Non Singular Origin of the Universe and its Present Vacuum Energy Density

We consider a non singular origin for the Universe starting from an Einstein static Universe, the so called "emergent universe" scenario, in the framework of a theory which uses two volume elements $\sqrt{-{g}}d^{4}x$ and $\Phi d^{4}x$, where $\Phi$ is a metric independent density, used as an additional measure of integration. Also curvature, curvature square terms and for scale invariance a dilaton field $\phi$ are considered in the action. The first order formalism is applied. The integration of the equations of motion associated with the new measure gives rise to the spontaneous symmetry breaking (S.S.B) of scale invariance (S.I.). After S.S.B. of S.I., it is found that a non trivial potential for the dilaton is generated. In the Einstein frame we also add a cosmological term that parametrizes the zero point fluctuations. The resulting effective potential for the dilaton contains two flat regions, for $\phi \rightarrow \infty$ relevant for the non singular origin of the Universe, followed by an inflationary phase and $\phi \rightarrow -\infty$, describing our present Universe. The dynamics of the scalar field becomes non linear and these non linearities are instrumental in the stability of some of the emergent universe solutions, which exists for a parameter range of values of the vacuum energy in $\phi \rightarrow -\infty$, which must be positive but not very big, avoiding the extreme fine tuning required to keep the vacuum energy density of the present universe small. Zero vacuum energy density for the present universe defines the threshold for the creation of the universe.Comment: 28 pages, short version of this paper awarded an honorable mention by the Gravity Research Foundation, 2011, accepted for publication in International Journal of Modern Physics

Sensor electroquímic de clor per a aigües potables

El lleixiu, amb el clor que conté, és necessari per a desinfectar l'aigua que prenem, però en dosis elevades podria intoxicar-nos. Per això, és important que les eines que detecten la quantitat de clor en l'aigua siguin fiables. Investigadors del Centre Nacional de Microelectrónica han creat un xip que permet verificar amb exactitud i de manera continuada la quantitat de clor en l'aigua

Caminando por sistemas productivos rentables

En la presente comunicación se analizan diferentes aspectos del suelo, sus características, la relación con el clima y las estrategias de producción agrícola para un mejor uso de los recursos.Trabajo galardonado con el Premio "Ing. Agr. Antonio J. Prego",Academia Nacional de Agronomía y Veterinaria (ANAV

Caminando por sistemas productivos rentables

En la presente comunicación se analizan diferentes aspectos del suelo, sus características, la relación con el clima y las estrategias de producción agrícola para un mejor uso de los recursos.Trabajo galardonado con el Premio "Ing. Agr. Antonio J. Prego",Academia Nacional de Agronomía y Veterinaria (ANAV

Micropatterning of bioactive glass nanoparticles on chitosan membranes for spatial controlled biomineralization

[Excerpt] Objectives: Chitosan membranes were patterned with bioactive glass nanoparticles (BG-NPs) capable of bone regeneration by a Microcontact Printing technique, in order to spatially control biomineralization and also cell adhesion and proliferation. [...

Can a parsimonious model implemented with satellite data be used for modelling the vegetation dynamics and water cycle in water-controlled environments?

[EN] Vegetation plays a key role in catchment's water balance, particularly in semi-arid regions that are generally water-controlled ecosystems. Nowadays, many of the available dynamic vegetation models are quite complex and they have high parametrical requirements. However, in operational applications the available information is quite limited. Therefore parsimonious models together with available satellite information can be valuable tools to predict vegetation dynamics. In this work, we focus on a parsimonious model aimed to simulate vegetation and hydrological dynamics, using both field measurements and satellite information to implement it. The results suggest that the model is able to adequately reproduce the dynamics of vegetation as well as the soil moisture variations. In other words, it has been shown that a parsimonious model with simple equations can achieve good results in general terms and it is possible to assimilate satellite and field observations for the model implementation. (C) 2016 Elsevier B.V. All rights reserved.The research leading to these results has received funding from the Spanish Ministry of Economy and Competitiveness and FEDER funds, through the research projects INTEGRA (CGL2011-28776-C02) and E-HIDROMED (CGL2014-58127-C3). The MODIS data were obtained through the online Data Pool at the NASA Land Processes Distributed Active Archive Center (LP DAAC), USGS/Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota (https://lpdaac.usgs.gov/get_data). The meteorological data were provided by the Spanish National Weather Agency (AEMET).Ruiz Pérez, G.; González-Sanchis, MDC.; Campo García, ADD.; Francés, F. (2016). Can a parsimonious model implemented with satellite data be used for modelling the vegetation dynamics and water cycle in water-controlled environments?. Ecological Modelling. 324:45-53. https://doi.org/10.1016/j.ecolmodel.2016.01.002S455332

Antimony tin oxide (ATO) screen-printed electrodes and their application to spectroelectrochemistry

Spectroelectrochemistry studies spectral changes as a function of applied potential or current. While there is no standard experimental setup, transparent electrodes are most typically used in transmission mode. Working in reflection mode forces light across the sample twice, resulting in higher sensitivities, but in turn requires the use of highly reflective electrodes. Here we present the production and characterization of screen-printed electrodes made from different antimony tin oxide (ATO) conducting particles. The resulting electrodes display excellent spectroelectrochemical properties, such as reflectivities up to 20 times higher than conventional graphite screen-printed electrodes, but with comparable electron transfer rates. These electrodes represent an attractive alternative to conventional materials and widen the choice of suitable electrode materials for electrochemistry in general and spectroelectrochemistry in particularFEDER funds managed by the Catalan Secretary of Universities and Research through project PROD-0000114 (Enterprise and Knowledge, Industry Department, Generalitat de Catalunya)

SEM and TEM evidence of mixed-layer illite-smectite formed by dissolutioncrystallization processes in continental Paleogene sequences in northwestern Argentina

In the northernmost Calchaquí Valley (Salta, Argentina), the Paleogene continental sediments show a transition from smectite, at the top, to R3 I-S (>90% illite) through R1 I-S (65–80% illite), in contrast to the remaining sectors, containing smectite up to the bottom. Samples at the base of the succession were characterized by high-quality step-scan X-ray diffraction (XRD), scanning electron microscopy (SEM) and analytical high-resolution transmission electron microscopy (HRTEM). Analysis by SEM demonstrated dissolution of primary phases (feldspars, micas and quartz) and crystallization of illite, I-S and kaolinite. As this alteration is not pervasive, an intermediate fluid/rock ratio could be inferred. The lattice-fringe images of the samples from upper parts of the sequence show abundant I1-rich areas, whereas in the lower parts of the sequence, illite packets and I3 I-S coexist and compositions evolve towards muscovite (tetrahedral-charge increase, principally compensated by Mgby-Al substitution in octahedral sites and by a slight decrease in Ca in interlayer sites). As burial temperatures were probably similar in all the samples, depth was not responsible for the illite formation at the bottom. The TEM textures suggest that illitization proceeded mainly by dissolution-crystallization. The active faults close to the northern Calchaquí Valley probably promoted the circulation of hot, deep fluids, favouring illitization