Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
A network of 26 GPS sites was implemented in Iran and Northern Oman to measure displacements in this part of the Arabia–Eurasia collision zone. We present the GPS velocity field obtained from three surveys performed in 1999 September, 2001 October and 2005 September and the deduced strain tensor. This study refines previous studies inferred from only the two first surveys. Improvements are significant in NE Iran. The present-day shortening rate across the mountain belts of NE Iran is estimated to 5 ± 1 mm yr−1 at about N11°, 2 ± 1 mm yr−1 of NS shortening across the eastern Kopet Dag and 3 ± 1 mm yr−1 of NS shortening across Binalud and Kuh-e-Sorkh. Our GPS measurements emphasize the varying character of the Kopet Dag deformation between its southeastern part with prevailing thrusting at low rates and its northwestern part with dominant strike-slip activity at increasing rates. The principal axes of the horizontal strain tensor appears very homogeneous from the Zagros to the Alborz and the Kopet-Dag (N20°) and in eastern Iran (Makran and Lut block: N30°). Only NW Iran suffers a variable strain pattern which seems to wrap the Caspian basin. The strain tensor map underlines the existence of large homogeneous tectonic provinces in terms of style and amplitude of the deformation.
ISSN: 0956-540X

insu-00346744
https://hal-insu.archives-ouvertes.fr/insu-00346744
DOI : 10.1111/j.1365-246X.2007.03477.x

Résumé : in mollusc hatcheries. Consequently, we assessed themost commonly used species to establish their growth and size profiles, their cytomorphological, biochemical, biomolecular identification as well as their cytometer signs, and also their ability to grow under extreme conditions of temperature and salinity. This work aimed at matching the conformity of the strains used in Argenton (dispatched to most of the French commercial hatcheries) to those of a referenced culture collection. A previous screening preceded this study, because of the 45 species and/or clones held originally, Argenton kept no more than 15 species. As most of the latter are also represented in referenced collection, our strains are therefore correctly identified. On the other hand, the combination of several approaches (characteristic of growth and size, cytomorphological description, establishment of biochemical and biomolecular profiles) to discriminate the different species was broadly successful. Nevertheless, flow cytometer measurements were extremely variable from sample to sample, dueto their high sensitivity to the microalga's physiological state. Accordingly, we have developed a method of identification which could be transferred at a national or international level, to the Institutions in charge of microalgae collections. Furthermore, we achieved relevant data to establish an identity card for each of the microalgae suitable for mollusc hatcheries.
La caractérisation des microalgues fourrage constituait l'un des points perfectibles au regard de ce qui est appliquée en microbiologie. Nous avons alors cherché à définir, pour les espèces les plus utilisées en écloserie, leurs profils de croissance et de taille, leur caractéristiques cytomorphologique, cytofluorimétrique, biochimique et biomoléculaire, et enfin, précisé leur aptitude au développement sous des conditions extrêmes de température et de salinité (écotolérance). Ce travail avait pour but de vérifier, d'une part, la conformité des souches utilisées à l'écloserie d'Argenton (auprès de laquelle se fournissent la plupart des écloseries commerciales françaises) en comparant les espèces utilisées à celles issues d'une collection référencée. Un premier balayage avait été réalisé avant la mise en place de cette étude puisque sur les 45 espèces et clones détenus originellement, Argenton ne possédait plus que 15 espèces. La plupart de ces dernières ayant leur équivalent en collection référencée notre souchier est désormais parfaitement identifiée. D'autre part, la confrontation de plusieurs approches, caractéristique de la croissance et de taille, description cytomorphologique, établissement des profils biochimique et biomoléculaire, écotolérance, signature cytofluorimétrique, pour discriminer les différentes espèces de microalgues fourrage a été globalement couronnée de succès. Seule cette dernière technique n'a pas permis de caractériser les espèces entre elles, les paramètres mesurés en cytométrie de flux étant particulièrement sensibles à l'état physiologique des microalgues, très variable d'un échantillon à un autre. Nous disposons dorénavant d'une méthode d'identification qu'il serait souhaitable de transférer, au niveau national voire international, auprès des organismes en charge des collections. De plus, nous disposons dorénavant de données pertinentes pour établir pour chacune des microalgues d'intérêt aquacole une véritable carte d'identité.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2004/rapport-1546.pdf
http://archimer.ifremer.fr/doc/00000/1546/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This paper aims to present an overview on the influence of rheological heterogeneity and mechanical anisotropy on the deformation of continents. After briefly recapping the concept of rheological stratification of the lithosphere, we discuss two specific issues: (1) as supported by a growing body of geophysical and geological observations, crust=mantle mechanical coupling is usually efficient, especially beneath major transcurrent faults which probably crosscut the lithosphere and root within the sublithospheric mantle; and (2) in most geodynamic environments, mechanical properties of the mantle govern the tectonic behaviour of the lithosphere. Lateral rheological heterogeneity of the continental lithosphere may result from various sources, with variations in geothermal gradient being the principal one. The oldest domains of continents, the cratonic nuclei, are characterized by a relatively cold, thick, and consequently stiff lithosphere. On the other hand, rifting may also modify the thermal structure of the lithosphere. Depending on the relative stretching of the crust and upper mantle, a stiff or a weak heterogeneity may develop. Observations from rift domains suggest that rifting usually results in a larger thinning of the lithospheric mantle than of the crust, and therefore tends to generate a weak heterogeneity. Numerical models show that during continental collision, the presence of both stiff and weak rheological heterogeneities significantly influences the large-scale deformation of the continental lithosphere. They especially favour the development of lithospheric-scale strike-slip faults, which allow strain to be transferred between the heterogeneities. An heterogeneous strain partition occurs: cratons largely escape deformation, and strain tends to localize within or at the boundary of the rift basins provided compressional deformation starts before the thermal heterogeneity induced by rifting are compensated. Seismic and electrical conductivity anisotropies consistently point towards the existence of a coherent fabric in the lithospheric mantle beneath continental domains. Analysis of naturally deformed peridotites, experimental deformations and numerical simulations suggest that this fabric is developed during orogenic events and subsequently frozen in the lithospheric mantle. Because the mechanical properties of single-crystal olivine are anisotropic, i.e. dependent on the orientation of the applied forces relative to the dominant slip systems, a pervasive fabric frozen in the mantle may induce a significant mechanical anisotropy of the whole lithospheric mantle. It is suggested that this mechanical anisotropy is the source of the so-called tectonic inheritance, i.e. the systematic reactivation of ancient tectonic directions; it may especially explain preferential rift propagation and continental break-up along pre-existing orogenic belts. Thus, the deformation of continents during orogenic events results from a trade-off between tectonic forces applied at plate boundaries, plate geometry, and the intrinsic properties (rheological heterogeneity and mechanical anisotropy) of the continental plates.
ISSN: 0040-1951

hal-01389719
http://hal.univ-reunion.fr/hal-01389719
http://hal.univ-reunion.fr/hal-01389719/document
http://hal.univ-reunion.fr/hal-01389719/file/vauchez_etal_rheology_1998_hal.pdf
DOI : 10.1016/S0040-1951(98)00137-1

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Regional-scale deformation taking place in a strongly anisotropic, yet homogeneous metapelitic protolith during an apparently single tectonic event was systematically investigated as a function of the distance to the main tectonic contact (i.e., the Filabres shear zone, a major detachment in the Betic Cordilleras, Spain). The density of C3' shear bands (or extensional crenulation cleavage) reworking the earlier S2 schistosity increases exponentially towards the contact, in parallel with the decrease in the size of the shear domains. Systematic variations in angles and shape ratios are also reported. Deformation and age patterns, however, suggest that this spectacular trend at least partly results from a progressive localization of the deformation through time. This fossilized shear strain gradient was thus produced somewhat diachronously. Such shear strain patterns nevertheless provide a mean to constrain the rheological properties for such weak lithologies and a mean to better understand crustal deformation.
ISSN: 0191-8141

insu-00545043
https://hal-insu.archives-ouvertes.fr/insu-00545043
https://hal-insu.archives-ouvertes.fr/insu-00545043/document
https://hal-insu.archives-ouvertes.fr/insu-00545043/file/JSGagardetal2.pdf
DOI : 10.1016/j.jsg.2010.11.011

Éditeur(s) : HAL CCSD Springer-Verlag Berlin Heidelberg
Résumé : International audience
The main biological function of reaction wood is to act as " muscle " for trees, enabling them to control their posture. The key property to achieve this function is the development of high mechanical stress during the formation of reaction wood cells, called " maturation strains ". Actually, reaction wood formation is basically the asymmetric formation of wood around the tree circumference, with higher maturation strains on the side where reaction wood is formed than on the opposite side. This asymmetry enables stems to bend upward or to compensate for the downward bending induced by gravity. At the cross section level, the performance in this biological function is linked not only to the magnitude of this asymmetry but also to an effect of the cross-sectional size (diameter) of the stem. Eccentric growth and variations in wood mechanical stiffness are second order effects that can modify this performance. Differences in maturation strains between reaction and non-reaction woods are related to their specific cell wall structure and composition. The swelling of the cell wall matrix during maturation and the effect of microfibril angle explain the differences in maturation strains between normal and compression wood. However, this mechanism fails in explaining the high maturation shrinkage of tension wood, and several hypotheses at the molecular levels are still under debate. How trees perceive their gravitational disequilibrium is also an open question for physiologists. Integrative biomechanical modelling (from the polymer level to the cell wall, cross section and whole tree levels) enables defining key variables that explain the performance of reaction wood as a system that insures the stem motricity. Maturation strains can be precisely measured only in recently formed wood at the tree surface, but their changes during the whole tree life can also be estimated by retrospective dendrochronological analysis through structural markers of reaction wood. Lastly, wood in living trees ensures general storage, defence, vascular and skeletal functions, that ask general questions about synergies and trade-offs as the structural characteristics of reaction wood can affect all these functions.
The Biology of Reaction Wood

ISBN : 978-3-642-10813-6
hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085
https://hal.archives-ouvertes.fr/hal-01452085/document
https://hal.archives-ouvertes.fr/hal-01452085/file/Chap_Gril_al_Biomechanical_action_biological_functions_2014.pdf

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
The association of experimental data showing that the plastic deformation of olivine, the main constituent of the upper mantle, is highly anisotropic and the ubiquitous seismic anisotropy in the upper mantle, which indicates that olivine crystals show coherent orientations over scales of tens to hundreds of kilometers, implies that the long-term deformation in the upper mantle is anisotropic. We propose a multiscale approach, based on a combination of finite element and homogenization techniques, to model the deformation of a lithospheric plate while fully considering the mechanical anisotropy stemming from a strain-induced orientation of olivine crystals in the mantle. This multiscale model explicitly takes into account the evolution of crystal preferred orientations (CPO) of olivine and of the mechanical anisotropy during the deformation. We performed a series of numerical experiments simulating the uniaxial extension of a homogeneous (100% olivine) but anisotropic plate to test the role of the olivine CPO on the plate mechanical behavior and the link between CPO and mechanical anisotropy evolution. Even for this simple solicitation, different orientations and intensity of the initial olivine CPO result in variable plate strengths and deformation regimes. A plate with an initial CPO where the olivine [100] and [010] axes are concentrated at 45 degrees to the extension direction has high resolved shear stresses on the easy (010)[100] and (001)[100] slip systems of olivine. This results in low strength and in deformation by transtension. Plates with an initial CPO where the maximum of [100] axes is parallel or normal to the extension direction show a high initial strength. Isotropic plates have an intermediate behavior. The progressive rotation of olivine [100] axes toward the imposed stretching direction results in hardening in all models, except in those characterized by an initial concentration of olivine [100] axes normal to the imposed extension, in which softening is followed by hardening.
ISSN: 1525-2027

hal-00420063
https://hal.archives-ouvertes.fr/hal-00420063
DOI : 10.1029/2009GC002423

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background : Trichoderma reesei is the main industrial source of cellulases and hemicellulases required for the hydrolysis of biomass to simple sugars, which can then be used in the production of biofuels and biorefineries. The highly productive strains in use today were generated by classical mutagenesis. As byproducts of this procedure, mutants were generated that turned out to be unable to produce cellulases. In order to identify the mutations responsible for this inability, we sequenced the genome of one of these strains, QM9136, and compared it to that of its progenitor T. reesei QM6a.Results : In QM9136, we detected a surprisingly low number of mutagenic events in the promoter and coding regions of genes, i.e. only eight indels and six single nucleotide variants. One of these indels led to a frame-shift in the Zn2Cys6 transcription factor XYR1, the general regulator of cellulase and xylanase expression, and resulted in its C-terminal truncation by 140 amino acids. Retransformation of strain QM9136 with the wild-type xyr1 allele fully recovered the ability to produce cellulases, and is thus the reason for the cellulase-negative phenotype. Introduction of an engineered xyr1 allele containing the truncating point mutation into the moderate producer T. reesei QM9414 rendered this strain also cellulase-negative. The correspondingly truncated XYR1 protein was still able to enter the nucleus, but failed to be expressed over the basal constitutive level.Conclusion : The missing 140 C-terminal amino acids of XYR1 are therefore responsible for its previously observed auto-regulation which is essential for cellulases to be expressed. Our data present a working example of the use of genome sequencing leading to a functional explanation of the QM9136 cellulase-negative phenotype.
ISSN: 1471-2164

Droits : http://creativecommons.org/licenses/by/
hal-01149671
http://hal.upmc.fr/hal-01149671
http://hal.upmc.fr/hal-01149671/document
http://hal.upmc.fr/hal-01149671/file/Lichius_2015_Genome_sequencing.pdf
DOI : 10.1186/s12864-015-1526-0

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Background: The impact of hepatitis B virus (HBV) genomic variability on the measurement of HBsAg level has been poorly evaluated. Objective: This study was designed to compare the performance of all the available assays measuring HBsAg level in this setting. Study design: A large selection of wild type HBV genotypes (n = 184) and HBsAg strains harboring mutations in the S gene (n = 81) from clinical samples was studied with three HBsAg quantification assays: Architect HBsAg (Abbott), LiaisonXL Murex HBsAg Quant (DiaSorin) and the Elecsys HBsAgII (Roche). Results: The overall percentage of positive results was 99.2% for Abbott, 98.9% for DiaSorin and 98.1% for Roche. Abbott and Roche assays provided an excellent concordance in HBsAg quantification (global mean bias of -0.006 logIU/mL). By contrast, DiaSorin underestimated HBsAg level with values 0.112 logIU/ml and 0.103 logIU/ml lower than Abbott and Roche, respectively. By contrast, DiaSorin slightly over quantified gtC(2.5% over the expected value) while Abbott provided values 6.2% lower than expected and 16.2% lower than what observed for the other genotypes. HBsAg quantitative assays were influenced by HBs protein substitutions irrespective to the genotype but no specific protein pattern that would particularly impair the quantification by one technique has been identified. However, Roche seemed to be particularly impacted by substitutions at 145 residue: 75% of under quantified samples carried a substituted 145 residue. Conclusion: This head-to-head comparison indicates a good correlation between all current systems used to quantify HBsAg but clearly shows an influence of both the genotype and the presence of "a" determinant variants in the absolute quantification of HBsAg. While these discrepancies may not translate into major clinical consequence, they may explain an absence of detection of weak concentration of HBsAg on some systems. (C) 2017 Elsevier B.V. All rights reserved.
ISSN: 1386-6532

hal-01588395
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01588395
DOI : 10.1016/j.jcv.2017.02.001
PUBMED : 28189936

Éditeur(s) : HAL CCSD
Résumé : In SW Yukon – SE Alaska, the boundary between the Pacific and North America plates is characterized by a syntaxis at the transition between the Aleutian subduction to the W and the Fairweather – Queen Charlotte strike-slip faults to the SE. The relative motion is oblique to the main fault structures, and the area is marked by the Yakutat block collision. From the Chugach – Saint Elias mountains in the plate boundary zone (up to 6 000 m high) to the intraplate strike-slip faults, markers of the present-day deformation give information on its partition in the system.During my PhD, I first measure surface deformation using a dense GPS network, deployed up to 500 km inland the North America plate. After precise processing and corrections of transient effects in the area (postseismic and glacial isostatic rebound), a new residual velocity field is produced for the syntaxis area, from which I derive strain rates. Those data allow me to quantify the fault slip rates for Fairweather and southern Denali strike-slip faults, and to characterize a bi-modal deformation pattern: Along the plate boundary, the deformation is localized on large-scale structures (accretionary prism to the W, Fairweather to the E); In the syntaxis area, strain rates are the highest and the GPS data shows a diffuse intraplate deformation, similar to an indentor pattern. The Yakutat block seems to strongly drive the North America plate deformation.This indentor pattern induces strong lateral variations on the large intraplate faults: the Denali – Totschunda – Duke River system. In a second part, I realize a regional geomorphological study to characterize the role and slip rate of those faults. From very high-resolution Digital Elevation Models (~ 1 m), a detailed cartography is done. On the basis of fieldwork observations, I measure offsets of fluvial and glacial markers, which are sampled for dating. A dextral cumulative deformation is highlighted on the northern Denali Fault, where as all southern Denali is marked by vertical deformation. This study allows me to quantify new slip rates for the system Denali – Totschunda – Duke River, and to show the leading role of the Totschunda (~ 14 mm/a) and Duke River (~ 6 mm/a) faults, contrary to the Denali Fault (~ 1 mm/a) North of the syntaxis.The new tectonic model for the Yakutat collision provides an important case study for the understanding of indentor systems. The concomitance of a rigid-block deformation (to the West) and diffuse deformation (to the East), as well as the near-zero slip rate on the lithospheric-scale southern Denali Fault highlight the major control of boundary conditions and the structural heritage on the orogen deformation.
Au SO Yukon – SE Alaska, la frontière entre les plaques Pacifique et Nord-Amérique est marquée par une syntaxe à la transition entre la subduction des Aléoutiennes à l’O et le décrochement de Fairweather – Queen Charlotte au SE. Le mouvement relatif est oblique et la région est marquée par la collision du bloc Yakutat. De la chaine des Chugach – Saint Elias en frontière de plaque (jusqu’à 6 000 m d’altitude) aux grands décrochements intraplaque, les marqueurs de la déformation actuelle apportent des informations sur sa partition dans ce système.Au cours de cette thèse, je m’intéresse dans un premier temps à mesurer la déformation de surface à l’aide d’un réseau GPS dense, déployé jusqu’à 500 km à l’intérieur de la plaque Nord-Amérique. Après un travail minutieux de traitement des données et de correction des effets transitoires (rebond post-glaciaire et post-sismique), un champ de vitesses résiduelles robuste et inédit est produit au niveau de la syntaxe, dont je dérive des taux de déformation. Ces données me permettent de quantifier les vitesses de glissement les failles décrochantes de Fairweather et Denali au Sud, et également de caractériser une déformation bimodale : En frontière de plaques, la déformation est localisée sur les grandes structures (prisme d’accrétion à l’O, Fairweather à l’E) ; Au niveau de la syntaxe, les taux de déformation sont les plus importants et les données GPS mettent en évidence une déformation intraplaque diffuse, similaire à un champ attendu à l’aplomb d’un indenteur. Le bloc Yakutat semble donc contrôler fortement la déformation de la plaque Nord-Amérique.Ce champ de déformation induit des variations latérales fortes sur les grandes failles intraplaque : le système Denali-Totschunda-Duke River. Dans une seconde partie, je réalise une étude géomorphologique régionale pour caractériser le rôle et la vitesse de ces failles. À partir de Modèles Numériques de Terrain très haute résolution (~ 1 m), une cartographie de détail est réalisée. Puis une mission de terrain me permet de mesurer des décalages sur des marqueurs fluviatiles et glaciaires et collecter des échantillons pour les dater. Je mets en évidence une déformation cumulée dextre sur le segment Nord de la faille de Denali, alors que toute la partie Sud déforme verticalement la surface. Cette étude me permet de quantifier de nouvelles vitesses de failles sur le système Denali-Totschunda-Duke River, et de montrer le rôle prépondérant des failles de Totschunda (~ 14 mm/a) et Duke River (~ 6 mm/a) contrairement à la faille de Denali (~ 1 mm/a) au Nord de la syntaxe.Le nouveau modèle cinématique proposé pour la région de collision Yakutat permet d’apporter un nouvel exemple à la compréhension des systèmes d’indenteur. La concomitance d’une déformation de blocs (à l’Ouest) et diffuse (à l’Est), ainsi que l’absence de déformation sur la faille lithosphérique de Denali Sud met en évidence le contrôle majeur des conditions aux limites et de l’héritage structural dans la déformation des orogènes.
https://hal.archives-ouvertes.fr/tel-01241688

tel-01241688
https://hal.archives-ouvertes.fr/tel-01241688
https://hal.archives-ouvertes.fr/tel-01241688/document
https://hal.archives-ouvertes.fr/tel-01241688/file/manuscrit_anais_v2_optimise.pdf

Résumé : Les forêts côtières inondables (FCI) des régions tropicales et subtropicales remplissent des fonctions écologiques nécessaires aux écosystèmes marins côtiers situés en aval et aux populations humaines vivant à proximité Aux Antilles, les mangroves et les forêts marécageuses à Pterocarpus officinalis sont structurés par des espèces ligneuses qui ont développé des adaptations particulières à la salinité, à l’inondation et aux substrats meubles sur lesquels elles reposent. Dans des contextes climatiques à forte saisonnalité, les saisons sèches prolongées entraînent de fortes variations de la salinité et du niveau de la nappe, que le changement climatique devrait amplifier. Les modèles climatiques de la région Caraïbe prévoient des saisons sèches plus sèches liées à une baisse des précipitations de 20 à 50 %. Or, la question des capacités de résistance et d’acclimatation des espèces ligneuses des FCI à des variations saisonnières marquées de leur environnement édaphique a été peu traitée dans la littérature scientifique.L’objectif de ce travail de thèse a été double. Il s’est agi, d'une part, de caractériser la structure et la croissance de faciès de végétation représentatifs des FCI antillaises et de mettre en évidence leurs déterminants. A cet effet, des individus adultes, des espèces ligneuses dominantes des FCI, (Avicennia germinans, Laguncularia racemosa, Pterocarpus officinalis, Rhizophora mangle), dans cinq faciès de végétation sur le gradient terre-mer, ont été suivis sur l'île de Grande-Terre (Guadeloupe). D’autre part, les effets de variations salines extrêmes sur la croissance et l’écophysiologie de ces quatre espèces ont été évalués au stade plantule par une expérience en conditions contrôlées.A travers cette étude, il a été montré que les différences de salinité et de fertilité entre les stationspermettent d’expliquer la composition et la structure des peuplements de FCI. Cette étude a égalementmontré que P. officinalis peut se maintenir dans une gamme de salinité plus large que ne l'indiquait lalittérature.Dans le contexte des Antilles où les marnages sont faibles, la saisonnalité du climat entraine des variations saisonnières importantes d’un ensemble de descripteurs édaphiques tels que le niveau de la nappe, la salinité du sol, le pH et le potentiel RedOx. L’inondation et la salinité des sols sont fortement corrélées aux variations mensuelles des précipitations. Les périodes sèches sont accompagnées de salinités élevées et d’une baisse du niveau de la nappe allant jusqu’à l’exondation des sols dans toutes les stations suivies. Les stress environnementaux liés à la saisonnalité entrainent une baisse de la production primaire. L’accroissement cambial mensuel des individus est fortement corrélé avec les précipitations et l’intensité du vent. Dans les stations de mangrove, la sècheresse édaphique régule la production primaire des palétuviers. En forêt marécageuse, la part de la sècheresse atmosphérique semble plus importante pour expliquer la production de P. officinalis. Aussi, les sècheresses édaphique et atmosphérique doivent être prises en compte toutes deux pour modéliser efficacement la croissance des peuplements des FCI.Lors de la saison sèche, le stress le plus important est le stress hydrique, lié à la diminution de la teneur en eau du sol et à l’augmentation de la salinité, qui entraine des contraintes physiologiques sur les palétuviers (ajustements stomatiques, pertes de surface foliaire et de conductivité hydraulique). Le stress ionique, lié à la toxicité des ions Na+ et Cl-, permet aussi d’expliquer une partie de la contrainte sur l’assimilation en carbone. En saison sèche, l’aération des sols ne se traduit pas par une amélioration des performances de croissance chez toutes les espèces. Aussi, la croissance cambiale maximale de toutes les espèces de FCI est réalisée en saison des pluies lorsque la salinité est faible et les niveaux d’inondation élevés.
In tropical and subtropical regions, flooded coastal forests provide essentials goods and services to local communities. In the Antilles, mangrove forests and the Pterocarpus officinalis swamp forest host tree species that are adapted to salinity, flooding and loose substrates. In areas were climatic seasonality is strong, dry seasons lead to strong fluctuations of soil salinity and water table level ; that climate change is likely to make stronger again. Climate model for the Caribbean project drier dry seasons with a decease of 20 to 50 % in annual rainfall amounts. However, resistance and acclimation ability of flooded coastal forest’s species to strong environmental fluctuations still remain poorly studied.This thesis aims two objectives. On the one hand, it aims to characterize the forest structure and monthly growth of vegetation structures representative of the Antillean flooded coastal forests and to highlight their determinants. In this respect, adult trees of the four dominant species of local flooded coastal forest (Avicennia germinans, Laguncularia racemosa, Pterocarpus officinalis, Rhizophora mangle), in five stations along a sea – land gradient were monitored on the Grande-Terre island (Guadeloupe). On the other hand, the effects of salinity variation patterns and salinity levels on growth performances and physiology of seedlings from the four same species were investigated through a greenhouse experiment.This study shows that differences among average salinity and soil fertility explain the vegetation structure of flooded coastal forest. It also extents, in the literature, the range of salinity in which P. officinalis can stand at the tree stage.In the Antilles were tidal range is small, climate seasonality lead to strong edaphic seasonal variations in water table level, soil salinity, pH and RedOx potential. Flooding and soil salinity are strongly correlated to monthly rainfall amounts: dry periods lead to high salinity and to a decrease in water table level under the soil surface. Seasonal environmental stresses lead to a decrease of primary production. Cambial growth was strongly correlated to monthly precipitation and average wind speed. In mangrove stations, edaphic drought determines primary production of mangrove trees, when, in swamp forest stations, atmospheric drought determines an important part of P. officinalis’ primary production.During the dry season, water stress is the more important environmental stress, both by the decrease in soil humidity and the increase in soil salinity, and leads to physiological strains (stomatal adjustment, loss of leaf area and hydraulic conductivity) for mangrove trees. Ionic toxicity of ions Na+ and Cl- also explains a part of the strain on carbon assimilation. During the dry season, re oxygenation of soils via low water table level does not lead to an increase of physiological traits. Thus, maximum cambial growth of all species is observed during the rainy season, when salinity is low and water table level is high.Flooded coastal forest’s species do not have the same ability to recover after a dry episode. In all the studied stations, A. germinans’ cambial growth rises back as soon as the rainy season starts, when, for one station, cambial growth of L. racemosa and R. mangle stay null during the three first month of the rainy season. This low ability to recover after a dry episode is correlated to a stronger impact of the dry season on the physiological traits of these two species.The greenhouse experiment shows that salinity variation patterns are to be taken into consideration for explaining seedlings’ growth and salinity tolerance. A stronger salinity increase impacts the growth of all the studied species; a punctual drop of salinity highlights that flooded coastal forest’s species differ in ability to take advantage of a low salinity episode. These results are coherent with field observations as cambial growth was fairly explained by monthly precipitation.

http://www.theses.fr/2013AGUY0674/document

Éditeur(s) : HAL CCSD Springer-Verlag
Résumé : International audience
High-resolution borehole strainmeters are usually installed in tectonically active regions in order to detect slow-slip events, and to estimate slow transients related to earthquake swarms. However, they are also sensitive to other numerous influences, internal or external. Furthermore, the quality of their coupling to the rock through cementation, and the mechanical properties of the rock mass around them, have a critical influence on their records. Many of the existing strainmeters present such problems, and the correction for these effects often remains a challenge. In this paper, we present the analysis of the records of a high-resolution borehole dilatometer (Sacks–Evertson), located in the seismically active rift of Corinth (Greece) (station TRZ in the Trizonia island). We show that the instrument suffers from an only partial-solid coupling, and that the nearby sea tides have a direct (through elastic response) and indirect (through pore-pressure diffusion) effect on the dilatation signal, which adds up to the solid tidal strain source. We propose a methodology that allows, in a first step, to better separate the internal (solid tide) from the external (air pressure, sea level) influences, by calculating a frequency-dependent transfer function outside the range of the tidal periods. We then extrapolate this function, in particular at the tidal periods. In a second step, the resulting variation with frequency of the coupling coefficients with sea level led us to estimate the proportion of instrument not solidly cemented to rock (thus in contact with water pore pressure), which is about 90 % of the total height. Despite the small proportion of solid coupling, the sensor resolution remains very good up to a few tens of hours of a time period, thanks to the confining effects of the rocks on the local pore pressure. These results allow us to correct for the external effects, and reduce the associated variance by 80–90 % (in the period range of minutes to days). The empirical correction of the sea level effect could be explained using a simple Boussinesq’s approximation and 1D pore-pressure diffusion model, which contributed to better constraint of some of the poro-elastic parameters in the vicinity of the instrument. After correction, the solid tidal signal at the 24-h period is almost anti-correlated with those of the theoretical solid tide. This surprising result is consistent with a similar anti-correlation observed for the longest period surface waves (200 s) comparing the TRZ dilatometer signals to the strain measured by a nearby borehole strainmeter (MOK, 15 km). This could be related to the presence of a shallow fault close to the instrument, which would creep in response to seismic wave-related stress.
ISSN: 0033-4533

hal-01122853
https://hal.archives-ouvertes.fr/hal-01122853
DOI : 10.1007/s00024-013-0742-2

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
TEM Study of Heavitree quartzite deformed at high temperatures and a pressure of 1.5 GPa with three different preparations: water-added, vacuum dried, and sodium doped show a wide range of dislocation microstructure. The vacuum dried sample has a very heterogeneous dislocation distribution varying from almost no dislocations to very high densities. Dislocation nucleation occurs by cross-slip mechanisms, such as Frank-Read sources and Orowan loops around hard inclusions. Shear bands develop in the basal plane composed of two closely spaced shear planes. Dislocations have straight segments and they are aligned along directions of dense packing, suggesting strong Peierls stress control due to the crystal structure. No voids, bubbles or dislocation walls where observed in the vacuum dried sample. The sodium-doped sample had a homogeneous high dislocation density. The water-added sample has a significantly lower, relatively uniform dislocation density. Bubbles associated with dislocations are seen in every grain. Dislocations were either present in loops around bubbles or as straight dislocations with small bubbles spaced along the dislocation line. Some of the long straight dislocations are aligned parallel to the c-axis. Sub-grains where very frequent, sometimes form cells of about 2 p,m in diameter with straight edges. Analysis of dislocations show 1/3 < a > and [c] dislocations in sub-grain walls and free 1/3 < a > dislocations on prism planes. There is clear evidence for dislocation climb with sub-grain walls, dislocation cells, dislocation junctions and dislocation debris of small loops. The major difference between vacuum dried and water-added samples are the homogeneity of the microstructure and evidence for climb in the water-added sample. Glide is clearly difficult, with a high Peierls stress in the vacuum dried sample as shown by areas of very low and very high dislocation density and the crystallographic control of dislocation line direction. The sodium-doped sample indicates that nucleation was easy by the high homogenous dislocation density, but no climb recovery has taken place. The density is high and the dislocations are strongly interacting causing tangles; no evidence for crystallographic control can be observed at these levels of strain. The activation energy for creep in Heavitree quartzite decreases with inferred water content of the specimens form 185 kJ mol(-1) for vacuum dried to 151 for 0.4 wt% water-added samples. Analysis of diffusion data for oxygen under hydrothermal conditions and inferred diffusion data for the hydrogarnet defect and dislocation velocity suggests activation energies for these processes are similar to the activation energy for the dislocation creep of Heavitree quartzite and other quartz aggregates. For data from the previously published experiments with the highest stress resolution there is a correlation between the A pre-factor in the power law creep equation and the activation energy for creep. It is speculated that the correlation may be due to variable hydrogarnet defect concentrations.
ISSN: 0031-9201

hal-00413112
https://hal.archives-ouvertes.fr/hal-00413112
DOI : 10.1016/j.pepi.2008.07.009

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
The mantle above a subducting slab is the site of complex interactions between deformation, partial melting, fluid migration and magma transport. To constrain these interactions and their effects on olivine deformation, we analyze microstructures, crystal preferred orientations, and water contents of peridotite xenoliths entrained by andesites of the Avacha volcano, southern Kamchatka arc. These xenoliths are refractory spinel harzburgites that have coarse-grained microstructures with widely spaced subgrain boundaries and sinuous grain boundaries in olivine, consistent with deformation by dislocation creep under low deviatoric stress (< 13 MPa) and with a significant contribution from diffusional processes. Analysis of crystal preferred orientations (CPO) indicates dominant activation of high-temperature, low-stress {0kl}[100] slip systems in olivine and of(100)[001] in orthopyroxene. In most samples, coarse opx crystals, elongated parallel to the lineation, enclose small olivine grains in crystallographic continuity with neighbouring crystals, indicating crystallization of orthopyroxene at the expense of olivine as a result of reactive percolation of Si-rich fluids coeval with the high-temperature deformation. Secondary crystallization of interstitial orthopyroxene led locally to development of opx-rich lenses parallel to the foliation, characterized by a decrease in olivine grain size and dispersion of the olivine CPO without changing the dominant slip systems. Half of the samples also show acicular orthopyroxene aggregates with which is associated a fine-grained matrix composed of rounded strain-free olivine, orthopyroxene, spinel, and rare amphibole crystals. This matrix occurs pervasively along grain boundaries or forms millimeter-scale irregular lenses and anastomosing veinlets that crosscut the coarse crystals and their ductile deformation structures. Both acicular orthopyroxene and the fine-grained matrix are interpreted as resulting from reactive transport of H2O-rich fluids under static conditions, probably in the lithospheric mantle. Infrared analyses show that olivine contains 1-8 center dot 6 ppm by weight of water. These low water contents are similar to those observed in spinel peridotites from other subduction zones and probably record both the low solubility of water in olivine at low pressure and dehydration during exhumation of the xenoliths. Water contents in orthopyroxene are highly variable (25-506 ppm H2O), probably recording spatially heterogeneous interaction with fluids or melts and compositional disequilibrium in the studied samples. Change in the dominant percolation mechanism from porous flow to fracturing suggests cooling, consistent with the low temperatures estimated from pyroxene thermometry (< 800-900 degrees C). The Avacha xenoliths therefore record pervasive deformation of a region of the mantle under asthenospheric conditions, followed by its accretion to the base of the lithosphere, probably as a result of cooling of the mantle wedge. Percolation of Si-rich fluids or hydrous melts is recorded at all stages; this probably enhanced diffusion and lowered deviatoric stresses during ductile deformation, but did not change the dominant slip direction in olivine from [100] to [001].
ISSN: 0022-3530

hal-00456053
https://hal.archives-ouvertes.fr/hal-00456053
DOI : 10.1093/petrology/egp085

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Functional ecology has long considered the support function as important, but its biomechanical complexity is only just being elucidated. We show here that it can be described on the basis of four biomechanical traits, two safety traits against winds (SW) and self-buckling (SB), and two motricity traits involved in sustaining an upright position, tropic motion velocity (MV) and posture control (PC). All these traits are integrated at the tree scale, combining tree size and shape together with wood properties. The assumption of trait constancy has been used to derive allometric scaling laws, but it was more recently found that observing their variations among environments and functional groups, or during ontogeny, provides more insights into adaptive syndromes of tree shape and wood properties. However, over-simplified expressions have often been used, possibly concealing key adaptive drivers. An extreme case of over-simplification is the use of wood basic density as a proxy for safety. Actually, since wood density is involved in stiffness, loads and construction costs, the impact of its variations on safety is non-trivial. Moreover, other wood features, especially the microfibril angle (MFA), are also involved. Furthermore, wood is not only stiff and strong, but it also acts as a motor for MV and PC. The relevant wood trait for that is maturation strain asymmetry. Maturation strains vary with cell wall characteristics such as MFA, rather than with wood density. Finally, the need for further studies about the ecological relevance of branching patterns, motricity traits and growth responses to mechanical loads is discussed.
ISSN: 0022-0957

hal-00909904
https://hal.archives-ouvertes.fr/hal-00909904
https://hal.archives-ouvertes.fr/hal-00909904/document
https://hal.archives-ouvertes.fr/hal-00909904/file/Integrative_biomechanics_for_tree_Fournier_al.pdf
DOI : 10.1093/jxb/ert279

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : A hypothetical mechanism for the generation of maturation stress in wood was tested experimentally. The hypothesis was that the maturation stress could partly originate in a physical mechanism related to daily changes in water pressure and associated diurnal strains. The matrix of lignin and hemicellulose, deposited in the cell wall during the night, would be put in compression by the effect of water tension during the next day. The cellulose framework, crystallizing during the day, would be put in tension by the decrease in tension at night and subsequent cell-wall swelling. This was tested on young saplings of sugi and beech. Half of the saplings were submitted to continuous lighting, which canceled diurnal strains. Saplings were tilted 40 degrees, and their uprighting movement was measured. The uprighting movement is directly due to the production of reaction wood and the concomitant development of large longitudinal maturation stress. It occurred in the continuously lighted plants at least as much as in control plants. We conclude that the generation of longitudinal maturation stress in tension or compression wood is not directly related to variations in water pressure and diurnal strains.
ISSN: 1435-0211

hal-01031891
https://hal.archives-ouvertes.fr/hal-01031891
DOI : 10.1007/s10086-005-0788-6

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study reports petrostructural observations in the pargasite and phlogopite-bearing Finero peridotite massif (Italian Western Alps), which suggest that the pervasive foliation in this massif was formed by deformation concomitant with percolation of hydrous Si-rich melts: (1) diffuse contacts, but systematic parallelism between the pyroxenitic layers and the foliation of the peridotite (2) strong shape and crystal preferred orientations (SPO and CPO), but subhedral or interstitial shapes and weak intracrystalline deformation of the hydrous phases, (3) CPO, but interstitial shapes of the pyroxenes, (4) very coarse olivine grain sizes, which are correlated to the olivine abundance, and (5) elongated shapes, but weak intracrystalline deformation, and extremely weak and highly variable CPO of olivine. The pervasive deformation of the Finero peridotite occurred therefore under conditions that allowed coexistence of H2O–CO2-bearing melts, pargasite, and spinel, that is, temperatures of 980–1080 °C and pressures <2 GPa. The petrostructural observations suggest that the presence of hydrous melts results in accommodation of large amounts of deformation by stress-controlled dissolution–precipitation and advective transport of matter by the melts and in fast grain boundary migration in olivine. By consequence, it produces significant rheological weakening. Water contents in olivine are <4 ppm wt., implying limited contribution of hydration of olivine to weakening. In addition, the analysis of protomylonites composing the external domains of the shear zones that overprint the pervasive foliation indicates that the transition to melt-free conditions results in enhanced contribution of dislocation creep to the deformation. The associated increase of the peridotites' strength leads to onset of strain localization. The latter is not correlated to the local abundance in pargasite or phlogopite, implying that crystallization of amphiboles or phlogopite, even at concentrations of 25 vol.%, does not produce rheological weakening in the upper mantle.
ISSN: 0012-821X

hal-01667879
https://hal.archives-ouvertes.fr/hal-01667879
DOI : 10.1016/j.epsl.2017.08.015

Éditeur(s) : HAL CCSD American Society for Biochemistry and Molecular Biology
Résumé : International audience
The budding yeast Saccharomyces cerevisiae is a major model organism for important biological processes such as mitotic growth and meiotic development, it can be a human pathogen, and it is widely used in the food-, and biotechnology industries. Consequently, the genomes of numerous strains have been sequenced and a very large amount of RNA profiling data is available. Moreover, it has recently become possible to quantitatively analyze the entire yeast proteome; however, efficient and cost-effective high-throughput protein profiling remains a challenge. We report here a new approach to direct and label-free large-scale yeast protein identification using a tandem buffer system for protein extraction, two-step protein prefractionation and enzymatic digestion, and detection of peptides by iterative mass spectrometry. Our profiling study of diploid cells undergoing rapid mitotic growth identified 86% of the known proteins and its output was found to be widely concordant with genome-wide mRNA concentrations and DNA variations between yeast strains. This paves the way for comprehensive and straightforward yeast proteome profiling across a wide variety of experimental conditions.
ISSN: 1535-9476

hal-00682837
https://hal.archives-ouvertes.fr/hal-00682837
DOI : 10.1074/mcp.M111.012682
PUBMED : 21997732

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Networks of localized conjugate compactive shear bands with large dihedral angles (corresponding to so-called shear-enhanced compaction bands) were generated in 3-layer plane strain finite-difference models. The central layer has elastic–plastic properties with a small positive internal friction coefficient, negative dilatancy factor, and the hardening modulus reducing during the deformation. The two other layers are elastic. The spatial organization of the networks in the central layer, resulting from the elastic–plastic instability of the 3-layer system, was shown to be dependent on the contrast of the elastic stiffness of the layers and on the friction between them. When the stiffness E of the elastic layers and/or the friction are small, the networks are rather symmetric (the bands of both orientation families are distributed homogeneously within the layer). An increase in E at high friction, results in the clustering of the bands of one orientation along a layer segment which is followed by another segment filled with the bands of the other orientation. Different network types are characterized by different band spacing which is smaller in the clustered networks. The intensity of inelastic deformation and hence of porosity reduction within the bands are also smaller in this case. The obtained band networks are very similar to those in nature where the same variability of the network organization is observed. Available geological and mechanical data confirm the conclusions from the modeling about the origin of this variability.
ISSN: 0040-1951

hal-01116201
https://hal.archives-ouvertes.fr/hal-01116201
DOI : 10.1016/j.tecto.2014.01.021

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Interactions between deformation and melt percolation yield important consequences for the evolution of the mantle lithosphere, controlling its composition and mechanical behavior. In the Lherz massif (Pyrenees, France), the analysis of structural relationships between harzburgites, lherzolites and pyroxenites and of the crystal-preferred orientations (CPO) of olivine and pyroxenes highlights a strong feedback between percolation of basaltic melts and deformation under near-solidus conditions at the lithosphere–asthenosphere boundary. Elongated harzburgite bodies up to tens of meters wide, which are the remnants of an old lithospheric mantle, preserve a constant foliation. This foliation is locally outlined by cm-scale flattened websteritic lenses. At the contact with the enclosing lherzolites, the harzburgite foliation is crosscut by the lherzolites foliation and by cm-wide websterite bands parallel to the contact. Strain intensity in the lherzolites increases with distance to the harzburgites. Based on these observations, we propose that reactive percolation was synchronous to the deformation and propose that variations in instantaneous melt fraction, due to pyroxenes and spinel crystallization during reactive melt transport, guided strain localization. Accordingly, the observed decrease in olivine CPO intensity and change in CPO patterns from harzburgites to distal lherzolites are interpreted as recording changes in the relative contribution of dislocation glide and diffusion processes, which is ruled by a balance between the instantaneous melt fraction and the local strain rate. We also propose that the pervasive websteritic layering in the refertilized lherzolites may result from deformation-assisted melt segregation in a system with decreasing permeability due to refertilization reactions. Finally, we discuss the possible timing and geodynamical context of the refertilization episode.
ISSN: 0012-821X

hal-00411724
https://hal.archives-ouvertes.fr/hal-00411724
DOI : 10.1016/j.epsl.2008.07.053

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
The origin of replication complex subunit ORC1 is important for DNA replication. The gene is known to encode a meiotic transcript isoform (mORC1) with an extended 5′-untranslated region (5′-UTR), which was predicted to inhibit protein translation. However, the regulatory mechanism that controls the mORC1 transcript isoform is unknown and no molecular biological evidence for a role of mORC1 in negatively regulating Orc1 protein during gametogenesis is available. By interpreting RNA profiling data obtained with growing and sporulating diploid cells, mitotic haploid cells, and a starving diploid control strain, we determined that mORC1 is a middle meiotic transcript isoform. Regulatory motif predictions and genetic experiments reveal that the activator Ndt80 and its middle sporulation element (MSE) target motif are required for the full induction of mORC1 and the divergently transcribed meiotic SMA2 locus. Furthermore, we find that the MSE-binding negative regulator Sum1 represses both mORC1 and SMA2 during mitotic growth. Finally, we demonstrate that an MSE deletion strain, which cannot induce mORC1, contains abnormally high Orc1 levels during post-meiotic stages of gametogenesis. Our results reveal the regulatory mechanism that controls mORC1, highlighting a novel developmental stage-specific role for the MSE element in bi-directional mORC1/SMA2 gene activation, and correlating mORC1 induction with declining Orc1 protein levels. Because eukaryotic genes frequently encode multiple transcripts possessing 5′-UTRs of variable length, our results are likely relevant for gene expression during development and disease in higher eukaryotes. © 2016 Taylor & Francis Group, LLC.
ISSN: 1547-6286

hal-01367153
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367153
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367153/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367153/file/Ndt80%20activates%20the%20meiotic%20ORC1%20transcript.pdf
PUBMEDCENTRAL : PMC5013992