Evolution of conducting channels in metallic atomic contacts under elastic deformation

We investigate both experimentally and theoretically the evolution of conductance in metallic one-atom contacts under elastic deformation. While simple metals like Au exhibit almost constant conductance plateaus, Al and Pb show inclined plateaus with positive and negative slopes. It is shown how these behaviors can be understood in terms of the orbital structure of the atoms forming the contact. This analysis provides further insight into the issue of conductance quantization in metallic contacts revealing important aspects of their atomic and electronic structures.

Emergence of half-metallicity in suspended NiO chains: Ab initio electronic structure and quantum transport calculations

Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of this material can become half metallic due to the lower coordination of their atoms. Here we present ab initio electronic structure and quantum transport calculations of ideal infinitely long NiO chains and of more realistic short ones suspended between Ni electrodes. While infinite chains are insulating, short suspended chains are half-metallic minority-spin conductors that displays very large magnetoresistance and a spin-valve behavior controlled by a single atom.

Relationship between static and dynamic elastic modulus of calcarenite heated at different temperatures: the San Julián's stone

The San Julián’s stone is the main material used to build the most important historical buildings in Alicante city (Spain). This paper describes the analysis developed to obtain the relationship between the static and the dynamic modulus of this sedimentary rock heated at different temperatures. The rock specimens have been subjected to heating processes at different temperatures to produce different levels of weathering on 24 specimens. The static and dynamic modulus has been measured for every specimen by means of the ISRM standard and ultrasonic tests, respectively. Finally, two analytic formulas are proposed for the relationship between the static and the dynamic modulus for this stone. The results have been compared with some relationships proposed by different researchers for other types of rock. The expressions presented in this paper can be useful for the analysis, using non-destructive techniques, of the integrity level of historical constructions built with San Julián’s stone affected by fires.

A quasi-elastic aquifer deformational behavior: Madrid aquifer case study

The purpose of this paper is to analyze the quasi-elastic deformational behavior that has been induced by groundwater withdrawal of the Tertiary detrital aquifer of Madrid (Spain). The spatial and temporal evolution of ground surface displacement was estimated by processing two datasets of radar satellite images (SAR) using Persistent Scatterer Interferometry (PSI). The first SAR dataset was acquired between April 1992 and November 2000 by ERS-1 and ERS-2 satellites, and the second one by the ENVISAT satellite between August 2002 and September 2010. The spatial distribution of PSI measurements reveals that the magnitude of the displacement increases gradually towards the center of the well field area, where approximately 80 mm of maximum cumulated displacement is registered. The correlation analysis made between displacement and piezometric time series provides a correlation coefficient greater than 85% for all the wells. The elastic and inelastic components of measured displacements were separated, observing that the elastic component is, on average, more than 4 times the inelastic component for the studied period. Moreover, the hysteresis loops on the stress–strain plots indicate that the response is in the elastic range. These results demonstrate the quasi-elastic behavior of the aquifer. During the aquifer recovery phase ground surface uplift almost recovers from the subsidence experienced during the preceding extraction phase. Taking into account this unique aquifer system, a one dimensional elastic model was calibrated in the period 1997–2000. Subsequently, the model was used to predict the ground surface movements during the period 1992–2010. Modeled displacements were validated with PSI displacement measurements, exhibiting an error of 13% on average, related with the inelastic component of deformation occurring as a long-term trend in low permeability fine-grained units. This result further demonstrates the quasi-elastic deformational behavior of this unique aquifer system.

La Facultad de Derecho de la Universidad de Alicante ante los nuevos planes de estudio

El artículo analiza la evolución de los planes de estudios de Derecho en los últimos treinta años.

Los espacios turísticos de la Comunidad Valenciana: ¿planificación territorial del turismo o evolución espontánea? Los planes regionales y el caso de Peñíscola

La ordenación territorial es la práctica que resulta imprescindible para organizar el uso turístico del espacio. Sin embargo, el objetivo pendiente de algunas autonomías continúa siendo la interrelación entre planificación territorial y planificación turística, dando paso al urbanismo como técnica de ordenación territorial del turismo. Este estudio plantea determinar si la ordenación territorial del turismo en la Comunidad Valenciana a escala autonómica, local e interrelación entre ambas, se encuentra en una etapa integradora o espontanea, y de igual modo, plasmar la problemática de la conceptualización del turismo desde la perspectiva territorial. Mediante la integración de los catorce indicadores propositivos, que Exceltur extrajo de Planes de Ordenación Territorial de distintas autonomías insulares y del litoral mediterráneo, se comprobaron las buenas prácticas en planificación territorial del turismo de la Estrategia Territorial, el Plan de Espacios Turísticos de la Comunidad Valenciana, así como del Plan General de Ordenación Urbana de Peñíscola. Asimismo un hecho que afecta a la elaboración, redacción y consecución de los planes territoriales y/o turísticos valencianos, es la conceptualización sesgada del término turismo, tal y como muestran los resultados de diversas entrevistas en profundidad realizadas a actores especializados en planificación. Los hallazgos de este estudio sugieren que la planificación territorial del turismo en la Comunidad Valenciana continúa su etapa espontánea, mientras que los municipios mantienen su independencia a la hora de gestionar la ordenación y la gestión territorial del turismo.

Revisiting the effect of foundation embedment on elastic settlement: A new approach

The effect of foundation embedment on settlement calculation is a widely researched topic in which there is no scientific consensus regarding the magnitude of settlement reduction. In this paper, a non-linear three dimensional Finite Element analysis has been performed with the aim of evaluating the aforementioned effect. For this purpose, 1800 models were run considering different variables, such as the depth and dimensions of the foundation and the Young’s modulus and Poisson’s ratio of the soil. The settlements from models with foundations at surface level and at depth were then compared and the relationship between them established. The statistical analysis of this data allowed two new expressions, with a mean maximum error of 1.80%, for the embedment influence factor of a foundation to be proposed and these to be compared with commonly used corrections. The proposed equations were validated by comparing the settlements calculated with the proposed influence factors and the true settlements measured in several real foundations. From the comprehensive study of all modelled cases, an improved approach, when compared to those proposed by other authors, for the calculation of the true elastic settlements of an embedded foundation is proposed.

Planes y planos. Sobre las enseñanzas en las escuelas de arquitectura

Reflexión sobre la enseñanza y el aprendizaje, sobre los docentes y los discentes, en las escuelas de Arquitectura y propuesta de una idea de plan de estudios que contemplara tres estadios: un preámbulo que discurre viajando por el ancho mundo; luego la carrera para hacer acopio de destrezas y aprendizajes; y, por fin, la práctica del proyecto de arquitectura en el estudio profesional.

A simple method to predict elastic settlements in foundations resting on two soils of differing deformability

This paper shows the analysis results obtained from more than 200 finite element method (FEM) models used to calculate the settlement of a foundation resting on two soils of differing deformability. The analysis considers such different parameters as the foundation geometry, the percentage of each soil in contact with the foundation base and the ratio of the soils’ elastic moduli. From the described analysis, it is concluded that the maximum settlement of the foundation, calculated by assuming that the foundation is completely resting on the most deformable soil, can be correlated with the settlement calculated by FEM models through a correction coefficient named “settlement reduction factor” (α). As a consequence, a novel expression is proposed for calculating the real settlement of a foundation resting on two soils of different deformability with maximum errors lower than 1.57%, as demonstrated by the statistical analysis carried out. A guide for the application of the proposed simple method is also explained in the paper. Finally, the proposed methodology has been validated using settlement data from an instrumented foundation, indicating that this is a simple, reliable and quick method which allows the computation of the maximum elastic settlement of a raft foundation, evaluates its suitability and optimises its selection process.

Half of a yellow sun

A beautiful sweeping story of two sisters caught up in the events of the Nigerian civil war, ending in chilling violence which shocked the entire world.