Recent advances in space geodetic techniques such as Very Long Baseline Interferometry, Global Navigation Satellite Services, Satellite Laser Ranging and advanced numerical weather prediction model simulations, provide huge tropospheric data sets with improved spatial temporal resolution. These data sets exhibit unique fluctuations that have a spatial-temporal structure which are thought to mimic the complex behaviour of the atmosphere. As a result, the analysis of non-stationary structure in the tropospheric parameters derived from geodetic and numerical model simulations could be used to probe the extent of universality in the dynamics of the atmosphere, with applications in space geodesy. In order to identify the physical causes of variability of tropospheric parameters, parametric and nonparametric data analyses strategies which are investigated and reported in this thesis, are used to inform on the geophysical signals embedded in the data structure. In the first task of this research work, it is shown that the fluctuations of atmospheric water vapour over southern Africa are non-linear and non-stationary. Secondly, the tropospheric data sets are transformed to stationarity and the stochastic behaviour of water vapour fluctuations are assessed by use of an automatic algorithm that estimates the model parameters. By using a data adaptive modelling algorithm, an autoregressive-movingaverage model was found to sufficiently characterise the derived stationary water vapour fluctuations. Furthermore, the non-linear and non-stationary properties of tropospheric delay due to water vapour were investigated by use of robust and tractable non-linear approaches such as detrended fluctuation analysis, independent component analysis, wavelet transform and empirical mode decomposition. The use of non-linear approaches to data analysis is objective and tractable because they allow data to speak for themselves during analysis and also because of the non-linear components embedded in the atmosphere system. In the thesis, we establish that the non-linear and non-stationary properties in the tropospheric data sets (i.e., tropospheric delay due to water vapour and delay gradients) could be triggered from strongly non-linear stochastic processes that have a local signature (e.g. local immediate topography, weather and associated systems) and/or exogenous. In addition, we explore and report on the presence of scaling properties (and therefore memory) in tropospheric parameters. This self-similar behaviour exhibit spatial-temporal dependence and could be associated with geophysical processes that drive atmosphere dynamics. Satellite Laser Ranging data are very sensitive to atmospheric conditions, which causes a delay of the laser pulse, hence an apparent range increase. A test for non-linearity is applied within specialised software for these data; it is found that the range residuals (i.e., the observed minus computed residuals) are improved when possible non-linearity of the locally measured meteorological parameters as applied to a range delay model are considered. / Thesis (PhD)--University of Pretoria, 2011. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

Cryopreservation of epididymal spermatozoa may be the only opportunity to preserve valuable genetics of males in cases of unforeseen injury or death. Stallion epididymal spermatozoa have been cryopreserved successfully and it has been demonstrated that stallion epididymal spermatozoa are fertile, and pregnancies as well as live foals have been produced. As spermatozoal quality parameters like motility, morphology and viability have a major influence on fertility and pregnancy rates, it is of great interest to describe these and investigate the influence of seminal plasma on these parameters. Fresh and post-thaw parameters (motility, morphology and viability) of stallion epididymal spermatozoa that have been and that have not been exposed to seminal plasma were evaluated, and directly compared to fresh and post-thaw parameters of ejaculated spermatozoa from the same stallions. Six sperm categories of each stallion (n= 4) were evaluated for motility, morphology and viability. These categories were fresh ejaculated spermatozoa (Fr-E), fresh epididymal spermatozoa that had been exposed to seminal plasma (Fr-SP+), fresh epididymal spermatozoa that had never been exposed to seminal plasma (Fr-SP-), frozen-thawed ejaculated spermatozoa (Cr-E), frozen-thawed epididymal spermatozoa that had been exposed to seminal plasma prior to freezing (Cr-SP+) and frozen-thawed epididymal spermatozoa that had never been exposed to seminal plasma (Cr-SP-). Results show that seminal plasma stimulates initial motility of fresh epididymal stallion spermatozoa while this difference in progressive motility is no longer present post-thaw; and that progressive motility of fresh or frozen-thawed ejaculated stallion spermatozoa is not always a good indicator for post-thaw progressive motility of epididymal spermatozoa. This study shows that seminal plasma has a positive influence on the incidence of overall sperm defects, midpiece reflexes and distal cytoplasmic droplets in frozen-thawed stallion epididymal spermatozoa while the occurance of midpiece reflexes is likely to be linked to distal cytoplasmic droplets. Furthermore, we could show that seminal plasma does not have an influence on viability of fresh and frozen-thawed morphologically normal epididymal spermatozoa. In conclusion, we recommend the retrograde flushing technique using seminal plasma as flushing medium to harvest and freeze stallion epididymal spermatozoa. AFRIKAANS : Bevriesing van epididimale spermatozoa mag die enigste geleentheid wees om waardevolle genetika van manlike diere te bewaar in die geval van onverwagse dood of besering. Epididimale spermatozoa van hingste is al suksesvol bevries, is bewys vrugbaar te wees en dragtighede sowel as lewendige vullens is deur die gebruik daarvan gelewer. Aangesien maatstawwe van spermgehalte soos beweeglikheid, morfologie en lewensvatbaarheid ‘n beduidende invloed uitoefen op vrugbaarheid en dragtigheidsyfers, is dit van groot belang om hierdie maatstawwe te omskryf en die invloed van seminale plasma daarop te ondersoek. Vars en ontdooide maatstawwe (beweeglikheid, morfologie en lewensvatbaarheid) van hings epididimale spermatozoa wat of aan seminal plasma blootgestel is of nie, is vergelyk met vars en ontdooide maatstawwe van geejakuleerde spermatozoa. Ses spermkategorieë van elke hings (n=4) is geevalueer vir beweeglikheid, morfologie en lewensvatbaarheid. Die kategorieë was vars geejakuleerde spermatozoa (Fr-E), vars epididimale spermatozoa wat blootgestel is aan seminale plasma (Fr-SP+), vars epididimale spermatozoa sonder blootstelling aan seminale plasma (Fr-SP-), ontdooide geejakuleerde spermatozoa (Cr-E), ontdooide epididimale spermatozoa blootgestel aan seminale plasma voor bevriesing (Cr-SP+) en ontdooide epididimale spermatozoa wat nooit blootgestel is aan seminale plasma nie (Cr-SP-). Uitslae toon dat seminale plasma die aanvanklike beweeglikheid van vars epididimale hings spermatozoa stimuleer, terwyl die verskil in lynbeweeglikheid nie meer teenwoordig is na ontdooiing nie; dat lynbeweeglikheid van vars epididimale spermatozoa of ontdooide geejakuleerde hings spermatozoa nie altyd ‘n goeie aanduiding is vir lynbeweeglikheid na ontdooiing nie. Hierdie studie toon dat seminale plasma ‘n positiewe invloed het op die voorkoms van algehele spermdefekte, midstukreflekse en distale sitoplasmiese druppeltjies in ontdooide hings epididimale spermatozoa terwyl die voorkoms van midstuk reflekse waarskynlik verband hou met distale sitoplasmiese druppletjies. Verder kon ons ook aantoon dat seminale plasma geen invloed het op die lewensvatbaarheid van vars en ontdooide morfologies normale epididimale spermatozoa nie. Ten slotte beveel ons aan dat retrograadse spoeling met seminale plasma as spoelmedium gebruik word wanneer hings epididimale spermatozoa versamel en bevries word. / Dissertation (MSc)--University of Pretoria, 2010. / Production Animal Studies / unrestricted

Imaging with the James Webb Space Telescope (JWST) will allow observations of the bulk of distant galaxies at the epoch of reionization. The recovery of their properties, such as age, color excess E(B-V), specific star formation rate (sSFR), and stellar mass, will mostly rely on spectral energy distribution fitting, based on the data provided by JWST's two imager cameras, namely the Near Infrared Camera (NIRCam) and the Mid Infrared Imager (MIRI). In this work we analyze the effect of choosing different combinations of NIRCam and MIRI broadband filters, from 0.6 to 7.7 mu m, on the recovery of these galaxy properties. We performed our tests on a sample of 1542 simulated galaxies, with known input properties, at z = 7-10. We found that, with only eight NIRCam broadbands, we can recover the galaxy age within 0.1 Gyr and the color excess within 0.06 mag for 70% of the galaxies. Additionally, the stellar masses and sSFR are recovered within 0.2 and 0.3 dex, respectively, at z = 7-9. Instead, at z = 10, no NIRCam band traces purely the lambda > 4000 angstrom regime and the percentage of outliers in stellar mass (sSFR) increases by > 20% (> 90%), in comparison to z = 9. The MIRI F560W and F770W bands are crucial to improve the stellar mass and the sSFR estimation at z = 10. When nebular emission lines are present, deriving correct galaxy properties is challenging at any redshift and with any band combination. In particular, the stellar mass is systematically overestimated in up to 0.3 dex on average with NIRCam data alone and including MIRI observations only marginally improves the estimation.

La Digestion Anaérobie (DA), ou méthanisation, est un procédé qui permet le traitement de déchets organiques et la production d’énergie renouvelable sous forme de biogaz. La DA par voie sèche permet en particulier la valorisation de substrats solides, offrant plusieurs possibilités aux traitements de résidus d’origine agricole tels les fumiers, des substrats constitués d’un mélange de paille, fèces et urine accumulés dans les litières des étables. Parmi les technologies disponibles en méthanisation, les « leach-bed reactors » (LBRs), constituent une option valide mais toutefois peu connue et peu développée soit au niveau scientifique qu’industriel.Dans le but d’optimiser ce procédé, plusieurs problématiques ont été affrontées : (i) la caractérisation bio-physico-chimique du fumier et du potentiel énergétique exprimé dans un LBR; (ii) l’optimisation de l’inoculation des réacteurs et de la température de digestion ; (iii) la co-digestion du fumier avec un substrat facilement biodégradable et la problématique reliées à la gestion des acides gras volatiles (AGVs) ainsi produits.Les résultats montrent que le fumier est un substrat lentement biodégradable qui nécessite un long temps de digestion. Cependant, il s’agit d’un déchet agricole adapté à la valorisation par méthanisation et dont les rendements de dégradation et de production de méthane en LBRs sont intéressants industriellement. Ce substrat est par conséquent une ressource organique précieuse dans le contexte agricole.Il a été montré que le fumier bovin contient une population méthanogène active capable de démarrer un procédé de digestion anaérobie efficacement sans l’ajout d’un inoculum externe spécifique, autant en mode mésophile que thermophile. Une analyse économique a démontré que cette propriété peut être exploitée afin de diminuer les coûts d’investissement initiaux d’un projet à l’échelle industrielle, en favorisant de cette manière le développement de la filière. De plus, les résultats montrent que pour la digestion du fumier en LBRs le mode thermophile ne comporte aucun intérêt par rapport à la production finale de méthane (qui est similaire pour les deux régimes) et que, au contraire, la valorisation par cogénération du méthane produit en thermophile diminue le rendement de production électrique surtout à cause d’une production de méthane très importante en début de digestion. Le régime mésophile parait donc être le mode de fonctionnement le plus adapté dans ce contexte.Enfin, le rôle joué par la percolation du lixiviat sur la mobilisation des AGV accumulés dans la fraction solide a été mis en lumière dans un réacteur de co-digestion traitant une fraction de lentement biodégradable (le fumier) et une fraction facilement biodégradable. Une stratégie a été développée afin d’étudier le problème de l’extraction et de la consommation des AGV dans le but d’améliorer le rendement global du procédé.Pour conclure, ce travail a permis d’optimiser certains paramètres fondamentaux dans la gestion d’un LBR. Cette technologie s’est révélée efficace dans le traitement du fumier, autant en mono-digestion qu’en co-digestion avec un substrat facilement biodégradable. Ces recherches montrent que l’utilisation des LBR est appropriée au contexte agricole et que la modification des paramètres de contrôle permet à ce procédé de répondre efficacement aux problématiques du terrain. Ce travail représente une avancée significative vers la compréhension et le développement des LBRs pour le traitement des résidus agricole et, plus globalement, des énergies renouvelables mobilisant des biomasses agricoles / Anaerobic Digestion (AD) is a process which allows the treatment of organic waste and the production of renewable energy. In particular, dry AD allows the treatment of solid organic substrates, offering several possibilities to the enhancement of agricultural waste such as spent livestock bedding (a mixture of straw, faeces and urine). Among the available biotechnologies in AD, leach-bed reactor (LBRs) is a promising but yet poorly known process both at scientific and industrial level.In order to develop this process, several issues have been studied: (i) the bio-physico-chemical characterization of spent animal bedding and its digestion potential in LBRs; (ii) the optimization of the start-up and the operating temperature of the digesters; (iii) the co-digestion of spent animal bedding with an easily-degradable substrate and the issues connected to the management of the volatile fatty acids (VFAs) produced.The results showed that spent animal bedding is a slowly-degradable substrate which needs a long digestion time. However, it is a substrate suitable to be treated through AD displaying high degradation and methane production rates when processed in LBRs. This substrate is, therefore, a valuable organic resource in the agricultural context.Spent animal bedding was shown to contain an active methanogenic population able to start the process efficiently, both in thermophilic and mesophilic temperature, without requiring a specific external inoculation. An economic study at industrial scale proved that this peculiarity can be used to diminish the investment costs and then promote the development of this process. Moreover, thermophilic temperature was proved to be less advantageous over mesophilic condition. In fact, despite the very close methane yield reached in both temperature range, the different biogas production rates in thermophilic conditions would lead to a reduction of the final electric energy production in this condition. Mesophilic temperature was then shown to be the best operating condition for this process.Finally, the role played by the leachate recirculation in the mobilization of the VFAs accumulating in the solid bulk was highlighted in the case of a reactor co-digesting slowly- (spent livestock bedding) and easily-degradable substrates. A strategy was even proposed to efficiently face such a problem by optimizing both the VFA extraction and consumption with the objectives of increasing the overall process efficiency.In the end, this work allowed to optimize some important parameters for the correct management of the LBRs. This technology was proved to be efficient in the treatment of spent livestock bedding, both as a sole substrate or in co-digestion with an easily-degradable substrate. This research study demonstrates that LBRs is an adapted process for the agricultural context and this technology can easily answer to the full scale issues usually encountered. This work represents a significant advance towards the comprehension and development of LBRs to treat agricultural waste and, more generally, to the development of renewable energies based on biomass

Mounting of lenses in opto-mechanical assemblies can create surface figure errors and refractive index changes through thermal and pre-load stresses. As lenses and barrels change in size under temperature changes, the optical performance degrades due to stress and surface deformations. Currently there is no way of determining the effect of these mechanical perturbations on the system wavefront without performing tedious finite element analysis. Most in-depth opto-mechanical analyses involve case-by-case studies with specific designs while previous general studies fail to take into account the complex geometries. The assumptions made by previous general studies ignore the effects of lens shape. These omissions can have a large effect on the stiffness, stress and surface figure error. A parametric model can combine the best of both an in-depth and general study. By parametrizing the model, a simple analysis can be executed for approximating the environmental-mechanical effects on optical performance. This eliminates the time it takes for an opto-mechanical design to be iterated for an optical or mechanical engineer. This tool could be used for early opto-mechanical design or for finite element analysis verification. The parametric model allows the exploration of the broader design study without confining it to a local design space.

The objective of this study was to compare prediction of meat tenderness by means of gene technologies (markers) with established physical estimates of meat tenderness. Weaned, young bulls (n = 60) were selected on phenotype from various commercial producers to represent a Brahman (Bos indicus; n = 20), Simmental (continental Bos Taurus; n = 20) and Nguni (Sanga; n = 20) crossbred group. After being raised under intensive feedlot conditions the animals were slaughtered according to normal South African slaughter procedures at an A-age (10 - 12 months) with a fatness class of two or three (lean-medium fatness). At slaughter the carcasses were not electrical stimulated because electrical stimulation influences the processes of meat tenderness, and the emphasis was on the expression of the inherent tenderness characteristics without external post mortem influences. Carcasses were halved, chilled at 4 ˚C within 2 hours post mortem. The M. longissimus thoracis et lumboram (LT and LL) of the right and left sides were removed from the third last rib to the last lumbar vertebra and sub sampled for shear force evaluations, SDS-PAGE, Western-blotting, myofibril fragmentation (MFL), sarcomere length (SL), calpain, calpastatin, total collagen, % collagen solubility and marker analysis. The position of sampling for each test was consistent and the different samples were either frozen immediately at -20 ˚C or -80 ˚C or vacuum packed and aged (2 ± 2 ˚C) for 7 or 14 days post mortem. Two single nucleotide polymorphism (SNP) markers were employed in this study for the bovine CAPN1 gene, which is found or situated on bovine chromosome 29, namely a SNP marker which is situated on exon nine (CAPN1-316) and the other on intron 17 (CAPN1-4751). The inhibitor, calpastatin (CAST) found on chromosome seven was also analysed in this study. Both the CAST markers (CAST and CAST-Brahman) lie in the three prime untranslated regions (3' UTR) of the CAST gene. Genotype data of two- markers were used to determine the two-marker haplotypes. The results of the study showed that differences exist in meat quality of the different crossbreds. Brahman- and Nguni-crosses had lower shear force values (more tender) than that of the Simmentaler-crosses under these specific experimental conditions. The pH decline did not differ significantly (p > 0.001) between the crossbreds. The carcass temperature and temperature decline rate although similar between the Brahman- and the Simmentaler-crosses for three hours and up to eight hours post mortem differed significantly from that of the Nguni-crosses (p < 0.006). The sarcomere lengths were mostly under 1.7 µm, which indicate that shortening (caused by rapid chilling) can not be eliminated. No significant differences were found between the different crossbreds for the calpastatin levels but significant differences were found for the µ-calpain activity and µ-calpain / calpastatin activity ratios. The Brahman-crosses had longer myofibril fragment lengths on average, indicating lower proteolysis / myofibrillar fragmentation compared to the other crossbreds. Myofibrillar protein degradation (titin, nebulin, desmin) and myofibrillar protein formation (30 kDa) during post mortem ageing was examined as a confirmation for the myofibril fragment length results. Significant differences between the crossbreds were found for titin degradation. Nguni-cross animals had significantly (p < 0.033) more titin present than the other crossbreds. Nebulin degradation showed a significant (p < 0.038) breed effect at 7 days post mortem and a significant degradation rate difference for breed types between 1 day and 7 days post mortem (p < 0.03) and 1 day and 14 days post mortem (p < 0.034). Desmin degradation evaluated with SDS-PAGE and Western-blotting indicated that the Simmentaler-cross animals had significantly (p < 0.018; p < 0.024, respectively) lower desmin levels compared to the other crossbreds. For the 30 kDa proteins there were no significant (p > 0.001) differences in data evaluated at 1 day, 7 and 14 days post mortem as well as for the formation rate. The results indicates that Brahman-crosses had the highest frequency for haplotypes that are associated with increased shear force, and thus tougher meat compared to the Simmentaler-crosses that had the highest frequency for haplotyes that are associated with lower shear force, and thus more tender meat, while Nguni-crosses were intermediate. A multiplex marker system incorporating both markers (316 and 4751) and indexes for the markers at CASTand CAPN1 genes were evaluated in this study. Considering the average index for the interactions between the CAST and CAPN1 genes, it can be concluded that the Nguni-cross was overall the breed with the highest potential for inherently tender meat. In general, the animals in this study had the tendency for tougher meat. The genetic markers (CAST and CAPN1) showed no association with Warner-Bratzler shear force (WBSF) (p > 0.05), which suggest that various mechanisms and environmental factors may be involved and give another outcome compared to the genetic make up. Simple correlation coefficients were generated between the different characteristics measured. If the group of animals in this study is indeed a typical representation of South African feedlot finished crossbred animals, the relatively high WBSF values emphasise the challenge to manipulate their intrinsic tenderness potential by making use of various pre- and post-slaughter techniques and procedures. / Dissertation (MSc(Agric) (Animal Science))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

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>Magister Scientiae - MSc / Engineered nanomaterials derived from various bulk materials are being developed in ever larger quantities and with very diverse chemical compositions. The physical and chemical properties of the smaller nanoparticles are very different compared to their larger bulk chemicals. Titanium dioxide nanoparticles (TiO2NPs) are an example of such an engineered nanomaterial. Titanium dioxide nanoparticles are mainly used as a pigment in many applications such as glazes, enamels, plastics, pharmaceuticals, cosmetics, and it is widely used in sunscreens. Human exposure to TiO2NPs can occur both during manufacturing and use.

The aim of diploma thesis is a comparison of flame and fusion laser cutting of thin metal sheets for ACO Industries k. s. company, where the experimental part was also realized. After consultation with company, the thesis was extended by data samples, which were cut by compressed air for comparison with other two gases. The optimization design of cutting parameters was created by Taguchi method. Afterwards the surface roughness of samples was measured. Based on Ra and Rz5 parameters, the samples were classified to classes based on their accuracy according to ISO 9013 standard. According to results the fusion method of laser cutting is more suitable method, especially for its good quality of cutting edge, which is not affected by the oxidic layer. Fusion method uses cutting speed two times higher than the flame method, which leads to decrease of time and financial consumption of the process despite of its higher hourly rate. In case of laser cutting of material by compressed air the quality of cut is insufficient in comparison with fusion or flame cutting method.

This master´s thesis deals with calibration and determination of uncertainties of measurement for focus variation microscope Alicona Infinite Focus G4. Together with calibration, a measurement of chosen parameters with calculation of measurement uncertainties of a component was realised. The thesis also describes the whole calibration process and terminology used in calibration, as well as the calibrated instrument, it´s parameters and usage in practice. The measurements were realized on premises of Intemac Solutions s.r.o. Obtained data were than processed using MS Excel, Gwyddion and TalyMap software. At the end of the thesis, practical recommendations are formulated.