Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Though the root biomass of tropical rainforest trees is concentrated in the upper soil layers, soil water uptake by deep roots has been shown to contribute to tree transpiration. A precise evaluation of the relationship between tree dimensions and depth of water uptake would be useful in tree-based modelling approaches designed to anticipate the response of tropical rainforest ecosystems to future changes in environmental conditions. We used an innovative dual-isotope labelling approach (deuterium in surface soil and oxygen at 120-cm depth) coupled with a modelling approach to investigate the role of tree dimensions in soil water uptake in a tropical rainforest exposed to seasonal drought. We studied 65 trees of varying diameter and height and with a wide range of predawn leaf water potential (I-pd) values. We confirmed that about half of the studied trees relied on soil water below 100-cm depth during dry periods. I-pd was negatively correlated with depth of water extraction and can be taken as a rough proxy of this depth. Some trees showed considerable plasticity in their depth of water uptake, exhibiting an efficient adaptive strategy for water and nutrient resource acquisition. We did not find a strong relationship between tree dimensions and depth of water uptake. While tall trees preferentially extract water from layers below 100-cm depth, shorter trees show broad variations in mean depth of water uptake. This precludes the use of tree dimensions to parameterize functional models.
ISSN: 0029-8549

hal-01032433
https://hal.archives-ouvertes.fr/hal-01032433
DOI : 10.1007/s00442-013-2724-6

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Little information exists on the effects of ocean acidification (OA) on the digestive and post-digestive processes in marine fish. Here, we investigated OA impacts (Δ pH = 0.5) on the trophic transfer of select trace elements in the clownfish Amphiprion ocellaris using radiotracer techniques. Assimilation efficiencies of three essential elements (Co, Mn and Zn) as well as their other short-term and long-term kinetic parameters in juvenile clownfish were not affected by this experimental pH change. In complement, their stomach pH during digestion were not affected by the variation in seawater pH. Such observations suggest that OA impacts do not affect element assimilation in these fish. This apparent pCO2 tolerance may imply that clownfish have the ability to self-regulate pH shifts in their digestive tract, or that they can metabolically accommodate such shifts. Such results are important to accurately assess future OA impacts on diverse marine biota, as such impacts are highly species specific, complex, and may be modulated by species-specific metabolic processes.
ISSN: 1932-6203

hal-01564009
https://hal-univ-perp.archives-ouvertes.fr/hal-01564009
https://hal-univ-perp.archives-ouvertes.fr/hal-01564009/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01564009/file/trophic%20transfer.pdf
DOI : 10.1371/journal.pone.0174344

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Polarization dependence second harmonic generation (P-SHG) microscopy is gaining increase popularity for in situ quantification of fibrillar protein architectures. In this report, we combine P-SHG microscopy, new linear least square (LLS) fitting and modeling to determine and convert the complex second-order non-linear optical anisotropy parameter ρ of several collagen rich tissues into a simple geometric organization of collagen fibrils. Modeling integrates a priori knowledge of polyhelical organization of collagen molecule polymers forming fibrils and bundles of fibrils as well as Poisson photonic shot noise of the detection system. The results, which accurately predict the known sub-microscopic hierarchical organization of collagen fibrils in several tissues, suggest that they can be subdivided into three classes according to their microscopic and macroscopic hierarchical organization of collagen fibrils. They also show, for the first time to our knowledge, intrahepatic spatial discrimination between genuine fibrotic and non-fibrotic vessels. CCl 4-treated livers are characterized by an increase in the percentage of fibrotic vessels and their remodeling involves peri-portal compaction and alignment of collagen fibrils that should contribute to portal hypertension. This integrated P-SHG image analysis method is a powerful tool that should open new avenue for the determination of pathophysiological and chemo-mechanical cues impacting collagen fibrils organization.
ISSN: 2045-2322

hal-01592192
https://hal.archives-ouvertes.fr/hal-01592192
https://hal.archives-ouvertes.fr/hal-01592192/document
https://hal.archives-ouvertes.fr/hal-01592192/file/s41598-017-12398-0.pdf
DOI : 10.1038/s41598-017-12398-0

Éditeur(s) : HAL CCSD
Résumé : The geological storage of CO 2 is considered as one of the solutions to the problem of global warming. The most possible scenarios of geological behavior of soil in the long term conditions has to be precisely defined to avoid catastrophic damages in the future. Chemical properties of saline water in the aquifer after the CO 2 injection becomes more acidic with time. Therefore, chemical degradation of rock occurs, which leads to modifications of its mechanical properties (chemo-mechanical coupling) [1]. In this paper an incremental model of chemo-mechanical coupling using homogenization approach (asymptotic expansion method [2,3]) is proposed. The paper is focused on the numerical computations for the X-ray tomography image of carbonate rock microstructure [4]. The chemical degradation of the microstructure is obtained as a homogeneous dissolution in each direction (Fig.1. – Fig.2.) For every porosity state numerical computations to obtain full, orthotropic elasticity tensor are performed. Therefore, the degradations functions for all components of the rigidity tensor were defined (Fig.3.). Moreover, results of numerical calculations of diffusion, tortuosity and permeability tensors are presented [5,6]. The link between geometrical properties and mechanical and transport parameters are discussed. The numerical analysis of the carbonate rock sample in long term conditions shows the increase of porosity and associated mechanical weakening of the rock. Moreover, the increase of diffusion, tortuosity and permeability tensors elements with time were observed. Finally, the solution of the one-dimensional macroscopic problem of soil settlement due to chemical dissolution of rock at constant load is presented. The method is universal, in the sense that the non-dimensional time scale is used.
ALERT Workshop 2013
Aussois, France

hal-01103175
https://hal.archives-ouvertes.fr/hal-01103175

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The present study investigated cerebral and muscle hemoglobin oxygen saturation (tissue oxygen index, TOI) in children with sickle cell anemia (SS), sickle cell hemoglobin C disease (SC) and healthy children (AA). TOI was measured by near-infrared spectroscopy (NIRS) and spectral analysis of the TOI variability was used to assess flowmotion and vasomotion. Arterial oxyhemoglobin saturation (SpO2), hemorheological and hematological parameters were also measured in SS and SC children. Both TOI were lower in SS compared to both AA and SC children, with SC exhibiting lower values than AA children. Cerebral vasomotion expressed in absolute values was enhanced in SS compared to AA and SC children. Muscle vasomotion did not differ between the three groups. Hematocrit, SpO2 and red blood cell deformability were positively associated with cerebral TOI in SS children. We demonstrated that 1) cerebral and muscle TOI were markedly decreased in SS children while the decrease of TOI was milder in SC children, 2) cerebral TOI level was associated with several biological markers in SS children only and 3) cerebral vasomotion was enhanced in SS, possibly to counterbalance the effects of chronic cerebral hypoxia.
ISSN: 1079-9796

hal-01668321
https://hal.univ-antilles.fr/hal-01668321
DOI : 10.1016/j.bcmd.2017.03.015

Éditeur(s) : HAL CCSD IWA Publishing
Résumé : International audience
This study proposes a new approach for improving resource quality management, monitoring and treatment plant management, whatever the environmental and climatic stressors. First trend analysis of water quality at a river basin scale, based on historical water quality data and multivariate exploitation (principal component analysis, PCA), led to a classification of the monitoring stations with regard to the main pressures (land use, urbanization and hydroclimatic impacts). This method was applied to the Vilaine's watershed, the largest river basin in Brittany, western France, and one which is under agricultural and urban pressure. A complementary research using a UV index was proposed for the evaluation of spatial and temporal variations of water quality. This approach may be considered as a useful and relevant tool to quickly assess the variation of water quality and the main explanatory factors. It also points out monitoring stations under specific stressors considered as outliers regarding UV parameters. Finally, PCA and UV index give complementary results. PCA allows factors influencing drinking water resource to be highlighted and the UV index allows global water quality under specific times and impacts to be reflected.
Water Science and Technology: Water Supply

hal-00878159
https://hal.archives-ouvertes.fr/hal-00878159
DOI : 10.2166/ws.2012.047

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Given a graph, its hyperbolicity is a measure of how close its distance distribution is to the one of a tree. This parameter has gained recent attention in the analysis of some graph algorithms and the classification of complex networks. We study on practical improvements for the computation of hyperbolicity in large graphs. Precisely, we investigate on relations between the hyperbolicity of a graph G and the hyperbolicity of its atoms, that are the subgraphs output by the clique-decomposition invented by Tarjan [51, 65]. We prove that the maximum hyperbolicity taken over the atoms is at most one unit off from the hyperbol-icity of G and the bound is sharp. We also give an algorithm to slightly modify the atoms, called the " substitution method " , which is at no extra cost than computing the clique-decomposition, and so that the maximum hyperbolicity taken over the resulting graphs is exactly the hyperbolicity of the input graph G. An experimental evaluation of our method for computing the hyperbolicity of a given graph from its atoms is provided for collaboration networks and biological networks. Finally, on a more theoretical side, we deduce from our results the first linear-time algorithm for computing the hyperbolicity of an outerplanar graph.
ISSN: 0304-3975

hal-01540756
https://hal.inria.fr/hal-01540756
https://hal.inria.fr/hal-01540756/document
https://hal.inria.fr/hal-01540756/file/CCDL-2017.pdf
DOI : 10.1016/j.tcs.2017.06.001

Éditeur(s) : Inter-Research
Résumé : The Biocean database was designed to collate the extremely large volume of data collected from different deep-sea ecosystem studies conducted by Ifremer's department of 'Environnement Profond' (Deep-Sea Environment). This database comes in a 6-application package: 2 of them are used on research vessels to collect operational data, whereas the others are used to link with a core database back on land. The latter are used to: (1) manage taxonomic nomenclature, (2) monitor the identification of faunal collections, (3) fill in chemical analyses results or measurement data files and (4) add or extract data from the database. Biocean was designed to facilitate ecosystem studies in the deep sea. It represents an important new resource for deep-sea ecologists and will have wide applications in biogeography and biodiversity studies at Ifremer, but also for the international community, as faunal data are linked to the Census of Marine Life information system OBIS (Ocean Biogeographic Information System). Biogeographical analyses of Biocean data recovered through the OBIS portal evidence an evolution in the deep-sea sampling strategies more focused in limited areas and is intended to reveal ecosystems functioning.
Marine Ecology Progress Series (0171-8630) (Inter-Research), 2006-07 , Vol. 316 , P. 215-224

Droits : 2006 Inter-Research
http://archimer.ifremer.fr/doc/2006/publication-1581.pdf
http://archimer.ifremer.fr/doc/00000/1581/

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
The dynamic model of plant growth GreenLab describes plant architecture and functional growth at the level of individual organs. Structural development is controlled by formal grammars and empirical equations compute the amount of biomass produced by the plant, and its partitioning among the growing organs, such as leaves, stems and fruits. The number of organs initiated at each time step depends on the trophic state of the plant, which is evaluated by the ratio of biomass available in plant to the demand of all the organs. The control of the plant organogenesis by this variable induces oscillations in the simulated plant behaviour. The mathematical framework of the GreenLab model allows to compute the conditions for the generation of oscillations and the value of the period according to the set of parameters. Two case-studies are presented, corresponding to emergence of oscillations associated to fructification and branching. Similar alternating patterns are commonly reported by botanists. In this article, two examples were selected: alternate patterns of fruits in cucumber plants and alternate appearances of branches in Cecropia trees. The model was calibrated from experimental data collected on these plants. It shows that a simple feedback hypothesis of trophic control on plant structure allows the emergence of cyclic patterns corresponding to the observed ones.
ISSN: 0973-5348

hal-00780592
https://hal-ecp.archives-ouvertes.fr/hal-00780592
https://hal-ecp.archives-ouvertes.fr/hal-00780592/document
https://hal-ecp.archives-ouvertes.fr/hal-00780592/file/Mathieu_2012_Published_mmnp201276p47.pdf
DOI : 10.1051/mmnp/20127603

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
STUDY QUESTION: Is there evidence at the population level of associations between different male genital disorders, outside Scandinavian countries? SUMMARY ANSWER: At an international scale, there is evidence for a number of correlations between rates of four male reproductive disorders (hypospadias, cryptorchidism, testicular cancer and low sperm concentration). WHAT IS KNOWN ALREADY: Some associations between these outcomes have been shown in studies focusing on individuals and mainly in Nordic European countries. These associations, together with histological evidence of a dysgenesis pattern in testicular tissue specimens, have generated the concept of the existence of a 'testicular dysgenesis syndrome' originating in utero. STUDY DESIGN, SIZE, DURATION: This is a geographical correlation study using cancer, malformations rates and sperm quality data collected between the years 1998 and 2005. PARTICIPANTS/MATERIALS, SETTING, METHODS: Incidence rates of testicular cancer were extracted from International Agency for Research on Cancer registries and Globocan, while cryptorchidism and hypospadias prevalence rates were obtained from EUROCAT and International Clearinghouse for Birth Defects Surveillance and Research registries. Sperm concentration data were extracted from recent studies using standardized methodology. A total of 39 registries and 9 sperm studies were selected. Non-parametric Spearman correlation tests were used to test the association between these four disorders. Correlations were computed for all registries together, for registries with high-quality matching coverage only and by continents. Sensitivity analyses were also conducted using data from prospective clinical studies to take into account potential bias related mainly to ascertainment of malformation rates. MAIN RESULTS AND THE ROLE OF CHANCE: We found positive correlations between testicular cancer and hypospadias (r = 0.32, P = 0.05) and between hypospadias and cryptorchidism (r = 0.70, P = 0.008). Stronger correlations were observed when using registries with high-quality matching coverage. Among these registries, differences between Europe and the rest of the world appeared (the positive correlation between testicular cancer and cryptorchidism was stronger outside Europe, r = 0.83, P = 0.01 compared with 0.40, P = 0.60 for European registries). A negative correlation between testicular cancer and sperm concentration was observed (r = -0.88, P = 0.002). These correlations support our initial hypothesis but remain only suggestive due to the intrinsic limitations in the study design (i.e. geographical correlation study) and do not allow causal inference. LIMITATIONS, REASONS FOR CAUTION: Differences in the ascertainment of malformations rates (definition, length of follow-up) make the international comparison difficult. The small number of registries for some conditions (cryptorchidism) or of studies (for sperm quality) and the absence of information about major risk factors such as ethnicity and socioeconomic status in the registries are also limitations. WIDER IMPLICATIONS OF THE FINDINGS: Our findings are in agreement with results of studies focusing on individuals and suggest that shared risk factors are present in the populations studied.
ISSN: 0268-1161

inserm-00863412
http://www.hal.inserm.fr/inserm-00863412
DOI : 10.1093/humrep/det111
PUBMED : 23670171

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Two in situ concrete/claystone interfaces were sampled at the laboratory level in the Andra Meuse/Haute Marne (France) Underground Research Laboratory (URL) in order to study five years of interactions between Callovian-Oxfordian (COx) claystone and two cementitious materials (concrete bottom slab and shotcrete on the walls of the main gallery), with a specific focus on sulfur. Combined mineralogical, chemical and sulfur isotopic investigations were carried out to define the degree of the perturbation of the sulfur system in the claystone and in both the cementitious materials. At both interfaces, results show that the main perturbation on the claystone side is the formation of scarce μm-sized gypsum, the sulfur content of which is essentially derived from pyrite oxidation. The distribution of gypsum is highly correlated with the fissure network of the damaged zone due to excavation of the gallery. Its presence is also often associated with a loss of cohesion of the concrete/claystone interface. Due to the small amounts of gypsum and its μm-size, measurements were performed by ion microprobe. Adaptations were needed on account of the reactivity of gypsum and sulfates in general under the beam. The use of ion microprobe analysis provided evidence of high local isotopic heterogeneity that could be attributed to kinetic fractionation effects. Some analyses suggest a minor contribution of dissolved sulfates in pore water of claystone and possibly of concrete. The perturbation on the concrete side is marked by a significant increase in the bulk sulfur content within three millimeters of the interface with the claystone, showing a sulfur gradient from claystone to concrete. The main objective of this work was to define the extent of the chemical and mineralogical perturbations, taking into account in situ URL conditions, i.e. hydrodynamic conditions (shotcrete sprayed on the gallery walls and subjected to ventilation of the galleries), damaged zone of claystone induced by excavation and multi-scale heterogeneity. This identifies the relevant parameters to better constrain predictive reactive transport models of concrete/claystone interactions at a realistic scale.
ISSN: 0079-1946

hal-01055790
https://hal-brgm.archives-ouvertes.fr/hal-01055790
DOI : 10.1016/j.pce.2014.01.003

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Four fibers from banana-trees (leaf, trunk) and coconut-tree (husk, fabric) were examined before their incorporation in cementitious matrices, in order to prepare insulating material for construction. Their botanical compositions have been determined following a method described previously. Thermal degradation of these fibers were studied between 200 and 700 °C under nitrogen gas flow. Temperature of pyrolysis was the experimental parameter investigated. The solid residues obtained were analyzed by classical elemental analysis, Fourier Transform Infra Red (FTIR) spectroscopy and were observed by Scanning Electron Microscopy (SEM). This study has shown (1) the relation between botanical, chemical composition with both localization of fibers in the tree and type of tree; (2) the rapid and preferential decomposition of banana fibers with increasing temperature of pyrolysis and (3) the rough samples are made of hollow fibers.
ISSN: 0960-8524

hal-00809780
https://hal.univ-antilles.fr/hal-00809780
DOI : 10.1016/j.biortech.2005.11.030

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Particle/gas and dust/gas partition coefficients (Kp and Kd) are two key parameters that address the partitioning of semi-volatile organic compounds (SVOCs) between gas-phase, airborne particles, and settled dust in indoor environment. A number of empirical equations to calculate the values of Kp and Kd have been reported in the literature. Therefore, the difficulty lies in the selection of a specific empirical equation in a given situation. In this study, we retrieved from the literature 38 empirical equations for calculating Kp and Kd values from the SVOC saturation vapor pressure and octanol/air partition coefficient. These values were calculated for 72 SVOCs: 9 phthalates, 9 polybrominated diphenyl ethers (PBDEs), 11 polychlorinated biphenyls (PCBs), 22 biocides, 14 polycyclic aromatic hydrocarbons (PAHs), 3 alkylphenols, 2 synthetic musks, tributylphosphate, and bisphenol A. The mean and median values of log10 Kp or log10 Kd for most SVOCs were of the same order of magnitude. The distribution of log10 Kp values was fitted to either a normal distribution (for 27 SVOCs) or a log-normal distribution (for 45 SVOCs). This work provides a reference distribution of the log10 Kp for 72 SVOCs, and its use may reduce the bias associated with the selection of a specific value or equation
ISSN: 0045-6535

hal-01295671
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01295671
DOI : 10.1016/j.chemosphere.2016.03.007
PUBMED : 27016817

Éditeur(s) : Edp Sciences S A
Résumé : It is estimated that fish aggregating devices (FADs) are now used for over 40% of world tropical tuna catches, making this technique a major phenomenon for high seas fisheries worldwide, and one that has experienced great expansion over the past three decades. The question of whether the FAD is a good or a bad tool for the exploitation of marine resources depends on many parameters. To respond to this question, it is necessary to distinguish different scales of exploitation (artisanal vs. industrial) and various types of FADs (anchored vs. drifting), but it is also very important to gather more data and conduct further research on this topic to gain a better understanding of the phenomenon and of its impacts. As such, twelve years after the first international conference devoted to FADs, which was held in Martinique (French West Indies), a new multi-scalar global assessment of FAD fisheries development and a review of the progress of research in this field was deemed vital. The latest international conference, "Tuna Fisheries and Fish Aggregating Devices", was held in Tahiti in November 2011, and it was an event that welcomed nearly 150 conference attendees from 40 different countries, three ocean regions, and the Mediterranean. This is an analysis of the relevant literature gathered by the author in the bibliographic database FADBASE. Then, the major issues already addressed by the scientific community are set out, and gaps and research priorities are highlighted for anchored and drifting FADs management.
Aquatic Living Resources (0990-7440) (Edp Sciences S A), 2013-01 , Vol. 26 , N. 1 , P. 25-35

Droits : EDP Sciences, IFREMER, IRD 2013
http://archimer.ifremer.fr/doc/00137/24835/22915.pdf
DOI:10.1051/alr/2013043
http://archimer.ifremer.fr/doc/00137/24835/

Résumé : New Artemia strain from Russia are now available on the market. They have been evaluated by comparison with Artemia from Great Salt Lake which are routinely used at the LAC hatchery,. Five criteria were compared and all of them were in favour of the American strain with 191 833 nauplii per gram while the Russian ones only gave 102 667 nii per gram. Another important criteria when using Artemia was hatching time which turned out to be longer for the Russian.
Des Artemia d’origine russe sont maintenant disponibles sur le marché. La comparaison avec des Artemia du Grand Lac Salé habituellement utilisées est effectuée afin de déterminer les caractéristiques de cette nouvelle marque d’Artemia. Sur les 5 critères testés, l’avantage est nettement en faveur de la souche américaine avec 191 833 nauplii par gramme contre 102 667 pour la souche russe. Le temps d’éclosion des Artemia russes semble relativement plus long, c’est donc un paramètre à considérer lors de l’utilisation de cette souche.

Droits : 2004 Ifremer
http://archimer.ifremer.fr/doc/00119/23005/20836.pdf
http://archimer.ifremer.fr/doc/00119/23005/

Éditeur(s) : HAL CCSD Botanical Society of America
Résumé :  
Tree buckling risk (actual height/critical buckling height) is an important biomechanical trait of plant growth strategies, and one that contributes to species coexistence. To estimate the diversity of this trait among wide samples, a method that minimizes damage to the plants is necessary. On the basis of the rarely used, complete version of Greenhill's model (1881, Proceedings of the Cambridge Philosophical Society 4(2): 65-73), we precisely measured all the necessary parameters on a sample of 236 saplings of 16 species. Then, using sensitivity (variance) analysis, regressions between successive models for risk factors and species ranks and the use of these models on samples of self- and nonself-supporting saplings, we tested different degrees of simplification up to the most simple and widely used formula that assumes that the tree is a cylindrical homogeneous pole. The size factor had the greatest effect on buckling risk, followed by the form factor and the modulus of elasticity of the wood. Therefore, estimates of buckling risk must consider not only the wood properties but especially the form factor. Finally, we proposed a simple but accurate method of assessing tree buckling risk that is applicable to a wide range of samples and that requires mostly nondestructive measurements.
ISSN: 0002-9122

hal-01032059
https://hal.archives-ouvertes.fr/hal-01032059

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Numerical programs for simulating flow and reactive transport in porous media is essential for predicting reservoir properties related to CO2 sequestration performance, subsurface storage and risk assessment. In this paper we solve the Navier Stokes' equation using finite difference method, on a simulated porous rock structure, to study the velocity distribution of fluid flowing through it under a constant pressure gradient. A reactive solute carried through the fluid is allowed to interact with the minerals in the rock. This chemical reaction dissolves the mineral which changes the rock structure thus affecting its flow properties. These changes of flow properties are studied with variation in reactive solute concentration and pressure field. The different mechanisms of dissolution responsible for the variation of flow properties for the different parameters is predicted. Before the onset of homogeneous dissolution, variation in porosity follows a power-law behaviour with change in permeability when the latter is scaled by the concentration of the reactive species. The simulation results are compared with available experimental data and found to give a reasonable match.
ISSN: 0022-1694

hal-00757760
https://hal.archives-ouvertes.fr/hal-00757760
DOI : 10.1016/j.jhydrol.2012.05.024

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
We use lithospheric-scale analog models to study the reactivation of pre-existing heterogeneities under oblique shortening and its relation to the origin of arcuate orogens. Reactivation of inherited rheological heterogeneities is an important mechanism for localization of deformation in compressional settings and consequent initiation of contractional structures during orogenesis. However, the presence of an inherited heterogeneity in the lithosphere is in itself not sufficient for its reactivation once the continental lithosphere is shortened. The heterogeneity orientation is important in determining if reactivation occurs and to which extent. This study aims at giving insights on this process by means of analog experiments in which a linear lithospheric heterogeneity trends with various angles to the shortening direction. In particular, the key parameter investigated is the orientation (angle α) of a strong domain (SD) with respect to the shortening direction. Experimental results show that angles α ≥ 75° (high obliquity) allow for reactivation along the entire SD and the development of a linear orogen. For α ≤ 60° (low obliquity) the models are characterized by the development of an arcuate orogen, with the SD remaining partially non-reactivated. These results provide a new mechanism for the origin of some arcuate orogens, in which orocline formation was not driven by indentation or subduction processes, but by oblique shortening of inherited heterogeneities, as exemplified by the Ouachita orogen of the southern U.S.
ISSN: 0278-7407

insu-01498544
https://hal-insu.archives-ouvertes.fr/insu-01498544
https://hal-insu.archives-ouvertes.fr/insu-01498544/document
https://hal-insu.archives-ouvertes.fr/insu-01498544/file/Calignano_et_al-2017-Tectonics.pdf
DOI : 10.1002/2016TC004424

Éditeur(s) : HAL CCSD Springer-Verlag
Résumé : We provide evidence for a plume-like upwelling beneath the Eifel hotspot, Western Germany, by using teleseismic shear-wave splitting to resolve the anisotropy associated with upwelling flow that is spreading laterally into the asthenosphere. The variation in fast-polarization azimuth we find across the Eifel hotspot is explained by a model of slowly upwelling material that is horizontally being deflected or sheared in a parabolic asthenospheric flow (PAF) pattern toward west-southwest, a direction that correlates with Eurasian absolute plate motion. We suggest that the lack of an age progression for Eifel volcanism, which is expected for a fixed-upwelling model, is a result of (1) sporadic volcanism due to a low excess plume temperature and/or varying crustal stresses that periodically relax and facilitate eruption, and (2) complex upwelling flow pathways and/or Late Tertiary changes in the slow Eurasian plate motion. The success of the PAF model in fitting the data is remarkable given the small number of parameters (four) and the consistency with the plate motion direction determined from geology and/or geodesy. This suggests that a predictable mantle-anisotropy pattern may exist also for other hotspots driven by plume-like upwellings, and that splitting can be a useful diagnostic to differentiate between plume-like and alternative sources for mantle hotspots.
Mantle plumes - a multidisciplinary approach

hal-00407986
https://hal.archives-ouvertes.fr/hal-00407986
DOI : 10.1007/978-3-540-68046-8

Éditeur(s) : HAL CCSD Paris : Français dans le monde
Résumé : Le n°45 de la revue "recherches et appliications, le français dans le monde" a été coordonné par Evelyne Rosen
International audience
L'approche actionnelle offre de nouvelles perspectives à l'évaluation sommative et certificative, dont les opérateurs européens, les méthodologues et les enseignants s'emparent peu à peu à la suite de théoriciens généralement anglo-saxons. Cependant, s'il est relativement aisé de définir désormais les paramètres fondamentaux des tâches évaluatives, l'analyse des performances qui en résultent nécessite une mise en perspective politique que le recours à des techniques statistiques ne pourra pas résoudre seul.
ISSN: 0994-6632

Droits : info:eu-repo/semantics/OpenAccess
halshs-01395782
https://halshs.archives-ouvertes.fr/halshs-01395782
https://halshs.archives-ouvertes.fr/halshs-01395782/document
https://halshs.archives-ouvertes.fr/halshs-01395782/file/Conception_et_validite_de_taches_evaluat.pdf