Design of passive methane oxidation biosystems considering their response to the presence of capillary barrier effect

La construction des biosystèmes d’oxydation passive du méthane (BOPM) est une option économique et durable pour réduire les émissions de méthane des sites d’enfouissement de déchets et des effets subséquents du réchauffement climatique. Les BOPM sont constitués de deux couches principales: la couche d'oxydation du méthane (MOL) et la couche de distribution du gaz (GDL). L'oxydation du méthane se produit dans la MOL par les réactions biochimiques des bactéries méthanotrophes, et la GDL est construite sous la MOL pour intercepter et distribuer les émissions fugitives de biogaz à la base de la MOL. Fondamentalement, l'efficacité d'un BOPM est définie en fonction de l'efficacité d'oxydation du méthane dans la MOL. Par conséquent, il est indispensable de fournir des conditions adéquates pour les activités bactériennes des méthanotrophes. En plus des paramètres environnementaux, l'intensité et la distribution du biogaz influencent l'efficacité des BOPM, et ils peuvent rendre le matériau de la MOL - avec une grande capacité d'accueillir les activités bactériennes - inutilisables en termes d'oxydation du méthane sur place. L'effet de barrière capillaire le long de l'interface entre la GDL et la MOL peut provoquer des émissions localisées de méthane, due à la restriction ou la distribution non uniforme de l’écoulement ascendant du biogaz à la base de la MOL. L'objectif principal de cette étude est d'incorporer le comportement hydraulique non saturé des BOPM dans la conception des BOPM, afin d’assurer la facilité et la distribution adéquates de l'écoulement du biogaz à la base de la MOL. Les fonctions de perméabilité à l'air des matériaux utilisés pour construire la MOL des BOPM expérimentaux au site d’enfouissement des déchets de St Nicéphore (Québec, Canada), ainsi que celles d'autres de la littérature technique, ont été étudiés pour évaluer le comportement d'écoulement non saturé du gaz dans les matériaux et pour identifier le seuil de migration sans restriction du gaz. Ce dernier seuil a été introduit en tant que un paramètre de conception avec lequel le critère de conception recommandé ici, c’est à dire la longueur de la migration sans restriction de gaz (LMSG), a été défini. La LMSG est considérée comme la longueur le long de l'interface entre la GDL et la MOL où le biogaz peut migrer à travers la MOL sans restriction. En réalisant des simulations numériques avec SEEP/W, les effets de la pente de l'interface, des paramètres définissant la courbe de rétention d'eau, de la fonction de la conductivité hydraulique du matériau de la MOL sur la valeur de la LMSG (représentant la facilité d'écoulement du biogaz à l'interface) et de la distribution de l'humidité (et par conséquent celle du biogaz) ont été évalués. Selon les résultats des simulations, la conductivité hydraulique saturée et la distribution des tailles de pores du matériau de la MOL sont les paramètres les plus importants sur la distribution de l'humidité le long de l'interface. Ce dernier paramètre influe également sur la valeur du degré de saturation et donc la facilité du biogaz à la base de la MOL. La densité sèche du matériau de MOL est un autre paramètre qui contrôle la facilité d'écoulement ascendant du biogaz. Les limitations principales de la présente étude sont associées au nombre de matériaux de MOL testés et à l'incapacité de SEEP/W de considérer l'évapotranspiration. Toutefois, compte tenu des hypothèses raisonnables dans les simulations et en utilisant les données de la littérature, on a essayé de réduire ces limitations. En utilisant les résultats des expériences et des simulations numériques, des étapes et des considérations de conception pour la sélection du matériau de MOL et de la pente d'interface ont été proposées. En effet,le comportement hydraulique non saturé des matériaux serait intégré dans les nécessités de conception pour un BOPM efficace, de sorte que la capacité maximale possible d'oxydation du méthane du matériau de la MOL soit exploitée.

Effect of HMEC on the consolidation of cement pastes: Isothermal calorimetry versus oscillatory rheometry

Chemical admixtures increase the theological complexity of cement pastes owing to their chemical and physical interactions with particles, which affects cement hydration and agglomeration kinetics. Using oscillatory rheometry and isothermal calorimetry, this article shows that the cellulose ether HMEC (hydroxymethyl ethylcellulose), widely used as a viscosity modifying agent in self-compacting concretes and dry-set mortars, displayed a steric dispersant barrier effect during the first 2 h of hydration associated to a cement retarding nature, consequently reducing the setting speed. However, despite this stabilization effect, the polymer increased the cohesion strength when comparing cement particles with the same hydration degree. (C) 2009 Elsevier Ltd. All rights reserved.

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Effect of Composition on the Physical Properties at Nanoscale of PZT Thin Films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of EVA on the fresh properties of cement paste

The improved workability effect of latex in dry mortars has not been fully clarified. The purpose of this research was to investigate the influence cif the EVA copolymer on the cement hydration and on the rheological properties of cement pastes. The results pointed to a minor influence of EVA on cement hydration and to a ball-bearing effect. In fact, the shear thinning behavior of reference paste at 15 min after mixing changed to shear thickening owing to the EVA addition. This behavior could be explained by the decrease in the interparticle separation distance as consequence of the solid content increase in case of shearing detachment of weakly adhered EVA particles from the cement particles surfaces. The expected EVA plasticizing effect was observed at 60 min. Such behavior points to the stabilization of EVA on the cement particles surfaces, thus resulting in a steric barrier effect. (C) 2011 Elsevier Ltd. All rights reserved.

Effect of EVA on the fresh properties of cement paste

The improved workability effect of latex in dry mortars has not been fully clarified. The purpose of this research was to investigate the influence of the EVA copolymer on the cement hydration and on the rheological properties of cement pastes. The results pointed to a minor influence of EVA on cement hydration and to a ball-bearing effect. In fact, the shear thinning behavior of reference paste at 15 min after mixing changed to shear thickening owing to the EVA addition. This behavior could be explained by the decrease in the interparticle separation distance as consequence of the solid content increase in case of shearing detachment of weakly adhered EVA particles from the cement particles surfaces. The expected EVA plasticizing effect was observed at 60 min. Such behavior points to the stabilization of EVA on the cement particles surfaces, thus resulting in a steric barrier effect.

Characterization and modeling of the barrier properties in nanostructured systems

The object of the present study is the process of gas transport in nano-sized materials, i.e. systems having structural elements of the order of nanometers. The aim of this work is to advance the understanding of the gas transport mechanism in such materials, for which traditional models are not often suitable, by providing a correct interpretation of the relationship between diffusive phenomena and structural features. This result would allow the development new materials with permeation properties tailored on the specific application, especially in packaging systems. The methods used to achieve this goal were a detailed experimental characterization and different simulation methods. The experimental campaign regarded the determination of oxygen permeability and diffusivity in different sets of organic-inorganic hybrid coatings prepared via sol-gel technique. The polymeric samples coated with these hybrid layers experienced a remarkable enhancement of the barrier properties, which was explained by the strong interconnection at the nano-scale between the organic moiety and silica domains. An analogous characterization was performed on microfibrillated cellulose films, which presented remarkable barrier effect toward oxygen when it is dry, while in the presence of water the performance significantly drops. The very low value of water diffusivity at low activities is also an interesting characteristic which deals with its structural properties. Two different approaches of simulation were then considered: the diffusion of oxygen through polymer-layered silicates was modeled on a continuum scale with a CFD software, while the properties of n-alkanthiolate self assembled monolayers on gold were analyzed from a molecular point of view by means of a molecular dynamics algorithm. Modeling transport properties in layered nanocomposites, resulting from the ordered dispersion of impermeable flakes in a 2-D matrix, allowed the calculation of the enhancement of barrier effect in relation with platelets structural parameters leading to derive a new expression. On this basis, randomly distributed systems were simulated and the results were analyzed to evaluate the different contributions to the overall effect. The study of more realistic three-dimensional geometries revealed a prefect correspondence with the 2-D approximation. A completely different approach was applied to simulate the effect of temperature on the oxygen transport through self assembled monolayers; the structural information obtained from equilibrium MD simulations showed that raising the temperature, makes the monolayer less ordered and consequently less crystalline. This disorder produces a decrease in the barrier free energy and it lowers the overall resistance to oxygen diffusion, making the monolayer more permeable to small molecules.

Combined effects of cellulose nanocrystals and silver nanoparticles on the barrier and migration properties of PLA nano-biocomposites

Poly(lactic acid) (PLA)-based high performance nano-biocomposites were prepared to be used in active food packaging. Pristine (CNC) and surfactant modified cellulose nanocrystals (s-CNC) with silver (Ag) nanoparticles were used as the matrix modifiers. Binary and ternary systems were prepared. Morphological investigations revealed the good distribution of silver nanoparticles in PLA ternary systems. The combination of s-CNC and Ag nanoparticles increased the barrier effect of the produced films while the results of overall migration for the PLA nano-biocomposites revealed that none of the samples exceeded the overall migration limit, since results were well below 60 mg kg−1 of simulant.

Photooxidative behavior of polystyrene-montmorillonite nanocomposites

The weathering behavior of polystyrene and polystyrene-montmorillonite composites containing 2.5, 5.0, and 7.5 wt% of montmorillonite (MMT) was investigated. Samples were exposed to UV radiation for periods of up to similar to 12 weeks and their molecular weight, chemical changes, and mechanical properties were monitored as a function of time. The addition of MMT was shown to improve the photostability of all composites investigated, probably because of a screen effect against UV radiation and barrier effect against diffusion of oxygen promoted by the silicate layers of MMT. Scanning electron microscopy of fracture surfaces of degraded samples showed that there is a degraded layer near the surface that provided a recovery of tensile strength of the samples.

Hot-dip galvanized steel dip-coatedwith ureasilicate hybrid in simulated concrete pore solution: Assessment of coating morphology and corrosion protection efficiency

The barrier effect and the performance of an organic–inorganic hybrid (OIH) sol–gel coating are highlydependent on the coating deposition method as well as processing conditions. In this work, studies onthe influence of experimental parameters using the dip coating method were performed. Factors suchas residence time (Rt), a curing step between each dip step and the number of layers of sol–gel OIHfilms deposited on HDGS to prevent corrosion in highly alkaline environments were studied. These OIHcoatings were obtained using a functionalized siloxane, 3-isociantepropyltriethoxysilane that reactedwith a diamino-functionalized oligopolymer (Jeffamine®D-230). The barrier efficiency of OIH coatings insimulated concrete pore solutions (SCPS) was assessed in the first moments of contact, by electrochemicalimpedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings inSCPS was monitored during eight days by macrocell current density. The morphological characterizationof the surface was performed by scanning electronic microscopy before and after exposure to SCPS.Glow discharge optical emission spectroscopy was used to obtain quantitative composition profiles toinvestigate the thickness of the OIH coatings as a function of the number of layers deposited and theinfluence of the Rt in the coating thickness.

Genetic variation in the European hake, Merluccius merluccius. Description of protein loci and genetic divergence between Atlantic and Mediterranean populations = Anàlisi de la variabilitat genètica en el lluç europeu, Merluccius merluccius. Descripció dels loci electroforètics i divergència genètica entre les poblacions atlàntica i mediterrània

We examined the genetic population structure of the european hake (Merluccius merluccius) using electrophoretically detectable population markers in 35 protein loci. Samples were collected from 7 locations in the Atlantic Ocean and Mediterranean Sea. Six loci were polymorphic using the 0.05 criterion of polymorphism. Sample heterozigosities ranged from 0.052 to 0.072 and averaged 0.0625. In this study, significant allele frequency differences were detected between Atlantic and Mediterranean populations in three polymorphic loci: GAPDH-1*, GPI-2* and SOD-1*. Two major genetic groups were considered: a North-Atlantic stock and the Mediterranean stock. The Nei genetic distance, D, (based on 33 loci) between samples from these two groups ranged from 0.002 to 0.006. Genetic differenciation between these areas appears to reflect the barrier effect of Strait of Gibraltar. On average over loci, 96.92 % of the total gene diversity was contained within samples, 0.23 % expressed differences among locations within areas, and 2.64 % differences between regions. A review of morphological variation together with the genetic data presented here suggest that the populations of hake from these areas are subdivided into two different stocks: the North-Atlantic stock and the Mediterranean stock. The most conservative approach to the management of these stocks is to consider the Atlantic and Mediterranean stocks independently from oneanother

Nanotecnologia aplicada à pele

A nanotecnologia foi introduzida nas áreas farmacêutica e cosmética, com o propósito de possibilitar o desenvolvimento de sistemas de veiculação de substâncias e para a optimização das formulações já existentes. As preparações de aplicação tópica têm elevada importância nas perspectivas terapêutica e cosmética, uma vez que a pele apresenta uma área de aplicação extensa e acessível, os efeitos sistémicos das substâncias a administrar por via tópica encontram-se geralmente reduzidos, exercendo na maioria das vezes um efeito local. Mais, a esta via estão normalmente associadas menos reacções adversas. Todavia, a pele é um órgão, dotado de um efeito barreira notável, que pode comprometer a administração de moléculas farmacológica/cosmetologicamente activas no alvo. Assim, é evidente a necessidade de conhecer a constituição da pele, pois a permeabilidade cutânea de substâncias é um desafio que só pode ser conseguido através da preparação de formulações capazes de ultrapassar essa mesma barreira. O trabalho exposto aborda sucintamente a nanocosmética, pois esta tem revelado elevados impactos económico, social e científico. A inexistência de informação sobre quais os produtos actualmente comercializados, cuja produção tenha por base a nanotecnologia, suscitaram o interesse em desenvolver uma revisão sobre esses mesmos produtos, assim como esclarecer alguns aspectos relacionados com as características da pele, que justificam o investimento e estudo exaustivo deste tipo de preparações.

Electrochemical Behaviour of the AA2024 Aluminium Alloy Modified with Self-Assembled Monolayers/Polyaniline Double Films

The electrochemical characteristics of the AA2024 aluminium alloy modified with octadecyltrimethoxysilane (ODTMS) + polyaniline (PANi) and propiltrimethoxysilane (PTMS) + (PANi) were studied in the present work. The results show that the different protective coatings shift the values of corrosion and pit potentials to more positive values making the system nobler and indicate that the double film ODTMS + PANi present the best protection against corrosion characteristics, that is probably due to the two contributions: anodic protection associated with the barrier effect.

PLA and Organoclays Nanocomposites: Degradation Process and Evaluation of ecotoxicity Using Allium cepa as Test Organism

In this study, nanocomposites of PLA and organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method and the obtained samples were characterized by transmission electron microscopy (TEM). Since composting is an important proposal to the final disposal of biopolymers, the influence of clays on the hydrolytic degradation process of PLA was evaluated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in compost. After degradation of the materials in composting environment, the evaluation of cytotoxic, genotoxic and mutagenic effects of compost aqueous extract was carried out using a bioassay with Allium cepa as test organism. The TEM micrographs permitted the observation of different levels of dispersion, including exfoliated regions. In the evaluation of hydrolytic degradation it was noted that the presence of organoclays can decrease the rate of degradation possibly due to the barrier effect of clay layers and/or the higher degree of crystallinity in the nanocomposite samples. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of PLA in studied materials. In the analysis performed by the bioassay using A. cepa as test organism, it was found that after degradation of the PLA and its nanocomposites the aqueous extract of compost samples induced a decreasing in the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to the negative control (distilled water). By comparing the results obtained for the nanocomposites in relative to pure polymer, there were no statistically significant differences. The types of the observed chromosomal aberrations indicated a possible genotoxic effect of the materials, which may be related to an aneugenic action of PLA degradation products. © 2013 Springer Science+Business Media New York.

Mobilidade e acessibilidade intraurbana: análise do efeito barreira na cidade de Rio Claro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)