Éditeur(s) : CARDI : Caribbean Agricultural Rechearch and Development Institute Université des Antilles. Service commun de la documentation
Extrait de : 52e congrès annuel de la Société caribéenne des plantes alimentaires / 52nd annual meeting of the Caribbean food crops society (CFCS), du 10 au 16 juillet 2016. INRA, CFCS
Description : Banana and plantain (Musa spp) are important foreign exchange earners in Guyana and the Windward Islands of the Caribbean. Black Sigatoka Disease (BSD) also referred to as black leaf streak disease is one of the most destructive diseases of banana and plantain and is present within the region. In Guyana within two years following its introduction in 2008, the industry was totally decimated, recording a 100% decline, turning the country to a net banana importer. Also, from 2009 ? 2012 the disease spread in the Windward Islands causing as much as 100% decrease in the export of banana. The disease is caused by the ascomycete fungus, Mycosphaerella fijiensis (anamorph Pseudocercospora fijiensis) and is aggressive, challenging to control and results in enormous crop damage if left uncontrolled. In an effort to develop an integrated management approach to the disease the Caribbean Agricultural Research and Development Institute (CARDI) with financial assistance from the Caribbean Development Bank (CDB) is evaluating five FHIA banana and plantain accessions and eight IITA plantain accessions for tolerance to BSD. The evaluation is presently conducted in four Caribbean countries, Dominica, Guyana, St Lucia and St Vincent and the Grenadines. In each country, four distinct agro- ecological zones were selected for the trial evaluation blocks and using a randomized block design, four blocks were established in each country. Five FHIA accessions: FHIA-01, FHIA-03, FHIA-18, FHIA-21 and FHIA-23 are being evaluated in Dominica, St Lucia and St Vincent and the Grenadines whereas, plantain accessions: PITA-17, PITA-21, PITA-22, PITA-23, PITA-24 and PITA-26 are to be evaluated in Guyana for tolerance to the disease. Cavendish are used as regional controls and as borders rows to increase disease pressure. The disease parameters evaluated are youngest leaf spotted (YLS), disease development time (DDT), leaf emission rate (LER), disease severity at 6 months, bunch emergence and harvest, and index of standing leaves. Agronomic data; days from planting to flowering, bunch weight, number of hands in bunch, average weight of hands and average number of fingers per hand and bunch, as well as organoleptic characteristics of both cooked and ripe fruits are also evaluated. The early data collection, of the FHIA only accessions, show trends in the disease tolerance and agronomic performance as well as their adaptability in the different agro-ecological zone. The trends indicate better disease tolerance of FHIA varieties with higher leaf counts before, at bunching and at harvest. The organoleptic test shows a preference to FHIA 03 and FHIA 21. La banane et le plantain (espèces de Musa) sont les acquéreurs de devises étrangères importants en Guyane et en Îles du Vent des Caraïbe. La maladie noire de Sigatoka (schéma) également désignée sous le nom de la maladie noire de filet de feuille est l'une des maladies les plus destructives de la banane et du plantain et est présente dans la région. En Guyane dans un délai de deux ans après son introduction en 2008, l'industrie a été totalement décimée, enregistrant une baisse de 100%, tournant le pays à un importateur net de banane. En outre, à partir de 2009-2012 la propagation de maladie en Îles du Vent causant pas moins de la diminution de 100% de l'exportation de la banane. La maladie est provoquée par le champignon d'ascomycète, fijiensis de Mycosphaerella (fijiensis anamorph de Pseudocercospora) et est agressive, contestant pour commander et les résultats dans l'énorme culture endommagent si laissé incontrôlé. Dans un effort de développer une approche intégrée de gestion à la maladie l'institut agricole des Caraïbes de recherche et développement (CARDI) avec l'aide financière de la banque de développement des Caraïbes (BDC) évalue des adhésions de banane et de plantain de cinq FHIA et huit adhésions de plantain d'IITA pour la tolérance au schéma. L'évaluation est actuellement effectuée quatre pays des Caraïbes, Dominique, Guyane, St Lucia et Saint-Vincent-et-les Grenadines. Dans chaque pays, quatre agro zones écologiques distinctes ont été sélectionnées pour les blocs d'essai d'évaluation et employant une conception de bloc randomisé, quatre blocs ont été établis dans chaque pays. Cinq adhésions de FHIA : FHIA-01, FHIA-03, FHIA-18, FHIA-21 et FHIA-23 sont évalués en Dominique, au St Lucia et au Saint-Vincent-et-les Grenadines tandis que, des adhésions de plantain : PITA-17, PITA-21, PITA-22, PITA-23, PITA-24 et PITA-26 doivent être évalués en Guyane pour la tolérance à la maladie. Cavendish sont employés en tant que contrôles régionaux et comme rangées de frontières pour augmenter la pression de la maladie. Les paramètres de la maladie évalués sont la plus jeune feuille repérée (YLS), le temps d'élaboration de la maladie (DDT), le taux d'émission de feuille (LER), la sévérité de la maladie à 6 mois, émergences et récoltes de groupe, et index des feuilles debout. Données agronomiques ; des jours de la plantation à la floraison, du poids de groupe, nombre de mains dans le poids de groupe et moyen des mains et du nombre moyen de doigts par main et groupe, aussi bien que les caractéristiques organoleptiques des fruits cuits et mûrs sont également évalués. La collecte de données tôt, des adhésions de FHIA seulement, exposition tend dans la tolérance de maladie et la représentation agronomique aussi bien que leur adaptabilité dans la zone agro-écologique différente. Les tendances indiquent qu'une meilleure tolérance de maladie des variétés de FHIA avec une plus haute feuille compte avant, à se rassembler et à la récolte. L'essai organoleptique montre une préférence à FHIA 03 et à FHIA 21.
Siècle(s) traité(s) : 21
Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V16266
V16266

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Talc is a hydrous magnesium rich layered silicate that is widely disseminated in the Earth from the seafloor to over 100 km depth, in ultra-high pressure metamorphism of oceanic crust. In this paper we determine the single crystal elastic constants at pressures from 0 to 12 GPa of talc triclinic (C 1¯) and monoclinic (C2/c) polytypes using ab initio methods. We find that talc has an extraordinarily high elastic anisotropy at zero pressure that reduces with increasing pressure. The exceptional anisotropy is complemented by a negative Poisson's ratio for many directions in crystal space. Calculations show that talc is not only one of very few common minerals to exhibit auxetic behaviour, but the magnitude of this effect may be the largest reported so far for a mineral. The compression (Vp) and shear (Vs) wave velocity anisotropy is 80% and 85% for the triclinic polytype. At pressures where talc is known be stable in the Earth (up to 5 GPa) the Vp and Vs anisotropy is reduced to about 40% for both velocities, which is still a very high value. Vp is slow parallel to the c-axis and fast perpendicular to it. This remains unchanged with increasing pressure and is observed in both polytypes. The shear wave splitting (difference between fast and slow S-wave velocities) at low pressure has high values in the plane normal to the c-axis, with a maximum near the alow asterisk-axis in the triclinic and the b-axis in the monoclinic polytype. The c-axis is the direction of minimum splitting. The pattern of shear wave splitting does not change significantly with pressure. The volume fraction of talc varies between 11 and 41% for hydrated mantle rocks, but the lack of data on the crystallographic preferred orientation (CPO) precludes a detailed analysis of the impact of talc on seismic anisotropy in subduction zones. However, it is highly likely that CPO can easily develop in zones of deformation due to the platy habit of talc crystals. For random aggregates of talc, the isotropic Vp, Vs and Vp/Vs ratio have significantly lower values than those of antigorite and may explain low-velocity regions in the mantle wedge. Vp/Vs ratios are more complex in anisotropic media because there are fast and slow S-waves, resulting in Vp/Vs1 and Vp/Vs2 ratios for every propagation direction, making interpretation difficult in deformed polycrystalline talc with a CPO. Talc on the subduction plate boundary can strongly influence guided wave velocity as CPO would develop in this region of intense shearing. The very low coefficient of friction (< 0.1) of talc above 100 °C could also explain silent earthquakes at shallow depths (ca 30 km) along the subduction plate boundaries, frequently responsible for tsunami.
ISSN: 0012-821X

hal-00411481
https://hal.archives-ouvertes.fr/hal-00411481
DOI : 10.1016/j.epsl.2008.07.047

Résumé : (Ownership) Received by the Rubenstein Library as a gift from Mariela Ferrer Jewett in 2010
Orestes Lorenzo, a former Cuban Air Force major, defected with his plane to the U.S. in 1990. A campaign to bring his family was then begun. This postcard showing his wife and children, was part of the effort by the Valladares Foundation to pressure the Cuban government for their release. In 1992, Mr. Lorenzo flew back to Cuba clandestinely and picked up his family at a prearranged location and then flew them out of Cuba to Florida.

Éditeur(s) : University of Florida Université des Antilles. Service commun de la documentation
Extrait de : 52e congrès annuel de la Société caribéenne des plantes alimentaires / 52nd annual meeting of the Caribbean food crops society (CFCS), du 10 au 16 juillet 2016. INRA, CFCS
Description : Under tropical and sub-tropical climates, a sustainable development of agriculture is challenging because of the pest pressure with favorable weather conditions. Implementation of appropriate cropping systems including growing cover crops and crop rotation plays a critical role, which can break up the food chain and life cycles of field pests. Some field trials have demonstrated that among all tested summer cover crops, sunn hemp (Crotalaria juncea L. cv. Tropic sun) can grow vigorously during the rainy summer, cover the land quickly and densely, and it can produce a large quantity of biomass in two to three months. More importantly, sunn hemp can suppress soil root-knot nematodes via releasing some nematicides through its roots and through the decomposition of plant residues. Therefore, growing cover crop â? ? sunn hemp during the crop off season and rotating with valuable vegetable crops in the growing season has become a promising cropping system under the subtropical climate. Such a result may have a potential to be implemented in Caribbean countries to improve the sustainable development of agriculture.

Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V16313
V16313

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The brittle to ductile transition (BDT) in rocks may strongly influence their transport properties (i.e., permeability, porosity topology ...) and the maximum depth and temperature where hydrothermal fluids may circulate. To examine this transition in the context of Icelandic crust, we conducted deformation experiments on a glassy basalt (GB) and a glass-free basalt (GFB) under oceanic crust conditions. Mechanical and micro-structural observations at a constant strain rate of 10(-5) s(-1) and at confining pressure of 100-300 MPa indicate that the rocks are brittle and dilatant up to 700-800 degrees C. At higher temperatures and effective pressures the deformation mode becomes macroscopically ductile, i.e., deformation is distributed throughout the sample and no localized shear rupture plane develops. The presence of glass is a key component reducing the sample strength and lowering the pressure of the BDT. In the brittle field, strength is consistent with a Mohr-Coulomb failure criterion with an internal coefficient of friction of 0.42 for both samples. In the ductile field, strength is strain rate-and temperature-dependent and both samples were characterized by the same stress exponent in the range 3 < n < 4.2 but by very different activation energy Q(GB) = 59 +/- 15 KJ/mol and Q(GFB) = 456 +/- 4 KJ/mol. Extrapolation of these results to the Iceland oceanic crust conditions predicts a BDT at similar to 100 degrees C for a glassy basalt, whereas the BDT might occur in non-glassy basalts at deeper conditions, i.e., temperatures higher than 550 +/- 100 degrees C, in agreement with the Icelandic seismogenic zone.
ISSN: 0148-0227

hal-00760905
https://hal.archives-ouvertes.fr/hal-00760905
DOI : 10.1029/2011JB008884

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We use first first-principle methods and the Peierls-Nabarro model to evaluate the resistance to glide, characterized by the Peierls stress, of glide systems for end-member MgSiO3 Perovskite at mantle pressures. [010](100) is the easiest glide system in Mg-Perovskite at all pressures. Peierls stresses increase systematically with pressure for all systems except [001](010), indicating the importance of lattice friction at lower mantle pressures. The ratio of the maximum Peierls stress for each system relative to the [010](100) value defines their critical resolved shear stress (CRSS). These CRSS are used in a visco-plastic self-consistent homogenization model to predict the evolution of crystal preferred orientations (CPO) during deformation of polycrystalline Mg-Perovskite. In axial compression, [100] tends to align with the compression direction, in agreement with in situ observations in axial compression experiments. In simple shear, [010] concentrates near the shear direction and (100), although more dispersed, tends to align near the shear plane, consistent with the dominant activity of the easier [010](100) system. The calculated seismic anisotropy for a 100% Mg-Perovskite aggregate using the CPO in simple shear and the elastic constants Of MgSiO3 perovskite at lower mantle pressures and temperatures is weak (>3% for P-waves with and >2% for S-waves) and decreases with increasing temperature and pressure. P-waves show the fastest propagation parallel to the lineation and S-waves fast polarization is in the foliation at 38 GPa and normal to the lineation at 88 GPa. This weak anisotropy is consistent with global seismological observations of a nearly isotropic lower mantle. There are however two regions where strain-induced Mg-Perovskite CPO could contribute to anisotropy; a) low temperature regions in the uppermost lower mantle, where the predicted S-wave polarization anisotropy may attain 1.6% with a fast polarization parallel to the foliation, b) in high high-temperature domains in the D '' layer, where Mg-Perovskite may be the major stable phase, leading to polarization of fast S-waves normal to the lineation for propagation directions at high angle to the lineation and an apparent isotropy for all other propagation directions.
ISSN: 0012-821X

hal-00411460
https://hal.archives-ouvertes.fr/hal-00411460
DOI : 10.1016/j.epsl.2008.03.058

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In petroleum industry, the difference between pore pressure (Pp) and minimum horizontal stress Sh (termed the seal or retention capacity) is of major consideration because it is often assumed to represent how close a system is to hydraulic failure and thus the maximum hydrocarbon column height that can be maintained. While Sh and Pp are often considered to be independent parameters, several studies in the last decade have demonstrated that Sh and Pp are in fact coupled. However, the nature of this coupling relationship remains poorly understood. In this paper, we explore the influences of the spatial pore pressure distribution on Sh/Pp coupling and then on failure pressure predictions and trap integrity evaluation. With analytical models, we predict the fluid pressure sustainable within a reservoir before failure of its overpressured shale cover. We verify our analytical predictions with experiments involving analogue materials and fluids. We show that hydraulic fracturing and seal breach occur for fluid pressure greater than it would be expected from conventional retention capacity. This can be explained by the impact of the fluid overpressure field in the overburden and the pressure diffusion around the reservoir on the principal stresses. We calculate that supralithostatic pressure could locally be reached in overpressured covers. We also define the retention capacity of a cover (RC) surrounding a fluid source or reservoir as the difference between the failure pressure and the fluid overpressure prevailing in shale at the same depth. In response to a localized fluid pressure rise, we show that the retention capacity does not only depend on the pore fluid overpressure of the overburden but also on the tensile strength of the cover, its Poisson's ratio, and the depth and width of the fluid source.
ISSN: 0264-8172

hal-00590497
https://hal.archives-ouvertes.fr/hal-00590497
DOI : 10.1016/j.marpetgeo.2010.08.007

Éditeur(s) : HAL CCSD Elsevier
Résumé : The dense hydrous magnesium silicate called the D phase is the most likely candidate to recycle hydrogen into the lower mantle in subduction zones. As seismology represents the preferred method to detect this mineral in subduction zones, the single crystal elastic tensor has been calculated using first principle methods. A triple cell (View the MathML source) was used to account for an ordered ideal composition of the D phase to lower mantle pressures. The elastic tensor of the mineral at ambient conditions is predicted to be C11 = 387.7, C33 = 287.7, C44 = 100.4, C12 = 108.0, C13 = 51.1, C14 = − 14.6 in GPa with bulk modulus at zero pressure Ko = 163 GPa and a statistical error of about 4.0 GPa for all constants. The pressure derivatives of the elastic constants have been determined to pressure of 80 GPa. Our tensor correctly predicts the published experimental measurements of linear compressibility along the a- and c-axes, the logarithmic pressure derivative of the c/a axial ratio and bulk modulus at zero pressure. It contradicts the experimentally measured elastic tensor reported by (Liu, L.-G., Okamoto, K., Yang, Y.-J., Chen, C.-C., Lin, C.-C., 2004. Elasticity of single-crystal phase D (a dense hydrous magnesium silicate) by Brillouin spectroscopy. Solid State Commun. 132, 517–520), which fails to reproduce the experimental compressibility data. Using the elastic constants and density predicted to 85 GPa, the seismic anisotropy of P- and S-waves has been calculated as a function of pressure. The single crystal has high P-wave velocities and shear wave splitting in the basal plane below 20 GPa. At high pressures, the maximum P-wave velocities have threefold symmetry normal to a-axes in the basal plane, whereas the maximum shear wave splitting is parallel to a-axes with twofold symmetry. The D phase has high Vp and Vs anisotropy at ambient pressure, 17.6% for Vp and 19.9% for Vs. The Vp anisotropy decreases with increasing pressure to about 30 GPa, while it remains constant at 8% from 30 to 85 GPa. The Vs anisotropy decreases to 17% at 20 GPa and then increases to 22% at 85 GPa. The isotropic velocity ratios of S to P (Rs/p), bulk sound to S (Rphi/s) and density to S (Rρ/s) are calculated as a function of pressure. The Rs/p shows very little variation with pressure with low value of 0.6, whereas both Rphi/s and Rρ/s increase with pressure to peak values of 2.8 and 2.0 respectively at about 60 GPa. The presence of the D phase in subducted horizontal ‘stagnant' plates in the circum Pacific could contribute to a number of seismic observations, such as the observed velocity heterogeneity at depths between 500 and 1000 km and the fast S-waves travelling horizontally with horizontal polarization in this depth range. Further the lower density of the D phase compared with anhydrous minerals could influence buoyancy of the hydrated ‘stagnant' slabs. The transformation of the D phase to perovskite plus ferripericlase during thermal annealing may be responsible for horizontal slab seismogenesis.
ISSN: 0012-821X

hal-00406379
https://hal.archives-ouvertes.fr/hal-00406379
DOI : 10.1016/j.epsl.2007.04.053

Éditeur(s) : HAL CCSD
Résumé : International audience
BACKGROUND: The effects of pressure-controlled (PC) ventilation on the ventilatory and haemodynamic parameters during laparoscopy procedures had not been carefully assessed. This prospective cross-over study was undertaken to compare how volume-controlled (VC) and PC modes could affect pulmonary mechanics, gas exchange, and cardiac function in patients undergoing laparoscopy. METHODS: Twenty-one patients undergoing laparoscopic urological procedures had their lungs ventilated at the beginning with VC ventilation. PC ventilation was instituted at the end of the VC sequence. Ventilator settings were adjusted to keep tidal volume, respiratory rate, and Fi(o(2)) constant in every mode. A complete set of ventilatory, haemodynamic, and gas exchange parameters was obtained under VC after 40 min of pneumoperitoneum and 20 min after switching for PC. Transoesophageal echocardiography was performed in order to evaluate systolic and diastolic function of the heart. RESULTS: When VC was switched to PC, peak airway pressure decreased [mean (sd) 32 (6) vs 27 (6) cm H(2)O; P < 0.0001], peak inspiratory flow increased [17 (3) vs 48 (8) litre min(-1); P < 0.0001), and dynamic compliance improved [+15 (8)%]. No difference was noted for static airway pressure, static compliance, and arterial oxygenation. No significant change could be demonstrated in the systolic [left ventricular end-systolic wall stress 66 (16) vs 63 (14) x 10(3) dyn cm(-2) m(-2)] or diastolic function [early diastolic velocity 10.3 (2.5) vs 10.5 (2.7) cm s(-1)]. CONCLUSIONS: In this study, no short-term beneficial effect of PC ventilation could be demonstrated over conventional VC ventilation in patients with pneumoperitoneum.
BJA

hal-00689758
https://hal.archives-ouvertes.fr/hal-00689758
DOI : 10.1093/bja/aem166
PUBMED : 17626027

Éditeur(s) : Yale University
Résumé : Sea-surface temperature images of the coastal upwelling regions off Northwest Africa show that the core of upwelling is sometimes located far from the coast. This has been documented in three regions that share a common feature, namely a wide and shallow continental shelf. This upwelling feature plays a key role in the ecology of the Canary Current System. It creates an innerfront which provides retention for biological material, e.g. fish eggs and larvae, in the highly productive nearshore environment. An analytical model has been developed based on a two dimensional extension of Ekman's solution. The linear and steady response of a homogeneous ocean forced by an upwelling-favorable wind provides a mechanism for the upwelling separation from the coast. The merging of the surface and bottom Ekman layers induces a very weak cross-shore circulation and a "kinematic barrier" for the Ekman transport divergence. In the case of an alongshore wind, the barrier is located near the isobath h ≈ 0.4D, where D is the thickness of Ekman layers. This yields an upwelling cell which is essentially concentrated in the region 0.5D < h < 1.25D, with upwelling occurring preferentially near the isobath h ≈ 0.6D. It turns out that the cross-shore width of upwelling scales with D/S, the ratio of Ekman depth to bottom topographic slope. The application of this solution to real bathymetric profiles rationalizes, not only the offshore upwelling observations in Northwest Africa, but also the influence of topography on the cross-shelf structure of a wind-driven coastal upwelling. The model also quantifies the effect of the cross-shore wind component showing how it drives the nearshore pressure gradient adjustment and how it affects the upwelling. A linear numerical experiment reproduces the theoretical steady solution, thereby allowing investigation of the transient regime. Relaxation of the hypothesis in the numerical model validates the linear assumption of the theory and then allows investigation of the sensitivity to friction parameterizations and the influence of stratification. The latter leads to an "oscillation" of the upwelling cell with seaward migration driven by outcropping and homogeneization of the water column, and, coastal incursion driven by a "boundary layers splitting" process caused by shoreward advection of the isopycnal dome and stratification of the inner shelf.
Journal of Marine Research (Yale University), 2008-09 , Vol. 66 , N. 5 , P. 589-616

Droits : 2008 Yale University
http://archimer.ifremer.fr/doc/2008/publication-6334.pdf
DOI:10.1357/002224008787536790
http://archimer.ifremer.fr/doc/00000/6334/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
We present a 2-D Contact Dynamics discrete element model for simulating initiation and motion of rock avalanches, integrating hillslope geometry, Mohr-Coulomb rock behavior, pore pressure before avalanche triggering, and avalanche trigger. Avalanche motion is modeled as a dense granular flow of dry frictional and cohesive particles. On the basis of granular physics and shear experiments, we review some of the theories for the unexpectedly long runout of rock avalanches. Different causes are evoked, according to the strength (strong or weak) of the slip surface relative to the bulk. "Mechanical fluidization'' and "acoustic fluidization'' theories state that agitation of rock particles reduces frictional strength, increasing runout. Conversely, granular mechanics suggests that, as "shear-strain'' rate increases, granular material becomes more agitated, more dissipative, and more resistant. Another theory states that dynamic fragmentation of clasts creates an isotropic pressure that drives longer runout. In contrast, granular mechanics suggests that fragmentation may induce fluidization and strengthening of the granular material, while particle size reduction (among others) induces weakening of the granular flow and enhances long runout. Runout is also enhanced for column-like rock masses collapsing from steep hillslopes. Long runout may also be linked to thermal weakening mechanisms at the slip surface (e.g., thermal pressurization, and shear melting), which may lower drastically the shear strength. The model is illustrated with a hypothetical example of a rain-triggered avalanche, mobilizing shallowly dipping layers. Several phases are identified, including slope failure, avalanche triggering resulting from slip weakening, and avalanche motion in which rocks are folded and sheared.
ISSN: 0148-0227

hal-00420883
https://hal.archives-ouvertes.fr/hal-00420883
DOI : 10.1029/2008JF001072

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The equilibrium phase relations of a mafic durbachite (53 wt.% SiO2) from the TA (TM) ebi pluton, representative of the Variscan ultrapotassic magmatism of the Bohemian Massif (338-335 Ma), have been determined as a function of temperature (900-1,100A degrees C), pressure (100-200 MPa), and H2O activity (1.1-6.1 wt.% H2O in the melt). Two oxygen fugacity ranges were investigated: close to the Ni-NiO (NNO) buffer and 2.6 log unit above NNO buffer (a dagger NNO + 2.6). At 1,100A degrees C, olivine is the liquidus phase and co-crystallized with phlogopite and augite at 1,000A degrees C for the whole range of investigated pressure and water content in the melt. At 900A degrees C, the mineral assemblage consists of augite and phlogopite, whereas olivine is not stable. The stability field of both alkali feldspar and plagioclase is restricted to low pressure (100 MPa) at nearly water-saturated conditions (< 3-4 wt.% H2O) and T < 900A degrees C. A comparison between experimental products and natural minerals indicates that mafic durbachites have a near-liquidus assemblage of olivine, augite, Ti-rich phlogopite, apatite and zircon, followed by alkali feldspar and plagioclase, similar to the mineral assemblage of minette magma. Natural amphibole, diopside and orthopyroxene were not reproduced experimentally and probably result from sub-solidus reactions, whereas biotite re-equilibrated at low temperature. The crystallization sequence olivine followed by phlogopite and augite reproduces the sequence inferred in many mica-lamprophyre rocks. The similar fractionation trends observed for durbachites and minettes indicate that mafic durbachites are probably the plutonic equivalents of minettes and that K- and Mg-rich magmas in the Bohemian Massif may have been generated from partial melting of a phlogopite-clinopyroxene-bearing metasomatized peridotite. Experimental melt compositions also suggest that felsic durbachites can be generated by simple fractionation of a more mafic parent and mixing with mantle-derived components at mid crustal pressures.
ISSN: 0010-7999

hal-00618418
https://hal.archives-ouvertes.fr/hal-00618418
DOI : 10.1007/s00410-009-0430-5

Éditeur(s) : University of Miami
Résumé : This paper describes the fishing activity in Martinique, French West Indies. It draws up the balance sheet of acquirements about marine resources of the island. The difficulties of fisheries management are discussed with reference to biologists and economists works in the last ten years. We also show how management efforts to decrease fishing pressure on reef resources has induced the implantation of a new technology: the Fish Aggregating Deviee. The differing histories of development of FADs in the French West Indies are compared. The positive results from the introduction of the FADs and the estimated risks due to the transferance of fishing pressure on the continental shelf is presented. The use of FADs to enhance the exploitation of marine resources is a concept that justifies.a cooperative plan throughout the Caribbean region
A partir d'une présentation synthétique de l'activité de pêche en Martinique, cette note dresse le bilan des connaissances actuelles sur l'état des ressources halieutiques de l'île. Les difficultés de la gestion des pêches sont discutées en référence aux travaux réalisés par les halieutes et les économistes des pêches au cours des dix dernières années. On montre comment un objectif de gestion, l'allégement de la pression de pêche sur les ressources démersales, a pu conduire à l'implantation d'une nouvelle technologie: le dispositif de concentration de poissons. Les différents contextes de développement des DCP observés dans les deux départements français des Antilles sont comparés. Les retombées positives de l'introduction des dispositifs sont évaluées mais le risque d'aboutir à un report d'une partie de la puissance de pêche sur le plateau est également évoqué. L'influence du DCP sur l'exploitation des ressources halieutiques constitue un argument supplémentaire pour intensifier la coopération caribéenne sur ce thème
Proceedings - Gulf and Caribbean Fisheries Institute, University of Miami (0072-9019) (University of Miami), 1998 , Vol. 50 , P. 249-261

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00113/22409/20106.pdf
http://archimer.ifremer.fr/doc/00113/22409/

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : La présente étude a été menée dans les cantons de la préfecture de Doufelgou au Nord Togo. Sur la base de la beauté du paysage, des richesses naturelles et des enquêtes semi-structurées, le potentiel écotouristique de cette préfecture a été évalué. Le traitement des données spatiales collectées a permis de réaliser la carte écotouristique et de proposer un circuit touristique. Trois catégories de potentialités ont été répertoriées : les potentialités naturelles, les potentialités culturelles et les potentialités anthropiques. Ces potentialités peu valorisées subissent à des degrés variables diverses pressions susceptibles de les mettre en péril. Cet article présente ces diverses potentialités et analyse les opportunités socio-économique et environnementale d’un développement écotouristique dans cette zone.
This study was conducted in the cantons of Doufelgou prefecture in Northern Togo. On the basis of the beauty of the landscape, natural resources and semi-structured surveys, the potential ecotourism in this prefecture was evaluated. The treatment of spatial data collected helped make ecotourism map and to propose a tourist circuit. Three categories of potential have been identified: the natural potential, cultural potential and human potential. These potentialities are little valued and suffer to varying degrees various pressures which may put them at risk. This paper presents various potential and carries an analysis on socio-economic and environmental benefits of ecotourism development in this area.
Doufelgou
Togo

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.6326
http://journals.openedition.org/etudescaribeennes/6326

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In many orogens, high-pressure (HP) metamorphic rocks such as eclogite occur as lenses in quartzofeldspathic gneiss that equilibrated at much lower pressures. The pressure–temperature–time (P–T–t) history of eclogite relative to host gneiss provides information about mechanisms and timescales of exhumation of orogenic crust. The Montagne Noire of the southern Massif Central, France, is an eclogite–bearing gneiss (migmatite) dome located at the orogen-foreland transition of the Variscan belt. Results of our study show that it contains the youngest eclogite in the orogen, similar in age to migmatite and granite that crystallized under low-pressure conditions. P–T conditions for an exceptionally unaltered eclogite from the central Montagne Noire were estimated using a pseudosection supplemented by garnet–clinopyroxene and Zr-in-rutile thermometry. Results indicate peak P∼1.4 GPaP∼1.4 GPa and View the MathML sourceT∼725°C for Mg-rich garnet rim (50 mol% pyrope) + omphacite (36 mol% jadeite) + rutile + quartz. U–Pb geochronology (LA-ICP-MS) of 16 zoned zircon grains yielded ∼360 Ma (4 cores) and ∼315 Ma (12 rims and cores). Rare earth element abundances determined by LA-ICP-MS for dated zircon are consistent with crystallization of ∼315 Ma zircon under garnet-stable, plagioclase-unstable conditions that we interpret to indicate high pressure; in contrast, the ∼360 Ma zircon core corresponds to crystallization under lower pressure plagioclase-stable conditions. Based on garnet zoning and inclusion suites, rutile textures and Zr zoning, P–T results, and zircon petrochronology, we interpret the ∼315 Ma date as the age of eclogite-facies metamorphism that only slightly preceded dome formation and crystallization at 315–300 Ma. This age relation indicates that eclogite formation at high pressure and migmatite dome emplacement at low pressure were closely spaced in time. We propose that collapse-driven material transfer from the hot orogen to the cool foreland resulted in thickening of the orogen edge, leading to eclogite facies metamorphism of the deep crust. Soon after, the low-viscosity partially molten crust flowed from the plateau toward the foreland, incorporating and exhuming eclogite. The P–T–t history of the Montagne Noire eclogite shows that some dome material ascended from >40 km depth to shallow crustal levels, likely in a single decompression event, and that migmatite domes are therefore very efficient at exhuming the deep crust.
ISSN: 0012-821X

hal-01243499
https://hal.archives-ouvertes.fr/hal-01243499
DOI : 10.1016/j.epsl.2015.08.026

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
At Cima di Gagnone, garnet peridotite and chlorite harzburgite lenses within pelitic schists and gneisses correspond to eclogite-facies breakdown products of hydrated peridotites and are suitable for studying dehydration of serpentinized mantle. Thermobarometry and pseudosection modelling yield peak temperatures of 750-850°C and pressures <3 GPa. The minimum temperature recorded by the garnet peridotite corresponds to the maximum conditions experienced by the chlorite harzburgite, suggesting that these rocks recrystallized cofacially at ∼800°C. Alternatively, they might have decoupled during subduction, as achieved in tectonically active plate interface boundaries. The major and rare earth element (REE) variability of the peridotites was mostly acquired during pre-subduction mantle evolution as a result of partial melting and reactive melt flow. The ultramafic suite is also characterized by fluid-mobile element enrichments (B, Pb, As, Sb, Cs, Li, U, Be), which confirm derivation from variably serpentinized protoliths. Similarity in the U, Pb, B, Li and Sr contents of the Gagnone peridotites to present-day oceanic serpentinites suggests that these elements were partly taken up during initial serpentinization by seawater-derived fluids. Positive Be, As and Sb anomalies suggest involvement of fluids equilibrated with crustal (metasedimentary) reservoirs during subsequent subduction metamorphism and peridotite entrainment in (meta)sediments. Fluid-mobile element enrichment characterizes all peak eclogitic minerals, implying that multiple hydration events and element influx pre-dated the eclogite-facies dehydration. Peak anhydrous minerals retain B, Li, As and Sb concentrations exceeding primitive mantle values and may introduce geochemical anomalies into the Earth's mantle. The relatively low contents of large ion lithophile elements and light REE in the Gagnone peridotites with respect to much higher enrichments shown by metasomatized garnet peridotite pods hosted in migmatites (Ulten Zone, Eastern Alps) suggest that the crustal rocks at Gagnone did not experience partial melting. The Gagnone garnet peridotite, despite showing evidence for chlorite dehydration, retains significant amounts of fluid-mobile elements documenting that no partial melting occurred upon chlorite breakdown. We propose that the Gagnone ultramafic rocks represent a prime example of multi-stage peridotite hydration and subsequent dehydration in a plate interface setting.
ISSN: 0022-3530

hal-01054319
https://hal.archives-ouvertes.fr/hal-01054319
DOI : 10.1093/petrology/egt068

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Phase equilibrium data pertaining to melting of simplified carbonated peridotite in the systems CaO-MgO-SiO2-CO2 and CaO-MgO-Al2O3-SiO2-CO2 at pressures of 10-26 GPa, corresponding to similar to 300-750 km depths in the Earth, are presented. In both the studied systems, liquid compositions, with changing crystalline phase assemblage, are carbonatitic throughout the studied pressure range. In the system CMS-CO2, melting phase relations are isobarically invariant; liquid is in equilibrium with forsterite + clinoenstatite + clinopyroxene + magnesite, forsterite + majorite + clinopyroxene + magnesite, wadsleyite + majorite + clinopyroxene + magnesite, ringwoodite + majorite + calcium-silicate perovskite + magnesite, magnesium-silicate perovskite + periclase + calcium-silicate perovskite + magnesite at 12, 14, 16, 20, and 26 GPa, respectively. In the system CMAS-CO2, a phase assemblage consisting of forsterite + orthopyroxene + clinopyroxene + magnesite + garnet + melt from 10 to 14 GPa is isobarically invariant. However, owing to the disappearance of orthopyroxene at pressures greater than 14 GPa, from 16 and up to at least 26 GPa, the solidus of simplified carbonated peridotite spans a divariant surface in pressure-temperature space. The liquid coexists with wadsleyite + clinopyroxene + garnet + magnesite, ringwoodite + calcium-silicate perovskite + garnet + magnesite, and magnesium-silicate perovskite + periclase + calcium-silicate perovskite + magnesite at 16, 20, and 26 GPa, respectively. A curious, and as yet unexplained, feature of our study is an abrupt drop in the solidus temperature between 14 and 16 GPa that causes a small amount of melting of carbonated mantle in the Transition Zone of the Earth. In the systems CMS-CO2 and CMAS-CO2 liquid compositions at 16 and 20 GPa are highly calcic bona fide carbonatites; however, these liquids revert to being magnesiocarbonatites at 10-14 and 26 GPa. In the system CMS-CO2, at 16 GPa we locate an isobaric invariant point consisting of wadsleyite + clinopyroxene + anhydrous B + magnesite + melt. The presence of anhydrous B at 16 GPa and 1475 degrees C is interesting, as it lies outside the composition space of the mantle peridotite analog we have studied. However, despite the presence of two highly magnesian silicate crystalline phases, wadsleyite and anhydrous B, at 16 GPa and 1475 degrees C, the liquid composition remains calcic with molar Ca-number [Ca/(Ca + Mg) x 100] of about 63. The melting reactions at 16 and 20 GPa (with or without anhydrous B) show that lime-bearing crystalline silicates play a fairly large part in generating and controlling the composition of the liquids. At 16 GPa, in the system CMS-CO2, we also report an experimental run at 1575 degrees C, in which liquid coexists with only wadsleyite and majorite. The liquid composition is less calcic (Ca-number 54) than that for other runs at lower temperatures, but is still more calcic than liquids at 10-14 and 26 GPa in both the studied systems. At present, the likely cause for these changes in the reported phase relations is not known. For normally assumed mantle temperatures, melting in the Transition Zone of the Earth, owing to the presence of carbonate, is probably unavoidable. The depth range of the drop in the carbonated peridotite solidus closely matches that of commonly observed low seismic velocities at similar to 400-600 km depth in the Earth.
ISSN: 0022-3530

hal-00669945
https://hal.archives-ouvertes.fr/hal-00669945
DOI : 10.1093/petrology/egr048

Éditeur(s) : HAL CCSD ACSM
Résumé : International audience
The aim of this study was to examine the effects of the cycle-run and run-cycle successions of the triathlon and duathlon, respectively, on respiratory muscle strength and endurance. Methods: Respiratory muscle strength was assessed by measuring maximal inspiratory (P1max) and expiratory {PEmax) pressures. Respiratory muscle endurance was assessed by measuring the time limit (Tlim). Twelve triathleles participated in a three-trial protocol. The first trial consisted of an incremental cycle test to assess the maximal oxygen uptake (VO2max) of triathletes. Trial 2 consisted of 20 min of cycling followed by 20 min of running (C-R), and trial 3 consisted of 20 min of running followed by 20 min of cycling (R-C). Trials 2 and 3 were performed at the same metabolic intensity (% VO2max). P1max and P1max were measured before and 10 min after C-R and R-C, and I min after the post-C-R and post-R-C Tlim measurements (P1max l'). Tlim was measured I d before and 30 min after C-R and R-C. Results: The results showed a significant decrease in P1max after C-R (126.7 ± 4.3 cmH2O, P < 0.05) and R-C (123.7 ± 4.9 cmH2O, P < 0.05) compared with the baseline values (130 ± 3.8 and 129.6 ± 4.3 cmH2O, respectively). P1max 1' showed a significantly greater decrease after R-C versus C-R(111.2 ± 5.5 cmH2O vs 121.2 ± 3.9 cmH2O,respectively, P < 0.001). Tlim after C-R (3.3 ± 0.3 min) decreased significantly compared with baseline values (4.19 ± 0.3min and 4.02 ± 0.3 min, respectively). However, the Tlim decrease after R-C was significantly greater than after C-R (P < 0.001). Conclusion: We concluded that respiratory muscle strength and endurance were less decreased after the cycle-run succession and that cycling induced a greater decrease in respiratory muscle endurance than running.
Medicine & Science in Sports & exercise

hal-00720796
https://hal.univ-antilles.fr/hal-00720796

Éditeur(s) : Elsevier
Résumé : High P-wave velocities (7.1-7.8 km/s) lower crustal bodies (LCBs) imaged along volcanic margins are commonly interpreted as plume and break-up-related thick mafic underplating. This interpretation is partly challenged in this paper based on new seismic observations and modelling of the outer Voring Basin (Norway). An exceptional strong amplitude reflection, the T Reflection, is particularly well defined below the North Gjallar Ridge (NGR) between 7 and 8 s TWT. The T Reflection is located near the volcanic lava flows emplaced during the NE Atlantic breakup (similar to 55-54 Ma ago) and coincides with the top of the LCB, forming a mid-crustal dome. Based on structural and temporal relationships, we show that the dome clearly influences the structural development of the NGR and predates the continental breakup at least by 10-15 Ma. Using a thermo-kinematical model, we tried also to investigate and quantify the relationships between the extension, LCB and the magmatic production. Modelling suggests that significant Paleocene-Early Eocene magmatism can be produced without any temperature anomaly in the mantle if differential stretching occurs during the break-up initiation. The conclusion of 2D thermo-kinematical parametric analysis is that the magmatic model predicts, either little extension (beta < 2) with no melting or high extension (beta > 5) with significant melting along the outer Voring Basin. We suggest that the continental part of the LCB could not necessarily be breakup-related and so magmatic, as has often been stated previously. It is concluded here that the continental part of the LCB observed beneath the outer Voring Basin may be partly (or fully) attributed to inherited, high-pressure granulite/eclogite lower crustal rocks. The real amount of mafic material emplaced along the outer Voring Basin could be 20-40% less than thought.
Tectonophysics (0040-1951) (Elsevier), 2006 , Vol. 412 , N. 3-4 , P. 255-278

Droits : 2005 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/2006/publication-1042.pdf
DOI:10.1016/j.tecto.2005.10.038
http://archimer.ifremer.fr/doc/00000/1042/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This special issue in honour of the late Olivier Jaoul brings together contributions from experimental and theoretical mineralogy, the area of most of Olivier's own work, focused for the most part on the Earth's mantle. The volume is divided into three sections; diffusion, deformation and seismic properties. New technological developments have often had a strong impact on research in this area, as again shown by Olivier's constant search to improve the resolution of the short diffusion profiles typical of major cations in mantle silicates. In the section on diffusion the impact of improved computer performance for modelling diffusion and point defect configurations on one hand, and high pressure experimental techniques on the other hand, highlight the continued development in this area. The section on deformation deals with wide range of subjects, including the deformation of olivine and quartz and the relation between deformation and diffusion, both subjects close to Olivier's personal interests. This illustrates the new possibilities to undertake deformation experiments at mantle pressures and temperatures, as well as improvement in high-fidelity viscoelastic measurements at high temperature. In the last section on seismic properties we discover theoretical developments on predicting properties near the Earth's surface and a new experimental application, which allows the determination of sound velocity at very high pressures with implications for the Earth's inner core.
ISSN: 0031-9201

hal-00475657
https://hal.archives-ouvertes.fr/hal-00475657
DOI : 10.1016/j.pepi.2008.09.009