Anomalous behaviour of thermoluminescence from quartz: a case of glow peaks from a Nigerian quartz
- Ogundare, F O, Chithambo, Makaiko L, Oniya, E O
- Authors: Ogundare, F O , Chithambo, Makaiko L , Oniya, E O
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6796 , http://hdl.handle.net/10962/d1003922
- Description: Anomalous behaviour displayed by a thermoluminescence (TL) glow peak as radiation dose increases in a Nigerian quartz is presented. The glow curves of the phosphor have four clear glow peaks. The peak temperatures of the first three glow peaks were found to be constant with change in radiation dose at 82, 148 and 200ºC for the sample readout at a heating rate of 1ºCs[superscript (-1)]. The peak temperature of the fourth peak, which is at around 320ºC for a sample irradiated to a dose of 63 Gy and heated at 1ºCs[superscript (-1)], displays anomalous behaviour with increase in dose relative to the first three peaks. The temperature at which this peak occurs increases with dose to about 335ºC for 177 Gy and then decreases thereafter as dose is further increased. The change is explained on the assumption that the peak may be complex consisting of several overlapping first-order glow peaks each with different TL behaviour.
- Full Text:
- Date Issued: 2006
- Authors: Ogundare, F O , Chithambo, Makaiko L , Oniya, E O
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6796 , http://hdl.handle.net/10962/d1003922
- Description: Anomalous behaviour displayed by a thermoluminescence (TL) glow peak as radiation dose increases in a Nigerian quartz is presented. The glow curves of the phosphor have four clear glow peaks. The peak temperatures of the first three glow peaks were found to be constant with change in radiation dose at 82, 148 and 200ºC for the sample readout at a heating rate of 1ºCs[superscript (-1)]. The peak temperature of the fourth peak, which is at around 320ºC for a sample irradiated to a dose of 63 Gy and heated at 1ºCs[superscript (-1)], displays anomalous behaviour with increase in dose relative to the first three peaks. The temperature at which this peak occurs increases with dose to about 335ºC for 177 Gy and then decreases thereafter as dose is further increased. The change is explained on the assumption that the peak may be complex consisting of several overlapping first-order glow peaks each with different TL behaviour.
- Full Text:
- Date Issued: 2006
ATP-sulphurylase: An enzymatic marker for biological sulphate reduction
- Oyekola, Oluwaseun O, Pletschke, Brett I
- Authors: Oyekola, Oluwaseun O , Pletschke, Brett I
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6461 , http://hdl.handle.net/10962/d1005790 , http://dx.doi.org/10.1016/j.soilbio.2006.05.014
- Description: Adenosine triphosphate-sulphurylase (ATPS) plays a major role in dissimilatory sulphate reduction. In this study, the level of ATPS activity was monitored in a time course study using a biosulphidogenic batch bioreactor system. A coincident decrease in ATPS activity with a decline in sulphate concentration and an increase in sulphide concentration as biosulphidogenesis proceeded was observed. Flask studies further showed sulphate to be stimulatory to ATPS, while sulphide proved to be inhibitory. The effect of ions (Ca^(2+), Cl^(−), Fe^(2+) and Zn^(2+)) on the ATPS activity was also investigated. Most of the ions studied (Ca^(2+), Cl^(−) and Fe^(2+)) were stimulatory at lower concentrations (40–120 mg/l) but proved toxic at higher concentrations (>120 mg/l). In contrast, Zn^(2+) was inhibitory even at low concentrations ( 40 mg/l). ATPS may potentially be used as an enzymatic marker for biological sulphate reduction in sulphate-rich wastewaters and natural environments (anaerobic systems such as soils and sediments found in freshwater and marine systems), providing all residual sulphide and interfering ions are removed using a simple preparative step.
- Full Text:
- Date Issued: 2006
- Authors: Oyekola, Oluwaseun O , Pletschke, Brett I
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6461 , http://hdl.handle.net/10962/d1005790 , http://dx.doi.org/10.1016/j.soilbio.2006.05.014
- Description: Adenosine triphosphate-sulphurylase (ATPS) plays a major role in dissimilatory sulphate reduction. In this study, the level of ATPS activity was monitored in a time course study using a biosulphidogenic batch bioreactor system. A coincident decrease in ATPS activity with a decline in sulphate concentration and an increase in sulphide concentration as biosulphidogenesis proceeded was observed. Flask studies further showed sulphate to be stimulatory to ATPS, while sulphide proved to be inhibitory. The effect of ions (Ca^(2+), Cl^(−), Fe^(2+) and Zn^(2+)) on the ATPS activity was also investigated. Most of the ions studied (Ca^(2+), Cl^(−) and Fe^(2+)) were stimulatory at lower concentrations (40–120 mg/l) but proved toxic at higher concentrations (>120 mg/l). In contrast, Zn^(2+) was inhibitory even at low concentrations ( 40 mg/l). ATPS may potentially be used as an enzymatic marker for biological sulphate reduction in sulphate-rich wastewaters and natural environments (anaerobic systems such as soils and sediments found in freshwater and marine systems), providing all residual sulphide and interfering ions are removed using a simple preparative step.
- Full Text:
- Date Issued: 2006
Effects of temperature and salinity on the standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi
- Allan, Elizabeth L, Froneman, Pierre W, Hodgson, Alan N
- Authors: Allan, Elizabeth L , Froneman, Pierre W , Hodgson, Alan N
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6831 , http://hdl.handle.net/10962/d1007567
- Description: The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15–30 °C), salinity (0–45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. The Q[subscript 10] value over the temperature range 15–25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15–35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop.
- Full Text:
- Date Issued: 2006
- Authors: Allan, Elizabeth L , Froneman, Pierre W , Hodgson, Alan N
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6831 , http://hdl.handle.net/10962/d1007567
- Description: The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15–30 °C), salinity (0–45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. The Q[subscript 10] value over the temperature range 15–25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O[subscript 2] mg wwt[superscript −1] h[superscript −1]. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15–35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop.
- Full Text:
- Date Issued: 2006
Kappia lobulata (Apocynaceae, Periplocoideae), a new genus from South Africa
- Venter, H J T, Dold, Anthony P, Verhoeven, R L, Ionta, G
- Authors: Venter, H J T , Dold, Anthony P , Verhoeven, R L , Ionta, G
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6556 , http://hdl.handle.net/10962/d1006015
- Description: Kappia, a new genus from the Fish River Valley in the Eastern Cape Province, South Africa is presented. At first described as Raphionacme lobulata Venter and R.L.Verh. [Venter, H.J.T., Verhoeven, R.L. 1988. Raphionacme lobulata (Periplocaceae), a new species from the eastern Cape Province, South Africa. South African Journal of Botany 54, 603–606.] based on a single specimen collected in 1936, recently discovered plants of this species proved it to be a new genus. In habit Kappia resembles Baseonema Schltr. and Rendle, Batesanthus N.E.Br., Mondia Skeels and Stomatostemma N.E.Br. However, as far as floral structure is concerned, Kappia reveals more affinity with Raphionacme Harv. DNA sequence data show Kappia to be distinct from Batesanthus, Mondia and Raphionacme Harv. and weakly supported as a sister to Stomatostemma.
- Full Text:
- Date Issued: 2006
- Authors: Venter, H J T , Dold, Anthony P , Verhoeven, R L , Ionta, G
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6556 , http://hdl.handle.net/10962/d1006015
- Description: Kappia, a new genus from the Fish River Valley in the Eastern Cape Province, South Africa is presented. At first described as Raphionacme lobulata Venter and R.L.Verh. [Venter, H.J.T., Verhoeven, R.L. 1988. Raphionacme lobulata (Periplocaceae), a new species from the eastern Cape Province, South Africa. South African Journal of Botany 54, 603–606.] based on a single specimen collected in 1936, recently discovered plants of this species proved it to be a new genus. In habit Kappia resembles Baseonema Schltr. and Rendle, Batesanthus N.E.Br., Mondia Skeels and Stomatostemma N.E.Br. However, as far as floral structure is concerned, Kappia reveals more affinity with Raphionacme Harv. DNA sequence data show Kappia to be distinct from Batesanthus, Mondia and Raphionacme Harv. and weakly supported as a sister to Stomatostemma.
- Full Text:
- Date Issued: 2006
Molecular biology studies on the coelacanth: a review
- Modisakeng, Keoagile W, Amemiya, Chris T, Dorrington, Rosemary A, Blatch, Gregory L
- Authors: Modisakeng, Keoagile W , Amemiya, Chris T , Dorrington, Rosemary A , Blatch, Gregory L
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6466 , http://hdl.handle.net/10962/d1005795
- Description: The discovery of the African coelacanth in 1938 and subsequently the Indonesian coelacanth in 1998 has resulted in a keen interest in molecular studies on the coelacanth. A major focus has been on the phylogenetic position of the coelacanth. Lobe-finned fish such as the coelacanth are thought to be at the base of the evolutionary branch of fish leading to tetrapods. These studies have further aimed to resolve the phylogenetic relationship of extant lobe-finned fish (two coelacanth species and the lungfishes) to vertebrates. Notwithstanding the lack of readily accessible good-quality coelacanth tissue, several major contributions to coelacanth molecular studies and biology have been possible. The mitochondrial genome sequences of both species of the coelacanth suggest that they diverged from one another 40–30 million years ago. A number of large gene families such as the HOX, protocadherin and heat shock protein clusters have been characterized. Furthermore, the recent successful construction of a large-insert (150–200 kilobase) genomic library of the Indonesian coelacanth will prove to be an invaluable tool in both comparative and functional genomics. Here we summarize and evaluate the current status of molecular research, published and databased, for both the African (Latimeria chalumnae) and the Indonesian (Latimeria menadoensis) coelacanth.
- Full Text:
- Date Issued: 2006
- Authors: Modisakeng, Keoagile W , Amemiya, Chris T , Dorrington, Rosemary A , Blatch, Gregory L
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6466 , http://hdl.handle.net/10962/d1005795
- Description: The discovery of the African coelacanth in 1938 and subsequently the Indonesian coelacanth in 1998 has resulted in a keen interest in molecular studies on the coelacanth. A major focus has been on the phylogenetic position of the coelacanth. Lobe-finned fish such as the coelacanth are thought to be at the base of the evolutionary branch of fish leading to tetrapods. These studies have further aimed to resolve the phylogenetic relationship of extant lobe-finned fish (two coelacanth species and the lungfishes) to vertebrates. Notwithstanding the lack of readily accessible good-quality coelacanth tissue, several major contributions to coelacanth molecular studies and biology have been possible. The mitochondrial genome sequences of both species of the coelacanth suggest that they diverged from one another 40–30 million years ago. A number of large gene families such as the HOX, protocadherin and heat shock protein clusters have been characterized. Furthermore, the recent successful construction of a large-insert (150–200 kilobase) genomic library of the Indonesian coelacanth will prove to be an invaluable tool in both comparative and functional genomics. Here we summarize and evaluate the current status of molecular research, published and databased, for both the African (Latimeria chalumnae) and the Indonesian (Latimeria menadoensis) coelacanth.
- Full Text:
- Date Issued: 2006
Observations of the habitats and biodiversity of the submarine canyons at Sodwana Bay
- Sink, K J, Boshoff, W, Samaai, Toufiek, Timm, P G, Kerwath, S E
- Authors: Sink, K J , Boshoff, W , Samaai, Toufiek , Timm, P G , Kerwath, S E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6771 , http://hdl.handle.net/10962/d1008065
- Description: The discovery of coelacanths, Latimeria chalumnae, in Jesser Canyon off Sodwana Bay in northern KwaZulu-Natal in 2000 triggered renewed interest in the deep subtidal habitats associated with submarine canyons. Information stemming from three recreational Trimix diving expeditions in Wright and Jesser canyons between April 1998 and June 2001 revealed distinct and diverse invertebrate and fish communities in the canyons of the Greater St Lucia Wetland Park (GSLWP). In total, 69 invertebrate taxa were collected from Wright Canyon, including at least 15 new records for South Africa plus 11 potential new species and 16 range or depth extensions. Divers documented the first five coelacanth specimens and obtained information on fish distribution and abundance. Five different habitat types were recognized supporting distinct biological communities; the sandy plains outside of the canyons, scattered rock outcrops within the sandy plains, the canyon margin, canyon walls and caves and overhangs. The canyon margin is the richest habitat and supports dense communities of invertebrate suspension feeders, as well as a diverse and abundant fish fauna. Dominant canyon invertebrates included sponges, black corals, gorgonians, alcyonarian soft corals and stylasterine lace corals. These invertebrates support a diverse epifauna including basket- and brittlestars, winged oysters and other molluscs. The canyons within the GSLWP protect large populations of commercially important linefish species including the sparids, Chrysoblephus puniceus, C. anglicus, Polysteganus praeorbitalis and P. caeruleopunctatus, as well as several species of serranids and lutjanids. Additional biological sampling and standardized quantitative sampling within the canyons and deep reefs is required to develop a better understanding of their biological communities and the factors that shape them.
- Full Text:
- Date Issued: 2006
- Authors: Sink, K J , Boshoff, W , Samaai, Toufiek , Timm, P G , Kerwath, S E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6771 , http://hdl.handle.net/10962/d1008065
- Description: The discovery of coelacanths, Latimeria chalumnae, in Jesser Canyon off Sodwana Bay in northern KwaZulu-Natal in 2000 triggered renewed interest in the deep subtidal habitats associated with submarine canyons. Information stemming from three recreational Trimix diving expeditions in Wright and Jesser canyons between April 1998 and June 2001 revealed distinct and diverse invertebrate and fish communities in the canyons of the Greater St Lucia Wetland Park (GSLWP). In total, 69 invertebrate taxa were collected from Wright Canyon, including at least 15 new records for South Africa plus 11 potential new species and 16 range or depth extensions. Divers documented the first five coelacanth specimens and obtained information on fish distribution and abundance. Five different habitat types were recognized supporting distinct biological communities; the sandy plains outside of the canyons, scattered rock outcrops within the sandy plains, the canyon margin, canyon walls and caves and overhangs. The canyon margin is the richest habitat and supports dense communities of invertebrate suspension feeders, as well as a diverse and abundant fish fauna. Dominant canyon invertebrates included sponges, black corals, gorgonians, alcyonarian soft corals and stylasterine lace corals. These invertebrates support a diverse epifauna including basket- and brittlestars, winged oysters and other molluscs. The canyons within the GSLWP protect large populations of commercially important linefish species including the sparids, Chrysoblephus puniceus, C. anglicus, Polysteganus praeorbitalis and P. caeruleopunctatus, as well as several species of serranids and lutjanids. Additional biological sampling and standardized quantitative sampling within the canyons and deep reefs is required to develop a better understanding of their biological communities and the factors that shape them.
- Full Text:
- Date Issued: 2006
Oceanographic environment of the Sodwana Bay coelacanths (Latimeria chalumnae), South Africa
- Roberts, M J, Ribbink, Anthony J, Morris, T
- Authors: Roberts, M J , Ribbink, Anthony J , Morris, T
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7156 , http://hdl.handle.net/10962/d1011883
- Description: Trimix scuba divers discovered coelacanths in Jesser Canyon at a depth of 104 m on the northern KwaZulu-Natal (KZN) coast (Sodwana Bay) in October 2000. The existence of these animals at such a shallow depth and in the swift and powerful Agulhas Current led to a suggestion that this might be an isolated group swept well away from the main population in the Comoros, where they live at depths of 200–350 m with little current. Subsequent observations from three manned submersible surveys and one remotely operated vehicle expedition together with recreational diver observations indicate that the South African population of coelacanths has at least 26 individuals, mostly occupying the depth range of 104–140 m in canyons. Seventeen CTD sections collected during four cruises in 2002 and 2003 indicate the temperature range in this habitat to be similar to that found in the Comoros Islands (that is, 15–22°C cf. 15–19°C in the Comoros). However, a 2.5-month-long time series of hourly data collected by a thermistor array deployed near a known coelacanth cave in Wright Canyon indicated greater variation than anticipated, with temperature changes between 16°C and 24°C occurring in a day. Dissolved oxygen levels in this depth zone were found to range between 3.0 ml l[superscript (–1)] and 4.8 ml l[superscript (–1)] compared to 3.5 ml l[superscript (–1)] in the Comoros. The low oxygen values along this coast are a result of the shallow oxygen minimum, which becomes shallower in the southwest Indian Ocean, particularly in the Agulhas Current, than in tropical latitudes. Current velocities measured using a ship-borne ADCP in the depth range 100–140 m at Sodwana were considerably higher than those measured in the Comoros habitat (20–60 cm s[superscript (–1)] cf. 3–4 cm s[superscript (–1)]) and may be an important factor explaining the coelacanths’ occupation of the canyons found along the northern KZN shelf-break.
- Full Text:
- Date Issued: 2006
- Authors: Roberts, M J , Ribbink, Anthony J , Morris, T
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7156 , http://hdl.handle.net/10962/d1011883
- Description: Trimix scuba divers discovered coelacanths in Jesser Canyon at a depth of 104 m on the northern KwaZulu-Natal (KZN) coast (Sodwana Bay) in October 2000. The existence of these animals at such a shallow depth and in the swift and powerful Agulhas Current led to a suggestion that this might be an isolated group swept well away from the main population in the Comoros, where they live at depths of 200–350 m with little current. Subsequent observations from three manned submersible surveys and one remotely operated vehicle expedition together with recreational diver observations indicate that the South African population of coelacanths has at least 26 individuals, mostly occupying the depth range of 104–140 m in canyons. Seventeen CTD sections collected during four cruises in 2002 and 2003 indicate the temperature range in this habitat to be similar to that found in the Comoros Islands (that is, 15–22°C cf. 15–19°C in the Comoros). However, a 2.5-month-long time series of hourly data collected by a thermistor array deployed near a known coelacanth cave in Wright Canyon indicated greater variation than anticipated, with temperature changes between 16°C and 24°C occurring in a day. Dissolved oxygen levels in this depth zone were found to range between 3.0 ml l[superscript (–1)] and 4.8 ml l[superscript (–1)] compared to 3.5 ml l[superscript (–1)] in the Comoros. The low oxygen values along this coast are a result of the shallow oxygen minimum, which becomes shallower in the southwest Indian Ocean, particularly in the Agulhas Current, than in tropical latitudes. Current velocities measured using a ship-borne ADCP in the depth range 100–140 m at Sodwana were considerably higher than those measured in the Comoros habitat (20–60 cm s[superscript (–1)] cf. 3–4 cm s[superscript (–1)]) and may be an important factor explaining the coelacanths’ occupation of the canyons found along the northern KZN shelf-break.
- Full Text:
- Date Issued: 2006
Oceanographic environment of the Sodwana Bay coelacanths (Latimeria chalumnae), South Africa
- Roberts, M J, Ribbink, A J, Morris, T
- Authors: Roberts, M J , Ribbink, A J , Morris, T
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7126 , http://hdl.handle.net/10962/d1010633
- Description: Trimix scuba divers discovered coelacanths in Jesser Canyon at a depth of 104 m on the northern KwaZulu-Natal (KZN) coast (Sodwana Bay) in October 2000. The existence of these animals at such a shallow depth and in the swift and powerful Agulhas Current led to a suggestion that this might be an isolated group swept well away from the main population in the Comoros, where they live at depths of 200–350 m with little current. Subsequent observations from three manned submersible surveys and one remotely operated vehicle expedition together with recreational diver observations indicate that the South African population of coelacanths has at least 26 individuals, mostly occupying the depth range of 104–140 m in canyons. Seventeen CTD sections collected during four cruises in 2002 and 2003 indicate the temperature range in this habitat to be similar to that found in the Comoros Islands (that is, 15–22°C cf. 15–19°C in the Comoros). However, a 2.5-month-long time series of hourly data collected by a thermistor array deployed near a known coelacanth cave in Wright Canyon indicated greater variation than anticipated, with temperature changes between 16°C and 24°C occurring in a day. Dissolved oxygen levels in this depth zone were found to range between 3.0 ml l[superscript (–1)] and 4.8 ml l[superscript (–1)] compared to 3.5 ml l[superscript (–1)] in the Comoros. The low oxygen values along this coast are a result of the shallow oxygen minimum, which becomes shallower in the southwest Indian Ocean, particularly in the Agulhas Current, than in tropical latitudes. Current velocities measured using a ship-borne ADCP in the depth range 100–140 m at Sodwana were considerably higher than those measured in the Comoros habitat (20–60 cm s[superscript (–1)] cf. 3–4 cm s[superscript (–1)]) and may be an important factor explaining the coelacanths’ occupation of the canyons found along the northern KZN shelf-break.
- Full Text:
- Date Issued: 2006
- Authors: Roberts, M J , Ribbink, A J , Morris, T
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7126 , http://hdl.handle.net/10962/d1010633
- Description: Trimix scuba divers discovered coelacanths in Jesser Canyon at a depth of 104 m on the northern KwaZulu-Natal (KZN) coast (Sodwana Bay) in October 2000. The existence of these animals at such a shallow depth and in the swift and powerful Agulhas Current led to a suggestion that this might be an isolated group swept well away from the main population in the Comoros, where they live at depths of 200–350 m with little current. Subsequent observations from three manned submersible surveys and one remotely operated vehicle expedition together with recreational diver observations indicate that the South African population of coelacanths has at least 26 individuals, mostly occupying the depth range of 104–140 m in canyons. Seventeen CTD sections collected during four cruises in 2002 and 2003 indicate the temperature range in this habitat to be similar to that found in the Comoros Islands (that is, 15–22°C cf. 15–19°C in the Comoros). However, a 2.5-month-long time series of hourly data collected by a thermistor array deployed near a known coelacanth cave in Wright Canyon indicated greater variation than anticipated, with temperature changes between 16°C and 24°C occurring in a day. Dissolved oxygen levels in this depth zone were found to range between 3.0 ml l[superscript (–1)] and 4.8 ml l[superscript (–1)] compared to 3.5 ml l[superscript (–1)] in the Comoros. The low oxygen values along this coast are a result of the shallow oxygen minimum, which becomes shallower in the southwest Indian Ocean, particularly in the Agulhas Current, than in tropical latitudes. Current velocities measured using a ship-borne ADCP in the depth range 100–140 m at Sodwana were considerably higher than those measured in the Comoros habitat (20–60 cm s[superscript (–1)] cf. 3–4 cm s[superscript (–1)]) and may be an important factor explaining the coelacanths’ occupation of the canyons found along the northern KZN shelf-break.
- Full Text:
- Date Issued: 2006
On the correlation between annealing and variabilities in pulsed-luminescence from quartz
- Authors: Chithambo, Makaiko L
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6797 , http://hdl.handle.net/10962/d1003923
- Description: Properties of luminescence lifetimes in quartz related to annealing between 500 and 900ºC have been investigated. The luminescence was pulse-stimulated at 470 nm from sets of granular quartz annealed at 500, 600, 700, 800, and 900ºC. The lifetimes decrease with annealing temperature from about 42 to 33 µѕ when the annealing temperature is increased from 500 to 900ºC. Luminescence lifetimes are most sensitive to duration of annealing at 600ºC, decreasing from 40.2 ± 0.7 µѕ by as much as 7 µѕ when the duration of annealing is changed from 10 to 60 min. However, at 800–900ºC lifetimes are essentially independent of annealing temperature at about 33 µѕ. Increasing the exciting beta dose causes an increase in the lifetimes of the stimulated luminescence in the sample annealed at 800ºC but not in those annealed at either 500 or 600ºC. The temperature-resolved distribution of luminescence lifetimes is affected by thermal quenching of luminescence. These features may be accounted for with reference to two principal luminescence centres involved in the luminescence emission process.
- Full Text:
- Date Issued: 2006
- Authors: Chithambo, Makaiko L
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6797 , http://hdl.handle.net/10962/d1003923
- Description: Properties of luminescence lifetimes in quartz related to annealing between 500 and 900ºC have been investigated. The luminescence was pulse-stimulated at 470 nm from sets of granular quartz annealed at 500, 600, 700, 800, and 900ºC. The lifetimes decrease with annealing temperature from about 42 to 33 µѕ when the annealing temperature is increased from 500 to 900ºC. Luminescence lifetimes are most sensitive to duration of annealing at 600ºC, decreasing from 40.2 ± 0.7 µѕ by as much as 7 µѕ when the duration of annealing is changed from 10 to 60 min. However, at 800–900ºC lifetimes are essentially independent of annealing temperature at about 33 µѕ. Increasing the exciting beta dose causes an increase in the lifetimes of the stimulated luminescence in the sample annealed at 800ºC but not in those annealed at either 500 or 600ºC. The temperature-resolved distribution of luminescence lifetimes is affected by thermal quenching of luminescence. These features may be accounted for with reference to two principal luminescence centres involved in the luminescence emission process.
- Full Text:
- Date Issued: 2006
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