étatiques et la pression des usagers. Mais quelles sont exactement les modalités du « rebond résiliant » qui doit assurer un retour à la normale après une crise et quel est le temps nécessaire à cela ? Plusieurs exemples sont étudiés du xvie siècle à aujourd’hui, de Gênes à Bilbao, du Havre aux ports de l’Andalousie : leurs temporalités, les conditions de leur élaboration, les modes d’action qu’elles exigent, mais aussi l’ensemble des représentations relevant du rapport au changement et les imaginaires dont elles se nourrissent.This book proposes a new approach to the history of ports, from the 16th century to the present day, by applying for the first time the concept of “resilience”