Computing efficiently the lattice width in any dimension

International audienceWe provide an algorithm for the exact computation of the lattice width of a set of points K in Z2 in linear-time with respect to the size of K. This method consists in computing a particular surrounding polygon. From this polygon, we deduce a set of candidate vectors allowing the computation of the lattice width. Moreover, we describe how this new algorithm can be extended to an arbitrary dimension thanks to a greedy and practical approach to compute a surrounding polytope. Indeed, this last computation is very efficient in practice as it processes only a few linear time iterations whatever the size of the set of points. Hence, it avoids complex geometric processings

The commercial push net fisheries for glass eels in France and its handling mortality

Glass eels, the young life stage of the endangered European eel entering the European continental waters, are exploited for human consumption (direct, or on-grown) and restocking. Restocking is considered as a potential contribution to the conservation of the stock. For this, the mortality of glass eels during capture should be low. We studied the handling mortality of glass eels obtained by commercial push net fisheries in different rivers in France in 2019 and 2020. The direct mortality of glass eels in 41 fishing trips of 29 boats varied from zero to 3.1% (mean 0.3%). Skin lesions identified by staining occurred in 31% (range: 4%–98%) of the eels. Post fishing mortality of glass eels varied from zero to 67.2%. The mean total fishing mortality was with 7.4% (range 0%–56.2%), considerably lower than in previous studies. The Sustainable Eel Group (SEG) issues certificates to fishers applying best practices for a responsible fishery. Comparing certified to uncertified fishers, the certified fishers have on average significant lower lesions and post-fishing mortality rates, However, some uncertified fishers have an equal or better glass eel quality than certified fishers. Noting that certified fishers score better on average, and avoid the worst scores, we conclude that the SEG-certification scheme for responsible fishing is effective

Escapement of a silver-phase eel population, Anguilla anguilla, determined from fishery in a Mediterranean lagoon (Or, France)

Escapement of silver eels from a Mediterranean lagoon was estimated by a capture–tagging–recapture and automated tag-reading study. The population of silver-phase eels in the lagoon was estimated to be 13.2 kg ha21, with an escapement rate from the commercial fishery of 76.8%

Etude de nouveaux composites de source renouvelable à base de copolyamide et de farine de bois

Les travaux présentés dans ce manuscrit sont consacrés à l'élaboration et l étude des propriétés physiques et thermiques d une nouvelle génération de composites bois/polymère.Ils sont composés d une matrice bio-sourcé le pebax®, qui est un thermoplastique élastomèreet de farine de bois de production locale, issue du pin maritime. La matrice pebax® a été choisie car elle présente plusieurs avantages, notamment, une élongation avant ruptureimportante, un point de fusion inférieur à 200C pour éviter la dégradation du bois au coursde la mise en oeuvre et un caractère hydrophile améliorant l affinité entre la matrice et lerenfort. Les composites ont été élaborés par extrusion bi-vis et injectés sous forme d haltèresnormalisées pour les tests mécaniques. Au cours de ces travaux, nous avons montré la bonne qualité de l interface entre le bois et la matrice, permettant de s'affranchir de l utilisation d agents compatibilisants. Nous avons aussi mis en évidence une forte amélioration de la stabilité thermique des composites sous atmosphère oxydante par rapport à celle de la matrice et du bois séparément. Les caractérisations mécaniques et rhéologiques effectuées sur les composites ont permis de montrer l effet rigidifiant de la farine de bois avec un taux critique entre 20% et 30% de charges pour lequel le comportement des composites évolue d un type élastomérique à celui de solide moins ductile. La dernière partie des travaux a été consacrée à l évaluation de la prise en eau des composites. En accord avec les travaux de la littérature, nous avons montré une augmentation de la prise en eau avec le taux de bois. De plus, nous avons démontré que le début de l absorption d eau de nos composites suit un mécanisme de diffusion de type Fickien.The physical properties and thermal stability of a new family of wood polymer composites (WPC) using a bio-based thermoplastic elastomer matrix (pebax® copolymers) were studied. The matrix is a polyether-b-amide thermoplastic elastomer which presents an important elongation at break, a melting point below 200C which helps prevent degradation of wood fibres. The hydrophilic character of pebax® leads to a good interaction with wood fibres. We have chosen several types of wood flour as reinforcement agent, focusing on wood flour from maritime pine. Composites compounds were made using a laboratory twin screw extruder prior to injection molding to obtain tensile test samples. We have demonstrated the good quality of the interface between wood fibres and matrix, without using any specific compatibilizing agent. Most importantly, we have pointed out a strong improvement of thermal stability of composites under air atmosphere, compared with the behaviour of the matrix or wood separately. We have also characterized the mechanical properties of these composites. The resulting data show an improvement of the tensile modulus with increasing wood content and a decrease of elongation at break, with a behaviour change from elastomeric to less stretchable solid behaviour between 20% and 30% of wood content.The last part of our work was dedicated to the evaluation of water absorption of thecomposites at different wood content. We have shown an increase of water absorption withincreasing wood content and we demonstrated a Fickian diffusion process at the onset ofwater absorption.PAU-BU Sciences (644452103) / SudocSudocFranceF

Session C5: Impact of Water Intake for Drinking Water Supply, on Downstream Eel Migration in the Fremur River

Abstract: The Fremur is a small coastal river located in northern Brittany, which discharges into the English Channel near Saint Malo (2°060W, 48°340N). Its catchment area spread over 60 km2 with a 17 km main stem. Three major dams (Pont Avet, Pont es Omnes and Bois Joli) located on the river, were previously impassable for fish, until the construction of fishpasses in 1996 (Feunteun et al., 1998). The highest one, Bois Joli dam, is 14 m high and holds a 3,9 million m3 reservoir used for drinking water supply. Downstream eels (Anguilla anguilla) migration is possible over the crest of the dam when overflowed as well as through the pumping pipe since 2012, following the pumping station construction. One kilometer downstream, at Pont-es-Omnès dam, a wolf trap allows to study eel downstream migration since 1996 (Acou et al., 2008). To study the potential impact of the water intake on eel downstream migration, in March 2012, a net was installed at the exit of a pipe, receiving the washing water, coming from the first filter preventing big materials, such as fish, to go further into the pumping station. The scientific follow-up stated in 2012 has allowed to trap more than 700 individuals belonging to 7 different species (6 of fish, 1 of crayfish). More than 170 eels were caught, including 89 during the 2012-2013 campaign. The study showed that eels use the pumping pipe independently of overflowing periods. Two periods of migration were highlighted, one in summer with a majority of yellow eels and the other one in winter with a majority of silver eels. The direct mortality was estimated between 2 and 100 %. The majority of eels showed symptoms of pathology like cutaneous erosions and bleedings. Since January 2013, the delayed mortality is studied by mark-release-recapture. Eels were marked with blue alcyan ink using a “Dermojet” at capture in the net and there were recaptured at the wolf trap at Pont-es- Omnès dam. First results indicate a high delayed mortality. These results highlight the major impact of water intake on downstream migrating eels. They underline the need to protect or to adapt water intake especially in the current context of eel decline

High temperature drying effect against resin exudation for maritime pine wood used as outdoor siding

International audienceThe effect of temperature during the wood drying process was studied in order to prevent resin exudation on the surface of maritime pine wood boards used as outdoor siding. Resin exudation is a crucial concern for the maritime pine industry, as it may strongly decrease the wood aesthetics during outdoor exposure. In a previous study, it was observed that the thermal history of rosin can change the softening point temperature of its compounds. Using heat treatment, this temperature can shift from about 40 °C–60 °C, which corresponds to the maximal surface temperature of an unpainted wood siding in a temperate climatic zone. In the present study, green wood boards from various trees were dried at various temperatures (60 °C, 90 °C, 120 °C and 150 °C) and directly evaluated after drying regarding their resistance to exudation. To perform this test, an infrared radiative system was developed in order to recreate summer outdoor conditions. The results show the absence of exudation for boards dried at high-temperature (150 °C). In order to better understand the effects of a heat treatment on resin compounds inside wood, they were studied using HPLC after extraction. The analysis was compared to a standard rosin used in a previous study showing strong similarity. These results highlight some new effects of high temperature drying which may offer new strategies for reducing resin exudation on outdoor wood siding by fixing the resin compounds inside the wood

Outils d’aide à la décision pour agir sur les risques d’intrusion dans les systèmes d’information portuaire basée sur la modélisation des chaînes cybercriminelles

International audienc

Towards an accurate description of the dissipation gradients at the micro-scale to describe the basic fatigue mechanisms

International audienc