Choosing best practices for managing impacts of trawl fishing on seabed habitats and biota

Bottom trawling accounts for almost one quarter of global fish landings but may also have significant and unwanted impacts on seabed habitats and biota. Management measures and voluntary industry actions can reduce these impacts, helping to meet sustainability objectives for fisheries, conservation and environmental management. These include changes in gear design and operation of trawls, spatial controls, impact quotas and effort controls. We review nine different measures and actions and use published studies anda simple conceptual model to evaluate and compare their performance. The risks and benefits of these management measures depend on the extent to which the fishery is already achieving management objectives for target stocks and the characteristics of the management system that is already in place. We offer guidance on identifying best practices for trawl-fisheries management and show that best practices and their likelihood of reducing trawling impacts depend on local, national and regional management objectives and priorities, societal values and resources for implementation. There is no universalbest practice, and multiple management measures and industry actions are required to meet sustainability objectives and improve trade-offs between food production and environmental protection

Narrow resonances in the continuum of the unbound nucleus 15^{15}F

The structure of the unbound $^{15}$F nucleus is investigated using the inverse kinematics resonant scattering of a radioactive $^{14}$O beam impinging on a CH$_2$ target. The analysis of $^{1}$H($^{14}$O,p)$^{14}$O and $^{1}$H($^{14}$O,2p)$^{13}$N reactions allowed the confirmation of the previously observed narrow $1/2^{-}$ resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2$^{-}$ and 3/2$^{-}$ resonances. The newly observed levels decay by 1p emission to the ground of $^{14}$O, and by sequential 2p emission to the ground state (g.s.) of $^{13}$N via the $1^-$ resonance of $^{14}$O. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2$^{-}$ and 3/2$^{-}$ resonances may be collectivized by the continuum coupling to nearby 2p- and 1p- decay channels. The observed excitation function $^{1}$H($^{14}$O,p)$^{14}$O and resonance spectrum in $^{15}$F are well reproduced in the unified framework of the GSM

Origine microstructurale de l'amorçage des fissures intergranulaires dans les alliages Al-Li 8090

This study is concerned with crack origin of 8090 Al-Li alloys tensile tested. Particular attention has been given on grain boundary crack or delamination. It has been shown that the origin of the fracture is due to a strong slip localisation on a one single slip system and to the appearance of a sinuous and coarse slip probably resulting from incompatible strains between adjacent grains, whatever the ageing conditions. Also, it has been shown that the intergranular precipitation increases the risk of intergranular cracks. But the slip localisation seems to be responsible for the delamination initiation. In the case of underaged condition a quantitative analysis from a model of dislocations piled up against grain boundary has been developed. This approach agrees with experimental results.L'objectif de ce travail était de comprendre et de modéliser l'amorçage des fissures dans les alliages Al-Li 8090 sollicités en traction monotone. Une attention particulière a été portée sur les fissures intergranulaires — ou de délaminage —. Nous avons montré que la forte localisation de la déformation sur un seul système de glissement, ainsi que l'apparition d'un glissement « sinueux » et intense résultant probablement des incompatibilités de déformation de grain à grain, sont à l'origine de l'amorçage des fissures, et cela quelles que soient les conditions de revenu. Nous avons montré aussi que la précipitation intergranulaire augmente le risque de délaminage. Mais l'interaction glissement-joints de grains semble tout de même être responsable de l'amorçage intergranulaire. Enfin, nous avons développé pour les états sous revenus une analyse quantitative basée sur un modèle d'empilements de dislocations contre les joints de grains qui est en accord avec les résultats expérimentaux

Understanding the cosmic abundance of

Simulations of explosive nucleosynthesis in novae predict the production of 22Na, a key astronomical observable to constrain nova models. Its gamma-ray line at 1.275 MeV has not yet been observed by the gamma-ray space telescopes. The 20Ne/22Ne ratio in presolar grains, a possible tool to identify nova grains, also depends on 22Na produced. Uncertainties on its yield in classical novae currently originate from the rate of the 22Na(p, γ)23Mg reaction. At peak novae temperatures, this reaction is dominated by a resonance at ER=0.204 MeV, corresponding to the Ex=7.785 MeV excited state in 23Mg. The resonance strengths measured so far disagree by one order of magnitude. An experiment has been performed at GANIL to measure the lifetime and the proton branching ratio of this key state, with a femtosecond resolution for the former. The reactions populating states in 23Mg have been studied with a high resolution detection set-up, i.e. the particle VAMOS, SPIDER and gamma tracking AGATA spectrometers, allowing the measurements of lifetimes and proton branchings. We present here a comparison between experimental results and shell-model calculations, that allowed us to assign the spin and parity of the key state. Rather small values obtained for reduced M1 matrix elements, M(M1) ≲ 0.5 µN, and proton spectroscopic factors, C2Sp<10−2, seem to be beyond the accuracy of the shell model. With the reevaluated 22Na(p, γ)23Mg rate, the 22Na detectability limit and its observation frequency from novae are found promising for the future space telescopes

Multivariate Archimax copulas

International audienc

EFFETS NON LINÉAIRES DE LA RELAXATION DE BORDONI ET ÉVOLUTION DES CONTRAINTES INTERNES

Nous avons étudié, dans le cas d'un aluminium 5N, l'évolution de la relaxation non linéaire de Bordoni en fonction de la température de recuit après déformation plastique. De ces résultats et de l'effet d'une contrainte statique sur le frottement intérieur, on déduit l'évolution des contraintes internes au cours du recuit. Cette évolution avec la température est similaire à celle observée sur des valeurs de contrainte interne obtenues par la méthode du dip-test, bien que les niveaux de contrainte observés soient différents.Evolution of non linear Bordoni relaxation has been studied as a function of annealing temperature of 5N aluminium plastically deformed. From these results and from the effect of applied stress on internal friction the evolution of internal stresses with annealing is deduced. This evolution is similar to this obtained by dip-test measurement although the stress levels are different

VARIATIONS DE L'ÉNERGIE RELATIVE DISSIPÉE AU COURS DE LA FATIGUE D'UN ALUMINIUM 5N

Lors d'essais de fatigue en traction-compression sur Al 5N à la température ambiante, nous avons déterminé l'énergie relative dissipée en fonction de différents paramètres : mode de déroulement du cycle, amplitude et fréquence et sur deux états initiaux différents, recuit et préfatigué à saturation. Les résultats expérimentaux sont analysés à partir des mécanismes microscopiques proposés habituellement pour expliquer le comportement cyclique.This paper is concerning with the evolution of dissipated relative energy during symmetric push-pull test of Al 5N at room temperature. On two microstructural state (annealed and prefatigued), effects of cycles conditions, frequency and amplitude strain have been determined. Experimental results have been analyzed as depending on classical microscopic mechanics suggested in fatigue behaviour