Utilisation de lignines Kraft comme agent de couplage dans des composites à base de polyéthylène de haute densité (HDPE) contenant des fibres d’écorce

Ce travail de recherche se décompose en trois parties. Le premier volet fait part des différentes approches étudiées dans la littérature concernant les bois-plastiques (WPC) et de différentes possibilités existantes tout en mettant en avant les résultats préliminaires obtenus. Il rapporte aussi le potentiel des lignines comme agent de couplage. L’objectif du second volet est l’optimisation de l’efficacité de ce nouveau type d’agent de couplage en combinant des lignines modifiées à un agent de couplage commercial (le polyéthylène maléaté: MAPE). Finalement, le dernier volet reprend les connaissances développées dans les précédentes parties tout en ajoutant deux aspects : la résistance aux cycles de gel-dégel et l’effet des extractions à l’eau et à la soude. Le problème des WPC est lié aux caractéristiques extrêmement opposées des fibres naturelles et de la matrice polymère, ce qui les rend incompatibles. Une multitude de traitements physiques ou chimiques peuvent améliorer la compatibilité et les interactions interfaciales entre les composants. L'impact environnemental et économique de l'utilisation de produits chimiques dérivés du pétrole et la demande de valoriser les coproduits du bois offrent la possibilité d'utiliser les lignines estérifiées dans la production d’une nouvelle génération de WPC. Nous avons démontré la faisabilité de composites à base de polyéthylène haute densité (HDPE) contenant 30% de fibres d’écorces d'épinette noire, avec 5% (basé sur la masse de l'écorce) de lignine Kraft estérifié à l'anhydride maléique. La combinaison de lignines Kraft estérifiées avec du MAPE (à teneurs égales) a permis d’optimiser l’efficacité de l’agent de couplage avec une nouvelle façon d'améliorer la compatibilité entre les fibres et la matrice. Étant donné que les fibres naturelles contiennent de la lignine, la lignine estérifiée (deux estérifications étudiées : succinique et maléique) a créé une structure qui a agit comme un intermédiaire entre les fibres d'écorce et la matrice HDPE hydrophobe, grâce à sa haute porosité permettant un ancrage mécanique intéressant et des liaisons de type van der Waals ou d’interactions π-π donnant du liant à cette nouvelle structure. On a déterminé l'effet de la composition d'agent de couplage comme étant un facteur majeur sur les propriétés mécaniques. Une analyse statistique a permis de trouver les meilleurs paramètres pour optimiser les propriétés mécaniques des composites et optimiser cette approche novatrice d’agent de couplage pour les WPC. Il a finalement été décidé d’étudier l’effet d’extractions à l’eau ou à la soude des écorces sur les caractéristiques mécaniques tout en intégrant une analyse de la résistance aux cycles gel-dégel dans le cas d’une application extérieure du matériau, correspondant au contexte québécois. Il a été démontré que les différentes extractions n'altèrent pas les propriétés mécaniques en flexion et en traction. Mais le test de résistance aux gels-dégels met en valeur les caractéristiques des WPC. Un meilleur comportement a été trouvé pour les formulations avec un agent de couplage combinant les lignines estérifiées avec du MAPE.This research work is divided into three parts. The first part is dedicated to the review of different approaches discussed in the literature concerning wood-plastic composites (WPC) and different possibilities while highlighting the preliminary results obtained. It also reported the potential of lignin as coupling agent. In the second part, the optimization of the effectiveness of this new type of coupling agent combining modified lignin with a commercial coupling agent (polyethylene maleate: MAPE) is discussed. Finally, the performance of the selected composites upon the freeze-thaw resistance tests and the effect of extractions (water and soda) on the characteristics (flexural and tensile properties) of composites containing bark fibers and modified lignin are presented in the last part. The problem of compatibility between the constituents of WPC is related to the extremely opposite characteristics of natural fibers and the polymer matrix. A multitude of physical or chemical treatments can improve compatibility and the interfacial interactions between components. The environmental and economic impact of the use of petroleum chemicals and the demand to valorize the co-products of wood transformation offers the possibility of using esterified lignin in the production of a new generation of WPC. We have demonstrated the feasibility of composite based on high density polyethylene (HDPE) containing 30% of black spruce bark fibers, with 5% (based on the mass of bark) of Kraft lignin esterified by maleic anhydride. The combination of esterified Kraft lignin with the MAPE (at equal levels) has been demonstrated to improve the compatibility between the bark fibers and the matrix. Given that natural fibers contain lignin, the esterified lignin (with succinic and maleic anhydride) is supposed to create a structure which acts as bond between the bark fibers and the hydrophobic matrix (HDPE). This action is related to the high porosity of esterified lignin as revealed by SEM, which allows for mechanical anchoring due to van der Waals or π–π interactions. The effect of the structure of coupling agent on the mechanical properties of the composites has been determined. A statistical analysis performed on the collected data made it possible to determine the best settings of parameters for optimal mechanical properties of composites, designed through the innovative approach of using esterified Kraft lignin as a coupling agent for WPC. Finally, the effect of water and soda extractions of bark fibers prior to their incorporation into composites was studied, on the mechanical characteristics of the composites. The composites with best mechanical performance were finally tested regarding freeze-thaw resistance since an outside application of the material, is anticipated in the Quebec context. However, the test for resistance to freeze-thaw positively influences the characteristics of WPC. It has been shown that different extractions do not affect the mechanical properties (flexural and tensile). Better behavior was found for formulations with a coupling agent combining lignin esterified with the MAPE

Quasi one-dimensional Ag nanostructures on Si(331)–(12 × 1)

We report on the deposition of sub-monolayer Ag on the Si(331)–(12 × 1) surface. The growth of one-dimensional Ag nanostructures is observed by means of low- temperature scanning tunneling microscopy and low energy electron diffraction. We find that the deposited Ag is organized in nanostructures consistently taking “sawtooth” shapes. While the structures are not perfectly organized, their back edges are atomically straight. The limitations of this system in terms of faceting are also discussed

The Willingness to Modify Portion Sizes or Eat New Protein Foods Largely Depends on the Dietary Pattern of Protein Intake

International audiencePromoting a more balanced animal/plant dietary protein ratio by changing portion sizes or introducing new foods is a promising means to improve diet quality, but little is known about the willingness of individuals to adopt such changes. Our objective was to assess the willingness to adopt dietary changes by these means. In a French cross-sectional study in 2018 (n = 2055), we analyzed the association between the willingness to eat smaller or larger portions or to introduce non-consumed protein foods and the current dietary patterns of individuals and their socio-demographic characteristics. These modifications had previously been identified as improving the nutrient adequacy of diets. Participants were more willing to eat smaller portion sizes than to introduce new foods and to eat larger portion sizes. The willingness for any modification varied depending on the food groups concerned. Participants were also more willing to eat larger portions and less willing to eat smaller portions when they were the most frequent consumers of the foods concerned. Participants were more willing to eat a new food if it was consumed in large quantities by individuals with a similar dietary pattern. This study underlines the importance of accounting for individual food habits when issuing nutritional recommendations

Valence band structure of the Si(331)-(12 × 1) surface reconstruction

Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 × 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating semiconducting behavior. An occupied surface state, presumably containing several spectral components, is found centered at − 0.6 eV exhibiting a flat energy dispersion. These results are confirmed by scanning tunneling spectroscopy and are consistent with recent first-principles calculations for our structural model

Brassinosteroid Applications Enhance the Tolerance to Abiotic Stresses, Production and Quality of Strawberry Fruits

Brassinosteriods (BRs) have increasingly been used to improve the yields and quality of various crops. In this work we studied the effect of two brassinosteroids, BB16 and EP24, on the growth promotion of Fragaria ananassa plants under normal conditions or exposed to water or saline stress. The influence of both BRs on the plant development and fruit quality was evaluated when cultivated in semi-hydroponic conditions. A marked growth-promoting effect was observed with both compounds when plants were cultivated under normal irrigation conditions and under saline and water stresses. BB16 and EP24 yielded plants with a higher dry weight, root length and surface, a higher number and area of leaves, a higher total weight of fruits per plant, and a higher percentage of fruits of commercial quality. Additionally, a higher content of chlorophyll, number of leaves, and increased dry weight was detected in plants treated with both BRs and exposed to water and saline stresses. Finally, when evaluating the production and quality of fruits obtained under semi-hydroponic conditions, we observed that the pre-harvest treatment with both compounds induced a higher fruit production and better quality of fruits. These results suggest the potential of these compounds to achieve a more sustainable management of strawberry cultivation.EEA FamailláFil: Furio, Ramiro Nicolás. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; Argentina.Fil: Salazar, Sergio Miguel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Salazar, Sergio Miguel. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia; ArgentinaFil: Mariotti Martinez, Jorge Alberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; Argentina.Fil: Martinez Zamora, Martin Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Martinez Zamora, Martin Gustavo. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Coll, Yamilet. Universidad La Habana. Facultad de Química. Centro de Estudios de Productos Naturales; CubaFil: Diaz Ricci, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Diaz Ricci, Juan Carlos. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina

Baghera Assessment Project, designing an hybrid and emergent educational society

Edited by Sophie Soury-Lavergne ; Available at: http://www-leibniz.imag.fr/LesCahiers/2003/Cahier81/BAP_CahiersLaboLeibniz.PDFResearch reportThe Baghera Assessment Project (BAP) has the objective to ex plore a new avenue for the design of e-Learning environments. The key features of BAP's approach are: (i) the concept of emergence in multi-agents systems as modelling framework, (ii) the shaping of a new theoretic al framework for modelling student knowledge, namely the cK¢ model. This new model has been constructed, based on the current research in cognitive science and education, to bridge research on education and research on the design of learning environments

How temperatures may affect the synthesis of fatty acids during olive fruit ripening: genes at work in the field

A major concern for olive cultivation in many extra-Mediterranean regions is the adaptation of recently introduced cultivars to environmental conditions different from those prevailing in the original area, such as the Mediterranean basin. Some of these cultivars can easily adapt their physiological and biochemical parameters in new agro-environments, whereas others show unbalanced values of oleic acid content. The objective of this study was to evaluate the effects of the thermal regime during oil synthesis on the expression of fatty acid desaturase genes and on the unsaturated fatty acid contents at the field level. Two cultivars (Arbequina and Coratina) were included in the analysis over a wide latitudinal gradient in Argentina. The results suggest that the thermal regime exerts a regulatory effect at the transcriptional level on both OeSAD2 and OeFAD2-2 genes and that this regulation is cultivar-dependent. It was also observed that the accumulated thermal time affects gene expression and the contents of oleic and linoleic acids in cv. Arbequina more than in Coratina. The fatty acid composition of cv. Arbequina is more influenced by the temperature regime than Coratina, suggesting its greater plasticity. Overall, findings from this study may drive future strategies for olive spreading towards areas with different or extreme thermal regimes serve as guidance for the evaluation olive varietal patrimony.EEA San JuanFil: Contreras Valentín, Ana Cibeles. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; Argentina.Fil: Contreras Valentín, Ana Cibeles. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pierantozzi, Pierluigi. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; Argentina.Fil: Pierantozzi, Pierluigi. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Maestri, Damian. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Maestri, Damian. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tivani, Martín. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; Argentina.Fil: Tivani, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Searles, Peter. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Brizuela, Magdalena. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Fernández, Fabricio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Catamarca; Argentina.Fil: Toro, Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cerro Azul; Argentina.Fil: Puertas, Carlos. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Junin; Argentina.Fil: Trentacoste, Eduardo R. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Junin; Argentina.Fil: Kiessling, Juan. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Alto Valle. Agencia de Extensión Rural Centenario; Argentina.Fil: Mariotti, Roberto. National Research Council. Institute of Biosciences and Bioresources; ItaliaFil: Baldoni, Luciana. National Research Council. Institute of Biosciences and Bioresources; ItaliaFil: Mousavi, Soraya. National Research Council. Institute of Biosciences and Bioresources; ItaliaFil: Fernández, Paula. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Agrobiotecnología y Biología Molecular; ArgentinaFil: Fernández, Paula. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Fernández, Paula. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Moschen, Sebastián. Instituto Nacional de Tecnología Agropecuaria (INTA).Estación Experimental Agropecuaria Famaillá; Argentina.Fil: Moschen, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Torres, Myriam Mariela.Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; Argentina.Fil: Torres, Myriam Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Molecular cytogenetics (FISH, GISH) of Coccinia grandis: A ca. 3 myr-old species of Cucurbitaceae with the largest Y/autosome divergence in flowering plants

The independent evolution of heteromorphic sex chromosomes in 19 species from 4 families of flowering plants permits studying X/Y divergence after the initial recombination suppression. Here, we document autosome/Y divergence in the tropical Cucurbitaceae Coccinia grandis, which is ca. 3 myr old. Karyotyping and C-value measurements show that the C. grandis Y chromosome has twice the size of any of the other chromosomes, with a male/female C-value difference of 0.094 pg or 10% of the total genome. FISH staining revealed 5S and 45S rDNA sites on autosomes but not on the Y chromosome, making it unlikely that rDNA contributed to the elongation of the Y chromosome; recent end-to-end fusion also seems unlikely given the lack of interstitial telomeric signals. GISH with different concentrations of female blocking DNA detected a possible pseudo-autosomal region on the Y chromosome, and C-banding suggests that the entire Y chromosome in C. grandis is heterochromatic. During meiosis, there is an end-to-end connection between the X and the Y chromosome, but the X does not otherwise differ from the remaining chromosomes. These findings and a review of plants with heteromorphic sex chromosomes reveal no relationship between species age and degree of sex chromosome dimorphism. Its relatively small genome size (0.943 pg/2C in males), large Y chromosome, and phylogenetic proximity to the fully sequenced Cucumis sativus make C. grandis a promising model to study sex chromosome evolution. Copyright © 2012 S. Karger AG, Base