Décrochements pelliculaires et gélifluxion en nappe sur le versant nord des drumlins, région du lac Minto, Québec subarctique

L'examen des photographies aériennes à l'échelle de 1/40 000 d'un secteur s'étendant à l'est de la baie d'Hudson, entre le 56° et le 58° de latitude nord, soit dans la région du lac Minto, a révélé l'existence de phénomènes d'érosion par des mouvements de masse sur le versant nord des drumlins. La description des formes d'érosion sur le terrain et l'étude des sols et des paléosols ont permis de distinguer deux processus responsables de l'évolution du versant d'un drumlin, soit les décrochements pelliculaires et la gélifluxion en nappe. Les premiers sont des mouvements rapides qui laissent des cicatrices très caractéristiques, généralement en forme d'hémicycles, alors que la gélifluxion en nappe se rapporte à des écoulements lents et superficiels de matériel sur une pente. L'interprétation des sols et 19 radiodatations obtenues à partir de matériel organique enfoui ont permis de distinguer deux phases dans l'évolution du versant: une phase de stabilité s'étendant de 7000-6000 ans BP (âge de la déglaciation) à ca 2200 ans BP (âge du plus ancien décrochement survenu sur le versant) et caractérisée par le développement de sols de type podzolique et une phase d'instabilité, de ca 2200 ans BP à nos jours. Les feux survenus dans le contexte d'une détérioration générale du climat au Néoglaciaire ont depuis cette date contribué à l'ouverture graduelle du paysage végétal et à la formation d'importantes combes à neige sur le versant nord des drumlins. Les modifications apportées au régime hydrique des sols auraient joué un rôle important dans le développement des mouvements de masse.Air photo (1/40 000) interpretation of a sector located east of Hudson Bay, between 56° and 58° N, in the lac Minto area, showed important slope erosion caused by mass movements on the north slope of drumlins. Skinflows and sheet gelifluction were identified as two distinctive processes involved in slope erosion, mostly from detailed field description of erosion features and soil and paleosol analysis. Skinflows left typical hemicyclic scars after rapid detachment failure, whereas sheet gelifluction refered to slow surficial flows of soil material along the slope. Two distinctive periods of slope development were identified from soil development and radiocarbon dating of 19 buried organic horizons : the first period, from 7000-6000 yr BP (approximate age of déglaciation) to 2200 yr BP (age of the oldest mass movement recorded along the slope), was characterized by podzol-like soil development and slope stability, and the second period, from ca 2200 yr BP to Present, by active slope erosion. Fire occurrences during the Neoglacial contributed to reduction of the forest cover and development of snowbanks on the north slope of drumlins. It is thought that a modified water soil regime was instrumental in the development of mass movements.Die Untersuchung von Luftaufnahmen im Massstab 1/40 000 eines Gebiets, das sich ostlich der Hudson Bay zwischen dem 56° und 58° nôrdlicher Breite erstreckt, d.h. im Gebiet des Minto-Sees, zeigt Erosionserscheinungen durch Bewegung von solidem Material auf dem Nordhang der Drumlins. Die Beschreibung der Erosionsformen und die Studie der Bôden und Palàobôden fùhrten zur Unterscheidung von zwei Prozessen, welche fur die Entwicklung des Hangs eines Drumlins verantwortlich sind, nàmlich Oberflàchen-Verschiebungen und Oberflâchen-Erdfluss. Die ersteren sind schnelle Bewegungen, die sehrtypische Narben hinterlassen, die im allgemeinen die Form von Halbkreisen haben, wohingegen der Oberflâchen-Erdfluss dem langsamen Abfluss von Material and er Oberflàche eines Hangs zugeschrieben wird. Die interpretation der Bôden und 19 Radiodatierungen, die aus vergrabenem organischem Material gewonnen wurden, fuhren zur Unterscheidung von zwei Phasen in der Entwicklung des Hangs : Eine Phase der Stabilitàt, die sich von 7000-6000 Jahren v.u.Z. (Zeit der Enteisung) bis etwa 2200 Jahre v.u.Z. erstreckt (Zeit der àltesten Verschiebung, die an dem Hang stattgefunden hat) und durch die Entwicklung von Podsolbôden charakterisiert ist und eine Phase der lnstabilitat von etwa 2200 Jahren v.u.Z. bis heute. Feuer, die im Kontext einer allgemeinen Verschlechterung des Klimas in der Neoglazialzeit auftraten, haben seit dieser Zeit zur schrittweisen Ôffnung der Walddecke und zur BiIdung bedeutender Schneebànke auf dem Nordhang der Drumlins gefuhrt. Die Verânderungen der Dynamik der Wasser-bewegungen in den Bôden sollen eine wichtige RoIIe in der Entwicklung der Bewegung von solidem Material gespielt haben

The INSU and DMN network of ST radars

Due to their capabilities of measuring wind profiles with good time and height resolution, Stratosphere-Troposphere (ST) are well adapted to carry out atmospheric research. In France, a Very High Frequency (VHF) and an Ultrahigh Frequency (UHF) ST radar are working for research purposes. The INSU (Institut National des Sciences de l'Univers) and the DMN (Direction de la Meteorologie Nationale) networks are discussed

Overcoming establishment thresholds for peat mosses in human-made bog pools

Globally, peatlands have been affected by drainage and peat extraction, with adverse effects on their functioning and services. To restore peat‐forming vegetation, drained bogs are being rewetted on a large scale. Although this practice results in higher groundwater levels, unfortunately it often creates deep lakes in parts where peat was extracted to greater depths than the surroundings. Revegetation of these deeper waters by peat mosses appears to be challenging due to strong abiotic feedbacks that keep these systems in an undesired bare state. In this study, we theoretically explore if a floating peat mat and an open human‐made bog lake can be considered two alternative stable states using a simple model, and experimentally test in the field whether stable states are present, and whether a state shift can be accomplished using floating biodegradable structures that mimic buoyant peat. We transplanted two peat moss species into these structures (pioneer sp. Sphagnum cuspidatum and later‐successional sp. S. palustre) with and without additional organic substrate. Our model suggests that these open human‐made bog lakes and floating peat mats can indeed be regarded as alternative stable states. Natural recovery by spontaneous peat moss growth, i.e., a state shift from open water to floating mats, is only possible when the water table is sufficiently shallow to avoid light limitation (<0.29 m at our site). Our experiment revealed that alternative stable states are present and that the floating structures facilitated the growth of pioneer S. cuspidatum and vascular plants. Organic substrate addition particularly facilitated vascular plant growth, which correlated to higher moss height. The structures remained too wet for the late‐successional species S. palustre. We conclude that open water and floating peat mats in human‐made bog lakes can be considered two alternative stable states, and that temporary floating establishment structures can induce a state shift from the open water state to peat‐forming vegetation state. These findings imply that for successful restoration, there is a clear water depth threshold to enable peat moss growth and there is no need for addition of large amounts of donor‐peat substrate. Correct species selection for restoration is crucial for success

Emissions of methane from northern peatlands : a review of management impacts and implications for future management options

This work was funded in part by the GHG-Europe project (EU grant agreement number: 244122) Greenhouse gases Europe projectPeer reviewedPublisher PD

Aquaporin-4 and GPRC5B: old and new players in controlling brain oedema

Brain oedema is a life-threatening complication of various neurological conditions. Understanding molecular mechanisms of brain volume regulation is critical for therapy development. Unique insight comes from monogenic diseases characterized by chronic brain oedema, of which megalencephalic leukoencephalopathy with subcortical cysts (MLC) is the prototype. Variants in MLC1 or GLIALCAM, encoding proteins involved in astrocyte volume regulation, are the main causes of MLC. In some patients, the genetic cause remains unknown. We performed genetic studies to identify novel gene variants in MLC patients, diagnosed by clinical and MRI features, without MLC1 or GLIALCAM variants. We determined subcellular localization of the related novel proteins in cells and in human brain tissue. We investigated functional consequences of the newly identified variants on volume regulation pathways using cell volume measurements, biochemical analysis and electrophysiology. We identified a novel homozygous variant in AQP4, encoding the water channel aquaporin-4, in two siblings, and two de novo heterozygous variants in GPRC5B, encoding the orphan G protein-coupled receptor GPRC5B, in three unrelated patients. The AQP4 variant disrupts membrane localization and thereby channel function. GPRC5B, like MLC1, GlialCAM and aquaporin-4, is expressed in astrocyte endfeet in human brain. Cell volume regulation is disrupted in GPRC5B patient-derived lymphoblasts. GPRC5B functionally interacts with ion channels involved in astrocyte volume regulation. In conclusion, we identify aquaporin-4 and GPRC5B as old and new players in genetic brain oedema. Our findings shed light on the protein complex involved in astrocyte volume regulation and identify GPRC5B as novel potentially druggable target for treating brain oedema

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Une histoire de la "Maison Archéologie & Ethnologie, René-Ginouvès"

A l'occasion des quinze ans d'existence de la Maison Archéologie & Ethnologie, René-Ginouvès (MAE) de Nanterre, Pierre Rouillard retrace, dans le dernier numéro de la revue du Comité pour l’histoire du CNRS, Histoire de la recherche contemporaine (CNRS Éditions), les grandes étapes de la création de la MAE. Des prémices de sa conception, avec les débats sur la discipline archéologique, dans les années 1960, jusqu'à son inauguration en 1998 et son intégration dans le réseau des MSH d'aujourd'h..