Microestructura y propiedades mecánicas del material masivo superconductor YBCO a 300 Y 77 K.

En este trabajo se realiza una caracterización mecánica y microestructural del material masivo superconductor YBCO. El material ha sido procesado mediante dos técnicas distintas, Top-Seeding Melt Growth (TSMG) y Bridgman, y este estudio profundiza en el efecto de la microestructura, el método de procesado y la temperatura de ensayo en el comportamiento mecánico de material. Con el fin de conseguir un amplio conocimiento de sus propiedades mecánicas se han realizado ensayos de resistencia a flexión, tenacidad de fractura y dureza Vickers a 300 y 77 K. Asimismo, se llevaron a cabo ensayos de nanoindentación y el tamaño crítico del defecto semielíptico. Los resultados obtenidos muestran que el comportamiento mecánico de los dos materiales está controlado por defectos y grietas, introducidas durante el procesado. También se ha encontrado un buen acuerdo entre el tamaño del defecto critico detectado experimentalmente con los valores obtenidos mediante de análisis de mecánica de fractura

Comportamiento mecánico de materiales masivos superconductores de segunda generación en función de la temperatura

En este trabajo se han analizado dos materiales masivos superconductores de base YBaCuO, con el objetivo de analizar la influencia del método de procesado (método de Bridgman y método Top-Seeding melt growth) y de la temperatura de ensayo en su comportamiento mecánico. Ambos materiales se ensayaron a temperatura ambiente (300 K) y a baja temperatura (77 K), realizándose ensayos rotura y de tenacidad de fractura en flexión en tres puntos. Además, en uno de los materiales, que presentaba anisotropía microestructural, se realizaron ensayos en las dos direcciones microestructuralmente más relevantes. Los resultados obtenidos muestran que el comportamiento mecánico del material está controlado por los defectos y grietas introducidas durante el procesado y, por lo tanto, si se quiere mejorar las propiedades, debería reducirse la cantidad y el tamaño de estas imperfeccione

Mating disruption trials for the olive moth, Prays oleae (Bern.), (Lep.: Yponomeutidae) in Trás-os-Montes olive groves (Northeast of Portugal).

The olive moth, Prays o/eae (Bern), is one of the most serious olive pests in the Mediterranean basin. The objective of the present study was to integrate environmentally safe methods for the control of the pest. Trials were carried out for three consecutive years (2002-2004) in an olive grove about 20 ha, in the ecological production region at Romeu (North of Mirandela)

Fracture micromechanisms and mechanical behavior of YBCO bulk superconductors at 77 and 300 K

In this study two YBa2Cu3O7−δ bulk superconductors were evaluated, with the aim of analyzing the influence of the processing method (TSMG and Bridgman) and the test temperature on their mechanical behavior. The relationship between their mechanical properties and fracture micromechanisms has also been studied. Both materials were tested at room and at service temperature. TPB tests were carried out to determine their mechanical behavior, strength and toughness. Moreover, one of the two materials, characterized by transversal microstructural anisotropy, was tested in two directions. Hardness of both materials at nano and micro scale was studied. The results show that the mechanical behavior of the materials is controlled by the defects and cracks that have been introduced during the processing of the materials. A good degree of agreement was found between the experimental crack defects detected by means of SEM and those gathered from the fracture mechanical analysis of the experimental dat

Effect of strain and magnetic field on the critical current and electric resistance of the joints between HTS coated conductors

Engineering of devices and systems such as magnets, fault current limiters or cables, based on High Temperature Superconducting wires requires a deep characterization of the possible degradation of their properties by handling at room temperature as well as during the service life thus establishing the limits for building up functional devices and systems. In the present work we report our study regarding the mechanical behavior of spliced joints between commercial HTS coated conductors based on YBCO at room temperature and service temperature, 77 K. Tensile tests under axial stress and the evolution of the critical current and the electric resistance of the joints have been measured. The complete strain contour for the tape and the joints has been obtained by using Digital Image Correlation. Also, tensile tests under external magnetic field have been performed and the effect of the applied field on the critical current and the electric resistance of the joints has been studied. Additionally, fatigue tests under constant cyclic stress and loading-unloading ramps have been carried out in order to evaluate the electromechanical behavior of the joints and the effect of maximum applied stress on the critical current. Finally, a preliminary numerical study by means of the Finite Element Method (FEM) of the electromechanical behavior of the joints between commercial HTS is presented

Effect of strain and magnetic field on the critical current and electric resistance of the joints between HTS coated conductors

Engineering of devices and systems such as magnets, fault current limiters or cables, based on High Temperature Superconducting wires requires a deep characterization of the possible degradation of their properties by handling at room temperature as well as during the service life thus establishing the limits for building up functional devices and systems. In the present work we report our study regarding the mechanical behavior of spliced joints between commercial HTS coated conductors based on YBCO at room temperature and service temperature, 77 K. Tensile tests under axial stress and the evolution of the critical current and the electric resistance of the joints have been measured. The complete strain contour for the tape and the joint has been obtained by using Digital Image Correlation. Also, tensile tests under external magnetic field have been performed and the effect of the applied field on the critical current and the electric resistance of the joints has been studied. Finally, a preliminary numerical study by means of Finite Element Method (FEM) of the mechanical behavior of the joints between commercial HTS is presented

Comportamiento mecánico de materiales masivos supercondcutores de segunda generación en función de la temperatura

En este trabajo se han analizado dos materiales masivos superconductores de base YBaCuO, con el objetivo de estudiar la influencia del método de procesado (método Bridgman y método Top-Seeding Melt Growth) y de la temperatura de ensayo en su comportamiento mecánico. Ambos materiales se ensayaron a temperatura ambiente (300 K) y a baja temperatura (77 K), determinandose la resistencia mecánica y la tenacidad a fractura en flexión en tres puntos. Además, en uno de los materiales, que presentaba anisotropía microestructural, se realizaron ensayos en las dos direcciones microestructuralmente más relevantes. Los resultados obtenidos muestran que el comportamiento mecánico del material está controlado por los defectos y grietas introducidas durante el procesado y, por lo tanto, si se quiere mejorar las propiedades, debería reducirse la cantidad y el tamaño de estas imperfecciones.Postprint (published version

Mutations in NDUFS1 Cause Metabolic Reprogramming and Disruption of the Electron Transfer

Complex I (CI) is the first enzyme of the mitochondrial respiratory chain and couples the electron transfer with proton pumping. Mutations in genes encoding CI subunits can frequently cause inborn metabolic errors. We applied proteome and metabolome profiling of patient-derived cells harboring pathogenic mutations in two distinct CI genes to elucidate underlying pathomechanisms on the molecular level. Our results indicated that the electron transfer within CI was interrupted in both patients by different mechanisms. We showed that the biallelic mutations in NDUFS1 led to a decreased stability of the entire N-module of CI and disrupted the electron transfer between two iron-sulfur clusters. Strikingly interesting and in contrast to the proteome, metabolome profiling illustrated that the pattern of dysregulated metabolites was almost identical in both patients, such as the inhibitory feedback on the TCA cycle and altered glutathione levels, indicative for reactive oxygen species (ROS) stress. Our findings deciphered pathological mechanisms of CI deficiency to better understand inborn metabolic errors