The importance of phytoplankton size in mediating trophic interactions within the plankton of a southern African estuary
- Authors: Froneman, P William
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6928 , http://hdl.handle.net/10962/d1011944
- Description: The influence of the phytoplankton size composition in mediating the trophic interactions between the bacteria, phytoplankton, microheterotrophs (<200 μm) and mesozooplankton (>200 μm) was investigated on three occasions in a warm temperate, temporarily open/closed estuary situated along the southern African coastline. Results of the investigation indicated that the microheterotrophs represented the most important consumers of bacteria and chlorophyll (chl)-a <5.0 μm. The low impact of the mesozooplankton on the bacteria and chl-a <5.0 μm during the study appeared to be related to the inability of the larger zooplankton to feed efficiently on small particles. During those periods when total chl-a concentration was dominated by picophytoplankton (<2.0 μm) and microphytoplankton (>20 μm), mesozooplankton were unable to feed efficiently on the chl-a due to feeding constraints. In response to the unfavorable size structure of the phytoplankton assemblages, mesozooplankton appeared to consume the microheterotrophs. The negative impact of the mesozooplankton on the microheterotrophs resulted in a decrease in the impact of these organisms on the bacteria and the chl-a <5.0 μm. This result is consistent with the predator-prey cascades. On the other hand, when the total chl-a was dominated by nanophytoplankton (2–20 μm), mesozooplankton were able to feed directly on the phytoplankton. Results of the study indicate that size structure of the phytoplankton assemblages within estuaries plays an important role in mediating the trophic interactions between the various components of the plankton food web.
- Full Text:
- Authors: Froneman, P William
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6928 , http://hdl.handle.net/10962/d1011944
- Description: The influence of the phytoplankton size composition in mediating the trophic interactions between the bacteria, phytoplankton, microheterotrophs (<200 μm) and mesozooplankton (>200 μm) was investigated on three occasions in a warm temperate, temporarily open/closed estuary situated along the southern African coastline. Results of the investigation indicated that the microheterotrophs represented the most important consumers of bacteria and chlorophyll (chl)-a <5.0 μm. The low impact of the mesozooplankton on the bacteria and chl-a <5.0 μm during the study appeared to be related to the inability of the larger zooplankton to feed efficiently on small particles. During those periods when total chl-a concentration was dominated by picophytoplankton (<2.0 μm) and microphytoplankton (>20 μm), mesozooplankton were unable to feed efficiently on the chl-a due to feeding constraints. In response to the unfavorable size structure of the phytoplankton assemblages, mesozooplankton appeared to consume the microheterotrophs. The negative impact of the mesozooplankton on the microheterotrophs resulted in a decrease in the impact of these organisms on the bacteria and the chl-a <5.0 μm. This result is consistent with the predator-prey cascades. On the other hand, when the total chl-a was dominated by nanophytoplankton (2–20 μm), mesozooplankton were able to feed directly on the phytoplankton. Results of the study indicate that size structure of the phytoplankton assemblages within estuaries plays an important role in mediating the trophic interactions between the various components of the plankton food web.
- Full Text:
The South African coelacanths — an account of what is known after three submersible expeditions
- Hissmann, K, Fricke, H, Schauer, J
- Authors: Hissmann, K , Fricke, H , Schauer, J
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7131 , http://hdl.handle.net/10962/d1011772
- Description: Using the manned submersible Jago, the habits, distribution and number of coelacanths within all main submarine canyons of the Greater St Lucia Wetland Park were studied during 47 survey dives, with a total bottom time of 166 hours at depths ranging from 46 to 359 m, between 2002 and 2004. Twenty-four individuals were positively identified from three of the canyons, primarily from inside caves at or close to the canyon edges at depths of 96–133 m with water temperatures between 16 and 22.5°C. The population size of coelacanths within the canyons is assumed to be relatively small; coelacanths are resident but not widespread nor abundant within the park.
- Full Text:
- Authors: Hissmann, K , Fricke, H , Schauer, J
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7131 , http://hdl.handle.net/10962/d1011772
- Description: Using the manned submersible Jago, the habits, distribution and number of coelacanths within all main submarine canyons of the Greater St Lucia Wetland Park were studied during 47 survey dives, with a total bottom time of 166 hours at depths ranging from 46 to 359 m, between 2002 and 2004. Twenty-four individuals were positively identified from three of the canyons, primarily from inside caves at or close to the canyon edges at depths of 96–133 m with water temperatures between 16 and 22.5°C. The population size of coelacanths within the canyons is assumed to be relatively small; coelacanths are resident but not widespread nor abundant within the park.
- Full Text:
Derivation of quantitative management objectives for annual instream water temperatures in the Sabie River using a biological index
- Rivers-Moore, N A, Jewitt, G P W, Weeks, D C
- Authors: Rivers-Moore, N A , Jewitt, G P W , Weeks, D C
- Date: 2005
- Language: English
- Type: text , Article
- Identifier: vital:7093 , http://hdl.handle.net/10962/d1012426
- Description: Adaptive management of river systems assumes uncertainty and makes provision for system variability. Inherent within this management approach is that perceived limits of 'acceptable' system variability are regarded not only as testable hypotheses, but also as playing a central role in maintaining biodiversity. While the Kruger National Park currently functions as a flagship conservation area in South Africa, projected increases in air temperatures as a consequence of global climate change present challenges in conserving this biodiversity inside the established land boundaries. Within the rivers of the Kruger National Park, a management goal of maintaining biodiversity requires a clearer understanding of system variability. One component of this is water temperature, an important water quality parameter defining the distribution patterns of aquatic organisms. In this study, Chiloglanis anoterus Crass (1960) (Pisces: Mochokidae) was selected as a biological indicator of changes in annual water temperatures within the Sabie River in the southern Kruger National Park. Relative abundances of C. anoterus were determined using standard electro-fishing surveys. The presence or absence of C. anoterus was linked to cumulative annual heat units using a logistic regression model, and a critical annual cumulative water temperature threshold estimated. A correlative relationship between this temperature threshold and a biological index using a C. anoterus condition factor provides river ecologists with a tool to assess ecologically significant warming trends in Sabie River water temperatures. A similar approach could be applied with relative ease to other Southern African river systems. Further testing of this hypothesis is suggested, as part of the adaptive management cycle.
- Full Text:
- Authors: Rivers-Moore, N A , Jewitt, G P W , Weeks, D C
- Date: 2005
- Language: English
- Type: text , Article
- Identifier: vital:7093 , http://hdl.handle.net/10962/d1012426
- Description: Adaptive management of river systems assumes uncertainty and makes provision for system variability. Inherent within this management approach is that perceived limits of 'acceptable' system variability are regarded not only as testable hypotheses, but also as playing a central role in maintaining biodiversity. While the Kruger National Park currently functions as a flagship conservation area in South Africa, projected increases in air temperatures as a consequence of global climate change present challenges in conserving this biodiversity inside the established land boundaries. Within the rivers of the Kruger National Park, a management goal of maintaining biodiversity requires a clearer understanding of system variability. One component of this is water temperature, an important water quality parameter defining the distribution patterns of aquatic organisms. In this study, Chiloglanis anoterus Crass (1960) (Pisces: Mochokidae) was selected as a biological indicator of changes in annual water temperatures within the Sabie River in the southern Kruger National Park. Relative abundances of C. anoterus were determined using standard electro-fishing surveys. The presence or absence of C. anoterus was linked to cumulative annual heat units using a logistic regression model, and a critical annual cumulative water temperature threshold estimated. A correlative relationship between this temperature threshold and a biological index using a C. anoterus condition factor provides river ecologists with a tool to assess ecologically significant warming trends in Sabie River water temperatures. A similar approach could be applied with relative ease to other Southern African river systems. Further testing of this hypothesis is suggested, as part of the adaptive management cycle.
- Full Text:
The great arch of unimagined bridges: integrative play therapy with an abused child
- Authors: McDermott, R
- Date: 2005
- Language: English
- Type: text , Article
- Identifier: vital:6272 , http://hdl.handle.net/10962/d1008272
- Description: This case study describes the early phases of integrative, long-term psychotherapy undertaken with a child subjected to chronic domestic trauma including violence, alcohol abuse, neglect, abandonment, and bereavement resulting from HIV/AIDS. Recent statistics on the prevalence of violent trauma, domestic abuse and HIV/AIDS in South Africa are reviewed, as are principles of trauma intervention that have been established across a range of psychotherapeutic modalities. Following from integrative trauma work undertaken locally, this therapeutic process acknowledges both indigenous and western frameworks of meaning, the latter most heavily informed by principles of analytical psychology. Selected aspects of the therapy are discussed in light of both perspectives, with reference to the child’s process of recovery. This paper seeks to add support to practised and published local work in which a range of possible healing practices, meanings, and experience are taken into account. It is proposed that such integrative efforts contribute towards an evolving African psychotherapy.
- Full Text:
- Authors: McDermott, R
- Date: 2005
- Language: English
- Type: text , Article
- Identifier: vital:6272 , http://hdl.handle.net/10962/d1008272
- Description: This case study describes the early phases of integrative, long-term psychotherapy undertaken with a child subjected to chronic domestic trauma including violence, alcohol abuse, neglect, abandonment, and bereavement resulting from HIV/AIDS. Recent statistics on the prevalence of violent trauma, domestic abuse and HIV/AIDS in South Africa are reviewed, as are principles of trauma intervention that have been established across a range of psychotherapeutic modalities. Following from integrative trauma work undertaken locally, this therapeutic process acknowledges both indigenous and western frameworks of meaning, the latter most heavily informed by principles of analytical psychology. Selected aspects of the therapy are discussed in light of both perspectives, with reference to the child’s process of recovery. This paper seeks to add support to practised and published local work in which a range of possible healing practices, meanings, and experience are taken into account. It is proposed that such integrative efforts contribute towards an evolving African psychotherapy.
- Full Text:
A fuzzy classification technique for predicting species' distributions: applications using invasive alien plants and indigenous insects
- Robertson, Mark P, Villet, Martin H, Palmer, Anthony R
- Authors: Robertson, Mark P , Villet, Martin H , Palmer, Anthony R
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6897 , http://hdl.handle.net/10962/d1011659 , http://dx.doi.org/10.1111/j.1366-9516.2004.00108.x
- Description: A new predictive modelling technique called the fuzzy envelope model (FEM) is introduced. The technique can be used to predict potential distributions of organisms using presence-only locality records and a set of environmental predictor variables. FEM uses fuzzy logic to classify a set of predictor variable maps based on the values associated with presence records and combines the results to produce a potential distribution map for a target species. This technique represents several refinements of the envelope approach used in the BIOCLIM modelling package. These refinements are related to the way in which FEMs deal with uncertainty, the way in which this uncertainty is represented in the resultant potential distribution maps, and the way that these maps can be interpreted and applied. To illustrate its potential use in biogeographical studies, FEM was applied to predicting the potential distribution of three invasive alien plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.), and three native cicada species (Capicada decora Germar, Platypleura deusta Thun. and P. capensis L.) in South Africa, Lesotho and Swaziland. These models were quantitatively compared with models produced by means of the algorithm used in the BIOCLIM modelling package, which is referred to as a crisp envelope model (the CEM design). The average performance of models of the FEM design was consistently higher than those of the CEM design. There were significant differences in model performance among species but there was no significant interaction between model design and species. The average maximum kappa value ranged from 0.70 to 0.90 for FEM design and from 0.57 to 0.89 for the CEM design, which can be described as 'good' to 'excellent' using published ranges of agreement for the kappa statistic. This technique can be used to predict species' potential distributions that could be used for identifying regions at risk from invasion by alien species. These predictions could also be used in conservation planning in the case of native species.
- Full Text:
- Authors: Robertson, Mark P , Villet, Martin H , Palmer, Anthony R
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6897 , http://hdl.handle.net/10962/d1011659 , http://dx.doi.org/10.1111/j.1366-9516.2004.00108.x
- Description: A new predictive modelling technique called the fuzzy envelope model (FEM) is introduced. The technique can be used to predict potential distributions of organisms using presence-only locality records and a set of environmental predictor variables. FEM uses fuzzy logic to classify a set of predictor variable maps based on the values associated with presence records and combines the results to produce a potential distribution map for a target species. This technique represents several refinements of the envelope approach used in the BIOCLIM modelling package. These refinements are related to the way in which FEMs deal with uncertainty, the way in which this uncertainty is represented in the resultant potential distribution maps, and the way that these maps can be interpreted and applied. To illustrate its potential use in biogeographical studies, FEM was applied to predicting the potential distribution of three invasive alien plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.), and three native cicada species (Capicada decora Germar, Platypleura deusta Thun. and P. capensis L.) in South Africa, Lesotho and Swaziland. These models were quantitatively compared with models produced by means of the algorithm used in the BIOCLIM modelling package, which is referred to as a crisp envelope model (the CEM design). The average performance of models of the FEM design was consistently higher than those of the CEM design. There were significant differences in model performance among species but there was no significant interaction between model design and species. The average maximum kappa value ranged from 0.70 to 0.90 for FEM design and from 0.57 to 0.89 for the CEM design, which can be described as 'good' to 'excellent' using published ranges of agreement for the kappa statistic. This technique can be used to predict species' potential distributions that could be used for identifying regions at risk from invasion by alien species. These predictions could also be used in conservation planning in the case of native species.
- Full Text:
An analysis of automatically scaled F1 layer data over Grahamstown, South Africa
- Jacobs, Linda, Poole, Allon W V, McKinnell, Lee-Anne
- Authors: Jacobs, Linda , Poole, Allon W V , McKinnell, Lee-Anne
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6808 , http://hdl.handle.net/10962/d1004194
- Description: This paper describes an analysis of automatically scaled F1 layer data over Grahamstown, South Africa (33.3°S, 26.5°E). An application for real time raytracing through the South African ionosphere was identified, and for this application real time evaluation of the electron density profile is essential. Raw real time virtual height data are provided by a Lowell Digisonde (DPS), which employs the automatic scaling software, ARTIST whose output includes the virtual-to-real height data conversion. Experience has shown that there are times when the raytracing performance is degraded because of difficulties surrounding the real time characterisation of the F1 region by ARTIST. The purpose of this investigation is to establish the extent of the problem, the times and conditions under which it occurs, with a view to formulating remedial alternative strategies, such as predictive modelling.
- Full Text:
- Authors: Jacobs, Linda , Poole, Allon W V , McKinnell, Lee-Anne
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6808 , http://hdl.handle.net/10962/d1004194
- Description: This paper describes an analysis of automatically scaled F1 layer data over Grahamstown, South Africa (33.3°S, 26.5°E). An application for real time raytracing through the South African ionosphere was identified, and for this application real time evaluation of the electron density profile is essential. Raw real time virtual height data are provided by a Lowell Digisonde (DPS), which employs the automatic scaling software, ARTIST whose output includes the virtual-to-real height data conversion. Experience has shown that there are times when the raytracing performance is degraded because of difficulties surrounding the real time characterisation of the F1 region by ARTIST. The purpose of this investigation is to establish the extent of the problem, the times and conditions under which it occurs, with a view to formulating remedial alternative strategies, such as predictive modelling.
- Full Text:
Endothermy in African Platypleurine Cicadas: the influence of body size and habitat (Hemiptera: Cicadidae)
- Sanborn, Allen F, Villet, Martin H, Phillips, Polly K F
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, Polly K F
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6925 , http://hdl.handle.net/10962/d1011912
- Description: The platypleurine cicadas have a wide distribution across Africa and southern Asia. We investigate endothermy as a thermoregulatory strategy in 11 South African species from five genera, with comparisons to the lone ectothermic platypleurine we found, in an attempt to ascertain any influence that habitat and/or body size have on the expression of endothermy in the platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Heat production in the laboratory elevated Tb to the same range as in animals active in the field. Maximum Tb measured during calling activity when there was no access to solar radiation ranged from 13.2° to 22.3°C above ambient temperature in the five species measured. The mean Tb during activity without access to solar radiation did not differ from the mean Tb during diurnal activity. All platypleurines exhibit a unique behavior for cicadas while warming endogenously, a temperature- dependent telescoping pulsation of the abdomen that probably functions in ventilation. Platypleurines generally call from trunks and branches within the canopy and appear to rely on endothermy even when the sun is available to elevate Tb, in contrast to the facultative endothermy exhibited by New World endothermic species. The two exceptions to this generalization we found within the platypleurines are Platypleura wahlbergi and Albanycada albigera, which were the smallest species studied. The small size of P. wahlbergi appears to have altered their thermoregulatory strategy to one of facultative endothermy, whereby they use the sun when it is available to facilitate increases in Tb. Albanycada albigera is the only ectothermic platypleurine we found. The habitat and host plant association of A. albigera appear to have influenced the choice of ectothermy as a thermoregulatory strategy, as the species possesses the metabolic machinery to elevate to the Tb range observed in the endothermic species. Therefore, size and habitat appear to influence the expression of thermoregulatory strategies in African platypleurine cicadas.
- Full Text:
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, Polly K F
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6925 , http://hdl.handle.net/10962/d1011912
- Description: The platypleurine cicadas have a wide distribution across Africa and southern Asia. We investigate endothermy as a thermoregulatory strategy in 11 South African species from five genera, with comparisons to the lone ectothermic platypleurine we found, in an attempt to ascertain any influence that habitat and/or body size have on the expression of endothermy in the platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Heat production in the laboratory elevated Tb to the same range as in animals active in the field. Maximum Tb measured during calling activity when there was no access to solar radiation ranged from 13.2° to 22.3°C above ambient temperature in the five species measured. The mean Tb during activity without access to solar radiation did not differ from the mean Tb during diurnal activity. All platypleurines exhibit a unique behavior for cicadas while warming endogenously, a temperature- dependent telescoping pulsation of the abdomen that probably functions in ventilation. Platypleurines generally call from trunks and branches within the canopy and appear to rely on endothermy even when the sun is available to elevate Tb, in contrast to the facultative endothermy exhibited by New World endothermic species. The two exceptions to this generalization we found within the platypleurines are Platypleura wahlbergi and Albanycada albigera, which were the smallest species studied. The small size of P. wahlbergi appears to have altered their thermoregulatory strategy to one of facultative endothermy, whereby they use the sun when it is available to facilitate increases in Tb. Albanycada albigera is the only ectothermic platypleurine we found. The habitat and host plant association of A. albigera appear to have influenced the choice of ectothermy as a thermoregulatory strategy, as the species possesses the metabolic machinery to elevate to the Tb range observed in the endothermic species. Therefore, size and habitat appear to influence the expression of thermoregulatory strategies in African platypleurine cicadas.
- Full Text:
In situ feeding rates of the copepods, Pseudodiaptomus hessei and Acartia longipatella, in a temperate, temporarily open/closed Eastern Cape estuary
- Authors: Froneman, P William
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6901 , http://hdl.handle.net/10962/d1011754
- Description: Size-fractionated chlorophyll-a (chl-a) concentrations and the in situ grazing rates of the copepods, Pseudodiaptomus hessei and Acartia longipatella, were assessed seasonally at the temporarily open/closed Kasouga estuary situated along the southeast coast of southern Africa. Total integrated chl-a concentration ranged between 1.17 and 12.18 mg chl-a m^(–3) and was always dominated by small phytoplankton cells (<20 μm), which comprised up to 86% (range 64–86%) of the total pigment. Total zooplankton abundance ranged between 2676 and 62 043 individuals m^(–3). These copepods numerically dominated the zooplankton counts, accounting for between 79% and 91% of the total. Gut pigment concentrations of the two species at night were significantly higher than the daytime values (P<0.05 in all cases). The observed pattern could be related to the marked diurnal vertical migration patterns exhibited by the copepods. Gut evacuation rates of P. hessei during the study ranged between 0.29 and 0.77 h^(–1) and between 0.39 and 0.58 h^(–1) for A. longipatella. The rate of gut pigment destruction for P. hessei and A. longipatella ranged between 55% and 81% and between 88% and 92% of the total chl-a ingested, respectively. The combined grazing impact of the two copepods ranged between 0.65 and 4.37 mg chl-a m^(–3), or between 4.3% and 35.9% of the available chl-a in the water column. Variations in the grazing activity of the two species could be attributed largely to seasonality in water temperature and shifts in the phytoplankton community structure and zooplankton abundance.
- Full Text:
- Authors: Froneman, P William
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6901 , http://hdl.handle.net/10962/d1011754
- Description: Size-fractionated chlorophyll-a (chl-a) concentrations and the in situ grazing rates of the copepods, Pseudodiaptomus hessei and Acartia longipatella, were assessed seasonally at the temporarily open/closed Kasouga estuary situated along the southeast coast of southern Africa. Total integrated chl-a concentration ranged between 1.17 and 12.18 mg chl-a m^(–3) and was always dominated by small phytoplankton cells (<20 μm), which comprised up to 86% (range 64–86%) of the total pigment. Total zooplankton abundance ranged between 2676 and 62 043 individuals m^(–3). These copepods numerically dominated the zooplankton counts, accounting for between 79% and 91% of the total. Gut pigment concentrations of the two species at night were significantly higher than the daytime values (P<0.05 in all cases). The observed pattern could be related to the marked diurnal vertical migration patterns exhibited by the copepods. Gut evacuation rates of P. hessei during the study ranged between 0.29 and 0.77 h^(–1) and between 0.39 and 0.58 h^(–1) for A. longipatella. The rate of gut pigment destruction for P. hessei and A. longipatella ranged between 55% and 81% and between 88% and 92% of the total chl-a ingested, respectively. The combined grazing impact of the two copepods ranged between 0.65 and 4.37 mg chl-a m^(–3), or between 4.3% and 35.9% of the available chl-a in the water column. Variations in the grazing activity of the two species could be attributed largely to seasonality in water temperature and shifts in the phytoplankton community structure and zooplankton abundance.
- Full Text:
Making sense of science through two languages: a South African case study
- Authors: Probyn, Margie J
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7025 , http://hdl.handle.net/10962/d1007209
- Description: Mzamo Senior Secondary School (not its real name) looks like any typical township school in South Africa: modern face-brick classroom blocks which conceal a serious lack of resources, material and human. Under apartheid the disparities in spending on white and African students meant hugely different teaching and learning contexts - including infrastructure, teacher training, pupil: teacher ratios and teaching materials. Today, 10 years into the new democracy and despite government’s efforts to equalize spending, the historic inequalities persist. The school is surrounded by township houses and shacks that reflect the high poverty levels in the Eastern Cape Province. Students at schools like this face an additional but less obvious problem – that of the language medium. Although in the Eastern Cape, Xhosa is the home language of 83,8% of the population and English speakers comprise only 3.7%, the official language medium in schools is English from the beginning of Grade 4 in the majority of schools. South Africa is a multilingual country with 11 official languages recognized in the Constitution of 1996 – 9 indigenous languages and the two colonial languages, English and Afrikaans.
- Full Text:
- Authors: Probyn, Margie J
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7025 , http://hdl.handle.net/10962/d1007209
- Description: Mzamo Senior Secondary School (not its real name) looks like any typical township school in South Africa: modern face-brick classroom blocks which conceal a serious lack of resources, material and human. Under apartheid the disparities in spending on white and African students meant hugely different teaching and learning contexts - including infrastructure, teacher training, pupil: teacher ratios and teaching materials. Today, 10 years into the new democracy and despite government’s efforts to equalize spending, the historic inequalities persist. The school is surrounded by township houses and shacks that reflect the high poverty levels in the Eastern Cape Province. Students at schools like this face an additional but less obvious problem – that of the language medium. Although in the Eastern Cape, Xhosa is the home language of 83,8% of the population and English speakers comprise only 3.7%, the official language medium in schools is English from the beginning of Grade 4 in the majority of schools. South Africa is a multilingual country with 11 official languages recognized in the Constitution of 1996 – 9 indigenous languages and the two colonial languages, English and Afrikaans.
- Full Text:
Pre-emigration reflections : Afrikaans speakers moving to New Zealand
- De Klerk, Vivian A, Barkhuizen, Gary
- Authors: De Klerk, Vivian A , Barkhuizen, Gary
- Date: 2004
- Language: English
- Type: Article , text
- Identifier: vital:6138 , http://hdl.handle.net/10962/d1011590
- Description: This article reports on the pre-emigration reflections of 15 Afrikaans speakers, all of whom were in the final stages of preparing to emigrate to New Zealand. The study explores the linguistic histories of the participants, their attitudes to their mother tongue (Afrikaans) and to English, and their views on South Africa's language policy and how it has influenced their decisions to leave the country. The paper also offers a view on possible long-term linguistic outcomes for these families.
- Full Text:
- Authors: De Klerk, Vivian A , Barkhuizen, Gary
- Date: 2004
- Language: English
- Type: Article , text
- Identifier: vital:6138 , http://hdl.handle.net/10962/d1011590
- Description: This article reports on the pre-emigration reflections of 15 Afrikaans speakers, all of whom were in the final stages of preparing to emigrate to New Zealand. The study explores the linguistic histories of the participants, their attitudes to their mother tongue (Afrikaans) and to English, and their views on South Africa's language policy and how it has influenced their decisions to leave the country. The paper also offers a view on possible long-term linguistic outcomes for these families.
- Full Text:
Recent African derivation of Chrysomya putoria from C. chloropyga and mitochondrial DNA paraphyly of cytochrome oxidase subunit one in blowflies of forensic importance
- Wells, J D, Lunt, N, Villet, Martin H
- Authors: Wells, J D , Lunt, N , Villet, Martin H
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6888 , http://hdl.handle.net/10962/d1011648
- Description: Chrysomya chloropyga (Wiedemann) and C. putoria (Wiedemann) (Diptera: Calliphoridae) are closely related Afrotropical blowflies that breed in carrion and latrines, reaching high density in association with humans and spreading to other continents. In some cases of human death, Chyrsomya specimens provide forensic clues. Because the immature stages of such flies are often difficult to identify taxonomically, it is useful to develop DNA-based tests for specimen identification. Therefore we attempted to distinguish between C. chloropyga and C. putoria using mitochondrial DNA (mtDNA) sequence data from a 593-bp region of the gene for cytochrome oxidase subunit one (COI). Twelve specimens from each species yielded a total of five haplotypes, none being unique to C. putoria. Therefore it was not possible to distinguish between the two species using this locus. Maximum parsimony analysis indicated paraphyletic C. chloropyga mtDNA with C. putoria nested therein. Based on these and previously published data, we infer that C. putoria diverged very recently from C. chloropyga.
- Full Text:
- Authors: Wells, J D , Lunt, N , Villet, Martin H
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6888 , http://hdl.handle.net/10962/d1011648
- Description: Chrysomya chloropyga (Wiedemann) and C. putoria (Wiedemann) (Diptera: Calliphoridae) are closely related Afrotropical blowflies that breed in carrion and latrines, reaching high density in association with humans and spreading to other continents. In some cases of human death, Chyrsomya specimens provide forensic clues. Because the immature stages of such flies are often difficult to identify taxonomically, it is useful to develop DNA-based tests for specimen identification. Therefore we attempted to distinguish between C. chloropyga and C. putoria using mitochondrial DNA (mtDNA) sequence data from a 593-bp region of the gene for cytochrome oxidase subunit one (COI). Twelve specimens from each species yielded a total of five haplotypes, none being unique to C. putoria. Therefore it was not possible to distinguish between the two species using this locus. Maximum parsimony analysis indicated paraphyletic C. chloropyga mtDNA with C. putoria nested therein. Based on these and previously published data, we infer that C. putoria diverged very recently from C. chloropyga.
- Full Text:
Science after a century at Rhodes University
- Authors: Woods, D R
- Date: 2004
- Language: English
- Type: Article , text
- Identifier: vital:7123 , http://hdl.handle.net/10962/d1006584
- Description: Rhodes Centenary issue , The small University of Rhodes (6142 students), in the rural city of Grahamstown, was established in 1904 as a result of a £50 000 grant from the Rhodes Trust in Oxford. It grew out of St Andrew’s College, which provided the first four professors and 41 students. The first paper from Rhodes in the South African Journal of Science (then called the Report of the South African Association for the Advancement of Science) was by Selmar Schonland, one of the university’s founding fathers. Entitled: ‘Biological and ethnological observations on a trip to the N.E. Kalahari’, it appeared in 1904. The following pages provide a glimpse into the growth and achievements of various departments in the faculties of Science and Pharmacy and associated institutes a century after the university was born.
- Full Text:
- Authors: Woods, D R
- Date: 2004
- Language: English
- Type: Article , text
- Identifier: vital:7123 , http://hdl.handle.net/10962/d1006584
- Description: Rhodes Centenary issue , The small University of Rhodes (6142 students), in the rural city of Grahamstown, was established in 1904 as a result of a £50 000 grant from the Rhodes Trust in Oxford. It grew out of St Andrew’s College, which provided the first four professors and 41 students. The first paper from Rhodes in the South African Journal of Science (then called the Report of the South African Association for the Advancement of Science) was by Selmar Schonland, one of the university’s founding fathers. Entitled: ‘Biological and ethnological observations on a trip to the N.E. Kalahari’, it appeared in 1904. The following pages provide a glimpse into the growth and achievements of various departments in the faculties of Science and Pharmacy and associated institutes a century after the university was born.
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The development of a toxicity database using freshwater macroinvertebrates, and its application to the protection of South African water resources
- Palmer, Carolyn G, Muller, Wilhelmine J, Gordon, Andrew K, Scherman, Patricia A, Davies-Coleman, Heather D, Pakhomova, L, de Kock, E
- Authors: Palmer, Carolyn G , Muller, Wilhelmine J , Gordon, Andrew K , Scherman, Patricia A , Davies-Coleman, Heather D , Pakhomova, L , de Kock, E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7073 , http://hdl.handle.net/10962/d1009528
- Description: There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies.
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- Authors: Palmer, Carolyn G , Muller, Wilhelmine J , Gordon, Andrew K , Scherman, Patricia A , Davies-Coleman, Heather D , Pakhomova, L , de Kock, E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7073 , http://hdl.handle.net/10962/d1009528
- Description: There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies.
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The wing coupling apparatus and the morphometric analysis of honeybee populations
- Hepburn, H Randall, Radloff, Sarah E
- Authors: Hepburn, H Randall , Radloff, Sarah E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6904 , http://hdl.handle.net/10962/d1011760
- Description: Significant differences between countries were found in the distribution of the number of hamuli within Apis andreniformis, A. florea, A. cerana and A. koschevnikovi. The mean hamuli numbers for Apis mellifera intermissa differed significantly among localities in Algeria. Significant differences in intercolonial variability between countries were found within A. cerana. There was no significant infraspecific variability within A. andreniformis, A. florea, A. koschevnikovi and A. m. intermissa. Significant differences in the mean number of hamuli occur between A. m. intermissa and A. andreniformis, A. florea and A. cerana; also between A. cerana/A. koschevnikovi and A. andreniformis and A. florea. Significant differences were found in the distribution and variability of the number of hamuli between species (populations). The mean numbers of hamuli for A. andreniformis differed from those of A. florea. Both these population means differed from those of A. cerana, A. koschevnikovi and A. m. intermissa. No significant differences were found between A. cerana and A. koschevnikovi. When the analysis included data for A. dorsata, A. nigrocincta, A. m. carnica, A. m. caucasica and A. m. ligustica, the results showed significant differences in hamuli numbers between A. andreniformis/A. florea and A. cerana/A. koschevnikovi/A. nigrocincta and A. m. intermissa/A. m. carnica/A. m. caucasica/A. m. ligustica. Hamuli numbers in A. dorsata significantly differed from those of other populations except A. m. intermissa. These results show that hamuli numbers are useful in the classification of honeybee populations. Whether hamuli would be useful in multivariate analysis depends on the correlation between the number of hamuli and the other characters used.
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- Authors: Hepburn, H Randall , Radloff, Sarah E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:6904 , http://hdl.handle.net/10962/d1011760
- Description: Significant differences between countries were found in the distribution of the number of hamuli within Apis andreniformis, A. florea, A. cerana and A. koschevnikovi. The mean hamuli numbers for Apis mellifera intermissa differed significantly among localities in Algeria. Significant differences in intercolonial variability between countries were found within A. cerana. There was no significant infraspecific variability within A. andreniformis, A. florea, A. koschevnikovi and A. m. intermissa. Significant differences in the mean number of hamuli occur between A. m. intermissa and A. andreniformis, A. florea and A. cerana; also between A. cerana/A. koschevnikovi and A. andreniformis and A. florea. Significant differences were found in the distribution and variability of the number of hamuli between species (populations). The mean numbers of hamuli for A. andreniformis differed from those of A. florea. Both these population means differed from those of A. cerana, A. koschevnikovi and A. m. intermissa. No significant differences were found between A. cerana and A. koschevnikovi. When the analysis included data for A. dorsata, A. nigrocincta, A. m. carnica, A. m. caucasica and A. m. ligustica, the results showed significant differences in hamuli numbers between A. andreniformis/A. florea and A. cerana/A. koschevnikovi/A. nigrocincta and A. m. intermissa/A. m. carnica/A. m. caucasica/A. m. ligustica. Hamuli numbers in A. dorsata significantly differed from those of other populations except A. m. intermissa. These results show that hamuli numbers are useful in the classification of honeybee populations. Whether hamuli would be useful in multivariate analysis depends on the correlation between the number of hamuli and the other characters used.
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Three decades of hydrological modelling research in South Africa
- Authors: Hughes, Denis A
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7072 , http://hdl.handle.net/10962/d1009526
- Description: This paper presents a review of the research undertaken in the field of hydrological modelling over roughly the last three decades, concentrating primarily on South African work in an international context. The focus is on deterministic, rainfall-runoff models and addresses issues related to model design as well as to the application of models in practice. I provide a brief description of what hydrological models are and what they are used for and discuss also the following issues: • Developments in understanding hydrological process and the extent to which these have filtered down into models. • Model calibration and parameter estimation. • Trends in data availability and how these have affected model development. • Trends in computer technology and their impacts on model development. I suggest that there have been substantial developments in the science and practice of hydrological modelling, but that there remain many problems that need to be addressed to improve the ability of models to contribute to the solution of problems of water resource management. Southern African scientists have contributed to the body of knowledge on hydrological modelling, despite the limited resources available compared to resources elsewhere. Internationally, the focus has not always been on the practical issues of model application and has commonly tended towards the more theoretical and mathematical issues of model calibration. This is not a trend that has found much favour in southern Africa (particularly amongst research funding agencies), where there are many problems of water resource management that have the potential to be resolved with existing models, applied in an appropriate way. The paper concludes by suggesting that further research needs to focus on the integration of the best in international developments with the tried and tested models that have been developed locally. The context of this research should be the search for more reliable estimations of water resource availability.
- Full Text:
- Authors: Hughes, Denis A
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7072 , http://hdl.handle.net/10962/d1009526
- Description: This paper presents a review of the research undertaken in the field of hydrological modelling over roughly the last three decades, concentrating primarily on South African work in an international context. The focus is on deterministic, rainfall-runoff models and addresses issues related to model design as well as to the application of models in practice. I provide a brief description of what hydrological models are and what they are used for and discuss also the following issues: • Developments in understanding hydrological process and the extent to which these have filtered down into models. • Model calibration and parameter estimation. • Trends in data availability and how these have affected model development. • Trends in computer technology and their impacts on model development. I suggest that there have been substantial developments in the science and practice of hydrological modelling, but that there remain many problems that need to be addressed to improve the ability of models to contribute to the solution of problems of water resource management. Southern African scientists have contributed to the body of knowledge on hydrological modelling, despite the limited resources available compared to resources elsewhere. Internationally, the focus has not always been on the practical issues of model application and has commonly tended towards the more theoretical and mathematical issues of model calibration. This is not a trend that has found much favour in southern Africa (particularly amongst research funding agencies), where there are many problems of water resource management that have the potential to be resolved with existing models, applied in an appropriate way. The paper concludes by suggesting that further research needs to focus on the integration of the best in international developments with the tried and tested models that have been developed locally. The context of this research should be the search for more reliable estimations of water resource availability.
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6-Hydroxymelatonin protects against cyanide induced oxidative stress in rat brain homogenates
- Maharaj, Deepa S, Walker, Roderick B, Glass, Beverley D, Daya, Santylal
- Authors: Maharaj, Deepa S , Walker, Roderick B , Glass, Beverley D , Daya, Santylal
- Date: 2003
- Language: English
- Type: Article , text
- Identifier: vital:6405 , http://hdl.handle.net/10962/d1006478
- Description: Both 6-hydroxymelatonin and N-acetyl-N-formyl-5-methoxykynurenamine are photodegradants and enzymatic metabolites of melatonin and are known to retain equipotent activity against potassium cyanide-induced superoxide generation compared to melatonin. It is not clear whether one or both of these metabolites is responsible for this effect. The present study therefore investigates the possible manner in which 6-hydroxymelatonin protects against oxidative stress induced by cyanide in rat brain homogenates. We examined the ability of 6-hydroxymelatonin to scavenge KCN-induced superoxide anion generation as well as lipid peroxidation. In addition, we also examined the effect of this indole on lactate dehydrogenase activity (LDH) as well as mitochondrial electron transport using dichlorophenol–indophenol as an electron acceptor. The results of this study show that 6-hydroxymelatonin significantly reduces KCN-induced superoxide anion generation, which is accompanied by a commensurate reduction in lipid peroxidation. Partial reversal of the KCN-induced reduction in mitochondrial electron transport is accompanied by a similar reversal of mitochondrial LDH activity blunted by KCN. It can thus be proposed that 6-hydroxymelatonin is potentially neuroprotective against KCN-induced neurotoxicity.
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- Authors: Maharaj, Deepa S , Walker, Roderick B , Glass, Beverley D , Daya, Santylal
- Date: 2003
- Language: English
- Type: Article , text
- Identifier: vital:6405 , http://hdl.handle.net/10962/d1006478
- Description: Both 6-hydroxymelatonin and N-acetyl-N-formyl-5-methoxykynurenamine are photodegradants and enzymatic metabolites of melatonin and are known to retain equipotent activity against potassium cyanide-induced superoxide generation compared to melatonin. It is not clear whether one or both of these metabolites is responsible for this effect. The present study therefore investigates the possible manner in which 6-hydroxymelatonin protects against oxidative stress induced by cyanide in rat brain homogenates. We examined the ability of 6-hydroxymelatonin to scavenge KCN-induced superoxide anion generation as well as lipid peroxidation. In addition, we also examined the effect of this indole on lactate dehydrogenase activity (LDH) as well as mitochondrial electron transport using dichlorophenol–indophenol as an electron acceptor. The results of this study show that 6-hydroxymelatonin significantly reduces KCN-induced superoxide anion generation, which is accompanied by a commensurate reduction in lipid peroxidation. Partial reversal of the KCN-induced reduction in mitochondrial electron transport is accompanied by a similar reversal of mitochondrial LDH activity blunted by KCN. It can thus be proposed that 6-hydroxymelatonin is potentially neuroprotective against KCN-induced neurotoxicity.
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Analysis of the calling songs of Platypleura hirtipennis (Germar, 1834) and P. plumosa (Germar, 1834) (Hemiptera: Cicadidae)
- Sanborn, Allen F, Phillips, Polly K F, Villet, Martin H
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6896 , http://hdl.handle.net/10962/d1011656
- Description: [From the introduction]: Most male cicadas produce a calling song in order to attract conspecific females. These songs have been shown to differ in closely related species (e.g. Alexander & Moore 1962; Villet 1988, 1989; Boulard 1995; Marshall & Cooley 2000; Sanborn & Phillips 2001) and in species which share habitats (e.g. Sueur 2002). The former is an inevitable part of the divergence of recognition signals that characterizes the speciation process in animals using acoustic signals (Villet 1995), while the latter would be expected from a signal that acts as a reproductive isolating mechanism (Claridge 1985; Marshall & Cooley 2000). Calling songs are therefore of value in resolving taxonomic problems in the cicadas.
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- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6896 , http://hdl.handle.net/10962/d1011656
- Description: [From the introduction]: Most male cicadas produce a calling song in order to attract conspecific females. These songs have been shown to differ in closely related species (e.g. Alexander & Moore 1962; Villet 1988, 1989; Boulard 1995; Marshall & Cooley 2000; Sanborn & Phillips 2001) and in species which share habitats (e.g. Sueur 2002). The former is an inevitable part of the divergence of recognition signals that characterizes the speciation process in animals using acoustic signals (Villet 1995), while the latter would be expected from a signal that acts as a reproductive isolating mechanism (Claridge 1985; Marshall & Cooley 2000). Calling songs are therefore of value in resolving taxonomic problems in the cicadas.
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Endothermy and chorusing behaviour in the African platypleurine cicada Pycna semiclara (Germar, 1834) (Hemiptera: Cicadidae)
- Villet, Martin H, Sanborn, Allen F, Phillips, Polly K F
- Authors: Villet, Martin H , Sanborn, Allen F , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6892 , http://hdl.handle.net/10962/d1011652 , http://dx.doi.org/10.1139/z03-119
- Description: Cicadas use acoustic signals to find mates and therefore offer a phylogenetically independent opportunity to test the generality of ideas about acoustic communication that were developed from studies of other animals. Pycna semiclara (Germar, 1834) (Hemiptera: Cicadidae) is a forest-dwelling platypleurine cicada that uses its calling song to form choruses and attract mates. Additionally, P. semiclara produces an encounter call that is involved in courtship and also in spacing males within choruses. Males generally call from exposed trunks and branches within the understory but clear of the undergrowth and fight with other males that call within about 50 cm of them. Choruses sing sporadically throughout the day but focus most of their calling activity into half-hour bouts at dawn and dusk. Body size and ambient temperature had no significant effect on spectral or temporal characteristics of the calling song. Body temperature measurements indicate that P. semiclara thermoregulates endothermically, with a body temperature of more than 22 °C above ambient temperature being measured during calling activity at dusk. Such endothermy provides an advantage to the cicadas by allowing them to call during crepuscular hours when atmospheric conditions are most optimal for acoustic communication and predation risks are minimal. Coincidentally, endogenously regulating body temperature allows the temporal characteristics of the call to be unaffected by ambient temperature changes.
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- Authors: Villet, Martin H , Sanborn, Allen F , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6892 , http://hdl.handle.net/10962/d1011652 , http://dx.doi.org/10.1139/z03-119
- Description: Cicadas use acoustic signals to find mates and therefore offer a phylogenetically independent opportunity to test the generality of ideas about acoustic communication that were developed from studies of other animals. Pycna semiclara (Germar, 1834) (Hemiptera: Cicadidae) is a forest-dwelling platypleurine cicada that uses its calling song to form choruses and attract mates. Additionally, P. semiclara produces an encounter call that is involved in courtship and also in spacing males within choruses. Males generally call from exposed trunks and branches within the understory but clear of the undergrowth and fight with other males that call within about 50 cm of them. Choruses sing sporadically throughout the day but focus most of their calling activity into half-hour bouts at dawn and dusk. Body size and ambient temperature had no significant effect on spectral or temporal characteristics of the calling song. Body temperature measurements indicate that P. semiclara thermoregulates endothermically, with a body temperature of more than 22 °C above ambient temperature being measured during calling activity at dusk. Such endothermy provides an advantage to the cicadas by allowing them to call during crepuscular hours when atmospheric conditions are most optimal for acoustic communication and predation risks are minimal. Coincidentally, endogenously regulating body temperature allows the temporal characteristics of the call to be unaffected by ambient temperature changes.
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Foam drug delivery in dermatology: beyond the scalp
- Purdon, Carryn H, Haigh, John M, Surber, Christian, Smith, Eric W
- Authors: Purdon, Carryn H , Haigh, John M , Surber, Christian , Smith, Eric W
- Date: 2003
- Subjects: Adis International Limited , Drug delivery systems , Skin disorders
- Language: English
- Type: text , Article
- Identifier: vital:6418 , http://hdl.handle.net/10962/d1006541
- Description: Consumers of topical formulations apply a wide spectrum of preparations, both cosmetic and dermatological, to their healthy or diseased skin. These formulations range in physicochemical nature from solid through semisolid to liquid. Pharmaceutical foams are pressurized dosage forms containing one or more active ingredients that, upon valve actuation, emit a fine dispersion of liquid and/or solid materials in a gaseous medium. Foam formulations are generally easier to apply, are less dense, and spread more easily than other topical dosage forms. Foams may be formulated in various ways to provide emollient or drying functions to the skin, depending on the formulation constituents. Therefore, this delivery technology should be a useful addition to the spectrum of formulations available for topical use; however, as yet, only a few are commercially available. Probably the most convincing argument for the use of foams is ease of use by the patient, and consumer acceptance. Most foam dosage forms used in dermatology to date have incorporated corticosteroids, although some products have also been used to deliver antiseptics, antifungal agents, anti-inflammatory agents, local anesthetic agents, skin emollients, and protectants. Although there is no clinical evidence that foam formulations are currently superior to other conventional delivery vehicles, these formulations have a clear application advantage and with continued developments in the science of supersaturation technology, it seems certain that foam delivery systems will retain their place in the dermatological and cosmetic armamentarium.
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- Authors: Purdon, Carryn H , Haigh, John M , Surber, Christian , Smith, Eric W
- Date: 2003
- Subjects: Adis International Limited , Drug delivery systems , Skin disorders
- Language: English
- Type: text , Article
- Identifier: vital:6418 , http://hdl.handle.net/10962/d1006541
- Description: Consumers of topical formulations apply a wide spectrum of preparations, both cosmetic and dermatological, to their healthy or diseased skin. These formulations range in physicochemical nature from solid through semisolid to liquid. Pharmaceutical foams are pressurized dosage forms containing one or more active ingredients that, upon valve actuation, emit a fine dispersion of liquid and/or solid materials in a gaseous medium. Foam formulations are generally easier to apply, are less dense, and spread more easily than other topical dosage forms. Foams may be formulated in various ways to provide emollient or drying functions to the skin, depending on the formulation constituents. Therefore, this delivery technology should be a useful addition to the spectrum of formulations available for topical use; however, as yet, only a few are commercially available. Probably the most convincing argument for the use of foams is ease of use by the patient, and consumer acceptance. Most foam dosage forms used in dermatology to date have incorporated corticosteroids, although some products have also been used to deliver antiseptics, antifungal agents, anti-inflammatory agents, local anesthetic agents, skin emollients, and protectants. Although there is no clinical evidence that foam formulations are currently superior to other conventional delivery vehicles, these formulations have a clear application advantage and with continued developments in the science of supersaturation technology, it seems certain that foam delivery systems will retain their place in the dermatological and cosmetic armamentarium.
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Hot-blooded singers: endothermy facilitates crepuscular signaling in African platypleurine cicadas (Hemiptera: Cicadidae: Platypleura spp.)
- Sanborn, Allen F, Villet, Martin H, Phillips, Polly K F
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6919 , http://hdl.handle.net/10962/d1011882
- Description: The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Maximum Tb measured was 22.1°C above ambient temperature during calling activity at dusk. The mean Tb during dusk activity did not differ from the mean Tb during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate Tb. Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.
- Full Text:
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6919 , http://hdl.handle.net/10962/d1011882
- Description: The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Maximum Tb measured was 22.1°C above ambient temperature during calling activity at dusk. The mean Tb during dusk activity did not differ from the mean Tb during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate Tb. Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.
- Full Text: