University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Soil carbon storage as influenced by tree cover in the Dehesa cork oak silvopasture of central-western Spain

Abstract: The extent of carbon (C) stored in soils depends on a number of factors including soil characteristics, climatic and other environmental conditions, and management practices. Such information, however, is lacking for silvopastoral systems in Spain. This study quantified the amounts of soil C stored at various depths (0–25, 25–50, 50–75, and 75–100 cm) under a Dehesa cork oak (Quercus suber L.) silvopasture at varying distances (2, 5, and 15 m) to trees. Soil C in the whole soil and three soil fractions (<53, 53–250, and 250–2000 μm) was determined. Results showed soil depth to be a significant factor in soil C stocks in all soil particle sizes. Distance to tree was a significant factor determining soil C stocks in the whole soil and the 250–2000 μm soil fraction. To 1 m depth, mean total C storage at 2, 5, and 15 m from cork oak was 50.2, 37, and 26.5 Mg ha−1, respectively. Taking into account proportions of land surface area containing these C stocks at varying distances to trees to 1 m depth, with a tree density of 35 stems ha−1, estimated landscape soil C is 29.9 Mg ha−1. Greater soil C stocks directly underneath the tree canopy suggest that maintaining or increasing tree cover, where lost from disease or management, may increase long term storage of soil C in Mediterranean silvopastoral systems. The results also demonstrate the use of soil aggregate characteristics as better indicators of soil C sequestration potential and thus a tool for environmental monitoring.

Motivación en las clases de educación física : un estudio de la perspectiva de las metas de logro en el contexto educativo

Abstract: Este estudio examino las relaciones entre las orientaciones de meta, el clima motivacional percibido, la percepcion de habilidad, la preferencia por tareas con diferente grado de dificultad, la satisfaccion, la diversion, la preferencia por distintos tipos de evaluacion y la valoracion que los estudiantes hacian de las clases de educacion fisica 280 estudiantes respondieron a una serie de cuestionarios para analizar las variables mencionadas Los resultados mostraron, de forma general, que la orientacion a la tarea, la percepcion de habilidad y la percepcion de un clima motivacional orientados a la tarea eranbuenos predictores de la preferencia por tareas desafiantes, la satisfaccion con experiencias de maestria, la diversion, la preferencia por contenidos evaluativos relativos al progreso personal y una alta valoracion de la educacion fisica Por el contrario la orientacion al ego, la percepcion de habilidad y la percepcion deun clima motivacional orientado al ego, aparecieron como predictores de la preferencia por tareas faciles, la satisfaccion con el exito normativo, el aburrimiento, la preferencia por la evaluacion del rendimiento comparativo y una menor valoracion de la educacion fisica

Topographic anatomy of the inferior pyramidal space: relevance to radiofrequency catheter ablation.

Abstract: Inferior Pyramidal Space and Ablation.Introduction: Radiofrequency catheter ablation carried out in the vicinity of the triangle of Koch risks damaging not only the AV conduction tissues but also their arterial supply. The aim of this study was to examine the relationship of the AV nodal artery to the inferior pyramidal space, the triangle of Koch, and the right atrial endocardial surface. Methods and Results: We studied 41 heart specimens, 24 by gross dissections and 17 by histologic sections. The proximity of the AV nodal artery to the surface landmarks of the triangle of Koch was variable, but it was notable that in 75% of specimens the artery passed close to the endocardial surface of the right atrium and within 0.5 to 5 mm of the mouth of the coronary sinus. In all specimens, the mean distance of the artery to the endocardial surface was 3.5 ± 1.5 mm at the base of Koch's triangle. The location of the compact AV node and its inferior extensions varied within the landmarks of the triangle. At the mid-level of Koch's triangle, the compact node was medially situated in 82% of specimens, but it was closer to the hinge of the tricuspid valve in the remaining 18% of specimens. In 12% of specimens, the inferior parts of the node extended to the level of the mouth of the coronary sinus. Conclusion: The nodal artery runs close to the orifice of the coronary sinus, the endocardial surface of the right atrium, the middle cardiac vein, and the specialized conduction tissues in most hearts. The nodal artery and/or the AV conduction tissues can be at risk of damage when ablative procedures are carried out at the base of the triangle of Koch.

Oxidation of Polynuclear Aromatic Hydrocarbons in Water. 3. UV Radiation Combined with Hydrogen Peroxide

Abstract: Oxidation in water of three polynuclear aromatic hydrocarbons (PAHs), fluorene, phenanthrene, and acenaphthene, with UV radiation combined with hydrogen peroxide has been studied. The effect of hydrogen peroxide concentration, pH, and bicarbonate ion has been investigated. Disappearance rates of PAHs are substantially increased with respect to those from UV radiation alone if proper conditions of hydrogen peroxide concentration and pH are established. Direct photolysis contribution decreases with the increasing hydrogen peroxide concentration and is the main way of degradation at acid pH (76% at pH 2 with 10-3 M hydrogen peroxide concentration, for fluorene oxidation). Rate constants of reactions between the hydroxyl radical and PAHs were found to be 9.9 × 109, 8.8 × 109, and 13.4 × 109 M-1 s-1, for fluorene, acenaphthene, and phenanthrene, respectively. Both UV radiation and UV/H2O2 oxidation of PAHs yield numerous intermediate compounds. Most of these compounds disappear as oxidation time is increased.