Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Two genome-wide association studies (GWASs) recently highlighted the HLA-DRA and HLA-DRB5 genes as associated with Parkinson disease (PD). However, because HLA-DRA displays a low level of polymorphisms and HLA-DRB5 is only present in approximately 20% of the population, these findings are difficult to interpret. Our aims were: (1) to replicate and investigate in greater detail the association between PD and the HLA-DR region; (2) to identify PD-associated HLA alleles; and (3) to perform a meta-analysis of our top finding. As part of 2 French population-based case-control studies of PD including highly ethnically homogeneous participants, we investigated the association between PD and 51 Single-nucleotide polymorphisms (SNPs) in the HLA-DR region. HLA-DRB1 alleles were imputed using the HLA(*) IMP software. HLA typing was performed in a subsample of the participants. We performed a meta-analysis of our top finding based on 4 GWAS data sets. Among 499 cases and 1123 controls, after correction for multiple testing, we found an association with rs660895 (OR/minor allele, 0.70; 95% CI, 0.57-0.87) within the HLA-DRB1 gene, which encodes the most polymorphic HLA-DR chain (DRβ). A meta-analysis (7996 cases, 36455 controls) confirmed this association (OR, 0.86; 95% CI, 0.82-0.91; P < .0001). SNP-based imputation of HLA alleles showed an inverse association between PD and the HLA-DRB1(*) 04 allele. We replicated an association between PD and the HLA-DR region and provided further insight into the loci and alleles involved. The highly polymorphic HLA-DRB1 locus contains rs660895, which represents a more legitimate candidate than previous ones. Our finding is in agreement with the hypothesis of an immune component in PD pathophysiology. © 2012 Movement Disorder Society.
ISSN: 0885-3185

inserm-00721562
http://www.hal.inserm.fr/inserm-00721562
http://www.hal.inserm.fr/inserm-00721562/document
http://www.hal.inserm.fr/inserm-00721562/file/Table1.pdf
http://www.hal.inserm.fr/inserm-00721562/file/Table2.pdf

Éditeur(s) : HAL CCSD Hindawi Publishing Corporation
Résumé : During the 1982-1984 bradyseismic crises in the Campi Flegrei area (Italy), the University of Wisconsin deployed a network of seismological stations to record local earthquakes. In order to analyse the potential of the recorded data in terms of tomographic imaging, a blind test was recently set up and carried out in the framework of a research project. A model representing a hypothetical 3D structure of the area containing the Campi Flegrei caldera was also set up, and a synthetic dataset of time arrivals was in turn computed. The synthetic dataset consists of several thousand P- and S-time arrivals, computed at about fourteen stations. The tomographic inversion was performed by four independent teams using different methods. The teams had no knowledge of either the input velocity model or the earthquake hypocenters used to create the synthetic dataset. The results obtained by the different groups were compared and analysed in light of the true model. This work provides a thorough analysis of the earthquake tomography potential of the dataset recording the seismic activity at Campi Flegrei in the 1982-1984 period. It shows that all the tested earthquake tomography methods provide reliable low-resolution images of the background velocity field of the Campi Flegrei area, but with some differences. However, none of them succeeds in detecting the hypothetical structure details (i.e. with a size smaller than about 1.5-2 km), such as a magmatic chamber 4 km deep and especially the smaller, isolated bodies, which represent possible magmatic chimneys and intrusions.
ISSN: 1687-885X

hal-00795584
https://hal.archives-ouvertes.fr/hal-00795584
DOI : 10.1155/2012/505286

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Giant earthquake (moment magnitude M-w >= 8.5) forecasts for subduction zones have been empirically related to both tectonic stresses and geometrical irregularities along the subduction interface. Both of these controls have been suggested as able to tune the ability of rupture to propagate laterally and, in turn, exert an important control on giant earthquake generation. Here we test these hypotheses, and their combined influence, by compiling a dataset of trench fill thickness (a proxy for smoothing of subducting plate relief by sediment input into the subduction channel) and upper plate strain (a proxy for the tectonic stresses applied to the subduction interface) for 44 segments of the global subduction network. We statistically compare relationships between upper plate strain, trench sediment thickness and maximal earthquake magnitude. We find that the combination of both large trench fill (>= 1 km) and neutral upper plate strain explains spatial patterns of giant earthquake occurrence to a statistically significant degree. In fact, the concert of these two factors is more highly correlated with giant earthquake occurrence than either factor on its own. Less frequent giant earthquakes of lower magnitude are also possible at subduction zones with thinner trench fill and compressive upper plate strain. Extensional upper plate strain and trench fill < 0.5 km appear to be unfavorable conditions, as giant earthquakes have not been observed in these geodynamical environments during the last 111 years. Citation: Heuret, A., C. P. Conrad, F. Funiciello, S. Lallemand, and L. Sandri (2012), Relation between subduction megathrust earthquakes, trench sediment thickness and upper plate strain, Geophys. Res. Lett., 39, L05304, doi: 10.1029/2011GL050712.
ISSN: 0094-8276

hal-00745636
https://hal.archives-ouvertes.fr/hal-00745636
https://hal.archives-ouvertes.fr/hal-00745636/document
https://hal.archives-ouvertes.fr/hal-00745636/file/heuretGRL2012.pdf
DOI : 10.1029/2011GL050712

Éditeur(s) : HAL CCSD Human Kinetics
Résumé : International audience
Purpose: Postexercise alveolar-capillary membrane-diffusing capacity (DLco) often decreases in highly trained endurance athletes and seems linked to their training status. To test the hypothesis that training status influences postexercise DLco, 13 male and 2 female triathletes (20.2 ± 4.4 y old, 175.2 ± 6.7 cm tall; weight in a range of 66.6 ± 7.4 kg to 67.4 ± 7.8 kg during the 1-y study) were randomized into experimental (n = 7) and control (n = 8) groups and performed VO2max cycle tests and simulated cycle-run successions (CR) of 30 min + 20 min after 3 periods in the competitive season. Methods: Both groups were tested before (pre- HTP) and after a 30-wk high-training period (HTP) with high training volume, intensity, and frequency. The experimental group was then also tested after a 6-wk low-training period (LTP) with low training volume, intensity, and frequency, while the control group continued training according to the HTP schedule for these 6 wk. Ventilatory data were collected continuously. DLco testing was performed before and 30, 60, and 120 min after the CR trials. Results: Whatever the period or group, DLco was significantly decreased 30 min after CR, with a significantly greater decrease in the experimental group than the control group in LTP (–15.7% and –9.3% of DLco, respectively). Conclusions: Six weeks of low training volume and intensity were sufficient to reverse the effects of high training volume and intensity on the alveolar-capillary membrane after a CR succession in competitive triathletes.
ISSN: 1555-0265

hal-01163434
https://hal.univ-antilles.fr/hal-01163434

Éditeur(s) : Universidad Autonoma de Baja California
Résumé : The pathogenicity of two V. penaeicida strains, AM101 and KH-1, with different geographic origin, and V. nigripulchritudo strain AM102, were investigated in juvenile blue shrimp species Litopenaeus stylirostris. Alive bacteria and protein fractions (PFs) obtained from cell-free supernatants (CFS) were used in experimental challenges. Strains AM102, AM101, and KH-1 produced respectively 60, 54 and 12% mortality at 96h after infection using 104 cfu mL-1 of bacterial suspension. Exocellular toxin-like factors were evidenced in CFS from the New Caledonian strains (AM102 and AM101) but not the Japanese strain (KH-1). At 48h post injection of each CFS, mortality rates were respectively 96,98 and 5% when these strains were cultivated at 20°C, whereas only O,16 and 5% mortality rates were observed when these strains were cultivated at 30°C. Clear differences in pathogenicity between both V. penaeicida strains of distinct geographic origin (AM101 and KH-1) were thus emphasized. Protein fractions were obtained from CFS of all the strains tested in this study and cultivated at 20°C, by ammonium sulphate precipitation. Whatever the used strain, significantly higher mortalities were produced with PFs obtained with 0-40% of ammonium sulphate saturation, in respect to those produced with PFs60 and PFs80. Shrimp injected with PFs40 from strains AM102, AM101 and KH-1, and at a 20-µg org-1 dose produced respectively 100, 90 and 60% mortality 46h after the challenge. The strain AM101 showed a mediam lethal dose of approximately 5µg protein org-1 (1-1.25 µg protein g-1 body weight) 59h after injection. The PFs40 from New Caledonian strains were fond sensitive to heating and proteinase K treatments, reinforcing thus the hypothesis of their proteinaceous nature. Surprisingly, PFs40 from each bacterial strain displayed similar protein bands by SDS-PAGE suggesting that the tested strains share a common exotoxic compound regardless their distinct geographic origin or species.
Ciencias Marinas (Universidad Autonoma de Baja California), 2003 , Vol. 29 , N. 1 , P. 77-88

Droits : Universidad Autonoma de Baja California
http://archimer.ifremer.fr/doc/2003/publication-2807.pdf
http://archimer.ifremer.fr/doc/00000/2807/

Éditeur(s) : HAL CCSD Taylor & Francis (Routledge)
Résumé : International audience
Several studies have focused on the role of students’ conceptions of intellectual ability, the learning process and the self-efficacy. However, these three parameters have not been integrated and analysed within the same model. Against this background, the objective of our research is to identify the links that develop between these three constructs. To this end, we have put forward two hypotheses: 1. The conception that intelligence is constructed directly and positively affects the conception that learning is a constructive process. This has a positive impact on perceived self-efficacy. 2. The conception that intelligence is a fixed trait directly and positively affects the conception that learning is a reproductive process and leads to lower perceptions of self-efficacy. To test these hypotheses, we conducted research using a questionnaire distributed among 1112 students in their last year of primary school. The questionnaires were subject to statistical analysis using structural equation modelling. The results confirm our hypotheses and thus show the relevance of our model.
ISSN: 0305-5698

hal-01532797
https://hal.univ-antilles.fr/hal-01532797
DOI : 10.1080/03055698.2016.1152172

Éditeur(s) : HAL CCSD Springer International Publishing
Résumé : The intensive farming practices that have been developed over the past 60 years are based mainly on the use of chemical inputs such as fertilisers and pesticides, mechanical tillage and monoculture. The limitations of these methods are now clear: long-term degradation of soil fertility, impacts on the environment and human health, high consumption of fossil fuels, low efficiency of inputs and threats to food security in a context of climate change. Would farming practices that rely on the activation of ecological processes be an alternative to achieve a balance between high productivity and environmental preservation? While many studies suggest a positive relationship between soil biodiversity and ecosystem services, there is considerable debate on the form such agricultural systems should take. This study reviewed the state of current knowledge and identified aspects requiring further research to achieve the aim of sustainable intensification of agriculture. The following major points emerged: 1) Most studies focused on the evaluation of individual practices. However, changes in farmers’ cropping practices to take advantage of soil biodiversity services would need to manage not only the interactions between various practices but also the trade-off between the technical and socio economic constraints of cropping systems. Advances in agricultural system design approaches may help to ensure appropriate trade-offs. 2) More attention should be given to drawing on knowledge from different sources: laboratory studies focusing on the ecological functions of soil biodiversity, experimental surveys on farmers’ fields to rank the farming practices and processes to be included in site-specific models, and on- station experiments to test hypotheses and acquire additional reference material. 3) Whereas advances in technical and scientific knowledge provide an increasing number of relevant indicators for characterizing biodiversity and ecological functions, studies are rarely targeted at the development of indicators that are accessible to farmers or their technical advisors. The lack of indicators accessible to grassroots players for evaluating the impacts of their decisions on soil biodiversity remains a serious obstacle to the development of innovative agro-ecological systems.
Sustainable Agriculture Reviews 14

ISBN : 978-3-319-06015-6
hal-01268743
https://hal.archives-ouvertes.fr/hal-01268743
DOI : 10.1007/978-3-319-06016-3_5
PRODINRA : 270786

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
BACKGROUND:In French Guiana, a French overseas territory in South America, 6 to 10 thousands undocumented persons work illegally in gold mining sites in the Amazonian forest. Precarious life conditions lead to poor health but few data exist on the health status of illegal gold miners in French Guiana. The objective of this article was to describe the sociodemographic and health status of this vulnerable population.METHOD:A prospective cross-sectional survey was conducted in 2015 on gold mine supply sites at the border between French Guiana and Suriname. Health status was assessed through medical examination, past medical history, haemoglobin concentration, and HIV and malaria testing. A questionnaire was used to collect data about the migration itinerary and life conditions on mining sites.RESULTS:Among the 421 adults included in the study, 93.8% (395/421) were Brazilian, mainly from Maranhão (55.7%, 220/395), the poorest Brazilian state. The sex ratio was 2.4. Overall, 48% of persons never went to school or beyond the primary level. The median time spent in gold mining was quite long (10 years), with a high turn-over. One third of the surveyed population (37.1%, 156/421) had high blood pressure, and only two had a medical follow-up. Most persons had experienced malaria (89.3%, 376/421). They declared frequent arboviroses and digestive disorders. Active leishmaniasis was observed in 8.3% of gold miners. Among women, 28.5% were anemic. Concerning HIV, 36.6% (154/421) of persons, mainly men, never got tested before and 6 were tested positive, which represented an HIV prevalence of 1.43% (95%CI =0.29-2.5).CONCLUSION:These findings support the hypothesis that mining in remote areas is linked to several specific illnesses. Theoretically, gold miners would be presumed to start their economical migration to French Guiana as a healthy group. However, their strenuous working and living conditions there lead to poor health caused by infectious and non infectious diseases. This description of their health status is precious for health policy planners in French Guiana given the importance of controlling communicable disease, and the severity and range of specific illnesses acquired by this neglected population.TRIAL REGISTRATION:Clinical trial registration PRS N° NCT02903706 . Retrospectively registered 09/13/2016.
ISSN: 1471-2458

inserm-01566314
http://www.hal.inserm.fr/inserm-01566314
http://www.hal.inserm.fr/inserm-01566314/document
http://www.hal.inserm.fr/inserm-01566314/file/2017%2C%20Douine%20-%20Illegal%20gold%20miners%20in%20French%20Guiana.pdf
DOI : 10.1016/S0140-6736(10)62169-1

Éditeur(s) : Vertigo
Résumé : Submersible exploration of the deep-sea floor during the last decades revealed new insights in this part of our planet with the discovery of an unsuspected diversity of ecosystems. Coral reefs, confined in our mind to warm and shallow tropical waters, have been observed at several hundreds meter depth along continental margins. Like their tropical counterparts, cold water corals are home for several invertebrate and fish species. The diversity and complexity of this rich ecosystem has just started to be studied. Documented and potential treats by human activities including bottom fishing and petroleum industry activities have to be considered and there is an urgent need to prevent further degradation of these vulnerable reefs. The objective of the CARACOLE cruise, lead by Ifremer and gathering geologists and biologists of several European countries, was to explore by robotic submersible several coral mounds off Ireland. This new approach revealed the real extent of the coral colonies, the diversity of the associated fauna and helped to test hypotheses to understand the mound formation.
L'exploration des fonds océaniques, notamment à l'aide des submersibles, a apporté ces dernières décennies un nouvel éclairage sur cette partie du globe, avec la découverte d'une diversité d'écosystèmes jusque là insoupçonnée. Des massifs de coraux, surtout connus des eaux chaudes et peu profondes des régions tropicales se développent à plusieurs centaines de mètres de profondeur le long des marges continentales. Ils servent de substrat, de refuge et de nourriture à de nombreux invertébrés et poissons, et sont à l'origine d'un écosystème riche dont la diversité et la complexité commencent tout juste à être étudiées. Malgré leur profondeur, ils sont soumis à l'impact des activités humaines, notamment la pêche par chalut qui a déjà détruit certains de ces "récifs" mais aussi la menace potentielle de l'exploration pétrolière. La campagne CARACOLE, menée par l'Ifremer et regroupant des géologues et biologistes européens spécialistes de ces milieux, avait pour objectif la prospection par submersible filoguidé de plusieurs monts de coraux au large de l'Irlande. Elle a permis d'évaluer l'étendue des colonies de coraux, de caractériser la faune associée et de tester différentes hypothèses pour expliquer leur formation.
Vertigo (Vertigo), 2004-12 , Vol. 5 , N. 3

Droits : 2004 Vertigo
http://archimer.ifremer.fr/doc/2004/publication-2364.pdf
http://archimer.ifremer.fr/doc/00000/2364/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The mycotoxin alternariol (AOH), a frequent contaminant in fruit and grain, is known to induce cellular stress responses such as reactive oxygen production, DNA damage and cell cycle arrest. Cellular stress is often connected to autophagy, and we employed the RAW264.7 macrophage model to test the hypothesis that AOH induces autophagy. Indeed, AOH treatment led to a massive increase in acidic vacuoles often observed upon autophagy induction. Moreover, expression of the autophagy marker LC3 was markedly increased and there was a strong accumulation of LC3-positive puncta. Increased autophagic activity was verified biochemically by measuring the degradation rate of long-lived proteins. Furthermore, AOH induced expression of Sestrin2 and phosphorylation of AMPK as well as reduced phosphorylation of mTOR and S6 kinase, common mediators of signaling pathways involved in autophagy. Transmission electron microscopy analyzes of AOH treated cells not only clearly displayed structures associated with autophagy such as autophagosomes and autolysosomes, but also the appearance of lamellar bodies. Prolonged AOH treatment resulted in changed cell morphology from round into more star-shaped as well as increased β-galactosidase activity. This suggests that the cells eventually entered senescence. In conclusion, our data identify here AOH as an inducer of both autophagy and senescence. These effects are suggested to be to be linked to AOH-induced DSB (via a reported effect on topoisomerase activity), resulting in an activation of p53 and the Sestrin2-AMPK-mTOR-S6K signaling pathway.
ISSN: 0300-483X

hal-01117627
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117627
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117627/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117627/file/Autophagy%20and%20senescence_accepted.pdf
PUBMED : 25456271

Éditeur(s) : HAL CCSD Geological Society of America
Résumé : International audience
Integrated Ocean Drilling Program Expedition 313 continuously cored uppermost Eocene to Miocene sequences on the New Jersey shallow shelf (Sites M27, M28, and M29). Previously, 15 Miocene (ca. 23-13 Ma) seismic sequence boundaries were recognized on several generations of multichannel seismic profi les using criteria of onlap, downlap, erosional truncation, and toplap. We independently recognize sequence boundaries in the cores and logs based on an integrated study of core surfaces, lithostratigraphy and process sedimentology (grain size, mineralogy, facies, and paleoenvironments), facies successions, stacking patterns, benthic foraminiferal water depths, downhole logs, core gamma logs, and chronostratigraphic ages. We use a velocitydepth function to predict the depths of seismic sequence boundaries that were tested by comparison with major core surfaces, downhole and core logs, and synthetic seismograms. Using sonic velocity (core and downhole), core density, and synthetic seismograms, we show that sequence boundaries correspond with acoustic impedance contrasts, although other stratal surfaces (e.g., maximum fl ooding and transgressive surfaces) also produce refl ections. Core data are suffi cient to link seismic sequence boundaries to impedance contrasts in 9 of 12 instances at Site M27, 6 of 11 instances at Site M28, and 8 of 14 instances at Site M29. Oligocene sequences have minimal lithologic and seismic expression due to deep-water locations on clinoform bottomsets. Miocene sequences (ca. 23-13 Ma) were sampled across several unconformity clinothems (prograding units) on topset, foreset, and bottomset locations. Excellent recovery allows core-seismic integration that confi rms the hypothesis that unconformities are a primary source of impedance contrasts. Our core-seismic-log correlations predict that key seismic surfaces observed in other sub surface investigations without core and/or well logs are stratal surfaces with sequence stratigraphic signifi cance.
EISSN: 1553-040X

insu-00946235
https://hal-insu.archives-ouvertes.fr/insu-00946235
DOI : 10.1130/GES00858.1

Éditeur(s) : HAL CCSD Thieme Publishing
Résumé : International audience
The aim of the present study was to compare the effects of prior cycling and a successive run on respiratory muscle performance during a cycle-run succession as performed in the triathlon. We hypothesized that despite the moderate intensity of exercise and the absence of exhaustion, the crouched cycling position would induce a decrease in respiratory muscle performance that would be reversed by the successive vertical run position. Ten male triathletes (22.6 +/- 1.1 yr) performed a four-trial protocol: (1) an incremental cycle test to assess maximal oxygen uptake (VO2max), (2) 20 min of cycling (C), (3) 20 min of running (R), and (4) 20 min of cycling followed by 20 min of running (C-R). Trials 2, 3 and 4 were performed at the same metabolic intensity, i. e., 75 % of VO2max. Respiratory muscle force was assessed by measuring maximal expiratory (P(Emax)) and inspiratory (P(Imax)) pressures from the functional residual capacity (FRC) before and 10 min after C, R, and C-R. Respiratory muscle endurance was assessed one day before and 30 min after C, R, and C-R, by measuring the time limit (T(lim)), which corresponds to the length of time a respiratory load can be sustained before the process of fatigue develops sufficiently to cause task failure. The results showed a similar significant decrease in P(Imax) (132.4 +/- 4.9 versus 125.7 +/- 5.6 cm H2O, p < 0.05) and T(lim) (5.22 +/- 0.28 versus 3.68 +/- 0.32 min, p < 0.05) post-C and post-C-R (133.7 +/- 4.0 versus 126.9 +/- 5.2 cm H2O, and 5.29 +/- 0.18 versus 3.49 +/- 0.41 min, respectively, p < 0.05) compared with the pre-trial values. In contrast, P(Imax) and T(lim) were not significantly decreased post-R (131.8 +/- 6.1 cm H2O versus 129.6 +/- 6.4 cm H2O, and 4.90 +/- 0.69 versus 4.40 +/- 0.56 min, respectively, p > 0.05). We concluded that moderate intensity exercise not performed to exhaustion induced a decrease in respiratory muscle performance. Moreover, the respiratory muscle fatigue induced by prior cycling was maintained, and neither reversed nor worsened, by the successive run.
ISSN: 0172-4622

hal-00720715
https://hal.univ-antilles.fr/hal-00720715

Éditeur(s) : HAL CCSD
Résumé : International audience
Ripley’s K function is the classical tool to characterize the spatial structure of point patterns. It is widely used in vegetation studies. Testing its values against a null hypothesis usually relies on Monte-Carlo simulations since little is known about its distribution.We introduce a statistical test against complete spatial randomness (CSR). The test returns the p-value to reject the null hypothesis of independence between point locations. It is more rigorous and faster than classical Monte-Carlo simulations. We show how to apply it to a tropical forest plot. The necessary R code is provided.
International Scholarly Research Network, ISRN Ecology

hal-01502637
https://hal-agroparistech.archives-ouvertes.fr/hal-01502637
https://hal-agroparistech.archives-ouvertes.fr/hal-01502637/document
https://hal-agroparistech.archives-ouvertes.fr/hal-01502637/file/2013_Marcon_Hindawi%20Publishing%20Corporation_%7B7A602F34-6983-47DE-924B-7CDC3B8D14F7%7D.pdf
DOI : 10.1155/2013/753475

Éditeur(s) : HAL CCSD Hindawi Publishing Corporation
Résumé : International audience
We generalize Ripley's K function to get a new function, M, to characterize the spatial structure of a point pattern relatively to another one. We show that this new approach is pertinent in ecology when space is not homogenous and the size of objects matters. We present how to use the function and test the data against the null hypothesis of independence between points. In a tropical tree data set we detect intraspecific aggregation and interspecific competition.
ISSN: 1687-9708

hal-01502623
https://hal-agroparistech.archives-ouvertes.fr/hal-01502623
DOI : 10.1155/2012/619281

Éditeur(s) : HAL CCSD Springer
Résumé : International audience
In science learning, context is an important dimension of any scientific object or phenomenon, and context-dependent variations prove to be as critical for deep understanding as are abstract concepts, laws and rules. The hypothesis presented is that a context gap between two students can be illuminating to highlight the respective general-particular aspects of an object or phenomenon. Furthermore, provoking a perturbation during the learning process to obtain the emergence of such an event could be a productive tutoring strategy. The authors introduce the emergence of context effects as a problem space, to be modeled in the system, and propose a model of the contextual dimension (MazCalc) associated with an analytical view of its modeling, based on a metaphor in physics. A Learning Scenario (Gounouy) has been designed and tested with two groups of learners in Guadeloupe and in Quebec, and MazCalc has been instantiated for this pilot study. Finally, an architecture of a Context-Aware Intelligent Tutoring System is presented, with services to learners, teachers and researchers.
Context in Computing

ISBN : 978-1-4939-1886-7
hal-01536054
https://hal.univ-antilles.fr/hal-01536054
DOI : 10.1007/978-1-4939-1887-4_17

Éditeur(s) : HAL CCSD
Résumé : For ecology scientists, spatial statistics are a set of tools allowing characterization of the structure of a point set, for instance a map of trees in a forest plot. This structure is defined implicitly as a departure from complete spatial randomness (CSR), the result of a Poisson point process. Inhomogeneity of the process and non-independence of points are its causes. As they cannot be disentangled by analyzing the data, so-called "spatial concentration" or "aggregation" (evenness due to repulsion also exists but is actually rare) usually concerns non-independence while intensity is assumed as known. The literature of point processes and measures of spatial structures is reviewed to clarify concepts and choices. The purpose of this thesis was to produce methodological enhancements. Its main results are: * A test for the most used statistic, Ripley's K function, against the null hypothesis of CSR. It can replace Monte-Carlo simulations used until now in the literature. * An extension of K to inhomogeneous processes, within a typology of available statistics (absolute, relative and topographic measures). When data is available as number of objects per zones (say a number of tree in each forest plot) rather than their exact position, information theory is used to define a general framework allowing to characterize spatial structure (of species) and diversity (of plots) as two aspects of a single measure of inequality. This framework is applied to Shannon's index of biodiversity to derive a self-sufficient definition of beta diversity, its calculation independently from the difference between gamma and alpha diversity, and a statistical test of significance against the null hypothesis that plots are samples of the same community. The way is paved for other applications to measures of diversity and spatial structures. As a conclusion, it appears clear that pattern characterization tools are a first step to deal with ecological questionings. Their development is still a matter of research. Yet, they are far from sufficient to address ecological processes as point processes ignore the temporal aspect of object locations.
Les statistiques spatiales sont pour les écologues un ensemble d'outils permettant de caractériser la structure d'un semis de points, par exemple une carte représentant des emplacements des arbres dans une parcelle de forêt. Cette structure est définie implicitement comme un écart à semis complètement aléatoire, résultat d'un processus de Poisson. L'hétérogénéité du processus ponctuel dont le semis de points est une réalisation et la non-indépendance des points en sont les causes indiscernables, ce qui amène généralement à supposer l'intensité du processus connu et nommer " concentration spatiale " ou " agrégation " (la régularité spatiale est possible, mais rare en pratique) la non-indépendance. Une revue de la littérature des processus ponctuels et des mesures de structures spatiales est fournie pour clarifier les concepts et les choix. L'objectif de ce travail de thèse était de produire des améliorations méthodologiques. Ses résultats principaux sont : * L'établissement d'un test pour la principale statistique utilisée, la fonction K de Ripley, permettant de s'affranchir de la méthode de Monte-Carlo utilisée dans la littérature pour rejeter l'hypothèse nulle d'un processus complètement aléatoire. * L'extension de K aux processus hétérogènes, dans le cadre d'une typologie claire des statistiques (absolues, relatives, topographiques). Lorsque la position exacte des objets n'est pas connue, mais que des effectifs par zone sont disponibles (par exemple des nombres d'arbres par parcelle), la théorie de l'information est utilisée pour définir un cadre général permettant de caractériser la structure spatiale (des espèces dans les parcelles) et la diversité (des parcelles, en termes d'espèces) comme deux aspects d'une même mesure d'inégalité. Ce cadre est appliqué à l'indice de biodiversité de Shannon pour définir clairement la mesure de diversité bêta, son calcul direct indépendamment de la différence entre diversités gamma et alpha, et fournir un test statistique de non nullité. La voie est ouverte pour l'application à d'autres mesures de diversité et de structure spatiale. En conclusion, il semble clair que ces outils de caractérisation sont un premier pas pour traiter les questions écologiques, leur développement étant toujours du domaine de la recherche. Ils sont cependant très insuffisants pour répondre à des questions liées aux processus écologiques, assez éloignés des processus ponctuels qui ignorent l'aspect temporel de l'installation des objets.
https://pastel.archives-ouvertes.fr/pastel-00540327

NNT : 2010AGPT0075
pastel-00540327
https://pastel.archives-ouvertes.fr/pastel-00540327
https://pastel.archives-ouvertes.fr/pastel-00540327/document
https://pastel.archives-ouvertes.fr/pastel-00540327/file/13_Marcon2010.pdf

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
This paper presents a synthesis of a multidisciplinary study carried out along the Nîmes Roman aqueduct, located in the southeast part of France. The study was motivated by archaeologists attempting to explain the partial destructions of only one aerial bridge of the aqueduct (Pont de la Lône). Given its close proximity to the Nîmes seismically active fault, a possible seismic origin for the destructions was invoked. Seismologists and structural engineers thus carried out a variety of field and numerical investigations to test the seismic hypothesis. Supporting field evidence was found first along the aerial bridge section of the aqueduct: broken stalactites, arch warping, cracks and destruction of the bridge just above a breast wall shortly after its construction. Secondly, the underground part of the canal was analysed: irregularity in the thickness of calcite deposits of the canal walls, presence of numerous cracks, horizontal shift of the otherwise linear structure of the canal and presence of calcite twins in the deposits, found only where the canal crosses the Nîmes fault system. Numerical modelling and experimental results show that (1) only the Pont de la Lône would have suffered serious damage under seismic solicitation (assuming an M6 earthquake at 10 km distance). The second aerial bridge, the three levels arches Pont du Gard, an historical monument still standing today, would have suffered less damage, due to its very different fundamental frequency of around 0.4 Hz, far from the amplified seismic near-field spectrum; (2) the numerical models also show that a fall of the canal wall would require a higher magnitude event (M > 6); (3) the presence of calcite twinning requires a differential static stress of 4 MPa or greater, which can only be achieved very close to the fault rupture of a M > 6 earthquake; (4) finally, local surface rupturing of such a fault would also corroborate the hypothesis that the observed offset of the canal may be partly seismically induced. Although other possible origins for each individual evidence may not be excluded, the observed spatiotemporal concentration of architectural/geological anomalies together with the numerical results allow us to support a possible co-seismic origin for these disorders, indirectly attesting to the potential seismic activity (M > 6) of the nearby Nîmes fault. Furthermore, following the conclusions of archaeological studies, the disorders occurred between 250 and 350 year AD, thus providing timing for this possible seismic event, an essential parameter in seismic hazard analysis. These results validate the archaeo-seismological approach as a tool that may help improve the knowledge of major infrequent earthquakes in areas of moderate seismic activity.
ISSN: 0921-030X

hal-00379064
https://hal.archives-ouvertes.fr/hal-00379064
DOI : 10.1007/s11069-008-9276-9

Éditeur(s) : Public Library Science
Résumé : Like hydrothermal vents along oceanic ridges, cold seeps are patchy and isolated ecosystems along continental margins, extending from bathyal to abyssal depths. The Atlantic Equatorial Belt (AEB), from the Gulf of Mexico to the Gulf of Guinea, was one focus of the Census of Marine Life ChEss (Chemosynthetic Ecosystems) program to study biogeography of seep and vent fauna. We present a review and analysis of collections from five seep regions along the AEB: the Gulf of Mexico where extensive faunal sampling has been conducted from 400 to 3300m, the Barbados accretionary prism, the Blake ridge diapir, and in the Eastern Atlantic from the Congo and Gabon margins and the recently explored Nigeria margin. Of the 72 taxa identified at the species level, a total of 9 species or species complexes are identified as amphi-Atlantic. Similarity analyses based on both Bray Curtis and Hellinger distances among 9 faunal collections, and principal component analysis based on presence/absence of megafauna species at these sites, suggest that within the AEB seep megafauna community structure is influenced primarily by depth rather than by geographic distance. Depth segregation is observed between 1000 and 2000m, with the middle slope sites either grouped with those deeper than 2000m or with the shallower sites. The highest level of community similarity was found between the seeps of the Florida escarpment and Congo margin. In the western Atlantic, the highest degree of similarity is observed between the shallowest sites of the Barbados prism and of the Louisiana slope. The high number of amphi-atlantic cold-seep species that do not cluster according to biogeographic regions, and the importance of depth in structuring AEB cold-seep communities are the major conclusions of this study. The hydrothermal vent sites along the Mid Atlantic Ridge (MAR) did not appear as "stepping stones" for dispersal of the AEB seep fauna, however, the south MAR and off axis regions should be further explored to more fully test this hypothesis.
Plos One (1932-6203) (Public Library Science), 2010-08 , Vol. 5 , N. 8 , P. 1-11

Droits : © 2010 Olu et al.
http://archimer.ifremer.fr/doc/00011/12207/8975.pdf
DOI:10.1371/journal.pone.0011967
http://archimer.ifremer.fr/doc/00011/12207/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The giant bathymodioline mussels from vents have been studied as models to understand the adaptation of organisms to deep-sea chemosynthetic environments. These mussels are closely related to minute mussels associated to organic remains decaying on the deep-sea floor. Whereas biological data accumulate for the giant mussels, the small mussels remain poorly studied. Despite this lack of data for species living on organic remains it has been hypothesized that during evolution, contrary to their relatives from vents or seeps, they did not acquire highly specialized biological features. We aim at testing this hypothesis by providing new biological data for species associated with organic falls. Within Bathymodiolinae a close phylogenetic relationship was revealed between the Bathymodiolus sensu stricto lineage (i.e. ``thermophilus'' lineage) which includes exclusively vent and seep species, and a diversified lineage of small mussels, attributed to the genus Idas, that includes mostly species from organic falls. We selected Idas iwaotakii (Habe, 1958) from this latter lineage to analyse population structure and to document biological features. Mitochondrial and nuclear markers reveal a north-south genetic structure at an oceanic scale in the Western Pacific but no structure was revealed at a regional scale or as correlated with the kind of substrate or depth. The morphology of larval shells suggests substantial dispersal abilities. Nutritional features were assessed by examining bacterial diversity coupled by a microscopic analysis of the digestive tract. Molecular data demonstrated the presence of sulphur-oxidizing bacteria resembling those identified in other Bathymodiolinae. In contrast with most Bathymodiolus s.s. species the digestive tract of I. iwaotakii is not reduced. Combining data from literature with the present data shows that most of the important biological features are shared between Bathymodiolus s.s. species and its sister-lineage. However Bathymodiolus s.s. species are ecologically more restricted and also display a lower species richness than Idas species.
ISSN: 1932-6203

hal-01545914
https://hal.archives-ouvertes.fr/hal-01545914
DOI : 10.1371/journal.pone.0069680

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : Plant leaf litter generally decomposes faster as a group of different species than when individual species decompose alone, but underlyingmechanisms of these diversity effects remain poorly understood. Because resource C : N: P stoichiometry (i.e. the ratios of these key elements) exhibits strong control on consumers, we supposed that stoichiometric dissimilarity of litter mixtures (i.e. the divergence in C : N: P ratios among species) improves resource complementarity to decomposers leading to faster mixture decomposition. We tested this hypothesis with: (i) a wide range of leaf litter mixtures of neotropical tree species varying in C : N: P dissimilarity, and (ii) a nutrient addition experiment (C, N and P) to create stoichiometric similarity. Litter mixtures decomposed in the field using two different types of litterbags allowing or preventing access to soil fauna. Litter mixture mass loss was higher than expected from species decomposing singly, especially in presence of soil fauna. With fauna, synergistic litter mixture effects increased with increasing stoichiometric dissimilarity of litter mixtures and this positive relationship disappeared with fertilizer addition. Our results indicate that litter stoichiometric dissimilarity drives mixture effects via the nutritional requirements of soil fauna. Incorporating ecological stoichiometry in biodiversity research allows refinement of the underlying mechanisms of how changing biodiversity affects ecosystem functioning.
ISSN: 0962-8452

hal-01204222
https://hal.archives-ouvertes.fr/hal-01204222
DOI : 10.1098/rspb.2014.1682
PRODINRA : 289918