410 research outputs found

    Using discrete Ricci curvatures to infer COVID-19 epidemic network fragility and systemic risk

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    The damage of the novel Coronavirus disease (COVID-19) is reaching unprecedented scales. There are numerous classical epidemiology models trying to quantify epidemiology metrics. Usually, to forecast epidemics, classical approaches need parameter estimations, such as the contagion rate or the basic reproduction number. Here, we propose a data-driven, parameter-free, geometric approach to access the emergence of a pandemic state by studying the Forman-Ricci and Ollivier- Ricci network curvatures. Discrete Ollivier-Ricci curvature has been used successfully to forecast risk in nancial networks and we suggest that those results can provide analogous results for COVID-19 epidemic time-series. We rst compute both curvatures in a toy-model of epidemic time-series with delays, which allows us to create epidemic networks. We also compared our results to classical network metrics. By doing so, we are able to verify that the Ollivier-Ricci and Forman-Ricci curvatures can be a parameter-free estimate for identifying a pandemic state in the simulated epidemic. On this basis, we then compute both Forman-Ricci and Ollivier-Ricci curvatures for real epidemic networks built from COVID-19 epidemic time-series available at the World Health Organization (WHO). This approach allow us to detect early warning signs of the emergence of the pandemic. The advantage of our method lies in providing an early geometrical data marker for the pandemic state, regardless of parameter estimation and stochastic modelling. This work opens the possibility of using discrete geometry to study epidemic networks. Keywords: COVID-19, SARS2, Forman-Ricci Curvature, Ollivier-Ricci curvature, Epidemiology, Topologi- cal Data Analysi

    Can artisanal “Coalho” cheese from Northeastern Brazil be used as a functional food?

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    AbstractBrazilian artisanal “Coalho” cheeses from six Northeast towns were investigated as a functional food based on their peptide profiles and antioxidant, zinc-binding and antimicrobial activities. The peptides (WSP) from “Coalho” cheese showed high antioxidant activity, the best value of TEAC being 2223±10.10μM, which means 91.1±0.43% oxidative inhibition and peptide concentration for IC50 of 7mg/mL (21μg of peptides) for sample from the town of Correntes. The smallest TEAC value (1896±17μM), which means 75.9±0.7% oxidative inhibition and IC50 of 10.5mg/mL (31.5μg of peptide), was obtained for samples from the town of São Bento do Una. The zinc-binding activities were: Arcoverde (72.21±0.24%) Cachoeirinha (75.02±0.02%), Capoeiras (61.78±0.65%), Correntes (75.47±0.5%), São Bento do Una (75.41±0.15%), and Venturosa (74.36±0.04%). The WSP extracts showed antimicrobial activity against Enterococcus faecalis, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa. All the results obtained suggest that “Coalho” cheese has potential as a functional food

    Feeding strategies and energy to protein ratio on tambaqui performance and physiology

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    The objective of this work was to evaluate the effect of feed deprivation and refeeding with diets containing different energy to protein ratios (E/P) on the performance and physiology of juvenile tambaqui (Colossoma macropomum). A 4x2 factorial arrangement with three replicates was used, with four E/P ratios (11.5, 10.5, 9.5, and 8.5 kcal g-1 digestible energy per protein) and two feeding regimens (with and without deprivation), during 60 days. Fish from the food-deprived group were fasted for 14 days and refed from the fifteenth to the sixtieth day, whereas the remaining fish were fed for 60 days. At the end of the experimental period, weight of fish subjected to food deprivation was lower than that of those continuously fed; however, this condition did not influence the physiological parameters analyzed. Tambaqui fed 11.5 kcal g-1 achieved lower final weight than those fed with the other diets, in both regimens. Among the physiological parameters, only plasma protein presented significant increase in fish fed 8.5 kcal g-1, in both feeding regimens, probably due to the higher dietary protein concentration. These results indicate that fish show a partial compensatory growth, and that 10.5 kcal g-1 can be recommended for the diet of juvenile tambaqui
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