This dissertation is concerned with studies of highly viscous Newtonian and non-Newtonian liquids in bubble columns with, and without, draft tubes. The importance of the parameters influencing bubble column reactors is discussed with reference to previous work. The shapes and rise velocities of single bubbles in these liquids were studied in an 8.8cm diameter column, and the gas holdup, resulting from continuous bubbling of gas into this column, was also measured. Agreement between holdup predicted by the equation of Nicklin et al (1962), and experimental data in die present work and that of other workers is good. The limiting result of Dumitrescu (1943) was found to apply for fully developed slug flow in viscous non-Newtonian liquids in large columns. Gas holdup, in a 15cm diameter bubble column with a draft tube, consisted of large bubbles (slugs), which rapidly rose through the liquid, and very small bubbles, which accumulated in the liquid. These small bubbles were generated near the gas distributor and also at the liquid surface; less than 1% of the total gas flowrate into the system was converted into small bubbles for a highly viscous Newtonian liquid. The gas holdup due to small bubbles in non-Newtonian liquids was much less than that in Newtonian liquids. Large bubble velocities deduced from the bubble column measurements were consistent with the single bubble measurements. Liquid velocities in the 15cm column were measured by a neutrally buoyant flow follower; the liquid circulation rate was found to decrease with an increase in liquid viscosity. A model to predict the liquid circulation rate is outlined. The effect of scale-up on the gas holdup and liquid circulation rate was also studied experimentally in a 60cm square bubble column with a 30cm square draft tube. The bubble size distribution in this column was similar to the 15cm column but liquid velocities were higher, and gas holdup was smaller in the 60cm column.

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Implantable cardiovascular biomaterials have been widely applied in multiple cardiovascular disorders such as coronary artery disease, heart failure, and abdominal aortic aneurysms. However the failure modes of cardiovascular biomaterials are not uncommon, which is mainly due to the complications on blood-contacting surfaces such as thrombosis, calcification, and inflammation. Endothelium locates the inner surface of vessel lumen and is a critical regulator of vascular homeostasis. However, a readily available functional autologous source of endothelium has been hard to achieve. Human blood outgrowth endothelial cells (BOECs), cultured from peripheral blood mononuclear cells are proliferative and express endothelial protein profiles and as such are a very promising novel cell source for cardiovascular biomaterials coating. Endothelial nitric oxide synthase (eNOS) is an important regulator of vascular homeostasis and loss of eNOS activity is a hallmark of endothelial dysfunction. My data demonstrated that BOECs express markedly lower eNOS protein, mRNA as well as activity levels when compared to mature endothelial cells (ECs). My first project was to use transient transfection methods along with minicircle DNA to enhance eNOS expression levels in BOECs. Two promoters were tested in BOECs, the CMV promoter (pMini-CMV-eNOS) and the EF1α promoter (pMini-EF1α-eNOS). Transfection with pMini-CMV-eNOS achieved 24.8 ± 5.1 times more eNOS expression when compared to null transfected cells at 24 hours, a marked improvement over that achieved with conventional PVAX plasmid (10.2 ± 4.7 fold increase) or pMini-EF1α-eNOS (8.2 ± 1.2 fold increase both compared to null transfected control). pMini-CMV-eNOS mediated overexpression improved cell migration and network formation. When cultured on Osteopontin (OPN) coated surfaces, transient transfection with plasmid eNOS in BOECs can markedly enhance cell spreading and adhesion to ECM modified surfaces. These results suggest that eNOS expression in BOECs is suboptimal and BOECs may be functionally improved by techniques to enhance expression of this critical homeostatic regulator. Extracellular matrix (ECM) proteins have been shown to negatively regulate eNOS expression and NO production in mature ECs. In addition, the deposition of Col IV and Col I in BOECs is higher compared to that in mature ECs. Thus, I have proposed that the lower eNOS expression/activity in BOECs compared to mature ECs is due to higher ECM deposition. When grown on fibronectin, type I collagen, type IV collagen and laminin, significantly decreased eNOS protein in HUVECs were found compared to cells on polystyrene. Interestingly, when cultured on polystyrene, BOECs express significantly more extracellular matrix (ECM) proteins especially type I collagen compared to mature ECs. Blocking collagen synthesis significantly enhanced eNOS expression in BOECs (1.77 ± 0.41 fold increase). My results suggest that the regulation of eNOS in BOECs and mature ECs is similar and the reduced eNOS level in BOECs may be due to their increased collagen production. ECM proteins regulate intracellular signaling transduction primarily through integrin signaling associated with focal adhesion complexes. I have proposed that ECM proteins regulation on eNOS signaling in BOECs and mature ECs is through integrin and integrin-associated proteins. Matrix mediated eNOS downregulation was blocked by β1 integrin siRNA and focal adhesion kinase siRNA transfection in both BOECs and HUVECs. In addition, inhibitors of actin polymerization (e.g. ROCK inhibitors and cytochalasin D) block the effect of ECM on eNOS signaling. Taken together, my results suggest that ECM proteins regulate eNOS expression via a β1 integrin/FAK/actin polymerization dependent mechanism.

A unique and novel method to study thromboembolism by direct observation was developed. High-definition videos of thrombus formation and embolization were successfully obtained in miniature flow cells using in-vitro, non-invasive, real-time techniques. Critical parameters of thromboembolism such as thrombus growth rate, thrombus growth direction, shear force on the thrombus at embolization, and adhesion strength of the thrombus to the foreign surface were determined. Thrombus growth was found predominantly in two locations: 1) in the flow recirculation zone just after the trailing edge of the small tubes (53%) and 2) at the leading edge of the small tubes (47%). In the small tubes, thrombus volume and shear force acting on the thrombus increased in a power-law like function of time. In the large tubes, thrombus volume and shear force acting on the thrombus increased in a linear like function of time. The slope of thrombus growth rate in the small tubes was significantly greater than that in the large tubes. Thrombus growth direction was also estimated by tracking the thrombus center of mass with respect to time and typically ranged from 15 to 35 degrees from the direction of flow. According to observations, embolization seems to occur via two possible mechanisms: 1) complete detachment of the thrombus by sliding off the foreign surface or 2) partial embolization of the thrombus by internal tearing. The estimated shear force on the thrombus at embolization was determined and was significantly greater in the small tubes than in the large tubes. The adhesion strengths of thrombi were calculated for the small tubes using the shear force at embolization and the estimated thrombus attachment area and ranged from 9.63 to 28.83 N/m2 (mean = 16.24 ± 2.59 N/m2 95% confidence), which was in good agreement with published results of platelet retention experiments. An experimental series demonstrated that the developed method could be used to study the effects of controlled variables on thromboembolism parameters. In that series, heparin concentration in blood, blood flow rate, and device design were studied one variable at a time to test their effects on thrombus growth parameters and adhesion strength. Because of the small number of data, these preliminary results were statistically insignificant but pointed the way for future studies.

Detailed introducition of non-contact temperature measurement and correct settings of the measurement device, which has great influence on correct temperature determination, is the aim of this diploma thesis. The experimental laboratory was established to verify dependencies by Compaq CM non-contact thermometer. Conclusions and recomendations are deduced from the measurement results and their analysis.

Small diameter synthetic vascular grafts have yet to be clinically successful due to luminal narrowing from thrombosis and intimal hyperplasia. Current attempts to address this issue include the development of materials that support endothelialisation and protein modification to the material surfaces that reduce thrombosis. The extracellular matrix protein elastin has been found to be one of the least thrombogenic components of blood vessels, and its purified and recombinant forms have shown reduced thrombogenicity in both in vitro and in vivo models. Biomaterial coatings of elastin-like polypeptides (ELPs) recombinantly produced in the Woodhouse laboratory showed reduced fibrinogen adsorption, platelet adhesion, and platelet activity. However, the reason for their relative non-thrombogenicity is still not fully understood. In this work, the leukocyte response to ELP-coated materials was investigated. In particular, ELP1 and ELP4, which differ in molecular weight and sequence length, were physically adsorbed to a polyethylene terephthalate surface (MylarTM), yielding 0.22 ± 0.13 μg/cm2 and 0.37 ± 0.19 μg/cm2 surface coverage, respectively, as determined by the colorimetric assay, FastinTM Elastin. These surfaces were exposed to flowing citrated whole blood for surface and bulk evaluation of leukocyte activity using scanning electron microscopy and flow cytometry, respectively. Little leukocyte activation was observed on the surface of the controls, low-density polyethylene and uncoated MylarTM. In the bulk, tissue factor (TF) expression (monocytes: ELP1 = 38.6 ± 16.3 %, ELP4 = 33.9 ± 18.1 %) and platelet-leukocyte aggregates determined by CD61 (monocytes: ELP1 = 63.1 ± 17.1 %, ELP4 = 61.8 ± 16.8 %; granulocytes: ELP1 = 62.7 ± 17.0 %, ELP4 = 60.5 ± 20.1 %) were both decreased compared to uncoated MylarTM, while CD11b upregulation (monocytes: ELP1 = 18.7 ± 2.2 %, ELP4 = 19.7 ± 2.7 %; granulocytes: ELP = 21.4 ± 3.7 %, ELP4 = 22.0 ± 3.2 %) was increased. The statistical dependence of TF expression and platelet-monocyte aggregates was tested; however, no correlation was found. Overall, platelet-leukocyte aggregate formation was reduced and there were conflicting results with regards to the reduction of leukocyte activation for the ELP coatings on MylarTM. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-10-10 15:34:51.802

Improvements upon current gas turbine sealing technology performance are essential for decreasing specific fuel consumption to meet stringent future efficiency targets. The clearances between rotating and static components of a gas turbine, which need to be sealed, vary over a flight cycle. Hence, a seal which can passively maintain an optimum clearance, whilst preventing contact between itself and the rotor, is extremely desirable. Various configurations of a Rolls Royce (RR) seal concept, the Large Axial Movement Face Seal (LAMFS), use static pressure forces to locate face seals. Prototypes were tested experimentally at the Osney Thermofluids Laboratory, Oxford. Firstly a proof-of concept rig (simulating a 2-D seal cross-section) manufactured by RR was re-commissioned. The simplest configuration using parallel seal faces induced an unstable seal housing behaviour. The author used this result, CFD, and analytical methods to improve the design and provide a self-centring ability. A fully annular test rig of this new seal concept was then manufactured to simulate a 3D engine representative seal. The full annulus eliminated leakage paths unavoidable in the simpler rig. A parametric program of experiments was designed to identify geometries and conditions which favoured best-practice design. The new seal design is in the process of being patented by Rolls Royce. A 'fluidic' seal was also investigated, showing very promising results. A test rig was manufactured so that a row of jets could be directed across a leakage cross-flow. An experimental program identified parameters which could achieve a combined lower leakage mass flow rate compared with the original leakage. Influence of jet spanwise spacing, injection angle, jet to mainstream pressure ratio, mainstream pressure difference and channel height were analysed. It is hoped this thesis can be used as a tool to further improve these seal concepts from the parametric trends which were identified experimentally.

Chez les vertébrés, les neurones qui contactent le LCR (NcLCR) sont présents autour des cavités ventriculaires et tout le long du canal central (cc). Par la combinaison d'enregistrements électrophysiologiques sur tranche de tronc cérébral et d'analyses immunohistochimiques, nous avons réalisé la première caractérisation de cette population neuronale chez la souris adulte. Nous montrons que les NcLCR sont présents autour du cc au niveau du complexe vagal dorsal (CVD), une structure bulbaire impliquée dans la régulation des fonctions autonomes, où ils sont principalement GABAergiques, reçoivent des afférences synaptiques GABA/Glycinergiques et expriment le canal PKD2L1 ("polycystin kidney disease 2-like 1"), un membre de la famille des canaux TRP ("transient receptor potential"). Nous montrons que l'activité de PKD2L1 est modulée par les variations de pH et d'osmolarité et que son augmentation module l'excitabilité des NcLCR. Finalement, nous démontrons que les NcLCR existent dans un état de maturité intermédiaire caractérisé par propriétés fonctionnelles de neurones matures combinées à la conservation de l'expression de marqueurs d'immaturités.Les NcLCR étant stratégiquement positionné entre le LCR et le parenchyme, ils pourraient détecter des signaux circulant grâce à l'activation de PKD2L1 puis distribuer le message collecté à leurs partenaires. Un tel rôle, apparaît particulièrement intéressant au niveau du CVD, un site de régulation majeur des fonctions autonomes et pourrait être démontré par l'identification du réseau neuronal où les NcLCR sont intégrés. / In vertebrates, cerebrospinal fluid contacting neurons (CSF-cN) are present around the ventricular cavities and along the central canal (cc). In this study, by the combination of whole cell patch-clamp recordings on brainstem slice and immunohistochemistry analysis, we realize the first characterization of this neuronal population in adult mice. We show that CSF-cN are present around the cc in the dorsal vagal complex (DVC), a major hindbrain structure regulating autonomic functions. There, CSF-cN are mostly GABAergics, receive GABA- and glycinergic synaptic entries and express functional polycystin kidney disease 2-like 1 (PKD2L1) channels. These channels are a subtype of the transient receptor potential (TRP) channels superfamily and this study represent the first analysis of PKD2L1 properties in a native system. We show that PKD2L1 channel activity is modulated by variations in extracellular pH and osmolarity and in turn, an enhanced activity of only few PKD2L1 channels participates in the modulation of CSF-cN excitability. Finally, we demonstrate that CSFcN exhibit another interesting property since they exist in an intermediate stage of maturity by displaying many mature functional properties combined to the conservation of the expression of immature markers.Because CSF-cN are strategically positioned between CSF and parenchyma, they could detect circulating signals through PKD2L1 activation and convey the collected messages to cellular partners. Such a role might be particularly relevant at the level of the DVC a major regulatory site for autonomic functions and should be demonstrated by identifying and characterizing the neuronal network CSFcN are involved in.

A non-contacting steel plate conveyance system based on the linear induction motor scheme, which can provide lift and propulsive forces simultaneously, is proposed. It has the features of high power density, direct drive, simple mechanical structure, and being able to reduce the operation noise. A magnetic equivalent circuit method and electromagnetic theory incorporating with 3-D finite element analysis are involved to investigate the static and quasi-dynamic properties and confirm the electrical and mechanical designs. To realize the dynamic behavior and develop the closed-loop control, a proper stationary reference frame transformation of the system voltage equations is also introduced. By considering the practical operational environment, a fuzzy-based control structure integrated with remote optical measurement system has been established and implemented by a DSP-based controller combined with required peripheral circuits. The experimental results show the applicability of such control strategies. With the systematic procedures for design, analysis, and control provided in this dissertation, implementation feasibility of the proposed system can be conveniently demonstrated.

Trickle-flow is traditionally modeled by means of hydrodynamic parameters such as liquid holdup, two-phase pressure drop and wetting efficiency. Several studies showed that these parameters are not only a function of flow conditions and bed properties, but also of the flow history and morphology of flow. These can have a major influence on the distribution in the bed. The effect of flow morphology on liquid holdup and pressure drop is widely discussed in literature, but little attention is paid to its effect on wetting efficiency. Trickle-bed reactor models suggest that not a only bed-averaged but also the distribution of wetting efficiency may be of importance for reactor performance. Both the average wetting efficiency and the distribution of wetting are probably a function flow history and morphology. The distribution of wetting efficiency for different flow morphologies were investigated by means of a colorometric method that was developed for this purpose. Representative wetting distributions could be obtained. Flow morphologies and liquid distributions were manipulated by means of the pre-wetting procedure that was performed prior to flow. Pulse and Levec pre-wetted beds were investigated. These distributions were explained in detail in terms of flow morphology. It was found that the average wetting efficiency in pulse pre-wetted beds are much higher than in Levec pre-wetted beds. All particles in the pulse pre-wetted beds at all investigated flow conditions were contacted by the flowing liquid. This was not the case for the Levec pre-wetted beds. It was found that the flow in Levec pre-wetted beds become similar to that in pulse pre-wetted beds at high liquid flow rates. It was investigated how these distributions can affect reactor modeling, based on popular particle-scale models that relate reactor efficiency to wetting efficiency. According to these models, the wetting efficiency distribution in pulse pre-wetted beds can be characterised by means of only its average value. This is not the case for Levec pre-wetted beds. These results are however a strong function of the models that were employed. Finally, some recommendations are made in terms of the preferred pre-wetting method or flow morphology for different types of reactions. These recommendations are also based on models and have not been verified with experiments. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2007. / Chemical Engineering / unrestricted