The purpose of this research was to study the factors that affecting the growth and Taxol production by Taxus species. Taxol, a complex diterpene alkaloid, is approved by the FDA for the treatment of ovarian and breast cancer. It was originally isolated from the bark of Taxus brevifolia. However, the bark contains very low concentrations of Taxol. Currently, Taxol is manufactured via a semi-synthetic method, but the production is limited and Taxol is stilI an expensive drug. Plant cell culture method has been recognized as a promising alternative for Taxol production. Nevertheless, the low or unstable productivity has become an obstacle to attain high yield of Taxol. This research focused on the experimental and computational modelling aspects of Taxol production in Taxus cell cultures. Callus and cell suspension cultures were successfully initiated from the seedlings of T. baccata. The addition of 1.5 % (w/v) insoluble polyvinylpolypyrrolidone (PVPP) and use of half strength of picloram in callus maintenance medium reduced the problem of cell darkening considerably. In suspension cultures, the non-ionic XAD-4 adsorbent was added to overcome the same problem. Fructose was the best carbon source compared to sucrose and glucose. The addition of fructose (10 gIL) on day 8 and methyl jasmonate (lOO IlM) on day 10 increased Taxol production to 17 mgIL from the suspension cultures initiated from needle explants of the seedlings. The experimental data obtained from this study were used in the development of the computer models: the kinetic model, fundamental and integrated dynamic metabolic flux analysis models. The in silico Taxus metabolism was reconstructed and computational metabolic flux balancing method was used in order to obtain fluxes of all the metabolic reactions with linear programming and optimisation in GAMS environment (General Algebraic Modeling System). The objective function of optimisation was either the maximisation of the specific growth rate or the maximisation of the specific Taxol production rate. Experimental values of nutrient uptake rates such as glucose, fructose and oxygen during the course of the batch culture were used as constraints to obtain different sets of optimised flux distributions for different periods of the batch culture. The computational results indicated that the transhydrogenase reactions were important to balance the need of NADPH for biosynthetic reactions in Taxus metabolism. The variation in biomass composition, inclusion of starch biosynthesis and degradation reactions, and Taxol precursors did not affect the growth of cells significantly. When the secondary cell wall biosynthesis was incorporated in the model, both growth and Taxol production rates were reduced. An increase in in silico Taxol production was observed when methyl jasmonate elicitation was combined with phenylalanine addition. An integrated dynamic model was constructed in order to combine the abilities of Excel- VBA and GAMS to optimise the objective function, handle mathematical kinetic expressions and visualise the outputs. As an example of its application, Taxol concentrations were automatically computed after the optimisation during the time course of the batch culture. These models can be developed further and used in future in order to define some strategies such as media formulation, precursor addition and genetic engineering targets in silico in order to manipulate the metabolism and increase the Taxol yield.

One of the major challenges in the field of nanocomposites has been to distribute and disperse high loading fractions of carbon nanotubes (CNT) in epoxy resins through a route that is scalable to high throughput. Furthermore, CNTs have been employed as an additional constituent in advanced carbon fibre composite materials to improve their poor matrix dominated properties in the drive to manufacture lighter and stronger composite structures. Attempts to produce epoxy based hierarchical composites (HC) with high CNT loadings by introducing nanoreinforcement in the resin have been plagued by processing difficulties related to viscosity and infiltration. Nonetheless, introducing just a few weight percent of CNTs into the matrix of continuous carbon fibre composites has been shown to enhance fracture toughness and compression performance. As such, this thesis tackles an effective way to combine carbon fibre, thermosetting resin and CNTs into hierarchical composites with high loadings of nanoreinforcement. To this end, a readily scalable powder based processing route was developed to produce epoxy based polymer nanocomposites (PNC) with a maximum CNT loading of 18.4 wt% (11.5 vol%). Due to the excellent CNT distribution and dispersion achieved during processing, some practically relevant physical and mechanical properties were enhanced even at the highest CNT loadings: 67 S/m and 0.77 W/ m·K electrical and thermal conductivities, respectively, and 5.5 GPa Young's modulus. Analytical micromechanical models to validate reinforcement due to CNTs were also explored. The nanocomposite powder was also employed as a constituent in a wet powder impregnation process to produce carbon fibre based HC laminates containing as much as 5.5 vol% CNTs (11.5 vol% CNTs in the matrix). The processing parameters were optimised to yield a laminate with 55% fibre volume fraction, making it suitable for structural applications. The through thickness electrical conductivity of the HC containing 5.5 vol% CNTs improved by an order of magnitude; however, the largest enhancement in interlaminar fracture toughness (20%) was observed at an intermediate loading of 2 vol% CNTs. The mechanical underperformance at high CNT loadings was attributed to the heterogeneous microstructure observed to different extents in both PNCs and HCs, and a number of solutions related to material selection and processing design were proposed.

This thesis describes a series of styrene (ST) and divinylbenzene (DVB) emulsion templated polymer foams prepared via low, medium and high internal phase emulsion templates (L/M/HIPE templates). The emulsion templates were stabilized using different commercially available technical surfactants and surfactant mixtures. Since the chemical nature of the chosen technical surfactants is unknown, the surfactants where characterized by means of Fourier Transform Infrared (FT-IR) and Nuclear Magnetic Resonance (NMR) spectroscopy, Electro Spray Ionization Mass- (ESI-MS) and Matrix-Assisted-Laser-Desorption-Ionization-Time-of-Flight-Mass Spectrometry (MALDI-TOF-MS). Additionally their adsorption at the water/ST:DVB interface was studied. The investigation regarding the preparation of surfactant stabilized emulsion templates and their polymerization products revealed that the most commonly used surfactant Span 80 is not the best suited surfactant to stabilize styrene/divinylbenzene emulsion templates which is why different surfactants were used in the thesis at hand. All successfully prepared poly(merized)HIPEs proved to have interconnected, open porous polymer foam structures. In contrast, the pore structure of polyMIPEs was open, closed or non-droplet shaped, depending on the surfactant used to stabilize the corresponding emulsion template. The mechanical compression properties of all prepared polyHIPEs were similar and independent of the HIPE formulation from which they were produced but the mechanical properties of polyMIPEs differed significantly. The influence of the surfactants on the morphology and mechanical properties of the resulting macroporous polymers will be discussed in detail. Furthermore, the relationship between the relative density (porosity) of the polymer foams and the mechanical response under compression was investigated. The semi-empirical models developed by Gibson and Ashby were applied and additionally modified to provide a more accurate description of the mechanical behaviour over a larger relative density range of polymer foams prepared via emulsion templating (polyL/M/HIPEs). This allows a prediction of the mechanical properties as a function of the relative density of the respective polymer foams and vice versa for the specified emulsion template formulation. It is obvious that the surfactant type and the internal phase volume ratio of the emulsion template used to produce macroporous polymer foams significantly determine their resulting mechanical properties, as clear transition states for polyH/M/LIPEs were identified in which the mechanical properties of these materials changed dramatically. The effect of the surfactant on the mechanical properties and the polymer foam morphology is discussed in terms of the surfactant's solubility in the polymer and thus in terms of its role as plasticizer. Finally, the influence of the pore size on the mechanical properties was investigated. It was found that the preparation process (emulsification and polymerization) of the emulsion templates is very crucial for the mechanical properties of the resulting polymer foams (reproducibility). More precisely, it was found out that the emulsion templates need to 'equilibrate' after emulsification. It was only for these emulsions that average pore sizes and mechanical properties could be reproduced.

The surface energetics of model pharmaceutical powders, were D-mannitol (Ph Eur Pearlitol® 160C, Roquette, France), Racemic Ibuprofen (2-(4-isobutylphenyl)propionic acid) (Shasun, London, U.K.), Aspirin (acetyl salicyclic acid) (Sigma-Aldrich, Poole, U.K.) and Paracetamol (p-hydroxyacetanilide) (98% Sigma-Aldrich, St. Louis, MO) were evaluated using a Finite Dilution Inverse Gas Chromatography FD-IGC technique. This yielded heterogeneous surface energy distributions, which provided a continuum of energies with surface coverage. These measurements were then analysed using novel computational methods of deconvolution, to better understand the effects of heterogeneity on the fundamental site contributions to surface energetics. The modelling approach developed branches into several components: Dispersive and Specific Energetics Modelling. The Dispersive component further expanded to Iterative and Analytical forms, with extensions to both. Physical mixtures of heterogeneous unsilanised and homogeneous Methyl-silane modified Mannitol, in both blended and unblended configurations, as well as blended mixtures of two homogeneous species, Methyl-silane and Fluoro-silane modified Mannitol, were measured to investigate the effect of mixing on surface energetics measured by FD-IGC. Mannitol was used as its functionalisation allowed for the production of markedly different energy profiles with a negligible effect on surface area and mechanical properties allowing for accurate knowledge of the amount of each surface used. The effect of mixed surface chemistry was also investigated to further understand the root cause of energetic heterogeneity measured by FD-IGC, this was achieved by the dual species silanisation of Mannitol using both Methyl- and Fluoro-Silane species, this was found to produce a heterogeneity distribution bound between the energies of the two silane species used in isolation. Further, this was investigated by the induction of a heterogeneity in a homogeneous polymeric material, Polyethylene, through surface modification with Sulfuric Acid. Finally the computational approaches developed were applied to the 3 polymorphic forms of a common pharmaceutical excipient Mannitol to investigate the effects of polymorphism on surface energetics. This showed that the different polymorphs exhibit extremely different energetic behaviour, further results for a mixed-polymorph suggest that it may be possible to infer energetic contributions of unknown quantities. Such information can be used to possibly screen for unwanted polymorphic contributions and also to find more appropriate polymorphic forms for pharmaceutic uses in terms of adhesive and dissolution properties as affected by surface energetics.

A conventional 2D (two-dimensional) culture, in T-flasks or multi-well plates, is commonly perfo med for the stem cell development; however, it is time and labour consuming process. Moreover, it is impractical to scale-up to high cell number production. Growing stem cells inside bioreactor might be a solution. 3D bioreactor is not only a solution for scalable production but also a mimic environment for in vivo system. Herein, sparged-type bioreactors (e.g. airlift bioreactor) were chosen as bioreactors to differentiate murine embryonic stem cells (mESCs) into type II pneumocytes in the lung. There are two main sections in this thesis: the design of airlift bioreactor using computational fluid dynamics (CFD) and the differentiation of mESCs into the alveolar progenitor cells in a sparged bioreactor. The airlift bioreactors provide a better environment, which theoretically has been known to simulate the gas-exchange interface encountered in the lung alveoli. They require a low power input and provide a low shear environment with good mixing. The hydrodynamics (gas holdup, superficial liquid velocity, and shear rate) and mass transfer (kLa, the volumetric mass transfer coefficient) features of different airlift designs were determined by CFD. The simulations were based on a 3D transient model, Eulerian-Eulerian approach, and two-phase liquid/gas model with all phases being treated as laminar flow. The superficial gas velocity was varied from 0.001 m/s to 0.02 m/s. The simulation results indicated that the hydrodynamics were corresponded to the data found in literatures and the gas holdup were agreed with an experiment validation. The CFD results also suggested that in which range of superficial gas velocity (ug) that the system can be operated without any fluctuation in terms of the hydrodynamics. In addition, the airlift bioreactor is suitable for shear sensitive cells with high mass transfer rate, e.g. kLa, = 180 hr-1 at ug= 0.01 m/s and normoxia (20% O2) condition. Hence, the results from these simulations have been initially utilised as a promising hypothesis to design an airlift bioreactor for the scalable and automatable culture in multiphase bioreactors. For the second part, mESCs were encapsulated in a calcium-alginate hydrogel to create a 3D environment then the encapsulated cells weregrown in both 3D static culture, in a T-flasks, and the sparged bioreactor. The gas, 5% CO2 and 20% O2, was directly sparged into the bioreactor. The A549 conditioned medium was used to induced the mESCs to the endodermal lineages, targeting for the alveolar type II cells, type II pneumocytes. The differentiated cells expressed lung cell markers: SPC (pneumocyte type II), and FoxA2 (endoderm marker). In experiments, the relative expression of SPC markers reached the maximum level, 10-fold increase, at day 14 and day 20 for 3D static culture and the sparged bioreactor, respectively. After day 20 of the differentiation process, the pneumocyte-like cells in static culture trend to lose their SPC expression whereas the cells in sparged bioreactor maintain relatively high SPC markers. At the end of a differentiation protocol, day 30, it was observed that both systems highly expressed the endodermal makers, FoxA2, i.e. approximately 2000-fold increase for static culture and 5000-fold increase for the sparged bioreactor. In conclusion, the direct gassing in the sparged bioreactor not only enhanced the differentiation of embryonic stem cells into type II pneumocytes but also mimicked the in vivo environment in the lung therefore the differentiated cells can maintain the lung phenotype for a long term culture, up to 5 weeks in vitro culture. This in vitro system would be beneficial for drug screening and regenerative medicine applications.

In order to investigate the full mass transfer potential of the CDC reactor as a three phase chemical reactor, model reactants were hydrogenated in the CDC operating as a packed bed and slurry reactor. Two model reactants, itaconic acid and 3-nitrobenzoic acid were chosen for study and hydrogenated using a 5% PdlC catalyst for all slurry reactions and a commercially prepared 3 w/w% PdlA1203 catalyst for all packed bed reactions. To further enhance the mass transfer capabilities of the CDC, swirlflow was fitted to the lower region of the column for both packed bed and slurry reactors. For all model hydrogenation reactions, the transport parameters were evaluated and compared for the different reactor configurations enabling evaluation of the mass transfer capabilities of the CDC reactors. Two very different reactions of commercial significance were studied in the CDC firstly, the consecutive hydrogenation of 2-butyne-l ,4-diol a possible reaction stage in the production of vitamin B 12 and the hydrogenation of soyabean oil, an essential step necessary for the production of margarine. For butynediol hydrogenation, substrate inhibition occurred, preventing the full capabilities of the CDC to be utilised. For comparison with reaction in the CDC, butynediol was hydrogenated in a small stirred reactor and comparable rates of reaction were observed. Soyabean oil was hydrogenated in both packed bed and slurry modes and showed comparable rates of reaction between the two different reaction modes. From the evaluated transport parameters and reaction kinetics, the CDC operated in both packed bed and slurry modes achieved reaction which was occurring under diffusion resistance free conditions, whereas normally soyabean oil is hydrogenated in conditions which are limited by resistances to diffusion. For both reaction modes, high linolenic selectivities were achieved. This study has shown that the CDC is suitable for use as a three phase chemical reactor providing a high degree of chemical reaction which is not limited by resistances to mass transfer. The CDC is particularly suitable for reactions were efficient mass transfer is required with chemical reaction.

No description available.

Since the standard photolithographic patterning technology possesses a number of sustainable issues, a “maskless” technology, Enface, has been proposed. Here, a patterned ‘tool’ placed opposite to the substrate within micrometre range is required. Etching or plating occurs by passing tailored current or voltage waveforms, provided that the electrolyte resistance is high. Enface is a resource efficient process as the use of chemicals is greatly reduced. This research project aimed to investigate the feasibility of Ni pattern transfer using Enface under stagnant conditions. It would be advantageous if Enface could be used for nickel deposition as it is a slow kinetic system and controlled by mixed mass transfer and kinetics which is a system where Enface has never been used before. An electrochemical cell has been specifically designed and an electrolyte was systemically developed as required by Enface. Polarisation experiments were carried out to determine applied current densities that would be used in galvanostatic plating experiments for pattern transfer of millimetre and micron scale features. Deposited features were comprehensively characterised to see the performance of the patterning process. Current distribution during the pattern transfer experiments was investigated by simulation and modelling using Elsy software. An electrolyte of 0.19 M nickel sulfamate was selected and shown to be capable of depositing nickel. Polarisation data from experiments in Enface system showed that each feature size requires a different applied current density. As expected, pattern transfers of metallic nickel were achieved for millimetre and micron scale features at a current efficiency of around 90 % with current spreading were observed. The deposited feature width broadens with increasing time and decreasing feature size. In addition, maximum thickness that could be achieved was around 0.5 μm due to entrapped gas bubbles leading to process termination. The gas bubbles were detrimental to the deposits resulting in a rough and inhomogeneous surface as well as photoresist degradation. Ultrasound agitation was shown to be capable of diminishing the effect of gas bubbles. However it requires an optimisation of applied power density to avoid negative effects of cavitation bubbles. The result of simulation showed a non-uniform current distribution across the feature width with the highest current density at the centre resulting in a bell-shaped surface profile which is in agreement with the experiments. However, the deposited shape evolution obtained from the experiments is consistently much better than those obtained from the simulation.

This thesis presents the experimental and theoretical investigations on the development of phase inversion in horizontal pipeline flow of two immiscible liquids. It aims to provide an understanding on the flow development across the phase inversion transition as well as the effect on pressure drop. Experimental investigation on phase inversion and associated phenomena were conducted in a 38mm I.D. liquid pipeline flow facility available in the Department of Chemical Engineering at University College London (UCL). Two sets of test pipelines are constructed using stainless steel and acrylic. The inlet section of the pipeline has also been designed in two different configurations – (1) Y-junction inlet to allow dispersed flow to be developed along the pipeline (2) Dispersed inlet to allow formation of dispersion immediately after the two phases are joined. Pressure drop along the pipeline is measured using a differential pressure transducer and is studied for changes due to redistribution of the phases during inversion. Various conductivity probes (ring probes, wire probes, electrical resistance tomography and dual impedance probe) are installed along the pipeline to detect the change in phase continuity and distribution as well as drop size distribution based on the difference in conductivity of the oil and water phases. During the investigation, the occurrence of phase inversion is firstly investigated and the gradual transition during the process is identified. The range of phase fraction at which the transition occurs is determined. The range of phase fraction becomes significantly narrower when the dispersed inlet is used. The outcome of the investigation also becomes the basis for subsequent investigation with the addition of glycerol to the water phase to reduce the interfacial tension. Based on the experimental outcome, the addition of glycerol does not affect the inversion of the oil phase while enhancing the continuity of the water phase. As observed experimentally, significant changes in pressure gradient can be observed particularly during phase inversion. Previous literatures have also reviewed that phase inversion occurs at the maximum pressure gradient. In a horizontal pipeline, pressure gradient is primarily caused by the frictional shear on the fluid flow in the pipe and, in turn, is significantly affected by the fluid viscosities. A study is conducted to investigate on the phase inversion point by identifying the maximum mixture viscosity (i.e. maximum pressure gradient) that an oil-in-water (O/W) and water-in-oil (W/O) dispersion can sustain. It is proposed that the mixture viscosity will not increase further with an increase in the initial dispersed phase if the inverted dispersion has a lower mixture viscosity. This hypothesis has been applied across a wide range of liquid-liquid dispersion with good results. This study however cannot determine the hysteresis effect which is possibly caused by inhomogeneous inversion in the fluid system. A mechanistic model is developed to predict the flow characteristics as well as the pressure gradient during a phase inversion transition. It aims to predict the observed change in flow pattern from a fully dispersed flow to a dual continuous flow during phase inversion transition. The existence of the interfacial height provides a selection criterion to determine whether a momentum balance model for homogeneous flow or a two-fluid layered flow should be applied to calculate the pressure gradient. A friction factor is also applied to account for the drag reduction in a dispersed flow. This developed model shows reasonable results in predicting the switch between flow patterns (i.e. the boundaries for the phase inversion transition) and the corresponding pressure gradient. Lastly, computational fluid dynamic (CFD) simulation is applied to identify the key interphase forces in a dispersed flow. The study has also attempted to test the limitation of existing interphase force models to densely dispersed flow. From the study, it is found that the lift force and the turbulent dispersion forces are significant to the phase distribution in a dispersed flow. It also provides a possible explanation to the observed flow distribution in the experiments conducted. However, the models available in CFX are still unable to predict well in a dense dispersion (60% dispersed). This study is also suggested to form the basis for more detailed work in future to optimize the simulation models to improve the prediction of phase inversion in a CFD simulation.

The present work describes the fundamental extension of an integral pool spreading, vaporisation and dissolution model, part of the Process Hazard Assessment Tool (Phast) software. The base model accounts for spills on land and water surfaces. For pools spreading on water, the model includes three successive regimes, gravity-resistive, viscous-resistive and viscous-surface tension. For the case of pool spreading on land, it accounts for the hold-up of liquid within the surface’s rough elements. Pool vaporisation considers two limiting cases: evaporation and boiling. The heat transfer mechanisms accounted for include conduction from the ground, convection from water and air, conduction from ice and solar incidence. The extended multi-component model tracks the transient pool inventory at each step. While the pool is boiling the liquid and vapour phases are in equilibrium. For evaporation, the model accounts for the diffusion of multiple components into air. The dissolution of water-soluble chemicals present in the mixture, a novel feature amongst existing multi-component pool models, is introduced by the present work. The application of the model to mixtures highlighted the drawbacks of approximating such systems by a single component evaporating pool. The implementation of a numerical algorithm based on Backward Differentiation Formula (BDF) showed improved numerical stability when compared to a widely used pool model (LPOOL by HGSYSTEM (Post, 1994)). The improvements were most noticeable when the model behaved as a stiff problem. The validation of the multi-component pool model against published experimental data shows good agreement for pool spreading and boiling on land and water surfaces. The pool evaporation model is in good agreement with the experimental data for low to medium volatility chemicals. Suggestions for further work include an extension to non-ideal mixtures; incorporate the modelling of chemical reactions and a stratified pool model.