An ecosystem service value chain analysis framework: a conceptual paper
- Rawlins, Jonathan M, De Lange, Willem J, Fraser, Gavin C G
- Authors: Rawlins, Jonathan M , De Lange, Willem J , Fraser, Gavin C G
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69321 , vital:29499 , https://doi.org/10.1016/j.ecolecon.2017.12.023
- Description: Modern day societies and economies are becoming increasingly vulnerable to the continued erosion of the stocks and flows of essential ecosystem services. Thus, the management of complex socio-economic systems to effectively provide these essential services has become a global priority policy and academic research area. Understanding how underlying processes and functions contribute towards the provision of final ecosystem services can facilitate improved dissemination of credible, legitimate and salient information to decision-makers. This paper presents an ecosystem service value chain analysis framework that applies basic system dynamics modelling in the form of causal loop diagrams to facilitate an alternative analysis of ecosystem service value chains. A scoping application of the framework is applied to a case study for flood attenuation services in the Baviaanskloof catchment in South Africa. The framework enables the identification of forward linkages and ripple effects in individual value chains of final ecosystem services as well as the identification and assessment of challenges and opportunities within individual causal pathways. Ultimately, providing the potential to advance strategies for improving the efficiency and effectiveness of final ecosystem service provision.
- Full Text: false
- Date Issued: 2018
- Authors: Rawlins, Jonathan M , De Lange, Willem J , Fraser, Gavin C G
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69321 , vital:29499 , https://doi.org/10.1016/j.ecolecon.2017.12.023
- Description: Modern day societies and economies are becoming increasingly vulnerable to the continued erosion of the stocks and flows of essential ecosystem services. Thus, the management of complex socio-economic systems to effectively provide these essential services has become a global priority policy and academic research area. Understanding how underlying processes and functions contribute towards the provision of final ecosystem services can facilitate improved dissemination of credible, legitimate and salient information to decision-makers. This paper presents an ecosystem service value chain analysis framework that applies basic system dynamics modelling in the form of causal loop diagrams to facilitate an alternative analysis of ecosystem service value chains. A scoping application of the framework is applied to a case study for flood attenuation services in the Baviaanskloof catchment in South Africa. The framework enables the identification of forward linkages and ripple effects in individual value chains of final ecosystem services as well as the identification and assessment of challenges and opportunities within individual causal pathways. Ultimately, providing the potential to advance strategies for improving the efficiency and effectiveness of final ecosystem service provision.
- Full Text: false
- Date Issued: 2018
Isn’t it time to start thinking about ‘developing’ academic developers in a more systematic way?
- Quinn, Lynn, Vorster, Jo-Anne
- Authors: Quinn, Lynn , Vorster, Jo-Anne
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66546 , vital:28961 , https://doi.org/10.1080/1360144X.2013.879719
- Description: publisher version , There is no defined route to becoming an academic developer. The research on pathways into the field (e.g. Kensington-Miller, Brailsford, and Gossman, 2012; McDonald, 2010; McDonald and Stockley, 2008) shows that in most cases ‘serendipity and chance played a role’ (McDonald, 2010, p. 40). Moreover, induction into academic development (AD) is often ad hoc, haphazard, and informal. Due to the changing higher education (HE) context, the field has grown exponentially and in many countries now plays a central role in institutions. This has generated increased demand for knowledgeable and competent developers that are able to contribute towards solving some vexing problems in contemporary HE. Current recruitment and induction processes of new developers do not necessarily meet this demand. In light of the above, we pose the question: given the changing context of HE and the field of AD, is it not time for us to induct newcomers into the field more systematically? As Kensington-Miller et al. (2012) suggest, we should not leave the induction of the next generation of developers to chance. We suggest that one way of ensuring appropriate induction is through a formal course for developers. Difficulties for newcomers to the field are illustrated by Kensington-Miller et al. (2012) when they report seeking ‘top tips’ at a HERDSA conference. We do not dismiss informal learning at conferences or the role of mentoring, coaching, apprenticeship, and so on, in inducting developers, nor do we minimise the benefits of relatively structured processes such as fellowship programmes, workshops, and postgraduate qualifications in related fields. However, these ways of induction may not offer novices the structured and systematic developmental opportunities needed to become developers able to fulfil varied, complex, and sometimes contradictory roles.
- Full Text: false
- Date Issued: 2014
- Authors: Quinn, Lynn , Vorster, Jo-Anne
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66546 , vital:28961 , https://doi.org/10.1080/1360144X.2013.879719
- Description: publisher version , There is no defined route to becoming an academic developer. The research on pathways into the field (e.g. Kensington-Miller, Brailsford, and Gossman, 2012; McDonald, 2010; McDonald and Stockley, 2008) shows that in most cases ‘serendipity and chance played a role’ (McDonald, 2010, p. 40). Moreover, induction into academic development (AD) is often ad hoc, haphazard, and informal. Due to the changing higher education (HE) context, the field has grown exponentially and in many countries now plays a central role in institutions. This has generated increased demand for knowledgeable and competent developers that are able to contribute towards solving some vexing problems in contemporary HE. Current recruitment and induction processes of new developers do not necessarily meet this demand. In light of the above, we pose the question: given the changing context of HE and the field of AD, is it not time for us to induct newcomers into the field more systematically? As Kensington-Miller et al. (2012) suggest, we should not leave the induction of the next generation of developers to chance. We suggest that one way of ensuring appropriate induction is through a formal course for developers. Difficulties for newcomers to the field are illustrated by Kensington-Miller et al. (2012) when they report seeking ‘top tips’ at a HERDSA conference. We do not dismiss informal learning at conferences or the role of mentoring, coaching, apprenticeship, and so on, in inducting developers, nor do we minimise the benefits of relatively structured processes such as fellowship programmes, workshops, and postgraduate qualifications in related fields. However, these ways of induction may not offer novices the structured and systematic developmental opportunities needed to become developers able to fulfil varied, complex, and sometimes contradictory roles.
- Full Text: false
- Date Issued: 2014
Teaching in higher education
- Authors: Quinn, Lynn
- Date: 2014
- Language: English
- Type: text , review
- Identifier: http://hdl.handle.net/10962/66557 , vital:28963 , https://doi.org/10.1080/1360144X.2014.908094
- Description: publisher version , As Becker and Denicolo point out in their introduction, traditionally most lecturers in higher education begin teaching with little or no formal training: ‘It is assumed if you were expert in your field you would be able, by some ill-defined means, to teach others’ (p. 1). This book aims to remedy that situation and does exactly what it sets out to do: it provides a useful, step-by-step training guide for teachers in higher education. It provides much needed advice for new academics for ways in which they can successfully combine their teaching and their research roles. It is written in an accessible style, draws on the experiences of people who have taught in higher education for some time, and provides practical advice for teaching in a range of contexts and for dealing with different challenges that may arise.
- Full Text: false
- Date Issued: 2014
- Authors: Quinn, Lynn
- Date: 2014
- Language: English
- Type: text , review
- Identifier: http://hdl.handle.net/10962/66557 , vital:28963 , https://doi.org/10.1080/1360144X.2014.908094
- Description: publisher version , As Becker and Denicolo point out in their introduction, traditionally most lecturers in higher education begin teaching with little or no formal training: ‘It is assumed if you were expert in your field you would be able, by some ill-defined means, to teach others’ (p. 1). This book aims to remedy that situation and does exactly what it sets out to do: it provides a useful, step-by-step training guide for teachers in higher education. It provides much needed advice for new academics for ways in which they can successfully combine their teaching and their research roles. It is written in an accessible style, draws on the experiences of people who have taught in higher education for some time, and provides practical advice for teaching in a range of contexts and for dealing with different challenges that may arise.
- Full Text: false
- Date Issued: 2014
Pedagogy for fostering criticality, reflectivity and praxis in a course on teaching for lecturers
- Quinn, Lynn, Vorster, Jo-Anne
- Authors: Quinn, Lynn , Vorster, Jo-Anne
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66590 , vital:28967 , https://doi.org/10.1080/02602938.2015.1066756
- Description: publisher version , Using the concepts of criticality, reflectivity and praxis, the paper presents an analysis of our reflections on participants’ responses to the assessment requirements for a course for lecturers on teaching. The context in which the course is being taught has changed considerably in the last few years in terms of the mode of delivery, as well as the number and diversity of participants. Our analysis has generated insights into ways in which the course is not meeting all the learning needs of the participants, nor preparing them adequately to demonstrate, in writing, their learning. Using insights gained, we suggest pedagogic processes and strategies for ensuring that the course focuses on both writing to learn and learning to write; and for assisting participants to acquire the practices to demonstrate their learning in written assessment tasks, using the requisite literacy including criticality, reflectivity and praxis.
- Full Text: false
- Date Issued: 2016
- Authors: Quinn, Lynn , Vorster, Jo-Anne
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66590 , vital:28967 , https://doi.org/10.1080/02602938.2015.1066756
- Description: publisher version , Using the concepts of criticality, reflectivity and praxis, the paper presents an analysis of our reflections on participants’ responses to the assessment requirements for a course for lecturers on teaching. The context in which the course is being taught has changed considerably in the last few years in terms of the mode of delivery, as well as the number and diversity of participants. Our analysis has generated insights into ways in which the course is not meeting all the learning needs of the participants, nor preparing them adequately to demonstrate, in writing, their learning. Using insights gained, we suggest pedagogic processes and strategies for ensuring that the course focuses on both writing to learn and learning to write; and for assisting participants to acquire the practices to demonstrate their learning in written assessment tasks, using the requisite literacy including criticality, reflectivity and praxis.
- Full Text: false
- Date Issued: 2016
The rooting system of Leptophloeum Dawson: New material from the upper Devonian, Famennian Witpoort Formation of South Africa
- Prestianni, Cyrille, Gess, Robert W
- Authors: Prestianni, Cyrille , Gess, Robert W
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/72732 , vital:30104 , https://doi.org/10.1016/j.revpalbo.2014.05.007
- Description: The rhizomorphs of Early (Devonian and Early Carboniferous) arborescent lycopsids are known from only a handful of taxa. That of Leptophloeum is previously described from a single fragmentary specimen from China that, in our opinion, has been incorrectly interpreted. Here we describe several relatively well-preserved examples of Leptophloeumrhizomorphs from the Famennian aged Waterloo Farm Lägerstatte of South Africa. We demonstrate an unlobed cormose morphology separated from the microphyll bearing axis by a smooth transition zone. This provides one of the few known examples of a cormose lycopsid rhizomorph dating back to the Devonian. We assign this material and all previously published South African Leptophloeum material to Leptophloeum rhombicum.
- Full Text: false
- Date Issued: 2014
- Authors: Prestianni, Cyrille , Gess, Robert W
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/72732 , vital:30104 , https://doi.org/10.1016/j.revpalbo.2014.05.007
- Description: The rhizomorphs of Early (Devonian and Early Carboniferous) arborescent lycopsids are known from only a handful of taxa. That of Leptophloeum is previously described from a single fragmentary specimen from China that, in our opinion, has been incorrectly interpreted. Here we describe several relatively well-preserved examples of Leptophloeumrhizomorphs from the Famennian aged Waterloo Farm Lägerstatte of South Africa. We demonstrate an unlobed cormose morphology separated from the microphyll bearing axis by a smooth transition zone. This provides one of the few known examples of a cormose lycopsid rhizomorph dating back to the Devonian. We assign this material and all previously published South African Leptophloeum material to Leptophloeum rhombicum.
- Full Text: false
- Date Issued: 2014
Towards a framework for assessing the sustainability of local economic development based on natural resources: honeybush tea in the Eastern Cape Province of South Africa
- Polak, James, Snowball, Jeanette D
- Authors: Polak, James , Snowball, Jeanette D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69201 , vital:29445 , https://doi.org/10.1080/13549839.2016.1196348
- Description: Despite the popularity of local economic development (LED) as a job creation and economic growth strategy in South Africa, many LED projects have not proved to be sustainable in the long-run, especially where human systems interact with biological ones. This article examines the relationship between sustainability and LED within the context of the emerging honeybush tea industry in the Eastern Cape. Data were gathered from provincial as well as local government policy documents and reports, and via key informant interviews. The data were analysed using Connelly’s [(2007). Mapping sustainable development as a contested concept. Local Environment, 12 (3), 259–278] three pronged approach to sustainable development as a lens through which to view the local industry. Findings showed that the industry offers many opportunities for development, including job creation in poorer, rural households; sustainable wild harvesting using a permit system; commercial cultivation; potential to develop social capital; potential for community-based LED; and product diversification. However, there are also corresponding challenges: There is currently no reliable data on the maximum sustainable yield, which is needed to guide quota allocations for entrepreneurial harvesters harvesting from wild stocks; possible biodiversity loss; and enforcing the permit scheme is proving difficult in remote rural areas.
- Full Text: false
- Date Issued: 2017
- Authors: Polak, James , Snowball, Jeanette D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69201 , vital:29445 , https://doi.org/10.1080/13549839.2016.1196348
- Description: Despite the popularity of local economic development (LED) as a job creation and economic growth strategy in South Africa, many LED projects have not proved to be sustainable in the long-run, especially where human systems interact with biological ones. This article examines the relationship between sustainability and LED within the context of the emerging honeybush tea industry in the Eastern Cape. Data were gathered from provincial as well as local government policy documents and reports, and via key informant interviews. The data were analysed using Connelly’s [(2007). Mapping sustainable development as a contested concept. Local Environment, 12 (3), 259–278] three pronged approach to sustainable development as a lens through which to view the local industry. Findings showed that the industry offers many opportunities for development, including job creation in poorer, rural households; sustainable wild harvesting using a permit system; commercial cultivation; potential to develop social capital; potential for community-based LED; and product diversification. However, there are also corresponding challenges: There is currently no reliable data on the maximum sustainable yield, which is needed to guide quota allocations for entrepreneurial harvesters harvesting from wild stocks; possible biodiversity loss; and enforcing the permit scheme is proving difficult in remote rural areas.
- Full Text: false
- Date Issued: 2017
The natural history and conservation of Indian Ocean Humpback Dolphins (Sousa plumbea) in South African waters
- Plön, Stephanie, Cockcroft, Victor G, Froneman, P William
- Authors: Plön, Stephanie , Cockcroft, Victor G , Froneman, P William
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68207 , vital:29219 , https://doi.org/10.1016/bs.amb.2015.08.005
- Description: Publisher version , Although most knowledge on the biology of Sousa plumbea has primarily come from South African waters, a number of research gaps remain on the natural history and status of the species in the region. Research on two populations in South African waters for which some historical data exist may aid in highlighting long-term changes in the biology and natural history of this little known coastal delphinid. Recent studies on the age, growth and reproduction of animals incidentally caught in shark nets in Richards Bay, KwaZulu-Natal, yielded a lower maximum age estimate of 24 (previously 46) growth-layer-groups (GLGs), sexual maturity of 7.5 and 8 GLGs in males and females (previously 12–13 and 10 GLGs, respectively), an ovulation rate of 0.2 and a 5-year calving interval (previously 0.3 and 3-year calving interval) than previously reported. These differences may be due to a difference in the interpretation of GLGs between observers or a predominance of young males being caught in the shark nets. Stomach content analysis revealed a change in the relative proportions of the main prey items over the past 25 years, but no difference in species richness or diversity was found between the sexes. No change in trophic level was recorded between 1972 and 2009. Field studies in Algoa Bay, Eastern Cape, conducted 16 years apart indicated a decline in the mean group size (from 7 to 3 animals), a decline in the maximum group size (from 24 to 13 animals), an increase in solitary individuals (15.4–36%), and a change in behaviour from predominantly foraging (64–18%) to mainly travelling (24–49%). The observed changes are suggestive of a change in food availability, resulting in a range shift or a potential decline in numbers. These studies indicate the importance of long-term studies to monitor population changes and their possible causes. A number of threats, such as shark nets, pollution (noise and chemical), and coastal development and disturbance, to the humpback dolphin populations in South Africa have been identified. Urgent action is required to ensure continued existence of the species in South African waters.
- Full Text: false
- Date Issued: 2015
- Authors: Plön, Stephanie , Cockcroft, Victor G , Froneman, P William
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68207 , vital:29219 , https://doi.org/10.1016/bs.amb.2015.08.005
- Description: Publisher version , Although most knowledge on the biology of Sousa plumbea has primarily come from South African waters, a number of research gaps remain on the natural history and status of the species in the region. Research on two populations in South African waters for which some historical data exist may aid in highlighting long-term changes in the biology and natural history of this little known coastal delphinid. Recent studies on the age, growth and reproduction of animals incidentally caught in shark nets in Richards Bay, KwaZulu-Natal, yielded a lower maximum age estimate of 24 (previously 46) growth-layer-groups (GLGs), sexual maturity of 7.5 and 8 GLGs in males and females (previously 12–13 and 10 GLGs, respectively), an ovulation rate of 0.2 and a 5-year calving interval (previously 0.3 and 3-year calving interval) than previously reported. These differences may be due to a difference in the interpretation of GLGs between observers or a predominance of young males being caught in the shark nets. Stomach content analysis revealed a change in the relative proportions of the main prey items over the past 25 years, but no difference in species richness or diversity was found between the sexes. No change in trophic level was recorded between 1972 and 2009. Field studies in Algoa Bay, Eastern Cape, conducted 16 years apart indicated a decline in the mean group size (from 7 to 3 animals), a decline in the maximum group size (from 24 to 13 animals), an increase in solitary individuals (15.4–36%), and a change in behaviour from predominantly foraging (64–18%) to mainly travelling (24–49%). The observed changes are suggestive of a change in food availability, resulting in a range shift or a potential decline in numbers. These studies indicate the importance of long-term studies to monitor population changes and their possible causes. A number of threats, such as shark nets, pollution (noise and chemical), and coastal development and disturbance, to the humpback dolphin populations in South Africa have been identified. Urgent action is required to ensure continued existence of the species in South African waters.
- Full Text: false
- Date Issued: 2015
Hsp40 Co-chaperones as drug targets: towards the development of specific inhibitors
- Pesce, Eva-Rachele, Blatch, Gregory L, Edkins, Adrienne L
- Authors: Pesce, Eva-Rachele , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66335 , vital:28937 , https://doi.org/10.1007/7355_2015_92
- Description: publisher version , The heat shock protein 40 (Hsp40/DNAJ) family of co-chaperones modulates the activity of the major molecular chaperone heat shock protein 70 (Hsp70) protein group. Hsp40 stimulates the basal ATPase activity of Hsp70 and hence regulates the affinity of Hsp70 for substrate proteins. The number of Hsp40 genes in most organisms is substantially greater than the number of Hsp70 genes. Therefore, different Hsp40 family members may regulate different activities of the same Hsp70. This fact, along with increasing knowledge of the function of Hsp40 in diseases, has led to certain Hsp40 isoforms being considered promising drug targets. Here we review the role of Hsp40 in human disease and recent developments towards the creation of Hsp40-specific inhibitors.
- Full Text: false
- Date Issued: 2016
- Authors: Pesce, Eva-Rachele , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66335 , vital:28937 , https://doi.org/10.1007/7355_2015_92
- Description: publisher version , The heat shock protein 40 (Hsp40/DNAJ) family of co-chaperones modulates the activity of the major molecular chaperone heat shock protein 70 (Hsp70) protein group. Hsp40 stimulates the basal ATPase activity of Hsp70 and hence regulates the affinity of Hsp70 for substrate proteins. The number of Hsp40 genes in most organisms is substantially greater than the number of Hsp70 genes. Therefore, different Hsp40 family members may regulate different activities of the same Hsp70. This fact, along with increasing knowledge of the function of Hsp40 in diseases, has led to certain Hsp40 isoforms being considered promising drug targets. Here we review the role of Hsp40 in human disease and recent developments towards the creation of Hsp40-specific inhibitors.
- Full Text: false
- Date Issued: 2016
Binding and entry of a non-enveloped T=4 insect RNA virus is triggered by alkaline pH
- Penkler, David L, Jiwaji, Meesbah, Domitrovic, Tatiana, Short, James R, Johnson, John E, Dorrington, Rosemary A
- Authors: Penkler, David L , Jiwaji, Meesbah , Domitrovic, Tatiana , Short, James R , Johnson, John E , Dorrington, Rosemary A
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/65995 , vital:28875 , https://doi.org/10.1016/j.virol.2016.08.028
- Description: publisher version , Tetraviruses are small, non-enveloped, RNA viruses that exclusively infect lepidopteran insects. Their particles comprise 240 copies of a single capsid protein precursor (CP), which undergoes autoproteolytic cleavage during maturation. The molecular mechanisms of capsid assembly and maturation are well understood, but little is known about the viral infectious lifecycle due to a lack of tissue culture cell lines that are susceptible to tetravirus infection. We show here that binding and entry of the alphatetravirus, Helicoverpa armigera stunt virus (HaSV), is triggered by alkaline pH. At pH 9.0, wild-type HaSV virus particles undergo conformational changes that induce membrane-lytic activity and binding to Spodoptera frugiperda Sf9 cells. Binding is followed by entry and infection, with virus replication complexes detected by immunofluorescence microscopy within 2 h post-infection and the CP after 12 h. HaSV particles produced in S. frugiperda Sf9 cells are infectious. Helicoverpa armigera larval virus biofeed assays showed that pre-treatment with the V-ATPase inhibitor, Bafilomycin A1, resulted in a 50% decrease in larval mortality and stunting, while incubation of virus particles at pH 9.0 prior to infection restored infectivity. Together, these data show that HaSV, and likely other tetraviruses, requires the alkaline environment of the lepidopteran larval midgut for binding and entry into host cells.
- Full Text: false
- Date Issued: 2016
- Authors: Penkler, David L , Jiwaji, Meesbah , Domitrovic, Tatiana , Short, James R , Johnson, John E , Dorrington, Rosemary A
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/65995 , vital:28875 , https://doi.org/10.1016/j.virol.2016.08.028
- Description: publisher version , Tetraviruses are small, non-enveloped, RNA viruses that exclusively infect lepidopteran insects. Their particles comprise 240 copies of a single capsid protein precursor (CP), which undergoes autoproteolytic cleavage during maturation. The molecular mechanisms of capsid assembly and maturation are well understood, but little is known about the viral infectious lifecycle due to a lack of tissue culture cell lines that are susceptible to tetravirus infection. We show here that binding and entry of the alphatetravirus, Helicoverpa armigera stunt virus (HaSV), is triggered by alkaline pH. At pH 9.0, wild-type HaSV virus particles undergo conformational changes that induce membrane-lytic activity and binding to Spodoptera frugiperda Sf9 cells. Binding is followed by entry and infection, with virus replication complexes detected by immunofluorescence microscopy within 2 h post-infection and the CP after 12 h. HaSV particles produced in S. frugiperda Sf9 cells are infectious. Helicoverpa armigera larval virus biofeed assays showed that pre-treatment with the V-ATPase inhibitor, Bafilomycin A1, resulted in a 50% decrease in larval mortality and stunting, while incubation of virus particles at pH 9.0 prior to infection restored infectivity. Together, these data show that HaSV, and likely other tetraviruses, requires the alkaline environment of the lepidopteran larval midgut for binding and entry into host cells.
- Full Text: false
- Date Issued: 2016
The elephant in the ‘room’: determinants of songbird assemblages in the Thicket Biome, South Africa
- 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.
- Full Text: false
- Date Issued: 2019
- 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.
- Full Text: false
- Date Issued: 2019
Thermoluminescence of the persistent-luminescence phosphor, BaAl2O4: a stuffed tridymite
- Pandey, A, Chithambo, Makaiko L
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
- Full Text: false
- Date Issued: 2018
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
- Full Text: false
- Date Issued: 2018
Food waste generation and potential interventions at Rhodes University, South Africa
- Painter, Kathleen, Thondhlana, Gladman, Kua, Harn W
- Authors: Painter, Kathleen , Thondhlana, Gladman , Kua, Harn W
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67733 , vital:29135 , https://doi.org/10.1016/j.wasman.2016.07.013
- Description: Publisher version , Estimation of food waste generation represents the first step when considering efforts to reduce waste generation and monitor food waste reduction against set targets. This study reports on an estimation of food waste generated in university dining halls at Rhodes University, South Africa. Daily food waste generation was estimated at about 555 g per student or 2 tonnes across all sample dining halls, translating to about 450 tonnes per year. The results show that food waste is influenced by an array of contextual factors, including distance to dining hall, gender composition of hall and meal times and meal options. It is estimated that the university could save up to US$ 80 000 annually for every 10% reduction in the current rate of food waste generation. Possible educational, technical and administrative interventions for food waste reduction are discussed.
- Full Text: false
- Date Issued: 2016
- Authors: Painter, Kathleen , Thondhlana, Gladman , Kua, Harn W
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67733 , vital:29135 , https://doi.org/10.1016/j.wasman.2016.07.013
- Description: Publisher version , Estimation of food waste generation represents the first step when considering efforts to reduce waste generation and monitor food waste reduction against set targets. This study reports on an estimation of food waste generated in university dining halls at Rhodes University, South Africa. Daily food waste generation was estimated at about 555 g per student or 2 tonnes across all sample dining halls, translating to about 450 tonnes per year. The results show that food waste is influenced by an array of contextual factors, including distance to dining hall, gender composition of hall and meal times and meal options. It is estimated that the university could save up to US$ 80 000 annually for every 10% reduction in the current rate of food waste generation. Possible educational, technical and administrative interventions for food waste reduction are discussed.
- Full Text: false
- Date Issued: 2016
Pecuniary interests and the rule against adjudicative bias: the automatic disqualification or objective reasonable approach?
- Okpaluba, Chuks, Juma, Laurence
- Authors: Okpaluba, Chuks , Juma, Laurence
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/129093 , vital:36217 , https://hdl.handle.net/10520/EJC122974
- Description: This article deals with the issue of bias arising from pecuniary interest of a judge. Essentially, it asks the question: when does the pecuniary interest of a judge diminish his/her ability to apply his/her mind impartially to the dispute before him/her. To answer this question, the article undertakes a synthesis of the various rules and tests applied across Commonwealth jurisdictions and then compares them with the South African approach as outlined in two recent cases, namely Bernert v ABSA Bank Ltd 2011 (3) SA 92 (CC) and Ndimeni v Meeg Bank Ltd (Bank of Transkei) 2011 (1) SA 560 (SCA). Broadly, the article discusses the key aspects of the automatic disqualification approach preferred by the English courts, the Canadian objective reasonable approach and the realistic possibility approach recently adopted by the Australian courts. The article concludes that the South African approach that places emphasis on the objective reasonable test, complemented by the realistic possibility approach, may be most suitable, given the nature of complaints so far dealt with by the courts and the full propriety of the injunction in section 34 of the Constitution.
- Full Text: false
- Date Issued: 2011
- Authors: Okpaluba, Chuks , Juma, Laurence
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/129093 , vital:36217 , https://hdl.handle.net/10520/EJC122974
- Description: This article deals with the issue of bias arising from pecuniary interest of a judge. Essentially, it asks the question: when does the pecuniary interest of a judge diminish his/her ability to apply his/her mind impartially to the dispute before him/her. To answer this question, the article undertakes a synthesis of the various rules and tests applied across Commonwealth jurisdictions and then compares them with the South African approach as outlined in two recent cases, namely Bernert v ABSA Bank Ltd 2011 (3) SA 92 (CC) and Ndimeni v Meeg Bank Ltd (Bank of Transkei) 2011 (1) SA 560 (SCA). Broadly, the article discusses the key aspects of the automatic disqualification approach preferred by the English courts, the Canadian objective reasonable approach and the realistic possibility approach recently adopted by the Australian courts. The article concludes that the South African approach that places emphasis on the objective reasonable test, complemented by the realistic possibility approach, may be most suitable, given the nature of complaints so far dealt with by the courts and the full propriety of the injunction in section 34 of the Constitution.
- Full Text: false
- Date Issued: 2011
The dialogue between the bench and the bar: implications for adjudicative impartiality
- Okpaluba, Chuks, Juma, Laurence
- Authors: Okpaluba, Chuks , Juma, Laurence
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/129078 , vital:36215 , https://hdl.handle.net/10520/EJC53998
- Description: What is the role of the judge in the conduct of a trial? Can he or she engage counsel in legal argument and ask questions on legal issues without breaking the brittle bond of justice or be said to have 'descended into the arena'? Assuming that these actions are permissible, at what point will the judge's dialogue with counsel or line of questioning go beyond permissible limits? These are the questions with which this article grapples. Based on an analysis of the Constitutional Court decisions in State v Basson (2) 2007 (1) SACR 566 (CC) and Bernert v ABSA Bank Ltd 2011 (3) SA 92 (CC), and several Supreme Court of Appeal and other Commonwealth decisions, the article explores the circumstances in which the recusal of judges has been sought, or judicial decisions have been challenged on appeal on the basis of an allegation that there have been violations of the principle of fair hearing as enshrined in the Constitution. The article draws on the 'apprehension of bias' jurisprudence to establish the utility of the presumption of impartiality and the hybrid test of double-reasonableness in contexts where a judge's conduct is in question. The article concludes that the dialogue between the bench and bar is a useful component of adjudication in our adversarial system and should be limited by the rules of impartiality only in very exceptional circumstances.
- Full Text: false
- Date Issued: 2011
- Authors: Okpaluba, Chuks , Juma, Laurence
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/129078 , vital:36215 , https://hdl.handle.net/10520/EJC53998
- Description: What is the role of the judge in the conduct of a trial? Can he or she engage counsel in legal argument and ask questions on legal issues without breaking the brittle bond of justice or be said to have 'descended into the arena'? Assuming that these actions are permissible, at what point will the judge's dialogue with counsel or line of questioning go beyond permissible limits? These are the questions with which this article grapples. Based on an analysis of the Constitutional Court decisions in State v Basson (2) 2007 (1) SACR 566 (CC) and Bernert v ABSA Bank Ltd 2011 (3) SA 92 (CC), and several Supreme Court of Appeal and other Commonwealth decisions, the article explores the circumstances in which the recusal of judges has been sought, or judicial decisions have been challenged on appeal on the basis of an allegation that there have been violations of the principle of fair hearing as enshrined in the Constitution. The article draws on the 'apprehension of bias' jurisprudence to establish the utility of the presumption of impartiality and the hybrid test of double-reasonableness in contexts where a judge's conduct is in question. The article concludes that the dialogue between the bench and bar is a useful component of adjudication in our adversarial system and should be limited by the rules of impartiality only in very exceptional circumstances.
- Full Text: false
- Date Issued: 2011
Waiver of the right to judicial impartiality: comparative analysis of South African and Commonwealth jurisprudence
- Okpaluba, Chuks, Juma, Laurence
- Authors: Okpaluba, Chuks , Juma, Laurence
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127138 , vital:35960 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC153154
- Description: This paper investigates whether judicial independence and impartiality entrenched in written constitutions and recognised by the common law as fundamental requirements of fair administration of justice can be subjected to the private law principles of waiver, estoppel or acquiescence. In an attempt to answer this question, the paper suggests that the starting point should be the interrogation of whether the right alleged to be waived emanates from the constitution or administrative law. At common law, a right can be waived, insofar as the party involved had knowledge of the right and failed to assert it.
- Full Text: false
- Date Issued: 2013
- Authors: Okpaluba, Chuks , Juma, Laurence
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127138 , vital:35960 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC153154
- Description: This paper investigates whether judicial independence and impartiality entrenched in written constitutions and recognised by the common law as fundamental requirements of fair administration of justice can be subjected to the private law principles of waiver, estoppel or acquiescence. In an attempt to answer this question, the paper suggests that the starting point should be the interrogation of whether the right alleged to be waived emanates from the constitution or administrative law. At common law, a right can be waived, insofar as the party involved had knowledge of the right and failed to assert it.
- Full Text: false
- Date Issued: 2013
Thermoluminescence of kunzite: a study of kinetic processes and dosimetry characteristics
- Ogundare, F O, Alatishe, M A, Chithambo, Makaiko L, Costin, G
- Authors: Ogundare, F O , Alatishe, M A , Chithambo, Makaiko L , Costin, G
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124701 , vital:35650 , https://doi.org/10.1016/j.nimb.2016.02.059
- Description: Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer.
- Full Text: false
- Date Issued: 2016
- Authors: Ogundare, F O , Alatishe, M A , Chithambo, Makaiko L , Costin, G
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124701 , vital:35650 , https://doi.org/10.1016/j.nimb.2016.02.059
- Description: Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer.
- Full Text: false
- Date Issued: 2016
Synthesis, characterisation and biological evaluation of novel anti-infective compounds bearing ferrocene, arylpyrrole, thiazolidinedione, quinoline and triazole moieties
- Authors: Oderinlo, Ogunyemi Olajide
- Date: 2019
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/114714 , vital:34016 , 10.21504/10962/114714
- Description: Expected release date-April 2022
- Full Text: false
- Date Issued: 2019
- Authors: Oderinlo, Ogunyemi Olajide
- Date: 2019
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/114714 , vital:34016 , 10.21504/10962/114714
- Description: Expected release date-April 2022
- Full Text: false
- Date Issued: 2019
Factors influencing the shape of CW-OSL signal obtained by stimulation of very deep traps in carbon-doped aluminium oxide: an experimental study
- Nyirenda, Angel N, Chithambo, Makaiko L
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115493 , vital:34149 , https://doi.org/10.1016/j.jlumin.2017.07.016
- Description: The optically stimulated luminescence from carbon-doped aluminium oxide (α-Al2O3:C) displays a peak with time under certain measurement conditions. In this paper, we present factors that influence the peak-like shape of continuous-wave optically stimulated luminescence (CW-OSL) signal. The report is based on the experimental study of OSL signals obtained by stimulation of very deep traps in α-Al2O3:C. Methods exploiting post-irradiation annealing, variable dose and temperature dependent OSL measurements were used in the investigation. It is found that the rising part of the CW-OSL peak is obtained when the rate of retrapping at the most optically active trap (main trap) exceeds the rate of direct radiative recombination following optical release of charges from all optically active traps. This is possible if, during optical stimulation, the primary trap responsible for OSL i.e. the main trap, is substantially unoccupied and the very deep, donor traps are substantially filled up. The rate of charge retrapping itself is deduced to depend on the occupancy of the acceptor traps i.e. shallow, main and secondary traps; concentration of charge carriers in the very deep, donor traps; the post-irradiation annealing temperature and the temperature at which the OSL is measured.
- Full Text: false
- Date Issued: 2017
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115493 , vital:34149 , https://doi.org/10.1016/j.jlumin.2017.07.016
- Description: The optically stimulated luminescence from carbon-doped aluminium oxide (α-Al2O3:C) displays a peak with time under certain measurement conditions. In this paper, we present factors that influence the peak-like shape of continuous-wave optically stimulated luminescence (CW-OSL) signal. The report is based on the experimental study of OSL signals obtained by stimulation of very deep traps in α-Al2O3:C. Methods exploiting post-irradiation annealing, variable dose and temperature dependent OSL measurements were used in the investigation. It is found that the rising part of the CW-OSL peak is obtained when the rate of retrapping at the most optically active trap (main trap) exceeds the rate of direct radiative recombination following optical release of charges from all optically active traps. This is possible if, during optical stimulation, the primary trap responsible for OSL i.e. the main trap, is substantially unoccupied and the very deep, donor traps are substantially filled up. The rate of charge retrapping itself is deduced to depend on the occupancy of the acceptor traps i.e. shallow, main and secondary traps; concentration of charge carriers in the very deep, donor traps; the post-irradiation annealing temperature and the temperature at which the OSL is measured.
- Full Text: false
- Date Issued: 2017
The influence of radiation-induced defects on thermoluminescence and optically stimulated luminescence of α-Al2O3: C
- Nyirenda, Angel N, Chithambo, Makaiko L
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119818 , vital:34786 , https://doi.org/10.1016/j.nimb.2017.02.077
- Description: It is known that when α-Al2O3:C is exposed to excessive amounts of ionising radiation, defects are induced within its matrix. We report the influence of radiation-induced defects on the thermoluminescence (TL) and optically stimulated luminescence (OSL) measured from α-Al2O3:C after irradiation to 1000 Gy. These radiation-induced defects are thermally unstable in the region 450–650 °C and result in TL peaks in this range when the TL is measured at 1 °C/s. Heating a sample to 700 °C obliterates the radiation-induced defects, that is, the TL peaks corresponding to the radiation induced defects are no longer observed in the subsequent TL measurements when moderate irradiation doses below 10 Gy are used. The charge traps associated with these radiation-induced defects are more stable than the dosimetric trap when the sample is exposed to either sunlight or 470-nm blue light from LEDs. TL glow curves measured following the defect-inducing irradiation produce a dosimetric peak that is broader and positioned at a higher temperature than observed in glow curves obtained before the heavy irradiation. In addition, sample sensitization/desensitization occurs due to the presence of these radiation-induced defects. Furthermore, both the activation energy and the kinetic order of the dosimetric peak evaluated when the radiation-induced defects are present in the sample are significantly lower in value than those obtained when these defects are absent. The radiation-induced defects also affect the shape and total light sum of the OSL signal as well as the position and width of the resultant residual phototransferred thermoluminescence main peak.
- Full Text: false
- Date Issued: 2017
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119818 , vital:34786 , https://doi.org/10.1016/j.nimb.2017.02.077
- Description: It is known that when α-Al2O3:C is exposed to excessive amounts of ionising radiation, defects are induced within its matrix. We report the influence of radiation-induced defects on the thermoluminescence (TL) and optically stimulated luminescence (OSL) measured from α-Al2O3:C after irradiation to 1000 Gy. These radiation-induced defects are thermally unstable in the region 450–650 °C and result in TL peaks in this range when the TL is measured at 1 °C/s. Heating a sample to 700 °C obliterates the radiation-induced defects, that is, the TL peaks corresponding to the radiation induced defects are no longer observed in the subsequent TL measurements when moderate irradiation doses below 10 Gy are used. The charge traps associated with these radiation-induced defects are more stable than the dosimetric trap when the sample is exposed to either sunlight or 470-nm blue light from LEDs. TL glow curves measured following the defect-inducing irradiation produce a dosimetric peak that is broader and positioned at a higher temperature than observed in glow curves obtained before the heavy irradiation. In addition, sample sensitization/desensitization occurs due to the presence of these radiation-induced defects. Furthermore, both the activation energy and the kinetic order of the dosimetric peak evaluated when the radiation-induced defects are present in the sample are significantly lower in value than those obtained when these defects are absent. The radiation-induced defects also affect the shape and total light sum of the OSL signal as well as the position and width of the resultant residual phototransferred thermoluminescence main peak.
- Full Text: false
- Date Issued: 2017
Spectral study of radioluminescence in carbon-doped aluminium oxide
- Nyirenda, Angel N, Chithambo, Makaiko L
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110067 , vital:33220 , https://doi.org/10.1016/j.radmeas.2018.06.026
- Description: The spectral emission study of the radioluminescence (RL) measured from carbon-doped aluminium oxide (α-Al2O3:C) at various temperatures between 30 and 300∘C is reported. The energy-resolved RL emission spectra measured at room temperature show seven gaussian emission bands centred at 1.75, 1.79, 1.85, 2.22, 2.96, 3.72 and 4.44 eV. The 2.96-eV emission, associated with F-centres, is the primary RL emission whereas the narrow (R-line) emission centred at 1.79 eV, associated with Cr3+ impurity ions, is the most intense secondary emission. However, the intensity of 1.79-eV emission decreases with repeated RL measurements. The central emission energy for F-centres is constant throughout the temperature range of investigation. The full width at half maximum (FWHM) for the F-centre emission band increases with temperature whereas the F-centre peak intensity exhibits thermal quenching behaviour at temperatures above 160∘C. On the other hand, the emission energy for the R-line emission of Cr3+ is constant for temperatures between 30 and 160∘C, whereas its peak intensity generally decreases with temperature. F-centres experience strong-coupling in their crystallographic sites with estimated electron-lattice coupling parameters of S = 5.0 ± 0.9, Ep = 0.079 ± 0.008 eV and ν = 1.91 × 1013 Hz where S, Ep and ν are the Huang-Rhys factor, the phonon energy and the phonon frequency, respectively. The RL spectra recorded while ramping the temperature of a sample at a constant rate have been compared against conventional TL spectra.
- Full Text: false
- Date Issued: 2018
- Authors: Nyirenda, Angel N , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110067 , vital:33220 , https://doi.org/10.1016/j.radmeas.2018.06.026
- Description: The spectral emission study of the radioluminescence (RL) measured from carbon-doped aluminium oxide (α-Al2O3:C) at various temperatures between 30 and 300∘C is reported. The energy-resolved RL emission spectra measured at room temperature show seven gaussian emission bands centred at 1.75, 1.79, 1.85, 2.22, 2.96, 3.72 and 4.44 eV. The 2.96-eV emission, associated with F-centres, is the primary RL emission whereas the narrow (R-line) emission centred at 1.79 eV, associated with Cr3+ impurity ions, is the most intense secondary emission. However, the intensity of 1.79-eV emission decreases with repeated RL measurements. The central emission energy for F-centres is constant throughout the temperature range of investigation. The full width at half maximum (FWHM) for the F-centre emission band increases with temperature whereas the F-centre peak intensity exhibits thermal quenching behaviour at temperatures above 160∘C. On the other hand, the emission energy for the R-line emission of Cr3+ is constant for temperatures between 30 and 160∘C, whereas its peak intensity generally decreases with temperature. F-centres experience strong-coupling in their crystallographic sites with estimated electron-lattice coupling parameters of S = 5.0 ± 0.9, Ep = 0.079 ± 0.008 eV and ν = 1.91 × 1013 Hz where S, Ep and ν are the Huang-Rhys factor, the phonon energy and the phonon frequency, respectively. The RL spectra recorded while ramping the temperature of a sample at a constant rate have been compared against conventional TL spectra.
- Full Text: false
- Date Issued: 2018