Search

International audience; Climate change is driving the need to investigate responses to water limitation of morphological traits involved in competition for light, the main resource for which crops and weeds compete in conventional temperature and tropical cropping systems, to better understand field crop-weed dynamics. Our objective was to develop an innovative approach to quantify weed species responses to water limitation, using three species. This approach combined (1) key morphological traits involved in competition for light (taken from a mechanistic crop-weed model) as criteria to analyse responses to water limitation and (2) a pot/greenhouse platform allowing automated precision-watering and daily quantification of soil water availability in each pot. For all species and growth stages, increased plant height per unit of aboveground biomass and production of smaller/thicker leaves were the most noteable responses. Plants with a strong increase in plant height per unit of aboveground biomass in response to water limitation maintained high levels of specific leaf area, even at low soil water availability. Increases in biomass allocation to roots (vs. aboveground parts) and leaves (vs. stems and reproductive organs) were also observed, but not for all species and growth stages. Overall, these effects of water limitation on morphological traits indicate strong interactions between competition for light and water.

30 book of abstracts; International audience

International audience

The balance of pollination competition and facilitation among co-flowering plants and abiotic resource availability can modify plant species and individual reproduction. Floral resource succession and spatial heterogeneity modulate plant-pollinator interactions across ecological scales (individual plant, local assemblage, and interaction network of agroecological infrastructure across the farm). Intraspecific variation in flowering phenology can modulate the precise level of spatio-temporal heterogeneity in floral resources, pollen donor density, and pollinator interactions that a plant individual is exposed to, thereby affecting reproduction. We tested how abiotic resources and multi-scale plant-pollinator interactions affected individual plant seed set modulated by intraspecific variation in flowering phenology and spatio-temporal floral heterogeneity arising from agroecological infrastructure. We transplanted two focal insect-pollinated plant species (L’équilibre des relations de compétition et de facilitation entre plantes pour la pollinisation et la disponibilité des ressources abiotiques affectent le succès reproducteur des espèces et des individus de plantes. La succession temporelle et l’hétérogénéité spatiale des ressources florales modifient les interactions plantes‐pollinisateurs à différentes échelles écologiques (individu végétal, assemblage plantes‐pollinisateurs local, réseau d’interactions des infrastructures écologiques à travers la ferme). Les variations intraspécifiques de phénologie de floraison peuvent moduler le succès reproducteur individuel en déterminant le niveau d’hétérogénéité spatio‐temporelle de densité de donneurs de pollen, des interactions plantes‐pollinisateurs et des ressources florales auxquelles un individu de plante est exposé. Nous avons mené une expérimentation pour tester comment la production de graines des plantes sauvages est affectée par les interactions plantes‐pollinisateurs à différentes échelles écologiques, ces interactions étant modulées par la phénologie florale et l’hétérogénéité spatio‐temporelle des ressources florales (découlant des infrastructures agroécologiques). Nous avons transplanté 144 individus de deux espèces végétales entomophiles (

The realization of the first wall (FW), which is composed of a protective tungsten (W) armor covering the structural steel material, is a critical challenge in the development of future fusion reactors. Due to the different coefficients of thermal expansion (CTE) of W and steel, the direct joining of them results in cyclic thermal stress at their bonding seam during the operation of the fusion reactor. To address this issue, this study benchmarks two joining concepts. The first concept uses an atmospheric plasma sprayed graded interlayer composed of W/steel composites with a varying content of W and steel to gradually change the CTE. The second concept uses a spark plasma sintered graded interlayer. Furthermore, in order to benchmark these concepts, a directly bonded W-steel reference joint as well as a W-steel joint featuring a vanadium interlayer were also tested. These joints were tested under steady-state high heat flux cyclic loading, starting from a heat flux of 1 MW/m2 up to 4.5 MW/m2, with stepwise increments of 0.5 MW/m2. At each heat flux level, 200 thermal cycles were performed. The joints featuring a sintered graded interlayer survived only until 1.5 MW/m2 of loading, while the joint featuring plasma sprayed graded interlayer and V interlayer survived until 3 MW/m2.

Book of abstract p.372; International audience; The carry-over effect of cover crops on weeds and crop productivity in the subsequent crops has been related to cover crop composition and cover crop termination methods but their interaction with soil resource availability remains poorly documented, as well as the relative importance of each of these factors. This study investigated the effect of cover crop management (i.e. cover crop mixture, fertilisation, irrigation, termination method and their combinations) on weed biomass and crop productivity in two subsequent crops (spring barley followed by winter linseed). We hypothesised that cover crop management could affect productivity of the subsequent crops through both weed suppression and nitrogen supply. Two experiments spanning a duration of two years were set-up, on two different fields in two different years, to investigate the effect of cover crop mixture (2 or 8 species including or not legume species, plus a bare soil control), water and nitrogen availability at cover crop sowing and cover crop termination methods (rolling, herbicide-use and winter-kill control) on weed biomass and crop productivity of the two subsequent unweeded, unfertilised and directly seeded crops. Weed biomass and crop productivity in both subsequent crops were affected by multiple interactions between cover crop mixture, soil resource availability, cover crop termination method and experiment. In experiment 1, combinations of cover crop management alternative to the reference (i.e. bare soil, without fertilisation and irrigation, winter-killed) mainly showed beneficial carry-over effects (i.e. lower weed biomass and higher crop productivity) in the subsequent spring barley while having no effect in winter linseed. In experiment 2, alternative combinations of cover crop management mainly showed no effects or detrimental carry-over effects (i.e. higher weed biomass and lower crop productivity) in spring barley while having some positive effects in winter linseed (i.e. only when cover crops were terminated with herbicide-use). Crop productivity was mainly affected by weed biomass which was significantly reduced almost only when cover crops were terminated with herbicide-use. Crop productivity was also affected but to a lesser extent by cover crop soil-mediated effects (e.g. nitrogen supply). These results highlight complex interactions between cover crop management and environmental conditions on the carry-over effects of cover crops in the subsequent crops. Cover crops may not play an essential role for weed management in no-till and herbicide-free systems, particularly at low levels of cover crop biomass production.

The problem of power exhaust is one of the grand challenges of nuclear fusion research today. In order to understand the physics phenomena occurring in the scrape-off layer and the divertor regions of tokamaks, it is essential to correctly determine the divertor plasma parameters, which are often measured by swept Langmuir probes (LPs). While the construction and operation of this diagnostic can be straightforward, the data analysis using three- or four-parameter fits presents a challenge and can potentially lead to erroneous values of electron temperature and ion saturation current. In this work, we present modelling and experiments aimed at determination of conditions for proper analysis of swept LPs using these two fitting models. Particle-in-cell modelling was employed to evaluate the sheath-expansion effects for particular probe geometry and plasma conditions, yielding a semi-empirical rule capable of predicting its magnitude. Experiments with unusually wide range of swept voltage in the divertor of the COMPASS tokamak explored the magnitude of voltage range required for successful analysis with either three or four-parameter fitting. With the use of our new semi-empirical rule, it is possible to improve the four-parameter fit reliability in situations where the available voltage range is limited. In addition, we introduce the tangent method—an independent and fast method of electron temperature estimation, which allows to reliably determine the available voltage range and as such assist more complex methods of probe analysis.

Perennial weeds have become an increasing problem with the reduction of herbicide use and tillage. Because of their capacity to regenerate from vegetative organs, such as roots and rhizomes, they must be controlled with different management techniques than annuals. To date, few studies exist on this topic and farmers often lack solutions to control perennials in their cropping systems. Management strategies must focus on the depletion of the regenerative organ reserves to hamper the production of new shoots. However, there is a need for a better understanding of below-ground organs physiology and the determining factors of their regrowth capacities. Our aim was to assess the number of shoots and their growth speed from one below-ground fragment according to 1) its weight, which is related to the amount of available reserves, and 2) the number of buds initially present (visible) on it. A pot experiment was carried out in a greenhouse: fragments of rhizomes of Elymus repens with different weights and different visible bud numbers were buried into 6-L pots. The number and length of the produced shoots were measured dynamically during the experiment. The effects of fragment weight and bud number on (1) the probability that a fragment produce at least one shoot and (2) shoot growth speed. The main results indicate a strong positive impact of the fragment weight, meaning that the more the reserves, the faster shoots grow, and a negative impact of the density of shoots on a same fragment, which implies a competition effet between the growing shoots. More perennial species are to be studied with the same intentions. These results will be used to model regrowth of perennials from below-ground fragments after tillage in a cropping system simulation model (FLORSYS). This model simulates daily weed dynamics and crop production over the years from cropping system and pedoclimate. The ultimate goal will be to identify agroecological weed management strategies and to help farmers to redesign their cropping systems.

Perennial weeds have become an increasing problem with the reduction of herbicide use andtillage. Because of their capacity to regenerate from vegetative organs, such as roots andrhizomes, they must be controlled with different management techniques than annuals. Todate, few studies exist on this topic and farmers often lack solutions to control perennials intheir cropping systems. Management strategies must focus on the depletion of theregenerative organ reserves to hamper the production of new shoots. However, there is aneed for a better understanding of below-ground organs physiology and the determiningfactors of their regrowth capacities.Our aim was to assess the number of shoots and their growth speed from one below-groundfragment according to 1) its weight, which is related to the amount of available reserves, and2) the number of buds initially present (visible) on it. Five species were investigated:Cirsium arvense, Sonchus arvensis, Convolvulus arvensis, Elymus repens and Rumex crispus.They were chosen for their frequency and harmfulness in arable crops in temperate regionsand for their difference in terms of multiplication strategy, which implies different vegetativeorgans. Two pot experiments were carried out in a greenhouse: fragments of roots andrhizomes with different weights or different visible bud numbers were buried into 6-L pots,and the number and length of the produced shoots were measured dynamically during theexperiment. The effects of fragment nature (creeping root, rhizome, taproot), weight and thenumber of buds on (1) the probability that a fragment produce a shoot, (2) shoot growth rate,(3) shoot number and (4) maximum shoot length were analyzed. Also, shoot length wasQuantified as a function of hydrothermal time since bud sprouting.These results will be used to model regrowth of perennials from below-ground fragmentsafter tillage in a cropping system simulation model (FLORSYS). This model simulates daily weeddynamics and crop production over the years from cropping system and pedoclimate. Theultimate goal will be to identify agroecological weed management strategies and to helpfarmers to redesign their cropping systems.

Cover crop (CC) mixtures appear as a promising agroecological tool to suppress weeds andmaintain crop productivity while reducing chemical inputs such as herbicides and nitrogenfertilizers. The weed suppressive effect of CC and CC nitrogen release have been related to CCcomposition, soil resource availability and CC termination methods but the relative effect ofthese factors and their interactions remain poorly documented, especially in the case of CCmixtures. Most studies have focused on the subsequent spring crop, and hence, lacked toinvestigate long-term carry over effects of CC. A two field: year experiment was conducted toinvestigate the effect of CC mixture (2 or 8 species including or not legume species, comparedto a bare soil control), resource availability (water and nitrogen) at CC sowing and CCtermination method (rolling and glyphosate, compared to a winterkill control) on weedbiomass and productivity of two subsequent unweeded, unfertilized and direct seeded crops(spring barley and winter linseed in year 1 and 2, respectively). In the context of reduction ofherbicide use, our experiments showed that the use of CC to reduce weed biomass in thesubsequent crop was not relevant when CC were terminated by winter or rolling since CCprobably protected weeds from winter instead of creating a physical barrier for weedemergence, weed community composition in crop being mainly represented by weedvolunteers. Weed biomass was the main driver of the subsequent crop productivity but thelatter was enhanced after fertilised or legume-based CC, probably because of a highernitrogen release. No relevant long-term effect of CC on the subsequent crop was observed inour experiment, probably because nitrogen was used by the previous crop and weedcommunity composition changed by year. Our results highlight the importance CCcomposition and management for weed suppression and crop productivity in low-intensitybiodiversity-based cropping systems.

For a future commercial fusion reactor the First Wall of the breeding blanket will require a joint between the structural steel and the plasma facing material tungsten. However, the difference in the coefficient of thermal expansion (CTE) between them results in thermal stresses at their interface during operation and this could result in premature failure of the joint. A functionally graded material (FGM), as an interlayer between tungsten and steel could reduce these stresses. In this study two processes, atmospheric plasma spraying (APS) and spark plasma sintering (SPS), are utilized to manufacture four different kinds of W-FGM-steel stacks: the first two include FGMs prepared by APS; W-V-75W-50W-25W-steel and W-50W-25W-steel, the other two include FGMs made by SPS; W-75W-50W-25W-steel and W-50W-25W-steel. This investigates: i) the influence of an additional V-interlayer; ii) the comparison of APS- and SPS-FGMs; and iii) the influence of FGM composition and thickness. In all these W-FGM-steel stacks, with a surface area of 12 mm x 12 mm, the thickness of each FGM sublayer (75W, 50W, 25W) is about 0.5 mm, whereas the bulk-W and bulk-steel are 3 mm thick. A sample of direct diffusion bonded W-steel joint is used as a reference. A high heat flux benchmark test was performed to investigate and compare the potential of the different joining technologies. For this, the stacks were soldered on a copper cooling module and exposed to high stationary loads at the JUDITH-2 facility. At each power level of 1 MW/m2, 2 MW/m2, 3 MW/m2 and 4 MW/m2 the samples were subjected to a component screening cycle to determine the component quality followed by up to 200 on/off cycles (30/30 s). By monitoring the surface temperature using an IR camera, the cooling capabilities of each sample and any local overheating as indication of bond failure can be determined.

Self-passivating Metal Alloys with Reduced Thermo-oxidation (SMART) are under development for the primary application as plasma-facing materials for the first wall in a fusion DEMOnstration power plant (DEMO). SMART materials must combine suppressed oxidation in case of an accident and an acceptable plasma performance during the regular operation of the future power plant. Modern SMART materials contain chromium as a passivating element, yttrium as an active element and a tungsten base matrix. An overview of the research and development program on SMART materials is presented and all major areas of the structured R&D are explained. Attaining desired performance under accident and regular plasma conditions are vital elements of an R&D program addressing the viability of the entire concept. An impressive more than 104-fold suppression of oxidation, accompanied with more than 40-fold suppression of sublimation of tungsten oxide, was attained during an experimentally reproduced accident event with a duration of 10 days. The sputtering resistance under DEMO-relevant plasma conditions of SMART materials and pure tungsten was identical for conditions corresponding to nearly 20 days of continuous DEMO operation. Fundamental understanding of physics processes undergone in the SMART material is gained via fundamental studies comprising dedicated modeling and experiments. The important role of yttrium, stabilizing the SMART alloy microstructure and improving self-passivating behavior, is under investigation. Activities toward industrial up-scale have begun, comprising the first mechanical alloying with an industrial partner and the sintering of a bulk SMART alloy sample with dimensions of 100 mm × 100 mm × 7 mm using an industrial facility. These achievements open the way to further expansion of the SMART technology toward its application in fusion and potentially in other renewable energy sources such as concentrated solar power stations.

Cover crop (CC) mixtures appear as a promising agroecological tool for weed management.Although CC supress weed growth by competing for resources, their suppressive effect undercontrasting levels of soil resource availability remains poorly documented. A two field: yearexperiment was conducted to investigate the weed suppressive effect of four CC mixtures.They were composed of 2 or 8 species including or not legume species and compared to abare soil control. The experiment included two levels of irrigation and nitrogen fertilisation atCC sowing. The objectives were to assess (i) weed and CC aboveground biomass response toCC mixtures and resource availability, (ii) the weed suppressive effect of CC mixtures across agradient of CC biomass and (iii) weed community response to CC mixtures and resourceavailability. CC and weed biomass were mainly influenced by interactions between CCmixtures and fertilisation and between CC mixtures and irrigation, with contrasted effectsbetween field: years. Nitrogen fertilisation increased biomass of non-legume based CCmixtures but this only resulted into a further reduction of weed biomass of little biologicalrelevance. Legume-based CC mixtures suppressed weeds to a greater extent without nitrogenfertilisation in year 2 but not in year 1, possibly due to contrasted initial soil nitrogenavailability (lower in year 2). Weed biomass generally benefited more from irrigation than CCmixtures. Among the 33 weed species recorded, weed communities in each plot weredominated by wheat volunteers, Geranium dissectum, Veronica persica and Echinochloa crusgalli, whose biomass varied depending on the interaction between year, CC mixture andresource availability. Our results revealed that competitive outcomes between CC mixturesand weed species were driven by a complex interaction between resource availability andspecies traits. Further experiments focusing on plant traits should improve our understandingof weed: CC competitive outcomes under various levels of resource availability.

The patent literature concerning thermal spraying for biomedical applications is reviewed in this contribution. The patents were compiled from multiple databases search spanning the 2005-2018 period. For clarity and ease of reading, the results have been grouped into sections according to four individual material groups (apatites, titanium, oxide ceramics, other), with the secondary sorting criterion being related to the specific bioapplication areas (maxillofacial, orthopedic, methods). Lastly, the patents are grouped according to the selected thermal spray method within the individual subsections. In the paper, recent R&D trends in this field are further identified and briefly commented.

The differences in the thermophysical properties between tungsten and steel create thermal stress peaks at its interface when joined directly for the breeding blanket of a fusion reactor. In order to solve this problem, a graded interlayer made of several layers of W/steel-composites is considered to reduce these stress peaks. Plasma spraying under an argon shrouded chamber was employed as a cost efficient manufacturing technique for such composites and field assisted sintering technology/spark plasma sintering was used to diffusion bond them with bulk-W and bulk-steel. Firstly, thermophysical characterizations were performed on these composites. Secondly, two approaches have been investigated to join bulk-W and 75 vol% W composite: direct joining and using a vanadium foil. Only vanadium foil resulted in successful bond formation at all the three bonding temperatures of 800 °C, 900 °C and 1000 °C. Thirdly, investigation of diffusion bonding parameters (temperature and time) for the joining of 25 vol% W, 50 vol% W, 75 vol% W and bulk-steel were studied and optimum process parameter were identified. Finally, this optimized parameter (1000 °C; 30 min) was employed to manufacture a complete 12 mm x 12 mm W-steel joint consisting of this graded interlayer.

Positron annihilation lifetime spectroscopy data taking for ELBE proposal POS19101496 by Sandrina Fernandes, Rez, CZ. Role of open volume defects in irradiated structural materials for fusion applications. Measurements performed 16.3.2019 at the MePS facility.

La dynamique des communautés adventices annuelles est fortement liée à la réserve de semences contenues dans le sol des parcelles cultivées. Le devenir de ces semences dans le sol dépend non seulement du milieu, des pratiques culturales réalisées mais aussi des caractéristiques biologiques de chaque espèce. Mieux connaître cette diversité des semences adventices reste indispensable dans une évaluation des services positifs et négatifs que peut rendre une communauté de mauvaises herbes.La diversité des semences adventices est importante à connaitre pour (1) savoir comment mieux gérer les adventices en limitant le recours aux herbicides de synthèse, (2) mieux comprendre leur rôle dans les chaines trophiques et ainsi favoriser leur régulation biologique (exemple de la prédation par les carabes) et (3), d’un point de vue méthodologique, faciliter la mise au point de nouvelles méthodes d’estimation du stock semencier dans les sols des parcelles cultivées.Cet article illustre la diversité des semences adventices en synthétisant les connaissances acquises sur seize espèces communément trouvées en parcelles de grande culture. Cette diversité s’exprime sur les plans botaniques, écologiques et biologiques, non seulement au niveau interspécifique (variabilité entre espèces) mais aussi au niveau intraspécifique (variabilité entre échantillons d’une même espèce). Cette variabilité intraspécifique, qui reste à ce jour peu explorée, indique qu’il est préférable de caractériser une espèce non pas par une valeur unique pour un caractère donné (par exemple, le poids de mille grains) mais plutôt par une plage de valeurs.

National audience; Les semences adventices peuvent survivre dans le sol durant de nombreuses années. Le stock semencier constitue ainsi un point fondamental du développement des communautés adventices, en lien avec leur stratégie de survie. Son étude apparaît donc comme un point crucial dans la compréhension de la dynamique des adventices. Au sein de l’UMR Agroécologie, des travaux sont menés pour étudier différents processus biologiques liés au cycle de vie des adventices, les phénomènes de résistance des adventices aux herbicides ainsi que les interactions entre les adventices et d’autres organismes (prédation des graines par des insectes par exemple). Pour soutenir ces activités de recherche, une collection de semences adventices a été développée. Elle est composée (1) d’une carpothèque qui est une collection de semences pour l’aide à l’identification des espèces adventices à partir de la semence, et (2) d’un ensemble de lots de semences qui ont pour vocation d’être utilisés à des fins expérimentales. Des prospections sont réalisées annuellement selon des protocoles respectant les populations d’adventices au champ. Le développement de nouvelles techniques, basées sur l’analyse de l’ADN contenu dans les sols, pourrait dans le futur contribuer à caractériser des stocks semenciers dans les sols. Néanmoins, le maintien d’un savoir botanique restera indispensable pour conserver une connaissance des adventices, et ainsi contribuer à leur gestion intégrée et durable. The weed seed collection of UMR Agroécologie (Dijon) Weed seeds can survive in the soil for many years. The soil seed bank plays a key role in the development of weed communities. Its study is crucial for understanding weed species dynamics. The unit of Agroecology investigates biological processes related to the weed life cycle, weed resistance to herbicides, and interactions between weeds and other organisms (for example, seed predation by insects). A weed seed collection was set up in order to support these research activities. It consists of (1) a seed library, in order to facilitate the identification of the weed species, and (2) a series of weed seed lots that are used for research experiments. Weed seeds harvests are carried out in fields, using protocols that do not endanger the survival of the weed populations. In the future, new techniques based on DNA may become very useful to identify species. However, maintaining a botanical knowledge at the seed, seedling and adult plant stages will remain crucial, in order to maintain knowledge of weeds improve, and thereby to propose integrated and sustainable weed management strategies.

National audience; Un essai pluriannuel en semis-direct a testé l’effet de couverts (quatre mélanges comparés à du sol nu) sous divers niveaux de ressources (en azote et en eau) sur la flore adventice et sur les cultures suivantes de la succession (orge de printemps puis lin d'hiver) conduites sans fertilisation et sans désherbage. Une augmentation du nombre d’espèces cultivées dans un mélange ne permet pas de mieux concurrencer les adventices. Un apport d’azote au semis permet au couvert de produire plus de biomasse de couvert mais ne réduit pas le salissement dans le couvert. Comparé à l’action du gel ou au roulage des couverts sur le gel, la destruction chimique du couvert (glyphosate) a réduit l’infestation par les adventices dans la culture suivante. Les couverts ne peuvent pas à eux seul assurer une régulation complète des adventices ; ils doivent donc être associés à d’autres pratiques à l’échelle de la succession pour permettre de limiter l’utilisation d’intrants de synthèse. Weed management in conservation agriculture: effect of cover crop mixture and management A 2-year experiment was conducted in conservation agriculture to test the effect of cover crop mixtures (4 mixes compared to bare soil) under contrasted level of soil resources (nitrogen and water) on weeds during the cover crop phase and their succeeding crops (i.e. spring barley and winter linseed) both being unfertilized and unsprayed with herbicide. Cover crop biomass was higher when the mix was composed of the lowest number of species. Nitrogen fertilization increase cover crop biomass of certain mixture but do not reduce the relative proportion of weed biomass. The chemical termination of cover crop (i.e. glyphosate) led to the lowest weed infestation in the spring barley, whereas frost and rolling were comparable. Cover crop cannot regulate weeds by itself, and cannot be consider as a substitute of weed management in crop. They are biological levers of weed management at the crop rotation scale.

Raphanus raphanistrum (wild radish) is a highly competitive weed in winter crops. Integrated weed management practices and decision-making tools benefit from the ability to predict seed longevity and dormancy status in the soil seed bank, as well as time and density of emergence in the field. We wondered if unique values taken from databases could serve for modelling purposes, whatever the origins of the weed populations. We investigated dormancy and longevity of fruits buried in the soil over a four-year seed burial experiment of two highly contrasted populations that differ by their biogeographical origin (oceanic versus continental climate), their habitat (arable field versus undisturbed) and their fruit size (thick versus thin fruit wall). High viability persisted over two years, followed by a rapid reduction, especially for the ‘continental-undisturbed-thin’ population. Dormancy cycling, with dormancy at its lowest in October, was observed for the ‘oceanic-arable-thick’ population, whilst a slow decrease without clear seasonal pattern was found for the other population. These results indicate different ways of regulating seed persistence in the soil, which might be taken into account when building demographic models. These differences could be due to interactions between fruit wall thickness and the other factors; it is possible that a thicker fruit wall increases longevity by promoting dormancy by physical restriction, but depending on temperature. Thinner fruit walls would make plants display other adaptive strategies to maximize survival time in the soil seed bank. Studies involving more populations and isogenic material are needed to address this specific question.

This work describes the fracture behaviour of the 14Cr ODS steel produced by mechanical alloying process, after high temperature exposures. Small specimens were exposed to helium gas in a furnace at 720 °C for 500 h. Another set of specimens was exposed to flowing liquid lead in the COLONRI II loop at 650 °C for 1000 h. All specimens were tested for the impact and tensile behaviour. The impact test results are compared to other sets of specimens in the as received state and after isothermal annealing at 650 °C for 1000 h. The impact curves of the exposed materials showed positive shifts on the transition temperature. While the upper shelf value did not change in the Pb exposed ODS steel, it significantly increased in the He exposed one. The differences are discussed in terms of surface and subsurface microscopy observation. The embrittlement can be explained as the effect of a slight change in the grain boundary and size distribution combined with the depletion of sub-surface region from alloying elements forming oxide scale on the surface.

Better managing crop : weed competition in cropping systems while reducing both nitrogen and herbicide inputs is a real challenge that requires a better understanding of crop and weed root architecture in relation to soil-nitrogen availability. An original approach was used which considered the parameters of a simulation model of root architecture as traits to analyse (a) the interspecific diversity of root system architecture, and (b) its response to soil-nitrogen availability. Two greenhouse experiments were conducted using three crop and nine weed species grown at two contrasted concentrations of soil-nitrogen availability. Plant traits were measured to characterise both overall plant growth and root architecture, with a focus on primary root emergence, root elongation and branching. The studied root traits varied among species (from a twofold to a fourfold factor, depending on the trait), validating their use as indicators to analyse the interspecific variability of root architecture. The largest interspecies differences were for two traits: ‘maximal apical root diameter’ and ‘interbranch distance’ (distance between two successive laterals on the same root). Conversely, most of the studied root traits varied little with soil-nitrogen availability (from no variation to a 1.1-fold factor, depending on the trait) even though soil-nitrogen availability varied with a 17-fold factor and impacted the overall shoot and root biomass. So, the root traits used in this article are stable whatever soil-nitrogen availability. As they reflect processes underlying root system architecture, this low effect of nitrogen suggests that the rules governing root architecture are little affected by plant nitrogen status and soil-nitrogen availability. We propose that the determinants of differences in root system architecture between soils with contrasted nitrogen availability mainly originate from differences in the amount of carbon allocated to and within the root system. Characterising each plant species by a combination of root traits gave insights regarding the potential species competitive ability for soil resources in agroecosystems.

The CoCrFeNiMn high entropy alloy and its strengthened version by in-situ formed dispersion of yttria nano-oxides prepared via mechanical alloying were investigated. The grain refinement of the one phase FCC alloy by presence of oxides was determined by microstructural analyses to be 50%. The positive effect of oxide dispersion on the strength properties was found to be between 30% and 70% for room and elevated temperatures, respectively. The resulting creep strain rates for the strengthened alloy were significantly lower, i.e., three orders for 30 MPa stress level, comparing the initial one, therefore, the pining mechanism was among others very effective.

A process of irradiating and ablating solid-state targets with hot plasma and fast ion streams in two Dense Plasma Focus (DPF) devices – PF-6 and PF-1000 was examined by applying a number of diagnostics of nanosecond time resolution. Materials perspective for use in chambers of the mainstream nuclear fusion facilities (mainly with inertial plasma confinement like NIF and Z-machine), intended both for the first wall and for constructions, have been irradiated in these simulators. Optical microscopy, SEM, Atomic Emission Spectroscopy, images in secondary electrons and in characteristic X-ray luminescence of different elements, and X-ray elemental analysis, gave results on damageability for a number of materials including low-activated ferritic and austenitic stainless steels, β-alloy of Ti, as well as two types of W and a composite on its base. With an increase of the number of shots irradiating the surface, its morphology changes from weakly pronounced wave-like structures or ridges to strongly developed ones. At later stages, due to the action of the secondary plasma produced near the target materials they melted, yielding both blisters and a fracturing pattern: first along the grain and then “in-between” the grains creating an intergranular net of microcracks. At the highest values of power flux densities multiple bubbles appeared. Furthermore, in this last case the cracks were developed because of microstresses at the solidification of melt. Presence of deuterium within the irradiated ferritic steel surface nanolayers is explained by capture of deuterons in lattice defects of the types of impurity atoms, pores and oxycarbonitride particles existed in the material.

Considerable progress has been made over the last decades in thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new problems and market requirements. This article aims to identify the current challenges limiting the evolution of these technologies and to propose research directions and priorities to meet these challenges. It was prepared on the basis of a collection of short articles written by experts in thermal spray who were asked to present a snapshot of the current state of their specific field, give their views on current challenges faced by the field and provide some guidance as to the R&D required to meet these challenges. The article is divided in three sections that deal with the emerging thermal spray processes, coating properties and function, and biomedical, electronic, aerospace and energy generation applications. Published version

National audience; Mieux comprendre les interactions entre compétition pour la lumière et pour l’eau est nécessaire pour concevoir des stratégies durables de gestion des adventices, dans un contexte de changement global. L’objectif de cette étude était de quantifier la réponse de trois espèces adventices à une limitation en eau et, pour cela, de tester une approche méthodologique innovante couplant l’utilisation d’une plateforme de phénotypage à haut débit et d’un modèle de simulation (FLORSYS). Cette étude a permis d’analyser la diversité des réponses des espèces adventices au stress hydrique et de hiérarchiser les processus en fonction de l’intensité de leur réponse à une limitation en eau. Elle a également montré l’intérêt de l’approche développée. Par la suite, celle-ci sera appliquée à l’analyse de la réponse en eau d’une large gamme d’espèces adventices. Les résultats obtenus permettront d’intégrer la compétition pour l’eau dans FLORSYS afin de pouvoir l’utiliser pour concevoir des stratégies de gestion robustes face à la contrainte hydrique.

National audience; Un essai pluriannuel en semi-direct a testé l’effet des couverts sur la flore adventice et sur les cultures suivantes conduites sans fertilisation et sans désherbage. Une augmentation du nombre d’espèces cultivées dans un mélange ne permet pas de mieux concurrencer les adventices. Un apport d’azote au semis permet au couvert de produire plus de biomasse de couvert mais ne réduit pas le salissement dans le couvert. Comparé à l’action du gel ou au roulage des couverts sur le gel, la destruction chimique du couvert (glyphosate) a réduit l’infestation des adventices dans la culture suivante. Les couverts ne peuvent pas à eux seul assurer une régulation complète des adventices et cela s’observe sur la culture suivante. Ils doivent donc être épaulés par d’autres pratiques à l’échelle de la rotation permettant de limiter l’utilisation d’intrants.

The objective of this study was to evaluate 12 perspective blackcurrant cultivars in relation to their suitability for table fruit production. Selected traits (fruit set, beginning of picking ripeness, length of cluster, weight of 100 fruits, fruit firmness and fruit taste) were evaluated in these cultivars. Each cultivar was grown in experimental planting of RBIP Holovousy Ltd., and was represented with three plants in two growing systems: as two-stem spindle with support and shaped bush. Planting was covered with foil mounted on the construction. Foil cover was used to obtain higher fruit quality, to protect plants against negative climatic factors and to allow harvest in optimum time regardless on the weather conditions. In most cases, more attractive fruits were obtained using the system of two-stem spindle compared with shaped bush. The longest clusters were found in cultivars 'Lota', 'Triton', 'Fokus' and 'Ometa'. The best taste was detected in cultivars 'Ometa', 'Demon', 'Fokus' and 'Ceres'.

National audience; Crop mixtures may decrease reliance on pesticides but reducing herbicide use might increase weeds. Individual-based crop models can provide management guidelines. In heterogeneous canopies, light availability of individual plants depends on their dominant or dominated position. Estimating nitrogen demand at the plant scale, independently of light environment, is a challenge for modelling. A relationship linking shoot nitrogen amount to leaf biomass (or leaf area) at optimal nitrogen nutrition was investigated to establish if it could allow estimating nitrogen demand at the plant scale independently of its light environment. Crop and weed species were grown in greenhouse under various nitrogen treatments and, for two species, under two light levels. At the plant scale, shoot nitrogen amount was proportional to leaf biomass (or leaf area) at optimal nitrogen nutrition at vegetative stage. At reproductive stage, the relationship was allometric. The effect of light on shoot nitrogen amount per leaf biomass was minor and greater when using leaf area. Using data from previous experiments showed that the relationship using leaf biomass was stable across diverse growing conditions. The relationship linking shoot nitrogen amount to leaf biomass at optimal nitrogen nutrition can be used to model nitrogen demand of individual plants in heterogeneous canopies.

International audience; Reducing herbicide use requires alternative strategies to regulate weeds. In the context of climate change, these alternative strategies must tolerate climatic hazards, among which is water deficit. Simulations models that predict the effects of cropping systems, in interaction with pedoclimate, on crop-weed demography are powerful tools to identify weed management strategies that tolerate climatic hazards. However, due to knowledge gaps, competition for water is rarely included in models of crop-weed demography, which can thus not be used to identify weed management strategies that tolerate water deficit. The present study aimed to quantify the response of weed species to water stress, and to identify mathematical formalisms to introduce competition for water into a crop-weed demography model, i.e. FLORSYS. In a greenhouse experiment, Alopecurus myosuroides, Amaranthus hybridus and Abutilon theophrasti were grown at 4-5 water regimes, ranging from 75 to 20% of the water holding capacity. Plants were grown individually in pots. Three times per day, each pot was automatically weighted and, whenever necessary, watered with a complete nutrient solution (N-P-K) to reach the targeted water regime. Seven weeks after germination, plants were sampled to measure plant growth traits. For the three species, leaf, stem and root biomasses were all affected by water regime. The intensity of the response to water stress differed among species, with A. theophrasti being the most sensitive and A. hybridus the least sensitive species. The higher the leaf area was when water availability was non-limiting, the more it was affected by the water regime. Data analysis (under progress) and literature are used to identify mathematical formalisms accounting for the response of annual crop and weed species to water stress, especially biomass production (photosynthesis) and allocation within the plant (aboveground vs. belowground, leaf vs. stem, reproductive vs. vegetative biomass). The aim is to identify generic equations, i.e. valid for a wide range of annual crop and weed species, each species being characterised by a set of specific parameters. These formalisms will be included in the FLORSYS model which simulates weed dynamics and crop canopy growth in virtual fields over the years with a daily time step. The final aim is to use the completed model to identify sustainable weed management strategies that are robust to climatic hazards.

International audience; Reducing herbicide use requires identifying alternative strategies to regulate weeds. Using crop species that are more competitive for resources than problematic weed species is one lever, but requires a better understanding of weed response to water stress. The present study aimed to quantify the response of three weed species to water stress. In a greenhouse experiment, Alopecurus myosuroides, Amaranthus hybridus and Abutilon theophrasti were grown at 4-5 water regimes, ranging from 75 to 20% of the water holding capacity. Plants were grown individually in pots. Each pot was automatically weighted three times per day, and watered whenever necessary to reach the targeted water regime. A nutrient-rich solution was used. The lower water regimes probably concurred with lower nutrient levels, in line with what is usually going on in agricultural fields. Seven weeks after germination, plants were sampled. For the three species, leaf, stem and root biomasses were affected by the water regimes. The intensity of the response to water stress differed among species, with A. theophrasti being the most sensitive and A. hybridus the least sensitive species. For plant leaf area, the ranking of plant species for the sensitivity to water regime was similar to the ranking for the potential plant leaf area (i.e. leaf area at 75 % of the water holding capacity). We will identify mathematical equations accounting for the response of plant growth and biomass allocation to water stress. The aim is to identify generic equations, i.e. valid for a wide range of annual species. They will be included in the FlorSys model which simulates weed dynamics and crop canopy growth in virtual fields over the years. The final aim is to use the completed model to identify sustainable weed management strategies that are robust to climatic hazards.

Dedicated experiments have been performed in the COMPASS tokamak to thoroughly study the power deposition processes occurring on poloidal and toroidal edges of castellated plasma-facing components in tokamaks during steady-state L-mode conditions. Surface temperatures measured by a high resolution infra-red camera are compared with reconstructed synthetic data from a 2D thermal model using heat flux profiles derived from both the optical approximation and 2D particle-in-cell (PIC) simulations. In the case of poloidal leading edges, when the contribution from local radiation is taken into account, the parallel heat flux deduced from unperturbed, upstream measurements is fully consistent with the observed temperature increase at the leading edges of various heights, respecting power balance assuming simple projection of the parallel flux density. Smoothing of the heat flux deposition profile due to finite ion Larmor radius predicted by the PIC simulations is found to be weak and the power deposition on misaligned poloidal edges is better described by the optical approximation. This is consistent with an electron-dominated regime associated with a non-ambipolar parallel current flow. In the case of toroidal gap edges, the different contributions of the total incoming flux along the gap have been observed experimentally for the first time. They confirm the results of recent numerical studies performed for ITER showing that in specific cases the heat deposition does not necessarily follow the optical approximation. Indeed, ions can spiral onto the magnetically shadowed toroidal edge. Particle-in-cell simulations emphasize again the role played by local non-ambipolarity in the deposition pattern.

Renewable energy sources are major components of the strategy to reduce harmful emissions and to replace depleting fossil energy resources. Data from remote sensing can provide information for multicriteria analysis for sources of renewable energy. Advanced land cover quantification makes it possible to search for suitable sites. Multicriteria analysis, together with other data, is used to determine the energy potential and socially acceptability of suggested locations. The described case study is focused on an area of surface coal mines in the northwestern region of the Czech Republic, where the impacts of surface mining and reclamation constitute a dominant force in land cover changes. High resolution satellite images represent the main input datasets for identification of suitable sites. Solar mapping, wind predictions, the location of weirs in watersheds, road maps and demographic information complement the data from remote sensing for multicriteria analysis, which is implemented in a geographic information system (GIS). The input spatial datasets for multicriteria analysis in GIS are reclassified to a common scale and processed with raster algebra tools to identify suitable sites for sources of renewable energy. The selection of suitable sites is limited by the CORINE land cover database to mining and agricultural areas. The case study is focused on long term land cover changes in the 1985-2015 period. Multicriteria analysis based on CORINE data shows moderate changes in mapping of suitable sites for utilization of selected sources of renewable energy in 1990, 2000, 2006 and 2012. The results represent map layers showing the energy potential on a scale of a few preference classes (1-7), where the first class is linked to minimum preference and the last class to maximum preference. The attached histograms show the moderate variability of preference classes due to land cover changes caused by mining activities. The results also show a slight increase in the more preferred classes for utilization of sources of renewable energy due to an increase area of reclaimed sites. Using data from remote sensing, such as the multispectral images and the CORINE land cover datasets, can reduce the financial resources currently required for finding and assessing suitable areas.

prod 2018-237 EA SPE BAP GESTAD INRA AGROSUP; National audience

The experimental study of damage to tungsten (W), molybdenum (Mo), and silicon carbide (SiC) surfaces induced by focused extreme ultraviolet laser radiation (λ ~ 47 nm/~1.5 ns/21–40 µJ) is presented. It was found that W and Mo behaved similarly: during the first shot, the damaged area is covered by melted and re-solidified material, in which circular holes appear – residua of just opened pores/bubbles, from which pressurized gas/vapors escaped. Next cracks and ruptures appear and the W has a tendency to delaminate its surface layer. Contrary, single-crystalline SiC has negligible porosity and sublimates; therefore, no escape of “pressurized” gas and no accompanying effects take place. Moreover, SiC at sublimating temperature decomposes to elements; therefore, the smooth crater morphology can be related to local laser energy density above ablation threshold. When more shots are accumulated, in all three investigated materials, the crater depth increases non-linearly with number of these shots. The surface morphology was investigated by an atomic force microscope, the surface structure was imaged by a scanning electron microscope (SEM), and the structure below the surface was visualized by SEM directed into a trench that is milled by focused ion beam. Additionally, structural changes in SiC were revealed by Raman spectroscopy.

Permeation barriers represent one of the crucial fields in materials development for thermonuclear fusion. Primary objective of the barriers is to suppress the permeation of hydrogen isotopes (mainly tritium) from future thermonuclear fusion facilities. Secondary objective is to reduce hydrogen retention in structural materials, potentially also improving their corrosion resistance. Expected reactor conditions put high demands on the material, as well as on the final barrier quality. Key properties are tritium permeation reduction, absence of defects (especially cracks), high-temperature stability and corrosion resistance, and compatibility with structural materials (mostly ferritic-martensitic steels). Regarding industrial scale production, ability of the deposition method to coat large complex surfaces is desirable. Thin nitride layers, identified as promising permeation barriers, were prepared by diffusion-based nitridation and physical vapour deposition (PVD) and characterized.

Elderberry cultivars ‘Albida’, ‘AllesA¶â€™, ‘Aurea’, ‘Bohatka’, ‘Dana’, ‘Haschberg’, ‘Heidegg 13’, ‘KA¶rsA¶r’, ‘Mammut’, ‘Pregarten’, ‘Riese aus VoAŸloch’, ‘Sambo’, ‘Sambu’, ‘Samdal’, ‘Sampo’, ‘Samyl’, ‘Weihenstephan’ and wild elderberry were grown in a unique experimental collection of elderberry at the Research and Breeding Institute of Pomology at Holovousy Ltd. This collection was examined for composition of substances in fruits because elderberry has high concentrations of compounds with antioxidative activity, especially anthocyanins, flavonoids and vitamins. The aim of this study was to compare content of selected substances in fruits of elderberry cultivars and wild elderberry. Results showed the highest juice yield in cultivars ‘AllesA¶â€™, ‘Haschberg’, ‘KA¶rsA¶r’ and ‘Samyl’. In contrast, the lowest juice yield was detected in fruits of wild elderberry as well as ‘Aurea’ and ‘Sambo’ cultivars. The highest total antioxidant capacity was found in fruits of ‘Haschberg’, followed by wild elderberry and ‘Weihenstephan’, ‘Pregarten’ and ‘Riese aus VoI²loch’. The lowest values were recorded in cultivars ‘Albida’ and ‘Aurea’. High content of reducing sugars was found in cultivars ‘Samdal’, ‘Haschberg’ and ‘KA¶rsA¶r’ compared to other cultivars and wild elderberry.

Elderberry (Sambucus nigra L.) is an underutilized crop on commercial fruit farms in the Czech Republic. Although the species is native, elderberry has not been grown commercially there, despite its great potential. Currently, there is interest among organic growers in growing elderberry as a complementary crop. Interest in elderberry blossoms and fruits has also been expressed by both domestic and foreign processing industries. A unique, experimental collection of elderberry in terms of cultivar numbers was developed at the Research and Breeding Institute of Pomology Holovousy Ltd. In 2009, the cultivars ‘Albida’, ‘AllesA¶â€™, ‘Aurea’, ‘Bohatka’, ‘Dana’, ‘Haschberg’, ‘Heidegg 13’, ‘KorsA¸r’, ‘Mammut’, ‘Pregarten’, ‘Riese aus VoAŸloch’, ‘Sambo’, ‘Sambu’, ‘Samdal’, ‘Sampo’, ‘Samyl’ and ‘Weihenstephan’ were planted. During ensuing years, this collection has been gradually supplemented with other cultivars including ‘Juicy’, ‘Tulbing’ and ‘Weisser Holunder’. Some of these cultivars were obtained from neighbouring countries, which have grown and carried out the research on this crop for a long time and have similar natural and climatic conditions. Vegetative and fruit characteristics of the different cultivars were evaluated under the conditions in the Czech Republic. Based on our findings, suitable elderberry cultivars were recommended for growers.

EASPEGESTAD INRA; Le tropisme racinaire correspond à l’orientation des racines au sein d’un système racinaire. On parle de gravitropisme positif lorsque le système racinaire s’étend principalement dans une direction verticale, et de plagiotropisme lorsque la direction est principalement horizontale, toutes les situations existant entre ces deux extrêmes. Notre objectif a été de mettre au point un dispositif permettant l’étude du tropisme racinaire adapté à une majorité d’espèces herbacées annuelles (adventices et cultivées, monocotylédones et dicotylédones), et permettant une croissance en 3-D du système racinaire. Le dispositif est constitué d’un bac contenant du sol, ainsi que des cadres grillagés empilés les uns sur les autres, afin de localiser la position des racines par leurs coordonnées (x, y) sur les différents cadres situés à différentes profondeurs dans le bac. Nous illustrons l’utilisation de ce dispositif pour caractériser le tropisme de deux espèces adventices.

EASPEGESTAD INRA; Mieux gérer la compétition culture : adventice dans des systèmes de culture moins dépendants de l’azote minéral et des herbicides nécessite de mieux connaître l’architecture racinaire des cultures et des adventices en lien avec la disponibilité en azote du sol. Pour cela, nous avons mené deux essais en serre sur douze espèces cultivées et adventices, cultivées à deux concentrations contrastées en azote du sol. Nous avons utilisé les paramètres d’un modèle d’architecture racinaire comme traits pour comparer les espèces et analyser la réponse de l’architecture racinaire à la disponibilité en azote. Les traits racinaires étudiés sont variables entre les espèces mais peu affectés par la disponibilité en azote du sol. La connaissance des caractéristiques racinaires des espèces fournit des informations sur leur aptitude à la compétition pour les ressources du sol.