Density-dependent incompressible fluids with non-Newtonian viscosity

We study the system of PDEs describing unsteady flows of incompressible fluids with variable density and non-constant viscosity. Indeed, one considers a stress tensor being a nonlinear function of the symmetric velocity gradient, verifying the properties of pcoercivity and (p − 1)-growth, for a given parameter p > 1. The existence of Dirichlet weak solutions was obtained in [2], in the cases p > 12/5 if d = 3 or p > 2 if d = 2, d being the dimension of the domain. In this paper, with help of some new estimates (which lead to point-wise convergence of the velocity gradient), we obtain the existence of space-periodic weak solutions for all p > 2. In addition, we obtain regularity properties of weak solutions whenever p > 20/9 (if d = 3) or p > 2 (if d = 2). Further, some extensions of these results to more general stress tensors or to Dirichlet boundary conditions (with a Newtonian tensor large enough) are obtained.Comisión Interministerial de Ciencia y Tecnologí

Standardization Framework for Sustainability from Circular Economy 4.0

The circular economy (CE) is widely known as a way to implement and achieve sustainability, mainly due to its contribution towards the separation of biological and technical nutrients under cyclic industrial metabolism. The incorporation of the principles of the CE in the links of the value chain of the various sectors of the economy strives to ensure circularity, safety, and efficiency. The framework proposed is aligned with the goals of the 2030 Agenda for Sustainable Development regarding the orientation towards the mitigation and regeneration of the metabolic rift by considering a double perspective. Firstly, it strives to conceptualize the CE as a paradigm of sustainability. Its principles are established, and its techniques and tools are organized into two frameworks oriented towards causes (cradle to cradle) and effects (life cycle assessment), and these are structured under the three pillars of sustainability, for their projection within the proposed framework. Secondly, a framework is established to facilitate the implementation of the CE with the use of standards, which constitute the requirements, tools, and indicators to control each life cycle phase, and of key enabling technologies (KETs) that add circular value 4.0 to the socio-ecological transition

Teaching evolution in Chile. History of a conflict documented in textbooks of secondary education

In this paper we analyzed the presence of the evolution in secondary education textbooks used en Chile since 1902 to 2003. Textbooks analysis of secondary education shows the disputes between evolutionisms and their opponents. Members of the clergy participated actively as antievolutionisms and several of the most outstanding evolutionisms were liberal and francmasones. The text of Bernardino Quijada marked a landmark and polarized to those in favor and detractors during half century. The evolutionary subject was reduced in second half of century XX, partly by the development of other biological fields, but also by ideological pressures of preservative religious sectors. During the last reforms, evolutionary theory oscillates between the compulsory and the optative contents of the programs of Chilean secondary education

Caracterización y propiedades de una vermiculita de Badajoz

A chemical, thermal and X-ray study about a sample of vermiculite from Badajoz has been carried out. The realized investigations, i. e. chemical analysis, exchangeable cations, cation-exchange capacity, dehydration curve, differential thermal analysis and X-ray study, show that this mineral is a not well crystalized, calcium and magnesium saturated, rather weathered vermiculite.Se ha efectuado un estudio químico y fisicoquímico de una vermiculita de Badajoz. Las determinaciones realizadas, análisis químico, cationes cambiables, capacidad de cambio, curva de deshidratación, análisis térmico diferencial y diagramas de difracción de rayos X, indican que el material investigado es una vermiculita, algo degradada, no muy bien cristalizada, cuyos cationes de cambio son magnesio y calcio, predominando este último

Cortical blindness secondary to posterior reversible encephalopathy syndrome, recovered by successful blood pressure management

We report a case of cortical blindness secondary to posterior leukoencephalopathy syndrome, which was successfully treated by blood pressure management. A 66-year-old white man presented at the emergency room complaining of severe frontal headache, disorientation, and progressive blurred vision. The initial physical examination disclosed a blood pressure of 200/176 mmHg. One hour later the patient exhibited mental confusion and bilateral blindness. Computed tomography and magnetic resonance imaging were performed, and a systemic workup was conducted, resulting in a diagnosis of posterior leukoencephalopathy syndrome. This syndrome is a rare manifestation of systemic hypertension that requires proper diagnosis and management to avoid irreversible brain damage. Early recognition of this condition and prompt control of the patient’s blood pressure are essential because they may bring about a reversal of the syndrome, which may otherwise result in permanent brain damageRelatamos um caso de cegueira cortical secundário à síndrome de leucoencefalopatia posterior recuperado pelo controle bem sucedido da pressão arterial. Um homem branco de 66 anos de idade compareceu à emergência com queixa de dor de cabeça frontal severa, desorientação e embaçamento progressivo da visão. O exame físico inicial revelou uma pressão arterial de 200/176 mmHg. Uma hora depois, o paciente apresentou confusão mental e cegueira bilateral. Após a tomografia e a ressonância nuclear magnética, o tratamento sistêmico foram realizados e o diagnóstico de síndrome da leucoencefalopatia posterior foi realizado. A síndrome de leucoencefalopatia posterior é uma manifestação rara de hipertensão sistêmica que requer um diagnóstico e gerenciamento adequados para evitar danos cerebrais irreversíveis. O reconhecimento precoce desta condição e o controle imediato da pressão arterial são essenciais porque podem levar à reversão da síndrome, o que, de outra forma, pode resultar em dano cerebral permanenteThis study was supported by a grant from ISCIII (RETICS Oftared, RD16/0008/003) cofunded by FEDERS

Alternative for summer use of solar air heaters in existing buildings

Producción CientíficaAmong solar thermal technologies for indoor heating, solar air heaters (SAH) are appealing for implementation on existing buildings due to their simplicity, fewer risks related to the working fluid, and possible independence from the building structure. However, existing research work mainly focuses on winter use and still fails in providing effective solutions for yearly operation, which would enhance their interest. With the aim of analysing an alternative summer use, this work firstly characterises a double channel-single pass solar air collector through experimentation. From the obtained results, modelling and simulation tasks have been conducted to evaluate the possibilities of using hot air, provided by the SAH, while operating under summer conditions within a closed loop, to feed an air-to-water heat exchanger for domestic hot water (DHW) production. The system is studied through simulation under two different configurations for a case study in Valladolid (Spain), during the period from May to September for different airflows in the closed loop. Results show that daily savings can vary from 27% to 85% among the different operating conditions; a configuration where make-up water is fed to the heat exchanger being preferable, with a dedicated water tank for the solar heated water storage of the minimum possible volume. The more favourable results for the harshest months highlight the interest of extending the use of the solar air heaters to the summer period

Approximation of Smectic-A liquid crystals

In this paper, we present energy-stable numerical schemes for a Smectic-A liquid crystal model. This model involve the hydrodynamic velocity-pressure macroscopic variables (u, p) and the microscopic order parameter of Smectic-A liquid crystals, where its molecules have a uniaxial orientational order and a positional order by layers of normal and unitary vector n. We start from the formulation given in [E’97] by using the so-called layer variable φ such that n = ∇φ and the level sets of φ describe the layer structure of the Smectic-A liquid crystal. Then, a strongly non-linear parabolic system is derived coupling velocity and pressure unknowns of the Navier-Stokes equations (u, p) with a fourth order parabolic equation for φ. We will give a reformulation as a mixed second order problem which let us to define some new energy-stable numerical schemes, by using second order finite differences in time and C 0 - finite elements in space. Finally, numerical simulations are presented for 2D-domains, showing the evolution of the system until it reachs an equilibrium configuration. Up to our knowledge, there is not any previous numerical analysis for this type of models.Ministerio de Economía y CompetitividadMinistry of Education, Youth and Sports of the Czech Republi

Mysteria Ssmi. Rosarii : verso heroico concinnata

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Numerical methods for solving the Cahn-Hilliard equation and its applicability to related Energy-based models

In this paper, we review some numerical methods presented in the literature in the last years to approximate the Cahn-Hilliard equation. Our aim is to compare the main properties of each one of the approaches to try to determine which one we should choose depending on which are the crucial aspects when we approximate the equations. Among the properties that we consider desirable to control are the time accuracy order, energy-stability, unique solvability and the linearity or nonlinearity of the resulting systems. In particular, we concern about the iterative methods used to approximate the nonlinear schemes and the constraints that may arise on the physical and computational parameters. Furthermore, we present the connections of the Cahn-Hilliard equation with other physically motivated systems (not only phase field models) and we state how the ideas of efficient numerical schemes in one topic could be extended to other frameworks in a natural way.Ministry of Education, Youth and Sports of the Czech RepublicMinisterio de Economía y Competitivida