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Various glucosylamines were synthesized from glucose and different alkyl amine compounds. These amino compounds are β- d -glucopyranosylamine (GPA), N -ethyl-β- d -glucopyranosylamine (EtGPA), N -butyl-β- d -glucopyranosylamine (BuGPA), N -hexyl-β- d -glucopyranosylamine (HeGPA), N -octyl-β- d -glucopyranosylamine (OcGPA), N -dodecyl-β- d -glucopyranosylamine (DoGPA), N -(2-hydroxyethyl)-β- d -glucopyranosylamine (HEtGPA) and N , N -di(2-hydroxyethyl)-β- d -glucopyranosylamine (DHEtGPA). They were tested for their antifungal activity against the growth of Coriolus versicolor and Poria placenta . An improvement of the antifungal activity with the increase of alkyl chain length was observed. DoGPA exhibited the best antifungal activity against both strains. It completely inhibited the fungal growth at 0.01 × 10 −3 mol mL −1 and 0.0075 × 10 −3 mol mL −1 for C. versicolor and P. placenta , respectively. For other glucosylamines higher concentrations were needed for complete inhibition of fungi.

Resol type resins were prepared in alkaline conditions (potassium hydroxide or potassium carbonate) using furfural obtained by acid hydrolysis of abundant renewable resources from agricultural and forestry waste residues. The structures of the resins were fully determined by 1H, 13C, and 2D NMR spectrometries with the help of four models compounds synthesized specially for this study. MALDI-Tof mass spectrometry experiments indicated that a majority of linear oligomers and a minority of cyclic ones constituted them. Composites were prepared with furfural–phenol resins and sisal fibers. These fibers were chosen mainly because they came from natural lignocellulosic material and they presented excellent mechanical properties. Thermal analyses (dTG and DSC) and electron microscopy images indicated that the composites displayed excellent adhesion between resin and fibers. Impact strength measurement showed that mild conditions were more suitable to prepare thermosets. Nevertheless, mild conditions induced a high-diffusion coefficient for water absorption by composites. Composites with good properties could be prepared using high proportion of materials obtained from biomass without formaldehyde. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

International audience; Environmentally friendly and potentially bioactive food packaging based on chitosan-coated papers were elaborated. The morphology and the microstructure of these new materials were characterized by infrared spectroscopy and scanning electron microscopy. These observations suggested that the chitosan penetrated deeply into the paper, embedding the cellulose fibers, instead of forming a layer as expected. Through the barrier properties against moisture, the liquid water sensitivity, and NMR-relaxometry measurements, the water interactions were evaluated on the chitosan films and the chitosan-coated papers. They revealed that the coating by a chitosan film forming solution improved the paper moisture barrier properties but the surface hydrophilicity remained high. Relaxometry studies showed that, due to its hydrophilic character, chitosan controlled the interaction with water, despite the very low amount of deposit. On the other hand, the mechanical properties of papers were unmodified by the chitosan coating, which did not fundamentally affect the solid structure of the papers.

Steady-state fluorescence emission spectra of various celluloses were measured at an excitation wavelength of 320 nm. Various spectra recorded in the solid state were compared: (1) ECF bleached papers made of hardwood, the anhydroglucose units of which were chemically modified at C1 and C6 or C2 and C3 positions with carboxylic groups; (2) microcrystalline cellulose; (3) cotton linters; and (4) delignified sisal fibers (mercerized or not). Fluorescence emission was quite independent of the carboxylic acid content and average molecular weight (determined by viscosimetry) of the cellulose polymers. Microcrystalline cellulose (Avicel), cotton linters, and mercerized delignified sisal cellulose were acetylated in homogeneous medium (DMAc/LiCl as solvent system) to obtain soluble polymers in dichloromethane for comparison of spectra recorded in the solid and liquid states. Fluorescence of cellulose acetates in solution (CH2Cl2) and in the solid state was compared under similar experimental conditions to non-esterified celluloses in the solid state. The importance of the solid state for fluorescence emission could be demonstrated. Fluorophores are present in minute amounts in the polymer and their favorable energy transfer for excitation in the solid state likely enhances fluorescence emission. Among numerous fluorophores, dityrosine appeared to be a good candidate for fluorescence because it displayed emission in the fluorescence range of cellulose. Dityrosine is an amino acid involved in the lignification of non-woody plants. Mercerized sisal impregnated with tyrosine in the presence of peroxidase and hydrogen peroxide did not show enhanced emission, in contrast to para-hydroxycinnamic acid (coumaric acid), which is also involved in the lignification process at least for non-woody plants. The origin of cellulose fluorescence remains uncertain and appears to have several origins. This study clearly underlines the importance of the solid state for enhancing fluorophore emission.

International audience

A finite element model was developed to study the influence of aerial architecture on the structural dynamics of trees. The model combines a complete description of the axes of the aerial architecture of the plant with numerical techniques suitable for dynamic nonlinear analyses. Trees were modeled on the basis of morphological measurements that were previously made on three 4-year-old Pinus pinaster Ait. saplings originating from even-aged stands. Calculated and measured oscillations were compared to evaluate model behavior. The computations allowed the characteristics of the fundamental mode of vibration to be estimated with satisfactory accuracy. Inclusion of a topological description of the aerial system in a mechanical model provided insight into the effect of tree architecture on tree dynamic behavior. Simplifications of the branching pattern in the model led to overestimations of the natural swaying frequency of saplings by 10 to 20%. Inadequate values of stem and root anchorage stiffness resulted in errors of 10 to 20%. Modeling results indicated that aerodynamic drag of needles is responsible for 80% of the damping in the studied trees. Additionally, damping of stem movement is reduced by one half when branch oscillations are not considered. It appears that the efficiency of the dissipative mechanisms depends directly on crown topology.

present adress STOKES : UMR AMAP; International audience; Togolese teak (Tectona grandis L.f) is highly resistant to pathogen attack, but variability in natural durability exists between trees of different ages, plantations and geographical zones. Therefore, further information concerning this parameter of wood quality is necessary; however, traditional testing methods are difficult and time-consuming to carry out. We tested the possibility of using colorimetry to determine durability in heartwood samples taken from a wide range of trees. Twelve hundred samples from 31 trees were exposed to four fungi: Pycnoporus sanguineus, Antrodia sp., Gloephylum trabeum, and Coriolus versicolor. Wood samples were grouped into three classes (inner, intermediate and outer heartwood). The colour parameters of each sample were then determined using the CIELAB (L*, a*, b*) system and results correlated with the %mass loss of wood after fungal attack. Tests showed that Antrodia sp. and C. versicolor resulted in

To determine if trees respond to dynamic and static loading in the same manner, 2-year-old maritime pine (Pinus pinaster Ait.) trees were subjected to different types of mechanical loading in the field. One block of trees (the control) were kept in pots and planted in the field at an angle of 0 or 45 degrees to the vertical. A similar block of leaning potted trees was planted nearby and subjected to frequent, unilateral wind loading for a period of 1 s every 2 min. Half the leaning trees were oriented toward the direction of wind loading and half were oriented along the axis of wind loading. The stem profile was measured three times during the growing season to quantify the rate of stem straightening. Compression wood formation and stem shape were measured in all plants. No differences in mean height or diameter were observed between blocks and all leaning trees straightened, but not at the same rate. Although no difference in the rate of apical straightening occurred between control and wind-treated trees, the righting response of the basal part of the stem of leaning trees subjected to wind was four times greater than that of leaning trees without wind. No differences in the righting response were observed between leaning trees growing toward and trees growing away from the source of wind. No significant differences in compression wood formation were found between control trees and wind-treated trees, indicating that other factors must determine the reorientation rate of leaning trees. Results are discussed with reference to the quality of compression wood in conifers and the mechanotransductive pathway in plants.

International audience; In order to determine the mechanical resistance of several forest tree species to rockfall, an inventory of the type of damage sustained in an active rockfall corridor was carried out in the French Alps. The diameter, spatial position and type of damage incurred were measured in 423 trees. Only 5% of trees had sustained damage above a height of 1.3 m and in damaged trees, 66% of broken or uprooted trees were conifers. Larger trees were more likely to be wounded or dead than smaller trees, although the size of the wounds was relatively smaller in larger trees. The species with the least proportion of damage through stem breakage, uprooting or wounding was European beech (Fagus sylvatica L.). Winching tests were carried out on two conifer species, Norway spruce (Picea abies L.) and Silver .r (Abies alba Mill.), as well as European beech, in order to verify the hypothesis that beech was highly resistant to rockfall and that conifers were more susceptible to uprooting or stem breakage. Nineteen trees were winched downhill and the force necessary to cause failure was measured. The energy (Efail) required to break or uproot a tree was then calculated. Most .r trees failed in the stem and spruce usually failed through uprooting. Beech was either uprooted or broke in the stem and was twice as resistant to failure as .r, and three times more resistant than spruce. Efail was strongly related to stem diameter in European beech only, and was signi.cantly higher in this species compared to Norway spruce. Results suggest that beech would be a better species to plant with regards to protection against rockfall. Nevertheless, all types of di.erent abiotic stresses on any particular alpine site should be considered by the forest manager, as planting only broadleaf species may compromise the protecting capacity of the forest e.g. in the case of snow avalanches. In order to determine the mechanical resistance of several forest tree species to rockfall, an inventory of the type of damage sustained in an active rockfall corridor was carried out in the French Alps. The diameter, spatial position and type of damage incurred were measured in 423 trees. Only 5% of trees had sustained damage above a height of 1.3 m and in damaged trees, 66% of broken or uprooted trees were conifers. Larger trees were more likely to be wounded or dead than smaller trees, although the size of the wounds was relatively smaller in larger trees. The species with the least proportion of damage through stem breakage, uprooting or wounding was European beech (Fagus sylvatica L.). Winching tests were carried out on two conifer species, Norway spruce (Picea abies L.) and Silver .r (Abies alba Mill.), as well as European beech, in order to verify the hypothesis that beech was highly resistant to rockfall and that conifers were more susceptible to uprooting or stem breakage. Nineteen trees were winched downhill and the force necessary to cause failure was measured. The energy (Efail) required to break or uproot a tree was then calculated. Most .r trees failed in the stem and spruce usually failed through uprooting. Beech was either uprooted or broke in the stem and was twice as resistant to failure as .r, and three times more resistant than spruce. Efail was strongly related to stem diameter in European beech only, and was signi.cantly higher in this species compared to Norway spruce. Results suggest that beech would be a better species to plant with regards to protection against rockfall. Nevertheless, all types of di.erent abiotic stresses on any particular alpine site should be considered by the forest manager, as planting only broadleaf species may compromise the protecting capacity of the forest e.g. in the case of snow avalanches.

The microstructure of fibrous networks in low density wood-based fibreboards elaborated with various processes is observed by X-ray tomography. Image analysis tools derived from mathematical morphology are used to process 3D images obtained and to recover 3D information on the fibres and the fibre network. A 3D model of random fibre networks developed by means of experimental information is presented. The parameters of the model correspond to internal architecture properties. Their influence on a local thermal conductivity is studied through finite element method.

Windthrow hazard of single trees and tree stands is assessed using a Decision Support System (DSS) created using ConFound©, a shell originally created for usage in geotechnics. Expert data consisting of (un)successful practices in windthrow prevention and mitigation, together with data available in the literature were combined to produce rules that will offer help and advice to end-users. The factors influencing tree stability are reviewed and discussed, together with the approach taken when constructing the frames of this DSS. The adaptation of windthrow hazard assessment methods from the UK and British Columbia to suit a user-friendly application are explained. The structure of the knowledge base on which the DSS is based is also explained in detail, together with the hierarchy of the project specific information that the user must enter in order to receive advice on the hazards pertaining to the site in question, as well as on the ways of their mitigation. The practical application of this DSS is illustrated through appropriate case studies, and the output is discussed. The target audience and the areas of application are reviewed and strategies for further development in this area are also suggested.

The arrangement of a plant's roots in the soil determines the ability of the plant to resist uprooting. We have investigated the influence of root morphology on anchorage using simple patterns of root systems and numerical simulation. The form and mechanical properties of roots were derived from results found in the literature. Major parameters determining soil characteristics, root patterns and strength were varied so that their influence could be evaluated. The design of the experimental method we used generated an optimal number of configurations of different root systems, the tensile resistances of which were calculated by two-dimensional finite element analysis. We could quantify the influence of specific parameters, e.g. branching angle, number of lateral roots and soil cohesion, as well as global parameters such as total contact area, basal diameter and volume of the whole root system. We found that the number of roots and the diameter of roots were major components affecting the resistance to uprooting. The combination of topology and biomass explained 70% of the variation of tensile resistance.

From load-unloading cycles applied on wood notched specimens subjected to three-point bending, we show that the concept of ‘equivalent LEFM’, usually used for the quasibrittle materials, can be successfully applied to the fracture behavior of wood in mode I. Within this equivalent linear elastic framework, the quasibrittle fracture behavior of wood leads to an R-curve which is evaluated and discussed. On the other hand, the estimate of the peak load (or maximum load) of a structure as a function of the corresponding R-curve is an important problem for a building material such as wood. After a review of some general results about the connection between the R-curve and the shape of the load-deflection curve, we propose a single equation, i.e., valid for a fracture test under load-control or displacement-control, allowing to estimate the crack length corresponding to every extremum of a load-deflection curve.

Vetiver grass (Vetiveria zizanioides), also known as Chrysopogon zizanioides, is a graminaceous plant native to tropical and subtropical India. The southern cultivar is sterile; it flowers but sets no seeds. It is a densely tufted, perennial grass that is considered sterile outside its natural habitat. It grows 0.5–1.5 m high, stiff stems in large clumps from a much branched root stock. The roots of vetiver grass are fibrous and reported to reach depths up to 3 m thus being able to stabilize the soil and its use for this purpose is promoted by the World Bank. Uprooting tests were carried out on vetiver grass in Spain in order to ascertain the resistance the root system can provide when torrential runoffs and sediments are trying to uproot the plant. Uprooting resistance of each plant was correlated to the shoot and root morphological characteristics. In order to investigate any differences between root morphology of vetiver grass in its native habitat reported in the literature, and the one planted in a sub-humid environment in Spain, excavation techniques were used to show root distribution in the soil. Results show that vetiver grass possesses the root strength to withstand torrential runoff. Planted in rows along the contours, it may act as a barrier to the movement of both water and soil. However, the establishment of the vetiver lags behind the reported rates in its native tropical environment due to adverse climatic conditions in the Mediterranean. This arrested development is the main limitation to the use of vetiver in these environments although its root strength is more than sufficient.

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Contrairement a beaucoup d'arbres feuillus, le bois de reaction des Eucalyptus n'est pas caracterise par les fibres G. Il peut cependant etre caracterise par ses deformations de maturation. La mesure des deformations residuelles longitudinales de maturation (DRLIVI) par relaxation de contraintes en peripherie des troncs a permis un classement continu et quantitatif d'echantillons de bois de clones crEucaetus hybrides du Congo. Ce type de mesure permet d'identifier mecaniquement le bois de tension. Les relations entre structure et proprietes mecaniques de ces bois ont ete etudiees par une analyse ultrastructurale et chimique des echantillons, en particulier par l'examen de la composition monomerique des lignines par thioacidolyse. Les resultats presentes ici montrent qu'il existe : i) une forte variabilite des DRLM avec des valeurs elevees, mome sur nos arbres peu penches et peu excentres, et malgre l'absence de fibres G ; ii) une correlation negative entre le niveau de DRLM, le taux de lignines et l'angle des microfibrilles de cellulose, iii) une correlation positive entre le niveau de DRLM et le rapport des taux de monomeres de lignines: unites syringyles 1 unites guaiacyles. La signification de ces correlations est discutee (causalite mecanique directe ou correlations plus complexes entre variables structurales). (Resume d'auteur)

International audience; The spread of a pathogen within an anthropized crop plot depends on many factors acting at contrasted spatio-temporal scales. This is of paramount importance for vine and powdery mildew, one of its airborne pathogen. We aimed at developing a coupled PDEs-ODEs model for plant-pathogen interactions at the plot scale level in order to assess the effects of various host heterogeneities on the epidemic spread.

Many engineering applications suffer from the ignorance of mechanical parameters. It is particularly true when soil model is necessary to assess soil behaviour [Meieret al., 2008]. Nevertheless, it is not always efficient to directly assess the values of all the parameters in the case of soil mechanics. Considering structural mechanics, [Li et al., 2007] also worked to propose an optimal design of a truss pylon respecting the stress constraints of the elements but it is not an easy task to solve considering the number and loading of the structure. Inverse analysis is an efficient solution to reach these aims. This technique becomes more and more popular thanks to the increase of the computing capabilities. Computing costs have decreased and allow to handle complex optimization problems through meta heuristic methods for example to identify the solution of the problem like the mechanical parameters of a behaviour model of a soil [Fontan et al., 2011, Levasseur et al., 2008], to define the best section of the beams composing a truss structure or to optimize wood-plastic composite mechanical properties designed for decking and taking into account the environmental impact during the life cycle of the product [Ndiaye et al., 2009]. The literature about inverse analysis is very rich and it covers many application fields like management or mechanical science as attesting the table number 1 in [Fontan et al., 2011] which presents several civil engineering applications (this table is not presented there). Most of the authors mentioned in this paper used the concept of inverse analysis to identify parameters either in structural mechanics [Li et al., 2007, Fontan 2011] or soil mechanics [Meier et al., 2008, Levasseur et al., 2008]. They were just using different mechanical models (analytical or numerical) or different algorithms to solve their problem (PSO, descent gradient, ant colony, genetic algorithm, etc.). Inverse analysis is based on the simple concept of solving an equation to find the n values Xn respecting equation 1, with M: the mechanical model corresponding to the real behaviour of the analysis and Ym: the m measurement carried out on site.

International audience; This paper deals with a numerical NDT method to identify mechanical parameters by inverse analysis using the particle swarm optimization algorithm. This method is using a finite element model of the structure to study in order to minimize the error between field data and data predicted by the FE model. The method is applied in the case of a laboratory experiment modelling a soil–structure interaction problem. Results stress the impact of the sensitivity of the solution to the accuracy of field measurements by simulating both different levels of measurement noise on data and using several placements of sensors.

Background Eucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal. Several breeding programmes have been launched worldwide to concomitantly improve growth performance and wood properties (WPs). In this study, an interspecific cross between Eucalyptus urophylla and E. grandis was used to identify major genomic regions (Quantitative Trait Loci, QTL) controlling the variability of WPs. Results Linkage maps were generated for both parent species. A total of 117 QTLs were detected for a series of wood and end-use related traits, including chemical, technological, physical, mechanical and anatomical properties. The QTLs were mainly clustered into five linkage groups. In terms of distribution of QTL effects, our result agrees with the typical L-shape reported in most QTL studies, i.e. most WP QTLs had limited effects and only a few (13) had major effects (phenotypic variance explained > 15%). The co-locations of QTLs for different WPs as well as QTLs and candidate genes are discussed in terms of phenotypic correlations between traits, and of the function of the candidate genes. The major wood property QTL harbours a gene encoding a Cinnamoyl CoA reductase (CCR), a structural enzyme of the monolignol-specific biosynthesis pathway. Conclusions Given the number of traits analysed, this study provides a comprehensive understanding of the genetic architecture of wood properties in this Eucalyptus full-sib pedigree. At the dawn of Eucalyptus genome sequence, it will provide a framework to identify the nature of genes underlying these important quantitative traits.

Summary Peripheral longitudinal growth stresses measurement discloses the mechanical state of the last xylem cells differentiated from cambium. The occurrence of a strain peak is generally an indication of a reorientation movement of the stem. However, it is not a rare occurrence to obtain some more complicated strain profiles. “Organisation pattern”, a new architectural concept developed by Edelin (1991), seems pertinent to “unusual” profiles analysis. This idea is illustrated through exemples from temperate and tropical monopodial and sympodial trees.

Diplôme : Dr. d'Université; The forest cultivation techniques of maritime pine in the South Western France deeply changed in the 1970’s. In particular the reforestation method shifted from assisted natural regeneration to intensive techniques including soil ploughing, phosphoric fertilization and seeding, then plantation with improved material in the 1980’s. As the proportion of “intensively cultivated” stands in final cut will increase drastically in the next decades, it is now necessary to anticipate the impact of these reforestation methods on the wood properties for the wood industry, from the analysis of the oldest.Trees were sampled from 14 stands in the South Western France covering a wide range of mean volume. On each stand, 4 trees were selected for physical properties measurement. Within ring wood density, latewood content, heartwood diameter and spiral grain angle were measured on wood disks collected at different heights within each tree. At the same time 8 trees were harvested and bucked into 2.2 m long logs. After drying, visual aspect and mechanical properties of the sawn boards were assessed.Based on the data, deterministic models were developed to predict the variables based on selected stand and tree characteristics. The models for heartwood content in cross section explain quite well the variation with height (more than 70% of the variation). The heights of green and dead branches were identified as important variables in the models for nature of knot in trees. The developed models, for spiral grain angle, radial variations of wood density and mechanical properties, have a relatively low level of prediction, but it has highlighted the effect of cambial age and ring width on these properties. The growth rate has so a negative impact on the mechanical properties of wood of maritime pine. Based on the mixed model analysis with repeated measurements structure, the trees and stand effect on the residual variation were estimated. Applied on silvicultural scenarios, these models have been used in a simplified approach to estimate the strength of timber that can potentially be obtained from the resource. The transfer of these models with forest managers could allow a better estimate of the quality of wood, and thus a better allocation in a post-storm context where the resource is scarce.; Les techniques de culture du pin maritime dans les Landes de Gascogne ont connu des changements importants à partir des années 1960. A côté de peuplements de sylviculture traditionnelle basée sur la régénération naturelle assistée, se sont succédés de nouveaux types de peuplements sous le vocable de « ligniculture ». La proportion de ces peuplements menés intensivement, dans la récolte des coupes rases en Aquitaine, va augmenter rapidement dans les dix prochaines années. Les données technologiques faisant actuellement défaut sur cette ressource, il est nécessaire d’anticiper dès aujourd’hui l’impact de ces pratiques sylvicoles sur les propriétés du bois.Des arbres ont été échantillonnés dans 14 parcelles réparties dans les Landes de Gascogne. Sur chaque parcelle, 4 arbres ont été sélectionnés pour les mesures des propriétés physiques. Les variations radiales de densité intra-cerne, de proportion de bois final, de duramen et d’angle du fil ont été mesurées. Parallèlement 8 arbres ont été exploités. Après sciage puis séchage, l’aspect visuel et les propriétés mécaniques des avivés obtenus ont été mesurés. Sur la base des données recueillies et de données d’études précédentes, des modèles déterministes ont été développés pour prédire les variations des caractéristiques étudiées. Ces modèles de la famille des modèles mixtes, sont constitués d’une partie « fixe » commune à l’ensemble des arbres et d’une partie aléatoire qui quantifie les écarts propres à la parcelle et aux arbres (appelés effet « parcelle » et effet « arbre »). Un modèle décrivant les variations avec la hauteur dans l’arbre du taux de duramen, basé sur l’âge des arbres a été développé, il explique plus de 70% de la variation. Les modèles décrivant les variations radiales de l’angle du fil, de la densité, et des propriétés mécaniques du bois ont un niveau de prédiction plus faible, mais un effet significatif de l'âge cambial et de la largeur de cerne sur ses propriétés a été mis en évidence. La vitesse de croissance a un impact négatif sur les propriétés mécaniques du bois de pin maritime.Appliqué à des scénarios sylvicoles ces modèles ont permis d'estimer le classement mécanique des sciages pouvant potentiellement être obtenus à partir de la ressource.Le transfert de ces modèles auprès des gestionnaires forestier pourrait permettre une meilleure estimation de la qualité des bois et donc leur meilleure allocation dans un contexte post tempête où la ressource en pin maritime en Aquitaine se fait rare.

Special Issue: Vegetation and Slope Stability; International audience; The influence of plant diversity on slope stability was investigated at early phases of succession in a mixed forest in Sichuan, China. The first phase comprised big node bamboo (Phyllostachys nidularia Munro) only. In the second phase, bamboo co-existed with deciduous tree species and in the third phase, deciduous species existed alone. Root density at different depths and root tensile strength were determined for each species. The factor of safety (FOS) was calculated for slopes with and without vegetation for each succession phase. For phase 2, FOS was determined for different species mixtures and positions. In phase 3, simulations were performed with a single tree at the top, middle or toe of the slope. Due to its shallow root system, bamboo contributed little to slope stability. In simulations with the tree at the top or middle of the slope, FOS decreased because tree weight added a surcharge to the slope. FOS increased with the tree at the bottom of the slope. Different mixtures of species along the slope had no influence on FOS. Differences in root tensile strength between species played a small role in FOS calculations, and tree size and density were the most important factors affecting slope stability, excluding hydrological factors

National audience

International audience; A method was developed to study the modifications of volume and shape of wheat flour dough during fermentation process by digital camera Various compositions and mixing conditions were Implemented in order to prepare dough pieces with different theological properties Results were analyzed in terms of porosity and stability defined as the shape ratio of the dough The kinetics of the two variables were fitted by simple mathematical models Porosity evolution was a lot influenced by the composition of the dough and results were found in agreement with those obtained by X-Ray Microtomography but less by the mixing conditions Conversely the stability was favoured by larger levels of specific mixing energy in the range (20 60 kJ/kg) The interpretation of these results suggested that gas production is the main variable governing expansion kinetics whereas theological properties mainly strain hardening has the most significant role on stability

International audience; A trimeric beta-O-4 lignin model bearing a styrene unit was polymerized in the presence of azobisisobutyronitrile as an initiator of free radical polymerization. The polymer analysis achieved by size exclusion chromatography (SEC), H-1, C-13, P-31 NMR, matrix-assisted laser desorption ionization combined with time-of-flight mass spectrometry (MALDI-ToF MS), differential scanning calorimetry, and thermogravimetry indicated its well-defined structure with good thermal stability at temperatures usually applied for alkaline pulping. SEC analysis proved a high degree of polymerization despite the size of the phenolic beta-O-4 units in the polymer structure. MALDI-ToF spectrometry indicated that the polymer is composed of phenolic beta-O-4 elements only. The chemical reactivity under alkaline conditions of the polymer was studied by both HPLC and P-31 NMR. These two methods revealed two main concurrent processes, which include an oxidation of the phenol part followed by C-alpha-C-beta bond cleavage, and formation of a quinone methide followed by its beta-O-4 bond cleavage.

National audience

National audience; In this work, we focus on a thermal insulating panel made of wood fibres. The making process is a non-woven fabric process that generates a high porosity and a very lowdensity material. Thermal properties were first investigated. This paper deals with mechanical properties that are involved in the production line, transport and handling in the construction site. An insulating panel was compressed (33% and 73%) and we followed in situ its internal deformation using X-ray microtomography. The results enlighten a special behaviour that is linked to the low-density structure of the panel. In particular, the fibres are not compressed and the macroscopic deformation of the sample generates only a new organisation of the fibres in the panel. These results are confirmed by morphological measurements that were performed by 3D image analysis.; On s'intéresse à des isolants thermiques à base de fibres de bois utilisés dans le bâtiment, de très forte porosité, élaborés par un procédé textile non tissé. Les propriétés thermiques ont fait l'objet des premières études et les propriétés mécaniques, intervenant lors du transport et de la manipulation, font l'objet de ce travail. Nous avons suivi in situ, grâce à la microtomographie X, les états de déformation interne d'un panneau d'isolation soumis à une sollicitation de compression transverse (33 % et 73 %). Le comportement particulier mis en lumière par l'accès à la déformation locale est relié à la très faible densité du matériau. En particulier, les fibres de bois ne sont pas individuellement mécaniquement comprimées et la déformation macroscopique du matériau n'engendre que leur réorganisation spatiale. Ces résultats sont mis en relation avec des caractéristiques morphologiques de structures évaluées par analyse d'image 3D.

International audience; The wearing course is the top surface layer of the road. The road surface has multiple functions the main one being traffic safety, which is conditioned by skid resistance. This skid resistance is conditioned by pavement texture. This paper presents an experimental procedure allowing to evaluate surface macrotexture evolution of an asphalt concrete specimen by laboratory testing. Specimen surface changes through the application of a sinusoidal repeated load at high temperature. The studied surface is scanned before and after mechanical testing using a laser profiler. Texture maps are analysed using Abbott curve which is also called bearing ratio curve. The 3D analysis enables to quantify macrotexture evolution under repeated traffic conditions and to analyze the influence of both temperature and binder.

Diplôme : Dr. d'Université; Au cours de cette étude, une méthode inédite de fonctionnalisation chimique de la matière lignocellulosique a été développée. Des groupes acyles de taille et de fonctionnalité variées ont ainsi été greffés à l’intérieur du bois, grâce à une réaction de transestérification entre les esters d’énol et les groupes hydroxyles des polymères lignocellulosiques. Les greffages ont été confirmés grâce aux spectroscopies infrarouge et RMN du 13C en phase solide. La stabilité dimensionnelle du bois acétylé à partir de l’acétate de vinyle ainsi que sa résistance aux attaques fongiques a été également évaluée, de même que la photostabilité du bois estérifié à partir des esters de vinyle aromatiques.

International audience; In this paper, we investigate a problem of qualitative modelling of a multi-step food process, French breadmaking. The French breadmaking process has been represented as a sequence of steps where each step is defined through its control variables, the state variables of its output, and the causal relations between the control and state variables. In addition, the output of a step is the input of the followed step, and then, the state variables of one step depend on its control variable and the state variables of its input. A qualitative model of mixing, certainly the most complex operation of breadmaking process, has been built up. Human experts reasoning has been represented through seven cognitive operations and a qualitative algebra (Q, approximate to, circle plus, circle times)has been defined to model the calculation of state variables of mixed dough from the mixing control variables and the ingredients (the mixing input) condition. The relations well known by the human experts and other relevant relations between state variables of the mixed dough have been found out through the qualitative equations established. The mixing model has been implemented using the QualiS(C) expert-system shell. The score established according to French standard of the dough after the mixing step was compared to the one computed. In most of the 81 cases simulated, satisfactory results were obtained since the only unfavourable cases had never been experimented by the experts before, which finally validated this approach, thus worth to be extended to the following steps of breadmaking process.

National audience

International audience; This article addresses the optimization of the quality of wood—plastic composites (WPC) designed for outdoor uses such as decking, taking into account the environmental impact during the life cycle of the product, from production to end of life (from ground to ground). In a context where several conflicting objectives must be satisfied simultaneously in the design process, meta-heuristic approaches provide efficient methods for optimization. Multi-objective particle swarm optimization (MO-PSO) has been chosen here to solve a complex problem in which physical properties such as creep and duration of load, water absorption and swelling, need to be improved with a limited impact on environment. This requires to get reliable information on material properties as related to its composition, environmental impacts through life cycle analysis (LCA), and to implement relevant information such as exhaustion of fossils resources through analytical or probabilistic models in the PSO algorithm in order to obtain a set of optimal solutions for the composite. This article shows the feasibility of this approach, which can be generalized in the design of any type of composite structures, provided objective functions can be specified.

International audience; This paper deals with the combination of radar technology and artificial neural networks (ANN) for the non-destructive evaluation of the water and chloride contents of concrete. Two networks were trained and tested to predict these concrete properties. Input data to the statistical models were extracted from time-domain signals of direct and reflected radar waves. ANN training and testing were implemented according to an experimental database of 100 radar measurements performed on concrete slabs having various water and chloride contents. Both networks were multi-layer-perceptrons trained according to back-propagation algorithm. The results of this research highlight the potential of artificial neural networks for solving the inverse problem of concrete physical evaluation using radar measurements. It was found that the optimized statistical models predicted water and chloride contents of concrete laboratory slabs with maximum absolute errors of about 2% and 0.5 kg/m3 of concrete, respectively.

International audience; In this paper, an Artificial Neural Network (ANN) is proposed for modelling the bond between conventional ribbed steel bars and concrete. The purpose is to predict the ultimate pull-out load from the concrete mix constituents (first ANN model) or the compressive strength (second ANN model) and from the steel bar diameter according to the RILEM test configuration [RILEM. Essai portant sur l’adhérence des armatures du béton: essai par traction. Materials and Structures 1970; 3 (3) 175–78]. The ANN models were implemented using an experimental database of 112 pull-out test results performed with ribbed bars 10 mm or 12 mm in diameter and three concrete mixes with different constituent proportions. A Multi-Layer-Perceptron was trained according to a back-propagation algorithm. The first model has six inputs (ANN-6): the diameter of the ribbed bar, the water to cement ratio, the gravel to sand ratio, the crushed to rolled gravel ratio, the type of cement and the concrete maturity. The second model has two inputs (ANN-2): the diameter of the bar and the concrete compressive strength. The ultimate pull-out load was the output data for both models. The results show that the implemented models have good prediction and generalisation capacity with low errors. The ANN-6 model is more accurate, regarding the generalisation capacity, than the ANN-2 model. Concrete mix constituents as input parameter, instead of the compressive strength, are more representative of the local phenomenon at the steel-ribs-to-concrete interface.

National audience; Plusieurs expérimentations ou observations, du semis à l'arbre de grande taille nous ont permis d'établir que des stimulations mécaniques sur le tronc, transmis aux racines, avaient un impact important sur le développement du système racinaire. Et ceci non seulement sur sa biomasse, mais aussi sur l'architecture. A partir d'un modèle architectural relativement stable, l'arbre renforce ainsi sélectivement les segments de racine qui lui permettent d'optimiser la résistance au déracinement. Les arbres adaptent aussi leur système racinaire à la profondeur de sol disponible, à la présence d'un horizon induré ou à une pente. Dans ce dernier cas, on observe une interaction entre géométrie du sol et perturbation mécanique. Enfin, les provenances de pin maritime de la côte atlantique française ont une architecture racinaire à 5 ans (pivot unique et renforcé), leur permettant de mieux résister au vent que les autres provenances de l'aire. La variabilité d'origine génétique intra-population est en revanche faible. Il y aurait donc un effet de sélection naturelle à l'échelle de l'aire de répartition, mais peu de possibilité de sélection à l'intérieur des provenances. [il s'agit d'une synthèse des résultats acquis à Bordeaux pendant une dizaine d'années sur les effets des stimulations mécaniques sur l'architecture des racines de structure, déjà présenté en partie à un séminaire CAQ + une partie présentée à un colloque COST en mai dernier]

On s’intéresse à des isolants thermiques à base de fibres de bois utilisés dans le bâtiment, de très forte porosité, élaborés par un procédé textile non tissé. Les propriétés thermiques ont fait l'objet des premières études et les propriétés mécaniques, intervenant lors du transport et de la manipulation, font l'objet de ce travail. Nous avons suivi in-situ, grâce à la microtomographie X, l'état de déformation interne d'un panneau d'isolation soumis à une sollicitation de compression transverse (33%). Le comportement particulier mis en lumière par l'accès à la déformation locale est relié à la très faible densité du matériau. En particulier, les fibres de bois ne sont pas comprimées et la déformation macroscopique du matériau n'engendre que leur réorganisation spatiale. Ces résultats sont mis en relation avec des caractéristiques morphologiques de structures évaluées par analyse d'image 3D., In this work, we focus on a thermal insulating panel made of wood fibres. The making process is a non-woven fabric process that generates a high porosity and a very lowdensity material. Thermal properties were first investigated. This paper deals with mechanical properties that are involved in the production line, transport and handling in the construction site. An insulating panel was compressed (33%) and we followed in-situ its internal deformation using X-ray microtomography. The results enlighten a special behavior that is linked to the low-density structure of the panel. In particular, the fibres are not compressed and the macroscopic deformation of the sample generates only a new organisation of the fibres in the panel. These results are confirmed by morphological measurements that were performed by 3D image analysis.

International audience; Chitosan was chemically modified to produce quaternary ammonium salts in order to improve its antimicrobial activity and physicochemical properties. Quaternization of N-alkyl chitosan derivatives was carried out using alkyl iodide to elaborate water-soluble cationic polyelectrolytes (N,N,N-trimethylchitosan, TMC). TMC was characterized by 1H NMR spectroscopy; the quaternization degree was determined from 1H NMR spectra and by titration of iodide ion. The antibacterial activity of hydroxypropylcellulose (HPC) films or coatings associated with chitosan or TMC as biocide was evaluated against the growth of Listeria monocytogenes and Salmonella typhimurium. The HPC−chitosan and HPC−TMC coatings exhibited a total inhibition on solid medium of both bacterial strains. Experiments conducted in liquid medium showed that the inhibitory activity against the growth of Listeria innocua was improved after chemical modification. Moreover, physicochemical properties of films were evaluated to determine their potential for food applications. The addition of the antibacterial agents showed a significant impact on the moisture barrier and mechanical properties of HPC films.

Diplôme : Dr. d'Université; This work concerns the mechanical testing, numerical analysis and modelling of cohesive fracture (Mode I) on the purpose to study the Resistance-curve behaviour and the size effect in wooden notched structures. The mechanical testing is combined with the numerical analysis to evaluate fracture properties by means of an equivalent LEFM approach based on the structure compliance. The Resistance-curve being revealed from the experiments, by means of a self-weight compensation method, correction puts into evidence that a non-negligible damaged domain (Fracture Process Zone) is under development in the crack front during the loading process. This being the case, among other fracture parameters issued from the Resistance-curve, the critical (asymptotic) energy release rate is determined, turning possible to use it in combination with other cohesive crack properties in the crack modelling (in Mode I). Thus, for a given geometry it is possible to monitor the critical dimension being revealed by the Fracture Process Zone (FPZ) during the crack propagation. The well known Bažant’s size effect law provides the scaling of the nominal strength through the asymptotic matching performed both on the small (Strength Theory) and on the large (LEFM) structure sizes. An analytical procedure is proposed to determine an additional asymptotic regime in the intermediate size range through a more accurate manner. Numerical validations of the proposed procedure are made and experimental data is presented revealing the scaling of the nominal strength through an envelop of values.; Ce travail concerne des expériences mécaniques, des analyses numériques et des modélisations analytiques de la rupture cohésives (Mode I), vis-à-vis de l’étude du comportement mis en évidence par la courbe de Résistance (Courbe-R) et l’effet d’échelle de structures entaillées en bois massif. Des expériences de fissuration sont combinées à des analyses numériques pour déterminer les propriétés de rupture au moyen d’une procédure appelée Théorie de la Mécanique de la Rupture Linéaire Élastique équivalente (TMRLE), basée sur la complaisance de la structure. La courbe-R, obtenue à partir des expériences, selon une méthode de correction du poids propre, montre l’existence d’un domaine endommagé (Zone de Processus de Rupture) de taille non négligeable se développant en fond de fissure. Dans des conditions de fissuration stationnaire, ce domaine atteint une taille critique, et l’énergie nécessaire pour faire propager la fissure avec ce domaine endommagé (par unité de surface de rupture), reste constante. Le taux de libération de l’énergie de fissuration ainsi attendu, joue un rôle important en Mécanique de la Rupture, car il est possible simuler le comportement quasi-fragile du matériau en combinaison avec les autres propriétés de cohésion. La loi d’effet d’échelle de Bažant, utilisée pour prévoir l’influence de la taille sur la contrainte nominale, est estimée à partir de la réunion de deux comportements asymptotiques réalisés sur de petites tailles (Analyse limite ou RdM) et des grandes tailles. Une procédure analytique est présentée pour évaluer le comportement asymptotique additionnel exhibé par la contrainte nominale dans le régime intermédiaire, de façon plus exacte. Une validation numérique est présentée, et l’information expérimentale vient confirmer ce comportement asymptotique.

International audience; To prevent the development and spread of spoilage and pathogenic microorganisms via meat foodstuffs, antimicrobial packaging materials could be a potential alternative solution. Instead of mixing antimicrobial compounds directly with food, incorporating them in films allows the functional effect at the food surface - where the microbial growth is mostly found - to be localized. Antimicrobial packagings include systems such as adding a sachet into the package, dispersing bioactive agents in the packaging, coating bioactive agents on the surface of the packaging material, or utilizing antimicrobial macromolecules with film forming properties or edible matrices. The potential of these technologies are evaluated for the preservation of meat and meat products.

International audience; In this paper we present a functional representation of human expert reasoning throughout its statements when assessing the condition of a given object. The human expert statements are represented as conjunctions of elementary propositions. We demonstrate that the conjunctions of elementary propositions can be represented as qualitative additions of qualitative functions in the Q-algebra (Q, ≈, ⌖, ). We validate our functional representation by formalizing a representative human expert reasoning: assessment of dough condition in function with the ingredients characteristics.

International audience; Within the framework of Bažant’s theory, the size effect on the ultimate fracture properties of notched structures is studied from an energy based asymptotic analysis in which the resistance curve behavior is considered through an analytic expression. The scaling on the relative crack length at peak load as well as the size effect on the corresponding resistance to crack growth are investigated. It is shown that, for intermediate structure sizes, the relative crack length at peak load decreases with respect to the structure size while the resistance grows. These scalings lead to a size effect on nominal strength which is in agreement with Bažant’s Size Effect Law (SEL) for small and large structures sizes, but for intermediate sizes, an additional asymptotic regime occurs instead of a simple crossover regime as expected in SEL. The slope and the extent in size of the additional asymptotic regime depend only on the exponent characterizing the curvature of the R-curve. The comparison between the resulting size effect and Bažant’s SEL shows that SEL provides an approximate size effect which is in agreement with the expected asymptotic behaviors, with the exception of the extreme cases corresponding to very strong and slight R-curve’s curvatures. On this basis, the safety design of large structures is discussed.

International audience; In the present work fracture (Mode I) was induced through three point-bending tests in two wood species used in timber construction: Maritime pine (Pinus pinaster Ait.) and Norway spruce (Picea abies L.). Load–displacement curves were experimentally determined and corresponding Resistance-curves (R-curves) obtained using an equivalent linear elastic approach. An inverse method is presented to identify cohesive crack properties of a cohesive crack bilinear model used to simulate fracture in both wood species, combining experimental data and a developed genetic algorithm. Good agreement between numerical and experimental load–displacement and R-curves was obtained. Conclusions are drawn from finite element simulations regarding the extent of the numerical cohesive zone computed for each studied wood.

International audience; The specific C-6 oxidation by TEMPO of chitosan and chitosan derivatives were studied to obtain tailored bioactive biopolymers. The modifications on chitosan presented many difficulties and showed the adverse effect of the amine moieties of chitosan on this reaction. Thus, protections of the amino groups by N-acetylation or N-phthaloylation were studied and followed by the C-6 specific oxidations of the resulting polymers. The desired 6-carboxychitosan could not be obtained after deprotection; the reactions with TEMPO led to degradation of the polymers. The specific oxidation of a potentially bioactive derivative of chitosan was then achieved by the oxidation of a quaternized chitosan: N,N,N-trimethylchitosan. N,N,N-Trimethyl-6-carboxychitosan was characterized by FTIR spectroscopy, 1H, and 13C NMR spectroscopy.

International audience; A novel route to wood modification by transesterification of vinyl esters is developed in the current study. The reaction between varied saturated and unsaturated vinyl esters and the hydroxyl groups of maritime pine sapwood (Pinus pinaster Soland) was examined using potassium carbonate as a catalyst. The esterification of wood was investigated by weight percent gain calculations (WPG), Fourier-transform infrared spectroscopy (FTIR) and 13C cross-polarization with magic-angle spinning nuclear magnetic resonance spectroscopy (13C CP–MAS NMR). Differences in the rates of modification were noted, depending on the vinyl ester used, but relatively high yields were obtained in all cases. The infrared and NMR spectra of the different esterified samples were analysed in detail and the assignment of the signals corresponding to the grafted acyl groups confirmed that esterification occurred.

Diplôme : Dr. d'Université; In this study different glucosylamines and amino desoxyglucoses were synthesized and characterised using various spectroscopic methods including IRFT, both 1H and 13C NMR spectroscopy and MALDI-Tof MS. Biological assessment of these compounds realised with two wood decay fungi, Coriolus versicolor and Poria placenta on one hand, and with three food microorganisms Listeria innocua, Salmonella typhimurium and Fusarium proliferatum on other hand, indicated a positive impact of both N-alkylation and degree of N-substitution and quaternisation on their growth inhibition. Furthermore, a biological impact of the amine position on sugar was studied. It was found that amine function attached to the C-1 of glucose conducted to the best antifungal activity against both C. versicolor and P. placenta while that fixed on the C-3 of glucose was indicated for antibacterial activity against L. innocua and S. typhimurium.; Au cours de ce travail, différents glucosylamines et aminodésoxyglucoses ont été synthétisés et caractérisés par différentes méthodes spectroscopiques dont l’IRTF, la RMN 1H, 13C et MALDI-Tof MS. L’étude des propriétés biologiques de ces molécules réalisée, d’une part, avec deux champignons du bois, Coriolus versicolor et Poria placenta, et d’autre part, avec trois microorganismes potentiellement rencontrés dans des aliments, Listeria innocua, Salmonella typhimurium et Fusarium proliferatum ont indiqué une contribution positive de la N-alkylation, du degré de N-substitution et de la quaternisation sur l’inhibition de leur croissance. Par ailleurs, l’impact sur la bioactivité, de la position du groupe amine sur le sucre, a été étudié. Il a été montré que la position du groupe amine sur le C-1 du glucose conduisait à une activité antifongique contre C. versicolor et P. placenta plus prononcée alors que la position C-3 du glucose était favorable à une activité antimicrobienne contre L. innocua et S. typhimurium.

International audience; Variations in parallel-to-grain static shear strength and perpendicular-to-grain tensile strength of Scots pine wood from mature stands in Finland and Sweden were studied by means of linear mixed model analyses. Approximately 35% of the total variation in shear strength could be described with readily available independent background variables; if the basic density was included, approximately two-thirds of the total variation could be controlled. In tensile strength perpendicular to grain, only approximately one-fourth of the total variation could be described with the respective background variables; the property was found to be independent on wood density, and the reasons for the absence of strength-density relationship are discussed.

Diplôme : Dr. d'Université; A large variety of curcuminoids Cs and tetrahydrocurcuminoids THCs was synthesized and their antioxidant properties were studied in detail by the radical DPPH° method. For the first time, it was shown that the higher antioxidant properties of THCs compared to their counterparts’ curcuminoids are due to the presence of benzylic hydrogen atoms in THCs. The association of THCs with a biopolymer chitosan, allowed the preparation of films presenting antioxidant and antibacterial properties. Interactions between THCs and chitosan were evidenced by UV-visible absorption spectroscopy. THCs and more particularly tetrahydrocurcumin inhibited development of Fusarium proliferatum fungi in cereals, and limited the production of associated mycotoxins.; Une grande variété de curcuminoïdes Cs et de tétrahydrocurcuminoïdes THCs a été synthétisée et leurs propriétés antioxydantes ont été étudiées en détail par la méthode du radical DPPH°. Pour la première fois, il a été montré que les propriétés antioxydantes supérieures des THCs par rapport à leurs homologues curcuminoïdes sont dues à la présence d’atomes d’hydrogène benzyliques dans les THCs. L’association de THCs avec un biopolymère, le chitosane, a permis l’élaboration de films à propriétés antioxydantes et antibactériennes. Des interactions entre les THCs et le chitosane ont été mises en évidence par spectroscopie d’absorption UV-visible. Les THCs et plus particulièrement la tétrahydrocurcumine, se sont révélés capables à la fois d’inhiber le développement de Fusarium proliferatum, champignon qui s’attaque aux céréales, et de limiter la production de mycotoxines issues de cette souche.

International audience