Price discovery, price behaviour, and efficiency of selected grain commodities traded on the agricultural products division of the JSE securities exchange
- Authors: Viljoen, Christo
- Date: 2004
- Subjects: Johannesburg Stock Exchange Stock exchanges -- South Africa International economic relations Primary commodities -- South Africa Grain trade -- South Africa Financial futures -- South Africa Price regulation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:952 , http://hdl.handle.net/10962/d1002686
- Description: Agricultural commodity derivatives were first introduced in South Africa in 1996 after the deregulation of the former marketing system. In the context of its proposed functions, namely price discovery and risk management, the question arose as to whether the futures market developed over time to performed its role efficiently. According to the Efficient Markets Hypothesis (EMH) an efficient market is one that accurately incorporates all information available at any point in time. The purpose of the research was to address the issue of price discovery efficiency, firstly, focusing on the weak-form methodology. Secondly, considering the behaviour of futures prices over time, the study addressed the concern of anomalies in daily returns – phenomena contradictory to the EMH by implication. Thirdly, as a means of defining the sources of inefficiency, the role of scheduled public information and its impact on futures prices was examined. Therefore, the primary objective of the research was to investigate and identify the main components of agricultural futures market inefficiency within the unique price formation structure of South African grain markets. The assessment of this problem is important in terms of evaluating the growth and development of the futures market for different grain commodities to date. The Exchange needs to review rules and regulations on a frequent basis in order to ensure proper functioning at all times especially in the case of a relatively new and fast growing market. The study contributed to the knowledge of understanding the price adjustment process and its implications for market efficiency in the context of the three grain markets considered. The weak-form efficiency was tested using a co-integration based model. Analysing daily spot and futures prices of white maize, yellow maize, and wheat, results indicated that all three markets were efficient and unbiased. Non-parametric tests revealed the significant presence of day-of-the-week and turn-of-the-month effects in the futures returns of the three commodities. Further non-parametric analyses suggested a high degree of uncertainty in futures returns around scheduled agricultural and macroeconomic information release dates also contributing significantly to the identified anomalies. It was concluded that (1) the markets’ ability to anticipate the contents of future information to be released, (2) the current skewed size distribution of broking members, (3) the significant role of the R/$ exchange rate in the price formation process of South African grains and, therefore, (4) the relationship to and influence of the broader economy enhanced the return effects (anomalies) creating opportunity for profitable arbitrage. This conclusion was mainly attributed to South Africa’s status as a price-taker in the world grain complex as well as the relatively short existence of the local agricultural futures markets.
- Full Text:
- Date Issued: 2004
Rights-based restitution in South Africa : developmental land reform or relocation in reverse?
- Authors: Roodt, Monty
- Date: 2004
- Subjects: Restitution -- South Africa , Land reform -- South Africa , Right of property -- South Africa , Land settlement -- South Africa , Land tenure -- South Africa , South Africa -- Commission on Restitution of Land Rights
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3351 , http://hdl.handle.net/10962/d1007211 , Restitution -- South Africa , Land reform -- South Africa , Right of property -- South Africa , Land settlement -- South Africa , Land tenure -- South Africa , South Africa -- Commission on Restitution of Land Rights
- Description: The main question of this thesis is to what extent the rights-based and market-driven nature of the restitution program has given rise to a legalistic and bureaucratic process that negates both the demand-driven and the developmental aspects of restitution as land reform. I answer this question by showing that the choice of a Constitutional model with a Bill of Rights provides the background for a rights-based land reform program. This is especially true for the restitution sub-program, one of the three branches along with redistribution and tenure of the overall land reform program. I then consider the debate around the property clause, and how its inclusion provided the context for a market and rights-based approach to land reform as opposed to a supply-led administrative approach. Because the property clause as a First Generation right prevents expropriation of land without market-related compensation, a complex and legalistic land reform program falling within the ambit of Second Generation rights was formulated to address the gross imbalance in land ownership in South Africa. I argue that the contemporary origin of Second Generation human rights lies within the context of class and anti-globalisation struggles for democracy, and that they are something to be fought for and defended. I discuss the distinction between First, Second and Third Generation rights and identify four spheres within which the struggle for Second and Third Generation rights takes place within modern democratic states. These are the state, the representative public sphere, civil society and the private sphere. I then deal with the problem of trying to turn "paper rights" into realisable rights for the more disadvantaged sectors of society. I also look at what impedes their realisation. I argue that a number of strategies are necessary to ensure the delivery of Second and Third Generation rights. These are an adequate legislative framework, a good communication strategy, the development of institutional capacity to deliver, and if all else fails, access to conflict resolution mechanisms. I consider the major impediments to the realisation of Second and Third Generation rights to be the way in which they are defined in relation to First Generation rights, especially the property clause, the way in which access to rights-backed resources through formal institutions are mediated by the operation of informal institutions, and the dearth of administrative competence in South Africa. My point is that in order for Second and Third Generation rights to have practical benefit for the dispossessed and poor, extraordinary measures are needed. The Restitution arm of the land reform program provides in theory just such extraordinary measures, albeit for only a section of the population. I analyse the effectiveness of the Land Claims Court in assisting restitution claimants and the rural poor to realize their rights. I trace the slow and haphazard shift from a positivistic statutory interpretation (narrow, literal, legalistic) to a purposive interpretation (informed by the Constitutional spirit and social purpose of the legislation) by the Court. This is followed by an analysis of the restitution business process, which means tracing the path of the claim from lodgement to settlement. I set out the costly, complex and legalistic implementation and policy process in some detail. My argument is that in order for a rights-based approach to overcome the impediments outlined in Chapter 3, as well as the property clause in the Constitution, its architects designed a complex process that in the end proved counter-productive in terms of its original aims. The failure of the process to deliver led in 1998 the then Minister of Land Affairs, Derek Hannekom, to appoint a Ministerial Review to investigate the problems. Problems included: slowness of delivery, the crisis of unplannability, low levels of trust between implementers, and high levels of frustration. Two issues are analysed more fully, the rights-driven approach as opposed to the rights-based approach and the lack of claimant participation in taking control of the restitution process. I examine the relationship of the Restitution Commission to the Department of Land Affairs and to municipal land use planning processes. The emphasis on rights within the restitution program had the effect of distancing restitution, especially in the first few years of the programs' existence, from the rest of the land reform program, as well as from the local government process of formulating land development objectives (LDOs), and the Integrated Development Planning (lOP) process. I look at the Port Elizabeth Land and Community Restoration Association (Pelcra) as a case study as it embodies an approach that tries to move beyond a mere reclaiming of rights in land and attempts to implement a developmental approach. I conclude that the rights-based restitution program in spite of its many shortcomings has had some success. It has moved slowly from an overly legalistic judicial program to a more administrative but still bureaucratic process, that has delivered only 27 percent of its product as land reform, the rest going to monetary compensation mainly in urban areas. Thus it can be argued that restitution has been more successful as a program to promote reconciliation along the lines of the Truth and Reconciliation Commission, than as a land reform program, especially if one regards land reform as the restoration of rural land to the indigenous population. There have also been some successful attempts by the Commission, such as in the case of PELCRA, to integrate the processing of its claims with local government planning processes, but progress in this direction remains patchy.
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- Date Issued: 2004
Spirituality in the fiction of Henry Rider Haggard
- Authors: Senior, John
- Date: 2004
- Subjects: Haggard, H. Rider (Henry Rider), 1856-1925 -- Religion Haggard, H. Rider (Henry Rider), 1856-1925 -- Criticism and interpretation Religion in literature Spirituality in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2209 , http://hdl.handle.net/10962/d1002252
- Description: Neither an unquestioning support for British imperialism nor a personal pre-Jungian philosophy were the driving forces behind Rider Haggard’s beliefs or his literature. These two concerns were secondary to the author’s fascination with the supernatural, a theme prominent in his era, but less so in our own. A declining faith in European religion provided the dominant focal point in Haggard’s work. Although there are important overtones of imperial concern and indeed points of Jungian significance in the texts, these are generally subservient to an intensive wide-ranging spiritual discourse. The place of Haggard’s work in history and its literary merit are thus misunderstood when his spiritualism is not taken into account. No analysis of the author’s work can be complete without first coming to terms with his spiritual ideas and then with their impact on other topics of significance to both the author and audiences of his day. The spiritual or religious aspect of his writing has been largely ignored because of its subtle nature and its relative unfashionability throughout most of the twentieth century in the critical and intellectual climate of the Western world. However, in the Victorian era, under the materialist impact of Darwin, Marx and industrialization, Europe's Christian God was pushed from centre stage, creating widespread spiritual hunger and anguish. In the resulting religious vacuum Haggard's overtures were of particular significance to his audience. In fact, when considered in terms of his immense contemporary popularity, the pervasive presence of spirituality throughout Haggard's works and in his personal writing gives some indication of the subject's enormous importance not only to the author, but to late Victorian society as a whole. In light of this Victorian significance, the spiritual element rises, by its constant presence and persistent foregrounding, to subvert not only the imperial and the Jungian, but even Haggard's overt adventure text by dealing directly with the underlying metaphysical crisis in Western society.
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- Date Issued: 2004
The concentration of ten metals in the tissues of shark species Squalus megalops and Mustelus mustelus (Chondrichthyes) occuring along the Southeastern coast of South Africa
- Authors: Erasmus, Christina Petronella
- Date: 2004
- Subjects: Sharks -- South Africa -- Effect of metals on. , Marine pollutio -- South Africa.
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11095 , http://hdl.handle.net/10948/d1019683
- Description: The southeastern coast of South Africa is deemed unpolluted and with the exception of a few localized areas, is believed to be pristine. This study aimed to (1) assess the concentration of metals in the water and sharks (Squalus megalops, Mustelus mustelus) from different sites along the southeastern coast, (2) determine the effects that metals have on each other and investigate the accumulation and storage of metals in different shark tissues, (3) determine the effects of length and sex on metal concentration and the presence of metallothioneins in the liver. Metal concentrations in water from seven sites along the southeastern coast revealed concentrations below the detection limit of the extraction method, except for iron at St. Francis Bay which was below the recommended levels as supplied by DWAF. Met al concentrations in S. megalops from the seven sites revealed significantly elevated levels in individuals from Algoa and St. Francis Bay when compared to the other 5 sites. This was observed for all metals except manganese, which had a higher concentration at Cape Agulhas. After comparing the metal levels in muscle tissue (S. megalops) with data from the Department of Health it was concluded that the sharks caught at Algoa and St. Francis Bay were unsuited for human consumption. Liver and vertebral tissues from both S. megalops and M. mustelus were deemed unsuited for human consumption but further research should be conducted especially on vertebral metal concentrations. Comparing the metal concentration in different tissue types of S. megalops and M. mustelus significant difference were observed and attributed to differences in the maturity (thus age) of the two species. Significant differences in the metal concentration of males and females for both the species were observed. A higher number of differences were however observed in M. mustelus than in S. megalops, most probably due to the differences in maturity. Length and weight vs. metal concentration regressions in the males and females of both species revealed more negative than positive trends. This was found to be in accordance with other studies from around the world. Using the life stages of S. megalops, significant differences in the average concentration of metals were observed between the life stages, with embryos usually having the highest concentration. The metal concentration series determined for S. megalops were similar to that which have been reported in the literature in that iron and zinc occupied the highest concentration positions while cadmium, copper and manganese occupied the last three. The spleen usually had the highest metal concentration except for aluminium in skin and arsenic in muscle tissue. Pearson correlation revealed significant negative correlations between cadmium and the mentioned metals suggesting that cadmium replaces essential metals such as manganese, iron and copper as. Negative correlations between essential metals were observed most probably due to the competition for binding positions on ligands. Positive correlations were observed between metals in sp ecific tissue types and may be indicative of synergistic effects, e.g. aluminium may result in the accumulation of other metals such as cadmium. Positive and negative correlations between a specific metal and different tissue types have also been observed and it appears that there are movement of metals between tissue types. Positive correlation for essential metals between yolk and other tissue have been observed, although no correlations for non-essential metals were observed. This could potentially indicate a mechanism that prevents the accumulation of nonessential metals in embryos. Though no metallothioneins were isolated form the liver, the presence of cadmium in other proteins indicate that that cadmium is substituted for essential metals, and as this may result in deleterious physiological effects, further studies should be conducted. In conclusion it can be said that although some of the results were expected there are still quite a few unanswered question and further studies should be conducted.
- Full Text:
- Date Issued: 2004
The concentration of ten metals in the tissues of shark species Squalus megalops and Mustelus mustelus (chondrichthyes) occuring along the Southeastern coast of South Africa
- Authors: Erasmus, Christina Petronella
- Date: 2004
- Subjects: Sharks -- South Africa -- Effect of metals on , Marine pollution -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11085 , http://hdl.handle.net/10948/328 , Sharks -- South Africa -- Effect of metals on , Marine pollution -- South Africa
- Description: The southeastern coast of South Africa is deemed unpolluted and with the exception of a few localized areas, is believed to be pristine. This study aimed to (1) assess the concentration of metals in the water and sharks (Squalus megalops, Mustelus mustelus) from different sites along the southeastern coast, (2) determine the effects that metals have on each other and investigate the accumulation and storage of metals in different shark tissues, (3) determine the effects of length and sex on metal concentration and the presence of metallothioneins in the liver. Metal concentrations in water from seven sites along the southeastern coast revealed concentrations below the detection limit of the extraction method, except for iron at St. Francis Bay which was below the recommended levels as supplied by DWAF. Met al concentrations in S. megalops from the seven sites revealed significantly elevated levels in individuals from Algoa and St. Francis Bay when compared to the other 5 sites. This was observed for all metals except manganese, which had a higher concentration at Cape Agulhas. After comparing the metal levels in muscle tissue (S. megalops) with data from the Department of Health it was concluded that the sharks caught at Algoa and St. Francis Bay were unsuited for human consumption. Liver and vertebral tissues from both S. megalops and M. mustelus were deemed unsuited for human consumption but further research should be conducted especially on vertebral metal concentrations. Comparing the metal concentration in different tissue types of S. megalops and M. mustelus significant difference were observed and attributed to differences in the maturity (thus age) of the two species. Significant differences in the metal concentration of males and females for both the species were observed. A higher number of differences were however observed in M. mustelus than in S. megalops, most probably due to the differences in maturity. Length and weight vs. metal concentration regressions in the males and females of both species revealed more negative than positive trends. This was found to be in accordance with other studies from around the world. Using the life stages of S. megalops, significant differences in the average concentration of metals were observed between the life stages, with embryos usually having the highest concentration. The metal concentration series determined for S. megalops were similar to that which have been reported in the literature in that iron and zinc occupied the highest concentration positions while cadmium, copper and manganese occupied the last three. The spleen usually had the highest metal concentration except for aluminium in skin and arsenic in muscle tissue. Pearson correlation revealed significant negative correlations between cadmium and the mentioned metals suggesting that cadmium replaces essential metals such as manganese, iron and copper as. Negative correlations between essential metals were observed most probably due to the competition for binding positions on ligands. Positive correlations were observed between metals in sp ecific tissue types and may be indicative of synergistic effects, e.g. aluminium may result in the accumulation of other metals such as cadmium. Positive and negative correlations between a specific metal and different tissue types have also been observed and it appears that there are movement of metals between tissue types. Positive correlation for essential metals between yolk and other tissue have been observed, although no correlations for non-essential metals were observed. This could potentially indicate a mechanism that prevents the accumulation of nonessential metals in embryos. Though no metallothioneins were isolated form the liver, the presence of cadmium in other proteins indicate that that cadmium is substituted for essential metals, and as this may result in deleterious physiological effects, further studies should be conducted. In conclusion it can be said that although some of the results were expected there are still quite a few unanswered question and further studies should be conducted.
- Full Text:
- Date Issued: 2004
The doctrine of duress in the law of contract and unjustified enrichment in South Africa
- Authors: Glover, Graham Brian
- Date: 2004
- Subjects: Contracts -- South Africa , Duress (Law) -- South Africa , Remedies (Law) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3672 , http://hdl.handle.net/10962/d1003187 , Contracts -- South Africa , Duress (Law) -- South Africa , Remedies (Law) -- South Africa
- Description: This thesis analyses the doctrine of duress and its application in the law of contract and unjustified enrichment in South Africa. Following an initial examination of the historical development of the doctrine from its roots in Roman and Roman-Dutch law, the study focuses on the current legal position in the two areas of law under review, identifies the substantive and formal deficiencies in the current approach, and suggests, using comparative authorities, how the law might be developed. As far as the law of contract is concerned, after exposing the difficulties inherent in the current approach, and placing the doctrine in its proper context in the South African law of contract generally, it is argued that the duress doctrine finds its juridical basis in the principle of good faith. A more modern and coherent test for duress is then proposed: one that concentrates on the question whether an illegitimate threat was made, which induced a contract in that it left the other person no reasonable choice but to succumb to the proposal. Additionally, the need for South African contract law to recognise and deal with cases of economic duress is emphasised. The study then shifts to an examination of the position in situations where non-contractual performances have occurred under duress: cases that are decided in terms of the principles of the law of unjustified enrichment. The current position is reviewed, and it is shown that the approach to duress cases is substantially different to the approach that applies in contract. An attempt is made to reconcile this problem. From a structural perspective, the nature and application of the relevant enrichment action where a non-contractual performance is made under duress (the condictio indebiti) is also investigated, in the light of approaches to enrichment adopted in both Germany and England, in an attempt to make better sense of this enrichment action in the South African context. The study closes with an analysis of the various contractual, delictual and enrichment remedies that are available once a case of duress has been proved.
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- Date Issued: 2004
The ecology and control of small hive beetles (Aethina tumida Murray)
- Authors: Ellis, James Douglas
- Date: 2004
- Subjects: Bee culture , Bee culture -- United States , Nitidulidae , Beetles -- Ecology , Beetles -- Control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5917 , http://hdl.handle.net/10962/d1016253
- Description: The small hive beetle (Aethina tumida Murray) is an endemic scavenger in colonies of honey bee (Apis mellifera L.) subspecies inhabiting sub-Saharan Africa. The beetle only occasionally damages host colonies in its native range and such damage is usually restricted to weakened/diseased colonies or is associated with after absconding events due to behavioral resistance mechanisms of its host. The beetle has recently been introduced into North America and Australia where populations of managed subspecies of European honey bees have proven highly susceptible to beetle depredation. Beetles are able to reproduce in large numbers in European colonies and their larvae weaken colonies by eating honey, pollen, and bee brood. Further, adult and larval defecation is thought to promote the fermentation of honey and large populations of beetles can cause European colonies to abscond, both resulting in additional colony damage. The economic losses attributed to the beetle since its introduction into the United States have been estimated in millions of US dollars. Although beetles feed on foodstuffs found within colonies, experiments in vitro show that they can also complete entire life cycles on fruit. Regardless, they reproduce best on diets of honey, pollen, and bee brood. After feeding, beetle larvae exit the colony and burrow into the ground where they pupate. Neither soil type nor density affects a beetle’s ability to successfully pupate. Instead, successful pupation appears to be closely tied to soil moisture. African subspecies of honey bees employ a complicated scheme of confinement (aggressive behavior toward and guarding of beetles) to limit beetle reproduction in a colony. Despite being confined away from food, adult beetles are able to solicit food and feed from the mouths of their honey bee guards. Remarkably, beetle-naïve European honey bees also confine beetles and this behavior is quantitatively similar to that in African bees. If confinement efforts fail, beetles access the combs where they feed and reproduce. Two modes of beetle oviposition in sealed bee brood have been identified. In the first mode, beetles bite holes in the cappings of cells and oviposit on the pupa contained within. In the second mode, beetles enter empty cells, bite a hole in the wall of the cell, and oviposit on the brood in the adjacent cell. Despite this, African bees detect and remove all of the infected brood (hygienic behavior). Similarly, European bees can detect and remove brood that has been oviposited on by beetles. Enhancing the removal rate of infected brood in European colonies through selective breeding may achieve genetic control of beetles. Additional avenues of control were tested for efficacy against beetles. Reducing colony entrances slowed beetle ingress but the efficacy of this method probably depends on other factors. Further, the mortality of beetle pupae was higher when contacting species of the fungus Aspergillus than when not, making biological control an option. Regardless, no control tested to date proved efficacious at the level needed by beekeepers so an integrated approach to controlling beetles remains preferred. The amalgamation of the data presented in this dissertation contributed to a discussion on the beetle’s ecological niche, ability to impact honey bee colonies in ways never considered, and the ability to predict the beetle’s spread and impact globally.
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- Date Issued: 2004
The effects of selected proline-based cyclic dipeptides on growth and induction of apoptosis in cancer cells
- Authors: Brauns, Seth Clint Aron
- Date: 2004
- Subjects: Cyclic peptides , Antineoplastic agents -- Testing , Apoptosis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11088 , http://hdl.handle.net/10948/396 , Cyclic peptides , Antineoplastic agents -- Testing , Apoptosis
- Description: An increasing number of cyclic dipeptides (CDPs) have been shown to exhibit important biological activity including antifungal, antibacterial, anticonvulsant and immunomodulatory activity. Furthermore, some CDP derivatives have been shown to exhibit antitumour activity in vitro and in vivo. Several proline-based CDPs that exhibit biological activity have been detected in various processed foods and beverages. In the present study, the potential of seven proline-based CDPs to inhibit cancer cell growth was investigated in HT-29 (colon), HeLa (cervical), MCF-7 (breast) and WHCO3 (oesophageal) cancer cell lines. The CDPs used in this study were cyclo(Phe-Pro), cyclo(Tyr-Pro), cyclo(Gly-Pro), cyclo(Pro- Pro), cyclo(His-Pro), cyclo(Leu-Pro) and cyclo(Thr-Pro). The sulforhodamine B (SRB) cell growth assay was used in an initial screening phase to investigate the effects of the CDPs in HT-29, HeLa and MCF-7 cells. After exposing the cells to 10mM of the respective CDPs for 48 hours, the SRB assay results showed that only cyclo(Phe-Pro) exhibited more than 50% growth inhibition (p<0.01) in the three cell lines. The other CDPs showed comparatively marginal growth-inhibitory effects, except for cyclo(Tyr-Pro), which exhibited a pronounced effect in MCF-7 cells compared to HT-29 and HeLa cells. The MTT assay was used to confirm the SRB assay results for cyclo(Phe-Pro) and cyclo(Tyr-Pro), extending the investigation to the use of the fourth cell line WHCO3 and using a longer exposure time of 72 hours. The MTT assay demonstrated a dosedependent (0.008-10 mM) growth inhibition by cyclo(Phe-Pro) with an IC50 value of 4.04 ± 1.15 mM for HT-29 cells. Cyclo(Phe-Pro) was subsequently used to investigate whether the growth-inhibitory effects of this CDP were related to the induction of apoptosis in HT-29 cells. Hoechst 33342 staining showed that 5mM cyclo(Phe-Pro) induced characteristic chromatin condensation and nuclear fragmentation in 18.3 ± 2.8% (p<0.01) of HT-29 cells after 72 hours. Furthermore, annexin V binding revealed that HT-29 cells treated with 5 mM cyclo(Phe-Pro) displayed phosphatidylserine externalization after 48 hours. In addition, it was shown that 10 mM cyclo(Phe-Pro) induced poly(ADP-ribose)polymerase PARP cleavage, one of the hallmark events of apoptosis. The use of the broad-range caspase inhibitor Z-VAD-FMK, showed that this PARP cleavage was caspase-dependent, which in turn was confirmed by demonstrating an increase in caspase-3 activity (p<0.01) in cyclo(Phe- Pro)-treated HT-29 cells. In conclusion, these findings demonstrate that cyclo(Phe-Pro) inhibited the growth of HT- 29, MCF-7, HeLa and WHCO3 cells, and induced apoptosis in HT-29 colon cancer cells, suggesting the potential antitumour activity of cyclo(Phe-Pro)-related CDPs.
- Full Text:
- Date Issued: 2004
The enzymology of enhanced hydrolysis within the biosulphidogenic recycling sludge bed reactor (RSBR)
- Authors: Enongene, Godlove Nkwelle
- Date: 2004
- Subjects: Hydrolysis , Sewage sludge , Sewage -- Purification -- Anaerobic treatment , Water -- Purification -- Biological treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4132 , http://hdl.handle.net/10962/d1015744
- Description: The hydrolysis of complex organic heteropolymers contained in municipal wastewater to simpler monomers by extracellular hydrolytic enzymes is generally considered the rate-limiting step of the biodegradation process. Previous studies of the Recycling Sludge Bed Reactor (RSBR) revealed that the hydrolysis of complex particulate organics, such as those contained in primary sludge (PS), was enhanced under anaerobic biosulphidogenic conditions. Although the mechanism was not fully understood, it appeared to involve the interaction of sulfide and sludge flocs. The current study was conducted using a 3500 ml laboratory-scale RSBR fed sieved PS at a loading rate of 0.5 kg COD/m³.day and an initial chemical oxygen demand (COD) to sulfate ratio (COD:SO₄) of 1:1. There was no significant accumulation of undigested sludge in the reactor over the 60-day experimental period and the quantity of SO₄ reduced indicated that the yield of soluble products from PS was at least as high as those reported previously for this system (> 50%). In the current study, the specific activities of a range of extracellular hydrolytic enzymes (L-alanine aminopeptidase, L-leucine aminopeptidase, arylsulphatase, α-glucosidase, β- glucosidase, protease and lipase) were monitored in a sulfide gradient within a biosulphidogenic RSBR. Data obtained indicated that the specific enzymatic activities increased with the depth of the RSBR and also correlated with a number of the physicochemical parameters including sulfide, alkalinity and sulfate. The activities of α- glucosidase and β-glucosidase were higher than that of the other enzymes studied. Lipase activity was relatively low and studies conducted on the enzyme-enzyme interaction using specific enzyme inhibitors indicated that lipases were probably being digested by the proteases. Further studies to determine the impact of sulfide on the enzymes, showed an increase in the enzyme activity with increasing sulfide concentration. Possible direct affects were investigated by looking for changes in the Michaelis constant (Km) and the maximal velocity (Vmax) of the crude enzymes with varying sulfide concentrations (250, 400 and 500 mg/l) using natural and synthetic substrates. The results showed no significant difference in both the Km and the Vmax for any of the hydrolytic enzymes except for the protease. The latter showed a statistically significant increase in the Km with increasing sulfide concentration. Although this indicated a direct interaction, this difference was not large enough to be of biochemical significance and was consequently not solely responsible for the enhanced hydrolysis observed in the RSBR. Investigation into the floc characteristics indicated that the biosulphidogenic RSBR flocs were generally small in size and became more dendritic with the depth of the RSBR. Based on the above data, the previously proposed descriptive models of enhanced hydrolysis of particulate organic matter in a biosulphidogenic RSBR has been revised. It is thought that the effect of sulfide on the hydrolysis step is primarily indirect and that the reduction in floc size and alteration of the floc shape to a more dendritic form is central to the success of the process.
- Full Text:
- Date Issued: 2004
The geology of the Proterozoic Haveri Au-Cu deposit, Southern Finland
- Authors: Strauss, Toby Anthony Lavery
- Date: 2004
- Subjects: Geology, Stratigraphic -- Precambrian , Geology, Stratigraphic -- Proterozoic , Ore deposits -- Finland , Geology -- Finland
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5081 , http://hdl.handle.net/10962/d1015978
- Description: The Haveri Au-Cu deposit is located in southern Finland about 175 km north of Helsinki. It occurs on the northern edge of the continental island arc-type, volcano-sedimentary Tampere Schist Belt (TSB) within the Palaeoproterozoic Svecofennian Domain (2.0 – 1.75 Ga) of the Fennoscandian Shield. The 1.99 Ga Haveri Formation forms the base of the supracrustal stratigraphy consisting of metavolcanic pillow lavas and breccias passing upwards into intercalated metatuffs and metatuffites. There is a continuous gradation upwards from the predominantly volcaniclastic Haveri Formation into the overlying epiclastic meta-greywackes of the Osara Formation. The Haveri deposit is hosted in this contact zone. This supracrustal sequence has been intruded concordantly by quartz-feldspar porphyries. Approximately 1.89 Ga ago, high crustal heat flow led to the generation and emplacement of voluminous synkinematic, I-type, magnetite-series granitoids of the Central Finland Granitoid Complex (CFGC), resulting in coeval high-T/low-P metamorphism (hornfelsic textures), and D₁ deformation. During the crystallisation and cooling of the granitoids, a magmatic-dominated hydrothermal system caused extensive hydrothermal alteration and Cu-Au mineralisation through the late-D₁ to early-D₂ deformation. Initially, a pre-ore Na-Ca alteration phase caused albitisation of the host rock. This was closely followed by strong Ca-Fe alteration, responsible for widespread amphibolitisation and quartz veining and associated with abundant pyrrhotite, magnetite, chalcopyrite and gold mineralisation. More localised calcic-skarn alteration is also present as zoned garnetpyroxene- epidote skarn assemblages with associated pyrrhotite and minor sphalerite, centred on quartzcalcite± scapolite veinlets. Post-ore alteration includes an evolution to more K-rich alteration (biotitisation). Late D₂-retrograde chlorite began to replace the earlier high-T assemblage. Late emanations (post-D₂ and pre-D₃) from the cooling granitoids, under lower temperatures and oxidising conditions, are represented by carbonate-barite veins and epidote veinlets. Later, narrow dolerite dykes were emplaced followed by a weak D₃ deformation, resulting in shearing and structural reactivation along the carbonate-barite bands. This phase was accompanied by pyrite deposition. Both sulphides and oxides are common at Haveri, with ore types varying from massive sulphide and/or magnetite, to networks of veinlets and disseminations of oxides and/or sulphides. Cataclastites, consisting of deformed, brecciated bands of sulphide, with rounded and angular clasts of quartz vein material and altered host-rock are an economically important ore type. Ore minerals are principally pyrrhotite, magnetite and chalcopyrite with lesser amounts of pyrite, molybdenite and sphalerite. There is a general progression from early magnetite, through pyrrhotite to pyrite indicating increasing sulphidation with time. Gold is typically found as free gold within quartz veins and within intense zones of amphibolitisation. Considerable gold is also found in the cataclastite ore type either as invisible gold within the sulphides and/or as free gold within the breccia fragments. The unaltered amphibolites of the Haveri Formation can be classified as medium-K basalts of the tholeiitic trend. Trace and REE support an interpretation of formation in a back-arc basin setting. The unaltered porphyritic rocks are calc-alkaline dacites, and are interpreted, along with the granitoids as having an arc-type origin. This is consistent with the evolution from an initial back-arc basin, through a period of passive margin and/or fore-arc deposition represented by the Osara Formation greywackes and the basal stratigraphy of the TSB, prior to the onset of arc-related volcanic activity characteristic of the TSB and the Svecofennian proper. Using a combination of petrogenetic grids, mineral compositions (garnet-biotite and hornblendeplagioclase thermometers) and oxygen isotope thermometry, peak metamorphism can be constrained to a maximum of approximately 600 °C and 1.5 kbars pressure. Furthermore, the petrogenetic grids indicate that the REDOX conditions can be constrained at 600°C to log f(O₂) values of approximately - 21.0 to -26.0 and -14.5 to -17.5 for the metasedimentary rocks and mafic metavolcanic rocks respectively, thus indicating the presence of a significant REDOX boundary. Amphibole compositions from the Ca-Fe alteration phase (amphibolitisation) indicate iron enrichment with increasing alteration corresponding to higher temperatures of formation. Oxygen isotope studies combined with limited fluid inclusion studies indicate that the Ca-Fe alteration and associated quartz veins formed at high temperatures (530 – 610°C) from low CO₂, low- to moderately saline (<10 eq. wt% NaCl), magmatic-dominated fluids. Fluid inclusion decrepitation textures in the quartz veins suggest isobaric decompression. This is compatible with formation in high-T/low-P environments such as contact aureoles and island arcs. The calcic-skarn assemblage, combined with phase equilibria and sphalerite geothermometry, are indicative of formation at high temperatures (500 – 600 °C) from fluids with higher CO₂ contents and more saline compositions than those responsible for the Fe-Ca alteration. Limited fluid inclusion studies have identified hypersaline inclusions in secondary inclusion trails within quartz. The presence of calcite and scapolite also support formation from CO₂-rich saline fluids. It is suggested that the calcic-skarn alteration and the amphibolitisation evolved from the same fluids, and that P-T changes led to fluid unmixing resulting in two fluid types responsible for the observed alteration variations. Chlorite geothermometry on retrograde chlorite indicates temperatures of 309 – 368 °C. As chlorite represents the latest hydrothermal event, this can be taken as a lower temperature limit for hydrothermal alteration and mineralisation at Haveri.The gold mineralisation at Haveri is related primarily to the Ca-Fe alteration. Under such P-T-X conditions gold was transported as chloride complexes. Ore was localised by a combination of structural controls (shears and folds) and REDOX reactions along the boundary between the oxidised metavolcanics and the reduced metasediments. In addition, fluid unmixing caused an increase in pH, and thus further augmented the precipitation of Cu and Au. During the late D₂-event, temperatures fell below 400 °C, and fluids may have remobilised Au and Cu as bisulphide complexes into the shearcontrolled cataclastites and massive sulphides. The Haveri deposit has many similarities with ore deposit models that include orogenic lode-gold deposits, certain Au-skarn deposits and Fe-oxide Cu-Au deposits. However, many characteristics of the Haveri deposit, including tectonic setting, host lithologies, alteration types, proximity to I-type granitoids and P-T-X conditions of formation, compare favourably with other Early Proterozoic deposits within the TSB and Fennoscandia, as well as many of the deposits in the Cloncurry district of Australia. Consequently, the Haveri deposit can be seen to represent a high-T, Ca-rich member of the recently recognised Fe-oxide Cu-Au group of deposits.
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- Date Issued: 2004
The reproductive biology and artificial breeding of ningu Labeo victorianus (Pisces: Cyprinidae)
- Authors: Rutaisire, Justus
- Date: 2004
- Subjects: Fishes -- Victoria, Lake , Cyprinidae -- Reproduction , Labeo -- Reproduction , Labeo
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5317 , http://hdl.handle.net/10962/d1005162
- Description: Lake Victoria, the largest tropical lake, has faced an unprecedented assault on its ecosystem through a variety of anthropomorphic causes that include the introduction of Nile perch Lates niloticus and over-fishing. As a result there have been species extinctions and declining fish population trends. This thesis explores options for reversing these declining population trends and the restoration of collapsed fisheries based on indigenous non-cichlid species. A candidate species was chosen - the cyprinid fish Labeo victorianus. This thesis studied various aspects of L. victorianus' reproductive biology in two geographically distant populations. These included general reproductive patterns in relation to proximate environmental conditions, gonadal development and recrudescence, sex development, characterisation of genetic and morphological diversity, and induced spawning. Fish from both populations were found to be potamodrometic, and highly fecund, iteroparous spawners. L. victorianus was also shown to be an undifferentiated gonochorist, where all individuals pass through an intersexual juvenile stage prior to differentiation, and maturation to either sex. Sexual maturity was attained at a significantly larger size within the Kagera River than that of Sio River fish – possibly as a response to genotypic and/or phenotypic differences. Spawning seemed to be synchronised with rainfall in Kagera River - a pattern that was not strictly adhered to with the Sio River. Thorough microscopic investigation of recrudescence patterns indicated there was uninterrupted spawning in fish from the Kagera River followed by Type I oocyte atresia. In contrast, there was a 90% spawning failure, as characterised by Type II oocyte atresia, within the Sio River population. Aspects of spermatogenesis and sperm ultrastructure using light- and ultramicrotomic methods are described. Although the populations had varying reproductive biology parameters and were morphologically distinct, they remained undifferentiated at the mitochondrial level. Both populations were characterised by low nucleotide diversity – a feature attributed to a bottleneck event. The option of captive breeding was explored by conducting induced spawning experiments. Success was only achieved with a decapeptide Gonadotropic Releasing Hormone ([D-Arg⁶, Pro⁹-NEt])-sGnRH) in combination with a water-soluble dopamine receptor antagonist metoclopramide. This thesis stresses the importance of a research-oriented approach in the conservation of Lake Victoria's indigenous fish resources. It was concluded that information needed for the development of management policies can be generated within a reasonably short time period, of approximately three years, with modest levels of funding support.
- Full Text:
- Date Issued: 2004
Towards the development of species-specific fish production models for small reservoirs in Southern Africa
- Authors: Potts, Warren M
- Date: 2004
- Subjects: Freshwater fishes -- Africa, Southern Fish populations -- Africa, Southern Fisheries -- Africa, Southern Sustainable fisheries -- Africa, Southern Labeo -- Reproduction Cyprinidae -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5330 , http://hdl.handle.net/10962/d1005176
- Description: The fish populations in small southern African reservoirs are largely unexploited and there is potential for fisheries development. However, the development of sustainable fisheries requires reliable estimates of potential yield or production. Empirical models that have been developed to predict fish production only apply to large water bodies and only predict total fish production, not the production of individual species. Small reservoirs generally have few commercially important species and therefore species-specific fish production models are an alternative approach. The small reservoirs of the Eastern Cape are dominated by the moggel (Labeo umbratus). The principal objectives of this thesis were to gain an understanding of the ecology of small reservoirs and the function of moggel in these systems. This information was used to design a research approach to rapidly develop species-specific models for small reservoirs in southern Africa. The limnology of two small reservoirs was compared. During the study period the reservoirs were turbid and showed a warm, monomictic pattern of thermal stratification. Anthropogenic pressure in the reservoir catchments appeared to be the overriding factor increasing the nutrient input to the reservoirs and consequently, influencing the biomass of algae in the reservoirs. The feeding biology of moggel in Katriver and Laing reservoirs was examined. Moggel are detrivorous and successfully digested diatoms. The slower growth rate of moggel in Katriver reservoir was attributed to the poorer nutritional value of the diet as a consequence of the lower concentration of diatoms in the detrital aggregate. The reproductive characteristics of moggel were examined in four reservoirs. Moggel were able to reproduce successfully in the reservoirs. This could be attributed to their r-selected reproductive strategy, with a high fecundity and an extended spawning season and their ability to spawn in a floodplain environment. Differences in recruitment success between years were found to be a consequence of the timing and duration of seasonal rains. The number of mature females in a population and the availability of suitable spawning habitat influenced recruitment success. The life history of the moggel in five reservoirs was compared. Growth appeared to be related to food availability, while mortality was lower in the populations where food was abundant and there were less predatory species. Size and age at maturity were not affected by environmental factors, but were dependent on growth and mortality. Three contrasting methods were used to estimate moggel gillnet selectivity. The Sechin, direct fyke net method and length-structured model all yielded similar results and correction factors obtained from the selectivity study were applied to the gillnet data to estimate the fish population size and structure in each reservoir. Using information from the life history and selectivity studies, the biomass and production of five moggel populations was estimated and related to abiotic and biotic factors in the reservoirs and their catchments. Moggel biomass and production was dependent on the biomass of algae, which was dependent on morphoedaphic characteristics of the reservoirs. Small, shallow reservoirs with a reasonable amount of human habitation in their catchments would sustain the highest algal biomass and provided they had adequate spawning habitat would also have the highest moggel biomass and production. The future research requirements for small reservoir fisheries are outlined and include a three-year program to develop a species-specific production model for any of the dominant species.
- Full Text:
- Date Issued: 2004
Variability in and coupling of larval availability and settlement of the mussel Perna perna : a spatio-temporal approach
- Authors: Porri, Francesca
- Date: 2004
- Subjects: Mussels -- South Africa Perna -- South Africa Perna -- Spawning Perna -- Larvae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5796 , http://hdl.handle.net/10962/d1005484
- Description: Population dynamics of many intertidal organisms are highly influenced by the abundance and distribution of planktonic larvae in the water column and their arrival on the shore. The brown mussel, Perna perna was used to investigate two of the primary processes that affect population size and dynamics, larval availability and settlement, on the south coast of South Africa. Perna perna is a dominant species on rocky shores of the southern and eastern coasts of South Africa. It creates three-dimensional beds that provide habitats for many other species and hence promotes biodiversity. Larval availability and settlement were examined at different spatial and temporal scales using a nested experimental design. To detect possible relationships between larval availability and settlement, the studies were simultaneous. Two sites, 4km apart, were chosen to investigate mussel settlement patterns. Within each site, three locations (300m from each other) were selected. At each location, five artificial settler collectors were placed at approximately 20cm intervals. Collectors were replaced at a range of time intervals, from daily to seasonal, for 16 months. Each intertidal location was paired with an offshore station, 500m from the shore, where larval availability was measured. At each offshore station, three vertical hauls were collected twice a month using a plankton net. Plankton sampling lasted for 14 months and was designed to examine variability on three temporal scales: seasonal, lunar and daily. The results showed no correlation between the distribution of larvae in the water and settlers on the shore. While larvae were abundant in the water at the start of sampling, they became very rare throughout the rest of the study at both sites and all locations. In contrast, distinct peaks of settler abundance were observed during the seasonal settlement study. In addition to the expected, strong temporal variation that emerged from both studies at all time scales, spatial patterns of variability were also observed. While no spatial effect was detected for the larvae in the water column, there was distinct spatial variation in settlement at the location level: some locations always showed higher settlement than others. These results suggest that, on scales of hundreds of meters to kilometers, larval availability and settlement are very unpredictable in time and that differential delivery of larvae occurs from nearshore waters to the shore. Although the effect of the state of the moon (new or full) was not significant in either study, more settlers seemed to arrive on the shore during new moon. Wind direction did not correlate significantly with settlement. However, the dropping of offshore winds and the prevalence of onshore winds, which are characteristic of summer, may be linked to the start of settlement. Nevertheless, further investigations on tidal or lunar cycles and on the influence of wind on surface currents are required to clarify the effects of moon and wind on settlement.
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- Date Issued: 2004