Assessing the carbon dynamics in natural and human-perturbed boreal aquatic systems

Most lakes and reservoirs worldwide are supersaturated with respect to water concentrations of carbon dioxide (CO2 ) and methane (CH 4 ), two potent greenhouse gases (GHG). Although surface water GHG concentrations have been measured for more than three decades in lakes and reservoirs around the globe, the mechanisms leading to GHG supersaturation are still obscure, with the relative contributions of the different GHG producing processes hotly debated. In this study, we evaluated the terrestrial organic matter (OM) exports from land to aquatic systems, followed by its degradation and contribution to the surface freshwaters GHG concentrations. Natural lakes, reservoirs as well as lakes and reservoirs with a wood harvested watershed were sampled in the summer of 2007 and analyzed for a broad variety of bulk water chemical parameters and OM molecular proxies. In order to collect sufficient quantities of OM for the amino acid (AA) and lipid molecular analyses, a tangential flow filtration reverse osmosis systems (TFF-RO) was used following the evaluation of its performance for total OM possible molecular fractionation and recoveries using FTIR, stable carbon isotope signatures (e 13 C) and total organic carbon (TOC) concentrations. No significant sample fractionation or carry over was obtained with recoveries ranging between 94.6 and 106.9 % using the TFF-RO system. All lakes and reservoirs sampled in this study were supersaturated in CO2 and CH4 , with wood harvested water bodies and the reservoir having significantly higher water surface CO2 concentrations and emissions to the atmosphere compared to the natural lakes. The bulk water and OM chemical and isotopic analyses showed that the increase in terrestrial dissolved organic carbon and total nitrogen concentrations positively influenced bacterial OM degradation, which drove CO 2 production. Molecular analyses showed a direct relationship between the increases in bacterial biomarker abundances in the dissolved and sedimentary OM fractions, and higher water CO2 concentrations. This result suggests that OM bacterial oxidation is the most important process leading to GHG production in freshwater aquatic system

Assessing carbon dynamics in natural and perturbed boreal aquatic systems

Most natural freshwater lakes are net greenhouse gases (GHG) emitters. Compared to 25 natural systems, human perturbations such as watershed wood harvesting and long term reservoir 26 impoundment lead to profound alterations of biogeochemical processes involved in the aquatic 27 cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in 28 five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon 29 dioxide (CO2), methane (CH4), oxygen (O2), and organic carbon (DOC), as well as total nitrogen 30 (TN) and phosphorus (TP). Dissolved and particulate organic matter, forest soil/litter and 31 leachates, as well as dissolved inorganic carbon (DIC) were analyzed for elemental and stable 32 isotopic compositions (atomic C:N ratios, δ13Corg, δ13Cinorg and δ15Ntot). We found links between 33 the export of terrestrial OM to these systems and the dissolved CO2 and O2 concentrations in the 34 water column, as well as CO2 fluxes to the atmosphere. All systems were GHG emitters, with 35 greater emissions measured for systems with larger inputs of terrestrial OM. The differences in 36 CO2 concentrations and fluxes appear controlled by bacterial activity in the water column and the 37 sediment. Although we clearly observed differences in the aquatic C cycle between natural and 38 perturbed systems, more work on a larger number of water bodies, and encompassing all four 39 seasons should be undertaken to better understand the controls, rates, as well as spatial and 40 temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of 41 GHG emissions (and other key variables) from natural and perturbed systems

Guidelines for Diagnosis and Management of Infective Endocarditis in Adults: A WikiGuidelines Group Consensus Statement.

IMPORTANCE Practice guidelines often provide recommendations in which the strength of the recommendation is dissociated from the quality of the evidence. OBJECTIVE To create a clinical guideline for the diagnosis and management of adult bacterial infective endocarditis (IE) that addresses the gap between the evidence and recommendation strength. EVIDENCE REVIEW This consensus statement and systematic review applied an approach previously established by the WikiGuidelines Group to construct collaborative clinical guidelines. In April 2022 a call to new and existing members was released electronically (social media and email) for the next WikiGuidelines topic, and subsequently, topics and questions related to the diagnosis and management of adult bacterial IE were crowdsourced and prioritized by vote. For each topic, PubMed literature searches were conducted including all years and languages. Evidence was reported according to the WikiGuidelines charter: clear recommendations were established only when reproducible, prospective, controlled studies provided hypothesis-confirming evidence. In the absence of such data, clinical reviews were crafted discussing the risks and benefits of different approaches. FINDINGS A total of 51 members from 10 countries reviewed 587 articles and submitted information relevant to 4 sections: establishing the diagnosis of IE (9 questions); multidisciplinary IE teams (1 question); prophylaxis (2 questions); and treatment (5 questions). Of 17 unique questions, a clear recommendation could only be provided for 1 question: 3 randomized clinical trials have established that oral transitional therapy is at least as effective as intravenous (IV)-only therapy for the treatment of IE. Clinical reviews were generated for the remaining questions. CONCLUSIONS AND RELEVANCE In this consensus statement that applied the WikiGuideline method for clinical guideline development, oral transitional therapy was at least as effective as IV-only therapy for the treatment of IE. Several randomized clinical trials are underway to inform other areas of practice, and further research is needed

Preservation of organic matter in sediments promoted by iron

The biogeochemical cycles of iron and organic carbon are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved iron. In soils, solid iron phases shelter and preserve organic carbon, but the role of iron in the preservation of organic matter in sediments has not been clearly established. Here we use an iron reduction method previously applied to soils to determine the amount of organic carbon associated with reactive iron phases in sediments of various mineralogies collected from a wide range of depositional environments. Our findings suggest that 21.5 ± 8.6 per cent of the organic carbon in sediments is directly bound to reactive iron phases. We further estimate that a global mass of (19–45) × 1015 grams of organic carbon is preserved in surface marine sediments as a result of its association with iron. We propose that these associations between organic carbon and iron, which are formed primarily through co-precipitation and/or direct chelation, promote the preservation of organic carbon in sediments. Because reactive iron phases are metastable over geological timescales, we suggest that they serve as an efficient ‘rusty sink’ for organic carbon, acting as a key factor in the long-term storage of organic carbon and thus contributing to the global cycles of carbon, oxygen and sulphur

Effects of interpersonal violence-related post-traumatic stress disorder (PTSD) on mother and child diurnal cortisol rhythm and cortisol reactivity to a laboratory stressor involving separation

Women who have experienced interpersonal violence (IPV) are at a higher risk to develop posttraumatic stress disorder (PTSD), with dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and impaired social behavior. Previously, we had reported impaired maternal sensitivity and increased difficulty in identifying emotions (i.e. alexithymia) among IPV-PTSD mothers. One of the aims of the present study was to examine maternal IPV-PTSD salivary cortisol levels diurnally and reactive to their child’s distress in relation to maternal alexithymia. Given that mother-child interaction during infancy and early childhood has important long-term consequences on the stress response system, toddlers’ cortisol levels were assessed during the day and in response to a laboratory stressor. Mothers collected their own and their 12-48 month-old toddlers’ salivary samples at home three times: 30 min after waking up, between 2-3 pm and at bedtime. Moreover, mother-child dyads articipated in a 120-min laboratory session, consisting of 3 phases: baseline, stress situation (involving mother-child separation and exposure to novelty) and a 60-min regulation phase. Compared to non-PTSD controls, IPV-PTSD mothers -but not their toddlers-, had lower morning cortisol and higher bedtime cortisol levels. As expected, IPV-PTSD mothers and their children showed blunted cortisol reactivity to the laboratory stressor. Maternal cortisol levels were negatively correlated to difficulty in identifying emotions. Our data highlights PTSDIPV-related alterations in the HPA system and its relevance to maternal behavior. Toddlers of IPV-PTSD mothers also showed an altered pattern of cortisol reactivity to stress that potentially may predispose them to later psychological disorders

Changement universel de la symétrie d'appariement dans les supraconducteurs KFe[indice inférieur 2]As[indice inférieur 2], RbFe[indice inférieur 2]As[indice inférieur 2] et CsFe[indice inférieur 2]As[indice inférieur 2]

Lors d'études précédentes, il a été observé que la température critique de la transition supraconductrice des matériaux KFe$_2$As$_2$ et CsFe$_2$As$_2$ diminue en fonction d'une pression hydrostatique pour ensuite remonter après avoir dépassé une certaine pression critique (17,5 et 14 kbar). La mesure du coefficient de Hall à température nulle, ainsi que des mesures des oscillations de de Haas-van Alphen, indique que ce changement brusque de comportement n'est pas dû à un changement dans la surface de Fermi. Afin d'expliquer ce phénomène, l'hypothèse apportée est celle d'un changement de la symétrie d'appariement des paires de Cooper. Une transition d'une symétrie de type d à une de type s est supportée par l'ajout d'impuretés, des mesures de conductivité thermique et l'évolution en pression de la résistivité. Dans le cadre de ce mémoire, la résistivité, l'effet Hall et le champ critique supérieur ont été mesurés pour le matériau RbFe$_2$As$_2$ en fonction d'une pression hydrostatique, complétant ainsi le portrait pour trois matériaux de même structure. Comme pour les deux premiers matériaux, une remontée de la température critique à une certaine pression critique (11 kbar) est observée, sans conséquence notable sur l'effet Hall. De plus, les données de champ critique supérieur, analysées conjointement à des données déjà prises pour KFe$_2$As$_2$, montrent un saut de la quantité $\frac{1}{T_c}\left(-\frac{\partial H_{c2}}{\partial T}\right)_{T_c}$ à la pression critique, ce qui indique un changement de la structure du gap supraconducteur et consolide le scénario d'un changement de la symétrie d'appariement des paires de Cooper

La gestion durable de l’agrile du frêne en milieu urbain

L'agrile du frêne (Agrilus planipennis) est un insecte exotique envahissant d'origine asiatique s'attaquant à toutes les espèces de frênes jusqu'à en causer la mort en quelques années. Ce ravageur a été détecté pour la première fois en 2002 dans le sud de l'Ontario et en 2008 dans la ville de Carignan au Québec. Depuis son introduction en Amérique du Nord, cet insecte a causé la mort de plusieurs millions de frênes autant en milieu urbain que forestier. Toutefois, c'est en milieu urbain que les pertes économiques sont les plus importantes, notamment en raison de l'abondance de frênes retrouvée. Ainsi, pour limiter les dégâts, les municipalités doivent impérativement élaborer un plan de gestion pour lutter contre cet insecte. L'objectif principal de cet essai est de mettre au point un outil de gestion régionale de l'agrile du frêne suffisamment flexible pour être en mesure de s'adapter à l'émergence de nouvelles connaissances scientifiques et d'initiatives gouvernementales. Cet outil a été développé afin qu'il puisse être utilisé par une organisation dont le mandat couvre l'ensemble du territoire de la province de Québec. Plus précisément, il vise à structurer l'approche de sensibilisation et d'aide technique auprès des municipalités en fonction de leur proximité avec les foyers d'infestation connus. Pour arriver à développer cette méthode de gestion, il est important de comprendre le contexte de la gouvernance canadienne et québécoise envers les espèces exotiques envahissantes et plus spécifiquement celui entourant l'agrile du frêne. Puis, il est nécessaire de connaître les grandes étapes qu'un plan de gestion de l'agrile en milieu urbain doit contenir : inventaire d'arbres, activités de dépistage, traitement de frênes à l'insecticide, abattage stratégique et un plan de communication auprès de la population. Puisqu'aucun moyen efficace d'éradication de l'agrile du frêne n'a encore été mis au point, l'approche à préconiser est celle visant à contrôler et ralentir la progression du ravageur. À cet effet, l'approche Slow Ash Mortality constitue la meilleure alternative de gestion de l'insecte. L'application de cette approche en milieu urbain consiste à gérer l'agrile par foyer d'infestation et à traiter un maximum de frênes à l'insecticide. Cependant, le manque d'implication du Gouvernement du Québec en matière de gestion des espèces exotiques envahissantes et particulièrement dans le cas de l'agrile du frêne représente un obstacle à la bonne gestion du ravageur sur le territoire. Ainsi, une meilleure collaboration des différents ministères concernés faciliterait l'utilisation de l'outil développé dans le présent travail