Water, oceanic fracture zones and the lubrication of subducting plate boundaries - insights from seismicity

We investigate the relationship between subduction processes and related seismicity for the Lesser Antilles Arc using the Gutenberg-Richter law. This power lawdescribes the earthquakemagnitude distribution, with the gradient of the cumulative magnitude distribution being commonly known as the b-value. The Lesser Antilles Arc was chosen because of its alongstrike variability in sediment subduction and the transition from subduction to strike-slip movement towards its northern and southern ends. The data are derived from the seismicity catalogues from the Seismic Research Centre of The University of the West Indies and the Observatoires Volcanologiques et Sismologiques of the Institut de Physique du Globe de Paris and consist of subcrustal events primarily from the slab interface. The b-value is found using a Kolmogorov-Smirnov test for a maximum-likelihood straight line-fitting routine. We investigate spatial variations in b-values using a grid-search with circular cells as well as an along-arc projection. Tests with different algorithms and the two independent earthquake cataloges provide confidence in the robustness of our results. We observe a strong spatial variability of the b-value that cannot be explained by the uncertainties. Rather than obtaining a simple north-south b-value distribution suggestive of the dominant control on earthquake triggering being water released from the sedimentary cover on the incoming American Plates, or a b-value distribution that correlates with on the obliquity of subduction, we obtain a series of discrete, high b-value 'bull's-eyes' along strike. These bull's-eyes, which indicate stress release through a higher fraction of small earthquakes, coincide with the locations of known incoming oceanic fracture zones on the American Plates. We interpret the results in terms of water being delivered to the Lesser Antilles subduction zone in the vicinity of fracture zones providing lubrication and thus changing the character of the related seismicity. Our results suggest serpentinization around mid-ocean ridge transform faults, which go on to become fracture zones on the incoming plate, plays a significant role in the delivery of water into the mantle at subduction zones

Treatment of complex fractures of the distal radius: a prospective randomised comparison of external fixation 'versus' locked volar plating

The traditional treatment of severely impacted fractures of the distal radius involves bridging external fixation and maintaining reduction by applying continuous traction. The recent technique using fixed-angle screws within volar plates is reported restore the radial length and the articular profile whilst avoiding joint distraction. It is also believed to produce better and quicker clinical results. To test these claims, we carried out a randomised controlled comparison of the efficiency of external fixation (EF) \u27versus\u27 open reduction and internal fixation (ORIF) in treating severely impacted fractures of the distal radius. A total of 39 patients were treated with EF, eventually associated with percutaneous pinning, whereas 36 underwent ORIF with a locked volar plate. There was no significant difference in the two groups with regard to changes in the ulnar variance. Articular reduction was poor in two patients in the EF group with residual step-offs exceeding 2mm; another patient of the EF group suffered a secondary loss of reduction, healing with a severe articular malunion (>2mm). By contrast, articular reduction was satisfactory in all the patients of the ORIF group. The clinical results on the Green and O\u27Brien rating were significantly better in the ORIF group than in the EF group (p<0.01 at 6 weeks, p<0.05 at 6 months). Nevertheless, open reduction and volar plating did not yield better subjective results than EF. However, although not statistically significant, patients treated by ORIF seemed to resume their usual activities quicker than those treated with EF, suggesting that this technique may be adapted to a greater extent in the case of active, young individuals

Réduire ou ralentir la fibrillation auriculaire : est-ce la bonne question en 2010 ?

RésuméPourquoi et comment traiter la fibrillation atriale ? Cette question a paru simple pendant de nombreuses années : la fibrillation atriale, trouble du rythme cardiaque, doit être traitée par des médicaments anti-arythmiques, tant qu’ils peuvent être efficaces. Les effets secondaires de ces médicaments, comme le bénéfice fréquemment apporté par un simple traitement bradycardisant a amené à discuter il y a une dizaine d’années deux stratégies thérapeutiques, réduire ou ralentir. Mais ce choix largement mis en avant dans les précédentes recommandations thérapeutiques, apparaît aujourd’hui réducteur. En 2010 on peut sans doute proposer deux objectifs thérapeutiques, traiter les symptômes et traiter le risque cardiovasculaire associée à la fibrillation. La gêne symptomatique entraînée par l’arythmie doit être toujours évaluée chez nos patients, volontiers selon la classification récente EHRA. Parallèlement la fibrillation fait partie du continuum cardiovasculaire, et constitue un marqueur de risque supplémentaire : il apparaît certain que le contrôle de ce risque supplémentaire associé à la fibrillation ne dépend pas uniquement du traitement de l’arythmie proprement dite.SummaryWhy and how to treat atrial fibrillation? This question seemed simple for many years: atrial fibrillation, a cardiac arrhythmia, should be treated with antiarrhythmic drugs, as long as they can be effective. Side effects of these drugs, as good benefit often provided by a simple bradycardic treatment led to discuss it some 10 years ago 2 therapeutic strategies: rhythm control or rate control. But this choice widely highlighted in the previous guidelines, now seems simplistic. In 2010 we can probably offer two therapeutic goals, treat symptoms and treat cardiovascular risk associated with atrial fibrillation. The discomfort caused by symptomatic arrhythmia should always be assessed in our patients, as by the recent EHRA classification. Meanwhile fibrillation is part of the cardiovascular continuum, and is a marker of an additional risk: it appears certain that the control of this additional risk does not depend solely on the treatment of the arrhythmia itself

Les effets pro-arythmiques des médicaments

RésuméLes effets pro-arythmiques des médicaments sont fréquents et graves, et sont associés à une surmortalité non négligeable. La polymédication augmente le nombre d’effets indésirables et d’interactions graves voire mortelles. Certains sont facilement évitables. Cependant, au-delà de l’allongement de l’intervalle QT, d’autres mécanismes peuvent avoir un rôle majeur comme les dysfonctions du RyR2, responsable d’arythmie calcium-dépendantes par surcharge calcique intracellulaire, avec apparition de post-dépolarisations tardives, sans modifications de l’intervalle QT. Les bloqueurs des canaux sodiques sont également un problème sérieux de part le risque de démasquer ou d’aggraver une dysfonction du canal sodique chez des patients atteints de syndrome de Brugada asymptomatique ou non. Leur dépistage à un stade précoce du développement des médicaments peut avoir un intérêt majeur.SummaryThe cardiac safety of new and marketed drugs is a major concern for public authorities, patients, physicians as well as pharmaceutical companies. Letal adverse drug reactions are indeed a leading cause of death worldwide and increase at a greater rate than the increase in total hospital admission. The increasing use of polypharmacy in current clinical practice is also associated to a growing number of side effects and interactions leading to fatal adverse events. Measurement of the QT interval is an established, albeit incomplete, approach to assess the proarrhythmic risk of a drug. Ventricular arrhythmia (VA) can be caused by a QT-prolonging drug inducing abnormal repolarization of the action potential (AP) of ventricular cardiomyocytes. Emerging evidence, derived from recent understanding of these mechanisms and of similar mechanisms reported for heart failure (HF), suggest that diastolic Ca2+ leak from the sarcoplasmic reticulum (SR) related to RyR2 dysfunction can induce Ca2+ dependent arrhythmia. In this report, we review mechanisms underlying drug-induced arrhythmogenic effects and Ca2+ dependent arrhythmia, and, for the latter, we discuss some of the issues associated to worsening of cardiac arrhythmias

Results of angular-stable locked intramedullary nails in the treatment of distal tibia fractures

AbstractIntroductionIntramedullary nailing in distal tibial fracture is controversial because of a lack of stability. The present study sought to assess radiological and clinical results for a new “angular-stable” locking system in difficult indications for intramedullary nailing.Material and methodA prospective study recruited 41 patients (41 tibias) with distal tibial fracture consecutively managed using angular-stable locked intramedullary nails. Radiologic assessment comprised AP and lateral lower-limb views, taken postoperatively and through to last follow-up. The mean distance was measured between fracture and joint line. Fusion, with or without malunion, primary reduction defect, non-union and secondary displacement were recorded, as were all complications.ResultsMean follow-up was 18±5 months; 3 patients were lost to follow-up. Mean fracture distance from the joint line was 63±25mm. Fusion was achieved within 3 months in 29 cases (76%); delayed fusion in 7 patients (18%) required secondary dynamization at a mean 3 months, with favorable evolution. Revision surgery was required in 2 cases: 1 for secondary displacement exceeding 10°, and 1 for non-union at 7 months. Other complications mainly comprised 4 malunions of less than 10° due to primary reduction defect.ConclusionAngular-stable locked lower-limb intramedullary nailing provided a very satisfactory fusion rate, with few complications. It is, however, a demanding procedure, especially as regards fracture reduction and nail positioning in the distal fragment.Prospective cohort studylevel IV

Publisher’s Note: “Dispersion calibration for the National Ignition Facility electron–positron–proton spectrometers for intense laser matter interactions” [Rev. Sci. Instrum. 92, 033516 (2021)] (Rev. Sci. Instrum. 92, 059902 (2021)

Electron-positron pairs, produced in intense laser-solid interactions, are diagnosed using magnetic spectrometers with image plates, such as the National Ignition Facility (NIF) Electron Positron Proton Spectrometers (EPPS). Although modeling can help infer the quantitative value, the accuracy of the models needs to be verified to ensure measurement quality. The dispersion of low-energy electrons and positrons may be affected by fringe magnetic fields near the entrance of the EPPS. We have calibrated the EPPS with six electron beams from a Siemens Oncor linear accelerator (linac) ranging in energy from $2.7$--$15.2$ $\mathrm{MeV}$ as they enter the spectrometer. A Geant4 TOPAS Monte-Carlo simulation was set up to match depth dose curves and lateral profiles measured in water at $100$ $\mathrm{cm}$ source-surface distance. An accurate relationship was established between the bending magnet current setting and the energy of the electron beam at the exit window. The simulations and measurements were used to determine the energy distributions of the six electron beams at the EPPS slit. Analysis of the scanned image plates together with the determined energy distribution arriving in the spectrometer provide improved dispersion curves for the EPPS.Comment: Published in Review of Scientific Instruments, 5 pages, 3 figures, This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishin

Belgian shipwrecks: hotspots for marine biodiversity

Hard bottom substrates at sea allow the development of communities that are often rich in terms of species diversity. Non-biogenic structures such as shipwrecks are an integral part of these substrates, even if they have an anthropogenic origin and the species assemblages they harbor could be for that reason qualified as 'exotic'. There are 200 recent shipwrecks on the Belgian Continental Shelf (BCS), which represent a large fraction of the hard substrate available locally; their presence has an additional interest if we know that the major part of the English Channel and Southern Bight of the North Sea consists almost exclusively of soft sediments. Five shipwrecks on the BCS will be studied in order to assess the meio- and macrofaunal diversity using direct observations and scuba sampling techniques. The soft sediments close to shipwrecks will also be studied to serve as model for areas relatively undisturbed by fisheries (untrawled). Added to this, the influence of shipwrecks on local hydrodynamics and sediment transport will favor the colonization by fragile epibenthic species and as a consequence increase habitat complexity. For each site, standard abiotic parameters and current vectors will be measured and modeled. The information will be centralized in a database and disseminated through a web site devoted to the biodiversity of the BCS. The results will be relevant to the management of the BCS; the anthropogenic hard substrates of shipwrecks can serve as a model for what will happen with the installation of offshore windmills. A brochure will increase public awareness of the importance of marine diversity, and increase public support for marine protected areas

Belgian shipwreck: hotspots for marine biodiversity BEWREMABI: final report

The main aim of the project is to document the fauna found on five shipwrecks in the Belgian part of the North Sea (map). While we have a fairly good understanding of the fauna of soft bottoms of our part of the North Sea, the fauna of these artificial hard substrates is largely unknown. Study of these habitats will allow us to understand species distribution patterns, and allow us to predict which species to expect on other artificial hard substrates, such as sokkels of wind mills. It is a two year research project carried out in the framework of the SPSD-II research action of the Belgian Federal Science Policy Office

CORASMA Program on Cognitive Radio for Tactical Networks: High Fidelity Simulator and First Results on Dynamic Frequency Allocation

International audienceThis paper reports some preliminary results of the "cognitive radio for dynamic spectrum management" (CORASMA) program that is dedicated to the evaluation of cognitive solutions for tactical wireless networks. It presents two main aspects of the program: the simulator and the the cognitive solutions proposed by the authors. The first part is dedicated to the simulator.We explain the rationale used to design its architecture, and how this architecture allows to assess and compare different cognitive solutions in an operational context. The second part addresses the dynamic frequency allocation topic that is part of the cognitive solutions tackled in the program CORASMA. We first give an overview of the challenges attached to this problem in the military context and then we expose the technical solutions studied by the authors for this purpose. Finally, we present some results obtained from the simulator as an illustration