Spatial and temporal variations of N2O evolution at the landscape-scale as affected by land use

Non-Peer ReviewedNitrous oxide has been widely recognized as a major scientific and environmental issue because of its involvement in global warming and destruction of the atmospheric ozone layer. Soils generally act as source of N2O, but the actual rates of N2O emission and the controls on these rates remained poorly understood. As a pre-requisite to quantify large-scale N2O emissions over a long term range, this study was conducted to determine the landscape- and seasonal-scale patterns of N2O emission. Nitrous oxide emissions were assessed at a hummocky glacio-lacustrine landscape in the Black soil zone. The study area was divided into three agronomic practices: an unfertilized canola site, a conventional fallow site, and a pasture site. A systematic grid design was employed at each site and N2O emission was monitored using closed chamber method. A clear landscape-scale pattern of N2O emission was observed in the unfertilized canola and conventional fallow sites; lower landscape positions showed higher N2O flux than the upper landscape positions. This pattern remained consistent throughout the season, with increased in N2O flux towards the mid-growing season (summer), decreased towards the end of the growing season (early fall), and virtually ceased by the onset of frost (late fall). Of the three sites tested, the pasture site showed the lowest N2O emission and activity was only observed during the summer samplings. Soil respiration and moisture content followed. similar spatial and temporal patterns as N2O emission. Results indicate that N2O production is controlled at the landform level by soil factors and at seasonal level by precipitation and temperature. Such relationships might be useful in generating a spatially-distributed model for quantifying N2O emission

Construction d'un critère d'optimalité pour plans d'expériences numériques dans le cadre de la quantification d'incertitudes

http://archive.numdam.org/ARCHIVE/RSA/RSA_2005__53_4/RSA_2005__53_4_87_0/RSA_2005__53_4_87_0.pdfInternational audienceDe nombreux phénomènes physiques sont étudiés à l'aide de simulateurs numériques coûteux, avec lesquels une variable d'intérêt - ou "réponse" - est une fonction déterministe des variables d'entrée (les facteurs). Cependant, on est souvent amené à évaluer la réponse sous forme d'incertitudes du fait de la méconnaissance du niveau des facteurs. Ainsi en Exploration/Production pétrolière, on s'intéresse par exemple à la distribution de la production d'huile d'un réservoir dans dix ans. Dans cet article nous construisons un critère conçu pour planifier les simulations de sorte que la quantification des incertitudes sur la réponse soit la meilleure possible. Baptisé "MC-V optimalité", le critère obtenu est alors équivalent à un critère IMSE (Integrated Mean Squared Error) où l'intégration est effectuée selon la distribution des facteurs. La démarche sera illustrée par l'exposé du contexte de l'Exploration/Production pétrolière dont l'étude est à l'origine de ce critère

The contamination of the surface of Vesta by impacts and the delivery of the dark material

The Dawn spacecraft observed the presence of dark material, which in turn proved to be associated with OH and H-rich material, on the surface of Vesta. The source of this dark material has been identified with the low albedo asteroids, but it is still a matter of debate whether the delivery of the dark material is associated with a few large impact events, to micrometeorites or to the continuous, secular flux of impactors on Vesta. The continuous flux scenario predicts that a significant fraction of the exogenous material accreted by Vesta should be due to non-dark impactors likely analogous to ordinary chondrites, which instead represent only a minor contaminant in the HED meteorites. We explored the continuous flux scenario and its implications for the composition of the vestan regolith, taking advantage of the data from the Dawn mission and the HED meteorites. We used our model to show that the stochastic events scenario and the micrometeoritic flux scenario are natural consequences of the continuous flux scenario. We then used the model to estimate the amounts of dark and hydroxylate materials delivered on Vesta since the LHB and we showed how our results match well with the values estimated by the Dawn mission. We used our model to assess the amount of Fe and siderophile elements that the continuous flux of impactors would mix in the vestan regolith: concerning the siderophile elements, we focused our attention on the role of Ni. The results are in agreement with the data available on the Fe and Ni content of the HED meteorites and can be used as a reference frame in future studies of the data from the Dawn mission and of the HED meteorites. Our model cannot yet provide an answer to the fate of the missing non-carbonaceous contaminants, but we discuss possible reasons for this discrepancy.Comment: 31 pages, 7 figures, 4 tables. Accepted for publication on the journal ICARUS, "Dark and Bright Materials on Vesta" special issu

Impact of natural (waves and currents) and anthropogenic (trawl) resuspension on the export of particulate matter to the open ocean: Application to the Gulf of Lion (NW Mediterranean)

Accepted manuscript version. Published version available at https://doi.org/10.1016/j.csr.2008.02.002. Licensed CC BY-NC-ND 4.0.Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. Resuspension by bottom trawling on shelves with strong fishing activity can modify the scale of natural disturbance by waves and currents. Recent field data show that the impact of bottom trawls on fine sediment resuspension per unit surface is comparable with that of the largest storms. We assessed the impact of both natural and anthropogenic processes on the dispersal of riverborne particles and shelf sediments on the Gulf of Lion shelf. We performed realistic numerical simulations of resuspension and transport forced by currents and waves or by a fleet of bottom trawlers. Simulations were conducted for a 16-month period (January 1998–April 1999) to characterise the seasonal variability. The sediment dynamics takes into account bed armoring, ripple geometry and the cohesive and non-cohesive characteristics of the sediments. Essential but uncertain parameters (clay content, erosion fluxes and critical shear stress for cohesive sediment) were set with existing data. Resuspension by waves and currents was controlled by shear stress, whereas resuspension by trawls was controlled by density and distribution of the bottom trawler fleet. Natural resuspension by waves and currents mostly occurred during short seasonal episodes, and was concentrated on the inner shelf. Trawling-induced resuspension, in contrast, occurred regularly throughout the year and was concentrated on the outer shelf. The total annual erosion by trawls (5.6×106 t y−1, t for metric tonnes) was four orders of magnitude lower than the erosion induced by waves and currents (35.3×109 t y−1). However the net resuspension (erosion/deposition budget) for trawling (0.4×106 t y−1) was only one order of magnitude lower than that for waves and currents (9.2×106 t y−1). Off-shelf export concerned the finest fraction of the sediment (clays and fine silts) and took place primarily at the southwestern end of the Gulf. Off-shelf transport was favoured during the winter 1999 by a very intense episode of dense shelf water cascading. Export of sediment resuspended by trawls (0.4×106 t y−1) was one order of magnitude lower than export associated with natural resuspension (8.5×106 t y−1). Trawling-induced resuspension is thought to represent one-third of the total export of suspended sediment from the shelf. A simulation combining both resuspension processes reveals no significant changes in resuspension and export rates compared with the sum of each individual process, suggesting the absence of interference between both processes.</p

A Demonstrator for the ATLAS Level-1 Muon to Central Trigger Processor Interface (MUCTPI)

The Level-1 Muon Trigger Interface (MUCTPI) to the Central Trigger Processor (CTP) receives trigger information from the detector- specific logic of the muon trigger. This information contains up to two muon-track candidates per sector. The MUCTPI combines the information of all sectors and calculates total multiplicity values for each of six programmable pT thresholds. It avoids double counting of single muons by taking into account the fact that some of the trigger sectors overlap. The MUCTPI sends the multiplicity values to the CTP which takes the final Level-1 decision. For every Level-1 Accept (L1A) the MUCTPI sends region-of-interest (RoI) information to the Level-2 trigger and event data to the data acquisition system. A demonstrator of the MUCTPI has been built which has the performance of the final system but has limited flexibility for calculating the overlap. The functionality and the performance of the demonstrator are presented

The triangular nasal notch sign in patients with Crohn&#039;s disease treated with tumor necrosis factor inhibitors

Tumor necrosis factor (TNF) inhibitors are used to treat a range of chronic inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis. Some of the cutaneous side effects of these drugs are well documented, such as infections, skin carcinomas, palmoplantar and skinfold pustulosis, psoriasis-like or eczema-like lesions. We are not aware of TNF inhibitor-induced nasal lesions in the literature. We report a case series demonstrating a specific pattern of cicatricial nasal fissure (triangular nasal notch) following nasal dermatitis episodes in patients treated with TNF inhibitors. This article is protected by copyright. All rights reserved