Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Despite the importance that problem-solving has received as a backbone in the area of Mathematics, the information on how it is taught and how teachers and students interact in the classroom is still incipient. For this reason, the objective of this study is to characterize the interaction between the teaching and learning processes established between teachers and students in Mathematics problem-solving classes. Methodologically, the typical classroom activities are described from 23 audio-visual records of the classes of public-school Mathematics teachers. The results show that the activities present in the problem-solving classes are of low cognitive complexity, with no major teacher feedback and with a predominance of monolithic participation structures.

Uruguay has a vocation for educational inclusion since the end of the 19th Century. From a theoretical point of view, educational inequality has always been overlapped by some element of socioeconomic inequality, ergo, most educational claims and policies have been focused on equalizing conditions of the home of origin. However, despite an important series of policies and programs for social inclusion, in one of the countries with the best social and equity indicators on the continent, approximately 60% of the population will never finish High School. The article tries a theoretical systematization and comparison of the main works associated with educational inequality at a national and international level. Among the main conclusions stands out the idea that socioeconomic inequality is only one piece of educational inequality. Therefore, acting solely on socioeconomic inequality is an exhausted theoretical and empirical reduction.

The educational environment faces an inevitable adaptation to the digital environment, where the uncritical consumption of information by students is constant. Ensuring critical consumption requires intensifying the processes of media and information literacy, linked to the digital competence of teachers, which can be reinforced by the use of multimedia products based on open data. The purpose of this research is to analyze the degree of digital literacy and media education that future teachers of Primary Education possess. A case study methodology was adopted, through semi-structured interviews with the teachers in charge of training future teachers in Primary Education at the University of Castilla la Mancha (Spain). The interpretation of results was made using the content analysis technique, with an exhaustive review model. The need to promote media and information literacy in the field of teacher training is concluded.

Xylotrechus arvicola is an insect pest on Vitis vinifera in the main wine-producing regions of Spain. X. arvicola larvae bore inside grapevine wood, which cause structural damages in the plants´ biomechanical properties. Grapevine wood affected and unaffected by larvae, were collected from vineyards. Compression and flexural tests were used to quantify biomechanical wood properties. Affected wood broke more quickly and endured a lower supported force than unaffected wood in both varieties and moisture states. Tempranillo was the most resistant variety on trunks, while Cabernet-Sauvignon was the most resistant variety on branches, where all infested varieties showed a lower rate of bending. Grapevine wood affected by X. arvicola larvae shows an important decrease in its resistance in both moisture states - dry and wet wood - and it is observed due to the faster break in time and a lower supported force. These damages give the affected wood greater sensitivity to external mechanical factors in the vineyards, such as strong winds, harvest weight and the vibration exerted by harvesting machines. The aspect of stress-time curves in all cases follow similar patterns, so in future studies might be possible to stablish relationships between both wet and dry samples and different infestation levels.

In wood structures, the elements subjected to bending stresses, such as the beams, present a fracture initiated in the tensile region, and under these conditions, the use of laminated composite materials is presented as an alternative solution in the form of repair or reinforcement. This research aimed to evaluate the influence of the use of carbon fibers laminated composites in tensile reinforcement in the direction parallel to grain of Pinus elliotti and Manilkara huberi wood species. The Viapol two-component epoxy adhesive was used in the lamination and fixation of the unidirectional carbon fiber in the wood species. Ten specimens with no defects (reference) and 10 specimens were prepared for each crack length (25 and 50mm) with and without the reinforcement (60mm × 50mm) by the laminated composite. The tensile tests were performed in accordance with the requirements of the Brazilian standard ABNT NBR 7190 (1997). From the results of the statistical analysis, the use of the carbon fiber composite was able to restore the tensile strength of the cracked samples (partial or total) in relation to samples without defects, demonstrating the potential of the laminates in carbon fibers as an alternative solution in repair for both wood species.

Se han aplicado dos tratamientos previos al proceso de pasteado etanol-sosa sobre madera de Eucalyptus globulus para evaluar su influencia sobre las propiedades de las pastas celulósicas obtenidas. Se aplica una primera etapa optimizada de autohidrólisis para maximizar la extracción de derivados hemicelulósicos preservando el glucano, seguida de una deslignificación enzimática mediante un sistema lacasa/mediador (siringaldehído). Se aplican diseños experimentales para la optimización de los procesos. Las condiciones de operación óptimas en la etapa de deslignificación enzimática han sido: concentración de lacasa 18,5 U/g, concentración de siringaldehído 1,5 %, temperatura 45 ºC y tiempo de operación 60 min., con las cuales se alcanza una eliminación del 16,8 % de la lignina existente en la materia prima y se afecta ligeramente al glucano (conservando entre el 82,2 % y 89,7 % del glucano inicial). Paralelamente se obtienen dos fases líquidas valorizables, ricas en derivados hemicelulósicos y polifenólicos. En este esquema de proceso para obtención de pasta celulósica etanol-sosa a partir de madera eucalipto requiere una menor concentración de reactivos químicos, menores tiempos de operación y temperaturas más bajas, lo que supone una mejora económica y medioambiental respecto del proceso convencional de pasteado.

The study assessed the effect of jatropha, linseed, eucalyptus, neem and jojoba oils on protection of three wood species (Acacia nilotica, Dalbergia sissoo and Pinus wallichiana) against termite attack by Odontotermes obesus. Conditioned and pre-weighed blocks of each wood species were vacuum-pressure impregnated with a 15% concentration of the oil-ethanol solutions.. Resistance of treated and untreated wood against termites was tested under laboratory as well as field conditions using choice and no-choice tests. Oil treated wood showed significant reductions in weight loss compared to control treatments. Complete termite mortality was recorded for all oil treatments except eucalyptus oil. Linseed oil showed good results in each treatment in terms of feeding resistance as well as mortality of termites followed by neem, jatropha, jojoba  and eucalyptus oil. The lower weight losses were found in both choice and no-choice field tests for linseed oil treated Dalbergia sissoo while untreated Pinus wallichiana sapwood had the greater weight loss. It was observed that the oil retention was significantly more in sapwood than in heartwoods. The retention of oils justified that wood with high oil retention showed more resistance against the termite except eucalyptus oil treatment of Pinus wallichiana.

Nondestructive testing (NDT) includes several highly efficient techniques for the estimation of the physical and mechanical properties of structural timber. Apart from visual grading, scientific research using Nondestructive testing on timber has been used in Spain since the 1990s. Nondestructive testing can be used for two different purposes: timber grading and the assessment of existing timber structures. The most common devices used in Spain are portable ones based on ultrasound, stress waves, vibration and probing techniques. Many statistical linear models for estimating the mechanical properties of new sawn timber and timber from existing structures have been proposed. Furthermore, several factors that affect Nondestructive testing measurements have been studied (moisture content, temperature, specimen dimensions, sensors position-grain angle…) and adjustment factors have also been proposed. Species have been characterized for visual grading standards from the 1980s to date. The large number of research works using different species, devices and procedures shows the need of homogenization and standardization of Nondestructive testing use. This paper presents a review of research works using Nondestructive testing on timber in Spain, in order to add to knowledge, elucidate the concepts to unify Nondestructive testing used and promote research group collaboration in the near future.

This study focuses on the evaluation of the mechanical behavior of two types of connections for intended use in rural Timber‑Concrete Composite traffic bridges. The two connection types used were the “X” type connection – XD and the dowel type connection – PD. Firstly, static shear tests in small-scale specimens were performed in both connection types and higher results were obtained for the XD series, both for stiffness and load carrying capacity. Secondly, the PD connection was chosen, based on practical and economical aspects, for further testing also in small-scale specimens, including cyclic tests. The influence of the number of cycles in the connection stiffness and load carrying capacity was evaluated. It was concluded that the load carrying capacity increased after the application of a pre-defined number of load cycles and that the connection stiffness increased 80.6% and 34.1% after 10,000 and 1,000 cycles, respectively, for different applied load levels. Also the increase of load level in the cyclic tests affected the performance of the connection, leading to a decrease in stiffness.

Increasing environmental pressures on toxic chemical wood preservatives lead to the development of natural and environmentally friendly wood preservatives. In this study, using possibilities of lichen (Usnea filipendula) and leaves of mistletoe (Viscum album) as potential natural wood preservative were researched. Impregnation procedure was applied at four different concentration levels and with two different extraction methods (hot water and methanol). The concentration levels were arranged as 3%, 5%, 10%, 15% for hot water and as 3.75%, 6.25%, 12.5%, 18.75% for methanol. The treatment procedure has been applied according to the ASTM D 1413 (1988) standard test method. The fungal decay test has been done according to the EN 113 (1996) standard test method using a brown rot fungus, Coniophora puteana for both treated test and untreated control samples. The best results were obtained at the highest concentration level of the solutions. However, the weight losses in treated test specimen have not met the standard requirements. Nevertheless, it can be assumed that both natural extracts provide promising protection performance.