pinecone/core-2020-05-10-deduplication huggingface dataset:
Geographical downscaling of outputs provided by an economic farm model calibrated at the regional level

International audienceThere is a strong need for accurate and spatially referenced information regarding policy making and model linkage. This need has been expressed by land users, and policy and decision makers in order to estimate both spatially and locally the impacts of European policy (like the Common Agricultural Policy) and/or global changes on farm-groups. These entities are defined according to variables such as altitude, economic size and type of farming (referring to land uses). European farm-groups are provided through the Farm Accountancy Data Network (FADN) as statistical information delivered at regional level. The aim of the study is to map locally farm-group probabilities within each region. The mapping of the farm-groups is done in two steps: (1) by mapping locally the co-variables associated to the farm-groups, i.e. altitude and land uses; (2) by using regional FADN data as a priori knowledge for transforming land uses and altitude information into farm-groups location probabilities within each region. The downscaling process focuses on the land use mapping since land use data are originally point information located every 18 km. Interpolation of land use data is done at 100 m by using co-variables like land cover, altitude, climate and soil data which are continuous layers usually provided at fine resolution. Once the farm-groups are mapped, European Policy and global changes scenarios are run through an agro-economic model for assessing environmental impacts locally
$c$-axis coupling in underdoped Bi2Sr2CaCu2O8 with varying degrees of disorder

10 pages , 9 FiguresInternational audienceThe dependence of the Josephson Plasma Resonance (JPR) frequency in heavily underdoped Bi2Sr2CaCu2O8+\delta on temperature and controlled pointlike disorder, introduced by high-energy electron irradiation, is cross-correlated and compared to the behavior of the ab-plane penetration depth. It is found that the zero temperature plasma frequency, representative of the superfluid component of the c-axis spectral weight, decreases proportionally with T_c when the disorder is increased. The temperature dependence of the JPR frequency is the same for all disorder levels, including pristine crystals. The reduction of the c-axis superfluid density as function of disorder is accounted for by pair-breaking induced by impurity scattering in the CuO2 planes, rather than by quantum fluctuations of the superconducting phase. The reduction of the c-axis superfluid density as function of temperature follows a T^{2}--law and is accounted for by quasi-particle hopping through impurity induced interlayer states
High-order lattice Boltzmann models for gas flow for a wide range of Knudsen numbers

The authors benefited from the use of the cluster at the Centre de Calcul Scientifique en R'egion Centre.International audienceThe lattice Boltzmann methods (LBMs) have successfully been applied to microscale flows in the hydrodynamic regime, such as flows of liquids in porous media. However, the LBM in its standard formulation does not produce correct results beyond the hydrodynamic regime, i.e., for slip and transitional ones. Following the work of Shan and He [ Phys. Rev. Lett. 80 65 (1998)], we propose to extend the LBM to these regimes in which nonequilibrium effects are obvious and require us to include a larger number of distribution-function moments
The Kamikatsura event and the Matuyama-Brunhes reversal recorded in lavas from Tjörnes Peninsula, northern Iceland

International audienceWe report paleomagnetic results from four overlapping stratigraphic sections (55 flows) through the lava pile in Tjörnes peninsula (North Iceland). The initial aim of our study was to check the existence of intermediate directions previously interpreted as belonging to the Matuyama-Brunhes geomagnetic reversal (MBR), and complete this record with Thellier-Thellier paleointensity determinations and 40Ar/39Ar radioisotopic dating. The directional results corroborate the findings by Kristjánsson et al. (1988): a sequence of reversed, transitional, normal, and transitional polarity (R-T-N-T) is found in each section. The polarity change is characterized by a jump from reversed virtual geomagnetic poles (VGPs) to a quasi-cluster of transitional VGPs located over China, followed by a second jump to a cluster of normal polarity before moving again towards intermediate polarities. Reversely magnetized flows exhibit a magnetic mineralogy well suited for paleointensity determination. Of these 25 flows, 20 yielded paleointensity estimates of good quality. Unfortunately, the systematic presence of coarse multidomain (MD) titanomagnetite in the transitional and normal polarity flows hampered paleointensity estimates for these flows. The Virtual Dipole Moments (VDM) calculated for the reversed polarity flows vary from 4.9 to 7.0 × 1022 Am2 with an arithmetic mean value of 5.5 ± 0.8 × 1022 Am2. This value is identical to the mean VDM obtained for the 0.3-5 Ma time window and thus strengthens the conclusion that the recent geomagnetic field strength is anomalously high compared to that older than 0.3 Ma. 40Ar/39Ar isochron ages were obtained with the incremental heating technique on groundmass separates or phenocryst-poor whole rock samples. Six of the transitionally magnetized lavas yielded isochron ages that are indistinguishable from one another at the 95% confidence level. The weighted average age is 862 ± 51 ka. In the upper part of this volcanic sequence, the normally magnetized flows yielded a weighted average age of 787 ± 40 ka. This finding supports the conclusion that a geomagnetic excursion within the Matuyama chron is recorded in the lower part of the Tjörnes volcanic sequence, whereas only the latest portion of the MBR is recorded by flows in the upper part of the lava pile. This conclusion is supported via comparison of the VGPs obtained from the lavas with those predicted by a geomagnetic field model
Monitoring volcanic thermal anomalies from space: Size matters

International audienceMeasuring temperatures on volcanoes from space provides important constraints on the transfer of mass and heat to the Earth's surface. Time series of multispectral infrared images, acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) between 2000 and 2009, were inspected to investigate fluctuations in thermal anomalies at both Mount Erebus (Antarctica) and Láscar volcano (Chile). Several thermal metrics were explored: i) maximum pixel temperatures above background, ii) the spatial extent of low, moderate and high temperature anomalies, and iii) the spatial extent of short-wave infrared anomalies. The maximum pixel temperature metric correlated to eruptive events at Láscar volcano yet displayed significant scatter at Erebus. The spatial extent of both temperature and short-wave infrared anomalies correlates well with eruptive activity at both volcanoes. Limited variation in the size of thermal anomalies was observed at Erebus throughout the time series due to the stability of a long-lived lava lake, with the exception of a seasonal expansion in low temperature anomalies associated with localized snow-melt at the peak. This finding has implications for the interpretation of low temperature anomalies at other volcanoes. At least two different types of precursory signals are identified at Láscar: i) a gradual increase and ii) a dip, in the size and intensity of thermal anomalies. These thermal precursors appear to be associated with different eruptive styles. The former precedes a relatively shallow, short lived eruption; the later a prolonged eruptive period. Such thermal precursors could therefore help to constrain not only the timing but also the style and duration of an imminent eruptive episode
Diagnosis and impacts of non-Gaussianity of innovations in data assimilation

International audienceThe Best Linear Unbiased Estimator (BLUE) has widely been used in atmospheric and oceanic data assimilation (DA). However, when the errors from data (observations and background forecasts) have non-Gaussian probability density functions (pdfs), the BLUE diers from the absolute Minimum Variance Unbiased Estimator (MVUE), minimizing the mean square a posteriori error. The non-Gaussianity of errors can be due to the inherent statistical skewness and positiveness of some physical observables (e.g. moisture, chemical species) or because of the nonlinearity of the data assimilation models and observation operators acting on Gaussian errors. Non-Gaussianity of assimilated data errors can be justied from a priori hypotheses or inferred from statistical diagnostics of innovations (observation minus background). ollowing this rationale, we compute measures of innovation non-Gaussianity, namely its skewness and kurtosis, relating it to: a) the non-Gaussianity of the individual error themselves, b) the correlation between nonlinear functions of errors, and c) the heteroscedasticity of errors within diagnostic samples. Those relationships impose bounds for skewness and kurtosis of errors which are critically dependent on the error variances, thus leading to a necessary tuning of error variances in order to accomplish consistency with innovations. We evaluate the sub-optimality of the BLUE as compared to the MVUE, in terms of excess of error variance, under the presence of non-Gaussian errors. The error pdfs are obtained by the maximum entropy method constrained by error moments up to fourth order, from which the Bayesian probability density function and the MVUE are computed. The impact is higher for skewed extreme innovations and grows in average with the skewness of data errors, especially if those skewnesses have the same sign. Application has been performed to the quality-accepted ECMWF innovations of brightness temperatures of a set of High Resolution Infrared Sounder (HIRS) channels. In this context, the MVUE has led in some extreme cases to a potential reduction of 20-60% error variance as compared to the BLUE
Metasomatic interactions between slab-derived melts and depleted mantle: Insights from xenoliths within Monglo adakite (Luzon arc, Philippines)

International audienceThe Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon arc crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it
On some implicit and semi-implicit staggered schemes for the shallow water and Euler equations

In this paper, we propose implicit and semi-implicit in time finite volume schemes for the barotropic Euler equations (hence, as a particular case, for the shallow water equations) and for the full Euler equations, based on staggered discretizations. For structured meshes, we use the MAC finite volume scheme, and, for general mixed quadrangular/hexahedral and simplicial meshes, we use the discrete unknowns of the Rannacher-Turek or Crouzeix-Raviart finite elements. We first show that a solution to each of these schemes satisfies a discrete kinetic energy equation. In the barotropic case, a solution also satisfies a discrete elastic potential balance; integrating these equations over the domain readily yields discrete counterparts of the stability estimates which are known for the continuous problem. In the case of the full Euler equations, the scheme relies on the discretization of the internal energy balance equation, which offers two main advantages: first, we avoid the space discretization of the total energy, which involves cell-centered and face-centered variables; second, we obtain an algorithm which boils down to a usual pressure correction scheme in the incompressible limit. Consistency (in a weak sense) with the original total energy conservative equation is obtained thanks to corrective terms in the internal energy balance, designed to compensate numerical dissipation terms appearing in the discrete kinetic energy inequality. It is then shown in the 1D case, that, supposing the convergence of a sequence of solutions, the limit is an entropy weak solution of the continuous problem in the barotropic case, and a weak solution in the full Euler case. Finally, we present numerical results which confirm this theory
New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean

International audienceThrough several examples we show that following sea-level fall and marginal erosion during the Messinian salinity crisis (MSC), clastic inputs into the eastern and western Mediterranean Sea are not distributed evenly in space and time but are mainly limited to the lower section of the Messinian salinity crisis depositional megasequence. Significant similarities around the basin allow us to propose a Mediterranean Messinian salinity crisis depositional episode that can be divided into two seismic megasequences: the Messinian lower megasequence (MLM) and the Messinian upper megasequence (MUM). Their distinctive seismic facies correspond to systems tracts deposited during three main stages that represent a complete sea level cycle. (1) A falling stage systems tract including mass transport deposits and forced regressive clinoforms deposited in in the early part of the falling stage, and related to the increasing rate of relative sea level fall. This stage is characterized by a marked shift in the depocenter towards the deep basins. (2) An early lowstand characterized by massive clastic inputs from major Messinian rivers (the Rhone, Nile, and Antalya Gulf rivers) or smaller river systems (offshore south Lebanon). These clastics were deposited in an oversaturated basin, as evidenced by the interfingering chaotic and transparent seismic facies of the Messinian lower megasequence (MLM). (3) A late lowstand, starting with rapid deposition of massive halite, with no detrital inputs into the deep basin. The upper part of the evaporites clearly onlaps the Messinian erosional surface at the margins and is evidence for a transition between a late lowstand stage and an early transgressive stage. These deposits belong to the Messinian upper megasequence (MUM). We interpret the transition between the two megasequences as the peak of the “salinity” crisis, the end of the relative sea level fall, and the maximum dispersal of sands into the deep Mediterranean basins
A cross-layer MAC and routing protocol based on slotted Aloha for Wireless Sensor Networks

nombre de pages : 13 paru en ligne : 26 avril 2015International audienceWireless Sensor Networks (WSN) consist of a large number of sensors which have limited battery power. One of the major issues in WSN is the need to improve the overall network lifetime. Hence, WSN necessitate energy-efficient routing protocols. In this paper, a cross-layer routing protocol (PLOSA) is designed to offer a high delivery rate, a low end-to-end delay and a low energy consumption. To achieve these goals, the transmission channel is divided into different slots and a sensor has access to a slot related to its distance from the collector. The transmissions are then ordered within the frame from the farthest nodes to the closest ones which is a key point in order to ease forwarding and to conserve energy. We have conducted simulation-based evaluations to compare the performance of the proposed protocol against the framed aloha protocol. The performance results show that our protocol is a good candidate for WSN
Direct small angle neutron scattering observation of stretched chain conformation in nanocomposites: more insight of polymer contributions in mechanical reinforcement

International audienceIn this paper we present a direct measurement of stretched chain conformation in polymer nanocomposites in a large range of deformation using a specific contrast-matched SANS method. Whatever the filler structure and the chain length the results show a clear identity of chain deformation in pure and reinforced polymer and offer a new insight of the polymer chain contribution in the mechanical reinforcement. It suggests that glassy layer or glassy paths, recently proposed, should involve only a small fraction of chains. As a result, the remaining filler contribution appears strikingly constant with deformation as explained by continuous locking-unlocking rearrangement process of the particles
Assessing the impact of climate variability and climate change on runoff in West Africa: The case of Senegal and Nakambe River basins

International audienceWest Africa and its people are very vulnerable to climate variability and changes. Increasing the knowledge of plausible trends of rainfall dry spell lengths (DSL) in the rainy season, and of runoff, enables the assessment of vulnerability and adaptive capacity of the system. These predictions are crucial from a water management and policy perspective. The analyses based on regional climate models (RCMs) and observed datasets exhibit non-stationary behavior and an increase of DSL. Our results highlight the difficulty of selected RCMs to reproduce present climate and their divergence in predicting future climate. Impacts on water resources depend not only on climate forcing but also on land surface conditions. Copyright © 2011 Royal Meteorological Society
Direct competition results from strong competiton for limited resource

International audienceWe study a model of competition for resource through a chemostat-type model where species consume the common resource that is constantly supplied. We assume that the species and resources are characterized by a continuous trait. As already proved, this model, although more complicated than the usual Lotka-Volterra direct competition model, describes competitive interactions leading to concentrated distributions of species in continuous trait space. Here we assume a very fast dynamics for the supply of the resource and a fast dynamics for death and uptake rates. In this regime we show that factors that are independent of the resource competition become as important as the competition efficiency and that the direct competition model is a good approximation of the chemostat. Assuming these two timescales allows us to establish a mathematically rigorous proof showing that our resource-competition model with continuous traits converges to a direct competition model. We also show that the two timescales assumption is required to mathematically justify the corresponding classic result on a model consisting of only finite number of species and resources (MacArthur, R. Theor. Popul. Biol. 1970:1, 1-11). This is performed through asymptotic analysis, introducing different scales for the resource renewal rate and the uptake rate. The mathematical difficulty relies in a possible initial layer for the resource dynamics. The chemostat model comes with a global convex Lyapunov functional. We show that the particular form of the competition kernel derived from the uptake kernel, satisfies a positivity property which is known to be necessary for the direct competition model to enjoy the related Lyapunov functional
Mitigation implications of midcentury targets that preserve long-term climate policy options

Midcentury targets have been proposed as a guide to climate change policy that can link long-term goals to shorter-term actions. However no explicit mitigation analyses have been carried out of the relationship between midcentury conditions and longer-term outcomes. Here we use an integrated assessment modeling framework with a detailed representation of the energy sector to examine the dependence of climate change outcomes in 2100 on emissions levels, atmospheric concentrations, and technology characteristics in 2050. We find that midcentury conditions are crucial determinants of longer-term climate outcomes, and we identify feasibility thresholds describing conditions that must be met by midcentury to keep particular long-term options open. For example, to preserve the technical feasibility of a 50% likelihood of keeping global average temperature at <2 degrees C above preindustrial in 2100, global emissions must be reduced by about 20% below 2000 levels by 2050. Results are sensitive to several assumptions, including the nature of future socio-economic development. In a scenario with high demand for energy and land, being below 2 degrees C with 50% likelihood requires a 50% reduction in emissions below 2000 levels by 2050, which is only barely feasible with known technologies in that scenario. Results suggest that a greater focus on midcentury targets could facilitate the development of policies that preserve potentially desirable long-term options
Evolution of extortion in Iterated Prisoner's Dilemma games

Iterated games are a fundamental component of economic and evolutionary game theory. They describe situations where two players interact repeatedly and have the ability to use conditional strategies that depend on the outcome of previous interactions, thus allowing for reciprocation. Recently, a new class of strategies has been proposed, so-called "zero-determinant" strategies. These strategies enforce a fixed linear relationship between one's own payoff and that of the other player. A subset of those strategies allows "extortioners" to ensure that any increase in one player.s own payoff exceeds that of the other player by a fixed percentage. Here, we analyze the evolutionary performance of this new class of strategies. We show that in reasonably large populations, they can act as catalysts for the evolution of cooperation, similar to tit-for-tat, but that they are not the stable outcome of natural selection. In very small populations, however, extortioners hold their ground. Extortion strategies do particularly well in coevolutionary arms races between two distinct populations. Significantly, they benefit the population that evolves at the slower rate, an example of the so-called "Red King" effect. This may affect the evolution of interactions between host species and their endosymbionts