Outcomes of the first meeting of the CAMEROON HIV RESEARCH FORUM (CAM-HERO)

Research is a vital component for the development of any country. In Cameroon, HIV Operational research is rapidly growing, however, it faces some intractable problems which can only be solved through an urgent, strategic, efficient, and collaborative approach involving key stakeholders. The Kribi meeting (09 and 10th December 2020) brought together under the auspices of the Ministry of Public Health leading HIV research organisations and connected HIV researchers and actors from different sectors. These actors disseminated and discussed recent research findings and worked out mechanisms to advance HIV research development, developed new ideas and identified priority research areas, with emphasis on translational research. The official launching and consolidation of Cam-HERO was a critical step and it is hoped that these synergistic efforts will catalyse attainment of the 95-95-95 goals in Cameroon

Atmospheric air plasma induces increased cell aggregation during the formation of Escherichia coli biofilms

Atmospheric air plasma has previously been shown to be a novel and effective method for biofilm eradication. Here we study the effects of plasma on both microbial inactivation and induced structural modification for forming biofilms. New structures are created from aggregates of extracellular polysaccharides and dead bacterial cells, forming a protective and resilient matrix in which the remaining living cells grow and reproduce under proper growth conditions. The new colonies are found to be more resilient in this state, reducing the efficacy of subsequent plasma treatment. We verify that the observed effect is not caused by chemicals produced by plasma reactive species, but instead by the physical processes of drying and convection caused by the plasma discharge

Propriétés réactives en post-décharge temporelle des décharges électriques glissantes dans l air humide (application à la dégradation de colorant azoïque et à la décontamination microbienne)

La décharge électrique glissante Glidarc dans l air humide est une source de plasma non thermique efficace dans l abattement de la pollution. Nous présentons dans ce mémoire l utilisation des propriétés réactives en post-décharge temporelle (c'est-à-dire après extinction de la décharge) du glidarc. Nous avons considéré dans un premier temps la dégradation en milieu acide du méthylorange, un colorant azoïque. Après exposition de la cible pendant des durées brèves à la décharge plasma, la dégradation en post-décharge temporelle s est effectuée suivant un processus global de 1er ordre avec conversion du colorant en N,N diméthyl-4- Nitroaniline comme produit majoritaire. D autre part, la post-décharge a été exploitée aussi pour inactiver les micro-organismes. Quatre micro-organismes dans les états planctonique et adhérent ont été considérés : Staphylococcus epidermidis et Leuconostoc mesenteroïdes comme bactéries à Gram positif, Hafnia alvei comme bactérie à Gram négatif et Saccharomyces cerevisiae comme modèle de levure. La post-décharge a été utilisée suivant deux voies : les cellules microbiennes étaient préalablement exposées la décharge pendant des durées brèves puis analysées en post-décharge ou alors elles étaient mises en contact avec une solution d eau activée par plasma . Dans tous les cas, on a obtenu des réductions significatives de la population microbienne suivant des cinétiques de 1er ordre. De tels résultas combinés avec la mise en évidence de la destruction par HNO2 et H2O2 suggèrent que les acides nitreux et peroxonitreux sont les principales espèces oxydantes impliquées dans le phénomène de post-décharge. Opérant en milieu acide, le rôle du cation nitrosonium NO+ a été également mis en évidence.The gliding electrical discharge "Glidarc" in the humid air is a source of non-thermal plasma at atmospheric pressure efficient for pollution abatement. We present in this thesis the benefit use of reactive properties in temporal post-discharge (i.e. after switch off the discharge) of glidarc. In the first step, we considered the degradation of acidic methyl orange, an azoic dye. After target exposure for short periods to the discharge plasma, a strong temporal post-discharge degradation of the dye giving N,N-dimethyl-4-Nitroaniline, as the major yellow intermediate product with a relevant overall first-order kinetics, was observed. On the other hand, post-discharge has also been used to inactivate micro-organisms. Four micro-organisms in planktonic and adherent forms were considered: Staphylococcus epidermidis and Leuconostoc mesenteroïdes as Gram-positive bacteria, Hafnia alvei as a gram-negative bacterium and Saccharomyces cerevisiae as a yeast model. The post-discharge was used in two ways: the microbial cells were previously exposed to discharge for short periods or they were inactivated by a solution of "plasma activated water . In all cases, significant reductions of the microbial populations were achieved with 1st order kinetic. Such results combined with the identification of the destruction by HNO2 and H2O2 suggest that nitrous and peroxonitrous acids are the main oxidizing species involved in the temporal post-discharge phenomenon. As the operation takes place under acidic medium, the role of nitrosonium NO+ was also highlighted.ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Unraveling the sorption mechanisms of ciprofloxacin on the surface of zeolite 4A (001) in aqueous medium by DFT and MC approaches

The adsorption mechanism of ciprofloxacin (CIP) and its ionic form were investigated using density functional theory (DFT) and molecular dynamics (MD), with the goal of forecasting their adsorption behavior in terms of gap energy, global reactivity descriptors, Fukui functions, adsorption energies, and density of state on the surface of zeolite 4A (001). Quantum chemical parameters related to the adsorption process were calculated, as well as the overall reactivity. According to DFT calculations, the zwetterionic form CIP± are the most stable and reactive and have a greater power of electron transfer compared to the other species. Under aqueous conditions, zeolite can adsorb ciprofloxacin (CIP) and its ionic forms, as revealed by molecular dynamics simulation. Ciprofloxacin in the zwitterionic form (CIP±) were more efficiently adsorbed to the surface of zeolite 4A (001) than the cationic (CIP+), anionic (CIP−), and neutral(CIP) forms; through the evaluation of adsorption energy, probability distribution, interaction, and density of state. The results also demonstrated that the compounds studied were adsorbed via the process of chemical bonding, which was confirmed by the negative values of the interaction energy. Furthermore, the negative adsorption energy values suggest a significant adsorption of all compounds, with electrostatic interactions (physisorption), diffusion into the pores, and n-π bonds (chemisorption) on the zeolite surface. The increase in adsorption energies and the proximity of the molecules studied to the zeolite surface indicate the predominance of chemisorption, and the adsorption of ciprofloxacin was found to be an exothermic and spontaneous process. Molecular dynamics (MD) modeling was in agreement with the DFT results

FeOx-kaolinite catalysts prepared via a plasma-assisted hydrolytic precipitation approach for Fenton-like reaction

Iron oxides (FeOx) supported on clay minerals are efficient catalysts for the Fenton-like degradation of organic pollutants in water. This study explores a new preparation route for such catalysts by exploiting the use of gliding arc plasma at atmospheric pressure for the precipitation-deposition of FeOx particles onto kaolinite. The physicochemical properties of the synthesized catalysts and their activity in the degradation of the azoic dye Acid orange 7 (AO7) are herein evaluated. Results show that the catalysts consist of nanosized goethite fibres onto clay particles. The BET surface area of the catalysts was greater than that of kaolinite and depended on the Fe weight percentage in each catalyst. As a consequence, these materials were very active when tested in the catalytic degradation of AO7 (C0 = 25 mg L−1). Abatement efficiencies of 86% and 50% in terms of bleaching and degradation respectively were obtained after 120 min, in the presence of 0.2 g L−1 of catalyst with 9.4 wt% of Fe. Increasing the catalyst dosage enhanced the abatement efficiency. For the catalyst dosage of 3 g L−1, the bleaching and degradation efficiencies were 100% and 80% respectively after only 80 min. Moreover, the catalyst was still active in neutral and basic media, even if lower abatement efficiencies were obtained for neutral and basic dye solutions. On the other hand, the AO7 abatement efficiency of catalyst with 4.4 wt% of Fe was almost equal to that with 9.4 wt%, suggesting that 4.4% of iron in the catalyst is sufficient to transform in a reasonable time, all H2O2 into hydroxyl radicals. Finally, the recycling tests showed that the catalysts remain active even after three consecutive uses

Combined Effects of Long-Living Chemical Species during Microbial Inactivation Using Atmospheric Plasma-Treated Water▿

Electrical discharges in humid air at atmospheric pressure (nonthermal quenched plasma) generate long-lived chemical species in water that are efficient for microbial decontamination. The major role of nitrites was evidenced together with a synergistic effect of nitrates and H2O2 and matching acidification. Other possible active compounds are considered, e.g., peroxynitrous acid

Impact on disinfection efficiency of cell load and of planktonic/adherent/detached state: case of Hafnia alvei inactivation by Plasma Activated Water

This paper describes the effects of initial microbial concentration and planktonic/adherent/detached states on the efficiency of plasma-activated water. This disinfecting solution was obtained by treating distilled water with an atmospheric pressure plasma produced by gliding electric discharges in humid air. The inactivation kinetics of planktonic cells of Hafnia alvei (selected as a bacterial model) were found to be of the first order. They were influenced by the initial microbial concentration. Efficiency decreased when the initial viable population N0 increased, and the inactivation rate kmax was linearly modified as a function of Log10 (N0). This relation was used to compare planktonic, adherent, and detached cells independently from the level of population. Bacteria adhering to stainless steel and high-density polyethylene were also sensitive to treatment, but at a lower rate than their free-living counterparts. Moreover, cells detached from these solid substrates exhibited an inactivation rate lower than that of planktonic cells but similar to adherent bacteria. This strongly suggests the induction of a physiological modification to bacteria during the adhesion step, rendering adherent—and further detached—bacteria less susceptible to the treatment, when compared to planktonic bacteria

Plasma synthesis of various polymorphs of tungsten trioxide nanoparticles using gliding electric discharge in humid air: characterization and photocatalytic properties

A gliding electric arc (glidarc) discharge generates a low-temperature plasma at atmospheric pressure. When the discharge occurs in humid air as the feed gas, the chemistry of a glidarc plasma consists of in situ formation of HO° and NO° as the primary chemical species. Tungsten trioxide (WO3) nanoparticles were successfully prepared by exposure of a liquid precursor to glidarc plasma. The WO3 samples were calcined at three different temperatures (300 °C, 500 °C and 800 °C), resulting in different pure polymorphs: γ-WO3 (at 300 °C), β-WO3 (at 500 °C) and α-WO3 (at 800 °C) according to x-ray diffraction analysis. The identification of WO3 compounds was also confirmed by attenuated total reflection Fourier transform infrared spectroscopy analysis. Increase in the calcination temperature of WO3 induced a decrease in its specific surface area according to Brunauer–Emmett–Teller nitrogen physisorption analysis. The UV-visible results showed that the absorption bands of plasma-WO3 samples were more intense than those of WO3 samples obtained by a precipitation route, a classical method used for comparison. Consequently, this parameter can improve the photocatalytic properties of WO3 under visible light. The photodegradation (in sunlight conditions) of gentian violet, chosen as a model pollutant, confirmed the photocatalytic properties of plasma-WO3 samples. This novel synthesis method has great potential to improve the efficiency of advanced tungsten trioxide-based functional material preparation, as well as in pollution-reducing and energy-saving tungsten extractive metallurgy