Journal of Next-Generation Research 5.0
Not a member yet
7559 research outputs found
Sort by
Awn Reduction and the Domestication of Asian Rice: A Syndrome or Crop Improvement Trait?
No full textInternational audienceAlthough wild progenitors of Asian cultivated rice have long awns, they are shorter or absent in domesticated landraces and cultivars. Thus, one may wonder when and why such transition from awned to awnless has occurred, i.e., is the reduction of awns a domestication syndrome trait or a trait that emerged during crop improvement? The proponents of an evolutionary model of rice domestication consider the loss/reduction of seed dispersal aids as a key domestication syndrome trait, apart from the fixation of seed retention. We challenge this view by showing that early cultivators had incentives for selecting long awns before and even after the fixation of the non-shattering trait. This is because long awns prevented seed predation by animals and facilitated harvest by means of the basket-beating method, which implies that their presence improved yield and labor efficiency. Our arguments also reveal that awns perhaps have persisted long after domestication and even after the introduction of sickles. Taken together, the reduction of awns may not fit into a domestication syndrome trait, but it can most plausibly be considered as a crop improvement trait
Allometric Models to Estimate Leaf Area for Tropical African Broadleaved Forests
No full textInternational audienc
A trace of recycled continental crust in the Réunion hotspot
No full textInternational audienceRéunion Island is the present surface expression of a major mantle plume whose homogeneity and isotopic signature, near the convergence point of many hotspot isotopic arrays, have long puzzled geochemists. This signature could, in part, reflect oversampling of the most recent (<0.53 Ma) Piton de la Fournaise volcano. To resolve this issue, we studied the older Piton des Neiges volcano and made a synthesis of the Sr-Nd-Pb isotope compositions of lavas produced during the early stage of La Réunion and contemporaneously at Mauritius, the second youngest island of the hotspot track.New samples from Piton des Neiges have 87Sr/86Sr from 0.70429 to 0.70441, 143Nd/144Nd from 0.51282 to 0.51290, 206Pb/204Pb from 18.765 to 19.004, 207Pb/204Pb from 15.558 to 15.605 and 208Pb/204Pb from 38.850 to 39.082. On a SrNd isotope plot, the extended isotope field defined by the Réunion and Mauritius volcanoes overlaps with the OIB field of the Society islands, where an EM-2 signature has been recognized. Réunion also has higher 207Pb/204Pb and 208Pb/204Pb ratios for a given 206Pb/204Pb than expected from a binary mixing between depleted and enriched mantle components. Thus, the overall Sr-Nd-Pb isotope variations shown by Réunion and Mauritius volcanoes require a third source component. In addition to the already known depleted and enriched mantle components, the third component involved in the mixing is interpreted as reflecting a small contribution (≤ 8%) of Seychelles/Madagascar-like continental crust, which is incorporated into the plume before it rises into the depleted mantle. This new model challenges the proposed existence of a hidden continent below the island of Mauritius, by suggesting that the continental component is located in the asthenosphere
Coviability of Social and Ecological Systems: Reconnecting Mankind to the Biosphere in an Era of Global Change.Vol.1 : The Foundations of a New Paradigm
No full textInternational audienc
La simulation numérique : de la prévision de l'irradiation solaire aux sciences du vivant
No full textThermodynamics of metamagnetoelectric effect in multiferroics
No full textInternational audienceMagnetoelectric coupling in multiferroics gives rise to various properties such as metamagnetoelectric effect since external fields act. In this study, a general thermodynamic framework is developed to investigate metamagnetoelectric effects in multiferroic materials. The model used is a quasi-two dimensional frustrated spin chain controlled by a static electric field in y-direction and magnetic field in z-direction. The effects of metamagnetoelectric transitions on entropy, heat capacity and on the linear magnetoelectric coupling factor are assessed using Fermi-Dirac statistics of quantum gases and the Landau theory. The entropy behavior is shown to be similar to that of the magnetic susceptibility. In fact, while the magnetic susceptibility characterizes the variations of magnetization and accordingly emphasizes the ferroic transition points of this order, the intrinsic physics of these transition points highlights a muddle occurring due to a rearrangement of magnetic moments in the system, and this is accurately described in terms of entropy. The transition effects due to this rearrangement described in terms of entropy at the corresponding critical points show different loop to that of the heat capacity. The opposite loop showed by the heat capacity compared to the entropy is its weakening at the exact transition point in spite of its strengthening during the transition process. It is also recorded only a few ranges of the electric field which allows the effect provided. The temperature dependence of the magnetoelectric coupling highlights how it is continuously weakened by the increase of temperature, leading to a second order transition from the metamagnetoelectric state
Evolution de l’aléa hydroclimatique sur le bassin versant de Fiherenana et caractérisation de la vulnérabilité de la ville de Toliara et de ses environs face à l’inondation
No full textInternational audienceDans le contexte du sud-ouest de Madagascar, souvent confronté à divers aléas hydrologiques, la ville de Toliara est soumise chaque année à des inondations rapides et dévastatrices qui semblent avoir augmenté en intensité et en fréquence. En outre, cette région est complètement représentative de la « fracture technologique entre les pays du Nord et les pays du Sud concernant la disponibilité des données et les contraintes de déploiement des modèles » (Payet, 2015). Les données hydrométriques à notre disposition dans cette région sont très incomplètes et cette étude propose une solution pour les compenser. Elle se divise en deux parties: la première partie est la reconstruction des données et la deuxième est la modélisation de ces dernières pour obtenir une représentation rigoureuse des chroniques. La partie reconstruction doit remplir les deux conditions suivantes: (i) représenter la dynamique globale de la série et (II) être assez simple pour faciliter l'analyse et l'interprétation à la fin de la modélisation. Nous offrons un moyen de reconstruire ces données manquantes en combinant des méthodes de décomposition saisonnière et une régression linéaire simple. Après cela, nous suivons une méthode statistique classique pour ajuster le modèle à nos chroniques. Nous obtenons deux types de modèle, un modèle de SARIMA qui est un modèle autorégressif saisonnier et un modèle REGARMA qui est une combinaison d'un modèle linéaire et de notre modèle SARIMA. Cette méthode peut aider les scientifiques travaillant dans le pays du Sud à exploiter au mieux les données, même incomplètes, sous réserve que soient bien considérées l’incertitude et les conditions liées à leur création
Pantasma: evidence for a Pleistocene circa 14 km diameter impact crater in Nicaragua
No full textInternational audienceThe circa 14 km diameter Pantasma circular structure in Oligocene volcanic rocks in Nicaragua is here studied for the first time to understand its origin. Geomorphology, field mapping, petrographic and geochemical investigations all are consistent with an impact origin for the Pantasma structure. Observations supporting an impact origin include outward-dipping volcanic flows, the presence of former melt-bearing polymict breccia, impact glass (with lechatelierite and low H 2 O, 10 km found in the America
Neurymenolide A, a Novel Mitotic Spindle Poison from the New Caledonian Rhodophyta Phacelocarpus neurymenioides
No full textInternational audienceThe marine α-pyrone macrolide neurymenolide A was previously isolated from the Fijian red macroalga, Neurymenia fraxinifolia, and characterized as an antibacterial agent against antibiotic-resistant strains that also exhibited moderate cytotoxicity in vitro against cancer cell lines. This compound was also shown to exhibit allelopathic effects on Scleractinian corals. However, to date no mechanism of action has been described in the literature. The present study showed, for the first time, the isolation of neurymenolide A from the New Caledonian Rhodophyta, Phacelocarpus neurymenioides. We confirmed the compound’s moderate cytotoxicity in vitro against several human cell lines, including solid and hematological malignancies. Furthermore, we combined fluorescence microscopy and flow cytometry to demonstrate that treatment of U-2 OS osteosarcoma human cells with neurymenolide A could block cell division in prometaphase by inhibiting the correct formation of the mitotic spindle, which induced a mitotic catastrophe that led to necrosis and apoptosis. Absolute configuration of the stereogenic center C-17 of neurymenolide A was deduced by comparison of the experimental and theoretical circular dichroism spectra. Since the total synthesis of this compound has already been described, our findings open new avenues in cancer treatment for this class of marine molecules, including a new source for the natural product
Planation surfaces of the Tian Shan Range (Central Asia): Insight on several 100 million years of topographic evolution
No full textInternational audienceIn Central Asia, numerous fragments of planation surfaces are visible within the present day topography. However, their precise timing of formations is still poorly constrained and it is not clear if they are remnants of a single extensive planation surface or if they represent different planation episodes. By reconstructing the landscape evolution of the Tian Shan region and by analyzing the relations between the planation surfaces preserved within the eastern Tarim Basin and the sedimentary record, we demonstrate that the numerous erosional surfaces preserved within the Tian Shan Range represent different episodes of surfaces genesis. These erosion events span from the late Paleozoic to the Early Cenozoic. The widespread preservation of large fragments of these surfaces within the Tian Shan Range implies that this region did not undergo strong relief building during most of its Mesozoic evolution but was dominated by plains associated to small hills along episodically active discrete tectonic structures. Finally, the preservation of these surfaces within the active Tian Shan Range implies a long-term, strong non-equilibrium state of the topography during its Cenozoic evolution. This was probably promoted by the arid to semi-arid climate prevailing since the Late Paleogene onset of relief building