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Desde que la pandemia de la COVID-19 se originó en Wuhan, China, las mascarillas se han utilizado como parte del equipo de protección personal y, por lo tanto, se volvieron esenciales para la protección de la salud humana contra la COVID-19. En México, las mascarillas que más se emplearon en la población fueron las mascarillas quirúrgicas desechables, mascarillas filtrantes N95 y KN95. Sin embargo, durante los inicios y la etapa de mayor transmisión, la población por desconocimiento hizo mal uso de las mascarillas, afectando al personal del sector salud. En este documento se abordan las características de las mascarillas, los materiales de fabricación más comúnmente empleados y cómo es que funcionan a través de diferentes mecanismos: mecanismo por impacto inercial, mecanismo por intercepción, mecanismo de difusión y mecanismo de atracción electrostática, con el propósito de explicar aspectos básicos pero esenciales de las mascarillas, y necesarios recordar ante futuras pandemias. Finalmente, se menciona la importancia de las investigaciones científicas para el entendimiento y desarrollo de las mascarillas.

Microbial communities are known to play a principal role in petroleum degradation. This study tries to determine the composition of bacteria in selected crude oil-contaminated soil from Tabasco and Tamaulipas states, Mexico. We determined the microbial populations living under these conditions. We evaluated the structure and diversity of bacterial communities in the contaminated soil samples. The most abundant phylum is proteobacteria. Next Generation Sequencing (NGS) analysis of the sampled soils from both states revealed that this phylum has the most relative abundance among the identified bacteria phyla. The heatmap represented the relative percentage of each genus within each sample and clustered the four samples into two groups. Moreover, this allowed us to identify many genera in alkaline soil from Tamaulipas, such as Skermanella sp., Azospirillum sp. and Unclassified species from the Rhodospirillaceae family in higher abundance. Meanwhile, in acidic soil from Tabasco, we identified Thalassospira, Unclassified members of the Sphingomonadaceae family and Unclassified members of the Alphaproteobacteria class with higher abundance. Alpha diversity analysis showed a low diversity (Shannon and Simpson index); Chao observed species in both Regions. These results suggest that the bacteria identified in these genera may possess the ability to degrade petroleum, and further studies in the future should elucidate their role in petroleum degradation.

Renewable energy sources have been regarded as the best alternative for energy generation because they are environmentally friendly and can be renewed. Among the sources of renewable energy is the photovoltaic system. The generation of energy through clean energies such as photovoltaic systems connected to the grid have shown sustained growth for years in residences, commercial centers, and industry. Therefore, a practical study of a photovoltaic system connected to the grid of a specific industry in the San Juan del Río region was carried out to determine the effectiveness and the cost efficiency of running a photovoltaic system connected to a grid. We also investigated the fastest possible time to get return on investment. The return on investment was estimated using the peak solar hours, numbers of panels, inverter, conductors, and DC and AC protectors. Although, the cost of starting a photovoltaic system can be quite expensive, our analysis revealed that the return on the investment can start to come to effect within a very short period. The policy implication of this is that the government should encourage investment on the photovoltaic system through financial support to firm and other policies that can make delivery cheaper for the customers.

Biofuel production has increased significantly in several countries in recent decades. Different evaluation techniques are required for their characterization. The study measures the properties of the obtained biodiesel and a commercial diesel sample, using the techniques of open circuit potential, linear scanning voltammetry and electrochemical impedance spectroscopy. The transesterification reaction between sunflower oil and methanol was carried out with ultrasound as the energy source. The determination of triglyceride conversion to biodiesel is performed by high performance liquid chromatography (HPLC), obtaining up to 99.79% with a yield of 93.40% at a transesterification temperature of 50 ∘C for 60 min with a methanol/oil molar ratio of 6:1. The potassium hydroxide catalyst concentration was 1.0 g catalyst/100 g oil. The biodiesel samples generally showed open circuit potential (OCP) values less than 790 mV and stabilization time less than 120 s, Linear sweep voltammograms (LSV) show no reaction peaks with current densities on the order of NanoAmpere, Electrochemical impedance spectroscopy (EIS) showed a capacitive system with impedances on the order of MΩ cm2 at low frequency; This information could help characterize biofuels and other similar materials.

The contingency measures put in place by the government during COVID-19 exposed the students to a new condition to which they must adapt. To understand how the students perceive and cope during the unplanned, changed learning mode, we conducted a study using an evaluation tool which seeks to understand the effect of the contingency measures associated with the emergence of the COVID-19 virus on the students. By assigning a data collection instrument to students who are part of 15 technological universities (TUs) and 7 polytechnic universities (PUs), we determined how they were affected by COVID-19. The questions intended to evaluate the social, economic, academic, emotional, and health effects experienced. A total of 6596 students were assessed in the study representing an appropriate percentage of the Mexican students. The outcome of the study showed that 12% of the students agreed with the online approach to learn adopted because of the contingency. A total of 39% reported that they have a good environmental space for online learning, 32% reported that they mostly take their classes via their mobile phones, and 3% said they lacked access to an internet facility and as such could not take their classes. A total of 14% reported that they have little access to the internet, while 42% reported that they regularly have internet, and both complained that internet fluctuation significantly affects their academic performance. Comparing the different modes of teaching, 52% believe an in-person class is the best approach to learning, but 22% agreed that a hybrid system will be effective. Through a multiple correspondence analysis (MCA) it was determined that, in the effects, there was no significant difference in relation to gender. The effects that most impacted the students were economic, connectivity, and a lack of physical activity.

University teachers have adapted to different situations during the development of distance learning due to the pandemic caused by the COVID-19 virus. This study was conducted by assigning a data collection instrument to 993 teachers who are part of 15 technological universities (TUs) and 7 polytechnic universities (PUs) to determine how they were affected by COVID-19. The questions asked were related to the social, economic, academic, emotional, and health effects experienced. The results show that 63% of the teachers working online complained that online teaching invaded their family privacy; 56% pointed out that working from home and the virtual classes affected their performance as teachers; 90% of the teachers thought that they dedicated too much extra to preparing for their classes; 15% were stressed; 4% felt negative under the new teaching scheme of virtual classes; finally, 38% of the teachers stated that repeated interaction with electronic devices had a lot of negative impacts on their emotional wellbeing. By means of a G-test, it was determined that gender was independent from the studied effects. Through a multiple correspondence analysis (MCA), it was determined that, of the total number of teachers who responded to the questionnaire, half were comfortable with the online teaching model and the other half were not. The most impacted effects were the economic, training and connectivity independently from the gender.