Utilization of temperature kinetics as a method to predict treatment intensity and corresponding treated wood quality : durability and mechanical properties of thermally modified wood

Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. However, this improvement of durability is realized at the expense of the mechanical resistance. Decay resistance and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. However, the introduction of a fast and accurate system for measuring this mass loss on an industrial scale is very difficult. Nowadays, many studies are conducted on the determination of control parameters which could be correlated with the treatment conditions and final heat treated wood quality such as decay resistance. The aim of this study is to investigate the relations between kinetics of temperature used during thermal treatment process representing heat treatment intensity, mass losses due to thermal degradation and conferred properties to heat treated wood. It might appear that relative area of treatment temperature curves is a good indicator of treatment intensity. Heat treatment with different treatment conditions (temperature-time) have been performed under vacuum, on four wood species (one hardwood and three softwoods) in order to obtain thermal degradation mass loses of 8, 10 and 12%. For each experiment, relative areas corresponding to temperature kinetics, mass loss, decay resistance and mechanical properties have been determined. Results highlight the statement that the temperature curves’ area constitutes a good indicator in the prediction of needed treatment intensity, to obtain required wood durability and mechanical properties such as bending resistance and Brinell hardness.LERMaB is supported by the French National Research Agency through the Laboratory of Excellence ARBRE (ANR-12- LABXARBRE-01), the authors gratefully acknowledge this ai

The methyltransferase domain of dengue virus protein NS5 ensures efficient RNA synthesis initiation and elongation by the polymerase domain

International audienceViral RNA-dependent RNA polymerases (RdRps) responsible for the replication of single-strand RNA virus genomes exert their function in the context of complex replication machineries. Within these replication complexes the polymerase activity is often highly regulated by RNA elements, proteins or other domains of multi-domain polymerases. Here, we present data of the influence of the methyltrans-ferase domain (NS5-MTase) of dengue virus (DENV) protein NS5 on the RdRp activity of the polymerase domain (NS5-Pol). The steady-state polymerase activities of DENV-2 recombinant NS5 and NS5-Pol are compared using different biochemical assays allowing the dissection of the de novo initiation, transition and elongation steps of RNA synthesis. We show that NS5-MTase ensures efficient RdRp activity by stimulating the de novo initiation and the elongation phase. This stimulation is related to a higher affinity of NS5 toward the single-strand RNA template indicating NS5-MTase either completes a high-affinity RNA binding site and/or promotes the correct formation of the template tunnel. Furthermore, the NS5-MTase increases the affinity of the priming nucleotide ATP upon de novo initiation and causes a higher catalytic efficiency of the polymerase upon elongation. The complex stimulation pattern is discussed under the perspective that NS5 adopts several conforma-tions during RNA synthesis

Effects of Age and Task Load on Drivers’ Response Accuracy and Reaction Time When Responding to Traffic Lights

International audienceDue to population aging, elderly drivers represent an increasing proportion of car drivers. Yet, how aging alters sensorimotor functions and impacts driving safety remains poorly understood. This paper aimed at assessing to which extent elderly drivers are sensitive to various task loads and how this affects the reaction time (RT) in a driving context. Old and middle-aged people completed RT tasks which reproduced cognitive demands encountered while driving. Participants had to detect and respond to traffic lights or traffic light arrows as quickly as possible, under three experimental conditions of incremental difficulty. In both groups, we hypothesized that decision-making would be impacted by the number of cues to be processed. The first test was a simple measure of RT. The second and third tests were choice RT tasks requiring the processing of 3 and 5 cues, respectively. Responses were collected within a 2 s time-window. Otherwise, the trial was considered a no-response. In both groups, the data revealed that RT, error rate (incorrect answers), and no-response rate increased along with task difficulty. However, the middle-aged group outperformed the elderly group. The RT difference between the two groups increased drastically along with task difficulty. In the third test, the rate of no-response suggested that elderly drivers needed more than 2 s to process complex information and respond accurately. Both prolonged RT and increased no-response rate, especially for difficult tasks, might attest an impairment of cognitive abilities in relation to aging. Accordingly, casual driving conditions for young drivers may be particularly complex and stressful for elderly people who should thus be informed about the effects of normal aging upon driving

Modeling the Influence of Knots on Douglas-Fir Veneer Fiber Orientation

This study presents a method for predicting the local fiber orientation of veneers made from peeled Douglas-fir logs based on the knowledge of the tree branch characteristics (location, radius, insertion angle, azimuth angle, and living branch ratio). This model is based on the Rankine oval theory approach and focuses on the local deviation of the fiber orientation in the vicinity of knots. The local fiber orientation was measured online during the peeling process with an in-house-developed scanner based on the tracheid effect. Two logs from the same tree were peeled, and their ribbons were scanned. The knot locations and fiber orientation were deduced from the scanner data. The first objective was to compare the fiber orientation model with measurements to enhance and validate the model for French Douglas-fir. The second objective was to link data measurable on logs to veneer quality.Région Bourgogne-Franche-Comté Ministère de l'Agriculture et de l'Alimentatio

Influence of veneer lathe checks on the mechanical properties of LVL

Laminated veneer lumber (LVL) is a high-performance engineered wood product made of several wood veneers bound together mostly in grain direction. Veneers are obtained thanks to peeling process. This cutting process induces lathe checks of the veneer with variable depth and spatial frequencies. In this work, we studied the influence of lathe checks on the mechanical properties of LVL thanks to a finite element model of LVL beams made of checked veneers. The checks were modelled as free spaces in the cross-section. Several typical check depths and frequencies were compared, with the beam tested edgewise or flatwise. The results show that the longitudinal modulus of elasticity and the shear modulus in flatwise bending are marginally affected by checking, while the shear modulus of the LVL beam is significantly reduced in edgewise bending if the check depth is important. This phenomenon is due to high shear deformations in the edgewise bending case, because checks are mainly horizontal in this state. Therefore, the check depth may also affect the resistance of LVL in edgewise bending, thus experimental testing of this assumption will be done

Anti-fungal and anti-termite activity of extractives compounds from thermally modified ash woods

Thermal 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

Multifunctionnality: sea fishing, shellfish culture activities and durability

Evaluation SMART - Auteur hors unité au moment de la publicationIn the context where striking a balance between safeguarding the resource, rationalisation of economic activity and maintenance of social objectives is more and more difficult, the asseftion of a multifunctionality of sea fishing and shellfish culture would also have, as for agriculture, to allow the continued existence of a significant uumber of entelprises because of the generated complementary incomes and finaucitrg of non commercial services ensuled within this framework. As in agriculture, specific measul'es would make it possible to genelate new activities in order to make them economically viable in the medium term in particular irnprovement of methods of fishing, diversification of the activities arrd enhancement of sea food products

BENDING, SHEARING, AND COMPRESSION PROPERTIES OF FAST GROWING FRENCH DOUGLAS FIR LVL

The French resource of large diameter Douglas fir is currently keeping growing, while these large diameter trees are complicated to process efficiently by the sawmilling industry. The rotary peeling process appeared to be particularly adapted as an alternative to the usual sawing. This primary processing method produces veneers used to make a wood engineering product material called Laminated Veneer Lumber (LVL). The manufacturing process of LVL enables the distribution of the resource defects, allowing for increased mechanical behaviour compared to the solid wood from which it comes from. The main objective of this study is to present the principal Douglas-fir heartwood LVL mechanical properties such as longitudinal and shear moduli of elasticity, bending, shear and compressive strengths. Up to now, there were no study on LVL derived from this resource. This study focuses on heartwood because of its very interesting natural durability properties for constructive outdoor applications. Moreover, a comparison with structural timber properties was also achieved to place the material in terms of mechanical performance among the market. Globally, this LVL material showed high compressive and shear properties. Nevertheless, even though the bending properties were significantly lower than data from Douglas-fir LVL literature, they are still quite acceptable for structural applications

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