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Dissertation submitted in compliance with the requirements for the Master's Degree in Technology: Chemical Sciences, Technikon Natal, 1998. / The demand for fried foods by the public and the number of people entering the fried food industry in the form of take-aways and fast food outlets both in the formal and informal sectors has increased tremendously. Frying fats and oils are very expensive, used in large quantities and is the most important ingredient used in the preparation of fried foods: Due to the high cost of these frying fats and oils, majority of the formal and informal traders are using the frying fats and oils to its maximum in order to reduce the overall cost. This has resulted in the preparation of poor quality offried foods. Considering all of the above, the aim of the proposed research was :- (a) to determine the quality of the frying fats and oils used by both the formal and informal sectors by performing both physical and chemical analyses and compare these with similar analyses performed on the unused frying fats and oils in order to ascertain the degree of deterioration of the used frying fats and oils (b) to investigate the method of disposal of the used frying fats and oils. (c) to contribute in educating both the consumers and the suppliers of fried foods by bringing the findings of this research to the attention of the Durban Metro Health Department. The used frying fats 'and oils were collected during the frying process by the environment health officer from the Durban Metro Health Department. These samples were placed in a refridgerator to prevent any further deterioration. The used and unused frying fats and oils were analysed for, the Free Fatty Acid and Acid Value contents; the quantitative separation of Monoglycerides, Diglycerides and Triglycerides; the Refractive Index; the Peroxide Values; the concentrations of Polar and Non-polar Compounds; the Viscosity and the identification of the various fatty acid methyl esters present in the samples. The analytical methods used were followed from the American Oil Chemists Society (AOCS) Official Method Handbook. The Free Fatty Acid and Acid Value results showed that twenty-five percent of the samples had a concentration of more than the maximum acceptable limit of 2.5%. It was evident that the types of food fried, the intermittent heating, frying / M

Magnetic fluids are synthetic materials that combine in a single medium the properties of fluids and magnetic materials. The action of a magnetic field on the magnetic fluid allows the design of new types of bearings and also provides conventional ones with new properties. This work presents a contribution to the study of the lubrication of linear isothermal non-conformal contacts with magnetic fluids under the action of a non uniform magnetic field perpendicular to the plane of the contact. The fluid is assumed to present extrinsic superparamagnetism. The regime of lubrication considered is the isoviscous-rigid. The analytical approach adopted considers small perturbations of the classical analytical solution already known for this type of contact. The main objectives of the work are: To establish the equations and assumptions that are necessary to treat the proposed lubrication problem To analyze the impact of the change in the apparent viscosity of the magnetic fluid on the thickness of the lubricating lm due to the presence of the magnetic field ° To develop an experimental technique able to deal with the problems that arise with the use of magnetic fluids in the lubrication of a two-disc machine The mathematical treatment of the proposed problem brings together the analytical methods adopted in fluid lm lubrication to the analysis of long isothermal hydrodynamic bearings and those from the magnetic-liquid fluid dynamics (ferrohydrodynamics) usually adopted to study the flow of magnetic fluids that present extrinsic superparamagnetism. The result is a coherent system of equations supported by a well defined set of assumptions. The solution obtained allows the study of the eventual change of the lm thickness that can be achieved by the application of a magnetic field across the contact. The work also discusses the experimental technique necessary to study the problem in a two-disc machine that runs with minute amounts of lubricant, applies a magnetic field across the contact and measures the lm thickness by a capacitance method. The work concludes by showing theoretically that the lm thickness can be either increased or reduced depending on the magnetic and viscous properties of the fluid and the intensity of the magnetic field. These conclusions are supported by experiments with a magnetic oil in a two-disc machine.

Thesis (M.Pharm.)--University of the Witwatersrand, Faculty of Health Sciences, 2013. / Essential oils are not only used singularly but have been used in combination for many years. There is, however, very little scientific evidence to support the claims made for combined antimicrobial efficacy. With this in mind, a study was designed to investigate the antimicrobial activity of Lavender (Lavandula angustifolia) essential oil, in combination with other essential oils with antimicrobial relevance. The micro-dilution minimum inhibitory concentration (MIC) assay was undertaken, whereby the fractional inhibitory concentration (ƩFIC) was calculated for 54 oil combinations. When lavender oil was assayed in 1:1 ratios with other oils, synergistic (23.5%), additive (52.5%), non-interactive (23.5%) and antagonistic (0.5%) interactions were observed. Four 1:1 combinations were synergistic against Candida albicans and Staphylococcus aureus (Lavandula angustifolia in combination with Daucus carota (ΣFIC 0.50 and 0.50); Juniperus virginiana (ΣFIC 0.50 and 0.50); Cinnamomum zeylanicum (ΣFIC 0.40 and 0.50) and Citrus sinensis (ΣFIC 0.42 and 0.38)). In order to understand the antimicrobial potential of these synergistic essential oil combinations, further antimicrobial analysis was undertaken whereby the oils were placed in varying ratios. Two of the four combinations (Lavandula angustifolia in combination with either Cinnamomum zeylanicum or Citrus sinensis), were identified as the most promising, demonstrating synergy at varying ratios, and thus the major chemical constituents of the essential oils were investigated further. The major chemical constituents identified in Lavandula angustifolia (GC-MS) were linalyl acetate (36.7%), linalool (31.4%) and terpinen-4-ol (14.9%). The GC-MS profiles for all other oils in the study were also confirmed. The major chemical constituents of the most promising essential oil combinations were investigated in equal and varying ratios to determine the effect of chemistry on antimicrobial outcome. When one of the major essential oil constituents (linalyl acetate) of Lavandula angustifolia was combined with limonene found in Citrus sinensis, synergistic interactions were noted for all nine combinations against C. albicans; including the ratio at which the two major constituents would be mixed should the two oils be combined. Lavandula angustifolia essential oil was placed in combination with four conventional antimicrobial agents (ciprofloxacin, chloramphenicol, fusidic acid and nystatin) to determine which of these agents in combination with Lavandula angustifolia would demonstrate the best antimicrobial effect. Synergy was determined for Lavandula angustifolia in combination with ciprofloxacin against S. aureus (ΣFIC of 0.49) and Lavandula angustifolia in combination with chloramphenicol against P. aeruginosa (ΣFIC of 0.29). No antagonism was noted for the combinations investigated. When placed in variable ratios it was identified that Lavandula angustifolia provided the pivotal role in the synergistic interactions observed against C. albicans and S. aureus, with ratios higher in Lavandula angustifolia essential oil concentration showing considerably better antimicrobial effects. In order to determine the antimicrobial effects of Lavandula angustifolia in triple essential oil combinations, the method of MODDE® Design of Experiments was employed. The Design of Experiments (MODDE 9.1®) software identified that Lavandula angustifolia (from the combination of Lavandula angustifolia: Citrus sinensis: Cedrus atlantica) and Thymus vulgaris (from the combination of Lavandula angustifolia: Daucus carota: Thymus vulgaris) were the essential oils with the greater antimicrobial effect in the combinations analysed. Lavender remains one of the most sought after essential oils. This comprehensive study on the antimicrobial effects of Lavender (Lavandula angustifolia) combinations demonstrates promising in vitro effects and lends some credibility for combined use in aromatherapy for the treatment of infections

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Analytical procedures have been developed for the quantitative analysis of phenols in crude oils and sedimentary rock pyrolysates and extracts. The procedures involve isolation of the phenolic components of the sedimentary organic matter by extraction with alkaline aqueous methanol, followed by the removal of carboxylic acids using a back extraction step. Co-extracted non-polar components are removed from the alkaline extract by liquid chromatography or by extracting it with hexane. The phenol isolates thus obtained were analysed by capillary GC, GC-MS and GC-FTIR. Recoveries of 70-95% were measured for C(subscript)0-C(subscript)3 alkylphenol compounds using these procedures.Crude oil samples (45) representing a range of locations, ages, depositional environments, maturities, source types, and biodegradation levels have been analysed for their phenol contents. A range of C(subscript)0-C(subscript)5 alkylphenols (approximately 40) were identified in crude oils using co-chromatography on up to three different stationary phases and by comparison of their retention times, mass spectral and infrared spectral properties with reference compounds. Isopropylmethylphenols (six) and sec-butylmethylphenols (nine) were synthesised for use in the identification of these compounds. A range of C(subscript)0-C(subscript)4 alkylphenols (24) were quantified using a dimethyl siloxane column (BP 1 or DB 1) and found to occur at concentrations ranging from 190x10(subscript)3 ng/g down to the limit of detection of 10 ng/g (ppb).The crude oil samples were classified into six groups based on their C(subscript)0-C(subscript)5 alkylphenol compositions. Group 1 crude oils have at least one isomer class in which the relative proportions of the alkylphenol isomers reflect their relative thermodynamic stabilities. The vast majority of samples, however, do not contain relative proportions of ++ / phenols which reflect their stabilities, and these differences have been used to group the remaining crude oils. Group 2 crude oils contain predominantly alkylphenols derived from natural product precursors. This group has been further subdivided into Group 2A in which samples have isopropylmethylphenol distributions dominated by carvacrol and thymol; and Group 2B which is comprised of crude oils that contain high relative abundances of methylphenols which can be derived from tocopherols. Group 3 crude oils have C(subscript)2-C(subscript)5 alkylphenol compositions dominated by ortho and para substituted phenols which are proposed to be formed from geosynthetic processes. Group 4 crude oils contain alkylphenol compositions in which the relative abundances of meta substituted compounds in six isomer classes are much greater than those expected from chemical equilibration. Group 5 comprises of samples which are biodegraded and as a consequence contain alkylphenols below the limit of detection. Group 6 crude oils contain very low concentrations of alkylphenols and comprises samples which are derived from source rocks that pre-date the widespread occurrence of land plants or contain negligible land plant input.Some alkylphenols in crude oil are structurally related to natural product precursors and therefore appear to be biomarkers. The monoterpenoid natural products carvacrol and thymol, or its rearrangement product 3-isopropyl-5-methylphenol, which occur in high relative abundances in Group 2A samples are such compounds. Because carvacrol and thymol occur widely in extant conifers and angiosperms, their presence in crude oils derived from source rocks deposited when these plant types were widespread suggests they also originate from these plants. A range of trimethylphenols and tetramethylphenols which occur in high relative abundances in Group 2B samples, are also ++ / reaction products obtained from heating alpha-tocopherol with aluminium smectite. This, together with the reported widespread occurrence of tocopherols in plant photosynthetic tissue and in sedimentary rocks, leads to the conclusion that tocopherols are likely precursors to these petroleum methylphenols.The lignin components of terrestrial plants also appear to be important precursors to petroleum alkylphenols. Strong evidence for this is provided by the observation that crude oils derived from source rocks which contain negligible higher plant input contain very low concentrations of kylphenols (Group 6). In order to determine the likelihood of lignins as precursors of petroleum alkylphenols, the phenol contents of coals of lignitic through to bituminous rank were examined. The unbound phenolic components of the lignite samples were analysed by isolating the phenols from their dichloromethane extracts, and the bound phenolic components were analysed by pyrolysis GC-MS. At lignitic rank the unbound methoxyphenols allowed taxonomical classification of the samples and the bound hydroxyphenols bore structural similarities to lignin moieties. The bound C(subscript)0-C(subscript)4 alkylphenol components of lignitic, subbituminous and bituminous coals in a sedimentary sequence were quantitatively analysed by isolating the phenols from their hydrous pyrolysates. In the coals of subbituminous and bituminous rank, the bound alkylphenol components could not easily be related to lignin precursors because molecular transformations of lignins are very severe at these ranks. The increases in the individual concentrations and relative proportions of alkylphenols with methyl and/or isopropyl substituent(s) in the ortho and para positions in the subbituminous coal pyrolysate were attributed to electrophilic methylation and isopropylation reactions occurring to lignin structures in ++ / coals during coalification. The dominance of ortho and para substituted methylphenols in coaly Group 3A crude oils which were also observed in the hydrous pyrolysates of coals suggests that the altered lignin structures in coals may be precursors of some of these petroleum methylphenols.Methylation, isopropylation and sec-butylation, are proposed as geosynthetic processes to account for the alkylphenol compositions of crude oils with phenol distributions dominated by ortho and para alkyl-substituted compounds (Group 3). Many crude oils show high relative abundances of ortho and para substituted C(subscript)1-C(subscript)5 alkylphenol isomers and some were also enriched in C(subscript)3-C(subscript)5 alkylphenols compared to kerogen pyrolysates. Because the alkylphenol products obtained from the laboratory alkylation of cresols have distributions which closely resemble those in these crude oils, it is proposed that similar alkylation processes occur in source rocks. Alkylation ratios reflecting the degree of methylation, isopropylation and sec-butylation, which were based on the relative abundance of the dominant alkylation products compared to their likely precursor ortho cresol, indicate that high levels of methylation occurred in crude oils over a wide range of maturities. In contrast, high levels of isopropylation and sec-butylation were observed only in mature samples. Selective dissolution of phenol isomers in crude oils by water contact was discounted as an explanation for the observed phenol distributions based on the relative distribution coefficients of phenols between isooctane and water.The alkylphenol compositions of the remaining crude oils appear to be produced from alteration processes occurring in the subsurface; these include oxidation and biodegradation processes. Oxidation of alkylphenols is proposed to account for the alkylphenol compositions of ++ / Group 4 crude oils. Because ortho and para substituted alkylphenols are more susceptible to oxidation than their meta substituted counterparts, the selective removal of these compounds via an oxidation process is suggested as an explanation for the high relative abundances of meta substituted isomers observed in these crude oils. A natural product origin for these compounds appears unlikely due to the lack of known natural products which could give rise to meta substituted alkylphenols with isopropyl substituents, and the diverse range of organisms required to give rise to the meta substituted phenols with n-alkyl substituents observed in Group 4 samples.Crude oils from two Australian basins which have undergone various levels of biodegradation were analysed to assess biodegradation effects on petroleum alkylphenol compositions. Alkylphenols could not be detected in the moderately to severely biodegraded crude oils (Group 5) whereas related non-biodegraded samples contained relatively higher levels of alkylphenols. The very low levels of phenols in the biodegraded samples (< 10 ppb) suggests that phenols are depleted via processes that occur during biodegradation. Because water washing often co-occurs with biodegradation, the very low levels of alkylphenols in these samples may also be due in part to the removal of these polar components via water dissolution.