Hubbard chain with a Kondo impurity

A Bethe Ansatz solution of a (modified) Hubbard chain with a Kondo impurity of arbitrary spin S at a highly symmetric line of parameter space is proposed and explored. Our results confirm the existence of a strong-coupling (line of) fixed-point(s) with ferromagnetic Kondo coupling as first hypothetized by Furusaki and Nagaosa on the basis of perturbative renormalization group calculations. For on-site Hubbard repulsion and ferromagnetic Kondo exchange, the ground state has spin S-1/2, i.e., is a singlet when S=1/2. The contributions of the impurity to the magnetic susceptibility and low-temperature specific heat are discussed. While the Wilson ratio is unity in the half-filled band, it is found to be a function of density and interaction away from half-filling.Comment: 5 pages, Revte

Scalar Symmetries of the Hubbard Models with Variable Range Hopping

Examples of scalar conserved currents are presented for trigonometric, hyperbolic and elliptic versions of the Hubbard model with non-nearest neighbour variable range hopping. They support for the first time the hypothesis about the integrability of the elliptic version. The two- electron wave functions are constructed in an explicit form.Comment: 9 pages, LaTex2e, no figure

The role of content and language in content and language integrated learning (CLIL) at university: Challenges and implications for ESP

In a context characterized by the increasing presence of CLIL programs in universities with a tradition of ESP courses, we analyze the case of a university in Catalonia (Spain) with regard to the position of CLIL and ESP. As CLIL programs are promoted to improve students' language proficiency in English, we explore the importance of language learning in these programs and the implications derived for ESP. Data were obtained from institutional documentation, class observation, and lecturer and student views on CLIL expressed in focus groups and a questionnaire. Findings show imprecise guidelines for CLIL implementation. Although we can observe an institutional shift from ESP to CLIL, the latter courses do not generally include language support. Lecturer and student perspectives provide useful insights for action that can be taken by ESP course designers to adapt courses to make them more relevant to students' discipline-related needs. Faced with these findings, we propose engaging in collaboration with content lecturers to develop graduates' proficiency in English. This collaboration can take place both through the integration of language in content courses and through the integration of content in ESP courses to make them more relevant to disciplines' communicative needs. (C) 2014 Elsevier Ltd. All rights reserved.Postprint (published version

The Yangian Symmetry of the Hubbard Models with Variable Range Hopping

We present two pairs of Y($sl_2$) Yangian symmetries for the trigonometric and hyperbolic versions of the Hubbard model with non-nearest-neighbour hopping. In both cases the Yangians are mutually commuting, hence can be combined into a Y($sl_2$)$\oplus$Y($sl_2$) Yangian. Their mutual commutativity is of dynamical origin. The known Yangians of the Haldane-Shastry spin chain and the nearest neighbour Hubbard model are contained as limiting cases of our new representations.Comment: 10 pages, Late

Erasmus students using English as a "lingua franca": does study abroad in a non-English-speaking country improve L2 English?

There is a lack of research on the impact of study abroad (SA) on the development of L2 English when students study in non-anglophone countries. The aim of the present study is to fill this gap by examining 39 Catalan/Spanish students who, as part of an Erasmus exchange, spent a term at universities in non-English-speaking European countries. In this context, English was used as the vehicular language for their studies and in their daily extracurricular activities when interacting with other students. Our research focuses the impact of this specific type of SA on students’ L2 English proficiency, and in particular their writing skills. Before and after the SA, students completed the Quick Oxford Placement Test (a general measure of L2 proficiency) and also drafted a short written paragraph in English. Their writing was analysed for syntactic complexity, lexical complexity and subordination. The results show that participants improved significantly after their SA on two out of the four measures: general L2 proficiency and lexical complexity. Though threshold levels of general proficiency have been posited for students’ ability to benefit linguistically from SA, in this case, L2 proficiency at the outset of the SA experience was found not to influence the development of writing skills, except on the measure of subordination. Implications are drawn for further research and pedagogic practice in developing English as a lingua franca skills in a European context.Peer ReviewedPreprin

The association of family and peer factors with tobacco, alcohol, and marijuana use among Chilean adolescents in neighborhood context

Research on adolescent use of substances has long sought to understand the family factors that may be associated with use of different substances such as alcohol, tobacco and marijuana. However, scant attention has been focused on these questions in Latin American contexts, despite growing concerns about substance use among Latin American youth. Using data from a sample of 866 Chilean youth, we examined the relationship of family and neighborhood factors with youth substance abuse. We found that in a Latin American context access to substances is an important predictor of use, but that neighborhood effects differ for marijuana use as opposed to cigarettes or alcohol. Age of youth, family and peer relationships, and gender all play significant roles of substance use.The study findings provide additional evidence that the use of substances is complex whereby individual, family, and community influences must be considered jointly to prevent or reduce substance use among adolescents.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3249750/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3249750/Accepted manuscrip