Theoretical evaluation of 15N isotopic methods for measuring symbiotic nitrogen fixation in the fied

International audienceIsotopic methods for the measurement of symbiotic N2 fixation by leguminous plants in the field rely on the use of differences in 15N enrichment between the N sources potentially available for leguminous crops, soil mineral N and atmospheric N2. This methodology has been fully documented, especially concerning limitations due to non uniform and non constant distribution of 15N and to the use of a reference plant to measure it. Although all authors recognise the necessity of isotopic methods for giving yield independent and time-integrated estimates of symbiotic fixation, they also agree that these methods intrinsically remain imperfect. Our aim in this chapter is (i) to briefly review the three major isotopic methods and recall the main assumptions they involve, (ii) to evaluate the theoretical precision of those methods by performing sensitivity analysis to all their parameters, in the perspective of precisely delimiting their validity domain and (iii) to quantify the error made when using the method with the largest spectrum of application and to propose solutions to minimise it. The natural abundance method (NA) is the simplest method as no added fertiliser is required. The method isotopic dilution (ID) requires 15N-labelled fertiliser application to increase 15N soil enrichment. The multi-enrichment technique (MET) relies on the use of several treatments receiving the same amount of fertiliser but labelled at variable 15N enrichments. Using an original mathematical analysis, we show that the precision of NA and MET is likely to be low if the difference in 15N abundance between the soil and atmosphere is low (lower than 8 ‰). Otherwise, the use of NA or MET requires a very precise determination of the isotopic fractionation rate due to symbiotic fixation (eFix). The ID method circumvents this problem. It has the largest validity domain as it can be used in soils slightly enriched in 15N and does not require such precise determination of eFix.. However, the main assumption of the ID method is that the relative uptake of soil and fertiliser N is identical for the fixing and the non fixing plants. If this assumption is not valid, large discrepancies can occur between the actual and calculated contributions of symbiotic fixation to the overall N acquisition by the plants (pA). This error was evaluated as a function of the level of pA, 15N enrichments of the soil and fertiliser and the proportion of fertiliser N retrieved by the legume to total mineral N. Recommendations for optimal application of 15N labelled fertiliser used to enrich the soil mineral N are given

L'algorithme ALERT. Pourquoi, qui, comment, quand?

peer reviewedLa réanimation guidée par téléphone consiste à guider le témoin d'un arrêt cardiaque, formé ou non à la réanimation cardio-pulmonaire, en lui donnant des consignes standardisées par téléphone. Ces instructions lui permettent de vérifier l'état de conscience de la victime, de dégager ses voies aériennes, d'apprécier la présence d'une respiration efficace et de mettre en train des compressions thoraciques en cas d'état de mort apparente. L'Algorithme Liégeois d'Encadrement à la Réanimation par Téléphone (ALERT) est un protocole original permettant aux dispatchers 112 de notre pays d'encadrer l'appelant durant la fenêtre de temps qui débute avec l'appel à l'aide pour se terminer à l'arrivée des équipes de secours spécialisés sur place. Son emploi est associé à un accroissement significatif de la fréquence et de la qualité des gestes de réanimation mis en train par le témoin permettant d'accroître les chances de survie de la victime d'un arrêt cardio-respiratoire extra-hospitalier (ACREH

How I treat... out-of-hospital cardiac arrest: The role of the emergency medical dispatcher

peer reviewe

Stress and distress: The art and science of dispatcher’s assisted cardiopulmonary resuscitation

peer reviewedChances of survival following a cardiac arrest are very low and inversely proportional to the duration of cardiovascular arrest. It is of critical importance to perform cardiopulmonary resuscitation (CPR) as soon as possible, even before the arrival of emergency medical team (EMT) on the scene. Therefore, early bystander CPR is a key factor in improving survival from out-of-hospital cardiac arrest (OOH-CA). In Belgium, the ALERT algorithm (Algorithme Liégeois d’Encadrement à la Réanimation par Téléphonea offers the opportunity to help bystanders perform CPR. Dispatchers’ assisted telephone CPR has introduced a new link in the chain of survival, that contributes to a reduced OOH-CA mortality rate but at the cost of increased responsibilities and stress. ALERT also gives a new role to bystanders; they are no longer just spectators but become actors when they witness a cardiac arrest. Our team was interested in the psychological burden of ALERT. Therefore, we evaluated the effects of CPR performed by untrained persons. We studied the potential influence of different coping strategies on this impact, as well as the possible correlation with the degree of attachment to the victim and the risk of developing PTSD (Post Traumatic Stress Disorder). We noticed that some psychological negative impact on the bystanders could be recognized. We also identified beneficial and detrimental coping strategies. In the future, we wonder if Video-CPR (V-CPR) might improve the quality of resuscitation

Nourrir les hommes : un dictionnaire

National audienceCe dictionnaire est le résultat d’un projet original qui croise perspectives nouvelles et point sur l’état des connaissances, qui mêle articles sur les grands espaces de la planète, les principaux types de production et d’acteurs et coups de projecteurs sur des aspects moins connus. Une équipe de plus de 40 spécialistes a été réunie pour offrir plus de 500 entrées sur près de 800 pages, fruits d’un choix raisonné. Illustrant l’ouverture de la géographie aux autres sciences humaines et au monde en général, de nombreux agronomes, agro-économistes, spécialistes de relations internationales, historiens ont été conviés à participer à cet ouvrage. Il est aussi l’occasion pour des praticiens de la question de porter leurs connaissances au-delà de leur communauté scientifique, de préciser les termes d’un débat complexe, de faire partager leurs expériences, leurs craintes, leurs espoirs et peut-être, à travers une meilleure connaissance de ces enjeux, contribuer, avec les armes qui sont les nôtres, à aider à nourrir les hommes