HAL Réunion (Univ- de la Réunion )
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Bilan et variabilité de l'ozone dans le sud-ouest de l'Océan Indien et impact(s) : approche multi-instrumentale, par télédétection et mesures in-situ sol et satellites
No full textDespite its low concentration, ozone plays a fundamental role in the Earth's atmosphere. Primarily formed in the tropical stratosphere, it acts as a natural filter against solar ultraviolet (UV) radiation, thereby protecting the biosphere. In addition to its protective function, ozone contributes to the global radiative balance by modulating the absorption of both ultraviolet and infrared solar radiation. Due to atmospheric dynamics, tropical regions exhibit lower total ozone columns compared to mid- and high-latitude regions, leaving their populations more exposed to UV radiation. Ozone distributions are subject to complex spatiotemporal variability, governed by both chemical and dynamical processes. Understanding these mechanisms is therefore essential for analyzing ozone trends and variability at local, regional, and global scales—an issue of major scientific and societal importance. This thesis is set within this context and aims to analyze the variability and long-term trends of ozone over the southwest Indian Ocean, with a particular focus on Reunion, through a multi-instrumental approach combining satellite observations and ground-based measurements. In this southern hemisphere region, where data are scarce, the work assessed the impact of the Hunga volcanic eruption on ozone distribution over the Indian ocean and updated the observed trends at Reunion for the period 1998-2021. The joint use of these datasets helped to improve understanding of the influence of biomass burning plumes on tropospheric ozone, as well as the role of large-scale transport in stratospheric ozone variability.Malgré sa faible concentration, l'ozone joue un rôle fondamental dans l'atmosphère terrestre. Principalement formé dans la stratosphère tropicale, il agit comme un filtre naturel contre le rayonnement ultraviolet (UV) solaire, protégeant ainsi la biosphère. En plus de son rôle protecteur, l'ozone influence le bilan radiatif global en modulant l'absorption du rayonnement solaire, tant ultraviolet qu'infrarouge. En raison de la dynamique atmosphérique, les régions tropicales présentent des colonnes totales d'ozone plus faibles que celles observées aux latitudes moyennes et polaires, exposant davantage leurs populations aux rayonnements UV. Les distributions de l'ozone sont soumises à une variabilité spatio-temporelle complexe, gouvernée par des processus chimiques et dynamiques. Comprendre ces mécanismes est donc essentiel pour analyser les tendances et la variabilité de l'ozone à différentes échelles – locale, régionale et globale – ce qui constitue un enjeu scientifique et sociétal majeur. Cette thèse s'inscrit dans ce contexte et vise à analyser la variabilité et les tendances à long terme de l'ozone dans le sud-ouest de l'océan Indien, en particulier à La Réunion, en s'appuyant sur une approche multi-instrumentale combinant observations satellitaires et mesures locales. Dans cette région de l'hémisphère sud, où les données sont rares, le travail a permis d'évaluer l'impact de l'éruption du volcan Hunga sur la distribution de l'ozone dans l'océan Indien, et de mettre à jour les tendances observées à La Réunion sur la période 1998-2021. L'exploitation conjointe des données a permis de mieux comprendre l'influence, entre autres, des panaches de feux de biomasse sur l'ozone troposphérique, ainsi que le rôle du transport à grande échelle dans la variabilité de l'ozone stratosphérique
Publicisation de la parole du dernier sultan de Grande Comore Said Ali Saïd Omar : faste et fureur d’un roi déchu
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Deterministic and stochastic processes drive sessile cryptobenthic community composition on coral reefs at different spatial scales
No full textInternational audienceCoral reefs host immense biodiversity. The species that live concealed within the reef matrix, the cryptobiome, represent a major component of this diversity and are essential to reef functioning. However, the drivers of their composition and distribution remain incompletely understood. We deployed 27 autonomous reef monitoring structures (ARMS) for 2 yr at 9 outer slope sites on the fringing reefs along the west and southwest coasts of Reunion Island (south-west Indian Ocean). Photo-analysis of the sessile cryptobenthic communities (SCCs) on ARMS plate faces revealed that Rhodophyta, Annelida, Bryozoa, Porifera, Foraminifera, and Ascidiacea were the most abundant taxa. Oceanic distance, habitat characteristics, and environmental parameters were analysed to assess factors controlling the SCCs at various spatial scales. Presence-absence and abundance-based dissimilarity metrics revealed the relative contributions of deterministic and stochastic processes driving SCC beta diversity. At the ARMS unit scale, SCC composition was strongly linked to plate face orientation and exposure to the environment. Along the Reunion coral reef coast, community dissimilarity was associated with discontinuities of reef habitat, grouping SCCs into 4 geographical zones based on environmental factors (sea surface temperature, wave height, water flow velocity). Our results suggest that the SCC membership of taxa may be primarily driven by stochastic processes such as random larval dispersal and settlement on each reef, while their relative abundance within the community may be influenced by deterministic niche-based processes. These findings improve our understanding of the drivers of coral reef biodiversity in support of the conservation of these ecosystems
Experimental Study of Magnetic Near-Field Microstrip Electronic Probe for PCB EMC Emission Measurement
No full textInternational audienceAn experimental study on magnetic near-field (NF) scanning of printed circuit board (PCB) emission radiation is developed in this paper. The design and installation of the electromagnetic (EM) NF scanner is introduced. The test bed of magnetic NF emission in the microwave frequency range is described. The methodology of the microstrip magnetic NF probe is discussed. The probe calibration process was performed following the IEC 61967-1 NF scanning standard. The NF scanner functioning is tested with passive microstrip circuit square loop probe and device under test (DUT) PCB radiation in the test plan positioned at 1-mm above the ground plane. Based on the standard test with I-shape 50-Ω transmission line (TL), the calibration process of radiated magnetic field was validated by comparison between HFSS® simulation and experimentation in very wideband frequency from 0.1-GHz to 3-GHz. Then, a nonstandard TL based DUT was experimented. Accordingly, the cartographies of scanned magnetic NF at two different test frequencies, 2 GHz and 3 GHz, are discussed. The NF scanner is under development for targeting the EMC radiated emission of PCB dedicated to operate in 6G wireless communication.</div
Origin, size distribution, and hygroscopic properties of marine aerosols in the southwestern Indian Ocean: results of six campaigns of shipborne observations
No full textInternational audienceThis study presents observations of marine aerosols made during six ship-based campaigns in the southwestern Indian Ocean in 2021 and 2023. A set of aerosol measurement instruments is used to study the spatial and temporal variability in the number and size distribution of marine aerosols, the concentration of cloud condensation nuclei (CCN), and the hygroscopic properties of aerosols (kappa-Köhler parameter, κ). It has been shown that the number of submicron aerosols measured varies much more significantly (ranging from 100 to over 3000 cm-3) than the number of CCN (60 to 500 cm-3 at 0.4 % supersaturation). As a result, the κ values obtained show considerable variability, ranging from 0.05 to 0.7. Four distinct scenarios are examined to elucidate some of these variations: (1) the predominance of pristine air masses in the eastern regions of the subtropical Indian Ocean, with highly variable κ values sensitive to the low aerosol concentration measured in this area; (2) the predominance of polluted air masses in the Mozambique Channel, with weakly hydrophilic aerosols; (3) a precipitation and storm event in the southern Indian Ocean, with highly variable κ values; and (4) a new particle formation event in the open ocean, with an increase in κ values as the newly formed particles grow to Aitken mode particles.The size distribution of the sampled marine aerosols was analyzed according to the origin of the air masses. In general, a shift of the Aitken and accumulation modes toward larger aerosol sizes was observed for continental and subtropical air masses in the Indian Ocean due to aging. Conversely, the modes shifted toward smaller sizes for air masses in the southern Indian Ocean due to higher primary marine emissions. Aerosols are more hydrophobic for continental air masses (κ ∼ 0.1), more hydrophilic and variable over the subtropical Indian Ocean (κ ranging from 0.2 to 0.6), and intermediate (κ ∼ 0.2) over the southern Indian Ocean. The κ of the subtropical Indian Ocean increases with wind intensity, while it remains stable in the southern Indian Ocean. This effect is attributed to the high proportion of primary organic matter, which is due to the important concentration of nanophytoplankton in the southern Indian Ocean. It has been shown that primary organic aerosols act as surfactants, thus counterbalancing the highly hydrophilic properties of NaCl
Territorial and gender-linked risk factors for Buruli ulcer in Southern Benin: A case-control study using geographic and behavioral surveying
No full textInternational audienceObjectives The manuscript examines the risk factors associated with Buruli ulcer in endemic regions of Benin, focusing on community practices, agricultural activities, and age and gender disparities. Methods The study, conducted from November 2021 to June 2024, used a prospective case-control approach combined with a geographic health survey. The study involved home interviews followed by guided tours of areas frequented by participants, allowing the precise identification of practices at risk of Buruli ulcer. Univariate analysis and stepwise backward stepwise logistic regression were carried out. Results Overall, 117 patients and 234 controls were included. Multivariate analysis showed that activities such as bathing (OR = 3.2, p = .04), farming in flooded areas (OR = 3.8, p = .02), and frequenting irrigation canals (OR = 5.0, p = .003) were independent risk factors for Buruli ulcer. The originality of this study was that these risks were not distributed in the same way across territory and depended on age and gender. Conclusion The findings suggest that public health interventions need to consider gender, age, territorial features, and local agricultural practices. Furthermore, integrating geographical and spatial data into epidemiological studies offers valuable insights helping to prevent the spread of this neglected tropical disease
Evaluation of Different Group Formation Methods in the Context of Distributed Pair Programming: Design and Experiment in Higher Education
No full textInternational audienceGroup formation is an important issue in collaborative learning, as properly formed groups can lead to better interactions between students and enhance their learning. This issue also applies to pair programming when it is used as a learning activity. When the number of students is important and/or students and teachers do not know each other very well, manual group formation, either by students or teachers, can become difficult. Many of the existing automatic methods used for automatic group formation in pair programming require a certain amount of personal information about the students, which can make the implementation of this kind of system difficult. Hence, in this paper we present an automatic pair formation method integrated to a distributed pair programming application. Our approach is based on personal data from the students collected with questionnaires within our platform, but also on trace data automatically collected from the pair programming activities completed by students. It has been experimented during an introductory programming course in higher education. The objective was to identify, among programming experience, self-efficacy, gender and past engagement in pair programming activities, the formation criteria that led to the best perceived compatibility and work distribution as well as performance. The results show that homogeneous pairs in self-efficacy are significantly better than heterogeneous pairs, both in terms of perceived compatibility and perceived work distribution
Assessment of Trioza erytreae microbiome and mitochondrial genome variability by integrated high-throughput sequencing approach
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/614339/)International audienceHuanglongbing, a devastating citrus disease, is associated with 'Candidatus Liberibacter asiaticus', 'Ca. L. africanus' or 'Ca L. americanus', bacteria transmitted by the psylloids Diaphorina citri and Trioza erytreae. Using a DNA-Seq and metabarcode sequencing integrated approach, the first catalogue of endosymbionts associated with T. erytreae from the Iberian Peninsula, South Africa and African Islands, was generated. The almost complete genome of two new bacteria, one facultative and one obligate, tentatively named Asaia-like endosymbiont of T. erytreae and Sodalis-like endosymbiont of T. erytreae, respectively, was assembled and annotated. The complete mitochondrial genomes of T. erytreae from the geographical areas studied were also assembled and phylogenetic analyses were performed, suggesting that T. erytreae populations currently present in the Iberian Peninsula and specimens analyzed from South Africa may have originated from a common ancestor. Similar results were obtained when the genetic distances between Sodalis-like endosymbiont of T. erytreae were taken into consideration, thus supporting the symbiont–host codivergence which suggests that this bacterium is approaching to an obligate status. Finally, a new genetic marker of T. erytreae, an insertion in the mitochondrial tRNA-Ser gene, was identified only in some European samples, showing for the first time the existence of two mixed subpopulations of T. erytreae. The integrated DNA-Seq and metabarcode sequencing approach used in this study, besides generating a catalogue of T. erytreae endosymbionts, provided novel data on the sequence variability of bacterial and insect mitochondrial genomes from different geographic areas, highlighting the possible original sources of currently spreading T. erytreae populations may be more complex than previously reported
Improving service performance in young tennis players: the superiority of dynamic over static motor imagery
No full textInternational audienceThis study investigated the effect of dynamic motor imagery (MI), combined with physical practice, on service performances. 12 young non-expert tennis players (Mage = 11.08 years), between 3 and 5 years of regular practice, volunteered to participate in this study. They completed 3 experimental counterbalanced sessions: Control (including a neutral task), Static MI (with external visual imagery) and Dynamic MI (with external visual imagery including slight movements miming the actual service), which included the completion of 10 services in match condition with a returner present. Percentage of success, serve speed, technical and efficiency scores (assessing the degree of difficulty in which the receivers found themselves following services) were used as dependent variables and performance indicators. The results revealed that compared to the Control session, both MI conditions (Static and Dynamic motor imageries) improved the percentage of successful serves as well as technical and efficiency scores, but the improvement was greater when using Dynamic MI compared to Static MI. We recommend the use of integrated dynamic motor imagery before actual execution, such as serving, to improve motor learning and performance
Une mise à jour de la check-list des bryophytes de la Réunion
No full textInternational audienceThe first checklist of bryophytes from Réunion, published in 2005, recorded 621 species for the island. Nearly 20 years later, the total number of bryophyte species reported has increased to 822. This significant growth in knowledge results from ongoing floristic exploration, and ecological studies examining diversity across elevational gradients. We here report 500 species of mosses, 313 species of liverworts, and nine species of hornworts, including 16 moss, 20 liverwort, and three hornwort taxa that are newly recorded for Réunion. Unsurprisingly, endemism levels have decreased with increased knowledge of the local and regional flora. Fifty bryophyte species are endemic (6.1%), comprising 37 mosses and 13 liverworts. We also indicate taxa described based on type material from either Réunion or the wider Madagascar region, and provide references linking each name to its first published report on the island. Future research on the flora should focus on clarifying the taxonomy of poorly known taxa. Additionally, targeted collecting efforts and inventories will help improve our understanding of species distributions, which is essential for informed conservation planning.La première liste des bryophytes de La Réunion, publiée en 2005, recensait 621 espèces pour l'île. Près de 20 ans plus tard, le nombre total d'espèces de bryophytes signalées a augmenté à 822. Cette croissance significative des connaissances résulte de l'exploration floristique continue et des études écologiques examinant la diversité à travers les gradients d'altitude. Nous rapportons ici 500 espèces de mousses, 313 espèces de hépatiques et neuf espèces d'anthocérotes, dont 16 mousses, 20 hépatiques et trois anthocérotes nouvellement enregistrées pour La Réunion. Comme prévu, les niveaux d'endémisme ont diminué avec l'amélioration des connaissances sur la flore locale et régionale. Cinquante espèces de bryophytes sont reportées endémiques (6,1 %), composées de 37 mousses et 13 hépatiques. Nous indiquons également les taxons décrits sur la base de matériel type 3 provenant soit de La Réunion, soit de la région plus large de Madagascar, et fournissons des références liant chaque nom à son premier rapport publié sur l'île. Les recherches futures sur la flore devraient se concentrer sur la clarification de la taxonomie des taxons peu connus. De plus, des efforts ciblés de collecte et des inventaires contribueront à améliorer notre compréhension des distributions des espèces, ce qui est essentiel pour une planification de la conservation éclairée