Thin film instability with thermal noise

We study the effects of stochastic thermal fluctuations on the instability of the free surface of a flat liquid film upon a solid substrate. These fluctuations are represented as a standard Brownian motion that can be added to the deterministic equation for the film thickness within the lubrication approximation. Here, we consider that while the noise term is white in time, it is coloured in space. This allows for the introduction of a finite correlation length in the description of the randomized intermolecular interaction. Together with the expected spatial periodicity of the flow, we find a dimensionless parameter, $\beta$, that accounts for the relative importance of the spatial correlation. We perform here the linear stability analysis (LSA) of the film under the influence of both terms, and find the corresponding power spectra for the amplitudes of the normal modes of the instability. We compare this theoretical result with the numerical simulations of the complete non-linear problem, and find a good agreement for early times. For late times, we find that the stochastic LSA predictions on the dominant wavelength remains basically valid. We also use the theoretical spectra to fit experimental data from a nanometric melted copper film, and find the corresponding times of the evolution as well as the values of the parameter, $\beta$

Nubes y otros meteoros. Vistos desde el Observatorio Meteorológico de Oviedo y su entorno

La presente publicación está enfocada no solo hacia la clasificación y cifrado de las nubes y otros meteoros sino también hacia la definición, descripción del meteoro y comentarios de su codificación. Las definiciones y clasificación de los distintos meteoros, así como la particular clasificación de las nubes y su cifrado en la Clave SYNOP, se han efectuado siguiendo las normas de la Organización Meteorológica Mundial (OMM), actualizadas en 2017

From Giant H II regions and H II galaxies to globular clusters and compact dwarf ellipticals

Massive starforming regions like Giant HII Regions (GHIIR) and HII Galaxies (HIIG) are emission line systems ionized by compact young massive star clusters (YMC) with masses ranging from $10^4$M$_\odot$ to $10^8$M$_\odot$. We model the photometric and dynamical evolution over a Hubble time of the massive gravitationally bound systems that populate the tight relation between absolute blue magnitude and velocity dispersion ($M_{B}-\sigma$) of GHIIR and HIIG and compare the resulting relation with that one of old stellar systems: globular clusters, elliptical galaxies, bulges of spirals. After 12~Gyr of evolution their position on the $\sigma$ vs. M$_B$ plane coincides -- depending on the initial mass -- either with the globular clusters for systems with initial mass $M < 10^6$M$_\odot$ or with a continuation of the ellipticals, bulges of spirals and ultracompact dwarfs for YMC with $M >10^6$M$_\odot$. The slope change in the $M_{B}-\sigma$ and $M_B$-size relations at cluster masses around $10^6$M$_\odot$ is due to the larger impact of the dynamical evolution on the lower mass clusters. We interpret our result as an indication that the YMC that ionize GHIIR and HIIG can evolve to form globular clusters and ultra compact dwarf ellipticals in about 12 Gyr so that present day globular clusters and ultra compact dwarf ellipticals may have formed in conditions similar to those observed in today GHIIR and HIIG.Comment: 11 pages, 6 figures, accepted for publication in MNRA

Remediation of Potential Toxic Elements from Wastes and Soils: Analysis and Energy Prospects

[EN] The aim of this study is to evaluate the application of the main hazardous waste management techniques in mining operations and in dumping sites being conscious of the inter-linkages and inter-compartment of the contaminated soils and sediments. For this purpose, a systematic review of the literature on the reduction or elimination of different potential toxic elements was carried out, focusing on As, Cd and Hg as main current contaminant agents. Selected techniques are feasible according to several European countries’ directives, especially in Spain. In the case of arsenic, we verified that there exists a main line that is based on the use of iron minerals and its derivatives. It is important to determine its speciation since As (III) is more toxic and mobile than As (V). For cadmium (II), we observed a certain predominance of the use of biotic techniques, compared to a variety of others. Finally, in mercury case, treatments include a phytoremediation technique using Limnocharis flava and the use of a new natural adsorbent: a modified nanobiocomposite hydrogel. The use of biological treatments is increasingly being studied because they are environmentally friendly, efficient and highly viable in both process and energy terms. The study of techniques for the removal of potential toxic elements should be performed with a focus on the simultaneous removal of several metals, since in nature they do not appear in isolation. Moreover, we found that energy analysis constitutes a limiting factor in relation to the feasibility of these techniques.SIUniversidad de Leó

The effects of scale-up and coal-biomass blending on supercritical coal oxy-combustion power plants

[EN] Carbon Capture and Storage (CCS) with biomass is called to be one of the most important technologies to reduce the climate change all over the world. In addition, supercritical pulverized coal plants have been pointed out as interesting power installations because its high efficiency. In this work, the effects of plants scaling and biomass-coal co-firing level on net present value (NPV), cost of energy (COE) and cost of CO2 avoided (CCA) have been studied on a supercritical pulverized combusting coal/biomass blends. Aspen Plus© was used to implement technical simulations. Finally, the main factors affecting plants viability were identified by a sensitivity analysis. The results obtained revealed that the use of biomass reduces the NPV in (-0.23,-1.75) M€/MWe, and increases the COE by (0.007,0.263) M€/MWe. However, plant scaling was found to be a more important factor, by reaching an impact of 4.32M€/MWe on NPV variation in best case. The reduction of oxy-plants viability by biomass using as raw material could be compensated by an increasing of the designed scale-up. Finally, 300 MWe power plants with 40-50% biomass co-firing level were identified as a compromise solution between economy and risk, improving in this way the interest for potential investmentSIThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Authors thanks the assistance of University of Oviedo (Spain) Chemical Engineering Department in the implementation of the technical simulations of this stud

Guideline for constructing nutrient balance in historical agricultural systemes (and its application to three case-studies in southern Spain)

The purpose of this paper is to provide interested researchers with a simple tool to evaluate the efficacy of different methods of fertility replenishment that have accompanied and made possible the contemporary agriculture. We propose a nutrient balance model created especially to be applied to the past. In the first part of this working paper each term in the balance is defined and specified the information the user must input into the model. The second part of this paper reports on the application of this methodology based on the balances of nutrients to the evolution of Andalusian agriculture since the mid 18th Century. The nutrient balances show the effects of agrarian growth in an environmentally limited context, offering reasonable doubt regarding the medium and long-term stability of certain forms of cultivation. The balances show that in the last decades of the 19th Century, productive intensification had reached its ceiling, with livestock numbers levelling off or clearly declining. The deficits of nutrients even began to exceed the fertilisation capacity of the available livestock. The intensification applied in unfertilised rotations and crops had to be sustained through the extraction of soil reserves.Soil fertility management, Nutrient balances, Past organic agricultures, Agrarian growth, Socio-ecological transition, Agricultural change