Modelación senosoidal: un experiencia en el laboratorio virtual de ciencias

En este trabajo se concibe a las prácticas de modelación como una actividad que articula dos entidades con la finalidad de intervenir en una de ellas, lo modelado, a partir de la otra, llamada modelo. Elaboramos un diseño de aprendizaje basado en la modelación de fenómenos por modelos senosoidales con la intención de aportar elementos para la caracterización de la construcción de la red de lo senosoidal. Las características de este diseño son la experimentación virtual, la interacción con datos, gráficas y ecuaciones algebraicas y/o diferenciales que modelan fenómenos periódicos, así como el ajuste de los datos con las herramientas tecnológicas que henos diseñado para este fin

A phenomenological explanation of the autoignition propagation under HCCI conditions

[EN] A phenomenological explanation about the autoignition propagation under HCCI conditions is developed in this paper. To do so, diffusive effects from the burned zones to the fresh mixture, pressure waves based effects and expansion effects caused by combustion are taken into account. Additionally, different Damkohler numbers have been defined and evaluated in order to characterize the phenomenon and quantify the relevance of each effect. The theoretical explanation has been evaluated by means of chemiluminescence measurements performed in a Rapid Compression Expansion Machine (RCEM), which allow to estimate the velocity of propagation of the autoignition front. The results showed that under HCCI conditions the autoignition propagation is controlled, in general, by the pressure waves established in the combustion chamber, since the characteristic time of the autoignition propagation is too short to assume the absence of pressure gradients in the chamber. Thus, the thermodynamic conditions reached behind the pressure wave promote the autoignition and explain the high propagation velocities associated to the reaction front. Besides, the results also showed that the contribution of diffusive phenomena on the propagation is negligible, since the characteristic time of diffusion is too long compared to the characteristic time of the autoignition propagation. Finally, the experimental measurements showed that the autoignition propagation is affected by a really relevant cycle-to-cycle variation. The turbulence generated by the combustion has, by definition, an aleatory behavior, leading to random heterogeneity distribution and, therefore, to somewhat random autoignition propagation.The authors would like to thank different members of the CMT-Motores TTrmicos team of the Universitat Politecnica de Valencia for their contribution to this work. The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lopez-Pintor (grant FPU13/02329). This research has been partially funded by FEDER and the Spanish Government through project TRA2015-67136-R.Desantes, J.; López, JJ.; García-Oliver, JM.; López-Pintor, D. (2017). A phenomenological explanation of the autoignition propagation under HCCI conditions. Fuel. 206:43-57. https://doi.org/10.1016/j.fuel.2017.05.075S435720

Experimental validation and analysis of seven different chemical kinetic mechanisms for n-dodecane using a Rapid Compression-Expansion Machine

[EN] Seven different chemical kinetic mechanisms for n-dodecane, two detailed and five reduced, have been evaluated under Engine Combustion Network (ECN) thermodynamic conditions by comparison to experimental measurements in a Rapid Compression-Expansion Machine (RCEM). The target ECN conditions are imposed at Top Dead Center (TDC), which cover a wide range of temperatures (from 850 K to 1000 K), oxygen molar fractions (0.21 and 0.15) and equivalence ratios (0.8, 0.9 and 1), while the pressure is fixed to keep a constant density at TDC equal to 22.8 kg/m(3). The results obtained have been used to validate the chemical kinetic simulations, which have been performed with CHEMKIN, by comparing both cool flames and high temperature ignition delays, as well as the heat released in each stage of the combustion process in case of having a two-stage ignition pattern. The experimental results show good agreement with the chemical kinetic simulations. In fact, the mean relative deviation in ignition delay between experiments and simulations among all the chemical mechanisms is equal to 18.0% (3 CAD) for both cool flames and high temperature ignition. In general, closer correspondence has been obtained for the ignition delay referred to the high-temperature stage of the process, being the cool flames phenomenon more difficult to reproduce. Moreover, the differences between the reduced mechanisms and the most detailed one have been analyzed, concluding that the enhanced specific reaction rates of the most reduced mechanisms cause differences not only on the ignition delays, but also on the Negative Temperature Coefficient (NTC) behavior and on the heat released during cool flames. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lopez-Pintor (grant FPU13/02329). This study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the COMEFF (TRA2014-59483-R) project.Desantes, J.; López, JJ.; García-Oliver, JM.; López-Pintor, D. (2017). Experimental validation and analysis of seven different chemical kinetic mechanisms for n-dodecane using a Rapid Compression-Expansion Machine. Combustion and Flame. 182:76-89. https://doi.org/10.1016/j.combustflame.2017.04.004S768918

The Role of Mitochondria in Brain Aging and the Effects of Melatonin

Melatonin is an endogenous indoleamine present in different tissues, cellular compartments and organelles including mitochondria. When melatonin is administered orally, it is readily available to the brain where it counteracts different processes that occur during aging and age-related neurodegenerative disorders. These aging processes include oxidative stress and oxidative damage, chronic and acute inflammation, mitochondrial dysfunction and loss of neural regeneration. This review summarizes age related changes in the brain and the importance of oxidative/nitrosative stress and mitochondrial dysfunction in brain aging. The data and mechanisms of action of melatonin in relation to aging of the brain are reviewed as well

Identificación de factores que influyen en la intención emprendedora de las personas en situación de discapacidad: Aproximación a partir de una revisión sistemática de literatura

Currently, there is a compelling need to understand the factors influencing the success or failure of new businesses, particularly those created by people with disabilities. This paper, thus, aims to identify the main variables reported in previous studies into entrepreneurship and disability and analyse how they can be used to strengthen the entrepreneurial processes of this population. The methodology used in this study included two phases: (1) a systematic literature review to collect high-quality investigations and extract relevant variables from them, and (2) a bibliometric analysis to present the results. Our main findings reveal a growing interest in investigating issues related to entrepreneurship and the determinants of success or failure among entrepreneurs with disabilities. Although formal and informal institutions have not been extensively studied in relation to the entrepreneurial intention of people with disabilities, they do have an impact on the entrepreneurial performance of this group of individuals.Actualmente, existe la necesidad de comprender los factores asociados con el éxito o el fracaso de los nuevos negocios creados por individuos, particularmente personas con discapacidad. Este trabajo, por tanto, tiene como objetivo identificar las principales variables que han sido reportadas en estudios previos sobre emprendimiento y discapacidad y analizar cómo pueden ser utilizadas para fortalecer los procesos emprendedores de esta población. La metodología consta de dos fases: (1) una revisión sistemática de la literatura para recopilar diferentes investigaciones de calidad y extraer de ellas las diferentes variables (2) un análisis bibliométrico que nos permitió presentar los resultados. Los principales hallazgos muestran un creciente interés en investigar temas relacionados con el espíritu empresarial y los factores que conducen al éxito o fracaso de los empresarios con discapacidad. Si bien las instituciones formales e informales no han sido ampliamente estudiadas en la intención emprendedora de las personas con discapacidad, sí tienen un impacto en el desempeño emprendedor de este grupo de personas

Ex Vivo Generation and Characterization of Human Hyaline and Elastic Cartilaginous Microtissues for Tissue Engineering Applications

This study was supported by grants FIS PI17/0393 and PI20/0318 from the Spanish Ministry of Science and Innovation (Instituto de Salud Carlos III); grants PI-0257-2017 and PE-0395- 2019 from Consejería de Salud y Familias, Junta de Andalucía, España; grant P18-RT-5059 from Consejería de Economía, Conocimiento, Empresas y Universidad, Junta de Andalucía, España; grant A-CTS-498-UGR18 from the University of Granada and Junta de Andalucía, España. It was co-funded by FEDER-ERDF funds.Authors are grateful to Fabiola Bermejo Casares for the technical histological assistance. Special thanks to Ariane Ruyffelaert for her critical review and proofreading service. This work forms part of the doctoral thesis conducted by David Sánchez Porras (Doctoral Program in Biomedicine, Doctoral School, University of Granada, Spain).Considering the high prevalence of cartilage-associated pathologies, low self-repair capacity and limitations of current repair techniques, tissue engineering (TE) strategies have emerged as a promising alternative in this field. Three-dimensional culture techniques have gained attention in recent years, showing their ability to provide the most biomimetic environment for the cells under culture conditions, enabling the cells to fabricate natural, 3D functional microtissues (MTs). In this sense, the aim of this study was to generate, characterize and compare scaffold-free human hyaline and elastic cartilage-derived MTs (HC-MTs and EC-MTs, respectively) under expansion (EM) and chondrogenic media (CM). MTs were generated by using agarose microchips and evaluated ex vivo for 28 days. The MTs generated were subjected to morphometric assessment and cell viability, metabolic activity and histological analyses. Results suggest that the use of CM improves the biomimicry of the MTs obtained in terms of morphology, viability and extracellular matrix (ECM) synthesis with respect to the use of EM. Moreover, the overall results indicate a faster and more sensitive response of the EC-derived cells to the use of CM as compared to HC chondrocytes. Finally, future preclinical in vivo studies are still needed to determine the potential clinical usefulness of these novel advanced therapy products.Instituto de Salud Carlos III Spanish Government FIS PI17/0393 PI20/0318Junta de Andalucia PI-0257-2017 PE-03952019Junta de Andalucia P18-RT-5059University of Granada A-CTS-498-UGR18Junta de Andalucia A-CTS-498-UGR18FEDER-ERDF fund

As mais antigas marmotas da Europa: Estudo métrico dos fósseis de Marmota do Plistocénico Inferior e Medio das jazidas de Sierra de Atapuerca (Burgos, Espanha)

ABSTRACT: The oldest European remains of marmots (Genus Marmota) are 0.8 my old and come from the site of Gran Dolina, Atapuerca. Dental measurements from the specimens recovered at Gran Dolina are compared with other Early Pleistocene fossil marmots from Croatia; as well as a set of Middle and Late Pleistocene marmots from France and Italy and Middle Pleistocene fossils from other sites at Sierra de Atapuerca. These fossils are also compared with four species of modern marmots, including? an extensive sample of Marmota marmota. Plotting the length of each dental piece of Gran Dolina versus its width, less than 25% of the Early Pleistocene specimens fall into the variability of Marmota marmota, meanwhile the Middle Pleistocene fossils fall within (or extremely close) to its variability. These Early Pleistocene marmots cannot be metrically assigned to the extant alpine marmot.RESUMO: Os vestígios europeus mais antigos de marmotas (género Marmota) têm 0.8 milhões de anos e provêm da Gran Dolina, Atapuerca. As medições realizadas em peças dentárias de marmotas fósseis encontrados em Gran Dolina são comparadas com exemplares de marmotas provenientes do Pleistocénico inferior da Croácia e do Pleistocénico Médio e Superior de França e Itália, bem como com exemplares encontrados em outras localidades do Pleistocénico médio da Serra de Atapuerca. Estes fósseis também são comparados com quatro espécies de marmotas modernas, incluindo uma extensa amostra de Marmota marmota. Ao plotar o comprimento de cada peça dentária de Gran Dolina face a sua largura, menos do 25% dos exemplares do Pleistocénico Inferior caem dentro da variabilidade existente em Marmota marmota. Os exemplares do Pleistocénico Médio estão dentro (ou extremamente próximos) da variabilidade de Marmota marmota. Os exemplares de marmotas do Pleistocénico Inferior de Gran Dolina não podem ser metricamente atribuídos à marmota alpina.info:eu-repo/semantics/publishedVersio

Estabilidad de las sales de quitosana, obtenidas por secado de aspersión, derivadas de quitina de langosta

Aim. The objective of this work was to develop and validate a method for determining the degree of molar deacetylation of chitosan acetate and chitosan lactate, as well as to study the stability of both salts. Materials and Methods. A spectrophotometric method was validated according to internationally-estab­lished quantitative techniques. Three industrial batches of chitosan acetate and chitosan lactate, obtained by spray drying, were stored under shelf life conditions for twelve months. Organoleptic characteristics, the degree of molar deacetylation, pH, loss on drying and microbiological count were determined at the beginning and end of the study. Results and Discussion. The statistical data proved that the two methods complied with international standards for the validation of analytical techniques. It was shown that the procedures developed were linear, specific, precise and accurate, so they can be used for the purposes of quality control and stability study of the polymer salts. Salts remained in powder form, with a light-yellow to dark-yellow coloration. Values of loss on drying (2.5 - 5.2 %) of chitosan salt using acetic or lactic acid, as a solvent, indicated the good quality of spray-dried particles of chitosan. Similar behavior was obtained regarding pH. The two salts stayed within the parameters that determine their quality, both in the initial stage and after twelve months at room temperature. Conclusion: Spray drying chitosan acetate and chitosan lactate, stored at room temperature in a dry place, in double polyethylene bags and multilayer paper bags, kept their physical, chemical and microbiological characteristics for a period of twelve months.Objetivos. Desarrollar y validar un método para la determinación del grado de desacetilación molar del acetato de quitosana y lactato de quitosana, y realizar el estudio de estabilidad de ambas sales. Material y Métodos. Un método espectrofotométrico fue validado según lo establecido internacional­mente para técnicas cuantitativas. Tres lotes industriales de acetato de quitosana y lactato de quitosana, obtenidos mediante secado por aspersión, fueron almacenados bajo condiciones de vida de estante du­rante doce meses. Se determinaron las características organolépticas, grado de desacetilación molar, pH, pérdida por desecación y el conteo microbiológico al inicio y final del estudio. Resultados y Discusión. El análisis estadístico demostró que ambos métodos cumplieron con los parámetros internacionales establecidos. Se demostró que los procedimientos desarrollados fueron lin­eales, específicos, precisos y exactos, por lo que pueden ser empleados en el control de calidad y estudio de estabilidad. Las sales se mantuvieron en forma de polvo de coloración amarillo claro u oscura. Los valores de pérdidas por desecación (2,5 – 5,2 %), para el acetato y lactato de quitosana, demuestran la cal­idad de las partículas de quitosana obtenidas por secado por aspersión. Un comportamiento similar fue obtenido para el pH. Las dos sales mantuvieron los parámetros que determinan su calidad, transcurridos los doce meses a temperatura ambiente. Conclusión: El acetato y el lactato de quitosana, almacenados a temperatura ambiente y en lugares secos, en bolsas dobles de polietileno y sacos de papel multicapas, conservan durante doce meses sus características físicas, químicas y microbiológicas

Algunos aportes al diagnóstico del síndrome de insuficienci arterial Vertebrobasilar extracraneal. Some contributions to the diagnosis of arterial, vertebrobasilar and extracranial insufficiency syndrome

Se estudian 280 pacientes atendidos en la consulta de patología vestibular del Hospital Universitario "Abel Santamaría" de Pinar del Río entre enero de 1998 y julio de 1999, por presentar vértigos. En la totalidad de los casos se utiliza un cuestionario con su código de calificación para identificar de manera rápida y eficaz el vértigo de origen cervical. Una vez establecido el diagnóstico de síndrome de insuficiencia arterial vertebrobasilar extracraneal en 100 pacientes, se estudian en cada uno de ellas las siguientes variantes: síntomas más representativos, edad y sexo, ocupación y alteración cervical causal. Se expone asimismo, el relativo valor diagnóstico de los Rx de columna cervical y el error de considerar la edad como un parámetro confiable para el diagnóstico cuando en cualquier etapa de la vida existen causas cervicales capaces de desencadenar el cuadro vertiginoso. DeCS: ENFERMEDAD DE MENIERE. ABSTRACT A sample of 280 patients suffering from dizziness attended the vestibular pathology service of Abel Santamaría Hospital between January 1998 and July 1999 is studied. A questionnaire with a scoring system for the rapid and effective of identification of dizziness of cervical nature is used. When the extracranial vertebrobasilar arterial insufficiency syndrome in 100 patients is established, the following variables are studied: the most representative symptoms, age and sex, occupation and casual cervical disorder, likewise, it is considered the relative diagnosis value of x - rays of the cervical column and the error in considering age as a reliable parameter in diagnosis taking into account that in very life stage there are cervical causes that may be able to give arousal to the vertiginous event. DeCS: MENIERE´S DISEASE

Algunos aportes al diagnóstico del síndrome de insuficienci arterial Vertebrobasilar extracraneal. Some contributions to the diagnosis of arterial, vertebrobasilar and extracranial insufficiency syndrome

Se estudian 280 pacientes atendidos en la consulta de patología vestibular del Hospital Universitario "Abel Santamaría" de Pinar del Río entre enero de 1998 y julio de 1999, por presentar vértigos. En la totalidad de los casos se utiliza un cuestionario con su código de calificación para identificar de manera rápida y eficaz el vértigo de origen cervical. Una vez establecido el diagnóstico de síndrome de insuficiencia arterial vertebrobasilar extracraneal en 100 pacientes, se estudian en cada uno de ellas las siguientes variantes: síntomas más representativos, edad y sexo, ocupación y alteración cervical causal. Se expone asimismo, el relativo valor diagnóstico de los Rx de columna cervical y el error de considerar la edad como un parámetro confiable para el diagnóstico cuando en cualquier etapa de la vida existen causas cervicales capaces de desencadenar el cuadro vertiginoso. DeCS: ENFERMEDAD DE MENIERE. ABSTRACT A sample of 280 patients suffering from dizziness attended the vestibular pathology service of Abel Santamaría Hospital between January 1998 and July 1999 is studied. A questionnaire with a scoring system for the rapid and effective of identification of dizziness of cervical nature is used. When the extracranial vertebrobasilar arterial insufficiency syndrome in 100 patients is established, the following variables are studied: the most representative symptoms, age and sex, occupation and casual cervical disorder, likewise, it is considered the relative diagnosis value of x - rays of the cervical column and the error in considering age as a reliable parameter in diagnosis taking into account that in very life stage there are cervical causes that may be able to give arousal to the vertiginous event. DeCS: MENIERE´S DISEASE