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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.
101

Crystallisation of active pharmaceutical ingredients using ionic liquids

Smith, Kenneth Baird January 2015 (has links)
It is proposed that Ionic Liquids offer a new opportunity for exploration into a novel medium for processing Active Pharmaceutical Ingredients, particularly with respect to habit control and polymorphic form. A review of relevant literature relating to ionic liquids properties, commercial applications and current research has been summarised together with background into fundamental crystallisation theory. Crystallisations using thermal methods were employed at laboratory scale and the physical properties of the resultant powders were analysed and compared to commonly encountered crystal forms. For paracetamol it was found that the morphology of the crystals could be manipulated, producing in some cases, habits not reported for conventional organic solvent crystallisation. This was achieved through changing both the IL used and the saturation of the system whilst in all cases retaining the most stable polymorph. ILs ILs to be ‘designed’ for a given API but greater understanding of the interactions between IL and solute are required first. Properties such as increased solvation power, thermal stability, liquidus range and low vapour pressure bring a number of advantages when designing industrial crystallisations. However ILs also have a number of disadvantages including phase separation problems.
102

Large deformation and crystallisation properties of process optimised cocoa butter emulsions

di Bari, Vincenzo January 2015 (has links)
The objectives of the research presented in this thesis were: (1) optimise the processing conditions for the production of water-in-cocoa butter emulsions; (2) understand the role of water droplets on the large deformation behaviour and crystallisation properties of emulsified systems. Results showed that a scraped surface heat exchanger could be used to produce tempered emulsions with a small average droplet size (~3 µm). In all systems stability was provided by the emulsifier and fat crystals forming a network both in the bulk and at the interface of the water droplets. Characterisation of the large deformation properties of emulsions showed that the elastic behaviour remained constant at low aqueous phase percentages while the strength at fracture decreased. This result suggests that water droplets act as stress-concentrator elements, which is probably due to their partial sintering with the bulk network. Results of crystallisation experiments have shown that the effect of droplets on kinetics of crystallisation depends on the degree of supercooling: only at relatively high temperatures (15, 20 °C) the dispersed droplets increased the kinetics of crystallisation compared to bulk cocoa butter (CB). With respect to polymorphic evolution, emulsified systems evolved faster toward more stable forms than bulk CB at all temperatures.
103

Protein extraction during soybase production : enhancing yields using cavitational techniques

Preece, Katherine Elizabeth January 2017 (has links)
Soybase is the aqueous extract produced directly from whole soybeans. Its main processing steps include milling, solubilisation, separation of solids, and heating. During this process, the waste stream okara produced typically contains 80% moisture and a considerable fraction of protein. A novel extraction model highlights this role of okara for the first time. Availability of protein and separation efficiency were identified as limiting factors of extraction through microstructure visualisation of the processing materials by a novel confocal laser scanning microscopy (CLSM) study. Ultrasound treatment of soy slurry and okara improved the protein extraction yield at lab-scale via enhanced solubility and to a less extent separation efficiency. Performing scale-up investigations showed a reduction in ultrasonic effects at pilot-scale due to higher energy intensities and reduced protein insolubility. Another cavitation technology explored was high pressure homogenisation (HPH). In contrast to ultrasound, HPH disrupted cells resulting in a better extraction assistance that should be explored further at pilot-scale. The work presented in this thesis provides the reader with an overview of the challenges faced during aqueous protein extraction from whole soybeans and novel routes for process intensification.
104

Bi-layered chromatography matrices for the purification of biological nanoplexes

Karnchanasri, Kritsadanchalee January 2013 (has links)
The preparations of SEC/IEC supports from commercially available, underivatised base matrices by AGE activation-partial bromination technique via two different approaches; (i) viscosity enhanced-reaction diffusion (VE-RD) and (ii) microwave-assisted reaction diffusion, were studied and optimised. Selected supports produced by both approaches were further evaluated by applying to packed bed chromatography system in order to purify target pDNA from neutralized E.coli cleared lysates.For VE-RD approach, viscosity enhancement by sucrose (< 0.032 Pa.s) was found to greatly aid the creation of thin inert outer layer. The optimum condition for SEC/IEC Sepharose CL-6B production observed was 10% single bromination at room temperature in 64% (w/v) aqueous sucrose without sodium acetate addition. The effects of different base matrices, conductivities, linear flow rate, target pDNA sizes and support preparations on chromatography performance were investigated. Microwave irradiation heated up the reaction in a rapid controlled manner compared to conventional heating. SEC/IEC Sepharose CL-6B produced via microwave-assisted reaction diffusion approach at 80oC with 10% partial bromination showed almost complete surface charge elimination with the highest SI value of 57.4. This support showed the high core binding capacity. However, a delayed pDNA breakthrough was also observed. It was noted that the plasmid forms remain unchanged after SEC/IEC column purification.
105

Solvothermal production of dimethylfuran from sugar derivatives toward future transport fuel

Kayode, Bayonle Ayokunle January 2015 (has links)
2,5-dimethylfuran (2,5-DMF) has gathered interest as an energy-dense compound with similar fuel properties to gasoline. This thesis describes the catalytic hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran, employing three different hydrogen donor sources (molecular H\(_2\), mixture of formic acid/triethylamine and 2-propanol). Transmission electron microscope analysis showed that the bio-Pd synthesised by D. desulfuricans were generally larger than both the monometallic Bio-Ru and bimetallic Bio-Pd/Ru synthesised by B. benzeovorans. Under optimised conditions in molecular H\(_2\), 5 wt% Ru/C catalyst achieved 95.1% 2,5-DMF yield in 2 hours; in contrast the 20 wt% Bio-Ru/Pd gave 60.3% yield of 2,5-DMF at identical conditions. Transfer hydrogenation of 5-HMF to 2,5-DMF was investigated over Ru/C catalyst in formic acid/triethylamine mixture achieving 92.1% 2,5-DMF yield in 4 hours at 210 \(^o\)C and 5:2 molar ratio. It is interesting to note that 56.7% 2,5-DMF yield was achieved using the 20 wt% Bio-Ru/Pd catalyst at identical conditions. Transfer hydrogenation of 5-hydroxymethylfurfural in 2-propanol was studied over 5 wt% Bio-Ru/Pd catalyst and 42.6 2,5-DMF yield was obtained at 260 \(^o\)C after 2 hours of reaction time. It is concluded that hydrogenation of 5-HMF in molecular H\(_2\) offer superior advantages to transfer hydrogenation in HCOOH/Et\(_3\)N mixture and 2-propanol in terms of product yield and selectivity.
106

Thermal energy storage using carbonate-salt-based composite phase change materials : linking materials properties to device performance

Li, Chuan January 2017 (has links)
Thermal energy storage (TES) has a crucial role to play in conserving and efficiently utilising energy, dealing with mismatch between demand and supply, and enhancing the performance and reliability of our current energy systems. This thesis concerns TES materials and devices with an aim to establish a relationship between TES device level performance to materials properties. This is a multiscale problem. The work focuses on the use of carbonate-salt-based composite phase change materials (CPCMs) for medium and high temperature applications. A CPCM consists of a carbonate salt based phase change material (PCM), a thermal conductivity enhancement material (TCEM, graphite flake in this work) and a ceramic skeleton material (CSM, MgO in this work). Both mathematical modelling and experiments were carried out to address the multiscale problem. The wettability of carbonate salt and MgO system is first studied, followed by exploring the CPCMs microstructure characteristics and formation mechanism, and then the effective thermal conductivity of the CPCMs is carried out based on the developed microstructures. At the last part, heat transfer behaviour of CPCMs based TES at component and device levels is investigated.
107

Emulsion design for reduced fat baking margarine

Morrison, Ross Stuart January 2016 (has links)
Water-in-Oil emulsions present a potential strategy for fat reduction in conventional baking margarine (and thereupon bakery products), by replacing a portion of the fat with a water-based fat mimetic. Using hydrocolloids, polymers, and stabilisers, this aqueous phase may be structured in such a way as to emulate the physical and mechanical behaviour of the fat, but with almost none of the associated energy contribution - presenting potential for a realistic, marketable solution towards weight management and calorie control. This work has adopted a holistic strategy in order to characterise and understand the various structural components and processes consolidating to form a final, optimized, baking margarine emulsion structure. The relationship between the microstructure and the physicomechanical properties of standalone structured aqueous hydrocolloid phases is studied, and modelled for more complex systems. Emulsification processing parameters were optimized for production of water in palm oil baking margarine emulsions, before then applying these learnings for successful formulation of reduced fat palm oil emulsions incorporating the structured aqueous phase. A conventional margarine process is optimised for a contemporary role of emulsification to successfully create fully emulsified 30% reduced fat baking margarine emulsions, with potential for considerably higher aqueous phase fractions depending upon particular baking application.
108

Horizontal gene transfer in bacterial co-cultures in micro-fabricated environments

Costello, Cait January 2012 (has links)
In recent years, the majority of research on surface patterning, as a means of precisely controlling cell positioning and adhesion on surfaces, has focused on eukaryotic cells. Such research has led to new insights into cell biology, advances in tissue engineering, and cell motility. In contrast, considerably less work has been reported on tightly-controlled patterning of bacteria, despite its potential in a wide variety of applications, including fabrication of in vitro model systems for studies of bacterial processes such as quorum sensing and horizontal gene transfer. We report a rapid and convenient method to generate patterned bacterial co-cultures using surface chemistry to regulate bacterial adhesion and liftoff patterning for controlling cellular positioning at the surface. A mannoside-terminated SAM formed an adhesive surface for bacterial monolayer formation, allowing fabrication of patterned regions using a subtractive microcontact printing process with a hydrogel stamp. The patterned substrates were subsequently inoculated with a second strain of bacteria from solution which deposited onto the unpatterned regions, forming a robust micropatterned coculture, providing platforms for spatially controlled studies of conjugation between donor and recipient bacterial cells. Towards this aim, donor cells were transformed with a modified conjugative plasmid that would bind fluorescent molecules and become visible upon entering a recipient cell. We discovered during the course of the project that bacterial co-cultures on metal surfaces exhibit slower growth rates than on semi-solid agar, and as such the time scale required for efficient conjugation lead to photobleaching of fluorescent foci. However, we were able to demonstrate through cultivation techniques that conjugation could occur in these micropatterned co-cultures after three hours.
109

Investigating foaming solutions generated by NaOH extraction of plant materials

Hudson, Paul Ronald January 2014 (has links)
This thesis covers extraction of hay with NaOH to produce foaming solutions which might be used to substitute or reduce the need for, oil based surfactant in detergents. Extraction time, temperature and NaOH concentration were found to have varying levels of influence on the properties of the extract solutions. Models were constructed to describe their effects on the% mass extracted from the hay, as well as extract solution absorbance, viscosity, and contact angle using response surface, experimental design methodology. The hay extract foam was examined along with other types of foaming solutions, using cryogenic SEM. Hay, rice straw and horse chestnut leaf extract foams were found to be particle stabilised and interesting images were captured showing their microstructures. Foaming was found to be due to lignin-carbohydrate complexes in hay extract solutions and proteins in horse chestnut leaf extract solutions. Finally correlations were sought between foaming of hay extract solutions and their other properties, e.g. Foaming of the hay solutions is due to lignin derivatives, hence solution absorbance correlates positively with foaming; and foaming is improved by increased solution viscosity hence its positive correlation with solution viscosity and % mass extracted from hay.
110

Investigation of fluid dynamics and emulsification in Sonolator liquid whistles

Ryan, David Jonathan January 2015 (has links)
The Sonolator liquid whistle is an industrial inline mixer used to create complex multiphase mixtures which form components of high value added liquid products. Despite its wide use, this device’s mechanism of operation is not well understood which has led to this combined experimental and computational study to elucidate key phenomena governing drop and jet break-up. The work has focused on single phase Particle Image Velocimetry (PIV) measurements of a model device to validate single phase Computational Fluid Dynamics (CFD) simulations to gain basic understanding of the flow fields which are responsible for the breakage behaviour, assuming dilute dispersions. Multiphase pilot plant experiments on a silicone oil-water-SLES emulsion have been used to characterise the droplet size reduction in a pilot scale Sonolator for both dilute and medium concentrations of the dispersed phase. An empirical model of droplet size was constructed based on pressure drop, dispersed phase viscosity and surfactant concentration. This empirical model was compared with the droplet breakage theories of Hinze, Walstra and Davies. Extra work mentioned in the appendices includes studies on cavitation in the Sonolator, with the cavitating flow conditions identified and the contribution to emulsification considered, and the usage of population balance methods to simulate droplet breakup in the environment indicated by CFD/PIV studies in order to investigate how the droplet size distributions measured in pilot plant studies came about.

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