Nuevas tendencias en especificaciones y su aplicación a los asfaltos procesados en el pais

Se efectúa una revisión y recopilación de las especificaciones para asfaltos para pavimentación que rigen en Europa y en Estados e Instituciones de normalización de EE.UU. Son evaluadas las nuevas tendencias imperantes en lo que concierne a la clasificación de los asfaltos por medidas de viscosidad a distintas temperaturas, teniendo en cuenta que tales medidas proveen un sistema uniforme para seguir los cambios en las propiedades de los asfaltos antes y después de ser envejecidos en laboratorio. Las determinaciones efectuadas abarcan un rango de temperatura entre 4 y 135°C. Se ensayaron asfaltos empleados en construcciones camineras del país, provenientes de productores locales. Los datos obtenidos permiten comparar el actual sistema de clasificación de los asfaltos según IRAM, frente a las nuevas tendencias que clasifican mediante viscosidad.A compilation and a review of specifications for paving asphalts used in Europe and in the United States is made. They are evaluated the new trends for the classification of asphalts based in their viscosity at different temperatures. These measurements provide a uniform system to evaluate changes in asphalt properties before and after laboratory aging. Temperature range used for the determinations is from 4 to 135°C. Locally produced paving asphalts were tested according to the new specifications. The data obtained allow a comparison between the current IRAM penetration system for the classifications of the asphalts, and the new tendency by viscosity. A comparison is included of limiting test values for the remaining assays in the current specifications

Envejecimiento de asfaltos durante el mezclado

En este trabajo se estudia, mediante ensayos de laboratorio, la alteración que sufren los asfaltos durante la operación de mezclado en usina. Empleando un mezclador de laboratorio, se prepararon mezclas asfálticas bajo condiciones controladas de tiempo y temperatura. El asfalto componente de la mezcla asfáltica fue recuperado mediante el método de Abson. Sobre este se estudió el grado de alteración mediante medidas de viscosidad, utilizando el microviscosímetro de placas deslizantes, y por espectrofoto- metría infrarroja. Además se estudió la acción inhibidora de ciertos aditivos recomendados como inhibidores de oxidación, tratando de poner de manifiesto su eficacia y forma de actuar.In this paper the alteration of asphalt cements that occur during the manufacture of paving mixtures in the plant mixing operation was studied, by laboratory testing. The bituminous mixtures were prepared in a laboratory mixer under controlled conditions (time and temperature). The asphalts under test were recovered by means of the Abson method. The alteration was studied measuring the viscosity with the sliding plate microviscometer and by infrarred spectra. Furthermore a study of the action of inhibitors of oxidation was made. This test was conducted to determine the effectiveness and the mechanism by which the antioxidants perform

Incidencia del envejecimiento del asfalto y del grado de fillerización en el fisuramiento de una carpeta asfáltica

Este trabajo estudia la incidencia que tiene el envejecimiento del asfalto y el aumento de MfillerM (como consecuencia de la degradación de los agregados pétreos) en las fisuras producidas en un pavimento urbano luego de un período prolongado de servicio. El envejecimiento del asfalto se estudia por medidas de consistencia y por espectrofotometría infrarroja. Se trata de poner en evidencia la influencia del grado de fillerización mediante ensayos mecánicos de estabilidad Hubbard Field, y por el estudio Teológico del sistema "filien-betún.This paper deals about the cracking produced by the bitumen ageing and by the increment of the mineral filler (as consequence of the aggregate degradation) of an urban pavement after a long-term performance. The ageing of the bitumen is studied by consistency measurements and by infrared spectrophotometry. The influence of the mineral filler is made evident by Hubbard Field stability and by the rheological behaviour of the filler- bitumen system

Paleomagnetic resu]ts of Jurassic rocks from Siena Harana

Los estudios paleomagnéticos en las Cordilleras Béticas empiezan a ser hoy en día numerosos. Los trabajos realizados hasta el presente tienen en común el que todos ellos indican la existencia de rotaciones, algunas de ellas muy importantes en magnitud, y la mayoría en sentido horario. Los vectores paleomagnéticos determinados han sido utilizados para establecer diferentes modelos cinemáticos. La mayoría de ellos postulan que las rotaciones observadas son acomodadas por el movimiento de fallas de salto en dirección o bien, en otros y no tan numerosos casos, por cabalgamientos.A continuación presentaremos los resultados de un estudio paleomagnético realizado en dos unidades alóctonas, una del Subbético Interno y otra de la Dorsal. El objetivo planteado al iniciar esta investigación fue el detenninar las características paleomagnéticas de los materiales elegidos y en segundo lugar establecer la existencia o no de rotaciones. El área escogida es Sierra Jarana, que se encuentra situada a unos 20 km al NNE de Granada, en el límite entre las zonas Internas y Externas de las Cordilleras Béticas. En esta sierra se han muestreado dos unidades: la Unidad de Sierra Harana y la Unidad de Cañamaya. Dichas unidades pertenecen respectivamente al Dominio Sudibérico (Subbético) y al Dominio de Alborán (Complejo de la Dorsal). Ambas unidades están constituidas por materiales mesozoicos y cenozoicos, aunque sus formaciones litoestratigráficas son de distinta naturaleza.Peer reviewe

Theoretical Analysis of STM Experiments at Rutile TiO_2 Surfaces

A first-principles atomic orbital-based electronic structure method is used to investigate the low index surfaces of rutile Titanium Dioxide. The method is relatively cheap in computational terms, making it attractive for the study of oxide surfaces, many of which undergo large reconstructions, and may be governed by the presence of Oxygen vacancy defects. Calculated surface charge densities are presented for low-index surfaces of TiO$_2$, and the relation of these results to experimental STM images is discussed. Atomic resolution images at these surfaces tend to be produced at positive bias, probing states which largely consist of unoccupied Ti 3$d$ bands, with a small contribution from O 2$p$. These experiments are particularly interesting since the O atoms tend to sit up to 1 angstrom above the Ti atoms, so providing a play-off between electronic and geometric structure in image formation.Comment: 9 pages, Revtex, 3 postscript figures, accepted by Surf. Scienc

Magic structures of helical multi-shell zirconium nanowires

The structures of free-standing zirconium nanowires with 0.6$-$2.8 nm in diameter are systematically studied by using genetic algorithm simulations with a tight-binding many body potential. Several multi-shell growth sequences with cylindrical structures are obtained. These multi-shell structures are composed of coaxial atomic shells with the three- and four-strands helical, centered pentagonal and hexagonal, and parallel double-chain-core curved surface epitaxy. Under the same growth sequence, the numbers of atomic strands in inner- and outer-shell show even-odd coupling and usually differ by five. The size and structure dependence of angular correlation functions and vibrational properties of zirconium nanowire are also discussed.Comment: 14 pages, 4 figure

Searching for signatures of chaos in gamma-ray light curves of selected Fermi-LAT blazars

Blazar variability appears to be stochastic in nature. However, a possibility of low-dimensional chaos was considered in the past, but with no unambiguous detection so far. If present, it would constrain the emission mechanism by suggesting an underlying dynamical system. We rigorously searched for signatures of chaos in Fermi-Large Area Telescope light curves of 11 blazars. The data were comprehensively investigated using the methods of nonlinear time series analysis: phase-space reconstruction, fractal dimension, maximal Lyapunov exponent (mLE). We tested several possible parameters affecting the outcomes, in particular the mLE, in order to verify the spuriousness of the outcomes. We found no signs of chaos in any of the analyzed blazars. Blazar variability is either truly stochastic in nature, or governed by high-dimensional chaos that can often resemble randomness.Comment: Pages : 7, figures: 5, accepted in MNRA

An interactive 3-D application for pain management: Results from a pilot study in spinal cord injury rehabilitation

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 ElevierResearch on pain following spinal cord injury (SCI) has revealed that patients not only experience several types of pain that could prove to be challenging to address, but also that each individual can interpret such pain in different subjective ways. In this paper we introduce a 3-D system for facilitating the efficient management of pain, and thus, supporting clinicians in overcoming the aforementioned challenges. This system was evaluated by a cohort of 15 SCI patients in a pilot study that took place between July and October 2010. Participants reported their experiences of using the 3-D system in an adapted version of the System Usability Scale (SUS) questionnaire. Statistically significant results were obtained with regards to the usability and efficiency of the 3-D system, with the majority of the patients finding it particularly useful to report their pain. Our findings suggest that the 3-D system can be an efficient tool in the efforts to better manage the pain experience of SCI patients