Heat-induced weight loss (WL) and chemical and dimensional changes of small specimens of beech (
Fagus sylvatica L.), Scots pine (
Pinus sylvestris L.) and Norway spruce (
Picea abies L.) wood were ...examined after thermal modification in the 190–245 °C temperature range. Treated specimens exhibited reductions in their oven-dry weight in line with the severity of the treatment, with the effect of increasing the temperature of exposure being greater than extending the period of treatment. Wood polysaccharides were found to be distinctly more labile than the lignin constituent; the latter increased possibly as a result of repolymerisation reactions trapping some degradation products in the process. Specimens shrank in the transversal plane in a tangential to radial ratio of 2:1 regardless of the treatment regime, while their length increased marginally for WL < 10–12%. It is proposed that the thermal modification leaves the cell wall material in a permanent strained state.
Colour evolution and colour changes were analysed from surface images of small specimens of three thermally-modified timber species using the CIEL*a*b* colour space. Upon heat exposure, the wood ...substance became orange and then approached grey irrespective of species; this was accompanied by a steady reduction in lightness. Colour changes were similar in the three woods at any given level of heat-induced weight loss (WL), whilst changes in the three coordinates of the CIEL*a*b* space in function of WL were different regardless of the wood species. For ΔL*, the profile was curvilinear and monotonous, while Δa* and Δb* bear a complex, non-linear profile. In turn, ΔE* was found to be highly influenced by the behaviour of ΔL*. It is proposed that ΔE* in thermally modified wood originates from chemical changes in the main wood polymers, more so in lignin than in polysaccharides, due to the darkening of the lignin itself. This was associated with the generation of chromophoric groups, mainly the increase in carbonyl groups appearing in the Fourier transform infrared spectra of lignin between 1710 and 1600 cm-1, particularly the emergence of quinone species.
•Q. crassifolia and Q. laurina woods have very similar polymer chemical constitution.•Oak barks have lots of extractives, and a large suberin fraction in the outer bark.•Q. crassifolia inner bark has ...potential for the production of Stiasny polyphenols.•Oaks wood fuel characteristics render them suitable as firewood or charcoal.
Herein, we describe the chemical composition of sapwood, heartwood and bark of Quercus laurina and Q. crassifolia, from Ixtlán de Juarez, Oaxaca, Mexico. We also report on the fuel characteristics of wood, bark and charcoal for these species. There was no significant difference in lignin (24.9–25.5%), α-cellulose (47.6–47.9%), and hemicellulose (22.4–23.2%) contents between Q. crassifolia and Q. laurina wood, while the ash content, hot water solubility, and total extractive content were higher in Q. crassifolia wood. The contribution of lignin, α-cellulose, hemicelluloses, suberin, and total extractives in barks, were 25.2–39.6%, 12.2–49.6%, 18.6–23.6%, 1.99–26.6%, and 12.7–31.7%, respectively. Bark had 4–8 times as much ash as the corresponding wood. The wood high heating value (HHV) of both oaks (19.3–19.4MJkg−1), was higher compared to other temperate hardwoods; the charcoal HHV varied from 32.0 to 33.3MJkg−1. Because of its high polysaccharide (69.7–70.8%) and low extractive (5.29–8.88%) and ash (0.30–0.95%) contents, wood of both species is deemed as suitable for the production of cellulosic pulp, while the content of suberin in the outer bark (20.1–26.6%), suggests its potential as biopolymers source. The fuel properties of wood and charcoal from both species indicate their aptitude as solid fuel.
Characterisation, quality assessment and property prediction are several of the major industrial challenges for widespread acceptance of thermally modified wood (TMW). This study shows the potential ...of the multivariate analysis of mid-infrared (MIR) spectral data for the prediction of impact strength, five mechanical parameters in bending, moisture content, weight loss, density and chemical composition of small specimens of thermally modified beech, Norway spruce and Scots pine woods. Anti-swelling efficiency was also studied using DRIFT spectroscopy for spruce wood only. Calibrations were successfully accomplished by partial least-squares regression, with R Y ² and Q CUM ² values >0.96 for 64 out of 67 models. Predictions were also successful, with relative prediction values >0 and RMSEP:SD ratios <1 in most cases. Changes in the MIR spectra of TMW show that bands arising from the lignin environment and new bands appearing due to the degradation of carbohydrates, giving negative loadings, were related to strength loss, while those bands arising from the polysaccharides were associated with property retention. It is concluded that this approach is a powerful tool to characterise a number of properties of TMW with a single after-treatment measurement.
To determine the epidemiology of congenital and acquired cytomegalovirus (CMV) infections in preterm infants and to analyze the efficacy of breast milk freezing in decreasing the vertical ...transmission rate of CMV.
During 2013 and 2014, preterm newborns who weighed ≤1500 g and were admitted to 22 Spanish neonatal units were included and screened for CMV infection according to the Spanish Neonatology Society recommendations. Each hospital treated the breast milk according to its own protocols.
Among the 1236 preterm neonates included, 10 had a congenital infection (0.8%) and 49 had an acquired infection (4.0%) (82% demonstrated positive PCR-CMV in breast milk). The neonates who received only frozen milk presented less frequently with acquired infection (1.2%) than those fed fresh milk (5.5%) (RR=0.22; 95% CI 0.05–0.90; P=0.017). The newborns who received bank milk followed by frozen or fresh breast milk more frequently had an acquired infection (2.1% or 2.2%, respectively) than those fed only frozen breast milk.
The incidence of congenital CMV infection in our sample is low, as described in the literature. To reduce acquired CMV infection, freezing breast milk might be an advisable procedure for preterm neonates born from seropositive mothers, either from the beginning of lactation or after a period of bank milk administration.
In the woodworking industry, image analysis is routinely used for quality control and for matching and classification during various processes. An extension of these automated systems for the ...prediction of physical properties of thermally modified wood (TMW) is enticing, because to date there is no generalised procedure for the quality assurance of TMW. In this work, the feasibility of predicting 13 physical parameters from the analysis of colour changes is demonstrated using small thermally modified specimens of three wood species. Simple linear regression models for anti-swelling efficiency, nominal density, heat-induced weight loss and 10 strength parameters in six forms of stress were all very or highly significant, with R2 statistics for the best predictor from 0.24 to 0.94. ΔE* was found to be a better predictor than ΔL* for most properties. Multiple linear regression with 11 colour variables increased the prediction ability of most models in terms of R2, although these improvements varied with the property and species concerned. The best models altogether were obtained by partial least squares regression, with relative prediction error values >0 in all cases. Our results demonstrate that physical properties of small specimens of TMW can be efficiently predicted with only one after treatment measurement of colour in the CIEL*a*b* colour space by means of image analysis of TMW surfaces. We anticipate that our approach would be a starting point for more refined modelling of physical properties of larger wood members and other properties of interest in TMW (e.g., decay resistance).
México es un centro de distribución para las especies del género Quercus, con 161 especies registradas, de las que 60 presentan características favorables para el aprovechamiento maderable. Aquí se ...describen las características anatómicas de la madera de Quercus laurina y Q. crassifolia, y se correlacionan con su densidad básica, contracción volumétrica y dureza. La madera de Q. laurina presentó brillo alto y veteado medio, mientras que en Q. crassifolia fueron medio y pronunciado, respectivamente. Ambas especies presentan porosidad anular, poros solitarios de forma oval, radios uniseriados, multiseriados y agregados, parénquima apotraqueal difuso en agregados, y fibras libriformes y fibrotraqueidas. En Q. laurina se determinó una correlación entre el espesor de pared de las fibras y la densidad básica (r = 0,97), y entre el diámetro de lumen de las fibras y la contracción volumétrica (r > 0,99). En Q. crassifolia, las correlaciones más altas se dieron entre la contracción volumétrica y el espesor de pared de las fibras (r = 0,97), y con el diámetro de las fibras (r = 0,93). En los dos encinos, la contracción volumétrica alta y la presencia de radios muy anchos, indican una mayor propensión de la madera a presentar grietas y rajaduras durante el proceso de secado.
Introducción: Los biocompuestos reforzados con fibras naturales son importantes por el aprovechamiento de residuos biodegradables y renovables.Objetivo: Evaluar el desempeño físico-mecánico de un ...biocompuesto laminar desarrollado con una matriz de polímero epóxica de baja viscosidad, reforzada con fibras de bagazo de Agave angustifolia Haw.Materiales y métodos: Se elaboraron 12 paneles combinando tres contenidos de fibra (18 %, 24 % y 30 %) con cuatro longitudes (1 mm, 3 mm, 6 mm y mezcla). Se realizaron pruebas mecánicas y los resultados se compararon con un patrón (resina pura). En la interfaz fibra-matriz se evaluaron tres tratamientos químicos (bicarbonato de sodio, vinil triethoxy silano e hidróxido de sodio) y su efecto en las propiedades físicomecánicas; además, se evaluó la hibridación con fibra de vidrio.Resultados y discusión: La incorporación de fibra redujo 15.27 % la resistencia última a la tracción y flexión del biocompuesto; sin embargo, incrementaron hasta 1/3 los módulos de tracción y flexión con respecto al patrón. El mejor tratamiento químico (bicarbonato de sodio) incrementó las propiedades mecánicas de las fibras (dureza 46 % y resistencia a la tracción 6 % y flexión 24 %) y la resistencia al impacto (38 %), mientras que la densidad y la resistencia a la humedad disminuyeron 17 % y 11 %, respectivamente. La combinación fibras agave/vidrio incrementó la resistencia a la flexión hasta 77.3 %.Conclusiones: Las fibras de A. angustifolia tienen potencial para implementarlas en la industria, ya que mejoran las propiedades mecánicas del material; además, su uso representaría una alternativa de manejo de los residuos de desecho.
The relationship between 27 mechanical parameters and density, shrinkage coefficients, moisture content, anisotropy ratio, and the fiber saturation point (FSP) in small specimens of
Quercus ...crassifolia
Humb. & Bonpl. and
Q. laurina
Humb. & Bonpl. wood, from Oaxaca, Mexico, is described. Wood from both oaks displayed low dimensional stability, while mechanical testing results revealed a strong material in most forms of stress, as well as a high impact-resistance wood. Wood mechanical properties in dry and green state were positively correlated with density, shrinkage coefficients, and FSP. Density was generally the single best predictor for mechanical strength, although the modulus of elasticity was a better predictor of the modulus of rupture in the bending tests. Univariate models to predict mechanical properties using the best regressor of the physical properties gave R
2
values from 0.104 (p = 0.015) to 0.494 (p < 0.001), whereas multivariate regression significantly increased the predictive power of the models, with R
2
values from 0.190 (p = 0.004) to 0.646 (p < 0.001).
El propósito del presente trabajo fue evaluar la resistencia a la pudrición blanca (Coriolus versicolor) y café (Coniophora puteana) en madera acetilada de pino escocés (Pinus sylvestris) y el efecto ...de la piridina como catalizador. Las pruebas de biodegradación se realizaron sobre cultivos puros en malta agar al 4% por 12 semanas, conforme a lo establecido en la norma europea EN1 13. Adicionalmente, se comparó la estabilidad dimensional de la madera impartida por la acetilización, en sistemas de modificación química catalizada y sin catalizar. La modificación química proporcionó resistencia a la biodegradación de la madera contra hongos de la pudrición café y blanca. Se requirió de un nivel de acetilización mayor para inhibir la pudrición café, en comparación con el requerido para impedir la pudrición blanca. Los patrones de pudrición y las pérdidas de peso registradas indicaron que la piridina como catalizador no influyó en la resistencia a la pudrición de la madera acetilada, cuando los resultados fueron comparados dentro de la misma especie de hongo. La estabilidad dimensional impartida por la acetilización, medida por la eficiencia de antiexpansión (ASE), resultó satisfactoria en ambos sistemas de reacción, aunque el sistema no catalizado fue significativamente más eficiente. Seconcluyó que la ganancia porcentual en peso, debida a la modificación química, es un buen indicador del grado de expansión parcial permanente de los bloques de madera, así como de la estabilidad dimensional y la resistencia a la pudrición de la madera acetilada.
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