Víctor Leborán

After the rapid spread with severe consequences in Europe and China, the SARS-CoV-2 virus is now manifesting itself in more vulnerable countries, including those in Latin America. In order to guide political decision-making via epidemiological criteria, it is crucial to assess the real impact of the epidemic. However, the use of large-scale population testing is unrealistic or not feasible in some countries. Based on a newly developed mathematical model, we estimated the seroprevalence of SARS-CoV-2 in Latin American countries. The results show that the virus spreads unevenly across countries. For example, Ecuador and Brazil are the most affected countries, with approximately 3% of the infected population. Currently, the number of new infections is increasing in all countries examined, with the exception of some Caribbean countries as Cuba. Moreover, in these countries, the peak of newly infected patients has not yet been reached.

A hierarchical definition of optical variability is proposed that links physical magnitudes to visual saliency and yields a more reductionist interpretation than previous approaches. This definition is shown to be grounded on the classical efficient coding hypothesis. Moreover, we propose that a major goal of contextual adaptation mechanisms is to ensure the invariance of the behavior that the contribution of an image point to optical variability elicits in the visual system. This hypothesis and the necessary assumptions are tested through the comparison with human fixations and state-of-the-art approaches to saliency in three open access eye-tracking datasets, including one devoted to images with faces, as well as in a novel experiment using hyperspectral representations of surface reflectance. The results on faces yield a significant reduction of the potential strength of semantic influences compared to previous works. The results on hyperspectral images support the assumptions to estimate optical variability. As well, the proposed approach explains quantitative results related to a visual illusion observed for images of corners, which does not involve eye movements.