4,460 research outputs found

    Obtaining the fatigue laws of bituminous mixtures from a strain sweep test: effect of temperature and aging

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    Fatigue is associated with the deterioration caused by applying repeated loads, and is affected by temperature or aging. Generally, time sweep tests are used to simulate fatigue, in order to obtain the fatigue laws. However, this requires too much time, often preventing its use. A method to estimate the fatigue laws from a strain sweep test is presented. The test was performed on a semi-dense mixture with different types of binder (unconditioned or aged) tested at different temperatures. This test is able to estimate fatigue laws more quickly, allowing the effect of different factors on the mixtures' fatigue life to be studied.Peer ReviewedPostprint (author's final draft

    El lenguaje de la inclusi贸n: un aprendizaje de doble v铆a en el 谩mbito universitario

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    El presente art铆culo desea contribuir a la reflexi贸n sobre la discriminaci贸n en contextos institucionales educativos, a partir de hallazgos tomados de una experiencia piloto realizada por el Departamento de Bienestar Estudiantil de la Universidad Polit茅cnica Salesiana (UPS) con estudiantes con alg煤n tipo de discapacidad, autodenominados grupo ASU Otredad, para intercambiar visiones con otros estudiantes de la UPS, y sensibilizar, a trav茅s de talleres vivenciales, sobre su situaci贸n personal y acad茅mica. En la primera parte se desarrolla la base te贸rica sobre la discriminaci贸n y el derecho a la inclusi贸n, analizando los factores estructurantes de la exclusi贸n ligados a imaginarios culturales que cada sociedad alimenta a trav茅s de estereotipos, cuya gama abarca categor铆as sociales: posici贸n de clase, tendencia ideol贸gica, religiosa, 茅tnica y g茅nero, hasta intereses particulares de los individuos que consideran al otro una amenaza en su proyecto de vida. De este modo, los detractores de la discriminaci贸n y la exclusi贸n, se refugian en la multicausalidad, exhibiendo las diferencias a partir de un pueril naturalismo, invisibilizando el real ejercicio del poder y sus repercusiones antihumanistas en efecto cascada. A partir de ello, el art铆culo decanta en una reflexi贸n en torno a los procesos de alteridad en el 谩mbito universitario subrayando la importancia de trabajar el tema de los prejuicios, en su construcci贸n y dimensi贸n social. En la segunda parte, se presentan resultados sobre la sistematizaci贸n de la experiencia vivida por estudiantes de la UPS, tras un proceso trabajado para explorar el tema de la exclusi贸n y la discriminaci贸n, sumando propuestas inclusivas organizadas desde la discusi贸n y la reflexi贸n colectiva. // In the present article it wants to contribute to the reflection on the discrimination in institutional educational contexts, from findings taken of a pilot experience realized by the Department of Student Well-being of the Technical University Salesiana (UPS) with students with some type of disability, autocalled group ASU Otredad, to exchange visions with other students of the UPS, and to sensitize, across existential workshops, on his personal and academic situation. In the first part the theoretical basis on discrimination and the right to inclusion is developed by analyzing the structural factors of exclusion linked to cultural imaginary each society fed through stereotypes, whose range covers social categories: class position, trend ideological, religious, ethnic and gender, to private interests of individuals considered a threat to the other in their life project. Thus, critics of discrimination and exclusion, take refuge in the multiple exhibiting differences from a puerile naturalism, obscuring the actual exercise of power and its anti-humanist implications in cascade effect. From this, Article decant in a reflection on otherness processes in universities stressing the importance of work on the issue of prejudice, in its construction and social dimension. In the second part, they result on the systematization of the experience of students UPS are available, after a process worked to explore the issue of exclusion and discrimination, adding inclusive proposals presented from the discussion and collective reflection

    Ageing and temperature effect on the fatigue performance of bituminous mixtures

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    The ageing of asphalt mixes, together with their exposure to low temperatures, causes a progressive increase of cracking. In this paper, the effect of ageing and temperature on the fatigue of asphalt concretes made with two types of binders, conventional (50/70) and polymer modified bitumen (PMB), is studied. For this purpose, specimens previously subjected to an accelerated laboratory ageing process were tested by a strain sweep test at different temperatures (-5掳C, 5掳C and 20掳C). Results were compared with the obtained from the unaged specimens showing the relative importance of ageing, temperature and type of bitumen on the parameters that determine the fatigue life of the mixture. The mixtures behaviour becomes more brittle with ageing and the decrease of temperature. However, ageing hardly has an effect on fatigue at lower temperatures. In general, mixtures made with polymer modified bitumen have a better fatigue performance to ageing and temperature.Peer ReviewedPostprint (published version

    Complexity of the behaviour of asphalt materials in cyclic testing

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    This paper compares the results obtained in two types of cyclic tension-compression tests, a time sweep test, constant strain amplitude, and a strain sweep test, increasing strain amplitude every 5000 cycles, called EBADE (standing for the Spanish words for strain sweep test). This comparison has shown that the rapid loss of stiffness during the initial part of cyclic testing is recoverable in bituminous materials. It has been found that reversible phenomena dominate in asphalt binders, while in mixtures are as important as damage. A damage equation has been proposed to describe the evolution of the material distress during the phase II in time sweep tests. In addition, a new methodology to estimate the fatigue law of bituminous mixtures is proposed.Peer ReviewedPostprint (author's final draft

    Microfiltracion marginal de inlays de ceromeros cementados con cementos de resina convencional v/s los cementos de resina autograbantes. Estudio in vitro

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    108 p.Introducci贸n: Diariamente como Odont贸logos nos vemos enfrentados a la problem谩tica de atender pacientes que necesitan rehabilitaciones complejas, de acci贸n indirecta. Para lograr con 茅xito el desaf铆o, necesitamos utilizar materiales altamente especializados en la uni贸n de estos sustratos, como son los cementos dentales. Se ha descrito que la etapa de cementaci贸n, es decir, desde que se inicia con la elecci贸n del agente cementante hasta que la restauraci贸n ya est茅 en boca, es de vital importancia, ya que alg煤n error que se produzca ac谩, se ver谩 traducido en el fracaso de la rehabilitaci贸n. En cl铆nica, es de suma importancia lograr una f茅rrea uni贸n entre la restauraci贸n y la pieza dentaria, no s贸lo para evitar el desalojo de la misma, sino tambi茅n para lograr un 铆ntimo contacto, una buena interacci贸n y un perfecto sellado de los tejidos, con el fin de evitar la posterior microfiltraci贸n bacteriana causante de caries recidivantes que se han detectado como la primera causa de falla en este tipo de restauraciones. Diversas son las propiedades y tratamientos que poseen los diferentes agentes cementantes que existen en el mercado y es responsabilidad del odont贸logo estar al tanto de lo que al respecto sucede. Es as铆, como la industria odontol贸gica ha creado un nuevo cemento, los cementos de resina autograbantes de curado dual, que no necesitan tratamiento previo de superficies, minimizando los pasos previos y la posibilidad de fracaso. El objetivo de la presente investigaci贸n es comparar los niveles de microfiltraci贸n a nivel de la uni贸n esmalte-cemento y dentina-cemento que se pueden obtener con un cemento de resina de curado dual y con este nuevo tipo de cementos autograbante Materiales y M茅todo: En treinta piezas dentarias humanas fueron talladas cavidades tipo inlay, donde un caj贸n proximal terminara 1 mm. bajo el LAC, en dentina y el otro, 1 mm. sobre, en esmalte, para luego confeccionarles incrustaciones de cer贸mero estandarizadas, las cuales se dividieron aleatoriamente en dos grupos. El grupo N潞 1, de quince muestras, el cual fue cementado con un cemento de resina convencional, Relyx ARC y el grupo N潞 2, de igual quince muestras, que fue cementado con un cemento de resina autograbante, Relyx Unicem. Cada grupo fue sometido a 250 ciclos de carga y termociclado para luego dejarlo por 48 horas en una soluci贸n de tinci贸n de azul de metileno al 0,2%. Luego de este tiempo se realiz贸 el corte de las piezas, para analizarlas bajo microscop铆a 贸ptica, determinando los distintos niveles de microfiltraci贸n que presentara cada interfase dentaria. Resultados: Para el caso del grupo N潞 1, con el cemento Relyx ARC, los valores de microfiltraci贸n para esmalte fueron: Nivel 0 (Ausente) 43,3%, Nivel 1 (Leve) 40,0%, Nivel 2 (Moderado) 3,3%, Nivel 3 (Severo) 10,0% y Nivel 4 (Avanzado) 3,3%; y para el caso de la dentina fueron: Nivel 0 (Ausente) 36,7%, Nivel 1 (Leve) 30,0%, Nivel 2 (Moderado) 10,0%, Nivel 3 (Severo) 13,3% y Nivel 4 (Avanzado) 10,0%. Para el grupo N潞 2 del cemento Relyx Unicem, los valores de microfiltraci贸n en esmalte fueron: Nivel 0 (Ausente) 6,7%, Nivel 1 (Leve) 56,7%, Nivel 2 (Moderado) 23,3%, Nivel 3 (Severo) 6,7% y Nivel 4 (Avanzado) 6,7%; y los valores para dentina fueron: Nivel 0 (Ausente) 13,3%, Nivel 1 (Leve) 63,3%, Nivel 2 (Moderado) 6,7%, Nivel 3 (Severo) 13,3% y Nivel 4 (Avanzado) 3,3%. Conclusiones: Al realizar el an谩lisis estad铆stico bajo las pruebas del test de Mann 鈥揥ithney, podemos concluir que el cemento Relyx ARC presenta valores de microfiltraci贸n m谩s bajos que el cemento Relyx Unicem y que esta diferencia es estad铆sticamente significativa, pero que esta diferencia se hace clara solo en la interfase de esmalte

    New Percichthyidae (Teleostei, Percoidei) from the early Pliocene of the Buenos Aires province (Argentina) and its biogeographical implications

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    Los registros paleoictiol贸gicos del Plioceno temprano de la localidad de Farola Monte Hermoso, al sur de la provincia de Buenos Aires (Argentina) son aun escasos y saltuarios. Durante este lapso, dicha localidad habr铆a estado vinculada a la paleocuenca del R铆o Colorado, por lo que se relacionar铆a con la Regi贸n Ictiogeogr谩fica Austral. En la presente contribuci贸n se describe un nuevo g茅nero y especie de Percichtyidae de gran tama帽o, procedente de los dep贸sitos fluviales de la Formaci贸n Monte Hermoso, el cual constituir铆a el grupo hermano de los generos sudamericanos Percichthys y Santosius. Este hallazgo, conjuntamente con otros registros paleoictiol贸gicos previos y an谩lisis moleculares de taxones actuales, sugieren un recambio ictiofaun铆stico de importancia para el Ne贸geno tard铆o en la regi贸n Patag贸nica. De este modo, la conformaci贸n actual de la ictiofauna patag贸nica seria de reciente data, posiblemente a partir del Pleistoceno.The paleoichthyological record from the early Pliocene of Farola Monte Hermoso locality, southern Buenos Aires province (Argentina) is still patchy and biased. During such time span, this locality may be related to the R铆o Colorado paleobasin, and consequently may have been related to the Austral Ichthyogeographical Region. In the present contribution we describe a new genus and species of a very large Percichthyidae, coming from fluvial deposits of the Monte Hermoso Formation. The new taxon constitutes the sister group of the genera Percichthys and Santosius. This finding, together with other pre- vious paleoichthyological records, as well as phylogenetic and phylogeographic molecular analyses of living taxa, suggest the existence of an ichthyofaunistic turnover for the late Neogene in the Patagonian region. In this way, the current composition of the Patagonian ichthyofauna would be of recent age, possibly from the Pleistocene.Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas. Oficina de Coordinaci贸n Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina. Fundacion de Historia Natural Felix de Azara; ArgentinaFil: Bogan, Sergio. Fundacion de Historia Natural Felix de Azara; ArgentinaFil: Tomassini, Rodrigo Leandro. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas. Centro Cient铆fico Tecnol贸gico Bah铆a Blanca. Instituto Geol贸gico del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Manera, Teresa. Universidad Nacional del Sur. Departamento de Geolog铆a; Argentin

    Nucleophile dependent formation of 6- and 7-membered N-heterocycles by platinum-catalysed cyclisation of 1,5-bisallenes

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    An unprecedented Pt-catalysed cyclisation of N-tethered 1,5-bisallenes in the presence of oxygen nucleophiles is reported, where formation of 6- or 7-membered rings is driven by the choice of nucleophile and the mechanism dictated by the nucleophile and the electronic properties of the bisallene. The reaction in the presence of alcohols gives preferentially vinyltetrahydropyridines with an extra alkoxy group and Pt-H as the active species in the catalytic cycle, while formation of di- and tetrahydroazepines with an extra hydroxyl group is favoured when water is used as nucleophile, via nucleophilic attack/carbocyclization as the favoured pathway. The products obtained are frequently found in the core of natural products with important biological activities, so understanding this complex mechanistic behaviour and exploiting this new methodology will have a big impact in organic synthesis and organometallic chemistry

    Blocking and unblocking in a navigation task

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    Rodrigo, Chamizo, McLaren, & Mackintosh (1997) demonstrated the blocking effect in a navigational task using a swimming pool: rats initially trained to use three landmarks (ABC) to find an invisible platform learned less about a fourth landmark (X) added later than did rats trained from the outset with these four landmarks (ABCX). The aim of the experiment reported here was to demonstrate unblocking using a similar procedure as in the previous work. Three groups of rats were initially trained to find an invisible platfom in the presence of three landmarks: ABC for the Blocking and Unblocking groups and LMN for the Control group. Then, all animals were trained to find the platform in the presence of four landmarks, ABCX. In this second training, unlike animals in the Blocking group to which only a new landmark (X) was added in comparison to the first training, the animals in the Unblocking group also had a change in the platform position. In the Control group, both the four landmarks and the platform position were totally new at the beginning of this second training. As in Rodrigo et al. (1997) a blocking effect was found: rats in the Blocking group learned less with respect to the added landmark (X) than did animals in the Control group. However, rats in the Unblocking group learned about the added landmark (X) as well as did animals in the Control group. The results are interpreted as an unblocking effect due to a change in the platform position between the two phases of training, similarly to what is normal in classical conditioning experiments, in which a change in the conditions of reinforcement between the two training phases of a blocking design produce an attenuation or elimination of this effect. These results are explained within an error-correcting connectionist account of spatial navigation (McLaren, 2002)

    El sesgo de publicaci贸n y la no reproducibilidad en el balance 茅tico de los proyectos de investigaci贸n con animales

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    La normativa que rige la investigaci贸n con animales establece la aprobaci贸n de proyectos de investigaci贸n tras haber sido sometidos a una valoraci贸n 茅tica costes-beneficios apropiada. El sesgo de publicaci贸n y la falta de reproducibilidad en la investigaci贸n animal socavan el adecuado balance 茅tico de los proyectos. Es necesario promover medidas que impliquen a todos los participantes (cient铆ficos, grupos editoriales, organismos gubernamentales y financiadores) y que generen un cambio en la cultura cient铆fica que revalorice los resultados negativos como parte del conocimiento cient铆fico general e incremente la calidad de las publicaciones

    Concentration by pervaporation of representative brown crab volatile compounds from dilute model solutions

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    In this work, the pervaporation technique is investigated in the separation of dilute solutions of volatile compounds from brown crab effluent in order to obtain a valuable food flavoring fraction. A systematic study of the pervaporation process has been carried out on dilute model solutions of some of the compounds identified in the brown crab effluent as typical volatile compounds. The membrane used in this work was a hydrophobic membrane with a selective layer of POMS (polyoctylmethyl siloxane). The effect of some operating variables, such as feed flow rate, feed concentration, feed temperature and permeate pressure was analyzed on the pervaporation performance of the membrane.MICINN through CTQ2008-04999- PP
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