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Direct-use value of smallholder crop production in a semi-arid rural South African village

  • Authors: Dovie, Delali B K , Witkowski, Ed T F , Shackleton, Charlie M
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181595 , vital:43750 , xlink:href="https://doi.org/10.1016/S0308-521X(02)00124-5"
  • Description: The monetary value of natural resources used by rural communities for subsistence is important when addressing issues affecting the livelihoods of impoverished rural households. There is therefore the need to attribute monetary values to non-marketed products from smallholder production systems in order to reliably account for resource availability and usage to further sound policy decisions. The objective of this paper is to present an empirical analysis of the direct-use and traded values of crop production by households, and to discuss the implications for policy development. The study was undertaken in combination with an evaluation of other livelihood sectors in Thorndale, a semi-arid rural village in the Limpopo province of South Africa. The net direct-use value of crops was estimated at $443.4 per household per annum across the village. Maize (Zea mays), watermelon (Citrullus, vulgaris), peanuts (Arachis hypogaea) and common beans (Phaseolus vulgaris) contributed over 90% to the total direct-use value of crops. Maize alone contributed 40% of this value per household at an estimated $652/ha. Marketing of resources was not a common practice, limited to only maize and peanuts. Farming was basically a rain-fed–mixed cropping system with low production inputs. Farmer support services, human capital development and tenure security were major areas identified for policy development.
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  • Date Issued: 2003

Electrochemical behavior and detection of dopamine and ascorbic acid at an iron (II) tetrasulfophthalocyanine modified carbon paste microelectrode

  • Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290279 , vital:56735 , xlink:href="https://doi.org/10.1002/elan.200390104"
  • Description: In this article the electrocatalytic behavior of an iron(II)tetrasulfophthalocyanine modified carbon paste microelectrode for the oxidation of dopamine (DA) and ascorbic acid (AA) is described. Although the oxidation potential of ascorbic acid is shifted by over 100 mV to more positive potentials, no peak separation could be obtained. This can be explained by the immediate homogeneous reduction of the oxidation product of dopamine by ascorbic acid in solution. However, this reaction induces a shift of the half-wave potential as a function of ratio of concentration of dopamine to ascorbic acid (cDA/cAA). Therefore it was possible to determine the cAA and cDA from this potential shift and the experimental peak current. Detection limits of 4.5±0.2×10−7 and 7.5±0.5×10−7 mol L−1 were obtained respectively for dopamine and ascorbic acid for cDA/cAA>0.01.
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  • Date Issued: 2003

Electrochemical behaviour of thiol-derivatised zinc (II) phthalocyanine complexes and their self-immobilised films at gold electrodes

  • Authors: Ozoemena, Kenneth I , Nyokong, Tebello
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290295 , vital:56737 , xlink:href="https://doi.org/10.1016/j.microc.2003.08.002"
  • Description: Electrochemical properties of novel, peripherally substituted zinc phthalocyanine complex, octa(4-methylphenylthio-) phthalocyaninatozinc(II) [ZnPc(SC6H4CH3)8] (1a) in DMF solution are presented. This complex showed five quasi-reversible/reversible, diffusion-controlled redox couples. Solution voltammetry of 1a showed little contrast with that of its alkythiol-derivative, octabutylthiophthalocyaninatozinc(II) [ZnPc(SC4H9)8] (1b) in that both thiol-substituents tend to show electron-withdrawing influence on the phthalocyanine ligands; complex 1a showing easier reduction and more difficult to oxidation when compared to 1b and other alkyl derivatives. The voltammetric features of the solid ultrathin films of 1a and 1b, immobilized on gold electrodes via the self-assembling technique, are also presented. Interestingly, the self-assembled films are stable and reproducible and provide good suppression to the following Faradaic processes; gold surface oxidation, solution ion species and underpotential deposition (UPD) of copper.
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  • Date Issued: 2003

Fuelwood availability and use in the Richtersveld National Park, South Africa

  • Authors: Shackleton, Charlie M , Guthrie, G , Keirungi, J , Stewart, J
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181461 , vital:43736 , xlink:href=" https://doi.org/10.4102/koedoe.v46i2.66"
  • Description: Concern has been voiced about the possible over-use of fuelwood from the riparian fringe by pastoralist herders in the Richtersveld National Park (RNP). This coincided with the current examination and modelling of the supply and use of ecosystem goods and services in the Gariep Basin as part of the Southern African Millennium Assessment (SAfMA). This paper reports on a study to index the current availability of deadwood within the riparian zone of RNP, its relationship with proximity to human habitation, and species preferences of the local herders. Deadwood availability was assessed per woody species and on the ground in 12 transects within the riparian fringe. Herders were interviewed regarding their species preferences, and the composition of woodpiles was examined. There was no relationship between the percentage of attached deadwood on the tree, or the percentage deadwood ground cover, and the distance from herder stockposts. Euclea pseudobenus and Tamarix usneoides were the dominant species in the riparian fringe. There was strong selection for Ziziphus mucronata as a fuelwood species and only marginal or random selection for E. pseudobenus. Tamarix usneoides and Prosopis sp. were abundant in the riparian zone, but were not used for fuelwood. There was a significant difference between species with respect to the mean proportion of the stem that was dead, the highest being Z. mucronata (± 28 % deadwood), followed by T. usneoides (± 12 %). Most of the Prosopis trees had no deadwood. Across all species, the mean percentage dead per tree was approximately 15 %. Additionally, detached deadwood covered just less than 9 % of ground area, averaged across all plots and transects. All the variables measured indicated that there seems to be little need for concern over the current fuelwood extraction activities of pastoralists within the RNP. There was no clear evidence of cutting of branches or deadwood. The abundance of both attached and detached deadwood was not depleted close to human habitation. There was still abundant deadwood, even on preferred species. The most preferred species (Ziziphus mucronata) had the greatest mean proportion of deadwood. The herders stated that they only used deadwood, and that there was plenty. They rarely used driftwood washed down the river, although there was an abundance of it. Thus, overall, there was no sign of depletion of the deadwood resource, even on favoured species, or degradation of the productive capacity for deadwood.
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  • Date Issued: 2003

Host-preference and density of woodrose-forming mistletoes (Loranthaceae) on savanna vegetation, South Africa

  • Authors: Dzerefos, Cathy M , Witkowski, Ed T F , Shackleton, Charlie M
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181487 , vital:43738 , xlink:href="https://doi.org/10.1023/A:1023991514968"
  • Description: In the Bushbuckridge region of South Africa host preference and density of two woodrose-forming mistletoes, Erianthemum dregei (Eckl. and Zeyh.) V. Tieghem and Pedistylis galpinii (Schinz ex Sprague) was quantified in relation to land-use (harvested or unharvested), rainfall (high, more than 660 or low , less than 660 mm year−1) and catenal position (top or lower slope). These two mistletoes are generalist hemi-parasites of savanna trees and shrubs occurring on 25 and 17 hosts respectively, seven of which are shared. Thirty-six percent of woody plant species recorded were found to be hosts. Although Sclerocarya birrea (A. Rich.) Hochst. comprised only 4% of woody plant density in the environment, it was the principal host for both mistletoes, accounting for 71% of total E. dregei and 42% of P. galpinii infection. Mistletoe infection relative to density of Ficus stuhlmanii, Trichilia emetica and Cassine transvaalensis indicated that these were preferential hosts to S. birrea. Mistletoe host preference was negatively correlated with host wood density. Mistletoe number per tree had a weak relationship to canopy size. Mistletoes of all size classes were denser at high rainfall relative to low rainfall sites. Interestingly, the overall mistletoe size class distribution was similar between harvested and unharvested sites. The ratio of living to dead mistletoe was 2 to 1 for E. dregei and 1.5 to 1 for P. galpinii. There are sufficient dead mistletoes in unharvested and harvested areas to satisfy present market demand. Living E. dregei predominated in harvested rather than unharvested areas suggesting that current-harvesting levels had little or no negative effect on the population. In contrast, P. galpinii was denser in unharvested areas possibly owing to its higher market value and thus higher harvesting levels.
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  • Date Issued: 2003

Indomethacin reduces lipid peroxidation in rat brain homogenate by binding Fe2+

  • Authors: Anoopkumar-Dukie, Shailendra , Lack, Barbara , McPhail, Kerry L , Nyokong, Tebello , Lambat, Zaynab , Maharaj, Deepat , Daya, Santy
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/304763 , vital:58487 , xlink:href="https://doi.org/10.1023/A:1021958016928"
  • Description: One of the hallmarks of Alzheimer's disease (AD) is the progressive degeneration of cholinergic neurons in the cerebral cortex and hippocampus. It is generally accepted that this neuronal degeneration is due to free-radical-induced damage. These free radicals attack vital structural components of the neurons. This implies that agents that reduce free radical generation could potentially delay the progression of AD. Free radical generation in the brain is assisted by the presence of iron, required by the Fenton reaction. Thus, agents that reduce iron availability for this reaction could potentially reduce free radical formation. Since non steroidal anti-inflammatory drugs (NSAIDS) have been shown to reduce the severity of AD, we investigated the possible mechanism by which indomethacin could afford neuroprotection. Our results show that indomethacin (1 mM) is able to reduce the iron-induced rise in lipid peroxidation in rat brain homogenates. In addition, our NMR data indicate that indomethacin binds the Fe2+/Fe3+ ion. This was confirmed by a study using UV/Vis spectrophotometry. The results imply that indomethacin provides a neuroprotective effect by binding to iron and thus making it unavailable for free radical production.
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  • Date Issued: 2003

Influence of cyclodextrins on the fluorescence, photostability and singlet oxygen quantum yields of zinc phthalocyanine and naphthalocyanine complexes

  • Authors: Tau, Prudence , Ogunsipe, Abimbola O , Maree, Suzanne , Maree, M David , Nyokong, Tebello
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/304775 , vital:58488 , xlink:href="https://doi.org/10.1142/S1088424603000562"
  • Description: The effects of formation of cyclodextrin inclusion complexes on the photochemical and photophysical properties of zinc phthalocyanine (ZnPc) and various peripherally substituted zinc phthalocyanines as well as zinc naphthalocyanine (ZnNPc) are investigated. The cyclodextrins employed were the hydroxypropyl-γ-cyclodextrin and unsubstituted β-cyclodextrin. Job's plots were employed to confirm the stoichiometry of the inclusion complexes and showed 2:1 and 4:1 (cyclodextrin:phthalocyanine) inclusion behavior. The phthalocyanine inclusion complexes showed larger singlet oxygen quantum yield (ϕΔ) values when compared to the free phthalocyanines before inclusion, for complexes 1 (zinc naphthalocyanine), 2 (zinc tetranitrophthalocyanine) and 4 (zinc tetra-tert-butylphenoxyphthalocyanine). The fluorescence quantum yields generally remained unchanged following inclusion.
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  • Date Issued: 2003

Photochemical studies of binuclear phenoxysubstituted phthalocyanines containing catecholate bridges

  • Authors: Seotsanyana-Mokhosi, Itumeleng , Maree, Suzanne , Maree, M David , Nyokong, Tebello
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/304808 , vital:58492 , xlink:href="https://doi.org/10.1142/S1088424603000239"
  • Description: Binuclear ZnPc complexes covalently bridged by catechol units have been synthesized and their absorption and photochemical properties examined. The complexes studied are 1,2-bis-2',9',16',23'-triphenoxyphthalocyaninatozinc benzene (6a), 1,2-bis-2'-9',16',23'-tri-4-carboxyphe-noxyphthalocyaninatozinc benzene (6b), 1,2-bis-2',9',16',23'-tri-4-nitrophenoxyphthalocyaninato- zinc benzene (6c) and 1,2-bis-2'-9',16',23'-tri-4-tert-butylphenoxyphthalocyaninatozinc benzene (6d). Larger intramolecular coupling was observed for 6b and 6c, containing the carboxyphenoxy and nitrophenoxy substituents, respectively, than for 6a and 6d. A single Q band peak was observed for the fluorescence spectra of 6b and 6c, whereas, 6a and 6d showed a split Q band. The absence of the high energy fluorescence peaks corresponding to absorbance peaks in the 640 nm region, suggests that the intramolecular coupling is broken by excitation for complexes 6b and 6c.
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  • Date Issued: 2003

Phthalocyanines and related complexes as electrocatalysts for the detection of nitric oxide

  • Authors: Nyokong, Tebello , Vilakazi, Sibulelo
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290346 , vital:56741 , xlink:href="https://doi.org/10.1016/S0039-9140(03)00356-4"
  • Description: Metallophthalocyanine (MPc) and metalloporphyrin complexes as well as some metalloproteins including myoglobin, hemoglobin, cyanocobalamin and cytochrome c catalyse the detection of nitric oxide (NO). The catalytic process often involve changes in the oxidation state of the catalyst. These complexes catalyse both the reduction and oxidation of NO. MPc complexes containing electroactive central metals such as CoPc and FePc generally show better catalytic activity towards the detection of NO than complexes containing electroinacive central metals. However, the involvement of ring based redox processes was confirmed for the homogenous NO catalysis using CoPc.
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  • Date Issued: 2003

Productivity and abundance of Sclerocarya birrea subsp. caffra in and around rural settlements and protected areas of the Bushbuckridge lowveld, South Africa

  • Authors: Shackleton, Charlie M , Botha, Jenny , Emanuel, P L
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/181607 , vital:43751 , xlink:href="https://doi.org/10.1080/14728028.2003.9752459"
  • Description: Sclerocarya birrea (A. Rich.) Hochst, subsp. caffra (Sond.) Kokwaro is a common species throughout the semi-arid savannas of southern Africa, and is sought after by rural communities. It is frequently maintained in homesteads and fields in an agroforestry situation. It has also been identified by a number of international and national institutes as a key species for domestication and commercialisation. Yet, the sustainability of the resource and local user knowledge and practices have not been considered. This study reports on the abundance and productivity of S. birrea in four rural villages and neighbouring protected areas in the Bushbuckridge lowveld of the Limpopo Province, South Africa, where its common name is marula. The density of marula stems was measured in homestead plots, arable fields and the surrounding communal rangelands of each village. Fruit production was assessed by regular counting of fruit fall from marked trees of known size. Within the villages, fruit production was monitored via local community groups. Additional monitoring of fruiting was conducted on marked trees within local protected areas. The proportion of households planting or nurturing marula trees was determined through interviews with a stratified random sample of households. The density of marula trees was significantly higher in protected areas than the neighbouring communal lands, fields or homesteads. However, the majority of trees in protected areas were small, while those in homesteads were large and mature. Density of adult fruit-bearing female trees, was similar between the protected areas and homesteads, but less in fields and communal lands. S. birrea trees were maintained in 79 % of homesteads and 58 % of fields. Mean fruit yield per tree was significantly higher from village trees (less than 17 000 fruits) than protected area trees (more than 3 500 fruits), even after accounting for differences in tree size. The fresh mass of individual fruits was also greater on village trees than on trees in protected areas. Both these characteristics suggest some degree of historical selection of the trees in the homesteads and fields. There was a positive relationship between tree size and number of fruits produced.
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  • Date Issued: 2003

Revised Schools and Sustainability Pack offers Curriculum Support

  • Authors: Olvitt, Lausanne L
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/389852 , vital:68489 , xlink:href="https://eeasa.org.za/wp-content/uploads/2016/12/Bulletin_vol24-_March-2003.pdf"
  • Description: Since the mid 1990s, the School Environmental Policy and Management Plan (SEP) Pack has supported educators in developing a whole-school environmental policy. This year, Share-Net has updated the pack in line with the South African revised National Curriculum and the National Environmental Education Programme (NEEP).
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  • Date Issued: 2003

Self-Assembled Monolayers of Cobalt and Iron Phthalocyanine Complexes on Gold Electrodes

  • Authors: Ozoemena, Kenneth I , Nyokong, Tebello , Westbroek, Philippe
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290363 , vital:56743 , xlink:href="https://doi.org/10.1002/elan.200302753"
  • Description: The self-assembling of the octa(hydroxyethylthio)-metallophthalocyanine {MOHETPc (M=Co and Fe)} complexes and their similar analogues, octabutylthiometallophthalocyanine {MOBTPc (M=Co and Fe)} complexes on gold electrodes are investigated. Comparative surface voltammetric insights into their distinct self-assembling properties with respect to the passivation of Faradaic processes and surface coverages, including their solution electrochemistry, suggest different orientations and non-cleavage of their CS bonds. In the pH 2−9 range, the reversible [M(III)Pc(−2)]+ / [M(II)Pc(−2)] redox couples show potential shifts close to −59 mV / pH. The gold electrodes modified with the SAMs of these species show electrocatalytic activity towards the oxidation of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in acidic media with detection limits in the region of 10−7–10−6 mol dm−3. These monolayers are stable and easily reproducible.
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  • Date Issued: 2003

Synthesis, spectral and electrochemical properties of a new family of pyrrole substituted cobalt, iron, manganese, nickel and zinc phthalocyanine complexes

  • Authors: Obirai, Joe , Rodrigues, Nazaré Pereira , Bedioui, Fethi , Nyokong, Tebello
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/304852 , vital:58496 , xlink:href="https://0-doi.org.wam.seals.ac.za/10.1142/S1088424603000641"
  • Description: A new family of pyrrole substituted metallophthalocyanine complexes, namely cobalt(II), iron(II), manganese(III), nickel(II) and zinc(II) tetrakis-4-(pyrrol-1-yl)phenoxy phthalocyanines (noted as M(TPhPyrPc), where M is the metallic cation) have been synthesized and fully characterized. In particular, the UV-visible spectra of the iron and nickel complexes showed extensive aggregation even at low concentrations. The cyclic voltammetry of the cobalt, iron and manganese complexes showed three to four redox couples assigned to metal and ring based processes. Spectroelectrochemistry of the manganese derivative confirmed that the synthesized complex is MnIII(TPhPyrPc-2) and that the reduction of MnII(TPhPyrPc-2) to be centred on the ring and rather than on the metal, forming the MnII(TPhPyrPc-4) species. Also, the electrochemical polymerization of these newly synthesized pyrrole-substituted phthalocyanines has been demonstrated in the case of the cobalt complex and the electrocatalytic activity of the obtained film has been tested towards the oxidation of L-cysteine.
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  • Date Issued: 2003

Synthesis, spectroscopy and photochemistry of octasubstituted thiol-derivatized phthalocyaninatozinc (II) complexes

  • Authors: Ozoemena, Kenneth I , Nyokong, Tebello
  • Date: 2003
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290401 , vital:56746 , xlink:href="https://doi.org/10.1016/S1387-7003(03)00218-1"
  • Description: Synthesis, spectroscopic and photochemical characterization of phenylthiol-derivatized zinc phthalocyanine complex: 2,3,9,10,16,17,23,24-octa(4-methylphenylthio-)phthalocyaninatozinc(II) [ZnPc(SC6H4CH3)8] (3a) and its alkanethiol derivative, 2,3,9,10,16,17,23,24-octabutylthiophthalocyaninatozinc(II) [ZnPc(SC4H9)8] (3b) are described. Spectroscopic analyses show that 3a has a higher aggregation tendency than 3b in organic solvents. Photochemical studies indicate that 3b is more photostable and more efficient at singlet oxygen generation than 3a.
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  • Date Issued: 2003

Investment management: an analysis of the risk-return profiles of the South African and Kenyan stock markets

  • Authors: Ndungu, Stanley Ngaruiya
  • Date: 2003-03
  • Subjects: Uncatalogued
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10962/191305 , vital:45082
  • Description: This study analyses the risk-return profiles of securities and constructed portfolio of the South African and Kenya’s stock markets. The analysis is done with cognisance of the dynamism that characterizes contemporary financial markets especially in the face of globalisation. To this end the study inter alia, considers the impact of the technological, information and telecommunications revolution particularly with regard to trading, delivery and settlement period. It also considers the factors that influence the business environment in each of the two markets and how these affect their risk return profiles. Key among the findings of the study are that, only a few sectors and securities in both the South African and Kenyan markets (S % and less than 1 % respectively) exhibited very high risk-return profiles while most of the rest (32 % and 40 % respectively) recorded low risk-return profiles. Overall, the business environment in South Africa is evidently better when compared to that of Kenya. Consequently, each country’s business environment may be used to explain the high/low risk return profiles. , Thesis (MA) -- Faculty of Commerce, Economics and Economic History, 2003
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  • Date Issued: 2003-03

Catalytic activity of iron and cobalt phthalocyanine complexes towards the oxidation of cyclohexene using tert-butylhydroperoxide and chloroperoxybenzoic acid

  • Authors: Sehlotho, Nthapo , Nyokong, Tebello
  • Date: 2004
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290257 , vital:56729 , xlink:href="https://doi.org/10.1016/j.molcata.2003.08.014"
  • Description: Cyclohexene oxidation using tert-butylhydroperoxide (TBHP) or chloroperoxybenzoic acid (CPBA) in the presence of iron(II) polychlorophthalocyanine (Cl16PcFe), iron(II) phthalocyanine (PcFe) and cobalt(II) phthalocyanine (PcCo), results in the formation of the following products: cyclohexene oxide, 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Adipic acid was also formed after long reaction times. The selectivity for 2-cyclohexene-1-one is favoured when Cl16PcFe or PcCo catalysts are employed, while PcFe is selective towards the formation of 2-cyclohexene-1-ol. The Cl16PcFe catalyst is transformed into a μ-oxo dimer (Cl16PcFeIIIOIIIFePcCl16) during the oxidation process. The catalytic process using the unsubstituted PcCoII and PcFeII catalysts involved PcMIII species as an intermediate. The active form of the Cl16PcFe catalyst was stable to degradation in that it was still active even after 4 weeks of continued catalysis.
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  • Date Issued: 2004

Determination of 2′, 3′-Dideoxyinosine Using Iron (II) Phthalocyanine Modified Carbon Paste Electrode

  • Authors: Ozoemena, Kenneth I , Stefan, Raluca-Ioana , Nyokong, Tebello
  • Date: 2004
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/300298 , vital:57914 , xlink:href="https://doi.org/10.1081/AL-200031940"
  • Description: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
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  • Date Issued: 2004

Electrochemical and catalytic properties of chromium tetraaminophthalocyanine

  • Authors: Obirai, Joe , Nyokong, Tebello
  • Date: 2004
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/300310 , vital:57915 , xlink:href="https://doi.org/10.1016/j.jelechem.2004.06.026"
  • Description: Chromium tetraaminophthalocyanine (CrIIITAPc) has been synthesized and its electrochemical and spectroelectrochemical properties reported. The first reduction and oxidation in this complex occur at the central metal, giving CrIITAPc and CrIVTAPc complexes, respectively, the latter having been observed for the first time. The CrIIITAPc species was polymerized onto glassy carbon (GCE) or indium tin oxide (ITO) electrodes and the polymer evolution confirmed by UV/Visible spectroscopy and by scanning electron microscopy. The polymers were employed for the catalytic oxidation of nitrite or nitric oxide, and the catalysis involved the CrIVTAPc−1 species.
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  • Date Issued: 2004

Electrochemical studies of manganese tetraamminophthalocyanine monomer and polymer

  • Authors: Obirai, Joseph , Nyokong, Tebello
  • Date: 2004
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/290330 , vital:56738 , xlink:href="https://doi.org/10.1016/j.electacta.2003.11.006"
  • Description: Manganese tetraaminophthalocyanine (MnTAPc) has been synthesised. The cyclic voltammetry and spectroelectrochemistry of the complex have been examined. Spectroelectrochemistry has been used to confirm that the species synthesised in this work contains MnIII, giving (OH)MnIIITAPc. The oxidation and reduction couples obtained from cyclic voltammetry have been assigned to MnIVPc−/MnIVPc2− (couple I), MnIVPc2−/MnIIIPc2− (couple I′), MnIIIPc2−/MnIIPc2− (couple II) and MnIIPc2−/MnIIPc3− (couple III). Electropolymerization of the MnTAPc onto either the indium tin oxide or glassy carbon electrode results in the in the formation of a poly-MnTAPc. The poly-MnTAPc shows improved reversibility at low pH. The poly-MnTAPc electrode was employed to analyse glycine.
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  • Date Issued: 2004

Emerging patterns of abstraction in environmental education: A review of materials, methods and professional development perspectives

  • Authors: O'Donoghue, Rob B , Russo, Vladimir
  • Date: 2004
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/373610 , vital:66707 , xlink:href="https://doi.org/10.1080/1350462042000258170"
  • Description: The epistemic unconscious is the history of the field. And it is clear that, to secure some chance of really knowing what one is doing, one has to unfold what is inscribed in the various relations of implication in which the thinker and his thoughts are caught up, that is, the presuppositions he engages and the inclusions and exclusions he unwittingly performs. (Bourdieu, 2000, p. 99).
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  • Date Issued: 2004
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