Seasonal variations in pore water and sediment geochemistry of littoral lake sediments (Asylum Lake, MI, USA)

BACKGROUND: Seasonal changes in pore water and sediment redox geochemistry have been observed in many near-surface sediments. Such changes have the potential to strongly influence trace metal distribution and thus create seasonal fluctuations in metal mobility and bioavailability. RESULTS: Seasonal trends in pore water and sediment geochemistry are assessed in the upper 50 cm of littoral kettle lake sediments. Pore waters are always redox stratified, with the least compressed redox stratification observed during fall and the most compressed redox stratification observed during summer. A 2-step sequential sediment extraction yields much more Fe in the first step, targeted at amorphous Fe(III) (hydr)oxides (AEF), then in the second step, which targets Fe(II) monosulfides. Fe extracted in the second step is relatively invariant with depth or season. In contrast, AEF decreases with sediment depth, and is seasonally variable, in agreement with changes in redox stratification inferred from pore water profiles. A 5-step Tessier extraction scheme was used to assess metal association with operationally-defined exchangeable, carbonate, iron and manganese oxide (FMO), organic/sulfide and microwave-digestible residual fractions in cores collected during winter and spring. Distribution of metals in these two seasons is similar. Co, As, Cd, and U concentrations approach detection limits. Fe, Cu and Pb are mostly associated with the organics/sulfides fraction. Cr and Zn are mostly associated with FMO. Mn is primarily associated with carbonates, and Co is nearly equally distributed between the FMO and organics/sulfide fractions. CONCLUSION: This study clearly demonstrates that near-surface lake sediment pore water redox stratification and associated solid phase geochemistry vary significantly with season. This has important ramifications for seasonal changes in the bioavailability and mobility of trace elements. Without rate measurements, it is not possible to quantify the contribution of various processes to natural organic matter degradation. However, the pore water and solid phase data suggest that iron reduction and sulfate reduction are the dominant pathways in the upper 50 cm of these sediments

L'énonciation féminine dans les lais médiévaux

On a conservé un peu plus d’une trentaine de lais français médiévaux, dont les douze plus connus, dits « de Marie de France », apparaissent sous forme d’un recueil précédé d’un prologue dans le ms. Harley 978 de la British Library. Ces récits courts ont un rapport complexe à l’oralité puisqu’ils se présentent comme la transposition en vers romans de récits chantés composés par les Bretons et racontant les aventures « vraies » d’hommes et de femmes du passé. La présence forte d’une voix narrative, surtout dans les prologues et les épilogues, encadre la narration des événements et la représentation des paroles prononcées par des sujets parlants, les personnages masculins et féminins des aventures originelles. Le présent article étudie comment les lais construisent les locuteurs et locutrices du récit (qu’il s’agisse du narrateur ou des personnages) par le biais du discours rapporté. Il s’intéresse plus particulièrement aux différences éventuelles existant entre la façon dont les lais rapportent les discours féminins et les discours masculins, et les compare à un autre genre de récits narratifs courts, celui des fabliaux. Enfin, l’article examine aussi si les lais anonymes se comportent différemment des lais dits « de Marie de France » (où la voix narrative est supposément féminine). Le but sera donc ici de savoir si la représentation des discours féminins dans les lais est affaire de genre littéraire (particulière aux lais en général) ou de genre sexué (lié au sexe de l’auteur(e)

The AVIATOR registry: the importance of evaluating long-term patient outcomes

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Aortic Valve Surgery in Nonelderly Patients: Insights Gained From AVIATOR

Aortic valve surgery in non-elderly patients represents a very challenging patient population. The younger the patient is at the point of aortic valve intervention, the longer their anticipated life expectancy will be, with longer exposure to valve-related complications and risk for re-operation. Although the latest international guidelines recommend aortic valve repair in patients with aortic valve insufficiency, what we see in the real world is that the vast majority of these aortic valves are replaced. However, current prosthetic valves has now been shown to lead to significant loss of life expectancy for non-elderly patients up to 50% for patients in their 40s undergoing mechanical aortic valve replacement. Bioprostheses carry an even worse long-term survival, with higher rates of re-intervention. The promise of trans-catheter valve-in-valve technology is accentuating the trend of bioprosthetic implantation in younger patients, without yet the appropriate evidence. In contrast, aortic valve repair has shown excellent outcomes in terms of quality of life, freedom from re-operation and freedom from major adverse valve-related events with similar life expectancy to general population as it is also found for the Ross procedure, the only available living valve substitute. We are at a time when the paradigm of aortic valve surgery needs to change for the better. To better serve our patients, we must acquire high quality real-world evidence from multiple centers globally - this is the vision of the AVIATOR registry and our common responsibility.status: publishe