Plutonium in Soils from Northeast China and Its Potential Application for Evaluation of Soil Erosion

Surface and soil core samples from northeast China were analyzed for Pu isotopes. The measured Pu-240/Pu-239 atomic ratios and Pu239 + 240/Cs-137 activity ratios revealed that the global fallout is the dominant source of Pu and Cs-137 at these sites. Migration behavior of Pu varying with land type and human activities resulted in different distribution of Pu in surface soils. A sub-surface maximum followed by exponential decline of Pu239 + 240 concentrations was observed in an undisturbed soil core, with a total Pu239 + 240 inventory of 86.9 Bq/m(2) and more than 85% accumulated in 0 similar to 20 cm layers. While only half inventory of Pu was obtained in another soil core and no sub-surface maximum value occurred. Erosion of topsoil in the site should be the most possible reason for the significantly lower Pu inventory, which is also supported by the reported Cs-137 profiles. These results demonstrated that Pu could be applied as an ideal substitute of Cs-137 for soil erosion study in the future.</p

First 236U data from the Arctic Ocean and use of 236U/238U and 129I/236U as a new dual tracer

The first dataset of 236U/238U in the water column of the Arctic Ocean (AO) is presented and shows the widest range of ratios reported so far in the open ocean, from (5±55±5) to (3840±260)×10−12(3840±260)×10−12. Surface samples and depth profiles were collected during two GEOTRACES expeditions in 2011–2012 and analyzed for the concentrations of 236U and 129I, with the aim of investigating whether the combination of 236U/238U and 129I/236U can be used as a new oceanographic tool in the AO. Results show that the distributions of the 236U/238U and 129I/236U atomic ratios are consistent with the different water masses in the AO. High 236U/238U and 129I/236U ratios in the upper water column (&gt;2000×10−12&gt;2000×10−12 and &gt;200, respectively) illustrate the penetration of Atlantic waters (AW) into the AO. Lower values were found in Pacific waters (PW) and deep waters of the AO. Rivers seem to represent a temporally and spatially-constrained third anthropogenic source of 236U but more data are needed to confirm this. In a simple mixing model, the combination of 236U/238U and 129I/236U reveals a high contribution (&gt;99%) of natural background waters (pre-nuclear era) in the deep and bottom waters of the Amerasian basin, indicating an apparent water mass renewal time of &gt;1000 years. Despite the relatively high apparent age of the Amerasian Basin deep waters, this work shows the potential of using the dual-tracer approach as a new oceanographic tool in the Arctic Ocean.</p

Les noms de réciprocité en français (Etude syntactico-sémantiqueTexte imprimé)

Nous avons traité dans cette étude de différents types de prédicats nominaux réciproques ou noms de réciprocité dans la perspective de décrire de manière explicite leurs propriétés syntactico-sémantiques. Il s'agit de noms qui se trouvent dans la construction de type "Il y a Npréd entre A et B" mettant en relation au moins deux éléments (humains, concrets, idées, etc.), ces derniers étant obligatoires; ils peuvent permuter dans la phrase sans que cette opération provoque de changement de sens. Notre description a comme objectif de contribuer à un objectif plus général qui consiste à établir une typologie sémantique d'une partie du lexique à savoir des noms prédicatifs et ce, dans le but d'un traitement automatique de la langue.In this study i examine different types of reciprocal nominal predicates or noun of reciprocity in order to give a full account on their syntactic and semantic properties. These nouns can be found in constructions with the structure "These is Npred between A and B", correlating obligatory at least two elements (humans, concrets, ideas, etc.). They can permute within the sentence without any effect of meaning. My analysis aims to contribute to a more general research working out a semantic typology of a part of the lexicon, the predicative nouns in the perspective of a natural language processing.PARIS13-BU Droit-Lettres (930792101) / SudocSudocFranceF