Efecto de las condiciones ambientales sobre las propiedades físico-mecánicas de tableros MDF

Four types of surface coating, on commercial MDF 19 mm thick panels, are used to study the behaviour of MDF panels under four different conditions of relative humidity. The behaviour of the panels is studied by means of the comparison between the initial and final (after conditioning) values of the Modulus of Rupture (MOR), Modulus of Elasticity (MOE), Internal Bonding (RTP), Equilibrium Moisture Content (HEH) and density. In some cases the evolution of some properties is monitorized during the conditioning treatment. Four different environmental conditions are considered, three of them constant (20º C/65 p. 100 rh, 20º C/90 p. 100 rh, 20º C/35 p. 100 rh) and one variable (20º C/35-90 p. 100 rh). Boards under a constant environment of 20ºC/90%rh used to exhibit a clear worse behaviour than under variable climate of 20º C/ 35-90 p. 100 rh. This general behaviour is just the opposite than the one exhibited by particleboards in a previous work.Cuatro tipos de acabados superficiales distintos, aplicados sobre tableros MDF comerciales de 19 mm de espesor, son empleados en el estudio del comportamiento de los tableros MDF ante diferentes condiciones de humedad ambiental. Para el análisis de este comportamiento se consideran los valores del Módulo de Rotura (MOR) y de Elasticidad (MOE) a flexión, así como de la Resistencia a la Tracción Perpendicular a las caras (RTP), de la Humedad de Equilibrio Higroscópico (HEH) y de la densidad. Todos estos valores son determinados al comienzo y al final de cada tratamiento, estudiándose en algunos casos su evolución a lo largo del proceso de acondicionado. De las cuatro condiciones ambientales consideradas, tres de ellas constantes (20º C/65 p. 100 Hr, 20º C/90 p. 100 Hr, 20º C/35 p. 100 Hr) y una variable (20º C/35-90 p. 100 Hr), la que parece influir más negativamente en las propiedades físico-mecánicas de los tableros MDF es la estable a 20ºC y 90 p. 100 Hr. Las condiciones cíclicas de humedad relativa (35-90 p. 100) parecen afectar a estos tableros mucho menos intensamente, siendo comportamiento el contrario del exhibido por el tablero de partículas (datos de un trabajo anterior)

Influencia de diversos factores en la calidad de la madera de uso estructural de P. sylvestris L

On a sample of 60 longs of P. sylvestris L. sourced from the Valsain (Segovia, Spain) forest and logged from eleven different stands with different site qualities, is studied the influence of the selvicultural characteristics, the morphological characteristics of the trees, the sawing systems and the gradind systems on the yield and structural quality of timber. The influence of the genetical characteristics of every tree, the proccesing factors of the logs and the properties of every board on the yield and quality of timber is clear. The site quality and the dasometric characteristics of the individual trees seems to have little influence on the studied variables.Sobre una muestra de 60 árboles de la especie P. sylvestris L. apeados en el monte Valsaín, Segovia (España) y obtenidos en 11 rodales de distintas calidades selvícolas, se estudia la influencia de dichas condiciones selvícolas, de las características de los árboles, del aserrado de las trozas y de la clasificación visual del material sobre el rendimiento y la calidad estructural de la madera de aserrio obtenida. Se evidencia la influencia de las características genéticas individuales de cada árbol, de las condiciones de aserrado y de las propiedades individuales de cada tabla en el rendimiento y calidad de la madera obtenida. Las condiciones selvícolas de los rodales y las características dasométricas de los árboles tienen escasa influencia sobre las variables estudiadas

Determinación de curvas para la estimación del contenido de humedad de diez maderas de frondosas mediante medidas de resistencia eléctrica

Accuracy in moisture content measurement is of great importance in the assurance of wood product quality and isnecessary to meet administrative and normative requirements. Improving the accuracy of resistance-type moisture meters,and meeting the normative demands of their annual calibration, requires the use of optimised curves relating electricalresistance to moisture content for the most commercially important wood types. The Samuelsson model, adjusted bylinear regression techniques, was used to describe the relationship between the electrical resistance and moisture contentof seven boreal and three tropical hardwoods available on the Spanish market. The curves produced can be used to predictthe moisture contents of these hardwoods via the measurement of their electrical resistance with an error of just ± 1.0%.These curves should also prove of great use in the calibration of wood resistance-type moisture meters.La precisión en la medida del contenido de humedad juega un papel fundamental no solo en el aseguramiento de lacalidad de los productos de la madera sino, también, en el cumplimiento de las exigencias normativas y administrativasque gravitan sobre los productos. Para ser capaces de mejorar la precisión de la medida tomada por los xilohigrómetrosde resistencia y cumplir con las exigencias normativas de calibración anual de los equipos, es necesario obtener curvasoptimizadas que relacionen la resistencia eléctrica con la humedad en las maderas de mayor importancia comercial.El modelo de Samuelsson, Log[Log(R) + 1] = a.h + b, ajustado mediante técnicas de regresión lineal, fue usado paradescribir la relación existente entre la resistencia eléctrica de la madera (R) y el contenido de humedad (h) de sietemaderas de frondosas boreales y tres de frondosas tropicales comercialmente disponibles en el mercado español. Lascurvas obtenidas pueden ser usadas para la predicción del contenido de humedad de dichas maderas, con un errormáximo de ± 1.0%, mediante la medición de su resistencia eléctrica. Estas curvas serían también de interés para lacalibración de medidores de humedad de madera por resistencia eléctrica

Cost-effectiveness analysis of stand-alone or combined non-invasive imaging tests for the diagnosis of stable coronary artery disease: results from the EVINCI study

Aim: This study aimed at evaluating the cost-effectiveness of different non-invasive imaging-guided strategies for the diagnosis of obstructive coronary artery disease (CAD) in a European population of patients from the Evaluation of Integrated Cardiac Imaging in Ischemic Heart Disease (EVINCI) study. Methods and results: Cost-effectiveness analysis was performed in 350 patients (209 males, mean age 59 ± 9 years) with symptoms of suspected stable CAD undergoing computed tomography coronary angiography (CTCA) and at least one cardiac imaging stress-test prior to invasive coronary angiography (ICA) and in whom imaging exams were analysed at dedicated core laboratories. Stand-alone stress-tests or combined non-invasive strategies, when the first exam was uncertain, were compared. The diagnostic end-point was obstructive CAD defined as > 50% stenosis at quantitative ICA in the left main or at least one major coronary vessel. Effectiveness was defined as the percentage of correct diagnosis (cd) and costs were calculated using country-specific reimbursements. Incremental cost-effectiveness ratios (ICERs) were obtained using per-patient data and considering “no-imaging” as reference. The overall prevalence of obstructive CAD was 28%. Strategies combining CTCA followed by stress ECHO, SPECT, PET, or stress CMR followed by CTCA, were all cost-effective. ICERs values indicated cost saving from − 969€/cd for CMR-CTCA to − 1490€/cd for CTCA-PET, − 3092€/cd for CTCA-SPECT and − 3776€/cd for CTCA-ECHO. Similarly when considering early revascularization as effectiveness measure. Conclusion: In patients with suspected stable CAD and low prevalence of disease, combined non-invasive strategies with CTCA and stress-imaging are cost-effective as gatekeepers to ICA and to select candidates for early revascularization

Cardiovascular imaging 2011 in the International Journal of Cardiovascular Imaging

Cardiovascular Aspects of Radiolog

Influencia de la anchura del anillo de crecimiento en la densidad y otras propiedades físico-mecánicas de la madera estructural de diversas especies

Mechanical quality of structural timber (50 mm x 150 mm x 3200 mm) is assessed by means of growth rates in different softwoods (P. radiata, P. pinaster, P. sylvestris), most of them fast growing species, and hardwoods (Populus sp. and Eucalyptus globulus) growing in Spain. The utility of using average density instead of growth rate is also assessed. Growth rate did not appreciably influence the density and bending properties of timber, and so its utility of prediction of mechanical quality of timber is very low.Se analiza la calidad predictiva de la anchura del anillo sobre la densidad y propiedades a flexión de la madera estructural (50 x 150 x 3200 mm) de diferentes especies de crecimiento rápido (Populus sp. Pinus sp. Eucalyptus globulus). Se discute la utilización alternativa de la densidad como criterio predictivo de la calidad, en sustitución de la anchura media del anillo de crecimiento. La anchura del anillo no explica suficientemente la variabilidad ni de la densidad ni de las propiedades a flexión de la madera estructural, por lo que su utilidad en la predicción de la calidad queda en entredicho

Caracterización mecánica de la madera aserrada de pino silvestre de los sistemas Central e Ibérico mediante probetas de tamaño estructural

A mechanical characterization of structural timber (150 x 50 x 3.000 mm) of different Spanish provenances of Pinus sylvestris is carried out, giving the characteristic values and strength classes corresponding to the quality classes considered in the UNE 56544 visual grading standard. A criticism of the cited UNE 56544 standard is also included, providing some solutions to the detected problems. A mechanical characterization of timber coming from young small dimater logs is also considered and a discussion about the influence of the intensity of thinnings into the mechanical properties and quality of timber is provided. The feasibility of the use of the UNE 56544 standard is also discussed. A final comparison with the results of other studies on Pinus pinaster and P. radiata is also carried out.En el presente trabajo se caracteriza mecánicamente madera aserrada de tamaño estructural (150 x 50 x 3.000 mm) de Pinus sylvestris de diferentes procedencias, aportando los valores característicos y clases de resistencia que corresponden a las clases de calidad definidas por la norma UNE 56544. Se efectúa, asimismo, una crítica de la citada norma UNE 56544 y se proponen soluciones a los problemas detectados. Se caracteriza mecánicamente madera aserrada de la misma especie, procedente de pies de pequeño diámetro y edad inferior al turno selvícola, extraído como consecuencia de la ejecución de claras y se analiza la influencia de la intensidad del tratamiento selvícola en los valores de resistencia y en los rendimientos en madera clasificada obtenidos. Se estudia la posibilidad del empleo de la misma norma UNE 56544 y la posibilidad de extrapolar los resultados obtenidos con madera "en turno" a los obtenidos con maderas "delgadas". Finalmente, se hace una c omparación con los resultados obtenidos para otras especies (P. radiata y P. pinaster) en estudios similares al presente

Características físico-mecánicas de las maderas de especies de crecimiento rápido de procedencia española

29 physico-mechanical and morphological properties of different timbers from five fast growing Spanish tree species were studied and analysed.Se determinan y analizan 29 características físico-mecánicas y morfológicas de maderas de cinco especies de crecimiento rápido de procedencia española (pinos radiata y gallego, chopo, castaño y eucalipto)

Three-dimensional full automated software in the evaluation of the left ventricle function: from theory to clinical practice

Left ventricular systolic function evaluation is an essential part of all transthoracic echocardiographic (TTE) studies. 3D echocardiography (3DE) is superior to 2D and is recommended as the method of choice. However, since it is time consuming and requires training, it is rarely performed. Different automatic analysis software tries to overcome these limitations but they need to be accurate and reproducible before they can be used clinically. The aim of this study was to test the accuracy and reproducibility of new 3D automatic quantitative software in everyday clinical practice. 69 patients referred to our Echo Lab for a clinically indicated echocardiographic examination were included. All patients underwent a full TTE with 3D image acquisition. Left ventricular volumes and ejection fraction (LVEF) were obtained using Heart Model software, and compared with conventional 3D volumetric data. Automated analysis was performed using three different sliders setting, with or without regional editing if necessary. 20 patients underwent a cardiac magnetic resonance (CMR) study the same day of the echo and automated measurements were also compared with a CMR reference. Intra- and inter-technique comparisons including linear regression with Pearson correlation coefficients and Bland–Altman analyses were calculated. Mean age of the patients was 59 years, with 49.3% male. The automated 3DE model demonstrated excellent correlation with the conventional 3DE measurements of LVEF, using three different sliders settings (r = 0.906; r = 0.898 and r = 0.940). Correlations with CMR values were very good as well (r = 0.888; r = 0.869; r = 0.913). Similarly, no significant differences were noted between the values of EDV and ESV, measured with the automated model or CMR, with excellent correlation (EDV: r = 0.892, r = 0.842, 0.910; ESV: r = 0.925, r = 0.860, r = 0.907). Finally, volumes calculated with the automated software were significantly greater than those obtained manually, but they showed a very good correlation (EDV: r = 0.875, r = 0.856, r = 0.891; ESV: r = 0.929, r = 0.879, r = 949). 3D automatic software for LV quantification is feasible and shows excellent correlations with both CMR and 3D echocardiography, considered the gold standard. No clinically relevant differences were noted when applying different border settings. This technique holds promise to facilitate the integration of 3D TTE into clinical practice