University of Johannesburg

About: University of Johannesburg is a education organization based out in Johannesburg, South Africa. It is known for research contribution in the topics: Population & Context (language use). The organization has 8070 authors who have published 22749 publications receiving 329408 citations. The organization is also known as: UJ.

The role of laser fluence in cell viability, proliferation, and membrane integrity of wounded human skin fibroblasts following helium-neon laser irradiation

Abstract: Background: In medicine, lasers have been used predominantly for applications, which are broadly termed low level laser therapy (LLLT), phototherapy or photobiomodulation. This study aimed to establish cellular responses to Helium-Neon (632.8 nm) laser irradiation using different laser fluences (0.5, 2.5, 5, 10, and 16 J/cm 2 ) with a single exposure on 2 consecutive days on normal and wounded human skin fibroblasts. Materials and Methods: Changes in normal and wounded fibroblast cell morphology were evaluated by light microscopy. Changes following laser irradiation were evaluated by assessing the mitochondrial activity using adenosine triphosphate (ATP) luminescence, cell proliferation using neutral red and an alkaline phosphatase (ALP) activity assay, membrane integrity using lactate dehydrogenase (LDH), and percentage cytotoxicity and DNA damage using the Comet assay.

Conserving large carnivores: dollars and fence

Abstract: Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km 2 , unfenced populations require budgets in excess of $2000 km 2 to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density-independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20–40 years.

3D reduced graphene oxide/FeNi3-ionic liquid nanocomposite modified sensor; an electrical synergic effect for development of tert-butylhydroquinone and folic acid sensor

Abstract: This paper reports an electroanalytical sensor developed based on reduced graphene oxide/FeNi3 (FeNi3/rGO)-ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate (HMPF6) carbon paste electrode (CPE) for determining the antioxidant additive tertbutylhydroquinone (TBHQ) in the presence of folic acid. The FeNi3/rGO synthesized by hydrothermal strategy and characterized by X-ray diffraction (XRD) and FESEM methods. The electrochemical response were found to be linearly symmetrical to TBHQ and folic acid concentrations in the range from 0.05 to 900 μM and 0.6–1100 μM with detection limits of 10.0 nM and 0.1 μM, respectively. The FeNi3/rGO/HMPF6/CPE showed high-quality for determination of TBHQ in the presence of folic acid in the real samples with the separation potential ∼600 mV.

Silver decorated magnetic nanocomposite (Fe3O4@PPy-MAA/Ag) as highly active catalyst towards reduction of 4-nitrophenol and toxic organic dyes

Abstract: Developing innovative technologies for the efficient treatment of wastewater containing toxic organic pollutants is of particular importance worldwide. Removal of organic contaminants from aqueous media through chemical reduction using noble metal-based nanocatalysts, and in the presence of NaBH4, as a reducing agent, has become an established approach in the last few years. Herein, we describe a simple method for the synthesis of a magnetic conducting polymer modified with mercaptoacetic acid (MAA) and silver nanoparticles (Ag NPs) as a promising catalyst for the reduction of organic pollutants. Ag NPs were deposited on the magnetic conducting polymer by the reduction of a silver salt precursor (AgNO3) without the need for a reducing agent or stabilizer. The developed Fe3O4@PPy-MAA/Ag nanocomposite was characterised using FE-SEM, TEM, XRD, XPS, BET and ATR-FTIR. The catalytic performance of the nanocatalyst during the reduction of 4-nitrophenol (4-NP) and organic dyes, namely, methylene blue (MB) and methyl orange (MO) was assessed in aqueous medium at 25 °C. The catalyst exhibited excellent catalytic activity for the reduction of all three targeted organic pollutants (4-NP, MO and MB). The pseudo-first-order rate constants were estimated as 0.5–14.3 × 10−2 min-1, 0.52–24.2 × 10−2 s−1 and 10.1–46.8 × 10−3 s−1 for the reduction of 4-NP, MO and MB, respectively. The magnetic catalyst was separated easily from the reaction medium and recycled without significant loss of catalytic activity up to eight successive cycles. In addition to its green synthesis and reusability, findings from this study show that Fe3O4@PPy-MAA/Ag nanocomposite has the potential efficiency and stability to make it an ideal catalyst in environmental applications via chemical reduction of toxic contaminants from wastewater.