International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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La production et la conservation des céréales dans les savanes au Sud du Tchad et au Nord-Cameroun: Ressources naturelles disponibles et techniques culturales employées
No full textThe endogenous cereal production and conservation systems, dependent on natural conditions, have marked the lifestyle (nomadic and sedentary) of the peoples currently located in southern Chad and northern Cameroon. However, at the current state of knowledge, the agricultural knowledge and skills of these peoples are little known if not very little known to the public. These endogenous cereal techniques are assimilated in the collective mind to regressive agricultural models. This scientific vacuum poses fundamental and practical problems such as the loss of historical landmarks within rural communities, the absence of an economic model adapted to the different climatic contexts in the rural world and a weak relationship between farmers and the rural physical environment. Beyond this deplorable situation, understanding production and conservation techniques should make it possible to understand the natural changes and technical-agricultural practices underway in traditional societies in North Cameroon and South Chad.Les systèmes endogènes de production et de conservation des céréales, tributaires des conditions naturelles, ont marqué le mode de vie (nomade et sédentaire) des peuples localisés actuellement au Sud du Tchad et au Nord-Cameroun. Cependant, à l’état actuel des connaissances, les savoirs et savoir-faire agricoles de ces peuples sont méconnus sinon très peu connus du public. Ces techniques céréalières endogènes sont assimilées dans le mental collectif à des modèles agricoles régressifs. Ce vide scientifique pose des problèmes fondamentaux et pratiques comme la perte des repères historiques au sein des communautés rurales, l’absence d’un modèle économique adapté aux différents contextes climatiques dans le monde rural et une faible relation entre agriculteurs et milieu physique rural. Au-delà de cette situation déplorable, l’appréhension des techniques de production et de conservation doit permettre de comprendre les mutations naturelles et pratiques technico-agricoles en cours dans les sociétés traditionnelles au Nord-Cameroun et au Sud du Tchad
Mass collection of magnetotactic bacteria from the permanently stratified ferruginous Lake Pavin, France
No full textInternational audienceObtaining high biomass yields of specific microorganisms for culture‐independent approaches is a challenge faced by scientists studying organisms recalcitrant to laboratory conditions and culture. This difficulty is highly decreased when studying magnetotactic bacteria (MTB) since their unique behavior allows their enrichment and purification from other microorganisms present in aquatic environments. Here, we use Lake Pavin, a permanently stratified lake in the French Massif Central, as a natural laboratory to optimize collection and concentration of MTB that thrive in the water column and sediments. A method is presented to separate MTB from highly abundant abiotic magnetic particles in the sediment of this crater lake. For the water column, different sampling approaches are compared such as in situ collection using a Niskin bottle and online pumping. By monitoring several physicochemical parameters of the water column, we identify the ecological niche where MTB live. Then, by focusing our sampling at the peak of MTB abundance, we show that the online pumping system is the most efficient for fast recovering of large volumes of water at a high spatial resolution, which is necessary considering the sharp physicochemical gradients observed in the water column. Taking advantage of aerotactic and magnetic MTB properties, we present an efficient method for MTB concentration from large volumes of water. Our methodology represents a first step for further multidisciplinary investigations of the diversity, metagenomic and ecology of MTB populations in Lake Pavin and elsewhere, as well as chemical and isotopic analyses of their magnetosomes
Disentangling magnetic and environmental signatures of sedimentary 10Be/9Be records
No full textInternational audienc
The Marsquake catalogue from InSight, sols 0–478
No full textInternational audienceThe InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission began collecting high quality seismic data on Mars in February 2019. This manuscript documents the seismicity observed by SEIS, InSight's seismometer, from this time until the end of March 2020. Within the InSight project, the Marsquake Service (MQS) is responsible for prompt review of all seismic data collected by InSight, detection of events that are likely to be of seismic origin, and curation and release of seismic catalogues. In the first year of data collection, MQS have identified 465 seismic events that we interpret to be from regional and teleseismic marsquakes. Seismic events are grouped into 2 different event families: the low frequency family is dominated by energy at long period below 1 s, and the high frequency family primarily include energy at and above 2.4 Hz. Event magnitudes, from Mars-specific scales, range from 1.3 to 3.7. A third class of events with very short duration but high frequency bursts have been observed 712 times. These are likely associated with a local source driven by thermal stresses. This paper describes the data collected so far in the mission and the procedures under which MQS operates; summarises the content of the current MQS seismic catalogue; and presents the key features of the events we have observed so far, using the largest events as examples
Lipoprotein Metabolism in Familial Hypercholesterolemia
No full textInternational audienceFamilial hypercholesterolemia (FH) is one of the most common genetic disorders in humans. It is an extremely atherogenic metabolic disorder characterized by lifelong elevations of circulating LDL cholesterol levels often leading to premature cardiovascular events. In this review we discuss the clinical phenotypes of heterozygous and homozygous FH, the genetic variants in four genes (LDLR/APOB/PCSK9/LDLRAP1) underpinning the FH phenotype as well as the most recent in vitro experimental approaches used to investigate molecular defects affecting the LDL receptor pathway. In addition, we review perturbations in the metabolism of lipoproteins other than LDL in FH, with a major focus on lipoprotein (a). Finally, we discuss the mode of action and efficacy of many of the currently approved hypocholesterolemic agents used to treat FH patients, with a special emphasis on the treatment of phenotypically more severe forms of FH
Guérir en Afrique : promesses et transformations
No full textAlors qu'à propos de l'Afrique le poids des maladies chroniques et des épidémies domine les discours internationaux, les avancées majeures en matière de santé au cours des trente dernières années restent dans l'ombre. Le projet de cet ouvrage est d'analyser les formes individuelles et collectives du "guérir" dans l'Afrique contemporaine. Dans une approche anthropologique, la guérison n'est pas définie seulement d'un point de vue médical, mais elle est une production matérielle et idéelle dans des cultures thérapeutiques qui articulent le local et le global, mais aussi le sanitaire, le religieux et l'économique. Les auteurs apportent des éclairages sur des questions telles que : la promesse de guérison et les effets de l'absence de notion d'incurabilité dans les offres thérapeutiques locales ; les capacités et limites du système médical dans la construction de la guérison clinique ; les tensions entre acteurs sanitaires et patients dans les perceptions de la guérison ; les interprétations et dissonances locales d'un discours d'éradication en santé publique. Au final, l'ouvrage éclaire non seulement les dimensions idéelles de la guérison dans leurs contextes sociaux mais aussi les effets des dissonances dans ses approches, du personnel au politique
Co-Ni-arsenide mineralisation in the Bou Azzer district (Anti-Atlas, Morocco): genetic model and tectonic implications
No full textInternational audienceThe two main types of mineralisation in the Co-Ni-As Bou Azzer district, i.e., “contact” mineralisation” and “cross-cutting” structures have been re-defined based on new field, structural, textural and mineralogical observations. The main orebodies consists of elongated lenses of massive Ni-Co-Fe arsenide minerals. These lenses occur in a core of carbonate or siliceous gangue and are almost exclusively located along the contact between serpentinite and a quartz diorite intrusion. Vein systems, cross-cutting the different lithologies, are ore-bearing only along segments in contact with the serpentinite and/or the massive mineralisation. The two orebody types share a rather similar mineralisation history, starting with a Ni-rich arsenide stage (mainly expressed within the massive mineralisation), followed by a massive Co-arsenide stage recognised in both mineralisation styles, and ending with Fe-rich arsenide and base metal sulphide stage.Detailed field observations, microstructural, tectonic, textural and mineralogical analyses led us to propose a genetic model for the Bou Azzer ore district in which massive mineralisation was formed by alteration and transformation of previously formed breccia levels composed of serpentinite (transformed to gangue) and magnetite/spinel (transformed to Co-Ni arsenide minerals) fragments. Inversely, a tectono-hydrothermal event controlled by a NE oriented transtension generated the vein system, associated certainly with partial leaching and reconcentration of metals from the massive mineralisation because veins are principally mineralised when crossing massive orebodies. We discuss a possible temporal continuum between the two mineralisation styles: massive mineralisation, coeval with serpentinisation (serpentine neoformation), is related to the transformation of brecciated lenses and vein mineralisation is formed as an infill of large fractures during transtensive tectonics. This model has significant tectonic implications, because serpentinite breccia lenses, favourable high-permeability environment for the massive mineralisation formation, can be compared to ophicalcic rocks developed in a context of mantle exhumation by detachment. Two types of textures can be differentiated within the massive mineralisation: i) Brecciated Massive Mineralisation, developed in the core of ophicalcic levels, and ii) Laminated Massive Mineralisation, supposed to form within ancient mylonitic serpentinite levels corresponding to intensive deformation zones. Although the geodynamic significance will not be addressed in this article, we propose and discuss an alternative model in which the presence of exhumed mantle rocks allows the formation of specific massive arsenide deposits
Investigation of several proxies to estimate sulfuric acid concentration under volcanic plume conditions
No full textInternational audienceSulfuric acid (H2SO4) is commonly accepted as a key precursor for atmospheric new particle formation (NPF). However, direct measurements of [H2SO4] remain challenging, thereby preventing the determination of this important quantity, and, consequently, a complete understanding of its contribution to the NPF process. Several proxies have been developed to bridge the gaps, but their ability to predict [H2SO4] under very specific conditions, such as those encountered in volcanic plumes (including, in particular, high sulfur dioxide mixing ratios), has not been evaluated so far. In this context, the main objective of the present study was to develop new proxies for daytime [H2SO4] under volcanic plume conditions and compare their performance to that of the proxies available in the literature. Specifically, the data collected at Maïdo during the OCTAVE (Oxygenated organic Compounds in the Tropical Atmosphere: variability and atmosphere–biosphere Exchanges) 2018 campaign, in the volcanic eruption plume of the Piton de la Fournaise, were first used to derive seven proxies based on knowledge of the sulfur dioxide (SO2) mixing ratio, global radiation, condensation sink (CS) and relative humidity (RH). A specific combination of some or all of these variables was tested in each of the seven proxies. In three of them (F1–F3), all considered variables were given equal weight in the prediction of [H2SO4], whereas adjusted powers were allowed (and determined during the fitting procedure) for the different variables in the other four proxies (A1–A4). Overall, proxies A1–A4 were found to perform better than proxies F1–F3, with, in particular, improved predictive ability for [H2SO4] > 2 × 108 cm−3. The CS was observed to play an important role in regulating [H2SO4], whereas the inclusion of RH did not improve the predictions. A last expression accounting for an additional sink term related to cluster formation, S1, was also tested and showed a very good predictive ability over the whole range of measured [H2SO4]. In a second step, the newly developed proxies were further evaluated using airborne measurements performed in the passive degassing plume of Etna during the STRAP (Synergie Transdisciplinaire pour Répondre aux Aléas liés aux Panaches volcaniques) 2016 campaign. Increased correlations between observed and predicted [H2SO4] were obtained when the dependence of predicted [H2SO4] on the CS was the lowest and when the dependence on [SO2] was concurrently the highest. The best predictions were finally retrieved by the simple formulation of F2 (in which [SO2] and radiation alone were assumed to explain the variations in [H2SO4] with equal contributions), with a pre-factor adapted to the STRAP data. All in all, our results illustrate the fairly good capacity of the proxies available in the literature to describe [H2SO4] under volcanic plume conditions, but they concurrently highlight the benefit of the newly developed proxies for the prediction of the highest concentrations ([H2SO4] > 2–3 × 108 cm−3). Moreover, the contrasting behaviours of the new proxies in the two investigated datasets indicate that in volcanic plumes, like in other environments, the relevance of a proxy can be affected by changes in environmental conditions and that location-specific coefficients do logically improve the predictions
