Critical currents at the Bragg glass to vortex glass transition

We present simulations of the transport properties of superconductors at the transition from the Bragg glass (BG) to the vortex glass (VG) phase. We study the frustrated anisotropic 3D XY model with point disorder, which has been shown to have a first order transition as a function of the intensity of disorder. We add an external current to the model and we obtain current-voltage curves as a function of disorder at a low temperature. We find that the in-plane critical current has a steep increase at the BG-VG transition, while the c-axis critical current has a discontinous jump down, this later result in agreement with the first-order character of the transition.Comment: 4 pages, 5 figures. Introduction changed. Accepted for publication in Physical Review Letter

Comment on ''On the problem of initial conditions in cosmological N-body simulations'' (Europhys. Lett. 57, 322)

In astro-ph/0109199, the initial conditions (IC's) of cosmological N-body simulations by the Virgo Consortium are analyzed and it is concluded that the density fluctuations are rather different from the desired ones. We have repeated the analysis of the IC's using our own code and the code provided by the authors of astro-ph/0109199, obtaining results that disprove the criticisms.Comment: 2 pages, 4 eps figures, epl.cls style fil

Technological Activities in CEE Countries: A Patent Analysis for the Period 1980-2009

The aim of this paper is to analyze the technological activities of Central and Eastern European (CEE) economies and to compare them with the technological activities of other world regions. Using data from the EPO World Wide Statistical Database for the period 1980-2009 the analysis is based on counts of priority patent applications over time. In terms of priority patent applications, CEE reduced its technological activities drastically in absolute and per capita terms after 1990. The level of priority patent applications in this world region maintained more recently a stable level below the performance of EU15, South EU and the former USSR. In what concerns technological specialization, the results suggest a division of labor in technological activities among world regions where Europe, Latin America and the former USSR are mainly specializing in sectors losing technological dynamism in the global patent activities (Chemicals and/or Mechanical Engineering) while North America, the Middle East (especially Israel) and Asia Pacific are increasingly specializing in Electrical Engineering, a sector with strong technological opportunities

Time-Frequency Relevant Features for Critical Articulators Movement Inference

Publication in the conference proceedings of EUSIPCO, Bucharest, Romania, 201

Information and Communication Technologies (ICT): Components, Dimensions, and its Correlates

Information and Communication Technologies (ICT) has been identified as one of the crucial factors that affect teaching effectiveness and student learning worldwide. UNESCO, many international organizations, and many governments emphasized the importance of ICT and try to incorporate ICT into education systems. This study examined self-assessed computer competency in thirteen ICT areas from two samples, e.g., the United States and Mexico. Reliability tests were conducted, and rank analysis was done among them. By using factor analysis, these thirteen areas were grouped into three categories: “basic ICT skills”; “advanced ICT skills;” and “multimedia skills and attitudes towards ICT”. Subjects showed the highest scores in basic ICT skills, which include knowledge of computer systems, use of the operating system, search internet and communication and networking. The multimedia skills and attitudes towards ICT demonstrated the second highest scores. Advanced ICT skills that include image processing, use of database, technological platforms, and web 2.0 tools was found to have the lowest competency scores among subjects. Multivariate analysis was also conducted and found that age and gender are two significant factors to predict ICT competency, and age was found to have a non-linear relationship on advanced ICT skills

Model for quantitative tip-enhanced spectroscopy and the extraction of nanoscale-resolved optical constants

Near-field infrared spectroscopy by elastic scattering of light from a probe tip resolves optical contrasts in materials at dramatically sub-wavelength scales across a broad energy range, with the demonstrated capacity for chemical identification at the nanoscale. However, current models of probe-sample near-field interactions still cannot provide a sufficiently quantitatively interpretation of measured near-field contrasts, especially in the case of materials supporting strong surface phonons. We present a model of near-field spectroscopy derived from basic principles and verified by finite-element simulations, demonstrating superb predictive agreement both with tunable quantum cascade laser near-field spectroscopy of SiO$_2$ thin films and with newly presented nanoscale Fourier transform infrared (nanoFTIR) spectroscopy of crystalline SiC. We discuss the role of probe geometry, field retardation, and surface mode dispersion in shaping the measured near-field response. This treatment enables a route to quantitatively determine nano-resolved optical constants, as we demonstrate by inverting newly presented nanoFTIR spectra of an SiO$_2$ thin film into the frequency dependent dielectric function of its mid-infrared optical phonon. Our formalism further enables tip-enhanced spectroscopy as a potent diagnostic tool for quantitative nano-scale spectroscopy.Comment: 19 pages, 9 figure