We prove that local complementation and vertex deletion, operations from which vertexminors are defined, can simulate edge contractions. As an application, we prove that the rank-width of a graph is linearly bounded in term of its tree-width.

Most readers will probably be familiar with Polaroid instant picture products – you push the button and the print is ejected and develops right before your eyes. For many years professional image-makers have been using the unique features of this technology to create wonderfully textured images. The process involved substituting watercolor paper for the printing surface supplied by Polaroid. As...

In this work, a novel model to simulate epidemic spreading is introduced. It is based on the use of two-dimensional cellular automata, where each cell stand for a square portion of the environment. It is suppose that the distribution of the population is homogeneous, that is, all cells have the same population. The laboratory simulations obtained seem to be in agreement with the real behavior o...