Analysis of partnership and conservation requirements for a threatened species, Acipenser sturio L., 1758: Towards the implementation of a recovery plan

El esturión atlántico Acipenser sturio L., 1758 es una especie amenazada cuyo último santuario es el ecosistema Gironda, Garona y Dordoña. Se encuentra estrictamente protegido en Francia desde 1981. Sin embargo, no se ha producido un significativo incremento de esta población. Hasta recientemente, como con el programa desarrollado para el salmón, los planes de recuperación de las especies migratorias se han centrado principalmente en la adquisición de conocimiento y en el desarrollo de programas estrictamente técnicos. Estos enfoques son insuficientes para integrar los requerimientos de supervivencia de las especies en la gestión ambiental. El análisis de las necesidades requeridas para la recuperación del esturión atlántico sugiere aspectos técnicos fácilmente manejables, y las medidas apropiadas están disponibles. Por otro lado, aspectos sociales de recuperación más complejos pueden frecuentemente interferir con la puesta en práctica de acciones técnicas. Como un hecho natural, la gestión de los ecosistemas acuáticos trata con múltiples actores, con diferentes intereses y varias competencias, que pueden, directa o indirectamente, influir en la consecución del programa de recuperación. La motivación de todos los grupos de actores y su inclusión en un proyecto colectivo es una de las maneras de realizar los objetivos de un programa de recuperación.The Atlantic sturgeon Acipenser sturio L., 1758 is a threatened species whose last sanctuary is the Gironde, Garonne and Dordogne ecosystem. It has been strictly protected throughout France since 1981. However, no significant increase of its population has occurred. Until recently, as with the programme developed for salmon, migratory species restoration plans have mainly been centred on knowledge acquisition and the development of strictly technical programmes. These approaches are insufficient to integrate species survival requirements in environmental management. The analysis of needs necessary for the recovery of Atlantic sturgeon suggests easily manageable technical aspects, providing proper means are available. On the other hand, far more complex social aspects of recovery can often interfere with the implementation of technical actions. As a matter of fact, aquatic ecosystem management deals with multiple actors, with different concerns and various competencies, which can directly or indirectly influence the achievement of a restoration programme. Motivating each group of actors and including them in a collective project is one of the ways to achieve the goals of a restoration programme.Instituto Español de Oceanografí

Numerical Investigations on the Fluid Behavior in the Near Wake of an Experimental Wind Turbine Model in the Presence of the Nacelle

Accurate predictions of the near wake of horizontal-axis wind turbines are critical in estimating and optimizing the energy production of wind farms. Consequently, accurate aerodynamic models of an isolated wind turbine are required. In this paper, the steady-state flow around an experimental horizontal-axis wind turbine (known as the MEXICO model) is investigated using full-geometry computational fluid dynamics (CFD) simulations. The simulations are performed using Reynolds-Averaged Navier-Stokes (RANS) equations in combination with the transitional k-kl-w turbulence model. The multiple reference frame (MRF) approach is used to allow the rotation of the blades. The impacts of the nacelle and blade rotation on the induction region and near wake are highlighted. Simulation cases under attached and detached flow conditions with and without the nacelle were compared to the detailed particle image velocimetry (PIV) measurements. The axial and radial flow behaviors at the induction region have been analyzed in detail. This study attempts to highlight the nacelle effects on the near wake flow and on numerical prediction accuracy under various conditions, as well as the possible reasons for these effects. According to simulation results, the rotation of blades dominates the near wake region, and including the nacelle geometry can improve both axial and radial flow prediction accuracy by up to 15% at high wind speeds. At low wind speeds, the nacelle effects can be ignored. The presence of the nacelle has also been shown to increase flow separation at the trailing edges of the blade airfoils, increasing both root and tip vorticities. Finally, small nacelle diameters are recommended to reduce flow separation on the blades and increase the average velocity downstream of the rotor, thereby optimizing wind farm output power

Airfoil Shape Optimization of a Horizontal Axis Wind Turbine Blade using a Discrete Adjoint Solver

In this study, airfoil shape optimization of a wind turbine blade is performed using the ANSYS Fluent Adjoint Solver. The aim of this optimization process is to increase the wind turbine output power, and the objective function is to maximize the airfoil lift to drag ratio (CL/CD). This study is applied to the NREL phase VI wind turbine, therefore, the S809 airfoil is used as a reference profile. First, for the validation of the applied numerical model, steady-state simulations are carried out for the S809 airfoil at various angles of attack. Then, the optimization is performed with the airfoil set at a fixed angle of attack, AOA= 6.1°, considering three Reynolds numbers, RE = 300 000, 480 000, 1 000 000 . Next, computations are performed for the fluid flow around the optimized airfoils at angles of attack ranging from 0° to 20°. The results show that (i) the lift to drag ratios of the optimized airfoils are significantly improved compared to the baseline S809 airfoil, (ii) this improvement is sensitive to the Reynolds number, and (iii) the CL/CD ratios are also improved for another angle of attack values. Thereafter, the optimized airfoils are used for the design of the NREL Phase VI blade and the aerodynamic performances of this new wind turbine are assessed using the open-source code QBlade. These latter results indicate that when the blades are designed with the optimized airfoils, the wind turbine aerodynamic performances increase significantly. Indeed, at a wind speed of 10 m/s, the power output of the wind turbine is improved by about 38% compared to that of the original turbine

Effects of Non-Sinusoidal Motion and Effective Angle of Attack on Energy Extraction Performance of a Fully- Activated Flapping Foil

Flapping foil energy harvesting systems are considered as highly competitive devices for conventional turbines. Several research projects have already been carried out to improve performances of such new devices. This paper is devoted to study effects of non-sinusoidal heaving trajectory, non-sinusoidal pitching trajectory, and the effective angle of attack on the energy extraction performances of a flapping foil operating at low Reynolds number (Re=1100). An elliptic function with an adjustable parameter S (flattening parameter) is used to simulate various sinusoidal and non-sinusoidal flapping trajectories. The flow around the flapping foil is simulated by solving Navier–Stokes equations using the commercial software Star CCM+ based on the finite-volume method. Overset mesh technique is used to model the flapping motion. The study is applied to the NACA0015 foil with the following kinetic parameters: a dimensionless heaving amplitude h0 = 1c, a shift angle between heaving and pitching motions f = 90 , a reduced frequency f = 0:14, and an effective angle of attack amax varying between 15 and 50 , corresponding to a pitching amplitude in the range q0 = 55:51 to 90:51 . The results show that, the non-sinusoidal trajectory affects considerably the energy extraction performances. For the reference case (sinusoidal heaving and pitching motions, Sh = Sq = 1), best performances are obtained for the effective angle of attack, amax = 40 . At small effective angle of attack amax 40 ), non-sinusoidal pitching motion has a negative effect. Performance improvement is quite limited with the combined motions non-sinusoidal heaving/sinusoidal pitching

Numerical Investigation of the Effects of Nonsinusoidal Motion Trajectory on the Propulsion Mechanisms of a Flapping Airfoil

The effect of nonsinusoidal trajectory on the propulsive performances and the vortex shedding process behind a flapping airfoil is investigated in this study. A movement of a rigid NACA0012 airfoil undergoing a combined heaving and pitching motions at low Reynolds number (Re¼11,000) is considered. An elliptic function with an adjustable parameter S (flattening parameter) is used to realize various nonsinusoidal trajectories of both motions. The two-dimensional (2D) unsteady and incompressible Navier–Stokes equation governing the flow over the flapping airfoil are resolved using the commercial software STAR CCMþ. It is shown that the nonsinusoidal flapping motion has a major effect on the propulsive performances of the flapping airfoil. Although the maximum propulsive efficiency is always achievable with sinusoidal trajectories, nonsinusoidal trajectories are found to considerably improve performance: a 110% increase of the thrust force was obtained in the best studied case. This improvement is mainly related to the modification of the heaving motion, more specifically the increase of the heaving speed at maximum pitching angle of the foil. The analysis of the flow vorticity and wake structure also enables to explain the drop of the propulsive efficiency for nonsinusoidal trajectories

Energy extraction performance improvement of a flapping foil by the use of combined foil

In this study, numerical investigations on the energy extraction performance of a flapping foil device are carried out by using a modified foil shape. The new foil shape is designed by combining the thick leading edge of NACA0012 foil and the thin trailing edge of NACA0006 foil. The numerical simulations are based on the solution of the unsteady and incompressible Navier-Stokes equations that govern the fluid flow around the flapping foil. These equations are resolved in a two-dimensional domain with a dynamic mesh technique using the CFD software ANSYS Fluent 16. A User Define Function (UDF) controls the imposed sinusoidal heaving and pitching motions. First, for a validation study, numerical simulations are performed for a NACA0012 foil undergoing imposed heaving and pitching motions at a low Reynolds number. The obtained results are in good agreement with numerical and experimental data available in the literature. Thereafter, the computations are applied for the new foil shape. The influences of the connecting area location between the leading and trailing segments, the Strouhal number and the effective angle of attack on the energy extraction performance are investigated at low Reynolds number (Re = 10 000). Then, the new foil shape performance was compared to those of both NACA0006 and NACA0012 baseline foils. The results have shown that the proposed foil shape achieves higher performance compared to the baseline NACA foils. Moreover, the energy extraction efficiency was improved by 30.60% compared to NACA0006 and by 17.32% compared to NACA0012. The analysis of the flow field around the flapping foils indicates a change of the vortex structure and the pressure distribution near the trailing edge of the combined foil compared to the baseline foils

Aerodynamic Performance Investigations of Savonius Twin-rotor Wind Turbines

The aim of this study is to evaluate the aerodynamic efficiency of a Savonius vertical-axis wind turbine. The approach used relies on resolving the Unsteady Reynolds Averaged Navier-Stokes equations (URANS), the turbulence being modeled by the k-ω SST model. The flow around the wind turbine is simulated using the arbitrary sliding interfaces technique. First, the study investigates the impact of blade shape on wind turbine efficiency by examining seven Savonius rotors constructed with distinct blade configurations. The results indicate that the highest aerodynamic performance is provided by the rotor with the elliptical blades, with a notable increase in the power coefficient of about 80% in comparison to the classic semi-circular profile. To further enhance the efficiency of the Savonius wind turbine, a twin-rotor configuration using the elliptical blades was studied. The results indicate a further enhancement in the power coefficient, reaching 110% compared to a single rotor with semicircular blades

Agroinoculation of Citrus tristeza virus Causes Systemic Infection and Symptoms in the Presumed Nonhost Nicotiana benthamiana

Citrus tristeza virus (CTV) naturally infects only some citrus species and relatives and within these it only invades phloem tissues. Failure to agroinfect citrus plants and the lack of an experimental herbaceous host hindered development of a workable genetic system. A full-genome cDNA of CTV isolate T36 was cloned in binary plasmids and was used to agroinfiltrate Nicotiana benthamiana leaves, with or without coinfiltration with plasmids expressing different silencing-suppressor proteins. A time course analysis in agroinfiltrated leaves indicated that CTV accumulates and moves cell-to-cell for at least three weeks postinoculation (wpi), and then, it moves systemically and infects the upper leaves with symptom expression. Silencing suppressors expedited systemic infection and often increased infectivity. In systemically infected Nicotiana benthamiana plants, CTV invaded first the phloem, but after 7 wpi, it was also found in other tissues and reached a high viral titer in upper leaves, thus allowing efficient transmission to citrus by stem-slash inoculation. Infected citrus plants showed the symptoms, virion morphology, and phloem restriction characteristic of the wild T36 isolate. Therefore, agroinfiltration of Nicotiana benthamiana provided the first experimental herbaceous host for CTV and an easy and efficient genetic system for this closterovirus

In-depth study of moderately young but extremely red, very dusty substellar companion HD206893B

Accepted for publication in Astronomy & Astrophysics. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.The substellar companion HD206893b has recently been discovered by direct imaging of its disc-bearing host star with the SPHERE instrument. We investigate the atypical properties of the companion, which has the reddest near-infrared colours among all known substellar objects, either orbiting a star or isolated, and we provide a comprehensive characterisation of the host star-disc-companion system. We conducted a follow-up of the companion with adaptive optics imaging and spectro-imaging with SPHERE, and a multiinstrument follow-up of its host star. We obtain a R=30 spectrum from 0.95 to 1.64 micron of the companion and additional photometry at 2.11 and 2.25 micron. We carried out extensive atmosphere model fitting for the companions and the host star in order to derive their age, mass, and metallicity. We found no additional companion in the system in spite of exquisite observing conditions resulting in sensitivity to 6MJup (2MJup) at 0.5" for an age of 300 Myr (50 Myr). We detect orbital motion over more than one year and characterise the possible Keplerian orbits. We constrain the age of the system to a minimum of 50 Myr and a maximum of 700 Myr, and determine that the host-star metallicity is nearly solar. The comparison of the companion spectrum and photometry to model atmospheres indicates that the companion is an extremely dusty late L dwarf, with an intermediate gravity (log g 4.5-5.0) which is compatible with the independent age estimate of the system. Though our best fit corresponds to a brown dwarf of 15-30 MJup aged 100-300 Myr, our analysis is also compatible with a range of masses and ages going from a 50 Myr 12MJup planetary-mass object to a 50 MJup Hyades-age brown dwarf...Peer reviewedFinal Accepted Versio

Widespread Endogenization of Genome Sequences of Non-Retroviral RNA Viruses into Plant Genomes

Non-retroviral RNA virus sequences (NRVSs) have been found in the chromosomes of vertebrates and fungi, but not plants. Here we report similarly endogenized NRVSs derived from plus-, negative-, and double-stranded RNA viruses in plant chromosomes. These sequences were found by searching public genomic sequence databases, and, importantly, most NRVSs were subsequently detected by direct molecular analyses of plant DNAs. The most widespread NRVSs were related to the coat protein (CP) genes of the family Partitiviridae which have bisegmented dsRNA genomes, and included plant- and fungus-infecting members. The CP of a novel fungal virus (Rosellinia necatrix partitivirus 2, RnPV2) had the greatest sequence similarity to Arabidopsis thaliana ILR2, which is thought to regulate the activities of the phytohormone auxin, indole-3-acetic acid (IAA). Furthermore, partitivirus CP-like sequences much more closely related to plant partitiviruses than to RnPV2 were identified in a wide range of plant species. In addition, the nucleocapsid protein genes of cytorhabdoviruses and varicosaviruses were found in species of over 9 plant families, including Brassicaceae and Solanaceae. A replicase-like sequence of a betaflexivirus was identified in the cucumber genome. The pattern of occurrence of NRVSs and the phylogenetic analyses of NRVSs and related viruses indicate that multiple independent integrations into many plant lineages may have occurred. For example, one of the NRVSs was retained in Ar. thaliana but not in Ar. lyrata or other related Camelina species, whereas another NRVS displayed the reverse pattern. Our study has shown that single- and double-stranded RNA viral sequences are widespread in plant genomes, and shows the potential of genome integrated NRVSs to contribute to resolve unclear phylogenetic relationships of plant species