Science & Mathematics

Litterfall is a major component of the carbon and nutrient cycles in forest ecosystems. Results of the present study are from a chronosequence of Douglas-fir stands monitored continuously for seven years. Aboveground litterfall was measured every three months, sorted by components, and analysed for major nutrients. Results make it possible to characterize the dynamics of organic matter and nutrient returns to the forest floor during stand development. Simple extrapolation was used to estimate the total return in litter, cumulated over a 70-year-rotation length. Already published data were collected in order to try to identify simple relationships capable of predicting the litterfall return from structural stand characteristics. These models failed to be predictive, due on the one hand to insufficient data, and, on the other hand, to data not always perfectly comparable. Litterfall is a quantitative ecological measurement necessary to validate the models of ecosystem function.

The results of a systematic investigation of charge exchange in Na or Mg vapours are described together with applications to the production and acceleration of negative heavy ion beams in a tandem accelerator. μA intensities of 20 keV beams.of Li-, Be-, B-, C-, O-, Na-, Al-, Si-, Cl-, Ca-, Fe-, and Au- have been obtained on test bench by charge exchange in Na, Mg, or K vapour of positive beams extracted from standard, universal ion sources. The measured emittance values of these beams are low compared to existing, universal negative sources. μA beams of Li-, Be-, B-, and Fe- have been injected and accelerated with good transmission in our EN tandem accelerator.

This paper investigates the asymmetric relationship between corporate tax avoidance and total factor productivity (TFP) using firm-level data for 141 European oil and gas companies, covering the period 2007 to 2015. Firstly, we rely on the novel mechanism advanced by Rovigatti and Mollisi (2018) to compute firms' TFP. Secondly, we resort to Canay's (2011) panel data fixed-effect quantile approach to assess the nonlinear, asymmetric effect that tax avoidance has on a firm's productivity. When investigating the tax avoidance phenomenon, we make the distinction between fiscal facilities provided by companies' holding structures and tax haven location. We discover that the impact of tax avoidance on TFP is not straightforward. On the one hand, fiscal facilities provided by holding structures have a mixed effect on TFP. On the other hand, tax haven location enhances the productivity of oil and gas companies from the extractive industry. Finally, we show that the impact of tax avoidance on TFP is stronger at higher quantiles, that is, for higher levels of productivity. Our findings show that offshore profit transfers represent a quite common practice for European oil and gas firms, in particular for the large companies, which helps them to increase their productivity. In our analysis we control for the role of ownership structure, firm size, intangibles, indebtedness and energy price dynamics. To check the robustness we use different approaches to compute the TFP and resort to a bootstrap panel quantile regression.

The goal of this note is to give the key steps of the proof of Merel's theorem on the boundedness of the torsion of elliptic curves

The reflected beam sputter source is a modification of a Hiconex 834 sputter source. Instead of target cones small cylindrical pills of target material are being used which are bombarded by the reflected cesium beam. Some output data, results on transmission and emittance measurements are presented. The source turns out to be superior to the original in most properties.

Generally the geostatistical simulation methods are used to generate several realizations of physical properties in the sub-surface, these methods are based on the variogram analysis and limited to measures correlation between variables at two locations only. In this paper, we propose a simulation of properties based on supervised Neural network training at the existing drilling data set. The major advantage is that this method does not require a preliminary geostatistical study and takes into account several points. As a result, the geological information and the diverse geophysical data can be combined easily. To do this, we used a neural network with multi-layer perceptron architecture like feed-forward, then we used the back-propagation algorithm with conjugate gradient technique to minimize the error of the network output. The learning process can create links between different variables, this relationship can be used for interpolation of the properties on the one hand, or to generate several possible distribution of physical properties on the other hand, changing at each time and a random value of the input neurons, which was kept constant until the period of learning. This method was tested on real data to simulate multiple realizations of the density and the magnetic susceptibility in three-dimensions at the mining camp of Val d'Or, Québec (Canada).

Un sol très acide des Basses Vosges, sous une futaie d'Épicéa de 80 ans, analysé en 1986, a été réanalysé en 1996. La fertilité chimique des horizons minéraux a peu varié, mais les sommes de Ca et de Mg échangeables de 0 à 35 cm, et totaux des couches holorganiques, ont fortement diminué, surtout en ce qui concerne le magnésium. Cette diminution, inquiétante pour l'avenir, est liée à la minéralisation des couches holorganiques et à la forte aluminisation des horizons minéraux qui, de ce fait, sont incapables de retenir les cations libérés par la minéralisation de OH. Ce phénomène s'oppose à la recharge du complexe adsorbant qui pourrait se produire quand la couche OH se minéralise par effet climatique ou en fin de révolution. Par ailleurs, la teneur en plomb et chrome des litières a diminué grâce à l'emploi de l'essence sans plomb.

The Japanese authorities have been measuring since March 16 th the radiation level around the Fukushima nuclear plant as well as in the 46 other prefectures of the country. Considering these daily measurements of radiation level in the air, in fallout, tap water, dust, soil, leafy vegetables and seawater, we propose to assess the population exposure to the radioactivity by using Bayesian networks. Bayesian networks are handy thanks to their dynamic component, calculating probability distributions in accordance with the " system state " variable (in this case, the exposure of the population) over time. 1. INTRODUCTION The aim of this study is to quantify the health impact of the radioactive discharges. We will distinguish external exposure through inhalation of radionuclides from internal exposure through ingestion of contaminated water or food because internal exposure is 20 times more dangerous than an external one. Because of the uncertainty due to the health impact assessment, the methodology chosen is a probabilistic modelling with Bayesian networks. More precisely, we are going to use a Dynamic Bayesian Network (DBN) enabling us, informed of the population exposure at some point, to simulate its evolution over time and then to detect when the threshold of 1 Sievert (at which the effects on health appear) is reached. We also hope to be able to answer the following question: depending on the areas, which contamination mode could be most important (external, internal or both)? Our goal is to define the areas to which the Japanese health authorities should really pay attention in the future in order to prevent as much as possible diseases related to exposure to radionuclides such as iodine-131 or cesium-137.

Introduction : la prise en charge de la douleur chez certains patients présentant une addiction aux opiacés ou à d’autres molécules peut être délicate pour le médecin prescripteur. C’est pourquoi le Centre Hospitalier Charles Perrens a créé une réunion de concertation pluridisciplinaire addictologie-neurologie-algologie-cognition (RCP). Objectif : nous avons étudié l’activité de la RCP et fait une analyse clinique du contenu. Méthodes : nous avons mené une étude descriptive rétrospective monocentrique de l’ensemble des comptes-rendus de RCP entre juin 2016 (création de la RCP) et décembre 2019 et chaque variable d’intérêt a été enregistrée dans un tableur Excel. Résultats : 33 RCP se sont tenues mensuellement avec une moyenne de 5 ± 1.6 dossiers et 11 ± 3.3 professionnels de santé par RCP. 95 patients ont été recrutés pour 147 discussions. Il s’agissait majoritairement d’hommes âgés de 48 ans souffrant de rachi-radiculalgies ou de céphalées depuis 14 ans et prenant des opiacés depuis 9 ans et discutés une seule fois. L’origine de la demande émanait principalement du CETD pour une intrication des problématiques douleur et addiction. Les propositions faites étaient principalement une réévaluation addictologique et psychiatrique du patient, une réévaluation de sa douleur et une adaptation des thérapeutiques déjà en place. Ces propositions étaient le plus souvent suivies et la problématique en voie de résolution. Conclusion : le nombre de dossiers discutés et la régularité des RCP témoignent de leur qualité. Il ressort des RCP l’importance de sensibiliser les médecins à repérer ces patients en amont pour une prise en charge adaptée et d’instaurer un suivi systématique.

A new heavy-ion accelerator facility is now under construction at the Oak Ridge National Laboratory. This paper presents a brief description of the scope and schedule of this project, a more complete discussion of the new large tandem accelerator which will be a major element of the facility, and a brief description of several studies which have been made or are in progress at Oak Ridge in preparation for operation of the tandem accelerator.

La race pose problème au marxisme : comment éviter de réduire le racisme à un « dommage collatéral » de l’oppression économique ? Comment éviter de formuler des hypothèses historiques trop contraignantes sur ses origines et sa portée ? E. San Juan Jr. propose ici, dans un texte séminal publié pour la première fois en 1989, de confronter ces problèmes à partir du concept d’hégémonie et de conjoncture. La race et les luttes antiracistes se conçoivent dès lors comme des résultats singuliers de stratégies hégémoniques.