Éditeur(s) : HAL CCSD
Résumé : Among erosion processes, river incision is classicaly described as a key process controlling erosion of landscapes. Incision efficiency is mainly influenced by climate and erodibility. This latter is not only dependent on the nature of the bedrock, but also on its past deformation, which affects its rheological effective properties, such as fracture density. The main objectives of this thesis are: (1) to better constrain the relationship between effective properties and erodibility, and (2) to quantify the influence of erodibility and erosion on both the temporal and spatial building or decay of the topography. Several numerical tools are developed. A 1D formalism of landscape evolution is introduced, including river incision with stochastic distribution of water discharge and hillslope landsliding. A new remeshing algorithm called Surface Lagrangian Remeshing (SLR) is developed as a complement to remeshing algorithms dealing with internal elements. It allows one to take into account long-term erosion into 2D Lagrangian numerical codes based on triangular finite elements. Then the potentiality of measuring erodibility in-situ using a Schmidt hammer (R) is assessed for the active orogen of Taiwan, the diagenetic Annot sandstones and St Clement fault zone. Results suggest a strong control of R by effective properties. A linear model based on effective medium theory is applied to a fault zone with an unmacthed resolution (750 measures, 25 measures per square meter). The model successfully correlates R to fracture density. These results demonstrate that effective elasticity as well as erodibility are sensitive to the density and type of fractures. Finally I focus on the erosional and rheological conditions that allows reproducing post-orogenic evolution of mountain belts. A model coupling surface erosion and regional isostatic uplift is consistent with observations. The topographic decay and decrease of the ratio of surface elevation over crustal root thickness is at first order controlled by the initial geometry of the mountain belt and erosion efficiency. This new model highlights the control ofclimate and erodibility on the topographic decay and of lithospheric rheology on the perseverance of crustal roots.
Parmi les processus d'érosion, l'incision des rivières est classiquement décrit comme un processus clé contrôlant l'érosion des paysages. L'efficacité de l'incision est principalement influencée par le climat et par l'érodabilité. Ce dernier paramètre ne dépend pas seulement de la nature du substratum rocheux, mais aussi de sa déformation passée qui affecte ses propriétés rhéologiques équivalentes. Les principaux objectifs de cette thèse sont: (1) de mieux contraindre les relations entre propriétés équivalentes et érodabilité, et (2) de quantifier l'influence de l'érosion et de l'érodabilité sur la formation ou la décadence, spatiale et temporelle, de la topographie. Plusieurs outils numériques sont développés. Un formalisme 1D d'évolution des paysages est proposé, prenant en compte simultanément l'incision des rivières avec une distribution stochastique des débits en eau et l'érosion des versants par glissements de terrain. Un nouvel algorithme de remaillage appelé Surface Lagrangian Remeshing (SLR) est développé. Il permet de prendre en compte l'érosion à long terme dans les codes numériques 2D Lagrangiens basés sur des éléments finis triangulaires. Ensuite, la possibilité de mesurer in-situ l'érodabilité avec un marteau de Schmidt (R) est évaluée pour: l'orogène actif de Taiwan, les grès diagénétiques d'Annot et la zone de faille de St Clément. Les résultats suggèrent un fort contrôle de R par les propriétés équivalentes des roches testées. Un modèle linéaire, basé sur la théorie des milieux équivalents, est appliqué à une zone de faille avec une résolution inégalée (750 mesures, 25 mesures par mètre carré). Le modèle permet de corréler avec succès la densité de fracture et R. Ces résultats démontrent empiriquement que l'élasticité équivalente ainsi que l'érodabilité sont sensibles à la densité et à la nature des fractures. Enfin j'étudie les conditions d'érosion et de rhéologie qui permettent de reproduire l'évolution des chaînes de montagnes post-orogéniques. Un modèle couplant érosion en surface et soulèvement isostatique régional est compatible avec les observations. Les taux de décroissance topographique et de diminution du rapport de l'élévation de surface sur l'épaisseur de racine crustale sont contrôlés au premier ordre par la géométrie initiale de la chaîne de montagne et par l'efficacité de l'érosion. Ce nouveau modèle met en évidence le contrôle du climat et de l'érodabilité sur la décroissance topographique et de la rhéologie lithosphérique sur la persévérance des racines crustales.
https://tel.archives-ouvertes.fr/tel-00602341

tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341/document
https://tel.archives-ouvertes.fr/tel-00602341/file/thesephilippesteer.pdf

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : The acquisition of reliable data sets representative of hydrological regimes and their variations is a critical concern for water resource assessment. For the subsurface, traditional approaches based on probe measurements, core analysis, and well data can be laborious, expensive, and highly intrusive, while only yielding sparse data sets. For this study, an innovative field survey, merging relative microgravimetry, magnetic resonance soundings, and hydrological measurements, was conducted to evaluate both surface and subsurface water storage variations in a semiarid Sahelian area. The instrumental setup was implemented in the lower part of a typical hillslope feeding to a temporary pond. Weekly measurements were carried out using relative spring gravimeters during 3 months of the rainy season in 2009 over a 350 × 500 m2 network of 12 microgravity stations. Gravity variations of small to medium amplitude (≤220 nm s−2) were measured with accuracies better than 50 nm s−2, revealing significant variations of the water storage at small time (from 1 week up to 3 months) and space (from a couple of meters up to a few hundred meters) scales. Consistent spatial organization of the water storage variations were detected, suggesting high infiltration at the outlet of a small gully. The comparison with hydrological measurements and magnetic resonance soundings involved that most of the microgravity variations came from the heterogeneity in the vadose zone. The results highlight the potential of time lapse microgravity surveys for detecting intraseasonal water storage variations and providing rich space-time data sets for process investigation or hydrological model calibration/evaluation
ISSN: 0043-1397

hal-00857351
https://hal.archives-ouvertes.fr/hal-00857351
DOI : 10.1002/wrcr.20235

Éditeur(s) : HAL CCSD Springer
Résumé : The analysis of gamma ray measurements provides valuable information about the basement's lithospherical model and the radioactive elements contained in the subsurface. To be exploited, the raw data need pre-processing operations which consist of corrections of the Compton effect, altimetry and the aircraft background, and 2D interpolations. These transformations may modify the data's stochastic component which reflects heterogeneities of the investigated medium. In this study, a fractal analysis is carried out on airborne gamma ray data measured in the Hoggar's area (Algeria). First, it is shown that the analyzed data exhibit fractal properties. Due to the dependence of the latter on the spatial location of the measures, the data can be considered as paths of multifractional Brownian motions. Another result worth noting is that the fractal nature of the raw data is not modified by the pre-processing operations. The fractal analysis can be then performed on the raw spectrometric measurements without submitting them to any pre-processing; thus, the stochastic component of the measurements is kept intact.
ISSN: 1866-7411

hal-00817494
https://hal.archives-ouvertes.fr/hal-00817494
DOI : 10.1007/s12517-011-0407-3

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This manuscript reports on a novel field experiment carried out on a microtidal beach in Camargue, France. For the first time in the field, a comprehensive description of the groundwater dynamics under sandy beach swash zone is presented. A cross-shore network of 15 buried pressure sensors is combined with terrestrial LiDAR measurements to study the swash-groundwater dynamics. The presented data focus on the decay of a moderate storm which allows to monitor the evolution of the groundwater pressure field in response to the retreat of the swash zone. Both horizontal and vertical head gradients are measured within the porous sand soil to estimate the groundwater flow field using Darcy’s law. Time-averaged analysis demonstrates the presence of a rather consistent groundwater circulation pattern under the swash zone, shifting offshore with the swash zone. The main tendency is an offshore directed flow, with infiltration/exfiltration in the upper/lower parts of the swash zone. Time-resolved analysis highlights the typical groundwater response to swash events which consists mainly of an overall infiltration flow during the bed inundation by the swash tongue, a seaward flow during the swash retreat and, for long backwash events, a localized exfiltration flow under the next incoming uprush.
ISSN: 0309-1708

hal-01412450
https://hal.archives-ouvertes.fr/hal-01412450
DOI : 10.1016/j.advwatres.2016.09.009

Éditeur(s) : HAL CCSD
Résumé : International audience
INTRODUCTION: There are no French guidelines for the management of complicated parapneumonic effusions. A national observational study was carried out to assess the main features of current clinical practice for this condition. MATERIAL AND METHODS: A questionnaire was sent by email to the 1500 members of the Société de Pneumologie de Langue Française (SPLF) between 15th November and 15th December 2012. RESULTS: There were 92 responders, i.e. a response rate of 6%. Of these, 87 physicians mentioned that they were involved in the management of patients with complicated parapneumonic effusions with a median number of cases of 10 per year (IQR: 5-20). Chest tube drainage was the main approach used for pleural fluid aspiration (n=51/87), followed by repeated thoracentesis (n=29/87) and early surgery (1/87). Five physicians answered both chest tube drainage or repeated thoracentesis and one physician either chest tube drainage or early surgery. Pleural fibrinolytics were never used by 20% of physicians, only in case of loculations by 70% and by 10% of respondents in all cases. Only 3 physicians combined fibrinolytics with DNAse. A double antibiotic dose was used by one third of physicians. All the physicians used respiratory physiotherapy during hospitalization and to aid recovery. Follow-up practices were heterogeneous. CONCLUSIONS: The management of complicated parapneumonic effusions varies significantly in France. National guidelines may be helpful to define best practice and aid in its implementation.
Revue Des Maladies Respiratoires

hal-01146851
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01146851
DOI : 10.1016/j.rmr.2015.01.001
PUBMED : 25725981

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Shrimp farming in New Caledonia typically uses a flow-through system with water exchange rates as a tool to maintain optimum hydrological and biological parameters for the crop. Moreover, the effluent shows hydrobiological characteristics (minerals, phytoplankton biomass and organic matter) significantly higher than that of the receiving environment. Separate surveys were carried out in a bay (CH Bay) with a medium-size intensive farm (30 ha) (PO) and in a mangrove-lined creek (TE Creek) near a larger semi-intensive farm (133 ha) (SO). Net loads of nitrogen exported from the semi-intensive farm and the intensive farm amounted to 0.68 and 1.36 kg ha(-1) day(-1), respectively. At CH Bay, discharge effects were spatially limited and clearly restricted to periods of effluent release. The high residence time at site TE favoured the installation of a feedback system in which organic matter was not exported. Mineralization of organic matter led to the release of nutrients, which in turn, caused in an increased eutrophication of this ecosystem. The study of the pico- and nanophytoplankton assemblages showed (i) a shift in composition from picophytoplankton to nanophytoplankton from offshore towards the coast and (ii) a shift within the picophytoplankton with the disappearance of Prochlorococcus and the increase of picoeucaryotes towards the shoreline. These community changes may partially be related to a nitrogen enrichment of the environment by shrimp farm discharges. Thus, in view of the recent addition of the New Caledonian lagoon to the UNESCO World Heritage list, the data presented here could be a first approach to quantify farm discharges and evaluate their impact on the lagoon. (C) 2010 Elsevier Ltd. All rights reserved.
Marine Pollution Bulletin (0025-326X) (Pergamon-elsevier Science Ltd), 2010 , Vol. 61 , N. 7-12 , P. 387-398

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00014/12527/9882.pdf
DOI:10.1016/j.marpolbul.2010.07.005
http://archimer.ifremer.fr/doc/00014/12527/

Éditeur(s) : HAL CCSD ACSM
Résumé : International audience
A 26-yr-old man with sickle cell trait (SCT) suddenly lost visual acuity in the left eye after a cycling race in hot tropical environment. The cause was massive central retinal vein occlusion (CRVO) with hemorrhaging that rapidly worsened to neovascular glaucoma. Although medically treated, the eye is now marked by total retinal detachment. Cardiovascular function assessment shows no electrocardiographic abnormalities, no anomaly in the supra-aortic tree, and no evidence of structural heart disease. Although normal coagulation markers values (i.e., activated partial thromboplastin time, prothrombin time, fibrinogen concentration, antithrombin III, factor V, proteins C and S) were observed 2.5 months after the clinical event, a transesophageal echocardiogram performed few hours after the incident revealed the presence of four thrombi in the left atrium suggesting a postexercise hypercoagulable state at that time. Hemorheological measurements at distance of the events demonstrated high red blood cell rigidity at baseline. Therefore, marked blood rheological impairment and activation of the coagulation pathway in response to the heavy and prolonged cycling race could have promoted CRVO in this cyclist carrying SCT. These data suggest that SCT could be considered as a risk factor for significant ocular complications when severe exercise is performed and support the idea that SCT is a contributing factor in blood rheology and vascular dysfunctions.
Medicine & Science in Sports & exercise

Droits : info:eu-repo/semantics/OpenAccess
hal-00698572
https://hal.univ-antilles.fr/hal-00698572
https://hal.univ-antilles.fr/hal-00698572/document
https://hal.univ-antilles.fr/hal-00698572/file/Hedreville_et_al_revised_MSSE-D-08-00064R2.pdf
DOI : 10.1249/MSS.0b013e31818313d0

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Adverse pregnancy outcomes entail a large health burden for the mother and offspring; a part of it might be avoided by better understanding the role of environmental factors in their etiology. Our aims were to review the assessment tools to characterize fecundity troubles and pregnancy-related outcomes in human populations and their sensitivity to environmental factors. For each outcome, we reviewed the possible study designs, main sources of bias, and their suggested cures. In terms of study design, for most pregnancy outcomes, cohorts with recruitment early during or even before pregnancy allow efficient characterization of pregnancy-related events, time-varying confounders, and in utero exposures that may impact birth outcomes and child health. Studies on congenital anomalies require specific designs, assessment of anomalies in medical pregnancy terminations, and, for congenital anomalies diagnosed postnatally, follow-up during several months after birth. Statistical analyses should take into account environmental exposures during the relevant time windows; survival models are an appropriate approach for fecundity, fetal loss, and gestational duration/preterm delivery. Analysis of gestational duration could distinguish pregnancies according to delivery induction (and possibly pregnancy-related conditions). In conclusion, careful design and analysis are required to better characterize environmental effects on human reproduction.
ISSN: 0193-936X

hal-01002724
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01002724
DOI : 10.1093/epirev/mxt011
PUBMED : 24363355

Éditeur(s) : HAL CCSD
Résumé : International audience
Background: Mounier-Kuhn syndrome (MKS) is a rare disorder characterized by enlargement of the trachea and main bronchi and associated with recurrent respiratory tract infections. Objective: This multicenter, retrospective study was carried out to describe respiratory conditions associated with tracheobronchomegaly. Methods: Nine institutions involved in the ‘Groupe d'Endoscopie de Langue Française' (GELF) participated in this study. A standard form was used to record patient characteristics, treatments and follow-up from medical charts. Results: Seventeen patients, 53% male, aged 58 ± 18 years at diagnosis were included. Recurrent infections revealed MKS in 88% of cases. Main comorbid conditions were diffuse bronchiectasis in 88% of patients and tracheobronchomalacia in 67% of cases. The exacerbation rate was 1.5 exacerbations/patient/year. The main non-respiratory morbid condition was gastroesophageal reflux disease in 29% of cases. Interventional bronchoscopy was performed in seven patients (41%), consisting of laser (n = 2) and tracheal stenting (n = 5). Complications related to stents were observed in 80% of cases with a mean stent duration of 8 months. Four deaths, including three due to respiratory causes, occurred during follow-up. Conclusions: This is the largest series of MKS reported in the literature, showing that bronchiectasis and tracheobronchomalacia are the main associated morbid conditions that constitute a challenge for treatment.
Respiration

hal-01331182
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01331182
DOI : 10.1159/000445029
PUBMED : 27022925

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : In the Sicilian fisheries, the swordfish (Xiphias gladius, Linnaeus 1758), caught from March to December with several gears which vary according to season, represents one of the most important economic resources. The size composition changes depending on the gear used, the way it is operated, the fishing area and season. The gears used for swordfish fishing (long-lines "for swordfish", drift-nets, harpoons as operated by typical boats named "feluche") mainly catch adult specimens. From August to December, a high number of very young swordfish specimens (1.5 to 4.5 kg) is also caught as by-catch during the albacore (Thunnus alalunga, Bonnaterre 1788) fishing which is carried out by a special long line and hooks only 3 cm long. It was observed that in the same season, fishing areas and with boats of similar type, the fishing of dolphin-fish (Coryphaena hippurus, Linnaeus 1758), using Fish Aggregating Devices (FADs) and purse seine, is hardly practised in spite of the resource availability swordfish. With the present work, which can be regarded as an initial approach to the problem of diversifying and managing fishing effort of swordfish, albacore and dolphin-fish, their fisheries are examined and discussed, not overlooking the economic aspect, by considering weather a reallocation of fishing effort among the previously said resources might avert the risk of swordfish stock depletion.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15299/12659.pdf
http://archimer.ifremer.fr/doc/00042/15299/

Résumé : Une étude de faisabilité de poutres en bois lamellé-collé a été menée en Guyane Française en utilisant les essences locales. Le but est de déterminer les paramètres de collage assurant la bonne résistance mécanique des assemblages par lamellation et par aboutage, nécessaires à la fabrication de poutres en bois lamellé-collé en climat tropical. Trois essences de bois abondantes de différentes densités ont été sélectionnées. Les adhésifs de types Mélamine-Urée-Formol et Résorcinol-Phénol-Formol ont été utilisées. Les paramètres de collage considérés sont : le grammage, le temps d’assemblage fermé et la pression.En utilisant les normes Européennes, plusieurs campagnes de tests ont été conduites sur des échantillons normalisés. Concernant le collage par lamellation, des tests élémentaires de délamination et de cisaillement des joints de colle ont été réalisés. Le test de délamination consiste en deux cycles d’immersion dans l’eau sous pression et de séchage, il induit de sévères variations d’humidité du bois susceptibles de créer des ouvertures des joints de colles. Le collage par aboutage est réalisé sur des poutres normalisées aboutées. Les entures sont obtenues grâce à un outillage standard communément utilisé pour les résineux. Les résultats ont mis en évidence l’influence des propriétés du bois et des paramètres de collage sur la résistance du joint et la résistance mécanique du produit. En effet, les paramètres du bois, tels que la densité, la rétractibilité et l’imprégnation, ont une forte influence sur le collage, en particulier sur la pression et le grammage nécessaires à la production d’un produit commercialisable. Il apparait qu’un bois de densité moyenne et poreux nécessite un grammage et une pression élevés comparé à un bois de densité élevée qui nécessite des valeurs moindres. Aussi, l’influence d’autres paramètres de fabrication, tels que le rabotage, l’encollage double face et simple face ainsi que l’épaisseur des lamelles, a été établie. Par contre il semblerait que le matériel communément utilisé pour l’aboutage des résineux n’est pas adapté aux feuillus tropicaux. En final, des paramètres de collage ont été validés pour la fabrication de lamellé-collé endémique en Guyane Française et une étude du coût de production d’une poutre lamellé-collé standard a identifié les conditions économiques d’une fabrication en Guyane Française.
A feasibility study of glued-laminated timber beams was carried out in French Guiana using local wood species. The aim of the study was to evaluate the gluing parameters that could ensure good mechanical properties for the manufactured glued-laminated beams in tropical climates. Three abundant wood species with different specific gravity were selected for the study. Melamine-Urea-Formaldehyde and Resorcinol-Phenol-Formaldehyde resins were used for gluing. The three gluing parameters considered are: adhesive spread rate, closing assembly time and gluing pressure.Using European standards, several laboratory tests were performed on normalized samples. The evaluation of a successful lamella’s gluing was done by using elementary tests of delamination and shearing. A delamination test consists of two cycles of water immersion at high pressure and drying which induces severe hygroscopic variation in wood thus causing joints opening. The finger-joints are made using a standard tool usually used for cutting softwoods. The performed tests revealed the influence of wood properties and the gluing parameters on the joint resistance and the mechanical properties of the product. Results show that wood properties such as specific gravity, shrinkage coefficient, and permeation, have a high degree of influence on the gluing step especially on the gluing pressure and on the adhesive spread rate needed to produce a commercial product. Furthermore, wood with medium specific gravity needs more adhesive and more pressure than the one with high specific gravity. Additionally, the effects of other manufacturing parameters, such as planning, double or simple side glue spreading and lamellae thicknesses, on the glue joint resistance were demonstrated. Finally, the common tools used for softwoods are not adapted to making the finger joints with tropical hardwoods.In conclusion, optimal gluing parameters for manufacturing glued-laminated timber beams in French Guiana were established and an economical study using standard glued-laminated timber beams revealed the economic conditions under which a successful manufacturing of these local beams can be implemented in French Guiana.

http://www.theses.fr/2011AGUY0484/document