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Sensitivity of high-frequency ground motion to kinematic source parameters
No full textEmpirical ground motion prediction equations are calibrated from past earthquake seismic recordings. Although they are often used to predict Peak Ground Acceleration (PGA) and its variability, the use of these equations to predict near-fault PGA remains questionable due to the scarcity of near-fault recordings for large earthquakes (e.g. Mai Encyclopedia of complexity and systems science (pp. 4435-4474). New York: Springer. 10.1007/978-0-387-30440-3_263. 2009). The simulation of strong ground motion offers an attractive alternative for the assessment of near-fault seismic hazards, but the a priori choice of the source parameters used to describe the fault rupture process remains a complex issue. In order to better understand the effects of rupture parameters on surface ground motion and to capture the key source ingredients that impact ground motion variability, we simulated ground motions produced by various M7 strike-slip rupture earthquake scenarios on vertical faults. We computed ground motion up to 5 Hz using the far-field approximation as well as at the near-field stations located at 5 km, 25 km and 70 km from the fault (assuming a visco-elastic medium). The kinematic rupture parameters are modeled using a statistical rupture model generator as proposed by Song et al. Geophysical Journal International,196(3), 1770-1786 (2014). Our work demonstrates that PGA is mostly generated by abrupt changes in the rupture propagation (e.g. stopping phases at the fault boundaries or strong heterogeneities of rupture speed along the fault). We observed that PGA is mostly controlled by average rupture speed and average stress drop (in the far-field), and to a lesser extent by the standard deviation of the rupture speed. It is worth noting that for the set of stations in study, the correlation between source parameters and spatial correlation length does not affect average PGA and related variability significantly
Resurgence risk for malaria, and the characterization of a recent outbreak in an Amazonian border area between French Guiana and Brazil
No full textBackground In 2017, inhabitants along the border between French Guiana and Brazil were affected by a malaria outbreak primarily due to Plasmodium vivax (Pv). While malaria cases have steadily declined between 2005 and 2016 in this Amazonian region, a resurgence was observed in 2017. Methods Two investigations were performed according to different spatial scales and information details: (1) a local study on the French Guiana border, which enabled a thorough investigation of malaria cases treated at a local village health center and the entomological circumstances in the most affected neighborhood, and (2) a regional and cross-border study, which enabled exploration of the regional spatiotemporal epidemic dynamic. Number and location of malaria cases were estimated using French and Brazilian surveillance systems. Results On the French Guianese side of the border in Saint-Georges de l'Oyapock, the attack rate was 5.5% (n = 4000), reaching 51.4% (n = 175) in one Indigenous neighborhood. Entomological findings suggest a peak of Anopheles darlingi density in August and September. Two female An. darlingi (n = 1104, 0.18%) were found to be Pv-positive during this peak. During the same period, aggregated data from passive surveillance conducted by Brazilian and French Guianese border health centers identified 1566 cases of Pv infection. Temporal distribution during the 2007-2018 period displayed seasonal patterns with a peak in November 2017. Four clusters were identified among epidemic profiles of cross-border area localities. All localities of the first two clusters were Brazilian. The localization of the first cluster suggests an onset of the outbreak in an Indigenous reservation, subsequently expanding to French Indigenous neighborhoods and non-Native communities. Conclusions The current findings demonstrate a potential increase in malaria cases in an area with otherwise declining numbers. This is a transborder region where human mobility and remote populations challenge malaria control programs. This investigation illustrates the importance of international border surveillance and collaboration for malaria control, particularly in Indigenous villages and mobile populations
On the natural and anthropogenic drivers of the Senegalese (West Africa) low coast evolution : Saint Louis Beach 2016 COASTVAR experiment and 3D modeling of short term coastal protection measures
No full textWest Africa's low and densely populated coasts crystallize most of the environmental and societal problems and resulting vulnerability. It is becoming urgent to document this coast and the natural and anthropogenic forces to understand its evolution. Saint Louis is a historic (World Heritage) city located on the Langue de Barbarie, a 10 km sandspit at the mouth of the Senegal River. Because of its location, it is vulnerable (erosion, flooding) to river and ocean variability. This intermediate barred microtidal beach is located in a storm-free intertropical environment, but is exposed to distant oblique energetic waves from high latitudes, causing one of the highest coastal drifts in the world (similar to 800,000 m(3)/year). As part of the COASTVAR project, an intensive international field experiment was conducted in Saint Louis from 4 to 13 December 2016 to quantify the natural protective role played by the sandbar, coastal currents and transient exchanges with the inner shelf. Many instruments have been deployed to measure waves, currents, bathymetry and topography. This article provides an overview on the objectives of the experiment, the deployment and the first results of the modeling of coastal protection strategy
Complementarity of empirical and process-based approaches to modelling mosquito population dynamics with Aedes albopictus as an example : application to the development of an operational mapping tool of vector populations
No full textMosquitoes are responsible for the transmission of major pathogens worldwide. Modelling their population dynamics and mapping their distribution can contribute effectively to disease surveillance and control systems. Two main approaches are classically used to understand and predict mosquito abundance in space and time, namely empirical (or statistical) and process-based models. In this work, we used both approaches to model the population dynamics in Reunion Island of the 'Tiger mosquito', Aedes albopictus, a vector of dengue and chikungunya viruses, using rainfall and temperature data. We aimed to i) evaluate and compare the two types of models, and ii) develop an operational tool that could be used by public health authorities and vector control services. Our results showed that Ae. albopictus dynamics in Reunion Island are driven by both rainfall and temperature with a non-linear relationship. The predictions of the two approaches were consistent with the observed abundances of Ae. albopictus aquatic stages. An operational tool with a user-friendly interface was developed, allowing the creation of maps of Ae. albopictus densities over the whole territory using meteorological data collected from a network of weather stations. It is now routinely used by the services in charge of vector control in Reunion Island
Cost-effectiveness of diagnostic algorithms including lateral-flow urine lipoarabinomannan for HIV-positive patients with symptoms of tuberculosis
No full textBackground Tuberculosis (TB) is the leading cause of death among HIV-positive patients. We assessed the cost-effectiveness of including lateral-flow urine lipoarabinomannan (LF-LAM) in TB diagnostic algorithms for severely ill or immunosuppressed HIV-positive patients with symptoms of TB in Kenya. Methods From a decision-analysis tree, ten diagnostic algorithms were elaborated and compared. All algorithms included clinical exam. The costs of each algorithm were calculated using a `micro-costing' method. The efficacy was estimated through a prospective study that included severely ill or immunosuppressed (CD4< 200cells/mu L) HIV-positive adults with symptoms of TB. The cost-effectiveness analysis was performed using the disabilityadjusted life year (DALY) averted as effectiveness outcome. A 4% discount rate was applied. Results The algorithm that added LF-LAM alone to the clinical exam lead to the least average cost per TB case detected (_ 47) and was the most cost-effective with a cost/DALY averted of (sic)4.6. The algorithms including LF-LAM, microscopy and X-ray, and LF-LAM and Xpert in sputum, detected a high number of TB cases with a cost/DALY averted of (sic)6.1 for each of them. In the comparisons of the algorithms two by two, using LF-LAM instead of microscopy (clinic&LAM vs clinicµscopy) and using LF-LAM along with GeneXpert in instead of GeneXpert in urine along with GeneXpert in sputum, (clinic&LAM&Xpert_sputum vs clinic&Xpert_sputum&Xpert_urine) led to the highest increase in the cost-effectiveness ratios (ICERs): (sic)- 7.2 and (sic)- 12.6 respectively. In these two comparisons, using LF-LAM increased the number of TB patients detected while reducing costs. Adding LF-LAM to smear microscopy alone or to smear microscopy and Xray led to the highest increase in the additional number of TB cases detected (31 and 25 respectively) with an incremental efficiency estimated at 134 and 344 DALYs respectively. The ICERs were (sic)22.0 and (sic)8.6 respectively. Conclusion Including LF-LAM in TB diagnostic algorithms is cost-effective for severely ill or immunosuppressed HIV-positive patients
Projected number of people with onchocerciasis-loiasis coinfection in Africa, 1995 to 2025
No full textBackground : Onchocerciasis elimination through mass drug administration (MDA) is hampered by coendemicity of Loa loa, as people with high L. loa microfilariae (mf) density can develop serious adverse events (SAEs) after ivermectin treatment. We assessed the geographical overlap of onchocerciasis and loiasis prevalence and estimated the number of coinfected individuals at risk of post-ivermectin SAEs in West and Central Africa from 1995 to 2025. Methods : Focusing on regions with suspected loiasis transmission in 14 countries, we overlaid precontrol maps of loiasis and onchocerciasis prevalence to calculate precontrol prevalence of coinfection by 5 km2 × 5 km2 pixel, distinguishing different categories of L. loa mf intensity. Using statistical and mathematical models, we predicted prevalence of both infections and coinfection for 2015 and 2025, accounting for the impact of MDA with ivermectin. Results : The number of people infected with onchocerciasis was predicted to decline from almost 19 million in 1995 to 4 million in 2025. Of these, 137 000 people were estimated to also have L. loa hypermicrofilaremia (>-20 000 L. loa mf/mL) in 1995, declining to 31 000 in 2025. In 2025, 92.8% of coinfected cases with loiasis hypermicrofilaremia are predicted to live in hypoendemic areas currently not targeted for MDA. Conclusions : Loiasis coinfection is a major concern for onchocerciasis elimination in Africa. We predict that under current strategies, at least 31 000 coinfected people still require treatment for onchocerciasis in 2025 while being at risk of SAEs, justifying continued efforts in research and development for safer drugs and control strategies
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No full textLe Mexique connaît depuis douze ans des violences extrêmes et massives modifiant en profondeur le traitement politique, culturel et social des disparus et des morts en masse. Devenue récemment une priorité dans l'agenda politique, la disparition, forcée ou non, reste une énigme pour les vivants hantés par l'incertitude et les fantômes. Face à l'inaction de l'État, les familles des victimes font "justice par elles-mêmes" et conjurent cette malemort par deux principales actions : "lire la terre" pour en faire émerger des fosses clandestines et "lire le cadavre" pour rendre une identité à ces morts qui dérangent. À partir d'une description ethnographique d'un dimanche de recherche de fosses clandestines menées en 2016 avec des familles du collectif "Les autres disparus" à Iguala, dans l'État du Guerrero, cet article démontre à quel point suivre les traces des disparus signifie davantage que mener de simples fouilles : les recherches de fosses clandestines concentrent l'opération de restauration d'un ordre matériel et symbolique face au puzzle macabre laissé par les violences politiques et criminelles. Elles constituent de nouveaux rituels modernes et réintroduisent du sens et du sacré là où les traces des crimes sont camouflées
Additive influences of soil and climate gradients drive tree community composition of Central African rain forests
No full textAim Examining tree species-environment association can offer insight into the drivers of vegetation patterns and key information of practical relevance to forest management. Here, we aim to quantify the contribution of climate and soil gradients to variation in Central African tree species composition (abundance and occurrence). Location Tropical rain forests of southern and eastern Cameroon. Methods We established 82 1-ha permanent plots across seven localities and censused all trees >= 10 cm in diameter, representing a total of 37,733 trees and 455 species. In 60 of those plots, we measured 10 soil variables describing texture and nutrients levels and extracted 10 bioclimatic variables from global-gridded climate databases. We synthesized the main environmental gradients by conducting principal component analyses on climate and soil data, respectively. We performed unconstrained and constrained non-symmetric correspondence analyses to account for the individual and joint contributions of climate and soil on species abundance and occurrence. Results Climate and soil contributed similarly to variances of species abundance and occurrence (12-15% variance for climate vs 11-12% variance for soil). Climate influence mostly concerns some abundant species, while some of the less abundant species were mainly driven by soil. Fractions of species variances accounted for by climate and soil show strong correlation when assessed from species occurrence and abundance data. Conclusion Variation in occurrence and abundance of tropical forest trees can be partly shaped by both climate and soil gradients in Cameroon, which emphasizes the importance to jointly consider soil and climate in species distribution modeling. Less abundant species may express environmental influence differently than abundant species and convey complementary information about community assemblage. Though showing congruent patterns here, species abundance and occurrence reflect different interacting community processes and both should be examined to better understand vegetation patterns
Commensalism outweighs phylogeographical structure in its effect on phenotype of a Sudanian savanna rodent
No full textThe murid rodent Praomys daltoni is widespread in Sudanian savanna and woodlands of West Africa, and previous study of mitochondrial DNA variability suggested that it encompasses the phenotypically (small, grey-bellied) and ecologically (commensal) distinct form, Praomys derooi. Here, we comprehensively examined the genetic and morphological diversity within the complex. Six mitochondrial lineages showed a fine-scale phylogeographical pattern, whereas delimitation based on nuclear loci pooled four of them into a single widespread unit. A newly discovered lineage from southern Mauritania stands apart from the rest of the complex and might represent an unrecognized species. At the same time, the internal position of P. derooi (C2 mitochondrial lineage) was confirmed by the multilocus analysis. The magnitude of genetic distances between major phylogeographical lineages was typical for interspecific divergence in other clades of Praomys, despite the little differences among them in morphology (skull and upper molar row shapes). The most pronounced morphological shift was associated with a transition to commensalism, especially in P. derooi, but also in other lineages. This makes the whole complex a suitable model for the study of phenotypic novelty, the evolution of commensalism and conditions for ecological speciation