Milieux et peuplements en Bas-Dauphiné

Date de l'opération : 2007 (PC) L’étude des sources historiques et cartographiques depuis la fin du Moyen Âge La période comprise entre la fin du Moyen Âge et le XIXe s. a fait l’objet de nouvelles recherches en 2007 qui documentent l’occupation et la gestion du sol et la démographie historique des quatre ou cinq derniers siècles, une période qui a vu un développement sociétal considérable dans les milieux palustres et alluviaux des Basses Terres dauphinoises, lors d’un épisode de péjoration ..

Comment élaborer un environnement interactif adapté à la formation par le projet ? Étude d'un processus de conception

International audienceAujourd'hui, la formation ouverte et à distance (FOAD), dans l'enseignement supérieur en France, a dépassé le stade des projets et des expérimentations pilotes. On parle de campus numérique, de plate-forme de formation à distance, de LCMS, de générateur de documents hypermédias, etc. En ce sens, les ingénieries et recherches, dans le domaine, semblent s'attacher prioritairement à des questions de médiatisation de contenus, de production standardisée, d'indexation normée par des méta-données en vue de leur ré-exploitation et/ou mutualisation. Comme si les problématiques de contenus étaient premières au regard de celles des relations de formation. D'autres travaux, comme ceux sur l'apprentissage coopératif et le travail collaboratif (Bourguin et al., 2002), mettent cependant l'accent sur l'instrumentation des relations et interactions sociales et cognitives des acteurs de la formation. C'est dans une perspective proche, bien qu'un peu différente, que s'inscrivent nos travaux, qui cherchent à articuler pratiques de travail et de recherche, par la modélisation d'instruments et de dispositifs, développés à partir de situations concrètes de travail. Notre démarche a consisté, en premier lieu, à conduire un processus d'ingénierie en réponse à une commande d'instrumentation d'un dispositif de formation existant. L'analyse de cette demande, la prise en compte de son contexte et le processus de conception lui-même ont permis de travailler sur une triple problématique : pédagogique, économique, technologique. Ce processus d'ingénierie a débouché sur la construction d'un dispositif, intitulé Appui et la mise au point d'une plate-forme, visant à prendre en compte cette problématique. Les usages du dispositif et leur réinterrogation nous ont permis, en second lieu, d'envisager, de façon plus générale, une modélisation de l'accompagnement de projet à distance à partir du système de représentation des actions et interactions, intégré dans le dispositif. En conclusion de l'article, nous situerons les limites du modèle élaboré, en questionnant les conditions de sa reproductibilité

Les fossés bordiers historiques et l'histoire agraire rhodanienne*

Une démarche collective menée depuis l'identification d'un réseau parcellaire jusqu'à son interprétation historique et paléoécologique est présentée. La constitution d'une équipe regroupée autour de la géoarchéologie, dans laquelle les travaux de photo-carto-interprétation ont pu directement donner lieu à des vérifications sur le terrain puis à des études naturalistes systématiques, permet de comprendre la dynamique de fonctionnement des réseaux hydrauliques et de proposer un premier schéma sur l'évolution des paysages agraires depuis deux mille ans. De telles études, conduites au centre même d'anciens terroirs cultivés, complètent avantageusement les données économiques recueillies sur les sites d'habitat.Historical ditches and agrarian history along the Rhone. -- The collective work ranging from identifying a network to making a historical and paleoecological interpretation thereof is presented. Forming a team around geoarcheology, wherein photo-carto-interpretations could be directly verified in the field and used for systematic naturalist studies, led to understanding how hydraulic networks worked and proposing an initial interpretation of how farming landscapes have evolved over the past two thousand years. Conducted in the heart of formerly cultivated zones, such studies complete economic data about dwelling sites

Les fossés bordiers historiques et l'histoire agraire rhodanienne

Une démarche collective menée depuis l'identification d'un réseau parcellaire jusqu'à son interprétation historique et paléoécologique est présentée. La constitution d'une équipe regroupée autour de la géoarchéologie, dans laquelle les travaux de photo-carto-interprétation ont pu directement donner lieu à des vérifications sur le terrain puis à des études naturalistes systématiques, permet de comprendre la dynamique de fonctionnement des réseaux hydrauliques et de proposer un premier schéma sur l'évolution des paysages agraires depuis deux mille ans. De telles études, conduites au centre même d'anciens terroirs cultivés, complètent avantageusement les données économiques recueillies sur les sites d'habitat.Historical ditches and agrarian history along the Rhone. -- The collective work ranging from identifying a network to making a historical and paleoecological interpretation thereof is presented. Forming a team around geoarcheology, wherein photo-carto-interpretations could be directly verified in the field and used for systematic naturalist studies, led to understanding how hydraulic networks worked and proposing an initial interpretation of how farming landscapes have evolved over the past two thousand years. Conducted in the heart of formerly cultivated zones, such studies complete economic data about dwelling sites

Evolution and management of humid landscapes in Northern Dauphiné (Rhône valley, France): contribution of charcoal and wood studies

National audienceEvolution and management of humid landscapes in Northern Dauphiné (Rhône valley, France): contribution of charcoal and wood studie

Blocking light in compact Riemannian manifolds

We study compact Riemannian manifolds for which the light between any pair of points is blocked by finitely many point shades. Compact flat Riemannian manifolds are known to have this finite blocking property. We conjecture that amongst compact Riemannian manifolds this finite blocking property characterizes the flat metrics. Using entropy considerations, we verify this conjecture amongst metrics with nonpositive sectional curvatures. Using the same approach, K. Burns and E. Gutkin have independently obtained this result. Additionally, we show that compact quotients of Euclidean buildings have the finite blocking property. On the positive curvature side, we conjecture that compact Riemannian manifolds with the same blocking properties as compact rank one symmetric spaces are necessarily isometric to a compact rank one symmetric space. We include some results providing evidence for this conjecture.Comment: 19 page

Intricate visibility effects from resolved emission of young stellar objects: the case of MWC158 observed with the VLTI

In the course of our VLTI young stellar object PIONIER imaging program, we have identified a strong visibility chromatic dependency that appeared in certain sources. This effect, rising value of visibilities with decreasing wavelengths over one base, is also present in previous published and archival AMBER data. For Herbig AeBe stars, the H band is generally located at the transition between the star and the disk predominance in flux for Herbig AeBe stars. We believe that this phenomenon is responsible for the visibility rise effect. We present a method to correct the visibilities from this effect in order to allow "gray" image reconstruction software, like Mira, to be used. In parallel we probe the interest of carrying an image reconstruction in each spectral channel and then combine them to obtain the final broadband one. As an illustration we apply these imaging methods to MWC158, a (possibly Herbig) B[e] star intensively observed with PIONIER. Finally, we compare our result with a parametric model fitted onto the data.Comment: 14 pages, 7 figure

Additional Clues for a Protective Role ofVitamin D in Neurodegenerative Diseases: 1,25-Dihydroxyvitamin D3 Triggers an Anti-Inflammatory Response in BrainPericytes

International audienceEpidemiological and experimental studies suggest that 1,25-dihydroxyvitamin D3 (1,25D) plays a neuroprotectiverole in neurodegenerative diseases including Alzheimer's disease. Most of the experimental data regarding the genes regulatedby this hormone in brain cells have been obtained with neuron and glial cells. Pericytes play a critical role in brain function thatencompasses their classical function in blood-brain barrier control and maintenance. However, the gene response of brain pericyteto 1,25D remains to be investigated. Analyses of the transcriptomic response of human brain pericytes to 1,25D demonstrate thathuman brain pericytes in culture respond to 1,25D by regulating genes involved in the control of neuroinflammation. In addition,ericytes respond to the pro-inflammatory cytokines tumor necrosis factor and Interferon by inducing the expression of theCYP27B1 gene which is involved in 1,25D synthesis. Taken together, these results suggest that neuroinflammation could triggerthe synthesis of 1,25D by brain pericytes, which in turn respond to the hormone by a global anti-inflammatory response. Thesefindings identify brain pericytes as a novel 1,25D-responsive cell type and provide additional evidence for the potential value ofvitamin D in the prevention or therapy of Alzheimer's disease and other neurodegenerative/neuropsychiatric diseases associatedwith an inflammatory component

Sculpting the disk around T Cha: an interferometric view

(Abridged) Circumstellar disks are believed to be the birthplace of planets and are expected to dissipate on a timescale of a few Myr. The processes responsible for the removal of the dust and gas will strongly modify the radial distribution of the dust and consequently the SED. In particular, a young planet will open a gap, resulting in an inner disk dominating the near-IR emission and an outer disk emitting mostly in the far-IR. We analyze a full set of data (including VLTI/Pionier, VLTI/Midi, and VLT/NaCo/Sam) to constrain the structure of the transition disk around TCha. We used the Mcfost radiative transfer code to simultaneously model the SED and the interferometric observations. We find that the dust responsible for the emission in excess in the near-IR must have a narrow temperature distribution with a maximum close to the silicate sublimation temperature. This translates into a narrow inner dusty disk (0.07-0.11 AU). We find that the outer disk starts at about 12 AU and is partially resolved by the Pionier, Sam, and Midi instruments. We show that the Sam closure phases, interpreted as the signature of a candidate companion, may actually trace the asymmetry generated by forward scattering by dust grains in the upper layers of the outer disk. These observations help constrain the inclination and position angle of the outer disk. The presence of matter inside the gap is difficult to assess with present-day observations. Our model suggests the outer disk contaminates the interferometric signature of any potential companion that could be responsible for the gap opening, and such a companion still has to be unambiguously detected. We stress the difficulty to observe point sources in bright massive disks, and the consequent need to account for disk asymmetries (e.g. anisotropic scattering) in model-dependent search for companions.Comment: Removed the word "first" in the abstract of the paper: "obtained with the first 4-telescope combiner (VLTI/Pionier)

Electronic structure of epitaxial graphene layers on SiC: effect of the substrate

Recent transport measurements on thin graphite films grown on SiC show large coherence lengths and anomalous integer quantum Hall effects expected for isolated graphene sheets. This is the case eventhough the layer-substrate epitaxy of these films implies a strong interface bond that should induce perturbations in the graphene electronic structure. Our DFT calculations confirm this strong substrate-graphite bond in the first adsorbed carbon layer that prevents any graphitic electronic properties for this layer. However, the graphitic nature of the film is recovered by the second and third absorbed layers. This effect is seen in both the (0001)and $(000\bar{1})$ 4H SiC surfaces. We also present evidence of a charge transfer that depends on the interface geometry. It causes the graphene to be doped and gives rise to a gap opening at the Dirac point after 3 carbon layers are deposited in agreement with recent ARPES experiments (T.Ohta et al, Science {\bf 313} (2006) 951)