Introducción:Los ciudadanos inesperados

Un espectro recorre América Latina. Y no es, como profetizaba KarlMarx para la Europa de 1848, el comunismo. Se trata de un fantasma que sobrevuela el nuevo continente desde la era de las independenciasy que hasta hoy no se ha logrado ahuyentar. Casi al mismo tiempo quesurgen las nuevas naciones y se define legalmente la ciudadanía (en elcaso mexicano con una cobertura muy amplia para la época), apareceel espectro de la enorme dificultad de realizar en la práctica dicha ciuda-danía. Las causas y las responsabilidades atribuidas por las elites políticase intelectuales a este problema han variado con el tiempo. Pero ayer y hoy la queja de periodistas, intelectuales y hombres públicos coincide enseñalar la ausencia de “verdaderos” ciudadanos. Una expresión recientede esa queja afirma que “el individuo no [es] ciudadano con derechosciviles, políticos y sociales, [es] cliente en un sistema donde los dere-chos se negocian” (Zuckermann, 2010)..

Tantilla taeniata

Number of Pages: 2Integrative BiologyGeological Science

Cricosaura, C. typica

Number of Pages: 3Integrative BiologyGeological Science

Tantilla schistosa

Number of Pages: 2Integrative BiologyGeological Science

Laemanctus longipes

Number of Pages: 4Integrative BiologyGeological Science

Phrynosoma solare

Number of Pages: 2Integrative BiologyGeological Science

Dendrophidion vinitor

Number of Pages: 2Integrative BiologyGeological Science

Aristelliger georgeensis

Number of Pages: 2Integrative BiologyGeological Science

Leptophis modestus

Number of Pages: 2Integrative BiologyGeological Science

Fatigue crack initiation and growth on a steel in the very high cycle regime with sea water corrosion

The authors acknowledge Arts et Métiers ParisTech and Foundation Arts et Métiers for the financial support of P.C. Paris’ stay at LAMEFIP. They acknowledge Vicinay Cadenas S.A. for its financial support, and both the PCP France-Mexique and the CONACYT for their financial support too.This paper is devoted to the effect of corrosion on the gigacycle fatigue strength of a martensitic–bainitic hot rolled steel used for manufacturing offshore mooring chains for petroleum platforms. Smooth specimens were tested under fully reversed tension between 1E6 and 1E10 cycles in three testing conditions and environments: (i) in air, (ii) in air after precorrosion and (iii) in air under real time artificial sea water flow. The fatigue strength at greater than 108 cycles is reduced by a factor more than five compared with non-corroded specimens. Fatigue cracks initiate at corrosion pits due to pre-corrosion, if any, or pits resulting from corrosion in real time during the cyclic loading. It is shown that under sea water flow, the fatigue life in the gigacycle regime is mainly governed by the corrosion process. Furthermore, the calculation of the mode I stress intensity factor at hemispherical surface defects (pits) combined with the Paris–Hertzberg–Mc Clintock crack growth rate model shows that fatigue crack initiation regime represents most of the fatigue life.PCP France Mexique, Conacyt, Arts et Métiers ParisTech (professeur invité Paul C Paris