Influence of the Compaction Pressure and Sintering Temperature on the Mechanical Properties of Porous Titanium for Biomedical Applications

In the present work, the use of porous titanium is proposed as a solution to the difference in stiffness between the implant and bone tissue, avoiding the bone resorption. Conventional powder metallurgical technique is an industrially established route for fabrication of this type of material. The results are discussed in terms of the influence of compaction pressure and sintering temperature on the porosity (volumetric fraction, size, and morphology) and the quality of the sintering necks. A very good agreement between the predicted values obtained using a simple 2D finite element model, the experimental uniaxial compression behavior, and the analytical model proposed by Nielsen, has been found for both the Young’s modulus and the yield strength. The porous samples obtained by the loose sintering technique and using temperatures between 1000 °C −1100 °C (about 40% of total porosity) are recommended for achieving a suitable biomechanical behavior for cortical bone partial replacement.Ministry of Economy and Competitiveness of the State General Administration of Spain grant MAT2015-71284-

La Mentoría como elemento de mejora en el proceso de enseñanza - aprendizaje

Este artículo describe una experiencia de mentoría llevada a cabo dentro de la Universidad de Granada con el objetivo de mejorar la calidad de la enseñanza que en ella se ofrece. Se han realizado diferentes actividades (grabaciones en vídeo y seminarios de formación) que han dado lugar a acciones de mejora concretas de la docencia, la tutoría y la evaluación de los alumnos. A tenor de los resultados de diferentes encuestas, la experiencia ha sido muy positiva no sólo para el profesor mentor y el profesor novel, sino también para sus alumnos.SUMMARY: This paper describes a mentoring experience carried out in the University of Granada with the aim of improving the quality of the education that this offers. Different activities have been performed (video recording and training seminars) which have given rise to concrete measures for the improvement of the teaching, the tutoring, and the evaluation of the students. According to the results of different surveys, the experience has been very positive not only for the mentor and the beginning teacher, but also for their students.Peer Reviewe

Distributed scheduling and data sharing in late-binding overlays

Pull-based late-binding overlays are used in some of today’s largest computational grids. Job agents are submitted to resources with the duty of retrieving real workload from a central queue at runtime. This helps overcome the problems of these very complex environments, namely, heterogeneity, imprecise status information and relatively high failure rates. In addition, the late job assignment allows dynamic adaptation to changes in the grid conditions or user priorities. However, as the scale grows, the central assignment queue may become a bottleneck for the whole system. This article presents a distributed scheduling architecture for late-binding overlays, which addresses these scalability issues. Our system lets execution nodes build a distributed hash table and delegates job matching and assignment to them. This reduces the load on the central server and makes the system much more scalable and robust. Moreover, scalability makes fine-grained scheduling possible, and enables new functionalities like the implementation of a distributed data cache on the execution nodes, which helps alleviate the commonly congested grid storage services

A Proposal for a Modified Moller-Plesset Perturbation Theory

A modified version of the Moller-Plesset approach for obtaining the correlation energy associated to a Hartree-Fock ground state is proposed. The method is tested in a model of interacting fermions that allows for an exact solution. Using up to third order terms improved results are obtained, even more accurate in the limit of loosely bound particles. This result suggests the possible convenience of the scheme for the study of chemical bound problems.Comment: 10 pages, 1 figur

Saproxylic beetles and syrphids (Coleoptera; Diptera: Syrphidae) of the “dehesa” from the western Iberian: the Biological Reserve of “Campanarios de Azaba” (Salamanca)

Se aporta la relación de especies de coleópteros y sírfidos saproxílicos que habitan en ecosistemas de dehesa del oeste ibérico. Se ha estudiado la Reserva Biológica de Campanarios de Azaba, provincia de Salamanca, designada en 2013 como primera Reserva Entomológica de España por la Asociación española de Entomología. Durante los 19 meses de muestreo se registraron 9.603 ejemplares de coleópteros saproxílicos pertenecientes a 157 especies (40 familias) y 477 ejemplares de sírfidos saproxílicos pertenecientes a 18 especies. Para la recolección del material se utilizaron trampas de emergencia y trampas de ventana. Entre los insectos capturados hay diez especies amenazadas, ya sea a nivel europeo o de España, que, a la vista de los resultados, mantienen poblaciones abundantes en este ecosistema de dehesa del oeste ibérico.We provide a checklist of the saproxylic beetles and syrphids species inhabiting the “dehesa” ecosystem from western Iberian. We have studied the Biological Reserve of “Campanarios de Azaba”, Salamanca province, designated in 2013 as the first Entomological Reserve by the “Asociación española de Entomología”. During the 19 months of sampling period a total of 9, 603 specimens of saproxylic beetles belong to 157 species (40 families) and 477 specimens of saproxylic syrphids belonging to 18 species. In order to collect the specimens we used both emergence and window traps. Among the captured insects are ten threatened species either at European and Spanish levels, which maintain abundant populations inhabiting this “dehesa” ecosystem.Esta investigación fue financiada por el Ministerio de Ciencia e Innovación (CGL2011-23658), Ministerio de Economía y Competitividad (CGL2012-31669) y Generalitat Valenciana (proyectos PROMETEO/2013/03412 y ACOMP/2014/140). A. R. H. agradece la beca predoctoral recibida por la Generalitat Valenciana a través del programa Santiago Grisolía (GRISOLIA/2010/080)

Path-integral molecular dynamics simulation of 3C-SiC

Molecular dynamics simulations of 3C-SiC have been performed as a function of pressure and temperature. These simulations treat both electrons and atomic nuclei by quantum mechanical methods. While the electronic structure of the solid is described by an efficient tight-binding Hamiltonian, the nuclei dynamics is treated by the path integral formulation of statistical mechanics. To assess the relevance of nuclear quantum effects, the results of quantum simulations are compared to others where either the Si nuclei, the C nuclei or both atomic nuclei are treated as classical particles. We find that the experimental thermal expansion of 3C-SiC is realistically reproduced by our simulations. The calculated bulk modulus of 3C-SiC and its pressure derivative at room temperature show also good agreement with the available experimental data. The effect of the electron-phonon interaction on the direct electronic gap of 3C-SiC has been calculated as a function of temperature and related to results obtained for bulk diamond and Si. Comparison to available experimental data shows satisfactory agreement, although we observe that the employed tight-binding model tends to overestimate the magnitude of the electron-phonon interaction. The effect of treating the atomic nuclei as classical particles on the direct gap of 3C-SiC has been assessed. We find that non-linear quantum effects related to the atomic masses are particularly relevant at temperatures below 250 K.Comment: 14 pages, 15 figure

Three-dimensional volume rendering in computed tomography for evaluation of the temporomandibular joint in dogs

Based on computed tomography (CT) images, volume rendering was used to obtain a three-dimensional representation of data (3DVR). The aims of this study included: describing the bone anatomy of the temporomandibular joint (TMJ) of dogs; comparing the TMJs of each dog by skull type and age; comparing 3DVR images with three-standard-plane CTs; assessing soft tissues adjacent to the TMJ and assessing pathological cases. Multidetector computed tomography scans of bilateral TMJs of 410 dogs were observed. From a ventral view, slight displacements in the positions of the skulls were seen, whereas from a caudal view, differences in amplitude of the articular space were observed. Dolichocephalic and mesaticephalic dogs showed more similar TMJ features than brachycephalic dogs. The shape of the TMJ bones were irregular in dogs under 1 year old. The 3DVR images related to the three-standard-plane CT improved the overall comprehension of the changes in the articular space amplitude and condylar process morphology. The fovea pterygoidea, mandibular fossa and retroarticular process were perfectly shown. A better spatial situation of adjacent soft tissues was obtained. The 3DVR represents an ancillary method to the standard-plane CT that could help in the understanding of the anatomy and diagnoses of different pathologies of the TMJ in dogs

Thermal transport in glassy selenium: The role of low-frequency librations

7 págs.; 3 figs.The experimental curves giving the temperature dependence of the thermal conductivity of glassy selenium are considered in detail. The observed behavior can be taken into account quantitatively if the densities of states for short-wavelength phonons as well as for low-energy librations arising from computer simulations are used for the calculations. In particular, it is shown that the lowest frequency excitations of a chain of selenium atoms can give due account of the plateau observed at temperatures about 2-10 K. The implications of the present findings for the current debate regarding the mechanisms for thermal transport in glasses are finally discussed. © 1994 The American Physical Society.This work has been supported by DGICYT Grant No. PB92-0114-C03Peer Reviewe