J. Antonio del Río

Renormalized Impact Factor

Many aspects determine the quality of scientific journals. The impact factor is one of these quantitative parameters. However, the impact factor has a strong dependence on the journal discipline. This dependence forbids a direct comparison between different journals without introducing external considerations. In this paper, a renormalized impact factor, Fr, inspired in the definition of dimensionless physical parameters, is proposed. Fr allows a direct comparison among journals classified into different categories and, furthermore, the time evolution analysis of the journals role in its field.

Clustering methodologies for identifying country core competencies

The technical structure of the Mexican science and technology literature was determined. A representative database of technical articles was extracted from the Science Citation Index for the year 2002, with each article containing at least one author with a Mexican address. Many different manual and statistical clustering methods were used to identify the structure of the technical literature (especially the science and technology core competencies), and to evaluate the strengths and weaknesses of each technique. Each method is summarized, and its results presented.

Classical field theory and stochastic properties of hyperbolic equations of dissipative processes

The set of damped hyperbolic transport equations is one of the wide class of equations for the description of dissipative physical processes. Deeper understanding into the structure of these physical phenomena can be obtained with the help of the Hamiltonian formalism. In the present paper, we show that the Hamilton–Lagrange formalism can be constructed for these kinds of transport equations. We obtain the Hamiltonian, the canonically conjugate quantities and the Poisson-bracket expressions for them. With this formalism we analyze the statistical properties of path fluctuations in the new conjugated thermodynamic variable space. We show that for short times the stochastic behavior under this new scope obeys the Chapman–Kolmogorov relationship.

Role of an Oxidant Mixture as Surface Modifier of Porous Silicon Microstructures Evaluated by Spectroscopic Ellipsometry.

Current research on porous silicon includes the construction of complex structures with luminescent and/or photonic properties. However, their preparation with both characteristics is still challenging. Recently, our group reported a possible method to achieve that by adding an oxidant mixture to the electrolyte used to produce porous silicon. This mixture can chemically modify their microstructure by changing the thickness and surface passivation of the pore walls. In this work, we prepared a series of samples (with and without oxidant mixture) and we evaluated the structural differences through their scanning electron micrographs and their optical properties determined by spectroscopic ellipsometry. The results showed that ellipsometry is sensitive to slight variations in the porous silicon structure, caused by changes in their preparation. The fitting process, based on models constructed from the features observed in the micrographs, allowed us to see that the mayor effect of the oxidant mixture is on samples of high porosity, where the surface oxidation strongly contributes to the skeleton thinning during the electrochemical etching. This suggests the existence of a porosity threshold for the action of the oxidant mixture. These results could have a significant impact on the design of complex porous silicon structures for different optoelectronic applications.