Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Evolution involves interplay between natural selection and developmental constraints(1-3). This is seen, for example, when digits are lost from the limbs during evolution(1,3,4). Extant archosaurs (crocodiles and birds) show several instances of digit loss(3,5,6) under different selective regimes, and show limbs with one, two, three, four or the ancestral number of five digits. The `lost' digits sometimes persist for millions of years as developmental vestiges(7-10). Here we examine digit loss in the Nile crocodile and five birds, using markers of three successive stages of digit development. In two independent lineages under different selection, wing digit I and all its markers disappear. In contrast, hindlimb digit V persists in all species sampled, both as cartilage, and as Sox9-expressing precartilage domains, 250 million years after the adult digit disappeared. There is therefore a mismatch between evolution of the embryonic and adult phenotypes. All limbs, regardless of digit number, showed similar expression of sonic hedgehog (Shh). Even in the one-fingered emu wing, expression of posterior genes Hoxd11 and Hoxd12 was conserved, whereas expression of anterior genes Gli3 and Alx4 was not. We suggest that the persistence of digit V in the embryo may reflect constraints, particularly the conserved posterior gene networks associated with the zone of polarizing activity (ZPA(11)). The more rapid and complete disappearance of digit I may reflect its ZPA-independent specification, and hence, weaker developmental constraints. Interacting with these constraints are selection pressures for limb functions such as flying and perching. This model may help to explain the diverse patterns of digit loss in tetrapods. Our study may also help to understand how selection on adults leads to changes in development.
ISSN: 0028-0836

hal-01545485
https://hal.archives-ouvertes.fr/hal-01545485
DOI : 10.1038/nature12336

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Signalling through the Wnt family of secreted proteins originated in a common metazoan ancestor and greatly influenced the evolution of animal body plans. In bilaterians, Wnt signalling plays multiple fundamental roles during embryonic development and in adult tissues, notably in axial patterning, neural development and stem cell regulation. Studies in various cnidarian species have particularly highlighted the evolutionarily conserved role of the Wnt/b-catenin pathway in specification and patterning of the primary embryonic axis. However in another key non-bilaterian phylum, Ctenophora, Wnts are not involved in early establishment of the body axis during embryogenesis. We analysed the expression in the adult of the ctenophore Pleurobrachia pileus of 11 orthologues of Wnt signalling genes including all ctenophore Wnt ligands and Fz receptors and several members of the intracellular b-catenin pathway machinery. All genes are strongly expressed around the mouth margin at the oral pole, evoking the Wnt oral centre of cnidarians. This observation is consistent with primary axis polarisation by the Wnts being a universal metazoan feature, secondarily lost in ctenophores during early development but retained in the adult. In addition, local expression of Wnt signalling genes was seen in various anatomical structures of the body including in the locomotory comb rows, where their complex deployment suggests control by the Wnts of local comb polarity. Other important contexts of Wnt involvement which probably evolved before the ctenophore/ cnidarian/bilaterian split include proliferating stem cells and progenitors irrespective of cell types, and developing as well as differentiated neuro-sensory structures.
ISSN: 1932-6203

hal-01544483
https://hal.archives-ouvertes.fr/hal-01544483
DOI : 10.1371/journal.pone.0084363

Résumé : Nous avons étudié les phénomènes de polyploïdisation chez l'igname Dioscorea alata qui comprend trois cytotypes diploïde (2n=40), triploïde (2n=60) et tétraploïde (2n=80) en vue d'optimiser les stratégies de production d'hybrides polyploïdes. Chez ce complexe polyploïde l'augmentation de la ploïdie est corrélée avec une augmentation de la vigueur et des rendements plus élevés et plus stables. Dans un premier temps nous avons démontré l'autotétraploïdie des variétés tétraploïdes à l'aide de trois approches différentes: des analyses d'hérédité de marqueurs microsatellites, l'observation de phénomènes de double réduction et l'étude des méioses des cellules mères de pollen. Nous avons ensuite déterminé quels sont les mécanismes les plus probables à l'origine des polyploïdes naturels via l'étude de la transmission de l'hétérozygotie parentale à l'aide de microsatellites et par l'étude des incompatibilités au niveau de l'albumen lors de différents croisements intracytotypes et intercytotypes en utilisant la cytométrie en flux. Les résultats obtenus montrent que les polyploïdes de D. alata seraient apparus via la formation de gamètes non réduits de clones diploïdes. Le pool triploïde se serait édifié et diversifié uniquement par voie femelle, du fait de la non viabilité des croisements intercytotypes et de la stérilité des femelles et mâles triploïdes. Le pool tétraploïde serait apparu par union de deux gamètes non réduits de clones diploïdes (polyploidisation sexuelle bilatérale). Par la suite ce pool aurait été diversifié via des croisements intercy
We studied polyploidisation phenomena in the yam Dioscorea alata that includes three cytotypes -diploid (2n=40), triploid (2n=60) and tetraploid (2n=80) -in order to optimise polyploid hybrid production strategies. In this complex polyploid, the increase in ploidy is correlated with an increase in vigour and higher and more stable yields. We first showed the autotetraploidy of tetraploid varieties using three different approaches: heredity analyses of microsatellite markers, the observation of double reduction phenomena, and the study of meiosis of pollen mother cells. We then determined the mechanisms most likely to be at the origin of natural polyploids through the study of the transmission of parental heterozygoty using microsatellites and the study of incompatibilities at the endosperm level at the time of different intracytotypic and intercytotypic crosses using flow cytometry. The results obtained reveal that the polyploids of D. alata probably appeared through the formation of non-reduced gametes of diploid clones. The triploid pool would then have been constituted and diversified through the female pathway as a result of the non-viability of intercytotypic crosses and the sterility of female and male triploids. The tetraploid pool would have appeared as a result of the union of two non-reduced gametes of diploid clones (bilateral sexual polyploidisation). This pool would then have diversified through intercytotypic crosses with the formation of 2n gamètes through both the female and the male pathway, as well as by intracytotypic crosses within the 4X pool.

http://www.theses.fr/2012AGUY0519/document

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
The Vertiskos Unit of northern Greece is an elongated basement belt with a complex poly-metamorphic history. It extends from Greece (Chalkidiki peninsula), to the south, up to Serbia, in the north, and arguably represents the westernmost part of the Rhodope Metamorphic Province (northern Greece to southern Bulgaria). The Vertiskos Unit experienced a medium pressure lower amphibolite-facies metamorphic overprint during the Alpine Orogeny. The available medium-temperature geochronology implies that it remained at temperature of approximately 300°C (or slightly higher) during Lower Cretaceous. In order to constrain its post-Lower Cretaceous thermal history, until near-surface exposure, we applied apatite fission track analysis. The central ages obtained range from 68.5 ± 3.8 to 46.6 ± 3.6 Ma (uppermost Cretaceous to Middle Eocene) and mean track lengths between 13 and 13.5 μm. We applied two inverse thermal modeling approaches using either each sample independently (high degree of freedomin the thermal history, better data fit) or all samples together interpreting them as a vertical profile (simpler thermal history, worse data fit). Irrespective of the modeling approach, we conclude that the bulk thermal history of the Vertiskos Unit crosses the high-temperature limit of the apatite partial annealing zone by the uppermost Cretaceous and reaches near-surface conditions as early as lower/middle Eocene. These results contrast with the thermal history of the other domains of the Rhodope Metamorphic Province further east (namely the Southern Rhodope Core Complex and the Northern Rhodope Complex) and establish the Vertiskos basement complex as the oldest exhumed coherent basement fragment of the Rhodope Metamorphic Province and Greece.
ISSN: 0278-7407

insu-01053579
https://hal-insu.archives-ouvertes.fr/insu-01053579
https://hal-insu.archives-ouvertes.fr/insu-01053579/document
https://hal-insu.archives-ouvertes.fr/insu-01053579/file/Kydonakis-brun-tectonics-2014.pdf
DOI : 10.1002/2014TC003572

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
To quantify the relationships between anisotropy. S-wave splitting and tectonics, we determined the seismic properties of lower-crustal and upper-mantle rocks outcropping in the lvrea Zone (Northem Italy). We obtained P-and S-wave seismic velocities by laboratory direct velocity measurements and/or by calculations based on the modal compositions of the rocks, the lattice preferred orientations (LPOs), and the single crystal stiffness coefficients. Measured P-and S-wave velocities (6.0-7 .5 km s-1 and 3.6-4.2 km s-1) are typical of the lower crust. The P-wave anisotropy is in the range 0-l 0%. Shear-wave birefringence is in the range 0.0-0.6 km s-1 , with typical values between 0.0 and 0.2 km s-1 • In many cases, the birefringence is clearly related to fabric elements (foliation, lineation). Mafic rocks such as anorthosite or pyroxene-bearing gabbros exhibit low P-wave anisotropies (< 5%) and low shear-wave birefringences (less than 0.1 km s-1). In contrast, the seismic properties of felsic rocks such as biotite-bearing gneisses and mafic rocks such as amphibolites display high V P anisotropy (10%) and strong birefringence (0.3 km s-1). Biotite and amphibole preferred orientations clearly control seismic anisotropy and particularly shear-wave splitting. In these rocks, maximum splitting is observed in directions parallel to the foliation with the fast split shear wave polarized parallel to the foliation plane. To have an overview of the seismic properties of this lower-crustal section at a broader scale, we calculated from our data the anisotropie seismic properties of several hypothetical samples that are perhaps more representative of the regional anisotropy than each sample individually. For instance, the average lower-crustal sample displays an anisotropy of 5.5% for P waves and a birefringence around 0.14 km s I for S waves propagating parallel to the foliation. We observe little splitting for waves propagating at high angle to the foliation.
ISSN: 0031-9201

hal-01389712
http://hal.univ-reunion.fr/hal-01389712
http://hal.univ-reunion.fr/hal-01389712/document
http://hal.univ-reunion.fr/hal-01389712/file/Barruol_Kern-PEPI96_hal.pdf
DOI : 10.1016/0031-9201(95)03124-3

Éditeur(s) : HAL CCSD
Résumé : In this paper we report a study of the mating system and gene flow of Sextonia rubra, a hermaphroditic, insect pollinated tropical tree species with a geographic distribution in the Guyana Plateau and the Amazon. Using five microsatellites we analysed 428 seeds of 27 open pollinated families at the experimental site "Paracou" in French Guiana. We observed, compared to other tropical tree species, a high level of genetic diversity. We estimated parameters of the mating system and gene flow by using the mixed mating model and the TwoGenerapproach. The estimated multilocus outcrossing rate, tm, was 0.992 indicating nearly complete outcrossing. A significant level of biparental inbreeding and a small proportion of full-sibs were estimated for the 27 seed arrays. The differentiation of allelic frequencies among the pollen pools was ΦFT = 0.061. We estimated mean pollen dispersal distances between 65 m and 89 m according to the dispersal models used. The joint estimation of pollen dispersal and density of reproductive trees gave an effective density estimate of 2.1-2.2 trees/ha
Silvae genetica

hal-01031483
https://hal.archives-ouvertes.fr/hal-01031483

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Upon subduction, the oceanic crust transforms to blueschists and eclogites, with seismic properties that gradually become similar to those of the surrounding mantle. In order to evaluate the anisotropy of blueschists and glaucophane-bearing eclogites, the elastic constants of glaucophane single-crystal plates from the Sesia-Lanzo Zone (Aosta Valley, Western Alps) were measured using Brillouin spectroscopy at ambient conditions. The mean P- and S-wave velocities are 7.8 and 4.6 km s−1 respectively, and the anisotropy is high (38.1% (AVP) and 27.3% (AVS)). Glaucophane develops strong LPO, characterized by the [001]-axes concentrated sub-parallel to the lineation, and the {110} poles concentrated sub-perpendicular to the foliation in both blueschist and eclogite rocks. The measured LPO is in good agreement with viscoplastic selfconsistent numerical models. Seismic properties of glaucophane-bearing blueschist and eclogite are calculated by combining measured LPO and the single-crystal elastic moduli of glaucophane with the other main mineral constituents of the rock: mostly epidote for blueschist, and omphacite and garnet for eclogite. Blueschists present stronger anisotropies (AVP=16.1% and AVS=10.3%) than eclogites (AVP=2.9% and AVS=1.7%). The shear-wave splitting and resulting delay times for a 7-km thick layer of eclogite or blueschist are low for the eclogite (b0.03 s), but signi!cant for blueschist (0.16 s). Application to the subducted oceanic crust yields a decrease of velocity contrast with the surrounding mantle and of anisotropy at depth depending on the temperature of the slab. The details of the velocity variations in subducted oceanic crust are dif!cult to reconcile with the blueschist-eclogite transition as probed by exhumed metamorphic rocks and may require additional phases such as lawsonite or chemical variations such as oxidation state.
ISSN: 0040-1951

hal-00564518
https://hal.archives-ouvertes.fr/hal-00564518
DOI : 10.1016/j.tecto.2010.09.011

Éditeur(s) : HAL CCSD
Résumé : The use of Xylopia frutescens extract as a C38 steel corrosion inhibitor in 1 M HCl solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. Potentiodynamic polarization curves indicated that Xylopia frutescens extract behaves as mixed-type inhibitor. Graphical methods are illustrated by synthetic data to determine the parameter of CPE (α, Q). The adsorption of the extract constituents was further discussed in view of Langmuir adsorption isotherm. The effect of temperature on the inhibition efficiency was investigated using EIS and potentiodynamic polarization. SEM and EDX observations confirmed the existence of protective inhibitor film on metal surface.
ISSN: 1938-6737

hal-01304527
https://hal.archives-ouvertes.fr/hal-01304527
DOI : 10.1149/06426.0001ecst
PRODINRA : 351608

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
Microstructures and crystallographic preferred orientation (CPO) of anorthosite samples interlayered in the upper and lower gabbro sections in the Oman ophiolite were analyzed in this paper. In the anorthosites registering the dynamics of the melt lenses, foliation is flat lying and starts to develop a few meters below the root zone of the sheeted dike complex (RZSDC). Microstructures and CPO of these rocks were developed in response to four different mechanisms: (1) density-controlled settling of plagioclase on the lens floor, (2) deposition of anorthosites related to convection currents, (3) melt compaction, and (4) uncompacted melt accumulation. In these anorthosites, the poles to (010) of plagioclase are parallel to the flow plane of convection, whereas the [100] axes and poles to (001) express the convection flow direction and the axis of convection rolls, respectively. The effect of subsidence of melt lens floor is recorded immediately below the RZSDC and is characterized by the rapid (but progressive) development of dipping foliation and lineation, reflecting the increase of deformation downsection. The degree of foliation and CPO development in the anorthosites is directly related to the distance of the center of the melt lenses before the subsidence starts. Despite the uncertain origin of the anorthosites from the lower gabbro section, all the samples lost the magmatic microstructural characteristics and presently are reequilibrated aggregates. However, they still preserve plagioclase CPO, where some of these patterns present similarities with the anorthosites from the upper gabbro section, but no evidence of intracrystalline deformation under high temperatures.
ISSN: 0278-7407

hal-00617446
https://hal.archives-ouvertes.fr/hal-00617446
DOI : 10.1029/2010TC002697

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : We present whole-rock major- and trace-element and Nd–Sr–Pb radiogenic isotope data for Cretaceous igneous suites from eastern Cuba. These rocks are related to the Greater Antilles paleo-island arc magmatism and have three different igneous styles. Group 1 consists of tholeiitic basalts and rare basaltic andesites that have normal mid-ocean ridge basalt (N-MORB)-like compositions similar to those found in back-arc basin basalts (TiO2 = 1·2–2·9 wt%; La/Yb(N) = 0·7–0·9, Th/Nb = 0·06–0·08, and initial 208Pb/ 204Pb = 37·65–37·74). Group 2 comprises basaltic and rare basaltic andesitic subvolcanic dykes with major- and trace-element and isotopic compositions similar to those of island arc tholeiites (TiO2 = 0·7–1·4 wt%; La/Yb(N) = 0·6–0·9, Th/Nb = 0·06–0·68, and initial 208Pb/ 204Pb = 37·74–38·25). Group 3 is composed of low-Ti (TiO2 = 0·3–0·9 wt%) calcalkaline igneous rocks that have an unambiguous subduction-related character (La/Yb(N) = 1·1–5·0, Th/Nb = 0·35–1·55, and initial 208Pb/ 204Pb = 37·94–38·39). The parental magmas of the three groups formed by variable melting degrees (< 5–25%) of spinel lherzolite, with more depleted mantle sources for Groups 2 and 3 than Group 1. The trace-element and radiogenic isotope compositions of primitive Group 3 samples are strongly bimodal. One subgroup of samples is characterized by low Ta/Yb (0·02–0·03) and Th/La (0·10–0·13), slightly subchondritic Nb/Ta (13·3–17·3), and relatively high initial 206Pb/204Pb (18·57–18·62) and {varepsilon}Nd (7·6–9·4). The remaining primitive Group 3 samples have higher Ta/Yb (0·06–0·11) and Th/La (0·24–0·32), and highly subchondritic Nb/Ta (7·6–9·1), coupled with lower initial 206Pb/204Pb (18·24–18·29) and {varepsilon}Nd (3·4–5·5). These signatures were induced by two distinct slab components that mainly reflect the contributions of Cretaceous Atlantic marine and North American continental sediments, respectively. Nb/Ta in the first subgroup was influenced by melting of rutile-bearing subducted crust, whereas in the second it was inherited from recycled continental sediments. The involvement of Atlantic and North American sediments in Cuban Cretaceous magmatism indicates that the Proto-Caribbean (North American-Proto Atlantic) lithosphere subducted beneath the Greater Antilles arc during the Late Cretaceous (pre-Campanian), consistent with geotectonic models involving onset of SW-dipping subduction beneath the Greater Antilles paleo-arc during the Aptian. The variable mantle source depletion and magnitude of the subduction component probably reflect different settings across the arc, from the arc front to a back-arc spreading ridge.
ISSN: 0022-3530

hal-00406373
https://hal.archives-ouvertes.fr/hal-00406373
DOI : 10.1093/petrology/egm040

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Polarized emittance measurements were acquired for synthetic forsterite, the pure magnesium end member of the olivines group, on the whole infrared spectral range and up to the melting point by using CO2 laser heating. The experimental data, fitted with a semi-quantum dielectric function model, allowed the retrieval of the temperature dependence of the absorption coefficient of forsterite both in the opaque and semi-transparent regions. The analysis of the phonon parameters indicates that the lattice dynamics evolve drastically with increasing temperature. The normal modes involving motions of the magnesium cations located in site 1 are the more impacted, and some of them vanish around 1,200 K. The results confirm that the enhancement of the lattice anharmonicity and the increasing mobility of the magnesium cations are closely linked and are at the origin of the anomalies observed in the evolution of the thermophysical properties. This complete set of spectroscopic data may be a step toward a more precise evaluation of the impact of thermal radiation heat transfer inside systems involving forsterite and quantification of their heat budget.
ISSN: 0342-1791

hal-00817079
https://hal.archives-ouvertes.fr/hal-00817079
DOI : 10.1007/s00269-013-0570-z

Résumé : Nos travaux ont permis d'étudier l'effet combiné de la maturation, du mûrissement et des périodes climatiques, sur le profil des composés bioactifs de la banane Musa Cavendish, issus des French West Indies (FWI). La teneur en polyphénols des bananes 400 Degrés Jour (dj) est restée inchangée, tandis que les bananes 600 et 900 dj ont présenté une augmentation significative de leurs teneurs en polyphénols pendant la maturation (pThe combined influence of maturation, ripening and climate periods on French West Indies (FWI) bananas, Musa Cavendish, bioactive compounds profile was studied. The polyphenol content of the 400 dd bananas remained unchanged, while the 600 and 900 dd bananas exhibited a significant polyphenol increase during ripening (p
http://www.theses.fr/2012AGUY0533

Éditeur(s) : HAL CCSD
Résumé : International audience
Fish is a rich source of essential nutrients for fetal development, but in contrast, it is also a well-known route of exposure to environmental pollutants. We assessed whether fish intake during pregnancy is associated with fetal growth and the length of gestation in a panel of European birth cohort studies. The study sample of 151,880 mother-child pairs was derived from 19 population-based European birth cohort studies. Individual data from cohorts were pooled and harmonized. Adjusted cohort-specific effect estimates were combined by using a random- and fixed-effects meta-analysis. Women who ate fish >1 time/wk during pregnancy had lower risk of preterm birth than did women who rarely ate fish (≤ 1 time/wk); the adjusted RR of fish intake >1 but <3 times/wk was 0.87 (95% CI: 0.82, 0.92), and for intake ≥ 3 times/wk, the adjusted RR was 0.89 (95% CI: 0.84, 0.96). Women with a higher intake of fish during pregnancy gave birth to neonates with a higher birth weight by 8.9 g (95% CI: 3.3, 14.6 g) for >1 but <3 times/wk and 15.2 g (95% CI: 8.9, 21.5 g) for ≥ 3 times/wk independent of gestational age. The association was greater in smokers and in overweight or obese women. Findings were consistent across cohorts. This large, international study indicates that moderate fish intake during pregnancy is associated with lower risk of preterm birth and a small but significant increase in birth weight.
The American Journal of Clinical Nutrition

hal-01118513
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118513
PUBMED : 24335057
DOI : 10.3945/ajcn.113.067421

Éditeur(s) : HAL CCSD
Résumé : International audience
The effect of alkaloids extracted from Isertia coccinea plant (AEIC) on the corrosion of C38 steel in 1 M hydrochloric acid was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Potentiodynamic polarization curves indicated that the extract behave as mixed-type inhibitor. The experimental data obtained from EIS method show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The inhibition efficiencies of the extract calculated by three methods show the same tendency. Inhibition was found to increase with increasing concentration of the plant extract. The results obtained show that the extract solution of the plant could serve as an effective inhibitor for the corrosion of C38 steel in hydrochloric acid solution. The apparent activation energy of the process taking place in inhibitor presence was determined on the ground of four temperature values in the range from 25 °C to 55 °C using the data obtained by two independent methods. Theoretical fitting of different isotherms, Langmuir, Temkin and Frunkin, were tested to clarify the nature of adsorption.
International journal of electrochemical science

hal-01097030
https://hal-agroparistech.archives-ouvertes.fr/hal-01097030

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The morphogenetic evolution of the Lesser Caucasus has been strongly influenced by Plio-Quaternary volcanic and tectonic events and Pleistocene glaciations. Fluvio-lacustrine environments, indicated by diatomaceous deposits, prevailed in the Syunik region of southern Armenia during the Pliocene and Pleistocene. The Pleistocene diatomaceous deposits studied contain leaf impressions and pollen, allowing local palaeoclimatic reconstructions. The chronology of morphogenetic events has been determined by 17 radiometric dates (K/Ar, Ar/Ar, U/Th), palaeomagnetic investigations and is placed in a spatial context by a detailed geomorphological map and a 24-km geological transect of the Vorotan valley, the main area studied. Before 1.21 Ma, tectonic movements (antecedents of the lower part of the Vorotan valley) generated extensive lake formations with diatomaceous deposits. From 993 ka, volcanic eruptions produced lava flows that covered the fluvio-lacustrine accumulations. During Marine Isotopic Stages 12, 6 and 4, glaciers and fluvio-glacial deposits were probably present overall the principal uplands and valleys of southern Armenia. At 53.68 ka (MIS 3), 12.6 ka, 10.78 ka and 4.14 ka (MIS 1), the development of travertines on some slopes and in some valleys highlights temperate and humid climatic phases. Palaeobotanical studies of leaf and pollen floras show that the vegetation changed several times from forested to steppic phases in response to the climate oscillations of the Lower Pleistocene. This work proposes a first morphogenic and palaeoclimatic reconstruction from the lower Pleistocene to the Postglacial period, when the first settlements of the population in the Lesser Caucasus were influenced by tectono-volcanic events, lake level changes and glacialeinterglacial oscillations forced by the obliquity orbital parameter (41 ky cycles).
ISSN: 1040-6182

hal-00481939
https://hal.archives-ouvertes.fr/hal-00481939
DOI : 10.1016/j.quaint.2010.02.008

Éditeur(s) : HAL CCSD National Research Council Canada
Résumé : International audience
In French Guiana, inflorescences of Philodendron squamiferum Poepp. (Araceae) were regularly visited by the scarab beetle Cyclocephala simulatrix Hölne and (Scarabaeidae, Coleoptera) occasionally by Cyclocephala tylifera Hölne. The flowering cycle lasted 2 days, and the protogynous inflorescence exhibited features typical of beetle pollination (floral chamber, food rewards, flower heating). The spadix temperature was measured during the entire flowering cycle in French Guiana and at the Montreal Botanical Garden. Both sets of measurements gave a similar temperature pattern. The spadix warmed up twice at the beginning of each evening with no notable heat production between the two peaks. These two temperature peaks were well synchronized with the arrival and departure of beetles
ISSN: 0008-4026

hal-01202724
https://hal.archives-ouvertes.fr/hal-01202724

Éditeur(s) : HAL CCSD De Gruyter
Résumé : International audience
A comparative study of 9H-pyrido[3,4-b]indole (norharmane) and 1-methyl-9H-pyrido[3,4-b]indole (harmane) as inhibitors for C38 steel corrosion in 1 M HCl solution at 25 °C was carried out. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behavior in the absence and presence of different concentrations of these inhibitors. The OCP as a function of time were also established. Cathodic and anodic polarization curves show that norharmane and harmane are a mixed-type inhibitors. Adsorption of indole derivatives on the C38 steel surface, in 1 M HCl solution, follows the Langmuir adsorption isotherm model. The ΔGads values were calculated and discussed. The potential of zero charge (PZC) of the C38 steel in inhibited solution was studied by the EIS method, and a mechanism for the adsorption process was proposed. Raman spectroscopy confirmed that indole molecules strongly adsorbed onto the steel surface. The electronic properties of indole derivates, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR).
ISSN: 0018-3830

hal-01093227
https://hal-agroparistech.archives-ouvertes.fr/hal-01093227
DOI : 10.1515/HF.2010.034

Éditeur(s) : HAL CCSD
Résumé : Poster
The Lesser Caucasus in Armenia is an active volcanic and tectonic zone which resulted from the collision of the Arabian and the Eurasian plates since Neogene times. The During Quaternary, Lesser Caucasus was uplifted (0.3 mm/yr; Mitchell and Westaway, 1999) and experienced extensional tectonics times. Large lakes developed in graben structures. The diatomitic sequences of the Shamb paleo-lake (South Armenia) offer a rare opportunity to give new insights of Western Asia paleo-climate. Based on macroflora analysis, Bruch and Gabrielyan (2002) proposed a cooling and drying general climate trend through Pleistocene times in relation with a general uplift of the chain. Several questions have to be answer for this poorly investigated region. Did the climate record humid glacials and arid interglacials as suggested northward in Kazakhstan? What are the vegetation and climate responses to orbital parameters and to the monsoon? Moreover the lesser Caucasus is known as the entrance way used by the first hominids in Eurasia during Pleistocene time. How was the environment at this time? We present an integrated palynological, 40Ar/39Ar isotopic and magnetostratigraphic study for the most complete section (Joannin et al., in press). 40Ar/39Ar dating of two volcaniclastic layers provided ages of 1.24 ± 0.03 and 1.16 ± 0.02 Ma (2. Magnetostratigraphic data show that the entire Shamb section is of reversed polarity which correlates with part of the Matuyama period (1.785-1.070 Ma). Pollen assemblages and macroremains diversity revealed an alternation of glacial and interglacial phases that are compared with climate changes inferred from the global isotopic curve. The Shamb section ranges from approximately 1.300 to 1.080 Ma in age (marine isotopic stages 40 to 31). The vegetation of the Lesser Caucasus developed in a mosaic pattern in a Pleistocene continental, mostly arid climate, similar to the present-day climate. The vegetation changes record a dominant climate response to the obliquity orbital parameter. The influence of precession could not be established from the Shamb data. Pollen and macroflora both indicate that glacial periods were cold and dry and that interglacials were warm with local humidity. The early Pleistocene climatic model for Western Asia is thus similar to the climatic model for the Mediterranean area. Bruch, A., Gabrielyan, I.G., 2002. Quantitative data of the Neogene climatic development in Armenia and Nakhichevan. Acta Universitatis Carolinae – Geologica 46, 41–48. Joannin, S., Cornée, J.J., Münch, P., Fornari, M., Vasiliev, J., Krijgsman, W., Nahapetyan, S., Gabrielyan, Y., Ollivier, V., Roiron, P., Chataîgnier, C. In press. Early Pleistocene climatic cycles in continental deposits of the Lesser Caucasus of Armenia inferred from palynology, magnetostratigraphy, and 40Ar/39Ar dating. Earth and Planetary Science Letters. Mitchell, J., Westaway, R., 1999. Chronology of Neogene and Quaternary uplift and magmatism in the Caucasus: constraints from K-Ar dating of volcanism in Armenia. Tectonophysics 304, 157–186.
EGU Eurasian Climate and Tectonics
Vienne, Austria

hal-00481799
https://hal.archives-ouvertes.fr/hal-00481799

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : 4 pages
International audience
We show that a point is solution of the Minty variational inequality of subdifferential type for a given function if and only if the function is increasing along rays starting from that point. This provides a characterization of the monotone polar of subdifferentials of lower semicontinuous functions: it is a common subset of their graphs which depends only on the function.
ISSN: 1862-4472

hal-00842670
https://hal.archives-ouvertes.fr/hal-00842670
ARXIV : 1307.1826
DOI : 10.1007/s11590-013-0693-7

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Analysis of microbial biodiversity is hampered by a lack of reference genomes from most bacteria, viruses, and algae. This necessitates either the cultivation of a restricted number of species for standard sequencing projects or the analysis of highly complex environmental DNA metagenome data. Single-cell genomics (SCG) offers a solution to this problem by constraining the studied DNA sample to an individual cell and its associated symbionts, prey, and pathogens. We used SCG to study marine heterotrophic amoebae related to Paulinella ovalis (A. Wulff) P.W. Johnson, P.E. Hargraves & J.M. Sieburth (Rhizaria). The genus Paulinella is best known for its photosynthetic members such as P.chromatophora Lauterborn that is the only case of plastid primary endosymbiosis known outside of algae and plants. Here, we studied the phagotrophic sister taxa of P.chromatophora that are related to P.ovalis and found one SCG assembly to contain -cyanobacterial DNA. These cyanobacterial contigs are presumably derived from prey. We also uncovered an associated cyanophage lineage (provisionally named phage PoL_MC2). Phylogenomic analysis of the fragmented genome assembly suggested a minimum genome size of 200Kbp for phage PoL_MC2 that encodes 179 proteins and is most closely related to Synechococcus phage S-SM2. For this phage, gene network analysis demonstrates a highly modular genome structure typical of other cyanophages. Our work demonstrates that SCG is a powerful approach for discovering algal and protist biodiversity and for elucidating biotic interactions in natural samples.
ISSN: 0022-3646

hal-01544797
https://hal.archives-ouvertes.fr/hal-01544797
DOI : 10.1111/jpy.12028