Nanoparticulate ZrO2/SO42- Catalyst for Biofuel Production

This study reports on the preparation of zirconia coatings based on monodispersed zirconium-oxo-alkoxy (ZOA) nanoparticles for conversion of free fatty acid (FFA) into biofuel. Monodispersed ZOA nanoparticles of 3.6 nm size were prepared by sol-gel method in a rapid micro-mixing reactor with turbulent fluids flow at 20°C. The ZOA nanopowders obtained after precipitation and nanocoatings deposited on glass beads, after subsequent sulfatation, drying and calcinations, show high catalytic activity towards esterification process. The biofuel yield in esterification of palmitic acid in methanol reached 67% (after t=3.5 hours) on nanopowders while it increases to 98% on nonocoatings

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

Etude theorique et experimentale d'un hydroelevateur eolien

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 77916 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Mixing-Time in T-Mixer Reactor

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On the Operation of T-mixer Chemical Reactors in the Cavitation Regime

International audienceThe apparition of the cavitation phenomenon in chemical precipitation reactors with rapid micromixing can significantly affect the elaboration process. The bubbles appear in the reactive fluid flow when the local hydrostatic pressure decreases down to the liquid vapour pressure, which also corresponds to the maximum energy input producing the micromixing. In this paper, we study the bubbles kinetics (trajectory, size and number density evolution along the outlet leg of our exocentric T-mixer) in water experimentally by light scattering SLS/DLS measurements and numerically via FLUENT software using the cavitation and population balance models. We conclude about the generation and oscillatory movement of cavitation bubbles with the most abundant sizes between 0.1 and 1 μm, which control allows exploring the cavitation regime of the reactors

Reassessment on the Operation of a T-mixer Chemical Reactor in the Cavitation Regime

International audienceIn a previous work in our team (Oualha et al., Chem Eng Trans, vol 73, 67-72 (2019)) it was shown that at large Reynold numbers (Re > 8000) a vapor phase appears by cavitation in T-mixer reactors used for chemical precipitation of nanoparticles. This phenomenon can affect dramatically the properties of the obtained nanoparticles. In the work of Oualha et al (2019), the apparent size (more precisely the hydrodynamic diameters) of vapor bubbles due to the cavitation, was in situ monitored in the reactor by using SLS (Static Light Scattering) and DLS (Dynamic Light Scattering) methods. A modeling was also given using Fluent software: calculated size population of bubble was provided. Unfortunately this population could not be directly compared to experimental data since the relationship between apparent and real size was unknown. In the present work, new DLS measurements using particles of calibrated sizes are presented to help us to interpret and comment our previous results on bubbles size distribution. They were obtained using a new apparatus designed and realized for the purpose of defining a method of true diameters measurement

Nucleation and growth of mixed vanadium-titanium oxo-alkoxy nanoparticles in sol-gel synthesis

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Novel Synthesis of Mixed Oxide Nanoparticles for Photocatalysis

International audienceVanadium oxo-alkoxy nanoparticles were prepared via sol-gel method, manually and in a chemical reactor with ultra-rapid micromixing. The materials were characterized by DLS, ATG-ATD, XRD and SEM methods. The influence of micromixing conditions on the particle size and growth kinetics was evaluated. Complementary, the preparation of mixed-oxide nanoparticles in presence of vanadium and titanium precursors was performed, showing a strong interaction between the two systems, promising for the fabrication of size-and compositional selective Ti-V oxide nanoparticles for photocatalysis

Plasma catalysis application of gold nanoparticles for acetaldehyde decomposition

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