Do microplastic loads reflect the population demographics along the southern African coastline?
- Nel, Holly A, Hean, Jeffrey W, Noundou, Xavier S, Froneman, P William
- Authors: Nel, Holly A , Hean, Jeffrey W , Noundou, Xavier S , Froneman, P William
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67961 , vital:29174 , https://doi.org/10.1016/j.marpolbul.2016.11.056
- Description: Publisher version , Plastic pollution is a major anthropogenic contaminant effecting the marine environment and is often associated with high human population densities and industrial activities. The microplastic (63 to 5000 μm) burden of beach sediment and surf-zone water was investigated at selected sites along the entire length of the South African coastline. It was predicted that samples collected in areas of high population density, would contain a higher microplastic burden than those along coasts that demonstrate very low population densities. With the exception of water column microplastics within Richard's Bay Harbour (413.3 ± 77.53 particles·m− 3) and Durban Harbour (1200 ± 133.2 particles·m− 3), there were no significant spatial differences in microplastic loads. This supports the theory that harbours act as a source of microplastics for the surrounding marine environment. Additionally, the absence of any spatial variation highlights the possible long range distribution of microplastic pollutants by large scale ocean currents.
- Full Text: false
- Date Issued: 2017
- Authors: Nel, Holly A , Hean, Jeffrey W , Noundou, Xavier S , Froneman, P William
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67961 , vital:29174 , https://doi.org/10.1016/j.marpolbul.2016.11.056
- Description: Publisher version , Plastic pollution is a major anthropogenic contaminant effecting the marine environment and is often associated with high human population densities and industrial activities. The microplastic (63 to 5000 μm) burden of beach sediment and surf-zone water was investigated at selected sites along the entire length of the South African coastline. It was predicted that samples collected in areas of high population density, would contain a higher microplastic burden than those along coasts that demonstrate very low population densities. With the exception of water column microplastics within Richard's Bay Harbour (413.3 ± 77.53 particles·m− 3) and Durban Harbour (1200 ± 133.2 particles·m− 3), there were no significant spatial differences in microplastic loads. This supports the theory that harbours act as a source of microplastics for the surrounding marine environment. Additionally, the absence of any spatial variation highlights the possible long range distribution of microplastic pollutants by large scale ocean currents.
- Full Text: false
- Date Issued: 2017
Journal development, scholar development and quality
- Rosenberg, Eureta, Togo, Muchaiteyi
- Authors: Rosenberg, Eureta , Togo, Muchaiteyi
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67314 , vital:29072 , https://doi.org/10.4314/SAJEE.V.33I1.1
- Description: publisher version , In reflecting on the contributions to Volume 33, it is evident that a variety of theories about learning and social change inform the scholars in environmental education, ranging from behaviourist, to social behavioural, constructivist and social constructivist learning theories, social and critical realism, and more. What unites these papers is a shared concern about learning in relation to the future well-being of the planet and its people. New scholars entering the field of environmental and sustainability education have the task of mastering not only the social– ecological subject matter of the field, but also their chosen learning theories. In this regard, drawing on the back copies of the SAJEE can be of great value. Much research and writing has already been done on curriculum, education and learning inside and outside of formal institutions, yet many more questions remain. The field is best advanced by noting and building on, challenging and advancing past studies and existing scholarship. The fact that all 33 Volumes of the SAJEE are available online, just a ‘few clicks away’ from any student or supervisor with Internet access, is therefore an enormous boon. We encourage readers and future authors to draw on the work in this and other environmental education journals as they conceptualise, design and reflect on their own studies.
- Full Text:
- Date Issued: 2017
- Authors: Rosenberg, Eureta , Togo, Muchaiteyi
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67314 , vital:29072 , https://doi.org/10.4314/SAJEE.V.33I1.1
- Description: publisher version , In reflecting on the contributions to Volume 33, it is evident that a variety of theories about learning and social change inform the scholars in environmental education, ranging from behaviourist, to social behavioural, constructivist and social constructivist learning theories, social and critical realism, and more. What unites these papers is a shared concern about learning in relation to the future well-being of the planet and its people. New scholars entering the field of environmental and sustainability education have the task of mastering not only the social– ecological subject matter of the field, but also their chosen learning theories. In this regard, drawing on the back copies of the SAJEE can be of great value. Much research and writing has already been done on curriculum, education and learning inside and outside of formal institutions, yet many more questions remain. The field is best advanced by noting and building on, challenging and advancing past studies and existing scholarship. The fact that all 33 Volumes of the SAJEE are available online, just a ‘few clicks away’ from any student or supervisor with Internet access, is therefore an enormous boon. We encourage readers and future authors to draw on the work in this and other environmental education journals as they conceptualise, design and reflect on their own studies.
- Full Text:
- Date Issued: 2017
Journal Development, Scholar Development and Quality
- Rosenberg, Eureta, Togo, Muchaiteyi
- Authors: Rosenberg, Eureta , Togo, Muchaiteyi
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127235 , vital:35980 , https://doi.org/10.4314/sajee.v.33i1.1
- Description: Recently, the 33-year journey of the Southern African Journal of Environmental Education (SAJEE) was the subject of reflection during an Open Access Publishing week convened by Rhodes University Library Services. Two former and current editors-in-chief shared the SAJEE’s story of publishing ‘from the margins into the centre’. In the early 1990s, the Journal was mailed to the Environmental Education Association of Southern Africa (EEASA) membership from the foyer of the Rhodes Education Department (which had the floor space for stuffing and stacking A4 envelopes). In the first decade of this century, the Journal arrived at a symbolic ‘centre’ with digital distribution, first on the EEASA website and then from the Open Access platform provided by African Journals Online (AJOL). The digital move was vital for sustained and increased distribution in a time of shrinking budgets and growing costs. The results, shared with the EEASA Council earlier this year, were nothing short of spectacular: In March 2017, the SAJEE received more than 1 250 article downloads (www.ajol.info/index.php/sajee), and the number of downloads have stayed above 500 each month subsequently (Figure 1). Views and downloads are recorded around the world including,
- Full Text:
- Date Issued: 2017
- Authors: Rosenberg, Eureta , Togo, Muchaiteyi
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127235 , vital:35980 , https://doi.org/10.4314/sajee.v.33i1.1
- Description: Recently, the 33-year journey of the Southern African Journal of Environmental Education (SAJEE) was the subject of reflection during an Open Access Publishing week convened by Rhodes University Library Services. Two former and current editors-in-chief shared the SAJEE’s story of publishing ‘from the margins into the centre’. In the early 1990s, the Journal was mailed to the Environmental Education Association of Southern Africa (EEASA) membership from the foyer of the Rhodes Education Department (which had the floor space for stuffing and stacking A4 envelopes). In the first decade of this century, the Journal arrived at a symbolic ‘centre’ with digital distribution, first on the EEASA website and then from the Open Access platform provided by African Journals Online (AJOL). The digital move was vital for sustained and increased distribution in a time of shrinking budgets and growing costs. The results, shared with the EEASA Council earlier this year, were nothing short of spectacular: In March 2017, the SAJEE received more than 1 250 article downloads (www.ajol.info/index.php/sajee), and the number of downloads have stayed above 500 each month subsequently (Figure 1). Views and downloads are recorded around the world including,
- Full Text:
- Date Issued: 2017
Learning Zulu: a secret history of language in South Africa
- Authors: Wylie, Dan
- Date: 2017
- Language: English
- Type: book review , text
- Identifier: http://hdl.handle.net/10962/61255 , vital:27997 , https://www.ajol.info/index.php/tvl/article/view/160848
- Description: Taking a leaf from the book under review, I’ll start by injecting an autobiographical element. Much of what Sanders examines here echoes my own experience, after Zimbabwe’s independence, of heading to a remote mission school to teach for two years. Part of my purpose was to learn better Shona, the majority language from which I had been systematically discouraged by my colonial education. It was, in a way, a gesture of reparation, or addressing a nagging “white guilt”, or at least of assuaging a sense of fruitless loss and exclusion. I was nowhere near as successful in attaining fluency as Sanders seems have been in learning Zulu; and now that I live in the Eastern Cape, my efforts to learn Xhosa have been similarly patchy and faltering. One thing is evident throughout Sanders’s dense discussions: long-term, assiduous application and pe¬riods of total immersion are vital—and as he points out, few whites in South Africa have carved out the time and energy to do so, while willy-nilly expecting the black majority to learn their language. (An endnote does aver that, according to census figures, a surprising 16,000-plus whites, and a similar number of Indians, in KwaZulu-Natal, list Zulu as their first language.)
- Full Text:
- Date Issued: 2017
- Authors: Wylie, Dan
- Date: 2017
- Language: English
- Type: book review , text
- Identifier: http://hdl.handle.net/10962/61255 , vital:27997 , https://www.ajol.info/index.php/tvl/article/view/160848
- Description: Taking a leaf from the book under review, I’ll start by injecting an autobiographical element. Much of what Sanders examines here echoes my own experience, after Zimbabwe’s independence, of heading to a remote mission school to teach for two years. Part of my purpose was to learn better Shona, the majority language from which I had been systematically discouraged by my colonial education. It was, in a way, a gesture of reparation, or addressing a nagging “white guilt”, or at least of assuaging a sense of fruitless loss and exclusion. I was nowhere near as successful in attaining fluency as Sanders seems have been in learning Zulu; and now that I live in the Eastern Cape, my efforts to learn Xhosa have been similarly patchy and faltering. One thing is evident throughout Sanders’s dense discussions: long-term, assiduous application and pe¬riods of total immersion are vital—and as he points out, few whites in South Africa have carved out the time and energy to do so, while willy-nilly expecting the black majority to learn their language. (An endnote does aver that, according to census figures, a surprising 16,000-plus whites, and a similar number of Indians, in KwaZulu-Natal, list Zulu as their first language.)
- Full Text:
- Date Issued: 2017
Pessimistic assessment of white shark population status in South Africa: comment on Andreotti et al.(2016)
- Irion, Dylan T, Noble, Leslie R, Kock, Alison A, Gennari, Enrico, Dicken, Matthew L, Hewitt, Adrian M, Towner, Alison V, Booth, Anthony J, Smale, Malcolm J, Cliff, Geremy
- Authors: Irion, Dylan T , Noble, Leslie R , Kock, Alison A , Gennari, Enrico , Dicken, Matthew L , Hewitt, Adrian M , Towner, Alison V , Booth, Anthony J , Smale, Malcolm J , Cliff, Geremy
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:35799 , https://doi.10.3354/meps12283
- Description: Andreotti et al. (2016; Mar Ecol Prog Ser 552:241−253) estimate an abundance (N) of 438 white sharks Carcharodon carcharias and a contemporary effective population size (CNe) of 333 individuals along the South African coast. N was estimated by using a mark-recapture analysis of photographic identification records from a single aggregation site (Gansbaai). CNe was calculated based on the levels of pairwise linkage disequilibrium of genetic material collected from 4 aggregation sites across approximately 965 km of South African coastline. However, due to the complex stock structure of white sharks and the model assumptions made by Andreotti et al. (2016), the conclusions drawn cannot be supported by their methods and data.
- Full Text:
- Date Issued: 2017
- Authors: Irion, Dylan T , Noble, Leslie R , Kock, Alison A , Gennari, Enrico , Dicken, Matthew L , Hewitt, Adrian M , Towner, Alison V , Booth, Anthony J , Smale, Malcolm J , Cliff, Geremy
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:35799 , https://doi.10.3354/meps12283
- Description: Andreotti et al. (2016; Mar Ecol Prog Ser 552:241−253) estimate an abundance (N) of 438 white sharks Carcharodon carcharias and a contemporary effective population size (CNe) of 333 individuals along the South African coast. N was estimated by using a mark-recapture analysis of photographic identification records from a single aggregation site (Gansbaai). CNe was calculated based on the levels of pairwise linkage disequilibrium of genetic material collected from 4 aggregation sites across approximately 965 km of South African coastline. However, due to the complex stock structure of white sharks and the model assumptions made by Andreotti et al. (2016), the conclusions drawn cannot be supported by their methods and data.
- Full Text:
- Date Issued: 2017
Potential of entomopathogenic fungal isolates for Control of the soil-dwelling life stages of Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) in citrus
- Coombes, Candice A, Hill, Martin P, Dames, Joanna F
- Authors: Coombes, Candice A , Hill, Martin P , Dames, Joanna F
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59885 , vital:27684 , https://doi.org/10.4001/003.025.0235
- Description: Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is a key pest of citrus in South Africa. In addition to the fruit damage caused, export markets such as the United States, South Korea and China regulate T. leucotreta as a phytosanitary organism in addition to restricting the use of pesticides on exported fruit (Grout & Moore 2015; SA-DAFF 2015). The bulk of citrus in South Africa is exported (Citrus Growers' Association 2015). Thus, the control of T. leucotreta is crucial. Consequently, the citrus industry adopts a zero tolerance approach controlling the pest, being strongly reliant on integrated pest management (Moore & Hattingh 2012). Numerous control options are available, but are largely limited to use against the above-ground life stages of this pest: eggs, neonates and adults (Moore & Hattingh 2012; Grout & Moore 2015).
- Full Text:
- Date Issued: 2017
- Authors: Coombes, Candice A , Hill, Martin P , Dames, Joanna F
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59885 , vital:27684 , https://doi.org/10.4001/003.025.0235
- Description: Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is a key pest of citrus in South Africa. In addition to the fruit damage caused, export markets such as the United States, South Korea and China regulate T. leucotreta as a phytosanitary organism in addition to restricting the use of pesticides on exported fruit (Grout & Moore 2015; SA-DAFF 2015). The bulk of citrus in South Africa is exported (Citrus Growers' Association 2015). Thus, the control of T. leucotreta is crucial. Consequently, the citrus industry adopts a zero tolerance approach controlling the pest, being strongly reliant on integrated pest management (Moore & Hattingh 2012). Numerous control options are available, but are largely limited to use against the above-ground life stages of this pest: eggs, neonates and adults (Moore & Hattingh 2012; Grout & Moore 2015).
- Full Text:
- Date Issued: 2017
Radioluminescence of annealed synthetic quartz
- Chithambo, Makaiko L, Niyonzima, P
- Authors: Chithambo, Makaiko L , Niyonzima, P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115504 , vital:34150 , https://doi.org/10.1016/j.radmeas.2017.02.005
- Description: The radioluminescence of synthetic quartz annealed at various temperatures up to 1000 °C is reported. The amplitude of the emission bands increases with annealing temperature. In addition, when samples are annealed at temperatures exceeding 700 °C, the intensity of the radioluminescence increases with duration of annealing. The corresponding emission spectra show seven emission bands at 2.04, 2.54, 2.77, 3.04, 3.40, 3.75 and 3.91 eV. The change in dominant emission band with annealing is consistent with annealing-induced variations in lifetimes determined previously from time-resolved optically stimulated luminescence spectra in the same samples.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L , Niyonzima, P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115504 , vital:34150 , https://doi.org/10.1016/j.radmeas.2017.02.005
- Description: The radioluminescence of synthetic quartz annealed at various temperatures up to 1000 °C is reported. The amplitude of the emission bands increases with annealing temperature. In addition, when samples are annealed at temperatures exceeding 700 °C, the intensity of the radioluminescence increases with duration of annealing. The corresponding emission spectra show seven emission bands at 2.04, 2.54, 2.77, 3.04, 3.40, 3.75 and 3.91 eV. The change in dominant emission band with annealing is consistent with annealing-induced variations in lifetimes determined previously from time-resolved optically stimulated luminescence spectra in the same samples.
- Full Text: false
- Date Issued: 2017
Suspense, the serious and the superman:
- Authors: Western, Rat
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147726 , vital:38664 , https://doi.org/10.1080/00043389.2012.11877164
- Description: When considering what to do with one’s Friday night, probably very few people would consider a two-hour formal lecture a top priority. But this is a Friday night in Grahamstown, where novelty in leisure and entertainment choices, outside of festival time, is a rarity. It is therefore unsurprising that, on the evening of 11 November 2011, the Rhodes Box Theatre is packed by 7 pm with a variety of students, academics, members of the local alternative scene and the general public.
- Full Text:
- Date Issued: 2017
- Authors: Western, Rat
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147726 , vital:38664 , https://doi.org/10.1080/00043389.2012.11877164
- Description: When considering what to do with one’s Friday night, probably very few people would consider a two-hour formal lecture a top priority. But this is a Friday night in Grahamstown, where novelty in leisure and entertainment choices, outside of festival time, is a rarity. It is therefore unsurprising that, on the evening of 11 November 2011, the Rhodes Box Theatre is packed by 7 pm with a variety of students, academics, members of the local alternative scene and the general public.
- Full Text:
- Date Issued: 2017
Temperature dependence of optically stimulated luminescence of α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115708 , vital:34217 , https://doi.org/10.1016/j.radmeas.2017.08.009
- Description: Thermal assistance and thermal quenching are two independently acting thermodynamic phenomena that simultaneously affect the stimulation of luminescence. We have studied thermal assistance to luminescence optically stimulated from α-Al2O3:C,Mg. Since thermal assistance causes only a minor change in the luminescence intensity, measurements were made after the sample had been pre-exposed to stimulating light to reduce its intensity significantly, that is, in the slow component of its decay curve. The luminescence intensity was monitored as a function of measurement temperature between 30 and 130 °C. The intensity goes through a peak at 60 °C due to competing effects of thermal assistance and thermal quenching. The initial increase of intensity is attributed to dominant thermal assistance whereas the subsequent decrease of intensity is ascribed to dominant thermal quenching. The activation energy for thermal assistance was calculated for the main electron trap of an un-annealed sample as 0.324 ± 0.020 eV and in a sample annealed at 900 °C as 0.416 ± 0.028 eV. Implications of such differences in the value of the activation energy for thermal assistance are considered.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/115708 , vital:34217 , https://doi.org/10.1016/j.radmeas.2017.08.009
- Description: Thermal assistance and thermal quenching are two independently acting thermodynamic phenomena that simultaneously affect the stimulation of luminescence. We have studied thermal assistance to luminescence optically stimulated from α-Al2O3:C,Mg. Since thermal assistance causes only a minor change in the luminescence intensity, measurements were made after the sample had been pre-exposed to stimulating light to reduce its intensity significantly, that is, in the slow component of its decay curve. The luminescence intensity was monitored as a function of measurement temperature between 30 and 130 °C. The intensity goes through a peak at 60 °C due to competing effects of thermal assistance and thermal quenching. The initial increase of intensity is attributed to dominant thermal assistance whereas the subsequent decrease of intensity is ascribed to dominant thermal quenching. The activation energy for thermal assistance was calculated for the main electron trap of an un-annealed sample as 0.324 ± 0.020 eV and in a sample annealed at 900 °C as 0.416 ± 0.028 eV. Implications of such differences in the value of the activation energy for thermal assistance are considered.
- Full Text: false
- Date Issued: 2017
Thermally-assisted optically stimulated luminescence from deep electron traps in α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L, Polymeris, G S
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L , Polymeris, G S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116133 , vital:34322 , https://doi.org/10.1016/j.nimb.2017.04.075
- Description: We report thermally-assisted optically stimulated luminescence (TA-OSL) in α-Al2O3:C,Mg. The OSL was measured at elevated temperatures between 50 and 240 °C from a sample preheated to 500 °C after irradiation to 100 Gy. That OSL could be measured even after the preheating is direct evidence of the existence of deep electron traps in α-Al2O3:C,Mg. The TA-OSL intensity goes through a peak with measurement temperature. The initial increase is ascribed to thermal assistance to optical stimulation whereas the subsequent decrease in intensity is deduced to reflect increasing incidences of non-radiative recombination, that is, thermal quenching. The activation energy for thermal assistance corresponding to a deep electron trap was estimated as 0.667 ± 0.006 eV whereas the activation energy for thermal quenching was calculated as 0.90 ± 0.04 eV. The intensity of the TA-OSL was also found to increase with irradiation dose. The dose response is sublinear from 25 to 150 Gy but saturates with further increase of dose. The TA-OSL dose response has been discussed by considering the competition for charges at the deep traps. This study incidentally shows that TA-OSL can be effectively used in dosimetry involving large doses.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L , Polymeris, G S
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/116133 , vital:34322 , https://doi.org/10.1016/j.nimb.2017.04.075
- Description: We report thermally-assisted optically stimulated luminescence (TA-OSL) in α-Al2O3:C,Mg. The OSL was measured at elevated temperatures between 50 and 240 °C from a sample preheated to 500 °C after irradiation to 100 Gy. That OSL could be measured even after the preheating is direct evidence of the existence of deep electron traps in α-Al2O3:C,Mg. The TA-OSL intensity goes through a peak with measurement temperature. The initial increase is ascribed to thermal assistance to optical stimulation whereas the subsequent decrease in intensity is deduced to reflect increasing incidences of non-radiative recombination, that is, thermal quenching. The activation energy for thermal assistance corresponding to a deep electron trap was estimated as 0.667 ± 0.006 eV whereas the activation energy for thermal quenching was calculated as 0.90 ± 0.04 eV. The intensity of the TA-OSL was also found to increase with irradiation dose. The dose response is sublinear from 25 to 150 Gy but saturates with further increase of dose. The TA-OSL dose response has been discussed by considering the competition for charges at the deep traps. This study incidentally shows that TA-OSL can be effectively used in dosimetry involving large doses.
- Full Text: false
- Date Issued: 2017
Thermoluminescence of α-Al2O3: C, Mg: kinetic analysis of the main glow peak
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119844 , vital:34788 , https://doi.org/10.1016/j.jlumin.2016.10.031
- Description: The kinetic analysis of the thermoluminescence of aluminium oxide doped with carbon and co-doped with magnesium (α-Al2O3:C,Mg) is reported. Measurements were made at 1 °C/s following beta irradiation to 1 Gy. The glow curve consists of a dominant peak at a peak-maximum Tm of 161 °C and six secondary peaks of weaker intensity at 42, 72, 193, 279, 330 and 370 °C. Kinetic analysis of the main peak, the subject of this report, was carried out using initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the main peak was determined as first order using various methods including the Tm–Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about ~1.36 eV and the frequency factor of the order of 1014 s−1. The peak area changes with heating rate in a manner that shows that the peak is affected by thermal quenching. The activation energy of thermal quenching was evaluated as 0.99±0.08 eV. A comparison of analytical results from the main peak before and after correction for thermal quenching show that the kinetic parameters of the main peak are not that affected by thermal quenching.
- Full Text: false
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/119844 , vital:34788 , https://doi.org/10.1016/j.jlumin.2016.10.031
- Description: The kinetic analysis of the thermoluminescence of aluminium oxide doped with carbon and co-doped with magnesium (α-Al2O3:C,Mg) is reported. Measurements were made at 1 °C/s following beta irradiation to 1 Gy. The glow curve consists of a dominant peak at a peak-maximum Tm of 161 °C and six secondary peaks of weaker intensity at 42, 72, 193, 279, 330 and 370 °C. Kinetic analysis of the main peak, the subject of this report, was carried out using initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the main peak was determined as first order using various methods including the Tm–Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about ~1.36 eV and the frequency factor of the order of 1014 s−1. The peak area changes with heating rate in a manner that shows that the peak is affected by thermal quenching. The activation energy of thermal quenching was evaluated as 0.99±0.08 eV. A comparison of analytical results from the main peak before and after correction for thermal quenching show that the kinetic parameters of the main peak are not that affected by thermal quenching.
- Full Text: false
- Date Issued: 2017
Unexpected transformations of 3-(bromoacetyl)coumarin provides new evidence for the mechanism of thiol mediated dehalogenation of α-halocarbonyls
- Magwenzi, Faith N, Khanye, Setshaba D, Veale, Clinton G L
- Authors: Magwenzi, Faith N , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66200 , vital:28916 , https://doi.org/10.1016/j.tetlet.2017.01.082
- Description: publisher version , The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.
- Full Text: false
- Date Issued: 2017
- Authors: Magwenzi, Faith N , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66200 , vital:28916 , https://doi.org/10.1016/j.tetlet.2017.01.082
- Description: publisher version , The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.
- Full Text: false
- Date Issued: 2017
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