Resumo Introdução. Atualmente existem estudos que exploram benefícios, impactos e aplicações da Realidade Virtual (VR) e da Realidade Aumentada (AR) em diferentes áreas tecnológicas e profissionais. Tem despertado o interesse pela investigação devido ao seu enorme potencial e à sua aplicação em todos os níveis de ensino. Os períodos de análise da informação bibliográfica tiveram como referência o período de 2010 a 2021. Objetivo. Descrever a aplicação de VR e AR no processo de aprendizagem no ensino universitário. Identificar as áreas temáticas determinando os domínios de aplicação nas diferentes áreas. Metodologia. Foi utilizado mapeamento misto sistemático. Foram revisados documentos indexados em bibliotecas digitais. Foi filtrado sistematicamente por meio de palavras-chave. Resultados. Existem grandes lacunas nas aplicações da RV, principalmente nas áreas de neurociências e enfermagem (3%), porém, há maiores estudos em ciências da computação (40%). Conclusão. As principais conclusões foram que na Scopus, no período de 2010 a 2021, predominou o maior percentual de menções sobre a aplicação de RV por áreas temáticas e domínios de aplicação. Na análise descobriu-se que existem várias lacunas na aplicação da RV e nas teorias de aprendizagem que não consideraram o desenvolvimento de aplicações de RV para ajudar e orientar nos resultados da aprendizagem, apenas para simulação e treinamento.

Resumen Introducción. En la actualidad existen estudios que exploran beneficios, impactos y aplicaciones de la realidad virtual (RV) y la realidad aumentada (RA) en diferentes áreas tecnológicas y profesionales. Esta temática ha despertado interés en la investigación debido a su enorme potencial y a su aplicación en todos los niveles de la educación. Los períodos de análisis de la información bibliográfica han tenido como referencia desde el 2010 a 2021. Objetivo. Describir la aplicación de la RV y RA en el proceso de aprendizaje en educación universitaria. Identificar las áreas temáticas determinando los dominios de aplicación en diferentes áreas. Metodología. Se utilizó el mapeo mixto sistemático. Se revisaron documentos indexados en las bibliotecas digitales. Se filtraron sistemáticamente mediante palabras claves. Resultados. Existen grandes brechas en las aplicaciones de la RV, fundamentalmente en las áreas de neurociencia y enfermería (3%); no obstante, existen mayores estudios en las ciencias de computación (40%). Conclusión. Los principales hallazgos han sido que en Scopus en el periodo 2010 a 2021 ha predominado el mayor porcentaje de menciones sobre la aplicación de la RV por áreas temáticas de los dominios de aplicación. En el análisis se ha descubierto que existen varios vacíos en la aplicación de la RV y en las teorías del aprendizaje que no han considerado el desarrollo de aplicaciones de RV para ayudar y orientar los resultados del aprendizaje, solo han sido para la simulación y el entrenamiento.

Abstract Introduction. Currently there are studies that explore benefits, impacts and applications of Virtual Reality (VR) and Augmented Reality (AR) in different technological and professional areas. It has sparked interest in research due to its enormous potential and its application at all levels of education. The periods of analysis of the Bibliographic information have been from 2010 to 2021 as a reference. Objective. Describe the application of VR and AR in the learning process in university education. Identify the thematic areas by determining the application domains in different areas. Methodology. Systematic mixed mapping was used. Documents indexed in digital libraries were reviewed. It was systematically filtered using keywords. Results. There are large gaps in the applications of VR, mainly in the areas of neuroscience and nursing (3%), however, there are greater studies in computer sciences (40%). Conclusion. The main findings have been that in Scopus in the period 2010 to 2021, the highest percentage of mentions about the application of VR by thematic areas and application domains has predominated. In the analysis it has been discovered that there are several gaps in the application of VR and in learning theories that have not considered the development of VR applications to help and guide towards learning results, they have only been for simulation and training.

Abstract The purpose of this paper is to conduct a literature review on the multinational's financial performance research evolution, using bibliometric and network analysis, in an attempt to map this knowledge area and identify emerging research trends. Likewise, this paper establishes the research currents that are currently emerging on the subject studied. From 687 records retrieved from Web of Science and Scopus, during the period between 2000 and 2021, a scientific mapping was carried out to identify the most relevant documents, authors, journals, institutions, and countries in the field, in addition, through A network analysis establishes the main groups of documents and the research directions they are assuming. Four main areas that emerge from the literature were identified: Financial performance of the MNE that carry out Corporate Social Responsibility (CSR) activities, the impact of the use and transfer of the competitive advantages of the MNE's, relationship of the diversification of MNE countries and finally, advantages of the countries in which the MNE are located, compared to financial performance. This document provides a bibliometric and network analysis, which details knowledge that had not been previously exposed by other reviews on the area, through objective and rigorous analysis based on a quantitative approach. Similarly, the main contribution of this document is to delineate the trends and emerging research topics on the financial performance of MNE's.

Resumen El propósito de esta investigación es realizar una revisión de la literatura sobre la evolución de la investigación en el desempeño financiero de los multinacionales, utilizando análisis bibliométrico y de redes, en un intento de mapear esta área de conocimiento e identificar tendencias emergentes de investigación. Igualmente, este artículo permite establecer las corrientes de investigación que emergen en la actualidad, sobre el tema estudiado. A partir de 687 registros recuperados de Web of Science y Scopus, durante el periodo comprendido entre 2000 y 2021, se realizó un mapeo científico para identificar los documentos, autores, revistas, instituciones y países más relevantes en el campo, además, a través de un análisis de redes se establecen los principales grupos de documentos y las direcciones de investigación que están asumiendo. Se identificaron cuatro principales áreas que emergen de la literatura: Desempeño financiero de las MNE 1que realizan actividades de Responsabilidad Social Empresarial (RSE), impacto del aprovechamiento y transferencia de las ventajas competitivas de las MNE's, relación de la diversificación de países de la MNE y finalmente, ventajas de los países en los que la MNE está ubicada, frente al desempeño financiero. Este documento proporciona un análisis bibliométrico y de redes, que detalla conocimientos que no habían sido expuestos previamente por otras revisiones sobre el tema, esto, a través de análisis objetivo y riguroso basado en un enfoque cuantitativo. De igual forma, la principal contribución de este documento es delinear las corrientes y temas de investigación emergentes sobre el desempeño financiero de las MNE. JEL: F23, F65, G31, L25, M16, M21.

Abstract Purpose: This study aims to determine whether, by means of the application of genetic algorithms (GA) through the traditional technical analysis (TA) using moving average convergence/divergence (MACD), is possible to achieve higher yields than those that would be obtained using technical analysis investment strategies following a traditional approach (TA) and the buy and hold (B&H) strategy. Design/methodology/approach: The study was carried out based on the daily price records of the NASDAQ financial asset during 2013-2017. TA approach was carried out under graphical analysis applying the standard MACD. GA approach took place by chromosome encoding, fitness evaluation and genetic operators. Traditional genetic operators (i.e. crossover and mutation) were adopted as based on the chromosome customization and fitness evaluation. The chromosome encoding stage used MACD to represent the genes of each chromosome to encode the parameters of MACD in a chromosome. For each chromosome, buy and sell indexes of the strategy were considered. Fitness evaluation served to defining the evaluation strategy of the chromosomes in the population according to the fitness function using the returns gained in each chromosome. Findings: The paper provides empirical-theoretical insights about the effectiveness of GA to overcome the investment strategies based on MACD and B&H by achieving 5 and 11% higher returns per year, respectively. GA-based approach was additionally capable of improving the return-to-risk ratio of the investment. Research limitations/implications: Limitations deal with the fact that the study was carried out on US markets conditions and data which hamper its application in some extend to markets with not as much development. Practical implications: The findings suggest that not only skilled but also amateur investors may opt for investment strategies based on GA aiming at refining profitable financial signals to their advantage. Originality/value: This paper looks at machine learning as an up-to-date tool with great potential for increasing effectiveness in profits when applied into TA investment approaches using MACD in welldeveloped stock markets.

Abstract: Background: Loeselia mexicana, known as Mexican false calico, or espinosilla in Spanish, is a widely distributed secondary forest plant with a significant number of medicinal and cosmetic uses. This species is threatened by the lack of regulation over collection methods and changes in land use. In vitro culture could be used to preserve the species by shoot induction, callus production and cell-suspension to obtain secondary metabolites; this would reduce the need to affect wild populations. Hypothesis: A combination of cytokinins and auxins can induce structural development in the plant, promoting the formation of shoots, roots or callus in vitro. By applying this combination to L. mexicana stem segments, we expected to observe new shoots or callus. Study site and dates: “El Teuhtli” volcano, Xochimilco; from June 2015 to February 2016. Methods: Distal stems cuttings were used as explants. They were disinfected with 1 % soap, 0.6 sodium hypochlorite and 70 % ethanol, and rinsed with distilled water. Two different times of disinfection with ethanol were tested. The distal stem segments were then planted in solid MS medium with 3, 5 or 7 mg L-1 KIN combined with 3 mg L-1 NAA, and 2 % AC. Results: A favorable response was observed in the treatment with 5 mg L-1 KIN and 3 mg L-1 NAA, which produced green callus with root in five weeks. Furthermore, a lower explant mortality rate was achieved, 46.66 % in three weeks, with a shorter disinfection time. Conclusions: Disinfection time is important for this species, and callus production is possible.

Resumen: Antecedentes: Loeselia mexicana, conocida como espinosilla, es una planta de vegetación secundaria con diversos usos medicinales y cosméticos. Esta especie podría estar amenazada debido a la falta de regulación en la colecta y por cambios en el uso del suelo. El cultivo in vitro es una alternativa para la preservación de la especie por inducción de brote, producción de callo, y células en suspensión para la obtención de metabolitos secundarios; esto reduce la necesidad de intervenir en las poblaciones silvestres. Hipótesis: La combinación de citocininas y auxinas puede inducir el desarrollo de las estructuras en la planta, promoviendo la formación in vitro de brotes, raíz o callo. Al aplicar esta combinación a segmentos de tallo de L. mexicana, se esperaba observar nuevos brotes o callo. Sitio de estudio y fechas: Volcán "El Teuhtli", Xochimilco, de junio de 2015 a febrero de 2016. Métodos: Se cortó la parte distal del tallo como explante. Se desinfectó con jabón al 1 %, cloro al 10 %, etanol a 70 % y se enjuagó con agua destilada. Se probaron dos tiempos con el etanol. Se sembró en MS sólido con 3, 5, o 7 mgL-1 de KIN combinado con 3 mgL-1 de ANA, y 2 % de CA. Resultados: En la combinación con 5 mgL-1 KIN y 3 mgL-1 ANA se observó una respuesta favorable al producir callo verde con raíz en cinco semanas. Además, con un menor tiempo de desinfección se logró una menor tasa de mortalidad de los esquejes, el 46.66 % en tres semanas. Conclusiones: El tiempo de desinfección es importante con esta especie, y es posible la producción de callo.

ABSTRACT Low alloy steels are used in many applications in the oil and gas industry. The addition of Ni in these steels improves their low temperature fracture toughness and hardenability, with a low penalty on weldability. However, ISO 15156-2 standard restricts Ni content up to a 1 wt% limit, requiring additional and expensive tests if higher Ni steels are to be used. This limit is based on the hypothesis that higher contents of Ni may negatively affect Sulfide Stress Cracking (SSC) resistance in sour service applications. On the other hand, several investigators have concluded that SSC resistance depends on microstructure and hardness rather than Ni content. The 1 wt% Ni limit imposed by ISO 15156-2 is controversial, as recently pointed out by other authors. This work aims to develop alloys and heat treatments tailored to obtain the same microstructure and hardness in steels with different Ni contents (from 0 to 5 wt %), therefore leaving Ni content as the main variable. This will allow, in a future stage of the project, to study the effect of Ni on the SSC crack propagation kinetics. Transformation temperaturesof the alloys were measured with differential scanning calorimetry (DSC). Characterization of the as-quenched samples confirmed a fully martensite microstructure. Tempering of the samples allowed obtaining hardness values near 22 HRC. Microstructure was evaluated with optical and scanning electron microscope and hardness measurements. Tensile tests were performed to evaluate mechanical properties as a function of Ni content.

RESUMEN Los aceros de baja aleación son ampliamente utilizados en la industria del gas y petróleo. La incorporación de Ni en estos aceros mejora la tenacidad a la fractura a bajas temperaturas y la templabilidad, con bajo impacto negativo en la soldabilidad. Sin embargo, la norma ISO 15156-2 restringe su uso hasta un máximo de 1 % en peso, exigiendo ensayos adicionales y costosos si se desean adoptar contenidos mayores de Ni. Este límite se basa en la hipótesis de que un exceso de Ni puede afectar negativamente la resistencia a la corrosión bajo tensión en medios con sulfhídrico (en inglés, Sulfide Stress Cracking (SSC)). Por otro lado, algunos investigadores han concluido que el fenómeno no depende del contenido de Ni, sino de la microestructura y dureza de la aleación, lo cual hace que el límite en composición del Ni planteado por la norma ISO 15156-2 sea controversial. El objetivo de este trabajo es desarrollar aleaciones y tratamientos térmicos que permitan obtener microestructura y dureza similares en aceros con distinto contenido de Ni (05% en peso), dejando así como variable principal el contenido de Ni. Estas muestras serán, en una etapa posterior del trabajo, utilizadas para estudiar la cinética de propagación de fisuras por SSC. Se realizaron mediciones de temperaturas de transformación de fases por calorimetría diferencial de barrido (DSC). La caracterización del material templado confirmó que las microestructuras finales obtenidas constituyen estructuras esencialmente martensíticas. Mediante tratamientos térmicos de revenido fue posible alcanzar valores de dureza menores que 22 HRC, tal como exige la norma ISO 15156-2 para maximizar la resistencia a SSC. La microestructura se evaluó mediante caracterización por microscopía óptica, electrónica de barrido (SEM) y dureza. A su vez, se caracterizaron las propiedades mecánicas de las aleaciones mediante ensayos de tracción.

Uma das necessidades básicas do ser humano é a habitação. O elemento básico é o concreto, a pedra artificial, que demanda grandes quantidades de agregados como areia e brita. Tanto a areia como as rochas que originam a brita são abundantes na natureza e, por isso, têm baixo valor agregado. Em virtude dessa condição, o custo logístico de transporte do porto de areia e da pedreira até chegar ao local de sua utilização onera, significativamente, o seu preço final. Medidas restritivas adotadas, nos grandes centros urbanos, como a proibição de circulação dos veículos de carga em determinadas áreas, horários preestabelecidos, rodízio municipal e especificação de tipos e tamanhos dos veículos, provocam a necessidade de uma frota maior e mais diversificada, além de maior quantidade pessoal.

One of the human being's basic needs is housing. In Brazil, the basic element for this is concrete, artificial stone, which demands a great amount of aggregates, such as sand and gravel. The sand and rocks are abundant in nature and gravel can be produced at low cost. However, transportation to the area of product utilization can be an incremental factor in the final cost logistics. Both sand and gravel have expressive price variations, which are not necessarily related to mining activities, but to logistic activities, mainly their distribution. Restrictive measures adopted in large urban centers, such as prohibition of hauling trucks in certain areas or during certain hours, alternate license plate end number system (even number plate ending can circulate on even-numbered days and visa versa), and axle-control, generate a need for a larger and more diversified fleet, not to mention more employees.