Mixing across fluid interfaces compressed by convective flow in porous media

We study the mixing in the presence of convective flow in a porous medium. Convection is characterized by the formation of vortices and stagnation points, where the fluid interface is stretched and compressed enhancing mixing. We analyze the behavior of the mixing dynamics in different scenarios using an interface deformation model. We show that the scalar dissipation rate, which is related to the dissolution fluxes, is controlled by interfacial processes, specifically the equilibrium between interface compression and diffusion, which depends on the flow field configuration. We consider different scenarios of increasing complexity. First, we analyze a double-gyre synthetic velocity field. Second, a Rayleigh-B\'enard instability (the Horton-Rogers-Lapwood problem), in which stagnation points are located at a fixed interface. This system experiences a transition from a diffusion controlled mixing to a chaotic convection as the Rayleigh number increases. Finally, a Rayleigh-Taylor instability with a moving interface, in which mixing undergoes three different regimes: diffusive, convection dominated, and convection shutdown. The interface compression model correctly predicts the behavior of the systems. It shows how the dependency of the compression rate on diffusion explains the change in the scaling behavior of the scalar dissipation rate. The model indicates that the interaction between stagnation points and the correlation structure of the velocity field is also responsible for the transition between regimes. We also show the difference in behavior between the dissolution fluxes and the mixing state of the systems. We observe that while the dissolution flux decreases with the Rayleigh number, the system becomes more homogeneous. That is, mixing is enhanced by reducing diffusion. This observation is explained by the effect of the instability patterns

Constraining Hybrid Natural Inflation with recent CMB data

We study the Hybrid Natural Inflation (HNI) model and some of its realisations in the light of recent CMB observations, mainly Planck temperature and WMAP-9 polarization, and compare with the recent release of BICEP2 dataset. The inflationary sector of HNI is essentially given by the potential $V(\phi) = V_0(1+a\cos (\frac{\phi}{f} ) )$, where $a$ is a positive constant smaller or equal to one and $f$ is the scale of (pseudo Nambu-Goldstone) symmetry breaking. We show that to describe the HNI model realisations we only need two observables; the spectral index $n_s$, the tensor-to-scalar ratio, and a free parameter in the amplitude of the cosine function $a$. We find that in order to make the HNI model compatible with the BICEP2 observations, we require a large positive running of the spectra. We find that this could over-produce primordial black holes in the most consistent case of the model. This situation could be aleviated if, as recently argued, the BICEP2 data do not correspond to primordial gravitational waves.Comment: V2: 12 pages, 5 figures and 1 table. Version accepted for publication in JCA

Evolution of dissolution patterns by mixing corrosion in karst systems

Póster presentado en la European Geosciences Union General Assembly, celebrada en Viena del 27 de abril al 2 de mayo de 2014.Conduit enlargement in a karst system is usually assumed to be controlled by non-linear kinetics that allow aggressive water to penetrate along fractures (Gabrovšek and Dreybrodt, 2000, Water. Resour. Res.). However, other mechanism known as mixing corrosion may be decisive for the geometry of the resulting dissolution patterns, at least at depth. Mixing corrosion is caused by the renovation of the dissolution capacity that happens when two waters saturated with respect to calcite but with different CO2 partial pressure mix. In this case, the reaction rate is mixing-controlled and can be quantified in terms of the mixing proportion of the conservative components of the chemical system (De Simoni et al. 2005, Water. Resour. Res.). Therefore, the porosity creation governed by the reaction rate will depend on the chemical differences between the end members and by the degree of mixing. The aim of this work is to study the evolution of the porosity and permeability within a carbonate matrix by mixing-driven dissolution under different diffusion regimes. The speciation of the chemical system is calculated using CHEPROO. Flow and transport are modeled using an ad hoc code that accounts for feedback between reactions, porosity creation and permeability changes. The effects of the initial porosity field, water chemistry and the resulting geometry of the dissolution patterns are explored for different scenarios.Peer reviewe

Análisis de tareas relacionadas con las nociones de límite y continuidad de funciones en libros de texto españoles

Consideramos que hacer matemáticas en una variedad de situaciones y contextos es un aspecto importante de la alfabetización o desarrollo de la competencia matemática. Partiendo del marco teórico PISA (OCDE, 2013), reconocemos que trabajar con cuestiones que llevan por sí mismas a un tratamiento matemático, a la elección de métodos matemáticos y a la organización por medio de representaciones, depende frecuentemente de las situaciones en las cuales se presentan los problemas (Rico, 2006)

Tracer test modeling for characterizing heterogeneity and local-scale residence time distribution in an artificial recharge site

Artificial recharge of aquifers is a technique for improving water quality and increasing groundwater resources. Understanding the fate of a potential contaminant requires knowledge of the residence time distribution (RTD) of the recharged water in the aquifer beneath. A simple way to obtain the RTDs is to perform a tracer test. We performed a pulse injection tracer test in an artificial recharge system through an infiltration basin to obtain the breakthrough curves, which directly yield the RTDs. The RTDs turned out to be very broad and we used a numerical model to interpret them, to characterize heterogeneity, and to extend the model to other flow conditions. The model comprised nine layers at the site scaled to emulate the layering of aquifer deposits. Two types of hypotheses were considered: homogeneous (all flow and transport parameters identical for every layer) and heterogeneous (diverse parameters for each layer). The parameters were calibrated against the head and concentration data in both model types, which were validated quite satisfactorily against 1,1,2-Trichloroethane and electrical conductivity data collected over a long period of time with highly varying flow conditions. We found that the broad RTDs can be attributed to the complex flow structure generated under the basin due to three-dimensionality and time fluctuations (the homogeneous model produced broad RTDs) and the heterogeneity of the media (the heterogeneous model yielded much better fits). We conclude that heterogeneity must be acknowledged to properly assess mixing and broad RTDs, which are required to explain the water quality improvement of artificial recharge basins.Peer ReviewedPostprint (published version

Modelling non-dust fluids in cosmology

Currently, most of the numerical simulations of structure formation use Newtonian gravity. When modelling pressureless dark matter, or `dust', this approach gives the correct results for scales much smaller than the cosmological horizon, but for scenarios in which the fluid has pressure this is no longer the case. In this article, we present the correspondence of perturbations in Newtonian and cosmological perturbation theory, showing exact mathematical equivalence for pressureless matter, and giving the relativistic corrections for matter with pressure. As an example, we study the case of scalar field dark matter which features non-zero pressure perturbations. We discuss some problems which may arise when evolving the perturbations in this model with Newtonian numerical simulations and with CMB Boltzmann codes.Comment: 5 pages; v2: typos corrected and refs added, submitted version; v3: version to appear in JCA

La malacofauna marina de las fases holocenas en la Cueva del Toll (Moià, Barcelona): nuevas aportaciones para el Neolítico nororiental

[EN]: The entrance to the South Gallery of the Toll Cave was discovered in the 40's of the last century. Since then, several works have highlighted the importance of the archaeo-pale-ontological site at both regional and peninsular levels. Focusing on the Holocene levels, the research suggests prolonged use of it, at least from Epicardial times to the late Bronze Age. Among the vast amount of material recovered, we highlight, to the interest of our study, several marine shells. Under the current research project, new specimens have been recovered. Tax-onomic identification shows that they are marine gastropods. The technology, use-wear and chemical analysis suggests that they were anthropically modified by making holes for use as hanging elements. The shells were being tinted with red pigment. The spatial and stratigraphic position of the specimens lead, us to interpret them as part of a single bead, deposited at the bottom of a Neolithic structure.[ES]: La entrada a la Galería Sur de la Cueva del Toll (Moià, Barcelona) fue descubierta en los años 40 del pasado siglo. Desde entonces, las distintas intervenciones realizadas han puesto de manifiesto la importancia del yacimiento arqueo-paleontológico tanto a nivel regional como peninsular. Centrándonos en los niveles holocenos de la cavidad, las investigaciones realizadas indican un uso prolongado de la misma, al menos desde el Neolítico Antiguo, hasta finales del Bronce inicial. Entre la variada cantidad de materiales recuperados destacan por el interés del presente estudio, varios restos de malacofauna marina. En el marco del actual proyecto de investigación, han sido recuperados nuevos ejemplares pertenecientes a las especies Columbella rustica y Nassarius cuvieri. El análisis tecnológico, traceológico y químico de las mismas sugiere que fueron modificadas antrópicamente mediante la realización de perforaciones para su uso, siendo tintadas con pigmentos rojizos. La posición estratigráfica y espacial de los ejemplares nos lleva a interpretar las mismas como parte de un único abalorio, depositado en el fondo de una estructura neolítica.El proyecto de intervención arqueológica esta cofinanciado por el Departamento de Cultura y Medios de Comunicación de la Generalitat de Cataluña.Peer Reviewe

Tracer test modeling for characterizing heterogeneity and local-sacle residence time distribution in an artificial recharge site.

Artificial recharge of aquifers is a technique for improving water quality and increasing groundwater resources. Understanding the fate of a potential contaminant requires knowledge of the residence time distribution (RTD) of the recharged water in the aquifer beneath. A simple way to obtain the RTDs is to perform a tracer test. We performed a pulse injection tracer test in an artificial recharge system through an infiltration basin to obtain the breakthrough curves, which directly yield the RTDs. The RTDs turned out to be very broad and we used a numerical model to interpret them, to characterize heterogeneity, and to extend the model to other flow conditions. The model comprised nine layers at the site scaled to emulate the layering of aquifer deposits. Two types of hypotheses were considered: homogeneous (all flow and transport parameters identical for every layer) and heterogeneous (diverse parameters for each layer). The parameters were calibrated against the head and concentration data in both model types, which were validated quite satisfactorily against 1,1,2-Trichloroethane and electrical conductivity data collected over a long period of time with highly varying flow conditions. We found that the broad RTDs can be attributed to the complex flow structure generated under the basin due to three-dimensionality and time fluctuations (the homogeneous model produced broad RTDs) and the heterogeneity of the media (the heterogeneous model yielded much better fits).We conclude that heterogeneity must be acknowledged to properly assess mixing and broad RTDs, which are required to explain the water quality improvement of artificial recharge basins

Aprovechamiento del cardo (Cynara cardunculus L.) para la producción de biomasa lignocelulósica, aceite y forraje verde

Aprovechamiento del cardo (Cynara cardunculus L.) es una especie perteneciente a la familia de las Compuestas (Asteraceae) lo mismo que el cártamo o el girasol. es una especie vivaz gracias a sus yemas de recambio que posee en el cuello de la raíz estando muy bien adaptada a las condiciones del clima mediterráneo de veranos secos y calurosos

Primeros terneros producidos in vitro tras punción ecoguiada de folículos ováricos

We report several experiments looking for an optimisation of the in vitro embryo production combined to repeated ovum pick-up (OPU-IVF). For this purpose, we tested two in vitro maturation protocols (with EGF and with VERO cells) and two culture systems (SOF and VERO cells + B2). We obtained 6.8 oocytes/session/cow from which 5.8 were selected for maturation. In vitro maturation with VERO cells permitted oocytes to develop up to the blastocyst stage. Day 7 blastocys rates after culture in SOF (16.7 percent) were similar to those obtained after culturing with VERO cells (26.9 percent). Day 21 pregnancy rates after transfer of fresh embryos produced in SOF or in co-culture with VERO cells were 66.6 and 37.5 percent respectively (p>0.05); however, only embryos produced in co-culture allowed to the birth of calves (33.3 percent). We did no find differences between day 21 pregnancy rates after transfer of frozen (71.4 percent) and vitrified embryos (46.4 percent). Only vitrified embryos allowed to obtain calves (20 percent). As a result, we have obtained the first calves after transfer of fresh and vitrified embryos produced by OPU-IVF in Spain.Se describe la puesta a punto de la aspiración transvaginal de ovocitos combinada con técnicas de producción de embriones in vitro (OPU-FIV). Se ensayaron dos sistemas de maduración (con EGF o con células VERO) y dos tipos de cultivo (SOF y cocultivo con células VERO + B2). Se obtuvieron 6,8 ovocitos/sesión/ vaca de los que 5,8 fueron aptos para maduración. La presencia de células VERO permitió el desarrollo embrionario hasta blastocisto. Los blastocistos obtenidos en día 7 tras cultivo en SOF (16,7 p.100) o en cocultivo con células VERO (26,9 p.100) fueron similares. Los porcentajes de gestación a 21 días tras la transferencia de embriones frescos fueron del 66,6 y 37,5 p.100 respectivamente (p>0,05), pero sólo los embriones producidos en cocultivo con células VERO dieron lugar a nacimientos (33,3 p.100). No hubo diferencias en las tasas de gestación a 21 días entre embriones congelados (71,4 p.100) y vitrificados (46,4 p.100). Sólo produjeron nacimientos los embriones vitrificados (20 p.100). Se han obtenido los primeros terneros nacidos en España por transferencia de embriones frescos y vitrificados producidos por OPU-FIV