Numerical study of an arcan tensile compression shear test in dynamic: application to bonded joints

This paper presents a numerical study of the Arcan TCS testing device under dynamic conditions. This test is commonly used to characterize the mechanical behavior of bonded joints subjected to combined quasi-static loadings. In this study, the question of its extensibility to dynamic loadings by the use of an impactor guided in a drop tower is investigated. A dedicated finite element model is built under the plane stress assumption. Stress distributions in the adhesive are analysed trought time ans space for several configurations

Creep of argillites under small mechanical loading

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Combinaciones de genes en arroz para el desarrollo de resistencia durable a Pyricularia grisea en Colombia

El añublo del arroz causado por Pyricularia grisea (Magnaporthe grisea) es el principal limitante de la producción en Colombia. La perdida de la resistencia ocurre en penodos de uno a tres años, con la excepción de los cultivares Oryzica Llanos 5 liberado en 1989 y Fedearroz 50 liberado en 1998. Con el objetivo de desarrollar cultivares con resistencia durable al añublo hemos analizado la estructura genética de poblaciones del patógeno utilizando técnicas moleculares como MGR-DNA y rep-PCR fingerprinting y estudiamos la diversidad y frecuencias de los genes de avirulencia/virulencia del hongo. P. grisea en Colombia es principalmente clonal. Cada clon o linaje exhibe un espectro de virulencia amplio. Sin embargo, algunos genes de resistencia son efectivos contra todos los aislamientos de un linaje. Los genes de avirulencia varian en frecuencia, sugiriendo que dichos genes de avirulencia pueden estar asociados con la supervivencia y reproducción, y por lo tanto, los genes de resistencia correspondientes a dichos genes de avirulencia serian más relevantes en el mejoramiento para una resistencia durable. Nuestros estudios nos permiten identificar y predecir la durabilidad de combinaciones de genes de resistencia basados en las frecuencias de genes de avirulencia. Hemos identificado los posibles genes de resistencia presentes en nuestras variedades de arroz e iniciado un programa de retrocruzamiento para incorporar las combinaciones de genes de resistencia deseadas en variedades de arroz de América Latina, a través de una selección asistida por marcadores moleculares, inoculaciones controladas con aislamientos del patógeno, y evaluaciones de campo. = Rice blast caused by Pyricularia grisea (Magnaporthe grisea) is the main limiting factor of rice production in Colombia. Resistance break down occurs after one to three years of cultivar release, with the exception of the commercial cultivars Oryzica Llanos 5 released in 1989 and Fedearroz 50 released in 1998. With the objective of developing rice cultivars with durable resistance to blast we have analyzed the genetic structure of blast pathogen populations using techniques such as MGR-DNA and rep-PCR fingerprinting and studied the diversity and frequencies of avirulence/virulence genes in the fungus. P. grisea in Colombia is mainly clonaI. Each clone or lineage exhibits a broad spectrum of virulence. However, some resistance genes are effective against all isolates of a linage. Avirulence genes vary in frequency, suggesting that these genes could be associated with pathogenic fitness. Therefore, the resistance genes corresponding to those avirulence genes would be more relevant in breeding for durable resistance. Our studies are allowing us to identify and predict the durability of resistance gene combinations based on the frequency of avirulence genes. We have identified the possible resistance genes present in our commercial rice cultivars and initiated a backcrossing program for incorporating desired combinations of resistance genes in rice varieties of Latin America through marker assisted selection, controlled inoculations with pathogenic isolates, and field evaluations

Advances in the testing of the hydro-mechanical behaviour of shales

The paper presents some of the advanced experimental techniques and apparatuses that have been developed by the authors for testing the hydromechanical behaviour of shales. A methodology established for the analysis of the water retention behaviour in non-isochoric conditions is introduced; the method allows for the determination of the main drying and wetting paths in addition to the volume change response upon total suction variations. A high-pressure oedometric cell is then presented; the apparatus allows for the analysis of the transition from the pre-yield behaviour to the normally consolidated state. The analysis of the settlement versus time curves yields information on the permeability of the material as a function of the void ratio. The test results are illustrated for two Mesozoic shales from the northern region of Switzerland, namely, the Opalinus Clay from Mont Terri and the so called "Brown Dogger" from the Schlattingen site in the Molasse Basin. © Springer-Verlag Berlin Heidelberg 2013