Tests comparatifs d'utilisabilité des plateformes Swissbib.ch et Data.bnf.fr

L’apparition des plateformes en Linked Open Data, permet d’entrevoir de nouvelles possibilités d’accès à l’information et offre de nouvelles opportunités en termes d’utilisabilité. Ainsi, ce travail est réalisé dans le cadre du projet linked.swissbib.ch qui vise à enrichir le catalogue swissbib.ch grâce au web sémantique. Le but de ce travail de bachelor est par le biais de tests comparatifs d’évaluer la satisfaction des utilisateurs vis-à-vis de ce nouveau type d’outil de recherche et la manière dont ils s’approprient ce dernier, face à l’utilisation d’un catalogue « standard » de recherche. Ainsi, ces tests se focalisent sur la plateforme data.bnf.fr développée en Linked Open Data et le méta catalogue swissbib.ch. L’objectif de cette méthode est de recueillir des données permettant la formulation de recommandations pour le développement de fonctionnalités en Linked Open Data pour la plateforme swissbib.ch. A travers ce mémoire, le processus qui a permis d’élaborer ce test dans l’objectif de répondre aux besoins du mandat est présenté de même que les résultats obtenus. Ces derniers mettent en avant le potentiel d’une plateforme en Linked Open Data face à l’utilisation d’un catalogue standard de recherche. En effet, il apparaît que la plateforme data.bnf.fr de par sa structure et ses fonctionnalités semble faciliter le processus de prise en main de l’outil et a un impact positif sur la satisfaction des utilisateurs par rapport à l’utilisation du méta catalogue swissbib.ch. Par conséquent, la plateforme data.bnf.fr semble être un modèle intéressant à suivre dans le cadre du développement de fonctionnalités en web sémantique pour swissbib.ch. Toutefois, les tests ont révélé également des éléments auxquels il faut être attentif dans une logique de structure telle qu’on peut la trouver sur data.bnf.fr. Enfin, ce travail a esquissé le potentiel de prise en main d’une plateforme LOD, notamment pour les participants n’étant pas rodés à l’utilisation des catalogues de bibliothèques. Cet aspect met en avant le potentiel du Linked Open Data afin de rendre les catalogues de bibliothèques davantage « user friendly »

RNA Control of HIV-1 Particle Size Polydispersity

HIV-1, an enveloped RNA virus, produces viral particles that are known to be much more heterogeneous in size than is typical of non-enveloped viruses. We present here a novel strategy to study HIV-1 Viral Like Particles (VLP) assembly by measuring the size distribution of these purified VLPs and subsequent viral cores thanks to Atomic Force Microscopy imaging and statistical analysis. This strategy allowed us to identify whether the presence of viral RNA acts as a modulator for VLPs and cores size heterogeneity in a large population of particles. These results are analyzed in the light of a recently proposed statistical physics model for the self-assembly process. In particular, our results reveal that the modulation of size distribution by the presence of viral RNA is qualitatively reproduced, suggesting therefore an entropic origin for the modulation of RNA uptake by the nascent VLP

Influence of citric acid and water on thermoplastic wheat flour/poly(lactic acid) blends. I: Thermal, mechanical and morphological properties

Wheat flour was plasticized with glycerol and compounded with poly(lactic acid) in a one-step twin-screw extrusion process in the presence of citric acid with or without extra water. The influence of these additives on process parameters and thermal, mechanical and morphological properties of injected samples from the prepared blends, was then studied. Citric acid acted as a compatibilizer by promoting depolymerization of both starch and PLA. For an extrusion without extra water, the amount of citric acid (2 parts for 75 parts of flour, 25 parts of PLA and 15 parts of glycerol) has to be limited to avoid mechanical properties degradation. Water, added during the extrusion, improved the whole process, minimizing PLA depolymerization, favoring starch plasticization by citric acid and thus improving phases repartition

Modelling of Physical Ageing in starch using the TNM equation

Gelatinised wheat starch, freeze dried and equilibrated at different RH, was aged at different temperatures and for different times. The Tool–Narayanaswamy–Moynihan (TNM) model was used to describe the ageing for all samples under all conditions. Three TNM parameters: x, Dh⁄ and A were determined experimentally using, respectively, the peak shift method (x) and the dependency of T0f (the limiting value of Tf) on the cooling rate (Dh⁄ and A). The non-linearity parameter x and the non exponential parameter b were also estimated by optimising a fit of the experimental normalised specific heat at different ageing times and temperatures to curves generated using the TNM model. The TNM model successfully described the normalised experimental data. It was found that the intermolecular forces were strong and the relaxation times depended more strongly on the glass structure than the glass temperature. The hydration level of the starch had a direct impact of the breadth of the relaxation time distribution. A dependency of the non-linearity parameter x on ageing temperature (peak shift method) was observed. This suggests that physical ageing is more complex than is described by TNM formalism

Thermomechanical characterization of an amylose-free starch extracted from cassava (Manihot esculenta, Crantz)

The aim of this study was to determine and compare the melting (Tm), glass transition (Tg) and mechanical relaxation (Tα) temperatures of a new waxy cassava starch. Thermal transitions measurements were obtained by Differential Scanning Calorimetry (DSC) and Dynamical Mechanical Thermal Analysis (DMTA). The experimental data showed a high correlation between water volume fraction and melting temperature (Tm) indicating that the Flory-Huggins theory can be used to describe the thermal behavior of this starch. The Tm of waxy cassava starch-water mixes were lower than a waxy corn starch-water reference system, but differences were not statistically significant. The mechanical relaxation temperatures taken at tan δ peaks were found 29–38 °C larger than Tg. The Tα and Tg measured for waxy cassava starch exhibited similar properties to the ones of waxy corn starch, implying that waxy cassava starch can be used in food and materials industry

Matériaux à base de maïs : de la qualité finale à la sélection variétale via le procédé de mise en forme

Que les matériaux à base de maïs soient considérés comme des substituts des matériaux plastiques, ou qu'ils se présentent comme des produits alimentaires expansés (céréales petit-déjeuner, biscuits...), il est important de pouvoir évaluer leurs propriétés mécaniques, pour adapter les conditions de transformation, favoriser la sélection de la matière première et optimiser leur qualité. Par analogie avec le modèle des solides composites, l'analyse thermomécanique dynamique (DMA) montre que le comportement dépend fortement de l'adhésion entre amidon et particules protéiques. Les variations de viscosité élongationnelle avec la teneur en protéines et son lien avec le module élastique E', pour T>Tg+30°C, suggèrent que cette morphologie est fonction des mécanismes d'écoulement et d'expansion lors du procédé. En établissant les relations structure-procédé-propriétés, ces travaux ont favorisé la sélection variétale et la conception de produits céréaliers à la texture optimisée

Agro-materials : a bibliographic review

Facing the problems of plastic recycling and fossil resources exhaustion, the use of biomass to conceive new materials appears like a reasonable solution. Two axes of research are nowadays developed : on the one hand the synthesis of biodegradable plastics, whichever the methods may be, on the other hand the utilization of raw biopolymers, which is the object of this paper. From this perspective, the “plastic” properties of natural polymers, the caracteristics of the different classes of polymers, the use of charge in vegetable matrix and the possible means of improving the durability of these agro-materials are reviewed

Physical and structural properties and thermal behaviour of starch-poly(ɛ-caprolactone) blend films for food packaging

[EN] Structural and physical properties (barrier, mechanical, and optical properties) and thermal behaviour of corn starch-PCL blend films, containing glycerol as plasticizer, obtained by compression moulding, at 160 °C and 130 bars, were studied. The stability on the films properties was also evaluated. Blend films showed phase separation of the polymers in a heterogeneous matrix with starch rich regions and PCL rich regions. Nevertheless, a small miscibility of PCL in the starch phase was detected trough the shift in the glass transition temperature of the starch phase, which leads to a partial inhibition of amylose crystallization during film formation and storage. The lack of interfacial adhesion of PCL and starch phases promoted films fragility and reduced stretchability, although elastic modulus of the films with small PCL ratios increased. Water barrier properties of starch films were improved as the PCL increased in the blend, but oxygen permeability increased. Due to the food compatibility of this polymer blends (without any toxic compound) these could be an interesting alternative for food packaging, where some drawbacks of starch films has been overcome.The authors acknowledge the financial support from the Ministerio de Economi'a y Competitividad (Spain) throughout the project AGL2013-42989-R. Rodrigo Ortega-Toro thanks the Conselleria de Educacio de la Comunitat Valenciana for the Santiago Grisolia grant. Authors also thank to Electron Microscopy Service of the UPV for their technical assistance.Ortega Toro, R.; Contreras, J.; Talens Oliag, P.; Chiralt, A. (2015). Physical and structural properties and thermal behaviour of starch-poly(ɛ-caprolactone) blend films for food packaging. Food Packaging and Shelf Life. 5:10-20. https://doi.org/10.1016/j.fpsl.2015.04.001S1020

The effect of polymer/plasticiser ratio in film forming solutions on the properties of chitosan films

In this work physical-chemical properties of chitosan/ glycerol film forming solutions (FFS) and the resulting films were analysed. Solutions were prepared using different concentrations of plasticising agent (glycerol) and chitosan. Films were produced by solvent casting and equilibrated in a controlled atmosphere. FFS water activity and rheological behaviour were determined. Films water content, solubility, water vapour and oxygen permeabilities, thickness, and mechanical and thermal properties were determined. Fourier transform infrared (FTIR) spectroscopy was also used to study the chitosan/glycerol interactions. Results demonstrate that FFS chitosan concentration influenced solutions consistency coefficient and this was related with differences in films water retention and structure. Plasticiser addition led to an increase in films moisture content, solubility and water vapour permeability, water affinity and structural changes. Films thermo-mechanical properties are significantly affected by both chitosan and glycerol addition. FTIR experiments confirm these results. This work highlights the importance of glycerol and water plasticisation in films properties.This work was supported by National Funds from FCT - Fundacao para a Ciencia e a Tecnologia, through project PEst-OE/EQB/LA0016/2011.Authors Joana F. Fundo, Andrea C. Galvis-Sanchez and Mafalda A. C. Quintas acknowledge FCT for research grants SFRH/ BD / 62176 / 2009, SFRH/BPD/37890/2007 and SFRH / BPD / 41715 / 2007, respectively