Valores del potencial de corrosión y de a resistencia de polarización de armaduras galvanizadas embebidas en hormigón

[ES]Muchas de las estructuras de hormigón armado se muestran exentas de corrosión aun después de períodos muy prolongados de servicio. Ello es debidq a que en el hormigón el electrolito está constituido por la fase líquida que rellena sus poros y que es, fundamentalmente, una disolución saturada de Ca(OH)2, con un pH alrededor de 13. A este elevado pH y a los potenciales de corrosión, E,corr» ^^^ presentan las armaduras, el acero se encuentra en la zona de pasividad descrita por Pouorbaix (1), fig. 1, permaneciendo protegido indefinidamente mientras no cambien las condiciones del medio. -03 -id corrosión j-^ inmunidad { I 1 j I I I' I •• " « i 1 \ ' 1 [ ®~^^^~-1 p--^\COiTOSion i "® -6 1 pasivo 1 -6 i ., ! aon ^corrosión * v j1 -^--^ 1 inmunidad :^"'\. 1 L. 1 1- 1 . í 1. j i 1 : -2 0 2 4 6 8 1 0 12 14 16-2 0 2 4 6 8 10 12 14 16 o) pH b) PH Fig. 1—Condiciones teóricas de corrosión, inmunidad y pasivación. (a) Del sistema hierro-agua a 25oC. (b) Del sistema zinc-agua a 25»C en presencia de CO2. Este cambio en las condiciones de servicio del hormigón capaz de introducir en la zona de corrosión al acero de las armaduras, se puede producir con relativa frecuencia. Así, (*) Texto integro del trabajo presentado al simposio de Electroquímica, celebrado en Madrid en octubre de 1978, dentro del Congreso del 75.o Aniversario de la Real Sociedad Española de Física y Química. (**) C. Andrade. Dra. en Química Industrial. Dpto. de Química del lETCC. J. A. González. Dr. en Química Industrial. Investigador Científico en el Dpto. de Corrosión y Protección del CENIM. 71 © Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://materconstrucc.revistas.csic.es la carbonatación del cemento disminuye el pH del hormigón y provoca una corrosión generalizada, la presencia de iones despasivantes o de fisuras conduce a corrosión localizada y, ñnalmente, la acción simultánea de tensiones mecánicas y factores agresivos puede ser la causa de corrosión bajo tensiones. Así pues, es aconsejable recurrir a una protección suplementaria de los aceros cuando se prevean situaciones que puedan provocar la corrosión de las armaduras. Entre los varios métodos de protección que se utilizan se viene ensayando desde hace varios lustros, con resultados muy contradictorios, la galvanización en caliente de los redondos (2) (3).Peer reviewe

Chocolat noir ou chocolat blanc? Le cacao et la santé cardiovasculaire

Epidemiological data show that a regular dietary intake of plant-derived foods reduces the risk of cardiovascular disease. Recent research indeed demonstrates interesting data about cocoa consumption, with high concentrations of polyphenols, and beneficial effects on blood pressure, insulin resistance and platelet function. Although still debated, a range of potential mechanisms through which cocoa might exert their benefits on cardiovascular health have been suggested: activation of nitric oxide, antioxidant, anti-inflammatory, anti-platelet effects, which might in turn improve endothelial function, lipid levels, blood pressure and insulin resistance. This article reviews available data about the effects of the consumption of cocoa and different types of chocolate on cardiovascular health, and outlines potential mechanisms involved on the basis of recent studies

Generalized Flow and Determinism in Measurement-based Quantum Computation

We extend the notion of quantum information flow defined by Danos and Kashefi for the one-way model and present a necessary and sufficient condition for the deterministic computation in this model. The generalized flow also applied in the extended model with measurements in the X-Y, X-Z and Y-Z planes. We apply both measurement calculus and the stabiliser formalism to derive our main theorem which for the first time gives a full characterization of the deterministic computation in the one-way model. We present several examples to show how our result improves over the traditional notion of flow, such as geometries (entanglement graph with input and output) with no flow but having generalized flow and we discuss how they lead to an optimal implementation of the unitaries. More importantly one can also obtain a better quantum computation depth with the generalized flow rather than with flow. We believe our characterization result is particularly essential for the study of the algorithms and complexity in the one-way model.Comment: 16 pages, 10 figure

Generalized Flow and Determinism in Measurement-based Quantum Computation

We extend the notion of quantum information flow defined by Danos and Kashefi for the one-way model and present a necessary and sufficient condition for the deterministic computation in this model. The generalized flow also applied in the extended model with measurements in the X-Y, X-Z and Y-Z planes. We apply both measurement calculus and the stabiliser formalism to derive our main theorem which for the first time gives a full characterization of the deterministic computation in the one-way model. We present several examples to show how our result improves over the traditional notion of flow, such as geometries (entanglement graph with input and output) with no flow but having generalized flow and we discuss how they lead to an optimal implementation of the unitaries. More importantly one can also obtain a better quantum computation depth with the generalized flow rather than with flow. We believe our characterization result is particularly essential for the study of the algorithms and complexity in the one-way model.Comment: 16 pages, 10 figure

Hydrothermal monitoring using embedded sensors of the actual roof system of the prado museum

El Prado Museum in Madrid has been recently submitted to a refurbishment of its roof which from been made with the traditional tiles has been changed to the use of modern waterproofing layers covered with a metallic lead finishing. Due to an unexpected damp patch that produced leaking in the hall in which Las Meninas by Velázquez was exhibited, the authors were commissioned by the Ministry of Education and Culture to study the suitability of the roof and its waterproofing properties. The study led to suggestions of modifications in the design of the roof layers, which are out of the scope of present paper. In present paper are given the behaviour of the sensors embedded in two specific areas of the roof. The sensors installed were of: temperature, relative humidity, measurement of local strain and detection of liquid water. The liquid water sensors reveal that some water is withheld in the layer just below the thermal insulation material, although it is standing. The results of over four years of readings show that the temperature attenuates over distance away from the outermost layer, where the readings are very high in summer, due to it consists of lead. During the colder seasons, in turn, the temperature in the inner layers of the roof is higher than in the outer layers. The strain recorded follows the logical evolution of temperature with no abnormal behaviour being detected. Some of relative humidity sensors had measuring problems due to water condensing on them. In summary however, if the behaviour in this area is extrapolated to the rest of the roof, it can be considered to perform correctly as intended. No more leaking events have been detected from the design modifications were incorporated to the existing roof