1,048 research outputs found
Linking Antarctic krill larval supply and recruitment along the Antarctic Peninsula
Antarctic krill (Euphausia superba) larval production and overwinter survival drive recruitment variability, which in turn determines abundance trends. The Antarctic Peninsula has been described as a recruitment hot spot and as a potentially important source region for larval and juvenile krill dispersal. However, there has been no analysis to spatially resolve regional-scale krill population dynamics across life stages. We assessed spatiotemporal patterns in krill demography using two decades of austral summer data collected along the North and West Antarctic Peninsula since 1993. We identified persistent spatial segregation in the summer distribution of euphausiid larvae (E. superba plus other species), which were concentrated in oceanic waters along the continental slope, and E. superba recruits, which were concentrated in shelf and coastal waters. Mature females of E. superba were more abundant over the continental shelf than the slope or coast. Euphausiid larval abundance was relatively localized and weakly correlated between the North and West Antarctic Peninsula, while E. superba recruitment was generally synchronized throughout the entire region. Euphausiid larval abundance along the West Antarctic Peninsula slope explained E. superba recruitment in shelf and coastal waters the next year. Given the localized nature of krill productivity, it is critical to evaluate the connectivity between upstream and downstream areas of the Antarctic Peninsula and beyond. Krill fishery catch distributions and population projections in the context of a changing climate should account for ontogenetic habitat partitioning, regional population connectivity, and highly variable recruitment
Rapid prefrontal cortex activation towards aversively paired faces and enhanced contingency detection are observed in highly trait-anxious women under challenging conditions
Relative to healthy controls, anxiety-disorder patients show anomalies in classical conditioning that may either result from, or provide a risk factor for, clinically relevant anxiety. Here, we investigated whether healthy participants with enhanced anxiety vulnerability show abnormalities in a challenging affective-conditioning paradigm, in which many stimulus-reinforcer associations had to be acquired with only few learning trials. Forty-seven high and low trait-anxious females underwent MultiCS conditioning, in which 52 different neutral faces (CS+) were paired with an aversive noise (US), while further 52 faces (CSâ) remained unpaired. Emotional learning was assessed by evaluative (rating), behavioral (dot-probe, contingency report), and neurophysiological (magnetoencephalography) measures before, during, and after learning. High and low trait-anxious groups did not differ in evaluative ratings or response priming before or after conditioning. High trait-anxious women, however, were better than low trait-anxious women at reporting CS+/US contingencies after conditioning, and showed an enhanced prefrontal cortex (PFC) activation towards CS+ in the M1 (i.e., 80â117 ms) and M170 time intervals (i.e., 140â160 ms) during acquisition. These effects in MultiCS conditioning observed in individuals with elevated trait anxiety are consistent with theories of enhanced conditionability in anxiety vulnerability. Furthermore, they point towards increased threat monitoring and detection in highly trait-anxious females, possibly mediated by alterations in visual working memory
Auto-ignition of near-ambient temperature H2/air mixtures during flame-vortex interaction
International audienceThis paper demonstrates auto-ignition in reactants at approximately 350 K, upstream of curved H 2 /air flame surfaces during flame/vortex interaction. Temperature fields were measured using laser Rayleigh scattering during head-on interactions of toroidal-vortices with stagnation flames. Repeatable ignition occurred along the ring of the vortex-slightly towards the center-when it was approximately 1 mm upstream of the wrinkled flame surface. The resultant outwardly propagating toroidal flame led to approximately twice the volumetric heat release rate over the duration of the interaction. The ignition occurred in a region of low fluid dynamic strain rate that was farther from the flame than the region of maximum vorticity. Evidence of additional ignition pockets was found upstream of other flame wrinkles, preferentially near the highest magnitude flame curvatures. Different hypotheses for explaining this observation are discussed. The possibility of substantial heat release driven by auto-ignition and complicated diffusion has implications for reaction rate closure models and transport models used in turbulent combustion simulations
Développement saprotrophe de fusarium graminearum (rÎle respectif de différents habitats naturels du champignon dans le processus d'infection du blé en Bourgogne ; recherche d'indicateurs prédictifs du risque de fusariose)
La fusariose est une des maladies les plus importantes altĂ©rant le blĂ© en Bourgogne. L espĂšce fongique Fusarium graminearum est l un des agents principaux de la maladie. L interaction hĂŽte-pathogĂšne peut entrainer la production de mycotoxines toxiques pour l homme et l animal.La seule alternative pour prĂ©venir le dĂ©veloppement de la maladie est de contrĂŽler l inoculum primaire dans son habitat naturel : les adventices, le sol et les rĂ©sidus de culture. En raison de la tendance Ă la rĂ©duction du travail du sol, une attention particuliĂšre doit ĂȘtre portĂ©e au rĂŽle des rĂ©sidus de culture dans la survie et le dĂ©veloppement de F. graminearum. Dans ce travail de thĂšse, deux approches ont Ă©tĂ© choisies pour mieux comprendre le dĂ©veloppement saprotrophe du champignon et ses consĂ©quences. La premiĂšre, Ă travers un essai en champ dans le contexte pĂ©doclimatique Bourguignon, avait pour but de dĂ©finir la part relative des diffĂ©rentes sources d inoculum dans le dĂ©veloppement de la fusariose et l accumulation des mycotoxines dans les grains. Cet essai devait en outre permettre de dĂ©terminer si des indicateurs prĂ©coces du dĂ©veloppement de la maladie sur Ă©pi et de l accumulation de mycotoxines pouvaient ĂȘtre identifiĂ©s. La seconde, Ă travers un essai en microcosmes, avait pour but de suivre le dĂ©veloppement de F. graminearum dans le sol et les rĂ©sidus.Ce travail a permis de souligner l importance de la gestion des rĂ©sidus de culture dans le dĂ©veloppement de la fusariose du blĂ©. Favoriser une dĂ©composition biologique rapide des rĂ©sidus de culture et/ou introduire des cultures intermĂ©diaires assainissantes constituent des perspectives de recherche sur lesquelles doivent porter nos effortsFusarium Head Blight (FHB), mainly caused by the fungal species Fusarium graminearum, is one of the most important disease altering wheat crops in Burgundy. Moreover the plant-pathogen interaction leads to the production of mycotoxins potentially toxic for humans and animals.The only alternative to date to prevent the development of the disease is to control the saprotrophic development of F. graminearum in its natural habitat, i.e. weeds, soil and crops residues. Due to the trend of reduced tillage, special attention should be paid to the role of crop residues in the survival and development of F. graminearum.Two approaches were chosen to better understand the saprotrophic development of F. graminearum and its consequences towards FHB. i) The first through a field experiment in the Burgundian pedoclimatic context aimed at defining the relative importance of the different sources of inoculum in the development of FHB and the accumulation of mycotoxins in grains. The field experiment was also to determine whether early indicators of disease development on ears and accumulation of mycotoxins could be identified. ii) The second, through test microcosms, was to follow the development of F. graminearum in the soil and crop residues.This work highlighted the importance of crop residues management in the development of FHB and gave new understanding about the survival of the fungus on these residues. Improve the biological decomposition of crop residues at the soil surface or/and using suppressive intermediate crops could be the next prospective to investigate to limit the soil inoculum potential of saprotrophic F. graminearumDIJON-BU Doc.Ă©lectronique (212319901) / SudocSudocFranceF
Of âraisinsâ and âyeastâ: mobilisation and framing in the East German revolution of 1989
There is no shortage of literature on the social movements that arose in East Germany in 1989. Numerous studies have shed light upon the nature, scale and dynamics of the uprising of that year. But on certain issues questions remain. No consensus exists, for example, on the relationship between the âcivic groupsâ (New Forum, Democratic Awakening, etc.) and the street protests of the autumn of 1989. Were these simply two facets of a single movement? Or are they better characterised as two distinct streams within the same movement delta? Did the street protests push the civic movement activists into the limelight? Or is it more accurate to say, with Reinfried Musch, that âthe civic movement brought the people onto the streetsâ?1 This paper considers two contrasting interpretations of these issues, and finds both wanting. An alternative interpretation is offered, one that draws upon Marc Steinberg's âdialogicalâ development of frame theory
Biochar Extracts Can Modulate the Toxicity of Persistent Free Radicals in the Nematode Caenorhabditis elegans
As an effective soil amendment, biochars require a comprehensive ecological evaluation before they can be widely used in agriculture because endogenous contaminants, such as environmentally persistent free radicals (EPFRs), certainly pose an ecological risk to soil invertebrates. In this study, Caenorhabditis elegans (C. elegans) was used as a model organism to investigate the neurotoxicity of two rice straw biochars pyrolyzed at 500 and 700 °C. After 24 h exposure to unwashed biochar, washed biochar, and leaching fluids (supernatants), the neurobehavioral parameters of C. elegans were determined in a liquid toxicity test. The results showed that the washed 700 °C biochar particles significantly impaired locomotion and prolonged the defecation interval at a biochar concentration of 4 g·wellâ1, while the unwashed biochar and supernatants caused no apparent impairment. Supporting this, electron paramagnetic resonance (EPR) results showed that the intensity of EPFRs in unwashed 700 °C biochar was stronger than that of the corresponding washed particles. This indicates that, in the liquid test, the EPR signal alone is not indicative of particle toxicity. The accessibility and activity of the EPFRs should be considered. Dissolved organic matter (DOM) was observed in the leaching fluids. The neurotoxic activity of the washed biochar was alleviated after the re-addition of leaching fluids to the washed biochar, suggesting that the dissolved organic materials modulate the reactivity of the EPFRs in the liquid phase. This study suggests that the leaching process may increase the risk of biochar when used in the field environment.National Natural Scientific Foundation of ChinaYunnan Province Basic Research ProjectNSFC-NCNPeer Reviewe
Phenol-rich fulvic acid as a water additive enhances growth, reduces stress, and stimulates the immune system of fish in aquaculture
Aquaculture has become imperative to cover the demands for dietary animal protein. Simultaneously, it has to overcome prejudices from excessive use of antibiotics and environmental impacts. Natural supplements are traditionally applied orally. In this study, we demonstrated another pathway: the gills. Humic substances are immunostimulants and a natural part of every aquatic ecosystem, making them ideal to be used as bath stimulants. Five and 50Â mg C/L of a fulvic acid-rich humic substance was added for 28Â days to the water of juvenile rainbow trout (Oncorhynchus mykiss). This fulvic acid is characterized by a high content of phenolic moieties with persistent free radicals and a high electron exchange capacity. The high concentration of the fulvic acid significantly increased growth and reduced the food conversion ratio and the response to a handling-stressor. Phagocytosis and potential killing activity of head kidney leukocytes were increased, as well as the total oxyradical scavenging capacity (TOSC) and lysozyme activity in the gills. In conclusion, immunostimulation via gills is possible with our fulvic acid, and the high phenolic content improved overall health and stress resistance of fish.Bundesministerium fĂŒr Wirtschaft und Energie
http://dx.doi.org/10.13039/501100006360Projekt DEALPeer Reviewe
The Sorption of Sulfamethoxazole by Aliphatic and Aromatic Carbons from Lignocellulose Pyrolysis
Massive biomass waste with lignocellulose components can be used to produce biochar for environmental remediation. However, the impact of lignocellulose pyrolysis on biochar structure in relation to the sorption mechanism of ionizable antibiotics is still poorly understood. In this paper, diverse techniques including thermogravimetric analysis and 13C nuclear magnetic resonance were applied to investigate the properties of biochars as affected by the pyrolysis of cellulose and lignin in feedstock. Cellulose-derived biochars possessed more abundant groups than lignin-derived biochars, suggesting the greater preservation of group for cellulose during the carbonization. Higher sorption of sulfamethoxazole (SMX) was also observed by cellulose-derived biochars owing to hydrogen bond interaction. Sorption affinity gradually declined with the conversion aliphatic to aromatic carbon, whereas the enhanced specific surface area (SSA) subsequently promoted SMX sorption as evidenced by increased SSA-N2 and SSA-CO2 from 350 to 450 °C. The decreased Kd/SSA-N2 values with increasing pH values implied a distinct reduction in sorption per unit area, which could be attributed to enhanced electrostatic repulsion. This work elucidated the role of carbon phases from thermal conversion of lignocellulose on the sorption performance for sulfonamide antibiotics, which will be helpful to the structural design of carbonaceous adsorbents for the removal of ionizable antibiotics
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