El español en el aula de inglés: un estudio empírico

This experiment explores the advantages of using the L1 in the EFL classroom in activities such as explicit presentation of form-based content. Two groups of 33 pupils -the control and the experimental- were taught a specific morphosyntactic structure -the passive- in five classes. Three tests were then administered -immediate, delayed and late- and the results compared. The independent variable was the use or non-use of the L1 in the five sessions of presentation and subsequent activities. The results of all parameters analyzed showed differences in favour of the control group; in many cases these differences were statistically significant according to Ttests applied at a significance level of 5% (a < .5). This suggests that, in a monolingual classroom, the minimal role played by the L1 accorded by the current orthodoxy of foreign-language teaching methodology should be revised; it does not, however, undermine the centrality of exposure to the L2 and interaction in it

Nuevas tendencias en el uso de la L1

This paper discusses certain changes that have taken place among theorists and publishers as regards the use of the mother tongue (L1) in EFL/ESL textbooks aimed at students who share a common L1. The general orthodoxy in the last three decades tended to consider that the L1 should not be present at all in either L2 classrooms or textbooks. This tendency seems to be shifting to a more comprehensive and flexible view of the role and possible use of the L1. Thus, nowadays a good number of textbooks with explicit use of L1 can be found in the Spanish market of EFL textbooks. This paper analyzes some of these textbooks, the activities they present in the L1 and the causes for the change

Input cost, capacity utilization and substitution in the short run

This article studies the behavior of input cost shares in an environment where labor is costly to adjust, materials can be adjusted at no cost and capital is fixed. A model relating cost shares with relative prices and adjustment costs is proposed, allowing joint estimation of the elasticity of substitution and the adjustment cost function, which is an unknown function of the utilization capacity. Based on a panel of more than 700 manufacturing firms, we find evidence of strong input share variations according to the degree of capacity utilization. The estimated shapes of adjustment costs curves of labor are in agreement with our theoretical model, and we obtain sensible elasticities of substitution estimates. Based on such estimates, we find evidence of a negative (positive) bias in downturns (recoveries) in conventional productivity growth measures

On the relationship between bilevel decomposition algorithms and direct interior-point methods

Engineers have been using bilevel decomposition algorithms to solve certain nonconvex large-scale optimization problems arising in engineering design projects. These algorithms transform the large-scale problem into a bilevel program with one upperlevel problem (the master problem) and several lower-level problems (the subproblems). Unfortunately, there is analytical and numerical evidence that some of these commonly used bilevel decomposition algorithms may fail to converge even when the starting point is very close to the minimizer. In this paper, we establish a relationship between a particular bilevel decomposition algorithm, which only performs one iteration of an interior-point method when solving the subproblems, and a direct interior-point method, which solves the problem in its original (integrated) form. Using this relationship, we formally prove that the bilevel decomposition algorithm converges locally at a superlinear rate. The relevance of our analysis is that it bridges the gap between the incipient local convergence theory of bilevel decomposition algorithms and the mature theory of direct interior-point methods

On the intrinsic and the spatial numerical range

For a bounded function $f$ from the unit sphere of a closed subspace $X$ of a Banach space $Y$, we study when the closed convex hull of its spatial numerical range $W(f)$ is equal to its intrinsic numerical range $V(f)$. We show that for every infinite-dimensional Banach space $X$ there is a superspace $Y$ and a bounded linear operator $T:X\longrightarrow Y$ such that $\bar{co} W(T)\neq V(T)$. We also show that, up to renormig, for every non-reflexive Banach space $Y$, one can find a closed subspace $X$ and a bounded linear operator $T\in L(X,Y)$ such that $\bar{co} W(T)\neq V(T)$. Finally, we introduce a sufficient condition for the closed convex hull of the spatial numerical range to be equal to the intrinsic numerical range, which we call the Bishop-Phelps-Bollobas property, and which is weaker than the uniform smoothness and the finite-dimensionality. We characterize strong subdifferentiability and uniform smoothness in terms of this property.Comment: 12 page

A hierarchy of topological tensor network states

We present a hierarchy of quantum many-body states among which many examples of topological order can be identified by construction. We define these states in terms of a general, basis-independent framework of tensor networks based on the algebraic setting of finite-dimensional Hopf C*-algebras. At the top of the hierarchy we identify ground states of new topological lattice models extending Kitaev's quantum double models [26]. For these states we exhibit the mechanism responsible for their non-zero topological entanglement entropy by constructing a renormalization group flow. Furthermore it is shown that those states of the hierarchy associated with Kitaev's original quantum double models are related to each other by the condensation of topological charges. We conjecture that charge condensation is the physical mechanism underlying the hierarchy in general.Comment: 61 page