In this work, we present a methodology to identify COVID-19 spreaders using the analysis of the relationship between socio-cultural and economic characteristics with the number of infections and deaths caused by the COVID-19 virus in different countries. For this, we analyze the information of each country using the complex networks approach, specifically by analyzing the spreaders countries based on the separator set in 5-layer multiplex networks. The results show that, we obtain a classification of the countries based on their numerical values in socioeconomics, population, Gross Domestic Product (GDP), health and air connections; where, in the spreader set there are those countries that have high, medium or low values in the different characteristics; however, the aspect that all the countries belonging to the separator set share is a high value in air connections. INDEX TERMS Complex networks, complex systems, COVID-19, multiplex networks, optimization, social networks.

Potentiometric studies are presented here on solid contact ion-selective electrodes, based on neutral carriers comprising structural sulfur−donating groups and an aliphatic chain, where the latter confers stability to the molecule for the formation of metal complexes. As result, an ISE was obtained for the potentiometric determination of mercury. This sensor allowed continuous mercury determinations at nanomolar levels within a wide concentration interval (1.0 × 10 −9 to 1.0 × 10 −1 ) molL −1 , with a detection limit of (9.1 ± 0.8) × 10 −10 molL −1 and a Nernstian response of (29.8 ± 0.4) mV decade −1 . This ISE can be used in the 0-6 pH interval, exhibiting a high selectivity toward the mercury ions even in the presence of interferents, and be used as an indicating electrode during potentiometric mercury titration with EDTA, because it is comparable with the commercial electrodes, within its same class. The main advantage of the ISE reported here is its nM LOD and that it does not require an internal reference.

e noncompetitive inhibition of laccase by mercury ions is reported, in particular focusing their effect over the enzyme catalytic activity. e enzymatic kinetics were obtained for different substrates (caffeic acid, gallic acid, and catechol), where caffeic acid displayed the greatest enzymatic activity. e laccase inhibition by mercury ions permitted to establish the inhibition effect through a mixed model (that actually displayed a behavior closer to that of the noncompetitive inhibitors) when evaluated by means of UV-Vis spectrophotometry, using caffeic acid as an electron donor. A mercury concentration of 2 mM led to 35% enzymatic inhibition after only a 2-minute incubation period. is method was used for quantification of mercury ions in aqueous solution, showing a detection limit of 15 ± 1 ppm. erefore, this work presented a novel perspective for the determination of the toxic Hg(II) ions that can be readily implemented into environmental remediation methods.

This research presents the construction and optimization of an acetylcholine, ACh, ion-selective electrode, ACh-ISE, aiming to use it for the quantification of the propoxur pesticide. This analytical quantification is based on the evaluation of the acetylcholinesterase enzyme inhibition percentage, %EI, provoked by the pesticide, as a function of propoxur concentration; where the %EI is followed by means of the potentiometric determination of acetylcholine that does not react with the enzyme, using the constructed ACh-ISE. It was found that the ACh-ISE depicted a sub-Nernstian slope of (42.7 ± 2.8) mV decade −1 , a ACh detection limit of 1.2 × 10 −5 mol l −1 , and the selectivity constants, K pot , of 0.03 and 0.24 for Na + and Choline + cations, respectively. K + and Ca 2+ did not interfere. This new method designed to determine propoxur attained an outstanding detection limit of (2.89 ± 0.97) × 10 −17 mol l −1 and a linear interval of (5.5 × 10 −15 -1.0 × 10 −4 ) mol l −1 .

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