Revistas Universidad del Bío-Bío
Not a member yet
3557 research outputs found
Sort by
Uptake of insecticides and fungicides by impregnable and refractory coniferous wood species treated with commercial bio-based emulsion gel formulations
Get PDFEven in dry state, wood can be prone to biological degradation. Preservation is a prerequisite to confer protection and durability to wood. This is conventionally achieved by impregnating the wood with pesticides. A key point in these treatments is the complex process of wood penetrability. We focused on the relation between the penetration of wood preservatives, wood microstructure, and the physical characteristics of formulations in the impregnation of the easily impregnable pine (Pinus sylvestris), and the refractory spruce (Picea abies). In this work, specimens from the two species were impregnated with three types of commercial bio-based emulsion gels formulations containing insecticides and fungicides. The effect of treatment method using dipping, surface spraying, and vacuum-impregnation, on the retention of the active agents was analyzed. Visual assessment, and qualitative and quantitative analyses of cypermethrin, permethrin and propiconazole by gas liquid chromatography coupled to mass spectroscopy showed enhanced penetration of the active agents, and revealed differences of penetration performance of each agent. The suitable combinations of solvents and surfactants used in the bio-based formulations enabled rapid wood penetration and high yields retention. The capacity of penetration and retention of our gel formulations is discussed in terms of the connectivity of the conducting cells network of the two wood species
Relación entre la velocidad de la onda acústica y distintas características de la madera, en árboles de Eucalyptus nitens con dimensiones aserrables
Get PDFEn el presente estudio se investigaron las relaciones entre la velocidad de la onda acústica obtenida en árboles en pie (VÁRBOL), y la obtenida en trozas (VTROZA), con distintas características de la madera, en árboles de Eucalyptus nitens con dimensiones aserrables, provenientes de una plantación de 18 años de edad, crecida en la región del Biobío, Chile. Se seleccionaron 9 árboles aleatoriamente. En cada árbol seleccionado se determinó la VÁRBOL en las exposiciones cardinales Norte, Sur, Este y Oeste del fuste. La VTROZA se midió en trozas de 2,4 m de largo, centradas en longitud; a la altura fija de 2 m y al 33 %, 66 % y 100 % de la altura comercial del árbol. Para cada troza se obtuvo el contenido de humedad verde (CHv), la densidad verde (Dv), la densidad básica (DB), el módulo de elasticidad dinámico (MOEd), el indicador de la tensión de crecimiento (GSI), el módulo de elasticidad en tensión (Et) y las tensiones de crecimiento longitudinales (σL). No hubo correlaciones significativas entre la VÁRBOL y las distintas características examinadas en la madera (CHv, Dv, DB, GSI, Et y σL). La velocidad de la onda acústica en trozas (VTROZA), cambió significativamente con la posición de la troza en el fuste, aumentando en dirección base – ápice. La VTROZA se correlacionó significativamente con distintos parámetros de calidad de la madera; ésta variable podría ser utilizada para clasificar trozas con un mayor módulo de elasticidad en tensión (Et), un menor contenido de humedad verde (CHv), y una menor densidad verde (Dv)
Evaluation of social vulnerability after the 2010 tsunami at Tumbes Cove – Chile through the “pressure and release” model
Get PDFThe 2010 tsunami in Chile exposed the absence of socio-natural disaster risk management at national and local levels. This article investigates the role of the government’s post-tsunami reconstruction process, as the articulating body for the most vulnerable communities. In particular, Tumbes cove, in the Biobío region, was studied, where vulnerability factors were identified in the face of tsunami flooding through closed surveys and interviews with key players, as well as organizing the information in matrices to identify perception after the reconstruction process. Vulnerability maps were generated using the “pressure and release” model of Wisner et al. (2006). Through five processes, it was observed that the macro-social levels would affect the micro social levels in their daily lives, in the management of socio-natural disasters, which would have an impact on the increase in vulnerability. We argue that the town of Tumbes is a case of a socio-economically and educationally vulnerable community, where the reconstruction process weakened community organizations due to the lack of knowledge of local leaders, thus contributing to the construction of greater vulnerabilities.El tsunami de 2010 ocurrido en Chile dejó al descubierto la ausencia de gestión de riesgos de desastres socio-naturales a nivel nacional y local. Este artículo indaga sobre el rol del proceso de reconstrucción gubernamental post-tsunami, como articulador de comunidades más vulnerables. Se estudió en particular la caleta Tumbes, de la región del Biobío, donde se identificaron factores de vulnerabilidad ante inundación por tsunami a través de encuestas cerradas y entrevistas a actores claves; información que se organizó en matrices con el fin de analizar la percepción de la comunidad tras el proceso de reconstrucción. Se generaron, asimismo, mapas de vulnerabilidad utilizando el modelo de “presión - descompresión” de Wisner et al. (2004). A través de cinco procesos se observó que los niveles macrosociales afectarían a los microsociales dentro de su cotidianidad en el manejo de desastres socio-naturales, los cuales influirían en el aumento de la vulnerabilidad. Se concluye que la localidad de Tumbes es un caso de comunidad socioeconómica y educativamente vulnerable, donde el proceso de reconstrucción debilitó las organizaciones comunitarias por el desconocimiento de liderazgos locales, lo que contribuyó a la generación de mayores vulnerabilidades.
 
Un modelo econométrico para determinar el valor de venta de proyectos inmobiliarios en la ciudad de Santiago
Get PDFSantiago city is located in Metropolitan Region of Santiago, it is the capital of the chilean Republic and 6,257,516 inhabitants live there. There is no finished study that shows the main variables that affect the final sales value of the real state projects of Santiago city. Therefor, using a linear regression model with a database of 552 real state projects in a range of 14 years, we determine which variables are the ones that most influence the final value of a real state Project in Santiago. We find that the most influential variables in the final price are the price of the land, construction cost and other real state expenses.La ciudad de Santiago se encuentra ubicada en la Región Metropolitana de Santiago, es la capital de la República de Chile y habitan en ella 6.257.516 habitantes. No existe un estudio acabado que muestre cuales son las principales variables que inciden en el valor de venta final de los proyectos inmobiliarios de la ciudad de Santiago. Por ello, utilizando un modelo de regresión lineal con una base de datos de 552 proyectos inmobiliarios en un rango de 14 años, determinamos qué variables son las que más influyen en el valor final de un proyecto inmobiliario en Santiago. Encontramos que las variables más influyentes en el precio final son el precio del terreno, costo de construcción y otros gastos inmobiliarios
Perfectionism and self-esteem in school children from Caracas
Get PDFThis research aims to determine the link between perfectionism and self-esteem in late childhood, after a characterization of both variables in the group of subjects. The design is cross-sectional and correlational. Participants were 94 children between 9 and 11 years old, students of a private primary school from Caracas (Venezuela). All subjects answered the Childhood Perfectionism Scale and the Personal Self-Esteem Subscale of the Inventory GRES-30AE-ni. The sample presented moderate levels of perfectionism and high self-esteem. Statistical contrasts revealed differences by sex: boys scored significantly higher in perfectionism and in two of their dimensions. A significant, considerable and negative relationship between self-esteem and negative perceptions of mistakes was found. These results are discussed considering the findings provided by previous research. Perhaps, strengthening self-esteem can help reduce the negative reactions children demonstrate when experiencing failure.Esta investigación tuvo como objetivo dar cuenta de la relación entre el perfeccionismo y la autoestima en la infancia tardía, previa caracterización de ambas variables en el grupo de participantes. El diseño fue correlacional y transversal. Participaron 94 niños de entre 9 y 11 años, alumnos de primaria en una institución educativa privada de Caracas (Venezuela). Los sujetos respondieron la Escala de Perfeccionismo Infantil y la Subescala Autoestima Personal del Inventario GRES-30AE-ni. La muestra presentó niveles moderados de perfeccionismo y altos de autoestima. Se encontraron diferencias en función del sexo: los chicos puntuaron significativamente más alto que las chicas en perfeccionismo y dos de sus dimensiones. Se encontró una relación significativa, considerable y negativa entre la autoestima y los correlatos negativos de los errores. Estos resultados se discuten considerando los hallazgos proveídos por investigaciones previas. Quizás, el fortalecimiento de la autoestima pueda contribuir en la reducción de las reacciones negativas que los niños experimentan ante el fracaso
Motivation in teachers of secondary education
Get PDFEl presente trabajo de investigación pretende significar la importancia de la motivación en la función docente, y en especial en la Educación Secundaria Obligatoria (ESO). El objetivo propuesto ha sido la realización de un estudio piloto, de carácter descriptivo, para conocer la motivación con la que los docentes realizan su tarea profesional; para ello, se procedió a la recogida de datos de cien profesores en un cuestionario con veinte preguntas para determinar los elementos intervinientes en dicha motivación. Los resultados mostraron que el 49% de los docentes no se sentían motivados en su ejercicio profesional; y de los componentes principales hallados, lo menos motivador fue: La falta de apoyo de las autoridades políticas y docentes; así como, las condiciones de trabajo; esto unido a la baja participación, preparación e interés mostradas por los alumnos, y a la baja “vocación” docente. Sin embargo, lo que más los motivaba era: La implicación psicoeducativa con los alumnos y la promoción y compromiso profesional con la educación, también la preparación técnica de los profesores. Se desprende del trabajo la necesidad de una actuación eficaz por parte de los poderes públicos y las autoridades educativas para minimizar los factores negativos incidentes en la motivación profesional.This research work aims to signify the importance of motivation in the teaching work, and especially in the Compulsory Secondary Education (CSE). The proposed objective has been conducting a pilot study, of descriptive character, in order to know the motivation with which teachers carry out their professional work. Data from one hundred teachers were collected through a questionnaire of twenty questions to determine the elements involved in this motivation. The results showed that 49% of teachers did not feel motivated in their professional practice; and of the main components found, the least motivating was: The lack of support from the political and educational authorities; as well as the working conditions; together with the low participation, preparation, and interest shown by the students, and the low teaching “vocation”. However, what motivated them most was the psychoeducational involvement with the students and the professional promotion and commitment with education, as well as the technical preparation of the teachers. A clear conclusion from this work that there is a need for effective action by public authorities and educational authorities to minimize the negative factors affecting professional motivation
Changes in colour and mechanical properties of wood polypropylene composites on natural weathering
Get PDFThis comparative study focused on understanding the effect of coupling agent and particle size on weathering behaviour of wood polypropylene composite. Two coupling agents, namely maleic anhydride grafted polypropylene and m-TMI (m-Isopropenyl-a,a- dimethylbenzyl isocyanate) grafted polypropylene were used in preparation of the composites. The composites were exposed to outdoor conditions for one year and changes in surface colour and mechanical properties were measured after 2, 4, 8 and 12 months of natural weathering. During the initial four months of weathering considerable colour change was observed with increase in lightness. Mechanical properties were unaffected largely for the initial four months and thereafter started declining. Overall, tensile strength decreased by about 15 % and flexural strength decreased by about 8 % after one year of weathering. The flexural modulus also decreased by about 10 %. Wood particle size was found to affect the aesthetic and strength of the composites after natural weathering. Coupling agents had a positive impact on mechanical properties however their influence on weathering degradation was not noticeable
Liquid water absorption in coated norway spruce: Impact of heartwood, sapwood, density and weather exposure
Get PDFWater is one of the most significant factors for the durability of wood. A common solution is to use a coating to protect and maintain low water content. However, little knowledge exists how the underlying wood substrate affects the water sorption of coated wood. Therefore, the liquid water absorption of coated and uncoated Norway spruce heartwood and sapwood with a variety of densities was measured by letting the panels float freely in the water. The effect of one year weathering of the coatings was also included. Coated heartwood and sapwood had no difference in water absorption in opposite to uncoated spruce. The influence of heartwood and sapwood seemed to have limited impact when a coating hindered the presence of free water. Wood density had a positive effect on the absorption of coated wood, i.e. low absorption for low-density samples, in opposite to uncoated samples. Low-density characteristic also contributed to a lower increase of water absorption after weather degradation, for samples with water-borne coatings. Natural weathering enhanced the effect of wood characteristics on coated samples, likely by an increase of coating permeability
Evaluation of different plant derived oils as wood preservatives against subterranean termite Odontotermes obesus
Get PDFThe 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