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A large number of commercial and some novel Brunel synthesised surfactants have been studied with a view to their potential usefulness for enhanced oil recovery (EOR) application. Ethoxylated phenols and their sulphonated derivatives were given especially high priority. The surfactants were well-characterised in order to understand their EOR potential. High pressure liquid chromatography, mass spectrometry, Raman spectrometry, nuclear magnetic resonance spectrometry and other quantitative techniques were used. Aspects of their behaviour (as single components and as blends with co-surfactants and co-solvents) which have been considered in terms of: (i) phase behaviour with brine and hydrocarbons (ii) adsorption onto various oxide surfaces (iii) interfacial properties such as surface tension, wetting, contact angles and viscosity (iv) stability Three different blends using sulphonated surfactants which: (i) produce a microeinulsion which is stable to high salinity brines over a large temperature range (ii) exhibit low adsorption onto reservoir rock (iii) interfacial tension as low as 10-2mNm-1 have been subsequently optimised. Core flooding tests carried out under reservoir conditions produced an additional 20% of the original-oil-in-place.

The aim of this study is to analyse political-security risk in Uganda. It emanates from the research question: Does Uganda pose a political-security risk to prospective foreign investment or involvement? The need to move beyond a political risk analysis without entering into a country risk analysis, poses the research problem to develop a political-security risk analysis framework and to apply it to Uganda. This problem generates three subsidiary questions: How appropriate (or inappropriate) are existing risk analysis frameworks? Do existing frameworks contain generic elements that can provide a basis for a synthesised framework? To what extent is a country specific framework applicable to other countries? Therefore, three sub-problems are addressed, namely to determine the appropriateness of selected frameworks; to identify generic elements to construct a synthesised framework; and to assess the applicability of this framework for the analysis of political-security risk in other African countries. Following a definition of the concepts risk, country risk, political risk and political-security risk (analysis), selected frameworks for risk analysis were analysed. The generic elements of these frameworks, namely The Economist (EIU), Business Environment Risk Intelligence (BERI), International Country Risk Guide (ICRG) and Political Risk Services (PRS) frameworks, were reduced to three categories and synthesised into a single framework which was applied to Uganda. The categories of risk indicators pertained to security, political and socio-economic risks respectively. These indicators and the allocated risk scores were used to construct a political-security risk index in respect of which the summed scores provided an index figure of risk that was interpreted in accordance with an interpretation scale. In respect of Uganda, its more recent political history was described and the political, security and socio-economic circumstances prevailing in the country analysed. These conditions were assessed and measured against the indicated risk factors and according to the risk index. The summed political-security risk index score for Uganda was 55.5 out of a maximum of 100. In accordance with the interpretation scale, this constitutes an intermediate risk. Based on this Uganda is not, at present, the most suitable destination for foreign investment or involvement. This does not disallow investment or involvement but if indeed the case, it should be done with circumspection. The situation is volatile to the extent that it can rapidly change for the better or the worse, depending on trends concerning the risk categories, or more specifically a turn of events in respect of a particular key risk indicator. Since the synthesised risk analysis framework is able to accommodate key variables pertaining to politics and security in African states, and since it has provided an indication of risk in respect of Uganda, it is suggested for application to other African states. The need for modification, based on the particularities of other countries, is not excluded. It is also proposed that similar exercises be conducted at intervals of six months. This will indicate whether the variables used were, in fact, valid and reliable, and whether additional variables should be included. The repetition of the analysis also indicates risk trends and allows for the monitoring of risks, which will be conducive to risk management. / Dissertation (MSS (Political Sciences))--University of Pretoria, 2003. / Political Sciences / unrestricted

We report a rapid additive-free synthesis of nanocrystals (NCs) of RHO-type ZIF-71 (1) of composition [Zn(dcim)₂] (dcim = 4,5-dichloroimidazolate) in 1-propanol as solvent at room temperature. NC-1 has a size of 30–60 nm and exhibits permanent microporosity with a surface area (SBET = 970 m² g−¹) comparable to that of microcrystalline material. When kept under the mother solution NC-1 undergoes transformation into a novel SOD-type polymorph (2), which in turn converts into known ZIF-72 (3) with lcs topology. It is shown that microcrystals (MCs) of 2 can be favourably synthesised using 1-methylimidazole as a coordination modulator. NC-2 with size <200 nm was prepared using NC-ZIF-8 as a template with SOD topology in a solvent assisted ligand exchange-related process. DFT-assisted Rietveld analysis of powder XRD data revealed that novel polymorph 2 possesses an unusual SOD framework conformation. 2 was further characterised with regard to microporosity (SBET = 597 m² g−¹) and thermal as well as chemical stability. DFT calculations were performed to search for further potentially existing but not-yet synthesised polymorphs in the [Zn(dcim)₂] system.

PhD (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / This research has investigated the effects of conjugation on the visible light absorption capacity of polyene modified TiO2 nanoparticles as well as the efficiency of these nanoparticles for the mineralisation of acetaminophen (APAP), a non-antibiotic and chloramphenicol (CAP), an antibiotic pharmaceutical compound (PC) which are commonly used worldwide. The efficiency of polyene modified TiO2 (CPE-TiO2) compared with bare TiO2 was further assessed for the mineralisation of the selected PCs under visible light. To achieve this aim, the synthesised nanoparticles were appropriately characterised and tested for the photocatalytic degradation of acetaminophen (APAP) and chloramphenicol (CAP), under visible light. Furthermore, the mechanism and the kinetics of photocatalytic degradation of the PCs were investigated by using high-performance liquid chromatography (HPLC) to monitor the photodegradation intermediates, e.g. Hydroquinone, p-nitrophenol and oxamic acid. The DRS UV-vis spectra result of the CPE-TiO2 indicated that it has a lower band-gap than bare TiO2 nanoparticles and demonstrated a better absorption ability in the wavelength range of 400-800 nm. This result was further confirmed by other optical analyses, such as electrochemical impedance spectrometry (EIS) and photoluminescence (PL). The analysis indicated a less recombination rate of electron/hole pairs in CPE-TiO2 compared to TiO2. Notably, CPE-TiO2 nanocomposite exhibited higher photocatalytic properties for both pollutants, compared to bare TiO2 under visible light. Importantly, photocatalytic degradation experiments demonstrated that the CPE modified nanoparticles were significantly more efficient for PCs degradation (94.21 % for APAP and 80.47% for CAP) compared to bare TiO2 (27.12% for APAP and 36.12% for CAP). The role of CPE-TiO2 photocatalysis in degrading APAP and CAP was examined by varying experimental parameters such as PC concentrations, catalyst loading and solution pH. All the parameters were observed to influence the degradation of the PCs to some extent, albeit, at optimum conditions, most of these PCs were degraded within 210 minutes of visible light irradiation. A significant relationship between the ionic state (+ve or -ve based on the pH) of the solution and CPE-TiO2 photocatalytic process was observed. For the mineralisation, CPE-TiO2 photocatalysis led to higher oxidation rates compared to direct photolysis and bare TiO2 photocatalysis. The results confirm that the co-existence of multiple bonds in poly-conjugated carbon chains with a reduced band-gap in CPE-TiO2 composite were able to enhance charge separation and migration as well as improve the photocatalytic efficiency. This study has clearly demonstrated that polyene modified TiO2 nanoparticles can be applied to degrade PCs in aqueous solution and offers an attractive option for small-scale pharmaceutical wastewater treatment. However, the complex nature of real effluents with co-existing pollutants and higher levels of organic and inorganic matter may call for possible coupling of a biological process as pre- or post-treatment to improve their biodegradability.