Consideraciones didácticas sobre la enseñanza de lenguas extranjeras asistida por ordenador.

El desarrollo de las nuevas tecnologías en las últimas décadas nos ha impulsado a reflexionar sobre las posibilidades que la tecnología multimedia puede aportar a la enseñanza de la lengua extranjera, con sus ventajas y limitaciones. Partiendo de la evolución de los distintos enfoques en este campo, examinamos algunos programas actuales en CD-ROM y evaluamos sus diferentes actividades y contenidos. También consideramos de qué manera Internet está cambiando la concepción de la enseñanza y el papel del profesor y del alumno

A generalized Chudley-Elliott vibration-jump model in activated atom surface diffusion

Here the authors provide a generalized Chudley-Elliott expression for activated atom surface diffusion which takes into account the coupling between both low-frequency vibrational motion (namely, the frustrated translational modes) and diffusion. This expression is derived within the Gaussian approximation framework for the intermediate scattering function at low coverage. Moreover, inelastic contributions (arising from creation and annihilation processes) to the full width at half maximum of the quasi-elastic peak are also obtained.Comment: (5 pages, 2 figures; revised version

Stochastic theory of lineshape broadening in quasielastic He atom scattering with interacting adsorbates

The activated surface diffusion of interacting adsorbates is described in terms of the so-called interacting single adsorbate approximation, which is applied to the diffusion of Na atoms on Cu(001) for coverages up to 20% in quasielastic He atom scattering experiments. This approximation essentially consists of solving the standard Langevin equation with two noise sources and frictions: a Gaussian white noise accounting for the friction with the substrate, and a white shot noise characterized by a collisional friction simulating the adsorbate-adsorbate collisions. The broadenings undergone by the quasielastic peak are found to be in very good agreement with the experimental data reported at two surface temperatures 200 and 300 K.Comment: 6 pages, 3 figure

Vacuum fluctuations and the conditional homodyne detection of squeezed light

Conditional homodyne detection of quadrature squeezing is compared with standard nonconditional detection. Whereas the latter identifies nonclassicality in a quantitative way, as a reduction of the noise power below the shot noise level, conditional detection makes a qualitative distinction between vacuum state squeezing and squeezed classical noise. Implications of this comparison for the realistic interpretation of vacuum fluctuations (stochastic electrodynamics) are discussed.Comment: 14 pages, 7 figures, to appear in J. Opt. B: Quantum Semiclass. Op

Line Shape Broadening in Surface Diffusion of Interacting Adsorbates with Quasielastic He Atom Scattering

The experimental line shape broadening observed in adsorbate diffusion on metal surfaces with increasing coverage is usually related to the nature of the adsorbate-adsorbate interaction. Here we show that this broadening can also be understood in terms of a fully stochastic model just considering two noise sources: (i) a Gaussian white noise accounting for the surface friction, and (ii) a shot noise replacing the physical adsorbate-adsorbate interaction potential. Furthermore, contrary to what could be expected, for relatively weak adsorbate-substrate interactions the opposite effect is predicted: line shapes get narrower with increasing coverage.Comment: 4 pages, 2 figures (slightly revised version

Neoteetonics of the eastern border of the Madrid basin

[Abstract] An analysis ofthe neotectonic activity and the current stress state of the eastern border of Madrid Basin has been carried ont using structural-methods (fault population analysis), as well as seismological methods. Two stress tensors have been established: - Tensor 1: with a N1500E shortening trend, characterized mainly by strikeslip faults. This tensor corresponds to the «Guadarrama» stress field (Capote et al., 1990), wihch causes the Central System structure; dated middle Aragonian -lower Pleistocene in the eastern border ofMadrid Basin (Muñoz Martín, 1993). - Tensor 2: dated post-Iower Pleistocene, with a N150° E extension trend, characterized basically by normal faults. Actual stress tensor deduced focal mechanisms by the seismological method is compatible with the paleostress field deduced for the middle-Iower Pleistocene (tensor 2)

Quantum Zeno and anti-Zeno effects in surface diffusion of interacting adsorbates

Surface diffusion of interacting adsorbates is here analyzed within the context of two fundamental phenomena of quantum dynamics, namely the quantum Zeno effect and the anti-Zeno effect. The physical implications of these effects are introduced here in a rather simple and general manner within the framework of non-selective measurements and for two (surface) temperature regimes: high and very low (including zero temperature). The quantum intermediate scattering function describing the adsorbate diffusion process is then evaluated for flat surfaces, since it is fully analytical in this case. Finally, a generalization to corrugated surfaces is also discussed. In this regard, it is found that, considering a Markovian framework and high surface temperatures, the anti-Zeno effect has already been observed, though not recognized as such.Comment: 17 pages, 1 figur

Quasi-elastic peak lineshapes in adsorbate diffusion on nearly flat surfaces at low coverages: the motional narrowing effect in Xe on Pt(111)

Quasi-elastic helium atom scattering measurements have provided clear evidence for a two-dimensional free gas of Xe atoms on Pt(111) at low coverages. Increasing the friction due to the surface, a gradual change of the shape of the quasi-elastic peak is predicted and analyzed for this system in terms of the so-called motional narrowing effect. The type of analysis presented here for the quasi-elastic peak should be prior to any deconvolution procedure carried out in order to better extract information from the process, e.g. diffusion coefficients and jump distributions. Moreover, this analysis also provides conditions for the free gas regime different than those reported earlier.Comment: 12 pages, 4 figures (revised version

New challenges for the definition of functional geographies

Studies from both Eurostat and the OECD shortly before the 2020/2021 Census ‘round’ concluded with one recommended approach to defining functional geographies (FGs). The question of which method to use in defining FGs for official statistics and policy has been superceded by challenging questions about the data to use for these definitions. One major concern stems from the decline of full Census-taking around the world, and in particular the reduced collection of the commuting data usually central to definitions of FGs. A more acute issue is that the 2020/2021 Census ‘round’ coincided with the Covid pandemic so that in many countries any commuting data collected reflects a brief and probably unique moment in time (eg. a total ‘lockdown’ in some countries). Defining FGs for official statistics and policy in the mid-2020s would ideally use data on ‘new normal’ patterns of commuting. Countries without a full register system or a new Census lack the necessary highly granular commuting data. This has led to increasing interest in the potential of call data from mobile phones as a surrogate for commuting data. This paper draws on research in Spain on the specific example of using data from mobiles to define a set of FGs. The approach taken is to evaluate the limits to the utility of mobile phone data by identifying a list of issues arising when using mobile phone data as a surrogate for Census commuting data, especially when seeking to define FGs

Magneto-Dielectric Effect in the S = 1/2 Quasi-Two Dimensional Antiferromagnet K2V3O8

We report the optical and magneto-optical properties of K2V3O8, an S=1/2 quasi-two-dimensional Heisenberg antiferromagnet. Local spin density approximation electronic structure calculations are used to assign the observed excitations and analyze the field dependent features. Two large magneto-optical effects, centered at ~1.19 and 2.5 eV, are attributed to field-induced changes in the V 4+ d to d on-site excitations due to modification of the local crystal field environment of the VO5 square pyramids with applied magnetic field. Taken together, the evidence for a soft lattice, the presence of vibrational fine structure on the sharp 1.19 eV magneto-optical feature,and the fact that these optical excitations are due to transitions from a nearly pure spin polarized V d state to hybridized states involving both V and O, suggest that the magneto-dielectric effect in K2V3O8 is driven by strong lattice coupling.Comment: Zipped file containing 8 pages, 12 figures, in press PR