The transient flow analysis is fundamental to the simulation of natural gas process, in order to adjust the system to real operative conditions and to obtain the highest level of efficiency, compliance and reliability. The simulation of natural gas pipelines and networks requires mathematical models that describe flow properties. Some models that have been developed year after year based on the laws of fluid mechanics that govern this process, interpreted as a system of equations difficult to solve. This investigation describes the fully implicit finite volume method for natural gas pipeline flow calculation under isothermal conditions and transient regime. The simplification, discretization scheme and implementation equations are approached throughout this paper. The model was subjected to two evaluations: sinusoidal variation of the mass flow and opening-closing valve at the outlet of the pipeline, it is compared with two models: fully implicit finite difference method and method of characteristics. This method proved to be efficient in the simulations of slow and fast transients, coinciding the flow oscillations with the natural frequency of natural gas pipeline.

The covid-19 pandemic has significantly affected education worldwide, including chemistry education. The abrupt transition to online learning and the need to adapt to new ways of teaching have posed significant challenges. Therefore, it is important to conduct a literature review with the aim of analyzing the main challenges and measures adopted in Chemistry teaching in the context of the covid-19 pandemic, to identify the most effective practices to address these challenges and to develop strategies to support learning. The methodology maintained a qualitative approach, of descriptive type, constituting a bibliographic review, based on the hermeneutic and analytical-synthetic research methods, as well as on the content analysis technique, for which a total of 57 publications from databases such as Scopus, Dialnet, Latindex and Scielo were taken as a sample, compiling high impact articles in Spanish, English and Portuguese. The results show that the pandemic has boosted the implementation of innovative measures and strategies in chemistry teaching, although it has also revealed the limitations and challenges that must be overcome to ensure quality education in the future. These new approaches need to be further evaluated and improved to ensure their effectiveness and accessibility for all students.

Foodborne diseases are a global health problem. Every year, millions of people die worldwide from these diseases. It has been determined that the high prevalence of these diseases is related to unfavorable socioeconomic conditions of the population. In this study, the relationship between foodborne diseases and socioeconomic conditions of the population was determined using principal component analysis as a multivariate statistical analysis technique. In this study, the socioeconomic variables of each Ecuador province and the prevalence of foodborne diseases (hepatitis A, salmonella, shigellosis and typhoid fever) during the years 2018 and 2019 were considered. The results show the relationship between foodborne diseases and the socioeconomic conditions of the population, as well as identifying regions more vulnerable to present high levels of prevalence of foodborne diseases, thus facilitating the implementation of social investment programs to reduce the prevalence of these diseases.

El aumento en la emisión de gases contaminantes causado por las actividades antropogénicas derivadas de la utilización de combustibles fósiles, es una de los principales problemas ambientales al que se le está buscando solución mediante la implementación de energías alternativas, con el fin de minimizar los efectos del calentamiento global y brindar seguridad energética. El aprovechamiento de residuos es uno de estos enfoques, este propone la utilización de materiales de desecho para la creación de nuevos productos sin afectar los cultivos destinados a la alimentación u otros servicios de primera necesidad. Es por ello que en varias investigaciones se ha analizado la utilización de diferentes tipos de biomasas como fuente de energía renovable, debido a que son de fácil adquisición y pueden ser convertidas en combustibles. El objetivo del presente estudio fue analizar el estado del arte del uso de la biomasa lignocelulósica como materia prima para la obtención de biocombustibles de segunda generación a través de una revisión de la literatura de los últimos diez años. Se realizó la búsqueda del empleo de la misma como materia prima para su bioconversión a combustible de segunda generación, desde la identificación de la estructura y composición de la matriz lignocelulósica, pretratamientos y parámetros que influyen en su conversión, posible formación de subproductos de carácter inhibidor, producción de biocombustible en Latinoamérica y Ecuador, hasta las perspectivas futuras de su viabilidad. La revisión de la literatura destacó que la generación de biocombustible a partir de biomasa lignocelulósica es considerada como una alternativa a la demanda energética, siendo así una solución al aumento de la emisión de gases de efecto invernadero y a la generación de residuos.

In aquaculture, balanced feed accounts for 50% to 70% of the operational costs of cultivating aquatic organisms. This feed is made from various raw materials that serve as protein sources, which significantly influence the final cost of the feed. Therefore, an electrophoretic study was conducted to compare the protein content in different raw materials and commercial diets used in animal feed. Electrophoretic profiles with standard concentration gels (SDS-PAGE) were used to separate protein fractions from animal-origin raw materials, including Earthworm Meals of Eisenia andrei (HLF) and Eisenia fetida (HLT), meat-bone meal (MBM), and fish meal (FM), as well as plant-origin meals, such as Leucaena leaf meal (LLM), corn meal (YCM), and wheat bran (WBM). Commercial diets (A, B, and C) were also evaluated. The protein content of the samples was determined. For electrophoretic analysis, a protease inhibitor cocktail was used, along with a molecular weight standard with a range from 250 to 4 kDa. The molecular weights of the diets ranged between 31.1 and 234.1 kDa, 36.3 and 190.4 kDa, and 4.281 and 95.685 kDa. Some of the protein bands in the analyzed samples (HLF, HLT, FM, YCM, and WBM) were very close to the reference protein bands at 148, 98, 64, 50, and 36 kDa, corresponding to the molecular weight standard used. Electrophoretic characterization provided insight into the different protein fractions, offering valuable information about their potential functional and nutritional properties. Electrophoresis is an essential analytical tool for assessing both the quality and safety of raw materials and foods.

Desde 2010 en Ecuador se estableció como política energética la utilización de gasolina con 10% de bioetanol, esto en favor de la reducción de emisiones de gases de efecto invernadero; sin embargo, hasta la fecha se comercializa gasolina con 5% de bioetanol solo en ciertas provincias del país. El objetivo de este estudio fue evaluar el desarrollo de la industria del bioetanol en Ecuador en la última década y su perspectiva hacia el futuro, para ello se presenta el marco legal sobre biocombustibles en el país, así como un análisis de datos e informes de la empresa EP Petroecuador que determinan la trayectoria de la industria del bioetanol en el país entre 2010 y 2020, además se realizó un análisis bibliográfico de diferentes estudios realizados sobre la obtención de bioetanol a partir de diferentes materias primas, así como de pruebas de funcionamiento realizadas en vehículos de diferentes marcas con gasolina Ecopaís. Con base en la información revisada, se concluyó que Ecuador puede optar por otras materias primas para la producción de bioetanol, siguiendo experiencias de otros países, para de esta manera poder cumplir con el objetivo de proveer a todo el país, gasolina con un 10% de bioetanol.