Effects of habitat patch size and isolation on the population structure of two siphonarian limpets
- Authors: Johnson, Linda Gail
- Date: 2011
- Subjects: Siphonaria , Limpets , Population biology , Marine ecology , Habitat selection , Animals -- Dispersal , Ecological heterogeneity , Animal populations , Biodiversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5679 , http://hdl.handle.net/10962/d1005364 , Siphonaria , Limpets , Population biology , Marine ecology , Habitat selection , Animals -- Dispersal , Ecological heterogeneity , Animal populations , Biodiversity
- Description: Habitat fragmentation is a fundamental process that determines trends and patterns of distribution and density of organisms. These patterns and trends have been the focus of numerous terrestrial and marine studies and have led to the development of several explanatory hypotheses. Systems and organisms are dynamic and no single hypothesis has adequately accounted for these observed trends. It is therefore important to understand the interaction of these processes and patterns to explain the mechanisms controlling population dynamics. The main aim of this thesis was to test the effect of patch size and isolation on organisms with different modes of dispersal. Mode of dispersal has previously been examined as a factor influencing the effects that habitat fragmentation has on organisms. Very few studies have, however, examined the mode of dispersal of marine organisms because it has long been assumed that marine animals are not directly influenced by habitat fragmentation because of large-scale dispersal. I used two co-occurring species of siphonariid limpets with different modes of dispersal to highlight that not only are marine organisms affected by habitat fragmentation but that they are affected in different ways. The two species of limpet, Siphonaria serrata and Siphonaria concinna, are found within the same habitat and have the same geographic range along the South African coastline, however, they have different modes of dispersal and development. The effect of patch size on organism density has been examined to a great extent with varied results. This study investigated whether habitat patch size played a key role in determining population density and limpet body sizes. The two species are found on the eastern and southern coasts of South Africa were examined across this entire biogeographic range. Patch size was found to have a significant effect on population density of the pelagic developer, S. concinna, but not the direct developing S. serrata. Patch size did play a role in determining limpet body size for both species. S. concinna body size was proposed to be effected directly by patch size whilst S. serrata body size was proposed to be affected indirectly by the effects of the S. concinna densities. The same patterns and trends were observed at five of the seven examined regions across the biogeographic range. The trends observed for S. concinna with respect to patch size conform to the source-sink hypothesis with large habitat patches acting as the source populations whilst the small habitat patches acted as the sink populations. Many previous studies have focused on the effects of habitat patch size at one point in time or over one season. I tested the influence of habitat patch size on the two species of limpets over a period of twelve months to determine whether the trends observed were consistent over time or whether populations varied with time. S. concinna showed a consistently significant difference between small and large patches; whilst S. serrata did not follow a consistent pattern. The mode of dispersal for the two limpets was used to explain the different trends shown by the two species. This examination allowed for the determining of source and sink populations for S. concinna through the examination of fluctuations in limpet body sizes and population densities at small and large habitat patches over twelve months. The direct developing S. serrata trends could not be explained using source-sink theory, as populations were independent from one another. S. serrata demonstrated body size differences at small and large patches which, may be explained by interspecific and intraspecific competition. Habitat isolation is known to play an important role in determining the structure of assemblages and the densities of populations. In this study the population density of the pelagic developing S. concinna showed a weak influence of degree of isolation whilst that of the direct developing S. serrata did not, which may be because of habitat patches along the South African coastline not having great enough degrees of isolation. The population size-structure was influenced directly influenced by isolation for S. concinna, whilst the different population size structure for S. serrata may be explained by assemblage co-dependence. The mode of dispersal showed effects on the relationship of population density and population size-structure with habitat size and isolation. This study indicates the importance of investigating patterns and processes across a range of spatial and temporal scales to gain a comprehensive understanding of factors effecting intertidal organisms.
- Full Text:
- Authors: Johnson, Linda Gail
- Date: 2011
- Subjects: Siphonaria , Limpets , Population biology , Marine ecology , Habitat selection , Animals -- Dispersal , Ecological heterogeneity , Animal populations , Biodiversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5679 , http://hdl.handle.net/10962/d1005364 , Siphonaria , Limpets , Population biology , Marine ecology , Habitat selection , Animals -- Dispersal , Ecological heterogeneity , Animal populations , Biodiversity
- Description: Habitat fragmentation is a fundamental process that determines trends and patterns of distribution and density of organisms. These patterns and trends have been the focus of numerous terrestrial and marine studies and have led to the development of several explanatory hypotheses. Systems and organisms are dynamic and no single hypothesis has adequately accounted for these observed trends. It is therefore important to understand the interaction of these processes and patterns to explain the mechanisms controlling population dynamics. The main aim of this thesis was to test the effect of patch size and isolation on organisms with different modes of dispersal. Mode of dispersal has previously been examined as a factor influencing the effects that habitat fragmentation has on organisms. Very few studies have, however, examined the mode of dispersal of marine organisms because it has long been assumed that marine animals are not directly influenced by habitat fragmentation because of large-scale dispersal. I used two co-occurring species of siphonariid limpets with different modes of dispersal to highlight that not only are marine organisms affected by habitat fragmentation but that they are affected in different ways. The two species of limpet, Siphonaria serrata and Siphonaria concinna, are found within the same habitat and have the same geographic range along the South African coastline, however, they have different modes of dispersal and development. The effect of patch size on organism density has been examined to a great extent with varied results. This study investigated whether habitat patch size played a key role in determining population density and limpet body sizes. The two species are found on the eastern and southern coasts of South Africa were examined across this entire biogeographic range. Patch size was found to have a significant effect on population density of the pelagic developer, S. concinna, but not the direct developing S. serrata. Patch size did play a role in determining limpet body size for both species. S. concinna body size was proposed to be effected directly by patch size whilst S. serrata body size was proposed to be affected indirectly by the effects of the S. concinna densities. The same patterns and trends were observed at five of the seven examined regions across the biogeographic range. The trends observed for S. concinna with respect to patch size conform to the source-sink hypothesis with large habitat patches acting as the source populations whilst the small habitat patches acted as the sink populations. Many previous studies have focused on the effects of habitat patch size at one point in time or over one season. I tested the influence of habitat patch size on the two species of limpets over a period of twelve months to determine whether the trends observed were consistent over time or whether populations varied with time. S. concinna showed a consistently significant difference between small and large patches; whilst S. serrata did not follow a consistent pattern. The mode of dispersal for the two limpets was used to explain the different trends shown by the two species. This examination allowed for the determining of source and sink populations for S. concinna through the examination of fluctuations in limpet body sizes and population densities at small and large habitat patches over twelve months. The direct developing S. serrata trends could not be explained using source-sink theory, as populations were independent from one another. S. serrata demonstrated body size differences at small and large patches which, may be explained by interspecific and intraspecific competition. Habitat isolation is known to play an important role in determining the structure of assemblages and the densities of populations. In this study the population density of the pelagic developing S. concinna showed a weak influence of degree of isolation whilst that of the direct developing S. serrata did not, which may be because of habitat patches along the South African coastline not having great enough degrees of isolation. The population size-structure was influenced directly influenced by isolation for S. concinna, whilst the different population size structure for S. serrata may be explained by assemblage co-dependence. The mode of dispersal showed effects on the relationship of population density and population size-structure with habitat size and isolation. This study indicates the importance of investigating patterns and processes across a range of spatial and temporal scales to gain a comprehensive understanding of factors effecting intertidal organisms.
- Full Text:
Electrochemical behavior of phthalocyanines containing high oxidation state central metals
- Chauke, Vongani, Arslanoglu, Yasin, Nyokong, Tebello
- Authors: Chauke, Vongani , Arslanoglu, Yasin , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247111 , vital:51547 , xlink:href="https://doi.org/10.1016/j.poly.2011.05.028"
- Description: The syntheses of 2,(3)-(peripheral) and 1,(4)-(non-peripheral) (2-mercaptopyridine)phthalocyanine complexes of titanium(IV) oxide (5a and 6a, respectively), vanadium(IV) oxide (7a and 8a, respectively) and tantalum(V) hydroxide (9a, peripheral only) and their electrochemical characterization are presented in this report. Their electrochemistry is compared to that of thiophenyl and thiobenzyl substituted derivatives. The non-peripherally substituted complexes are more difficult to reduce than peripherally substituted derivatives. In addition, the mercaptopyridine substituted derivatives are more difficult to reduce compared to benzylmercapto and phenylmercapto derivatives, and aryl easier reduce than alkyl substitution. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes.
- Full Text:
- Authors: Chauke, Vongani , Arslanoglu, Yasin , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247111 , vital:51547 , xlink:href="https://doi.org/10.1016/j.poly.2011.05.028"
- Description: The syntheses of 2,(3)-(peripheral) and 1,(4)-(non-peripheral) (2-mercaptopyridine)phthalocyanine complexes of titanium(IV) oxide (5a and 6a, respectively), vanadium(IV) oxide (7a and 8a, respectively) and tantalum(V) hydroxide (9a, peripheral only) and their electrochemical characterization are presented in this report. Their electrochemistry is compared to that of thiophenyl and thiobenzyl substituted derivatives. The non-peripherally substituted complexes are more difficult to reduce than peripherally substituted derivatives. In addition, the mercaptopyridine substituted derivatives are more difficult to reduce compared to benzylmercapto and phenylmercapto derivatives, and aryl easier reduce than alkyl substitution. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes.
- Full Text:
Electrochemical, microscopic and spectroscopic characterization of benzene diamine functionalized single walled carbon nanotube-cobalt (II) tetracarboxy-phthalocyanine conjugates
- Mugadza, Tawanda, Nyokong, Tebello
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247859 , vital:51624 , xlink:href="https://doi.org/10.1016/j.jcis.2010.10.057"
- Description: In this paper we report on the synthesis and characterization of 1,4-benzene diamine (BDA) functionalized single walled carbon nanotubes linked to cobalt (II) tetracarboxy-phthalocyanine. The characterization of the conjugate was through UV–vis, FTIR and X-ray diffraction (XRD) spectroscopies and by transmission electron microscope (TEM) and electrochemical methods. The conjugate is used for the electrochemical characterization of diuron. The catalytic rate constant for diuron was 4.4 × 103 M−1 s−1 and the apparent electron transfer rate constant was 18.5 × 10−6 cm s−1. The linear dynamic range was 1.0 × 10−5–2.0 × 10−4 M, with a sensitivity of ∼0.42 A mol−1L cm−2 and a limit of detection of 0.18 μM using the 3δ notation.
- Full Text:
- Authors: Mugadza, Tawanda , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247859 , vital:51624 , xlink:href="https://doi.org/10.1016/j.jcis.2010.10.057"
- Description: In this paper we report on the synthesis and characterization of 1,4-benzene diamine (BDA) functionalized single walled carbon nanotubes linked to cobalt (II) tetracarboxy-phthalocyanine. The characterization of the conjugate was through UV–vis, FTIR and X-ray diffraction (XRD) spectroscopies and by transmission electron microscope (TEM) and electrochemical methods. The conjugate is used for the electrochemical characterization of diuron. The catalytic rate constant for diuron was 4.4 × 103 M−1 s−1 and the apparent electron transfer rate constant was 18.5 × 10−6 cm s−1. The linear dynamic range was 1.0 × 10−5–2.0 × 10−4 M, with a sensitivity of ∼0.42 A mol−1L cm−2 and a limit of detection of 0.18 μM using the 3δ notation.
- Full Text:
Electrooxidation of Chlorophenols Catalyzed by Nickel Octadecylphthalocyanine Adsorbed on Single‐Walled Carbon Nanotubes
- Khene, Samson, Nyokong, Tebello
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247198 , vital:51555 , xlink:href="https://doi.org/10.1002/elan.201100155"
- Description: We described the synthesis of nickel octadecylphthalocyanine (NiPc(C10H21)8), followed by its adsorption on single-walled carbon nanotubes (SWCNT) to form SWCNT-NiPc(C10H21)8 conjugates. SWCNT-NiPc(C10H21)8 was used to modify a glassy carbon electrode (GCE) and for the electrooxidation of 4-chlorophenol and 2,4-dichlorophenol. The SWCNT and NiPc(C10H21)8 have a synergistic effect on each other in terms of improving electrocatalysis for the detection of chlorophenols. The stability of the electrode improved in the presence of NiPc(C10H21)8 or NiPc compared to the bare GCE. The presence of SWCNT improves the electrocatalytic behaviour of NiPc(C10H21)8 but not of unsubstituted NiPc. All modified electrodes showed improved stability towards the detection of 2,4-dichlorophenol. The best stability for 4-CP detection was observed in the presence of SWCNT for NiPc(C10H21)8.
- Full Text:
- Authors: Khene, Samson , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247198 , vital:51555 , xlink:href="https://doi.org/10.1002/elan.201100155"
- Description: We described the synthesis of nickel octadecylphthalocyanine (NiPc(C10H21)8), followed by its adsorption on single-walled carbon nanotubes (SWCNT) to form SWCNT-NiPc(C10H21)8 conjugates. SWCNT-NiPc(C10H21)8 was used to modify a glassy carbon electrode (GCE) and for the electrooxidation of 4-chlorophenol and 2,4-dichlorophenol. The SWCNT and NiPc(C10H21)8 have a synergistic effect on each other in terms of improving electrocatalysis for the detection of chlorophenols. The stability of the electrode improved in the presence of NiPc(C10H21)8 or NiPc compared to the bare GCE. The presence of SWCNT improves the electrocatalytic behaviour of NiPc(C10H21)8 but not of unsubstituted NiPc. All modified electrodes showed improved stability towards the detection of 2,4-dichlorophenol. The best stability for 4-CP detection was observed in the presence of SWCNT for NiPc(C10H21)8.
- Full Text:
Elephants, compassion, and the largesse of literature
- Authors: Wylie, Dan
- Date: 2011
- Language: English
- Type: Text
- Identifier: vital:582 , http://hdl.handle.net/10962/d1018924
- Description: [From the text] Why is it that we do not raise a monument, a mausoleum, nor even a humble gravestone, to mark the death of every elephant? We habitually, even compulsively, do this for other humans, occasionally for treasured pets. Yet we do not do it for the most charismatic, gigantic, culturally resonant land animal we will ever encounter. Why not? Some possible answers. One: too much work. Another: we regard other animals as less conscious than ourselves; we are the only creatures who deserve to have our deaths so commemorated. A third: wild animals are part of wild ecosystems; it is ‘natural’ for them to die and to be reabsorbed namelessly back into those ecosystems. We humans, on the other hand, consider ourselves somehow separate from those ecosystems: we shield ourselves from ‘Nature’ with bricks and literatures while we live, with marble and epitaphs after we die.
- Full Text:
- Authors: Wylie, Dan
- Date: 2011
- Language: English
- Type: Text
- Identifier: vital:582 , http://hdl.handle.net/10962/d1018924
- Description: [From the text] Why is it that we do not raise a monument, a mausoleum, nor even a humble gravestone, to mark the death of every elephant? We habitually, even compulsively, do this for other humans, occasionally for treasured pets. Yet we do not do it for the most charismatic, gigantic, culturally resonant land animal we will ever encounter. Why not? Some possible answers. One: too much work. Another: we regard other animals as less conscious than ourselves; we are the only creatures who deserve to have our deaths so commemorated. A third: wild animals are part of wild ecosystems; it is ‘natural’ for them to die and to be reabsorbed namelessly back into those ecosystems. We humans, on the other hand, consider ourselves somehow separate from those ecosystems: we shield ourselves from ‘Nature’ with bricks and literatures while we live, with marble and epitaphs after we die.
- Full Text:
Elizabeth Costello and the Biography of the Moral Philosopher
- Authors: Jones, Ward E
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275635 , vital:55065 , xlink:href="https://doi.org/10.1111/j.1540-6245.2011.01462.x"
- Description: Imagine someone who informs you that her conversion to vegetarianism began when she read Charlotte's Web or viewed the film Babe. Both stories invite the reader to celebrate the events surrounding a pig being saved from the butcher. What kind of role would her spectatorship of this book or film have played in her conversion? It is perhaps improbable to suspect that she would have undergone this kind of extreme moral conversion solely on the basis of her engagement with one of these fictions; perhaps more likely is the scenario in which her engagement was only one part of a lengthy process of her moral change of mind. In any event, it is certainly possible that our imagined vegetarian would see her encounter with Charlotte's Web or Babe as playing a justificatory role in her conversion. In looking back at her conversion, she might say something like this: “I know that I was young and impressionable, but the way in which the book (or film) made me feel about its characters moved me to further reflect upon animals and the animal industry, and I now realize that it was right to do so.” On her own view, at least, her spectatorship motivated and warranted her taking the further steps that ultimately led to her conversion. If she is right, then fictional narratives can possess—to at least some degree—what Raimond Gaita refers to as an ethical “authority.”
- Full Text:
- Authors: Jones, Ward E
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/275635 , vital:55065 , xlink:href="https://doi.org/10.1111/j.1540-6245.2011.01462.x"
- Description: Imagine someone who informs you that her conversion to vegetarianism began when she read Charlotte's Web or viewed the film Babe. Both stories invite the reader to celebrate the events surrounding a pig being saved from the butcher. What kind of role would her spectatorship of this book or film have played in her conversion? It is perhaps improbable to suspect that she would have undergone this kind of extreme moral conversion solely on the basis of her engagement with one of these fictions; perhaps more likely is the scenario in which her engagement was only one part of a lengthy process of her moral change of mind. In any event, it is certainly possible that our imagined vegetarian would see her encounter with Charlotte's Web or Babe as playing a justificatory role in her conversion. In looking back at her conversion, she might say something like this: “I know that I was young and impressionable, but the way in which the book (or film) made me feel about its characters moved me to further reflect upon animals and the animal industry, and I now realize that it was right to do so.” On her own view, at least, her spectatorship motivated and warranted her taking the further steps that ultimately led to her conversion. If she is right, then fictional narratives can possess—to at least some degree—what Raimond Gaita refers to as an ethical “authority.”
- Full Text:
Elucidation of the complex Baylis-Hillman reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone
- Idahosa, Kenudi C, Molefe, Duduzile M, Pakade, Vusumzi E, Brown, Michael E
- Authors: Idahosa, Kenudi C , Molefe, Duduzile M , Pakade, Vusumzi E , Brown, Michael E
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6574 , http://hdl.handle.net/10962/d1004137
- Description: DABCO-catalyzed reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone (MVK) affords a mixture of products, comprising the ‘normal’ Baylis-Hillman adduct, theMVKdimer and a pair of diastereomeric bis-(MVK)Baylis-Hillman adducts. 1HNMRspectroscopy-based kinetic studies have provided clear insights into the competing pathways and product distribution in this complex reaction.
- Full Text:
- Authors: Idahosa, Kenudi C , Molefe, Duduzile M , Pakade, Vusumzi E , Brown, Michael E
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6574 , http://hdl.handle.net/10962/d1004137
- Description: DABCO-catalyzed reaction of 3-methoxy-2-nitrobenzaldehyde with methyl vinyl ketone (MVK) affords a mixture of products, comprising the ‘normal’ Baylis-Hillman adduct, theMVKdimer and a pair of diastereomeric bis-(MVK)Baylis-Hillman adducts. 1HNMRspectroscopy-based kinetic studies have provided clear insights into the competing pathways and product distribution in this complex reaction.
- Full Text:
Emplacement of the 2.44 Ga ultramafic layered Kemi intrusion, Finland PGE, geochemical and Sm-Nd isotopic implications
- Authors: Linkermann, Sean Aaron
- Date: 2011
- Subjects: Chromite -- Finland -- Kemi , Mining geology -- Finland -- Kemi , Geochemistry -- Finland -- Kemi , Petrology -- Finland -- Kemi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4940 , http://hdl.handle.net/10962/d1005552 , Chromite -- Finland -- Kemi , Mining geology -- Finland -- Kemi , Geochemistry -- Finland -- Kemi , Petrology -- Finland -- Kemi
- Description: Europe’s largest chrome deposit is hosted by the 2.44 Ga Kemi ultramafic layered intrusion. The lower half of the intrusion consists of peridotites, pyroxenites and chromitite layers while the upper half consists of websterites, gabbronorites and leucogabbros. The mafic minerals of the lower and upper parts of the intrusion are altered to serpentine, chlorite, talc, amphiboles and carbonates. However, the original mineralogy is still preserved in the middle part of the intrusion. Earlier work on the Kemi intrusion concentrated mainly on the economically important chromitite layers and suggested that these layers were formed through contamination of a single pulse of primitive magma by underlying Archaean basement crustal material. The broad variations of the major element concentrations reflect variations in the mode of the Kemi rocks. The petrology, which shows olivine- and orthopyroxene-dominated rocks in the lower portion of the intrusion to plagioclase- and clinopyroxene-dominated rocks in the upper portion, shows a gross consistency with a fractional crystallization process.The incompatible elements are relatively enriched in the lower portion of the intrusion which is not consistent with a broad fractional crystallization process. These variations suggest that the ultramafic portion of the KemiIntrusion is relatively enriched in trapped liquid compared to the mafic portion.ε2.44 Nd values ranges from +4 (consistent with depleted mantle source) to -10 (indicating a contribution from Archaean crust). The lower peridotites, pyroxenites and websterites have ε2.44 Nd values ranging between depleted mantle signatures and -2, whereas the gabbroic cumulates have ε2.44 Nd values which cover a range from around -5 to -10. Nd isotopic variation in the lower part of the profile is punctuated by distinct spikes to lower ε2.44 Nd corresponding to the chromitite horizons. Both the lower and upper portions of the Kemi Intrusion show enrichment of LREEC1 relative to HREEC1. The LREEC1 enriched values start to increase markedly from about the 1000 meter mark and continue to increase in value towards the roof of the intrusion.The main enrichment of PGE (ΣPPGE = 55 to 148 ppb) occurs approximately 90 to 160 m above the basal contact, beginning within andcontinuing above the main chromitite ore horizon. The mantle-normalized PGE abundances of the main chromitite horizon and the peridotites and pyroxenites below it show enrichment of IPGEPM (Os + Ir + Ru) relative to PPGEPM (Rh + Pd + Pt). In contrast, the overlying rocks are characterised by enrichment of PPGEPM relative to IPGEPM. These PGE-patterns suggest the influence of two distinct controlling processes above and below the main chromitite reef.The isotopic data are consistent with the initial introduction of multiple pulses of depleted mantle-derived magma crystallising olivine and pyroxene. Before the parent magma was fed into the Kemi magma chamber, it underwent crustal contamination and assimilation in a staging chamber within the lower crust. Some of these pulses were “critically crustally contaminated”, inducing chromite saturation and precipitation. The modelling also predicts minor in-situ contamination of the parent magma in the Kemi chamber with its wall and roof rocks. Above the main chromitite layer (about 160 m above the basal contact), the chromite content decreases and the PPGEPM/IPGEPM values increase which is consistent with scavenging of the IPGE into the lowermost layers and/or evolving magma compositions. Above 1000 m, the isotopic and REE data indicate a new magma pulse which has also been extensively contaminated in the staging magma chamber before emplacement into the Kemi magma chamber. The contamination in the staging magma chamber increased which is reflected in a progressively larger crustal component towards the top of the Kemi Intrusion
- Full Text:
- Authors: Linkermann, Sean Aaron
- Date: 2011
- Subjects: Chromite -- Finland -- Kemi , Mining geology -- Finland -- Kemi , Geochemistry -- Finland -- Kemi , Petrology -- Finland -- Kemi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4940 , http://hdl.handle.net/10962/d1005552 , Chromite -- Finland -- Kemi , Mining geology -- Finland -- Kemi , Geochemistry -- Finland -- Kemi , Petrology -- Finland -- Kemi
- Description: Europe’s largest chrome deposit is hosted by the 2.44 Ga Kemi ultramafic layered intrusion. The lower half of the intrusion consists of peridotites, pyroxenites and chromitite layers while the upper half consists of websterites, gabbronorites and leucogabbros. The mafic minerals of the lower and upper parts of the intrusion are altered to serpentine, chlorite, talc, amphiboles and carbonates. However, the original mineralogy is still preserved in the middle part of the intrusion. Earlier work on the Kemi intrusion concentrated mainly on the economically important chromitite layers and suggested that these layers were formed through contamination of a single pulse of primitive magma by underlying Archaean basement crustal material. The broad variations of the major element concentrations reflect variations in the mode of the Kemi rocks. The petrology, which shows olivine- and orthopyroxene-dominated rocks in the lower portion of the intrusion to plagioclase- and clinopyroxene-dominated rocks in the upper portion, shows a gross consistency with a fractional crystallization process.The incompatible elements are relatively enriched in the lower portion of the intrusion which is not consistent with a broad fractional crystallization process. These variations suggest that the ultramafic portion of the KemiIntrusion is relatively enriched in trapped liquid compared to the mafic portion.ε2.44 Nd values ranges from +4 (consistent with depleted mantle source) to -10 (indicating a contribution from Archaean crust). The lower peridotites, pyroxenites and websterites have ε2.44 Nd values ranging between depleted mantle signatures and -2, whereas the gabbroic cumulates have ε2.44 Nd values which cover a range from around -5 to -10. Nd isotopic variation in the lower part of the profile is punctuated by distinct spikes to lower ε2.44 Nd corresponding to the chromitite horizons. Both the lower and upper portions of the Kemi Intrusion show enrichment of LREEC1 relative to HREEC1. The LREEC1 enriched values start to increase markedly from about the 1000 meter mark and continue to increase in value towards the roof of the intrusion.The main enrichment of PGE (ΣPPGE = 55 to 148 ppb) occurs approximately 90 to 160 m above the basal contact, beginning within andcontinuing above the main chromitite ore horizon. The mantle-normalized PGE abundances of the main chromitite horizon and the peridotites and pyroxenites below it show enrichment of IPGEPM (Os + Ir + Ru) relative to PPGEPM (Rh + Pd + Pt). In contrast, the overlying rocks are characterised by enrichment of PPGEPM relative to IPGEPM. These PGE-patterns suggest the influence of two distinct controlling processes above and below the main chromitite reef.The isotopic data are consistent with the initial introduction of multiple pulses of depleted mantle-derived magma crystallising olivine and pyroxene. Before the parent magma was fed into the Kemi magma chamber, it underwent crustal contamination and assimilation in a staging chamber within the lower crust. Some of these pulses were “critically crustally contaminated”, inducing chromite saturation and precipitation. The modelling also predicts minor in-situ contamination of the parent magma in the Kemi chamber with its wall and roof rocks. Above the main chromitite layer (about 160 m above the basal contact), the chromite content decreases and the PPGEPM/IPGEPM values increase which is consistent with scavenging of the IPGE into the lowermost layers and/or evolving magma compositions. Above 1000 m, the isotopic and REE data indicate a new magma pulse which has also been extensively contaminated in the staging magma chamber before emplacement into the Kemi magma chamber. The contamination in the staging magma chamber increased which is reflected in a progressively larger crustal component towards the top of the Kemi Intrusion
- Full Text:
Energy versus angular momentum in black hole binaries
- Damour, T, Nagar, A, Pollney, D, Reisswig, C
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
Enhancing the Configuration and Design of Sound Systems through Simulation
- Otten, Frederick, Foss, Richard
- Authors: Otten, Frederick , Foss, Richard
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427125 , vital:72416 , https://www.aes.org/e-lib/browse.cfm?elib=15848
- Description: Audio Engineers are required to design and deploy large multi-channel sound systems which meet a set of requirements and use networking technologies such as Firewire and Ethernet. Bandwidth utilsation and latency need to be considered. Network Simulation can be used to accurately model a network and return such information. This paper discusses a software system which has been developed to create a simulation of a network using the AES-X170 protocol for command and control. This system shows information about bandwidth and latency and is able to detect problems with parameter relationships. It also provides the ability to perform offline editing. These features significantly enhance audio engineers' ability to effectively design, configure and evaluate sound systems.
- Full Text:
- Authors: Otten, Frederick , Foss, Richard
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427125 , vital:72416 , https://www.aes.org/e-lib/browse.cfm?elib=15848
- Description: Audio Engineers are required to design and deploy large multi-channel sound systems which meet a set of requirements and use networking technologies such as Firewire and Ethernet. Bandwidth utilsation and latency need to be considered. Network Simulation can be used to accurately model a network and return such information. This paper discusses a software system which has been developed to create a simulation of a network using the AES-X170 protocol for command and control. This system shows information about bandwidth and latency and is able to detect problems with parameter relationships. It also provides the ability to perform offline editing. These features significantly enhance audio engineers' ability to effectively design, configure and evaluate sound systems.
- Full Text:
Ericoid mycorrhizal fungi and potential for inoculation of commercial berry species (Vaccinium corymbosium L.)
- Authors: Bizabani, Christine
- Date: 2011
- Subjects: Ericaceae , Mycorrhizas , Fynbos
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4136 , http://hdl.handle.net/10962/d1016127
- Description: Ericaceous plants are the richest growth form of the fynbos vegetation of South Africa. The fynbos is characterized by highly leached acidic soils, low mineral nutrients and climatically it is a winter rainfall and dry summer region. Ericoid mycorrhizal fungi associate with Erica species enhancing their ability to access essential nutrients for survival under unfavourable growth conditions. The aim of this study was to select local Ericaceae plant species and to isolate, identify and characterize the ericoid endophytes and assess these isolates as potential inocula for commercial berry species. Two ericaceous plants Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth. were identified from the Mountain Drive area of Grahamstown, Eastern Cape. Root staining was used to confirm the mycorrhizal status of both plants. Hyphal coils typical of ericoid association were observed within the epidermal cells of the hair roots under a light microscope. The endophytes were successfully isolated in pure culture on 2% malt extract agar (MEA) and modified Fontana medium. Cultural morphology and microscopy were used for initial identification. Two slow growing isolates were selected. These isolates were further subjected to molecular identification; extracted DNA was amplified using ITS1 and ITS4 fungal primers. The rDNA gene internal transcriber spacer (ITS) was then sequenced and analyzed by comparison to sequences in the GenBank. On the basis of percentage sequence identity Lachnum Retz. species and Cadophora Lagerb. & Melin species were identified as the ericoid endophytes of E. cerinthoides and E. demmissa respectively. The optimum growth parameters of the fungal isolates were determined in 2% MEA incubated at varying temperatures and pH. It was established that both species had optimum growth at 27⁰C and pH 5. The Ericaceae species are sometimes found in metal contaminated sites were ericoid fungi have been proved to alleviate toxicity of their host. The fungal isolates were grown in increasing concentration of Cu²⁺ and Zn²⁺ in 2% MEA. The growth of Lachnum species decreased with increasing Zn²⁺ ions above 2.7 mM while Cadophora species showed a change in morphology and also decreased in growth with increased ion concentration. However there were no significant differences recorded in the growth of Cadophora and Lachnum species on increasing Cu²⁺ concentration. Lachnum and Cadophora isolates were formulated into a semi solid inoculum and inoculated onto micropropagated Vaccinni corymbosum L. plantlets of 5 different varieties. Colonization was low for all varieties, Elliott and Brightwell varieties recorded the highest colonization of 35% and 31% respectively. Lachnum species infected roots showed potential ericoid structures while the Cadophora inoculated plantlets had hyphal coils within the cortical cells typical of ericoid mycorrhizas. Inoculation significantly enhanced the shoot growth of Brightwell and Elliott varieties. The Chandler variety inoculated with Lachnum species showed improved shoot dry weight. The Bluecrop and Elliott varieties inoculated with Cadophora and Lachnum accumulated more root biomass. All inoculated Bluecrop plantlets had an improved canopy growth index. Brightwell plantlets inoculated with Lachnum species also had an enhanced canopy growth index. The growth responses were variable within varieties and between varieties. Treatments with the Cadophora and Lachnum have shown potential in the promotion of growth of the Blueberry species. The findings indicate the need to conduct trials under conditions which simulate the commercial growth conditions so as explore the optimum potential of the isolates.
- Full Text:
- Authors: Bizabani, Christine
- Date: 2011
- Subjects: Ericaceae , Mycorrhizas , Fynbos
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4136 , http://hdl.handle.net/10962/d1016127
- Description: Ericaceous plants are the richest growth form of the fynbos vegetation of South Africa. The fynbos is characterized by highly leached acidic soils, low mineral nutrients and climatically it is a winter rainfall and dry summer region. Ericoid mycorrhizal fungi associate with Erica species enhancing their ability to access essential nutrients for survival under unfavourable growth conditions. The aim of this study was to select local Ericaceae plant species and to isolate, identify and characterize the ericoid endophytes and assess these isolates as potential inocula for commercial berry species. Two ericaceous plants Erica cerinthoides L. and Erica demmissa Klotzsch ex Benth. were identified from the Mountain Drive area of Grahamstown, Eastern Cape. Root staining was used to confirm the mycorrhizal status of both plants. Hyphal coils typical of ericoid association were observed within the epidermal cells of the hair roots under a light microscope. The endophytes were successfully isolated in pure culture on 2% malt extract agar (MEA) and modified Fontana medium. Cultural morphology and microscopy were used for initial identification. Two slow growing isolates were selected. These isolates were further subjected to molecular identification; extracted DNA was amplified using ITS1 and ITS4 fungal primers. The rDNA gene internal transcriber spacer (ITS) was then sequenced and analyzed by comparison to sequences in the GenBank. On the basis of percentage sequence identity Lachnum Retz. species and Cadophora Lagerb. & Melin species were identified as the ericoid endophytes of E. cerinthoides and E. demmissa respectively. The optimum growth parameters of the fungal isolates were determined in 2% MEA incubated at varying temperatures and pH. It was established that both species had optimum growth at 27⁰C and pH 5. The Ericaceae species are sometimes found in metal contaminated sites were ericoid fungi have been proved to alleviate toxicity of their host. The fungal isolates were grown in increasing concentration of Cu²⁺ and Zn²⁺ in 2% MEA. The growth of Lachnum species decreased with increasing Zn²⁺ ions above 2.7 mM while Cadophora species showed a change in morphology and also decreased in growth with increased ion concentration. However there were no significant differences recorded in the growth of Cadophora and Lachnum species on increasing Cu²⁺ concentration. Lachnum and Cadophora isolates were formulated into a semi solid inoculum and inoculated onto micropropagated Vaccinni corymbosum L. plantlets of 5 different varieties. Colonization was low for all varieties, Elliott and Brightwell varieties recorded the highest colonization of 35% and 31% respectively. Lachnum species infected roots showed potential ericoid structures while the Cadophora inoculated plantlets had hyphal coils within the cortical cells typical of ericoid mycorrhizas. Inoculation significantly enhanced the shoot growth of Brightwell and Elliott varieties. The Chandler variety inoculated with Lachnum species showed improved shoot dry weight. The Bluecrop and Elliott varieties inoculated with Cadophora and Lachnum accumulated more root biomass. All inoculated Bluecrop plantlets had an improved canopy growth index. Brightwell plantlets inoculated with Lachnum species also had an enhanced canopy growth index. The growth responses were variable within varieties and between varieties. Treatments with the Cadophora and Lachnum have shown potential in the promotion of growth of the Blueberry species. The findings indicate the need to conduct trials under conditions which simulate the commercial growth conditions so as explore the optimum potential of the isolates.
- Full Text:
Evaluating The Potential Contribution Of Episodic Toxicity Data To Environmental Water Quality Management In South Africa
- Gordon, Andrew K, Mantel, Sukhmani K M, Muller, Nikite W J
- Authors: Gordon, Andrew K , Mantel, Sukhmani K M , Muller, Nikite W J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438310 , vital:73450 , ISBN 978-1-4312-0070-2 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/KV259-10.pdf
- Description: An important aspect of the dynamics of nutrients and pollutants in natural systems is captured in the concept of allochthony, founded on the observation that nutrients and energy in a variety of forms are transferred between adjacent habitats, com-munities and ecosystems that are not routinely considered as connected. Different forms of nutrients and energy move across the conceptual boundaries of habitats via organisms’ activities or physical processes such as wind or water currents, and these transfers can represent important food subsidies. Such cross-partition ecolog-ical subsidies can augment the nutritional condition, biomass and biodiversity of communities, particularly where local production (or autochthony) alone may be inadequate to support local food webs. Furthermore, organic subsidies can influ-ence population dynamics, community interactions and ecosystem processes, and can represent dominant flux inputs in ecosystem budgets. Our intention was to explore organic nutrient fluxes in relation to a primarily lotic (i.e. flowing) aquatic sys-tem at the scale of a hydrological catchment.
- Full Text:
- Authors: Gordon, Andrew K , Mantel, Sukhmani K M , Muller, Nikite W J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438310 , vital:73450 , ISBN 978-1-4312-0070-2 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/KV259-10.pdf
- Description: An important aspect of the dynamics of nutrients and pollutants in natural systems is captured in the concept of allochthony, founded on the observation that nutrients and energy in a variety of forms are transferred between adjacent habitats, com-munities and ecosystems that are not routinely considered as connected. Different forms of nutrients and energy move across the conceptual boundaries of habitats via organisms’ activities or physical processes such as wind or water currents, and these transfers can represent important food subsidies. Such cross-partition ecolog-ical subsidies can augment the nutritional condition, biomass and biodiversity of communities, particularly where local production (or autochthony) alone may be inadequate to support local food webs. Furthermore, organic subsidies can influ-ence population dynamics, community interactions and ecosystem processes, and can represent dominant flux inputs in ecosystem budgets. Our intention was to explore organic nutrient fluxes in relation to a primarily lotic (i.e. flowing) aquatic sys-tem at the scale of a hydrological catchment.
- Full Text:
Evaluating the sustainable management of the State indigenous forests in the Eastern Cape Province
- Authors: Quvile, Nkosipendule
- Date: 2011
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:793 , http://hdl.handle.net/10962/d1004130
- Description: This research assesses the state of sustainability of State indigenous forests in the Eastern Cape and provides recommendations to improve their sustainability. The Eastern Cape Indigenous Forest Management Audit (ECIFMA) report of 2009 provided the primary data for this assessment (DAFF, 2009). The research was inspired by the fact that the global challenge of forestry destruction and degradation where the extent of forests is being reduced at an alarming rate of 6% annually. It became essential for global leaders to develop policies and strategies that sought to promote sustainable forest management. The monitoring of sustainability of forests was only possible through use of globally and nationally developed sets of criteria and indicators. Eleven forest estates responsible for the management of State indigenous forests in the Eastern Cape were selected for this research. The choice was influenced by the availability of audit data from the ECIFMA report of 2009. This report contained performance information of 41 indicators under 18 criteria for monitoring sustainable forest management as extracted from the PCI&S assessment checklist developed for monitoring the sustainability of indigenous forests in South Africa (DWAF, 2005). The data was refined using the MCA methods (ranking and scoring) as described by Mendoza and Prabhu (2000). These methods yielded to the determination of the performance of indicators of forest sustainability. It was thus important to conclude the research by responding to the following questions: • What is the state of sustainability of the State indigenous forests in the Eastern Cape? • What recommendations could be made to improve the sustainability of State indigenous forests? It was found that the State indigenous forests were not managed in a sustainable manner. The research report is concluded by providing concrete recommendations to improve forest sustainability.
- Full Text:
- Authors: Quvile, Nkosipendule
- Date: 2011
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:793 , http://hdl.handle.net/10962/d1004130
- Description: This research assesses the state of sustainability of State indigenous forests in the Eastern Cape and provides recommendations to improve their sustainability. The Eastern Cape Indigenous Forest Management Audit (ECIFMA) report of 2009 provided the primary data for this assessment (DAFF, 2009). The research was inspired by the fact that the global challenge of forestry destruction and degradation where the extent of forests is being reduced at an alarming rate of 6% annually. It became essential for global leaders to develop policies and strategies that sought to promote sustainable forest management. The monitoring of sustainability of forests was only possible through use of globally and nationally developed sets of criteria and indicators. Eleven forest estates responsible for the management of State indigenous forests in the Eastern Cape were selected for this research. The choice was influenced by the availability of audit data from the ECIFMA report of 2009. This report contained performance information of 41 indicators under 18 criteria for monitoring sustainable forest management as extracted from the PCI&S assessment checklist developed for monitoring the sustainability of indigenous forests in South Africa (DWAF, 2005). The data was refined using the MCA methods (ranking and scoring) as described by Mendoza and Prabhu (2000). These methods yielded to the determination of the performance of indicators of forest sustainability. It was thus important to conclude the research by responding to the following questions: • What is the state of sustainability of the State indigenous forests in the Eastern Cape? • What recommendations could be made to improve the sustainability of State indigenous forests? It was found that the State indigenous forests were not managed in a sustainable manner. The research report is concluded by providing concrete recommendations to improve forest sustainability.
- Full Text:
Evaluating the Wald entropy from two-derivative terms in quadratic actions
- Brustein, R, Gorbonos, D, Hadad, M, Medved, A J M
- Authors: Brustein, R , Gorbonos, D , Hadad, M , Medved, A J M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6816 , http://hdl.handle.net/10962/d1004326
- Description: We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.
- Full Text:
- Authors: Brustein, R , Gorbonos, D , Hadad, M , Medved, A J M
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6816 , http://hdl.handle.net/10962/d1004326
- Description: We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.
- Full Text:
Evaluation of the in vitro differential protein adsorption patterns of didanosine-loaded nanostructured lipid carriers (NLCs) for potential targeting to the brain
- Kasongo, Kasongo W, Jansch, Mirko, Müller, Rainer H, Walker, Roderick B
- Authors: Kasongo, Kasongo W , Jansch, Mirko , Müller, Rainer H , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184035 , vital:44160 , xlink:href="https://doi.org/10.3109/08982104.2010.539186"
- Description: The preferential in vitro adsorption of apolipoprotein E (Apo E) onto the surface of colloidal drug carriers may be used as a strategy to evaluate the in vivo potential for such systems to transport drugs to the brain. The aim of this research was to investigate the in vitro protein adsorption patterns of didanosine-loaded nanostructured lipid carriers (DDI-NLCs), using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), in order to establish the potential for NLCs to deliver DDI to the brain. NLC formulations were manufactured using high-pressure homogenization using a lipid matrix consisting of a mixture of Precirol® ATO 5 and Transcutol® HP. The 2-D PAGE analysis revealed that NLCs in formulations stabilized using Solutol® HS 15 alone or with a ternary surfactant system consisting of Solutol® HS 15, Tween® 80, and Lutrol® F68, preferentially adsorbed proteins, such as Apo E. Particles stabilized with Tween® 80 and Lutrol® F68 did not adsorb Apo E in these studies, which could be related to the relatively large particle size and hence small surface area observed for these NLCs. These findings have revealed that DDI-loaded NLCs may have the potential to deliver DDI to the brain in vivo and, in addition, to Tween® 80, which has already been shown to have the ability to facilitate the targeting of colloidal drug delivery systems to the brain. Solutol® HS 15–stabilized nanoparticles may also achieve a similar purpose.
- Full Text:
- Authors: Kasongo, Kasongo W , Jansch, Mirko , Müller, Rainer H , Walker, Roderick B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184035 , vital:44160 , xlink:href="https://doi.org/10.3109/08982104.2010.539186"
- Description: The preferential in vitro adsorption of apolipoprotein E (Apo E) onto the surface of colloidal drug carriers may be used as a strategy to evaluate the in vivo potential for such systems to transport drugs to the brain. The aim of this research was to investigate the in vitro protein adsorption patterns of didanosine-loaded nanostructured lipid carriers (DDI-NLCs), using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), in order to establish the potential for NLCs to deliver DDI to the brain. NLC formulations were manufactured using high-pressure homogenization using a lipid matrix consisting of a mixture of Precirol® ATO 5 and Transcutol® HP. The 2-D PAGE analysis revealed that NLCs in formulations stabilized using Solutol® HS 15 alone or with a ternary surfactant system consisting of Solutol® HS 15, Tween® 80, and Lutrol® F68, preferentially adsorbed proteins, such as Apo E. Particles stabilized with Tween® 80 and Lutrol® F68 did not adsorb Apo E in these studies, which could be related to the relatively large particle size and hence small surface area observed for these NLCs. These findings have revealed that DDI-loaded NLCs may have the potential to deliver DDI to the brain in vivo and, in addition, to Tween® 80, which has already been shown to have the ability to facilitate the targeting of colloidal drug delivery systems to the brain. Solutol® HS 15–stabilized nanoparticles may also achieve a similar purpose.
- Full Text:
Evaluation of the kinetics and mechanism of drug release from Econazole nitrate nanosponge loaded Carbapol Hydrogel
- Sharma, Renuka, Walker, Roderick B, Pathak, Kamla
- Authors: Sharma, Renuka , Walker, Roderick B , Pathak, Kamla
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6437 , http://hdl.handle.net/10962/d1006614
- Description: The objective of this study was to investigate the mechanism of release of econazole nitrate (EN) nanosponges loaded hydrogel and to compare it with EN hydrogel so as to develop an extended release topical drug delivery system of EN. Nanosponges of EN were prepared using ethyl cellulose and PVA by emulsion solvent evaporation method. On the basis of pharmacotechnical evaluation nanosponges with least particle size of 230.1 nm and good rheological properties were formulated as hydrogel (F1 – F7). In vitro drug release data of EN nanosponges loaded hydrogels in phosphate buffer pH 6.8 and 7.4 when analysed by GraphPad Prism software version 4.0 San Diego, USA best fitted the Makoid-2 Banakar model (R value greater than 0.98). The Korsmeyer-Peppas release exponent (n) ranged between 0.331 – 0.418, which confirmed diffusion as the principle mechanism of drug release. The release mechanism was further confirmed by calculating the ratio of exponents A/B ratio derived from the Kopcha model.
- Full Text:
- Authors: Sharma, Renuka , Walker, Roderick B , Pathak, Kamla
- Date: 2011
- Language: English
- Type: text , Article
- Identifier: vital:6437 , http://hdl.handle.net/10962/d1006614
- Description: The objective of this study was to investigate the mechanism of release of econazole nitrate (EN) nanosponges loaded hydrogel and to compare it with EN hydrogel so as to develop an extended release topical drug delivery system of EN. Nanosponges of EN were prepared using ethyl cellulose and PVA by emulsion solvent evaporation method. On the basis of pharmacotechnical evaluation nanosponges with least particle size of 230.1 nm and good rheological properties were formulated as hydrogel (F1 – F7). In vitro drug release data of EN nanosponges loaded hydrogels in phosphate buffer pH 6.8 and 7.4 when analysed by GraphPad Prism software version 4.0 San Diego, USA best fitted the Makoid-2 Banakar model (R value greater than 0.98). The Korsmeyer-Peppas release exponent (n) ranged between 0.331 – 0.418, which confirmed diffusion as the principle mechanism of drug release. The release mechanism was further confirmed by calculating the ratio of exponents A/B ratio derived from the Kopcha model.
- Full Text:
Exchange rate behavior in the cases of the Zambian Kwacha and Malawian Kwacha : is there misalignment?
- Magwizi, Brenda Thandekha, Rhodes University
- Authors: Magwizi, Brenda Thandekha , Rhodes University
- Date: 2011
- Subjects: Foreign exchange rates -- Zambia Foreign exchange rates -- Malawi International relations -- Case studies -- Zambia International relations -- Case studies -- Malawi
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:974 , http://hdl.handle.net/10962/d1002708
- Description: The exchange rate is the price of one currency against another currency or currencies of a group of countries. Real exchange rates are important because they show the external competitiveness of a country‟s economy. Thus, when the exchange rate of a country is misaligned, this will affect its trade, production and the welfare of people. This study analysed macroeconomic determinants of the real exchange rate and dynamic adjustment of the real exchange rate as a result of shocks to these determinants. The study also determined the extent of misalignment of the real exchange rate in Malawi and Zambia and identified variables that contributed to it. Such information is important to policy makers. Quarterly data were used for both countries from 1980:1-2008:4. The literature review identified those variables that determine the exchange rate and these include government consumption, foreign aid, net foreign assets, commodity prices, terms of trade, domestic credit, openness and the Balassa Samuelson effect (technological progress). To determine the long-run relationship between the exchange rate and its determinants, we employed the Johansen approach and the Vector Error Correction Model (VECM). For robustness check on the long-run and shortrun effects of determinants on the exchange rate, variance decomposition and impulse response analyses were used. Results in the study show that in Malawi for both models, an increase in LAID, LGCON and LTOT resulted in real exchange rate depreciation and increases in LDC, NFA and LNEER resulted in an appreciation. In Zambia, increases in LAID, LGCON, LOPEN and LTOT caused the real exchange rate to depreciate while increases in LDC, NFA and LCOPPER led to an appreciation. Lagged LREER and LNEER were found to have short run effects on the equilibrium exchange rate for Malawi and lagged LCOPPER and LDC for Zambia. Periods of exchange rate misalignment were found in both countries. It was also found that the coefficient of speed of adjustment in Malawi in models 1 and 2 indicate that 11% and 27% of the variation in the real exchange rate from its equilibrium adjust each quarter respectively. The speed of adjustment for Zambia in both models was 45% and 47% respectively, higher than that of Malawi. Foreign aid has proven to be important in exchange rate misalignment in both countries, though this was not really expected in the case of Zambia. Given these results, it may be of interest to policy makers to understand which variables impact most on the exchange rate and how misalignment due to these determinants can be minimised.
- Full Text:
- Authors: Magwizi, Brenda Thandekha , Rhodes University
- Date: 2011
- Subjects: Foreign exchange rates -- Zambia Foreign exchange rates -- Malawi International relations -- Case studies -- Zambia International relations -- Case studies -- Malawi
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:974 , http://hdl.handle.net/10962/d1002708
- Description: The exchange rate is the price of one currency against another currency or currencies of a group of countries. Real exchange rates are important because they show the external competitiveness of a country‟s economy. Thus, when the exchange rate of a country is misaligned, this will affect its trade, production and the welfare of people. This study analysed macroeconomic determinants of the real exchange rate and dynamic adjustment of the real exchange rate as a result of shocks to these determinants. The study also determined the extent of misalignment of the real exchange rate in Malawi and Zambia and identified variables that contributed to it. Such information is important to policy makers. Quarterly data were used for both countries from 1980:1-2008:4. The literature review identified those variables that determine the exchange rate and these include government consumption, foreign aid, net foreign assets, commodity prices, terms of trade, domestic credit, openness and the Balassa Samuelson effect (technological progress). To determine the long-run relationship between the exchange rate and its determinants, we employed the Johansen approach and the Vector Error Correction Model (VECM). For robustness check on the long-run and shortrun effects of determinants on the exchange rate, variance decomposition and impulse response analyses were used. Results in the study show that in Malawi for both models, an increase in LAID, LGCON and LTOT resulted in real exchange rate depreciation and increases in LDC, NFA and LNEER resulted in an appreciation. In Zambia, increases in LAID, LGCON, LOPEN and LTOT caused the real exchange rate to depreciate while increases in LDC, NFA and LCOPPER led to an appreciation. Lagged LREER and LNEER were found to have short run effects on the equilibrium exchange rate for Malawi and lagged LCOPPER and LDC for Zambia. Periods of exchange rate misalignment were found in both countries. It was also found that the coefficient of speed of adjustment in Malawi in models 1 and 2 indicate that 11% and 27% of the variation in the real exchange rate from its equilibrium adjust each quarter respectively. The speed of adjustment for Zambia in both models was 45% and 47% respectively, higher than that of Malawi. Foreign aid has proven to be important in exchange rate misalignment in both countries, though this was not really expected in the case of Zambia. Given these results, it may be of interest to policy makers to understand which variables impact most on the exchange rate and how misalignment due to these determinants can be minimised.
- Full Text:
Exchange rate pass-through to domestic prices in Kenya
- Authors: Mnjama, Gladys Susan
- Date: 2011
- Subjects: Kenya -- Economic conditions , Kenya -- Economic conditions -- Econometric models , Foreign exchange rates -- Kenya , Stocks -- Prices -- Kenya , Banks and banking -- Kenya , Cointegration , Econometrics , Inflation (Finance) -- Kenya
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:975 , http://hdl.handle.net/10962/d1002709 , Kenya -- Economic conditions , Kenya -- Economic conditions -- Econometric models , Foreign exchange rates -- Kenya , Stocks -- Prices -- Kenya , Banks and banking -- Kenya , Cointegration , Econometrics , Inflation (Finance) -- Kenya
- Description: In 1993, Kenya liberalised its trade policy and allowed the Kenyan Shillings to freely float. This openness has left Kenya's domestic prices vulnerable to the effects of exchange rate fluctuations. One of the objectives of the Central Bank of Kenya is to maintain inflation levels at sustainable levels. Thus it has become necessary to determine the influence that exchange rate changes have on domestic prices given that one of the major determinants of inflation is exchange rate movements. For this reason, this thesis examines the magnitude and speed of exchange rate pass-through (ERPT) to domestic prices in Kenya. In addition, it takes into account the direction and size of changes in the exchange rates to determine whether the exchange rate fluctuations are symmetric or asymmetric. The thesis uses quarterly data ranging from 1993:Ql - 2008:Q4 as it takes into account the period when the process of liberalization occurred. The empirical estimation was done in two stages. The first stage was estimated using the Johansen (1991) and (1995) co integration techniques and a vector error correction model (VECM). The second stage entailed estimating the impulse response and variance decomposition functions as well as conducting block exogeneity Wald tests. In determining the asymmetric aspect of the analysis, the study followed Pollard and Coughlin (2004) and Webber (2000) frameworks in analysing asymmetry with respect to appreciation and depreciation and large and small changes in the exchange rate to import prices. The results obtained showed that ERPT to Kenya is incomplete but relatively low at about 36 percent in the long run. In terms of asymmetry, the results showed that ERPT is found to be higher in periods of appreciation than depreciation. This is in support of market share and binding quantity constraints theory. In relation to size changes, the results show that size changes have no significant impact on ERPT in Kenya.
- Full Text:
- Authors: Mnjama, Gladys Susan
- Date: 2011
- Subjects: Kenya -- Economic conditions , Kenya -- Economic conditions -- Econometric models , Foreign exchange rates -- Kenya , Stocks -- Prices -- Kenya , Banks and banking -- Kenya , Cointegration , Econometrics , Inflation (Finance) -- Kenya
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:975 , http://hdl.handle.net/10962/d1002709 , Kenya -- Economic conditions , Kenya -- Economic conditions -- Econometric models , Foreign exchange rates -- Kenya , Stocks -- Prices -- Kenya , Banks and banking -- Kenya , Cointegration , Econometrics , Inflation (Finance) -- Kenya
- Description: In 1993, Kenya liberalised its trade policy and allowed the Kenyan Shillings to freely float. This openness has left Kenya's domestic prices vulnerable to the effects of exchange rate fluctuations. One of the objectives of the Central Bank of Kenya is to maintain inflation levels at sustainable levels. Thus it has become necessary to determine the influence that exchange rate changes have on domestic prices given that one of the major determinants of inflation is exchange rate movements. For this reason, this thesis examines the magnitude and speed of exchange rate pass-through (ERPT) to domestic prices in Kenya. In addition, it takes into account the direction and size of changes in the exchange rates to determine whether the exchange rate fluctuations are symmetric or asymmetric. The thesis uses quarterly data ranging from 1993:Ql - 2008:Q4 as it takes into account the period when the process of liberalization occurred. The empirical estimation was done in two stages. The first stage was estimated using the Johansen (1991) and (1995) co integration techniques and a vector error correction model (VECM). The second stage entailed estimating the impulse response and variance decomposition functions as well as conducting block exogeneity Wald tests. In determining the asymmetric aspect of the analysis, the study followed Pollard and Coughlin (2004) and Webber (2000) frameworks in analysing asymmetry with respect to appreciation and depreciation and large and small changes in the exchange rate to import prices. The results obtained showed that ERPT to Kenya is incomplete but relatively low at about 36 percent in the long run. In terms of asymmetry, the results showed that ERPT is found to be higher in periods of appreciation than depreciation. This is in support of market share and binding quantity constraints theory. In relation to size changes, the results show that size changes have no significant impact on ERPT in Kenya.
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Exchange rates behaviour in Ghana and Nigeria: is there a misalignment?
- Authors: Mapenda, Rufaro
- Date: 2011 , 2011-11-09
- Subjects: Foreign exchange rates -- Ghana , Foreign exchange rates -- Nigeria , Economic development -- Ghana , Economic development -- Nigeria , Foreign exchange administration -- Ghana , Foreign exchange administration -- Nigeria , International relations
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:976 , http://hdl.handle.net/10962/d1002710 , Foreign exchange rates -- Ghana , Foreign exchange rates -- Nigeria , Economic development -- Ghana , Economic development -- Nigeria , Foreign exchange administration -- Ghana , Foreign exchange administration -- Nigeria , International relations
- Description: Exchange rates are believed to be one of the major driving forces behind sustainable macroeconomic growth and it is therefore important to ensure that they are at an appropriate level. Exchange rate misalignment is a situation where the actual exchange rate differs significantly from its equilibrium value, resulting in either an overvalued or an undervalued currency. The problem with an undervalued currency is that it will increase the domestic price of tradable goods whereas an overvalued currency will cause a fall in the domestic prices of the tradable goods. Persistent exchange rate misalignment is thus expected to result in severe macroeconomic instability. The aim of this study is to estimate the equilibrium real exchange rate for both Ghana and Nigeria. After so doing, the equilibrium real exchange rate is compared to the actual real exchange rate, in order to assess the extent of real exchange rate misalignment in both countries, if any such exists. In order test the applicability of the equilibrium exchange rate models, the study draws from the simple monetary model as well as the Edwards (1989) and Montiel (1999) models. These models postulate that the variables which determine the real exchange rate are the terms of trade, trade restrictions, domestic interest rates, foreign aid inflow, income, money supply, world inflation, government consumption expenditure, world interest rates, capital controls and technological progress. Due to data limitations in Ghana and in Nigeria, not all the variables are utilised in the study. The study uses the Johansen (1995) model as well as the Vector Error Correction Model (VECM) to estimate the long- and the short-run relationships between the above-mentioned determinants and the real exchange rate. Thereafter the study employs the Hodrick-Prescott filter to estimate the permanent equilibrium exchange rate. The study estimates a real exchange rate model each for Ghana and Nigeria. Both the exchange rate models for Ghana and Nigeria provide evidence of exchange rate misalignment. The model for Ghana shows that from the first quarter of 1980 to the last quarter of 1983 the real exchange rate was overvalued; thereafter the exchange rate moved close to its equilibrium value and was generally undervalued with few and short-lived episodes of overvaluation. In regard to real exchange rate misalignment in Nigeria prior to the Structural Adjustment Program in 1986 there were episodes of undervaluation from the first quarter of 1980 to the first quarter of 1984 and overvaluation from the second quarter of 1984 to the third quarter of 1986; thereafter the exchange rate was generally and marginally undervalued.
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- Authors: Mapenda, Rufaro
- Date: 2011 , 2011-11-09
- Subjects: Foreign exchange rates -- Ghana , Foreign exchange rates -- Nigeria , Economic development -- Ghana , Economic development -- Nigeria , Foreign exchange administration -- Ghana , Foreign exchange administration -- Nigeria , International relations
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:976 , http://hdl.handle.net/10962/d1002710 , Foreign exchange rates -- Ghana , Foreign exchange rates -- Nigeria , Economic development -- Ghana , Economic development -- Nigeria , Foreign exchange administration -- Ghana , Foreign exchange administration -- Nigeria , International relations
- Description: Exchange rates are believed to be one of the major driving forces behind sustainable macroeconomic growth and it is therefore important to ensure that they are at an appropriate level. Exchange rate misalignment is a situation where the actual exchange rate differs significantly from its equilibrium value, resulting in either an overvalued or an undervalued currency. The problem with an undervalued currency is that it will increase the domestic price of tradable goods whereas an overvalued currency will cause a fall in the domestic prices of the tradable goods. Persistent exchange rate misalignment is thus expected to result in severe macroeconomic instability. The aim of this study is to estimate the equilibrium real exchange rate for both Ghana and Nigeria. After so doing, the equilibrium real exchange rate is compared to the actual real exchange rate, in order to assess the extent of real exchange rate misalignment in both countries, if any such exists. In order test the applicability of the equilibrium exchange rate models, the study draws from the simple monetary model as well as the Edwards (1989) and Montiel (1999) models. These models postulate that the variables which determine the real exchange rate are the terms of trade, trade restrictions, domestic interest rates, foreign aid inflow, income, money supply, world inflation, government consumption expenditure, world interest rates, capital controls and technological progress. Due to data limitations in Ghana and in Nigeria, not all the variables are utilised in the study. The study uses the Johansen (1995) model as well as the Vector Error Correction Model (VECM) to estimate the long- and the short-run relationships between the above-mentioned determinants and the real exchange rate. Thereafter the study employs the Hodrick-Prescott filter to estimate the permanent equilibrium exchange rate. The study estimates a real exchange rate model each for Ghana and Nigeria. Both the exchange rate models for Ghana and Nigeria provide evidence of exchange rate misalignment. The model for Ghana shows that from the first quarter of 1980 to the last quarter of 1983 the real exchange rate was overvalued; thereafter the exchange rate moved close to its equilibrium value and was generally undervalued with few and short-lived episodes of overvaluation. In regard to real exchange rate misalignment in Nigeria prior to the Structural Adjustment Program in 1986 there were episodes of undervaluation from the first quarter of 1980 to the first quarter of 1984 and overvaluation from the second quarter of 1984 to the third quarter of 1986; thereafter the exchange rate was generally and marginally undervalued.
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Exploring how teachers acquire content knowledge of marine and coastal issues to contextualize the natural science curriculum
- Authors: Mbuyazwe, Vuyiswa
- Date: 2011
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:21017 , http://hdl.handle.net/10962/6016
- Description: The transformation process in the South African curriculum has highlighted a need for teachers to change from being passive implementers of curriculum. They are required to interpret the curriculum, adapt materials and develop lesson plans that will be responsive in their own context. They are also required to use materials and mediate learning. This research explores teacher acquisition of content knowledge on marine and coastal issues and probes how teachers work with materials in the development of lesson plans to contextualize the curriculum. A participatory action research process engaged 3 teachers in a contextualizing process of curriculum development. I started to work with the teachers to adapt and re-develop coastal and marine resources to support learning in local context. The research developed in two phases. The first examined existing teacher knowledge of marine and coastal issues and probed how content was integrated into lesson planning. Teachers identified knowledge acquisition as the priority to enable them to work with the materials and curriculum in their context. The second phase set out to enhance teachers’ knowledge of marine and coastal resources through workshops and field trips to improve the adaptation and use of materials. To document these processes and outcomes in the context of this study, I employed a range of data generation strategies including questionnaires, workshops and classroom observations, field notes, focus group discussion and the review of lesson plans, learners’ work and materials used. All participants collaboratively discussed and reflected on the process, but I was responsible for the final interpretation presented here. This study showed that teachers are still entrenched in their normal practice of working with content as facts and definitions, the delivery of abstract propositions that is not aligned with the curriculum goals. The new curriculum required teachers to change their teaching practice by using materials to mediate learning in context. The data revealed a mismatch between teacher practices and what the curriculum required from them.
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- Authors: Mbuyazwe, Vuyiswa
- Date: 2011
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:21017 , http://hdl.handle.net/10962/6016
- Description: The transformation process in the South African curriculum has highlighted a need for teachers to change from being passive implementers of curriculum. They are required to interpret the curriculum, adapt materials and develop lesson plans that will be responsive in their own context. They are also required to use materials and mediate learning. This research explores teacher acquisition of content knowledge on marine and coastal issues and probes how teachers work with materials in the development of lesson plans to contextualize the curriculum. A participatory action research process engaged 3 teachers in a contextualizing process of curriculum development. I started to work with the teachers to adapt and re-develop coastal and marine resources to support learning in local context. The research developed in two phases. The first examined existing teacher knowledge of marine and coastal issues and probed how content was integrated into lesson planning. Teachers identified knowledge acquisition as the priority to enable them to work with the materials and curriculum in their context. The second phase set out to enhance teachers’ knowledge of marine and coastal resources through workshops and field trips to improve the adaptation and use of materials. To document these processes and outcomes in the context of this study, I employed a range of data generation strategies including questionnaires, workshops and classroom observations, field notes, focus group discussion and the review of lesson plans, learners’ work and materials used. All participants collaboratively discussed and reflected on the process, but I was responsible for the final interpretation presented here. This study showed that teachers are still entrenched in their normal practice of working with content as facts and definitions, the delivery of abstract propositions that is not aligned with the curriculum goals. The new curriculum required teachers to change their teaching practice by using materials to mediate learning in context. The data revealed a mismatch between teacher practices and what the curriculum required from them.
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