Complete breeding failures in ivory gull following unusual rainy storms in North Greenland

Natural catastrophic events such as heavy rainfall and windstorms may induce drastic decreases in breeding success of animal populations. We report the impacts of summer rainfalls on the reproductive success of ivory gull (Pagophila eburnea) in north-east Greenland. On two occasions, at Amdrup Land in July 2009 and at Station Nord in July 2011, we observed massive ivory gull breeding failures following violent rainfall and windstorms that hit the colonies. In each colony, all of the breeding birds abandoned their eggs or chicks during the storm. Juvenile mortality was close to 100% at Amdrup Land in 2009 and 100% at Station Nord in 2011. Our results show that strong winds associated with heavy rain directly affected the reproductive success of some Arctic bird species. Such extreme weather events may become more common with climate change and represent a new potential factor affecting ivory gull breeding success in the High Arctic

Parasitoids indicate major climate-induced shifts in arctic communities

Climatic impacts are especially pronounced in the Arctic, which as a region is warming twice as fast as the rest of the globe. Here, we investigate how mean climatic conditions and rates of climatic change impact parasitoid insect communities in 16 localities across the Arctic. We focus on parasitoids in a widespread habitat,Dryasheathlands, and describe parasitoid community composition in terms of larval host use (i.e., parasitoid use of herbivorous Lepidoptera vs. pollinating Diptera) and functional groups differing in their closeness of host associations (koinobionts vs. idiobionts). Of the latter, we expect idiobionts-as being less fine-tuned to host development-to be generally less tolerant to cold temperatures, since they are confined to attacking hosts pupating and overwintering in relatively exposed locations. To further test our findings, we assess whether similar climatic variables are associated with host abundances in a 22 year time series from Northeast Greenland. We find sites which have experienced a temperature rise in summer while retaining cold winters to be dominated by parasitoids of Lepidoptera, with the reverse being true for the parasitoids of Diptera. The rate of summer temperature rise is further associated with higher levels of herbivory, suggesting higher availability of lepidopteran hosts and changes in ecosystem functioning. We also detect a matching signal over time, as higher summer temperatures, coupled with cold early winter soils, are related to high herbivory by lepidopteran larvae, and to declines in the abundance of dipteran pollinators. Collectively, our results suggest that in parts of the warming Arctic,Dryasis being simultaneously exposed to increased herbivory and reduced pollination. Our findings point to potential drastic and rapid consequences of climate change on multitrophic-level community structure and on ecosystem functioning and highlight the value of collaborative, systematic sampling effort

Post deposition heat treatment of cold sprayed C355 deposits for repair: Microstructure and mechanical properties

Cold gas dynamic spray is increasingly used for dimensional repair in the aerospace sector as it is capable of producing dense, oxide-free deposits of significant thickness and with good levels of adhesion and inherent mechanical strength. There is significant interest in extending the application of cold spray deposits to include structural, load-bearing repairs. However, particularly for high strength aluminium alloys, cold spray deposits can exhibit high levels of porosity and micro-cracks, leading to mechanical properties that are inadequate for most load bearing applications. In this work, heat treatment was investigated as a potential means of improving the properties of a cold sprayed Al alloy C355 deposit. C355 alloy deposits were produced using two process gas temperatures (350°C and 500°C) and three gas pressures (40, 50 and 60 bar) using a commercially available HPCS system. Microstructural analysis of the coatings revealed that the optimal microstructure (ca. 1% porosity) was obtained at 500°C and 60 bar. Therefore, coatings produced with process conditions of 500°C and 60 bar were heat treated at 175, 200, 225, 250°C for 4h in air and the evolution of the microstructure and microhardness was analysed. The results show that heat treatment at 225°C can decrease porosity (<0.2%) and retain high hardness (105 HV0.05vs 130 HV0.05as-sprayed). Further investigation was performed on as-sprayed and 225°C heat treated deposits. The results show that this heat treatment can halve residual stress (-50 MPa vs -100 MPa as-sprayed), and improve tensile properties (UTS). Therefore, this work has demonstrated that the heat treatment of C355 cold sprayed deposits at 225°C can significantly improve their properties

Influence of alpha-ZrP fillers and process conditions on the morphology and the gas barrier properties of filled PA6 films

International audienceComposite films based on polyamide 6 and lamellar unmodified -ZrP nanofillers have been prepared for low filler amounts (less than 2 wt %) using cast process or blowing process. Whatever be the filler content and the film process conditions, the lamellar nanofillers were not intercalated by the polymer chains and microcomposites were obtained. On the other hand, the matrix crystalline structure highly depended on the presence of fillers and on the film process conditions. The nature of the crystalline phase and its orientation were shown to play a major role on the film barrier properties to helium. For instance, the presence of crystalline phase associated to a specific orientation of the crystalline lamellae parallel to the film surface could significantly contribute to enhance barrier properties. This specific morphology was favored by the presence of -ZrP in the formulation but depended also on the process conditions

Caractérisation des dépôts organiques initiaux formés sur des surfaces en contact l'eau potable : un critère pour sélectionner des matériaux anti-biofilm

International audienceL’accumulation très rapide (en quelques heures) de matière organique sur des surfaces en contact avec l’eau (eaux de mer, ou eaux douces) a été décrite depuis les années 1970. Le dépôt ainsi formé souvent nommé « film conditionnant » est évidemment très fin (quelques nanomètres) et non continu. Il est généralement considéré comme une étape critique dans l’initiation du biofilm même si la littérature montre des résultats souvent contradictoires. Cependant dans le cas des eaux potables en réseau de distribution, la formation de ce dépôt de polymères organiques et son impact sur l’adhésion des cellules bactériennes sont non documentés.Aussi dans le cadre d'une étude visant à caractériser les performances anti-adhésives de 12 matériaux polymériques (11 montrant une surface hydrophobe et 1 organisé sous forme d’hydrogel), nous avons caractérisé les dépôts organiques et quantifié les cellules bactériennes accumulés en 24 h (20°C) d'immersion dans l’eau potable, sous un régime faiblement turbulent. La microscopie à force atomique (AFM) en mode force-volume a permis de déterminer la balance hydrophobe/hydrophile, les forces d'adhésion, longueur et nature des polymères organiques déposés sur ces surfaces innovantes.Après 24 heures d’immersion, les matériaux apparaissaient « salis » par des polymères organiques (fréquence de détection entre 12 et 63 %, longueurs de contour de 200 à >1000 nm, forces d’adhésion des polymères de 0,2 à 2 nN, selon les matériaux) et des bactéries de 0 à 2x104 cellules/cm2 selon les matériaux testés. L'ajustement des données d'AFM à deux modèles décrivant le comportement mécanique de macromolécules types polysaccharides (FJC: Freely Joined Chain) et polypeptides (WLC:Worm-Like Chain) montre que (i) les signatures polysaccharidiques dominent les segments de polymères du film conditionnant (70%), et (ii) que des segments protéiques (20%) sont aussi présents suggérant la présence de glycoprotéines au sein du film conditionnant.Via une étude statistique (RLM: régression linéaire multiple et analyses de corrélation incluant de 12 à 54 essais et 14 variables), nous avons cherché à déterminer trois relations entre (i) les caractéristiques physico-chimiques des matériaux avant et après immersion dans l’eau, (ii) ces mêmes caractéristiques à 24 h et le nombre de bactéries adhérées, et (iii) les propriétés physico-chimiques de surface, du biofilm conditionnant et la nettoyabilité des surfaces (par flush hydrodynamique + chlore à 50 mg/l). De plus une analyse statistique (CAH: classification ascendante hiérarchique) a permis la hiérarchisation objective des matériaux selon leurs performances anti-biofilm sous trois critères : faible film conditionnant, faible nombre de bactéries, efficacité de nettoyage

Caractérisation des dépôts organiques initiaux formés sur des surfaces en contact l'eau potable : un critère pour sélectionner des matériaux anti-biofilm

International audienceL’accumulation très rapide (en quelques heures) de matière organique sur des surfaces en contact avec l’eau (eaux de mer, ou eaux douces) a été décrite depuis les années 1970. Le dépôt ainsi formé souvent nommé « film conditionnant » est évidemment très fin (quelques nanomètres) et non continu. Il est généralement considéré comme une étape critique dans l’initiation du biofilm même si la littérature montre des résultats souvent contradictoires. Cependant dans le cas des eaux potables en réseau de distribution, la formation de ce dépôt de polymères organiques et son impact sur l’adhésion des cellules bactériennes sont non documentés.Aussi dans le cadre d'une étude visant à caractériser les performances anti-adhésives de 12 matériaux polymériques (11 montrant une surface hydrophobe et 1 organisé sous forme d’hydrogel), nous avons caractérisé les dépôts organiques et quantifié les cellules bactériennes accumulés en 24 h (20°C) d'immersion dans l’eau potable, sous un régime faiblement turbulent. La microscopie à force atomique (AFM) en mode force-volume a permis de déterminer la balance hydrophobe/hydrophile, les forces d'adhésion, longueur et nature des polymères organiques déposés sur ces surfaces innovantes.Après 24 heures d’immersion, les matériaux apparaissaient « salis » par des polymères organiques (fréquence de détection entre 12 et 63 %, longueurs de contour de 200 à >1000 nm, forces d’adhésion des polymères de 0,2 à 2 nN, selon les matériaux) et des bactéries de 0 à 2x104 cellules/cm2 selon les matériaux testés. L'ajustement des données d'AFM à deux modèles décrivant le comportement mécanique de macromolécules types polysaccharides (FJC: Freely Joined Chain) et polypeptides (WLC:Worm-Like Chain) montre que (i) les signatures polysaccharidiques dominent les segments de polymères du film conditionnant (70%), et (ii) que des segments protéiques (20%) sont aussi présents suggérant la présence de glycoprotéines au sein du film conditionnant.Via une étude statistique (RLM: régression linéaire multiple et analyses de corrélation incluant de 12 à 54 essais et 14 variables), nous avons cherché à déterminer trois relations entre (i) les caractéristiques physico-chimiques des matériaux avant et après immersion dans l’eau, (ii) ces mêmes caractéristiques à 24 h et le nombre de bactéries adhérées, et (iii) les propriétés physico-chimiques de surface, du biofilm conditionnant et la nettoyabilité des surfaces (par flush hydrodynamique + chlore à 50 mg/l). De plus une analyse statistique (CAH: classification ascendante hiérarchique) a permis la hiérarchisation objective des matériaux selon leurs performances anti-biofilm sous trois critères : faible film conditionnant, faible nombre de bactéries, efficacité de nettoyage

Design of a scaling reduction system for geothermal applications

The aim of the EU 2020 GeoSmart project relies on the demonstration of innovative solutions to improve the flexibility and the efficiency of geothermal heat and power systems. This specific study focuses on issues related to silica scaling and its deposition on the reinjection wells. A limiting constraint for geothermal plants to fully utilize the thermal energy form well fluids is in fact the need to reinject geothermal brine at a high enough temperature to prevent thermodynamic fouling by silica scale deposition. GeoSmart aims to develop a solution based on retention system technology to control and reduce the silica scale formation before re-injection. Lowering reinjection temperature would strongly increase plant efficiency by providing extra useful heat. Based on silica scaling numerical simulation, the effects of parameters like pH, temperature and brine composition on silica polymerization and scaling deposition rates, the design and optimization of the retention system has been developed. The design aims to promote polymerization phenomena inside the tank so that scaling is consequently inhibited in the reinjection well pipes. Chemical additives and specific coatings have also been evaluated to guarantee the optimal required conditions. The case study is based on real-data referred to operational conditions and brine composition of the Zorlu Kizildere plant in Turkey. The economic and environmental impact of the retention system has been evaluated with positive outcomes. The in-site test and validation at industrial level of the above mentioned technology will be provided during the next activities of the GeoSmart projec

Parasitoids indicate major climate-induced shifts in arctic communities

Climatic impacts are especially pronounced in the Arctic, which as a region is warming twice as fast as the rest of the globe. Here, we investigate how mean climatic conditions and rates of climatic change impact parasitoid insect communities in 16 localities across the Arctic. We focus on parasitoids in a widespread habitat,Dryasheathlands, and describe parasitoid community composition in terms of larval host use (i.e., parasitoid use of herbivorous Lepidoptera vs. pollinating Diptera) and functional groups differing in their closeness of host associations (koinobionts vs. idiobionts). Of the latter, we expect idiobionts-as being less fine-tuned to host development-to be generally less tolerant to cold temperatures, since they are confined to attacking hosts pupating and overwintering in relatively exposed locations. To further test our findings, we assess whether similar climatic variables are associated with host abundances in a 22 year time series from Northeast Greenland. We find sites which have experienced a temperature rise in summer while retaining cold winters to be dominated by parasitoids of Lepidoptera, with the reverse being true for the parasitoids of Diptera. The rate of summer temperature rise is further associated with higher levels of herbivory, suggesting higher availability of lepidopteran hosts and changes in ecosystem functioning. We also detect a matching signal over time, as higher summer temperatures, coupled with cold early winter soils, are related to high herbivory by lepidopteran larvae, and to declines in the abundance of dipteran pollinators. Collectively, our results suggest that in parts of the warming Arctic,Dryasis being simultaneously exposed to increased herbivory and reduced pollination. Our findings point to potential drastic and rapid consequences of climate change on multitrophic-level community structure and on ecosystem functioning and highlight the value of collaborative, systematic sampling effort.Peer reviewe

Advanced Modeling and Simulation Tools to Address Build-Up Issues in Additive Manufacturing by Cold Spray

International audienc