The Optimal Tax Rule in the Presence of Time Use

Using Mexican data on household time use and consumption, we find significant substitution between goods and time in home production and different elasticities of substitution for different household commodities. Adding these findings to the Ramsey optimal tax problem, we show it is optimal to impose higher taxes on market goods used in the production of commodities with a lower elasticity of substitution between goods and time. The reason is that government wants to minimize the distortionary substitution from market purchases toward untaxed time use in home production. This is an analog of the classical Corlett and Hague (1953-1954) result, differing in that we allow for the possibility of substitution between goods and time in the production of commodities. Leaving aside distributional considerations, we conclude that higher taxes should be imposed on market goods used in the production of `Eating` and lower taxes imposed on market goods used in the production of `Recreation`.Optimal taxation, Time use, Elasticity of substitution.

Stem hydraulic capacitance decreases with drought stress : implications for modelling tree hydraulics in the Mediterranean oak Quercus ilex

Hydraulic modelling is a primary tool to predict plant performance in future drier scenarios. However, as most tree models are validated under non-stress conditions they may fail when water becomes limiting. To simulate tree hydraulic functioning under moist and dry conditions, the current version of a water flow and storage mechanistic model was further developed by implementing equations that describe variation in xylem hydraulic resistance (RX) and stem hydraulic capacitance (CS) with predawn water potential (ΨPD). The model was applied in a Mediterranean forest experiencing intense summer drought, where six Quercus ilex trees were instrumented to monitor stem diameter variations and sap flow, concurrently with measurements of predawn and midday leaf water potential. Best model performance was observed when CS was allowed to decrease with decreasing ΨPD. Hydraulic capacitance decreased from 62 to 25 kg m-3 MPa-1 across the growing season. In parallel, tree transpiration decreased to a greater extent than the capacitive water release and the contribution of stored water to transpiration increased from 2.0% to 5.1%. Our results demonstrate the importance of stored water and seasonality in CS for tree hydraulic functioning, and they suggest that CS should be considered to predict the drought-response of trees with models

Standardization of activated sludge for biodegradation tests

Activated sludges are an inoculum source commonly used in biodegradation studies, as wastewater treatment facilities constitute an entry point to the environment for many chemicals. In this paper, the main issues relating to the use of activated sludge in biodegradability tests are presented. Special attention is also devoted to discussing the factors affecting both the activity of the microbial communities and the test results. After a short survey of the state of the art of microbiology of activated sludge, the paper focuses on the methods used to reduce the variations in the diversity, quality and quantity of these communities. Finally, use of surrogates as reference materials in biodegradability tests is discussed

Ultrastable glasses portray similar behaviour to ordinary glasses at high pressure

Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous liquids and on the evolution of the glass transition temperature. Here we compare the pressure dependence of the onset of devitrification, Ton, between two molecular glasses prepared from the same material but with extremely different ambient-pressure kinetic and thermodynamic stabilities. Our data clearly reveal that, while both glasses exhibit different dTon/dP values at low pressures, they evolve towards closer calorimetric devitrification temperature and pressure dependence as pressure increases. We tentatively interpret these results from the different densities of the starting materials at room temperature and pressure. Our data shows that at the probed pressures, the relaxation time of the glass into the supercooled liquid is determined by temperature and pressure similarly to the behaviour of liquids, but using stability-dependent parametersPostprint (published version

Properties of galaxies at the faint end of the Hα\alpha luminosity function at z∼0.62z\sim0.62

Studies measuring the star formation rate density, luminosity function, and properties of star-forming galaxies are numerous. However, it exists a gap at $0.5<z<0.8$ in H$\alpha$-based studies. Our main goal is to study the properties of a sample of faint H$\alpha$ emitters at $z\sim0.62$. We focus on their contribution to the faint end of the luminosity function and derived star formation rate density, characterising their morphologies and basic photometric and spectroscopic properties. We use a narrow-band technique in the near-infrared, with a filter centred at 1.06 $\mu$m. The data come from ultra-deep VLT/HAWK-I observations in the GOODS-S field with a total of 31.9 h in the narrow-band filter. We perform a visual classification of the sample and study their morphologies from structural parameters available in CANDELS. Our 28 H$\alpha$-selected sample of faint star-forming galaxies reveals a robust faint-end slope of the luminosity function $\alpha=-1.46_{-0.08}^{+0.16}$. The derived star formation rate density at $z\sim0.62$ is $\rho_\mathrm{SFR} = 0.036_{-0.008}^{+0.012} M_{\odot}~\mathrm{yr^{-1}~Mpc^{-3}}$. The sample is mainly composed of disks, but an important contribution of compact galaxies with S\'ersic indexes $n\sim2$ display the highest specific star formation rates. The luminosity function at $z\sim0.62$ from our ultra-deep data points towards a steeper $\alpha$ when an individual extinction correction for each object is applied. Compact galaxies are low-mass, low-luminosity, and starburst-dominated objects with a light profile in an intermediate stage from early to late types.Comment: Published in Astronomy & Astrophysics. 19 pages, 14 figures. New version includes language edited by the journa

Numerical simulation of drying of Pinus pseudostrobus wood with Comsol Multiphysics

In this work, we present the second part of our investigation. In the first part, we have published a semi-empirical model for drying. In this second part, we present the numerical solution of a drying model for Pinus pseudostrobus (Mexican softwood). The model take into account a multiphysics approach. The model describes the moisture mobilities and profiles. The system of partial differential equations were solved in COMSOL 3.4 with the UMFPACK solver. Three primary variables are solved; the moisture content; the temperature; and the density of dry air. The model is validated by comparison. We have compared the phenomenological model versus experimental data and versus a semiempirical model

Immersive Robotic Telepresence for Remote Educational Scenarios

[EN] : Social robots have an enormous potential for educational applications and allow for cognitive outcomes that are similar to those with human involvement. Remotely controlling a social robot to interact with students and peers in an immersive fashion opens up new possibilities for instructors and learners alike. Using immersive approaches can promote engagement and have beneficial effects on remote lesson delivery and participation. However, the performance and power consumption associated with the involved devices are often not sufficiently contemplated, despite being particularly important in light of sustainability considerations. The contributions of this research are thus twofold. On the one hand, we present telepresence solutions for a social robot’s location-independent operation using (a) a virtual reality headset with controllers and (b) a mobile augmented reality application. On the other hand, we perform a thorough analysis of their power consumption and system performance, discussing the impact of employing the various technologies. Using the QTrobot as a platform, direct and immersive control via different interaction modes, including motion, emotion, and voice output, is possible. By not focusing on individual subsystems or motor chains, but the cumulative energy consumption of an unaltered robot performing remote tasks, this research provides orientation regarding the actual cost of deploying immersive robotic telepresence solutions.S

Un probable complexe militaire romain d'époque républicaine en Béturie turdule : notes préliminaires sur le campement de "Pedrosillo" (Casas de Reina, Badajoz, Espagne)

International audienceLas últimas campañas de prospección llevadas a cabo en el territorio de la pequeña ciudad de Regina (Casas de Reina, Badajoz), situada en la llanura septentrional de Sierra Morena, han dado lugar al descubrimiento fortuito de un lugar inédito que interpretamos como un complejo militar romano de época republicana. El examen minucioso del conjunto de estos restos nos ha llevado a considerar la hipótesis de que nos encontrábamos ante la presencia de un campamento romano de primera época; más concretamente ante un complejo militar republicano que en principio podría situarse en la época de la conquista y/o de las guerras lusitanas (en torno al 140 a.C.). Pero, además, también al siglo II d.C. pertenecen los únicos paralelos conocidos para este campamento en la península Ibérica: nos referimos a Numancia [Renieblas I, II y III] y Águilar de Anguita (cerca de Sigüenza).Des prospections récentes menées sur le territoire de la petite ville antique de Regina (Casas de Reina, Badajoz), sur le piémont septentrional de la Sierra Morena, ont donné lieu à la découverte d'un site inédit que nous interprétons – en attendant les indispensables travaux de sondages ¬comme un possible complexe militaire romain de campagne. L'examen de l'ensemble des vestiges et des photographies aériennes conduit à envisager l'hypothèse d'un campement de haute époque datant vraisemblablement de la conquête et/ou des guerres lusitaniennes (circa 140 av. J.¬C.). C'est aussi au IIe s. av. J.¬C. qu'appartiennent les seuls parallèles connus pour la péninsule Ibérique (camps de Numance [Renieblas I, II et III] et d'Águilar de Anguita, près de Sigüenza)

Les guerres lusitaniennes entre mythe, histoire et réalité : réflexions autour du complexe militaire romain du ‘Pedrosillo' (Casas de Reina, Badajoz, Espagne)

International audienceArchaeological prospections carried out around the ancient Roman city of Regina, in septentrional edge of the Morena Sierra, allowed the fortuitous discovery of a great Roman military complex of Republican period, probably in relation with the Roman conquest and/or the Lusitanians wars. The proximity of this military camp compared to various possible objectives encourages the authors to analyze the historical but difficult problematic of this zone of Beturia. They are based for that on the archaeological and literary sources, proposing the possible role of Viriathus, the legendary Lusitanian chief.Des prospections archéologiques menées autour de l'ancienne ville romaine de Regina, en bordure septentrionale de la Sierra Morena, ont permis la découverte fortuite d'un vaste complexe militaire romain d'époque républicaine, datant vraisemblablement de la conquête et/ou des guerres lusitaniennes. La proximité de ce campement par rapport à divers objectifs possibles incite les auteurs à analyser la difficile problématique historique de cette zone de la Béturie. Ils s'appuient pour cela sur les sources archéologiques et littéraires, mettant en avant le rôle possible du grand chef lusitanien Viriathe