Éditeur(s) : HAL CCSD Springer
Résumé : Third International Workshop, MLMI 2012, Held in Conjunction with MICCAI 2012
International audience
Universal Nearest Neighbours (unn) is a classifier recently proposed, which can also effectively estimates the posterior probability of each classification act. This algorithm, intrinsically binary, requires the use of a decomposition method to cope with multiclass problems, thus reducing their complexity in less complex binary subtasks. Then, a reconstruction rule provides the final classification. In this paper we show that the application of unn algorithm in conjunction with a reconstruction rule based on the posterior probabilities provides a classification scheme robust among different biomedical image datasets. To this aim, we compare unn performance with those achieved by Support Vector Machine with two different kernels and by a k Nearest Neighbours classifier, and applying two different reconstruction rules for each of the aforementioned classification paradigms. The results on one private and five public biomedical datasets show satisfactory performance.
Machine Learning in Medical Imaging
Nice, France

hal-00958909
https://hal.archives-ouvertes.fr/hal-00958909
https://hal.archives-ouvertes.fr/hal-00958909/document
https://hal.archives-ouvertes.fr/hal-00958909/file/Miccai.pdf
DOI : 10.1007/978-3-642-35428-1_15

Éditeur(s) : Scientific Technical Research Council Turkey-tubitak
Résumé : In 2002, the Bosphorus outlet was mapped using an EM 300 multibeam echo-sounder together with a Chirp sonar system. This survey, carried out on board the Ifremer RV 'Le Suroit' in the frame of the BlaSON project, completes the data previously acquired directly at the mouth of the Bosphorus by Di Iorio et al. (1999) in the frame of a NATO SACLANT Undersea Research project using jointly the NATO RV Alliance, and the Turkish Navy Survey ship 'Cubuklu'. This acoustic imaging has identified a canyon system at the slope and a shallow marine fan, which contains shelf incisions extending the Istanbul Strait incision. Multibeam bathymetry, ultra-high resolution seismic profiling and coring correlations on this subaqueous fan area allowed reconstruction of morphology and patterns of sediment distribution indicative of high energy sediment transport processes. The discovery of a shallow water/shelf type fan directly off shore from the Bosphorus and connected to its outlet is consistent with the theories of sudden discharges of large volumes of water. Age dating obtained at the bottom of this subaqueous shelf fan yielded an age of 6700 yr C-14 BP (uncorrected age) for the first marine mollusc encountered at the base. This is in accordance with a last and abrupt reconnection of the Marmara Sea to the Black Sea. A detailed morphological map of the shelf and slope along with seismic profile interpretation and core correlation is presented here. A synthesis is proposed to explain the formation of this subaqueous fan and its relationship with the last connection between Black and Marmara seas aft er the Last Glacial Maximum. This interpretation can be summarized as follows: stage A corresponds to the first erosion surface seen on the shelf related to the Last Glacial Maximum low stand; stage B is the ravine surface onlapping to ca. -30, -40 m; stage C is a second erosional surface related to a sea level fall and eroding most of underlying Unit 1B; and stage D corresponds to the onset of the fan deposit during a period of high water run-off from the Black Sea entering from the Bosphorus. Avulsion branches show that this fan has been active for a long time.
Turkish Journal Of Earth Sciences (1300-0985) (Scientific Technical Research Council Turkey-tubitak), 2011 , Vol. 20 , N. 3 , P. 287-305

Droits : 2011 TÜBİTAK
http://archimer.ifremer.fr/doc/00036/14676/13677.pdf
http://archimer.ifremer.fr/doc/00036/14676/

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy P - Oxford Open Option A Oxford University Press (OUP)
Résumé : International audience
It is well known that sedimentary rocks having same porosity can have very different pore size distribution. The pore distribution determines many characteristics of the rock, among which its transport properties are often the most useful. Multifractal analysis is a powerful tool that is increasingly used to characterize the pore space. In this study, we performed multifractal analysis of pore distribution on simulated sedimentary rocks using the relaxed bidisperse ballistic deposition model (RBBDM). The RBBDM can generate a 3-D structure of sedimentary rocks of variable porosity by tuning the fraction p of particles of two different sizes. We also performed multifractal analysis on two samples of real sedimentary rock to compare with the simulation studies. One sample, an oolitic limestone is of high porosity (40 per cent) while the other is a reefal carbonate of low porosity, around 7 per cent. 2-D sections of X-ray microtomographs of the real rocks were stacked sequentially to reconstruct the real rock specimens. Both samples show multifractal character. The results from analysis of real rock agree quite well with the simulated structure of low porosity. The simulated rock of high porosity showed a weak multifractal nature though the real rock sample of similar porosity was found to be strongly multifractal. We propose a ‘structure parameter’ ξ which is a function of porosity and the generalized dimensions, and controls the transport properties of the rock.
ISSN: 0956-540X

hal-01174142
https://hal.archives-ouvertes.fr/hal-01174142
DOI : 10.1093/gji/ggu417

Éditeur(s) : HAL CCSD
Résumé : International audience
This paper deals with the study of the kinematic dimension of scribbling activities executed by kindergarten children aged from 3 to 6 years old from three grades. For this purpose, three sigma-lognormal features, six classical ones and one hybrid feature related to visuo-motor skills are extracted from scribbles realized using five different Type Grib. The statistical analysis of these data illustrates that sigma-lognormal modeling can satisfactorily reconstruct kindergarten children’s scribbles. Moreover, this preliminary study confirms that there are significant differences between grades with respect to six of the features we studied, regardless of the nature of the scribbling movement made by children. These features are related to rapidity, fluidity and precision of linear and curvilinear movements used for scribbling tasks.
17th Biennial Conference of the International Graphonomics Society
Pointe-à-Pitre, Guadeloupe

hal-01165910
https://hal.univ-antilles.fr/hal-01165910
https://hal.univ-antilles.fr/hal-01165910/document
https://hal.univ-antilles.fr/hal-01165910/file/IGS_2015_submission_28.pdf

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Le violent séisme qui a secoué Haïti et sa capitale le 12 janvier 2010 dernier a laissé des séquelles au sein de la population haïtienne déjà fragilisée par la violence, la pauvreté et aussi par des catastrophes naturelles répétées (ouragans, inondations, érosion, etc.). Ce séisme, aussi prévisible qu’il soit, est une catastrophe naturelle et humanitaire sans précédent dont les principales causes sont l’absence de constructions et d’infrastructures solides, bâties selon les normes parasismiques, l’occupation anarchique de l’espace urbain par les populations et les nombreuses irrégularités incontestées observées dans le domaine de l’urbanisme. En outre, ce séisme s’est produit à un moment où l’on commençait à observer dans le pays un élan de stabilisation sur le plan politique, un mouvement de croissance économique ainsi qu’un début d’amélioration des conditions de vie des populations. La catastrophe est venue freiner cette dynamique socioéconomique tout en amplifiant les problèmes existants et en engendrant d’autres difficultés et d’autres défis. Cet article analyse, à travers des témoignages de première main et un état des lieux, les différents impacts de cette catastrophe sur la population locale ainsi que les interrogations et les incertitudes diverses de cette population concernant son avenir.
On January the twelfth 2010, Haiti and its capital have been devastated by a very strong earthquake that has provoked many aftereffects among the local population since that population had already been weakened before by street violence, poverty and by frequent natural disasters such as hurricanes, floods... That earthquake, even foreseeable, has given way to an important disaster whose causes are the absence of well built infrastructures and buildings, the anarchic use of urban spaces by the population, and multiple irregularities in town planning issues. Furthermore, that earthquake took place in a moment when that population was on its way of improvement politically, socially and economically. The disaster has stopped that dynamic, intensifying the existing problems and challenges, and creating new ones. This article analyze – through first hand testimonies, statements and observations – the impacts of such a disaster on the local population as well as diverse inquiries and doubts of that population on its future.
Haïti

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.4842
http://journals.openedition.org/etudescaribeennes/4842

Éditeur(s) : HAL CCSD European Geosciences Union (EGU)
Résumé : International audience
Holocene climate fluctuations and human activity since the Neolithic have shaped present-day Mediter-ranean environments. Separating anthropogenic effects from climatic impacts to better understand Mediterranean pale-oenvironmental changes over the last millennia remains a challenging issue. High-resolution pollen analyses were un-dertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the late Holocene, and three superimposed arid events are recorded at 4600–4300, 2800–2400 and 1300–1100 cal BP. These periods of high-frequency climate variability coincide in time with the rapid climatic events observed in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of sclerophyllous taxa and loss of forest cover result from anthropogenic impact. Classical Antiquity is characterized by a major reforestation event related to the concentration of rural activity and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while the cover of olive, chestnut and walnut expands in relation to increasing human influence. The present-day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.
ISSN: 1814-9324

hal-01447627
https://hal-univ-tlse2.archives-ouvertes.fr/hal-01447627
https://hal-univ-tlse2.archives-ouvertes.fr/hal-01447627/document
https://hal-univ-tlse2.archives-ouvertes.fr/hal-01447627/file/Azuara%20et%20al%202015_cor.pdf
DOI : 10.5194/cp-11-1769-2015

Éditeur(s) : HAL CCSD European Geosciences Union (EGU) European Geosciences Union
Résumé : The Moroccan Mediterranean coast is located in one of the area's most vulnerable to extreme weather events or tsunami hazards. The objective of this research is to reconstruct the historical extreme submersion-event record using sea-induced deposits preserved in coastal lagoon. The Nador lagoon is the largest Moroccan lagoon (115 km2). It is located along the western Mediterranean, which has a high cyclogenetic character and is exposed to tsunamis from the Alboran Sea. The sandy barrier which separates the lagoon from the Mediterranean Sea is marked by much overwash, which indicate how intensely it has been exposed to the adverse sea events through history. Using the UWITEC© gravity coring platform, an undisturbed MC4.5 core (1.15 m long) was successfully sampled in the studied lagoon. To identify extreme sea events, a multi-proxy approach was applied combining sedimentological and geochemical data. Three paleoevents were identified; all of them are concentrated over the last 500 years, and the most recent event corresponds to the 1889 storm. For the others deposits, it is difficult to determine exactly their origin; however, the high frequency of storm events over the relevant period and the absence of historical tsunamis evidence is more in favor of the meteorological origin.
ISSN: 1561-8633

hal-01146451
https://hal.archives-ouvertes.fr/hal-01146451
DOI : 10.5194/nhess-15-203-2015

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Tropical cyclone (TC) waves can severely damage coral reefs. Models that predict where to find such damage (the 'damage zone') enable reef managers to: 1) target management responses after major TCs in near-real time to promote recovery at severely damaged sites; and 2) identify spatial patterns in historic TC exposure to explain habitat condition trajectories. For damage models to meet these needs, they must be valid for TCs of varying intensity, circulation size and duration. Here, we map damage zones for 46 TCs that crossed Australia's Great Barrier Reef from 1985–2015 using three models – including one we develop which extends the capability of the others. We ground truth model performance with field data of wave damage from seven TCs of varying characteristics. The model we develop (4MW) out-performed the other models at capturing all incidences of known damage. The next best performing model (AHF) both under-predicted and over-predicted damage for TCs of various types. 4MW and AHF produce strikingly different spatial and temporal patterns of damage potential when used to reconstruct past TCs from 1985–2015. The 4MW model greatly enhances both of the main capabilities TC damage models provide to managers, and is useful wherever TCs and coral reefs co-occur.
ISSN: 2045-2322

Droits : http://creativecommons.org/licenses/by/
hal-01330362
https://hal-univ-perp.archives-ouvertes.fr/hal-01330362
https://hal-univ-perp.archives-ouvertes.fr/hal-01330362/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01330362/file/srep26009.pdf
DOI : 10.1038/srep26009

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We present a new set of brittle microtectonic measurements carried out in the Pliocene and Quaternary rocks outcropping in several key sectors of the western Betic and Rif orogen, the so-called Gibraltar orogenic arc. This data set, along with available earthquake focal mechanisms and borehole breakouts, allowed us to compile the Pliocene and Quaternary stress map of this area. This map provides new constraints for tectonic models and the present-day tectonic activity of the proposed active eastward subduction of oceanic lithosphere beneath the Gibraltar Arc and roll-back. The horizontal maximum compressive stress (S-Hmax) is NW-SE in the Betic Orogen and N-S/NNW-SSE in the southern Rif Cordillera. There is a significant consistency between S-Hmax and the displacement field deduced from GPS measurements with respect to the African plate: both appear to reflect the NW-SE convergence between the African and the European plates that is perturbed in the Rif. We propose that part of the eastern Rif behaves as a quasi-rigid block welded to the stable African plate. This block is bounded by important faults that localized most of the deformation disturbing the stress and surface displacement field. Pliocene to Quaternary N-S to NW-SE Africa-Europe plate convergence seem to be associated to the reorganization of the remnant Early Miocene subduction system in a continental-continental collision framework. Three-dimensional reconstruction of available seismic tomography plotted against the intermediate seismicity shows that only part of the old subduction system, whose orientation ranges from N20 degrees E to N100 degrees E, remains active: the portion ranging from N30 degrees E to N40 degrees E, orthogonal to the regional convergence. (C) 2011 Elsevier Ltd. All rights reserved.
ISSN: 0264-3707

hal-00671033
https://hal.archives-ouvertes.fr/hal-00671033
DOI : 10.1016/j.jog.2010.12.003

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia-Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing convergence history between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during convergence (as testified by the successive Sanandaj-Sirjan, Kermanshah and Urumieh-Dokhtar magmatic arcs), the P-T-t history of the few Zagros blueschists, the convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW-NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115-85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene-Eocene (60-40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30-0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj-Sirjan Zone: 20-15 Ma, High Zagros: ~12-8 Ma; Simply Folded Belt: 5-0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole convergence history. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes.
ISSN: 0016-7568

insu-00616582
https://hal-insu.archives-ouvertes.fr/insu-00616582
https://hal-insu.archives-ouvertes.fr/insu-00616582/document
https://hal-insu.archives-ouvertes.fr/insu-00616582/file/692.full.pdf
DOI : 10.1017/S001675681100046X

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
The Ama Drime range located at the transition between the high Himalayan range and south Tibet is a N-S active horst that offsets the South Tibetan Detachment System (STDS). Within the horst, a paragneissic unit, possibly attributed to the upper Himalayan crystalline series, overly the lower Himalayan crystalline series Ama Drime orthogneissic unit containing large metabasite layers and pods that have experienced pressure >= 1.4 GPa. Combining structural analysis with new and published pressure-temperature (P-T) estimates as well as U-Th/Pb, Ar-39/Ar-40 and (U-Th)/He ages, the P-T-deformation-time (P-T-D-t) paths of the main units within and on both sides of the horst are reconstructed. They imply that N-S normal faults initiated prior to 11 Ma and have accounted for a total exhumation <= 0.6 GPa (22 km) that probably occurred in two phases: the first one until similar to 9 Ma and the second one since 6 to 4 Ma at a rate of similar to 1 mm/yr. In the Ama Drime unit, 1 to 1.3 GPa (37 to 48 km) of exhumation occurred after partial melting since similar to 30 Ma until similar to 13 Ma, above the Main Central Trust (MCT) and below the STDS when these two fault systems were active together. The switch from E-W (STDS) to N-S (Ama Drime horst) normal faulting between 13 and 12 Ma occurs at the time of propagation of thrusting from the MCT to the Main Boundary Thrust. These data are in favor of a wedge extrusion or thrust system rather than a crustal flow model for the building of the Himalaya. We propose that the kinematics of south Tibet Cenozoic extension phases is fundamentally driven by the direction and rate of India underthrusting.
ISSN: 0278-7407

hal-00486405
https://hal.archives-ouvertes.fr/hal-00486405
DOI : 10.1029/2009TC002551

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Fromthe Proterozoic to the Quaternary, the evolution of the Earthwas characterised by recurrent periods of glaciation.However, the margins of many ancient ice-sheets are poorly defined on palaeogeographic reconstructions.The extent and outlines of ancient ice sheets can be better understood through careful documentation ofsediments deposited at the ice-sheet margin. An outstanding example is provided herein based on an end-Ordovician archive in Libya (Tihemboka area, Murzuq Basin). The four sets of structures include: i) subglacialglaciotectonic structures and soft sediment deformations from flowing glacier ice, such as intraformational glacialstriae, intraformational deformation (shear planes, sheath folds), normal microfaults, and large-scaleglaciotectonic folds-and-thrusts; (ii) structures resulting from overpressured subglacial (meltwater) flowssuch as clastic dykes and tunnel valleys; (iii) proglacial depositional structures and facies related to highmagnitudemeltwater floods such as sandstone intraclasts, large-scale bedforms resulting from supercriticalflows, climbing-dune cross-stratification and kettle holes; and (iv) deformation structures resulting from freefloating and nonglacier ice such as ice-keel scours and ice-crystal marks. Such a set of structures points to anice-marginal (essentially continental) depositional setting, and provides an excellent suite of criteria to identifymargins of ancient ice sheets in the stratigraphic record. At a regional scale, a reconstruction through time andspace of the related depositional wedge is proposed. This corresponded to a seismic-scale (N120 m in thickness,40 km in length) ice-marginal wedge in front of an essentially warm-based ice-sheet inducing concomitantlarge-scale glaciotectonic deformation, glacial basin and tunnel valley downcuttings. The related ice-front wasassociated with high-energy meltwater flows feeding a network of deeply incised proglacial channels downstreamand, beyond them, a fluvioglacial deltaic system. Shallow ice-marginal permafrost most likely affectedthe depositional wedge. At a larger scale, the Tihemboka ice-marginal wedge is interpreted as related to a stillstandperiod over the Gondwana platform, developed over an estimated interval of a few thousands of years.Based on these data, the conditions that arose in a particularly favourable context for the development, the preservationand the identification of ice-marginal wedges in the geological record are reviewed. Significantmeltwater-derived sediment deposition and aggradation in an accommodation space resulting either frompreglacial inheritance, glacial downcuttings and/or glacio-isostatic lithospheric flexure, or active tectonic subsidence(>1 Myr) are required for their formation and subsequent preservation.
ISSN: 0012-8252

insu-01184739
https://hal-insu.archives-ouvertes.fr/insu-01184739
DOI : 10.1016/j.earscirev.2015.06.006

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Detection and attribution of human influence on sea level rise are important topics that have not yet been explored in depth. We question whether the sea level changes (SLC) over the past century were natural in origin. SLC exhibit power law long-term correlations. By estimating Hurst exponent through Detrended Fluctuation Analysis and by applying statistics of Lennartz and Bunde [2009], we search the lower bounds of statistically significant external sea level trends in longest tidal records worldwide. We provide statistical evidences that the observed SLC, at global and regional scales, is beyond its natural internal variability. The minimum anthropogenic sea level trend (MASLT) contributes to the observed sea level rise more than 50% in New York, Baltimore, San Diego, Marseille, and Mumbai. A MASLT is about 1 mm/yr in global sea level reconstructions that is more than half of the total observed sea level trend during the XXth century.
ISSN: 0094-8276

hal-01336190
https://hal.archives-ouvertes.fr/hal-01336190
https://hal.archives-ouvertes.fr/hal-01336190/document
https://hal.archives-ouvertes.fr/hal-01336190/file/BECKER2014a.pdf
DOI : 10.1002/2014GL061027

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide with observations on chemically modified woods, either “artificially”, or by natural extractives.
Wood Science and Technology

hal-01096868
https://hal-agroparistech.archives-ouvertes.fr/hal-01096868
DOI : 10.1007/S00226-010-0393-8

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Multiproxy analyses were performed on core MS27PT recovered in hemipelagic sediments deposited on the Nile margin in order to reconstruct Nile River palaeohydrological fluctuations during the last 100,000 years. The strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source, oscillating between a dominant aeolian Saharan contribution during arid periods and a dominant Nile River contribution during pluvial periods. Iron content shows a strong correlation with strontium and neodymium isotopes. This allows the use of a high-resolution continuous Fe record as a proxy of Blue Nile sediment input over the last 100,000 years. The detailed Fe record, with approximately 10 years resolution during pluvial periods, is consistent with subtropical African records of well-dated lake level fluctuations and thus constitutes a first continuous high resolution record of the East African monsoon regime intensity over Ethiopia.;The detailed Fe record shows the two main known pluvial periods attributed to strengthening of the African monsoon over Ethiopia, the Nabtian period from 14 to 8 ka cal BP and the Saharan period from 98 to 72 ka BR For the first time, the last glacial period (Marine Isotope Stage (MIS) 2,3 and 4) is documented with a continuous record showing large oscillations between high and low East African palaeo-monsoon regimes.;The end of the Nabtian period occurred at 8 ka in core MS27PT, i.e. much earlier than on the East Equatorial African region where it ended around 5.5 ka. We interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the Eastern Ethiopian Highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka. During the last glacial period, two wet periods are present around 60-50 ka BP and 38-30 ka BP. These two humid periods are in phase with the rise of atmospheric CH4 concentrations suggesting that wetland tropical African area was one of the sources of the atmospheric CH4 during the MIS 3. During the Last Glacial Maximum and MIS 4, high Saharan aeolian influxes in phase with records of aeolian dust deposited in East Antarctica are documented. This study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low- and high-latitude climate variability at millennial timescales.
ISSN: 0277-3791

hal-00496481
https://hal.archives-ouvertes.fr/hal-00496481
DOI : 10.1016/j.quascirev.2010.02.006

Éditeur(s) : American Geophysical Union
Résumé : We present four companion digital models of the age, age uncertainty, spreading rates, and spreading asymmetries of the world's ocean basins as geographic and Mercator grids with 2 arc min resolution. The grids include data from all the major ocean basins as well as detailed reconstructions of back-arc basins. The age, spreading rate, and asymmetry at each grid node are determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading. Ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments. The age uncertainties for grid cells coinciding with marine magnetic anomaly identifications, observed or rotated to their conjugate ridge flanks, are based on the difference between gridded age and observed age. The uncertainties are also a function of the distance of a given grid cell to the nearest age observation and the proximity to fracture zones or other age discontinuities. Asymmetries in crustal accretion appear to be frequently related to asthenospheric flow from mantle plumes to spreading ridges, resulting in ridge jumps toward hot spots. We also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age-depth relationships. The new set of grids helps to investigate prominent negative depth anomalies, which may be alternatively related to subducted slab material descending in the mantle or to asthenospheric flow. A combination of our digital grids and the associated relative and absolute plate motion model with seismic tomography and mantle convection model outputs represents a valuable set of tools to investigate geodynamic problems.
Geochemistry Geophysics Geosystems - G3 (1525-2027) (American Geophysical Union), 2008-04 , Vol. 9 , P. NIL_18-NIL_36

Droits : 2008 American Geophysical Union
http://archimer.ifremer.fr/doc/2008/publication-3900.pdf
DOI:10.1029/2007GC001743
http://archimer.ifremer.fr/doc/00000/3900/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Ctenophores are a phylum of non-bilaterian marine (mostly planktonic) animals, characterised by several unique synapomorphies (e.g., comb rows, apical organ). Relationships between and within the nine recognised ctenophore orders are far from understood, notably due to a paucity of phylogenetically informative anatomical characters. Previous attempts to address ctenophore phylogeny using molecular data (18S rRNA) led to poorly resolved trees but demonstrated the paraphyly of the order Cydippida. Here we compiled an updated 18S rRNA data set, notably including a few newly sequenced species representing previously unsampled families (Lampeidae, Euryhamphaeidae), and we constructed an additional more rapidly evolving ITS1 + 5.8S rRNA + ITS2 alignment. These data sets were analysed separately and in combination under a probabilistic framework, using different methods (maximum likelihood, Bayesian inference) and models (e.g., doublet model to accommodate secondary structure; data partitioning). An important lesson from our exploration of these datasets is that the fast-evolving internal transcribed spacer (ITS) regions are useful markers for reconstructing high-level relationships within ctenophores. Our results confirm the paraphyly of the order Cydippida (and thus a ``cydippid-like'' ctenophore common ancestor) and suggest that the family Mertensiidae could be the sister group of all other ctenophores. The family Lampeidae (also part of the former ``Cydippida'') is probably the sister group of the order Platyctenida (benthic ctenophores). The order Beroida might not be monophyletic, due to the position of Beroe abyssicola outside of a clade grouping the other Beroe species and members of the ``Cydippida'' family Haeckeliidae. Many relationships (e.g. between Pleurobrachiidae, Beroida, Cestida, Lobata, Thalassocalycida) remain unresolved. Future progress in understanding ctenophore phylogeny will come from the use of additional rapidly evolving markers and improvement of taxonomic sampling.
ISSN: 0944-2006

hal-01544475
https://hal.archives-ouvertes.fr/hal-01544475
DOI : 10.1016/j.zool.2014.06.004

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In the southeastern corner of the Tyrrhenian basin, in the central Mediterranean Sea, a tight alignment of earthquakes along a well-defined Benioff zone marks one of the narrowest active trenches worldwide, where one of the last fragment of the former Tethys ocean is consumed. Seismic tomography furnishes snapshot images of the present-day position of this slab, and seismic anisotropy allows to reconstruct the past kinematics of the subduction process. Using seismic anisotropy fast directions as a proxy for the present and past mantle flow, we look backward for the seismic traces of the slab motion through the western-central Mediterranean mantle, from the starting locus of subduction toward its present day position. The result of combining independent data sets provides a coherent pattern of anisotropy that illustrates an example of slab rollback from its initiation point to its present-day position.
ISSN: 0012-821X

hal-01389115
http://hal.univ-reunion.fr/hal-01389115
http://hal.univ-reunion.fr/hal-01389115/document
http://hal.univ-reunion.fr/hal-01389115/file/Lucente_medit_EPSL2006_hal.pdf
DOI : 10.1016/j.epsl.2005.10.041

Éditeur(s) : HAL CCSD Editions Paralia CFL
Résumé : The wave-dominated beach barrier of Villeneuve-Lès-Maguelone extends between Palavas and Frontignan (Gul f of Lions, northernmost Me diterranean Sea), along a slightly natural sandy protected area char acterized by typical and well-expressed morphologies. In the nearshore, the sea bottom shows one or two approximately rectilinear sand bars. In 2010-2011, we pe rformed a 6 month-long monitoring (autumn 2010/late spring 2011) of a 500 meter-long se gment along this sand barrier. We used RTK D-GPS offering centimeter resolution to acquire sets of elevation data on the beach and the upper shoreface. The study is innovative because a full morphologic monitoring was performed each time the wave/ wind conditions changed significantly. These changes were tracked in real-time thanks to a set of hydrodynamic equipments deployed at sea, including well-known DREAL buoys. We identify from well- documented data: (1) a beach reconstruction cycle at the shorelin e after a moderate storm event (wave height at 3-4 m) and (2) how a sand bar in the nearshore migrates to the shoreline and drives the shoreline shift.
ISSN: 1760-8716

hal-00854402
https://hal.archives-ouvertes.fr/hal-00854402
DOI : 10.5150/jngcgc.2012.023-C

Éditeur(s) : HAL CCSD L'Harmattan
Résumé : International audience
Apprendre dans un certain contexte, apprendre en prenant appui sur le contexte, apprendre en dépit de décalages contextuels : voilà ce que questionnent les approches contextualisées dans l’enseignement, l’apprentissage, la médiation et la socialisation. Dans ce cadre, la contextualisation didactique, telle que nous la définissons, se fixe trois objectifs : identifier et analyser les paramètres contextuels en jeu dans l’interaction apprenant-acquisitions ; proposer des ajustements ainsi que des reconstructions des processus didactiques et de médiation afin de réduire les inadaptations contextuelles ; évaluer les effets des approches contextualisées mises en œuvre.Cet ouvrage collectif, dans la suite de Contextualisations didactiques : approches théoriques (L’Harmattan, 2013) et de Contextes, effets de contexte et didactique des langues (L’Harmattan, 2014), s’articule autour de ces trois objectifs en questionnant l’adaptation contextuelle de certains dispositifs, les facilitations ou résistances engendrées par les effets de contextes, ainsi que les impacts de supports d’enseignement en relation avec le contexte.
https://hal.univ-antilles.fr/hal-01529540

ISBN : 978-2-243-07837-3
hal-01529540
https://hal.univ-antilles.fr/hal-01529540