Rapid epidemic expansion of the SARS-CoV-2 Omicron variant in southern Africa

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic in southern Africa has been characterised by three distinct waves. The first was associated with a mix of SARS-CoV-2 lineages, whilst the second and third waves were driven by the Beta and Delta variants, respectively1-3. In November 2021, genomic surveillance teams in South Africa and Botswana detected a new SARS-CoV-2 variant associated with a rapid resurgence of infections in Gauteng Province, South Africa. Within three days of the first genome being uploaded, it was designated a variant of concern (Omicron) by the World Health Organization and, within three weeks, had been identified in 87 countries. The Omicron variant is exceptional for carrying over 30 mutations in the spike glycoprotein, predicted to influence antibody neutralization and spike function4. Here, we describe the genomic profile and early transmission dynamics of Omicron, highlighting the rapid spread in regions with high levels of population immunity

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

cellules solaires photovoltaïques organiques à base de matériaux réticulables

1Les meilleurs rendements des cellules organiques sont aujourd'hui de l'ordre de 5 % [1]. Cependant, même pour des applications portables et jetables, les durées de vie reportées de l'ordre de quelques milliers d'heures sont actuellement insuffisantes à la commercialisation. Les durées de vie sont fortement liées à la stabilité des matériaux. Aussi, pour atteindre de bons rendements, il est nécessaire d'atteindre un état métastable avec une séparation de phase spécifique entre les matériaux donneurs et accepteurs d'électrons. Nous proposons ici l'utilisation de matériaux réticulables afin de mettre en forme ces couches minces bi-matériaux, d'atteindre l'état de phase le plus favorable, puis par réticulation, par UV par exemple, de figer cet état. L'idée est de développer des cellules photovoltaïques organiques (OPV) élaborées à base de matériaux conjugués capables de réticuler en un réseau tridimensionnel de molécules liées les unes aux autres de façon covalente. De part la très bonne stabilité physique et chimique de ces couches, une notable amélioration des durées de vies et de la fiabilité est attendue. Nous avons récemment démontré la faisabilité de l'utilisation de « petites molécules » réticulables par voie sol-gel dans des dispositifs électroniques [2]. Nous présenterons ici les différentes voies envisagées. Des polymères dérivés du polythiophène capables de réticuler par voie sol-gel ou par voie photochimique (UV) seront présentés. Les performances des dispositifs seront discutées en fonction de cette réticulation. [1] M. Reyes-Reyes, K. Kim and D.L. Carroll, Appl. Phys. Lett., 2005, 87, 083506. [2] O. J. Dautel, G. Wantz, R. Almairac, D. Flot, L. Hirsch, J-P. Lère-Porte, J-P. Parneix, F. Serein-Spirau, L. Vignau, J. J. E. Moreau, J. Am. Chem. Soc., 2006, 128, 4892-4901

A simple vibrating sample magnetometer for macroscopic samples

We here present a simple model of a vibrating sample magnetometer (VSM). The system allows recording magnetization curves at room temperature with a resolution of the order of 0.01 emu and is appropriated for macroscopic samples. The setup can be mounted with different configurations depending on the requirements of the sample to be measured (mass, saturation magnetization, saturation field, etc.). We also include here examples of curves obtained with our setup and comparison curves measured with a standard commercial VSM that confirms the reliability of our device.Fil: Lopez Dominguez, Virginia Elena. Universidad Complutense de Madrid; España. Instituto de Ceramica y Vidrio de Madrid; España. Northwestern University; Estados UnidosFil: Quesada, A.. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Guzmán Mínguez, J. C.. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Moreno, L.. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Lere, Martin Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Spottorno, J.. Universidad Complutense de Madrid; EspañaFil: Giacomone, Mariel. Universidad Complutense de Madrid; EspañaFil: Fernández, J. F.. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Hernando, A.. Universidad Complutense de Madrid; EspañaFil: García, M. A.. Universidad Complutense de Madrid; España. Instituto de Ceramica y Vidrio de Madrid; Españ

Systèmes Thienylène-Phénylène sous l'œil du physico-chimiste. Apport du couplage SPE-UV/Quantochimie.

Il existe de nombreuses familles d'oligomères Π-conjugués, telles que celles des oligothiophènes et des oligophénylènes, qui représentent une classe importante de semi-conducteurs. [1] Les propriétés électroniques et optiques sont liées à la fois à la nature des motifs conjugués et également à la longueur de la conjugaison. Plusieurs questions importantes se posent : comment déterminer puis prévoir leurs propriétés, quantifier expérimentalement les interactions inter-cycles, aller plus loin dans la description de ces modèles ? Nous montrerons que l'apport de la physico-chimie s'avère ici intéressant et qu'en particulier la spectroscopie photoélectronique à rayonnement UV, en phase gazeuse, peut être un outil puissant afin de mettre en évidence et quantifier la « magnitude » des interactions Πphényle-Πthiophène. [2] Couplé à la quantochimie, ce « tandem » permet d'aller encore plus loin dans l'étude de ces systèmes, notamment en précisant la nature et l'allure des orbitales intervenant dans la délocalisation mais également en décrivant la nature des interactions favorisant la quasi-planéité de ces systèmes : interactions électrostatique, électronique ... ? Ainsi vous pourrez d'une part comprendre quel rôle jouent les substituants au niveau de la structure géométrique de ces composés et d'autre part « visualiser » expérimentalement leur implication dans la délocalisation. [1] a) S. Hotta, S. A. Lee, Synth. Met. 1999, 101, 551; b) S. Hotta, S. A. Lee, T. Tamaki J. Heterocyclic Chem. 2000, 37, 25; c) S. Hotta, S. A. Lee, H. Kimura J. Heterocyclic Chem. 2000, 37, 25. [2] S. Lois, J.-Ch. Florès, J.-P. Lère-Porte, F. Serein-Spirau, J.E.Moreau, K. Miqueu, J.-M. Sotiropoulos, P. Baylère, M. Tillard, C. Belin Eur. Org. Chem. sous press

Study of fluorescent piconjugated materials used as nitroaromatics chemosensors

To be able to detect explosives ultra-traces has become a societal need particularly to anticipate terrorist attacks. During the last decade, despite wellstudied heavy analytical techniques, more sensitive and portable new gas-chemosensors have been developed. The sensor principle is based on a sensitive material interacting with the gaseous analyte. These interactions can induce a variation of the intrinsic properties of the material. For example, it can be fluorescence quenching easily identified with a spectrofluorimeter. In this paper, several organic materials have been identified as promising fluorescent explosives sensors and especially as nitroaromatic sensors. These sensors materials are polymers which backbone is a regularly alternated linking of π-conjugated segments (called fluorophores) and chiral unit