International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Improving the accuracy of genomic predictions in an outcrossing species with hybrid cultivars between heterozygote parents: a case study of oil palm (Elaeis guineensis Jacq.)
No full textThe authors acknowledge the CETIC (African Center of Excellence in Information and Communication Technologies) for support, and thank the UMR AGAP genotyping technology platform (CIRAD, Montpellier), the DArT company (www.diversityarrays.com) and the CIRAD-UMR AGAP HPC data center of the South Green bioinformatics platform (http://www.southgreen.fr/) for their help. This research was partly funded by a grant from PalmElit SAS.International audienceGenomic selection (GS) is a method of marker-assisted selection revolutionizing crop improvement, but it can still be optimized. For hybrid breeding between heterozygote parents of different populations or species, specific aspects can be considered to increase GS accuracy: (1) training population genotyping, i.e., only genotyping the hybrid parents or also a sample of hybrid individuals, and (2) marker effects modeling, i.e., using population-specific effects of single nucleotide polymorphism alleles model (PSAM) or across-population SNP genotype model (ASGM). Here, this was investigated empirically for the prediction of the performances of oil palm hybrids for yield traits. The GS model was trained on 352 hybrid crosses and validated on 213 independent hybrid crosses. The training and validation hybrid parents and 399 training hybrid individuals were genotyping by sequencing. Despite the small proportion of hybrid individuals genotyped and low parental heterozygosity, GS prediction accuracy increased on average by 5% (range 1.4-31.3%, depending on trait and model) when training was done using genomic data on hybrids and parents compared with only parental genomic data. With ASGM, GS prediction accuracy increased on average by 3% (- 10.2 to 40%, depending on trait and genotyping strategy) compared with PSAM. We conclude that the best GS strategy for oil palm is to aggregate genomic data of parents and hybrid individuals and to ignore the parental origin of marker alleles (ASGM). To gain a better insight into these results, future studies should examine the respective effect of capturing genetic variability within crosses and taking segregation distortion into account when genotyping hybrid individuals, and investigate the factors controlling the relative performances of ASGM and PSAM in hybrid crops
Optimal Control Problems Of Parabolic Fractional Sturm-Liouville Equations In A Star Graph
No full textInternational audienceIn the present paper we deal with parabolic fractional initial-boundary value problems of Sturm-Liouville type in an interval and in a general star graph. We first give several existence, uniqueness and regularity results of weak and very-weak solutions. We prove the existence and uniqueness of solutions to a quadratic boundary optimal control problem and provide a characterization of the optimal contol via the Euler-Lagrange first order optimality conditions. We then investigate the analogous problems for a fractional Sturm-Liouville problem in a general star graph with mixed Dirichlet and Neumann boundary controls. The existence and uniqueness of minimizers, and the characterization of the first order optimality conditions are obtained in a general star graph by using the method of Lagrange multipliers
Impact of mechano-sorptive loading on crack propagation of notched beams of White fir and Okume
No full textInternational audienceThe paper presents the experimental results of the crack process induced by viscoelastic effect and mechanical loadings. The notched specimens are White fir and Okume with dimensions equal to 160x12x60mm and notch length of 20mm. These specimens were tested in 3-point bending for 5 days under an initial stress of 80% of the rupture stress. At the end of these 5 days, we applied a second stress corresponding to 100% of the rupture stress. These tests were carried out under a sorption cycle of 45-75% relative humidity and at a constant temperature of 20°C. Monitoring of the crack propagation was performed by using an USB microscope. The results show that the crack propagation is accentuated by the drying effects on the one hand and by the effects of the applied stress on the other hand. The results show that crack propagation is influenced by viscoelastic effects, and by mechano-sorptive effects as shown in Figure 1. The crack propagation is more important when mechano-sorptive effects occur, especially during the drying
Tropical Cyclone Impact and Forest Resilience in the Southwestern Pacific
No full textInternational audienceTropical cyclones (TCs) can have profound effects on the dynamics of forest vegetation that need to be better understood. Here, we analysed changes in forest vegetation induced by TCs using the normalized difference vegetation index (NDVI). We used an accurate historical database of TC tracks and intensities, together with the Willoughby cyclone model to reconstruct the 2D surface wind speed structure of TCs and analyse how TCs affect forest vegetation. We used segmented linear models to identify significant breakpoints in the relationship between the reconstructed maximum sustained wind speed (Wmax) and the observed changes in NDVI. We tested the hypothesis that the rate of change in damage caused by TCs to forest and recovery time would increase according to Wmax thresholds as defined in the widely used Saffir–Simpson hurricane wind scale (SSHWS). We showed that the most significant breakpoint was located at 50 m/s. This breakpoint corresponds to the transition between categories 2 and 3 TCs in the SSHWS. Below this breakpoint, damages caused to forest vegetation and the time needed to recover from these damages were negligable. We found a second breakpoint, with a sharp increase in damages for winds >75 m/s. This suggested that extremely intense tropical cyclones, which might be more frequent in the future, can cause extreme damages to forest vegetation. Nevertheless, we found high variation in the observed damages and time needed to recover for a given Wmax. Further studies are needed to integrate other factors that might affect the exposure and resistance to TCs as well as forests’ capacity to recover from these disturbances
Bien-être des étudiants et projection dans l’avenir
No full textTic... Tac... Le temps passe... Ne vous êtes-vous jamais demandé comment se fait-il que certaines heures durent des années et que d’autres ne durent qu’une minute ? Pendant la pandémie, le temps vous aura-t-il paru long ? Court ? Bizarre ? Ordinaire ? Différent ? Pour les jeunes, en cours de formation, dont certains enjeux identitaires vocationnels sont importants, comment font-ils pour se construire un avenir professionnel quand ils se retrouvent dans un temps vécu comme « entre parenthèse » (Genevois et al., 2020) et que les modifications des adaptions à la formation sont nombreuses ? Dans quelle temporalité se retrouvent les jeunes et les étudiants pour tenter de maintenir une continuité psychique identitaire dans une rupture sociale ? Depuis longtemps, les recherches montrent que les très jeunes enfants, avant l’entrée dans le langage, perçoivent le rythme et synchronisent le rythme en interaction avec autrui (Fraisse, 1956) ; ils se construisent une temporalité présente, passée et future, et un avenir désiré leur permettant d’attendre, notamment grâce, encore une fois, à l’entourage (Fraisse, 1967). Le langage leur permet de créer des représentations prototypiques d’événements et de repérages temporels (planification) et localisés dans le temps (Tartas, 2010). Mais, pendant la pandémie mondiale de COVID-19, la désynchronisation sociale aurait-elle perturbé en profondeur les constructions de ces bases de l’enfance ? Quelles formes d’adaptation et de choix les jeunes et les étudiants sont-ils prêts à faire lorsqu’on les positionne dans des situations de dilemmes moraux (Piaget, 1946 ; Selman, 1980) sous forme manichéenne ? Comment se re-structurent et s’adaptent les dimensions identitaires des transitions professionnelles ordinaires (Perez-Roux, 2014) lors de la pandémie (Lefer Sauvage et al., 2020) ? Face à des étudiants qui se déclarent dans un temps suspendu en période de confinement total en mars–mai 2020, qu’en est-il deux ans après, quand la pandémie sévit toujours
Exploring Dihydroflavonol‐4‐Reductase Reactivity and Selectivity by QM/MM‐MD Simulations
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The thermal properties of hydrothermally altered andesites from La Soufrière de Guadeloupe (Eastern Caribbean)
No full textInternational audienceThe heat flux of an active volcano provides crucial information on volcanic unrest. The hydrothermal activity often responsible for volcanic unrest can be accompanied by an increase in the extent and intensity of hydrothermal alteration, which could influence the thermal properties of the volcanic edifice. Therefore, an understanding of the influence of alteration on the thermal properties of rocks is required to better interpret volcano heat flux data. We provide laboratory measurements of thermal conductivity, thermal diffusivity, and specific heat capacity for variably altered (intermediate to advanced argillic alteration) andesites from La Soufrière de Guadeloupe (Eastern Caribbean). We complement these data with previously published data for altered basaltic-andesites from Merapi (Indonesia) and new data for altered rhyodacites from Chaos Crags (USA). Our data show that thermal conductivity and thermal diffusivity decrease as a function of increasing porosity, whereas the specific heat capacity does not change systematically. Thermal conductivity decreases as a function of alteration (the percentage of secondary minerals) for the rocks from La Soufrière and Merapi (from ~1.6 to ~0.6 W·m−1·K−1 as alteration increases from ~1.5 to >75 wt%), but increases for the rocks from Chaos Crags (from ~1.1 to ~1.5 W·m−1·K−1 as alteration increases from ~6 to ~15 wt%). Although the thermal diffusivity of the rocks from Chaos Crags increases from ~0.65 to ~0.75–0.95 mm2·s−1 as alteration increases from ~6 to ~15 wt%, the thermal diffusivity of the rocks from La Soufrière and Merapi does not appear to be greatly influenced by alteration. The specific heat capacity is not significantly affected by alteration, although there is a slight trend of increasing specific heat capacity with alteration for the rocks from La Soufrière. We conclude that the decrease in thermal conductivity as a function of alteration in the rocks from La Soufrière and Merapi is the result of the low conductivity of the secondary mineral assemblage, and that a combination of the high thermal conductivity of cristobalite and the reduction in porosity as a result of the void-filling mineral precipitation can explain the increase in thermal conductivity in the rocks from Chaos Crags. Calculations show that an increase in alteration of a dome or edifice can result in decreases and increases in heat flow density, depending on the type of alteration. Therefore, alteration-induced changes in the thermal properties of dome or edifice rocks should be considered when interpreting volcano heat flux data. We conclude that it is important not only to monitor the extent and evolution of alteration at active volcanoes, but also the spatial distribution of alteration type
Vivre en Afrodystopie: Rencontre avec Joseph Tonda: Séminaire LAM, septembre 2021
No full textEsquisses | Les Afriques dans le mondeJoseph Tonda, professeur de sociologie et d’anthropologie à l’université Omar Bongo de Libreville au Gabon, a présenté son dernier ouvrage, Afrodystopie. La vie dans le rêve d’Autrui, publié chez Karthala en 2021, au séminaire LAM du 30 septembre 2021. L’auteur revient par exemple sur les relations de subordination des imaginaires et sur la critique du capitalisme mondialisé à partir de concepts forgés depuis son expérience de l’analyse de la sorcellerie. Auparavant, il a notamment publié, aux éditions Karthala également, Le Souverain moderne. Le corps du pouvoir en Afrique centrale (Congo, Gabon) (2005) et L’impérialisme postcolonial. Critique de la société des éblouissements (2015).Ce texte est un compte rendu de l’intervention de l’auteur, des commentaires des deux discutants – Elara Bertho, chercheure CNRS à LAM, et Sylvère Mbondobari, professeur de littérature francophone à l’Université Bordeaux Montaigne et enseignant-chercheur à LAM –, et des échanges qui ont suivi
Very High-Resolution Satellite-Derived Bathymetry and Habitat Mapping Using Pleiades-1 and ICESat-2
No full textInternational audienceAccurate and reliable bathymetric data are needed for a wide diversity of marine research and management applications. Satellite-derived bathymetry represents a time saving method to map large shallow waters of remote regions compared to the current costly in situ measurement techniques. This study aims to create very high-resolution (VHR) bathymetry and habitat mapping in Mayotte island waters (Indian Ocean) by fusing 0.5 m Pleiades-1 passive multispectral imagery and active ICESat-2 LiDAR bathymetry. ICESat-2 georeferenced photons were filtered to remove noise and corrected for water column refraction. The bathymetric point clouds were validated using the French naval hydrographic and oceanographic service Litto3D® dataset and then used to calibrate the multispectral image to produce a digital depth model (DDM). The latter enabled the creation of a digital albedo model used to classify benthic habitats. ICESat-2 provided bathymetry down to 15 m depth with a vertical accuracy of bathymetry estimates reaching 0.89 m. The benthic habitats map produced using the maximum likelihood supervised classification provided an overall accuracy of 96.62%. This study successfully produced a VHR DDM solely from satellite data. Digital models of higher accuracy were further discussed in the light of the recent and near-future launch of higher spectral and spatial resolution satellites