Computability of the causal boundary by using isocausality

Recently, a new viewpoint on the classical c-boundary in Mathematical Relativity has been developed, the relations of this boundary with the conformal one and other classical boundaries have been analyzed, and its computation in some classes of spacetimes, as the standard stationary ones, has been carried out. In the present paper, we consider the notion of isocausality given by Garc\'ia-Parrado and Senovilla, and introduce a framework to carry out isocausal comparisons with standard stationary spacetimes. As a consequence, the qualitative behavior of the c-boundary (at the three levels: point set, chronology and topology) of a wide class of spacetimes, is obtained.Comment: 44 pages, 5 Figures, latex. Version with minor changes and the inclusion of Figure

Isocausal spacetimes may have different causal boundaries

We construct an example which shows that two isocausal spacetimes, in the sense introduced by Garc\'ia-Parrado and Senovilla, may have c-boundaries which are not equal (more precisely, not equivalent, as no bijection between the completions can preserve all the binary relations induced by causality). This example also suggests that isocausality can be useful for the understanding and computation of the c-boundary.Comment: Minor modifications, including the title, which matches now with the published version. 12 pages, 3 figure

Testing the BalassA-Samuelson hypothesis in two different groups of countries: OECD and Latin America

This paper studies the Balassa-Samuelson hypothesis (BSH) in the context of two areas with strong differences in economic development, twelve OECD countries and twelve Latin American economies, taking the USA as the benchmark. Applying panel cointegration techniques, we find that while the first stage of the hypothesis, which links productivities and prices, is satisfied in each group of countries, the second stage, which relates relative sector prices with the real exchange rate, only holds in the Latin American area. The failure of the latter in the OECD countries as a whole is reflected in departures from PPP in the tradable sectors.Balassa-Samuelson effect, Panel cointegration, Economic development, Exchange rate systems

Proposed Methodology to Evaluate CO2 Capture Using Construction and DemolitionWaste

Since the Industrial Revolution, levels of CO2 in the atmosphere have been constantly growing, producing an increase in the average global temperature. One of the options for Carbon Capture and Storage is mineral carbonation. The results of this process of fixing are the safest in the long term, but the main obstacle for mineral carbonation is the ability to do it economically in terms of both money and energy cost. The present study outlines a methodological sequence to evaluate the possibility for the carbonation of ceramic construction waste (brick, concrete, tiles) under surface conditions for a short period of time. The proposed methodology includes a pre-selection of samples using the characterization of chemical and mineralogical conditions and in situ carbonation. The second part of the methodology is the carbonation tests in samples selected at 10 and 1 bar of pressure. The relative humidity during the reaction was 20 wt %, and the reaction time ranged from 24 h to 30 days. To show the e ectiveness of the proposed methodology, Ca-rich bricks were used, which are rich in silicates of calcium or magnesium. The results of this study showed that calcite formation is associated with the partial destruction of Ca silicates, and that carbonation was proportional to reaction time. The calculated capture e ciency was proportional to the reaction time, whereas carbonation did not seem to significantly depend on particle size in the studied conditions. The studies obtained at a low pressure for the total sample were very similar to those obtained for finer fractions at 10 bars. Presented results highlight the utility of the proposed methodology

El condado y sus vinos. Historia y presente

En número dedicado a: Huelv

Modeling the AC Electrokinetic Behavior of Semiconducting Spheres

We study theoretically the dielectrophoresis and electrorotation of a semiconducting microsphere immersed in an aqueous electrolyte. To this end, the particle polarizability is calculated from first principles for arbitrary thickness of the Debye layers in liquid and semiconductor. We show that the polarizability dispersion arises from the combination of two relaxation interfacial phenomena: charging of the electrical double layer and the Maxwell–Wagner relaxation. We also calculate the particle polarizability in the limit of thin electrical double layers, which greatly simplifies the analytical calculations. Finally, we show the model predictions for two relevant materials (ZnO and doped silicon) and discuss the limits of validity of the thin double layer approximation

Dipolophoresis and Travelling-Wave Dipolophoresis of Metal Microparticles

We study theoretically and numerically the electrokinetic behavior of metal microparticles immersed in aqueous electrolytes. We consider small particles subjected to non-homogeneous ac electric fields and we describe their motion as arising from the combination of electrical forces (dielectrophoresis) and the electroosmotic flows on the particle surface (induced-charge electrophoresis). The net particle motion is known as dipolophoresis. We also study the particle motion induced by travelling electric fields. We find analytical expressions for the dielectrophoresis and induced-charge electrophoresis of metal spheres and we compare them with numerical solutions. This validates our numerical method, which we also use to study the dipolophoresis of metal cylinders.Spanish Research Agency MCI under contract PGC2018-099217-B-I00

Ingeniería concurrente y tecnologías de la información

La ingeniería concurrente (CE por sus siglas en inglés) es un enfoque para la manufactura que permite el diseño y desarrollo simultáneo de productos, procesos y actividades de apoyo. Aunque éste no es un concepto nuevo, ha recibido recientemente cierto empuje de tecnologías de la información como el Internet o algunas técnicas de Inteligencia Artificial. Específicamente, el uso de agentes de software y lenguajes para el manejo de conocimiento pueden aportar una base confiable y flexible para el desarrollo de plataformas de ingeniería concurrente. Este artículo presenta una introducción a los conceptos relacionados con CE, el papel que los agentes de software y el modelado de datos juegan en ella, y describe brevemente un caso de estudio

Development of chitosan based hydrogels as bio-inks for rapid prototyping technologies

The ongoing demand of organs is growing significantly in the last years. There are a lot of people who need a transplant and they are in the waiting list because there are not enough donors to supply all the people. For that reason, fields as Tissue Engineering are studying new ways to create or restore tissues and organs. Among them, 3D bioprinting is emerging more popular and it consists in creating 3D tissue constructs with bioink, the material used to print, and pre-designed structures previously designed with computer-aided design. Bioink is a combination of biomaterials and living cells. This project focuses its attention in finding a thermo-sensitive hydrogel, stable liquid solutions at refrigerated temperature that turn into gel upon an increase of temperature. They are composed of chitosan and a polyol-phosphate salt and they must serve as a bioink. Then, with the possible candidates as bioinks, studies of rheology and printability are performed. Three candidates are the best ones to be used as bioinks for their low gelation time, the time in which the solution/gel transition occurs, and their pH similar to the physiological one. Further studies, as degradation tests, allow the selection of two of them as the best candidates. Rheology studies help to understand the flow behaviour of the solutions and the viscoelastic properties of the solutions by measuring the storage modulus, which represents the elastic behaviour of the material, and the loss modulus, which represents the viscous behaviour. Then, an exhaustive study on printability gives the best combinations of parameters that affect the final printed structures that are printed with the two candidates as bioink. These parameters are the state of the ink, the diameter of the nozzle, the addition or no addition of PBS solution to the printbed and the temperatures at which the syringe and the printbed must be. Good results on bioprintring are achieved proving that the two thermo-sensitive solutions composed of chitosan and a polyol-phosphate salt are good candidates as bioinks.Outgoin

Phenotypic variation among natural populations of pines: implications for the management and conservation of genetic resources

En el campo de la genética, es necesario conocer las causas y efectos de la variación en los rasgos que influyen en las características de los individuos en sus hábitats naturales. El objetivo de esta tesis es investigar la variación fenotípica entre la población natural de pinos a escala local y regional, y definir sus implicaciones en el uso y conservación de los recursos genéticos. En el primer paso, analizamos la relación entre la varianza dentro de la población en rasgos fenotípicos relacionados con su eficacia biológica, la plasticidad fenotípica de estos rasgos y la heterogeneidad ambiental. En segundo lugar, evaluamos la variación genética inter e intraespecífica en la tolerancia a la sequía de plántulas. En tercer lugar, identificamos áreas para la conservación genética y propusimos medidas para la conservación y uso sostenible de los recursos genéticos forestales de pinos.Departamento Instituto Universitario de Investigación en Gestión Forestal SostenibleDoctorado en Conservación y Uso Sostenible de Sistemas Forestale