Comparative analysis of domestic water heating thermosiphon systems tested according to the Standard ISO 9459-2

Permiso concedido para subir el documentoThe Standard ISO 9459-2 is a standard for the characterization of thermal performance of domestic water heating systems without auxiliary heating. In this study, 18 domestic water heating thermosiphon systems have been tested according to this international standard. The objective of the paper is to carry out a comparative analysis of the results obtained in these systems as a function of their volume and type of heat exchanger (tubular and double jacket). A comparative analysis of systems performance will be carried out by calculating the performance without thermal loss (a1/A) and solar fraction fSOL in different reference locations for different volume/area ratios. Also, a comparative analysis of systems performance and solar fraction will be carried out at different locations between a tubular heat exchanger tank and a double jacket heat exchanger tank. The different values obtained will be compared for the storage tank’s heat loss coefficient (Us). It will determinate the useful energy (energy with temperature above 45ºC) for the degree of mixing in the storage tank during a draw-off test

Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories

Indexación: Web of ScienceBackground: Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria. Results: In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles. Conclusions: Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.http://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-016-0477-

Energy frictional dissipating algorithm for rigid and ellastic body’s contact problems

An Energy Frictional Dissipating Algorithm (EFDA) for time integration of Coulomb frictional impact–contact problems is presented. Using the Penalty Method, and in the context of a conserving framework, linear and angular momenta are conserved and energy is consistently dissipated. Published formulations were stable, forcing the energy dissipation to be monotonic in order to prevent unstable energy growth. The shortcoming of many was that they were not able to reproduce the real kinematics and dissipation of physical processes, provided by analytical formulations and experiments. EFDA formulates a conserving framework based on a physical energy dissipation estimator. This framework uses an enhanced Penalty contact model based on a spring and a dashpot, enforcing physical frictional energy dissipation, controlling gap vibrations and modifying the velocities and contact forces during each time step. The result is that the dissipated energy, kinematics and contact forces are consistent with the expected physical behavior

Analysing teamwork in higher education: an empirical study on the antecedents and consequences of team cohesiveness

Uno de los factores más importantes del trabajo en equipo es la cohesión entre sus miembros. Sin embargo, escasos trabajos analizan sus antecedentes y consecuencias. El presente estudio utiliza el modelo Input-Process-Output para analizar el impacto de factores individuales y de la tarea sobre la cohesión del equipo, así como la influencia de la cohesión del equipo sobre la eficacia del mismo. En base a una encuesta a 160 alumnos que realizaron trabajos en grupo, los resultados muestran que el grado de cooperación y el comportamiento colaborativo tienen una influencia positiva en la cohesión del equipo, mientras que la carga de trabajo y la complejidad de la tarea tienen una influencia negativa en la misma. Además, la cohesión del equipo influye positivamente en el aprendizaje percibido, la satisfacción con el trabajo en equipo y la calidad esperada. Finalmente, tanto el aprendizaje percibido como la calidad esperada predicen la satisfacción con el trabajo en equipo.One of the most important components of effective teamwork is cohesiveness. However, few empirical studies on the antecedents and consequences of group cohesiveness exist. In response to this gap, the current study draws on the Input-Process-Output model of team effectiveness to investigate the impact of individual and task factors on team cohesiveness, as well as the influence of team cohesiveness on students’ perceived learning, satisfaction with teamwork, and expected quality in the outcome. Based on a survey of 160 undergraduate students who worked in groups, the findings show that cooperativeness and collaborative behaviour have a positive influence on team cohesiveness, while workload and task complexity have a negative influence on it. Additionally, team cohesiveness is positively related to perceived learning, satisfaction with teamwork, and expected quality. Finally, both perceived learning and expected quality predict satisfaction with teamwork

Giving Voice to Women: Social Representations and Experiences of Breastfeeding

Breastfeeding is a central issue in research from a gender perspective. We consider breastfeeding as a biopsychosocial, diverse and plural process, which generates ambivalent experiences in mothers. Our research was aimed to increase the understanding of thoughts and experiences of mothers. Ten women, primiparous and non-primiparous mother, were interviewed at two moments in time. The results showed that the breastfeeding period was shorter than the time recommended by health organizations, the reasons to breastfeed were related to the well-being of their children and women´s social support came from their partners.Breastfeeding is a central issue in research from a gender perspective. We consider breastfeeding as a biopsychosocial, diverse and plural process, which generates ambivalent experiences in mothers. Our research was aimed to increase the understanding of thoughts and experiences of mothers. Ten women, primiparous and non-primiparous mother, were interviewed at two moments in time. The results showed that the breastfeeding period was shorter than the time recommended by health organizations, the reasons to breastfeed were related to the well-being of their children and women´s social support came from their partners

Thermodynamic Limits of the Use of PCM Simultaneously in Photovoltaic Modules and in Building

Permiso obtenido por la institución para subir el documentoThe paper quantifies the thermodynamic limits on the energy and exergy use that would result from the use of PCM in photovoltaic BIPV modules versus not using PCM, by limiting module temperature to 298 K and the thermal energy use in buildings according to a set of hypotheses. The results obtained have been extended to six different climates. The results show that the maximum use of PCM depends heavily on the climate, therefore in hot climates as Seville, Cairo and Nairobi, the improvements in energy efficiency are very important (multiplied from 6 to 9 times), while in cold climates as London and Helsinki, the improvements are not that significant (multiplied from 1.5 to 2 times). The exergetic efficiency improvements range of about 5% for all climates, due to the low operating temperature of the PCM. These materials requirements are significant, ranging between 31 and 193 kg/m2, with thicknesses between 3.9 and 24.2 cm/m2

Experiences for a scientific literacy that promotes environmental justice at different educational levels

La situación medioambiental en el siglo XXI refleja un problema complejo que nos afecta de manera desigual. La educación ambiental requiere de un enfoque socio-científico que amplíe su perspectiva para promover la comprensión de las situaciones reales, y conducir a un posicionamiento fundamentado y crítico de la sociedad para la justicia ambiental. Para conseguirlo, necesitamos una alfabetización científica desde un enfoque Científico, Tecnológico, Social y Ambiental (CTSA). Con este fin, realizamos tres intervenciones de aula en diferentes niveles educativos estructuradas en tres fases: a) distribución de información conceptual; b) reflexión a través del pensamiento crítico, y c) elaboración de propuestas para solucionar los problemas tratados. En cada propuesta, se presentan contenidos relativos a problemáticas de contaminación y se relacionaron con los problemas de salud humana y ambiental. El análisis de estas actividades se realizó a partir de las notas de los comentarios más relevantes, dibujos y/o un trabajo. Todo ello nos indica que su diseño es adecuado para enlazar la distribución de conocimientos, con la participación en la toma de decisiones, elementos clave para el desarrollo de una educación para la justicia ambientalThe environmental situation in the 21st century reflects a complex problem that affects us unequally. Environmental education requires a socio-scientific approach that broadens this perspective in order to promote the understanding of real situations, and leads to an informed and critical positioning of society for Environmental Justice. To do so, we need a scientific literacy from a Scientific, Technological, Social and Environmental (STSE) approach. To this aim, we carried out three classroom involvements in different educational levels structured in three phases: (a) Distribution of little known conceptual information about the problem; (b) reflection about it the promotion of critical thinking, and c) preparation of proposals to solve the problem. In each proposal, content related to pollution issues was presented and related to human and environmental health problems. The analysis of these activities was carried out taking into account the most relevant notes from conversation, drawings and/or class works. All data indicates that their design is adequate to link the knowledge distribution with students’ participation in decision-making: key elements for the development of an education for environmental justic