Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Homogenization models are widely used to predict the evolution of texture (crystal preferred orientations) and resulting anisotropy of physical properties in metals, rocks, and ice. They fail, however, in predicting two main features of texture evolution in simple shear (the dominant deformation regime on Earth) for highly anisotropic crystals, like olivine: (1) the fast rotation of the CPO towards a stable position characterized by parallelism of the dominant slip system and the macroscopic shear and (2) the asymptotical evolution towards a constant intensity. To better predict CPO-induced anisotropy in the mantle, but limiting computational costs and use of poorly-constrained physical parameters, we modified a viscoplastic self-consistent code to simulate the effects of subgrain rotation recrystallization. To each crystal is associated a finite number of fragments (possible subgrains). Formation of a subgrain corresponds to introduction of a disorientation (relative to the parent) and resetting of the fragment strain and internal energy. The probability of formation of a subgrain is controlled by comparison between the local internal energy and the average value in the polycrystal. A two-level mechanical interaction scheme is applied for simulating the intracrystalline strain heterogeneity allowed by the formation of low-angle grain boundaries. Within a crystal, interactions between subgrains follow a constant stress scheme. The interactions between grains are simulated by a tangent viscoplastic self-consistent approach. This two-level approach better reproduces the evolution of olivine CPO in simple shear in experiments and nature. It also predicts a marked weakening at low shear strains, consistently with experimental data.
ISSN: 0012-821X

hal-01243503
https://hal.archives-ouvertes.fr/hal-01243503
DOI : 10.1016/j.epsl.2015.08.018

Éditeur(s) : HAL CCSD
Résumé : Diffusion du document : INRA Antilles-Guyane, UMR ECOFOG, 97387 Kourou, Guyane (France) Diplôme : Diplôme d'Ingénieur des Techniques Forestières
il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION
Le stage est principalement centré sur l'étude des traits de croissance, de physiologie et de morphologie foliaire sur des populations de plantules d'Eperua falcata (en forêt et en serre ) et de Sextonia rubra (en serre) afin d' étudier la diversité et la différenciation entre pieds mères, d'une part, et l'héritabilité d'autre part. L'héritabilité est une mesure du degré de transmission d'un caractère ; elle représente (en terme statistique) le rapport de la variance phénotypique d'origine génétique. A travers une analyse de variance (ANOVA) on a pu estimer les différentes composantes de la variance (génétique et résiduelle) des traits pour les deux espèces. Les différences génétiques trouvées entre pieds mères jouent un rôle important dans la variabilité des traits. Pour E. falcata, les héritabilités obtenues nous donnent, dans certains traits, des valeurs fortes et similaires en serre et en forêt (ex. l'épaisseur) et dans d'autres, des résultats assez variables à cause de l'interaction génotype- environnement. Par contre pour le S. rubra, les valeurs d'héritabilité sont très homogènes dans la majorité des traits étudiés en serre. Cela montre que, du point de vue écologique aussi bien que du point de vue de gestion, il est indispensable de prendre en compte la variabilité individuelle et héritable, l'adaptabilité et l'adaptation au milieu, comme paramètres de tout modèle des communautés végétales de la Forêt Tropicale Humide. L'ensemble des résultats nous donne une forte motivation pour poursuivre les analyses, dans le temps ou dans la reformulation de la conception des dispositifs avec des transplantations réciproques en pleine forêt.
https://hal.archives-ouvertes.fr/hal-01189280

hal-01189280
https://hal.archives-ouvertes.fr/hal-01189280
PRODINRA : 22857

Éditeur(s) : HAL CCSD Elsevier
Résumé : Rh (Rhesus) is a major blood group system in man, which is clinically significant in transfusion medicine. Rh antigens are carried by an oligomer of two major erythroid specific polypeptides, the Rh (D and CcEe) proteins and the RhAG glycoprotein, that shared a common predicted structure with 12 transmembrane a-helices (M0 to M11). Non erythroid homologues of these proteins have been identified (RhBG and RhCG), notably in diverse organs specialized in ammonia production and excretion, such as kidney, liver and intestine. Phylogenetic studies and experimental evidence have shown that these proteins belong to the Amt/Mep/Rh protein superfamily of ammonium/methylammonium permease, but another view suggests that Rh proteins might function as CO2 gas channels. Until recently no information on the structure of these proteins were available. However, in the last two years, new insight has been gained into the structural features of Rh proteins (through the determination of the crystal structures of bacterial AmtB and archeaebacterial Amt-1. Here, models of the subunit and oligomeric architecture of human Rh proteins are proposed, based on a refined alignment with and crystal structure of the bacterial ammonia transporter AmtB, a member of the Amt/ Mep/Rh superfamily. This alignment was performed considering invariant structural features, which were revealed through Hydrophobic Cluster Analysis, and led to propose alternative predictions for the less conserved regions, particularly in the N-terminal sequences. The Rh models, on which an additional Rh-specific, N-terminal helix M0 was tentatively positioned, were further assessed through the consideration of biochemical and immunochemical data, as well as of stereochemical and topological constraints. These models highlighted some Rh specific features that have not yet been reported. Among these, are the prediction of some critical residues, which may play a role in the channel function, but also in the stability of the subunit structure and oligomeric assembly. These results provide a basis to further understand the structure/function relationships of Rh proteins, and the alterations occurring in variant phenotypes.
ISSN: 1246-7820

hal-00068842
https://hal.archives-ouvertes.fr/hal-00068842

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Endocrine disrupting chemicals and especially oestrogen receptor (ER) agonists have been extensively studied over the years due to their potential effects on sexual development and reproduction in vertebrates, notably fish. As ER agonists can exist as complex mixtures in the aquatic environment, evaluating the impact of combined exposure on oestrogenic effects has become increasingly important. Use of predictive models such as concentration addition (CA) and independent action (IA) has allowed assessment of combined estrogenic effects of complex multi-compound mixtures of ER agonists in various fish in vitro and in vivo experimental models. The present work makes use of a transgenic zebrafish strain, tg(cyp19a1b-GFP), which expresses the green fluorescent protein (GFP) under the control of the cyp19a1b (brain aromatase or aromatase B) gene to determine the oestrogenic potency of ER agonists alone or in mixtures. In these studies, tg(cyp19a1b-GFP) zebrafish embryos were exposed for four days (from one to five days post fertilization) to five different oestrogenic chemicals; 17α-ethinylestradiol (EE2), 17β-estradiol (E2), estrone (E1), bisphenol A (BPA) and 4-tert-octylphenol (OP), and three mixtures of up to four of these compounds. The mixture of BPA, OP and E2 was also tested with primary cultures of rainbow trout hepatocytes by analysing the ER-mediated induction of the oestrogenic biomarker vitellogenin in order to compare the performance of the two methods for assessing oestrogenic effects of complex mixtures. The three tested mixtures were predominantly acting in an additive manner on the expression of GFP. Additivity was indicated by the overlap of the 95% confidence interval of the concentration response curves for the observed data with the CA and IA prediction models, and model deviation ratios within a factor of two for a majority of the mixture concentrations. However, minor deviations determined as more than additive effects for the mixture of EE2, E1 and E2 and less than additive effects for the mixture of BPA, OP, EE2 and E1 were observed at the higher mixture concentrations tested. The successful prediction of additivity by CA and IA in tg(cyp19a1b-GFP) zebrafish embryos and deviations at high mixture concentrations seemed to correspond well to results obtained in the rainbow trout hepatocyte assay. The present results clearly show the usefulness of combining predictive modelling and use of in vitro bioassays for rapid screening of oestrogenic effects of complex mixtures and environmental samples.
ISSN: 0166-445X

hal-00877351
https://hal.archives-ouvertes.fr/hal-00877351
DOI : 10.1016/j.aquatox.2013.05.001
PUBMED : 23721851

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Energy dissipation is observed on seismic data when a wave propagates through a porous medium, involving different frequency regimes depending on the nature of rock and fluid types. We focus here on the role of partial fluid saturation in unconsolidated porous media, looking in particular at P-wave phase velocity and attenuation. The study consists in running an experiment in a sand-filled tank partially saturated with water. Seismic propagation in the tank is generated in the kHz range by hitting a steel ball on a granite plate. Seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation. Several imbibition/drainage cycles were performed between the water and gas residual saturations. A Continuous Wavelet Transform applied on seismic records allowed us to extract the direct P-wave at each receiver.We observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage. Phase velocities and inverse quality factors are then jointly inverted to get a final poro-visco-elastic model of the partially saturated sand that satisfactorily reproduces the data. The model formulation consists in generalizing the Biot theory to effective properties of the fluid and medium (permeability and bulk modulus) in order to properly explain the phase velocity variation as a function of the saturation. The strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding, adding to Biot's losses. This study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct P-waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media.
ISSN: 0956-540X

hal-00779920
https://hal.archives-ouvertes.fr/hal-00779920
https://hal.archives-ouvertes.fr/hal-00779920/document
https://hal.archives-ouvertes.fr/hal-00779920/file/Barriere_et_al_HAL.pdf
DOI : 10.1111/j.1365-246X.2012.05691.x

Éditeur(s) : Public Library Science
Résumé : The blue mussel, Mytilus edulis, is a commercially important species, with production based on both fisheries and aquaculture. Dynamic Energy Budget (DEB) models have been extensively applied to study its energetics but such applications require a deep understanding of its nutrition, from filtration to assimilation. Being filter feeders, mussels show multiple responses to temporal fluctuations in their food and environment, raising questions that can be investigated by modeling. To provide a better insight into mussel–environment interactions, an experiment was conducted in one of the main French growing zones (Utah Beach, Normandy). Mussel growth was monitored monthly for 18 months, with a large number of environmental descriptors measured in parallel. Food proxies such as chlorophyll a, particulate organic carbon and phytoplankton were also sampled, in addition to non-nutritious particles. High-frequency physical data recording (e.g., water temperature, immersion duration) completed the habitat description. Measures revealed an increase in dry flesh mass during the first year, followed by a high mass loss, which could not be completely explained by the DEB model using raw external signals. We propose two methods that reconstruct food from shell length and dry flesh mass variations. The former depends on the inversion of the growth equation while the latter is based on iterative simulations. Assemblages of food proxies are then related to reconstructed food input, with a special focus on plankton species. A characteristic contribution is attributed to these sources to estimate nutritional values for mussels. M. edulis shows no preference between most plankton life history traits. Selection is based on the size of the ingested particles, which is modified by the volume and social behavior of plankton species. This finding reveals the importance of diet diversity and both passive and active selections, and confirms the need to adjust DEB models to different populations and sites.
Plos One (1932-6203) (Public Library Science), 2014-10 , Vol. 9 , N. 10 , P. 1-13

Droits : 2014 Picoche et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
http://archimer.ifremer.fr/doc/00218/32895/31380.pdf
http://archimer.ifremer.fr/doc/00218/32895/31381.pdf
http://archimer.ifremer.fr/doc/00218/32895/31382.pdf
http://archimer.ifremer.fr/doc/00218/32895/31383.pdf
http://archimer.ifremer.fr/doc/00218/32895/31384.pdf

Éditeur(s) : HAL CCSD Springer
Résumé : International audience
Thermoelastic behavior of different marble types was analyzed using computational modeling and experimental measurements. Eight marble samples with different composition, grain size, grain boundary geometry, and texture were investigated. Calcitic and dolomitic marbles were considered. The average grain size varies from 75 μm to 1.75 mm; grain boundary geometry differs from nearly equigranular straight grain boundaries to inequigranular-interlobate grain boundaries. Four typical marble texture types were observed by EBSD measurements: weak texture; strong texture; girdle texture and high-temperature texture. These crystallographic orientations were used in conjunction with microstructure-based finite element analysis to compute the thermoelastic responses of marble upon heating. Microstructural response maps highlight regions and conditions in the marble fabric that are susceptible to degradation phenomena. This behavior was compared to the measured thermal expansion behavior, which shows increasing residual strains upon repetitive heating-cooling cycles. The thermal expansion behavior as a function of temperature changes can be classified into four categories: (a) isotropic thermal expansion with small or no residual strain; (b) anisotropic thermal expansion with small or no residual strain; (c) isotropic thermal expansion with a residual strain; and (d) anisotropic thermal expansion with residual strain. Thermal expansion coefficients were calculated for both simulated and experimental data and also modeled from the texture using the MTEX software. Fabric parameters control the amount and directional dependence of the thermal expansion. Marbles with strong texture show higher directional dependence of the thermal expansion coefficients and have smaller microstructural values of the maximum principal stress and strain energy density, the main precursors of microcracking throughout the marble fabric. In contrast, marbles with weak texture show isotropic thermal expansion behavior, have a higher propensity to microcracking, and exhibit higher values of maximum principal stress and strain energy density. Good agreement between the experimental and computational results is observed, demonstrating that microstructure-based finite-element simulations are an excellent tool for elucidating influences of rock fabric on thermoelastic behavior.
ISSN: 1866-6280

hal-00858095
https://hal.archives-ouvertes.fr/hal-00858095
DOI : 10.1007/s12665-013-2406-z

Éditeur(s) : HAL CCSD
Résumé : The main purpose of this thesis was to characterize and to model the hydrodynamic and thermochemical processes leading to the alteration of the wellbore cement materials under borehole conditions. Percolation experiments were performed on fractured cement samples under CO2 storage conditions (60°C and 10MPa). Injection flow rate was dictated by the fracture aperture of each sample. CO2 enriched brine was flowed along the fracture aperture, and permeability changes as well as chemical evolution of major cations were continuously acquired during the experiment time. Reaction paths developed by the alteration of the cement were characterized using microtomography and ESEM images. The experiments conducted using samples presenting large fracture apertures during 5h showed that permeability was maintained constant during the experiment time. Three reacted layers were displaying by the alteration of portlandite and CSH. Long term experiment (26h) conducted with large initial fracture aperture showed a decrease of the permeability after 15hours of CO2 exposure. Otherwise, experiments performed on samples presenting narrow apertures indicated the conversion of portlandite and CSH to calcite leading to the permeability reduction and the fracture clogging. Assemblages of phases and chemical changes were modelled using GEMS-PSI speciation code. We studied also using a coupled transport-reactive model the conditions leading to the cement alteration and the formation of associated layers.
L'objectif de cette thèse était de modéliser à partir des expériences de percolation-réactive, les processus hydrodynamique et réactionnel qui gouvernent l'altération des ciments de puits. Différentes expériences ont été réalisées dans des conditions représentatives de celles du stockage du CO2. Des échantillons fracturés ont été utilisés pour injecter une saumure enrichie en CO2 à 60°C et 10MPa et à différentes pressions partielles de CO2. Le débitd'injection variait en fonction des propriétés hydrauliques de l'échantillon exposé. L'injection d'une saumure enrichie en CO2 à débit constant à travers une fracture supposée plane a permis d'étudier les modifications des propriétés hydrodynamiques et ces conséquences sur la géochimie et la microstructure du ciment altéré. L'impact dynamique de l'évolution microstructurale a été mis en évidence. Les expériences conduites sur des échantillons présentant de larges ouvertures, réalisées sur une durée de 5 h, ont montré que la perméabilité était maintenue constante le long de l'expérience. Trois couches d'altération se sont développées consécutivement à la dissolution de la portlandite et la décalcification des CSH. L'altération a entrainé la précipitation des carbonates et de la silice amorphe à proximité de la fracture. Dans le cas d'une expérience longue durée appliquant les mêmes conditions que précédemment on a observé que la croissance de la silice amorphe a entrainé la diminution de la perméabilité. Par ailleurs les expériences effectuées sur des échantillons présentant de faibles ouvertures, ont indiqué que la conversion de la portlandite en calcite conduit au colmatage de la fracture. L'évolution des assemblages de phases conduisant à la formation des carbonates et de la silice amorphe a été modélisée à partir du code géochimique GEMS. Les mécanismes de diffusion et les processus de mise en place des couches d'altération ont été étudiés à partir d'un modèle analytique et d'un modèle de transport réactif à partir du code géochimique PHREEQC.
https://tel.archives-ouvertes.fr/tel-01038034

tel-01038034
https://tel.archives-ouvertes.fr/tel-01038034
https://tel.archives-ouvertes.fr/tel-01038034/document
https://tel.archives-ouvertes.fr/tel-01038034/file/theseabdoulghafour.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We describe an experimental system including monitoring of temperature, pressure, pH, oxidation reduction potential and optical density at 600 nm, designed for studying the role of microorganisms on the geological sequestration Of CO2 and its transformation into solid carbonate phases. Measurements were performed in an artificial ground water (AGW) supplemented with urea (2 g.l(-1)) and equilibrated at controlled temperatures with a gaseous phase before bacterial inoculation. We used the ureolytic strain Bacillus pasteurii as a model carbonate precipitating bacteria and showed that it can successfully promote strong pH increases by ureolysis in the AGW equilibrated with CO2 pressures of up to I bar. Increasing salinities (5.8,13.5 and 35.0 g.l(-1)) have a positive effect on the rate of pH increase, whereas the effect of increasing temperatures (30,35 and 38 degrees C) is less important. Calcium is also shown to have a specific positive influence on the rate of ureolysis. The number of viable cells present in solution decreases greatly during the carbonate precipitation event but the population partially recovers once precipitation is over.
ISSN: 0009-2541

hal-00445282
https://hal.archives-ouvertes.fr/hal-00445282
DOI : 10.1016/j.chemgeo.2008.12.012

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

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

Éditeur(s) : HAL CCSD
Résumé : 1 p.
For groundwater issues (potential leakages in waste repository, aquifer management ...), the development of modeling techniques is far ahead of the actual knowledge of aquifers. This raises two fundamental issues: 1) which and how much data are necessary to make predictions accurate enough for aquifer management issues; 2) which models remain relevant to describe the heterogeneity and complexity of geological systems. The French observatory H+ was created in 2002 with the twofold motivation of acquiring a large database for validating models of heterogeneous aquifers, and of surveying groundwater quality evolution in the context of environmental changes. H+ is a network of 4 sites (Ploemeur, Brittany, France; HES Poitiers, France; Cadarache, France; Campos, Mallorca, Spain) with different geological, climatic, and economic contexts. All of them are characterized by a highly heterogeneous structure (fractured crystalline basement for Ploemeur, karstified and fractured limestone for Poitiers, Cadarache and Mallorca), which is far to be taken into account by basic models. Ploemeur is exploited as a tap-water plant for a medium-size coastal city (15,000 inhabitants) for 20 years. Each site is developed for long term investigation and monitoring. They involves a dense network of boreholes, detailed geological and geophysical surveys, periodic campaigns and/or permanent measurements of groundwater flow, water chemistry, geophysical signals (including ground motions), climatic parameter, etc. Several large-scale flow experiments are scheduled per year to investigate the aquifer structure with combined geophysical, hydrogeological, and geochemical instruments. All this information is recorded in a database that has been developed to improve the sustainability and quality of data, and to be used as a collaborative tool for both site researchers and modelers. This project lasts now for 5 years. It is a short time to collect the amount of information necessary to apprehend the complexity of aquifers; but it is already enough to obtain a few important scientific results about the very nature of the flow heterogeneity, the origin and residence time of water elements, the kinetic of geochemical processes, etc. We have also developed new methods to investigate aquifers (in-situ flow measurements, flow experiment designs, groundwater dating, versatile in-situ probes, etc.). This experience aiming at building up long term knowledge appears extremely useful to address critical issues related to groundwater aquifers: the structure and occurrence of productive aquifer in crystalline basement, the assessment of aquifer protection area in the context of highly heterogeneous flow, the biochemical reactivity processes, the long term evolution of both water quantity and quality in the context of significant environmental changes, for instance.
AGU, Fall Meeting 2008
San Francisco, United States

insu-00375980
https://hal-insu.archives-ouvertes.fr/insu-00375980

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO2. Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO2, water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intra-annual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent.
ISSN: 1932-6203

hal-01268529
https://hal.archives-ouvertes.fr/hal-01268529
https://hal.archives-ouvertes.fr/hal-01268529/document
https://hal.archives-ouvertes.fr/hal-01268529/file/journal.pone.0092337.PDF
DOI : 10.1371/journal.pone.0092337

Éditeur(s) : HAL CCSD
Résumé : International audience
More and more animal species are endangered every day on earth. In order to study their adaptation to world and climate change and their chances of survival, numerous initiatives have been taken that mostly need human intrusion into animal communities. Today mobile devices enable researchers to go beyond this limit. In this paper, we propose an original solution that consists on a new framework for detecting individual songs in a bird population and identifying remotely by this way their collective behavior in movements without human interaction. Movement patterns are elicited by analyzing data collected via wireless sensors fitted with microphone. Whereas similar methods use mobile devices fitted on some specimens, we rather propose fixed sensors. We demonstrate that this solution provides a good answer to technical constraints assessed by the context and we discuss results of experimental simulations that allow to define optimized parameters for the architecture to be set up on the ground. Experimental results are provided and show the relative impact of different parameters such as the number of sensors or the population size on the detection rate.
Proceedings of the 8th International Conference on Advances in Mobile Computing and Multimedia (MOMM 2010)

hal-00601641
https://hal.archives-ouvertes.fr/hal-00601641

Éditeur(s) : HAL CCSD Springer/Terra Scientific Publishing Company
Résumé : We analyse the results of Thellier palaeointensity experiments modified so that the measured magnetisation at any stage may be decomposed into components of natural remanent magnetisation (NRM) and laboratory thermal remanent magnetisation (TRM). We demonstrate that the very long high temperature tails of pTRM acquired by multidomain (MD) grains may be detected in Thellier experiments without recourse to explicit pTRM tail check measurements. This can save time in the experimental process and provides a more sensitive indication of how MD behaviour may affect that particular experiment than either pTRM tail checks or the observation of zigzagging in an IZZI experiment. We observe that the action of imparting a pTRM tail also involves some removal of NRM. However, the pTRM tails are not the analogues of classical overprints as may be intuitively expected but instead appear to favour remagnetisation over demagnetisation. This and other observed behaviour is not consistent with any phenomenological model of MD TRM but is consistent with predictions made by kinematic theory.
ISSN: 1343-8832

hal-00407946
https://hal.archives-ouvertes.fr/hal-00407946

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Neurogenesis initiates during early development and it continues through later developmental stages and in adult animals to enable expansion, remodeling, and homeostasis of the nervous system. The generation of nerve cells has been analyzed in detail in few bilaterian model organisms, leaving open many questions about the evolution of this process. As the sister group to bilaterians, cnidarians occupy an informative phylogenetic position to address the early evolution of cellular and molecular aspects of neurogenesis and to understand common principles of neural development. Here we review studies in several cnidarian model systems that have revealed significant similarities and interesting differences compared to neurogenesis in bilaterian species, and between different cnidarian taxa. Cnidarian neurogenesis is currently best understood in the sea anemone Nematostella vectensis, where it includes epithelial neural progenitor cells that express transcription factors of the soxB and atonal families. Notch signaling regulates the number of these neural progenitor cells, achaete-scute and dmrt genes are required for their further development and Wnt and BMP signaling appear to be involved in the patterning of the nervous system. In contrast to many vertebrates and Drosophila, cnidarians have a high capacity to generate neurons throughout their lifetime and during regeneration. Utilizing this feature of cnidarian biology will likely allow gaining new insights into the similarities and differences of embryonic and regenerative neurogenesis. The use of different cnidarian model systems and their expanding experimental toolkits will thus continue to provide a better understanding of evolutionary and developmental aspects of nervous system formation.
ISSN: 1759-7692

Droits : http://creativecommons.org/licenses/by-nc/
hal-01405097
http://hal.upmc.fr/hal-01405097
http://hal.upmc.fr/hal-01405097/document
http://hal.upmc.fr/hal-01405097/file/Rentzsch_et_al-2016-Wiley_Interdisciplinary_Reviews__Developmental_Biology.pdf
DOI : 10.1002/wdev.257

Éditeur(s) : Elsevier
Résumé : A study was conducted using a bioenergetics approach to generate information on energy requirement and feed utilization of Litopenaeus stylirostris. Animals (initial mean weight 21 +/- 1 g were fed ad libitum six experimental diets, ranging from 25 to 58% crude protein (CP), for 50 days. Weight gain increased from 21 to 30 g with increasing dietary protein level. Survival rates averaged 80%. Basal metabolism (HeE) and heat increment of feeding (HiE) were monitored using respirometry. HeE was on average I U shrimp(-1) day(-1) or 47 U kg live weight(-1) day (22 kJ/kg(0.8). d(-1)), slightly more than what is observed in fish. HiE averaged 0.2 W/sbrimp(-1) day(-1) or 10 W kg live weight(-1) day(-1) (4 kJ/kg(0.8) d(-1)). It represented 3 1 % and 12% digestible energy intake (DET) for shrimp fed on 58% CP and 25% CP diet respectively. Non-fecal (UE + ZE) energy calculated on the basis of N-ammonia excretion averaged 0.2 jig N-ammonia/g dry wt./ mn or 25 J live shrimp(-1) day(-1) in fasting stage and increased to 40 J in post-prandial stage. Ammonia production increased with increasing dietary crude protein (CP). The O:N ratio indicated that protein was increasingly used as an energy substrate as CP increased. The information was used to construct an energy budget for shrimp fed a protypical 40% CP diet. Gross energy intake (IE) was estimated at 6.5 W live shrimp(-1) day(-1); digestible energy intake (DEI) at 5, urinary and branchial excretion (UE +ZE) at 1.2, total heat production (HE) at 3.2; recovered energy (RE) at 0.6 (or 11% DEI). L. stylirostris adults issued from domesticated strain appeared to be more efficiently utilizing (i.e. converting into carcass energy) protein than carbohydrates. This preliminary energy budget can be used to construct theoretical feed requirement and waste outputs model for L. stylirostris. (C) 2007 Published by Elsevier B.V.
Aquaculture (0044-8486) (Elsevier), 2007-10 , Vol. 271 , N. 1-4 , P. 439-448

Droits : 2007 Published by Elsevier B.V.
http://archimer.ifremer.fr/doc/2007/publication-6263.pdf
DOI:10.1016/j.aquaculture.2006.05.062
http://archimer.ifremer.fr/doc/00000/6263/

Éditeur(s) : Gauthier-Villars
Résumé : Several models for the evolution of complex life histories have assumed a carrying capacity for both larval and postlarval stages. In addition, the densities of larvae in laboratory experiments are often so high that there is competition for food. Published values for maximal clearance rates and estimated abundances of larvae suggest that these assumptions and experimental conditions are unrealistic for most marine larvae. For most ciliated larvae, maximum clearance rates are at most a few mi of water daily, and their estimated larval concentrations are at most one to several larvae per liter. Therefore these larvae appear to be too scarce for their grazing to affect their food supply. Larvae of most species are also scarce relative to co-occurring planktonic animals that feed on particles in the same size range. Larvae of many species are scarce relative to co-occurring larvae with a similar feeding apparatus. These observations suggest that larvae of most species have a negligible effect on their food supply. Exceptions could occur when a single species of larva dominates the zooplankton; such circumstances appear to be rare, although extreme aggregations of larvae dominated by a single species could be missed by pump or net samples. Analogous but more conjectural arguments can be made for density-dependent attraction of predators to larval prey. These inferences apply to single species, not to meroplanktonic larvae as a whole: in some coastal waters, larvae of benthic invertebrates comprise a large portion of the multicellular planktonic animals. Also, a species' larval growth may be food-limited in many waters, even when the abundance of food is independent of the abundance of its larvae.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1996 , Vol. 19 , N. 3-4 , P. 399-407

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00094/20495/18164.pdf
http://archimer.ifremer.fr/doc/00094/20495/

Éditeur(s) : HAL CCSD
Résumé : International audience
More and more animal species are endangered. In order to study and protect them, several measures have been taken, which now seem to show their limit. This work focuses on the counting process, a key issue for any project that aims to protect animals. Indeed, this paper proposes an algorithm for automatic counting of singing birds in their habitat by using wireless sensors fitted with microphone. Sensors are used to record audio samples of bird songs. These samples are used to extract some kinds of song fingerprint that are thereafter used to recognize the bird species, through a classification process. Afterwards, by analyzing data which have been collected by a central base, the network structure derived from detection fields of sensors, allows our algorithm to propose an estimate of singing birds in the habitat. This paper details the counting algorithm which uses graph theory and audio inputs comparison. Finally, we demonstrate our scheme efficiency through experimentations.
Local Computer Networks (LCN)
Clearwater, United States

hal-00786165
https://hal.archives-ouvertes.fr/hal-00786165
DOI : 10.1109/LCNW.2012.6424060

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699
Background and Aims Plastic tree-shelters are increasingly used to protect tree seedlings against browsing animals and herbicide drifts. The biomass allocation in young seedlings of deciduous trees is highly disturbed by common plastic tree-shelters, resulting in poor root systems and reduced diameter growth of the trunk. The shelters have been improved by creating chimney-effect ventilation with holes drilled at the bottom, resulting in stimulated trunk diameter growth, but the root deficit has remained unchanged. An experiment was set up to elucidate the mechanisms behind the poor root growth of sheltered Prunus avium trees. Methods Tree seedlings were grown either in natural windy conditions or in tree-shelters. Mechanical wind stimuli were suppressed in ten unsheltered trees by staking. Mechanical stimuli (bending) of the stem were applied in ten sheltered trees using an original mechanical device. Key Results Sheltered trees suffered from poor root growth, but sheltered bent trees largely recovered, showing that mechano-sensing is an important mechanism governing C allocation and the shoot-root balance. The use of a few artificial mechanical stimuli increased the biomass allocation towards the roots, as did natural wind sway. It was demonstrated that there was an acclimation of plants to the imposed strain. Conclusions This study suggests that if mechanical stimuli are used to control plant growth, they should be applied at low frequency in order to be most effective. The impact on the functional equilibrium hypothesis that is used in many tree growth models is discussed. The consequence of the lack of mechanical stimuli should be incorporated in tree growth models when applied to environments protected from the wind (e.g. greenhouses, dense forests).
ISSN: 0305-7364

hal-01032056
https://hal.archives-ouvertes.fr/hal-01032056
DOI : 10.1093/aob/mcn054

Éditeur(s) : HAL CCSD
Résumé : Water vapour is highly variable in the atmosphere with concentration reaching saturation in the tropics and with dry areas over elevated continental region. Good knowledge of the amount of integrated water vapour in the air is necessary to predict phase changes and in particular precipitation. Water vapour variability measurements are still insufficient with standard observing systems. Moreover accurate GPS antenna positioning is affected by the refractivity index variation in the troposphere. Consequently, vertical positioning component estimation is difficult. This variation is directly linked to distribution of variables such as pressure, temperature and humidity along the path between satellite and receiver. Here we study more specifically heavy rains et notably Cevenols events. This thesis work consists to check the GPS measurement validity to quantify water vapour in comparison with measurements from radiosoundings and meteorological model outputs. GPS observations and flux surface information have been analysed to see if water vapour quantification by GPS allowed characterising heavy rain events (cumulative rainfall amount greater than 150 mm). Then, we tested the GPS data assimilation impact on cumulative precipitation forecasts using the high resolution Meteo France AROME model (2.5 km). Finally the quality and the contribution of GPS measurement on sea is evaluated for water vapour measurement. This study has been realised in the framework of VAPIMED experiment.
La vapeur d'eau varie largement dans l'atmosphère avec des concentrations allant de la saturation dans les tropiques à des zones presque sèches au-dessus des zones continentales élevées. Une bonne connaissance du contenu en vapeur d'eau dans l'air est nécessaire pour la prévision des changements de phases, notamment les précipitations. La mesure de la variabilité de la vapeur d'eau est une lacune des systèmes d'observation. Par ailleurs, il est apparu que le positionnement précis des antennes GPS était affecté par la variation de l'indice de réfraction dans la troposphère, ce qui rend particulièrement difficile l'estimation de la composante verticale. Cette variation est directement liée à la distribution des variables pression, température et humidité sur les trajets satellite-récepteur. On s'intéresse ici à l'étude des précipitations intenses et notamment aux épisodes Cévenols. Ce travail de thèse consiste à vérifier la validité de la mesure GPS pour la quantification de la vapeur d'eau en la comparant avec des mesures issues de radiosondage et des sorties de modèle météorologique. On cherche à analyser si la quantification de vapeur d'eau par GPS permet de caractériser les forts événements précipitants (cumuls supérieurs à 150 mm) à l'aide d'observations conjointes sur les flux de surface. On étudie ensuite l'impact de l'assimilation de données GPS issues d'un réseau GPS dense sur la prévision des cumuls de pluies dans le modèle à hauterésolution (2.5 km) AROME de Météo France. Finalement on évalue la qualité et l'apport de la mesure de vapeur d'eau par GPS en mer dans le cadre d'une campagne de mesure VAPIMED).
https://tel.archives-ouvertes.fr/tel-00444081

Droits : info:eu-repo/semantics/OpenAccess
tel-00444081
https://tel.archives-ouvertes.fr/tel-00444081
https://tel.archives-ouvertes.fr/tel-00444081/document
https://tel.archives-ouvertes.fr/tel-00444081/file/These_KBoniface.pdf