Josef A. Sifuentes

Learn More
An outbreak of post-rhinoplasty nasal cellulitis due to Mycobacterium chelonae in a secondary care centre is described. A case-control study demonstrated that the use of inadequately sterilized surgical equipment in the Otorhinolaryngology Department was a risk factor. The causal organism was cultured from the equipment, from the surface of the operating(More)
A case-control study was conducted on an epidemic of bacteremia and meningitis caused by Serratia marcescens in the neonatal intensive care unit and special care nursery of a general hospital in Mexico City, Mexico. A 19.9% incidence of bacteremia and meningitis was recorded in contrast to 1.4% and 3.7% during preepidemic and post-epidemic periods; a 69%(More)
Results of a three-year prospective study of amikacin as the only aminoglycoside used at the Instituto Nacional de la Nutrición "Salvador Zubirán" are presented. During the initial three-month baseline period, resistance to amikacin, gentamicin, and tobramycin among 870 gram-negative bacterial isolates was 3.2 percent, 17.4 percent, and 11.2 percent,(More)
The definitive diagnosis of spontaneous bacterial peritonitis is made by a positive ascitic fluid culture. Causative organisms cannot be isolated in up to 65% of patients with well-defined spontaneous bacterial peritonitis, probably due to inadequate ascites culture techniques. We prospectively compared two ascites culture methods: conventional (on(More)
The Progressive GMRES algorithm, introduced by Beckermann and Reichel in 2008, is a residual-minimizing short-recurrence Krylov subspace method for solving a linear system in which the coefficient matrix has a low-rank skew-Hermitian part. We analyze this algorithm, observing a critical instability that makes the method unsuitable for some problems. To work(More)
How does GMRES convergence change when the coefficient matrix is perturbed? Using spectral perturbation theory and resolvent estimates, we develop simple, general bounds that quantify the lag in convergence such a perturbation can induce. This analysis is particularly relevant to preconditioned systems, where an ideal preconditioner is only approximately(More)
How does GMRES convergence change when the coefficient matrix is perturbed? Using spectral perturbation theory and resolvent estimates, we develop simple, general bounds that quantify the lag in convergence such a perturbation can induce. This analysis is particularly relevant to preconditioned systems, where an ideal preconditioner is only approximately(More)
In this paper, a bilinear mathematical model of ordinary differential equations is introduced to investigate the transmission dynamics of polio virus in Nigeria. The effect of vaccines versus environmental clean-up efforts on disease transmission is discussed. In the modeling process, Monte Carlo simulations were employed to approximate the values of three(More)
Abstract This report discusses the size and shape comparison of objects represented by two sets of three dimensional data. We examine geometric invariants such as pairwise distances, distances from the centroid, and the volumes of the tetrahedrons. We examine rigid motion estimation using Procrustes analysis, the iterative closest point algorithm, and(More)