Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000. / Oxygen transport across biofilms and membranes may be a limiting factor in the operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in which fungi are immobilized within the wall of a porous polysulphone capillary membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide) were investigated in a bare membrane (without a biofilm being present). The work provides a basis for further transport study in membranes where biomass is present. The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet membranes. The diaphragm-cell method employs two well-stirred compartments separated by the desired membrane to be tested. The membrane is maintained horizontally. -The gas (solute) concentration in the lower compartment is measured versus time, while the concentration in the upper liquid-containing compartment is maintained at a value near zero by a chemical reaction. The resistances-in-series model can be used to explain the transfer rate in the system. The two compartments are well stirred; this agitation reduces the resistances in the liquid boundary layers. Therefore it can be assumed that in this work the resistance in the membrane will be dominating. The method was evaluated using oxygen as a test. The following factors were found to influence mass transfer coefficient: i) the agitation in the two compartments; ii) the concentration of the reactive solution and iii) the thickness of the membrane.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2006 / A protocol already exists for fabrication of a capillary membrane having an internal ultrafiltration skin supported by a finger-like pore structure in the external capillary wall (Jacobs and Leukes, 1996; Jacobs and Sanderson, 1997). These membranes have been produced at the Institute of Polymer Science, University of Stellenbosch, South Africa. Two major applications emerged from the development of these internally skinned membranes. One application was in the production of potable water by Ultra-filtration (UF) from sources containing coloured water. A second application was in the immobilization of a white rot fungus in a ."gradostat" membrane bioreactor. Here a nutrient gradient through the membrane wall and fungal mat can be established and manipulated in order to stimulate continuous production of secondary metabolites (extra-cellular enzymes). These enzymes are useful in the degradation of polycyclic aromatic compounds, notably PCB species in contaminated water and soils (Jacobs and Sanderson, 1997). Two objectives emerged from experiences with the above applications. The first objective was to improve membrane performance in UF applications. In this case a reduction was sought in trans-membrane pressure differential required to attain a desired flux without sacrificing rejection. The pressure required for a given desired flux across a membrane depends on the resistance of the membrane skin layer and of its supporting sub-layer which together comprises the capillary wall and defmes its overall structure. If any of these resistances could be reduced, the overall resistance to transport of water would be reduced. Then it would be possible to operate the membrane at lower trans-membrane pressure differences. On the other hand, operation with higher pressure would also increase flux but require a thicker capillary wall to resist this pressure. In the attempt to optimise these properties of the capillary membrane, capillary membranes produced in the study reported here were tested to find the relationship of flux performance with the structures that resulted from varying key parameters affecting structure and integrity. The objective in the case of immobilizing fungi in membrane bioreactor applications was to attain thicker walls thus providing better support for the fungal mass. The internally skinned capillary membrane has finger-like microvoids that start next to the UF skin layer and extend across the capillary membrane wall and open at the external membrane periphery, giving an ideal structure for retaining the fungal biomass. The idea of a membrane with this type of morphology to immobilize white rot fungi was to anchor the growing fungus within these microvoids which imitate the natural environment in which these organisms live, that is, in the fibrous structure of decaying wood. The requirement to inoculate the microvoids with fungal spores (reproductive cells), implies that they need to be accessible from the outside, requiring a membrane wall that is externally unskinned. In the formation ofthe capillary membrane the processes of formation of the porous UP skin and the finger-like microvoids are mainly governed by diffusion of solvent out of a polymer dope (gel phase) and of non-solvent into the dope phase. Such exchanges are of primary importance between the bore fluid (containing non-solvent) and dope (containing solvent) or between the external spinning bath (high in solvent content) and dope. Diffusion effects also occur between the nascent pore voids and the precipitating polymer matrix. There are also expected to be some convection effects due to shear between the bore fluid and the moving dope gel phase and due to shrinkage ofthe gel phase. The variables selected for experimentation m the study reported here were: the dope extrusion rate (DER); dope composition (viscosity effects); bore fluid flow rate (BFF); bore fluid composition and wall thickness and diameter effects (determined largely by spinneret dimensions). Each of these has an expected effect on membrane structure and its resulting performance. Most were varied over narrow ranges indicated in the literature and by experience to be effective and critical. In addition, the effects of altering the walI thickness were investigated by using two different spinneret sizes. The external spinning bath composition (solvent content) was reported in the literature to be a particularly important parameter in the formation of externally unskinned membranes. Maintaining a high content of solvent in the external spinning bath could prevent skin formation. Too high a solvent content could, however, prevent phase transition and lead to later precipitation ofa dense skin on contact with the non-solvent in the later (humidification and rinsing) steps in the fmishing of the capillary membrane product. The external bath composition was therefore varied so as to find the bath composition that would match the cloud point for the polymer dope employed. As expected, the thickness of the membranes increased with DER increase. However, it was found that there is a critical wall thickness where an external skin layer is formed as a result of increasing the DER. A certain volumetric ratio ofDER to BFF (1,5:1 for this study) was therefore maintained in order to produce externally unskinned membranes. This shows that although the final membrane structure is detennined by the casting dope formulation, the fabrication protocol plays an equally important role in controlling structural properties and perfonnance. There was no significant change with the membrane thickness as a result of changing BFF but the voids became longer and more in number as the BFF was increased. Too high solvent content (99% NMP in this study) resulted in an external skin layer being formed. According to Smolders et.al. (1992), when the solvent content in the external spinning bath is too high, the polymer at the surface of the newly fonned membrane slowly dissolves in the external spinning bath re-forming a dope-like solution. When the newly formed membrane passes through the humidifier, the dope-like solution solidifies to form an external skin. At the same instance, too low solvent (93% for this study) resulted in external skin being fonned. Externally unskinned membranes were formed at 94 and 96% NMP bath composition. The use of a small spinneret resulted in very thin walled externally unskinned membranes.

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Made available in DSpace on 2018-08-01T22:57:56Z (GMT). No. of bitstreams: 1 tese_6914_Laisa Barroso Ribeiro PPGBF Dissertacao de mestrado 21 08 2015 Orientadora Profa Dra Ana Paula Bittencourt.pdf: 1615838 bytes, checksum: 4ec46cda64c8ecf496eb91b48761a25c (MD5) Previous issue date: 2015-08-21 / A relação maternal perinatal tem fundamental importância no desenvolvimento de circuitos neurais saudáveis que permanecerão como herança mental ao longo da vida. Logo, eventos adversos nesse período tem potencial para desencadear psicopatologias na idade adulta, aumentando a vulnerabilidade a transtornos psiquiátricos e abuso de substâncias. Neste trabalho foi realizada a Separação Maternal (SM) em ratos Wistar machos, no intuito de mimetizar um evento estressor sustentado na infância de humanos. Em seguida, os animais foram submetidos ao protocolo de Enriquecimento Ambiental, uma estratégia não farmacológica empregada num período de plasticidade cerebral, como estratégia potencial para reverter os efeitos prejudiciais da SM. Na idade adulta, procederam-se os testes comportamentais, para aferição de depressão, ansiedade e abuso de álcool, e bioquímicos, como a dosagem de corticosterona plasmática, indicativo da reatividade do eixo hipotálamo-hipófise-adrenal (HHA) ao estresse agudo, e dosagem de dopamina e seus metabólitos em estruturas envolvidas em processo de gratificação cerebral via mesocorticolímbica (núcleo accumbens e córtex pré-frontal). A análise estatística foi realizada por meio do teste t de Student, análise de variância de uma via, duas vias, três vias ou medidas repetidas. Observamos que um protocolo de SM mais extenso tem maior impacto no desenvolvimento de comportamento depressivo na idade adulta. Não observamos hiperresponsividade do eixo HHA em animais separados em resposta a estresse agudo. O EA aumentou a preferência pelo consumo de sacarose e SM e EA concomitantemente aumentaram os comportamentos ativos no Teste do Nado Forçado, sugerindo potencial antidepressivo do EA. O EA parece ter potencial ansiolítico, ao reduzir a ansiedade aprendida aversiva no Teste de Odor de Predador, sem efeito significativo da SM nesses comportamentos. A SM aumenta a preferência pelo consumo de etanol e o EA foi capaz de prevenir esse efeito. No córtex pré-frontal a SM aumentou a quantidade de dopamina e o EA aumentou o turnover dopaminérgico, sugerindo recuperação até certo ponto da atividade dopaminérgica cortical. No núcleo accumbens, SM e EA concomitantemente reduziram os níveis de DOPAC, sem alteração no turnover dopaminérgico. SM e EA parecem não interferir nas memórias de curta e longa duração. Dessa forma, observamos por meio de alterações comportamentais e bioquímicas que eventos adversos perinatais aumentam a vulnerabilidade ao desenvolvimento de abuso de álcool e outros transtornos psiquiátricos na idade adulta; e o EA, empregado na fase de plasticidade neural, tem potencial para exercer efeito compensatório sobre os déficits gerados.

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Lorsque l'on manipule un signal audio, il est généralement utile d'opérer un isolement du ou des éléments sonores que l'on cherche à traiter. Cette étape est couramment appelée séparation de sources audio. Il existe de nombreuses techniques pour estimer ces sources et plus on prend en compte d'informations à leur sujet plus la séparation a des chances d'être réussie. Une façon d'incorporer des informations sur une source est l'utilisation d'un signal de référence qui va donner une première approximation de cette source. Cette thèse s'attache à explorer les aspects théoriques et appliqués de la séparation de sources audio guidée par signal de référence. La nouvelle approche proposée appelée SPOtted REference based Separation (SPORES) examine le cas particulier où les références sont obtenues automatiquement par détection de motif, c'est-à-dire par une recherche de contenu similaire. Pour qu'une telle approche soit utile, le contenu traité doit comporter une certaine redondance ou bien une large base de données doit être disponible. Heureusement, le contexte actuel nous permet bien souvent d'être dans une des deux situations et ainsi de retrouver ailleurs des motifs similaires. L'objectif premier de ce travail est de fournir un cadre théorique large qui une fois établi facilitera la mise au point efficace d'outils de traitement de contenus audio variés. Le second objectif est l'utilisation spécifique de cette approche au traitement de bandes-son de films avec par exemple comme application leur conversion en format surround 5.1 adapté aux systèmes home cinéma. / In audio signal processing, source separation consists in recovering the different audio sources that compose a given observed audio mixture. They are many techniques to estimate these sources and the more information are taken into account about them the more the separation is likely to be successful. One way to incorporate information on sources is the use of a reference signal which will give a first approximation of this source. This thesis aims to explore the theoretical and applied aspects of reference guided source separation. The proposed approach called SPOtted REference based Separation (SPORES) explore the particular case where the references are obtained automatically by motif spotting, i.e., by a search of similar content. Such an approach is useful for contents with a certain redundancy or if a large database is be available. Fortunately, the current context often puts us in one of these two situations and finding elsewhere similar motifs is possible. The primary objective of this study is to provide a broad theoretical framework that once established will facilitate the efficient development of processing tools for various audio content. The second objective is the specific use of this approach to the processing of movie soundtracks with application in 5.1 upmixing for instance.