135 research outputs found
2008, une année d'animations au service des sciences de la Terre en Bretagne.
Bilan régional de l'Année Internationale de la PlanÚte TerreVous trouverez dans ce rapport un bilan du "programme CAREN" pour l'Année de la Terre, ou plus exactement de l'Année Internationale de la PlanÚte Terre 2008. Il s'agit d'une année patronnée par l'UNESCO et l'Union Internationale des Sciences Géologiques (IUGS) avec un programme scientifique et des animations de sensibilisation du "grand public" partout dans le monde, avec une idée forte : "Les Géosciences au service de l'humanité" L'effort du programme scientifique a porté sur 10 grands thÚmes multidisciplinaires, concernant la société : - la Terre et la santé - construire un environnement sain - le climat - climats anciens, climats futurs - les eaux souterraines - pour un usage durable - l'océan - la PlanÚte Bleue - les sols - l'épiderme de la Terre - la Terre profonde - de la croûte au noyau - les mégapoles - aller plus loin, construire autrement - les risques naturels - minimiser les risques, maximiser la prévention - les ressources - vers un usage durable - la Terre et la vie - origine de la biodiversité (thÚme co-dirigé par l'Allemagne et la France) La Fédération Française de Géologie (dont Cécile Robin - MC à l'université de Rennes 1 / Géosciences Rennes - est la correspondante en Bretagne) et le CAREN (Centre armoricain de recherches en environnement, et plus particuliÚrement le laboratoire de Géosciences Rennes), ainsi que le BRGM Bretagne, se sont engagés dans cette manifestation internationale et ont proposé un ensemble d'animations de culture scientifique sur le thÚme "Représenter et comprendre la Terre" (sous la forme d'expositions, festivals, conférences, excursions, interventions dans les écoles, etc. etc.), qui ont touché au final prÚs de 8000 personnes.Vous trouverez donc dans ce rapport un bilan complet de ce programme d'animations en Bretagne
La MĂ©diterranĂ©e au pied des Andes : lâinvention des paysages viticoles dans le CĂŽne Sud ?
Au sein de la nouvelle planĂšte vitivinicole, lâArgentine et le Chili sâaffichent comme leaders du sous-continent latino-amĂ©ricain en termes de superficie viticole (8e et 10e rangs mondiaux), de volume de vins produits (5e et 8e rangs mondiaux) et de volumes exportĂ©s (9e et 5e rangs mondiaux) (OIV, 2012). Si la culture de la vigne date dans les deux pays de la colonisation et est donc ancienne, elle a subi depuis une vingtaine dâannĂ©es une transformation profonde des modes de culture et des pr..
Les liens invisibles entre agriculture de proximité et commerce alimentaire dit "ethnique"
International audienceLa littĂ©rature scientifique concernant les agricultures de proximitĂ©, i.e. celles qui se pratiquent Ă proximitĂ© des marchĂ©s quâelles desservent, sâest beaucoup renouvelĂ©e ces derniĂšres annĂ©es sous lâeffet dâun intĂ©rĂȘt rĂ©affirmĂ© pour lâagriculture urbaine et pĂ©riurbaine . Si ces Ă©tudes ont surtout Ă©tĂ© attentives aux logiques de reterritorialisation que traduisent ces agricultures, certains auteurs soulignent la nĂ©cessitĂ©, dâune part, de mieux apprĂ©hender la diversitĂ© de ces agricultures de proximitĂ©, de leurs protagonistes, de leurs facteurs dâĂ©volution et, dâautre part, de reconsidĂ©rer leurs transformations du point de vue agricole (gĂ©ographie et sociologie agricoles, agronomie) . Elles appellent de surcroĂźt une mise en tension avec les situations dâinjustice socio-spatiale qui naissent tant de lâĂ©volution des relations villes / campagnes que de la dynamique des systĂšmes agro-alimentaires . De nouvelles formes de vulnĂ©rabilitĂ© se repĂšrent en effet : difficultĂ©s dâaccĂšs Ă une alimentation de qualitĂ© pour les consommateurs ; mise Ă lâĂ©cart dâune partie des consommateurs et des producteurs des nouveaux rĂ©seaux malgrĂ© la proximitĂ© gĂ©ographique ; prĂ©carisation des conditions de travail de certains agriculteurs .La recherche exploratoire dont nous proposons de prĂ©senter les rĂ©sultats dans cette communication se penche sur des pratiques agricoles qui se dĂ©ploient en marge des agricultures de proximitĂ© classiquement Ă©tudiĂ©es et des reprĂ©sentations positives associĂ©es actuellement aux agricultures urbaines et pĂ©riurbaines du point de vue des « populations aisĂ©es et Ă©duquĂ©es » des centres-villes. Elle vient souligner la diversitĂ© de cette nouvelle catĂ©gorie tant en termes dâacteurs que de modes dâexploitation (statut foncier, main dâĆuvre, assolements, commercialisationâŠ.)Un premier travail sur deux paysages dâ« agriculture de filiĂšres longues » (la Plaine de France dans le Val-dâOise et le Comtat Venaissin dans les Bouches-du-RhĂŽne) a ainsi permis de mettre Ă jour lâexistence de certaines formes dâexploitations agricoles directement liĂ©es Ă des marchĂ©s urbains de niche du commerce dit « ethnique » (alimentation mĂ©diterranĂ©enne ou asiatique). Le caractĂšre « invisible » ou cachĂ© de ces formes dâagricultures de proximitĂ© (lieux dâinstallation, parcellaire singulier, statut prĂ©caire, informalitĂ©âŠ) a impliquĂ© de mobiliser plusieurs mĂ©thodes dâinvestigation : exploration empirique, observation participante sur lâexploitation, entretiens semi-directifs et photo-interprĂ©tation, enquĂȘtes sur les marchĂ©s de revente. Les premiers rĂ©sultats obtenus permettent de montrer lâexistence de liens originaux entre le commerce dit « ethnique » implantĂ© dans les centres urbains et la rĂ©organisation spatiale des espaces agricoles de proximitĂ©. Ils apportent aussi des Ă©lĂ©ments sur les diffĂ©rentes trajectoires des travailleurs agricoles au sein de ces rĂ©seaux dâagriculture de proximitĂ©
Seeds and plant protection substances for French organic oilseed crops: what are the challenges for tomorrow?â
Organic production systems rely on different combinations of agronomic levers to ensure their sustainability, notably seeds and crop protection products. These inputs were mostly developed for conventional farming, which is the main market, and then evaluated under organic conditions. However, the growth of organic farming raises the question of producing inputs more specifically designed for this type of production, with its technical constraints, concepts and ethics. Recently, changes to European regulations on organic farming have opened up new perspectives, particularly in terms of varietal selection and evaluation, with introduction of the notions of âorganic varietyâ and âorganic heterogeneous materialâ. These two notions challenge and question the concept of variety, as well as the classic methods for evaluating their performance. With regard to crop protection products, a number of products can now be used on oilseed crops, including basic substances, low-risk substances and biocontrol agents but, the list remains limited, particularly for sunflower and soybean. However, new innovations are emerging, particularly in biocontrol agents, which augur new possibilities for controlling diseases and pests for which no solution is currently available. It is therefore necessary to support research in order to provide rapid solutions, and also to ensure that regulations evolve to promote their integration and availability to farmers. The use of inputs (seeds and plant protection products) in organic farming is governed by a number of European regulations, which are sometimes difficult to harmonize
Sunflower Associated With Legumes-Based Cover Crop : A Way To Increase Nitrogen Availability For The Following Winter Wheat?
Sunflower is one of the most important crop of organic crops systems in the South of France. In this region, sunflower is mostly cultivated before soft winter wheat, which is very often deficient in nitrogen because of a lack of nitrogen in the soil when the wheat needs it. To increase the soil nitrogen availability, one way is to introduce a legumes-based cover crop before wheat, which is sown just after the previous crop harvest. Thus, the time between sunflower harvest and wheat sowing is often too short to produce enough biomass. An alternative is to sow the cover crop during the sunflower cultivation, so to be intercropped into it. In a trial repeated over 3 years (from 2015 to 2017) in the southwest of France, Terres Inovia tested this practice, by intercropping 3 kinds of legumes-based cover crops into sunflower: alfalfa, purple vetch and legumes mixture. Over the 3 years, the growth of the cover crops was satisfying, and the average amount of nitrogen returned to soil after cover crops destruction was of 40 kg N/ha for purple vetch, 18 kg N/ha for alfalfa and 19.5 kg N/ha for legumes mixture. Nevertheless, cover crops impact severely sunflower performance because of competition for water and poor weed control due to no hoeing. Sunflower yield was reduced on average by 45% over the 3 years. This economic loss was partially compensated by a benefit on wheat yield, which was observed in 2016 and 2018, but only for wheat following sunflower intercropped with alfalfa
Random walks and polymers in the presence of quenched disorder
After a general introduction to the field, we describe some recent results
concerning disorder effects on both `random walk models', where the random walk
is a dynamical process generated by local transition rules, and on `polymer
models', where each random walk trajectory representing the configuration of a
polymer chain is associated to a global Boltzmann weight. For random walk
models, we explain, on the specific examples of the Sinai model and of the trap
model, how disorder induces anomalous diffusion, aging behaviours and Golosov
localization, and how these properties can be understood via a strong disorder
renormalization approach. For polymer models, we discuss the critical
properties of various delocalization transitions involving random polymers. We
first summarize some recent progresses in the general theory of random critical
points : thermodynamic observables are not self-averaging at criticality
whenever disorder is relevant, and this lack of self-averaging is directly
related to the probability distribution of pseudo-critical temperatures
over the ensemble of samples of size . We describe the
results of this analysis for the bidimensional wetting and for the
Poland-Scheraga model of DNA denaturation.Comment: 17 pages, Conference Proceedings "Mathematics and Physics", I.H.E.S.,
France, November 200
A global perspective on marine photosynthetic picoeukaryote community structure
A central goal in ecology is to understand the factors affecting the temporal dynamics and spatial distribution of microorganisms and the underlying processes causing differences in community structure and composition. However, little is known in this respect for photosynthetic picoeukaryotes (PPEs), algae that are now recognised as major players in marine CO2 fixation. Here, we analysed dot blot hybridisation and cloningâsequencing data, using the plastid-encoded 16S rRNA gene, from seven research cruises that encompassed all four ocean biomes. We provide insights into global abundance, α- and ÎČ-diversity distribution and the environmental factors shaping PPE community structure and composition. At the class level, the most commonly encountered PPEs were Prymnesiophyceae and Chrysophyceae. These taxa displayed complementary distribution patterns, with peak abundances of Prymnesiophyceae and Chrysophyceae in waters of high (25:1) or low (12:1) nitrogen:phosphorus (N:P) ratio, respectively. Significant differences in phylogenetic composition of PPEs were demonstrated for higher taxonomic levels between ocean basins, using Unifrac analyses of clone library sequence data. Differences in composition were generally greater between basins (interbasins) than within a basin (intrabasin). These differences were primarily linked to taxonomic variation in the composition of Prymnesiophyceae and Prasinophyceae whereas Chrysophyceae were phylogenetically similar in all libraries. These data provide better knowledge of PPE community structure across the world ocean and are crucial in assessing their evolution and contribution to CO2 fixation, especially in the context of global climate change
1H-NMR-Based Metabolic Profiling of Maternal and Umbilical Cord Blood Indicates Altered Materno-Foetal Nutrient Exchange in Preterm Infants
Background: Adequate foetal growth is primarily determined by nutrient availability, which is dependent on placental nutrient transport and foetal metabolism. We have used 1H nuclear magnetic resonance (NMR) spectroscopy to probe the metabolic adaptations associated with premature birth. Methodology: The metabolic profile in 1H NMR spectra of plasma taken immediately after birth from umbilical vein, umbilical artery and maternal blood were recorded for mothers delivering very-low-birth-weight (VLBW) or normo-ponderal full-term (FT) neonates. Principal Findings: Clear distinctions between maternal and cord plasma of all samples were observed by principal component analysis (PCA). Levels of amino acids, glucose, and albumin-lysyl in cord plasma exceeded those in maternal plasma, whereas lipoproteins (notably low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) and lipid levels were lower in cord plasma from both VLBW and FT neonates. The metabolic signature of mothers delivering VLBW infants included decreased levels of acetate and increased levels of lipids, pyruvate, glutamine, valine and threonine. Decreased levels of lipoproteins glucose, pyruvate and albumin-lysyl and increased levels of glutamine were characteristic of cord blood (both arterial and venous) from VLBW infants, along with a decrease in levels of several amino acids in arterial cord blood. Conclusion: These results show that, because of its characteristics and simple non-invasive mode of collection, cord plasma is particularly suited for metabolomic analysis even in VLBW infants and provides new insights into the materno-foetal nutrient exchange in preterm infants
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