Three systems were compared in the first case study: (1). pre-dissolved β-carotene nanoemulsion (d< 200nm); (2). corn oil emulsion (d< 200nm) with β-carotene crystals being added before digestion; (3). phosphate buffer saline with β-carotene being added before digestion. Oil-in-water nanoemulsions were formed by high-pressure homogenization using Tween 20 as emulsifier and corn oil as carrier oil and then they were subjected to a simulated mouth, stomach and small intestine digestion. The rate and extent of free fatty acid production in small intestine decreased in the order (2)>(1)>(3); whereas the β-carotene bioaccessibility decreased in the order (1)>>(2)>(3). In system (3), even without any fat content, there is still noticeable consumption of NaOH, which is due to the ester bonds existing in the non-ionic surfactant (Tween 20). In the second case study, we developed two comparing groups by differentiating their oil concentration (20%, 4% respectively). The bioaccessibility of the high fat group is only half of the low fat group due to the insufficient digestion of fat in the former group. In the third case study, the bioaccessibility of nobiletin with different physical states (crystalized vs solubilized) and in different delivery system (conventional emulsion vs nanoemulsion) was compared. Not like β-carotene, the bioaccessibility of nobiletin as crystals in slightly lower than it is as solubilized state. Meanwhile, in conventional emulsion, the bioaccessibility is slightly lower than in nanoemulsion. This study provides important information for developing effective delivery systems for lipophilic bioactive components in food and beverage applications.

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 1985. / Geology / unrestricted

This diploma thesis is focused on the issue of pneumatic components testing and air leakage measurement. The current state of the given issue is summarized based on the analysis of leak testing methods in accordance with valid legislation. The aim of this thesis is to design methods for pneumatic components testing according to specification. As part of method verification, a pneumatic circuit with a pressure control system has been assembled, on which functionality tests of provided components and leak tests by the pressure-drop method have been performed. The results of these tests have been subsequently evaluated as consistent with the specification.

Typical microwave components such as antennas are large in size and occupy considerable space. Since multiple standards are utilized in modern day systems and thus multiple antennas are required, it is best if a single component can be reconfigured or tuned to various bands. Similarly phase shifters to provide beam scanning and polarization reconfigurable antennas are important for modern day congested wireless systems. Tunability of antennas or phase shifting between antenna elements has been demonstrated using various techniques which include magnetically tunable components on ferrite based substrates. Although this method has shown promising results it also has several issues due to the use of large external electromagnets and operation in the magnetically saturated state. These issues include the device being bulky, inefficient, non-integrable and expensive. In this thesis, we have tried to resolve the above mentioned issues of large size and large power requirement by replacing the large electromagnets with embedded bias windings and also by operating the ferrites in the partially magnetized state. New theoretical models and simulation methodology have been used to evaluate the performance of the microwave passive components in the partially magnetized state. A multilayer ferrite Low Temperature Cofired Ceramic (LTCC) tape system has been used to verify the performance experimentally. There exists a good agreement between the theoretical, simulation and measurement results. Tunable antennas with tuning range of almost 10 % and phase shifter with an FoM of 83.2/dB have been demonstrated in this work, however the major contribution is that this has been achieved with bias fields that are 90 % less than the typically reported values in the literature. Finally, polarization reconfigurability has also been demonstrated for a circular patch antenna using a low cost additive manufacturing technique. The results are promising and indicate that highly integrated ferrite based tunable components are feasible in small form factor, without the need of the large electromagnets and coils, and thus can be operated at very low bias levels as compared to the ones which are operated in the saturated state with external bias mechanisms.

Cowpeas (Vigna unguiculata L. Walp) are legumes recognised as a good source of proteins in developing countries. Cowpeas are mostly utilised as cooked whole seeds. This is often achieved only after boiling for up to 2 hours, resulting in high energy consumption and a long time for food preparation. Micronisation of pre-conditioned cowpeas (± 41 % moisture at 153 °C) reduces their cooking time. During micronisation, cowpea seeds are exposed to electromagnetic radiation with a wavelength range of 1.8 to 3.4μm. For biological materials, the penetration of infrared rays into the food material causes intermolecular vibration, this result in a rapid increase in temperature and water vapour pressure within the seed. Micronisation changes physico-chemical properties of cowpea seeds that may affect sensory properties of cooked cowpeas. Micronisation may also affect cowpea bioactive components such as phenolic compounds and hence their antioxidant properties and bioactive properties. This study aimed at (1) determining the effects of micronisation of pre-conditioned cowpeas on sensory properties of cooked cowpeas and (2) determining the effects of mironisation of pre-conditioned cowpeas on the phenolic compounds, radical scavenging properties and their protective effects against oxidative damage of biomolecules (i.e. low density lipoproteins (LDL), deoxyribonucleic acid (DNA) and red blood cells (RBC). © University of Pretoria vi Micronisation significantly reduced cowpea cooking time by 28 to 49 %, depending on cowpea type. There were significant (P<0.05) increases in roasted aroma and flavour, mushy texture and splitting in all micronised samples. Bechuana white, a light brown cowpea type, was more mushy and split than others. There were significant decreases in firmness, mealiness and coarseness after micronisation for all cowpea types. Micronised cowpeas were darker (lower L* values) than unmicronised cooked cowpeas. Darkening was more evident in light coloured than dark coloured cowpea types. Although micronisation reduces cowpea cooking time, it also affects sensory properties of cowpeas. This might have an influence on consumer acceptance of micronised cowpeas. Twenty seven phenolic compounds were identified in the cowpea types studied: 6 phenolic acids, 14 flavonols and 7 flavan-3-ols. Protocatechuic acid, p-coumaric acid, 4- hydroxybenzoic acid and ferulic acid were the major phenolic acids in cowpeas. Catechin, catechin-3-O-glucoside, myricetin, rutin, quercetin and its mono and diglycosides were present in all cowpea types analysed. Dr Saunders (701.7−849.2 μg/g) (red in colour) and Glenda (571.9−708.1 μg/g) (dark brown in colour) contained the highest total phenolic contents, followed by Bechuana white (361.5−602.3 μg/g) (light brown in colour) and Blackeye (152.0−224.5 μg/g) (cream in colour). More of the flavonols were identified in red and dark brown compared to light brown and cream cowpea types. The red cowpea type contained all the dimers and oligomeric flavan-3-ol species identified in this study. In all cowpea types, extracts from unmicronised (uncooked) cowpeas inhibited copperinduced LDL oxidation in a dose dependent manner. Extracts from all samples analysed exhibited protective effects against AAPH (2, 2'-azobis (2-amidinopropane) hydrochloride) induced RBC haemolysis and DNA damage. Extracts from more pigmented cowpeas, i.e. Dr Saunders, Glenda and Bechuana white, had significantly (P<0.05) higher levels of total phenolics, total flavonoids and radical scavenging properties than Blackeye (less pigmented). Extracts from more pigmented cowpeas also offered higher protection against AAPH-induced DNA and copper-induced LDL oxidation damage than extracts from less pigmented cowpeas. These results indicate protection of biomolecules e.g. DNA, LDL and RBC) from oxidative damage and have a potential to reduce oxidative stress implicated in the development of chronic diseases. This is because cowpea phenolic compounds possess the ability to reduce oxidative damage associated with development of these diseases. © University of Pretoria vii Pigmented cowpea types may be recommended for health applications as they show more potential as source of antioxidants compared to the less pigmented cowpeas. Extracts from micronised (uncooked and cooked) samples of Dr Saunders and Glenda cowpeas had significantly higher concentrations of ferulic acid and p-coumaric acid compared with unmicronised samples. Para-coumaric acid concentrations were higher in all micronised samples of Blackeye cowpeas than in unmicronised samples. The micronisation process could release cell wall bound ferulic acid and p-coumaric, increasing their concentrations in micronised samples. On the contrary, extracts from all micronised samples of Bechuana white and Glenda cowpeas had lower concentrations of catechin than unmicronised samples. Results indicated that total extractable phenolics were lower in micronised samples of cowpea types than unmicronised samples. Futhermore, extracts from micronised samples of all cowpea types showed less protective effect against LDL oxidation than extracts from unmicronised samples. However, for most cowpea types there was no significant difference in total flavonoid contents (TFC) and Trolox equivalent antioxidant capacity (TEAC) values of cooked samples of both micronised and unmicronised. Micronisation did not affect the protective effects of cowpeas against AAPH-induced RBC haemolysis and oxidative DNA damage. Micronisation, followed by cooking, may have generated heat-induced antioxidants such as Maillard reaction products contributing to radical scavenging properties in micronised (cooked) cowpea samples. Though micronised samples had lower concentrations of some phenolic compounds and total extractable phenolics than unmicronised samples, micronised cowpea samples still exhibited radical scavenging properties and offered protective effects against oxidative damage of LDL, DNA and RBC and therefore may offer potential health benefits to consumers. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Food Science / Unrestricted

Context: As most modern browsers fully support the new set of APIs called Web Components, it is crucial to investigate how developers could use them to enhance the performance and developer experience of web development. When considering this, it is fitting to investigate both the technical and practical differences between modern libraries powered by the APIs, versus traditional libraries which do not. Objectives: In this study, traditional libraries using Virtual DOM got investigated to find out which differences exist when compared to modern ones using Web Components. To find out how this next generation of front-end libraries could utilize these new APIs to improve the build process of websites. If the APIs offer alternative ways for developers to achieve better performance and developer experience. Realization:  In order to fulfill the objectives, an empirical study and a literature review were conducted. In the literature review, we investigated how a set of well-known front-end libraries technically compares to new and aspiring Web Components based libraries. In the empirical study, a new Web Components library was built from the ground up with inspiration from Vuejs. With the help of modern code styles to achieve a fresh developer experience. Results: The results of the study show that Web Components based libraries tend to be quite powerful and offer excellent all-around performance. The created library, Kirei, reflected this as it became a powerful all-around library that offers a great developer experience. It also performed equally well or even better than Vue on most benchmarks. However, Vue was better at creating new elements while Kirei excelled at updating elements. In a way, the libraries excitingly contrasted with each other. Conclusions: While Vue and React are fundamentally different from Lit-Element, Heresy, and Kirei, they are alike in some sense. Most of the differences come from how the libraries apply updates to the DOM. While Web Components based libraries patch only the dynamic parts, Virtual DOM has to diff both the dynamic and static parts. Moreover, Kirei proved to be a robust framework that could compete with Vue and React. In some benchmarks, it proved to have an upper edge in performance.

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Principal surfaces are smooth two-dimensional surfaces that pass through the middle of a p-dimensional data set. They minimise the distance from the data points, and provide a nonlinear summary of the data. The surfaces are nonparametric and their shape is suggested by the data. The formation of a surface is found using an iterative procedure which starts with a linear summary, typically with a principal component plane. Each successive iteration is a local average of the p-dimensional points, where an average is based on a projection of a point onto the nonlinear surface of the previous iteration. Biplots are considered as extensions of the ordinary scatterplot by providing for more than three variables. When the difference between data points are measured using a Euclidean embeddable dissimilarity function, observations and the associated variables can be displayed on a nonlinear biplot. A nonlinear biplot is predictive if information on variables is added in such a way that it allows the values of the variables to be estimated for points in the biplot. Prediction trajectories, which tend to be nonlinear are created on the biplot to allow information about variables to be estimated. The goal is to extend the idea of nonlinear biplot methodology onto principal surfaces. The ultimate emphasis is on high dimensional data where the nonlinear biplot based on a principal surface allows for visualisation of samples, variable trajectories and predictive sets of contour lines. The proposed biplot provides more accurate predictions, with an additional feature of visualising the extent of nonlinearity that exists in the data.

Concentrations of microorganisms and chemical components in groundwater are serious threats for groundwater resources sustainability and contribute to technical and health problems. Recent studies and reports in Gotland revealed huge concerns about water quality in the area. In this master thesis a range of methods such as GIS and statistical analysis including multivariate analysis and non-parametric analysis, have been used in order to identify natural and human factors which affect groundwater contamination. Main focus of the study was on using existing data and available databases in analyses. Consequently, several important factors such as land use, overlaying soil cover, soil thickness, bedrock, elevation, distance to deformation and fracture zones and slope were evaluated considering 8 variables including micro-organisms and chemical components. The results clarified several significant factors which statistically affected the micro-biological and chemical components of groundwater. These relations can be used for development of risk maps which can be used in spatial planning.

Using greenhouse pot techniques, 32 drilling mud components were tested to see if, at a high rate of addition, they reduced plant growth. Green beans and sweet corn were the test plants. The excellent black, silt loam, slightly acidic, uncultivated Dagor soil (Cumulic Haploxeroll) was used for most tests. Rates used were considered to be abnormal level (high rate) and usual (low rate) amounts that might be added in commonly used drilling muds. Drilling mud components that caused no observable or statistically significant reductions of plant yield are the following: Super Visbestos, (Asbestos), asphalt, Ben-Ex (a vinyl acetate and maleic anhydride copolymer), bentonite, Cypan (sodium polyacrylate), DME (ethoxylated nonyl phenol), Super Lube Flow (gilsonite), paraformaldehyde, Separan-AP- 273 (Dow-made, Shell-supplied polymer), sodium acid pyrophosphate, and sodium carboxymethyl cellulose. Drilling mud components that barely caused a statistical significant (5 percent level) reduction in yield for only one of the two plant species when added to the soil only and, therefore, is of questionable hazard to plant growth are the following: Barite (BaSO4), Desco (modified tannin), Drillaid 412 (a filming amine), Drillaid 405 (diesel oil replacement), Kelzan-XC (a xanthan gum), Pipe dope, Lingo (lignite), Soltex (sulfonated asphalt?), and Witconnate 1840 (sulfonated tall oil). Drilling mud components causing significant reduction in plant growth mostly at only the high addition rates to soil-mud mixtures are the following: Desco (modified tannin?), Dextrid (a non-fermenting starch), pregelatinized starch, Q-Broxin (an iron chromelignosulfonate), Gendril Thik (guar gum), and Kwik-Seal. The most severe reductions in plant growth were caused by the following materials: Sodium hydroxide at the high rate (which was used in the soil-mud mixture with calcium lignosulfonate and with lignite), diesel oil and potassium chloride at both rates. The latter salt completely inhibited plant germination. Probable causes for plant growth reductions, photographic and visual records, and a discussion of the results is presented in some detail.