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

Design of unknown input fuzzy observer for vehicle dynamics estimation with road geometry consideration

methodology for estimating vehicle dynamics whith road geometry consideration is presented in this paper. Vehicle sideslip and roll parameters are estimated in the presence of the road bank angle and the road curvature as unknown inputs. The unknown inputs are then estimated using the observer results. This information about the road geometry and vehicle parameters is needed in the driver assistance systems to be able to calculate the risk index of a rollover or a lane departure crashes. Taking into account the unmeasured variables, an unknown inputs (TS) observer is then designed on the basis of the measure of the roll rate, the steering angle and the lateral offset given by the distance between the road centerline and the vehicle axe at a look-ahead distance. Synthesis conditions of the proposed fuzzy observer are formulated in terms of Linear Matrix Inequalities (LMI) using Lyapunov method. Simulation results show good efficiency of the proposed method to estimate both vehicle dynamics and road geometry

Phosphate sludge-based ceramics: Microstructure and effects of processing factors

International audienceThe potential use of clay amended phosphate sludge in lightweight aggregates manufacturing was assessed. For this purpose, the microstructure of heated blends was examined with X-ray diffraction, thermal analysis and scanning electron microscope and impedance spectroscopy, and their physical properties were followed as a function of heating temperature, soaking time and clay content. For the latter study, the full factorial design was used. The results showed that phase neoformation involved the breakdowns of the clay minerals and lime of carbonates. Moreover, the sintering process was significant as the clay content exceeded 5 wt% and 900< T< 1000 degrees C. In such a condition, the sintering was chiefly controlled by melt. The results of the full factorial design showed that the increase of one of the processing factors affected positively water absorption, density and compressive strength. These effects were mainly linked to the conjugate formations of calcaluminosilicate and viscous phase. The results also pointed out that the effects of the interactions between the factors on the measured properties were almost negligible. By using the full factorial design, the optimum values of the physical properties were evaluated

Elaboration and characterization of PMN–xPT solid ceramics used in a numerical simulation of a piezoelectric transducer for a loudspeaker application

International audienceSolid ceramics (1 − x)PbMg1/3Nb2/3O3–xPbTiO3 (PMN–xPT) have been prepared and characterized in the present work. Three PMN–xPT compositions were used with x taking the values of 0.31, 0.33 and 0.35. For the three compositions, an analysis of the dielectric behavior has been made, in order to determine the phase transition temperatures and Curie’s temperatures by measuring the dielectric constants and the dielectric losses as a function of temperature and frequency. A typical behavior to that of ferroelectric relaxor materials was noted by the increase of the PT’s rate. Ferroelectric character was analyzed by studying the evolution of polarization as a function of the applied field for the different samples, with the variation of the temperature. The hysteresis loop was strongly modified by the action of the temperature. The remnant polarization, as well as the coercive field, decreases with the increase of the temperature and increase with the increase of the applied field. Due to their high dielectric and ferroelectric properties, a numerical simulation by a finite element analysis software was made on PMN–0.35PT pellets, used for a loudspeaker application. The mechanical and acoustic behaviors of the piezoelectric transducer were investigated

Aloe vera mucilage as an eco-friendly corrosion inhibitor for bronze in chloride media: Combining experimental and theoretical researches

Aloe vera (L.) Burm.F. (=Aloe barbadensis Mill.), a widely recognized medicinal plant, holds a prominent position due to its potent cosmetic and medicinal attributes. The objective of this work is to develop a new eco-friendly corrosion inhibitor for bronze B66 that is non-toxic, simple to apply, cost-effective, stable, and reversible. To achieve this goal, we initially devised an improved and cost-efficient method for extracting Aloe vera mucilage (AVM). Then we tested as corrosion inhibitor for bronze B66 in 3 % NaCl using gravimetric measurements, electrochemical methods and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-Ray analysis (EDX). The electrochemical assessments validated the findings from the gravimetric analysis and demonstrated that our inhibitor significantly modifies the electrochemical process mechanism at the B66/3% NaCl interface. The corrosion rate of bronze decreases with the inhibitor's presence, and its inhibitory effectiveness amplifies with higher concentrations, reaching an efficiency of 86 % at 750 ppm. The mechanism of metallic copper and corrosion Acemannan inhibitor was explored through DFT studies and molecular dynamics simulation

Exploring the Importance of Human Resources Marketing in the Context of Digital transformation. A Case Study in the Public Administration

&lt;p&gt;The objective of this study is to explore the importance and role of human resources marketing in the successful digital transformation process of public organizations in Morocco.&nbsp; Current human resources management models, particularly in the context of digital transformation, consider the experience and satisfaction of human capital as an important criterion for excellence and value creation, hence the growing interest of organizations in HR marketing practices. In HR marketing, employer branding is one of the most important issues, as it affects employer identity and has an impact both internally with employees and externally.&nbsp; This exploratory study is based on a literature review highlighting the links between HR marketing and the digital transformation process, particularly in the context of public administration, as well as a qualitative study based on semi-structured interviews with sixteen managers and subordinates from two pilot public departments in Morocco in the field of administrative modernization and organizational change implementation.&lt;strong&gt;&nbsp; &lt;/strong&gt;Semi-structured interviews focus on HR marketing adoption, digital HR management implementation, employee engagement and employer branding in the age of digital transformation. The results are analyzed using thematic analysis with NVIVO content analysis software.&nbsp; The main conclusions are as follows: it is through the implementation of a change management and HR marketing policy, including in particular the enhancement of the employer brand, that digital transformation will be able to impact the HR function and lead to an evolution in strategic HR positioning, customer value creation and agile leadership.&lt;/p&gt

Mechanical strength characterization and modeling of hydroxyapatite/tricalcium phosphate biocomposite using the diametral-compression test

This study reports the enhanced mechanical resistance of the composite bioceramics of hydroxyapatite (HAP) and tricalcium phosphate (β-TCP) used as bone substitute. HAP/β-TCP mixture was prepared by wet mixing of powders and characterized. Effects of powder manufacturing and sintering temperature on the densification, microstructure and mechanical properties of the composite were studied. The rupture strength (σr) was calculated using the Brazilian test. At 1250 °C, the relative density and mechanical strength of the HAP/β-TCP ceramics reached the maximum value of 89% and 43 MPa, respectively. Experimental results were modeled by the finite element method to determine the stress distribution in the compacted disc

Influence of the Nature and Rate of Alkaline Activator on the Physicochemical Properties of Fly Ash-Based Geopolymers

The influence of alkali cations on mix design of geopolymers is essential for their mechanical, thermal, and electrical performance. This research investigated the influence of alkali cation type on microscale characteristics and mechanical, dielectric, and thermal properties of fly ash-based geopolymer matrices. The geopolymers were elaborated via class F fly ash from the thermal plant Jorf Lasfar, El Jadida (Morocco), and several alkaline solutions. Morphological, structural, mechanical, dielectric, and thermal characteristics of materials synthesized via fly ash with different proportions of KOH and NaOH aged 28 days were evaluated. The physicochemical properties of class F fly ash-based geopolymers were assessed using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX) analyses. Based on readings of the results obtained, XRD and FTIR analysis detected the creation of semicrystalline potassium/sodium aluminate-silicate hydrate (KASH/NASH) gel in the elaborated matrices after the geopolymerization reaction. The SEM analysis proved the formation of alkali alumina-silicate hydrate gel in the raw material particles after the polycondensation stage. Experimental compressive strength data indicated that the highest compressive strength (39 MPa) was produced by the alkaline activator (75% KOH/25% NaOH). The dielectric parameters values of the elaborated materials changed depending of the mass ratios KOH/NaOH. Dielectric findings demonstrated that geopolymers containing 100% NaOH have better dielectric performances. The fire resistance study revealed that the geopolymer binders induced by KOH are stable up to 600°C. Based on these results, it can be deduced that the formulated geopolymer concrete possesses good mechanical, dielectric, and fire resistance properties