Free Vibration Analysis of Isotropic Plates by Alternative Hierarchical Finite Element Method Based on Reddy’s C1 HSDT

This paper presents the free vibration analysis of isotropic thick rectangular plates, based on higher order shear deformation theory (HSDT). The plate theory ensures a zero shear-stress condition at the top and bottom surfaces of the plate, and do not requires a shear correction factor. The model requires inter-element C1 continuity for the transverse displacement. To overcome this hindrance, a new hierarchical p-element with six degrees of freedom per node is developed and used to find natural frequencies of thick plates. Convergence studies and comparison have been carried out for with different boundaries conditions. It is shown that the present element enables rapid convergence

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

Effects of physical forcing on COastal ZOoplankton community structure: study of the unusual case of a MEDiterranean ecosystem under strong tidal influence (Project COZOMED-MERMEX).

International audienceThe COZOMED-MERMEX project aims at understanding how hydrodynamic forcing (currents, tides, winds)combine with anthropogenic forcing and climate to affect the variability of coastal Mediterranean zooplanktoncommunities under contrasting tidal influence. This study includes (i) a zero state of knowledge via a literaturereview of existing data and (ii) a case study on the system Boughrara lagoon - Gulf of Gabes. This ecosystemgives major services for Tunisia (about 65% of national fish production) but is weakened by its situation in aheavily anthropized area and under influence of urban, industrial and agricultural inputs. Besides this regionis subject to specific climate forcing (Sahelian winds, scorching heat, intense evaporation, flooding) whichpossible changes will be considered. The expected issues are (i) to improve our knowledge of hydrodynamicforcing on zooplankton and ultimately on the functioning of coastal Mediterranean ecosystems impacted byanthropogenic and climatic effects and (ii) to elaborate management tools to help preserving good ecologicalstatus of these ecosystems: hydrodynamic circulation model, mapping of isochrones of residence times, mappingof the areas of highest zooplankton abundances (swarms), and sensitive areas, etc. This project strengthensexisting scientific collaborations within the MERMEX program (The MerMex Group, 2011) and in the frameof an international joint laboratory (COSYS-Med) created in 2014. A first field mulidisciplinary campaign wasperformed in October 2016. The strategy combined measurements of sea level and currents (mooring of ADCP,Argonaute and tidal gauges), hydrological description of water masses (horizontal and vertical transect with aMinibat equipped with CTD, fluorescence and turbidity sensors) and discrete sampling of nutrients, DOC, POC,pico, nano, microphytoplankton and mesozooplankton. The first results allow a description of water currents andshows a good coupling between tidal cycles (ebb-flood and spring tide neap tide) and the dynamics of planktoniccompartments in the lagoon