Metallophthalocyanines as electrocatalysts and superoxide dismutase mimics
- Authors: Matemadombo, Fungisai
- Date: 2010
- Subjects: Mimicry (Chemistry) Electrocatalysis Superoxide dismutase Electrochemistry Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4325 , http://hdl.handle.net/10962/d1004985
- Description: Syntheses, spectral, electrochemical, and spectroelectrochemical studies of iron, cobalt, and manganese phthalocyanines are reported. The novel coordination of cobalt tetracarboxy metallophthalocyanine to an electrode premodified with aryl radicals and its use in the detection of thiocyanate are reported. This work describes the catalytic activity of cobalt phthalocyanine (CoPc) derivatives adsorbed onto glassy carbon electrodes for the electrocatalytical detection of nitrite, Lcysteine, and melatonin. The modified electrodes efficiently detected nitrite. The CoPc derivative modified electrodes proficiently detected L-cysteine whereas an un-modified electrode could not. This work presents the innovative electrochemical detection of melatonin using electrodes adsorbed with CoPc derivatives. These electrodes detected melatonin at more favorable electrochemical parameters relative to an un-modified gold electrode. The limits of melatonin detection of the modified electrodes lay in the 10⁻⁷ to 10⁻⁶ M region. The modified electrodes accurately detected capsule melatonin concentrations as specified by the supplier and could differentiate between a mixture of melatonin, tryptophan, and ascorbic acid. They reliably detected nitrite, L-cysteine, and melatonin in the 10⁻⁴ to 10⁻² M region. Metallophthalocyanine complexes substituted with thio groups were employed as self assembled monolayers (SAMs). Voltammetry, impedance, atomic force microscopy, and scanning electrochemical microscopy proved that the SAMs all act as selective and efficient barriers to ion permeability. All the SAMs in this work can be used as effective electrochemical sensors of nitrite and L-cysteine in the 10⁻⁴ to 10⁻² M region with competitive limits of detection whereas an un-modified electrode cannot detect Lcysteine. The manganese phthalocyanine SAM modified electrodes are arguably better nitrite and L-cysteine electrocatalysts relative to their iron and cobalt counterparts. Manganese phthalocyanines were used as superoxide dismutase (SOD) mimics. All manganese phthalocyanine complexes in this work acted as SOD mimics in an enzymatic system of superoxide production. From cellular studies, complexes 6d, 6e, 8d, 8e act as intracellular SOD mimics and are without significantly high cellular toxicity.
- Full Text:
- Authors: Matemadombo, Fungisai
- Date: 2010
- Subjects: Mimicry (Chemistry) Electrocatalysis Superoxide dismutase Electrochemistry Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4325 , http://hdl.handle.net/10962/d1004985
- Description: Syntheses, spectral, electrochemical, and spectroelectrochemical studies of iron, cobalt, and manganese phthalocyanines are reported. The novel coordination of cobalt tetracarboxy metallophthalocyanine to an electrode premodified with aryl radicals and its use in the detection of thiocyanate are reported. This work describes the catalytic activity of cobalt phthalocyanine (CoPc) derivatives adsorbed onto glassy carbon electrodes for the electrocatalytical detection of nitrite, Lcysteine, and melatonin. The modified electrodes efficiently detected nitrite. The CoPc derivative modified electrodes proficiently detected L-cysteine whereas an un-modified electrode could not. This work presents the innovative electrochemical detection of melatonin using electrodes adsorbed with CoPc derivatives. These electrodes detected melatonin at more favorable electrochemical parameters relative to an un-modified gold electrode. The limits of melatonin detection of the modified electrodes lay in the 10⁻⁷ to 10⁻⁶ M region. The modified electrodes accurately detected capsule melatonin concentrations as specified by the supplier and could differentiate between a mixture of melatonin, tryptophan, and ascorbic acid. They reliably detected nitrite, L-cysteine, and melatonin in the 10⁻⁴ to 10⁻² M region. Metallophthalocyanine complexes substituted with thio groups were employed as self assembled monolayers (SAMs). Voltammetry, impedance, atomic force microscopy, and scanning electrochemical microscopy proved that the SAMs all act as selective and efficient barriers to ion permeability. All the SAMs in this work can be used as effective electrochemical sensors of nitrite and L-cysteine in the 10⁻⁴ to 10⁻² M region with competitive limits of detection whereas an un-modified electrode cannot detect Lcysteine. The manganese phthalocyanine SAM modified electrodes are arguably better nitrite and L-cysteine electrocatalysts relative to their iron and cobalt counterparts. Manganese phthalocyanines were used as superoxide dismutase (SOD) mimics. All manganese phthalocyanine complexes in this work acted as SOD mimics in an enzymatic system of superoxide production. From cellular studies, complexes 6d, 6e, 8d, 8e act as intracellular SOD mimics and are without significantly high cellular toxicity.
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An historical perspective of income tax legislation in South Africa, 1910 to 1925
- Authors: Surtees, Peter Geoffrey
- Date: 1986
- Subjects: Income tax -- South Africa , Income tax -- Law and legislation -- South Africa , Income tax -- South Africa -- History
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:898 , http://hdl.handle.net/10962/d1004578 , Income tax -- South Africa , Income tax -- Law and legislation -- South Africa , Income tax -- South Africa -- History
- Description: From Introduction: This work considers the period from Union, 31 May 1910 until promulgation of the Income Tax Act No. 40 of 1925.(1) It will describe the means, both financial and otherwise, by which the fledgling Government of the Union of South Africa contrived to balance its budget, and will consider the various sources of revenue available up to 1914, when the Government of Gen. Louis Botha first decided that a tax on income was necessary in order to maintain the solvency of the new State. Similarly the political pressures which shaped the nature of the Income Tax Acts up to 1925 will be discussed, and the political principles (or expediencies, depending on the degree of cynicism of the reader) which led the parties in power from time to time to make the decisions they did regarding the provisions of the various Acts. The effect of external political situations such as the Great War of 1914 - 1918 will be examined, as will the consequences of the rebellion of 1914 and the strikes of 1913 and 1922. The legislation predictably spawned a considerable body of litigation as taxpayers hastened to find and exploit loopholes in it; the resultant Income Tax Cases, in the Income Tax Special Court, Supreme Court and Appeal Court, formed the embryo of a body of judicial precedent which today encompasses some two thousand case reports. A few of the cases decided in the period up to 1925 are still quoted today; for example, CIR v Lunnon 1924 AD 1 SATC 7. The relevant cases from the period will enjoy consideration, with descriptions of how their verdicts affected either subsequent income tax principles or later legislation. Also considered will be the inception during this period of the way in which income tax legislation largely develops: the legislature promulgates an Act, the taxpayers discover legitimate ways to reduce their tax burden and the Minister of Finance consequently causes the Act to be changed in order to protect the tax base. Thereupon the resolute taxpayers seek loopholes anew. The effect of economic conditions on income tax legislation will engage attention; several such conditions cast their shadows into the House of Assembly during that 15 year period, notably the post-war recession and the drought of 1919. The selection of this period is apposite for several reasons: it covers the period during which income tax legislation came into being; - it includes several notable political occurrences. thus making possible a consideration of their effect on income tax legislation; it includes a natural cataclysm. namely a major drought. which also had an effect on subsequent Income Tax Acts; - a sufficient number of income tax cases was heard during the period to afford a fair indication both of how the body of case law would develop and how it would perpetually interplay with the legislation; it clearly illustrates the differences between the two great political parties of the time, differences largely caused by the vested interests of each; the dominant South African Party, with its need to retain the support of the commercial and particularly the mining sectors, and the smaller but even then growing National Party with its face set firmly towards the rural constituencies and the embattled farmers; - the period culminates in the Income Tax Act of 1925, a significant change from its predecessors, and the second Income Tax Act of the Pact Government. The imposition of taxes by the respective provinces does not form part of this work, as the scope of the discussion is limited to the various Income Tax Acts, and their development has been overseen by the central government.
- Full Text:
- Authors: Surtees, Peter Geoffrey
- Date: 1986
- Subjects: Income tax -- South Africa , Income tax -- Law and legislation -- South Africa , Income tax -- South Africa -- History
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:898 , http://hdl.handle.net/10962/d1004578 , Income tax -- South Africa , Income tax -- Law and legislation -- South Africa , Income tax -- South Africa -- History
- Description: From Introduction: This work considers the period from Union, 31 May 1910 until promulgation of the Income Tax Act No. 40 of 1925.(1) It will describe the means, both financial and otherwise, by which the fledgling Government of the Union of South Africa contrived to balance its budget, and will consider the various sources of revenue available up to 1914, when the Government of Gen. Louis Botha first decided that a tax on income was necessary in order to maintain the solvency of the new State. Similarly the political pressures which shaped the nature of the Income Tax Acts up to 1925 will be discussed, and the political principles (or expediencies, depending on the degree of cynicism of the reader) which led the parties in power from time to time to make the decisions they did regarding the provisions of the various Acts. The effect of external political situations such as the Great War of 1914 - 1918 will be examined, as will the consequences of the rebellion of 1914 and the strikes of 1913 and 1922. The legislation predictably spawned a considerable body of litigation as taxpayers hastened to find and exploit loopholes in it; the resultant Income Tax Cases, in the Income Tax Special Court, Supreme Court and Appeal Court, formed the embryo of a body of judicial precedent which today encompasses some two thousand case reports. A few of the cases decided in the period up to 1925 are still quoted today; for example, CIR v Lunnon 1924 AD 1 SATC 7. The relevant cases from the period will enjoy consideration, with descriptions of how their verdicts affected either subsequent income tax principles or later legislation. Also considered will be the inception during this period of the way in which income tax legislation largely develops: the legislature promulgates an Act, the taxpayers discover legitimate ways to reduce their tax burden and the Minister of Finance consequently causes the Act to be changed in order to protect the tax base. Thereupon the resolute taxpayers seek loopholes anew. The effect of economic conditions on income tax legislation will engage attention; several such conditions cast their shadows into the House of Assembly during that 15 year period, notably the post-war recession and the drought of 1919. The selection of this period is apposite for several reasons: it covers the period during which income tax legislation came into being; - it includes several notable political occurrences. thus making possible a consideration of their effect on income tax legislation; it includes a natural cataclysm. namely a major drought. which also had an effect on subsequent Income Tax Acts; - a sufficient number of income tax cases was heard during the period to afford a fair indication both of how the body of case law would develop and how it would perpetually interplay with the legislation; it clearly illustrates the differences between the two great political parties of the time, differences largely caused by the vested interests of each; the dominant South African Party, with its need to retain the support of the commercial and particularly the mining sectors, and the smaller but even then growing National Party with its face set firmly towards the rural constituencies and the embattled farmers; - the period culminates in the Income Tax Act of 1925, a significant change from its predecessors, and the second Income Tax Act of the Pact Government. The imposition of taxes by the respective provinces does not form part of this work, as the scope of the discussion is limited to the various Income Tax Acts, and their development has been overseen by the central government.
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A study of the predators and parasites of Planococcus citri (Risso) (Homoptera) on vines in the Western Cape Province, South Africa
- Authors: Whitehead, Vincent Booth
- Date: 1959
- Subjects: Hemiptera , Parasites , Insect pests -- Biological control , Grapes -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5896 , http://hdl.handle.net/10962/d1013425
- Description: [Introduction] In the Western Cape Province the mealybug, Planococcus citri (Risso), was first reported on vines in 1930 by Joubert (1943a). By 1935 this mealybug had spread to the Hex River Valley, and subsequently to all the main table grape producing areas of the Western Cape Province. At present Pl. citri is the most important insect pest of the table grape industry and can, if not effectively controlled, result in a loss of at least five per cent of the export table grape crop (Kriegler, 1954). Some preliminary work on the natural enemies of Pl. citri on vines was carried out by Stubbings in 1948, but no further work of this nature has been undertaken in this area since then. The fact that the natural enemies can be an effective check to this mealybug on vines in the Western Cape Province has been known for a number of years (Potgieter, 1937; Hattingh, 1943; Joubert, 1943a; Myburgh, 1951). The present work is an attempt to obtain some basic knowlege of the population fluctuations of the insects concerned in this biological control. Surveys undertaken have shown that there is a complex of primary, secondary and possibly tertiary Hynenopterous parasites associated with Pl. citri. The presence of hyperparasites reduces the efficiency of the primary parasitic Hymenoptera. The usefulness of these primary parasites is further reduced as they only occur in effective numbers for a short period of the year. On the other hand, although attacked by some parasites, the numerous coccinellids found preying on Pl. citri are of more importance in reducing the mealybug populations, as they are present on the vines in effective numbers for the greater part of the year.
- Full Text:
- Authors: Whitehead, Vincent Booth
- Date: 1959
- Subjects: Hemiptera , Parasites , Insect pests -- Biological control , Grapes -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5896 , http://hdl.handle.net/10962/d1013425
- Description: [Introduction] In the Western Cape Province the mealybug, Planococcus citri (Risso), was first reported on vines in 1930 by Joubert (1943a). By 1935 this mealybug had spread to the Hex River Valley, and subsequently to all the main table grape producing areas of the Western Cape Province. At present Pl. citri is the most important insect pest of the table grape industry and can, if not effectively controlled, result in a loss of at least five per cent of the export table grape crop (Kriegler, 1954). Some preliminary work on the natural enemies of Pl. citri on vines was carried out by Stubbings in 1948, but no further work of this nature has been undertaken in this area since then. The fact that the natural enemies can be an effective check to this mealybug on vines in the Western Cape Province has been known for a number of years (Potgieter, 1937; Hattingh, 1943; Joubert, 1943a; Myburgh, 1951). The present work is an attempt to obtain some basic knowlege of the population fluctuations of the insects concerned in this biological control. Surveys undertaken have shown that there is a complex of primary, secondary and possibly tertiary Hynenopterous parasites associated with Pl. citri. The presence of hyperparasites reduces the efficiency of the primary parasitic Hymenoptera. The usefulness of these primary parasites is further reduced as they only occur in effective numbers for a short period of the year. On the other hand, although attacked by some parasites, the numerous coccinellids found preying on Pl. citri are of more importance in reducing the mealybug populations, as they are present on the vines in effective numbers for the greater part of the year.
- Full Text:
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