“Peer pressure” and “Peer normalization” : discursive resources that justify gendered youth sexualities
- Authors: Macleod, Catriona I , Jearey-Graham, Nicola
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:6312 , http://hdl.handle.net/10962/d1019877 , https://link.springer.com/article/10.1007/s13178-015-0207-8
- Description: “Peer pressure” is associated in the scientific literature with a range of risky sexual behaviors and with undermining public sexual health messages. Interventions are instituted encouraging young people to resist peer pressure or to model positive peer norms. Taking a discursive psychology perspective, we show how young people themselves use the discourses of “peer pressure to have sex” and “peer normalization of sex” to explain and justify youth sexual activity. Using data from focus group discussions about youth sexualities with students at a South African further education and training college, we show how participants outlined a need for young people to be socially recognizable through engaging in, and talking about, sex and how they implicated peer norms in governing individual sexual behavior. Both discourses pointed to a gendering of peer-endorsed sexual norms: masculine virility, the avoidance of shameful virgin or gay positions, and multiple sexual partners were emphasized for men, while the necessity of keeping a boyfriend and avoiding a “slut” position were foregrounded for women. These discourses potentially undermine the aims of public sexual health programs targeting youth. Nuanced engagement with peer group narratives, especially how sexual activity is explained and justified in a gendered fashion, is indicated. , Full text access on Publisher website: https://link.springer.com/article/10.1007/s13178-015-0207-8
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A high-level architecture for efficient packet trace analysis on gpu co-processors
- Authors: Nottingham, Alastair , Irwin, Barry V W
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429572 , vital:72623 , 10.1109/ISSA.2013.6641052
- Description: This paper proposes a high-level architecture to support efficient, massively parallel packet classification, filtering and analysis using commodity Graphics Processing Unit (GPU) hardware. The proposed architecture aims to provide a flexible and efficient parallel packet processing and analysis framework, supporting complex programmable filtering, data mining operations, statistical analysis functions and traffic visualisation, with minimal CPU overhead. In particular, this framework aims to provide a robust set of high-speed analysis functionality, in order to dramatically reduce the time required to process and analyse extremely large network traces. This architecture derives from initial research, which has shown GPU co-processors to be effective in accelerating packet classification to up to tera-bit speeds with minimal CPU overhead, far exceeding the bandwidth capacity between standard long term storage and the GPU device. This paper provides a high-level overview of the proposed architecture and its primary components, motivated by the results of prior research in the field.
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A kernel-driven framework for high performance internet routing simulation
- Authors: Herbert, Alan , Irwin, Barry V W
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429585 , vital:72624 , 10.1109/ISSA.2013.6641048
- Description: The ability to provide the simulation of packets traversing an internet path is an integral part of providing realistic simulations for network training, and cyber defence exercises. This paper builds on previous work, and considers an in-kernel approach to solving the routing simulation problem. The inkernel approach is anticipated to allow the framework to be able to achieve throughput rates of 1GB/s or higher using commodity hardware. Processes that run outside the context of the kernel of most operating system require context switching to access hardware and kernel modules. This leads to considerable delays in the processes, such as network simulators, that frequently access hardware such as hard disk accesses and network packet handling. To mitigate this problem, as experienced with earlier implementations, this research looks towards implementing a kernel module to handle network routing and simulation within a UNIX based system. This would remove delays incurred from context switching and allows for direct access to the hardware components of the host.
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Deep Routing Simulation
- Authors: Irwin, Barry V W , Herbert, Alan
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430353 , vital:72685 , https://www.academic-bookshop.com/ourshop/prod_2546879-ICIW-2013-8th-International-Conference-on-Information-Warfare-and-Security.html
- Description: This paper discusses a dataset of some 16 million packets targeting port 445/tcp collected by a network telescope utilising a /24 netblock in South African IP address space. An initial overview of the collected data is provided. This is followed by a detailed analysis of the packet characteristics observed, including size and TTL. The peculiarities of the observed target selection and the results of the flaw in the Conficker worm's propagation algorithm are presented. An analysis of the 4 million observed source hosts is reported, grouped by both packet counts and the number of distinct hosts per network address block. Address blocks of size /8, 16 and 24 are used for groupings. The localisation, by geographic region and numerical proximity, of high ranking aggregate netblocks is highlighted. The observed shift in geopolitical origins observed during the evolution of the Conficker worm is also discussed. The paper concludes with some overall analyses, and consideration of the application of network telescopes to the monitoring of such outbreaks in the future.
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Synthesis of phthalocyanine conjugates with gold nanoparticles and liposomes for photodynamic therapy
- Authors: Nombona, Nolwazi , Maduray, Kaminee , Antunes, Edith M , Karsten, Aletta , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245798 , vital:51406 , xlink:href="https://doi.org/10.1016/j.jphotobiol.2011.11.007"
- Description: The efficiency of [2,9,17,23-tetrakis-(1,6-hexanedithiol)phthalocyaninato]zinc(II) as a photodynamic therapy (PDT) agent was investigated. This compound belongs to the second generation of photosensitizers currently tested for the cellular photo-damage of cancer cells. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizer were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J cm−2. The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
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Histological validation of gonadal macroscopic staging criteria for Labeo cylindricus (Pisces: Cyprinidae)
- Authors: Booth, Anthony J , Weyl, Olaf L F
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124593 , vital:35634 , https://doi.org/10.1080/15627020.2000.11657094
- Description: Histological examination of gametogenesis revealed that the current staging criteria used to assess gonadal recrudescence of the redeye labeo, Labeo cylindricus, were adequate. Gametogenesis was qualitatively similar to that of freshwater teleosts with a clearly defined seasonal reproductive cycle. L. cylindricus undergoes seasonal gross morphological and cytological gonadal changes with previtellogenesis dominating during the winter, vitellogenic development during spring and summer culminating in large-scale spawning at the end of summer. Post-spawning mass atresia of oocytes was evident in autumn. The histological data presented support macroscopical evidence that L. cylindricus is a synchronous iteroparous spawner, reproducing over a short period each year throughout its life-span.
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Synthesis, photophysical and photochemical properties of octa-substituted antimony phthalocyanines
- Authors: Modibane, Desmond Kwena , Nyokong, Tebello
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/264226 , vital:53711 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.052"
- Description: This work reports on the synthesis and photophysicochemical parameters of unsubstituted [SbIIIPc]+I3- and octa-phenoxy ([SbIIIOPPc]+I3-) and -4-t-butylphenoxy ([SbIIIOTBPPc]+I3-) substituted antimony phthalocyanines. Photophysical and photochemical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide and toluene. The excitation spectra of oxidized antimony (Sb(V)Pc) derivates were similar to absorption spectra. Low fluorescence quantum yields, high triplet quantum yields and low triplet lifetimes were observed as the result of heavy atom (antimony ion).
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(Ferrocenylpyrazolyl)zinc(II) benzoates as catalysts for the ring opening polymerization of ε-caprolactone
- Authors: Obuah, Collins , Lochee, Yemanlall , Jordaan, Johan H.L. , Otto, Daniel P. , Nyokong, Tebello , Darkwa, James
- Language: English
- Type: Article
- Identifier: vital:7264 , http://hdl.handle.net/10962/d1020273
- Description: The reaction of Zn(OAc)2 and C6H5COOH or 3,5-NO2-C6H3COOH with 3-ferrocenylpyrazolyl-methylenepyridine (L1), 3-ferrocenyl-5-methylpyrazolyl-methylenepyridine (L2), 3-ferrocenylpyrazolyl-ethylamine (L3) and 3-ferrocenyl-5-pyrazolyl-ethylamine (L4) afford the corresponding complexes [Zn(C6H5COO)2(L1)] (1), [Zn(C6H5COO)2(L2)] (2), [Zn(3,5-NO2-C6H3COO)2(L1)] (3), [Zn(3,5-NO2-C6H3COO)2(L2)] (4), [Zn(C6H5COO)2(L3)] (5), [Zn(C6H5COO)2(L4)] (6), [Zn(3,5-NO2-C6H3COO)2(L3)] (7) and [Zn(3,5-NO2-C6H3COO)2(L4)] (8). These complexes behave as catalysts for the ring opening polymerization of ɛ-caprolactone to produce polymers with molecular weight that range from 1480 to 7080 g mol−1 and exhibited moderate to broad PDIs. Evidence of these complexes acting as catalysts was obtained from both the polymerization data and kinetic studies. The polymerization data show that variation of the [CL]/[C] from 100 to 800 produced PCL with relatively the same molecular weight indicative of a catalyst behavior. The appearance of induction period in kinetic plots strengthens the fact that these complexes are catalysts rather than initiators. MALDI-TOF MS and 1H NMR data show di-hydroxy end groups, which support the coordination mechanism rather than insertion mechanism. To understand the broad PDIs obtained for some of the polymer, the electronic properties of the zinc complexes were investigated using cyclic voltammetry. The results show that the zinc complexes containing amine based ligands are highly electrophilic therefore making them unstable, hence the broad PDIs observed for zinc complexes containing amine based ligands. Among the eight complexes investigated, complex 7 is the most active catalyst with kp value of 1.18 × 10−7 h−1 mol−1 at 110 °C. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2015.02.007
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A comparative photophysicochemical study of phthalocyanines encapsulated in core–shell silica nanoparticles
- Authors: Fashina, Adedayo , Amuhaya, Edith , Nyokong, Tebello
- Language: English
- Type: text
- Identifier: vital:7271 , http://hdl.handle.net/10962/d1020286 , Original publication is available at http://dx.doi.org/10.1016/j.saa.2014.08.062
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Comparative electrocatalytic studies of nanocomposites of mixed and covalently linked multiwalled carbon nanotubes and 4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninato cobalt(II)
- Authors: Nyoni, Stephen , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7285 , http://hdl.handle.net/10962/d1020332
- Description: Electrocatalytic behavior of 4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninato cobalt(II) (CoPyPc) when mixed or covalently mixed to multiwalled carbon nanotubes (MWCNTs) is reported. Infra-red spectroscopy was used to confirm amide linkage of the covalently linked nanocomposite. Rotating disk electrode (RDE) and cyclic (CV) voltammetry studies were used for the electrochemical characterization of the prepared phthalocyanine and MWCNT nanocomposite. The electrocatalytic effects of the nanocomposites of the cobalt phthalocyanine derivative were then investigated towards l-cysteine oxidation using both RDE and CV experiments, and the electrocatalytic performance of the covalently linked cobalt phthalocyanine-MWCNT was found to be superior over the mixed nanocomposite. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2015.05.038
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Effects of Redox Mediators on the Catalytic Activity of Iron Porphyrins towards Oxygen Reduction in Acidic Media
- Authors: He, Qinggang , Wu, Gang , Liu, Ke , Khene, M Samson , Li, Qing , Mugadza, Tawanda , Deunf, Elise , Nyokong, Tebello , Chen, Shaowei W
- Language: English
- Type: Article
- Identifier: vital:7291 , http://hdl.handle.net/10962/d1020354
- Description: The effects of different redox mediators on the oxygen reduction reaction (ORR) catalyzed by an iron porphyrin complex, iron(III) meso-tetra(N-methyl-4-pyridyl)porphine chloride [FeIIITMPyP], in 0.1 M triflic acid were investigated by cyclic voltammetry (CV) and spectroelectrochemistry in conjunction with density functional theory (DFT) calculations. The formal potentials of the FeIIITMPyP catalyst and the redox mediators, as well as the half-wave potentials for the ORR, were determined by CV in the absence and presence of oxygen in acidic solutions. UV/Vis spectroscopic and spectroelectrochemical studies confirmed that only the 2,2′-azino-bis(3-ethylbenzothiazioline-6-sulfonic acid)diammonium salt (C18H24N6O6S4) showed effective interactions with FeIIITMPyP during the ORR. DFT calculations suggested strong interaction between FeIIITMPyP and the C18H24N6O6S4 redox mediator. The redox mediator caused lengthening of the dioxygen iron bond, which thus suggested easier dioxygen reduction. Consistent results were observed in electrochemical impedance spectroscopic measurements for which the electron-transfer kinetics were also evaluated. , Original publication is available at http://dx.doi.org/10.1002/celc.201402054
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Effects of ZnO nanohexagons and nanorods on the fluorescence behavior of metallophthalocyanines
- Authors: D’Souza, Sarah , Moeno, Sharon , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7263 , http://hdl.handle.net/10962/d1020272
- Description: This paper looks at the fluorescence behavior of zinc phthalocyanines: 2,(3),9(10),16(17),23(24)-tetrakis-(mercaptoacetic acid phthalocyaninato) zinc(II) (ZnTMAAPc), 2,(3),9(10),16(17),23(24)-tetrakis-(mercaptopropanoic acid phthalocyaninato) zinc(II) (ZnTMPAPc) and (OH)AlPcSmix (the latter contains a mixture of the di-, tri- and tetra-sulfonated derivatives with an average of three sulfonated groups per molecule) in the presence of ZnO nanoparticles. Fluorescence lifetimes of Pc complexes generally decreased in the presence of ZnO nanoparticles, with generally longer lifetimes for ZnO nanohexagons compared to ZnO nanorods. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2014.09.012
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Electrocatalytic activity of bimetallic Au–Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine
- Authors: Maringa, Audacity , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7245 , http://hdl.handle.net/10962/d1020250
- Description: Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 μA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 μA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 μM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine. , Original publication is available at http://dx.doi.org/10.1016/j.jcis.2014.10.056
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Electrode Modification Using Alkynyl Substituted Fe(II) Phthalocyanine via Electrografting and Click Chemistry for Electrocatalysis
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7284 , http://hdl.handle.net/10962/d1020329
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM. , Original publication is available at http://dx.doi.org/10.1002/elan.201500212
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Electrode modification using nanocomposites of electropolymerised cobalt phthalocyanines supported on multiwalled carbon nanotubes
- Authors: Nyoni, Stephen , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7293 , http://hdl.handle.net/10962/d1020356
- Description: A polymer of tetra(4)-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II) (CoPyPc) has been deposited over a multiwalled carbon nanotube (MWCNT) platform and its electrocatalytic properties investigated side by side with polymerized cobalt tetraamino phthalocyanine (CoTAPc). X-ray photoelectron spectroscopy, scanning electron microscopy and cyclic voltammetry studies were used for characterization of the prepared polymers of cobalt phthalocyanine derivatives and their nanocomposites. l-Cysteine was used as a test analyte for the electrocatalytic activity of the nanocomposites of polymerized cobalt phthalocyanines and multiwalled carbon nanotubes. The electrocatalytic activity of both polymerized cobalt phthalocyanines was found to be superior when polymerization was done on top of MWCNTs compared to bare glassy carbon electrode. A higher sensitivity for l-cysteine detection was obtained on CoTAPc compared to CoPyPc. , Original publication is available at http://dx.doi.org/10.1007/s10008-015-2985-6
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Enhanced optical limiting behaviour of indium phthalocyanine derivatives when in solution or embedded in poly(acrylic acid) or poly(methyl methacrylate) polymers
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7256 , http://hdl.handle.net/10962/d1020265
- Description: The optical limiting performance of indium phthalocyanine-based polymer thin-films with large nonlinear absorption coefficients (βeff) and low limiting threshold intensity (Ilim) are described. The absorption cross-sections and the population dynamics of the excited states are also reported. The excited state absorption cross-sections (σexc) are shown to depend on the transition moment between the T1 and T2 states. βeff values have been shown to be related to the population density of the molecules in the T1 state. The improved optical limiting performance recorded for the investigated phthalocyanine complexes in the presence of polymer matrices has been attributed to the aggregation effects of the complexes in the polymer thin-films. The optical properties of the indium phthalocyanine moieties were found to possess robust sensitivity to a change of the polymer materials. , Original publication available at http://dx.doi.org/10.1016/j.jphotochem.2015.02.003
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Enhanced triplet state parameters for zinc carboxy phenoxy phthalocyanine following conjugation to ascorbic acid: effects of adsorption on single walled carbon nanotubes
- Authors: Ogbodu, Racheal O , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7265 , http://hdl.handle.net/10962/d1020274
- Description: Zinc phthalocyanine bearing four ascorbic acid units (formed via ester bond between zinc carboxy phenoxy phthalocyanines and ascorbic acid) was synthesized and characterized using different spectroscopic methods. The complex (with or without ascorbic acid) was further adsorbed onto single walled carbon nanotubes (SWCNTs) and further characterized using Raman spectroscopy, X-ray diffractometry, transmission electron microscopy and thermogravimetric analysis. The photophysical properties of the complexes were studied. The synthesized complex showed better photophysical properties when compared to the carboxy phenoxy phthalocyanines alone, this is evident in the increase of the triplet quantum yields (ΦT), triplet life-times (τT) and singlet oxygen quantum yields (ΦΔ). The zinc phthalocyanines bearing ascorbic acid showed improved triplet life-times even in the presence of SWCNTs. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2015.01.032
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Enhanced triplet state yields in aqueous media of asymmetric zinc phthalocyanines when conjugated to silver nanoflowers
- Authors: D’Souza, Sarah , George, Reama , Göksel, Meltem , Atilla, Devrim , Durmuş, Mahmut , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7279 , http://hdl.handle.net/10962/d1020315
- Description: Novel low symmetry water-soluble zinc phthalocyanines (ZnPcs, complexes 1 and 2) were synthesized and then mixed with silver nanoflowers. Photophysical and photochemical studies were performed in order to determine the efficiency of complexes 1 and 2 as photosensitizers when alone and when combined with the silver nanoflowers. The Pcs show low fluorescence quantum yields and excellent triplet quantum yields of 0.78 (for 1) and 0.66 (for 2) in aqueous media. The triplet quantum yield values increased to 0.80 and 0.89, respectively, in the presence of silver nanoflowers. Long triplet lifetimes ranging from 180 to 200 μs in DMSO were obtained for complexes 1, 2 and their conjugates with silver nanoflowers. , Original publication is available at http://dx.doi.org/10.1016/j.poly.2015.08.017
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Facile synthesis, spectroscopic and electrochemical properties, and theoretical calculations of porphyrin dimers with a bridging amide-bonded xanthene moiety
- Authors: Liang, Xu , Xu, Li , Li, Minzhi , Mack, John , Stone, Justin , Nyokong, Tebello , Jiang, Yu , Kobayashi, Nagao , Zhu, Weihua
- Language: English
- Type: Article
- Identifier: vital:7292 , http://hdl.handle.net/10962/d1020355
- Description: A free base porphyrin dimer bridged by a flexible amide-bonded xanthene moiety and its binuclear zinc(II) complex zinc(II) complex were synthesized and characterized. Structural characterization by MS and 1H NMR spectroscopy confirmed the bridged porphyrin dimer structure. The properties of the dimers were characterized by IR, UV-visible absorption, fluorescence and magnetic circular dichroism (MCD) spectroscopy, and electrochemistry studies. Theoretical calculations were carried out to analyze the electronic structures of porphyrin dimers with a bridging amide-bonded xanthene moiety. , Original publication is available at http://dx.doi.org/10.1142/S1088424615500492
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Fluorescence behavior and singlet oxygen generating abilities of aluminum phthalocyanine in the presence of anisotropic gold nanoparticles
- Authors: Mthethwa, Thandekile , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7258 , http://hdl.handle.net/10962/d1020267
- Description: Gold nanoparticles (spheres, rods and bipyramids) were synthesized. The nanocrystals were characterized by UV–visible spectrometry, transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The as prepared gold nanoparticles were then conjugated to a quaternized 2,(3)-tetra [2-(dimethylamino) ethanethio] substituted Al(OH) phthalocyanine (complex 1). The conjugation of phthalocyanines with gold nanoparticles resulted in a decrease in the fluorescence quantum yields and lifetimes. Conversely, an increase in the singlet oxygen quantum yields was observed for the conjugated complex 1 in the presence of AuNPs. , Original publication is available at http://dx.doi.org/10.1016/j.jlumin.2014.09.005
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