El daño progresivo que se produce en la superficie de un componente como resultado de su movimiento relativo a las partes adyacentes de trabajo, tiene profundas consecuencias económicas que implican no sólo los costes de sustitución, sino también los gastos relacionados con la inactividad de la máquina y pérdida de producción. En este artículo se presenta la implementación de un método para la revisión sistemática de literatura con el fin de establecer las metodologías con las que se aborda el modelamiento del proceso de desgaste entre sólidos deslizantes y el estado actual de dicha temática de investigación. La revisión sistemática de literatura es una nueva opción en la recopilación y análisis de bibliografía en ingeniería. Con esta metodología de búsqueda, recopilación, clasificación y análisis de información se logra reducir el tiempo y el esfuerzo para el planteamiento de una problemática de investigación. En el presente artículo se analizaron 50 estudios que cumplían las restricciones de la metodología de búsqueda, además se concluye que el modelamiento de las dinámicas termomecánicas presentes en un par deslizante no es aún un tema consolidado, que no se identifican con claridad cuáles son las variables que relacionan de forma directa la generación de fenómenos térmicos en el proceso y la variación de la tasa de desgaste.

Across various animal groups, adaptation to the challenging conditions of cave environments has resulted in convergent evolution. We document a Neotropical cavefish system with ample potential to study questions related to convergent adaptation to cave environments at the population level. In the karstic region of the Andes of Santander, Colombia, cave-dwelling catfish in the genus Trichomycterus exhibit variable levels of reduction of eyes and body pigmentation relative to surface congeners. We tested whether cave-dwelling, eye-reduced, depigmented Trichomycterus from separate caves in Santander were the result of a single event of cave colonization and subsequent dispersal, or of multiple colonizations to caves by surface ancestors followed by phenotypic convergence. Using mitochondrial DNA sequences to reconstruct phylogenetic relationships, we found that caves in this region have been colonized independently by two separate clades. Additional events of cave colonization – and possibly recolonization of surface streams – may have occurred in one of the clades, where surface and cave-dwelling populations exhibit shallow differentiation, suggesting recent divergence or divergence with gene flow. We also identify potentially undescribed species and likely problems with the circumscription of named taxa. The system appears promising for studies on a wide range of ecological and evolutionary questions.

Since March 6, when Colombia confirmed its first case of the coronavirus disease (Covid-19), the country healthcare system, with a limited testing capability, has struggled to monitor and report current cases. At the outbreak of a virus, data on cases is sparse and commonly severe cases, with a higher probability of a fatal resolution, are detected at a higher rate than mild cases. In addition, in an under-sampling situation, the number of total cases is under-estimated leading to a biased case fatality rate estimation, most likely inflating the virus mortality. Real time estimation of case fatality ratio can also be biased downwards by overlooking the delay between symptoms onset to death. In this communication, using reported data from Instituto Nacional de Salud up to December 28, we estimate the case fatality rate for Covid-19 in Colombia and some of its regions and cities adjusting for delay from onset to death. We then apply the method proposed by Russell et al., and use our corrected case fatality rate to estimate the percentage of Covid-19 cases reported in Colombia as 42.95% (95% confidence interval: 42.50-43.41), which corresponds to a total of 3'661,621 estimated Covid-19 cases in the country.

Across various animal groups, adaptation to the extreme conditions of cave environments has resulted in 15 convergent evolution of morphological, physiological, and behavioral traits. We document a Neotropical cave fish system with ample potential to study questions related to convergent adaptation to cave environments at the population level. In the karstic region of the Andes of Santander, Colombia, cave-dwelling catfishes in the genus Trichomycterus exhibit variable levels of reduction of eyes and body pigmentation relative to surface congeners. We tested whether cave-dwelling, eye reduced, depigmented Trichomycterus from separate caves in Santander 20 were the result of a single event of cave colonization and subsequent dispersal, or of multiple colonizations to caves by surface ancestors followed by phenotypic convergence. Using mitochondrial DNA sequences to reconstruct phylogenetic relationships of Trichomycterus from Santander, we found that caves in this region have been colonized independently by two separate clades. Additional events of cave colonization -and possibly recolonization of surface streams-may have occurred in one of the clades, where surface and cave-dwelling 25 populations exhibit shallow mtDNA differentiation, suggesting recent divergence or divergence in the face of gene flow. We also identified various taxonomic challenges including both a considerable number of potentially undescribed species and likely problems with the circumscription of named taxa. The system appears especially promising for studies on a wide range of ecological and evolutionary questions. 30