Composites of linear low density polyethylene and short sisal fibres: The effects of peroxide treatment

Influence of sisal fibre content and different concentrations of dicumyl peroxide (DCP) on the thermal, mechanical and viscoelastic properties of short sisal fibre—linear low-density polyethylene (LLDPE) composites was investigated. Significant improvement of tensile strength was found after peroxide induced grafting between fibres and PE matrix. The stress relaxation measurements also suggest better stability upon prolonged loading of the samples prepared with 1% of DCP. It was shown, on the other hand, that higher DCP concentrations could have detrimental effects on the PE matrix, especially at low fibre contents.     

Heat treatment of medium-temperature Sasol-Lurgi gasifier coal-tar pitch for polymerizing to higher value products

Two coal-derived pitch samples, one a medium temperature pitch from a Sasol-Lurgi gasifier and the other from a high temperature coking process, have been heat treated to induce polymerization, both separately and as a mixture of pitches (co-pyrolysis). The initial pitch samples and the heat-treated samples have been examined by size exclusion chromatography (SEC) in 1-methyl-2-pyrrolidinone (NMP), by UV-fluorescence spectroscopy (UV-F), by solid state ¹³C NMR; elemental analyses of the initial pitch samples have been carried out. The Sasol-Lurgi pitch showed larger apparent sizes, more alkyl and carbonyl functions, and smaller polycyclic aromatic hydrocarbon (PAH) groups than the high temperature pitch. Co-pyrolysis of the two pitches indicated that polymerized product from the Sasol-Lurgi pitch can be used as an extender for high-temperature binder pitch.     

The Missing Link in Cooperative Governance and Housing Delivery: Lessons from Mangaung Local Municipality

This paper examines post-apartheid housing delivery in the Mangaung Local Municipality – previously known as the Bloemfontein–Botshabelo–Thaba Nchu region. The paper assesses housing delivery against the background of existing literature on housing delivery, as evaluated from a city perspective and against the notion of cooperative governance. It is suggested that various guidelines from policy and practice at the provincial level impact negatively on housing delivery at the local level. Furthermore, it is argued that despite some innovative attempts to address aspects of informal settlement upgrading, integrated housing development and participation have not received adequate attention. Finally, the paper also questions the lack of appropriate guidelines in respect of housing delivery in some hidden urbanities of South Africa.     

Reduction of fumonisin B1 and zearalenone by lactic acid bacteria in fermented maize meal

Fusarium species are fungi that infect maize products worldwide and elaborate mycotoxins, which have been associated with cancer. This study was carried out to investigate the potential of lactic acid bacteria fermentation in reducing mycotoxin concentration and toxicity in maize meal products. Maize meal was spiked separately with fumonisin B1 and zearalenone and then allowed to ferment for 4 days. The potential cytotoxicity of the mycotoxin-spiked fermented extracts was also investigated using the SNO human esophageal carcinoma cell line (the SNO cell line was explanted from a cancer patient, S.N., a 62-year-old Zulu man, in July 1972). A significant decrease (P < 0.05) in the concentration of the two mycotoxins was observed, with a 56 to 67% and a 68 to 75% reduction in the third and fourth days, respectively. The two mycotoxins were not detectable in commercially fermented maize meal (amahewu) samples. After fermentation, mycotoxin-spiked maize meal samples containing lactic acid bacteria culture were comparatively less toxic to SNO cells than were samples without lactic acid bacteria. However, this difference in toxicity was not significant (P > 0.05). These results indicate that lactic acid bacteria fermentation can significantly reduce the concentration of mycotoxins in maize. However, such a reduction may not significantly alter the possible toxic effects of such toxins. The exact mechanism of toxin reduction warrants further investigation.     

Role of particle size in visible light photocatalysis of Congo Red using TiO<Subscript>2</Subscript>·[ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>]<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanocomposites

TiO₂·[ZnFe₂O₄] _x (x = 0·0-0·5) nanocomposites (NCs) with an average particle size of 72·4 nm were synthesized by the method of co-precipitation/hydrolysis (CPH). For the comparison of particle-size dependent effects, a set of polycrystalline samples with similar compositions was also prepared by solid state reaction (SSR) route. Average particle size for SSR prepared samples was about 3·0 μm. All the samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer, Raman spectroscopy and Fourier transform infra-red (FTIR) spectroscopy. Their visible light photocatalytic activity was tested for the degradation of Congo Red dye. Maximum photodegradation was observed for the NC with x = 0·1 synthesized by CPH (particle size, 71 nm). Similar composition prepared by SSR method (particle size, 6·19 μm) showed lower photoactivity in comparison even with that observed for pure TiO₂ (particle size, 4·03 μm). It was, therefore, concluded that enhanced photodegradation is directly related to the reduced particle size of the composites, which implies that photosensitization is the process primarily involved. Although, doping of TiO₂ with ZnFe₂O₄ does extend the cut-off wavelength towards visible parts of the spectrum, its contribution in the enhancement is not as significant as that due to the photosensitization.     

Selective surgical management in penetrating neck injuries

OBJECTIVE: To evaluate selective operative management in penetrating neck trauma. DESIGN: A chart review. SETTING: A university-affiliated hospital in Johannesburg, South Africa. PATIENTS: All adults admitted to the hospital between January 1988 and June 1993 with a penetrating neck wound. Excluded were patients in whom there was no suspicion of an occult injury that might need further investigation. There were 755 patients in the study. INTERVENTIONS: Immediate surgical exploration (group A, 613 patients) and observation with constant monitoring (group B, 142 patients). MAIN OUTCOME MEASURES: Unnecessary explorations in group A and missed significant injuries in group B. RESULTS: In group A there was a 3% incidence of unnecessary explorations, and 4.2% of the patients died. In group B there was a 9.1% incidence of missed injuries, and 2.8% of the patients died as a result of the delayed diagnosis. Overall the death rate was 4%. CONCLUSION: Selective operative intervention for penetrating neck trauma results in fewer negative explorations and a death rate comparable to those of series that support mandatory neck exploration.     

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

In a study of the phenomenon of catalyst deactivation during storage, Au/TiO₂ catalyst was stored under various conditions, viz. vacuum, nitrogen, air, refrigeration, dark, and light, and tested for CO oxidation activity at regular intervals. The data shows that the catalyst deactivates under all the storage conditions over 12 months and that storage in vacuum significantly enhances the rate and extent of deactivation. Storage in light accelerates the deactivation. The catalyst appears to deactivate through a combination of Au(III) reduction, Au nanoparticle agglomeration, loss of surface hydroxyl groups, loss of surface moisture, and accumulation of surface carbonates and formates. The rate and extent of catalyst deactivation can be limited by storing the catalyst in the dark at sub ambient temperature (refrigerator) and under inert atmosphere.     

Alkyl transfer reactions on solid acids. The disproportionation of ethylbenzene and toluene on H-mordenite and HY zeolites

The disproportionation of ethylbenzene and toluene have been compared on two zeolites, H-mordenite and HY. The online examination of products as a function of time on stream reflect the different processes occurring on the two zeolites. The relative activities expressed on a unit aluminium center basis, are in line with their relative cracking (n-heptane) activities reported by others, showing that no extraneous factors affect activity. The data set provides a baseline for the activity of these two zeolites for future use in comparing other more complex alkylation reactions involving mononuclear and binuclear aromatic molecules.     

Resistance of Lung Cancer Cells Grown as Multicellular Tumour Spheroids to Zinc Sulfophthalocyanine Photosensitization

Photodynamic therapy (PDT) is phototherapeutic modality used in the treatment of neoplastic and non-neoplastic diseases. The photochemical interaction of light, photosensitizer (PS) and molecular oxygen produces singlet oxygen which induces cell death. Zinc sulfophthalocyanine (ZnPcS_mix) has been shown to be effective in A549 monolayers, multicellular tumor spheroids (MCTSs) (250 µm) and not on MCTSs with a size of 500 µm. A549 cells used in this study were grown as MCTSs to a size of 500 µm in order to determine their susceptibility to PDT. ZnPcS_mix distribution in MCTSs and nuclear morphology was determined using a fluorescent microscope. Changes in cellular responses were evaluated using cell morphology, viability, proliferation, cytotoxicity, cell death analysis and mitochondrial membrane potential. Untreated MCTSs, showed no changes in cellular morphology, proliferation, cytotoxicity and nuclear morphology. Photoactivated ZnPcS_mix also showed no changes in cellular morphology and nuclear morphology. However, photoactivated ZnPcS_mix resulted in a significant dose dependant decrease in viability and proliferation as well as an increase in cell membrane damage in MCTSs over time. ZnPcS_mix photosensitization induces apoptotic cell death in MCTSs with a size of 500 µm and more resistantance when compared to monolayer cells and MCTSs with a size of 250 µm.