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Toward an understanding of microalgae EPS-based selectivity and binding mechanisms for trace metal ions using Love wave acoustic and voltammetric sensors in seawater
No full textInternational audienceA biosensor using microalgal extracellular polymeric substances (EPS) for real-time monitoring of six trace metals in seawater, combining acoustic and electrochemical signatures for high sensitivity
Dynamique territoriale et repli identitaire dans les quartiers de N’Djamena : entre fragmentation urbaine et quête de cohésion sociale
No full textInternational audienceN’Djamena, the capital of Chad, is experiencing rapid and disorganised urbanisation, driven by strong population growth and ineffective public management. This dynamic has fostered a growing sense of identity withdrawal: residents increasingly prioritise their ethnic or community affiliations over national identity. The phenomenon is further exacerbated by political manipulation, land rivalries and failures of governance, undermining social cohesion and limiting prospects for peace and sustainable development. The study focuses particularly on the city’s districts, analysing the impact of territorial fragmentation on identity dynamics and inter-community tensions. It examines how the lack of urban planning fuels land and identity conflicts, while assessing the role of traditional mediations (national languages, chieftaincies) in social resilience. A comparison is also made between districts that have experienced violence and those with more mixed populations. The methodology combines qualitative interviews, field observations and quantitative analyses (descriptive statistics, factor analysis). Data is drawn from reports, local surveys, interviews and indicator tables. Using these tools, the study highlights the ethnic mosaic of N’Djamena: some districts remain associated with specific groups, while internal mobility complicates the social mapping. Tensions are mainly expressed around land issues and the absence of planning, exacerbating violence and hindering integration, especially on the outskirts. In response, the National Strategy for Social Cohesion (2024-2029) aims to strengthen the rule of law and dialogue but suffers from a lack of coordination and citizen participation. The study recommends more inclusive territorial governance, fair spatial planning, the strengthening of traditional mediations and the development of participatory tools to establish lasting peace in N’Djamena.urlr.me/m4FUgyN’Djamena, la capitale du Tchad, fait face à une urbanisation rapide et désorganisée, provoquée par une forte croissance démographique et une gestion publique inefficace. Cette dynamique a favorisé un repli identitaire croissant : les habitants privilégient leur appartenance ethnique ou communautaire au détriment de l’identité nationale. Ce phénomène est exacerbé par des manipulations politiques, des rivalités foncières et des failles de gouvernance, compromettant la cohésion sociale et limitant les perspectives de paix et de développement durable. L’étude s’intéresse particulièrement aux quartiers de la ville, analysant l’impact de la fragmentation territoriale sur les dynamiques identitaires et les tensions intercommunautaires. Elle examine comment l’absence de planification urbaine alimente les conflits fonciers et identitaires, tout en évaluant le rôle des médiations traditionnelles (langues nationales, chefferies) dans la résilience sociale. Une comparaison est également menée entre les quartiers ayant connu des violences et ceux à population plus mixte. La méthodologie adoptée combine entretiens qualitatifs, observations de terrain et analyses quantitatives (statistiques descriptives, analyse factorielle). Les données proviennent de rapports, enquêtes locales, entretiens et tableaux d’indicateurs. Grâce à ces outils, l’étude met en lumière la mosaïque ethnique de N’Djamena : certains quartiers restent associés à des groupes spécifiques, tandis que la mobilité interne complexifie la cartographie sociale. Les tensions s’expriment principalement autour du foncier et de l’absence de planification, exacerbant les violences et entravant l’intégration, notamment en périphérie. Face à ce constat, la Stratégie Nationale de Cohésion Sociale (2024-2029) vise à renforcer l’État de droit et le dialogue, mais souffre d’un manque de coordination et de participation citoyenne. L’étude recommande une gouvernance territoriale plus inclusive, un aménagement équitable, le renforcement des médiations traditionnelles et le développement d’outils participatifs pour instaurer une paix durable à N’Djamena.urlr.me/m4FUg
Newtonioside, a new cytotoxic cerebroside and other constituents from the stem bark of Newtonia buchananii (Fabaceae) and their chemophenetic significance
No full textInternational audienceThe phytochemical investigation of the methanol extract from the stem bark of Newtonia buchananii (Fabaceae) led to the isolation and identification of one new cerebroside, named Newtonioside (1), together with six known compounds: 3β-hydroxyolean-12-ene (2), β-sitosterol (3), stigmasterol (4), 3-O-β-D-glucopyranosylolean-12-ene (5), 3-O-β-D-xylopyranosyl-(1 → 2)-β-D-glucopyranosyl-27-hydroxyalphitolic acid (6), and 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyl-27-hydroxyalphitolic acid (7). Their structures were established based on extensive spectroscopic analyses (1D and 2D NMR, HR-ESI-MS) and comparisons with literature data. Compound 1 exhibited significant cytotoxic activity against the LN229 glioblastoma cell line (IC50 = 3.92 ± 0.36 μM), showing greater potency than the reference drug oxaliplatin (IC50 = 12.03 ± 0.91 μM). This is the first report of these metabolites from the genus Newtonia and from N. buchananii, marking only the second phytochemical study of this species. The occurrence of cerebrosides in N. buchananii expands the chemical diversity known within the Fabaceae family and provides further insight into the chemophenetic relationships of this genus
Coral degradation alters community diversity and stability of fish and invertebrate assemblages following recruitment
No full textInternational audienceHabitat degradation is one of the most pervasive threats to coral reef ecosystems, and the intensification of global and local disturbances is expected to further exacerbate its impacts. While many studies have investigated the effects of coral degradation on fish and invertebrates separately, its impact on the settlement and recruitment of entire coral-associated communities remains poorly understood. To fill this gap, we experimentally quantified how coral status (live versus dead) and ecological process (settlement: after 7 d, and recruitment: after 28-30 d) shape the abundance, diversity and community composition of coral-dwelling organisms in the back reef of Mo’orea, French Polynesia. Live corals supported significantly higher abundance, species richness and Shannon diversity at the recruitment stage, whereas no differences were detected during settlement. Similarly, recruits on live coral exhibited lower compositional variability, fostering a more ecologically stable community over time. Both coral status and ecological process significantly influenced taxonomic and feeding guilds, although their effects were independent. Overall, our findings demonstrate that live corals provide structurally complex, resource-rich habitats that enhance biodiversity and promote the establishment of more stable and functionally diverse communities. Coral degradation, in contrast, disrupts these dynamics, affecting not only fish communities but the entire benthic assemblage associated with corals, altering key ecological functions and potentially reducing reef resilience. Understanding how coral degradation affects settlement and recruitment across taxa is essential for preserving healthy coral structures, which should be prioritized to sustain the ecological integrity and trophic functioning of reef ecosystems
Emergence, global dispersal, and local adaptations of Yersinia pestis, the agent of plague
No full textInternational audienceYersinia pestis , the causative agent of plague, is a zoonotic bacterium that split at least 6,000 years ago from Yersinia pseudotuberculosis through plasmid acquisition, gene loss, and point mutations. These genetic events enabled a shift from the fecal-oral route to vector-borne transmission and facilitated systemic spread. In the course of its evolutionary history, Y. pestis has caused an unaccountable number of human outbreaks, at both regional and pandemic scales, of which three global pandemics have been documented from historical sources. The bacterium currently persists in sylvatic (enzootic) natural foci across Africa, Asia, and the Americas. Its persistence depends on the co-occurrence of reservoir hosts (mainly mammals) and competent vectors, primarily mammal ectoparasites, and their occurrence is shaped by environmental conditions. However, ecological variation among foci and limited epidemiological data still hinder our understanding of plague dynamics. This review examines the genetic evolution of Y. pestis , traces the bacterium’s history, including its global spread, and presents the main actors of sylvatic plague involved in the bacterium’s maintenance, with a special emphasis on the knowledge of vectors and hosts in countries that have reported cases of plague over the past decade. The global dispersal of Y. pestis has led to its adaptation to several distinct environments, highlighting the need for a comprehensive surveillance strategy for a better understanding of the ecological drivers of Y. pestis persistence and transmission within each of the geographical regions it is maintained in the natural environment
Accretion of volatile elements on Earth without the need of a late veneer
No full textInternational audienceVolatile elements are essential for life development and planetary evolution. However, the timing of their delivery to terrestrial planets remains unclear. Sulfur, selenium, and tellurium are volatiles, but also siderophile elements. Their abundances in Earth’s mantle can be used to determine whether volatile elements were delivered to Earth during or after the segregation of the core. Here, we experimentally measured their partition coefficients between core-forming metal and mantle silicate under pressure, temperature, and oxygen fugacity conditions relevant to a deep magma ocean. Our results show that these elements exhibit similar partitioning behaviors, indicating that core-mantle equilibrium preserves their chondritic relative abundances. If a volatile-rich late veneer has been delivered to Earth after core segregation, it must have been limited in mass, making up a maximum of 0.1% Earth’s mass. This suggests that volatile elements, including water, were accreted continuously during Earth’s growth rather than being delivered predominantly by a late veneer of volatile-rich material such as carbonaceous chondrites
Constraining the Thermochemical Structure of Mars Through Joint Inversion of Multidisciplinary Geophysical Data
No full textInternational audienceAbstract Understanding Mars' deep interior is essential to reconstruct its geological history, thermal evolution, and present‐day dynamics. To this end, the NASA InSight mission has provided unprecedented seismic observations. However, strong trade‐offs between temperature and composition in seismic interpretations continue to limit our ability to resolve interior models. To address this challenge, we account for electromagnetic induction data from Mars Global Surveyor as an additional, independent constraint. We develop a joint probabilistic inversion framework that simultaneously fits seismic body wave arrival times, electrical conductivity, the Love number, and the moment of inertia. A key feature of our approach is the integration of Mars' long‐term thermal evolution within the forward model, along with mineral physics and petrology data, to better constrain geodynamical parameters. We explore three different mantle compositions (Sanloup et al., 1999, https://doi.org/10.1016/s0031‐9201(98)00175‐7 ; Taylor, 2013, https://doi.org/10.1016/j.chemer.2013.09.006 ; Yoshizaki & McDonough, 2020, https://doi.org/10.1016/j.gca.2020.01.011 ) and consider both radially homogeneous and heterogeneous (with a basal molten layer (Samuel et al., 2023, https://doi.org/10.1038/s41586‐023‐06601‐8 )) mantle scenarios. For homogeneous mantle models, two families of solutions emerge regardless of the bulk composition: one with low Mg content and high potential temperature, which better reproduces electrical conductivity data due to a thicker lithosphere, and another with high Mg content and lower potential temperature. Models with a heterogeneous mantle reproduce electrical conductivity data less accurately, due to thinner lithospheres, and the mantle composition of Yoshizaki and McDonough (2020, https://doi.org/10.1016/j.gca.2020.01.011 ) appears to be less consistent with the full data set. To further refine models of Mars' interior, future efforts should focus on acquiring electromagnetic data with reduced uncertainties and seismically constraining more precisely the depth of mantle discontinuities associated with mineral phase transitions
L'EVOLUTION DES PARTIS POLITIQUES EN REPUBLIQUE DEMOCRATIQUE DU CONGO
No full textInternational audienceThe evolution of political parties in the Democratic Republic of Congo is linked to the political history of this state. Indeed, it is since its accession to sovereign political independence that political parties have participated in the country's political arena with all their dynamism. It should be noted that even before independence, there was already the presence of certain ethnic associations that aimed to integrate into the political sphere, but under their ethnic banner. Examples include the Alliance of the Bakongo, the Association of the Tshokwe, the Convention of Katangese Nationalists, the Rally of Eastern Congo, etc.It is worth noting that during the Belgian Congo era, there were no political parties; instead, there were cultural associations. These associations finally transformed into political parties on the eve of the elections that led to the DRC's independence in June 1960. The democratic process was subsequently interrupted by the establishment of the Popular Movement of the Revolution (MPR) as the sole party.Indeed, in recent electoral cycles in the DRC, the proliferation of political parties has reached considerable proportions. The 2006 electoral process saw over 230 political parties participate, some of which emerged from splits, including the UDPS and its offshoots. In 2011, over 400 parties were registered by the Ministry of the Interior, including new political parties created in response to conflict and a lack of democracy within existing parties, such as the UNC and the ATD. In 2018, 599 political parties were officially registered by the Ministry of the Interior, and the majority of new parties created throughout this electoral process largely aimed to gain political ground within the existing coalition forces (FCC, CACH, and LAMUKA). In the midst of the electoral process in preparation for the elections scheduled for 2023, there are currently more than 1000 political parties officially registered by the Ministry of the Interior.L'évolution des partis politiques en République Démocratique du Congo est liée à histoire politique de cet Etat. En effet, c'est depuis son accession à l'indépendance souveraine sur le plan politique que les partis politiques prennent part à l'arène politique du pays avec tout son dynamisme. Notons qu'avant même cette indépendance, il se notait déjà la présence des certaines associations ethniques qui, visaient à intégrer le domaine politique mais sous leur casquette ethnique, on peut citer L'alliance des Bakongo, l'association des Tshokwe, la Convention des Nationalistes Katangais, le Rassemblement de l'Est du Congo, etc… Notons qu'à l'époque du Congo-Belge, il n'existait pas de partis politiques, il s'agissait des associations culturelles. Ces dernières se sont finalement converties en partis politiques à la veille des élections ayant débouché à l'indépendance de la RDC en juin 1960. Le processus démocratique a été ensuite interrompu par l'instauration du Mouvement populaire de la révolution (MPR) comme parti unique. En effet, au cours de derniers cycles électoraux qu'a connu la RDC, la prolifération des partis politiques a pris une ampleur considérable. Au processus électoral de 2006, il se notait la présence de plus de 230 partis politiques qui ont pris part aux échéances électorales, et certains de ces partis était issu de la scission, entre autres l'UDPS et ses ailes. En 2011, plus de 400 partis ont été enregistrés par le ministère de l'intérieur, parmi lesquels des nouveaux partis politiques créés suite au conflit et manque de démocratie au sein de partis politiques, à l'occurrence de l'UNC, de l'ATD. En 2018, 599 partis politiques ont été enregistrés officiellement par le ministère de l'intérieur, et la majorité de nouveaux partis politiques créés tout au long de ce processus électoral visaient en grande partie la quête du positionnement politique partant des forces présentes (FCC, CACH et LAMUKA). En plein processus électoral en vue des échéances électorales prévues en 2023, il y a présentement plus de 1000 partis politiques enregistrés officiellement par le ministère de l'Intérieur.</div