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Éditorial : Quarante années de publications sur les migrations internationales
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Analyse du vieillissement cognitif dans l’autisme à travers les performances et le ressenti des difficultés.
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Study of rhodamine B degradation by persulfate
No full textInternational audienceABSTRACT Many studies have investigated the nonradical pathway of rhodamine B (RB) degradation by activated persulfate (PS). However, PS can also react with RB by direct oxidation, without activation. In this study, the kinetic and mechanistic investigation of this pathway was conducted by examining the effects of the initial PS concentration, ethanol addition, and temperature. The direct reaction between PS and RB exhibited a second-order rate constant of 0.037 M−1 s−1 at temperatures ranging from 9 to 25 °C. At elevated temperatures, the sulfate radicals (SRs) produced by the dissociation of PS react with RB and compete with direct oxidation. The reaction between SR and RB had second-order rate constants of 5.0 × 106, 1.7 × 107, 3.5 × 107, and 7.81 × 107 M−1 s−1 at 25, 40, 50, and 60 °C, respectively. A comparative study was conducted to evaluate these rate constants against those reported in the literature. A reaction scheme for the direct oxidation of RB by PS is finally proposed based on data obtained from UV-Vis and HPLC-MS2 methods
Influence of two breakup models on the droplet behavior in a cellular gaseous detonation
No full textInternational audienceSimulations of two-phase detonation, such as those presented in Watanabe et al (2021), often rely on a breakup model based on simplified assumption, such as a linear decrease in the droplet diameter. However, large droplets can produce small droplets through mechanisms such as shear induced entrainment (SIE) and Rayleigh-Taylor Piercing, rendering this simplified assumption in-accurate. Additionally, a distribution of droplet diameter after the breakup process is expected. The size of these droplets is closely linked to the time scales associated with heating, evaporation, breakup, and velocity relaxation. Consequently, any changes in the prediction of the droplet diameter after the breakup can significantly influence the dynamics of two-phase detonation. The study evaluates the influence of breakup model on the behavior of a droplet in a cellular gaseous detonation. To efficiently compare the droplet behavior under two distinct breakup models, we employed a one-way coupling approach. This method was chosen to specifically isolate the effect of the flow fields on droplet dynamics. This preliminary work will compare the results obtained from two different breakup models. The first model operates under simplified assumption that the droplet diameter changes linearly during the breakup process. In contrast, the second model incorporates two distinct peaks in the diameter distribution. First results will be communicated at the conference
Multiplex vs . singleplex assay for the simultaneous identification of the three components of avian malaria vector-borne disease by DNA metabarcoding
No full textInternational audienceAccurate detection and identification of vector-host-parasite systems are key to understanding their evolutionary dynamics and to design effective disease prevention strategies. Traditionally, microscopical and serological techniques were employed to analyse arthropod blood meals for host/parasite detection, but these were limited in taxonomic resolution and only to pre-selected taxa. In recent years, molecular techniques have emerged as a promising alternative, offering enhanced resolution and taxonomic range. While singleplex polymerase chain reaction (PCR) assays were used at first to identify host, vector and parasite components in separate reactions, today multiple primer pairs can be combined in a single reaction, i.e. , multiplex, offering substantial time and cost savings. Nonetheless, despite the potential benefits of multiplex PCR, studies quantifying its efficacy compared to singleplex reactions are scarce. In this study, we used partially digested mosquito blood meals within an avian malaria framework to jointly identify the host, vector and parasite using multiplex DNA metabarcoding, and to compare it with separate singleplex PCRs. We aimed to compare the detection probabilities and taxonomic assignments between both approaches. We found both to have similar performances in terms of detection for the host and the vector, but singleplex clearly outperformed multiplex for the parasite component. We suggest adjusting the relative concentrations of the PCR primers used in the multiplex assay could increase the efficiency of multiplex in detecting all the components of the studied multi-species system. Overall, the results show that multiplex DNA metabarcoding can be an effective approach that could be applied to any vector-borne interaction involving blood-feeding arthropods. Our insights from this proof-of-concept study will help improve laboratory procedures for accurate and cost-efficient medical diagnosis of vector-borne diseases, the spread of which is globally exacerbated by current climate change
Volcanic forcing of the Lomagundi–Jatuli carbon isotope excursion
No full textInternational audienceThe Lomagundi–Jatuli Event (LJE), Earth’s most pronounced and prolonged positive carbon isotope excursion, followed the Great Oxidation Event and remains enigmatic in origin. We present a Pb–Pb isochron age of 2,194 ± 5 Ma for black shales from the Francevillian FB Formation, Gabon—an LJE type locality—coinciding with the emplacement of the Large Igneous Province that gave rise to the extensive Birimian–Eburnean orogenic segment. This orogeny produced very large volumes of juvenile crust in the form of oceanic plateau basalts that were eventually reworked through subduction and collisions. These processes released substantial volcanic CO 2 into the ocean–atmosphere system, disrupting the carbon and oxygen cycles for 100 to 200 My. Volcanic outgassing likely outpaced alkalinity production from weathering, leading to an increase in the δ 13 C of sedimentary carbonates. Reanalysis of global δ 13 C–δ 18 O datasets reveals a previously unrecognized dual bimodality, attributed here to episodic volcanic degassing and subsequent oceanic carbonate saturation. Weathering of emergent crust enhanced nutrient fluxes, driving primary productivity and organic carbon burial. We further propose that volcanic CO 2 emissions modulated the Dole Effect by shifting the balance between terrestrial and marine photosynthetic oxygen production, altering atmospheric oxygen isotope ratios independently of climate. These processes collectively drove the δ 13 C excursion of the LJE and may have fostered conditions conducive for early eukaryotic evolution
Un bon mot in via dei Coronari : misères d’un faussaire de Rome au XVIIe siècle
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Regards croisés. Lire, voir, écouter les arts, le théâtre et la nouvelle, de la Renaissance au XXIe siècle: Mélanges en l’honneur de Corinne Lucas Fiorato
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Effect of reflection wall distance and supply conditions on reflective shuttling detonation combustor
No full textInternational audienceIn a reflective shuttling detonation combustor (RSDC), detonation waves propagate between the two reflection walls of a thin combustion chamber. As the chamber is two-dimensional and does not have any curvature, optical and pressure measurements can be conducted simultaneously. In this study, pressure measurements as well as self-luminous and schlieren visualizations were performed using a chamber with a reflection wall distance of 90 mm with ethylene and oxygen. Consequently, the detonation wave number increased from 2 to 5 following the total mass flux, indicating that the wave number depended on the reflection wall distance because the maximum wave number increased with increasing distance. In addition, although the reflection wall distance was varied, the mode transition, in which the wave number increased from 1 to 2, 2 to 3, and 3 to 4, occurred at similar values to the critical value at which the maximum mixture fill height was non-dimensionalized by the cell size. The dimensionless detonation wave propagation distance, that is, the reflection wall distance divided by the wave number and maximum mixture fill height, was 3.0 ± 0.3, which is almost the same as that of the previous 45 mm combustor. Additionally, when the ratio of the reflective wall distance to the wave number is the same, the dimensionless quantities match, except in a few cases. Comparing the model results with the schlieren results, different trends were caused by non-ideal phenomena arising from the supply conditions, such as the equivalence ratio and the relationship between the plenum pressure and combustion pressure