A study of the kinetics of a high temperature thermoluminescence peak in annealed natural quartz
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110007 , vital:33213 , DOI: 10.1016/j.jlumin.2018.08.077
- Description: Thermoluminescence of a high temperature secondary glow-peak in natural quartz annealed at 900 °C is reported. The glow-curve of a sample irradiated to 10 Gy and measured at 1 °C/s shows three peaks; the main peak at 71 °C and two other weaker-intensity peaks at 125 °C and 177 °C. For reference, the peaks are labelled as I, II and III. This study is concerned with the secondary peak at 177 °C (peak III). The electron trap responsible for peak III is stable at ambient temperature as determined by monitoring the peak intensity after various delays between irradiation and measurement. The activation energy and frequency factor of the peak were estimated as ~1.24 eV and ~10¹² s⁻¹ respectively. The dose response of the peak in the range 1–300 Gy is sublinear. The influence of either partial heating or irradiation dose on the peak position suggest that the peak follows non-first-order kinetics.
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Action for increasing energy-saving behaviour in student residences at Rhodes University, South Africa
- Authors: Ancha, Angel , Bulunga, Lindelwa , Thondhlana, Gladman
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67801 , vital:29146 , https://doi.org/10.1108/IJSHE-07-2017-0107
- Description: Publisher version , Purpose: In response to increasing energy demand and financial constraints to invest in green infrastructure, behaviour change energy-saving interventions are increasingly being considered as a tool for encouraging pro-environmental behaviour in campus residences. This paper aims to report on a pilot programme aimed at reducing energy consumption via behaviour change interventions, variably applied in residences at Rhodes University, South Africa. Design/methodology/approach: Data were collected via structured questionnaires, energy consumption records and post-intervention programme focus group discussions. Findings: Participant residences that received a mix of different interventions in the forms of pamphlets, face-to-face discussions, incentives and feedback recorded more energy reductions of up to 9 per cent than residences that received a single or no intervention. In post-experiment discussions, students cited personal, institutional and structural barriers to pro-environmental energy-use behaviour. Practical implications: Overall, the results of this study suggest that information provision of energy-saving tips combined with regular feedback and incentives can result in energy-use reductions in university residences, which may yield environmental and economic benefits for universities, but addressing barriers to pro-environmental behaviour might maximise the results. Originality/value: Given the lack of literature on energy conservation in the global South universities, this study provides the basis for discussing the potential for using behavioural interventions in universities for stirring pathways towards sustainability.
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An ecosystem service value chain analysis framework: a conceptual paper
- 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.
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Characteristics of the thermoluminescence of Sm3+-doped P2O5-K2O-MgO-Al2O3-ZnF2 glass
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/109979 , vital:33211 , https://doi.org/10.1016/j.radmeas.2018.06.005
- Description: We report the thermoluminescence of Sm3+-doped P2O5-K2O-MgO-Al2O3-ZnF2 glass. A glow-curve measured at 1 °C/s after beta irradiation to 10 Gy shows two peaks; a broad high intensity one at 214.0 ± 0.4 °C and a weaker intensity peak at 75.2 ± 0.8 °C. The dependence of peak position on partial heating as well as on irradiation suggest that the main peak at 214 °C is a combination of several overlapping peaks. The activation energy of the different components of the main peak, calculated using the initial-rise method, differ showing that the components are distinct. The reproducibility, fading and dose response were examined by considering the dominant component of the main peak. The intensity of the peak changes with heating rate in a manner consistent with thermal quenching.
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Designing writing groups to support postgraduate students’ academic writing: a case study from a South African university
- Authors: Wilmot, Kirstin
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66267 , vital:28926 , https://doi.org/10.1080/14703297.2016.1238775
- Description: publisher version , This paper reports on a writing group pilot programme implemented at a South African university. Drawing on literature, anonymous student evaluations and facilitator observations, it discusses the use of writing groups for supporting postgraduate academic writing practices. Developed within a broader postgraduate academic writing support programme, the paper discusses a case study of two pilot writing groups: a multidisciplinary long-term group and a disciplinary short-term ‘writing-intensive’ group. The findings indicate that the overall experience of the writing group was a positive one, with each group presenting varied ‘success’ aspects as well as challenges. Insights gleaned may contribute to our understanding of how these groups can be utilised to support postgraduate students and how different kinds of groups can be developed to serve particular student needs. The paper concludes with a discussion of the inclusion of a disciplinary expert, which proved particularly useful in this pilot.
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General features and kinetic analysis of thermoluminescence from annealed natural quartz
- Authors: Thomas, Sunil , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/112885 , vital:33670 , https://doi.org/10.1016/j.jlumin.2018.02.003
- Description: The aim of this study is to explore the thermoluminescence properties of beta irradiated natural quartz annealed at 900 °C, that is, beyond its second phase inversion temperature of 867 °C. The sample was annealed to improve its sensitivity and to deplete any residual charge from electron traps. The glow-curve corresponding to 10 Gy shows three peaks when measured at 1 °C/s; a dominant one at 71 °C, the subject of this report, and two other ones at 125 and 177 °C. The dose response of the main peak was studied in the range 1–300 Gy. The activation energy of the main glow-peak was evaluated as ~1 eV. Kinetic analyses using various methods show that the main glow-peak follows first order kinetics.
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HOP expression is regulated by p53 and RAS and characteristic of a cancer gene signature
- Authors: Mattison, Stacey A , Blatch, Gregory L , Edkins, Adrienne L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66278 , vital:28928 , https://doi.org/10.1007/s12192-016-0755-8
- Description: publisher version , The Hsp70/Hsp90 organising protein (HOP) is a co-chaperone essential for client protein transfer from Hsp70 to Hsp90 within the Hsp90 chaperone machine. Although HOP is upregulated in various cancers, there is limited information from in vitro studies on how HOP expression is regulated in cancer. The main objective of this study was to identify the HOP promoter and investigate its activity in cancerous cells. Bioinformatic analysis of the -2500 to +16 bp region of the HOP gene identified a large CpG island and a range of putative cis-elements. Many of the cis-elements were potentially bound by transcription factors which are activated by oncogenic pathways. Luciferase reporter assays demonstrated that the upstream region of the HOP gene contains an active promoter in vitro. Truncation of this region suggested that the core HOP promoter region was -855 to +16 bp. HOP promoter activity was highest in Hs578T, HEK293T and SV40- transformed MEF1 cell lines which expressed mutant or inactive p53. In a mutant p53 background, expression of wild-type p53 led to a reduction in promoter activity, while inhibition of wild-type p53 in HeLa cells increased HOP promoter activity. Additionally, in Hs578T and HEK293T cell lines containing inactive p53, expression of HRAS increased HOP promoter activity. However, HRAS activation of the HOP promoter was inhibited by p53 overexpression. These findings suggest for the first time that HOP expression in cancer may be regulated by both RAS activation and p53 inhibition. Taken together, these data suggest that HOP may be part of the cancer gene signature induced by a combination of mutant p53 and mutated RAS that is associated with cellular transformation.
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Influence of annealing on thermoluminescence of natural quartz: kinetic analysis and experimental study of apparent inverse thermal quenching
- Authors: Folley, Damilola E , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/109996 , vital:33212 , https://doi.org/10.1016/j.radmeas.2018.04.010
- Description: The influence of annealing on the main thermoluminescence glow-peak of natural quartz is reported. For comparison, results from un-annealed quartz are included. The glow-curve measured at 1 °Cs−1 after beta irradiation to 50 Gy revealed six peaks each for quartz annealed at 800 °C for 1 h and the un-annealed sample. The main peak in both quartzes was observed at 72 °C. This report focusses on kinetic analysis of the main peak. The analysis was carried out using various methods consisting of the initial rise, whole glow-peak, peak shape, variable heating rate and phosphorescence-based methods. The activation energy obtained using the various methods ranges between and for the annealed sample and between and for the un-annealed sample. The result suggests that annealing has little effect on the activation energy. The luminescence intensity decreased with heating rate in the un-annealed sample in a manner suggestive of thermal quenching. In contrast, the dependence of intensity on heating rate in the annealed sample is influenced by the dose the sample is irradiated to. Whereas thermal quenching was noted for a dose of 50 Gy in the un-annealed sample, the annealed sample showed evidence of thermal quenching at a low dose of 3 Gy with the opposite effect when irradiated to 50 Gy. The activation energies of thermal quenching were found as and for the un-annealed and annealed samples respectively. We ascribe the apparent dependence of thermal quenching on dose in the annealed sample to competition between radiative and non-radiative transitions at the recombination centre.
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Invaded habitat incompatibility affects the suitability of the potential biological control agent Listronotus sordidus for Sagittaria platyphylla in South Africa
- Authors: Martin, Grant D , Coetzee, Julie A , Lloyd, Melissa , Nombewu, Sinoxolo E , Ndlovu, Mpilonhle S , Kwong, Raelene M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103926 , vital:32323 , https://doi.org/10.1080/09583157.2018.1460314
- Description: Sagittaria platyphylla (Engelmann) J.G. Smith (Alismataceae) was first recorded in South Africa in 2008 and is considered to be an emerging weed with naturalised populations occurring throughout the country. A biological control programme was initiated in Australia and surveys conducted between 2010 and 2012 yielded potential agents, including the crown feeding weevil, Listronotus sordidus Gyllenhal (Coleoptera: Curculionidae). The potential of L. sordidus as a candidate biological control agent against S. platyphylla in South Africa was examined. Although adult feeding was recorded on a number of plant species, oviposition and larval development indicated a narrow host range restricted to the Alismataceae. In South Africa, S. platyphylla populations are primarily found in inundated systems. However, laboratory studies showed that L. sordidus did not oviposit on inundated plants, potentially nullifying the impact of the insect on South African populations. It is suggested that even though L. sordidus is a damaging, specific agent, its limited impact on inundated plant populations in South Africa does not justify the inherent risk associated with the release of a biological control agent.
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Largest reported groups for the Indo-Pacific bottlenose dolphin (Tursiops aduncus) found in Algoa Bay, South Africa: trends and potential drivers
- Authors: Bouveroux, Thibaut N , Caputo, Michelle , Froneman, P William , Plön, Stephanie
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67913 , vital:29168 , https://doi.org/10.1111/mms.12471
- Description: Publisher version , This study investigates how group size of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) changes temporally, spatially, and/or with predominant behavior at two discreet sites along the Eastern Cape coastline of South Africa: Algoa Bay and the Wild Coast. The mean group size of bottlenose dolphins was large with an average of 52 animals. Significantly larger groups were observed in Algoa Bay ( = 60, range = 1–600) than off the Wild Coast ( = 32.9, range = 1–250). In Algoa Bay, the mean group size increased significantly over the study period, from an average 18 animals in 2008 to 76 animals in 2016. Additionally, the largest average and maximum group sizes ever reported both in South Africa and worldwide, were recorded in Algoa Bay (maximum group size = 600). Neither season nor behavior had a significant effect on mean group size at both sites. Similarly environmental variables such as the depth and substrate type also had no influence on group size. It remains unclear which ecological drivers, such as predation risk and food availability, are leading to the large groups observed in this area, and further research on abundance and distribution of both predators and prey is necessary.
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Major security incidents since 2014: an African perspective
- Authors: Van Heerden, Renier , Von Solms, Sune , Vorster, Johannes
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68291 , vital:29234 , https://ieeexplore.ieee.org/abstract/document/8417326/
- Description: Publisher version , The integration of technology in the modern society provides many benefits, but with increased connectivity comes increased risk where governments, businesses and individuals are vulnerable to a variety of cyber-attacks. Many of the large information security attacks of the last decade can be seen as an attack on 'foreign” systems or individuals when viewed from an African perspective, with no direct impact on an individual in Africa. However, information security experts in Africa states that although some of these attacks might not have had a direct impact of the African individual, but never the less should not be ignored as it does indirectly influence the African individual. The experts state that even if the individuals or businesses are not directly influenced by an attack, it should not be ignored as similar attacks might influence them in the future. They emphasise that these attacks should improve their cybersecurity awareness and behaviour, in order to prevent similar attacks from impacting them.
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Optically stimulated luminescence of ultra-high molecular weight polyethylene: a study of dosimetric features
- Authors: Chithambo, Makaiko L , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110035 , vital:33217 , https://doi.org/10.1016/j.radmeas.2018.06.006
- Description: We report the dosimetric features of ultra-high molecular weight polyethylene (UHMWPE) using luminescence optically stimulated using 470 nm blue light. Samples irradiated to between 1 and 1000 Gy produces luminescence that increases with irradiation dose to produce a linear dose response between 1 and 1000 Gy. The sample was determined not to be affected by pre-dose in tests using a pre-dose of 4000 Gy. This characteristic precludes the need for elaborate background erasing routines typical of dosimetry experiments. The signal has good reproducibility. We used this property to test recovery of ‘unknown’ doses with encouraging results. It was observed that luminescence can also be stimulated using 870 nm infrared light. The dose response, fading, pre-dose effect and the ability to optically stimulate luminescence from the polymer is discussed in terms of curing involving free-radicals.
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Photoluminescence and thermoluminescence properties of BaGa2O4
- Authors: Noto, L L , Poelman, D , Orante-Barrón, V R , Swart, H C , Mathevula, Langutani E , Nyenge, R , Chithambo, Makaiko L , Mothudi, B M , Dhlamini, M S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116037 , vital:34292 , https://doi.org/10.1016/j.physb.2017.07.059
- Description: Rare–Earth free luminescent materials are fast becoming important as the cost of rare earth ions gradually increases. In this work, a Rare–Earth free BaGa2O4 luminescent compound was prepared by solid state chemical reaction, which was confirmed to have a single phase by X-ray Diffraction. The Backscattered Electron image and Energy Dispersive X-ray spectroscopy maps confirmed irregular particle and homogeneous compound formation, respectively. The Photoluminescence spectrum displayed broad emission between 350 to 650 nm, which was deconvoluted into two components. The photoluminescence excitation peak was positioned at 254 nm, which corresponds with the band-to-band position observed from the diffuse reflectance spectrum. The band gap was extrapolated to 4.65 ± 0.02 eV using the Kubelka-Munk model. The preliminary thermoluminescence results indicated that the kinetics involved were neither of first nor second order. Additionally, the activation energy of the electrons within the trap centres was approximated to 0.61 ± 0.01 eV using the Initial Rise model.
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Phototransferred thermoluminescence and thermally-assisted optically stimulated luminescence dosimetry using α-Al2O3:C,Mg annealed at 1200°C
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/105422 , vital:32511 , https://doi.org/10.1016/j.jlumin.2018.08.085
- Description: We report phototransferred thermoluminescence (PTTL) and thermally-assisted optically stimulated luminescence (TA-OSL) of α-Al2O3:C,Mg annealed at 1200 °C. PTTL is TL measured from an irradiated phosphor after its exposure to light. The other theme of this study, TA-OSL is the additional amount of luminescence optically stimulated from a sample over and above the amount that would be measured at room temperature. A sample irradiated to 10 Gy and preheated to 230 °C at 1 °C/s followed by illumination by 470 nm blue light produced four PTTL peaks at 53, 80, 102 and 173 °C. The PTTL peaks occur at the same positions as the corresponding conventional TL peaks. Their kinetic parameters are also similar. The intensity of the PTTL peaks increased with duration of illumination to a maximum within 200 s for doses between 1 Gy and 10 Gy. The dose response of each of the PTTL peaks at 80, 102 and 173 °C is linear within 1–15 Gy. The rate of fading is low and the peaks are reproducible. When the irradiated sample is optically stimulated at temperatures between 30 °C and 300 °C, after preheating to 500 °C, the intensity of its TA-OSL goes through a peak with temperature at 200 °C. Using the rising edge of the plot, activation energy of thermal assistance for a deep electron trap was estimated as (0.21 ± 0.02) eV. The TA-OSL dose response is sublinear from 10–250 Gy and saturates thereafter. The PTTL and TA-OSL analyses signify that the concentration of deep traps in α-Al2O3:C,Mg increased after annealing at 1200 °C. As a result, the sample produced better PTTL and TA-OSL response than when annealed at lower temperature.
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Phototransferred thermoluminescence of synthetic quartz: analysis of illumination-time response curves
- Authors: Chithambo, Makaiko L , Niyonzima, P , Kalita, Jitumani M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111020 , vital:33364 , https://doi.org/10.1016/j.jlumin.2018.02.029
- Description: Phototransferred thermoluminescence (PTTL) induced in synthetic quartz by 470 nm blue light is reported. The glow curve measured at 5 °C/s up to 500 °C after irradiation to 100 Gy shows six peaks at 94, 116, 175, 212, 280 and 348 °C labelled I through VI and another one at 80 °C (labelled A1). PTTL is only observed for peaks A1 and I and is induced at peak A1 as long as peak III has been removed by preheating and at peak I after preheating to deplete peak VI. The inducement of PTTL even when all peaks have been removed points to deep electron traps in the quartz also acting as donors in addition to the putative ones below 500 °C. The PTTL intensity as a function of duration of illumination for A1 goes through a peak and decreases monotonically or to a stable value depending on the preheating temperature. The change of PTTL intensity as a function of illumination time is described using a set of coupled linear differential equations. The number of acceptors and donors in a particular system described in this way is influenced by the preheating temperature.
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Protection of internally displaced persons in Kenya under the Prevention, Protection and Assistance to Internally Displaced Persons and Affected Communities Act of 2012: an appraisal
- Authors: Juma, Laurence
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126122 , vital:35851 , https://hdl.handle.net/10520/EJC-107c9cba58
- Description: This article discusses Kenya’s Prevention, Protection and Assistance to Internally Displaced Persons and Affected Communities Act of 2012, which is among the very few national legislations globally that addresses the plight of internally displaced persons. While it records the momentous achievement in creating a viable and legally enforceable legislative framework for the protection of IDPs, the article highlights some of the areas that could be improved for the Act to realise its promise. It notes for example the inchoate manner in which institutions are created and the lack of resources. The article while isolating these challenges also suggests numerous ways in which such challenges can be overcome. It underscores the need for harmonised legal regimes, improvement of data collection and proper monitoring programmes, all which can be achieved and strengthened by a supportive political establishment as well as strategic amendments to various provisions of the Act.
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Protection of rights of urban refugees in Kenya: revisiting Kituo Cha Sheria v The Attorney General
- Authors: Juma, Laurence
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125174 , vital:35740 , DOI: 10.25159/2522-6800/3291
- Description: This article discusses the judgment in the landmark case of Kituo Cha Sheria and Others v Attorney General in the light of the emerging rights jurisprudence in the area of refugee rights. It also explores the impact the judgment could have on the articulation of the rights of urban refugees in Kenya. Based on the assumption that Kenya’s 2010 Constitution provides an opportunity for the robust enforcement of rights, the article analyses the key rights and protection imperatives that were at the centre of the dispute. These include the right to dignity, freedom of movement and to work, and also the principle of refoulement. These rights are at the core of the protection agenda for urban refugees.
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Spectral study of radioluminescence in carbon-doped aluminium oxide
- 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.
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The effect of annealing and beta irradiation on thermoluminescence spectra of α-Al2O3: C, Mg
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/112875 , vital:33669 , https://doi.org/10.1016/j.jlumin.2017.12.036
- Description: The effect of annealing on thermoluminescence spectra of beta irradiated α-Al2O3:C,Mg has been studied. Measurements were made on an un-annealed sample and samples annealed at 600, 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy shows a high intensity peak at 163 °C and six secondary peaks of weaker intensity at 43, 73, 195, 280, 329 and 370 °C. When the samples are annealed at 700 or 900 °C, an additional secondary peak appears at 100 °C. The thermoluminescence spectrum of an un-annealed sample measured at 1 °C/s between 300 and 700 nm shows the main emission band at ~ 410 nm and subsidiary emission bands at ~ 325 and 485 nm. The emission from samples annealed at 700 and 900 °C show similar bands except for a decrease in intensity of the emission at 485 nm. The emission bands at 325, 410 and 485 nm are attributed to F+, F and F22+(2Mg) -centres respectively. The decrease of the emission band at 485 nm is deduced to be due to the destruction of the F22+(2Mg) centre at 700 °C. The emission bands are unaffected by irradiation dose between 10 and 320 Gy. However, when the sample is annealed at or beyond 700 °C, any effects on the F+ and F centres emission can be easier distinguished particularly for doses greater than 10 Gy.
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The effect of pre-dose on thermally and optically stimulated luminescence from α-Al2O3C, Mg and α-Al2O3: C
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111011 , vital:33363 , https://doi.org/10.1016/j.apradiso.2018.06.012
- Description: We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.
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