Book Review: From the Outside In
- Authors: Magadla, Siphokazi
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/298628 , vital:57722 , xlink:href="https://doi.org/10.1080/10220461.2019.1610042"
- Description: From the Outside In: Domestic Actors and South Africa’s Foreign Policy presents an exciting collection of chapters that explore various and often-ignored domestic actors and their relationships within the state, including government departments and local government; and non-governmental organisations such as labour unions, big business and social movements. The editors evoke the imagery of the ‘chess game of foreign policy’, used by scholars such as Joseph Nye,1 to argue that power in international relations is distributed like a ‘three-dimensional chessboard’ consisting of military power, economic power and transnational relations.
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- Date Issued: 2019
Cost-effectiveness of public policy for the long‐term conservation of private lands: What is the deal?
- Authors: Nolte, Christopher , de Vos, Alta , Schöttker, Olivier
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415837 , vital:71293 , xlink:href="https://www.proquest.com/scholarly-journals/cost-effectiveness-public-policy-long-term/docview/2326874018/se-2"
- Description: Long-term strategies for private-land conservation are experiencing a surge in scholarly attention. This interest is timely and justified. Globally, many important biodiversity values occur on private lands and are therefore subject to private land use decisions that can threaten their persistence in the absence of protection. Public and private actors spend billions of dollars annually to ensure the long-term protection and enhancement of public ecosystem services on private lands. Many governments recognize and strengthen “privately protected areas” (PPAs) as part of long-term protection obligations under the Aichi Biodiversity Targets (Stolton, Redford, and Dudley, 2014). As public policy makers deliberate over the best strategies to enhance private-land protection, they need to understand how cost-effective these different policy options are, and how they compare to each other.
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- Date Issued: 2019
Effect of bromination on the optical limiting properties at 532 nm of BODIPY dyes with p-benzyloxystyryl groups at the 3, 5-positions
- Authors: Ngoy, Bokolombe P , May, Aviwe K , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187507 , vital:44665 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.08.012"
- Description: The optical limiting (OL) properties of 3,5-di-p-benzyloxystyrylBODIPY dyes that contain both protons and bromine atoms at the 2,6-positions have been investigated by using the Z-scan technique at 532 nm on the nanosecond timescale. There is relatively weak absorbance at 532 nm under ambient light conditions, because the incorporation of p-benzyloxystyryl groups at the 3,5-positions results in a ca. 140 nm red shift of the main BODIPY spectral band to the 640–670 nm range. Reverse saturable absorbance (RSA) profiles that are consistent with an excited state absorption (ESA) mechanism involving the T1 and/or S1 states are observed in CH2Cl2 solution. Second order hyperpolarizability values of ca. 8 × 10−30 esu are obtained and this demonstrates that the dyes are potentially suitable for use in OL applications at 532 nm. There is a slight enhancement of the OL properties upon bromination, due to increased intersystem crossing to the triplet manifold, but the enhancement of the OL properties is less significant than has been observed with metal phthalocyanine complexes.
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- Date Issued: 2019
Synthesis and photophysicochemical properties of novel axially di-substituted silicon (IV) phthalocyanines and their photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus
- Authors: Sen, Pinar , Sindelo, Azole , Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186757 , vital:44531 , xlink:href="https://doi.org/10.1016/j.synthmet.2019.116203"
- Description: In this study, novel silicon (IV) phthalocyanine axially di-substituted with benzimidazole moieties (3) and its quaternized derivative (4) have been synthesized and fully characterized. The photophysical and photochemical properties of both phthalocyanines such as absorption, fluorescence and, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were investigated in solutions. These new silicon phthalocyanines exhibited low fluorescence but produced high singlet oxygen yields in both DMSO (compound 3 and 4) and aqueous media (compound 4). The quaternization of Si(IV)Pc (3) improved the triplet state quantum yield (ΦT) 0.61 to 0.83, consequently singlet oxygen generation (ΦΔ) increased to 0.69 from 0.42. Photodynamic antimicrobial chemotherapy activities (PACT) of Si(IV)Pc photosensitizers were determined towards Staphylococcus aureus. The higher efficiency was obtained with cationic derivative (4) giving reduction percentage value of 99.75%.
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- Date Issued: 2019
Optical limiting and femtosecond pump-probe transient absorbance properties of a 3, 5-distyrylBODIPY dye
- Authors: Ngoy, Bokolombe P , May, Aviwe K , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186835 , vital:44538 , xlink:href="https://doi.org/10.3389/fchem.2019.00740"
- Description: The optical limiting (OL) properties of a 3,5-di-p-benzyloxystyrylBODIPY dye with an p-acetamidophenyl moiety at the meso-position have been investigated by using the open-aperture Z-scan technique at 532 nm with 10 ns laser pulses. There is a ca. 140 nm red shift of the main spectral band to 644 nm relative to the corresponding BODIPY core dye, due to the incorporation of p-benzyloxystyryl groups at the 3,5-positions. As a result, there is relatively weak absorbance across most of the visible region under ambient light conditions. Analysis of the observed reverse saturable absorbance (RSA) profiles demonstrates that the dye is potentially suitable for use in optical limiting applications as has been reported previously for other 3,5-distyrylBODIPY dyes. Time-resolved transient absorption spectroscopy and kinetic studies with femtosecond and nanosecond scale laser pulses provide the first direct spectral evidence that excited state absorption (ESA) from the S1 state is responsible for the observed OL properties.
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- Date Issued: 2019
Synthesis and properties of chiral amide-bonded porphyrin dimers with various functional bridging blocks
- Authors: Zhu, Weihua , Haider, Syed Najeeb-uz-Zaman , Zhang, Honglin , Attatsi, Isaac K , Mack, John , Dingiswayo, Somila , Nyokong, Tebello , Song, Yuting , Xu, Haijun , Liang, Xu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186791 , vital:44534 , xlink:href="https://doi.org/10.1016/j.dyepig.2019.107740"
- Description: Eight porphyrin dimers with various functional bridging blocks and chiral amide-bonds were synthesized and characterized. An analysis of the spectroscopy and electrochemistry has been carried out to demonstrate that the chiral properties can be modified by changing the interchromophoric through-space coupling distance between the two porphyrin chromophores by introducing various bonding and bridging blocks.
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- Date Issued: 2019
A comparative study of the singlet oxygen generation capability of a zinc phthalocyanine linked to graphene quantum dots through π-π stacking and covalent conjugation when embedded in asymmetric polymer membranes
- Authors: Mafukidze, Donovan M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187461 , vital:44655 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.11.096"
- Description: Following the establishment of graphene quantum dots as potential phthalocyanine supports in photoactive membrane preparation for phthalocyanines lacking linkage functional groups, the practical efficiency of p-p stacking versus covalent linkage was investigated. Synthesized materials were characterized using FT-IR, Raman, powder X-ray diffraction, and UVeVis spectroscopies and also by transmission electron and scanning electron microscopies. Phthalocyanine loadings onto graphene quantum dots of 0.40 mg/mg and 0.14 mg/mg (Pc mass/conjugate mass) for the p-p stacked and covalent linked conjugates respectively were observed. Covalent linkage to graphene quantum dots proved to be functionally superior to p-p linkage, where singlet oxygen quantum yield value of the phthalocyanine in the membrane for the covalent linked conjugate was approximately twice that of the p-p stacked membrane.
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- Date Issued: 2019
New type of metal-free and Zinc (II), In (III), Ga (III) phthalocyanines carrying biologically active substituents: Synthesis and photophysicochemical properties and photodynamic therapy activity
- Authors: Sen, Pinar , Managa, Muthumuni , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186971 , vital:44552 , xlink:href="https://doi.org/10.1016/j.ica.2019.03.010"
- Description: This study reports on novel phthalocyanines having benzimidazole units which are known to have biological properties. 4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl) substituted metal-free, Zn(II), In(III) and Ga(III) phthalocyanines were synthesized, these newly synthesized molecules that were substituted by oxygen bridges were fully characterized. For the purpose of determining their potency for photodynamic therapy, the photophysicochemical properties were investigated in DMSO. The H2Pc (4) showed higher fluorescence quantum yield and fluorescence lifetime as compared to metallated phthalocyanines derivatives. However, the highest singlet oxygen (ΦΔ) and triplet state quantum yields (ΦT) values were obtained with the In(III)Pc (5).
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- Date Issued: 2019
Collaborative stewardship in multifunctional landscapes: toward relational, pluralistic approaches
- Authors: Cockburn, Jessica , Cundell, Georgina , Shackleton, Shenoa , Rouget, Mathieu , Zwinkels, Marijn , Cornelius, Susanna A , Metcalf, Liz , van den Broek, D
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/390297 , vital:68535 , xlink:href="https://doi.org/10.5751/ES-11085-240432"
- Description: Landscape stewardship offers a means to put social-ecological approaches to stewardship into practice. The growing interest in landscape stewardship has led to a focus on multistakeholder collaboration. Although there is a significant body of literature on collaborative management and governance of natural resources, the particular challenges posed by multifunctional landscapes, in which there are often contested interests, require closer attention. We present a case study from South Africa to investigate how collaborative stewardship can be fostered in contested multifunctional landscapes. We conducted this research through an engaged transdisciplinary research partnership in which we integrated social-ecological practitioner and academic knowledge to gain an in-depth understanding of the challenges of fostering collaboration. We identified five overarching factors that influence collaboration: contextual, institutional, social-relational, individual, and political-historical. Collaborative stewardship approaches focused on the development of formal governance institutions appear to be most successful if enabling individual and social-relational conditions are in place. Our case study, characterized by high social diversity, inequity, and contestation, suggests that consensus-driven approaches to collaboration are unlikely to result in equitable and sustainable landscape stewardship in such contexts. We therefore suggest an approach that focuses on enhancing individual and social-relational enablers. Moreover, we propose a bottom-up patchwork approach to collaborative stewardship premised on the notion of pluralism. This would focus on building new interpersonal relationships and collaborative capacity through small collective actions. Taking a relational, pluralistic approach to fostering collaborative stewardship is particularly important in contested, socially heterogeneous landscapes. Drawing on our study and the literature, we propose guiding principles for implementing relational, pluralistic approaches to collaborative stewardship and suggest future research directions for supporting such approaches.
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- Date Issued: 2019
Risk assessment to interpret the physiological host range of Hydrellia egeriae, a biocontrol agent for Egeria densa
- Authors: Smith, Rosalie , Mangan, Rosie , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/418053 , vital:71504 , xlink:href="https://doi.org/10.1007/s10526-019-09942-4"
- Description: Egeria densa Planchon (Hydrocharitaceae) is a submerged macrophyte native to South America. It forms part of a new suite of invasive aquatic plants that has benefited from open nutrient-rich freshwater systems following the successful biological control of floating aquatic plants in South Africa. The specificity of the leaf-mining fly, Hydrellia egeriae Rodrigues (Diptera: Ephydridae) was tested, using traditional laboratory host-specificity testing (i.e., no-choice and paired choice). Only one non-target species, Lagarosiphon major Deeming (Hydrocharitaceae) supported larval development during pair-choice tests. In order to avoid the rejection of a safe and potentially effective agent, continuation (i.e., multiple generations) tests were conducted to measure the ability of the non-target species to nutritionally support a population indefinitely. None of these species could sustain a viable agent population for more than three generations. Laboratory host-specificity tests are limited as they exempt certain insect-host behaviours. To enhance the interpretation of host-specificity results, a risk assessment was conducted using agent preference (i.e., choice tests) and performance (i.e., choice and continuation tests) results. The feeding and reproductive risk that H. egeriae poses to non-target species is below 2%. Based on these findings, permission for its release in South Africa has been obtained.
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- Date Issued: 2019
Photophysical and nonlinear optical characteristics of pyridyl substituted phthalocyanine-detonation nanodiamond conjugated systems in solution
- Authors: Matshitse, Refilwe , Khene, Samson M , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187079 , vital:44563 , xlink:href="https://doi.org/10.1016/j.diamond.2019.03.013"
- Description: In this study photophysical, nonlinear absorption and optical limiting properties of detonation nanodiamonds (DNDs)-phthalocyanine nanoconjugate systems containing: 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyaninato (H2TPPc), 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato zinc(II) (ZnTPPc) and 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato silicon(IV) hydroxide (Si(OH)2TPPc), were investigated in dimethylsulfoxide solution. Pcs were non-covalently linked to nanondiamonds (also covalently linked for Si(OH)2TPPc) and investigated using 532 nm laser excitation at 10 ns pulses for their optical limiting properties. Complexes that have higher triplet state absorption also possessed enhanced nonlinear optical behaviour following reverse saturable absorption mechanism. Superior optical performance is observed when the Pcs had a central metal with axial ligands conjugated to DNDs in solution. Nanoconjugate of DNDs-Si(OH)2TPPc and respective Pc in solution gave the highest imaginary third-order susceptibility (Im[X(3)]) and hyperpolarizability (γ) at 2.91 × 10−8 and 3.17 × 10−8 esu and 3.88 × 10−28 and 4.22 × 10−28 esu, respectively, with Ilim value of 0.47 and 0.39 J·cm−2.
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- Date Issued: 2019
A novel axially palladium (II)-Schiff base complex substituted silicon (IV) phthalocyanine
- Authors: Sen, Pinar , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186813 , vital:44536 , xlink:href="https://doi.org/10.1016/j.poly.2019.114135"
- Description: In this study, a novel silicon(IV) phthalocyanine is reported for the first time as a phthalocyanine derivative bearing axially a palladium(II)-Schiff base complex. The photophysical and photochemical properties of the new Si(IV)Pc, such as absorption, fluorescence, singlet oxygen quantum yields, triplet state quantum yields and exited state lifetimes were measured in DMSO. The new silicon phthalocyanine displayed very low fluorescence, showing efficient intersystem crossing resulting in high triplet and high singlet oxygen quantum yields in DMSO. When compared with the unsubstituted SiPcCl2, the singlet oxygen quantum yield value (UD = 0.47) in relation to the triplet quantum yield (UT = 0.82), which is an important determinant for PDT applications, increased. The photodynamic antimicrobial chemotherapy activity (PACT) of new Si(IV)Pc towards Staphylococcus aureus was determined in comparison to the unsubstituted SiPcCl2. The results of the photodynamic antimicrobial effect study demonstrated that the Pd(II) complex substituted SiPc (5) possesses excellent photodynamic activity with a reduction percentage value of 99.94% and a log red value of 3.26.
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- Date Issued: 2019
Tyrannical masters no more?: Promissory insurance warranties after Viking Inshore Fishing (Pty) Ltd v Mutual and Federal Insurance Co Ltd
- Authors: Glover, Graham B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186701 , vital:44526 , xlink:href="https://hdl.handle.net/10520/EJC-1b0c21b6eb"
- Description: Federal Insurance Co Ltd for the law on promissory insurance warranties are considered. The article begins with an overview of the traditional position, which has been that such warranties are to be strictly interpreted and enforced, no matter the harshness of the result. Thereafter, the article discusses the contrasting decisions in Viking Inshore Fishing (Pty) Ltd v Mutual and Federal Insurance Co Ltd in the Western Cape High Court and the SCA. Wallis JA suggested on appeal that the strict traditional approach to promissory warranties was no longer appropriate, but without having to decide the point. The article next considers the implications of an obiter dictum of the SCA, in a matter relating to a court exercising admiralty jurisdiction, on insurance law in general. Thereafter, the article proposes that Wallis JA’s comments indicate an important change to our law on promissory warranties, specifically in relation to the need for there to be a causal link between the insured’s breach of the warranty and the loss suffered, before an insurer may exercise the power to repudiate the contract. Although others have made the causal-link argument before, this article tries to explain and situate this development in two doctrinal contexts: the modern law on contractual interpretation; and the doctrine of public policy. A supplementary argument relates to the drawing together of the law on promissory warranties with the rules relating to cancellation for major breach, in cases where an insurer pursues that remedy.
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- Date Issued: 2019
Corrosion resistance of aluminum against acid activation: Impact of benzothiazole-substituted gallium phthalocyanine
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa N , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187545 , vital:44670 , xlink:href="https://doi.org/10.3390/molecules24010207"
- Description: This study describes the adsorption behavior of organic inhibitors at the aluminum-HCl solution interface and their corrosion inhibition performance. The organic inhibitors employed are: 4-(benzo [d]thiazol-2ylthio)phthalonitrile (BTThio) and tetrakis[(benzo[d]thiazol-2-yl-thio)phthalocyaninato]gallium(III) chloride (ClGaBTThioPc). The corrosion behavior of these inhibitors is investigated using electrochemical and computational techniques. Open circuit potential results reveal predominant cathodic character for the mechanism of aluminum corrosion inhibition by the inhibitors. Inhibition efficiency values from potentiodynamic polarization measurements increase from 46.9 to 70.8% for BTThio and 59.7 to 81.0% for ClGaBTThioPc within the concentration range of 2 to 10 µM. Scanning electron microscopy (SEM) measurements reveal protection of the metal surface from acid attack, in the presence of the inhibitors and energy dispersive X-ray (EDX) measurements show that the most probable way by which the inhibitors protect the metal surface would be by shielding it from the corrosion attacks of Cl− from the acid. Quantum chemical parameters corroborate well with experimental findings.
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- Date Issued: 2019
The contribution of land tenure diversity to the spatial resilience of protected area networks
- Authors: de Vos, Alta , Cumming, George S
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416421 , vital:71347 , xlink:href="https://doi.org/10.1002/pan3.29"
- Description: The relationship between diversity and resilience is relatively well‐established for ecological systems, but remains much less explored for socio‐economic systems. Institutional diversity can have particular relevance for protected areas, whose managerial responses to environmental change depend on their legal basis, ability to make and enforce rules and socio‐political acceptance and endorsement. 2. Protected area expansion strategies are increasingly turning to private land con‐ servation to increase the configuration and connectivity of national protected area networks. Yet, we know little about the relative role of privately owned pro‐ tected areas in protecting threatened and poorly protected (under‐represented) habitats, and in the overall connectivity of the national protected area network. 3. We present an empirical assessment of protected area tenure diversity across South Africa.
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- Date Issued: 2019
The relative representation of ecosystem services and disservices in South African newspaper media
- Authors: Mclellan, V , Shackleton, Charlie M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/179699 , vital:43162 , https://doi.org/10.1080/26395916.2019.1667442
- Description: Newspapers are key information sources and may influence both public opinion and policy. Previous studies have analysed the portrayal of ecosystem disservices in newspapers, but none have assessed the relative coverage between disservices and services, or how it might have changed over time. We report on the relative frequency and depiction of ecosystem services and disservices in South African, English newspapers over a 15-year period. We used a SABINET search complemented by key-informant interviews with environmental journalists. For each article we recorded if it covered ecosystem services or disservices, the type of service or disservice, and article tone and length. Overall, 2,201 articles were found, of which 25% were on services and 75% on disservices. The number of articles per year declined over the 15-year period for services, but not disservices. The most common services were energy and craft materials, food production, recreation and culture, and disservices were human health, heat waves and floods. Articles on ecosystem services were 25–40% longer than those on disservices. Article lengths on both declined over the 15 years. The greater reporting of ecosystem disservices over services is likely to influence public opinion and environmental decision-making accordingly.
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- Date Issued: 2019
Co (ii) Tetraphenyltetraphenanthroporphyrin@ MWCNTs
- Authors: Gu, Tingting , Tao, Jaiyu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Xu, Haijin , Li, Minzhi , Liang, Xu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234580 , vital:50210 , xlink:href="https://doi.org/10.1039/C9NJ01707K"
- Description: Herein, a cobalt(II)tetraphenyltetraphenanthroporphyrin (Co(II)TPTPP) with phenanthrene-fused pyrrole rings was synthesized and characterized. Moreover, a detailed analysis of its optical and redox properties was carried out by comparing the results obtained via optical spectroscopy and electrochemistry with the trends predicted via a series of DFT and TD-DFT calculations. The electrochemistry results demonstrated that the π-expanded Co(II)TPTPP interacted strongly with multiwall carbon nanotubes (MWCNTs), which were finally immobilized on carbon nanotubes via noncovalent interactions and further deposited on glassy carbon. This strong immobilization via π–π stacking between Co(II)TPTPP and MWCNTs leads to significantly stable electrochemically catalyzed hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), which provides a new insight into the understanding electron transfer channels.
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- Date Issued: 2019
Woza Albert! (Student Editions)
- Authors: Krueger, Anton
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229598 , vital:49691 , xlink:href="https://doi.org/10.1080/10137548.2018.1560975"
- Description: Publishing Woza Albert! back in 1983 was a smart move by Methuen Publishing, since it went on to become South Africa’s most canonical dramatic text. As Temple Hauptfleisch points out in his introduction to this new edition, the play has become one of the most anthologized and produced of all South African plays, a regular prescribed work…particularly so in the new curricula introduced since 1994…a major work in the South African literary canon, one of the most studied and produced of the plays from the turbulent 1980s.
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- Date Issued: 2019
Assessing household food insecurity experience in the context of deforestation in Cameroon
- Authors: Ngome, Precillia I T , Shackleton, Charlie M , Degrande, Ann , Nossi, Eric J , Ngome, Francis
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398180 , vital:69382 , xlink:href="https://doi.org/10.1016/j.foodpol.2019.02.003"
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- Date Issued: 2019
Photophysicochemical and photodynamic therapy properties of metallophthalocyanines linked to gold speckled silica nanoparticles
- Authors: Dube, Edith , Oluwole, David O , Niemuwa, Nwaji , Prinsloo, Earl , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187472 , vital:44657 , xlink:href="https://doi.org/10.1016/j.pdpdt.2019.01.019"
- Description: This work reports on the linkage of 2(3),9(10),16(17),23(24) tetrakis [(benzo[d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (1) and indium(III) chloride (2) to gold speckled silica (GSS) nanoparticles via gold to sulphur (Au-S) and gold to nitrogen (Au-N) self-assembly to form the conjugates: 1-GSS and 2-GSS. The formed conjugates were characterized using microscopic and spectroscopic techniques, and the photophysicochemical properties and photodynamic therapy (PDT) activity against human breast adenocarcinoma cell line (MCF-7 cells) were studied. The conjugates afforded decrease in fluorescence quantum yields with corresponding increase in triplet and singlet oxygen quantum yields when compared to phthalocyanines alone. Singlet oxygen is cytotoxic to cancer cells hence it is important for PDT. The in vitro dark toxicity of complex 2 and 2-GSS against MCF–7 cells showed ≥93% viable cells within concentration ranges of 10–160 μg/mL. 2–GSS showed enhanced PDT activity with less than 50% viable cells at 80 μg/mL as compared to 2 and GSS alone which showed > 60% viable cells within 10–160 μg/mL. The observed improvements in the PDT activity of 2-GSS could be attributed to the high singlet oxygen generation of 2-GSS compared to 2 alone in addition to the phototoxicity of GSS.
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- Date Issued: 2019