Electron correlations, spontaneous magnetization and momentum density in quantum dots

The magnetization of quantum dots is discussed in terms of a relatively simple but exactly solvable model Hamiltonian. The model predicts oscillations in spin polarization as a function of dot radius for a fixed electron density. These oscillations in magnetization are shown to yield distinct signature in the momentum density of the electron gas, suggesting the usefulness of momentum resolved spectroscopies for investigating the magnetization of dot systems. We also present variational quantum Monte Carlo calculations on a square dot containing 12 electrons in order to gain insight into correlation effects on the interactions between like and unlike spins in a quantum dot.Comment: 6 pages, 4 figure

Qmethod: A package to explore human perspectives using Q methodology

Q is a methodology to explore the distinct subjective perspectives that exist within a group. It is used increasingly across disciplines. The methodology is semi-qualitative and the data are analysed using data reduction methods to discern the existing patterns of thought. This package is the first to perform Q analysis in R, and it provides many advantages to the existing software: namely, it is fully cross-platform, the algorithms can be transparently examined, it provides results in a clearly structured and tabulated form ready for further exploration and modelling, it produces a graphical summary of the results, and it generates a more concise report of the distinguishing and consensus statements. This paper introduces the methodology and explains how to use the package, its advantages as well as its limitations. I illustrate the main functions with a dataset on value patterns about democracy.During the development of this package, the author was funded by the Department of Research of the Basque Government. The author is grateful to Steven Brown and Peter Schmolck for making Q datasets publicly available and for allowing the Lipset dataset to be used in this R package; to Laurent Gatto for his advice in developing it; and to Ben Fried, two anonymous reviewers, and the editor for their useful comments on the manuscript.This is the final published version of the article. It was originally published in The R Journal (Zabala A, The R Journal, 2014, 6(2),163-173). The final version is available at http://journal.r-project.org/archive/2014-2/zabala.pd

Magnetism in Atomic-Sized Palladium Contacts and Nanowires

We have investigated Pd nanowires theoretically, and found that, unlike either metallic or free atomic Pd, they exhibit Hund's rule magnetism. In long, monoatomic wires, we find a spin moment of 0.7 Bohr magnetons per atom, whereas for short, monoatomic wires between bulk leads, the predicted moment is about 0.3 Bohr magnetons per wire atom. In contrast, a coaxial (6,1) wire was found to be nonmagnetic. The origin of the wire magnetism is analyzed.Comment: 6 pages, including 4 figure

Conclusiones

El tema general que aglutina los trabajos presentados en este volumen pobreza, exclusión social y discriminación étnico-racial en América Latina y el Caribe ha sido abordado por los autores en sus múltiples interrelaciones, destacándose en todos el rol de la discriminación étnico-racial en los procesos de producción y reproducción de pobreza. De tal manera, los temas específicos tratados, a saber, discriminación laboral, género y familia, cultura e identidad, implicaciones sociales y políticas, más que un diagnóstico de la problemática en la región, han dado cuenta de las múltiples interrelaciones existentes entre esos fenómenos, y de las diversas aristas que ellos suponen para la investigación y transformación social. Los retos que quedan planteados para la continuidad en el estudio y discusión sobre los temas de pobreza, exclusión social y discriminación étnico-racial en América Latina y el Caribe pueden resumirse en los siguientes: desarrollo de estudios comparativos en la región; logro de mayor vínculo e incidencia en la esfera de la toma de decisiones; profundización en el análisis de las diversas experiencias de desarrollo en la región y de los impactos específicos de las políticas y programas sociales; y consideración de los criterios y propuestas de los actores sociales involucrados, así como de la sociedad civil

Precolonial institutions and deforestation in Africa

We find that local institutions inherited from the precolonial era continue to play an important role in natural resource governance in Africa. Using satellite image data, we find a significant and robust relationship between deforestation and precolonial succession rules of local leaders (local chiefs). In particular, we find that those precolonial areas where local leaders were appointed by ‘social standing’ have higher rates of deforestation compared to the base case of hereditary rule and where local leaders were appointed from above (by paramount chiefs). While the transmission mechanisms behind these results are complex, we suggest that areas where local leaders were appointed by social standing are more likely to have poorer institutions governing local leadership and forest management.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.landusepol.2015.10.03

Fish assemblages across the Mediterranean Sea and the effects of protection from fishing = I Popolamenti ittici nel Mediterraneo e gli effetti della protezione dall’impatto della pesca

Several studies have assessed the effectiveness of individual marine protected areas (MPAs) in protecting fish assemblages, but regional assessments of multiple parks are scarce. Here fish surveys using visual census were done in marine parks and fished areas at 31 locations across the Mediterranean Sea. Fish species richness, diversity and biomass (especially of top predators) were higher in MPAs compared to fished areas, and community structure differed significantly between MPAs and fished areas. Results suggest that MPAs are generally effective means to protect and recover fish populations and assemblages

Spontaneous Magnetization and Electron Momentum Density in 3D Quantum Dots

We discuss an exactly solvable model Hamiltonian for describing the interacting electron gas in a quantum dot. Results for a spherical square well confining potential are presented. The ground state is found to exhibit striking oscillations in spin polarization with dot radius at a fixed electron density. These oscillations are shown to induce characteristic signatures in the momentum density of the electron gas, providing a novel route for direct experimental observation of the dot magnetization via spectroscopies sensitive to the electron momentum density.Comment: 5 pages (Revtex4), 4 (eps) figure

Comment on “Phase contribution of image potential on empty quantum well states in Pb islands on the Cu(111) surface”

1 página, 1 figura.-- PACS numbers: 68.37.Ef, 68.65.Fg, 73.21.FgThis work was partially funded by MCINN(FIS2010- 19609-C02-01) and G.V-UPV/EHU(IT-366-07).Peer reviewe