A quantitative approach of the morphological changes in the middle Garonne river (South-west France) during the last 150 years

International audienceThe aim of this study is to periodize the geomorphological evolution of the Middle Garonne river from Toulouse to the tarn junction from middle 19th century to Present, in order to highlight the respective role of climate vs anthropization as diving force

Construction géohistorique du "sauvage" de la Garonne toulousaine : quelle part de naturalisé dans les paysages fluviaux ? part. 1

International audienceThe Garonne between Toulouse and the confluence of the Tarn is composed of many wetlands. Here, v arious protective dev ices would label a "wild" dim ension to the river, supporting its maintenance and conservation without actually questioning their original condition. Given this situation, how to consider the part of naturalness of river landscapes of the Garonne today ? According to managers, the Garonne has a strong image of "wild" river while geohistorical heritage rather shows Garonne im pacted by human activities. This work explores the meaning of the gap between the reality and geohistorical conveyed by contemporary representations of the river.La Garonne toulousaine (entre Toulouse et la confluence du Tarn) est composée de nombreuses annexes fluviales : bras-morts, zones humides et ripisylves. Ici, différents dispositifs de protection labellisent une dimension « sauvage » pour le fleuve, favorisant son maintien et sa conserv ation sans réellement s'interroger sur leur état d'origine. Face à ce constat, com m ent considérer la part de naturalité des paysages fluviaux de la Garonne toulousaine aujourd'hui ? Au dire des gestionnaires, la Garonne possède une image forte de fleuve « sauvage » alors que l'héritage géohistorique montre plutôt une Garonne impactée par les activités humaines. Ce travail interroge le sens du décalage entre cette réalité géohistorique et l'image véhiculée par les représentations contemporaines du fleuve

A Practical Catalytic Reductive Amination of Carboxylic Acids

We report reductive alkylation reactions of amines using carboxylic acids as nominal electrophiles. The two-step reaction exploits the dual reactivity of phenylsilane and involves a silane-mediated amidation followed by a Zn(OAc)2-catalyzed amide reduction. The reaction is applicable to a wide range of amines and carboxylic acids and has been demonstrated on a large scale (305 mmol of amine). The rate differential between the reduction of tertiary and secondary amide intermediates is exemplified in a convergent synthesis of the antiretroviral medicine maraviroc. Mechanistic studies demonstrate that a residual 0.5 equivalents of carboxylic acid from the amidation step is responsible for the generation of silane reductants with augmented reactivity, which allow secondary amides, previously unreactive in zinc/phenylsilane systems, to be reduced

Le gisement de méga-fossiles ligneux de Bourret (moyenne vallée de la Garonne) : processus de formation et signification climatique

International audienceLe gisement de mégafossiles ligneux de Bourret est le plus important identifié à ce jour en vallée de Garonne. La datation14C de 8 des 17 troncs subfossiles de Quercus extraits s’échelonne entre 8 300 et 4 200 ans cal. BP. Elles attestent du caractèrepartiellement remanié du gisement. Certains de ces bois ont subi une ou des phases de stockage temporaire d’une durée compriseentre 4 100 et 1 000 ans avant d’être incorporés définitivement dans la basse plaine. Les bois les plus anciens ont donc connu unehistoire complexe comportant une phase d’injection dans le chenal, de stockage dans des unités intermédiaires, puis une érosion etune nouvelle phase de dépôt avec la charge de fond. Les bois les plus jeunes résultent quant à eux d’une injection directe depuis laripisylve dans le système fluvial. L’agrégation des dates obtenues sur ce site et sur les sites découverts antérieurement s’organisent en3 agrégats (env. 8 200, 5 200 et 4 200 ans cal. BP). Ceci suggère que l’injection des bois dans le système fluvial est liée à des phasesde forte activité hydrosédimentaire. Le synchronisme avec les Rapid Climate Changes (RCC) suggère un contrôle climatique sur ceprocessus, ce qui nous amène à proposer un schéma conceptuel de formation des gisements de bois fossiles

The subfossil tree deposits from the Garonne Valley and their implications on Holocene alluvial plain dynamics

International audienceSubfossil tree trunks deposits are common in large rivers, but their status as a source for dating alluvial sequences and palaeoenvironmental studies is still discussed. Particularly their origin and the process(es) of deposition as well as a possible remobilization were pointed as a limit to their use to document river alluvial changes. In this work we report the discovery of the largest subfossil trunks deposits in the Garonne valley. These new data are compared to the previous ones. A set of 17 tree trunks and more than 300 smaller wood fragments were collected. The xylologic study shows the prevalence of Quercus and a single occurrence of Ulmus. These two hardwood species are commonly associated with riparian forest. The 14C dating carried out on seven trunks and a single branch of Quercus on the outermost identified growth rings, indicates age ranging from 8400-8000 cal. BP for the oldest fragment (bough) to 4300-4000 cal. BP for the most recent tree trunk. Radiocarbon ages of the trunks are aggregated into two main periods: 5300-5600 cal. BP (four trunks) and 4300-4000 cal. BP (three trunks). The radiocarbon (charcoal) dating of the top of the alluvial sequence overlaying the trunks gives an age between 1965-1820 and 1570-1810 cal. BP, i.e. between the 2nd and the 5th c. AD. In addition, the discovery of two unpublished subfossil tree trunks deposits in Finhan are reported (six trunks). At the light of these results, we discuss previously proposed models for the Garonne floodplain building

Synthesis of 2,6-trans-tetrahydropyrans using a palladium-catalyzed oxidative heck redox-relay strategy

The C-aryl-tetrahydropyran motif is prevalent in nature in a number of natural products with biological activity; however, this challenging architecture still requires novel synthetic approaches. We demonstrate the application of a stereoselective Heck redox-relay strategy for the synthesis of functionalized 2,6-trans-tetrahydropyrans in excellent selectivity in a single step from an enantiopure dihydropyranyl alcohol, proceeding through a novel exo-cyclic migration. The strategy has also been applied to the total synthesis of a trans-epimer of the natural product centrolobine in excellent yield and stereoselectivity

A Fishery Manager's Guidebook, Second Edition

A Fishery Managers' Guidebook was first published as an FAO Fisheries Technical Paper in 2002 to meet the need for information and guidance on the broad and often complex task of fisheries management. Based on subsequent experience and feedback gained from publication of the first edition, this new volume, has been expanded to provide broader coverage of the key elements of the task and updated in order to keep track of the rapid developments in theory and practice as academics and practitioners struggle to confront the many challenges facing modern fisheries management

Prioritization of candidate causal genes for asthma in susceptibility loci derived from UK Biobank

Kim Valette et al. perform a genomic study on asthma integrating genome-wide association study, functional mapping using lung and blood transcriptome-wide profiles, as well as Mendelian randomization. They show candidate causal genes expressed in lung and blood tissues that are putative therapeutic targets for asthma