Night-time gravity waves detected with multi-frequency airglow imager
- Authors: Machubeng, Karabo Pebane
- Date: 2021-04
- Subjects: Gravity waves , Airglow , Gravity waves -- Seasonal variations , All Sky Imager
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178341 , vital:42931
- Description: This thesis shows the statistics of atmospheric gravity waves (AGWs) observed in the OI emission 557.7 nm at _97 km altitude using an all-sky imager based in Sutherland, South Africa (32.37_ S, 20.81_ E) in the year 2017. The wavelengths were determined using the propagation vector method, velocity was determined using the cross correlation of 1D FFT and the period was determined using the equation that relates wavelength and velocity. It was found that the horizontal wavelength in summer was almost evenly distributed between 10 and 40 km and for autumn, winter and spring were mostly between 10 and 30 km. The favoured speeds were between 40 and 50 m/s in autumn, as well as 30 and 50 m/s in summer, but the AGWs in winter had a bimodal speed distribution of 20 - 40 and 50 - 70 m/s. The majority of periods observed in all seasons were less than 20 minutes with a dominant peak of 5 - 10 minutes in autumn and spring. There was no favoured propagation direction for spring, but AGWs favoured a southeastward propagation in summer, and a southward propagation in autumn and winter. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Machubeng, Karabo Pebane
- Date: 2021-04
- Subjects: Gravity waves , Airglow , Gravity waves -- Seasonal variations , All Sky Imager
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178341 , vital:42931
- Description: This thesis shows the statistics of atmospheric gravity waves (AGWs) observed in the OI emission 557.7 nm at _97 km altitude using an all-sky imager based in Sutherland, South Africa (32.37_ S, 20.81_ E) in the year 2017. The wavelengths were determined using the propagation vector method, velocity was determined using the cross correlation of 1D FFT and the period was determined using the equation that relates wavelength and velocity. It was found that the horizontal wavelength in summer was almost evenly distributed between 10 and 40 km and for autumn, winter and spring were mostly between 10 and 30 km. The favoured speeds were between 40 and 50 m/s in autumn, as well as 30 and 50 m/s in summer, but the AGWs in winter had a bimodal speed distribution of 20 - 40 and 50 - 70 m/s. The majority of periods observed in all seasons were less than 20 minutes with a dominant peak of 5 - 10 minutes in autumn and spring. There was no favoured propagation direction for spring, but AGWs favoured a southeastward propagation in summer, and a southward propagation in autumn and winter. , Thesis (MSc) -- Faculty of Science, Physics and Electronics, 2021
- Full Text:
- Date Issued: 2021-04
Photodynamic antimicrobial chemotherapy against Staphylococcus aureus and Escherichia coli sensitized using indium (III) cationic porphyrins linked to core-shell magnetic nanoparticles
- Authors: Makola, Lekgowa Collen
- Date: 2021-04
- Subjects: Photochemotherapy , Photosensitizing compounds , Staphylococcus aureus , Escherichia coli , Indium , Porphyrins , Magnetic nanoparticles , Quaternize
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/177225 , vital:42801
- Description: Photodynamic antimicrobial chemotherapy (PACT) is a well-known antimicrobial therapy technique used against multi-drug resistant pathogens. In this study, the syntheses, characterization, photophysicochemical properties, and the applications of symmetrically and asymmetrically substituted cationic indium (III) porphyrins linked to silver/copper ferrite core-shell (Ag/CuFe2O4) magnetic nanoparticles (MNPs) as potential photosensitizers for PACT are reported. The synthesized complexes include axially modified porphyrins quaternized through an axial ligand. All the asymmetrically substituted porphyrins were linked to the NPs via an ester bond and the symmetrically substituted porphyrins were linked (peripherally and /or axially) via self-assembly (Ag-S and/or Ag-N). The impact of axial modification, peripheral substituents, conjugation to the NPs, the number of positive charges, and the chain length of the alkyl halides quaternizing agents on PACT efficacy and photophysicochemical properties of porphyrins were studied. High singlet oxygen quantum yields and antimicrobial log reductions were observed. Lipophilicity and hydrophilicity of the porphyrins were also studies, where the complexes quaternized with methyl iodide showed relatively high hydrophilicity character. Upon in vitro PACT studies, the quaternized complexes were observed to have 0% viable colony, signifying their effectiveness. Moreover, the highest log reductions of 9.27 were observed against S. aureus and 9.58 were observed against E. coli. The findings from this work delineate that singlet oxygen generation alone is not a distinct factor on the PACT efficacy of the porphyrin complexes, since some of the complexes have practically the same singlet oxygen quantum but different PACT activity. However, other contributing factors including water solubility play a significant role. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Makola, Lekgowa Collen
- Date: 2021-04
- Subjects: Photochemotherapy , Photosensitizing compounds , Staphylococcus aureus , Escherichia coli , Indium , Porphyrins , Magnetic nanoparticles , Quaternize
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/177225 , vital:42801
- Description: Photodynamic antimicrobial chemotherapy (PACT) is a well-known antimicrobial therapy technique used against multi-drug resistant pathogens. In this study, the syntheses, characterization, photophysicochemical properties, and the applications of symmetrically and asymmetrically substituted cationic indium (III) porphyrins linked to silver/copper ferrite core-shell (Ag/CuFe2O4) magnetic nanoparticles (MNPs) as potential photosensitizers for PACT are reported. The synthesized complexes include axially modified porphyrins quaternized through an axial ligand. All the asymmetrically substituted porphyrins were linked to the NPs via an ester bond and the symmetrically substituted porphyrins were linked (peripherally and /or axially) via self-assembly (Ag-S and/or Ag-N). The impact of axial modification, peripheral substituents, conjugation to the NPs, the number of positive charges, and the chain length of the alkyl halides quaternizing agents on PACT efficacy and photophysicochemical properties of porphyrins were studied. High singlet oxygen quantum yields and antimicrobial log reductions were observed. Lipophilicity and hydrophilicity of the porphyrins were also studies, where the complexes quaternized with methyl iodide showed relatively high hydrophilicity character. Upon in vitro PACT studies, the quaternized complexes were observed to have 0% viable colony, signifying their effectiveness. Moreover, the highest log reductions of 9.27 were observed against S. aureus and 9.58 were observed against E. coli. The findings from this work delineate that singlet oxygen generation alone is not a distinct factor on the PACT efficacy of the porphyrin complexes, since some of the complexes have practically the same singlet oxygen quantum but different PACT activity. However, other contributing factors including water solubility play a significant role. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
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