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Two Models for the Orbital Modulation of Gamma Rays in Cyg X-3
Get PDFJournal Article, Centre for Space Research, North-West University, PotchefstroomWe model the currently available γ-ray data on Cyg X-3 from the Fermi Large Area Telescope. Thanks to Cyg X-3’s very strong γ-ray activity during 2018–2021, the data quality has significantly improved. We study the strong orbital modulation of the γ-rays observed at high γ-ray fluxes. The modulation, as found earlier, is well modeled by anisotropic Compton scattering of the donor blackbody emission by relativistic electrons in a jet strongly misaligned with respect to the orbital axis. We confirm that this model fits well both the average γ-ray modulation light curve and the spectrum. However, we find that if the jet were aligned with the spin axis of a rotating black hole, it would undergo geodetic precession with a period of ∼50 yr. However, its presence is ruled out by both the γ-ray and radio data. Therefore, we consider an alternative model in which the average jet direction is aligned, but it is bent outside the orbit owing to the thrust of the donor stellar wind, and thus precesses at the orbital period. The γ-ray modulation then appears as a result of the variable Doppler boosting of synchrotron self-Compton jet emission. This model also fits the data well. However, the fitted bending angle is much larger than the theoretical one based on the binary and wind parameters as currently known. Thus, both models disagree with important aspects of our current theoretical understanding of the system. We discuss possible ways to find the correct model
Molecular characterization of multi-drug resistant Acinetobacter baumannii isolated from wastewater effluents
No full textMaster of Science in Biology, North-West University, MafikengBackground: Multidrug-resistant Acinetobacter baumannii strains have increasingly resulted in nosocomial outbreaks worldwide, leaving limited options for treatment. A. baumannii strains are equipped with a multitude of antibiotic resistance mechanisms rendering them resistant to most of the currently available antibiotics. Several Acinetobacter species live in different ecosystems such as soil, freshwater, wastewater and solid wastes. In this study, we assessed the occurrence of A. baumannii which is the major clinically important species of the genus Acinetobacter, from local wastewater outlets (Mahikeng wastewater treatment plant) in the North West Province, South Africa. The study profiled the antibiogram, antibiotic resistance and virulent genes of A. baumannii. Presumptive Acinetobacter species were subjected to molecular identification by using Acinetobacter genus-specific primers targeting the SP4 gene. The confirmed Acinetobacter species were further delineated into A. baumannii using species-specific primer sets (OXA-51 & ITS). Similarly, virulence genes, namely, OmpA and CsuE were determined using molecular techniques. The presence of blaOXA genes encoding OXA-type carbapenemases (OXA-23 & OXA-58) was also assessed using a polymerase chain reaction.
Results: A total of 33 samples were collected from wastewater effluents and analyzed presumptively by cultural methods for the presence of Acinetobacter species using MacCockey agar. Twenty (20) presumptive Acinetobacter isolates were recovered phenotypically of which 11 were confirmed positive for the Acinetobacter species. Of the 11 Acinetobacter isolates 8 (72,72%) were confirmed to be A. baumannii using species-specific primer sets (OXA-51 & ITS). The presence of these clinically important Acinetobacter species in wastewater outlets suggests that they can thrive in aquatic environments. Isolates showed high resistance to antimicrobial agents such as ampicillin; (87,5%), ticarcillin (87,5%) and tetracycline (50%) which are most frequently used to treat infections caused by Acinetobacter species. All the isolates were susceptible to cefotaxime, ceftriaxone, gentamicin and piperacillin/tazobactam. MAR indexes for different isolates revealed 7 (87.50%) with MAR index greater than 0.2 and 1 (12.50%) less than 0.2. Both carbapenem-resistant genes (OXA-23 & OXA-58) were detected in only two (25%) isolates. The detection of virulence genes (ITS, OmpA and csuE) was performed and results obtained were 100%, 87,5% and 50% for each gene, respectively
Scaffolding African Language Intellectualisation: The Case of Sesotho and Setswana at a South African University
Get PDFJournal Article, Faculty of Humanities, North--West University, Vanderbijlpark campusThe call for the intellectualisation of African languages has become a topical agenda towards their use as languages of teaching and learning in institutions of higher learning in Africa. In their enunciation of language policies, South African universities are guided by the Department of Higher Education and Training (DHET)’s Language Policy Framework for Public Higher Education Institutions (LPFPHEI). The thrust of this paper is to interrogate how the language policy of one university in South Africa enables the intellectualisation of African languages. The study deploys Ruiz’s notion of language as a resource to examine the potential embedded within the university’s language policy to foster the intellectualisation of Sesotho and Setswana for use as LoTLs in a variety of disciplines. The university is one of the institutions of higher learning with the most recently revised language policy approved in 2022, hence its selection as the case study. The paper concludes that an enabling language policy that speaks to the linguistic realities, coupled with a variety of support structures within the university and also spelling out the implementation plan is what will result in the fruitful re-intellectualisation of African language
Metabolomic profiling and 16 S rRNA metabarcoding of endophytes of two Aloe species revealed diverse metabolites
Get PDFJournal Article, Faculty of Natural and Agricultural Science, North--West UniversityAloe species are often used interchangeably for medicinal and cosmeceutical applications, presenting a challenge to the biological efficacy consistency of some herbal preparations. Sustainable production of high-quality commonly used medicinal plants remains a limitation for commercialisation. Thus, this study investigated the potential for plant substitution by examining bacterial endophytes capable of producing similar host plant secondary metabolites. The metabolite profiles and endophytic bacterial communities of endangered Aloe lettyae were compared with those of Aloe longibracteata using nuclear magnetic resonance spectroscopy and 16 S rRNA gene sequencing. Only 15 metabolites were significantly different between A. lettyae and A. longibracteata based on metabolite concentrations. However, both plants’ functionality and potential application remain comparable. Phytohormones, including indole-3-acetate and 5-hydroxyindole-3-acetate, were more concentrated in A. lettyae than A. longibracteata. Metabolites such as tyrosine, allantoin, and myo-inositol, with human health benefits, were annotated in both species. Aloe lettyae harboured a phylogenetically diverse bacteria community compared to A. longibracteata, with a higher richness of bacterial species, indicating a likelihood of diverse metabolic capabilities among the bacteria. Dominant endophytes, including Bacillus, Comamonas, and Pseudomonas, possess enzymes contributing to various metabolic pathways. The enzymes have the potential to impact the synthesis, or breakdown of plant metabolites, consequently influencing the overall metabolic composition of the host plant. Therefore, this study supports the interchangeability of A. lettyae and A. longibracteata due to their ability to produce similar metabolites, and although the Aloe species exhibit phylogenetically diverse endophytic communities, the feasibility of utilizing their endophytes as producers of secondary metabolites remains viabl
Narratives as a way of conceptualising the field of comparative education
No full textNorth-West University, Potchefstroom, South Africa; Department of Education.Based on the authors’ wide reading in the field, this article suggests the notion of the narrative as a fitting and meaningful way of conceptualising and mapping the field of comparative education. Four prominent narratives can be identified in not only the field of comparative education (and the scholarly discourse on education) but also the public discourse on education. These are the narratives of the capability theory, neoliberal economics, the creed of human rights, and the call for social justice. These narratives are contrasted, and guidelines are offered for further research on reconstructing and reflecting on the current state of comparative education and its future trajectory
Impact of subtype C‑specific amino acid variants on HIV‑1 Tat‑TAR interaction: insights from molecular modelling and dynamics
Get PDFJournal Article, Faculty of Natural and Agricultural Science, North--West UniversityBackground HIV-1 produces Tat, a crucial protein for transcription, viral replication, and CNS neurotoxicity. Tat interacts with TAR, enhancing HIV reverse transcription. Subtype C Tat variants (C31S, R57S, Q63E) are associated with reduced transactivation and neurovirulence compared to subtype B. However, their precise impact on Tat-TAR binding is unclear. This study investigates how these substitutions affect Tat-TAR interaction. Methods We utilized molecular modelling techniques, including MODELLER, to produce precise three-dimensional structures of HIV-1 Tat protein variants. We utilized Tat subtype B as the reference or wild type, and generated Tat variants to mirror those amino acid variants found in Tat subtype C. Subtype C-specific amino acid substitutions were selected based on their role in the neuropathogenesis of HIV-1. Subsequently, we conducted molecular docking of each Tat protein variant to TAR using HDOCK, followed by molecular dynamic simulations. Results Molecular docking results indicated that Tat subtype B (TatWt) showed the highest affinity for the TAR element (-262.07), followed by TatC31S (-261.61), TatQ63E (-256.43), TatC31S/R57S/Q63E (-238.92), and TatR57S (-222.24). However, binding free energy analysis showed higher affinities for single variants TatQ63E (-349.2 ± 10.4 kcal/ mol) and TatR57S (-290.0 ± 9.6 kcal/mol) compared to TatWt (-247.9 ± 27.7 kcal/mol), while TatC31S and TatC31S/ R57SQ/63E showed lower values. Interactions over the protein trajectory were also higher for TatQ63E and TatR57S compared to TatWt, TatC31S, and TatC31S/R57SQ/63E, suggesting that modifying amino acids within the Arginine/ Glutamine-rich region notably affects TAR interaction. Single amino acid mutations TatR57S and TatQ63E had a significant impact, while TatC31S had minimal effect. Introducing single amino acid variants from TatWt to a more representative Tat subtype C (TatC31S/R57SQ/63E) resulted in lower predicted binding affinity, consistent with previous findings. Conclusions These identified amino acid positions likely contribute significantly to Tat-TAR interaction and the differential pathogenesis and neuropathogenesis observed between subtype B and subtype C. Additional experimental investigations should prioritize exploring the influence of these amino acid signatures on TAR binding to gain a comprehensive understanding of their impact on viral transactivation, potentially identifying them as therapeutic target
The variety of extreme blazars in the AstroSat view
Get PDFJournal Article, Centre for Space Research, North-West University, Potchefstroom CampusContext. Among the blazar class, extreme blazars have exceptionally hard intrinsic X-ray/TeV spectra, and extreme peak energies in their spectral energy distribution (SED). Observational evidence suggests that the non-thermal emission from extreme blazars is typically non-variable. All these unique features present a challenging case for blazar emission models, especially regarding those sources with hard TeV spectra.
Aims. We aim to explore the X-ray and GeV observational features of a variety of extreme blazars, including extreme-TeV, extreme-synchrotron (extreme-Syn), and regular high-frequency-peaked BL Lac objects (HBLs). Furthermore, we aim to test the applicability of various blazar emission models that could explain the very hard TeV spectra.
Methods. We conducted a detailed spectral analysis of X-ray data collected with AstroSat and Swift-XRT, along with quasi-simultaneous γ-ray data from Fermi-LAT, for five sources: 1ES 0120+340, RGB J0710+591, 1ES 1101−232, 1ES 1741+196, and 1ES 2322−409. We took three approaches to modelling the SEDs: (1) a steady-state one-zone synchrotron-self-Compton (SSC) code, (2) another leptonic scenario of co-accelerated electrons and protons on multiple shocks applied to the extreme-TeV sources only (e–p co-acceleration scenario), and (3) a one-zone hadro-leptonic (ONEHALE) code. The latter code is used twice to explain the γ-ray emission process: proton synchrotron and synchrotron emission of secondary pairs.
Results. Our X-ray analysis provides well-constrained estimates of the synchrotron peak energies for both 1ES0120+340 and 1ES1741+196. These findings categorise these latter objects as extreme-synchrotron sources, as they consistently exhibit peak energies above 1 keV in different flux states. The multi-epoch X-ray and GeV data reveal spectral and flux variabilities in RGB J0710+591 and 1ES 1741+196, even on timescales of days to weeks. As anticipated, the one-zone SSC model adequately reproduces the SEDs of regular HBLs but encounters difficulties in explaining the hardest TeV emission. Hadronic models offer a reasonable fit to the hard TeV spectrum, though with the trade-off of requiring extreme jet powers. On the other hand, the lepto-hadronic scenario faces additional challenges in fitting the GeV spectra of extreme-TeV sources. Finally, the e–p co-acceleration scenario naturally accounts for the observed hard electron distributions and effectively matches the hardest TeV spectrum of RGB J0710+591 and 1ES 1101−232
Improved prairie dog optimization algorithm by dwarf mongoose optimization algorithm for optimization problems
Get PDFJournal Article, Faculty of Natural and Agricultural Science -- North-West University, Potchefstroom CampusRecently, optimization problems have been revised in many domains, and they need powerful search methods to address them. In this paper, a novel hybrid optimization algorithm is proposed to solve various benchmark functions, which is called IPDOA. The proposed method is based on enhancing the search process of the Prairie Dog Optimization Algorithm (PDOA) by using the primary updating mechanism of the Dwarf Mongoose Optimization Algorithm (DMOA). The main aim of the proposed IPDOA is to avoid the main weaknesses of the original methods; these weaknesses are poor convergence ability, the imbalance between the search process, and premature convergence. Experiments are conducted on 23 standard benchmark functions, and the results are compared with similar methods from the literature. The results are recorded in terms of the best, worst, and average fitness function, showing that the proposed method is more vital to deal with various problems than other methods.Industry, Innovation and Infrastructur
Investigation of Novel Isatinylhydantoin Derivatives as Potential Anti-Kinetoplastid Agents
Get PDFJournal Article.Centre of Excellence for Pharmaceutical Sciences (Pharmacen), Faculty of Health Sciences, North-West University, PotchefstroomNeglected tropical diseases are a group of infectious diseases with a high endemicity in developing countries of Africa, Asia, and the Americas. Treatment for these diseases depends solely on chemotherapy, which is associated with severe side effects, toxicity, and the development of parasitic resistance. This highlights a critical need to develop new and effective drugs to curb these diseases. As a result, a series of novel isatinylhydantoin derivatives were synthesized and evaluated for in vitro antikinetoplastid activity against seven human- or animal-infective Trypanosoma and two human-infective Leishmania species. The synthesized derivatives were tested for potential cytotoxicity against human, animal, and parasite host-related cell lines. Theisatinylhydantoin hybrid 4b bearing 5-chloroisatin and pbromobenzyl moieties, showed strong trypanocidal activity against blood-stage T. congolense parasites; however, the promising in vitro trypanocidal potency of 4b could not be translated to in vivo treatment efficacy in a preliminary animal study. Compounds 5, 2b, and 5b, were the most active against amastigotes of L. donovani, showing higher leishmanicidal activity than the reference drug, amphotericin B. These compounds were identified as early antileishmanicidal leads, and future investigations will focus on confirming their antileishmanial potential through in vivo efficacy evaluation as well as their exact mechanism of action
A multivariate dataset on water–energy–food nexus: Multi-actor governance for social justice
Get PDFArticle, Faculty of Law (Law; Justice and Sustainability)--Northwest University, Potchefstroom CampusThe article presents and validates an extensive multivariate dataset that offers insights into water–energy–food (WEF) nexus governance for social justice at the intra-household, household, and community levels. The lack of insights in the WEF nexus debate that take social justice and governance into account is what spurred the data collection. The initial process involved scoping the originally selected investigated sites and their suitability. Once the research areas were identified, the data were collected from 1184 households in the Matatiele, Magareng, and Greater Taung Local Municipalities in South Africa, using a semi-structured questionnaire and KoboCollect software. The freely available software was installed on Android Tablets which were used by the enumerators. The questionnaires were initially piloted in Matatiele Local Municipality, testing for internal validity and skip patterns, as well as time to complete the questionnaire. The reliability of the Likert responses from the questionnaire was evaluated using Cronbachʼs alpha. The questionnaire was then refined for data collection and utilized a total of twenty-two (22) locally trained enumerators who were employed at the investigated sites. These enumerators were trained in administering the questionnaire and the use of the KoboCollect software used in data collection. The enumerators also received training on how to conduct the survey ethically, including informed permission, confidentiality, and the option to withdraw from the interview. The design of the data collection process was a cross-sectional survey that was conducted between 6 June and 4 August 2022, using purposive sampling. At the end of each data collection day, the enumerators uploaded their collected data into the KoboTool cloud, which allowed the lead in the survey to assess the data and effect any correctional measures on the questionnaire if the need arose. The enumerators also used a WhatsApp chat group to communicate real time opportunities and challenges in the questionnaire, which allowed the lead in the survey to constantly update the questionnaire. The multivariate questionnaire was divided into sections of socioeconomic and demographic characteristics, community level governance, decision-making, food, energy, and water security, social justice, legal knowledge, and rights to utilize these resources. The dataset will be of significance to multi-disciplinary researchers focusing on WEF security, governance, and social justice in Southern Africa. Furthermore, environmental and sustainability practitioners can find valuable insights from the provided data. The employed methodology is replicable and adaptable, enabling real-time monitoring of social justice and governance in the context of food, energy, and water security. The real time monitoring of governance and social justice in water, energy and food allows for the possibility of continual data collection and updating,and if a longitudinal design is adopted, it can be used for impact inquiry of any interventions or policies