Structure and electrical properties in the K1/2Bi1/2TiO3-K1/2Bi1/2ZrO3 solid solution (KBT-KBZ)

International audienceThe present work is devoted to the study of the Zr 4þ /Ti 4 substitution in the K1/2Bi1/2Ti(1-x)ZrxO3 solid solution (x ¼ 0.0 to x ¼ 1.0), based upon the K1/2Bi1/2TiO3 (KBT) ferroelectric compound. The tetragonal distortion of KBT is suppressed by this substitution and leads to the cubic compound K1/2Bi1/2ZrO3 (KBZ). These results agree with the values of the ionic radii of the Zr 4þ and Ti 4 ions (rTi 4þ ¼ 0.605 A˚ and rZr 4þ ¼ 0.72 A˚ ). Close to KBT (x 0.05), the symmetry remains tetragonal. For higher values of x, the ''a'' lattice parameter (cubic indexing) follows Vegard's law, thus confirming the formation of a solid solution. The transformation from tetragonal to cubic proceeds via an intermediate pseudocubic symmetry (0.1 x < 0.5), for which the X-ray diffraction peaks present small broadening and asymmetry. For x 0.5 and up to the KBZ compound (a 4.158 A˚ ), the samples are cubic but some extra peaks are also observed, indicating the occurrence of a secondary phase. The microstructure shows fine-grained ceramic samples for the first range, while for the KBZ-rich range the grains are micrometer-sized and associated to very small grains of the secondary phase. Piezoelectricity is observed for the tetragonal and pseudocubic range, the substitution quickly reducing the piezoelectric properties. The measurement of the dielectric properties revealed close to KBT a dielectric anomaly probably associated to the tetragonal-cubic phase transition. For thepseudocubic and cubic range, a broad dielectric anomaly is observed around 300 8C, corresponding to a relaxor behavior

Análisis de falla de la represa Marcacocha del distrito de Uco provincia de Huari-Ancash

Publicación a texto completo no autorizada por el autorEl documento digital no refiere asesorRealiza los cálculos para verificar la estabilidad de la represa Marcacocha y deslizamiento de la estructura bajo el método clásico y el criterio técnico P.E.T. (Presa Elemental Triangular). Para aumentar la estabilidad y seguridad de la estructura se plantea una alternativa de solución, un modelo de contrafuerte que cumplirá con los reglamentos establecidos en la construcción de represas.Trabajo de suficiencia profesiona

Molecular characterization of Listeria monocytogenes isolated from animal products in a city of Northern Brazil

Listeria monocytogenes, a foodborne pathogen causes listeriosis, a fatal disease in about 30% of cases that affects mainly immunocompromised persons. The aim of this research was to characterize L. monocytogenes pulsed-field gel electrophoresis (PFGE) types isolated from meat products collected at public markets in Araguaina city, TO. Sixty samples of raw ground beef and frescal sausage were analyzed during the second half of 2008. Five out of 30 samples (16.7%) of raw ground beef tested positive for L. monocytogenes, three of which were classified as serotype 1/2b and two as serotype 4b. Among the 30 samples of sausage collected, two strains of L. monocytogenes were isolated (6.7%), one of them belonging to serotype 1/2a and the other belonging to serotype 1/2b. The restriction enzymes used were ApaI and SmaI. Similarities among the strains were determined by Dice coefficient. The macro restriction profile obtained by using SmaI enzyme allowed the distribution of seven strains in two clusters, two pulsotypes and two subtypes. The result indicates that L. monocytogenes isolates, belonging to serotype 4b, 1/2a and 1/2b, are strongly correlated within the same serotype group, and in some cases among different serotypes, suggesting that they have a common source

Magnetic resonance imaging biomarkers for chronic kidney disease: a position paper from the European Cooperation in Science and Technology Action PARENCHIMA

Functional renal magnetic resonance imaging (MRI) has seen a number of recent advances, and techniques are now available that can generate quantitative imaging biomarkers with the potential to improve the management of kidney disease. Such biomarkers are sensitive to changes in renal blood flow, tissue perfusion, oxygenation and microstructure (including inflammation and fibrosis), processes that are important in a range of renal diseases including chronic kidney disease. However, several challenges remain to move these techniques towards clinical adoption, from technical validation through biological and clinical validation, to demonstration of cost-effectiveness and regulatory qualification. To address these challenges, the European Cooperation in Science and Technology Action PARENCHIMA was initiated in early 2017. PARENCHIMA is a multidisciplinary pan-European network with an overarching aim of eliminating the main barriers to the broader evaluation, commercial exploitation and clinical use of renal MRI biomarkers. This position paper lays out PARENCHIMA’s vision on key clinical questions that MRI must address to become more widely used in patients with kidney disease, first within research settings and ultimately in clinical practice. We then present a series of practical recommendations to accelerate the study and translation of these techniques