Living on borrowed time – Amazonian trees use decade‐old storage carbon to survive for months after complete stem girdling

Nonstructural carbon (NSC) reserves act as buffers to sustain tree activity during periods when carbon (C) assimilation does not meet C demand, but little is known about their age and accessibility; we designed a controlled girdling experiment in the Amazon to study tree survival on NSC reserves. We used bomb-radiocarbon (14C) to monitor the time elapsed between C fixation and release (‘age’ of substrates). We simultaneously monitored how the mobilization of reserve C affected δ13CO2. Six ungirdled control trees relied almost exclusively on recent assimilates throughout the 17 months of measurement. The Δ14C of CO2 emitted from the six girdled stems increased significantly over time after girdling, indicating substantial remobilization of storage NSC fixed up to 13–14 yr previously. This remobilization was not accompanied by a consistent change in observed δ13CO2. These trees have access to storage pools integrating C accumulated over more than a decade. Remobilization follows a very clear reverse chronological mobilization with younger reserve pools being mobilized first. The lack of a shift in the δ13CO2 might indicate a constant contribution of starch hydrolysis to the soluble sugar pool even outside pronounced stress periods (regular mixing). © 2018 The Authors. New Phytologist © 2018 New Phytologist Trus

Les institutions judiciaires royale et seigneuriale dans le Maine au XVIIIe siècle

Dans le cadre de la formation de l’État dit « moderne », cet article examine la coexistence de deux systèmes judiciaires dans le Maine du xviiie siècle, les justices royale et seigneuriale. L’étude concrète de cette justice où coexistent deux sources d’autorité apporte en effet un éclairage sur la monarchie d’Ancien Régime. L’analyse des dynamiques institutionnelles permet de dépasser l’idée d’un État royal conquérant et formateur d’une modernité étatique face à l’archaïsme seigneurial. L’inégale représentation de la justice royale, la grande quantité de sièges seigneuriaux, l’importance des dynamiques locales ainsi que le poids de l’esprit féodal au sein de ces deux justices permettent de relativiser l’œuvre centralisatrice et rationalisante du pouvoir central. On observe un processus d’uniformisation plus complexe au sein duquel les justices seigneuriales détiennent une influence multiple, et où s’établit un dialogue entre les autorités centrale et locale.This article examines the existence of two competing judicial and legal systems in eighteenth-century Maine, the royal and seigniorial justices, in the context of the formation of the “modern” state. This study aims to throw light on how the two competing systems worked in Ancien Régime France. The analysis of the institutional dynamics demonstrates that the dichotomy of, on the one hand, an all-conquering and modernising royal state and, on the other, an archaic seigniorial system is not justified. Rather, the patchy representation of royal justice, the large quantity of seigniorial courts, the importance of local dynamics and the weight of the feudal mind-set, revitalised the state’s centralising and rationalising endeavours. The process of standardisation accommodated the seigniorial judicial institutions by establishing a balance of power between local and central authorities through negotiation and compromise

Méthode de visualisation adaptée aux simulations d'ordre élevé. Application à la compression-reconstruction de champs rayonnés pour des ondes harmoniques

Bien que les méthodes d'ordre élevé permettent de réaliser des simulations très précises et peu coûteuses, il y a un manque d'outils pour analyser et exploiter les résultats obtenus par ces nouveaux schémas. L'objectif de cette thèse est de mettre en place un cadre et des algorithmes efficaces pour visualiser des solutions calculées par des méthodes d'ordre élevé. Notre approche est basée sur la construction d'une approximation affine optimisée de la solution numérique qui peut être post-traitée dans un logiciel de visualisation standard. Un maillage de représentation est créé via un indicateur d'erreurs a posteriori qui contrôle l'erreur de visualisation entre la solution numérique et sa représentation ponctuellement. Une stratégie est établie afin d'assurer que les (dis)continuités soient bien rendues. Un travail particulier est développé pour traiter les éléments d'ordre élevé (éléments courbes) et utilise notamment des indicateurs d'erreurs a posteriori spécifiques. Des exemples numériques montrent le potentiel de la méthode de visualisation. Dans une seconde partie, nous nous intéressons au calcul et à la reconstruction de champs rayonnés pour des problèmes d'ondes en régime harmonique. Nous proposons une méthodologie pour générer une reconstruction précise de champs rayonnés tout en limitant le nombre d'informations nécessaires (i.e. en compressant les données). Pour ce faire, nous nous appuyons sur des fonctions de base composées de polynômes d'ordre élevé et d'ondes planes, ainsi que sur un développement du noyau de la formule intégrale servant au rayonnement. La méthode de visualisation permet alors de représenter fidèlement (décompression) les cartographies obtenues.While high order methods allow to perform very accurate simulations with low costs, there is a lack of tools to analyze and exploit results obtained by these new schemes. The objective of this thesis is to design a framework and efficient algorithms to visualize solutions computed by high order methods. Our approach is based on the construction of an optimized affine approximation of the numerical solution which can be handled by any standard visualization software. A representation mesh is created via an a posteriori estimate which control visualization error between the numerical solution and its representation, and is performed pointwise. A strategy is established to ensure that (dis)continuities are well-rendered. A special work is done to treat high order elements (curved elements) and in particular use specific a posteriori estimates. Several numerical examples demonstrate the potential of the visualization method. In a second part, we examine the computation and reconstruction of radiated fields for wave problems in harmonic regime. We propose a methodology to generate an accurate reconstruction of radiated fields while limiting the information needed (i.e. compressing the data). For this purpose, we rely on basis functions composed of high order polynomials and plane waves, as well as a development of the kernel used for the integral representation. The visualization method allows to faithfully represent (decompression process) the cartographies obtained

Transport and cooling of singly-charged noble gas ion beams

The transport and cooling of noble gas singly-charged ion beams by means of a Radio Frequency Quadrupole Cooler Buncher (RFQCB) have been studied at the LIMBE low energy beam line of the GANIL facility. Ions as light as $^{4}He^+$ have been cooled and stored before their extraction in bunches using $H_2$ as buffer gas. Bunches characteristics have been studied as a function of the parameters of the device. Sizeable transmissions of up to 10 $$ have been obtained. A detailed study of the lifetime of ions inside the buncher has been performed giving an estimate of the charge exchange cross-section. Results of a microscopic Monte-Carlo transport code show reasonable agreement with experimental data.Comment: 13 figure

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Analyse de Apprendre avec le multimédia, où en est-on ?

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Screening for elderly patients admitted to the emergency department requiring specialized geriatric care

BACKGROUND: There is a need for a brief geriatric assessment (BGA) tool to screen elderly patients admitted to the Emergency Department (ED) for their risk of a long hospital stay. OBJECTIVE: To examine whether a BGA administered to elderly patients admitted to the ED may predict the risk of a long hospital stay in the geriatric acute care unit. METHODS: This study had a prospective cohort study design, enrolling 424 elderly patients (mean age 84.0 +/- 6.5 years, 31.6% male) who were evaluated in the ED using a BGA composed of the following items: age, gender, number of medications taken daily, history of falls during the past 6 months, Mini-Mental State Examination (MMSE) score, and non-use of home-help services (i.e., living alone without using any formal or informal home services or social help). The length of stay (LOS) was calculated in days. Patients were separated into three groups based on LOS: low (<8 days), intermediate (8-13 days), and high (>13 days). RESULTS: The prevalence of male gender was higher among patients with the longest LOS compared to those with intermediate LOS (p = 0.002). There were more patients with a history of falls in the high LOS group compared to the intermediate LOS group (p = 0.001) and the low LOS group (p < 0.001). The classification tree showed that male patients with an MMSE score <20 who fell with age under 85 years formed the end node with the greatest relative risk (RR) of a long hospital stay (RR = 14.3 with p < 0.001). CONCLUSIONS: The combination of a history of falls, male gender, cognitive impairment, and age under 85 years identified elderly ED patients at high risk of a long hospital stay