Effect of hot calendering on physical properties and water vapor transfer resistance of bacterial cellulose films

This work investigates the effect of hot calendering on bacterial cellulose (BC) films properties, aiming the achievement of good transparency and barrier property. A comparison was made using vegetal cellulose (VC) films on a similar basis weight of around 40 g.m-2. The optical-structural, mechanical and barrier property of BC films were studied and compared with those of highly beaten VC films. The Youngs moduli and tensile index of the BC films are much higher than those obtained for VC (14.5 16.2 GPa vs 10.8 8.7 GPa and 146.7 64.8 N.m.g-1 vs 82.8 40.5 N.m.g-1), respectively. Calendering increased significantly the transparency of BC films from 53.0 % to 73.0 %. The effect of BC ozonation was also studied. Oxidation with ozone somewhat enhanced the brightness and transparency of the BC films, but at the expenses of slightly lower mechanical properties. BC films exhibited a low water vapor transfer rate, when compared to VC films and this property decreased by around 70 % following calendering, for all films tested. These results show that calendering could be used as a process to obtain films suitable for food packaging applications, where transparency, good mechanical performance and barrier properties are important. The BC films obtained herein are valuable products that could be a good alternative to the highly used plastics in this industry.The authors thank FCT (Fundação para a Ciência e Tecnologia) and FEDER (Fundo Europeu de Desenvolvimento Regional) for the financial support of the project FCT PTDC/AGR-FOR/3090/2012— FCOMP-01-0124-FEDER-027948 and the awarding of a research grant for Vera Costa

Growth-dependent phenotypic variation of molluscan shells: implications for allometric data interpretation

In recent years, developmental plasticity has received increasing attention. Specifically, some studies highlighted a possible association between shell shape and growth rates in intertidal gastropods. We use a growth vector model to study how hypothetical growth processes could underlie developmental plasticity in molluscs. It illustrates that variation in instantaneous shell growth rate can induce variability in allometric curves. Consequently, morphological variation is time-dependent. Basing our model parameters on a study documenting the results of transplants experiments of three gastropods ecomorphs, we reproduce the main aspects of the variation in size, shape, and growth rates among populations when bred in their own habitat or transplanted to another ecotype habitat. In agreement with empirical results, our simulation shows that a flatter growth profile corresponds to conditions of rapid growth. The model also allows the comparison of allometric slopes using different subdata sets that correspond to static and ontogenetic allometry. Our model highlights that depending on subdata sets, the main effects could be attributed to source population or environment. In addition, convergence or divergence of allometric slopes is observed depending on the subdata sets. Although there is evidence that shell shape in gastropods is to some extent growth rate dependent, gaining a general overview of the issue is challenging, in particular because of the scarcity of studies referring to allometry. We argue that the dynamics of development at the phenotypic level constitute a non-reducible level of investigation if one seeks to relate the observed amount of phenotypic variation to variability in the underlying factors

Synthèse lipochimique et étude de composés à chaine ramifiée pour lubrifiant. Convention ADEME (AGRICE - CIRAD - VALAGRO - CHRISTOL GREASE n. 95 01 066. Rapport final décembre 1998

Le présent rapport concerne la mise au point de protocoles de synthèse ainsi que la fabrication d'échantillons d'esters à structure ramifiée à partir d'acides gras saturés ou monoinsaturés à chaîne normale, notamment d'origine tournesol oléique. Il associe le CIRAD, un centre technique spécialiste des agroressources VALAGRO et un industriel du domaine de la lubrification CHRISTOL-GREASE. Ce travail qui est centré sur la "voie cétonique" explorée par le CIRAD, permet d'obtenir des esters via la condensation d'acides gras en cétones, l'hydrogénation de ces dernières en alcools secondaires et l'estérification par une deuxième coupe d'acides gras. La procédure de synthèse fait intervenir la catalyse hétérogène pour les deux premières étapes, ne nécessite que l'éthanol et l'eau comme solvants et permet d'atteindre un rendement très élevé en produit fini. Elle est transposable à l'échelle industrielle. Parmi les nombreuses molécules synthétie d'origine 100% végétale dépassant le cadre du présent contrat. De plus la versatilité de la voie de synthèse qui a été peu exploitée au cours de cette première année du programme de recherche devrait permettre d'affiner la structure de l'ester afin d'ajuster les propriétés. Les composés déjà obtenus ou projetés au cours de la phase suivante pourront trouver des applications dans des domaines variés. Le présent rapport dresse d'ailleurs un panorama optimiste du marché potentiel des lubrifiants d'origine végétale. L'approche technico-économique montre que le coût de production estimé de ces composés nouveaux, même à une échelle modeste, resterait compatible avec les exigences du marché. (Résumé d'auteur

Modular and Decentralized PCU

This paper presents the studies made on the definition and design of a decentralized and modular electrical architecture of Power Conditioning Unit (PCU). The modular PCU is able to cover a large range of mission demands by adapting the number of power modules (PM) while the electrical interfaces remain the same. A decentralized architecture is proposed where each module is able to control the solar arrays and to manage the batteries. It appears that this kind of architecture becomes feasible thanks to digital circuits and using a communication bus [1]. Breadboards are being tested in order to validate the concept. Reliability and robustness aspects are studied and a redundant architecture is tested

Modular and Decentralized PCU

This paper presents the studies made on the definition and design of a decentralized and modular electrical architecture of Power Conditioning Unit (PCU). The modular PCU is able to cover a large range of mission demands by adapting the number of power modules (PM) while the electrical interfaces remain the same. A decentralized architecture is proposed where each module is able to control the solar arrays and to manage the batteries. It appears that this kind of architecture becomes feasible thanks to digital circuits and using a communication bus [1]. Breadboards are being tested in order to validate the concept. Reliability and robustness aspects are studied and a redundant architecture is tested