Fernando Fernández-Sánchez

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In this paper, we show, by means of a linear scaling in time and coordinates, that the Chen system, given by x=a(y-x), y=(c-a)x+cy-xz, ż=-bz+xy, is, generically (c≠0), a special case of the Lorenz system. First, we infer that it is enough to consider two parameters to study its dynamics. Furthermore, we prove that there exists a homothetic transformation(More)
INTRODUCTION The incidence of intraepithelial anal neoplasia is increasing in certain risk behaviour groups, and human papillomavirus (HPV) infection is involved in its pathogenesis. The systematic use of anal cytology, and more recently HPV detection by hybrid capture and genotyping, have been introduced into screening programs in recent decades. (More)
An important task for the understanding of the dynamics of parameterized systems of autonomous ordinary differential equations is the determination of the organizing centres as well as the bifurcations they exhibit (see, e.g. [Guckenheimer & Holmes, 1983; Kuznetsov, 1995; Nayfeh & Balachandran, 1995; Wiggins, 1996] as general references). The combination of(More)
In the referenced paper, the authors use the undetermined coefficient method to prove analytically the existence of homoclinic and heteroclinic orbits in a Lorenz-like system. If the proof was correct, the existence of horseshoe chaos would be guaranteed via the Sil'nikov criterion. However, we hereby show that their demonstration is incorrect for two(More)
BACKGROUND AND OBJECTIVE Occult bacteremia represents 3% of blood cultures drawn in the Emergency Department. In most cases, the evolution is unknown. The aim of the study is to analyze the results obtained after implementation of an intervention program for these patients. PATIENTS AND METHODS We describe the results of an early intervention program for(More)