International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Mayotte 2018 eruption likely sourced from a magmatic mush
No full textInternational audienceDespite significant advancements in understanding crustal melt transport, determining the shallow magmatic architecture at any given volcanic system remains a significant challenge with geophysical methods alone. In this study, we present a new conceptual model combining previously studied models for geomechanical magma reservoirs and dyke-shaped conduits. Supplementary to previous work, we include a model for porous mush adjacent to a visco-elastic magma reservoir during the eruption. This addition enables physically consistent magma recharge into the elastic magma reservoir by porous flow instead of employing an arbitrary mantle magma recharge parameterization. We compare our conceptual model with an illustrative test case - the submarine 2018 Mayotte eruption in the Comoros Islands (∼6.55 km3 Bulk Rock Volume, ∼3.5 km water depth, ∼35 km estimated deep magma reservoir). We estimate a magma effusion rate history using a new continuous-time inversion of surface deformation data. A single magma reservoir cannot match the observed eruptive history for any reservoir geometry or crustal and magmatic material properties. However, the presence of a porous mush adjacent to the magma reservoir helps to reconcile the model with the observations. The additional magma flux from the mush region sustains the long eruption at a low effusion rate, as is observed off Mayotte, with a decreasing effusion rate after few months of eruptions and a low persistent effusion rate since then. The mush flow dynamics are a direct consequence of reduced pressure in the magma reservoir during the eruption. Thus, our model provides a parsimonious and physically motivated explanation of the Mayotte eruptive history. Since many historical basaltic eruptions worldwide, such as sometime observed at Piton de la Fournaise, Volcan Arenal, and Laki, have a similar effusion rate history shape as Mayotte, magmatic mushes may be a key component for explaining long-lived basaltic eruptions
Impact of offsets on assessing the low-frequency stochastic properties of geodetic time series
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Les contrats d'emprunt de l'Etat du CamerounContribution à l'identification de leurs régimes juridiques
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Éduquer aux Coronavirus dans une perspective interculturelle du savoir : des représentations sociales qui empêchent la pratique d’éducation à la santé ?
No full textInternational audienceAfter the first lockdown March-June 2020, when classes restart, the teachers from the trainee schools (PES) were confronted with their own knowledge on the SARS-CoV-2 Coronavirus. Their opinions on the SARS-CoV-2 Coronavirus are part of culturally constructed social representations. This identification could be important to explore how they plan to use this notion in their teaching of health education. Four semi-directive interviews are proposed to PES in Mayotte, in a particular moment: a probable return to the classroom, just after lockdown period. Results showed that the construction of knowledge around Coronaviruses is included in culture, but also the identification of pedagogical activities that contribute to a certain form of health education epistemology (Jourdan et al., 2002). The incorporating of the intercultural perspective into health education practices will be considered
Effet des caractéristiques de l'équipe dirigeante sur la performance organisationnelle des Sociétés Anonymes au Tchad
No full textInternational audienceThe issue of organizational effectiveness correlated to the executive manager has since agency theory been the subject of several debates and still arouses discussions among theorists and practitioners of management today. In companies, this question is at the heart of shareholder’s concerns and is a major challenge for executive managers. This article, which follows on from the Upper Echelon Theory, studies beyond the main executive manager, the relationship between the characteristics of the entire Top Management Team and the organizational effectiveness of Public Limited Companies in Chad. The poor effectiveness of African firms over the last quarter century (UNIDO, 2016) and the accompanying plethora of dismissals of executive managers (CEOs and CIOs) has contributed to a growing scientific debate on the affecting of the Top Management Team characteristics on organizational effectiveness. Based on knowledge from the academic literature leading to the formulation of four research hypotheses first, and a sample of 78 Public Limited Companies in Chad secondly, the results of this study showed a significant effect of the characteristics of Top Management Team on organizational effectiveness.La problématique de la performance organisationnelle corrélée à l’équipe dirigeante a depuis la théorie de l’agence fait l’objet de plusieurs débats et suscite encore aujourd’hui des discussions tant chez les théoriciens que chez les praticiens du management. Dans les entreprises, cette question est au cœur des préoccupations des actionnaires et constitue un défi majeur pour les dirigeants. Cet article qui s’inscrit dans la continuité de la théorie des échelons supérieurs étudie, au-delà du principal dirigeant, la relation entre les caractéristiques de toute l’équipe dirigeante et la performance organisationnelle des Sociétés Anonymes au Tchad. La piètre performance dégagée au cours de ce dernier quart de siècle par les entreprises africaines (UNIDO, 2016) et le nombre pléthore de limogeages des dirigeants (PDG et DG) qui l’accompagne ont contribué à l’augmentation de la vivacité du débat scientifique sur l’influence des caractéristiques de l’équipe dirigeante sur la performance organisationnelle. A partir des connaissances issues de la littérature académique ayant débouché sur la formulation de quatre hypothèses de recherche d’une part, et d’un échantillon de 78 Sociétés Anonymes opérant au Tchad d’autre part, les résultats de cette étude ont montré un effet significatif des caractéristiques de l’équipe dirigeante sur la performance organisationnelle
Non-Recursive LSAWfP Models are Structured Workflows
No full textInternational audienceWorkflow languages play a key role in the discipline of Business Process Management (BPM): they allow business processes to be modelled in order to simplify their automatic management by means of BPM systems. Numerous workflow languages addressing various issues (expressiveness, formal analysis, etc.) have been proposed. In the last decade, some workflow languages based on context-free grammars (having then formal semantics) and offering new perspectives to process modelling, have emerged: LSAWfP (a Language for the Specification of Administrative Workflow Processes) is one of them. LSAWfP has many advantages over other existing languages, but it is its expressiveness (which has been very little addressed in previous works) that is studied in this paper. Indeed, the work in this paper aims to demonstrate that any non-recursive LSAWfP model is a structured workflow. Knowing that the majority of commercial BPM systems only implement structured workflows, the result of this study establishes that, although LSAWfP is still much more theoretical, it is a language with commercial potential
Contribution of omics to biopreservation: Toward food microbiome engineering
No full textInternational audienceBiopreservation is a sustainable approach to improve food safety and maintain or extend food shelf life by using beneficial microorganisms or their metabolites. Over the past 20 years, omics techniques have revolutionised food microbiology including biopreservation. A range of methods including genomics, transcriptomics, proteomics, metabolomics and meta-omics derivatives have highlighted the potential of biopreservation to improve the microbial safety of various foods. This review shows how these approaches have contributed to the selection of biopreservation agents, to a better understanding of the mechanisms of action and of their efficiency and impact within the food ecosystem. It also presents the potential of combining omics with complementary approaches to take into account better the complexity of food microbiomes at multiple scales, from the cell to the community levels, and their spatial, physicochemical and microbiological heterogeneity. The latest advances in biopreservation through omics have emphasised the importance of considering food as a complex and dynamic microbiome that requires integrated engineering strategies to increase the rate of innovation production in order to meet the safety, environmental and economic challenges of the agri-food sector
Intracaldera explosions and lava emissions during the 2007 caldera collapse of Piton de la Fournaise, La Réunion Island
No full textInternational audienceThe March-April 2007 Piton de la Fournaise basaltic eruption was the most significant eruption on La Réunion Island in historical times. On 2 April, a fissure opened on the southeastern flank of the volcano. Vigorous fountains fed lavas that rapidly reached the coast. Three days later, on the 5-6 April, major caldera collapse occurred at the summit, affecting the floor and walls of Dolomieu caldera. Monitoring records, primarily webcam images, have been analysed and integrated with geophysical data to reconstruct the chronology of events at the summit during caldera collapse. Those events included progressive subsidence of the former caldera floor, landslides, explosions, lava emissions and steam fumaroles, and lasted until 19 April though diminished greatly in frequency after 7 April. For two days after the main caldera collapse on 5 April, subsidence increments, intracaldera lava emission and explosions were closely associated in time and in location. Abundant steam and wet talus on the caldera walls imply that the shallow hydrothermal system and/or groundwater were exposed by subsidence. The presence of juvenile components in ash deposited at the summit during caldera collapse and the close link between intracaldera lavas and explosions suggest that many explosions were phreatomagmatic. Although caldera collapse was related to magma withdrawal from beneath the summit via the flank vent activity, numerous intracaldera lava emissions indicated that magma was nevertheless present at the summit during caldera collapse. We infer that the lava emissions were fed by an intrusion emplaced at the end of March into the eastern summit region and that the intrusion was being actively recharged during caldera collapse. Caldera collapse involved a complex combination of magma withdrawal and magma replenishment at separate summit reservoirs
Geochronology and correlations in the Central African Fold Belt along the northern edge of the Congo Craton: New insights from U-Pb dating of zircons from Cameroon, Central African Republic, and south-western Chad
No full textInternational audienceThe Central African Fold Belt (CAFB) is the least well-known of all major Pan African belts. Here, we present new geochronologic work carried out in several critical areas of western Central African Republic, the region standing between northern Cameroon and southwestern Chad, and southern Cameroon. Our results allow us to: (1) clarify the regional extension of the Congo Craton in SE Cameroon and in the SW Central African Republic; (2) demonstrate that the units thrust along the northern edge of the Congo Craton from Cameroon to the Central African Republic are comparable in nature and in age; (3) better constrain the limits and described better the role of the Adamawa-Yadé crustal block during the Pan-African pre-collisional and collisional events in relation to the Congo Craton and the Yaoundé-Yangana nappe units to the South, and to the Poli-Leré magmatic arc to the North and; (4) clarify some of the elements of correlation with NE Brazil. Overall, a model involving two subduction zones is proposed to explain the evolution of the Pan-African belt north of the Congo Craton. The main steps include; (1) break-up and basin development from the early Tonian to at least 620 Ma on the northern edge of the Congo Craton, and on both the southern and the northern edges of the Adamawa-Yadé Block, concomitantly with the development of the Poli-Leré arc in northern Cameroon and Chad; (2) pre-tectonic plutonism in all domains since c. 800 Ma with culmination between 650 and 620 Ma; (3) collisional events starting around 620 Ma with metamorphism reaching the granulite facies at c. 600 Ma in all the domains; (4) nappe tectonics with thrusting of the Yaoundé-Yangana units onto the Congo Craton, accretion of the Poli-Leré arc to Adamawa-Yadé Block, and widespread syntectonic magmatism (600–580 Ma) with emplacement partly controlled by transcurrent regional shear zones, and emplacement of post-tectonic granitoids (c. 550 Ma) in both Adamawa-Yadé block and Poli-Leré magmatic arc. Collisional and post-collisional (620–550 Ma) events were synchronous along the entire belt from Central Africa to Brazil
Could Sterile Aedes albopictus Male Releases Interfere with Aedes aegypti Population in Reunion Island?
No full textInternational audienceIn Reunion Island, the feasibility of an Aedes albopictus control program using the Sterile Insect Technique (SIT) is studied. Because, in some regions, Ae. albopictus is living in sympatry with Aedes aegypti, the impact of releasing millions of sterile male Ae. albopictus on female Ae. aegypti reproduction needs to be assessed. Thus, to study the potential heterospecific matings, a marking technique using rhodamine B has been used. Rhodamine is given in solution to male mosquitoes to be incorporated into the male body and seminal fluid and transferred during mating into the bursa inseminalis and spermathecae of females. The presence of rhodamine in females occurred in 15% of cases when Ae. aegypti females were offered non-irradiated Ae. albopictus males, 5% when offered irradiated Ae. albopictus males and 18% of cases in the inverse heterospecific matings. Moreover, our results also showed that these matings gave few eggs but were not viable. Finally, the results showed that whatever the type of mating crosses, females in cages previously crossed with males of another species can re-mate with males of their species and produce an equivalent amount of egg compared to females only mated with conspecific males. Despite the promiscuity of the males and females in small cages for three days, heterospecific mating between sterile male Ae. albopictus and female Ae aegypti, 95% of the females have not been inseminated suggesting that in the field the frequency satyrization would be very low