Capillary-Wave Model for the Solidification of Dilute Binary Alloys

Starting from a phase-field description of the isothermal solidification of a dilute binary alloy, we establish a model where capillary waves of the solidification front interact with the diffusive concentration field of the solute. The model does not rely on the sharp-interface assumption, and includes non-equilibrium effects, relevant in the rapid-growth regime. In many applications it can be evaluated analytically, culminating in the appearance of an instability which, interfering with the Mullins-Sekerka instability, is similar to that, found by Cahn in grain-boundary motion.Comment: 17 pages, 12 figure

La praxis pedagógica

La Pedagogía puede considerarse praxis tanto en su vertiente teórica como práctica. La Pedagogía "teórica" debe revalorizarse en términos de praxis. No sólo explicativa o interpretativa, también transformativa, mediadora entre otras prácticas educativas. Pero en esta ponencia queremos referirnos a la Pedagogía en su vertiente práctica, cuando es práctica y no sólo pensamiento. La Pedagogía como práctica es interacción intersubjetiva, deliberativa, argumentativa, imbuída o informada éticamente, que requiere de variados "saber hacer" (savoir faire), que en el sentido aristotélico es a la vez praxis (relación entre sujetos) y poiesis (relación de los sujetos con objetos). Interacción incluida y atravesada por la realidad social, que también es práctica social subjetiva objetivada, condicionante, como alienante o liberadora. Nos preguntamos en qué consiste su especificidad, y cuáles son sus nexos con otras prácticas educativas. Sabemos que a diferencia del momento reflexivo con énfasis analítico, la praxis demanda una mirada sintética, orientada a la acción; y a diferencia de limitarse al conocimiento de la realidad, requiere de la utopía; conlleva un carácter propositivo, una elección de valores ético políticos, una construcción de sentidos culturales, que trascienden la descripción y la explicación. Referirse a la Pedagogía requiere una distinción reflexiva entre "lo pedagógico" -que trata sobre la educación- y "lo didáctico" -que trata sobre la enseñanza. Reconocemos que no puede haber educación sin enseñanza, pero también que la enseñanza no agota la educación. Temas como ciudadanía, género, violencia, trabajo, no se resuelven dictando clases o desarrollando unidades didácticas particulares. La Pedagogía y la intervención pedagógica abordan la participación de diversos actores educacionales, no limitados a los enseñantes; toman decisiones acerca de relevancias temáticas, previas al planeamiento didáctico; trabajan sobre los ámbitos institucionales, no sólo en el análisis sino en la intervención guiada por valores. Específicamente, la Pedagogía recupera las nociones de formación y humanismo, implícitas en la propuesta del "Bildung"

The genus Bolbelasmus in the western and southern regions of the Mediterranean Basin (Coleoptera: Geotrupidae: Bolboceratinae)

The Bolbelasmus Boucomont, 1911 species of the western and southern regions of the Mediterranean Basin (Northern Africa, Iberian Peninsula and France) are revised. The following three new species are described: Bolbelasmus brancoi Hillert & Král sp. nov. and Bolbelasmus howdeni Hillert & Král sp. nov., both from Spain and Gibraltar, and Bolbelasmus nikolajevi Hillert, Arnone, Král & Massa sp. nov. from Egypt, Libya and Tunisia. Bolbelasmus vaulogeri (Abeille de Perrin, 1898) stat. restit. is removed from synonymy with B. bocchus (Erichson, 1841) and reinstated as a separate species. Bolbelasmus romanorum Arnone & Massa, 2010 is considered a junior subjective synonym of B. vaulogeri. Lectotypes for Bolboceras bocchus Erichson, 1841 and Bolboceras vaulogeri Abeille de Perrin, 1898 are designated. Relevant diagnostic characters (head, pronotum, elytron, external male genitalia) are illustrated. Identifi cation keys for both males and females, and an annotated list of the Western Palaearctic representatives of the genus Bolbelasmus are presented. Finally, fi rst records are given for B. gallicus (Mulsant, 1842) from Corsica and the Midi-Pyrénées region of France, B. keithi Miessen & Trichas, 2011 from the Greek island of Rhodes, and B. unicornis (Schrank von Paula, 1789) from the Tuscany province of Italy

El reconocimiento en las representaciones mutuas de los sujetos del campo profesional de la educación

Este trabajo presenta algunos resultados, leídos desde la Teoría del Reconocimiento, del Proyecto de Investigación “Sujetos sociales del campoprofesional de la educación: representaciones mutuas e interacción delos especialistas en educación en función docente y no docente”, radicado en el IICE (Instituto de Investigacionesen Ciencias de la Educación, Facultadde Filosofía y Letras, Universidadde Buenos Aires). De acuerdo com nuestro estudio, el Reconocimiento es una categoría que aparece en el discurso espontáneo de los trabajadores del campo profesional de la educación.Para los investigadores pareceser un analizador fértil en la lecturade la información, la construcción de los datos, y la interpretación de conjunto del campo profesional como campo de poder

Oxygen on Ni(111): A multiple-scattering analysis of the near-edge x-ray-absorption fine structure

Oxygen chemisorption and oxide formation on a Ni(111) surface have been monitored by using the near-edge x-ray-absorption fine-structure technique. The adsorption site of oxygen in the p(2×2) and (√3 × √3 )R30° superstructures has been determined by a multiple-scattering analysis. In both structures the oxygen occupies a threefold-coordinated fcc site with a nearest-neighbor O-Ni bond length of 1.85±0.05 Å on a Ni(111) surface relaxed outwards by ∼0.15 Å

Assessment techniques, database design and software facilities for thermodynamics and diffusion

The purpose of this article is to give a set of recommendations to producers of assessed thermodynamic data, who may be involved in either the critical evaluation of limited chemical systems or the creation and dissemination of larger thermodynamic databases. Also, it is hoped that reviewers and editors of scientific publications in this field will find some of the information useful. Good practice in the assessment process is essential, particularly as datasets from many different sources may be combined together into a single database. With this in mind, we highlight some problems that can arise during the assessment process and we propose a quality assurance procedure. It is worth mentioning at this point, that the provision of reliable assessed thermodynamic data relies heavily on the availability of high quality experimental information. The different software packages for thermodynamics and diffusion are described here only briefly

Freirean dialogues of yesterday and today

A partir de los textos de Paulo Freire, se presentan diálogos —entendidos como controversias, argumentaciones, enriquecimientos— sobre la teología de la liberación, el desarrollismo, el marxismo, la pedagogía moderna, el Qué hacer de Lenin, el papel de lxs maestrxs, la conciencia y el liderazgo. Sin duda, su pensamiento puede ser objeto de críticas, y sin duda toma de la Modernidad muchos componentes, defendibles o cuestionables: el tema de la conciencia, el lugar del conocimiento científico y del docente, la división naturaleza-cultura, la división razón-emoción. Pero nada de ello disminuye su mérito de haber debatido teóricamente y ensayado —como praxis— una relación pedagógica alternativa y opuesta a la tradicional. Esto significa que los cambios en educación, incluso en el caso de una revolución como la freireana y aun cuando haya minado las bases de la educación moderna, no pueden trocar una totalidad por otra, sino que contienen elementos nuevos y viejos; de estos, algunos deberán ser desechados, pero otros perdurarán, porque al ser adecuados, o necesarios, o incompletos y abiertos a transformaciones, trascienden una época.Starting from Paulo Freire’s texts, this article features dialogues - understood as controversies, arguments, enrichments —about liberation theology, the development theory, marxism, modern pedagogy, Lenin’s What to do, the role of teachers, conscience and leadership—. No doubt his thoughts can be criticized, and he undoubtedly takes on Modernity many components, defensible or questionable: the theme of consciousness, the place of scientific knowledge, the place of teachers, the nature-culture division, the reason-emotion division. But none of this diminishes his merit of having theoretically debated and rehearsed —as praxis— a pedagogical relationship alternative and opposite to the traditional. Which means that changes in education, even in the case of a revolution like the freirean, and even when it has undermined the bases of modern education, cannot turn a totality for another totality, but instead contain new and old elements; some of them must be discarded, but others will endure, because if they are adequate, or necessary, or incomplete and open to new transformations, they transcend an era

Missing-row reconstruction in the system (2×1)O/Ag(110): A surface extended x-ray-absorption fine-structure study

Oxygen K-edge surface extended x-ray-absorption fine-structure studies on the (2×1)O/Ag(110) system confirm the long-bridge adsorption site with a nearest-neighbor O-Ag bond length of 2.05±0.03 Å. They show that oxygen adsorbs close to the surface inducing a reconstruction of the missing-row type. Structural similarities of the (2×1)O phases on Ni(110), Cu(110), and Ag(110) are discussed

Multiple sclerosis and psychiatric disorders : comorbidity and sibling risk in a nationwide Swedish cohort

Background: Psychiatric disorders are known to be prevalent in Multiple Sclerosis (MS). Objective: To study comorbidity between MS and bipolar disorder, schizophrenia and depression in a nation-wide cohort and to determine whether shared genetic liability underlies the putative association. Methods: We identified ICD-diagnosed patients with MS (n=16,467), bipolar disorder (n=30,761), schizophrenia (n= 22,781) and depression (n=172,479) in the Swedish National Patient Register and identified their siblings in the Multi-Generation Register. The risk of MS was compared in psychiatric patients and in matched unexposed individuals. Shared familial risk between MS and psychiatric disorders was estimated by sibling comparison. Results: The risk of MS was increased in patients with bipolar disorder (hazard ratio [HR] 1.8, 95% confidence interval [CI] 1.6-2.2, p<0.0001) and depression (HR 1.9, 95% CI 1.7-2.0, p<0.0001). MS risk in schizophrenia was decreased (HR 0.6, 95% CI 0.4-0.9, p=0.005). The association between having a sibling with a psychiatric disorder and developing MS was not significant. Conclusion: We found a strong positive association between MS and bipolar disorder and depression that could not be explained by genetic liability. The unexpected negative association between MS and schizophrenia might be spurious or indicate possible protective mechanisms that warrant further exploration.Stockholm County CouncilThe Swedish Research CouncilKarolinska InstitutetAccepte

First-principles study of ternary fcc solution phases from special quasirandom structures

In the present work, ternary Special Quasirandom Structures (SQSs) for a fcc solid solution phase are generated at different compositions, $x_A=x_B=x_C=\tfrac{1}{3}$ and $x_A=\tfrac{1}{2}$, $x_B=x_C=\tfrac{1}{4}$, whose correlation functions are satisfactorily close to those of a random fcc solution. The generated SQSs are used to calculate the mixing enthalpy of the fcc phase in the Ca-Sr-Yb system. It is observed that first-principles calculations of all the binary and ternary SQSs in the Ca-Sr-Yb system exhibit very small local relaxation. It is concluded that the fcc ternary SQSs can provide valuable information about the mixing behavior of the fcc ternary solid solution phase. The SQSs presented in this work can be widely used to study the behavior of ternary fcc solid solutions.Comment: 20 pages, 7 figure