Predicting soil water and mineral nitrogen contents with the STICS model for estimating nitrate leaching under agricultural fields

The performance of the STICS soil-crop model for the dynamic prediction of soil water content (SWC) and soil mineral nitrogen (SMN) in the root zone (120 cm) of seven agricultural fields was evaluated using field measurements in a coarse-grained alluvial aquifer of the Garonne River floodplain (southwestern France) from 2005 to 2007. The STICS model was used to simulate drainage and nitrate concentration in drainage water in all the agricultural fields of the study area, in order to quantify and assess the temporal and spatial variability of nitrate leaching into groundwater. Simulations of SWC and SMN in the seven monitored fields were found to be satisfactory as indicated by root mean square error (RMSE) and model efficiency being 6.8 and 0.84% for SWC and 22.8 and 0.92% for SMN, respectively. On average, SWC was slightly overestimated by a mean difference of 10 mm (3%) and there was almost no bias in SMN estimations (<0.5%). These satisfactory results demonstrate the potential for using the STICS model to accurately simulate nitrate leaching. Across the study area, simulated drainage and nitrate concentration were extremely variable from one field to another. For some fields, simulated mean annual nitrate concentration in drainage water exceeded 300 mg NO3 − L−1 and predicted nitrate leaching was close to 100 kg N ha−1, while other fields had very low nitrate losses. About 15% of the farmers’ fields were responsible for 60–70% of nitrate leaching. The SMN in late autumn, before winter drainage, was found the main determining factor explaining this variability. This situation may be attributed to unsatisfactory cumulative nitrogen management over the medium term. Ineffective nitrogen management was found to be more detrimental than a single annual incident of overfertilization, particularly in situations of deep soils and in cases of low or highly variable drainage between years

Evaluation of the impact of various agricultural practices on nitrate leaching under the root zone of potato and sugar beet using the STICS soil–crop model

The quaternary aquifer of Vitoria-Gasteiz (Basque Country, Northern Spain) is characterised by a shallow water table mainly fed by drainage water, and thus constitutes a vulnerable zone in regards to nitrate pollution. Field studies were performed with a potato crop in 1993 and a sugar beet crop in 2002 to evaluate their impact on nitrate leaching. The overall predictive quality of the STICS soil–crop model was first evaluated using field data and then the model was used to analyze dynamically the impacts of different crop management practices on nitrate leaching. The model was evaluated (i) on soil nitrate concentrations at different depths and (ii) on crop yields. The simulated values proved to be in satisfactory agreement with measured values. Nitrate leaching was more pronounced with the potato crop thanwith the sugar beet experiment due to i) greater precipitation, ii) lower N uptake of the potato crop due to shallow root depth, and iii) a shorter period of growth. The potato experiment showed that excessive irrigation could significantly increase nitrate leaching by increasing both drainage and nitrate concentrations. The different levels of N-fertilization examined in the sugar beet study had no notable effects on nitrate leaching due to its high N uptake capacity. Complementary virtual experiments were carried out using the STICS model. Our study confirmed that in vulnerable zones agricultural practices must be adjusted, that is to say: 1) N-fertilizer should not be applied in autumn before winter crops; 2) crops with low N uptake capacity (e.g. potatoes) should be avoided or should be preceded and followed by nitrogen catch crops or cover crops; 3) the nitrate concentration of irrigation water should be taken into account in calculation of the N-fertilization rate, and 4) Nfertilization must be precisely adjusted in particular for potato crops

Macrocellular Pd@ionic liquid@organo-Si(HIPE) heterogeneous catalysts and their use for Heck coupling reactions

International audienceSupported ionic liquid phases (SILPs) within macrocellular silica-based foams are prepared by a simple impregnation in organic solvents. Thin ionic liquid layers with thicknesses of 6 to 12 nm were obtained. The SILs mobility has been evidenced through NMR solid state spectroscopy. Subsequently, palladium salts are efficiently trapped within the SILPs, while an in situ palladium hydrogenation allowed an efficient reduction and formation of 10 nm diameter palladium metal nanoparticles. These hybrid foams are used as heterogeneous macrocellular catalysts for the Heck coupling reaction of iodobenzene and cyclohexyl acrylate, where palladium leaching appears to be very low. Despite recyclability minimized through the entrapment of detrimental ammonium salts within the macroporous network during the reaction, competitive TONs and TOFs were reached, while separation of the products can be reached at ease, due to the fact that both palladium species and by-products are trapped within the monolithic foams

Toward a Play Management System for Play-Based Learning

International audienceThis position paper is dedicated to describing a preliminary model of an integrated system, called Play Management System (PMS). PMS is designed to support both players and teachers to deliver, use, manage and track play situations. This PMS model results from a design-based research methodology. Our approach focuses on (1) the learners and the situation that emerges when they play the game, rather than the system dedicated to play and (2) the teachers who want to manage a game-based learning situation. Thus, we argue for a shift from a game-based to a play-based perspective. 1 Introduction Within a context marked by the development of alternative pedagogies, this position paper aims to describe a model of an integrated system, called Play Management System (PMS), dedicated to support players and teachers to deliver, use, manage and track play situations. The purpose of this article is to propose an innovative approach for implementing a play-based learning approach by (1) focusing on the learners and taking into consideration the situation that emerges when they play rather than the artifact dedicated to play (play vs game) and (2) focusing on the teachers who want to implement and manage a play-based learning situation in their classroom (play management vs game design). Thus, we address the issue of teachers' requirements for the orchestration of a play situation within an educational context. In the first section of this paper, we advocate for a player-centered approach for game-based learning. The second section presents a game developed during the project and the design-based research methodology adopted for designing this game. The third section describe

High efficiency silicon nitride surface grating couplers

High efficiency surface grating couplers for silicon nitride waveguides have been designed, fabricated, and characterized. Coupling efficiencies exceeding 60 % are reported at a wavelength of 1.31 μm, as well as angular and wavelength -3 dB tolerances of 4° and 50 nm, respectively. When the wavelength is increased from 1310 nm to 1450 nm the coupling efficiency progressively decreases but remains above 20 % at 1450 nm. The influence of the duty ratio of the grating has also been investigated: maximum coupling efficiency was obtained at 50 % duty ratio

Ultra-deep whole genome bisulfite sequencing reveals a single methylation hotspot in human brain mitochondrial DNA

While DNA methylation is established as a major regulator of gene expression in the nucleus, the existence of mitochondrial DNA (mtDNA) methylation remains controversial. Here, we characterized the mtDNA methylation landscape in the prefrontal cortex of neurological healthy individuals (n=26) and patients with Parkinson’s disease (n=27), using a combination of whole-genome bisulphite sequencing (WGBS) and bisulphite-independent methods. Accurate mtDNA mapping from WGBS data required alignment to an mtDNA reference only, to avoid misalignment to nuclear mitochondrial pseudogenes. Once correctly aligned, WGBS data provided ultra-deep mtDNA coverage (16,723 ± 7,711) and revealed overall very low levels of cytosine methylation. The highest methylation levels (5.49 ± 0.97%) were found on CpG position m.545, located in the heavy-strand promoter 1 region. The m.545 methylation was validated using a combination of methylation-sensitive DNA digestion and quantitative PCR analysis. We detected no association between mtDNA methylation profile and Parkinson’s disease. Interestingly, m.545 methylation correlated with the levels of mtDNA transcripts, suggesting a putative role in regulating mtDNA gene expression. In addition, we propose a robust framework for methylation analysis of mtDNA from WGBS data, which is less prone to false-positive findings due to misalignment of nuclear mitochondrial pseudogene sequences.publishedVersio

Commit-Chains: Secure, Scalable Off-Chain Payments

Current permissionless blockchains suffer from scalability limitations. To scale without changing the underlying blockchain, one avenue is to lock funds into blockchain smart-contracts (collateral) and enact transactions outside, or off- the blockchain, via accountable peer-to-peer messages. Disputes among peers are resolved with appropriate collateral redistribution on the blockchain. In this work we lay the foundations for commit-chains, a novel off-chain scaling solution for existing blockchains where an untrusted and non-custodial operator commits the state of its user account balances via constant-sized, periodic checkpoints. Users dispute operator misbehavior via a smart contract. The commit-chain paradigm enables for the first time that off-chain users can receive payments while being offline. Moreover, locked funds can be managed efficiently at constant communication costs, alleviating collateral fragmentation. We instantiate two account-based commit-chain constructions: NOCUST, based on a cost-effective challenge-response dispute mechanism; and NOCUST-ZKP, which provides provably correct operation via zkSNARKs. These constructions offer a trade-off between correctness, verification, and efficiency while both are practical and ensure key properties such as balance safety; that is, no honest user loses coins. We implemented both constructions on a smart contract enabled blockchain. Our evaluation demonstrates that NOCUST\u27s operational costs in terms of computation and communication scale logarithmically in the number of users and transactions, and allow very efficient lightweight clients (a user involved in e.g. 100 daily transactions only needs to store a constant 46 kb of data, allowing secure payments even on mobile devices). NOCUST is operational in production since March 2019