4 research outputs found
Triangular â 7 and quadrilateral â 5 subdivision schemes: regular case
This paper is devoted to the study of triangular â 7 and quadrilateral â 5 surface subdivisions. Both approximation and interpolatory subdivision schemes are considered, with illustrative examples of both scalar-valued and matrix-valued 7 and 5 subdivision masks that satisfy the sum rule of sufficiently high orders. In particular, âoptimal â Sobolev smoothness is determined and Hölder smoothness estimates are presented. AMS 2000 classification: Primary 65D17, 65D18; Secondary 41A1
Cross-Reactivity of SARS-CoV-2 Laboratory Diagnostics to Endemic Diseases in Africa: A Diagnostic Accuracy Study
Background: Serology is a great tool to assess the level of immunity against SARS-CoV-2 in settings with limited access to molecular diagnostics. However, African populations displays a particular immunological profile with massive circulation of infectious agents from different aetiologies that can affect assays performance.Methods: We evaluated the OMEGA Diagnostics COVID-19 ELISA-IgG and the ID ScreenÂź SARS-CoV-2-N IgG Indirect in Senegal using a panel of 636 blood samples covering several African-endemic diseases and healthy donors to determine test sensitivity and specificity. The sensitivity panel of sera includes 461 serum samples collected from 91 patients hospitalized for COVID-19 disease. COVID-19 cases were confirmed by qRT-PCR and samples were collected on an interval of three days until viral clearance. In addition, 272 sera obtained from COVID-19 negative individuals were selected from a well-documented biobank of sera collected before the COVID-19 outbreak.Finding: High-cross reactivity have been found in individuals with a history of exposure to Chikungunya, HIV, malaria (Plasmodium falciparum), rheumatoid factor as well as healthy donors with respective specificities of 55%, 41.8%, 70%, 70% and 75%. ELISA experiments with commercial assays targeting either SARS-CoV-2 Nucleocapsid protein and Spike 2 protein or nucleocapsid protein only suggest that cross-reactivity might be directed against Spike 2 protein and not Nucleocapsid protein. Further samples characterisation reveals that anti-malaria IgG is the leading cause of such poor specificities, but exposure to other diseases contributed as well.Interpretation: We anticipate that COVID-19 seroprevalence can be biased if assays are not contextualized. Since malaria is endemic in African settings, we propose that a particular attention must be given in serological surveillance of COVID-19 or anti-SARS-CoV-2 antibodies quantification as vaccines are being rolled out
Le projet majeur africain de la Grande Muraille Verte
Lâinitiative de la Grande Muraille Verte (GMV), projet transcontinental, est une rĂ©ponse de lâAfrique Ă la dĂ©sertification, Ă la pauvretĂ© et au changement climatique. Elle repose sur une approche concertĂ©e, multisectorielle, mettant en synergie des actions de lutte contre ces trois flĂ©aux majeurs pour le continent africain. La particularitĂ© de la GMV est, tout en crĂ©ant et consolidant une ligne de dĂ©fense par des activitĂ©s de reboisement et dâamĂ©nagement, de contribuer efficacement au dĂ©veloppement intĂ©grĂ© des zones rurales et dâaider Ă la lutte contre la pauvretĂ© dans le cadre dâun dĂ©veloppement durable. Il sâagit de lâinstallation et de la mise en valeur intĂ©grĂ©e dâespĂšces vĂ©gĂ©tales Ă valeur Ă©conomique adaptĂ©es aux terres arides et aux particularitĂ©s locales, de bassins de rĂ©tention, de systĂšmes de production agricoles et autres activitĂ©s gĂ©nĂ©ratrices de revenus. La GMV intĂšgre ainsi plusieurs systĂšmes des plantations artificielles anciennes ou nouvelles, des unitĂ©s agro-sylvo-pastorales. Des zones de parcours villageoises ou intercommunautaires, des parcs animaliers, des rĂ©serves communautaires et des couloirs de migration de faune. Cet Ă©difice transcontinental est une rĂ©fĂ©rence de modĂšle dâintĂ©gration sous-rĂ©gional mettant en exergue une initiative originale initiĂ©e par des pays fortement assujettis aux phĂ©nomĂšnes de dĂ©sertification et de changement climatique Il constitue un ModĂšle Multisectoriel de DĂ©veloppement IntĂ©grĂ© des Zones Andes (MDI/ZA). DĂ©diĂ© Ă la lutte contre tes effets et lâavancĂ©e de la dĂ©sertification, Ă la restauration et la mise en valeur des zones dĂ©gradĂ©es et au mĂ©canisme de dĂ©veloppement propre dĂ» Ă sa forte capacitĂ© de sĂ©questration de carbone. Lâouvrage vise un large public, notamment les scientifiques, enseignants, dĂ©cideurs, techniciens charges de la mise en Ćuvre de la GMV et permet dâapprĂ©cier lâoriginalitĂ© du projet dans son approche concertĂ©e et multisectorielle et ses rĂ©sultats dans le dĂ©veloppement intĂ©grĂ© des zones arides a semi-arides