971 resultados para Wood chemicals


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Palatal clicks are most interesting for human echolocation. Moreover, these sounds are suitable for other acoustic applications due to their regular mathematical properties and reproducibility. Simple and nondestructive techniques, bioinspired by synthetized pulses whose form reproduces the best features of palatal clicks, can be developed. The use of synthetic palatal pulses also allows detailed studies of the real possibilities of acoustic human echolocation without the problems associated with subjective individual differences. These techniques are being applied to the study of wood. As an example, a comparison of the performance of both natural and synthetic human echolocation to identify three different species of wood is presented. The results show that human echolocation has a vast potential.

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Información paleoecológica relativa a la distribución de táxones arbóreos durante el holoceno, basado en restos fósiles leñosos.

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Background Obeche wood dust is a known cause of occupational asthma where an IgE-mediated mechanism has been demonstrated. Objective To characterize the allergenic profile of obeche wood dust and evaluate the reactivity of the proteins by in vitro, ex vivo and in vivo assays in carpenters with confirmed rhinitis and/or asthma Materials and methods An in-house obeche extract was obtained, and two IgE binding bands were purified (24 and 12 kDa) and sequenced by N-terminal identity. Specific IgE and IgG, basophil activation tests and skin prick tests (SPTs) were performed with whole extract and purified proteins. CCD binding was analyzed by ELISA inhibition studies. Results Sixty-two subjects participated: 12 with confirmed occupational asthma/rhinitis (ORA+), 40 asymptomatic exposed (ORA−), and 10 controls. Of the confirmed subjects, 83% had a positive SPT to obeche. There was a 100% recognition by ELISA in symptomatic subjects vs. 30% and 10% in asymptomatic exposed subjects and controls respectively (p<0.05). Two new proteins were purified, a 24 kDa protein identified as a putative thaumatin-like protein and a 12 kDa gamma-expansin. Both showed allergenic activity in vitro, with the putative thaumatin being the most active, with 92% recognition by ELISA and 100% by basophil activation test in ORA+ subjects. Cross-reactivity due to CCD was ruled out in 82% of cases. Conclusions Two proteins of obeche wood were identified and were recognized by a high percentage of symptomatic subjects and by a small proportion of asymptomatic exposed subjects. Further studies are required to evaluate cross reactivity with other plant allergens.

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Se analiza la influencia de las principales actuaciones selvicolas en la calidad de la madera. Turno, Espaciamiento, Poda, Abonado, Riego y Tratamiento contra plagas.

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Los Clics palatales son sonidos interesantes para la ecolocalización humana pero tambien pueden utilizarse para determinar propiedades de la madera como para poder identificar tres especies diferentes de madera. Los resultados muestran que la ecolocalización humana tiene un enorme potencial.

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El objetivo del estudio es determinar el efecto de tratamiento de la madera de Pinus sylvestris con sustancias protectoras en las propiedades mecánicas. Para ello se utilizan 40 muestras de madera libre de defectos de Pinus sylvestris L. tratándose con protectores orgánicos (Vacsol Azure WR 2601) 50 con protectores hidrosolubles (Tanalith E 3492) y 40 muestras de control sin tratamiento. Se evaluó la resistencia mecánica a la flexión estática, módulo de elasticidad y la fuerza de compresión paralela a la fibra fueron comparados con madera no tratada. El análisis de regresión entre la penetración y la fuerza de compresión paralela se realizó con las muestras tratadas con conservante a base de agua. Resultados principales: Los resultados indican que la madera tratada (con cualquiera de los productos) presenta un aumento estadísticamente significativo de la resistencia mecánica en todas las tres características mecánicas. Los resultados obtenidos difieren de estudios anteriores llevada a cabo por otros autores. No hubo correlación entre la resistencia a la compresión en paralelo y el grado de impregnación de la madera con base de agua de cobre azoles. La explicación más probable para estos resultados se refiere a cambios en la presión durante el tratamiento. El uso de muestras de control no tratadas en lugar de las muestras tratadas sólo con agua es más probable para producir resultados significativos en los estudios de resistencia mecánica . La investigación pone de relieve que la madera tratada presenta un aumento estadísticamente significativo en el Modulo de Elasticidad, módulo de rotura a la flexión estática y resistencia a la compresión paralela. No hubo correlación entre la resistencia a la compresión en paralelo y el grado de impregnación con conservante hidrosoluble.

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This study analyses the variation of main physical-mechanical properties of wood along the longitudinal and radial directions of the tree for Abies alba Mill. growing in the Spanish Pyrenees. Small clear specimens were used to study the properties of volumetric shrinkage (VS), density (?), hardness (H), bending strength (MOR), modulus of elasticity (MOE), maximum compressive strength parallel to the grain (MCS) and impact strength (K). Several models of properties variation in the longitudinal and radial directions were analyzed. Main trends of variation of properties throughout the tree stem were identified although none of them could be fitted to predictive statistical models. Along the longitudinal direction, the properties studied followed a downward trend from the base to the crown, which was not significant in all cases, indicating that no differences in quality existed. Throughout the radial direction the trend is upward for the first 40-50 growth rings, after which it slopes downwards, more gently at first until rings 70-75 and then more steeply. This behaviour is related to variation in wood structure from the pith to the bark, depending on whether the wood is juvenile, sapwood or heartwood, and to wood maturity and microfibril angle. Authors encourage carrying further studies on other populations of A. alba in the Spanish Pyrenees to check if the trends found in this study apply to other provenances.

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Resumen: Descripción: vista de Portaceli desde el monte muy frondoso. La Cartuja se deduce en segundo término

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Nondestructive techniques are widely used to assess existing timber structures. The models proposed for these methods are usually performed in the laboratory using small clear wood specimens. But in real situations many anomalies, defects and biological damage are found in wood. In these cases the existing models only indicate that the values are outside normality without providing any other information. To solve this problem, a study of non-destructive probing methods for wood was performed, testing the behaviour of four different techniques (penetration resistance, pullout resistance, drill resistance and chip drill extraction) on wood samples with different biological damage, simulating an in-situ test. The wood samples were obtained from existing Spanish timber structures with biotic damage caused by borer insects, termites, brown rot and white rot. The study concludes that all of the methods offer more or less detailed information about the degree of deterioration of wood, but that the first two methods (penetration and pullout resistance) cannot distinguish between pathologies. On the other hand, drill resistance and chip drill extraction make it possible to differentiate pathologies and even to identify species or damage location. Finally, the techniques used were compared to characterize their advantages and disadvantages.

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La madera termotratada es madera modificada mediante un proceso térmico a elevadas temperaturas que le proporciona mayor estabilidad dimensional y durabilidad sin incorporar productos químicos perjudiciales para el medio ambiente. Hasta el momento se ha aplicado fundamentalmente a madera de coniferas por motivos económicos, siendo su uso más habitual en ambientes exteriores o de elevada humedad, como elementos de revestimiento no estructurales, carpinterías, mobiliario de jardín, etc. En la presente tesis se estudia la viabilidad de la madera termotratada de frondosas para uso estructural, en particular fresno (Fraxinus excelsior L) y haya (Fagus sylvatica L). Con este fin, y considerando que el termotratamiento modifica la estructura interna de la madera resultando en un nuevo material, se realizan estudios experimentales y numéricos para su caracterización. Estos trabajos se desarrollan bajo el enfoque de la Mecánica de Fractura debido a la pérdida de resistencia y aumento de fragilidad que presenta el material, especialmente a tracción perpendicular a las fibras. Así mismo, se lleva a cabo una recopilación de las bases, fundamentos y metodologías de esta teoría aplicados a madera sin tratar y otros materiales debido a la inexistencia de este tipo de estudios en madera termotratada. De igual manera se realiza un programa de caracterización mecánica del material para determinar sus propiedades elásticas considerando un modelo ortótropo, necesarios en la investigación del comportamiento a fractura. El trabajo derivó en el desarrollo de un nuevo método de ensayo para la determinación multiparamétrica a partir de un sólo espécimen, proporcionando resultados mucho más robustos que los obtenidos con la metodología convencional de ensayos. En base a los trabajos realizados, considerando las limitaciones de resistencia y fragilidad, así como la dudosa aplicabilidad de las normativas existentes en madera sin tratar, se aconseja no utilizar tratamientos térmicos intensos en elementos estructurales primarios. Se propone su aplicación en elementos secundarios, de manera que un posible colapso no implique una pérdida de fiabilidad global de la estructura. Se estudia la viabilidad de un panel sandwich innovador y ecológico para fachadas expuesto a cargas de viento, compuesto de madera termotratada en las caras y panel aislante de fibras de madera con función estructural en el alma. Esta investigación se desarrolló dentro del proyecto de investigación Europeo "Holiwood", Holistic implementation of European thermal treated hardwood (TMT) in the sector of construction industry and noise protection by sustainable, knowledge-based and value added products, perteneciente al sexto Programa Marco. ABSTRACT Hcat-trcatcd wood is modified wood by a thermal process at high temperatures which provides greater dimensional stability and durability without adding harmful chemicals to the environment. It has been mainly applied to softwoods due mainly to economical reasons, being its most common use outdoors or in high humidity environments, as non-structural elements, furniture, etc. The present Thesis studies the feasibility of heat-treated hardwoods for structural uses, particularly ash (Fraxinus excelsior L) and beech (Fagus sylvatica L). To this end, and considering that heat treatment modifies the internal structure of the wood resulting in a new material, experimental and numerical studies are performed for its characterization. This investigation is developed under the approach of Fracture Mechanics due to the loss of strength and the increase in brittlcncss of the material, especially in tension perpendicular to the grain. Likewise, it holds a collection of the bases, foundations and methodologies of this theory applied to untreated wood and other materials due to the lack of such studies in heat-treated wood. In addition, studies for the mechanical characterization of the material are performed in order to determine the elastic properties considering an orthotropic model. This work is necessary in the investigation of the fracture behavior. It led to the development of a new test method for multiparameter determination by using just a single specimen, providing much more robust results than those obtained with conventional test methodology. Based on this investigation, and considering the limitations of strength and brittleness, and the questionable applicability of existing standards for untreated wood, it is advised not to use intense heat treatments in primary structural elements. It is proposed the application to secondary elements, so that a possible collapse does not involve a loss of overall reliability of the structure. It is studied the feasibility of an innovative and ecological sandwich panel for facades exposed to wind loads, composed by heat-treated wood faces and insulating wood fiberboard with structural function in the core. This investigación was developed within the European research project "Holiwood", Holistic implementation of European thermal treated hardwood (TMT) in the sector of construction industry and noise protection by sustainable, knowledge-based and value added products, of the Sixth Framework Program.

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Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

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This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Acknowledgements: We thank Ms Margaret Fraser, Ms Samantha Flannigan, and Dr Wing Yee Kwong for their expert assistance. The staff at Grampian NHS Pregnancy Counselling Service were essential for collecting fetuses. We thank Professor Geoffrey Hammond and Dr Marc Simard, University of British Colombia for helpful comments on the manuscript. Supported by grants as follows: Scottish Senior Clinical Fellowship (AJD); Chief Scientist Office (Scottish Executive, CZG/1/109 to PAF, & CZG/4/742 (PAF & PJOS); NHS Grampian Endowments 08/02 (PAF, SB & PJOS); the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no 212885 (PAF & SMR); the Medical Research Council grants MR/L010011/1 (PAF & PJOS) and MR/K018310/1 (AJD). None of the funding bodies played any role in the design, collection, analysis, and interpretation of data, in the writing of the manuscript, nor in the decision to submit the manuscript for publication

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A rapidly growing area of genome research is the generation of expressed sequence tags (ESTs) in which large numbers of randomly selected cDNA clones are partially sequenced. The collection of ESTs reflects the level and complexity of gene expression in the sampled tissue. To date, the majority of plant ESTs are from nonwoody plants such as Arabidopsis, Brassica, maize, and rice. Here, we present a large-scale production of ESTs from the wood-forming tissues of two poplars, Populus tremula L. × tremuloides Michx. and Populus trichocarpa ‘Trichobel.’ The 5,692 ESTs analyzed represented a total of 3,719 unique transcripts for the two cDNA libraries. Putative functions could be assigned to 2,245 of these transcripts that corresponded to 820 protein functions. Of specific interest to forest biotechnology are the 4% of ESTs involved in various processes of cell wall formation, such as lignin and cellulose synthesis, 5% similar to developmental regulators and members of known signal transduction pathways, and 2% involved in hormone biosynthesis. An additional 12% of the ESTs showed no significant similarity to any other DNA or protein sequences in existing databases. The absence of these sequences from public databases may indicate a specific role for these proteins in wood formation. The cDNA libraries and the accompanying database are valuable resources for forest research directed toward understanding the genetic control of wood formation and future endeavors to modify wood and fiber properties for industrial use.