Portail "HAL-Francophonie Afrique et Océan Indien"
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Reconstitution comparée des écosystèmes Weichselien et Saalien Supérieur en Europe de l’ouest et du sud
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Microalgae Phycobiliproteins: The Pigment-Protein as Food Additives
No full textInternational audienceThe phycobiliproteins (FBPs) are antenna pigments composed of apoprotein covalently bound to phycobilin (tetrapyrrole chain chromophores). The main FBPs are phycoerytrin (PE), phycocyanin (PC) and allophycocyanin (APC) that absorb at 550, 620 and 650 nm respectively and are associated with phycobilisomes in cyanobacteria and rhodophytes. At present, it is of industrial-biotechnological interest to use natural dyes mainly blue pigments with food-grade quality. The main known source is phycocyanin (PC) although unstable for use in industrial food processes because it degrades at temperatures above 45 °C and it is sensible to light and pH. Recently, it was reported that some extremophile microorganisms, such as the thermophilic red algae Cyanidioschyzon merolae, are able to produce PC which is stable to pH 5 at 83 °C, but with a half-life time of 40 min. Another interesting example is an halophylic cyanobacteria Euhalothece sp. that can grow at 45 °C, pH 6–9 and 12% NaCl which allows low risk of microbial contamination. The PC from this cyanobacterium was purified up to analytical grade (purity > 2) and was stable at 45 °C, pH 5–8. These strains open the possibility to explore more biotechnological conditions that would allow to generate a pigment with a longer half time for industrial use (Contreras-Ropero et al. in Results Eng 23, 2024; Parsaeimehr et al. in Algal Res 66:102805, 2022). The last studies about phycobiliproteins have been focused on the way to prevent the loss of color due to PC degradation. In this regard several preservatives substances were tested such as citric acid, fructose, beet pectin, crosslinking with methylglyoxal (MGO). Formulation in anionic micelles was also investigated. The PC from Spirulina platensis improved its stability in presence of citric acid (4 mg/mL) at 35 °C during 15 days. It has been shown a correlation between sugars (mainly fructose) and PC stability, but the use is limited for pastry and confectionery due to the high sugar content. On the other hand, Sodium Dodecyl Sulfate micelles stabilize the non-protonated (blue) forms of PC and prevent the formation of protonated forms (green) at low pH. The challenge in the field of phycobiliproteins is to improve the stability at high temperatures for its use in food in order to guarantee food safety and overall quality. This can be achieved by using genetic, molecular tools and biotechnological approaches including extremophile microorganisms
From demand deficit to development strategy: Navigating mini-grid viability in a fragile context
No full textInternational audienceFour in five people without access to electricity live in Sub-Saharan Africa, where mini-grids are seen as a key solution. Yet investment remains constrained by low and unpredictable demand, especially in fragile settings. We study electricity demand in North Kivu (Democratic Republic of Congo), using pre-grid census and survey data combined with six years of post-connection consumption records. Five key findings emerge: (i) demand is highly heterogeneous across and within localities, with pockets of low uptake; (ii) pre-grid covariates explain some variation but have limited predictive power for realized connection and consumption; (iii) SMEs consume far more per connection than households while making up a small share of connections; (iv) consumption rises after connection and then plateaus, indicating slow movement up the energy ladder; (v) conflict shocks temporarily depress consumption, but usage rebounds, highlighting resilience in the face of insecurity. We further examine how an integrated, demand-building strategy by the local operator can partially mitigate these challenges. The case highlights that mini-grid viability in fragile settings may depend less on improved demand forecasting and more on the capacity to build and coordinate demand alongside infrastructure, with implications for policy design, risk-sharing finance, and the role of public and donor support
Seasonal variations of Titan’s haze and mist layers monitored by VIMS-IR onboard Cassini
No full textInternational audienceThe Cassini orbiter around Saturn monitored Titan with multiple instruments 13 years, between 2004 to 2017. This is about half of a Titan year and this period included a major seasonal change at the North Spring Equinox (NSE) in 2009 that could be observed. The Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini produced a large amount of observations of Titan generally presented under the form of spectro-images. The observations with the IR part of VIMS detector are taken in a spectral range between 0.88 to 5.12μm and with a resolving power between R= λ/Δλ = 120 and 180. The spatial resolution of the images depends on the observation and is few hundreds of meters at the best. In this study, we retrieved the distribution of the photochemical haze (above 80 km) and the condensate mist layer (below 80 km) as a function of latitude, altitude, and tile throughout the Cassini era. We found a haze latitudinal distribution with an extinction increasing from the south to the north at the beginning of the Cassini mission. The distribution evolved around the North Spring Equinox and a turnover was completely achieved at the end of the Cassini mission. This evolution is linked to the stratospheric circulation that blows from the summer hemisphere to the winter polar region. The latitudinal distribution of the mist layer evolves differently than the haze distribution because it depends on both the circulation pattern in the low atmosphere and on the conditions of condensation for several species. The distribution of the mist layer is also modulated with the seasons, but always increases from the equator and inter-tropical latitude band to the poles
Metagenomic screening of the virome of symptomatic tomato plants from La Réunion Island uncovers a complex of viruses including a newly identified whitefly-transmitted polerovirus
No full textInternational audienceUsing unbiased high-throughput sequencing for metagenomic screening of viruses in diseased tomato plants, we identified a viral complex that includes viruses previously reported in tomato crops on La Réunion Island as well as a novel polerovirus, tentatively named "tomato necrotic yellowing virus" (ToNYV, proposed species, "Polerovirus ToNYV"). Molecular characterization and phylogenetic analysis revealed that ToNYV is closely related to two recently described poleroviruses from Africa and the Middle East, one of which is transmitted by the whitefly Bemisia tabaci, a trait uncommon among poleroviruses. Our transmission experiments demonstrated that ToNYV is also transmitted by B. tabaci and is prevalent across major tomato-growing regions of La Réunion. These findings highlight the value of metagenomic virome analysis in diseased plants for identifying novel viruses potentially involved in emerging plant diseases, either individually or as components of viral complexes
Retrait francophone de l'anglais officiel à Madagascar : accaparement élitiste du capital linguistique et approfondissement des fractures sociolinguistiques.
No full textABSTRACT:The withdrawal of English's official status in Madagascar in 2010, decided under the transitional presidency of Andry Rajoelina, abrogates its promotion in 2007 by Marc Ravalomanana as the third official language, alongside Malagasy and French. This article demonstrates that far from a mere pragmatic adjustment, this decision reveals an elitist capture of linguistic capital by Francophone elites, perpetuating an internal linguistic colonialism, exacerbating fractures between urban bilinguals and rural Malagasy monolinguals, who are largely excluded from global opportunities. A rigorous methodological tool, Alex Mucchielli's semio-contextual approach, serves as the analytical pivot of this study: unlike classic unidimensional structuralist analyses of a language, it offers a multidimensional analysis, conceiving official languages as polysemic signs whose deep meaning emerges from seven interconnected contexts (spatial, temporal, expressive, normative, positional, relational, physical-sensory). Applied originally to the Malagasy case, this communicational approach unveils how the withdrawal of English consolidates the symbolic power of French, the quintessential colonial elitist marker, against a language perceived as a disruptive threat from globalization and Anglophone partnerships.Le retrait de l'officialité de l'anglais à Madagascar en 2010, décidé sous la présidence transitoire d'Andry Rajoelina, abroge sa promotion en 2007 par Marc Ravalomanana comme troisième langue officielle, aux côtés du malgache et du français. Cet article démontre que loin d'un simple ajustement pragmatique, cette décision révèle un accaparement élitiste du capital linguistique par les élites francophones, perpétuant un colonialisme linguistique interne, aggravant les fractures entre urbains bilingues et ruraux monolingues malgachophones, majoritairement exclus des opportunités globales. Un outil méthodologique rigoureux, l'approche sémio-contextuelle d'Alex Mucchielli constitue le pivot analytique de cette étude : contrairement aux analyses structuralistes unidimensionnelles classiques d'une langue, elle offre une analyse multidimensionnelle, concevant les langues officielles comme des signes polysémiques dont le sens profond émerge et naît de sept contextes interconnectés (spatial, temporel, expressif, normatif, positionnel, relationnel, physique-sensoriel). Appliquée de manière originale au cas malgache, cette approche communicationnelle démasque comment le retrait de l'anglais consolide le pouvoir symbolique du français, marqueur colonial élitiste par excellence, face à une langue perçue comme menace disruptive de la mondialisation et des partenariats anglophones
Microbiological Quality Assessment of Raw Camel Milk Consumed in N'Djamena, Chad
No full textInternational audienceCamel milk is an important food resource in Sahelian regions; however, its consumption in raw form exposes populations to microbiological risks. This prospective experimental investigation assessed the microbiological quality of raw camel milk using 30 samples collected from the 7ᵗʰ, 9ᵗʰ, and 10ᵗʰ districts of N’Djamena between 1 April and 30 June 2022. Standard microbiological techniques were applied to analyze total mesophilic aerobic flora (TMAF), total and thermotolerant coliforms, Staphylococcus aureus, yeasts and molds, as well as Salmonella. Microbial loads ranged from 2.27×10⁴ to 1.81×10⁵ CFU/mL (TMAF), 2.27×10³ to 6.41×10⁴ CFU/mL (total coliforms), 4.55×10² to 4.09×10⁴ CFU/mL (thermotolerant coliforms), and 4.55×10² to 1.82×10⁴ CFU/mL (S. aureus). Yeasts and molds were detected in several samples (4.55×10² to 9.32×10⁴ CFU/mL). No Salmonella was isolated. Overall, 70% of the samples complied with standards, 10% were acceptable, and 17% unsatisfactory. The presence of unsatisfactory samples poses a potential risk to consumer health and may contribute to foodborne diseases. These findings highlight the need to strengthen good hygiene practices during milking and marketing
Assessing simplified approaches in modeling rainfall-induced landslides using Richards' equation with Biot poroelasticity
No full textInternational audienceCoupled Hydro-Mechanical (HM) models, which involve the interaction between fluid flow and mechanical processes in porous media, are essential for simulating rainfall-induced landslides (RILS). A common strategy to investigate RILS is through the Biot poroelasticity approach combined with the Local Factor of Safety concept. While the two-phase flow and mechanical equations are well-documented for modeling HM processes in variably saturated conditions, the use of Richards' Eq. (RE) in this context remains underexplored. This paper aims to address this gap by providing a comprehensive formulation for coupling RE with mechanical equations and evaluating the impact of various model simplifications on the reliability of RILS predictions. We present the theoretical development of the original mathematical model that leads to a strong coupling between flow and mechanical equations. We also review the different simplification approaches proposed in the literature to reduce the complexity of the original model. A straightforward implementation of these approaches in COMSOL is provided, with validation against established benchmarks. Through a comparative analysis of different approaches, using both hypothetical benchmark and real case study in Azerbaijan, this study provides new insights into the balance between model complexity and prediction accuracy. While simplified approaches are commonly used in literature, this study advocates for the fully coupled model, which delivers the most reliable results. The employment of advanced numerical techniques enhances the computational performance of the fully coupled model, making it competitive with simplified approaches
From policy to practice in cervical cancer prevention in Reunion Island
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Opinion note on nonlinearity in induced polarization
No full textInternational audienceThe extension of direct current resistivity methods to induced polarization methods has enriched the tools available for subsurface exploration. This enrichment involves an increase in the number of parameters used in the models, as well as addressing different physical phenomena than those observed with direct current. Accounting for nonlinearities, if they exist, can further enhance the sophistication of our models. Nonlinearities are often observed, particularly in laboratory experiments. However, we question their origin, and the experiment described here suggests that the nonlinearities observed under typical experimental conditions may be artifacts related to the electrodes, rather than reflecting the actual response of the subsurface. Indeed, we first replaced the polarizable injection electrodes with non-polarizable electrodes. The nonlinearities observed due to the presence of harmonics were significantly reduced. Then, we replaced the voltage control with a current control, which completely eliminated the nonlinearities still present. We know that it is impossible to prove the non-existence of a phenomenon that does not exist. This fundamental epistemological principle (as pointed out by Russell and Popper) means that we are not claiming that nonlinearity does not exist. We are simply describing an experiment that can raise doubts about its existence