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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
461

Comparative effect of haemodynamic variables and rheological properties of the blood on the margination and adhesion of leukocytes and platelets

Watts, Tim January 2010 (has links)
The work in this thesis used an in vitro flow system, which incorporated a capillary viscometer, to systematically determine the effects that haemodynamic variables, or rheological properties of the perfused, fluorescently-labelled blood, had on the behaviour of leukocytes and platelets. By varying shear rate and stress, blood haematocrit, and aggregation and deformability of red cells, we obtained evidence that leukocyte adhesion was dictated by the number of free-flowing cells 'marginated' near the vessel wall and the force experienced by their initial adhesive bonds. Platelet adhesion was dependent on the velocity of the free-flowing cells near the vessel wall and the force experienced by the platelets once adhered. In contrast to leukocytes, variation in platelet adhesion appeared less dependent on variation in the number of free-flowing cells near the vessel wall, but dictated more by the width of the peripheral plasma layer; a thinner plasma layer promoting more efficient platelet adhesion. Overall, this thesis provides evidence that the differential margination and adhesion of leukocytes and platelets is largely a result of the difference in their size. Thus, it seems that the sizes of RBC, leukocytes and platelets are all adapted to provide efficient immune and haemostatic responses in different regions of the circulation.
462

Coal fly ash and the circular economy

Blissett, Robert January 2015 (has links)
Coal fly ash (CFA) can be regarded as a unique material with the potential to be a showcase waste to illustrate the concept of the circular economy. The application of a processing scheme to power station CFA allows the exploitation of multiple components of the product. The CFA can be separated into low density, carbon, and magnetic concentrates as well as the residual fly ashes. This work contributes to a growing body of research that suggests multi component utilisation of CFA is technologically, environmentally, and economically imperative. The thesis explores five separate but related themes that attempt to increase the exploitation of CFA. In the first it is shown that CFA products that are derived from a commercial scale processing scheme exhibit differences in bulk chemistry, mineralogy, and particle size. In the second theme, a study of the rheology of CFA suspensions was conducted. The third aspect of the thesis explores the current method of recovering cenospheres from bulk CFA. The fourth part of the thesis covers the separation of carbon from CFA using an environmentally benign waste material such as vegetable oil. Finally, a silver activated titanium dioxide floating photocatalyst has been manufactured using cenospheres as an industrially derived substrate.
463

Characterisation of anode supported microtubular SOFC process on pure methane reduction and operation

Lee, Tae Jung January 2010 (has links)
The optimisations of reduction and operation of Ni-YSZ anode supported micro tubular cells on pure methane were studied. A major problem of SOFCs is nickel anode performance on methane and higher hydrocarbons. The aim of this work was to study the effect of reduction and operation of anode-supported microtubular SOFCs using methane as both reductant and fuel. The results were compared to those from optimised operation using hydrogen. To measure mechanical strength, the three point bending test was employed. Temperature programmed oxidation (TPO) results were investigated to measure the carbon deposition on the anode in order to assess potential damage to the cermet catalyst. Also field emission scanning electron microscope (FE-SEM) and Energy-Dispersive X-ray spectroscopy EDS results were analysed on the anode surface.
464

Continuous aerobic processing of piggery effluent : a new approach to quantifying the fate of the nitrogen component

Greatorex, James Michael January 1995 (has links)
The primary objective was the preparation of a complete mass balance around an aerobic treatment system for pig slurry, to quantify the various forms of nitrogen entering and leaving under different conditions. The purpose of this was to assess the effect of such treatment conditions in terms of the amount of polluting forms of nitrogen generated from the slurry. A laboratory scale reactor (designed for this study) was operated under three separate residence times of 2, 4, and 8 days, and aeration level indicated by a redox value in the range of E\(_{Ag/AgCl}\) = +100 to +200 mV; the latter two giving nitrifying conditions. Emissions of di-nitrogen gas are a major component of a nitrogen mass balance, yet one which has been often neglected because of difficulties in distinguishing it from that in the atmosphere. A novel technique was developed in which atmospheric N\(_2\) in the reactor headspace was removed by flushing the system with an 80/20 gas mixture of argon/oxygen. This left microbially derived N\(_2\) available for collection and analysis by mass spectrometry. Established methods were applied for the measurement of other gaseous nitrogen emissions (NH\(_3\), N\(_2\)O, NO) and other forms of nitrogen in the slurry (organic-N, NH\(_4^+\), NO\(_2^-\) and NO\(_3^-\)). The steam distillation technique for nitrite and nitrate was found to be unreliable, therefore, high performance liquid chromatography was used as an alternative. The existence of the intermediate nitrified N form of hydroxylamine is postulated but was not quantified in this study. The presence of unidentified components in raw slurry was investigated using HPLC, but only chloride and acetate could be recognised with a high degree of confidence. Mean N\(_2\) concentrations measured were 774 mg l\(^{-1}\) in the 4 day treatment and 523 mg l\(^{-1}\) in the 8 day treatment. Emissions of the environmentally damaging N\(_2\)O gas were quantified as being 514 mg l\(^{-1}\) in the 4 day treatment and 219 mg l\(^{-1}\) in the 8 day. The lower emissions from the 8 day treatment are attributed to improved contact between oxygen and slurry, reducing the prevalence of zones favourable for denitrification. In the final mass balance study, overall nitrogen leaving the system equalled 86 (±18) % of that entering in the 2 day treatment, 113 (±10) % in the 4 day treatment, and 104 (±21) % in the 8 day treatment. The variation in values was attributed to errors in the liquid phase analysis of slurry nitrogen compounds.
465

Development of mucoadhesive biopolymers for food formulation

Ali, Mohd Faizal January 2015 (has links)
Development of mucoadhesive biopolymer has received great attention in the pharmaceutical application due to its ability to retain the drug dosage at the specific targeted area. This special property could be applied in food formulation for optimum delivery of the active ingredients in the mouth. This research was carried out to study, correlate and review several in vitro analytical methods that can be used in development process for characterisation of mucoadhesive polymer. Four well known mucoadhesive biopolymers namely, chitosan, pectin, sodium alginate and sodium carboxymethyl cellulose (CMC) were used in this study. A modified rheological characterisation was used to study the interaction between the biopolymers with mucin and the assessment was based on the viscosity synergism. The detachment force characterisation was carried out via pull-off and tensile test using texture analyser and atomic force microscopy (AFM). Kinetic interaction study was done using quartz crystal microbalance with dissipation monitoring (QCMD) and interpretation of data from the modified rheological characterisation. Meanwhile, the removal of biopolymer emulsion after water flushing in a flow cell was observed under a microscope. It was found that mucoadhesion properties of tested biopolymers were affected by the concentration of biopolymer solutions, molecular weight, contact time, ionic strength and pH. Sodium alginate was characterised as the most mucoadhesive material by all the methods while QCMD shows CMC has the highest interaction with mucin layer compared to sodium alginate and pectin.
466

High temperature processing of kaolinitic materials

Thomas, Rachel Elizabeth January 2010 (has links)
Calcination, is the process of heating a substance, to a temperature below its fusing point, with a resultant loss of water. It is one of the most important techniques currently used to enhance the properties, and therefore value, of kaolin. The overall aim of this project was to provide a better understanding of the principles of the kaolin calcination reaction in order to enhance the efficiency, quality and sustainability of the Imerys calcining operations. This research has shown a strong correlation between the chemistry of kaolin and the colour of the calcined product. This is due to the influence of contaminant materials on the colour of the hydrous kaolin, which in turn affects the calcined material. The strongest colour influencing factor is the presence of iron, particularly if it is present on the surface of the kaolin. Surface iron is currently reduced using a reductive bleaching process. This has an improving influence on even the most contaminated kaolins, however there can be quite a lot of interbatch variability. Despite its effect on colour the chemistry of kaolin has little influence on post calcination reactivity. Reactivity is due to physical factors such as particle and agglomerate size and the penetration of heat into the material. Any kaolin will calcine to produce a low reactivity product; provided the heat is able to penetrate into the bed and that the material is able to remain at temperature for sufficient time for the calcination reaction to occur. Another outcome of the research was the discovery that a higher temperature and shorter time period has little on the end calcined product but has implications for lower energy usage.
467

Imaging the development of a bone-to-bone ligament construct

Bannerman, Alistair L. January 2016 (has links)
Ligament injuries are commonplace, with poor native healing leaving injury sites exposed to instability and further damage. A number of surgical methods have been established for reconstruction using a range of materials, but these have a high failure rate and a number of undesirable side-effects. Much recent work has been focused on the development of tissue engineered ligament grafts. One of the major challenges for this is the formation of an effective ligament-bone interface. In native tissue a multi-phase interface enables smooth transfer of forces between the mechanically mismatched bone and ligament tissue, however this has proved hard to replicate. Previous work has developed a bone-bone ligament construct model intended to emulate the native interface through formation of a mineralised region by soluble cement anchors. Development and optimisation of the model has seen an increasing mechanical strength, but the mechanisms involved are poorly understood. This study investigates the development of the ligament construct through the use of multiple complimentary imaging techniques to provide information on the biological, chemical, and topological development of the construct as it forms from initially homogeneous and separate materials to a complex non-homogeneous system.
468

Liquid air energy storage : process optimization and performance enhancement

Peng, Xiaodong January 2018 (has links)
Liquid Air Energy Storage (LAES) aims to large scale operations a~d-:_has caught the attention due to the advantages of high energy density, a highly competitive capital cost, no geographical constraints and environmental friendliness. However, the situation is getting more challenging due to its disappointed performance in the current configuration. This thesis focuses increase the system performance of the LAES technology, particularly through developing novel thermodynamic cycles for an increased use of the thermal energy and system optimization strategies. The improvements to the LAES mainly aim at two points: increasing power output by using compression heat and rising the liquification rate through external cold sources. To effectively use the heat, three integrated LAES systems with the Organic Rankine Cycle (ORC) are proposed, termed LAES-ORC-VCRC system, LAES-ORC-ARC system and LAES-ORC system respectively according to different cooling methods. External cold sources, such as Liquefied Natural Gas (LNG), can be used to enhance air liquefication, and hence two integrated LAES systems, termed the LAES-LNG and the LAES-LNG-CS, are investigated and optimized.
469

Development of a biorelevant dynamic model of human proximal colon : a tool for designing colon-specific drug delivery systems

Stamatopoulos, Konstantinos January 2017 (has links)
A novel Dynamic Colon Model (DCM) that represents the anatomy and physiology of the human proximal colon was developed. Analysis of the hydrodynamics was performed using Positron Emission Particle Tracking (PEPT) system and Positron Emission Tomography (PET). The pressures generated by the wall motion of the DCM tube compared with the available published in vivo data. The hydrodynamics in USP 2 dissolution apparatus were also assessed using Particle Image Velocimetry (PIV) and Planar Induced Fluorescence (PLIF). Areal distribution and individual striation methods showed high mixedness level close to tip. PEPT experiments were performed using particles of different buoyancy. Use of different particles gave different results in terms of velocities and residence times within the DCM tube. PET images showed that antegrade propagating waves of amplitude lower than the minimum threshold used in vivo studies were associated with flow episodes. In addition, flow episodes can occur which are not related to the wall motion. Dissolution profiles of theophylline, a high water soluble drug, released from a hydrophilic matrix obtained at viscous shear thinning media, mimicking the dewatering process in the human colon. The novel DCM provides a realistic colonic environment, enabling biorelevant in vitro assessment of the in vivo performance of dosage forms.
470

Experimental and computational study of non-turbulent flow regimes and cavern formation of non-Newtonian fluids in a stirred tank

Adams, Luke Wayne January 2009 (has links)
When non-Newtonian fluids are mixed in a stirred tank at low Reynolds numbers caverns can be formed around the impeller. If the fluid contains a yield stress the cavern has a fixed boundary where no flow occurs outside of it. When the fluid does not contain a yield stress a pseudo-cavern is formed, the cavern boundary is not fixed since flow can occur outside of it, but the majority of the flow is present in a region around the impeller. Mixing and cavern formation of a variety of non-Newtonian fluids are studied using experimental techniques and computational fluid dynamics (CFD). Cavern data extracted from both methods are compared with mechanistic cavern prediction models. An adapted planar laser induced fluorescence technique showed that mixing inside of a shear thinning Herschel-Bulkley fluid is very slow. Positron emission particle tracking obtained flow patterns and cavern sizes of three rheologically complex opaque fluids. CFD was able to predict the data obtained from both experimental techniques fairly well at low Reynolds numbers. A toroidal cavern model provided the best fit for single phase fluids but for the opaque fluids all models drastically over predicted the cavern size, with the cylindrical model only predicting cavern heights at high Reynolds numbers.

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