514 research outputs found
SAFT-γ force field for the simulation of molecular fluids: 4. A single-site coarse-grained model of water applicable over a wide temperature range
In this work, we develop coarse-grained (CG) force fields for water, where the effective CG intermolecular interactions between particles are estimated from an accurate description of the macroscopic experimental vapour-liquid equilibria data by means of a molecular-based equation of state. The statistical associating fluid theory for Mie (generalised Lennard-Jones) potentials of variable range (SAFT-VR Mie) is used to parameterise spherically symmetrical (isotropic) force fields for water. The resulting SAFT-γ CG models are based on the Mie (8-6) form with size and energy parameters that are temperature dependent; the latter dependence is a consequence of the angle averaging of the directional polar interactions present in water. At the simplest level of CG where a water molecule is represented as a single bead, it is well known that an isotropic potential cannot be used to accurately reproduce all of the thermodynamic properties of water simultaneously. In order to address this deficiency, we propose two CG potential models of water based on a faithful description of different target properties over a wide range of temperatures: our CGW1-vle model is parameterised to match the saturated-liquid density and vapour pressure; our other CGW1-ift model is parameterised to match the saturated-liquid density and vapour-liquid interfacial tension. A higher level of CG corresponding to two water molecules per CG bead is also considered: the corresponding CGW2-bio model is developed to reproduce the saturated-liquid density and vapour-liquid interfacial tension in the physiological temperature range, and is particularly suitable for the large-scale simulation of bio-molecular systems. A critical comparison of the phase equilibrium and transport properties of the proposed force fields is made with the more traditional atomistic models
Determination of optimal thermal inertia of building materials for housing in different Chilean climate zones
In recent years, several studies on residential energy consumption and new strategies for its reduction have been carried out. The literature reports that thermal inertia can have an influence on energy demand and, to a greater extent, on the thermal comfort of the buildings. The performance of thermal inertia in buildings located in different regions or countries has been analysed, comparing structures or materials having high and low thermal inertia through energy simulations or empirical studies. However, the optimal thermal inertia of a building according to different climates has not been established. In this study, optimum values were determined for the different properties that define thermal inertia (thermal conductivity, specific heat capacity, and density) that would allow to maintain the indoor annual operative temperature within the thermal comfort range (18–24°C) of a standard dwelling. Energy simulations were carried out in DesignBuilder using climate data from 10 cities in different Chilean climate zones. The results show the minimum thermal conductivity as optimal regardless of climate (0.025 and 0.03 W/(m∙K)), while the optimal density ranges fluctuate between 1800 and 2500 kg/m3 varying according to the climate zone. Finally, it was determined that specific heat capacity was not influential in the thermal comfort of the analysed dwelling
A corresponding-states framework for the description of the Mie family of intermolecular potentials
The Mie (λr, λa) intermolecular pair potential has been suggested as an alternative to the traditional Lennard–Jones (12–6) potential for modelling real systems both via simulation and theory as its implementation leads to an accuracy and flexibility in the determination of thermophysical properties that cannot be obtained when potentials of fixed range are considered. An additional advantage of using variable-range potentials is noted in the development of coarse-grained models where, as the superatoms become larger, the effective potentials are seen to become softer. However, the larger number of parameters that characterise the Mie potential (λr, λa, σ, ϵ) can hinder a rational study of the particular effects that each individual parameter have on the observed thermodynamic properties and phase equilibria, and higher degeneracy of models is observed. Here a three-parameter corresponding states model is presented in which a cohesive third parameter α is proposed following a perturbation expansion and assuming a mean-field limit. It is shown that in this approximation the free energy of any two Mie systems sharing the same value of α will be the same. The parameter α is an explicit function of the repulsive and attractive exponents and consequently dictates the form of the intermolecular pair potential. Molecular dynamics simulations of a variety of Mie systems over a range of values of α are carried out and the solid–liquid, liquid–vapour and vapour–solid phase boundaries for the systems considered are presented. Using the simulation data, we confirm that systems of the same α exhibit conformal phase behaviour for the fluid-phase properties as well as for the solid–fluid boundary, although larger differences are noted in the solid region; these can be related to the approximations in the definition of the parameter. Furthermore, it is found that the temperature range over which the vapour–liquid envelope of a given Mie system is stable follows a linear dependency with α when expressed as the ratio of the critical–point temperature to the triple–point temperature. The limit where potentials of the Mie family will not present a stable fluid envelope is predicted in terms of the parameter α and the result is found to be in excellent agreement with previous studies. This unique relation between the fluid range and the cohesive parameter α is shown to be useful to limit the pairs of Mie exponents that can be used in coarse-grained potentials to treat real systems in order to obtain temperature ranges of stability for the fluid envelope consistent with experiment
Clinical considerations on the posology of direct oral anticoagulants
Los anticoagulantes dicumarínicos han demostrado su eficacia en pacientes con fibrilación auricular no valvular. Sin embargo, presentan desventajas como la necesidad de ajustar la dosis y la interacción con fármacos y alimentos. Por su parte, los anticoagulantes orales de acción directa se presentan como una alternativa eficaz y segura con un manejo clínico menos complejo. Existe un considerable debate sobre los criterios de selección de las pautas posológicas de los anticoagulantes orales de acción directa. Las diferencias entre ellos y sus pautas de administración han despertado dudas sobre los criterios de selección clínicos, farmacocinéticos y farmacodinámicos que avalan dicha posología. Esta revisión analiza de forma crítica las evidencias disponibles y su impacto en la selección final del esquema posológic
Genetic uniqueness of Cryptosporidium parvum from dairy calves in Colombia
Fecal specimens from 432 pre-weaned calves younger than 35 days were collected over a 2-year period (2010–2012) from 74 dairy cattle farms in the central area of Colombia. These samples were microscopically examined for the presence of Cryptosporidium oocysts, and positive specimens were selected for molecular examination. Microscopy revealed that 115 calves (26.6%) from 44 farms (59.5%) tested positive. Oocyst shedding was recorded in calves aged 3-day-old onwards, although the infection rate peaked at 8–14 days (40.7%). Infection rates were higher in diarrheic (52.2%) than in non-diarrheic calves (19.9%) (p < 0.0001, ¿2), and infected calves had up to seven times more probability of having diarrhea than non-infected calves. Cryptosporidium species and subtypes were successfully identified in 73 samples from 32 farms. Restriction and sequence analyses of the SSU rRNA gene revealed C. parvum in all but two isolates identified as Cryptosporidium bovis. Sequence analyses of the 60-KDa glycoprotein (gp60) gene revealed eight subtypes within the IIa family. An unusual subtype (IIaA18G5R1) was the most prevalent and widely distributed (more than 66% specimens and 68% farms) while the subtype most frequently reported in cattle worldwide (IIaA15G2R1) was found in less than 13% of specimens and 16% farms. The remaining subtypes (IIaA16G2R1, IIaA17G4R1, IIaA20G5R1, IIaA19G6R1, IIaA20G6R1, and IIaA20G7R1) were restricted to 1–3 farms. This is the first large-sample size study of Cryptosporidium species and subtypes in Colombia and demonstrates the genetic uniqueness of this protozoan in cattle farms in this geographical area
Influencia del complejo de embalses Mequinenza-Ribarroja-Flix (Río Ebro) en la morfología del cauce situado aguas abajo
Cuando se construye un embalse, el cauce que se sitúa aguas abajo de la presa suele sufrir alteraciones de diversa índole fundamentalmente porque se modifican las características de su caudal líquido y sólido. En este trabajo se analiza el tipo de alteraciones que se han dado en el río Ebro a lo largo de un tramo de aproximadamente 40 km de longitud que se localiza aguas abajo del complejo de embalses de Mequinenza-Ribarroja-Flix. Las principales alteraciones reconocidas son: ausencia de sedimentación, degradación de barras en los puntos más próximos a la presa, revegetación de barras y orillas, y pérdida de sedimentos finos con el consiguiente acorazamiento del lecho y de las barras. Dos factores han propiciado tales modificaciones, que han conducido prácticamente a la estabilidad del cauce, son la presencia de abundantes gravas y una elevada tasa de asentamiento vegetal en la sección. Asimismo se analiza la evolución morfosedimentaria del río desde 1927 hasta la fecha de construcción de estos embalses, años sesenta, y se determina que dicha evolución estaba controlada por episodios de crecidas catastróficas. En el período de estudio se registraron dos eventos de esta naturaleza. En este trabajo se describen también tanto las consecuencias derivadas de los mismos, como el papel tan destacado que jugó en su desarrollo un afluente del Ebro, el río Ciurana. Finalmente, los resultados obtenidos referentes a la dinámica fluvial, anterior y posterior a la construcción de los embalses, se aplican a la evolución sedimentaria del Delta del Ebro, formado a poca distancia del tramo estudiado
Comentario de interpretación y aplicación de la normativa argentina: Resolución ANAC N° 527/2015
The Civil Aviation National Administration (ANAC), Aviation Authority in Argentina, has regulated the operation of the Unmanned Air Vehicles (UAV), conmmonly known as ‘drones’- establishing clear and precise rules for holders and operators. In this way, the argentinian regulation, tends to make possible the development and the evolution of a booming industry and market guaranteeing the safety of all users of the civil aviation system. In this chapter, the mentioned regulation is going to be analyzed in detail.La Administración Nacional de Aviación Civil (ANAC), Autoridad Aeronáutica en la República Argentina, ha reglamentado recientemente la operación de los Vehículos Aéreos No Tripulados (VANT), conocidos popularmente como “drones”, estableciendo reglas claras y precisas para los explotadores y operadores. Así, la normativa argentina, tiende a posibilitar el desarrollo y la evolución de un mercado y una industria pujantes, a la vez que a garantizar la seguridad operacional de todos los usuarios del sistema de aviación civil. En este capítulo, se analizará en detalle el contenido de la referida reglamentación
INFLUENCIA DEL TIPO DE CACAO (Theobroma cacao L.) EN LAS CARACTERÍSTICAS DEL FERMENTO Y SECADO
The influence of the type of cacao (Theobroma cacao L.) on the characteristics of fermented cacao in wood boxes and dried in a greenhouse-type solar dryer was evaluated, of the clones H12, H13, RIM 44, RIM 88, RIM 105, CARMELO, CRIOLLO INIFAP and LAGARTO, which were processed the day after collection. The fermentation was carried out for five days, with removal of the fermented pulp every 24 h. The drying was done for five days. The physical characteristics of the grain were measured, as well as the chemical quality profile. The fermentation index presented an increase as the fermentative process advanced, reaching 45 to 58 % on day 2, and values above 95 % on day 5. The fermentation time in wooden boxes, of the grains of clones RIM 44, RIM 88, RIM 105, CARMELO and CRIOLLO INIFAP, is four days. The drying to 7 % moisture in a greenhouse-type drier lasted five days in grains of clones RIM 44, RIM 88, RIM 105, CARMELO and CRIOLLO INIFAP. Under these conditions, the grains of clones H12, H13 and LAGARTO were dried in six days. During drying, the moisture, acidity, tannins and cotyledon proteins decreased, but the pH increased. In conclusion, the physical-chemical profile of the dry grain varied in function of the clones evaluated, which presented great potential in the chocolate industry due to their high fat content and good antioxidant capacityPara evaluar la influencia del tipo de cacao (Theobroma cacao L.) sobre características del cacao fermentado en cajas de madera y secado en secador solar tipo invernadero; de los clones H12, H13, RIM 44, RIM 88, RIM 105, CARMELO, CRIOLLO INIFAP y LAGARTO, fueron procesados al siguiente día de la recolección. La fermentación se realizó durante cinco días, con remociones de la masa fermentante cada 24 h. El secado se hizo por cinco días. Al grano se le midió las características físicas, así como el perfil de calidad química. El índice de fermentación presentó un incremento a medida que transcurrió el proceso fermentativo, alcanzando de 45 a 58 % en el día 2 y valores mayores a 95 % en el día 5. El tiempo de fermentación, en cajas de madera, de los granos de los clones RIM 44, RIM 88, RIM 105, CARMELO, CRIOLLO INIFAP es de cuatro días. El secado a humedad de 7 % en secador tipo invernadero tuvo una duración de cinco días en los granos de los clones RIM 44, RIM 88, RIM 105, CARMELO y CRIOLLO INIFAP. En estas condiciones los granos de los clones H12, H13 y LAGARTO fueron secados en seis días. En el secado disminuyeron la humedad, acidez, taninos, proteínas del cotiledón, pero se incrementó el pH. En conclusión, el perfil físico-químico del grano seco varió en función de los clones evaluados, los cuales presentan una gran potencial en la industria chocolatera por su alto contenido de grasa y buena capacidad antioxidante
La educacion ambiental (ea) como Herramienta de la responsabilidad social (rs)
Las estrategias educativas actuales no muestran indicadores donde se destaque el papel de la Educación Ambiental (EA) en el enriquecimiento de valores para la convivencia colectiva, y en este aspecto, el cuidado de los recursos. Es aquí donde se hace necesario el enfoque prioritario de la materia en entidades destinadas a la educación, para la formación de individuos capaces de asumir, plantear, desarrollar y solventar la problemática ambiental y dar paso al desarrollo humano y al desarrollo sostenible. En materia de desarrollo y formación, los procesos de enseñanza - aprendizaje de la EA han sido abordados por la relevancia que representa pero no con la suficiente seriedad que ella merece. En el presente artículo se analiza la EA como proceso y herramienta de reproducción cultural y formación de ciudadanos críticos que contribuyan a la gestión de la Responsabilidad Social (RS). Para ello, se hace una recopilación de información académica y científica que permite profundizar en el propósito que se plantea, estableciéndose las relaciones que subyacen de cada uno de los contenidos epistémicos analizados.AbstractThe current educational strategies do not show indicators which highlight the role of environmental education (EE) in the enrichment of values for the collective coexistence, and in this respect, for the care of resources. This is where the subject priority approach becomes necessary in educational institutions for the education of individuals capable of assuming, proposing, developing and solving environmental problems and giving way to human development and sustainable development. As far as development and education, the EE teaching - learning Luna Azul ISSN 1909-2474 No. 35, julio - diciembre 2012 ©Universidad de Caldas revista.luna.azúl. 2012; 35: 94-115 processes have been addressed because of the relevance they have but not with the seriousness they deserve. This article analyzes EE as a process and a tool of cultural reproduction and education of critical citizens who contribute to the management of Social Responsibility (SR). To achiueve this goal, collection of scholarly and scientific information that allows deepening in the proposed purpose is carried out, establishing relationships that underlie each of the epistemic contents analyzed.Las estrategias educativas actuales no muestran indicadores donde se destaque el papel de la Educación Ambiental (EA) en el enriquecimiento de valores para la convivencia colectiva, y en este aspecto, el cuidado de los recursos. Es aquí donde se hace necesario el enfoque prioritario de la materia en entidades destinadas a la educación, para la formación de individuos capaces de asumir, plantear, desarrollar y solventar la problemática ambiental y dar paso al desarrollo humano y al desarrollo sostenible. En materia de desarrollo y formación, los procesos de enseñanza - aprendizaje de la EA han sido abordados por la relevancia que representa pero no con la suficiente seriedad que ella merece. En el presente artículo se analiza la EA como proceso y herramienta de reproducción cultural y formación de ciudadanos críticos que contribuyan a la gestión de la Responsabilidad Social (RS). Para ello, se hace una recopilación de información académica y científica que permite profundizar en el propósito que se plantea, estableciéndose las relaciones que subyacen de cada uno de los contenidos epistémicos analizados.AbstractThe current educational strategies do not show indicators which highlight the role of environmental education (EE) in the enrichment of values for the collective coexistence, and in this respect, for the care of resources. This is where the subject priority approach becomes necessary in educational institutions for the education of individuals capable of assuming, proposing, developing and solving environmental problems and giving way to human development and sustainable development. As far as development and education, the EE teaching - learning Luna Azul ISSN 1909-2474 No. 35, julio - diciembre 2012 ©Universidad de Caldas revista.luna.azúl. 2012; 35: 94-115 processes have been addressed because of the relevance they have but not with the seriousness they deserve. This article analyzes EE as a process and a tool of cultural reproduction and education of critical citizens who contribute to the management of Social Responsibility (SR). To achiueve this goal, collection of scholarly and scientific information that allows deepening in the proposed purpose is carried out, establishing relationships that underlie each of the epistemic contents analyzed
Un Modelo Pedagógico Para La Educación Ambiental Desde La Perspectiva De La Modificabilidad Estructural Cognitiva
El artículo tiene como objetivo formular un modelo pedagógico para la educación ambiental atendiendo a la urgencia de crear mecanismos e instrumentos que contribuyan con el desarrollo sostenible del planeta. Para ello, se abordan los principales aspectos teóricos sobre educación, pedagogía, modelos pedagógicos y corrientes de la educación ambiental. Para el diseño se ha analizado e incorporado en el modelo la teoría de la Modificabilidad Estructural Cognitiva y la Experiencia de Aprendizaje Mediado del Reueven Feuerstein. El diseño responde a las exigencias de la sociedad actual y a una perspectiva del medio ambiente desde diversos enfoques. Asimismo, plantea un rol del maestro y del educando como agentes dinamizadores de la construcción del conocimiento y lamodificación de conductas responsables con el medio ambiente.AbstractThe objective of this article is to formulate a pedagogical model for environmental education in response to the urgent need to create mechanisms and instruments that contribute to global sustainable development. To do so, the main theoretical aspects of education, pedagogy, pedagogical models and trends in environmental education are addressed. The Structural Cognitive Modifiability and Mediated Learning Experience Reueven Feuerstein theories have been analyzed and incorporated in the design. The design responds to the demands of modern society and to an environmental perspective from different approaches. Likewise, the role of teacher and the role of the learner as revitalizing agents of knowledge construction and modification of responsible behaviors with the environment are described.El artículo tiene como objetivo formular un modelo pedagógico para la educación ambiental atendiendo a la urgencia de crear mecanismos e instrumentos que contribuyan con el desarrollo sostenible del planeta. Para ello, se abordan los principales aspectos teóricos sobre educación, pedagogía, modelos pedagógicos y corrientes de la educación ambiental. Para el diseño se ha analizado e incorporado en el modelo la teoría de la Modificabilidad Estructural Cognitiva y la Experiencia de Aprendizaje Mediado del Reueven Feuerstein. El diseño responde a las exigencias de la sociedad actual y a una perspectiva del medio ambiente desde diversos enfoques. Asimismo, plantea un rol del maestro y del educando como agentes dinamizadores de la construcción del conocimiento y lamodificación de conductas responsables con el medio ambiente.AbstractThe objective of this article is to formulate a pedagogical model for environmental education in response to the urgent need to create mechanisms and instruments that contribute to global sustainable development. To do so, the main theoretical aspects of education, pedagogy, pedagogical models and trends in environmental education are addressed. The Structural Cognitive Modifiability and Mediated Learning Experience Reueven Feuerstein theories have been analyzed and incorporated in the design. The design responds to the demands of modern society and to an environmental perspective from different approaches. Likewise, the role of teacher and the role of the learner as revitalizing agents of knowledge construction and modification of responsible behaviors with the environment are described
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