Ultra low frequency (ULF) waves observed at mid to low latitudes during daytime using low Earth orbit (LEO) satellite and ground-based data.

Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.The launch of German geoscience satellite CHAMP inspired the increased interest in the study of ultra low frequency waves. In this work data from low Earth orbiting (LEO) German CHAMP satellite and South African ground-based magnetometer data were used to study geomagnetic pulsations, in particular continuous pulsations, Pc3, with periods in the range 10-45 seconds. Both Fast Fourier Transform (FFT) and Maximum Entropy Spectral Analysis (MESA) were used as analysis techniques to compute and compare spectra. We simulated a Pc3 oscillation using a sinusoidal function in order to test and establish appropriate parameters to use on the application of these analysis techniques. In this study the region chosen for a low latitude geomagnetic pulsations study excludes high current regions such as polar regions where field aligned currents occur. The structure of low-latitude pulsations was studied by comparing satellite and ground magnetic field measurements. The magnetic field measurements observed in the topside ionosphere by CHAMP were compared to Hermanus data for times when CHAMP crossed the ground station L-shell. The data were analysed for Pc3 pulsation activity using the MESA method to visualise field line resonance (FLR) in the vector magnetometer data. A number of discrete frequency oscillations for the fast mode wave were observed, one of which drives FLR at characteristic latitude as detected by both ground and satellite measurements. The toroidal mode frequency on CHAMP experiences a Doppler shift due to the rapid motion across the resonance region. Polarization hodograms in the resonance region show the expected 900 rotation of the field line resonant magnetic field components. We present first time ob- servations of toroidal standing Alfv´en mode oscillation with clearly L-dependent frequencies in the inner magnetosphere for L < 3. Our observations show FLR frequency continuously increasing as a function of decreasing latitude down to L = 1.6 and then decrease as a result of the larger plasma density of the upper ionosphere. The L-dependent frequency oscillations were observed in the presence of broadband compressional wave spectra. Our observation confirms the well-known magnetohydrodynamic (MHD) wave theoretical prediction of a compressional wave being the driver of the field line resonance, and that the Pc3 pulsations do not have a source with the same frequency structure. Keywords: ULF waves, Fast Fourier Transform, Maximum Entropy Spectral Analysis, CHAMP satellite, Geomagnetic pulsations, Pc3, Alfv´en wave, Field line resonance

The water quality and ecological status of the Diep river catchment, Western Cape, South Africa

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)The study illustrates the current ecological integrity of the Diep River system, based on the recent river health assessment using the South African Scoring System version 5 (2000-2003) and the water quality data (1996-2002). Some of the major land-use impacts on the river system are highlighted

Modelling cosmic ray intensities along the Ulysses trajectory

Time dependent cosmic ray modulation in the inner heliosphere is studied by comparing results from a 2-D, time-dependent cosmic ray transport model with Ulysses observations. A compound approach, which combines the effects of the global changes in the heliospheric magnetic field magnitude with drifts to establish a realistic time-dependence, in the diffusion and drift coefficients, are used. We show that this model results in realistic cosmic ray modulation from the Ulysses launch (1990) until recently (2004) when compared to 2.5-GV electron and proton and 1.2-GV electron and Helium observations from this spacecraft. This approach is also applied to compute radial gradients present in 2.5-GV cosmic ray electron and protons in the inner heliosphere. The observed latitude dependence for both positive and negative charged particles during both the fast latitude scan periods, corresponding to different solar activity conditions, could also be realistically computed. For this an additional reduction in particle drifts (compared to diffusion) toward solar maximum is needed. This results in a realistic charge-sign dependent modulation at solar maximum and the model is also applied to predict charge-sign dependent modulation up to the next expected solar minimum

Biochemical and structural characterization of family VII hybrid carboxyl esterases from Bacillus sp.

M.Sc. (Biochemistry)Abstract: The use of enzymes as biocatalysts in industrial processes has prompted the search for novel biocatalysts with improved properties. Carboxyl esterases are amongst the most used biocatalysts in various industrial processes, including pharmaceutical, food and textile industries. The most attractive properties of these enzymes are the high regio- and stereospecificity and stability and activity in organic solvent. However, natural enzymes are poorly suited for industrial applications that often occur under extreme conditions such as elevated temperature. As a result, there is a need to optimize/improve properties of enzymes prior to application at industrial scale. Protein engineering is a technique that was introduced in order to study structure-function properties of enzymes and (or) to design mutant enzymes with new or desirable properties. In a previous study, three carboxyl esterase-encoding genes from selected Bacillus species were previously cloned, functionally expressed in Escherichia coli DE3 (BL21) and their kinetic data recorded. Carboxylesterases from Bacillus pumilus and Bacillus licheniformis showed the highest activity at 45 °C and pH 7.5 and 8.0, respectively. Both enzymes lost more than 60% residual activity after 10 min incubation at temperatures above 50 °C. On the other hand, a carboxyl esterase from Geobacillus kaustophilus was observed to be relatively stable with the highest activity recorded at 60 °C and pH 8.0. When the amino acid sequences of the above-mentioned enzymes and selected members of the family VII of lipolytic enzymes were aligned it was observed that, the N-terminal regions were relatively conserved while C-terminal regions were variable. These observations formed the basis of the current study which is aimed..

Impact of hodt genetic polymorphism at IL-6 gene promoter at position-174G/C on the occurence of HBV and HCV among HIV/AIDS patients in Limpopo Province, South Africa

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A study of L-dependent Pc3 pulsations observed by low Earth orbiting CHAMP satellite

Field line resonances (FLR) driven by compressional waves are an important mechanism for the generation of ULF geomagnetic pulsations observed at all latitudes during local daytime. References to observations of toroidal standing Alfvén mode oscillations with clearly L-dependent frequencies from spacecraft in the outer magnetosphere for L&gt;3 are limited in the literature. Such observations in the inner magnetosphere for L&lt;3 have not yet been reported in the literature. This study offers two interesting case studies of observations of ULF waves by the low Earth orbiting CHAMP satellite. The magnetic field measurements from CHAMP, which are of unprecedented accuracy and resolution, are compared to Hermanus magnetometer data for times when CHAMP crosses the ground station L-shell, namely for 13 February 2002 and 18 February 2003. The data were analysed for Pc3 pulsation activity using the Maximum Entropy Spectral Analysis (MESA) method to visualise FLRs in the vector magnetometer data. For the first time observations of Pc3 toroidal oscillations with clearly L-dependent frequencies for lower L-shell values (L&lt;3) observed by an LEO satellite are reported. These observations show FLR frequencies increasing as a function of decreasing latitude down to L=1.6 and then decreasing as a result of the larger plasma density of the upper ionosphere. The L-dependent frequency oscillations were observed in the presence of a broadband compressional wave spectrum. Our observations thus confirm the well-known magnetohydrodynamic (MHD) wave theoretical prediction of a compressional wave being the driver of the field line resonance

A study of the time-dependent modulation of galactic cosmic rays in the heliosphere

Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2005.Time-dependent cosmic ray modulation in the heliosphere is studied by using a two-dimensional time dependent modulation model. To compute realistic cosmic ray modulation a compound approach is used, which combines the effect of the global changes in the heliospheric magnetic field magnitude and the current sheet tilt angle to establish realistic time dependent diffusion and drift coefficients. This approach is refined by scaling down drifts additionally (compared to diffusion) towards solar maximum. The amount of drifts needed in the model to realistically compute 2.5 GV proton and electron and 1.2GV electron and helium intensities, as measured by Ulysses from 1990 to 2004, is established. It is shown that the model produces the correct latitudinal gradients evident from the observations during both the Ulysses fast latitude scan periods. Also, much can be learned on the magnitude of perpendicular diffusion in the polar direction, K┴θ, especially for solar minimum conditions and for polarity cycles when particles drift in from the poles. For these periods K┴θ = 0.12K║ in the polar regions (with K║ the parallel diffusion coefficient)and K┴θ /K║ can vary between 0.01 to even 0.04 in the equatorial regions depending on the enhancement factor toward the poles. The model is also applied to compute radial gradients for 2.5 GV cosmic ray electrons and protons in the inner heliosphere. It is shown that, for solar minimum, and in the equatorial regions, the protons (electrons) have a radial gradient of 1.9 %/AU (2.9 %/AU), increasing for both species to a very fluctuating gradient varying between 3 to 4 %/AU at solar maximum. Furthermore, the model also computes realistic electron to proton and electron to helium ratios when compared to Ulysses observations, and charge-sign dependent modulation is predicted up to the next solar minimum expected in 2007. Lastly the model is also applied to model simultaneously galactic cosmic ray modulation at Earth and along the Voyager 1 trajectory, and results are compared with> 70 MeV count rates from Voyager 1 and IMP8. To produce realistic modulation, this model gives the magnitude of perpendicular diffusion in the radial direction as K┴r/K║= 0.035 and that the modulation boundary seemed to be situated between at 120 AU and 140 AU.Master