Volumen 7 No. 1 (2016)
Permanent URI for this collectionhttps://dspace-test.ucuenca.edu.ec/handle/123456789/25170
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Item Influence of autogenous shrinkage on mass transport properties of concrete(Universidad de Cuenca, 2016-06) Velez Guayasamin, Alexis SantiagoAutogenous shrinkage in concrete is defined as the change of volume after initial setting occurs. It develops at very early ages as a result of chemical shrinkage and self-desiccation effect. These produce significant microcracks in high-strength concrete allowing the entrance of aggressive agents such as carbon dioxide, chlorides, and sulphates which cause concrete deterioration. Although considerable research of autogenous shrinkage has been done, uncertainty remains concerning the influence in concrete durability. Therefore, the purpose of this study was to quantify and analyse the effect of autogenous shrinkage on the mass transport properties of concrete using three transport tests: oxygen diffusion, oxygen permeation, and water absorption. Two methods, for three different binders, were first carried out to determine a control mixture that produces the least autogenous shrinkage: adding SRA and curing in a fog room. Subsequently, transport test results between the selected control mixture and mixtures highly affected by autogenous shrinkage were compared for different binders. Results revealed that specimens with SRA presented the least autogenous shrinkage; therefore, it is suggested to be considered as control samples. It was also found that autogenous shrinkage significantly affects the transport coefficients in concrete made with secondary cementitious materials which from a serviceability point of view could reduce the life span for any structure made with high-strength concrete. This investigation also confirmed that most of the autogenous deformation occurs during the first two weeks after casting therefore enough care should be taken when curing.Item Análisis crítico de la planificación urbana de la Ciudad de Cuenca(Universidad de Cuenca, 2016-06) Donoso Correa, Mario ErnestoCities all over the world must maintain a livable urban environment. New York and Barcelona were once examples to follow, but the urban vision of expansion during the last decades has given way to a paradigm that poorly comprises the development trends of the late 20th and early 21st century. Urban planning insufficiently ponders the aspirations of the urban dwellers and the city socioeconomic functions, resulting in imbalances, characterized by increasing traffic jams, social and economic injustice, and environmental degradation. As the case in the city of Cuenca, urban development clearly illustrates a poorly controlled expansion with serious frictions in labor and housing markets, with little room for green spaces within and around the city, as was the case in the past. This study attempts to illustrate the discrepancy between the theory and practice in the field of urban planning using as case study the Andean city of Cuenca. Whereas the new urban planning doctrine speaks of an intricate balance between the socioeconomic and environmental functions in the urban space, the city looks everyday more disorganized. In addition, to explaining the current planning situation of Cuenca city, on the basis of theoretical and philosophical grounds the shortcomings in urban planning are pinpointed. Good practice of urban design and planning should be based on a sound understanding of the dynamic and complex character of cities. With the manuscript the author aims to boost the scientific discussion on sound environmental and sustainable urban planning.Item Evaluación de la extracción de plomo y cadmio de vajilla cerámica vidriada(Universidad de Cuenca, 2016-06) Flores Zamora, Marittza Eleanor; Idrovo Gallegos, Marcela Margarita; Flores Zamora, Damián VicenteThis article assesses if a single extraction, by applying a standardized test method, which simulates extreme conditions of use, determines the total content of lead and cadmium in ceramic ware pieces that come into contact with food, and their implication in the analytical result. The test method was applied several times on ceramic reference materials with different initial concentrations of lead and cadmium as to quantify the successive liberation of both metals. The leachate at each application was analyzed by atomic absorption. Results showed that a single application of the test method does not extract all of the lead and cadmium in glazed tableware pottery. Subsequent liberations for all tested ceramic pieces with different initial concentration were noticed. For cadmium the following variation in extractions were recorded: 40 to 95% in the first extraction, 0 to 28% in the second, 0.2 to 21% in the third, and 1 to 40% in the fourth leachate test. For lead, the subsequent values were recorded: a leachate varying between 50 and 93% in the first test, between 2 and 24% in the second, between 2 and 18% in the third and between 2 and 17% in the fourth extraction. The results reveal that the total amount of lead and cadmium released in a single standard test do not reflect the total content of lead and cadmium that ceramic pieces after long-term use liberate.Item Diferencia de daños por herbívoros entre hojas jóvenes de color rojo y verde, ¿podría tratarse de mimetismo vegetal?(Universidad de Cuenca, 2016-06) Jara Torres, Pablo PatricioThe presence of red coloration on young leaves of some plant species in tropical forests could serve as signal for herbivores of the presence of chemical defenses, resulting in the escape damage by herbivores. The specific objectives of this study were to compare between green and red young leaves: a) levels of herbivore damage, b) the hardness and c) the acceptability of plant tissue by generalist herbivores (grasshoppers Vellea mexicana). Red young leaves had significantly less damage by herbivores than young green leaves; hardness was also significantly lower in the red young leaves, while the acceptability of foliage by herbivores showed no significant difference between the two types of leaves. It is suggested that the red coloration may represent an effective strategy of low investment of resources that would allow vulnerable young leaves to escape the damage caused by herbivores.Item Especificidad del hongo micorrizico (Rhizoctonia sp.) en Phalaenopsis sp., Cymbidium sp., Trichoceros antenifer, Oncidium excavatum, y Cyrtochilum sp.(2016) Ordoñez Tenesaca, Silvia Liliana; Pillacela Zhunio, Dora Priscila; Salazar Orellana, Marjorie Jazmin; Peña Tapia, Denisse FabiolaOrchids produce abundant small seeds, lacking endosperm, cotyledons and reserve substances to support germination. That is why the seeds strategically establish a symbiotic relationship with a mycorrhizal fungus favoring germination and development. The aim of this study was to determine whether the mycorrhizal fungus Rhizoctonia sp. establishes a specific association with five orchid genera that stimulates seed germination. Two culture media were used: 1) PhytamaxTM and 2) oatmeal- agar+Rhizoctonia sp. The germination was assessed at day 45 and 75 and showed no specificity between the fungus Rhizoctonia sp. and Trichoceros antenifer, the orchid species from which the fungus was isolated. Germination in three of the five genera tested was higher in the treatment oatmeal agar+Rhizoctonia sp., showing in this treatment increased sizes and the development of vigor plants; although these data were not evaluated. The results also suggest that the host plant of the inoculated fungus could have an advantage in terms of time required for germination, but other species are also favored with the inoculum even if isolated from a different species.Item Validación de curvas antropométricas de crecimiento intrauterino: Hospital Vicente Corral, Cuenca, Ecuador, 2013(Universidad de Cuenca, 2016-06) Díaz Granda, Lourdes Elizabeth; Díaz Granda, Ruth Cumandacross-sectional study was conducted at the Vicente Corral Hospital of Cuenca (Ecuador) in February-August 2013 to assess the intrauterine growth curves according to the Latin American Center for Perinatal Care (CLAP), Olsen, Alarcon-Pittaluga, Battaglia-Lubchenco, Babson-Benda with the objective of identifying the most appropriate anthropometric pattern of fetal growth for the classification of newborns until Ecuador possesses its own patterns. The sample was composed of newborns whose mothers were under age 21. The inclusion criteria were children born alive, with gestational age between 22 and 42 weeks, meeting all anthropometric measures. Children with congenital malformations were disregarded. The sensitivity, specificity and Cohen kappa index of the studied anthropometric curves as weight, height, head circumference and sex of the newborn were evaluated. The curves of CLAP (36.6 to 43.5%) and Olsen’s (37 to 40.9%) identified similar percentages of PEG. Babson-Benda curves detected very few PEG (1.3-2.8%). For the variable weight: Olsen’s curves showed good sensitivity (81.8-97.6%), very good specificity (91.8-97.5%) and kappa index (0.807-0.873). The Alarcon-Pittaluga curve showed very good sensitivity (98.2-99.5%); goodspecificity (74.9-77.9%) and kappa index (0.707-0.717). The Battaglia-Lubchenco curve showed low sensitivity (40.0-42.8%), very good specificity (99.3-100.0%) and moderate kappa index (0.449-458). Babson-Benda curve presented very low sensitivity (3.5-6.4%), very good specificity (100.0%) and poor kappa index (0.044-0.072). In summary, the anthropometric Olsen’s curves seem to be most adequate and recommended to be used as standard until Ecuador possesses its own curves. It is recommended neither to use the Babson-Benda nor the Battaglia-Lubchenco curves.Item Generando números de Pitágoras(Universidad de Cuenca, 2016-06) Vásquez Bernal, Marco Vinicio; Vásquez Chiquito, Mercedes ElizabethThe paper presents a general way to define three natural numbers (triple) that satisfy the Pythagorean relationship; it is the sum of the squares of two numbers is equal to the square of a larger number, through a process much more general than known so far. We even propose formulas that in function of two parameters find these sets of three elements, the results of which are presented in tables. Results confirm the idea that there are an infinite number of triples that meet the Pythagorean relationship. Further the use of the tables is illustrated how to build relationships where the sum of the squares of more than two numbers equals the square of another.Item Credit application systems for investments in agriculture and livestock in rural areas in Latin America(Universidad de Cuenca, 2016-06) Herrero Olarte, SusanaA lack of resources to improve inputs and tools is the fundamental cause of the lack of food security, according to families and organizations interviewed in marginalized and isolated communities (MICs) in Latin America. Families living in these types of communities have access to inputs either through donations or through credits. Marginalization and isolation tend to favor opting for credits because it becomes imperative to be able to rely on sustainable interventions, due to the little attention that these types of communities receive from government offices and development cooperation agencies. Among the methodologies for accessing credits in MICs, special mention should be made of credit lines, solidarity group programs (SGPs), and local financial structures (LFSs) or community banks. The analysis performed herein concludes that LFSs or community banks yield the best results.Item Estrategias que los padres cuencanos utilizan para criar a sus hijos(2016) Arpi Peñaloza, Nube del Rocío; Conforme Zambrano, Elsa Gardenia; Palacios Madero, María Dolores; Mora Oleas, Janeth Catalina; Villavicencio Alvarado, Luis FernandoItem Actitudes docentes hacia la educación inclusiva en Cuenca(2016) Clavijo Castillo, Ruth Germania; López Calle, Claudio Hernán; Cedillo Quizhpe, Isabel Cristina; Mora Oleas, Janeth Catalina; Ortiz Ochoa, William AlfredoItem Desempeño numérico de los niños de primer año de básica(Universidad de Cuenca, 2016-06) Bojorque Iñegues, Gina Catalina; Heredia Tapia, Julio MoisésChildren´s numerical skills in kindergarten (first year of basic education in Ecuador) highly predicts their academic achievement on later age, suggesting that an early evaluation of this abilities is fundamental in order to implement remedial programs that help children to improve their future academic achievement. The aim of the present study was to examine first grade children´s numerical skills via the Early Mathematical Test. Participants were 100 first grade children from four private schools of Cuenca. Results indicated that children show a good level of numerical skills, and that their ability to establish logical relations was superior than their ability to count. No gender differences were observed. Additionally, significant differences in children´s numerical performance between schools were found. The theoretical and practical implications are discussed.