Research Articles (University of Pretoria)

Permanent URI for this collectionhttp://hdl.handle.net/2263/121

This collection offers open access to the full text of research articles published by staff, students and affiliates of the University of Pretoria. These items are identical in content to their published counterparts. It is linked to the Research Information System and complements the Annual Research Report.

Access to the full text of UP theses and dissertations is available at UP Electronic Theses and Dissertations.

Information and guidelines for authors/ submitters available at http://www.ais.up.ac.za/openup/index.htm.

For inquiries regarding this collection or items in the collection, please contact : Hendriette Jansen van Vuuren
Tel.: +27 12 420 4712

Browse

Now showing 1 - 20 of 41265

Temporal changes in the bacterial microbiome of the salivary gland and midgut tissues of Rhipicephalus sanguineus (s.l.) ticks in South Africa
(Nature Research, 2025-05) Ackermann, Rebecca; Gall, Cory A.; Brayton, Kelly A.; Collins, Nicola E.; Van Wyk, Ilana; Wentzel, Jeanette; Kolo, Agatha O,; Oosthuizen, Marinda C.
Tick-borne bacterial pathogens from animals play a significant role in the (re)emergence of human diseases. Rhipicephalus sanguineus sensu lato, a globally prevalent tick, predominantly parasitises domestic dogs but can also feed on humans. We characterised temporal changes in the bacterial microbiome of the midgut and salivary gland tissues of R. sanguineus s.l. ticks and analysed their potential as reservoirs for pathogenic bacteria. A 16 S microbiome and amplicon sequence variant (ASV) approach was used to study the bacteria present in the tissues of R. sanguineus s.l. ticks collected from dogs in Hluvukani, a village in a rural community in Bushbuckridge, Mpumalanga, South Africa, in 2016, 2017 and 2019. Post processing, we obtained 43,161 total sequence reads which were clustered into ASVs by sample year. The final ASVs dataset consisted of seven genera: Coxiella, Anaplasma, Escherichia/Shigella, Ehrlichia, Borrelia, Rickettsia and Wolbachia. No differences in the microbiome profiles of the MG and SG tissues were noted. Coxiella endosymbionts dominated the microbiome in all years. Anaplasma was first detected in 2017, and an increase in Anaplasma levels was detected in 2019, when compared to 2017. All other genera were present at low levels. With the exclusion of Wolbachia, the other detected genera could have pathogenic potential, highlighting the role that R. sanguineus s.l. might play as a reservoir of pathogens.
The potential of the South African plant Tulbaghia Violacea Harv for the treatment of triple negative breast cancer
(Nature Research, 2025-02) Alaouna, Mohammed; Molefi, Thulo; Khanyile, Richard; Chauke-Malinga, Nkhensani; Chatziioannou, Aristotelis; Luvhengo, Thifhelimbilu Emmanuel; Raletsena, Maropeng; Penny, Clement; Hull, Rodney; Dlamini, Zodwa; rodney.hull@up.ac.za
Triple-negative breast cancer (TNBC) is difficult to treat and has a low five-year survival rate. In South Africa, a large percentage of the population still relies on traditional plant-based medicine. To establish the utility of both methanol and water-soluble extracts from the leaves of Tulbaghia violacea, cytotoxicity assays were carried out to establish the IC50 values against a TNBC cell line. Cell cycle and apoptosis assays were carried out using the extracts. To identify the molecular compounds, present in water-soluble leaf extracts, NMR spectroscopy was performed. Compounds of interest were then used in computational docking studies with the anti-apoptotic protein COX-2. The IC50 values for the water- and methanol-soluble extracts were determined to be 400 and 820 µg/mL, respectively. The water-soluble extract induced apoptosis in the TNBC cell line to a greater extent than in the normal cell line. RNAseq indicated that there was an increase in the transcription of pro-apoptotic genes in the TNBC cell line. The crude extract also caused these cells to stall in the S phase. Of the 61 compounds identified in this extract, five demonstrated a high binding affinity for COX-2. Based on these findings, the compounds within the extract show significant potential for further investigation as candidates for the development of cancer therapeutics, particularly for TNBC.
Presidential approval ratings and stock market performance in Latin America
(Wiley, 2025-09) Jaichand, Yuvana; Van Eyden, Renee; Gupta, Rangan; renee.vaneyden@up.ac.za
This paper examines the time-varying causality between presidential approval (PAR) and stock market performance, measured by stock returns and realised volatility, focussing on four prominent Latin American countries: Brazil, Chile, Colombia, and Mexico, from 1990M01 to 2016M05. We use a time-varying causality test, which is robust to structural breaks, to uncover a bidirectional causal relationship between PAR and stock market performance. Our results remain robust when controlling for macroeconomic conditions, PAR in other Latin American countries and US PAR. Our analysis is extended to include the bond market, identifying a significant bivariate causal relationship between PAR and bond market performance.
How do religious icons read-and-write?
(University of Stellenbosch, Department of Old and New Testament, 2025) Lombaard, Christoffel Johannes Stephanus; Joubert, Lisel
This contribution starts off with a broad understanding of icons and their communication, and the implications this has for religious discourse today. The focus then moves to icons within the Christian Orthodox traditions to indicate aspects of the interaction of text, image and presence. The final part returns to the implication of "seeing" icons for reading texts and hence for the possibility of again in our age encountering God in texts. Analysing the communicative dynamics of icons from the Reformed strand of Protestant Christianity, a tradition which exhibits a stronger inclination to biblical hermeneutics than to icons as operative faith impulses, combines these two interpretative traditions as a service to the unfolding post-secular intellectual and societal climate unfolding internationally.
Fediša Modikologo : breaking the intergenerational cycle of violence against women and children. Theoretical framework and protocol for a prospective cohort study
(F1000 Research, 2025-08) Jewkes, Rachel; Ramsoomar, Leane; Nothling, Jani; Willan, Samantha; Mbowane, Venice; Chirwa, Esnat; Mhlongo, Shibe; Phakoe, Maureen; Pass, Desiree; Zembe, Amanda; Sibiya, Louis; Seocharan, Ishen; Paile, Charntel; Washington, Laura; Woollett, Nataly; Dekel, Bianca; Jama-Shai, Nwabisa; Machisa, Mercilene; Mahlangu, Pinky; Seepamore, Boitumelo; Christofides, Nicola; Glass, Tracy; Govindasamy, Darshini; Carries, Stanley; Ketelo, Asiphe; Abrahams, Naeemah
In South Africa, after two decades of national femicide surveillance, we know comparatively little about what places women who experience intimate partner violence (IPV) at risk of intimate partner femicide. Further we have not mapped the multi-generational health, social and economic impact of severe IPV on women subjected to it, and their children, nor the consequences of help-seeking, nor described what helps, STET recovery trajectories. This study aims to deepen understanding of risk factors for femicide and the health, social and economic impacts of severe IPV on women and their families, including understanding risk and resilience to intergenerational cycling of violence. It further aims to describe how statutory and community measures operate to enable recovery and safety. Following pilot research, we developed a prospective questionnaire-based cohort study with three components, and plan for nested qualitative research. The primary cohort will enrol 12,000 women experiencing severe IPV, recruited using non-probabilistic methods (mostly referral from services and community members, and chain-recruitment). Following a baseline interview, participants will complete annual on-line surveys to track key outcomes for five years. The main questionnaire will measure exposure to range of different forms of IPV in the past year, lifetime trauma exposure history, childhood background, health, social and economic circumstances and help-seeking practices. A sub-cohort of the women (a 20% sub-sample), will be followed more intensively over 3 years. Among these, the children aged 6 years and over, of consenting mothers, will also be followed for three years. Deaths in the cohorts will be tracked through the National Population Register through participants’ national identity numbers. Mixed-methods verbal autopsies will be conducted with friends or family members of deceased participants. Results will guide femicide prevention nationally, and will build understanding of what is needed to prevent intergenerational cycling of violence and enable recovery of exposed women and children. PLAIN LANGUAGE SUMMARY ‘Fediša Modikologo: breaking the intergenerational cycle of violence against women and children. Theoretical framework and protocol for a prospective cohort study’ describes the plans for research that will be conducted by the South African Medical Research Council and partners in four diverse sites in South Africa with women who have experienced severe intimate partner violence and their children. This study aims to help us to understand what places women at risk of the most severe impacts of intimate partner violence, including loss of life, and to describe the myriad of ways in which their experiences, and attempts to protect themselves and their families, impact their health, social circumstances and finances. It also aims to help us understand how children are impacted by growing up in a home with violence and what may influence whether they go on to use violence themselves in their lives. We are recruiting 12,000 women who have recently experienced severe intimate partner violence into the study and we will interview them with a questionnaire, and provide counselling, over 5 years. We will as k a sub-group of these women to come for more intensive interviews, and if they agree, to invite their children, aged 6 years and over, as well. We will identify and investigate any deaths. The results will guide femicide prevention nationally, and will build understanding of what is needed to prevent the worst outcomes and enable recovery among exposed women and children.
The VP7 protein of the African horse sickness virus core particle facilitates binding to Culicoides sonorensis cells in an RGD-independent manner
(Elsevier, 2025-11) Buyens, Ariel Renée Monique; Van Staden, Vida; Theron, Jacques; jacques.theron@up.ac.za
African horse sickness, caused by African horse sickness virus (AHSV) that is transmitted by midges of the Culicoides genus, leads to rapid mortality among horses. Proteases in the saliva of Culicoides midges cleave the VP2 outer capsid protein, resulting in infectious sub-virus particles that have increased infectivity for the Culicoides vector insect and Culicoides-derived cells (KC cells). The AHSV VP7 protein has an arginine-glycine-aspartate (RGD) motif, but the functional relevance of this protein and motif in facilitating binding to insect cells is unknown. To investigate, core-like particles (CLPs) were produced using the baculovirus expression system through the co-expression of VP3 and sVP7, which is a soluble version of the AHSV-4 VP7 protein. Insect cell binding assays indicated that the CLPs bind to KC cells, suggesting a role for VP7 in this interaction. Subsequently, recombinant baculoviruses expressing mutant sVP7 proteins were synthesized, in which the RGD motif was either deleted or mutated. All RGD-mutated sVP7 proteins, except for the deletion of the RGD motif, formed trimers and, when co-expressed with VP3, assembled into CLPs that retained the ability to bind to insect cells. These findings indicate that VP7 facilitates the binding of CLPs to insect cells through an RGD-independent mechanism. HIGHLIGHTS • VP7 is the outermost protein of AHSV core particles and possesses an RGD motif. • AHSV CLPs, formed by VP3 and VP7 proteins, bind to Culicoides-derived insect cells. • RGD-mutant CLPs retain the ability to bind to insect cells. • VP7 acts as an attachment protein for insect cells, independent of the RGD motif. • The findings provide new insights into early AHSV–insect vector interactions.
‘Please Mister President, have mercy…’ : the Church’s calling to reach out to refugees and migrants
(AOSIS, 2025-08) Meiring, Piet (Pieter Gerhard Jacobus), 1941-
President Donald Trump’s executive order to deport illegal migrants and refugees in the United States of America once again brought the plight of millions of migrants and asylum seekers worldwide to the attention of church leaders locally as well as within the ecumenical community. Revisiting the Old and New Testaments’ message on the calling of God’s people to reach out to the ‘other’ in the community, the article points to six perspectives on the church’s calling to minister the migrants and refugees. The perspectives are: (1) all Christians are foreigners and sojourners in the world; (2) following in the footsteps of Jesus; (3) standing with the Lord against injustice; (4) welcoming migrants and refugees into the church; (5) praying for the harassed and helpless; (6) joining in journeys of hope. The circumstances of refugees and migrants, as well as the churches’ calling to minister to them, are high on the agenda. In local churches, in the ecumenical community as well as institutions of theological training, much attention is given to the subject. INTRADISCIPLINARY AND/OR INTERDISCIPLINARY IMPLICATIONS : This article offers a number of perspectives to reach out to the marginalised that may serve as guidelines in the fields of missiology, practical theology, ethics, church history and ecumenical studies to focus on the calling of the Church internationally as well as in South Africa. The article also offers a literature study of older and more recent publications on the subject, presenting several relevant perspectives.
Empowering challenges of missional ecclesiology and leadership at the grassroots level
(AOSIS, 2025-06) Knoetze, Johannes Jacobus; johannes.knoetze@up.ac.za
This article examines the work of Nelus Niemandt within both the academy and the church, with a particular focus on his understanding of missionality as shaped by his perspectives on spirituality, ecclesiology and leadership. It also explores key elements of discernment and service leadership. To have a better understanding of service leadership, attention is given to the diak- word-group in the New Testament. While some critiques suggest that Niemandt’s writings on ecclesiology and leadership lack practical application, this article highlights the tangible impact of his work at the grassroots level. Specifically, it considers outcomes within the Dutch Reformed Church, such as the adoption of a missional ecclesiology and the development of new ministerial pathways to equip and empower missional leaders. This article concludes with two examples from the development of the additional ministerial tracks. Two members who did the studies witness of how a missional ecclessiological understanding in the Dutch Reformed Church has made it possible for them to live their calling. It is also clear from these witnesses that in many congregations we still have a long walk in obedience and discernment to become more missional than institutional. INTRADISCIPLINARY AND/OR INTERDISCIPLINARY IMPLICATIONS : The article represents a critical engagement with the model of missional leadership in the field of missiology, focusing on church ministry at the grassroots level.
Unhiding female characters in the parable of the sower : reimagining fields and farms
(AOSIS, 2025-05) Du Toit, Charel D.; Van Eck, Ernest; u11291852@tuks.co.za
This article employs an unhiding reading methodology to explore the presence of women in Luke’s agrarian parables, specifically focussing on the parable of the sower. By engaging with Van Eck’s research on the realistic reading of the parables in their 1st-century socio-economic context and implementing Du Toit’s unhiding reading, the authors argue that women, although not explicitly mentioned, would have been imagined as present, active and important participants in agricultural labour by the original hearers of these parables. Drawing on historical evidence of women’s involvement in textile production, fieldwork and harvest activities, the article challenges traditional androcentric interpretations and highlights the integral role of women in the parable of the sower, and other agrarian parables. INTRADISCIPLINARY AND/OR INTERDISCIPLINARY IMPLICATIONS : An unhiding reading will be suggested at the end of this article, an alternative reading aiming to offer a more comprehensive understanding of the parables, grounded in the lived realities of a 1st-century Mediterranean audience.
‘In step’ with the living God : rhythms and habits for churches faithful to their calling
(AOSIS, 2025-07) Smith, Thomas Jacobus; tom.smith@up.ac.za
This article reflected on the development of a congregational prototype called In pas met die lewende God [‘In step’ with the Living God], that aids congregations in the process of missional transformation. Although this prototype was developed and implemented by a diverse team, the influence of Nelus Niemandt in shifting the denominational culture towards a participation in the missio Dei was significant and was a precursor to the development. My own journey with this process has been deeply shaped by Niemandt’s theological imagination and mentorship, which continue to echo through the practices and movements described here. INTRADISCIPLINARY AND/OR INTERDISCIPLINARY IMPLICATIONS : The article outlined the origin of ‘In step’ and then described the structure of the instrument, with particular attention to its emphasis on cultivating rhythms and practices that embody the missional theology as well as the holding environment for ‘In step’. Finally, the article reflected on lessons learned in partnering with local congregations as they engage with the habits and rhythms proposed in the In step process. These lessons can be used for further research for missional ecclesiology and transformation.
Effects of phosphorus on the corrosion characteristics of weathering steel in industrial environments
(Springer, 2025) Gan, Le; Lei, Yicong; Jiang, Yu; Siyasiya, Charles Witness; Tang, Zhenghua
Please read abstract in the article.
Quantile gravity : economic integration agreements, least traded goods, and less developed economies
(Wiley, 2025-09) Bergstrand, Jeffrey H.; Clance, Matthew W.; matthew.clance@up.ac.za
Gravity-equation estimates of the elasticity of trade with respect to bilateral trade costs – or of coefficient estimates of binary variables for the presence or absence of economic integration agreements (EIAs) – are central to determining quantitatively economic welfare impacts of trade-policy liberalizations. Despite decades of study, trade economists have largely focused on conditional mean estimates of a (constant) trade elasticity or of an EIA dummy variable's (common) effect in a “gravity-equation” specification. In this paper, we provide a novel panel-data quantile regression approach to estimating EIAs' partial effects across (conditional) quantiles that avoids Jensen's Inequality, avoids the incidental parameters problem associated with three-way fixed effects, and allows zeros. To motivate the potential economic usefulness of our approach, we examine two distinct “cases.” First, using quantile regressions across a broad swath of country-pairs and EIAs at the disaggregated trade-flow level, we provide systematic evidence that supports the Arkolakis (2010) proposition; trade-flow growth effects of any type of EIA are larger for goods with lower initial sales. Second, we show that the partial effects of EIAs on trade flows are considerably larger for developing countries' exporters across quantiles.
Teaching, research, and everything in between : an autoethnographic account of academic identity
(Wiley, 2025-12) Du Toit, Elda; elda.dutoit@up.ac.za
This analytic autoethnography offers a critical and personal reflection on two decades (2005–2025) of academic life at a South African university. Framed within South Africa's shifting higher education landscape, the study explores academic identity formation through eight thematic lenses: from early experiences as an unprepared lecturer to the challenges and rewards of research, postgraduate supervision, pedagogic innovation, academic citizenship, and institutional service. Despite the increasing demand for excellence across teaching, research and service, the narrative reveals a persistent lack of formal preparation and mentoring for new academics, highlighting a systemic oversight in academic development. However, alongside these structural challenges, the account affirms the deeply fulfilling nature of academic work when driven by curiosity, care and purpose. Alternating between cycles of self-doubt and confidence, fatigue and renewal, the role of the lecturer-researcher emerges as both intellectually rigorous and emotionally resonant. By drawing on the author's lived experience, supported by theoretical frameworks on professional development, emotional labour, and transformative learning, the article contributes to a growing body of scholarship that rehumanises academic life. It calls for greater institutional recognition of academic work's emotional and relational dimensions while affirming the value of narrative inquiry in understanding and sustaining academic passion.
Insights into the optoelectronic and thermoelectric properties of lead-free Rb2NaIrF6 double perovskite compound : a first-principles study
(Elsevier, 2025-08) Mbilo, Mwende; Musembi, Robinson; Kachira, John Peter; Onsate, Wisley Nyangau; Keheze, Fanuel Mugwanga; Mapasha, Refilwe Edwin
Please read abstract in the article.
Optimal design of risk-based average charts for autocorrelated measurements
(Elsevier, 2025-12) Saghir, Aamir; Khan, Zahid Younas; Malela-Majika, Jean Claude; Kosztyán, Zsolt Tibor
Please read abstract in the article. HIGHLIGHTS • Developed two Risk-Based (RB) average charts for monitoring autoregressive processes • Design improves RB chart cost-efficiency under autocorrelated conditions • TCharts validated via real-world data and autocorrelated simulations • Sensitivity analysis conducted to support practical implementation
Kinetic analysis of anaerobic coal desulfurization : impact of particle size on sulfur content, ash and calorific value
(Elsevier, 2025-09) Makgato, Seshibe; Pappula, Bridjesh; Oyewo, Opeyemi; Yusuf, Tunde Lewis; Kumar, Naveen; Onwudiwe, Damian; Makgwane, Peter
Kinetic parameters are essential for improving desulfurization efficiency by providing insight into coal properties, reaction rates linked to ash, sulfur content, and calorific value, and for guiding process optimization. The current study develops a kinetic model and evaluates the desulfurization behavior of a bacterial consortium under anaerobic conditions for steam coal. Four particle size fractions (+4.60 mm, -4.60 + 2.30 mm, -2.30 + 1.00 mm, and -0.85 mm) were analyzed. Kinetic parameters were estimated and validated using the AQUASIM software. Over 20 days, total sulfur in the finest coal fraction (-0.85 mm) decreased from 1.45 wt.% to 0.50 wt.% corresponding to a 65.5% desulfurization efficiency under temperature condition of 23 ± 3 °C. Upon increasing the temperature to 30 ± 2 °C, sulfur removal was further improved, with the total sulfur content decreasing to 0.40 wt.%, yielding an overall removal efficiency of 72.4%. Ash in this fraction dropped from 34.2 wt.% to 23.2 wt.%, indicating a 32.2 % reduction. The calorific value improved accordingly, enhancing coal quality. Kinetic analysis showed that reaction rates increased with decreasing particle size, with the -0.85 mm fraction exhibiting the highest reaction rate constant (kmc = 17.474 h⁻¹), while the +4.60 mm fraction recorded the lowest (kmc = 11.105 h⁻¹). Sulfur content and ash removals followed first-order kinetics, confirming that reaction rates were concentration-dependent, while changes in calorific value followed second-order kinetics (R² > 97 %), suggesting more complex dependencies. These findings highlight the critical role of particle size in anaerobic biodesulfurization efficiency and provide a reliable kinetic framework for optimizing microbial coal treatment. HIGHLIGHTS • Particle size significantly influences desulfurization kinetics. • Sulfur and ash reduction followed first-order kinetics, whereas calorific value enhancement followed second-order kinetics. • Reaction Rate Constants Correlate with Particle Size. • Kinetic parameters (kmc and Kc) were modelled using Monod-type equation. • Desulfurization treatment improved coal quality.
Artificial intelligence-assisted modelling of heavy metal adsorption using cellulose-based and bio-waste adsorbents : a focus on ANN and ANFIS architectures
(Elsevier, 2025-12) Kumari, Binu; Seedat, Naadhira; Moothi, Kapil; Roopchund, Rishen
This review explores the application of artificial intelligence (AI) models, specifically artificial neural networks (ANN) and adaptive neuro-fuzzy inference systems (ANFIS), in predicting heavy metal adsorption performance using bio-based adsorbents. Focus is placed on sustainable materials such as cellulose nanocrystals (CNCs), agricultural waste-derived biochar, and microbial biomass. The review compiles more than 60 studies over the past decade, analysing model structures, input-output variables, training algorithms, and validation strategies. Performance metrics reveal that most ANN models achieve R² > 0.98, with NARX-ANN reaching as high as 0.9998 in time-resolved batch adsorption simulations. ANFIS models offer added interpretability through fuzzy rule extraction, though their adoption remains limited. Optimization techniques such as particle swarm optimization (PSO) and genetic algorithms (GA) improved RMSE by 5–15%.Comparative evaluation shows variability in model generalization depending on input complexity and adsorbent type. Despite promising results, the review identifies gaps in dataset standardization, model validation, and real-world applicability under multicomponent or noisy conditions. The novelty of this review lies in its cross-comparative benchmarking of ANN and ANFIS architectures applied specifically to bio-adsorbents, and its recommendations for engineering-grade AI deployment in environmental remediation systems. Future research should incorporate deep learning, sensor integration, and regulatory-informed optimization to enhance model robustness and scalability in wastewater treatment applications. HIGHLIGHTS • AI techniques such as ANN and ANFIS model heavy metal adsorption with high accuracy. • Bio-based adsorbents (e.g., CNC, biomass) are central to eco-friendly water treatment. • NARX-ANN achieves R² = 0.9998 in modeling batch adsorption kinetics. • ANFIS improves interpretability using fuzzy rule-based logic. • Key gaps include cross-validation, regulatory constraints, and dataset diversity.
Adsorption of tetracycline using silica nanoparticles : a comparative study of sodium silicate-derived and fly ash-derived silica nanoparticles
(Elsevier, 2025-09) Houghton, Eric Emmanuel; Yapi, Litha; Tichapondwa, Shepherd Masimba; shepherd.tichapondwa@up.ac.za
Fly ash (FA), a fine particulate residue produced from the combustion of coal in thermal power plants, is generated in substantial quantities and presents significant challenges related to its environmental management and disposal. Repurposing FA can mitigate waste accumulation while contributing to sustainable environmental solutions. One promising approach is utilising FA as an adsorbent for removing pollutants from aqueous solutions, particularly emerging contaminants (ECs). In this study, silica nanoparticles were synthesised from FA (FA-SiNPs) and subsequently modified with iron to produce Fe-SiNPs. As a control, silica nanoparticles were synthesised directly from a sodium silicate solution (SSSNPs). The different silica nanoparticles were used as adsorbents to remove tetracycline (TC) from aqueous solutions under identical conditions, to compare their adsorption performance. Under the identical conditions, Fe-SiNPs demonstrated superior performance, achieving 59 % removal of TC, compared to 30 % and 20 % removal by FA-SiNPs and SSSNPs, respectively. The enhanced adsorption capacity of Fe-SiNPs was attributed to the presence of iron, which facilitated TC removal through chelation. Upon optimisation of experimental parameters, a maximum TC removal efficiency using Fe-SiNPs of 86 % was observed at the optimal dosage of 5 g/L within a pH range of 4 to 5. The adsorption kinetics were best described by the Elovich model, whereas the equilibrium data fitted the Langmuir isotherm model with a maximum adsorption capacity of 32.31 mg/g at 30 °C. Thermodynamic analysis revealed that the adsorption process was both spontaneous and exothermic in nature. The adsorption of TC on Fe-SiNPs involved chemisorption, electrostatic attraction and hydrogen bonding. This study highlights the potential of FA-derived silica nanoparticles, particularly Fe-SiNPs, as cost-effective and sustainable adsorbents for TC removal from contaminated water. HIGHLIGHTS • Silica nanoparticles synthesized from fly ash (FA-SiNPs) and sodium silicate (SSSNPs). • FA-SiNPs were modified with iron to produce Fe-SiNPs. • Fe-SiNPs showed the highest tetracycline (TC) removal efficiency. • TC adsorption capacity of Fe-SiNPs reached 32.31 mg/g. • Adsorption on Fe-SiNPs involved electrostatic forces, chemisorption, and H-bonding.
Copper-based electrochemical sensor derived from halogen-substituted Schiff base for selective detection of neurotransmitter dopamine : insight from DFT and docking analysis
(Elsevier, 2025-11) Waziri, Ibrahim; Yusuf, Tunde Lewis; Saha, Chandan; Sookai, Sheldon; Adeyinka, Adedapo Sunday; Muller, Alfred J.
Please read abstract in the article.
Turing patterns across geometries : a proven DSC-ETDRK4 solver from plane to sphere
(Elsevier, 2025-08) Owolabi, Kolade M.; Pindza, Edson; Mare, Eben
This paper presents a unified and robust numerical framework that combines the Discrete Singular Convolution (DSC) method for spatial discretization with the Exponential Time Differencing Runge–Kutta (ETDRK4) scheme for temporal integration to solve reaction–diffusion systems. Specifically, we investigate the formation of Turing patterns – such as spots, stripes, and mixed structures – in classical models including the Gray–Scott, Brusselator, and Barrio–Varea–Aragón–Maini (BVAM) systems. The DSC method, employing the regularized Shannon’s delta kernel, delivers spectral-like accuracy in computing spatial derivatives on both regular and curved geometries. Coupled with the fourth-order ETDRK method, this approach enables efficient and stable time integration over long simulations. Importantly, we rigorously establish the necessary theoretical results – including convergence, stability, and consistency theorems, along with their proofs – for the combined DSC-ETDRK4 method when applied to both planar and curved surfaces. We demonstrate the capability of the proposed method to accurately reproduce and analyze complex spatiotemporal patterns on a variety of surfaces, including the plane, sphere, torus, and bumpy geometries. Numerical experiments confirm the method’s versatility, high accuracy, and computational efficiency, making it a powerful tool for the study of pattern formation in reaction–diffusion systems on diverse geometries.

Browse

Recent Submissions