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Invasive alien aquatic plants in South African freshwater ecosystems:

- Hill, Martin P, Coetzee, Julie A, Martin, Grant D, Smith, Rosali, Strange, Emily F

Authors: Hill, Martin P , Coetzee, Julie A , Martin, Grant D , Smith, Rosali , Strange, Emily F
Date: 2020
Language: English
Type: text , book
Identifier: http://hdl.handle.net/10962/176271 , vital:42680 , ISBN 978-3-030-32394-3 , 10.1007/978-3-030-32394-3
Description: South Africa has a long history of managing the establishment and spread of invasive fioating macrophytes. The past thirty years of research and the implementation of nation-wide biological and integrated control programmes has led to widespread control of these species in many degraded freshwater ecosystems. Such initiatives are aimed at restoring access to potable freshwater and maintaining native biodiversity.
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Date Issued: 2020

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More than a century of biological control against invasive alien plants in South Africa: a synoptic view of what has been accomplished

- Hill, Martin P, Moran, V Clifford, Hoffmann, John H, Neser, Stefan, Zimmermann, Helmuth G, Simelane, David O, Klein, Hildegard, Zachariades, Costas, Wood, Alan R, Byrne, Marcus J, Paterson, Iain D, Martin, Grant D, Coetzee, Julie A

Authors: Hill, Martin P , Moran, V Clifford , Hoffmann, John H , Neser, Stefan , Zimmermann, Helmuth G , Simelane, David O , Klein, Hildegard , Zachariades, Costas , Wood, Alan R , Byrne, Marcus J , Paterson, Iain D , Martin, Grant D , Coetzee, Julie A
Date: 2020
Language: English
Type: text , book
Identifier: http://hdl.handle.net/10962/176260 , vital:42679 , ISBN 978-3-030-32394-3 , 10.1007/978-3-030-32394-3
Description: Invasive alien plant species negatively affect agricultural production, degrade conservation areas, reduce water supplies, and increase the intensity of wild fires. Since 1913, biological control agents ie plant-feeding insects, mites, and fungal pathogens, have been deployed in South Africa to supplement other management practices (herbicides and mechanical controls) used against these invasive plant species. We do not describe the biological control agent species.
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Date Issued: 2020

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Rethinking ICT4D Impact Assessments: reflections from the Siyakhula Living Lab in South Africa

- Mthoko, Hafeni, Khene, Caroline

Authors: Mthoko, Hafeni , Khene, Caroline
Date: 2019
Language: English
Type: text , conference paper
Identifier: http://hdl.handle.net/10962/105286 , vital:32495 , https://doi.org/10.1007/978-3-030-11235-6_4
Description: The approach to outcome and impact assessments of ICTD has often relied solely on identifying project effects in relation to project baseline data; however, such an approach limits the potential learning that could be occurring throughout a project’s lifecycle. Impact assessments should be conducted in a comprehensive manner, taking into account the evaluation data that has been captured from the initiation of the project through to its implementation, and beyond. This study sought to reflect on the implementation of an impact assessment framework that is based on a comprehensive approach to evaluation. The framework was implemented in the Siyakhula Living Lab to assess for its outcomes and impacts on the community. A pragmatic approach was applied through a reflective process, to assess the utility of the framework within this context. Semi-structured interviews with project stakeholders were conducted to further gain insight into the comprehensive approach to conducting impact assessments. It was found that a comprehensive approach to assessing impacts provided a meaningful way to understand the effects of the ICTD initiative, and provided an overview of project areas that required improvement. However, it was found that the proposed assessment framework required a customisation component in order to modify it to better suit the project context. The way in which future impact assessments are conducted can draw on the lessons gained from following a more comprehensive approach to evaluation, and thus improve learning over time.
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Date Issued: 2019

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Temperature dependence of persistent luminescence in CaAl2O4: Eu2+, Nd3+ related to beta irradiation and optical excitation

- Kalita, Jitumani M, Chithambo, Makaiko L

Authors: Kalita, Jitumani M , Chithambo, Makaiko L
Date: 2019
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/105158 , vital:32470 , https://doi.org/10.1016/j.jlumin.2018.10.062
Description: Mechanisms responsible for the emission of persistent luminescence in CaAl2O4:Eu2+,Nd3+ are typically studied following excitation by ultraviolet or visible light. In contrast, we have studied the persistent luminescence from this material after beta irradiation and optical excitation. These studies have been carried out at 25 °C as well as at various temperatures up to 100 °C. A thermoluminescence (TL) glow curve measured at 1 °C/s following beta irradiation showed a glow peak at 63 °C. On the other hand, a glow curve measured after 15 s of optical excitation by polychromatic white light shows a peak at 102 °C. The partial heating procedure reveals that each of the TL peaks consist of several overlapping components. The TL in each case was analysed for kinetic parameters. The initial rise analysis carried out on the rising edge of the overlapping components shows that the activation energy of the component peaks corresponding to beta irradiation is consistent at (0.59 ± 0.01) eV. In comparison, activation energies corresponding to optical excitation increases with the partial heating temperature from (0.71 ± 0.01) eV to (0.76 ± 0.01) eV. The activation energy of (0.59 ± 0.01) eV is ascribed to an oxygen vacancy whereas the range of activation energies between (0.71 ± 0.01) eV and (0.76 ± 0.01) eV is ascribed to the 4 f levels of the Nd dopant.
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Date Issued: 2019

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The elephant in the ‘room’: determinants of songbird assemblages in the Thicket Biome, South Africa

- Parker, Daniel M

Authors: Parker, Daniel M
Date: 2019
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/105134 , vital:32468 , https://doi.org/10.1080/01584197.2018.1562847
Description: When vegetation structure is altered, songbird communities may be affected. Despite speculation that African Elephant (Loxodonta africana) browsing impacts bird communities, existing data are limited. I sampled the bird communities of the Albany Thicket Biome at 10 sites in the Eastern Cape, South Africa, half with elephants and half without. Songbird community parameters were best predicted by how long elephants had been present, elephant density and the percentage cover of thicket vegetation. The sites where elephants had been present for longer had more bird species and increased songbird density and diversity. However, bird density also increased with increasing thicket vegetation cover and this is a phenomenon unlikely to be compatible with long-term elephant presence. There was an almost equal split between the number of bird species that appeared to be negatively affected by changes in habitat structure (47%) and those which benefited (53%). Smaller birds were generally more abundant as vegetation structural integrity increased and larger birds were more abundant when vegetation structural integrity declined. The browsing of elephants could be viewed as facilitative for songbirds in the short term. However, this effect may not persist in the long term because all elephant populations (notorious tree-fellers) in the Eastern Cape are found in fenced areas where natural migration is not possible. More broadly, my data provide important insight into how avian communities respond to habitat transformation at the local and regional scales.
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Date Issued: 2019

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The influence of dopants on thermoluminescence of Sr2MgSi2O7

- Thomas, Sunil, Kalita, Jitumani M, Chithambo, Makaiko L, Ntwaeaborwa, Odireleng M

Authors: Thomas, Sunil , Kalita, Jitumani M , Chithambo, Makaiko L , Ntwaeaborwa, Odireleng M
Date: 2019
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/105148 , vital:32469 , https://doi.org/10.1016/j.jlumin.2018.12.035
Description: We report the influence of dopants on the thermoluminescence of Sr2MgSi2O7. Samples studied comprise undoped Sr2MgSi2O7 and doped versions, namely, Sr2MgSi2O7:Dy3+, Sr2MgSi2O7:Eu3+, Sr2MgSi2O7:Tb3+ and Sr2MgSi2O7:Tb3+,Eu3+ phosphors. All samples show a broad glow peak near 60 °C when measured at 1 °C/s after irradiation to 10 Gy. The peak changes with partial heating, irradiation and fades between irradiation and measurement in a manner expected of a composite one. The behaviour is used to exemplify the analysis of a composite peak on the basis that particular features reflect those of the dominant component.
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Date Issued: 2019

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Thermally and optically stimulated luminescence of natural red and blue corundum (Al2O3)

- Kalita, Jitumani M, Thomas, Sunil, Chithambo, Makaiko L

Authors: Kalita, Jitumani M , Thomas, Sunil , Chithambo, Makaiko L
Date: 2019
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/105177 , vital:32472 , https://doi.org/10.1016/j.jlumin.2018.09.058
Description: We report the thermoluminescence (TL) and optically stimulated luminescence (OSL) of natural corundum (Al2O3) of two varieties; one red and the other blue. X-ray fluorescence spectroscopy of the samples show that the concentration of Al2O3 in the red corundum is 43.05% and 46.87% in the blue corundum. TL measurements carried out on un-annealed samples and samples annealed at 700 °C, 900 °C and 1200 °C show that the TL sensitivity increases with annealing. The sensitivity of the red corundum reaches a maximum after annealing at 900 °C whereas that of the blue corundum increases with annealing up to the maximum annealing temperature of 1200 °C used in this study. Both samples have a complex glow curve between 30 °C and 500 °C. The composite nature of the glow curves is deduced to be due to a continuum in the trap distribution in the crystal. The activation energy of the traps vary between 0.70 eV and 1.15 eV. The dose response of the red corundum under TL is linear within 100‒1000 Gy whereas that of the blue corundum is superlinear for the same dose range. The TL of both samples is reproducible but the signal fades with time between irradiation and measurement. Both samples produce OSL under 470 nm blue light stimulation. The dose response of the OSL is superlinear within 100‒1000 Gy. It is found that the samples also produce thermally-assisted OSL (TA-OSL) at elevated temperature. The TA-OSL intensity of the red corundum increases with dose up to 400 Gy and saturates thereafter. On the other hand, the intensity of the blue corundum increases consistently with dose from 100 Gy to 1000 Gy.
Full Text: false
Date Issued: 2019

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