Phototransferred thermoluminescence and thermally-assisted optically stimulated luminescence dosimetry using α-Al2O3:C,Mg annealed at 1200°C
- Kalita, Jitumani M, Chithambo, Makaiko L
- 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.
- Full Text: false
- Date Issued: 2018
- 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.
- Full Text: false
- Date Issued: 2018
A study of the kinetics of a high temperature thermoluminescence peak in annealed natural quartz
- Thomas, Sunil, Chithambo, Makaiko L
- 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.
- Full Text: false
- Date Issued: 2018
- 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.
- Full Text: false
- Date Issued: 2018
The effect of annealing and beta irradiation on thermoluminescence spectra of α-Al2O3: C, Mg
- Kalita, Jitumani M, Chithambo, Makaiko L
- 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.
- Full Text: false
- Date Issued: 2018
- 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.
- Full Text: false
- Date Issued: 2018
Spermatophore dimorphism in the chokka squid Loligo reynaudii associated with alternative mating tactics
- Sato, Noriyosi, Iwata, Yoko, Shaw, Paul W, Sauer, Warwick H H
- Authors: Sato, Noriyosi , Iwata, Yoko , Shaw, Paul W , Sauer, Warwick H H
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127070 , vital:35952 , https://doi.10.1093/mollus/eyy002
- Description: Chokka squid (Loligo reynaudii) have characteristic alternative mating tactics: ‘consort’ males temporarily pair with and guard a female and transfer spermatophores onto her oviduct opening inside the mantle cavity, whereas ‘sneaker’ males rush towards a mating pair and transfer spermatophores onto the female’s buccal membrane near her sperm storage organ. Differences in mating behaviours and their related sperm-storage sites clearly constrain the fertilization process and can drive dimorphism between consort and sneaker males. The presence and character of male dimorphism has not yet been fully examined in this species, but consort males are commonly much larger than sneaker males. We observed clear dimorphism in spermatangia (the sperm mass ejaculated from the spermatophore), consistently associated with the two alternative sperm storage sites on the female’s body. Observations of spermatophores stored in the Needham’s sac of mature males confirmed that small males produce ‘sneaker-type’ spermatangia whereas larger males produce ‘consort-type’ spermatangia, and no individuals possessed both types. Therefore, by association, the mating tactic adopted (including the sperm deposition site used) by individual males can be determined from observation of their spermatangial type, without requiring direct behavioural observation of mating. This ability to infer information about mating tactic will improve our understanding of the reproductive system and mating dynamics in this species.
- Full Text:
- Date Issued: 2018
- Authors: Sato, Noriyosi , Iwata, Yoko , Shaw, Paul W , Sauer, Warwick H H
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/127070 , vital:35952 , https://doi.10.1093/mollus/eyy002
- Description: Chokka squid (Loligo reynaudii) have characteristic alternative mating tactics: ‘consort’ males temporarily pair with and guard a female and transfer spermatophores onto her oviduct opening inside the mantle cavity, whereas ‘sneaker’ males rush towards a mating pair and transfer spermatophores onto the female’s buccal membrane near her sperm storage organ. Differences in mating behaviours and their related sperm-storage sites clearly constrain the fertilization process and can drive dimorphism between consort and sneaker males. The presence and character of male dimorphism has not yet been fully examined in this species, but consort males are commonly much larger than sneaker males. We observed clear dimorphism in spermatangia (the sperm mass ejaculated from the spermatophore), consistently associated with the two alternative sperm storage sites on the female’s body. Observations of spermatophores stored in the Needham’s sac of mature males confirmed that small males produce ‘sneaker-type’ spermatangia whereas larger males produce ‘consort-type’ spermatangia, and no individuals possessed both types. Therefore, by association, the mating tactic adopted (including the sperm deposition site used) by individual males can be determined from observation of their spermatangial type, without requiring direct behavioural observation of mating. This ability to infer information about mating tactic will improve our understanding of the reproductive system and mating dynamics in this species.
- Full Text:
- Date Issued: 2018
Influence of annealing on thermoluminescence of natural quartz: kinetic analysis and experimental study of apparent inverse thermal quenching
- Folley, Damilola E, Chithambo, Makaiko L
- 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.
- Full Text: false
- Date Issued: 2018
- 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.
- Full Text: false
- Date Issued: 2018
Biological activity of plant extracts and isolated compounds from Alchornea laxiflora: Anti-HIV, antibacterial and cytotoxicity evaluation
- Ndinteh, Derek T, Olivier, D K, Noundou, Xavier S, Krause, Rui W M, Mnkandhla, D, Isaacs, Michelle, Hoppe, Heinrich C, Muganza, F M, Mbafor, J T, Van Vuuren, S F, Patnala, S
- Authors: Ndinteh, Derek T , Olivier, D K , Noundou, Xavier S , Krause, Rui W M , Mnkandhla, D , Isaacs, Michelle , Hoppe, Heinrich C , Muganza, F M , Mbafor, J T , Van Vuuren, S F , Patnala, S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126634 , vital:35907 , https://doi.org/10.1016/j.sajb.2018.08.010
- Description: This study was designed to assess the cytotoxicity, anti-HIV and antibacterial efficacy of various solvent extracts of roots, stem and leaves of Alchornea laxiflora, as well as five compounds isolated from its methanolic stem extract viz.; ellagic acid (1); 3-O-methyl-ellagic acid (2), 3-O-β-d-glucopyranosyl-β-sitosterol (3), 3-O-acetyl-oleanolic acid (4) and 3-O-acetyl-ursolic acid (5). The tested crude extracts were prepared from several solvent polarities including: hexane (Hex), chloroform (CHCl3), ethyl acetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O). The anti-HIV properties were assessed on HIV-1 subtype C integrase while the cytotoxicity was tested against Hela cells. The antibacterial activity was studied on a panel of pathogens including gastrointestinal, skin, respiratory and urinary-tract infection causing Gram positive bacteria viz.; Bacillus cereus (ATCC 11778), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25923) and Staphylococcus saprophyticus (ATCC 15305)] and Gram-negative bacteria, i.e., Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Moraxella catarrhalis (ATCC 23246). All the tested samples were determined to be non-toxic due to the low inhibitions observed. The most potent anti-HIV activity was observed for the methanolic extract of A. laxiflora root (ALR4) with an IC50 value of 0.21 ng/ml, which was more active than chicoric acid used as reference drug (6.82 nM). Roots, stem and leaves of A. laxiflora extracts exhibited antibacterial activities against most of the Gram-positive bacteria with the minimum inhibitory concentrations (MIC) ranging between 50 and 63 μg/ml. Compounds 1–5 displayed antibacterial activities against S. saprophyticus with MIC values as low as 4 μg/ml. The results inferred from this study demonstrate the potential of A. laxiflora root as a source for new anti-HIV drugs and scientifically validate the traditional use of A. laxiflora in the treatment of gastrointestinal, skin, respiratory and urinary tract related infections. These results reaffirm the ethnopharmacological significance of African traditional medicines.
- Full Text:
- Date Issued: 2018
- Authors: Ndinteh, Derek T , Olivier, D K , Noundou, Xavier S , Krause, Rui W M , Mnkandhla, D , Isaacs, Michelle , Hoppe, Heinrich C , Muganza, F M , Mbafor, J T , Van Vuuren, S F , Patnala, S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126634 , vital:35907 , https://doi.org/10.1016/j.sajb.2018.08.010
- Description: This study was designed to assess the cytotoxicity, anti-HIV and antibacterial efficacy of various solvent extracts of roots, stem and leaves of Alchornea laxiflora, as well as five compounds isolated from its methanolic stem extract viz.; ellagic acid (1); 3-O-methyl-ellagic acid (2), 3-O-β-d-glucopyranosyl-β-sitosterol (3), 3-O-acetyl-oleanolic acid (4) and 3-O-acetyl-ursolic acid (5). The tested crude extracts were prepared from several solvent polarities including: hexane (Hex), chloroform (CHCl3), ethyl acetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O). The anti-HIV properties were assessed on HIV-1 subtype C integrase while the cytotoxicity was tested against Hela cells. The antibacterial activity was studied on a panel of pathogens including gastrointestinal, skin, respiratory and urinary-tract infection causing Gram positive bacteria viz.; Bacillus cereus (ATCC 11778), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25923) and Staphylococcus saprophyticus (ATCC 15305)] and Gram-negative bacteria, i.e., Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Moraxella catarrhalis (ATCC 23246). All the tested samples were determined to be non-toxic due to the low inhibitions observed. The most potent anti-HIV activity was observed for the methanolic extract of A. laxiflora root (ALR4) with an IC50 value of 0.21 ng/ml, which was more active than chicoric acid used as reference drug (6.82 nM). Roots, stem and leaves of A. laxiflora extracts exhibited antibacterial activities against most of the Gram-positive bacteria with the minimum inhibitory concentrations (MIC) ranging between 50 and 63 μg/ml. Compounds 1–5 displayed antibacterial activities against S. saprophyticus with MIC values as low as 4 μg/ml. The results inferred from this study demonstrate the potential of A. laxiflora root as a source for new anti-HIV drugs and scientifically validate the traditional use of A. laxiflora in the treatment of gastrointestinal, skin, respiratory and urinary tract related infections. These results reaffirm the ethnopharmacological significance of African traditional medicines.
- Full Text:
- Date Issued: 2018
Thermoluminescence of annealed synthetic quartz: the influence of annealing on kinetic parameters and thermal quenching
- Dawam, Robert R, Chithambo, Makaiko L
- Authors: Dawam, Robert R , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110050 , vital:33218 , https://doi.org/10.1016/j.radmeas.2018.06.004
- Description: The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 oCs−1 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 0.90±0.02eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 0.65±0.02eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 0.65±0.02eV, 0.82±0.02eV and 0.95±0.06eV. Evidently, annealing affects recombination processes in synthetic quartz.
- Full Text: false
- Date Issued: 2018
- Authors: Dawam, Robert R , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110050 , vital:33218 , https://doi.org/10.1016/j.radmeas.2018.06.004
- Description: The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 oCs−1 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 0.90±0.02eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 0.65±0.02eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 0.65±0.02eV, 0.82±0.02eV and 0.95±0.06eV. Evidently, annealing affects recombination processes in synthetic quartz.
- Full Text: false
- Date Issued: 2018
General features and kinetic analysis of thermoluminescence from annealed natural quartz
- Thomas, Sunil, Chithambo, Makaiko L
- 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.
- Full Text: false
- Date Issued: 2018
- 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.
- Full Text: false
- Date Issued: 2018
A New Synthetic Method for Tetraazatricyclic Derivatives and Evaluation of Their Biological Properties
- Odame, Felix, Betz, Richard, Hosten, Eric C, Krause, Jason, Isaacs, Michelle, Hoppe, Heinrich C, Khanye, Setshaba D, Sayed, Yasien, Frost, P Carminita, Lobb, Kevin A, Tshentu, Zenixole
- Authors: Odame, Felix , Betz, Richard , Hosten, Eric C , Krause, Jason , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Sayed, Yasien , Frost, P Carminita , Lobb, Kevin A , Tshentu, Zenixole
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123189 , vital:35413 , https://doi.org/10.1002/slct.201802930
- Description: Herein, we propose novel quinolones incorporating an INH moiety as potential drug templates against TB. The quinolone-based compounds bearing an INH moiety attached via a hydrazide–hydrazone bond were synthesised and evaluated against Mycobacterium tuberculosis H37Rv (MTB). The compounds were also evaluated for cytotoxicity against HeLa cell lines. These compounds showed significant activity (MIC90) against MTB in the range of 0.2–8 μM without any cytotoxic effects. Compounds 10 (MIC90; 0.9 μM), 11 (MIC90; 0.2 μM), 12 (MIC90; 0.8 μM) and compound 15 (MIC90; 0.8 μM), the most active compounds in this series, demonstrate activities on par with INH and superior to those reported for the fluoroquinolones. The SAR analysis suggests that the nature of substituents at positions −1 and −3 of the quinolone nucleus influences anti-MTB activity. Aqueous solubility evaluation and in vitro metabolic stability of compound 12 highlights favourable drug-like properties for this compound class.
- Full Text:
- Date Issued: 2018
- Authors: Odame, Felix , Betz, Richard , Hosten, Eric C , Krause, Jason , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D , Sayed, Yasien , Frost, P Carminita , Lobb, Kevin A , Tshentu, Zenixole
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123189 , vital:35413 , https://doi.org/10.1002/slct.201802930
- Description: Herein, we propose novel quinolones incorporating an INH moiety as potential drug templates against TB. The quinolone-based compounds bearing an INH moiety attached via a hydrazide–hydrazone bond were synthesised and evaluated against Mycobacterium tuberculosis H37Rv (MTB). The compounds were also evaluated for cytotoxicity against HeLa cell lines. These compounds showed significant activity (MIC90) against MTB in the range of 0.2–8 μM without any cytotoxic effects. Compounds 10 (MIC90; 0.9 μM), 11 (MIC90; 0.2 μM), 12 (MIC90; 0.8 μM) and compound 15 (MIC90; 0.8 μM), the most active compounds in this series, demonstrate activities on par with INH and superior to those reported for the fluoroquinolones. The SAR analysis suggests that the nature of substituents at positions −1 and −3 of the quinolone nucleus influences anti-MTB activity. Aqueous solubility evaluation and in vitro metabolic stability of compound 12 highlights favourable drug-like properties for this compound class.
- Full Text:
- Date Issued: 2018
Characteristics of the thermoluminescence of Sm3+-doped P2O5-K2O-MgO-Al2O3-ZnF2 glass
- Thomas, Sunil, Chithambo, Makaiko L
- 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.
- Full Text: false
- Date Issued: 2018
- 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.
- Full Text: false
- Date Issued: 2018
Establishment of “The South African Bioinformatics Student Council” and activity highlights:
- Rafael, Candice Nancy, Ambler, Jon, Niehaus, Antoinette, Ross, James, Tastan Bishop, Özlem
- Authors: Rafael, Candice Nancy , Ambler, Jon , Niehaus, Antoinette , Ross, James , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148250 , vital:38723 , https://doi.org/10.14806/ej.23.0.903
- Description: The South African Society for Bioinformatics1 (SASBi) was officially formed in September 2012 during a joint Congress with the South African Genetics Society (SAGS). Prior to this there was no official body to represent bioinformatic researchers and students in the country. The establishment of SASBi also led to the establishment of the Student Society as a platform for students to meet and discuss their research activities, but also to socialise and broaden their network of knowledge and friendships. A small group of students joined as volunteers to pioneer and set up a SASBi Student Council (SASBiSC). As a first step, one representative, selected from the attendees present at the first Joint Congress of SASBi and SAGS, was elected to the main SASBi Council.
- Full Text:
- Date Issued: 2018
- Authors: Rafael, Candice Nancy , Ambler, Jon , Niehaus, Antoinette , Ross, James , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148250 , vital:38723 , https://doi.org/10.14806/ej.23.0.903
- Description: The South African Society for Bioinformatics1 (SASBi) was officially formed in September 2012 during a joint Congress with the South African Genetics Society (SAGS). Prior to this there was no official body to represent bioinformatic researchers and students in the country. The establishment of SASBi also led to the establishment of the Student Society as a platform for students to meet and discuss their research activities, but also to socialise and broaden their network of knowledge and friendships. A small group of students joined as volunteers to pioneer and set up a SASBi Student Council (SASBiSC). As a first step, one representative, selected from the attendees present at the first Joint Congress of SASBi and SAGS, was elected to the main SASBi Council.
- Full Text:
- Date Issued: 2018
Beneficial effects of medicinal plants in fish diseases
- Stratev, Deyan, Zhelyazkov, Georgi, Noundou, Xavier S, Krause, Rui W M
- Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier S , Krause, Rui W M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126177 , vital:35856 , https://doi.org/10.1007/s10499-017-0219-x
- Description: Fish are constantly in contact with pathogens inhabiting water. High populationdensity as well as poor hydrodynamic conditions and feeding lead to an increased sensitivitytowards infections. In order to prevent major economic losses due to diseases, variousmedications are used for treatment and prevention of infections. The use of antimicrobialdrugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms.Alternatives are being sought over the last few years to replace antibiotics, and medicinalplants are one of available options for this purpose. These plants are rich in secondarymetabolites and phytochemical compounds, which have an effect against viral, bacterial, andparasitic diseases in fish. Their main advantage is their natural origin and most of these plantsdo not represent threat for human health, the fish, and the environment. The goal of this reviewis to present information on the treatment of viral, bacterial, and parasitic diseases in fishthrough medicinal plants, with focus on the mechanisms of action of the identified secondarymetabolites, fractions, or plant extracts.
- Full Text:
- Date Issued: 2018
- Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier S , Krause, Rui W M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126177 , vital:35856 , https://doi.org/10.1007/s10499-017-0219-x
- Description: Fish are constantly in contact with pathogens inhabiting water. High populationdensity as well as poor hydrodynamic conditions and feeding lead to an increased sensitivitytowards infections. In order to prevent major economic losses due to diseases, variousmedications are used for treatment and prevention of infections. The use of antimicrobialdrugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms.Alternatives are being sought over the last few years to replace antibiotics, and medicinalplants are one of available options for this purpose. These plants are rich in secondarymetabolites and phytochemical compounds, which have an effect against viral, bacterial, andparasitic diseases in fish. Their main advantage is their natural origin and most of these plantsdo not represent threat for human health, the fish, and the environment. The goal of this reviewis to present information on the treatment of viral, bacterial, and parasitic diseases in fishthrough medicinal plants, with focus on the mechanisms of action of the identified secondarymetabolites, fractions, or plant extracts.
- Full Text:
- Date Issued: 2018
Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: an antimalarial, antitrypanosomal and cytotoxity evaluation
- Meyer, Franck, Isaacs, Michelle, Noundou, Xavier S, Krause, Rui W M, Teinkela, J E M, Hoppe, Heinrich C, Mpondo, Albert E M, Azebaze, Anatole G B, Nguemfo, Edwige L, Wintjens, Rene
- Authors: Meyer, Franck , Isaacs, Michelle , Noundou, Xavier S , Krause, Rui W M , Teinkela, J E M , Hoppe, Heinrich C , Mpondo, Albert E M , Azebaze, Anatole G B , Nguemfo, Edwige L , Wintjens, Rene
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126142 , vital:35853 , https://doi.org/10.1016/j.sjbs.2017.07.002
- Description: The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC50 value 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC50 of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC50 value of 9.5 μg/mL) and trypanocidal (IC50 value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.
- Full Text:
- Date Issued: 2018
- Authors: Meyer, Franck , Isaacs, Michelle , Noundou, Xavier S , Krause, Rui W M , Teinkela, J E M , Hoppe, Heinrich C , Mpondo, Albert E M , Azebaze, Anatole G B , Nguemfo, Edwige L , Wintjens, Rene
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126142 , vital:35853 , https://doi.org/10.1016/j.sjbs.2017.07.002
- Description: The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC50 value 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC50 of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC50 value of 9.5 μg/mL) and trypanocidal (IC50 value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.
- Full Text:
- Date Issued: 2018
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