Das RNA-guided adaptive Immunsystem CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated) immunisiert prokaryotische Zellen gegenüber mobilen genetischen Elementen (MGEs). Bei der Adaption wird eine kurze Nukleinsäurensequenz (prespacer) von den MGEs gewonnen, verarbeitet und schließlich als spacer in das CRISPR-Array integriert. Cas1 und Cas2, die Hauptbestandteile der Adaption, bilden einen Integrase-Komplex, welcher neue spacer in das CRISPR-Array integriert. Der molekulare Mechanismus für die Adaptiondes Typ II-A Systems, welches cas9, cas1, cas2, csn2 und tracrRNA codiert, ist bis heute nicht vollständig verstanden. Daher untersuchten wir die Anforderungen der verschiedenen Cas-Proteine für den Adaptionsprozess. Wir verifizierten die Adaptions-Aktivität von Typ II-A Systemen des Streptococcus thermophilus LMD-9 anhand von Adaptionsstudien nach Phagen-Infektion. Dabei beobachteten wir höhere Akquisitionsraten im CRISPR3-Lokus im Vergleich zum CRISPR1-Lokus. Unsere Plasmid-basierte Adaptionsstudie bestätigte die Notwendigkeit von Cas9, zusätzlich zu Cas1, Cas2 und Csn2 bei der Adaption. Der yeast two-hybrid und der pull-down Ansatz zeigten sowohl spezifische Interaktionen zwischen den Cas-Proteinen, als auch Interaktionen zwischen Cas-Proteinen sowie DNA-Reparatur Proteinen. Die Regionen der Cas1 und Cas9 Interaktion wurden durch SPOT peptide assay identifiziert. Zusammenfassend weist unsere Studie darauf hin, dass Cas-Proteine sowohl mit Proteinen innerhalb, als auch außerhalb des CRISPR-Cas Systems interagieren, und bietet somit eine Basis für die Erforschung der möglichen Funktionen von DNA-Reparatur Proteinen in CRISPR-Cas Systemen und vice versa. / The RNA guided adaptive immune system CRISPR (clustered regularly interspaced short palindromic repeats) Cas (CRISPR-associated) immunizes prokaryotic cells against mobile genetic elements (MGEs). During spacer acquisition stage, a short nucleic acid sequence (prespacer) is acquired from the MGEs, processed and finally integrated into the CRISPR array as a spacer, which serves as genetic memory to defend against the invasion of the cognate MGEs. The molecular mechanism for the spacer acquisition of the type II A systems, which encode cas9, cas1, cas2, csn2 and tracrRNA, is still not fully understood. Therefore, we investigated the requirement of the different Cas proteins for spacer acquisition. We verified the acquisition activity of the type II A systems of Streptococcus thermophilus LMD 9 via spacer acquisition studies by phage challenge. We observed higher acquisition rates in the CRISPR3 locus compared to the CRISPR1 locus. Our plasmid-based spacer acquisition study confirmed in addition to Cas1, Cas2 and Csn2 the requirement of Cas9 for spacer acquisition. Yeast two hybrid and pull down approaches revealed specific interactions among the Cas proteins, as well as interactions between Cas and DNA repair proteins. The interaction regions of Cas1 with Cas9 were identified by SPOT peptide assay. Altogether, our study suggests that Cas proteins interact with proteins within and beyond the CRISPR Cas systems, and it provides a basis for the investigation of the potential roles of DNA repair proteins in the CRISPR Cas systems and/or vice versa.

Orientador: Dionízio Paschoareli Júnior / Resumo: Este trabalho apresenta um método que visa possibilitar a gestão do aparente impasse envolvendo três agentes do setor elétrico. A Distribuidora de Energia que visa lucros, o Regulador que impõe às Distribuidoras, metas permanentes de melhor desempenho juntamente com viés de redução das tarifas e o Consumidor que deseja qualidade de fornecimento de energia e tarifas justas. Este método possibilita identificar e priorizar com precisão qual circuito de um sistema elétrico é mais adequado para os investimentos em melhoria de desempenho, quantificar o ganho de qualidade após as melhorias e avaliar técnica e economicamente se o benefício obtido em melhoria de qualidade produzirá retorno financeiro para remunerar o investimento. Para o desenvolvimento deste método, os dados de desempenho do sistema elétrico foram tratados estatisticamente para identificar quais ocorrências podem ser mitigadas com ações da distribuidora. Foi desenvolvida uma matriz de decisão multiatributos, referenciada pelos parâmetros de desempenho do sistema elétrico, para possibilitar a ordenação das regiões elétricas prioritárias para investimentos em melhorias. As ações técnicas de melhorias consideram a utilização de redes compactas e através de medições de desempenho destas redes e a comparação com o desempenho de redes nuas, foi possível estabelecer o potencial de redução do número de ocorrências após a implantação. Foi estabelecido critérios para identificar a taxa de melhoria de desempenho, que estabelece... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This paper presents a methodology which supports the management of this apparent impasse involving three electricity sector agents. The Utility Company which focus on profit, the Regulator that imposes on Distributors permanent goals of better performance together with tariff reduction biases, and the Consumer who seeks for quality of energy supply and fair tariffs. This method makes it possible to accurately identify and prioritize which circuit of an electrical system is most appropriate for investments in performance improvement and to technically and economically evaluate whether the benefit obtained in quality improvement will yield financial return for the investment. For the development of this method, the performance data of the electrical system was treated statistically to identify which occurrences could be mitigated by distributor actions. A multi-attribute decision matrix was developed, supported by the performance parameters of the electric system, to enable the ordering of the priority electric regions for investments in improvements. The technical actions of improvements consider the use of spacer cable system. Through performance measurements of these networks, it was possible to establish the potential of reducing the number of occurrences after the implantation. To identify the rate of performance improvement a criterion has been established which establishes the correlation between the modernized network extension and the reduction of the number of occurre... (Complete abstract click electronic access below) / Doutor

Innovative 3D spacer fabrics made from individual planes and connecting layers present great potential as complexly shaped textile preforms in lightweight composite applications. As one of the most flexible textile manufacturing methods, flat knitting enables the production of intricately shaped textile structures. The major advantages coupled with flat knitting techniques include the ability to produce multi-layer reinforcements, a diminishing waste, reducing production time and near-net shaping. This research includes the further development of flat knitting technology and the manufacturing processes of innovative, customized 3D spacer fabrics for high performance composite applications. Novel 3D spacer fabrics have been developed in different geometries using glass-polypropylene commingled hybrid yarns for complex shaped thermoplastic composite components. Reinforcement yarns have been integrated into spacer fabric structures with up to 4 reinforcement layers to improve mechanical performance. Furthermore, the successful addition of “sensor networks” created by integrating functional yarns into the 3D spacer fabrics could be used for structural health monitoring. Innovative integration concepts, which accommodate different positioning of the reinforcement yarns into the knit structures, can be used to adjust the mechanical properties of the finished knit composites. Moreover, the tensile properties have been accurately predicted based on the mathematical models formulated. The developed flat knitted 3D spacer fabrics are very promising for applications in lightweight composites, mechanical engineering, protective textiles, civil engineering and architectural designs. / Innovative 3D-Spacer Fabrics bestehend aus individuellen Deckflächen und Verbindungsstegen bieten ein großes Potential als komplex geformte textile Halbzeuge für Leichtbauverbundwerkstoffanwendungen. Mit Hilfe des Flachstrickens, welches einer der flexibelsten textilen Herstellungsprozesse ist, lassen sich komplex geformte textile Strukturen herstellen. Belastungsgerechte Verstärkungen, Abfallreduzierung, endkonturnahe Fertigung sind nur einige der großen Vorteile der modernen Flachstricktechnik. Die Forschungsarbeit beinhaltet die Entwicklung der Flachstricktechnologie und des Herstellungsprozesses für innovative 3D-Spacer Fabrics für Hochleistungsverbundwerkstoffe. Neuartige 3D-Spacer Fabrics wurden in unterschiedlichen Geometrien entwickelt, in dem Glas-/ Polypropylen Commingling-Hybridgarn für komplex geformte thermoplastische Verbundwerkstoffkomponenten eingesetzt wird. Verstärkungsfäden wurden für hochmechanische Belastungen in die Spacer-Fabric-Strukturen in bis zu 4 Verstärkungschichten integriert. Die erfolgreiche Umsetzung und Entwicklung von Sensornetzwerken durch die Integration von funktionalen Fäden in die 3D-Spacer Fabrics kann für die strukturelle Zustandsüberwachung genutzt werden. Die innovativen Integrationskonzepte erlauben die differenzierte Orientierung von Verstärkungsfäden in den Gestrickstrukturen, wodurch eine starke Beeinflussung der mechanischen Eigenschaften der Gestrickverbundwerkstoffe herbeigeführt wird. Darüber hinaus wurden die Zugeigenschaften basierend auf den entwickelten mathematischen Modellen vorhergesagt. Die entwickelten flachgestrickten 3D-Spacer Fabrics sind sehr vielversprechend beispielweise für die Anwendung in Leichtbauverbundwerkstoffen, im Maschinenbau, in Schutztextilien, im Bauingenieurwesen und Architekturdesign.

Le microbiote pulmonaire complexe de patients atteints de mucoviscidose (MV) peut être modifié par des facteurs de l'hôte (état clinique), xénobiotiques (antibiothérapie, habitat) ainsi que bactériens (pathogènes, commensaux). Notre étude a porté sur ces facteurs bactériens et plus particulièrement sur l'effet de Pseudomonas aeruginosa sur la structuration des microbiotes MV. Le but de notre travail a été d'étudier la structure et la composition des microbiotes pulmonaires chez des patients MV en fonction de la présence ou non de P. aeruginosa, ainsi que l'effet de ces microbiotes sur ce pathogène. Différentes approches nous ont permis de mettre en évidence ces résultats : i) certains genres bactérien (Stenotrophomonas, Prevotella) contenus dans un microbiote particulier plus pauvre et moins diverse sont associés préférentiellement à la présence de P. aeruginosa, ii) aucune diminution de richesse et de diversité n'est observée en amont d'une primo-colonisation par P. aeruginosa mais celle-ci entraine ultérieurement une diminution de richesse du microbiote, iii) le microbiote MV in vitro s'appauvrit et diminue en diversité plus rapidement lors d'une colonisation par une souche ayant un phénotype de « primo-colonisation », iv) les souches de primo-colonisation sont plus virulentes que les souches issues de colonisation chronique, v) ces souches sécrètent des molécules appartenant à la famille des 4-hydroxy-2-heptylquinoline (HAQs) bactéricides vis-à-vis de S. aureus. Une meilleure compréhension de cette modulation des microbiotes MV par P. aeruginosa offriraient de nouvelles stratégies thérapeutiques afin notamment de contrer l'implantation de ce pathogène au niveau pulmonaire et de limiter le développement d'infections chroniques chez les patients MV / Cystic fibrosis microbiota could be modified by different factors such as host factor (clinical state), xenobiotic factor (antibiotic, environment) or bacterial factors (pathogen, commensal). Our study focused on bacterial factors and more particularly on the impact of Pseudomonas aeruginosa on the CF microbiota structure. The objectives were to study the structure and the composition of CF microbiota whether the presence or not of P. aeruginosa and the impact of the CF microbiota on this pathogen. Different experimentations were used to get results : i) bacterial genus (Stenotrophomonas, Prevotella) were preferentially associated with P. aeruginosa in a poor and no diverse microbiota, ii) no previous decrease of microbiota richness was observed when the initial P. aeruginosa pulmonary colonization took place but this event was associated with a later decrease of microbiota richness, iii) In vitro model of CF microbiota showed a more important richness and diversity decrease with early colonization strains, iv) early colonization strains were more virulent than chronic colonization strains, v) these strains secreted bactericid molecules toward Staaphylococcus aureus belonging to 4-hydroxy-2-heptylquinoline (HAQs). Improve our understanding on how P. aeruginosa could modulate CF microbiota could permit to find new therapeutic strategies to prevent the early colonization and then to limit the chronic infections in CF patients

The need for innovative lightweight materials are rapidly increased in the recent years, owing to their cost-effective, high-strength, environmentally-sound use of materials and process technologies, in addition to that they reduce the weight of a product. The characteristics of 3D-spacer fabrics as one of the most important lightweight materials in future are multifaceted not only owing to its extremely light materials, but also because of exceptionally high stiffness to weight ratio compared to other constructions. It is also one possible method for improving the properties of fabric-reinforced composites. It can enhance the through-the-thickness properties, such as shear strength, dimensional stability, damage, tolerance, and fracture toughness that are critical for many structural applications. Spacer fabric has been employed in high-technology applications because of its critical mechanical properties related to high tensile strength, tear strength and stiffness. Furthermore, its multidirectional structures allow with more reinforcement along the thickness direction leading to an increase in stiffness and strength properties. The fundamental aim of this thesis exists in the development of a new kind of woven spacer fabrics for the light weight composites materials, in an effort to weave spacer fabrics that can not be realized with the old technology which are mentioned above. Therefore, the work in brief focuses on two main goals: 1. Development of a new kind of spacer fabrics for composites in the lightweight constructions. 2. Development of special devices of a narrow weaving machine for standing the process of the new kind of spacer fabrics production. The slippage strength test had to be carried out for the floated warp yarns through the ground fabrics by using different elements of woven fabric structures variables represented in different fabric constructions, different weft densities and different repeats of constructions by using different materials. The importance of this test related to the backward-movement of the floated warp yarns which is the crucial stage in the weaving process of spacer fabrics during the backward-movement. The results of this test determine the required forces for the backward-movement, on the other side it is the best method to observe the behavior of structure elements during the backward movement. The results of the slippage strength had been statistically analyzed, and the weaving process for the spacer fabrics had been achieved. It was concluded that the best properties for the woven spacer fabrics and the optimum case for the weaving process on the test weaving machine had been achieved when the following items are realized: Development of the narrow weaving machine is closed in assisting operations, let-off and take-up and enhancement for take-up processes. Extra let-off and take-up devices must be constructed at the weaving machine. Extra let-off device has to be used for controlling the floated warp yarns of ground fabrics. On the other side, extra take-up and the developed take-up devices have to be used for controlling the woven spacer fabrics. The experimental results give fundamental knowledges for the next steps in research and development of woven spacer fabrics made of high-performance yarns on the wide weaving machine. / Die Ziele der Arbeit bestanden in der Entwicklung der Geometrie der Spacer Fabrics und der notwendigen Falteneinrichtung an der Bandwebmaschine. Spacer Fabrics werden ausschließlich aus zwei Deckflächen, die durch eingewebte Stege verbunden sind, gefertigt. Zur Entwicklung der Spacer Fabrics muss eine Doppelnadel-Bandwebmaschine mit zwei Webfächern eingesetzt werden. Für die Faltenwebeinrichtung werden der entwickelte Extra-Kettablass und der Extra-Abzug benötigt. Der Antrieb und die Steuerung des Extra-Abzuges erfolgen durch einen Synchronantrieb und der Antrieb und die Steuerung des Extra-Ablasses durch Pneumatik.Eine frei programmierbare Steuerung der Faltenwebeinrichtung ermöglicht eine sichere und optimierte Synchronisation zwischen Webprozess und Faltenbildung. Im Ergebnis einer systematischen Strukturentwicklung von Spacer Fabrics und der Simulation ihrer günstigen Herstellung mittles eines speziell entwickelten Slippage Strength Tests werden die optimalen Strukturen ermittelt. Die experimentellen Untersuchungen bringen grundlegende Erkenntnisse für die folgenden Forschungsschritte zur Entwicklung von gewebten Spacer Fabrics mit Hochleistungsgarnen auf Doppelgreiferwebmaschinen.

Företaget Ortoma utvecklar i samarbete med Sahlgrenska Universitetssjukhus och Smart Textiles ett implantat som ska placeras mellan ländryggens taggutskott för att lindra spinal stenos. Implantatet ska ha en kuddeliknande form och bära den last som uppstår mellan taggutskotten, det ska även återställa distansen mellan dem. De flesta implantat på marknaden idag är tillverkade i hårda material, exempelvis titan, för att bära upp den höga last som uppstår i ryggen. Detta ger ofta friktionsskador på bendelar och kan även innebära ett stort operationsingrepp. Följande examensarbete syftar därför till att utveckla ett textilt ytskikt till ett implantat i en sömlös tredimensionell konstruktion som ska klara en kompressionslast på 10 kN. Tre olika typer av provkroppar handvävdes i 100 % Dyneema®. En remsa, en tub och en tredimensionell kudde som sedan fylldes med silikon. Samtliga provkroppar vävdes i två olika grundbindningar, tvåskaft och batavia. För att utvärdera och jämföra de båda bindningarna testades provkropparna med egenutvecklade dragprovnings- och kompressionstester. De konstruktioner som påvisade högst brottlast i samtliga tester var vävda i grundbindningen batavia, vilken innehöll nästan tre gånger så många inslag per centimeter som bindningen tvåskaft. Inslag per centimeter visade sig vara den parameter som till största del avgjorde skillnaden mellan provkropparnas styrka eftersom mängden material då blev betydligt större. De tredimensionella kuddarna klarade en belastning på strax över 10 kN under kompressionstestet. Dock observerades en svag länk i konstruktionen vid övergången mellan dubbelväv och enkelväv, vilken behöver utvecklas vidare. Genom en förfinad konstruktionsteknik och vidare utveckling skulle det textila ytskiktet som utvecklats under projektet kunna konkurrera med dagens implantat. Tillverkningen skulle kunna ske i en Jacquardvävstol med skyttel och skulle då få en kortare produktionstid, samt möjliggöra en individuell anpassning av implantatet.

Inconel alloys are commonly used as structural materials in nuclear reactors. One of these alloys, the Inconel X-750, is a γ’ Ni3(Al, Ti) strengthened superalloy extensively used in the cores of reactors, such as spacers in CANada Deuterium Uranium (CANDU) fuel channels. Prior to their application in commercial reactors, accelerated irradiation tests had been conducted in liquid metal fast reactors. Results did not indicate any problem stemming from significant fast neutron irradiation. However, recently it has been found that the ex-service CANDU Inconel X-750 spacers became severely brittle after a lengthy exposure to reactor environment. The underlying mechanism remains unclear and thus forms the focus of this current investigation, predominantly through transmission electron microscopy (TEM). This dissertation unfolds with the literature review in Chapter 2, followed by presentation of novel techniques in Chapter 3 on the preparation of TEM samples from small reactor components, namely the spacers. Chapter 4 presents TEM characterizations of ex-service spacers removed from the reactors. To simulate neutron irradiation over wide temperature range in an effort to understand the damage mechanisms, heavy ion irradiations were conducted and reported in Chapter 5 and 6. Irradiations are found to significantly alter the stability of the primary strengthening phase γ’, a systematic experimental study of which is presented in Chapter 7. To fully understand the effects of transmutation produced helium on irradiation induced cavity and dislocation microstructures, TEM in-situ heavy ion irradiations with hot/cold pre-injected helium were conducted and reported in Chapter 8 and 9. Helium was found to play an important role in the irradiation-induced instability of γ’ in nickel-based superalloys, the discussion of which is presented in Chapter 10. As one of the most important defect structures induced from irradiation, the stacking-fault-tetrahedra, were dynamically observed and are described in a journal manuscript in Appendix A. In addition to broadening current understanding of material degradation mechanism for in-service CANDU spacer, this study also provides comprehensive information on irradiation damage in nickel based superalloys, irradiation induced lattice defects and phase instability in face centered cubic alloys, as well as helium’s effects on cavity formation, dislocation evolution, and phase transformation. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-09-06 15:21:02.334

Garry oak (Quercus garryana Douglas ex. Hook) is a white oak (Quercus sect. Quercus) with a geographic range extending from southwestern BC to south-central California. It is the only native white oak in BC and Washington, and is the northernmost species of the California Floristic Province-Pacific Northwest white oak clade. I used molecular methods to address the following questions: 1) What are the patterns of genetic variation within Garry oak? 2) How do these patterns vary geographically, and how did the spatial distribution of the gene lineages come to occupy its current geographical range? 3) Does Garry oak show evidence of genetic interaction with other white oak species in western North America? 4) Is there morphological or genetic evidence to support the three described varieties of Garry oak? I obtained samples of Garry oak from 117 localities over its geographic range, as well as samples of two other California white oaks (Q. lobata and Q. douglasii) and a Rocky Mountain species (Q. gambelii). Analyses of DNA sequence data from four plastid DNA regions revealed 24 distinct molecular variants (haplotypes) in Garry oak. These show a strong south-to-north decrease in genetic diversity, consistent with post-glacial northward expansion. Haplotypes present in the northern part of the range provide evidence of two separate northward migrations, only one of which reached the northern range limit of Garry oak in BC. I found that Garry oak shared plastid DNA haplotypes with two other white oak species, indicating that it hybridizes with other oaks in the southern part of its range. The nuclear ribosomal ITS phylogeny showed poor resolution, but both cpDNA and nrDNA may indicate that Q. garryana is more closely related to the white oaks of central North America than was previously thought. My findings also suggest that the three currently recognized varieties of Garry oak (var. garryana, breweri and semota) are not well differentiated genetically, but show morphological variation at the regional level. This study shows the phylogeographic patterns within Q. garryana. In addition, it contributes to conservation efforts in Garry oak ecosystems by indicating regions of high genetic diversity in Garry oak, including genetically unique populations that may be especially worthy of preservation. / Graduate

Orientador: José Vicente Tagliarini / Resumo: Introdução: a doença degenerativa da coluna cervical é prevalente e incapacitante, levando a dor e sintomas neurológicos. A cirurgia de discectomia e fusão por via anterior é bem estabelecida para o seu tratamento, sendo realizada com a colocação de dispositivos interssomáticos (cages) e placas anteriores. Novos cages ancorados prometem diminuir a disfagia pós-operatória deste procedimento. Objetivo: verificar por meio de uma revisão sistemática a efetividade da utilização de cages ancorados na redução de disfagia pós-operatória sem prejuízo dos outros benefícios obtidos com a cirurgia. Métodos: foram pesquisadas as bases de dados Embase, MEDLINE, LILACS, Scopus, Web of Science e Cochrane CENTRAL. Foram reunidos estudos observacionais e experimentais que avaliaram a utilização de cages com placas anteriores e cages ancorados em pacientes com doença degenerativa da coluna cervical. Os desfechos avaliados foram disfagia, aumento do escore JOA, diminuição do escore NDI, fusão pós-operatória, aumento da lordose cervical, tempo de cirurgia, perda intraoperatória de sangue e resultados bons/excelentes pelos critérios de Odom. Para metanálise foi empregado o software RevMan 5.3 fornecido pela Colaboraçao Cochrane. Resultados: o número total de pacientes em 30 estudos selecionados foi de 2178, sendo 1089 em cada grupo. Em 48 horas, 30 dias, 90 dias e 12 meses após a cirurgia, houve menores índices de disfagia no grupo dos cages ancorados, chegando a RR 0,15 (IC95% 0,08-0,27, I2=0%) n... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Introduction: cervical degenerative disc disease is a highly prevalent and disabling disease, leading to pain and neurologic symptoms as weakness and radiculopathy. Anterior cervical diskectomy and fusion (ACDF) is a well stabilished procedure for its treatment, usually performed by placing a spacer (cage) with the addition of an anterior fixation plate. New anchored spacers have been introduced with the promise of a faster less morbid procedure. Study goals: to perform a systematic review for the analysis of postoperative dysphagia between standard and anchored anterior cervical spacers, also taking into consideration quality-of-life and radiologic parameters. Methods: a comprehensive search was performed in the MEDLINE, Scopus, Web of Science, LILACS and Cochrane CENTRAL databases. Observational and interventional studies evaluating outcomes after ACDF with conventional cage-plate construct and anchored spacers were selected. The following outcomes were evaluated: dysphagia, JOA/mJOA score, NDI score, fusion rates, cervical lordosis improvement, operative time, intraoperative blood loss and rate of good/excellent outcomes by Odom’s criteria. The RevMan software (v5.3) was used to perform meta-analysis. Results: a total of 2178 patients were enrolled in 30 studies, with 1079 patients in both control and intervention groups. At all postoperative moments (48 hours, 30 days, 90 days and 12 months), there was a significantly lower rate of dysphagia in the anchored spacer group, ... (Complete abstract click electronic access below) / Mestre

Hollow fibre and spiral wound membrane (SWM) modules are the most common commercially available membrane modules. The latter dominate especially for RO, NF and UF and are the focus of this study. The main difficulty these types of modules face is concentration polarisation. In SWM modules, the spacer meshes that keep the membrane leaves apart also help reduce the effects of concentration polarisation. The spacer filaments act as flow obstructions, and thus encourage flow destabilisation and increase mass transfer enhancement. One of the detrimental aspects of the use of spacers is an increase of pressure losses in SWM modules. This study analyses the mechanisms that give rise to mass transfer enhancement in narrow spacer-filled channels, and investigates the relationship between flow destabilisation, energy losses and mass transfer. It shows that the regions of high mass transfer on the membrane surface correlate mainly with those regions where the fluid flow is towards the membrane. Based on the insights gained from this analysis, a series of multi-layer spacer designs are proposed and evaluated. In this thesis, a Computational Fluid Dynamics (CFD) model was used to simulate steady and unsteady flows with mass transfer in two- and three-dimensional narrow channels containing spacers. A solute with a Schmidt number of 600 dissolving from the wall and channel Reynolds numbers up to 1683 were considered. A fully-developed concentration profile boundary condition was utilised in order to reduce the computational costs of the simulations. Time averaging and Fourier analysis were performed to gain insight into the dynamics of the different flow regimes encountered, ranging from steady flow to vortex shedding behind the spacer filaments. The relationships between 3D flow effects, vortical flow, pressure drop and mass transfer enhancement were explored. Greater mass transfer enhancement was found for the 3D geometries modelled, when compared with 2D geometries, due to wall shear perpendicular to the bulk flow and streamwise vortices. Form drag was identified as the main component of energy loss for the flow conditions analysed. Implications for the design of improved spacer meshes, such as extra layers of spacer filaments to direct the bulk flow towards the membrane walls, and filament profiles to reduce form drag are discussed.