Journal of Next-Generation Research 5.0
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Synchronisation entre l’objet de recherche et le terrain : réflexions méthodologiques et éthiques à partir de regards croisés dans nos parcours d’apprenti-chercheur
No full textInternational audienc
The chikungunya outbreak in Reunion: epidemic or environmental crisis ?
No full textInternational audienc
Genetic population structure and demography of an apex predator, the tiger shark Galeocerdo cuvier
No full textInternational audiencePopulation genetics has been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and subtropical marine ecosystems. While the global and Indo‐West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the western Indian (WIO) and within the western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR, COI, and cytb). A weak genetic differentiation was observed between the WIO and the WPO, suggesting high genetic connectivity. This result agrees with previous studies and highlights the importance of the pelagic behavior of this species to ensure gene flow. Using approximate Bayesian computation to couple information from both nuclear and mitochondrial markers, evidence of a recent bottleneck in the Holocene (2,000–3,000 years ago) was found, which is the most probable cause for the low genetic diversity observed. A contemporary effective population size as low as 111 [43,369] was estimated during the bottleneck. Together, these results indicate low genetic diversity that may reflect a vulnerable population sensitive to regional pressures. Conservation measures are thus needed to protect a species that is classified as Near Threatened
EXPLOITATION DES RESSOURCES NATURELLES EN AFRIQUE CENTRALE ET DEGRADATION DE L’ENVIRONNEMENT : ANALYSE CRITIQUE DU PRINCIPE DE SOUVERAINETE PERMANENTE SUR LES RESSOURCES NATURELLES
No full textLa stratégie de destination intelligente, facteur clé des mutations des destinations touristiques vulnérables ?
No full textInternational audienceTourism becomes an increasingly competitive market. The challenge of destinations relies on the capacity to reinvent oneself. This paper analyses le concept of tourism destination as a strategic tool for tourism development. We propose a form of territorial organization based on quintuple helix model. This one allows to ensuring the necessary agility for the success of a tourist mutation
Agricultural control of Radopholus similis in banana and plantain plantations
No full textInternational audienceThe nematode Radopholus Similis is the most significant parasitic nematode of the banana plant and the banana plantain plant in the world. R. Similis feeds on the root tissues and causes damages going from simple root lesions, reducing the crop yield, to the fall of seedlings. Because of these damages, R. Similis is one of the most regulated pests of plant but its control still implies toxic nematicides with limited efficiency and harmful ecological impact.Our global aim is to design more efficient and sustainable control strategies, including alternative methods to nematicides such as crop rotation or fallow practice. Our approach is based on a hybrid model describing the plant-nematode interactions over several cropping seasons. During the fallow, in the absence of host, the pest population undergoes a rapid decay.We formulate an optimisation problem to determine the fallow periods that maximise the multi-seasonal yield over a finite and fixed time horizon. Two cases are considered: a constant or variable fallow periods. The existence of an optimalsolution is proven and its location is computed. Numerical simulations are providedto illustrate our results
Appraising structural interpretations using seismic data—theoretical elements
No full textInternational audienceStructural interpretation of seismic images can be highly subjective, especially in complex geological settings. A single seismic image will often support multiple geologically valid interpretations. However, it is usually difficult to determine which of those interpretations are more likely than others. We refer to this problem as structural model appraisal herein. We propose the use of misfit functions to rank and appraise multiple interpretations of a given seismic image. Given a set of possible interpretations, we compute synthetic data for each structural interpretation, then compare these synthetic data against observed seismic data; this allows us to assign a data-misfit value to each structural interpretation. Our aim is to find data-misfit functions which enable a ranking of interpretations. To do so, we formalize the problem of appraising structural interpretations using seismic data and derive a set of conditions to be satisfied by the data-misfit function for a successful appraisal. We investigate both vertical seismic profiling and surface seismic configurations. An application of the proposed method to a realistic synthetic model shows promising results for appraising structural interpretations using vertical seismic profiling data, provided the target region is well illuminated. However, we find appraising structural interpretations using surface seismic data to be more challenging, mainly due to the difficulty of computing phase-shift data-misfits
Transcriptomic analysis reveals protein homeostasis breakdown in the coral Acropora millepora during hypo-saline stress
No full textInternational audienceBackgroundCoral reefs can experience salinity fluctuations due to rainfall and runoff; these events can have major impacts on the corals and lead to bleaching and mortality. On the Great Barrier Reef (GBR), low salinity events, which occur during summer seasons and can involve salinity dropping ~ 10 PSU correlate with declines in coral cover, and these events are predicted to increase in frequency and severity under future climate change scenarios. In other marine invertebrates, exposure to low salinity causes increased expression of genes involved in proteolysis, responses to oxidative stress, and membrane transport, but the effects that changes in salinity have on corals have so far received only limited attention. To better understand the coral response to hypo-osmotic stress, here we investigated the transcriptomic response of the coral Acropora millepora in both adult and juvenile life stages to acute (1 h) and more prolonged (24 h) exposure to low salinity.ResultsDifferential gene expression analysis revealed the involvement of both common and specific response mechanisms in Acropora. The general response to environmental stressors included up-regulation of genes involved in the mitigation of macromolecular and oxidative damage, while up-regulation of genes involved in amino acid metabolism and transport represent specific responses to salinity stress.ConclusionsThis study is the first comprehensive transcriptomic analysis of the coral response to low salinity stress and provides important insights into the likely consequences of heavy rainfall and runoff events on coral reefs
Geomagnetic jerks and rapid hydromagnetic waves focusing at Earth's core surface
No full textInternational audienceGeomagnetic jerks are abrupt changes in the second time derivative—the secular acceleration—of Earth’s magnetic field that punctuate ground observatory records. As their dynamical origin has not yet been established, they represent a major obstacle to the prediction of geomagnetic field behaviour for years to decades ahead. Recent jerks have been linked to short-lived, temporally alternating and equatorially localized pulses of secular acceleration observed in satellite data, associated with rapidly alternating flows at Earth’s core surface. Here we show that these signatures can be reproduced in numerical simulations of the geodynamo that realistically account for the interaction between slow core convection and rapid hydromagnetic waves. In these simulations, jerks are caused by the arrival of localized Alfvén wave packets radiated from sudden buoyancy releases inside the core. As they reach the core surface, the waves focus their energy towards the equatorial plane and along lines of strong magnetic flux, creating sharp interannual changes in core flow and producing geomagnetic jerks through the induced variations in magnetic field acceleration. The ability to numerically reproduce jerks offers a new way to probe the physical properties of Earth’s deep interior
Health and Energy at MADEV 2017 Photovoltaic Hybrid Systems for remote villages: Systemes Hybrides Photovoltaiques pour les villages isolés
No full textInternational audienceElectricity access in remote areas of Sub-Saharan Africa is limited due to high costs of grid extension to areas characterised by low population and low energy densities. Photovoltaic hybrid systems can be computed using an energy balance equation involving one unknown. For hypothetical village with an average daily energy demand of 153.6 kWh/d, the monthly energy output of photovoltaic modules at Garoua, Cameroon, enabled the evaluation of feasible photovoltaic hybrid (PVHS) options. An option with a renewable energy fraction of 0.557 having lower initial investments is suggested for electrification of more remote villages in Sub-Saharan African countries which have high solar radiation levels. This option comprises a 23.56 kWp PV array, a 15 kWp PV inverter, a 25 kW bi-directional inverter, a battery bank of capacity 324.48 kWh and a 25 kW diesel generator with an operating time of 1309 h/yr or 3.59h/d. The size of the PV array determined is smaller compared to the sizes of PV arrays which have been evaluated in the range 30-45 kWp using HOMER software for medium villages in Senegal.L’access à l’éléctricité en Afrique Sub-saharienne est limité par le cout élevé d’extension des resaux electriques vers les zones isolées caracterisés par une faible densité de la population et une faible densité de consummation de l’energie electrique. Les systemes hyrides photovoltaiques peuvent étre evalués avec une equation energétique à un inconue. Pour un village hypothetique avec une demande énergétique quotidienne de 153.6 kWh/jr, les productions énergetique mensuelles des modules photovotaiques à Garoua, au Cameroun, ont permis l’evaluation des options photovoltatiques hybrides realisables. Une option avec une fraction d’énergie renouvelable de 0,557 ayant un investment initial inféreur est suggerée pour l’électrification de villages plus éloignés dans l’Afrique subsaharienne qui ont des niveaux élevés de rayonnement solaires. Cette option comprend un générateur photovotaique de 23,56 kWc, un onduleur photovoltaique de 15 kWc, un inverseur bidirectionnel de 25 kW, un groupe de batterie d’une capacité de 324.48 kWh, et un groupe electrogene diesel de 25 kW avec un temps de fonctionnement de 1309 h/an ou 3.59h/j. La taille du générateur photovoltaique determiné est inférieur à celle des générateurs photovoltaiques dans la plage allant de 30 à 45 kWc à l’aide du logiciel HOMER pour les villages moyenne du Senegal comptant 750 habitants