Abstract
We report on the synthesis and characterization of V
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nanoparticles grown using a sol–gel method at different calcination temperatures. We observed a surprising reduction in the optical ...band gap from 2.20 to 1.18 eV with increasing calcination temperature from 400 to 500 °C. Raman and X-Ray diffraction measurements indicated slight changes in the lattice parameters induced by the growth process. However, density functional theory calculations of the Rietveld-refined and pristine structures revealed that the observed optical gap reduction could not be explained by structural changes alone. By introducing oxygen vacancies to the refined structures, we could reproduce the reduction of the band gap. Our calculations also showed that the inclusion of oxygen vacancies at the vanadyl position creates a spin-polarized interband state that reduces the electronic band gap and promotes a magnetic response due to unpaired electrons. This prediction was confirmed by our magnetometry measurements, which exhibited a ferromagnetic-like behavior. Our findings suggest that oxygen vacancies play a crucial role in band gap reduction and the promotion of a ferromagnetic-like response in an otherwise paramagnetic material. This provides a promising route to engineer novel devices.
Abstract The article presents the results of computational modeling of a rigid pavement with load applied to the edge of the slab, for which a multipurpose software (ABAQUS / CAE) based on the finite ...element method is used. First, it is explained in detail how computational modeling is performed, taking as reference two types of rigid pavements (pavement with and without concrete shoulder). In the process, the main characteristics and hypotheses taken to model the load, the edge conditions and the characteristics of the materials are presented. The mesh density and the finite element type to be used are also analyzed, based on an experimental design. In order to reduce computation times, studies were conducted to make geometric simplifications to the domain. The final solution is contrasted with the Westergaard´s theory and the results of a finite element software already experimentally validated according to the bibliography (EverFE v2.24). Studies of some of the most important factors for pavement designing were conducted. Finally, graphs are shown in specific conditions of geometry and materials, which will serve as practical tools for use in design methods.
•We present results from an ethnographic study on Venezuelan migrants’ access to healthcare in seven Latin American cities.•COVID-19 has worsened conditions of informality and health inequities for ...Venezuelan migrants.•The main obstacles to healthcare access are legal, financial, and relating to discrimination and information asymmetry.•Migrants rely on alternative care, such as telemedicine, extralegal doctors, and pharmacies.
This research seeks to understand how COVID-19 has affected access to healthcare among migrants in Latin American cities. Using ethnographic research methods, we engaged with Venezuelans living in conditions of informality in four Colombian cities—Barranquilla, Cucuta, Riohacha, and Soacha—and three Peruvian cities—Lima, Trujillo, and Tumbes. We conducted 130 interviews of both Venezuelan migrants and state and non-governmental actors within the healthcare ecosystems of these cities. We found that forced migrants from Venezuela in both Colombia and Peru face common obstacles along their access trajectories to healthcare, which we summarize as legal, financial, and relating to discrimination and information asymmetry. By limiting effective access to care during the pandemic, these obstacles have also affected migrants’ ability to cover the costs of basic needs, particularly food and housing. Our study also found a prevalent reliance on alternative forms of care, such as telemedicine, easy-to-access pharmacies, and extralegal care networks. We conclude that COVID-19 has exacerbated preexisting conditions of informality and health inequities affecting Venezuelan migrants in Colombia and Peru.
The energy efficiency of irrigation systems is an aspect of great importance in all design and management processes; For this reason, an investigation was carried out in the "Tio Pedro" farm located ...in the municipality of Venezuela, Ciego de Avila province during the years 2021 and 2022 with the objective of estimating the general energy yield in the furrow irrigation system. During this period, the pump unit offers the following average operating regime: pump flow rate of 61.1 L s.sup.-1; pumping time of 2,8 hours and pumping head of 18.2 m. This behavior reduces a hydraulic power of 10.9 kW and a pump efficiency of 85.2%. The energy supplied in pumping was 429.4 kWh and the energy absorbed in the evaluated period was 631.9 kWh. In relation to the energy parameters of the system, an energy balance of the supply of 7,4 m was obtained; a system energy load index of 15.2 m; an energy efficiency of the pumping of 68.2% (excellent) and a general energy efficiency of the system of 34.0% (normal). Keywords: Hydraulic Efficiency, Hydraulic Power, Energy Efficiency of Pumping. La eficiencia energetica de los sistemas de riego es un aspecto de gran importancia en todos los procesos de diseno y manejo; por este motivo se desarrollo una investigacion en la finca "Tio Pedro" ubicada en el municipio de Venezuela, provincia Ciego de Avila durante los anos 2021 y 2022 con el objetivo de estimar el rendimiento energetico general en el sistema de riego por surcos. Durante este periodo la unidad de bombeo funciono con el siguiente regimen de operacion promedio: caudal de bombeo de 61,1 L s.sup.-1; tiempo de bombeo de 2,8 horas y carga de bombeo de 18,2 m. Este comportamiento determino una potencia hidraulica de 10,9 kW y rendimiento de la bomba de 85,2%. La energia suministrada en el bombeo fue de 429,4 kWh y la energia absorbida en el periodo evaluado de 631,9 kWh. En relacion con los parametros energeticos del sistema se obtuvo un balance energetico del suministro de 7,4 m; un indice de carga energetica del sistema de 15,2 m; un rendimiento energetico del bombeo de 68,2% (excelente) y un rendimiento energetico general del sistema de 34,0% (normal). Palabras clave: Eficiencia hidraulica, potencia hidraulica, rendimiento energetico del bombeo.
The energy efficiency of irrigation systems is an aspect of great importance in all design and management processes; For this reason, an investigation was carried out in the "Tio Pedro" farm located ...in the municipality of Venezuela, Ciego de Avila province during the years 2021 and 2022 with the objective of estimating the general energy yield in the furrow irrigation system. During this period, the pump unit offers the following average operating regime: pump flow rate of 61.1 L s.sup.-1; pumping time of 2,8 hours and pumping head of 18.2 m. This behavior reduces a hydraulic power of 10.9 kW and a pump efficiency of 85.2%. The energy supplied in pumping was 429.4 kWh and the energy absorbed in the evaluated period was 631.9 kWh. In relation to the energy parameters of the system, an energy balance of the supply of 7,4 m was obtained; a system energy load index of 15.2 m; an energy efficiency of the pumping of 68.2% (excellent) and a general energy efficiency of the system of 34.0% (normal).
Background. Different species of thrips are listed as important pests in berries. They cause damage to leaves, flowers and fruits, which cause poor development and deformation of the berry, and loss ...of production; some species are associated with plant pathogens transmission. Objectives. To determine the species of thrips (Thysanoptera) associated with blackberry and blueberry and their seasonal abundance, in the producing region of Los Reyes, Michoacán, Mexico and to determine the most attractive sticky trap color to collect thrips. Methodology. The thrips were captured monthly through direct collection on the plants, and with sticky traps (yellow and blue), from April 2021 to August 2022. Results. 1,615 specimens were obtained, all from Thripidae family, belonging to four genera and six species. Frankliniella and Scirtothrips were the most abundant genera and accounted 96% of the material collected. F. occidentalis was most abundant in blackberry var. Laurita and Elvira, and S. dorsalis in blackberry var. Dasha and blueberry var. Arana. F. bruneri and F. minuta and Plesiothrips ayarsi were first recorded as occasional species, and Neohydatothrips gracilipes as frequent in blackberry var. Dasha and Laurita. The sticky yellow traps caught more thrips. The greater abundance coincided with periods of sprouting and flowering of both crops. Implications. The determination of thrips species that damage berries cultivation and their population fluctuation are fundamental for the implementation of an integrated management program. Conclusions. These results enrich the information of the Mexican fauna of Thysanoptera in berries, as well as the attraction to the color of certain traps and seasonal abundance.
The study was carried out at the Tio Pedro farm in the municipality of Venezuela, in the province of Ciego de Avila, with the objective of proposing mathematical models to estimate the hydraulic ...parameters of a pumping system using the furrow irrigation technique for the cultivation of black bean. The results showed expected fluctuations in hydraulic parameters such as flow rate, head, hydraulic power, pumping time, and pumped volume. Functional relationships were found between flow and pumping head, as well as between hydraulic power, flow and pumping head. These ratios can improve pump system performance, save energy, and increase pump efficiency. In addition, functions were developed to predict the characteristic curves of the load, the efficiency of the pump and the system in general. These results can improve energy efficiency and water management in agriculture. Keywords: Pumping Head, Flow, Electrical Power, Hydraulic Power. El estudio se realizo en la finca Tio Pedro en el municipio de Venezuela, en la provincia de Ciego de Avila, tuvo como objetivo proponer modelos matematicos para estimar los parametros hidraulicos de un sistema de bombeo utilizando la tecnica de riego por surcos para el cultivo del frijol negro. Los resultados mostraron fluctuaciones esperadas en los parametros hidraulicos como caudal, carga, potencia hidraulica, tiempo de bombeo y volumen bombeado. Se encontraron relaciones funcionales entre el caudal y la carga de bombeo, asi como entre la potencia hidraulica, el caudal y la carga de bombeo. Estas relaciones pueden mejorar el funcionamiento del sistema de bombeo, ahorrar energia y aumentar la eficiencia de la bomba. Ademas, se desarrollaron funciones para predecir las curvas caracteristicas de la carga, la eficiencia de la bomba y del sistema en general. Estos resultados pueden mejorar la eficiencia energetica y la gestion del agua en la agricultura. Palabras clave: carga de bombeo, caudal, potencia electrica, potencia hidraulica.
The study was carried out at the Tio Pedro farm in the municipality of Venezuela, in the province of Ciego de Avila, with the objective of proposing mathematical models to estimate the hydraulic ...parameters of a pumping system using the furrow irrigation technique for the cultivation of black bean. The results showed expected fluctuations in hydraulic parameters such as flow rate, head, hydraulic power, pumping time, and pumped volume. Functional relationships were found between flow and pumping head, as well as between hydraulic power, flow and pumping head. These ratios can improve pump system performance, save energy, and increase pump efficiency. In addition, functions were developed to predict the characteristic curves of the load, the efficiency of the pump and the system in general. These results can improve energy efficiency and water management in agriculture.
Introduction. Some species of thrips in the genus Frankliniella (Thysanoptera: Thripidae) are of quarantine importance in various crops in the Central American region. Meanwhile, several species of ...this genus have been reported as part of the visitor fauna and flowering plants, not only in plants with agricultural production. Objective. To record the species of Frankliniella associated with avocado trees and their cultivars weeds in the central region of Costa Rica and to present a key for the identification of these thrips. Materials and methods. Sampling was carried out every two months in three different zones in the central region of Costa Rica during the years 2019 to 2021. Thrips from avocado and weeds were collected by tapping branches and were prepared for viewing under a conventional light microscope and identified by their morphology. Results. Twenty-two species of Frankliniella were identified, eighteen of which were associated with weeds growing in the same cultivars, while five species were directly associated with the foliage and flowers of the avocado tree. Conclusion. In the central region of Costa Rica, three species of the genus Frankliniella were found on the avocado tree during flowering stage: F. alonso, F. doris and F. nita, one species on the foliage: F. sandovalensis, and one species on both foliage and flowering: F. cephalica.
Introducción. Algunas especies de trips del género Frankliniella (Thysanoptera: Thripidae) son de importancia cuarentenaria en diversos cultivos en la región Centroamericana, sin embargo, diversas especies de dicho género han sido reportadas como parte de la fauna visitadora de la floración, no solo en plantas con producción agrícola. Objetivo. Registrar las especies de Frankliniella asociadas a los árboles de aguacate y sus arvenses, en la región central de Costa Rica y presentar una clave para la identificación de dichos trips. Materiales y métodos. Los muestreos se realizaron cada dos meses en tres diferentes zonas en la región central de Costa Rica, durante los años 2019 y 2021. Los trips del aguacate y de las plantas arvenses se recolectaron mediante el golpe de ramas, estos fueron preparados para su visualización en un microscopio convencional de luz e identificados por medio de su morfología. Resultados. Se identificaron veintidós especies de Frankliniella, dieciocho de ellas se asociaron a arvenses que crecen en los mismos cultivares, mientras que cinco especies se asociaron directamente al follaje y flor del árbol de aguacate. Conclusión. En la región central de Costa Rica, del género Frankliniella se encontraron tres especies: F. alonso, F. doris y F. nita sobre el árbol de aguacate durante la etapa de floración, una sola especie del follaje: F. sandovalensis y una sola especie tanto en el follaje como en la floración: F. cephalica.
The increase in competition for the use of water makes it an increasingly scarce resource for agricultural irrigation; it is necessary to search for alternative sources, such as the reuse of ...wastewater in agriculture that represents benefits for the soil and crops. The research was carried out with the objective of evaluating the quality of treated residual water in stabilization ponds for agricultural irrigation purposes, from the analysis of the physical, chemical and microbiological parameters of residual water. The main results indicate the presence of a facultative lagoon with efficiencies of 50%, 53%, 98% and 94% for the removal of biochemical oxygen demand, chemical oxygen demand, thermotolerant coliforms and total coliforms, respectively. That accounts for 74% of total operation efficiency of the lagoon with 2 mg*L.sup.-1 of dissolved oxygen in it. These values indicate that the effluent from the stabilization pond can be used for irrigation of cooked food crops according to the recommendations of the World Health Organization for Latin America and the Caribbean. Keywords: Alternative Source, Total Coliforms, Thermotolerant Coliforms, Efficiencies, Agriculture. El incremento de la competencia por el uso del agua hace que esta sea un recurso cada vez mas escaso para el riego agricola; siendo necesaria la busqueda de fuentes alternas, como la reutilizacion de las aguas residuales en la agricultura que representan beneficios para el suelo y los cultivos. La investigacion se realizo con el objetivo de evaluar la calidad del agua residual depurada en lagunas de estabilizacion del municipio de Moron en la provincia de Ciego de Avila, Cuba, con fines de riego agricola a partir del analisis de los parametros fisicos, quimicos y microbiologicos del agua residual. Los principales resultados indican la presencia de una laguna facultativa, eficiencias de remocion de coliformes termotolerantes de 98%, eficiencias de remocion de coliformes totales de 94%, eficiencias de remocion de demanda quimica de oxigeno de 53%, eficiencias de remocion de demanda bioquimica de oxigeno de 50%, eficiencia total de funcionamiento de la laguna de 74% y oxigeno disuelto de 2 mg*L.sup.-1. Estos valores indican que el efluente de la laguna de estabilizacion puede ser utilizarse para la irrigacion de cultivos alimenticios cocidos segun las recomendaciones de la Organizacion Mundial de la Salud para America Latina y el Caribe. Palabras clave: Agua residual, coliformes totales, coliformes termotolerantes, eficiencias, reutilizacion.
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