Showing papers by "University of Johannesburg published in 2019"

Textile dye wastewater characteristics and constituents of synthetic effluents : a critical review

Abstract: Textile industries are responsible for one of the major environmental pollution problems in the world, because they release undesirable dye effluents. Textile wastewater contains dyes mixed with various contaminants at a variety of ranges. Therefore, environmental legislation commonly obligates textile factories to treat these effluents before discharge into the receiving watercourses. The treatment efficiency of any pilot-scale study can be examined by feeding the system either with real textile effluents or with artificial wastewater having characteristics, which match typical textile factory discharges. This paper presents a critical review of the currently available literature regarding typical and real characteristics of the textile effluents, and also constituents including chemicals used for preparing simulated textile wastewater containing dye, as well as the treatments applied for treating the prepared effluents. This review collects the scattered information relating to artificial textile wastewater constituents and organises it to help researchers who are required to prepare synthetic wastewater. These ingredients are also evaluated based on the typical characteristics of textile wastewater, and special constituents to simulate these characteristics are recommended. The processes carried out during textile manufacturing and the chemicals corresponding to each process are also discussed.

Origin of angiosperms and the puzzle of the Jurassic gap

Abstract: Angiosperms are by far the most species-rich clade of land plants, but their origin and early evolutionary history remain poorly understood. We reconstructed angiosperm phylogeny based on 80 genes from 2,881 plastid genomes representing 85% of extant families and all orders. With a well-resolved plastid tree and 62 fossil calibrations, we dated the origin of the crown angiosperms to the Upper Triassic, with major angiosperm radiations occurring in the Jurassic and Lower Cretaceous. This estimated crown age is substantially earlier than that of unequivocal angiosperm fossils, and the difference is here termed the ‘Jurassic angiosperm gap’. Our time-calibrated plastid phylogenomic tree provides a highly relevant framework for future comparative studies of flowering plant evolution. A study reconstructed angiosperm phylogeny on the basis of plastome data representing 2,351 angiosperm and 187 gymnosperm species, and dated the origin of crown angiosperms to be significantly earlier than the estimates based on fossil data.

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.

Combination of searches for invisible Higgs boson decays with the ATLAS experiment

Abstract: Dark matter particles, if sufficiently light, may be produced in decays of the Higgs boson. This Letter presents a statistical combination of searches for H→invisible decays where H is produced according to the standard model via vector boson fusion, Z(ll)H, and W/Z(had)H, all performed with the ATLAS detector using 36.1 fb^{-1} of pp collisions at a center-of-mass energy of sqrt[s]=13 TeV at the LHC. In combination with the results at sqrt[s]=7 and 8 TeV, an exclusion limit on the H→invisible branching ratio of 0.26(0.17_{-0.05}^{+0.07}) at 95% confidence level is observed (expected).

Electron and photon performance measurements with the ATLAS detector using the 2015-2017 LHC proton-proton collision data

Abstract: This paper describes the reconstruction of electrons and photons with the ATLAS detector, employed for measurements and searches exploiting the complete LHC Run 2 dataset. An improved energy clustering algorithm is introduced, and its implications for the measurement and identification of prompt electrons and photons are discussed in detail. Corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies, and the measurement of the charge of reconstructed electron candidates are determined using up to 81 fb−1 of proton-proton collision data collected at √s=13 TeV between 2015 and 2017.

ATLAS b-jet identification performance and efficiency measurement with tt¯ events in pp collisions at √s = 13 TeV

Abstract: The algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the s ...

A new epirubicin biosensor based on amplifying DNA interactions with polypyrrole and nitrogen-doped reduced graphene: Experimental and docking theoretical investigations

Abstract: Epirubicin is an effective anticancer drug, but naturally causes several side effects. Hence the determination of this drug in biological samples, plays a key role in evaluating its effects and side effects. In this research, a novel label-free DNA-based biosensor was fabricated for the analysis of epirubicin in biological samples. The sensor was fabricated through modifying a pencil graphite electrode with polypyrrole, nitrogen doped reduced graphene (for improving the electrical conductivity) and salmon sperm ds-DNA (PP/NrG/ds-DNA/PGE) and the changes in the electrode signal were used for the determination of epirubicin. The PP/NrG/ds-DNA/PGE showed a high sensitivity for epirubicin in the concentration range of 0.004–55.0 μM and had a detection limit of 1.0 nM. For further evaluations, the interactions between ds-DNA bases and epirubicin were investigated through a theoretical docking study and the obtained data confirmed the intercalation of epirubicin in the minor grooves of ds-DNA with guanine bases. The PP/NrG/ds-DNA/PGE was used for the analysis of epirubicin in injection and urine samples.

A novel electrochemical epinine sensor using amplified CuO nanoparticles and a n-hexyl-3-methylimidazolium hexafluorophosphate electrode

Abstract: This study suggests a carbon paste electrode modified with CuO nanoparticles and n-hexyl-3-methylimidazolium hexafluorophosphate (CPE/CuO-NPs/HMIPF6) as a powerful tool for the analysis of epinine for the first time. It has been confirmed that CPE/CuO-NPs/HMIPF6 can improve the sensitivity of epinine electro-oxidation and reduce the overvoltage of this drug compared to an unmodified electrode. The CuO nanoparticles are characterized by XRD and TEM methods. The CPE/CuO-NPs/HMIPF6 exhibited a detection limit of 0.2 μM and a dynamic range of 0.7–900 μM for analysis of epinine by the square wave voltammetric method. Epinine determination was performed successfully by CPE/CuO-NPs/HMIPF6 in serum and urine samples.

Rapid covalent-probe discovery by electrophile fragment screening

Abstract: Covalent probes can display unmatched potency, selectivity, and duration of action; however, their discovery is challenging. In principle, fragments that can irreversibly bind their target can overcome the low affinity that limits reversible fragment screening, but such electrophilic fragments were considered nonselective and were rarely screened. We hypothesized that mild electrophiles might overcome the selectivity challenge and constructed a library of 993 mildly electrophilic fragments. We characterized this library by a new high-throughput thiol-reactivity assay and screened them against 10 cysteine-containing proteins. Highly reactive and promiscuous fragments were rare and could be easily eliminated. In contrast, we found hits for most targets. Combining our approach with high-throughput crystallography allowed rapid progression to potent and selective probes for two enzymes, the deubiquitinase OTUB2 and the pyrophosphatase NUDT7. No inhibitors were previously known for either. This study highlights the potential of electrophile-fragment screening as a practical and efficient tool for covalent-ligand discovery.

A review of biochar properties and their roles in mitigating challenges with anaerobic digestion

Abstract: Anaerobic digestion (AD) is an established organic waste management technology, producing biogas and organic fertiliser as end-products. Despite being an established technology, AD still faces key challenges, including process inefficiencies due to substrate-induced instability and product quality assurance; inability to digest highly lignocellulosic biomass without pre-treatment; and management of effluents and emissions. Commercial grade carbon-based materials have been employed as stabilising agent to improve process efficiency. Biochar, a by-product from biomass pyrolysis, has recently been identified as a sustainable alternative material to commercial grade carbon-based adsorbent used in AD. This review highlights the challenges with the AD process and the limitations of the various conventional approaches in its management. An exposition of the characteristics of biochar and the physico-chemical properties of biochar, that can simultaneously promote AD process stability, increase biomethane yield rate and the agronomic quality of digestate, are presented and discussed.

Study of the rare decays of B s 0 and B 0 mesons into muon pairs using data collected during 2015 and 2016 with the ATLAS detector

Abstract: A study of the decays B0 s ! + and B0 ! + has been performed using 26 : 3 fb of 13TeV LHC proton-proton collision data collected with the ATLAS detector in 2015 and 2016. Since the detector resolut ...

A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog

Abstract: The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present the second catalog of LAT-detected GRBs, covering the first 10 yr of operations, from 2008 to 2018 August 4. A total of 186 GRBs are found; of these, 91 show emission in the range 30–100 MeV (17 of which are seen only in this band) and 169 are detected above 100 MeV. Most of these sources were discovered by other instruments (Fermi/GBM, Swift/BAT, AGILE, INTEGRAL) or reported by the Interplanetary Network (IPN); the LAT has independently triggered on four GRBs. This catalog presents the results for all 186 GRBs. We study onset, duration, and temporal properties of each GRB, as well as spectral characteristics in the 100 MeV–100 GeV energy range. Particular attention is given to the photons with the highest energy. Compared with the first LAT GRB catalog, our rate of detection is significantly improved. The results generally confirm the main findings of the first catalog: the LAT primarily detects the brightest GBM bursts, and the high-energy emission shows delayed onset as well as longer duration. However, in this work we find delays exceeding 1 ks and several GRBs with durations over 10 ks. Furthermore, the larger number of LAT detections shows that these GRBs not only cover the high-fluence range of GBM-detected GRBs but also sample lower fluences. In addition, the greater number of detected GRBs with redshift estimates allows us to study their properties in both the observer and rest frames. Comparison of the observational results with theoretical predictions reveals that no model is currently able to explain all results, highlighting the role of LAT observations in driving theoretical models.

Ecological footprint, urbanization, and energy consumption in South Africa: including the excluded

Abstract: The study explores the relationship between ecological footprint, urbanization, and energy consumption by applying the ARDL estimation technique on data spanning 1965–2014 for South Africa. After applying the unit root test that accounts for a break in the data, the Bayer and Hanck (J Time Ser Anal 34:83–95, 2013) combined cointegration test affirms cointegrating relationship among the variables. Findings further reveal that economic growth and financial development exact a deteriorating impact on the environment in the short run. However, the same was not true for both energy use and urbanization. While urbanization and energy use promote environmental quality in the long run, financial development and economic growth degrade it further. The long-run findings of our study are confirmed to be robust as reported by the fully modified OLS (FMOLS), dynamic OLS (DOLS), and the canonical cointegrating regression (CCR) estimates. The direction of causality supports the energy-led growth hypothesis for South Africa. Policy outcomes and directions, and the possibility of promoting sustainable growth without degrading the environment are discussed.

A Bibliometric Review of Research on Educational Administration: Science Mapping the Literature, 1960 to 2018.

Abstract: This systematic review used “science mapping” as a means of understanding the evolution of research in educational administration (EA). The review sought to document the size, growth trajectory, an...

Application of Porphyrins in Antibacterial Photodynamic Therapy.

Abstract: Antibiotics are commonly used to control, treat, or prevent bacterial infections, however bacterial resistance to all known classes of traditional antibiotics has greatly increased in the past years especially in hospitals rendering certain therapies ineffective. To limit this emerging public health problem, there is a need to develop non-incursive, non-toxic, and new antimicrobial techniques that act more effectively and quicker than the current antibiotics. One of these effective techniques is antibacterial photodynamic therapy (aPDT). This review focuses on the application of porphyrins in the photo-inactivation of bacteria. Mechanisms of bacterial resistance and some of the current ‘greener’ methods of synthesis of meso-phenyl porphyrins are discussed. In addition, significance and limitations of aPDT are also discussed. Furthermore, we also elaborate on the current clinical applications and the future perspectives and directions of this non-antibiotic therapeutic strategy in combating infectious diseases.

Biological collections for understanding biodiversity in the Anthropocene.

Abstract: Global change has become a central focus of modern biology. Yet, our knowledge of how anthropogenic drivers affect biodiversity and natural resources is limited by a lack of biological data spanning the Anthropocene. We propose that the hundreds of millions of plant, fungal and animal specimens deposited in natural history museums have the potential to transform the field of global change biology. We suggest that museum specimens are underused, particularly in ecological studies, given their capacity to reveal patterns that are not observable from other data sources. Increasingly, museum specimens are becoming mobilized online, providing unparalleled access to physiological, ecological and evolutionary data spanning decades and sometimes centuries. Here, we describe the diversity of collections data archived in museums and provide an overview of the diverse uses and applications of these data as discussed in the accompanying collection of papers within this theme issue. As these unparalleled resources are under threat owing to budget cuts and other institutional pressures, we aim to shed light on the unique discoveries that are possible in museums and, thus, the singular value of natural history collections in a period of rapid change.This article is part of the theme issue 'Biological collections for understanding biodiversity in the Anthropocene'.

Observation of inverse Compton emission from a long γ-ray burst

Abstract: Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission1,2. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands1-6. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock7-9. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C10,11. Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10-6 to 1012 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.

Electron reconstruction and identification in the ATLAS experiment using the 2015 and 2016 LHC proton-proton collision data at s=13 TeV

Abstract: Algorithms used for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC) are presented in this paper; these algorithms a ...

A nanostructure voltammetric platform amplified with ionic liquid for determination of tert-butylhydroxyanisole in the presence kojic acid

Abstract: The electrochemical behavior of tert-butylhydroxyanisole antioxidant was investigated at a surface of carbon paste electrode amplified with MgO nanoparticle and n-methyl-3-butylimidazolium bromide as conductive binder (CPE/MgO-NPs-/M3BIBr). The oxidation voltammogram of tert-butylhydroxyanisole was shown an irreversible signal with a diffusion controlled system. Using pH investigation data, we suggested a possible mechanism for electro-oxidation of tert-butylhydroxyanisole. The oxidation current varied linearly with tert-butylhydroxyanisole concentration in the range 0.1–700 µM with detection limit 0.04 µM. The CPE/MgO-NPs-/M3BIBr was resolved overlapping signal of tert-butylhydroxyanisole and kojic acid as two important antioxidants for the first time. The CPE/MgO-NPs-/M3BIBr was applied to the analysis of tert-butylhydroxyanisole in food samples such as edible oil and chilli sauce.