Influence of Dichromate Ions on Corrosion Processes on Pure Magnesium

The corrosion behavior of Mg is of interest because of its growing use as an alloy in the transportation industry and also because it is a major component of some intermetallic phases in Al alloys, such as the deleterious S (Al2CuMg)-phase found in AA2024-T3. Pure Mg corrodes rapidly in a chloride-containing solution and even dissolves in water if the surface hydroxide is damaged by scratching the surface, for example. Uniform dissolution is drastically reduced in NaCl solutions (from 0.01 to 0.5 M) with the addition of very dilute concentrations of dichromate (10-4 M). However, it is replaced by a strong localized attack in the form of fast filiform-like attack. On a large-grained sample with a defined defect structure, the attack can be seen to propagate at twin boundaries. Orientation imaging microscopy analysis found that corrosion was limited to planes near {0001} orientations with propagation being in prismatic directions. Auger electron spectroscopy analysis shows that interaction of chromate with the Mg hydroxide results in incorporation of reduced chromium ions in the hydroxide surface layer. Formation of a more resistant surface film could explain the very local nature of the corrosion in this case. The interaction between dichromate ions and Mg hydroxide can also explain the higher corrosion resistance of S-phase particles in chloride solutions containing dilute dichromate, although differences in the surface film formed compared to pure Mg are observed. Sputter-etching of the surface in order to assess the depth of the attack revealed that very hard or isolating corrosion products difficult to sputter are produced along the filiform path and that chromium compounds are not integrated in the corrosion products. Focused ion beam sectioning followed by scanning electron microscopy investigation of the sectioned area, demonstrates the presence of a continuous protective surface film. Adhesion between the Mg hydroxide and the metal is lost at the location of the corrosion filament, suggesting that the mechanism of propagation is similar to filiform corrosion under a coating. The depth of attack is a couple of micrometers with large cracks present within the corroded area that could induce severe surface damage.This work was supported by the Air Force Office of Scientific Research under contract no. F49620-96-1-0479

2022 Update of the consensus on the rational use of antithrombotics and thrombolytics in Veterinary Critical Care (CURATIVE) Domain 6: Defining rational use of thrombolytics

Objectives To systematically review available evidence and establish guidelines related to the use of thrombolytics for the management of small animals with suspected or confirmed thrombosis. Design PICO (Population, Intervention, Control, and Outcome) questions were formulated, and worksheets completed as part of a standardized and systematic literature evaluation. The population of interest included dogs and cats (considered separately) and arterial and venous thrombosis. The interventions assessed were the use of thrombolytics, compared to no thrombolytics, with or without anticoagulants or antiplatelet agents. Specific protocols for recombinant tissue plasminogen activator were also evaluated. Outcomes assessed included efficacy and safety. Relevant articles were categorized according to level of evidence, quality, and as to whether they supported, were neutral to, or opposed the PICO questions. Conclusions from the PICO worksheets were used to draft guidelines, which were subsequently refined via Delphi surveys undertaken by the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) working group. Results Fourteen PICO questions were developed, generating 14 guidelines. The majority of the literature addressing the PICO questions in dogs is experimental studies (level of evidence 3), thus providing insufficient evidence to determine if thrombolysis improves patient-centered outcomes. In cats, literature was more limited and often neutral to the PICO questions, precluding strong evidence-based recommendations for thrombolytic use. Rather, for both species, suggestions are made regarding considerations for when thrombolytic drugs may be considered, the combination of thrombolytics with anticoagulant or antiplatelet drugs, and the choice of thrombolytic agent. Conclusions Substantial additional research is needed to address the role of thrombolytics for the treatment of arterial and venous thrombosis in dogs and cats. Clinical trials with patient-centered outcomes will be most valuable for addressing knowledge gaps in the field

2022 Update of the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) Domain 6: Defining rational use of thrombolytics

Objectives: To systematically review available evidence and establish guidelines related to the use of thrombolytics for the management of small animals with suspected or confirmed thrombosis. Design: PICO (Population, Intervention, Control, and Outcome) questions were formulated, and worksheets completed as part of a standardized and systematic literature evaluation. The population of interest included dogs and cats (considered separately) and arterial and venous thrombosis. The interventions assessed were the use of thrombolytics, compared to no thrombolytics, with or without anticoagulants or antiplatelet agents. Specific protocols for recombinant tissue plasminogen activator were also evaluated. Outcomes assessed included efficacy and safety. Relevant articles were categorized according to level of evidence, quality, and as to whether they supported, were neutral to, or opposed the PICO questions. Conclusions from the PICO worksheets were used to draft guidelines, which were subsequently refined via Delphi surveys undertaken by the Consensus on the Rational Use of Antithrombotics and Thrombolytics in Veterinary Critical Care (CURATIVE) working group. Results: Fourteen PICO questions were developed, generating 14 guidelines. The majority of the literature addressing the PICO questions in dogs is experimental studies (level of evidence 3), thus providing insufficient evidence to determine if thrombolysis improves patient-centered outcomes. In cats, literature was more limited and often neutral to the PICO questions, precluding strong evidence-based recommendations for thrombolytic use. Rather, for both species, suggestions are made regarding considerations for when thrombolytic drugs may be considered, the combination of thrombolytics with anticoagulant or antiplatelet drugs, and the choice of thrombolytic agent. Conclusions: Substantial additional research is needed to address the role of thrombolytics for the treatment of arterial and venous thrombosis in dogs and cats. Clinical trials with patient-centered outcomes will be most valuable for addressing knowledge gaps in the field

Corrosion behavior of friction stir welded lap joints of AA6061-T6 aluminum alloy

In this work, the corrosion behaviors of friction-stir lap welding of 6061-T6 Al-alloy are studied. The friction-stir lap welding was performed under different welding conditions (rotation speed and welding speed). The corrosion behavior of the parent alloy, the weld nugget zone (WNZ), and the heat affected zone (HAZ) of each welded sample working as an electrode, were investigated by the Tafel polarization test in 3.5 wt. (%) NaCl at ambient temperature. The morphology of the corroded surface of each region was analyzed by scanning electron microscopy together with energy dispersive spectroscopy (SEM-EDS). The results showed that the corrosion resistance of the parent alloy was better than the WNZ and the HAZ in both welding conditions. Localized pit dissolution and intergranular corrosion were the dominant corrosion types observed in the parent alloy, WNZ, and HAZ. The parent alloy, WNZ, and HAZ exhibited similar corrosion potentials (Ecorr) after T6 heat treatment. This treatment had a better effect on the corrosion resistance of the welded regions than the parent alloy

Genetic signatures of variation in population size in a native fungal pathogen after the recent intensive plantation of its host tree

Historical fluctuations in forests’ distribution driven by past climate changes and anthropogenic activities can have large impacts on the demographic history of pathogens that have a long co-evolution history with these host trees. Using a population genetic approach, we investigated that hypothesis by reconstructing the demographic history of Armillaria ostoyae, one of the major pathogens of the maritime pine (Pinus pinaster), in the largest monospecific pine planted forest in Europe (south-western France). Genetic structure analyses and approximate Bayesian computation approaches revealed that a single pathogen population underwent a severe reduction in effective size (12 times lower) 1080–2080 generations ago, followed by an expansion (4 times higher) during the last 4 generations. These results are consistent with the history of the maritime pine forest in the region characterized by a strong recession during the last glaciation (~19 000 years ago) and massive plantations during the second half of the nineteenth century. Results suggest that recent and intensive plantations of a host tree population have offered the opportunity for a rapid spread and adaptation of their pathogens

Large Scale Metric Learning for Distance-Based Image Classification on Open Ended Data Sets

International audienceMany real-life large-scale datasets are open-ended and dynamic: new images are continuously added to existing classes, new classes appear over time, and the semantics of existing classes might evolve too. Therefore, we study large-scale image classification methods that can incorporate new classes and training images continuously over time at negligible cost. To this end we consider two distance-based classifiers, the k-nearest neighbor (k-NN) and nearest class mean (NCM) classifiers. Since the performance of distance-based classifiers heavily depends on the used distance function, we cast the problem into one of learning a low-rank metric, which is shared across all classes. For the NCM classifier we introduce a new metric learning approach, and we also introduce an extension to allow for richer class representations. Experiments on the ImageNet 2010 challenge dataset, which contains over one million training images of thousand classes, show that, surprisingly, the NCM classifier compares favorably to the more flexible k-NN classifier. Moreover, the NCM performance is comparable to that of linear SVMs which obtain current state-of-the-art performance. Experimentally we study the generalization performance to classes that were not used to learn the metrics. Using a metric learned on 1,000 classes, we show results for the ImageNet-10K dataset which contains 10,000 classes, and obtain performance that is competitive with the current state-of-the-art, while being orders of magnitude faster