•Utilization of an algebraic differential approach and a modified, augmented system (immersion) of the A-SIR model.•Development of a non redundant and model-free observer. No reconstruction of known ...variables. Full model is not required•The estimation algorithm is robust. Asymptotically stable (noise-free) or ultimate uniformly bounded (noise).•.•Reconstruction of the variables of interest by means of integration processes (Liouvillian system).•Validation of the methodology with real data reported by the Mexican Government.
Due to the current COVID-19 pandemic, much effort has been put on studying the spread of infectious diseases to propose more adequate health politics. The most effective surveillance system consists of doing massive tests. Nonetheless, many countries cannot afford this class of health campaigns due to limited resources. Thus, a transmission model is a viable alternative to study the dynamics of the pandemic. The most used are the Susceptible, Infected and Removed type models (SIR). In this study, we tackle the population estimation problem of the A-SIR model, which takes into account asymptomatic or undetected individuals. By means of an algebraic differential approach, we design a model-free (no copy system) reduced-order estimation algorithm (observer) to determine the different non-measured population groups. We study two types of estimation algorithms: Proportional and Proportional-Integral. Both shown fast convergence speed, as well as a minimal estimation error. Additionally, we introduce random fluctuations in our analysis to represent changes in the external conditions and which result in poor measurements. The numerical results reveal that both model-free estimators are robust despite the presence of these fluctuations. As a point of reference, we apply the classical Luenberger type observer to our estimation problem and compare the results. Finally, we consider real data of infected individuals in Mexico City, reported from February 2020 to March 2021, and estimate the non-measured populations. Our work’s main goal is to proportionate a simple and therefore, an accessible methodology to estimate the behavior of the COVID-19 pandemic from the available data, such that the competent authorities can propose more adequate health politics.
Intermedia agenda setting predicts a high degree of convergence between news media agendas. However, the rise of social media forces a re-examination of this expectation. Using the 8.8-earthquake of ...February 27, 2010 in Chile as a case study, this article compares which topics were covered by professional journalists on broadcast news and Twitter, analyzing both cross-sectional and longitudinal trends. A positive, reinforcing influence was found among the journalistic agendas of TV and Twitter. However, counter to the idea that social media are echo chambers of traditional media, it was found that Twitter influences TV news more so than the other way around. Thus, the study provides an early lens into the agenda setting function of social media among television news professionals, and its findings are consistent with Twitter succeeding among journalists due to its provision of valuable information.
Many school systems across the globe turned to online education during the COVID-19 pandemic. This context differs significantly from the prepandemic situation in which massive open online courses ...attracted large numbers of voluntary learners who struggled with completion. Students who are provided online courses by their high schools also have their behavior determined by actions of their teachers and school system. We conducted experiments to improve participation in online learning before, during, and right after the COVID-19 outbreak, with 1,151 schools covering more than 45,000 students in their final years of high school in Ecuador. These experiments tested light-touch interventions at scale, motivated by behavioral science, and were carried out at three levels: that of the system, teacher, and student. We find the largest impacts come from intervening at the system level. A cheap, online learning management system for centralized monitoring increased participation by 0.21 SD and subject knowledge by 0.13 SD relative to decentralized management. Centralized management is particularly effective for underperforming schools. Teacher-level nudges in the form of benchmarking emails, encouragement messages, and administrative reminders did not improve student participation. There was no significant impact of encouragement messages to students, or in having them plan and team-up with peers. Small financial incentives in the form of lottery prizes for finishing lessons did increase study time, but was less cost-effective, and had no significant impact on knowledge. The results show the difficulty in incentivizing online learning at scale, and a key role for central monitoring.
Chile has become one of the countries most affected by COVID-19, a pandemic that has generated a large number of cases worldwide. If not detected and treated in time, COVID-19 can cause multi-organ ...failure and even death. Therefore, it is necessary to understand the behavior of the spread of COVID-19 as well as the projection of infections and deaths. This information is very relevant so that public health organizations can distribute financial resources efficiently and take appropriate containment measures. In this research, we compare different time series methodologies to predict the number of confirmed cases of and deaths from COVID-19 in Chile.
The methodology used in this research consisted of modeling cases of both confirmed diagnoses and deaths from COVID-19 in Chile using Autoregressive Integrated Moving Average (ARIMA henceforth) models, Exponential Smoothing techniques, and Poisson models for time-dependent count data. Additionally, we evaluated the accuracy of the predictions using a training set and a test set.
The dataset used in this research indicated that the most appropriate model is the ARIMA time series model for predicting the number of confirmed COVID-19 cases, whereas for predicting the number of deaths from COVID-19 in Chile, the most suitable approach is the damped trend method.
The ARIMA models are an alternative to modeling the behavior of the spread of COVID-19; however, depending on the characteristics of the dataset, other methodologies can better predict the behavior of these records, for example, the Holt-Winter method implemented with time-dependent count data.
El 25 de agosto de 1769, Johann Caspar Lavater envió a Moses Mendelssohn una dedicatoria junto con la traducción de algunas secciones de La palingénésie philosophique, de Charles Bonnet. En esta ...dedicatoria, Lavater desafió a Mendelssohn a refutar públicamente los argumentos de Bonnet sobre la verdad del cristianismo o, en caso contrario, “hacer lo que Sócrates habría hecho si hubiera leído esta obra y la hubiera encontrado irrefutable”. En su réplica a Lavater, Mendelssohn interpreta este desafío como un llamado a la conversión. El objetivo del presente artículo es analizar el modo en que los ideales de conocimiento y evidencia de Lavater están inextricablemente unidos a su celo misionero.
This paper presents a methodology and design of a model-free-based proportional-integral reduced-order observer for a class of nondifferentially flat systems. The problem is tackled from a ...differential algebra point of view, that is, the state observer for nondifferentially flat systems is based on algebraic differential polynomials of the output. The observation problem is treated together with that of a synchronization between a chaotic system and the designed observer. Some basic notions of differential algebra and concepts related to chaotic synchronization are introduced. The PI observer design methodology is given and it is proven that the estimation error is uniformly ultimately bounded. To exemplify the effectiveness of the PI observer, some cases and their respective numerical simulation results are presented.
En “Acerca de la pregunta: ¿qué significa ilustrar?” de 1784, Mendelssohn sostiene que la ilustración que está conectada con la vocación esencial (wesentlich Bestimmung) del ser humano en tanto que ...ser humano puede entrar en conflicto no solo con la moralidad –las vocaciones extra-esenciales (außerwesentlichen Bestimmungen)– sino también con la vocación esencial del ciudadano, esto es, como miembro de un Estado. En estos casos, afirma Mendelssohn, es necesario cierto cuidado y precaución, cierta prudencia (Klugheit), en el uso de la ilustración. El presente trabajo tiene como objetivo analizar el significado de esta apelación a la prudencia, por parte de Mendelssohn, como símbolo de una Ilustración que, en su compromiso radical con la humanidad, propone una aguda indagación sobre la “situacionalidad” de la razón y su poder emancipador, en la compleja interacción entre teoría y práctica.
In this work, we present a globally Mittag-Leffler bounded high-gain observer for fractional order nonlinear systems with unmodeled dynamics and additive measurement noise at the output. Our proposal ...starts from an alternative representation of the fractional order system, whose output does not depend on the additive measurement noise and in which the original system’s output is treated as an additional state variable. This representation allows us two things: 1) to simultaneously estimate the state variables and the uncertain term and 2) to incorporate into the design scheme a fractional integral-type contribution, which is useful to give robustness against the measurement noise and the unmodeled dynamics, as well as to attenuate the noise amplification, typical of any high-gain observer. Through the corresponding mathematical analysis, we prove that the estimation error of the proposed observer is uniformly bounded and converges asymptotically to a globally Mittag-Leffler compact attractive set, this is, the proposed observer is globally Mittag-Leffler bounded. Additionally, we show that under certain conditions, such as an integer derivation order or the absence of measurement noise, the proposed observer exhibits some particular properties. Finally, we consider a continuously stirred biochemical reactor to exemplify our design methodology. The numerical results confirm that the observer is able to accurately estimate the state variables as well as the uncertainty term of the fractional model. In other words, the globally Mittag-Leffler bounded high-gain observer is robust against measurement noise and uncertainties.
•A novel high-gain Mittag-Leffler bounded observer is designed.•An alternative representation of the original FO system is used.•A fractional integral-type contribution makes the observer robust.•Simultaneous estimation of the state and the unmodeled dynamics of the system.•Some particular properties of the high-gain observer are also presented.
The problem of state observation in incommensurate fractional order systems has been poorly studied. Currently some observers that have been proposed are based on a copy of the system, which causes ...them to be highly dependent on the system parameters, additionally they are redundant (estimate variables that are available). So this paper proposes a novel fractional observer against parametric uncertainties for a certain type of incommensurate fractional order systems. The fractional observer design is based on a property concerning observability in incommensurate fractional order systems which allows us to construct the observer only considering the available output and its fractional derivatives. On the other hand, the convergence analysis of the observation error is carried out using a particular approach of fractional order systems related to the Global Mittag-Leffler boundedness. We prove that there is a compact set GMLA (Globally Mittag-Leffler Attractive, according to Definition 4) where the system that represents the observation error dynamics is attractive and we also prove that the observation error is uniformly bounded. Additionally, the fractional observer is model-free i.e., a system copy is not required, this gives robustness in spite of parametric uncertainties and it is also reduced order therefore one observer must be designed for each variable that we want to estimate consequently the observer is non-redundant (no estimation of variables that are already available). Moreover, our proposed fractional observer can be designed for commensurate fractional order systems and we also show that if we consider integer derivative order, the proposed fractional observer presents certain properties. Finally, in order to show the effectiveness of the proposed fractional observer, an incommensurate fractional order Rössler hyperchaotic system is considered as a numerical example and an incommensurate fractional model of the COVID-19 pandemic as a real-world application.
•A fractional PI observer for incommensurate fractional order systems is presented.•Fractional systems with parametric uncertainty are considered.•The observation error dynamics is Globally Mittag-Leffler bound.•The proposed fractional observer is model-free, no copy of the system is required.•Development of a non redundant fractional observer.
A 56‐year‐old woman debuted with a palpable painless mass in the anterior thorax wall at the level of the second and third right parasternal intercostal space, which progressively increased in size ...over 5 months accompanied by localized skin rash, mild dyspnea and chest pain when changing position. Imaging studies showed a soft tissue mass measuring 75 × 62 mm and a density of 34 Hounsfield Units that had caused the lysis of the costal arches and grew expansively towards the anterior mediastinum, without identifying mediastinal adenopathies only by this imaging method. Core biopsy was performed, which was initially diagnosed as histiocytic sarcoma (HS); however, when the diagnostic panel was expanded to include molecular and NGS studies, the final diagnosis was anaplastic large cell lymphoma with ALK::ATIC fusion. Here, we report a very rare neoplasm with unusual clinical presentation, histopathology and molecular features.
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