Influence of gravel and adjuvant on the compressive strength and water absorption of concrete

Concrete is the most commonly used material in civil engineering, given its economic cost and ease of manufacture. Its strength depends on the characteristics of its constituents. A good mix makes it possible to build solid, durable and economical structures. The present work aims to characterize the gravel of the Eastern region (quarry of eastern Morocco) by granulometric analysis and water absorption. Then, the studied gravel is used to produce three types of concrete (B20, B25 and B30), which were assessed in terms of water absorption and compressive strength. The last step is to study the effect of an adjuvant, more specifically a water reducer, on mechanical characteristics of local concrete. B25 concrete was chosen for the last step since it is the most used type in the region. Results show that adding a water reducer adjuvant, in this case ‘Chrysoplast’, can improve the compressive strength of concrete if the percentage added is accurately determined

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Transhumant pastoralism, sustainable management of natural resources and endemic ruminant livestock in the sub-humid zone of West Africa

Transhumant pastoralism is one of the dominant livestock production systems in West Africa, and it is characterized by seasonal and cyclical movement of varying degrees between complementary ecological areas. The common pattern of transhumance is moving herds from areas with pasture and water scarcity such as the Sahelian zone to areas where the forage and water are found, often in the sub-humid zone. Whereas the transhumant herds from the Sahel are mainly Zebu breeds, endemic ruminant livestock (ERL) are the dominant breeds in sub-humid zone of West Africa because of their tolerance to tsetse-borne trypanosomosis disease. These livestock fulfill different functions in the livelihood of rural communities in the region. To identify potential areas of interventions for sustainable natural resource management to improve ERL productivity, a desk study that included spatial mapping was performed to review and document the existing knowledge on transhumance in West Africa. Additionally, group discussions were held to analyze the (actual or potential) effects of transhumant herds on natural resource management and ERL in the sub-humid zone. This study covered sub-humid zone in The Gambia, Guinea, Mali and Senegal. The key question we addressed in this study was as follows: What are the key trends and changes in transhumant pastoralism and how do these impact sustainable management of natural resources including endemic livestock? The results of the desk study and group discussions showed that there have been more southerly movements by transhumant pastoralists into the sub-humid zone over the past three decades and this has contributed to growing competition for grazing resources. The presence of transhumant herds in the sub-humid zone has a potential impact on management and conservation of ERL through crossbreeding with transhumant Zebu breeds from the Sahel but only study sites in Mali showed a high risk

Rift Valley Fever: One Health at Play?

Rift Valley fever (RVF) is a mosquito-borne viral infection mostly encountered in Africa. In its acute form, it severely affects domestic and wild ruminants, dromedaries, and humans. It is considered as an emerging disease, with increased frequency in several regions, and a spread potential to many areas under the influence of two main drivers: Environmental (including climatic) changes and animal mobility (livestock trade, transhumance). In this chapter, we discuss the peculiarities of RVF epidemiology in Sahelian Africa and we show how the joint influence of these two drivers may trigger RVF epidemics. The public health impact of RVF can be severe, with tens of thousands of human cases and hundreds of fatalities recorded during large epidemics. Beyond its direct, negative effects on public and animal health, RVF has large economic consequences related to bans on livestock importation from infected countries. Solutions are available to improve surveillance and control of RVF in Sahelian Africa according to well-defined, risk-based strategies. The implementation of coordinated actions between Public Health and Animal Health authorities would represent an important advance in the One Health joint approach of RVF for better prevention, early detection, and reaction

Foncier, droit et propriété en Mauritanie

Le présent ouvrage réunit des articles inédits, majoritairement écrits par des Mauritaniens, et propose une réflexion sur des thèmes cruciaux pour la société mauritanienne contemporaine, à savoir la question foncière et l’accès au sol. Issues d’une recherche collective qui porte sur la propriété en milieu musulman, les contributions rendent compte des évolutions de la société mauritanienne depuis l’Indépendance jusqu’aux changements rapides récents, marqués par la fin du nomadisme, les réformes foncières ou encore l’urbanisation accélérée du pays. L’approche diachronique souligne les décalages parfois importants entre le droit juridique, tel que défini et appliqué par la loi, et les pratiques quotidiennes des habitants. Les articles ancrent leurs réflexions aussi bien en milieu rural qu’urbain, le long du fleuve Sénégal comme dans les territoires ruraux de parcours, en milieu sédentaire autant que nomade. Cet ouvrage apporte un autre regard sur les enjeux contemporains de l’accès au sol, de la formalisation des droits de propriété et de la sécurisation de la tenure foncière