International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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A multi-seasonal model of the dynamics of the African maize stalk borer
No full textInternational audienceIn this paper, we build a simple, multi-seasonal mathematical model describing the dynamics of the maize stalk borer Busseola fusca (Lepidoptera: Noctuidae). We consider in this model the main harmful stages of the pests and the control methods used by farmers to reduce pest populations from one maize cropping season to another. Firstly, immature stages are controlled during the maize cropping season by applying pesticides to destroy the eggs and immature larvae present on the plant leaves. secondly, crop residues harboring the larvae are burnt or buried in the soil after the harvest. The semi-discrete model obtained is studied and the basic reproduction number of the pests is computed. The numerical simulations carried out illustrate the theoretical results and also allow us to find the minimum quantity of larvae to be destroyed at the end of each maize cropping season to eradicate pest populations in the fields
Recherche qualitative pluridisciplinaire et Covid 19. Le projet CO-DATA-LAB
No full textInternational audienceCe chapitre décrit une collaboration entre les auteurs de disciplines de management différentes engagés, de 2020 à 2021 dans une série d’enquêtes qualitatives en ligne destinées à observer les impacts de la crise sanitaire découlant de la pandémie de la Covid-19 sur le management. Les conditions de ce type de collaboration sont analysées puis une proposition de généralisation est présentée avec le projet CO-DATA-LAB en particulier sur le partage collectif de données et les possibilités de leur analyse pluridisciplinaire
Modeling and Prediction of Aftershock Activity
No full textInternational audienceWe provide an overview of the basic models of the aftershock processes and advanced methods used to predict postseismic hazard. We consider both the physical mechanisms for aftershock generation and models of aftershocks and time-dependent models of aftershock processes. In particular, we provide a validation of the aftershock process using a superposition of the Gutenberg-Richter and Omori-Utsu laws. We show that the key role in assessment of postseismic hazard is earthquake productivity, which characterizes the ability of earthquakes to produce subsequent shocks. We discuss the recently established exponential law of earthquake productivity and show that the exponential form is invariant under variations in magnitude and focus depth. Being in discordance with the popular epidemic type aftershock sequence (ETAS) model, the law makes it possible to build a corrected model. We study versions of theoretical validation for the Båth law, which specifies the mean difference between the magnitudes of the main shock and the largest aftershock. We consider also the time-dependent Båth law. We provide a detailed review of modern approaches and methods for dealing with the estimation of the magnitude of the largest aftershock. As well, we review the problem of estimating the duration of aftershocks with magnitudes equal to or greater than a specified value, the hazardous period
L'urgence écologique, un impératif juridique
No full textSous la contrainte d'habiter différemment la planète, l'urgence écologique se traduit par une urgence juridique. Le réchauffement climatique et l'effondrement de la biodiversité proviennent de la façon d'exister des sociétés modernes qui a conduit à l'anthropocène. Le droit des sociétés modernes souffre de deux maux qui sont à l'origine de l'état de la biosphère : une séparation de l'homme du reste du vivant objectivisé et l'absence de reconnaissance de l'interdépendance entre les êtres vivants dont l'homme fait partie. Le mantra onusien de "vivre en harmonie avec la nature" se complait dans un dualisme qui favoriserait une mutation du droit de l'environnement s'il parvenait à se dégager d'un anthropocentrisme et un ethnocentrisme maintenu dans un objectif de "développement". L'urgence juridique est de ré-instituer les communs, relocaliser le droit afin de promouvoir une solidarité écologique en termes d'interdépendance, conférer un statut au vivant de collectif humain/non-humain dans la perspective d'un régime juridique de coviabilité socio-écologique
Preponderance of additive and non-additive variances for growth, ecophysiological and wood traits in Eucalyptus hybrid genotype-by-spacing interaction
No full textInternational audienceThe objective of this study was to better understand the underlying gene action in eucalyptus, under different plantation densities, for a different set of traits: growth, bark thickness, ecophysiological, and wood chemical property traits. We estimated the magnitude and relative proportion of the various genetic variance components using a eucalyptus genotype by spacing (G x S) interaction experiment. A clonally replicated progeny test including 888 clones belonging to 64 full-sib families of Eucalyptus urophylla x Eucalyptus grandis hybrid was used to estimate genetic parameters using genomic information to assess relationship matrix. Two densities (833 and 2500 trees/ha) were used representing contrasted environments in terms of individual tree available resource. Results showed that for height and circumference, additive-by-spacing (A x S) interaction variance increased from 18 to 55 months old, while dominance-by-spacing (D x S) interaction variance decreased. For bark thickness, specific leaf area, nitrogen, calcium, and magnesium, A x S interaction variance was preponderant. For wood chemical properties, except with Klason lignin, genetic additive effects strongly interacted with spacing compared to non-additive effects
Classification of Vegetation classes by using Time Series of Sentinel-2 images for large scale mapping in Cameroon
No full textInternational audienceSentinel-2 satellites provide dense image time series exhibiting high spectral, spatial and temporal resolutions. These images are in particular of utter interest for Land-Cover (LC) mapping at large scales. LC maps can now be computed on a yearly basis at the scale of a country with efficient supervised classifiers, assuming suitable training data are available. However, the efficient exploitation of large amount of Sentinel-2 imagery still remain challenging on unexplored areas where state-of-the-art classifiers are prone to fail. This paper focuses on Land-Cover mapping over Cameroon for the purpose of updating the Very High Resolution national topographic geodatabase. The ι 2 framework is adopted and tested for the specificity of the country. Here, experiments focus on generic vegetation classes (five) which enables providing robust focusing masks for higher resolution classifications. Two strategies are compared: (i) a LC map is calculated out of a year long time series and (ii) monthly LC maps are generated and merged into a single yearly map. Satisfactory accuracy scores are obtained (>94% in Overall Accuracy), allowing to provide a first step towards finer-grained map retrieval
InSight Constraints on the Global Character of the Martian Crust
No full textInternational audienceAnalyses of seismic data from the InSight mission have provided the first in situ constraints on the thickness of the crust of Mars. These crustal thickness constraints are currently limited to beneath the lander that is located in the northern lowlands, and we use gravity and topography data to construct global crustal thickness models that satisfy the seismic data. These models consider a range of possible mantle and core density profiles, a range of crustal densities, a low-density surface layer, and the possibility that the crustal density of the northern lowlands is greater than that of the southern highlands. Using the preferred InSight three-layer seismic model of the crust, the average crustal thickness of the planet is found to lie between 30 and 72 km. Depending on the choice of the upper mantle density, the maximum permissible density of the northern lowlands and southern highlands crust is constrained to be between 2,850 and 3,100 kg m−3. These crustal densities are lower than typical Martian basaltic materials and are consistent with a crust that is on average more felsic than the materials found at the surface. We argue that a substantial portion of the crust of Mars is a primary crust that formed during the initial differentiation of the planet. Various hypotheses for the origin of the observed intracrustal seisimic layers are assessed, with our preferred interpretation including thick volcanic deposits, ejecta from the Utopia basin, porosity closure, and differentiation products of a Borealis impact melt sheet
Supplémentation des formules infantiles en acides docosahexaénoïque et arachidonique : effets sur le développement de l'enfant et difficultés associées à leur introduction
No full textInternational audienceThe postnatal period is characterized by rapid growth and development. Lipids, especially long-chain polyunsaturated fatty acids (LC-PUFA) such as docosahexaenoic (DHA) and arachidonic (ARA) acids, play an essential role during this period. The main objective of infant formulas is to be biomimetic of the “golden standard” i.e. breast milk, both in terms of composition and structure, thus offering the best possible alternative to breastfeeding when it has failed and/or is not possible. In this context, European regulations have evolved and now require DHA supplementation of formulas. Formulas are also fortified with ARA, another PUFA essential for child development, although there is no requirement for a minimum content. Their high degree of unsaturation makes these fatty acids particularly sensitive to lipid oxidation, making their inclusion in infant formulas more difficult. The objective of this review is therefore to provide a state of the art on the various key parameters that allow better control of LC-PUFA supplementation in infant formulas.La période postnatale est caractérisée par une croissance et un développement rapide. Les lipides, et plus particulièrement les acides gras polyinsaturés à longues chaînes (AGPI-LC), tels que les acides docosahexaénoïque (DHA) et arachidonique (ARA), jouent un rôle essentiel durant cette période. L’objectif principal des formules infantiles est d’être biomimétique de « l’étalon d’or » : le lait maternel, aussi bien en termes de composition que de structure, pour ainsi offrir la meilleure alternative possible à l’allaitement lorsqu’il a échoué et/ou n’est pas possible. Dans ce contexte, la réglementation européenne a évolué et impose désormais la supplémentation des formules en DHA. Elles sont également fortifiées en ARA, autre AGPI indispensable pour le développement de l’enfant, bien qu’aucune obligation ne soit établie quant à sa teneur minimale. Leur important degré d’insaturation rend ces acides gras particulièrement sensibles à l’oxydation lipidique, complexifiant ainsi leur introduction dans les formules infantiles. L’objectif de cette revue est donc de faire un état de l’art sur les différents paramètres clés permettant de mieux maîtriser la supplémentation des formules infantiles en AGPI-LC