Uniciencia 2021-07-31T00:00:00-06:00 Yuri Morales López Open Journal Systems <p>The mission of <strong>Uniciencia</strong>&nbsp;journal is to share, without profit, research results and offer high quality inputs to the national and international scientific community in such a way that they allow the scientific and cultural development of our society. It is a&nbsp;semiannual&nbsp;journal that began in 1984. The journal is indexed in: Scopus, SciELO, Redalyc, LATINDEX Catalog, DOAJ, Emerging Source Citation Index (ESCI), among others.<br><strong>Publishing Entity</strong>: Faculty of Exact and Natural Sciences. Universidad Nacional, Costa Rica.<br><strong>Thematic areas</strong>: biology, physics, computer science, mathematics, chemistry, topography and geodesy (and their teaching).<br><strong>E-ISSN</strong>: 2215-3470<br><strong>Contact</strong>: Yuri Morales-López, Editor • <strong>Email</strong>:</p> Effect of two surfactants on in vitro permeation of butorphanol through horse nasal mucosa 2021-05-04T15:40:55-06:00 María Inés Velloso Héctor Alfredo Andreeta María Fabiana Landoni <p>The aim of the present study was to evaluate the effect of two surfactants on <em>in vitro </em>permeation of butorphanol through equine nasal mucosa. Franz diffusion cells and equine nasal mucosa were used. Three formulations were developed based on citric acid, sodium citrate, sodium chloride, and butorphanol tartrate and administered at a 24.4 g cm<sup>-3</sup> dose. Control formulation lacked any penetration enhancer. Formulation 1 (F1) had a cationic surfactant (cetrimonium bromide) and formulation 2 (F2) had a non-ionic surfactant (Tween 80). Statistically comparing flux values at the steady state (J<sub>ss</sub>), apparent permeability coefficient (K<sub>p</sub>), and lag-time from control, F1 and F2 for the respiratory region does not show statistically significant differences (α= 0.05). However, statistically significant differences were found on the J<sub>ss</sub> and K<sub>p, </sub>values from control, F1, and F2 in olfactory mucosa. A statistical analysis on the latter showed significant differences between the J<sub>ss</sub> values of F1 and F2 and between control and F2. Based on this, Tween 80 proved to be a promising excipient in developing intranasal butorphanol formulations in equines since it increases its passage through the nasal mucosa. These results are very promising to continue with the development of intranasal butorphanol formulation in equines.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Optimization of larval culture for the production of juvenile spotted snapper Lutjanus guttatus in Costa Rica 2021-05-04T15:40:56-06:00 Jonathan Chacón-Guzmán Milagro Carvajal-Oses Ángel Herrera-Ulloa <p>The technological foundation of the <em>Lutjanus guttatus</em> aquaculture was developed in Costa Rica in 2002 by Parque Marino del Pacífico. The first juvenile mass production was obtained in 2005; small-scale commercial farms were established in 2006; and the first technology transfer to the private sector began in 2008. Based on these advances, the need to optimize the production of juveniles was identified. With this objective, three larval crops obtained from natural spawning of second-generation (F2) breeders were evaluated and biologically described. Three families n = 8 each: 1.45 ± 0.21 kg, 1.33 ± 0.12 kg, and 1.28 ± 0.10 kg from an aquaculture farm were acclimatized in the laboratory until they spawned. A total of 100,000 eggs were incubated per spawning (density: 520 eggs mL<sup>-1</sup>). Larvae (90 thousand/tank) were seeded with an initial total length (TL) equal to 2.25 mm and fed with enriched rotifers, microalgae produced in helical photobioreactors, and artemia nauplii. Growth, survival, cannibalism, size variability, and deformities obtained were registered. A total of 22,837 juveniles were harvested on day 60 after spawning. During harvest, the juvenile’s total length (TL) was 57.8 ± 7.82 mm, Absolute Growth Rate (AGR) was 0.93 mm d<sup>-1</sup>, Specific Growth Rate (SGR) was 5.41% d<sup>-1</sup>, Condition Factor (K) was 1.089, average survival was 8.4 % and total eye deformities were 6.3 %. Methodologies used to obtain natural quality spawning, improvement of live food produced by photobioreactors, and separation by size were effective aspects for the larval culture of the species, although starvation in the first days of exogenous feeding, metamorphosis, and cannibalism continue to be factors affecting final survival.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Multitemporal analysis of plant associations and land use changes in a high Andean locality, Puno-Peru 2021-05-04T15:40:55-06:00 Alfredo Loza-Del-Carpio Irene Taype-Huamán <p>Unplanned changes in the use of high Andean territories have become more evident, leading to a loss of productive areas and important ecosystem services. Under this context, the objective of this study was to characterize the temporal changes in vegetation and land use in the high Andean district of Cabana (Peru). Vegetation types were determined based on the predominant species; these areas, together with the frequent forms of land use, were quantified using a supervised analysis of Landsat images with a 30 m spectral resolution, obtained during March and April 2000, 2005, 2010, and 2016. Six types of plant associations were identified whose areas decreased 2000 ha, from the initial 12500 in 16 years (16.27%). By 2000 the <em>Muhlenbergetum fastigiatae</em> association had the highest coverage (43.96%), but in 2016 <em>Calamagrostio vicunaro - Festucetum dolichophyllae</em> predominated (47.31%). Crop areas increased from 5133 ha (27%) to 7115 ha (37%) of the district surface, while degraded soils extended from 35 to 120 ha, sparsely vegetated areas from 17 to 30 ha and wetland reduced from 179 to 29.7 ha. Urban coverage grew 40.7 % annually. Land use with no territorial ordering basis caused detriment in vegetation and compromised the sustainable use of natural resources.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Bacterial pathogens and their antimicrobial resistance in tilapia culture in Guatemala 2021-05-04T15:40:56-06:00 Josué García-Pérez Juan B. Ulloa-Rojas Susana Mendoza-Elvira <p>The aim of this study was to identify the main bacterial pathogens affecting tilapia aquaculture in Guatemala during 2018-2019 and evaluate their resistance to the most widely used antibiotics in the aquaculture industry of the area. Fish weighing between 50 and 1,000 g were collected from different production centers. The most frequent external and internal macroscopic signs were recorded for each organism. In addition, bacteriological samples of blood fluid, ulcers and other hemorrhagic areas, anterior kidney, spleen, meninges, liver, and heart were isolated. The isolated pathogenic bacteria were identified at the species level through biochemical tests. Finally, susceptibility was assessed with the following antibiotics oxytetracycline (40 µg), florfenicol (40 µg), enrofloxacin (40 µg), and fosfomycin (40 µg) by the disk diffusion method. The most common clinical signals were skin ulcers, hyperemic areas, body melanization, pale and soft liver, liver vasculitis, and intestinal congestion and bleeding. A total of 16 pathogenic bacteria strains were isolated from tilapia samples. The most frequent genera were <em>Aeromonas</em> (70%: 3 spp), followed by <em>Plesiomonas, Burkholderia, Pseudomonas, Shewanella, </em>and<em> Streptococcus</em> (6%; 1 sp). Isolated bacteria strains showed resistance to oxytetracycline (25%) and fosfomycin (25%) and sensitivity to florfenicol and enrofloxacin. This is the first report related to the most frequent bacterial pathogens and their antimicrobial resistance in tilapia culture in Guatemala.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Preliminary inventory of atmospheric emissions (SO2, NOx and TSP) from different industrial sectors in Costa Rica 2021-05-04T15:40:56-06:00 Daniel Alfaro-Alfaro Luis Salas-Morelli Bryan Sánchez-Mejías José Mora-Barrantes José Pablo Sibaja-Brenes Henry Borbón-Alpízar <p>The use of fuels, urbanization growth, and economic development have influenced the generation of atmospheric pollutants such as NOx (nitrogen oxides), SO<sub>2</sub> (sulfur dioxide), and TSPs (Total Suspended Particles). The Costa Rican industrial sector has different category companies such as glass melting and manufacturing of food products and clothing, which release emissions of these pollutants into the atmosphere. The main objective of this research is to generate a preliminary inventory of atmospheric emissions (NOx, SO<sub>2,</sub> and TSP) from different industrial sectors in Costa Rica. The inventory was conducted in 2019 and included samplings and measurements of pollutants from chimneys of different production processes (companies) from 2014 and 2015.&nbsp; The sampling and the corresponding measurement of pollutant concentrations (NOx, SO<sub>2</sub> and TSP) were conducted using Testo 350 to measure NOx and SO<sub>2</sub> and an APEX portable particle counter to quantify TSPs. Data was tabulated using Microsoft Excel, while graphics were generated using R programming language in the R studio interface. The industrial sector entitled “manufacturing of food products” presents the highest amounts of pollutants, with values equal to 1246.14 tons/year, 1959.54 tons/year and 651.01 tons/year for NOx, SO<sub>2,</sub> and TSP, respectively, for 2014; and 2,622.14 tons/year, 3,257.64 tons/year and 346.40 tons/year, respectively, for 2015.&nbsp;</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Changes in land cover in coastal erosion hotspots in the southern Caribbean of Costa Rica during the period 2005-2017 2021-05-04T15:40:56-06:00 Luis Sandoval-Murillo Gustavo Barrantes-Castillo <p>Studies conducted in recent years have warned us about the effects generated by changes in the coastline along the Southern Costa Rican Caribbean coast. The objective of this research is to evaluate this effect on land cover along the southern Costa Rican Caribbean coast. The methodology used consisted of surveying and comparing land cover from 2005 and 2016 (with field verification for 2017) along a 200 m wide coastal strip based on large-scale aerial photographs using ArcGis Map Algebra. In addition, covers affected by coastal erosion during the 2005-2010 and 2010-2016 periods are established by overlapping them with 2005 land covers, which helped identify the areas that changed from a beach to another type of use in the Cieneguita-Airport, Westfalia, Bananito, Cahuita-Puerto Vargas, Manzanillo, and Sixaola sectors. Results obtained indicate that, in the Cieneguita-Airport, Westfalia, Bananito, Manzanillo, and Sixaola segments, the main cover change was from beach to sea, with readjustments in other types of cover, while in Cahuita-Puerto Vargas the main change was from forest to ocean. In the Cieneguita-Airport segment, urban cover increased, which raises the risk of coastal erosion and public goods exposure. It is concluded that the effects of coastal erosion that occurred in critical points along the southern Caribbean have changed land cover. Beaches, grass, and coastal vegetation are the most affected since they are changed by sea surfaces, except for Cahuita National Park, where the ocean is eroding high- and low-density forests.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Effect of a Wind Lens diffuser on turbulent flow 2021-05-04T15:40:56-06:00 Gustavo Richmond-Navarro Pedro Casanova-Treto Franklin Hernández-Castro <p>This article is aimed to measure the effect of a wind lens diffuser on turbulent flow. The study was conducted in the boundary layer wind tunnel of the Research Institute for Applied Mechanics at Kyushu University, Japan, between March and May 2019. A hot wire anemometer with a moving mechanism was used to conduct three tests. First, a characterization of the flow inside the wind tunnel was measured without the grid. Second, the turbulence intensity in the wind tunnel axis was measured this time with the grid in place. Third, the wind lens effect on the incident wind speed was determined at different levels of turbulence intensity. The wind speed in the tunnel without the turbulence grid was almost constant, approximately 9.6 m/s. When the grid was placed, a decreasing turbulence intensity was recorded in the axis of the wind tunnel, from 28.6 % at 500 mm from the grid to 5 % turbulence intensity at 3100 mm from the grid. When the effect of the wind lens was measured on the turbulent flow, wind speed increased up to 20 %. The wind lens proved suitable for wind turbines operating in turbulent flow, by increasing wind speed in all tests and generating a greater increase in the conditions with greater turbulence intensity.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Nesting of arboreal ants (Hymenoptera: Formicidae) in artificial substrates in coffee plantations in the Colombian Andes 2021-05-04T15:40:56-06:00 Andrés Jireh López-Dávila Selene Escobar-Ramírez Inge Armbrecht <p>Ants can provide pest biocontrol for coffee crops; however, this ecosystem service may decline in intensively managed plantations due to the loss of nesting resources. Considering how to increase the number of ants, we studied if they nest in different types of artificial substrates attached to coffee bushes both in shade-grown and sun-grown coffee plantations. Three independent tests were conducted at some coffee plantations in southwestern Colombia with the purpose of answering the following questions: 1) Do ants nest in artificial substrates made from recyclable materials? 2) Do the types of substrate (materials and configuration) and coffee management (shade-grown vs. sun-grown coffee) affect colonization rates, richness, and identity of colonizing ants? 3) Does time affect substrate colonization rates? Each experiment independently compared different substrate materials and designs, in both shade and sun-grown coffee. Results showed preference of one of the substrates offered and higher nesting rates in shade-grown plantations. Eight ant species were found nesting in artificial substrates, most of them being arboreal generalists. A higher number of ant species colonized substrates in shade-grown plantations; however, the effect was not statistically significant. <em>Nesomyrmex asper</em> and <em>Crematogaster </em>spp. were always found nesting in both types of plantation. There was a trend to increase nesting activity with time in shade-grown coffee but not in sun-grown coffee. Evidence supports that offering artificial substrates enhances arboreal ant nesting in coffee plantations.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Origin of color variations of thin, nano-sized layers of volcanic cinder from the Sierra Negra Volcano of the Galapagos Islands 2021-05-04T15:40:55-06:00 Alexis Debut Theofilos Toulkeridis Andrea V. Vaca Carlos R. Arroyo <p>Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magmas of basaltic or andesitic composition cool quickly. It is typically dark in color, ranging from black to red depending on its chemical composition. Sometimes fresh cinder samples show a variety of shiny metallic colors on its surface ranging from blue to gold to silver. The origin of these colors has remained unknown up to now. Cinder samples from an eruptive event occurred in October 2005 have been collected in the surroundings of the Sierra Negra volcano in the Galápagos Islands. The samples’ crystallographic structure, chemical composition, and surface morphology have been analyzed using X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and a field gun emission scanning electron microscopy (SEM), respectively. Based on an extensive physical and chemical analysis, we were able to demonstrate that these colors are due to a light interference phenomenon. These results have a great potential to be used for a wide variety of purposes such as determining the temperature and composition of magma and evaluating volcanic samples for planetary studies.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Socio-environmental aspects affecting water contamination in an urban area 2021-06-21T18:23:56-06:00 Rolando Sánchez-Gutiérrez Carolina Alfaro-Chinchilla Kimberly Ledezma-Zamora Ligia Hernando-Echeverría Carmen Mora-Aparicio Roy Pérez-Salazar <p>The purpose of the research was to identify and analyze the most relevant socio-environmental aspects causing contamination of water resources in an urban area. The study used descriptive research with a mixed approach, in which, through the collection of primary and secondary information, data was obtained related to socio-environmental perception, change patterns in land use, identification of potential sources of water contamination by discharge, and the current condition of wastewater management in the area. The information was obtained through a preliminary perception survey, field verification, satellite images, databases from regulatory authorities, and other sources. The surveyed population’s perception regarding water supply is satisfactory; however, no interest was perceived regarding home wastewater management. The analysis of land use showed a progressive increase in the use of urban land and a decrease in the use of forest areas over the last years. In addition, over 230 potential sources of water contamination were found between direct and indirect discharges. Regarding regulated discharges, the operational reports showed compliance with national regulation, even though the net organic load was high. The commercial activities and urban development negatively affect the area and accelerate water pollution. Therefore, water bodies are under constant pressure, which must be managed using participatory processes with an integrated management approach.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Workload in a group of Latin American teachers during the COVID-19 pandemic 2021-05-04T15:40:55-06:00 Leonardo Flavio Medina-Guillen Gustavo Jared Quintanilla-Ferrufino Margarita Palma-Vallejo Mónica Fernanda Medina Guillen <p><strong>Introduction</strong>. The viral disease Covid-19 -currently a pandemic- forced to accommodate measures of social distancing with the intention of limiting its expansion, including: teleworking and online (virtual) teaching.&nbsp; Would the sudden shift from face-to-face classroom to virtual education result in teacher work overload?&nbsp; If so, what are the influencing factors? <strong>Objective. </strong>Analyze the workload of teachers in Latin America, at three different educational levels, during the COVID-19 pandemic in June and July 2020. <strong>Methods.</strong> Quantitative, descriptive, cross-sectional study. A 37-question questionnaire was used, with a Hernández-Nieto content validity coefficient of 0.99 and a temporal stability coefficient 0.91. Statistical analysis was performed using Excel 2019, measures of central tendency and frequency analysis were used.&nbsp; <strong>Results.</strong> 887 teachers were surveyed for whom sociodemographic characteristics are detailed and their personal, technical, institutional and space load factors assessed.&nbsp; Student dropout percentage was also ascertained.&nbsp; <strong>Conclusion.</strong> The surveyed teachers perceived an increase in workload due to the factors studied, intertwined with an increase in student desertion.&nbsp; The abrupt change in the modality from face-to-face to virtual education has generated a reorganization of work and family life, teleworking from home requires a clear delimitation by teachers of the work schedules and functions involved in the various aspects of online education.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## An approach to didactic-mathematical knowledge of future Basic Education teachers to teach elementary mathematics 2021-05-04T15:40:56-06:00 Nataly Pincheira Claudia Vásquez Belen Giacomone <p>This paper presents a global analysis of the results obtained in an exploratory study about the didactic-mathematical knowledge (CDM) that future Basic Education teachers have in order to teach elementary mathematics. For this purpose, the math practices of 157 Chilean teachers under training were analyzed based on the CDM-Elementary Mathematics questionnaire, which includes six open ended questions to evaluate partial and initial aspects of such knowledge. The questions are based on the thematic areas proposed by the Chilean school curriculum and are closely related to the mathematical content of numbers and operations, patterns and algebra, measurement, geometry, data and probability. Results show that the level of performance obtained by future teachers is limited regarding didactic-mathematical knowledge for the different categories, when reaching an average of 24 points out of a total of 42. In addition, the thematic areas with the greatest difficulty are measurement, data, and probabilities. In conclusion, programs should be created to support teacher training in order to successfully address the teaching of elementary mathematics in the basic education classroom.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Comparing probabilities in urns: A study with primary school students 2021-05-04T15:40:56-06:00 Luis Armando Hernández-Solís Carmen Batanero María M. Gea Rocío Álvarez-Arroyo <p>The study aimed to explore the strategies used by Costa Rican primary school students when comparing urn probabilities. The sample was intentional and consisted of 55 6<sup>th</sup> graders. Using an interpretive approach, we analyzed the children’s responses to a questionnaire of five probability comparison items taken from previous studies, including different levels of proportional reasoning. Results indicate that problems in the first levels of proportional reasoning were solved easily by students, while problems at higher levels increased in difficulty. One-variable strategies, which compare only the favorable or unfavorable cases in both urns, are predominant; although there are correspondence strategies, few students show complete proportional reasoning. Aside from slight variations, results are similar to previous studies, which suggests that this task is influenced more by the child’s level of maturity than the instruction received.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Knowledge of preservice elementary teachers on fractions 2021-05-04T15:40:56-06:00 Elena Castro-Rodríguez Luis Rico <p>In this paper, we studied the knowledge on didactic contents reflected by future elementary teachers when answering questions related to teaching and learning fractions. Following a qualitative methodology, specifically a case study, 9 senior pre-service elementary teachers were interviewed using a structured approach. The topic was presented to the subjects using a narrative they had previously written on how to initiate the concept of fractions with school children. After reading it, they were asked questions regarding task design, learning objectives, and mistakes and difficulties. Results identified two trends in the participants’ knowledge: a procedural or technical trend in which the stated knowledge emphasizes procedures, processes, or action modes, and a conceptual or cognitive trend in which the stated knowledge emphasizes the functional understanding of fractions and their relationships. As a conclusion, it is essential that initial teacher training emphasizes mathematical as well as didactic contents.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Pedagogical effectiveness in the school organizational culture and the professional learning community 2021-05-04T15:40:56-06:00 Derling José Mendoza Velazco Magda Francisca Cejas Martínez Mercedes Navarro Cejas Elizeth Mayrene Flores Hinostroza Karina Maribel Castillo Pinos <p>The objective of this study was to analyze teacher effectiveness in the organizational culture of schools and the professional learning community. This was a quantitative research, with a simple random sample of 359 elementary teachers at the initial, basic, and general unified level in the cities of Cuenca and Azogues, Ecuador. Four Likert-type questionnaires of five answer options were applied as instruments, with the t, F, and Scheffé test analysis method. Using correlation and multiple regression analysis, results indicated that teachers respond to school organization according to their personal characteristics. The school organizational culture is gradually being transformed into a positive and ideal culture. The professional learning community had a positive effect on teachers' effectiveness. In conclusion, the organizational culture of the school and the professional learning community should go beyond the interactive dimension and move towards the integration dimension to improve the school in order to obtain greater pedagogical effectiveness.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Competencies of pre-service mathematics teachers when transforming the representations of a function 2021-05-04T15:40:56-06:00 Tulio Amaya De Armas Arjuna Gabriel Castellanos Luis Roberto Pino-Fan <p>This paper aimed to analyze the competencies of pre-service secondary school mathematics teachers when transforming the representations of a function. The information was collected during the second half of 2019 and was processed using the content analysis technique. For this qualitative study, researchers interacted with pre-service teachers while they solved problems involving functions and prepared a class that they later simulated before their professor and classmates. The sample included 36 students from the Mathematics Education Program of a Chilean university. Results show that pre-service teachers were able to produce multiple ways of representations of the analyzed functional relationships, which facilitated the analysis and establishment of connections with sociocultural elements.&nbsp; However, some participants faced difficulties with perceptual fluency, which prevented them from establishing connections. The partial meanings of the functions were articulately modified until they became one, in which time multiple representations were produced and articulated. In conclusion, interventional processes should be implemented to help future teachers make more comprehensive analyzes of functions and have an operational use of their knowledge, in order to minimize learning difficulties in students.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Structures in direct and inverse forms of a function evidenced by 7–8-year-old students 2021-05-04T15:40:56-06:00 María D. Torres María C. Cañadas Antonio Moreno Pedro Gómez <p>This study aimed to identify and compare the structures evidenced by primary school students in direct and inverse forms of a function, both working with particular cases and generalizing from an early algebra functional approach. The study was qualitative, exploratory, and descriptive. A contextualized task was designed involving the linear function y=x+4 in direct and inverse variations. Six 2nd graders (7-8 years of age) from a school in Granada (Spain) participated in the study performing a designed task during semi-structured interviews conducted in the 2017-2018 school year. We described the structures evidenced in both variations with particular cases and the general case. All six students identified adequate structures in the direct variation of the function at least once during the interview. Adequate structures were also observed in the inverse variation. However, some students did not respond to this section or were not asked these questions. The majority of the structures that students generalized were produced when explicitly asked for generalization, in both direct and inverse variations of the function. When using the relationship between two variables, differences were found between structures identified by students in both direct and inverse variations. Most of the structures identified were adequate for the problem, which encourages work with both variations of linear functions in primary education.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Argument schemes of high school students when using GeoGebra in the context of tessellations 2021-05-04T15:40:55-06:00 Guadalupe Morales Ramírez Víctor Larios Osorio Norma Rubio Goycochea <p>This paper identifies and describes the arguments presented by a group of high school students when justifying their responses to geometric situations and using GeoGebra, a dynamic geometry software. The argumentation process showed to be deficient for the group of 15-18-year-old students from the Universidad Autónoma de Querétaro (UAQ) high school. Students were given a sequence of activities involving isometric transformations, in which they manipulated applets and created semi-regular tessellations using the GeoGebra software. The research was a descriptive case study. The epistemic configurations of the theoretical framework of the Ontosemiotic Approach to Mathematical knowledge and Instruction (OSA) were used for the analysis of the students’ arguments, while argumentation schemes were used for the analysis of the results. These results suggest that, in the argumentation process, students resort to empirical and factual argumentation schemes, which was evidenced by the use of informal language and little mathematical language. In addition, the visual perception favored by the GeoGebra software was essential to develop the argumentation process, although it played the role of argument rather than a support to the process.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Analysis of definitions of limit provided by University students 2021-05-04T15:40:55-06:00 Yosenith González-Flores Ana Belén Montoro-Medina Juan Francisco Ruiz-Hidalgo <p>This paper serves two objectives: analyze the definitions provided by college students for the concept of limit at a point in a function as well as design and validate a category system to carry it out. The definitions of limit were provided by 38 university students in the Biology and Engineering in Industrial Chemistry program, enrolled in a Differential and Integral Calculus course during the first semester of 2018, at Universidad Nacional, Costa Rica. <em>A priori</em> categories were used and complemented with other categories of an inductive nature, which emerged during the analysis of the responses. These categories were validated through a reliability analysis. Approximately half of the students’ answers showed the limit category as an object and over three-quarters showed the limit category as a process. In addition, approximately half of their answers showed the categories terms of relative position and general lack of coordination of the processes. The category system created allowed for the analysis of information units in an organized, simple, and replicable way. Finally, students showed a dual conception of limit either as an object, fixed and static notion, or as a process, processual and dynamic notion. Furthermore, the content analysis described in the methodology may allow future researchers to create a similar category system or use this one for research in other contexts.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Suitability criteria used by future primary school teachers in the assessment of math educational videos 2021-05-04T15:40:55-06:00 María Burgos Navarro María José Castillo Céspedes <p>This research describes the criteria implicitly used by a group of future primary school teachers when assessing the adequacy of the planned didactical trajectory after watching two videos in an educational channel to teach sixth graders a specific content, percentages. The content analysis methodology is used to examine the written reports prepared by 61 third-year students enrolled in the class Design and Development of Primary Education Mathematics Curriculum during the 2019-2020 school year, as part of the Primary Teacher Education program at the University of Granada, Spain. Their reports were assessed based on the authors’ <em>a priori</em> consensus analysis of the didactic suitability of educational videos. Results show that student teachers implicitly use epistemic and interactive criteria to a great extent, as well as cognitive, affective, and ecological criteria. Although in general their assessments are quite inaccurate, student teachers recognize the need for teachers to analyze the relevance of these resources before recommending them to their students, which have acquired a fundamental role in education with the virtual teaching format due to the arrival of COVID-19. The paper highlights the importance of giving educators the opportunity to reflect on the practice by incorporating tools that allow them to direct their attention to relevant aspects in the teaching and learning process.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement## Norms that regulate the management of virtual mathematics classes in the COVID-19 context 2021-06-21T18:36:14-06:00 Cristina N. Peña Luis R. Pino-Fan Adriana Assis <p>The standards regulating class management and learning negotiation is a topic of interest to the mathematics education research community. In the context of virtuality as a result of the Covid-19 pandemic, it is necessary to study the type of standards emerging to regulate interactions in math classes. In this study, standards regulating online high school geometry classes are characterized. As a theoretical reference, the didactic analysis model proposed by the Ontosemiotic Approach (OSA) is considered, particularly the notions of mathematics teacher’ practices and the standard classification system. The research is developed under a qualitative-naturalistic paradigm in which researchers analyzed two classes on metric relationships in circumferences taught to Chilean third-year high school students (15-16 years). In conclusion, the standards regulating the interaction processes in an online classroom are characterized, and teachers’ adaptability is shown in an exceptional-virtual context, where standards are established and changed when necessary to guarantee the optimization of the students’ learning.</p> 2021-07-31T00:00:00-06:00 ##submission.copyrightStatement##