Revistas Universidad del Bío-Bío
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Anti-fungal and anti-termite activity of extractives compounds from thermally modified ash woods
Get PDFThermal modification of wood is a promising alternative to chemical and biocidal modification processes, increasing the biological durability and dimensional stability of wood. However, the wood-decay resistance properties of heat-treated wood are still not well known. The main objective of this study was to determine the biological resistance of heat-treated ash wood, and assess the antifungal and anti-termite activity of extractive compounds from heat-treated ash woods, depending on the intensity of the modification process (2 hours at 170, 200, 215, 228 (°C) - steam pressure). Untreated and heat-treated wood samples were extracted with water or acetone. The extracts were then used to determine inhibition effectiveness against white-rot (Trametes versicolor) and brown-rot (Rhodonia placenta) fungi. Whatman papers impregnated with extractives were used to evaluate the inhibition of termite feeding. Lastly, the extractives were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS) and compared for their level of anti‑termite and antifungal activity. The results showed that the degree of antifungal activity of these extracts depended on the solvent used during the extraction process and varied depending on heat treatment intensity. The extracts were more effective against brown-rot than white-rot fungi. However, the anti-termite activity of heat-treated ash wood extracts was not really significant. A GC-MS analysis showed that the main share of the extractives in untreated wood was removed. In addition, new chemical elements were generated by the thermal degradation of wood polymers (lignin and hemicelluloses), including aliphatic acids, monosaccharides and other products resulting from their dehydration reaction. The most abundant element was syringaldehyde, from lignin derived compounds, which might explain the antifungal activities of thermally treated ash wood extracts
Editorial
Get PDFEfímera, es la condición que relata, entre otras, la corta pervivencia de un hecho, emotivo, histórico, físico o social. En principio, la condición inmanente de la arquitectura parece predeterminada por la necesidad de permanecer por sobre, o más allá de la vida humana, sea individual, generacional o colectiva. La mayoría de las historias de la arquitectura canónicas han privilegiado la construcción de un relato sostenido en obras de cientos de años de existencia, cargando sobre su interpretación no solo la expresión de una época, sino de un lugar y muchas veces como testigos de una tradición aparentemente eterna. Aquí comparecen pirámides, basílicas, parlamentos, etc. El siglo XX puede haber sido uno de los primeros momentos donde se planteó la arquitectura como una cuestión de menor supervivencia temporal, posiblemente, pues la racionalidad advirtió la posibilidad de la mutación, el cambio o la caducidad
Radial variation in cell morphology of melia azedarach planted in northern vietnam
Get PDFThe radial variation in cell morphology of ten-year-old Melia azedarach trees planted in northern Vietnam was experimentally investigated. The earlywood fiber lumen diameter and latewood fiber lumen diameter were almost unchanged from pith to 6th ring before significantly decreasing and remaining constant from 7th ring outwards. In contrast, fiber cell wall thickness in both earlywood and latewood increased from pith to 7th ring before becoming stable towards the bark. The maturation age of earlywood vessel lumen diameter estimated by segmented regression analysis indicated that wood of the Melia azedarach could be classified into core wood and outer wood, and the boundary between core and outer wood may be located at 7th ring from pith. This should be taken into account in wood processing using M. azedarach grown in northern Vietnam
Urban growth and socioespatial segregation in Valdivia
Get PDFEste artículo analiza e interpreta el crecimiento urbano reciente y los procesos de segregación socioespacial en la ciudad de Valdivia (Chile), y su relación con el avance del mercado inmobiliario. La ciudad, pese a su tamaño medio, crecimiento moderado y buenos indicadores de calidad de vida, estaría reproduciendo lógicas similares a otras urbes de mayor tamaño. Para el estudio, se aplica una metodología que combina datos estadísticos con entrevistas en profundidad a actores-clave, y se elabora, además, una matriz de restricciones que sintetiza espacialmente y por componentes la segregación existente. Como resultado, se identifican los sectores con mayor y menor crecimiento inmobiliario, ahondando en las formas y tipologías del mismo; así como la percepción de los fenómenos de segregación existentes en Valdivia. De esta manera, junto con un análisis que pone su énfasis en ciudades de menor tamaño y dinamismo, se generaría un aporte metodológico que podría ser aplicado a otros casos de estudio.This article analyzes and interprets recent urban growth and socio-spatial segregation trends in the city of Valdivia (Chile), relating them, at the same time, to the progress of the real estate market. Despite being a medium-sized city, with moderate growth and good quality of life indicators, it would seem to be reproducing similar logics as other larger cities. For this reason, a methodology that combines statistical data with in-depth interviews with key players is applied and a restriction matrix that summarizes existing segregation spatially and by components is made. As a result, this study is able to identify the sectors with the highest and lowest real estate growth, considering both their forms and typologies; as well as the perception about existing segregation phenomena in Valdivia. In this way, alongside an analysis that places emphasis on smaller, less dynamic cities, a methodological contribution would be generated that could be applied to other case studies
Resistance to garbage and dynamics of territorialization through the use of exposed writing
Get PDFEste texto ofrece una caracterización empírica de una dinámica de resistencia a la presencia de basura en el espacio público y a la contaminación observable actualmente en un barrio pericentral de la ciudad de Santiago de Chile. El foco de análisis está puesto en las inscripciones gráficas, en el entendido de que, a través de ellas, los habitantes enfrentan el problema indicado activando nuevas dinámicas de territorialización y generando nuevas formas de dar inteligibilidad al barrio y a los sujetos que lo habitan. La información empleada fue generada mediante un procedimiento de catastro sistemático de las inscripciones gráficas del barrio, su registro fotográfico y georreferenciación, para hacer viable un análisis pragmático, tanto de su contenido como de su emplazamiento, con base en los conceptos de la antropología de las escrituras urbanas expuestas. El artículo entrega una comprensión sistemática de la relevancia de prácticas, usualmente banalizadas, mediante las cuales los habitantes despliegan formas de resistencia a la desposesión territorial y epistémica que afecta a los territorios del capitalismo urbano actual.This text presents an empirical characterization of a resistance dynamic to the presence of garbage in the public space and the contamination currently seen in a peri-central neighborhood of Santiago de Chile. The focus of the analysis is placed on the street writing, understanding that the inhabitants, through these, face this problem, activating new dynamics of territorialization and generating new ways of providing intelligibility to the neighborhood and to the subjects living there. The information was generated through a systemic listing of the neighborhood’s street writing, its photographic record and geo-referencing, to make a pragmatic analysis viable, both of its content and its location, based on the anthropological concepts of the exposed urban writing. The article provides a systematic understanding of the relevance of practices, usually trivialized, by which inhabitants display means of resistance to territorial and epistemic dispossession that affect the territories of the current urban capitalism
Peru's innovation system: characterization based on a model structured according to three operational levels
Get PDFEl presente trabajo se concentrará en determinar las características generales del sistema de innovación en el Perú, para luego proponer un modelo estructurado de tres niveles: Político, Operacional y de Generadores de Investigación, Desarrollo, Innovación y Emprendimiento (I+D+i+e). Destaca el que estos tres niveles están orientados a la búsqueda de la generación de la innovación. Se considera que la innovación se produce principalmente en la relación entre las empresas y organizaciones que tienen contacto directo con las necesidades y requerimientos de la sociedad (el mercado). Para ello, se requiere el involucramiento, la cooperación y la participación de todos los involucrados: estado, empresa y academia de manera horizontal y orientada por resultados.This work will focus on the general characteristic of the innovation system in Peru, and then it will propose a structured three-tier model: Political; Operational; and Research, Development, Innovation and Entrepreneurship Generators (R+D+i+e). The three levels are oriented to the search for the generation of innovation. Innovation is considered to occur mainly in the relationship between organizations and businesses that have direct contact with the needs and requirements of society (the market).To make R+D+i+e in Peru work in an outstanding way, it is required the involvement, cooperation, and participation of all those involved: the state, businesses, and result-oriented academic organizations
Socio-emotional competences in the educational context: A reflection from contemporary pedagogy
Get PDFThis essay aims to reflect on the changes and transformations generated by the educational model focused on student learning, that have impacted the teacher training. This professional training has been faced with the need to develop socio-emotional competences in teachers, as it is a relevant variable, according to different studies, which affects not only the academic performance of students, but also favors the climate in the classroom, school coexistence and citizenship training. At the present, it is possible to observe that contemporary pedagogy values the incidence that emotions have in the teaching and learning process, raising the need to generate teacher training programs in socio-emotional competences and the interest in researching four areas: The socio-emotional competences of teachers, the socio-emotional skills of students, civic and citizenship training, and skills for the development of the school climate and coexistence.Este ensayo tiene como objetivo reflexionar acerca de los cambios y la transformación que ha generado el modelo educativo centrado en el aprendizaje de los estudiantes respecto a la formación del profesorado, la que se ha visto enfrentada a la necesidad de desarrollar competencias socioemocionales en los docentes, debido a que es una variable relevante, según distintas investigaciones, que incide no sólo en el rendimiento académico de los alumnos; sino que favorece el clima en el aula, la convivencia escolar y la formación ciudadana. En la actualidad se observa que la pedagogía contemporánea valora la incidencia que tienen las emociones en el proceso de enseñanza y aprendizaje, al plantear la necesidad de generar programas de formación docente en competencias socioemocionales y el interés por investigar cuatro ámbitos: las competencias socioemocionales de los docentes, las competencias socioemocionales de los estudiantes, la formación cívica y ciudadana, y las competencias para el desarrollo del clima y convivencia escolar
The influence of ultraviolet radiation on the colour of thermo-mechanically modified beech and oak wood
Get PDFThe study examined the influence of ultraviolet radiation on the colour of thermo-mechanically modified beech (Fagus sylvatica ) and oak (Quercus robur). The wood colour parameters were measured using the mathematical CIE L*a*b* and L*C*h colour space models. The higher the temperature of thermo-mechanical treatment, the least susceptible beech and oak wood was to a change in L*, a* and b* under the influence of light irradiation. The greatest changes in the colour of non-densified and densified beech and oak wood occurred after 20 h of light irradiation. The higher the temperature of thermo-mechanical treatment, the smaller were the total changes in the colour of beech and oak wood under the influence of ultraviolet radiation. The total changes in the colour of beech densified at temperatures of 100°C and 150°C that took place under the influence of ultraviolet radiation were twice as high as in the case of densified oak wood. The colour of oak wood modified at a temperature of 200°C did not change significantly in 300 h of light irradiation
Nondestructive testing used on timber in spain: A literature review
Get PDFNondestructive 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
The properties of particles produced from waste plywood by shredding in a single-shaft shredder
Get PDFThe present work regards an attempt to obtain particles from the post-industrial pine plywood in a single-shaft shredder. A screen mesh size determines the wood particles characteristics. In the work 10–, 14–, 25– and 38–mm mesh size screens were used. The urea-formaldehyde (UF) and phenol-formaldehyde (PF) bonded plywood were shredded separately, so that the effect of the binder type could be analyzed. The determined fractional composition, bulk density, dimensions and surface area of the particles were compared to the industrial virgin pine particles dedicated to the core layer of particleboards. The results showed that the particles obtained from a 14–mm mesh screen exhibited properties closest to those found for the virgin particles