Is Colombia an example of successful containment of the 2020 COVID-19 pandemic? A critical analysis of the epidemiological data, March to July 2020

Background: Colombia detected its first coronavirus disease 2019 (COVID-19) case on March 2, 2020. From March 22 to April 25, it implemented a national lockdown that, apparently, allowed the country to keep a low incidence and mortality rate up to mid-May. Forced by the economic losses, the government then opened many commercial activities, which was followed by an increase in cases and deaths. This paper presents a critical analysis of the Colombian surveillance data in order to identify strengths and pitfalls of the control measures. Methods: A descriptive analysis of PCR-confirmed cases between March and July 25 was performed. Data were described according to the level of measurement. Incidence and mortality rates of COVID-19 were estimated by age, sex, and geographical area. Sampling rates for suspected cases were estimated by geographical area, and the potential for case underestimation was assessed using sampling differences. Results: By July 25, Colombia (population 50 372 424) had reported 240 745 cases and 8269 deaths (case fatality rate of 3.4%). A total of 1 370 271 samples had been analyzed (27405 samples per million people), with a positivity rate of 17%. Sampling rates per million varied by region from 2664 to 158 681 per million, and consequently the incidence and mortality rates also varied. Due to geographical variations in surveillance capacity, Colombia may have overlooked up to 82% of the actual cases. Conclusion: Colombia has a lower case and mortality incidence compared to other South American countries. This may be an effect of the lockdown, but may also be attributed, to some extent, to geographical differences in surveillance capacity. Indigenous populations with little health infrastructure have been hit the hardest

A theoretical study of the mechanism of rearrangement of dihydropyrimidines into pyrroles

Pyrimidines, pyrroles, cycloreversion,CO extrusion, Two possible mechanisms for the transformation of a 1,4-dihydropyrrolo[3,2-b]pyrrole derivative into a tetrasubstituted pyrrole have been studied theoretically and one of them has been found in reasonable accord with the experimental data. This mechanismis part of the very rare example of rearrangement of dihydropyrimidines into pyrroles

Extremal states for photon number and quadratures as gauges for nonclassicality

Rotated quadratures carry the phase-dependent information of the electromagnetic field, so they are somehow conjugate to the photon number. We analyze this noncanonical pair, finding an exact uncertatinty relation, as well as a couple of weaker inequalities obtained by relaxing some restrictions of the problem. We also find the intelligent states saturating that relation and complete their characterization by considering extra constraints on the second-order moments of the variables involved. Using these moments, we construct performance measures tailored to diagnose photon-added and Schr\"odinger catlike states, among others.Comment: 6 pages, 4 color figures. Comments welcome

Numerical approximation of the fractional Laplacian on R using orthogonal families

In this paper, using well-known complex variable techniques, we compute explicitly, in terms of the F12 Gaussian hypergeometric function, the one-dimensional fractional Laplacian of the complex Higgins functions, the complex Christov functions, and their sine-like and cosine-like versions. Then, after studying the asymptotic behavior of the resulting expressions, we discuss the numerical difficulties in their implementation, and develop a method using arbitrary-precision arithmetic that computes them accurately. We also explain how to create the differentiation matrices associated to the complex Higgins functions and to the complex Christov functions, and study their condition numbers. In this regard, we show how arbitrary-precision arithmetic is the natural tool to deal with ill-conditioned systems. Finally, we simulate numerically the fractional nonlinear Schrödinger equation using the developed tools

A pseudospectral method for the one-dimensional fractional Laplacian on R

In this paper, we propose a novel pseudospectral method to approximate accurately and efficiently the fractional Laplacian without using truncation. More precisely, given a bounded regular function defined over R, we map the unbounded domain into a finite one, and represent the resulting function as a trigonometric series. Therefore, the central point of this paper is the computation of the fractional Laplacian of an elementary trigonometric function. As an application of the method, we also do the simulation of Fisher's equation with fractional Laplacian in the monostable case

La utilidad de las evaluaciones de sistemas educativos: el valor de la consideración del contexto.

En este artículo se hace una revisión de los procedimientos de evaluación de sistemas educativos. A partir de esta revisión, se analizan algunos factores relacionados con la baja utilidad de este tipo de evaluaciones. El análisis se dirige hacia el diseño deficiente de los cuestionarios de contexto. Se observa que los cuestionarios de contexto no llegan a explicar el rendimiento. Su baja capacidad de explicación del rendimiento es la causa de la baja utilidad de las evaluaciones de sistemas educativos; pues no permiten establecer recomendaciones de mejora. Se propone una base teórica y metodológica alternativa para diseñar los cuestionarios de contexto. Este tipo de metodología para diseñar los cuestionarios de contexto para la evaluación de sistemas educativos tiene como finalidad última poder asegurar la calidad teórica de los constructos que se miden, y aportar una base sólida para definir un modelo explicativo que permita extraer mayor utilidad de la información con que se trabajan las evaluaciones de sistemas. Esta propuesta indica la necesidad de tomar como referencia las aportaciones de la investigación educativa, un modelo sistémico que ayude a dar coherencia a los planes de evaluación, considerar las necesidades de información de las partes interesadas en la evaluación y un procedimiento más riguroso de diseño de instrumentos. Esta metodología es la base de otros trabajos que se presentan en este mismo número de la revista y que se citan en este artículo

Método de evaluación de la calidad del servicio de una unidad de atención al usuario en una empresa de servicio de agua en Colombia

This research study proposes a method to evaluate the quality of service of a user service unit in a water service company in Colombia. Based on the theoretical foundation associated with the quality of service and the Six Sigma concept, service quality dimensions were identified to consolidate their valuation and to analyze the results in terms of defects per parts per million (DPMO), sigma level, and performance. It was found that the performance of the service quality dimensions was satisfactory due to the results obtained in all calculated metrics. The results showed that the user's attention center had an excellent performance during this research study. In conclusion, the present study provides a service quality evaluation method to the service sector in a public service company by using Six Sigma. © 2020 Centro de Informacion Tecnologica. All rights reserved