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Optimal control strategies applied to a mathematical model of meningitis
No full textIn this paper, we deal with the problem of optimal control for the transmission dynamics of the meningococcal meningitis. The problem is a mathematical model described by a system of nonlinear differential equations. Based on this, two controls are formulated and the resulting system is solved as an optimal control problem. Aiming to minimize the number of illnesses or deaths in the population, we used a control representing a vaccination and another one representing a treatment strategy. We prove that these controls are capable of reducing the number of carriers and infectious individuals. Numerical simulations are carried out to show how to perform the two strategies
Solidarity and advocacy at a South African institution: tracing convivial efforts for institutional equity
No full textThis study sought to (a) delink dominant articulations of institutional diversity, equity, and inclusion (DEI), often conceptualized prescriptively from North Atlantic and Eurocentric epistemologies, and (b)describe efforts to engage in solidarity and advocacy from institutional equity spaces at a South African University. To that end, we anchored our research in postcolonial African communication and conducted an ethnographic study that spanned over 12 months (virtually) and 1 month (in site) with the Equity Lab Collective (ELC), an institutional equity entity at a South African University. Our findings revealed that the ELC engaged in advocacy and solidarity in two ways. First, the Collective followed a convivial approach, fostering an environment of openness, incompleteness, and complex care for others. Second, they prioritized co-presencial commitments, building relationships sustained by ancestral knowledge, intersectional awareness, and a commitment to challenging the status quo, without being afraid of tension. We present theoretical expansions and provocation
Enhancing federated learning performance in realistic network conditions using a customised udp protocol and greedy parameter aggregation
No full textEnhancing federated learning performance in realistic network conditions using a customised udp protocol and greedy parameter aggregation Federated Learning (FL) is an emerging paradigm enabling decentralized Machine Learning (ML) model training and updates while prioritizing data privacy. Extensive research in this field has led to the development and enhancement of multiple solutions, including as TensorFlow and PyTorch, to facilitate decentralized ML simulations. However, existing frameworks often have limited capabilities for customizing network configurations and transport protocols to create realistic network environments. Transport layer protocols, situated at Layer 4 of the Open Systems Interconnection (OSI) model, facilitate end-to-end communication between multiple hosts, ensuring data is reliably transmitted across the network. This study leverages the NS-3 network simulator alongside Ten- Sor Flow's deep learning framework to create a realistic network environment tailored for Federated Learning applications. To address the specific efficiency and reliability requirements of these applications, a modified User Datagram Protocol (UDP) was developed. A detailed implementation of the proposed NS-3-based Federated Learning simulator is provided, along with an in-depth explanation of the modified UDP protocol. The simulator was employed to validate the simulation by comparing the performance of standard and modified UDP protocols using the CIFAR-10 (Canadian Institute for Advanced Research) and MNIST (Modified National Institute of Standards and Technology) datasets. Results indicate that the modified UDP model demonstrated robust performance, achieving an accuracy of 78% under poor network conditions, representing only a 2% decline from the 80% accuracy attained in ideal conditions. This performance is primarily attributed to its effective packet retrieval mechanism, whereas the standard UDP protocol model suffered a significant performance drop, achieving only 10% accuracy under poor network conditions, corresponding to a 69% decline from its performance in ideal conditions
A qualitative process evaluation of community-based participatory research and human-centered design in the ‘let’s talk about vaccines’ approach in Mozambique and Malawi
No full textBackground: Ensuring full coverage of childhood vaccination programmes is a persistent challenge in low- and middle-income countries. Urgent action is required to ensure catch up of missed immunisations in children, while simultaneously building trust and demand within communities to sustainably address existing immunization gaps. This paper summarizes the findings of a process evaluation of the ‘Let’s talk about vaccines’ approach by VillageReach in Mozambique and Malawi. The approach used community-based participatory research to identify the barriers to childhood vaccination faced by caregivers and healthcare workers, with human-centered design to codesign potential interventions to improve under two immunization access and uptake. Methods: To evaluate the implementation of the ‘Let’s talk about vaccines’ approach we conducted a qualitative process evaluation guided by the Reach Effectiveness Adoption Implementation Maintenance framework and Consolidated Framework for Implementation Research (CFIR). We completed a total of 76 qualitative interviews and 85 self-administered surveys among caregivers, healthcare workers, health officials and other stakeholders involved in the approach. We transcribed the interviews verbatim and analysed them using thematic analysis and constructs of the RE-AIM and CFIR frameworks. We analysed the survey results in Excel. Results: Key elements of the approach contributing to high fidelity to community-based participatory research principles in both countries, included diverse collaborative study and project teams, involvement of eight caregiver researchers, novel and traditional participatory methods, and extensive mobilization efforts. Success factors for human-centered design in the ideation and prototyping phase included fostering equal participation and empathy, value placed on each participant’s input, mitigating inherent power differences, interactive feedback processes, and extensive iterative processes leading to tangible solutions. Challenges included adjusting to new methods and contextual realities. Factors influencing the potential adoption of the approach included locally developed solutions, participant involvement, collaboration, a major advantage over alternative approaches, ease of use of the co-created interventions, alignment with government objectives, and adaptability for system-wide integration into immunization programming. The potential sustainability of the approach was supported by the involvement of health ministries, health professionals, community representatives, and capacity building of local structures. However, resource and incentive constraints posed as a potential challenge to maintaining long-term motivation and action. Conclusion: The evaluation findings from the ‘Let’s talk about vaccines’ approach highlighted key elements for applying community-based participatory research and human-centered design to collaboratively identify immunization barriers and create tangible solutions to overcome them. By integrating these approaches into routine immunization programs, it can potentially improve vaccination efforts for children under two in low and middle-income countries, leading to lasting change. Supporting policies that prioritize community involvement in research, program design and implementation and sustainable funding enhances immunization strategies, ensuring that they are tailored to local needs
Euclid: a complete einstein ring in NGC 6505
No full textWe report the discovery of a complete Einstein ring around the elliptical galaxy NGC 6505, at z = 0.042. This is the first strong gravitational lens discovered in Euclid and the first in an NGC object from any survey. The combination of the low redshift of the lens galaxy, the brightness of the source galaxy (IE = 18.1 lensed, IE = 21.3 unlensed), and the completeness of the ring make this an exceptionally rare strong lens, unidentified until its observation by Euclid. We present deep imaging data of the lens from the Euclid Visible Camera (VIS) and Near-Infrared Spectrometer and Photometer (NISP) instruments, as well as resolved spectroscopy from the Keck Cosmic Web Imager (KCWI). The Euclid imaging in particular presents one of the highest signal-to-noise ratio optical/near-infrared observations of a strong gravitational lens to date. From the KCWI data we measure a source redshift of z = 0.406. Using data from the Dark Energy Spectroscopic Instrument (DESI) we measure a velocity dispersion for the lens galaxy of σ∗ = 303 ± 15 km s-1. We model the lens galaxy light in detail, revealing angular structure that varies inside the Einstein ring. After subtracting this light model from the VIS observation, we model the strongly lensed images, finding an Einstein radius of 2.″5, corresponding to 2.1 kpc at the redshift of the lens. This is small compared to the effective radius of the galaxy, Reff ∼ 12.″3. Combining the strong lensing measurements with analysis of the spectroscopic data we estimate a dark matter fraction inside the Einstein radius of fDM = (11.1-3.5+5.4)% and a stellar initial mass-function (IMF) mismatch parameter of αIMF = 1.26-0.08+0.05, indicating a heavier-than-Chabrier IMF in the centre of the galaxy
Grappling with Refusal, Self-representation, and Visual Sovereignty at the Knoflokskraal Khoisan Reclaim
No full textIn 2020, a group Khoisan activists began occupying state-owned land near Grabouw, South Africa. Knoflokskraal has since attracted thousands of residents against the backdrop of widespread disappointment with land reform, heritage policies, and various forms of socio-economic marginalisation. The common labelling of Knoflokskraal as a “land invasion” overlooks the unique features of this self-styled “reclaim”, not least the agency that its residents embody in asserting a sense of indigenous visual sovereignty. Drawing on ethnographic fieldwork conducted in 2022 among residents and community representatives, we highlight instances of interlocutors refusing to go along with mainstream research practices and conforming to widely held expectations surrounding Khoisan representation, but instead imprinting their presence on the landscape in unique ways. Knoflokskraal offers a rare glimpse into self-representation through land reform beyond the purview of the government. Read through the lens of refusal, this case study also prompts researchers to grapple with broader issues relating to research practices, indigenous agency, and visual sovereignty
Enhanced lactic acid production from potato peel waste via MnO2 nanoparticle-assisted simultaneous saccharification and fermentation: Process optimization and kinetic studies
No full textThis study focused on optimizing lactic acid production from potato peel waste facilitated by MnO2 nanoparticle (NP). Also, kinetic analysis was conducted, utilizing the growth constant (Kg), logistic function, and modified Gompertz model to evaluate the process dynamics under optimized conditions and the control experiment (without NP). Under optimized conditions (0.034 wt% MnO2 NP, 6.02 pH, 34 ◦C temperature, and 14.90 wt% solid loading), notable increases in biomass and lactic acid concentrations of 2.85 g/L and 41.26 g/L were achieved representing a 1.16 and 1.42-fold increments respectively. In addition, the inclusion of MnO2 NP increased the maximum potential lactic acid concentration (Pm) and production rate, reaching 32.89 g/L and 1.51 g/L/h, respectively, compared to the control’s values of 29.80 g/L and 1.43 g/L/h. This study underscores the potential of MnO2 NP in boosting lactic acid bioprocessing and yield towards enhanced bioconversion of agricultural waste to useful products
Persistence of ancestral khoesan mitochondrial patterns incontemporary South African populations
No full textintroduction
southern africa has been inhabited by hunter-gatherers for at least 20,000 years and has received diverse immigration flows in the last 2000 years. the original inhabitants have interacted with the pastoralist migrants from eastern africa (∼2000 ybp), followed by the southern bantu migration arriving some 1000 ybp, and more recently with the european and asian settlers after the 17th century. many of the original khoekhoe and san inhabitants have either become extinct or have disappeared through admixture in south africa (sa), in a sex-biased manner involving khoesan women.
methods
in this study, we generated mitochondrial dna (mtdna) control region (cr) sequences for 247 south african individuals. the sampling effort was concentrated in regions and populations with historical links to the khoesan population groups: admixed (coloured, griqua), nama (khoekhoe) and bantu in three provinces. here we evaluate the composition and extent of connectivity between population groups and regions, and to assess the distribution of haplotypes for the practical application of mtdna cr data in forensic identifications.
results
the analysis of the newly generated sequences revealed 142 distinct haplotypes, of which 122 were unique. haplogroup l0 was predominant (overall 71.7%). a high-frequency l0d2a haplotype dominated the pool of the admixed groups with 10%–12.5% incidence overall or per region. comparative analysis with 545 extant mtdna cr sequences from south african khoesan and admixed descendants revealed extensive population structure and high within-group haplotype sharing.
conclusion
the observed population and regional variations, combined with the prevalence of high-frequency haplotypes, align with patterns of matrilocality. these findings highlight the limitations of using mtdna control region analysis for forensic applications in south africa
Investigation of the effects of temperature and humidity on yields of a complementary medicine product under regulatory stability conditions
No full textBackground: The South African Health Products Regulatory Authority (SAHPRA) mandated that all complementary and alternative medicines (CAM) that were marketed and sold in the South African market be registered with the regulatory authority (RA) or have a submission for registration under review with the RA by June 2021, staring with submissions for registration from February 2020(1). The deadline was extended to February 2022. In order to apply for registration of the CAM and continue marketing the product within the South African market, stability data of the finished pharmaceutical product (FPP) was required (2). The environmental storage conditions for which stability data must be generated before registration was stipulated as 25°C ± 2°C/60% RH ± 5% RH or 30°C ± 2°C/65% RH ± 5% RH for 6 months and 40°C ± 2°C/75% RH ± 5% RH for 6 months. Product X is a CAM product that has been manufactured at a South African local pharmaceutical manufacturing company since2020 and sold in the South African market for more than 3 years. The product uses herbal material encapsulated in a hard glean capsule (HGC) to deliver its effects. The batch manufacturing records (BMRs) required the recording of the environmental manufacturing temperatures (TME) and relative humidity percentage (RH %) at theme of manufacture of Product X. The percentage yield of capsules manufactured was also calculated and recorded to ensure quality control of the product during manufacture
Transition metal phosphides for efficient hydrogen evolution: synthesis, multiscale regulation, and industrial prospects
No full textAchieving scalable green hydrogen generation through water electrolysis hinges on discovering affordable yet highly effective hydrogen evolution reaction (HER) catalysts to replace traditional Pt-based options. Transition metal phosphides (TMPs) have risen as attractive electrocatalysts, featuring tunable electronic structures, excellent conductivity, and robust stability. This review systematically examines recent advances in TMPs-based HER catalysts, bridging fundamental research and industrial applications. We first elucidate structure-activity relationships and HER mechanisms, then critically evaluate scalable synthesis methods. Multiscale optimization strategies are comprehensively discussed, including atomic-scale engineering, nanostructural design, and hybrid composites, with experimental-theoretical correlations quantifying performance enhancements. Notably, we highlight breakthroughs in achieving industrial current densities (≥500 mA cm−2) while maintaining stability. Key challenges in in-situ characterization, durability, and practical deployment are identified, with targeted solutions proposed to accelerate commercialization. This work provides critical insights for designing next-generation HER electrocatalysts to enable sustainable hydrogen production at scale