23,612 results on '"Steyn A"'
Search Results
2. Executing a Successful Third Shot Drop in Pickleball
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Steyn, D. G., Mithrush, Troy, Koentges, Chris, Andrews, Susan, and Plourde, Andre
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Physics - Physics and Society ,Physics - Fluid Dynamics - Abstract
We define and investigate a successful third shot drop in pickleball using a numerical model of pickleball ball aerodynamics. Our overall objective is to investigate the ranges of initial speeds, angles and spins that result in a successful third shot drop. We conclude that the initial speed must be in the range $10.9~ms^{-1}$ to $13~ms^{-1}$ for down-the-line shots and $13.3~ ms^{-1}$ to $16~ms^{-1}$ for cross-court shots. The initial angle must be in the range $15.5$ degrees to $22.5$ degrees for down-the-line shots and $12.5$ degrees to $18$ degrees for cross-court shots. We conclude that the effects of spin on the third shot drop are of secondary importance. We believe these results could be useful as a guide to coaches and players wanting to develop this crucial aspect of the game of pickleball.
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- 2024
3. Technical Status Report on Plasma Components and Systems in the context of EuPRAXIA
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Biagioni, A., Bourgeois, N., Brandi, F., Cassou, K., Corner, L., Crincoli, L., Cros, B., Dufrénoy, S. Dobosz, Douillet, D., Drobniak, P., Faure, J., Gatti, G., Grittani, G., Lorenz, S., Jones, H., Lucas, B., Massimo, F., Mercier, B., Molodozhentsev, A., Monzac, J., Pattathil, R., Sarri, G., Sasorov, P., Shalloo, R. J., Steyn, L., Streeter, M., Symes, D., Thaury, C., Vernier, A., and Wood, J. C.
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Physics - Plasma Physics ,Physics - Accelerator Physics - Abstract
The EuPRAXIA project aims to construct two state-of-the-art accelerator facilities based on plasma accelerator technology. Plasma-based accelerators offer the possibility of a significant reduction in facility size and cost savings over current radio frequency (RF) accelerators. The two facilities - one laser-driven one a beam-driven - are envisioned to provide electron beams with an energy in the range of 1-5 GeV and beam quality comparable to existing RF machines. This will enable a versatile portfolio of applications from compact free-electron laser (FEL) drivers to sources for medical and industrial imaging. At the heart of both facilities is the use of plasma-based accelerator components and systems which encompass not only the accelerating medium itself, but also a range of auxiliary systems such as plasma-based electron beam optics and plasma-based mirrors for high-intensity lasers. From a technical standpoint, a high-degree of control over these plasma devices will be essential for EuPRAXIA to achieve its target performance goals. The ability to diagnose and characterize these plasma devices and to simulate their operation will be further essential success factors. Additionally, compatibility with extended operation at high-repetition rates and integration into the accelerator beamline will also prove crucial. In this work, we aim to review the current status of plasma components and related systems for both laser-driven and beam-driven plasma accelerators and to assess challenges to be addressed regarding implementation at future EuPRAXIA facilities., Comment: 25 pages, 11 figures
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- 2024
4. Revealing hidden structures in the Zone of Avoidance -- a blind MeerKAT HI Survey of the Vela Supercluster
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Rajohnson, Sambatriniaina H. A., Kraan-Korteweg, Renée C., Frank, Bradley S., Chen, Hao, Staveley-Smith, Lister, Serra, Paolo, Steyn, Nadia, Kurapati, Sushma, Pisano, D. J., and Goedhart, Sharmila
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Astrophysics - Astrophysics of Galaxies - Abstract
We conducted the MeerKAT Vela Supercluster survey, named Vela$-$HI, to bridge the gap between the Vela SARAO MeerKAT Galactic Plane Survey (Vela$-$SMGPS, $-2^{\circ} \leq b \leq 1^{\circ}$), and optical and near-infrared spectroscopic observations of the Vela Supercluster (hereafter Vela$-$OPT/NIR) at $|b| \gtrsim 7^{\circ}$. Covering coordinates from $263^{\circ} \leq \ell \leq 284^{\circ}$ and $1^{\circ} \leq b \leq 6.2^{\circ}$ above, and $-6.7^{\circ} \leq b \leq -2^{\circ}$ below the Galactic Plane (GP), we sampled 667 fields spread across an area of ${\sim} \rm 242 ~deg^2$. With a beam size of ${\sim} 38'' \times 31''$, Vela$-$HI achieved a sensitivity of $\langle \rm rms \rangle = 0.74$ mJy beam$^{-1}$ at 44.3 km s$^{-1}$ velocity resolution over ${\sim}$67 hours of observations. We cataloged 719 galaxies, with only 211 (29%) previously documented in the literature, primarily through the HIZOA, 2MASX, and WISE databases. Among these known galaxies, only 66 had optical spectroscopic redshift information. We found marginal differences of less than one channel resolution for all galaxies in common between HIZOA and Vela$-$SMGPS, and a mean difference of $70 \pm 15$ km s$^{-1}$ between optical and HI velocities. Combining data from Vela$-$SMGPS, Vela$-$HI, and Vela$-$OPT/NIR confirmed the connection of the Hydra/Antlia filament across the GP and revealed a previously unknown diagonal wall at a heliocentric velocity range of $6500-8000$ km s$^{-1}$. Vela$-$HI reinforces the connection between the first wall at $18500-20000$ km s$^{-1}$ and the inner ZOA. The second wall seems to traverse the GP at $270^{\circ} \leq \ell \leq 279^{\circ}$, where it appears that both walls intersect, jointly covering the velocity range $18500-21500$ km s$^{-1}$., Comment: Accepted for publication in MNRAS, this version contains the full catalogue of detections
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- 2024
5. Exploring Program Delivery in the Further Education and Training Phase of South African Secondary Schools amidst the COVID-19 Pandemic: Challenges, Mitigation Strategies and Transformative Approaches
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Louise Fullard, Charl Wolhuter, Aaron Nhlapo, and Hennie Steyn
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This paper investigates the challenges, mitigation strategies and transformative approaches in educational programme delivery in South African education amidst the adverse influence of the pandemic in schools' Further Education and Training phase with a focus on the integration of technology-enhanced effective teaching and learning; using data obtained from interviews of a data-rich sample of the school management team and teachers of five schools. The noteworthy contribution of this paper to knowledge in the context of Comparative and International Education pertains to transformative strategies for technology-enhanced programme delivery in education. This paper's final objective is to link the explored findings of challenges, trends and innovations in the South African education system to the theme of this book focusing on the different worlds common education challenges. Furthermore, the findings emphasised the need for innovation and transformation toward a technology-enhanced education environment, especially in the Fifth Industrial Revolution milieu. In addition, this paper presented noteworthy recommendations for educational stakeholders and future research. [For the complete Volume 22 proceedings, see ED656158.]
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- 2024
6. Critical Diversity Literacy: A Framework for Multicultural Citizenship Education
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Melissa Steyn and Kudzaiishe Peter Vanyoro
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We propose the Critical Diversity Literacy (CDL) framework for citizenship education in contemporary heterogeneous societies. It encourages an anti-essentialist, power-conscious awareness of difference beyond notions of citizenship that have been constitutive of the nation and tend to normalise masculinity, patriarchy, heterosexuality, able-bodiedness and whiteness. Using intersectionality and decoloniality heuristics, we approach multicultural citizenship from the multiple axes of our identities as we inhabit the world more complexly than mere belonging to the nation-state. The framework synthesises insights from contemporary social theory into a usable scaffolding for diversity capacitation. The ten principles focus on intersectionality, social identities and positioning, historical awareness, diversity vocabulary, the coded nature of hegemonic power and personal engagement. Taken together, they promote an approach to multicultural citizenship that focuses on social justice and pushes us to recognise the lived experience of citizenship 'from below'. The framework has proved useful in designing curricula and interventions in different contexts and sectors and can be utilised to develop age-appropriate materials in schools.
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- 2024
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7. Simulation-based assessment of railhead repair welding process parameters
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Andersson, Björn, Steyn, Erika, Ekh, Magnus, and Josefson, Lennart
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- 2025
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8. Lithium from Salar Brines: Flowsheet Development, Engineering, and Economic Challenges in Project Development
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Ford, K. J. R., Brown, M. J., Pourdasht, M., Steyn, J. W., and Metallurgy and Materials Society of CIM, editor
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- 2025
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9. HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey -- III. Unveiling the obscured part of the Vela Supercluster
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Rajohnson, Sambatriniaina H. A., Kraan-Korteweg, Renée C., Chen, Hao, Frank, Bradley S., Steyn, Nadia, Kurapati, Sushma, Pisano, D. J., Staveley-Smith, Lister, Serra, Paolo, Goedhart, Sharmila, and Camilo, Fernando
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Astrophysics - Astrophysics of Galaxies - Abstract
We conducted a search for HI emission of the gas-rich galaxies in the Vela region ($260^{\circ} \leq \ell \leq 290^{\circ}, -2^{\circ} \leq b \leq 1^{\circ}$) to explore the Vela Supercluster (VSCL) at $V_\mathrm{hel} \sim 18000$ km s$^{-1}$, largely obscured by Galactic dust. Within the mostly RFI-free band ($250 < V_\mathrm{hel} < 25000$ km s$^{-1}$) of MeerKAT, the analysis focuses on $157$ hexagonally distributed pointings extracted from the SARAO MeerKAT Galactic Plane Survey located in the Vela region (Vela$-$SMGPS). These were combined into 10 contiguous mosaics, covering a ${\sim}90$ deg$^2$ area. Among the $843$ HI detected sources, 39 were previously discovered in the Parkes HIZOA survey ($V_\mathrm{hel} < 12000$ km s$^{-1}$; rms $\sim 6$ mJy beam$^{-1}$). With the improved rms level of the Vela$-$SMGPS, i.e., $0.29 - 0.56$ mJy beam$^{-1}$, our study unveils nearly 12 times more detections (471 candidates) in that same velocity range. We furthermore could identify $187$ galaxy candidates with an HI mass limit reaching $\log (M_{\rm HI}/\rm M_{\odot}) = 9.44$ in the VSCL velocity range $V_\mathrm{hel} \sim 19500 \pm 3500$ km s$^{-1}$. We find indications of two wall-like overdensities that confirm the original suspicion that these walls intersect at low latitudes around longitudes of $\ell \sim 272^{\circ} - 278^{\circ}$. We also find a strong signature most likely associated with the Hydra/Antlia extension and evidence of a previously unknown narrow filament at $V_\mathrm{hel} \sim 12000$ km s$^{-1}$. This paper demonstrates the efficiency of systematic HI surveys with the SKA precursor MeerKAT, even in the most obscured part of the Zone of Avoidance (ZOA)., Comment: Accepted for publication in MNRAS, this version contains the full catalogue of detections
- Published
- 2024
10. Identifying coronal sources of L1 solar wind disturbances using the Fisk heliospheric magnetic field and potential field extrapolations during three solar minima
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Steyn, P. J., Johnson, D., Botha, G. J. J., and Régnier, S.
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Astrophysics - Solar and Stellar Astrophysics ,Physics - Space Physics - Abstract
The solar minima between solar cycles 22-23, 23-24 and 24-25 are the best observed minima on record. In situ solar wind and interplanetary magnetic field measurements by the WIND and ACE spacecraft at L1 with one-hour cadence are explored using wavelet analyses for the most quiescent year during each minimum. Times of local peaks in periodicities are identified in the solar wind velocity, magnetic field components, and proton number densities. The measured radial velocities at these times are used to trace magnetic field lines to the photosphere using two models. The first is the Fisk heliospheric magnetic field that traces field lines from L1 to the photosphere. They connect exclusively to solar poles and in 88% instances to locations of polar coronal holes. The second model uses the Parker spiral to trace from L1 to the solar source surface and potential field extrapolations from the source surface to the photosphere. These field lines terminate at equatorial and mid-latitude coordinates of which some are located close to coronal holes. This study connects for the first time coronal hole signatures in the ecliptic plane at L1 with polar coronal holes using the Fisk field. It shows how sources from both the solar equator and poles influence the solar wind at L1 and how the two models compliment each other to identify these sources.
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- 2024
11. A temporal cortex cell atlas highlights gene expression dynamics during human brain maturation
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Steyn, Christina, Mishi, Ruvimbo, Fillmore, Stephanie, Verhoog, Matthijs B., More, Jessica, Rohlwink, Ursula K., Melvill, Roger, Butler, James, Enslin, Johannes M. N., Jacobs, Muazzam, Sauka-Spengler, Tatjana, Greco, Maria, Quiñones, Sadi, Dulla, Chris G., Raimondo, Joseph V., Figaji, Anthony, and Hockman, Dorit
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- 2024
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12. Phycoremediation of industrial wastewater: review of algae consortia
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Walters, C., Steyn, M., Ndlela, L., Nocanda, X., Moloi, M., and Oberholster, P.
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- 2024
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13. Life Cycle Assessment of an Avocado: Grown in South Africa—Enjoyed in Europe
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Blaauw, Sheldon A., Broekman, André, Maina, James W., Steyn, Wynand J. v. d. M., and Haddad, William A.
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- 2024
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14. On new tests for the Poisson distribution based on empirical weight functions
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Kirui, Winnie, Bothma, Elzanie, Smuts, Marius, Steyn, Anke, and Visagie, Jaco
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Statistics - Methodology ,Mathematics - Statistics Theory - Abstract
We propose new goodness-of-fit tests for the Poisson distribution. The testing procedure entails fitting a weighted Poisson distribution, which has the Poisson as a special case, to observed data. Based on sample data, we calculate an empirical weight function which is compared to its theoretical counterpart under the Poisson assumption. Weighted Lp distances between these empirical and theoretical functions are proposed as test statistics and closed form expressions are derived for L1, L2 and L1 distances. A Monte Carlo study is included in which the newly proposed tests are shown to be powerful when compared to existing tests, especially in the case of overdispersed alternatives. We demonstrate the use of the tests with two practical examples.
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- 2024
15. A comprehensive review of hempcrete as a sustainable building material
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Steyn, Kari, de Villiers, Wibke, and Babafemi, Adewumi John
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- 2025
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16. Metabolic biomarkers of clinical outcomes in severe mental illness (METPSY): protocol for a prospective observational study in the Hub for metabolic psychiatry
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Arish Mudra Rakshasa-Loots, Christina Steyn, Duncan Swiffen, Katie F. M. Marwick, Robert K. Semple, Rebecca M. Reynolds, Karl Burgess, Stephen M. Lawrie, Stafford L. Lightman, Saturnino Luz, and Daniel J. Smith
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Metabolomics ,Depression ,Psychosis ,Schizophrenia ,Bipolar disorder ,Sleep ,Psychiatry ,RC435-571 - Abstract
Abstract People with severe mental illness have high rates of obesity, type 2 diabetes, and cardiovascular disease. Emerging evidence suggests that metabolic dysfunction may be causally linked to the risk of severe mental illness. However, more research is needed to identify reliable metabolic markers which may have an impact on mental health outcomes, and to determine the mechanisms behind their impact. In the METPSY research study, we will investigate the relationship between metabolic markers and clinical outcomes of severe mental illness in young adults. We will recruit 120 young adults aged 16–25 years living in Scotland with major depressive disorder, bipolar disorder, schizophrenia, or no severe mental illness (controls) for a prospective observational study. We will assess clinical symptoms at three in-person visits (baseline, 6 months, and 12 months) using the Structured Clinical Interview for DSM-5, and collect blood samples at each of these visits for agnostic profiling of metabolic biomarkers through an untargeted metabolomic screen, using the rapid hydrophilic interaction liquid chromatography ion mobility mass spectrometry method (RHIMMS). Participants will also complete remote assessments at 3 and 9 months after the baseline visit: Ecological Momentary Assessments to measure mental health, wrist actigraphy to measure rhythms of rest and activity, and continuous glucose monitoring to measure metabolic changes. Throughout the 12-month enrolment period, we will also measure objective markers of sleep using a radar sleep monitor (Somnofy). Using advanced statistical techniques and machine learning analysis, we will seek to better understand the mechanisms linking metabolic health with mental health in young adults with schizophrenia, bipolar disorder, and severe depression. Clinical trial number: Not applicable
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- 2025
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17. Empowering Parents to Support Their Children to Survive and Thrive in School: A Present-Day Challenge
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Steyn, Hennie
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This paper accentuated the importance of the availability of suitable programs to train parents to support their children to survive and thrive in school. Parents have a role to play in supporting their children to fully benefit from their education. Parents should set a positive home environment to support the learning of children. It was also indicated that the training needs of the parents can be described and used as topics for the modules of a training program as part of non-formal education. It was also explained that the program should be delivered in the format of distance education by using e-training platform to deliver the programs in an attainable, sustainable and affordable manner. [For the complete Volume 21 proceedings, see ED629259.]
- Published
- 2023
18. Promoting and Hindering Factors in Mathematics Teaching in South African High Schools
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Mokgwathi, Mathelela Steyn, Graham, Marien Alet, and de Villiers, Johannes Jozua Rian
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This study explores what factors enable or prevent South African educators from carrying out effective mathematics teaching. The objectives are to explore the qualifications and experience of those involved, which skills, tools, and resources they use and what barriers they encounter. A qualitative approach using an interpretivist paradigm with multiple case studies was used. Eighteen participants were interviewed, and the data were analysed using qualitative content analysis. Findings showed that the barriers impeding effective mathematics teaching included lack of resources, teachers leaving the profession and many principals not attending workshops or professional development programmes. From the findings, we recommend the Department of Basic Education encourage more teachers to specialise in mathematics and that more funding is directed toward allocating the necessary resources to schools where resources are lacking. The department can provide incentives to encourage more student teachers to pursue mathematics teaching.
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- 2023
19. A Collaborative Approach among Teachers to Support the Teaching of Learners with Visual Impairment in the Foundation Phase
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Jossie Steyn, Mariette Koen, and Hantie Theron
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In this article, we explore how collaboration between Foundation Phase teachers could address and support the teaching of Foundation Phase learners with visual impairments (VI). By actively involving teachers in the research process, teachers contributed to changes that promoted the inclusion and success of FP learners with VI. This qualitative study implemented participatory action learning and action research (PALAR) as the research design of choice. Participants were recruited using purposive sampling, and the action learning set (ALS) comprised seven Foundation Phase teachers. Data generation entailed three cycles. Cycle One was relationship building, i.e. forming a shared vision for our study, negotiating an ethical agreement, and then determining the specific challenges Foundation Phase teachers have to face. During Cycle Two, we determined how we could address and support the educational needs of Foundation Phase learners with VI. During Cycle Three, we determined the strategies and guidelines that Foundation Phase teachers may use to enhance the teaching of learners with VI. Data generation encompassed ALS discussions, photovoice and reflective journal entries conducted throughout the three cycles. However, this article exclusively focuses on the ALS discussions. Data were analysed using thematic content analysis to design action plans collaboratively by means of which to assist Foundation Phase teachers working with learners with VI. The North-West University (NWU) and the Department of Education of the Western Cape (RSA) granted ethical clearance. The two themes derived from the findings highlighted the crucial importance of collaboration among parents, caregivers, teachers, and stakeholders in addressing the educational needs of FP learners affected by VI effectively, while also highlighting the importance of working together in designing strategies and guidelines for teaching FP learners with VI.
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- 2024
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20. The SARAO MeerKAT 1.3 GHz Galactic Plane Survey
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Goedhart, S., Cotton, W. D., Camilo, F., Thompson, M. A., Umana, G., Bietenholz, M., Woudt, P. A., Anderson, L. D., Bordiu, C., Buckley, D. A. H., Buemi, C. S., Bufano, F., Cavallaro, F., Chen, H., Chibueze, J. O., Egbo, D., Frank, B. S., Hoare, M. G., Ingallinera, A., Irabor, T., Kraan-Korteweg, R. C., Kurapati, S., Leto, P., Loru, S., Mutale, M., Obonyo, W. O., Plavin, A., Rajohnson, S. H. A., Rigby, A., Riggi, S., Seidu, M., Serra, P., Smart, B. M., Stappers, B. W., Steyn, N., Surnis, M., Trigilio, C., Williams, G. M., Abbott, T. D., Adam, R. M., Asad, K. M. B., Baloyi, T., Bauermeister, E. F., Bennet, T. G. H., Bester, H., Botha, A. G., Brederode, L. R. S., Buchner, S., Burger, J. P., Cheetham, T., Cloete, K., de Villiers, M. S., de Villiers, D. I. L., Toit, L. J. du, Esterhuyse, S. W. P., Fanaroff, B. L., Fourie, D. J., Gamatham, R. R. G., Gatsi, T. G., Geyer, M., Gouws, M., Gumede, S. C., Heywood, I., Hokwana, A., Hoosen, S. W., Horn, D. M., Horrell, L. M. G., Hugo, B. V., Isaacson, A. I., Józsa, G. I. G., Jonas, J. L., Jordaan, J. D. B. L., Joubert, A. F., Julie, R. P. M., Kapp, F. B., Kriek, N., Kriel, H., Krishnan, V. K., Kusel, T. W., Legodi, L. S., Lehmensiek, R., Lord, R. T., Macfarlane, P. S., Magnus, L. G., Magozore, C., Main, J. P. L., Malan, J. A., Manley, J. R., Marais, S. J., Maree, M. D. J., Martens, A., Maruping, P., McAlpine, K., Merry, B. C., Mgodeli, M., Millenaar, R. P., Mokone, O. J., Monama, T. E., New, W. S., Ngcebetsha, B., Ngoasheng, K. J., Nicolson, G. D., Ockards, M. T., Oozeer, N., Passmoor, S. S., Patel, A. A., Peens-Hough, A., Perkins, S. J., Ramaila, A. J. T., Ratcliffe, S. M., Renil, R., Richter, L. L., Salie, S., Sambu, N., Schollar, C. T. G., Schwardt, L. C., Schwartz, R. L., Serylak, M., Siebrits, R., Sirothia, S. K., Slabber, M. J., Smirnov, O. M., Tiplady, A. J., van Balla, T. J., van der Byl, A., Van Tonder, V., Venter, A. J., Venter, M., Welz, M. G., and Williams, L. P.
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Astrophysics - Astrophysics of Galaxies - Abstract
We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251\deg $\le l \le$ 358\deg and 2\deg $\le l \le$ 61\deg at $|b| \le 1.5\deg $). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8" and a broadband RMS sensitivity of $\sim$10--20 $\mu$ Jy/beam. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908--1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE HII region candidates are not true HII regions; and a large sample of previously undiscovered background HI galaxies in the Zone of Avoidance., Comment: Accepted for publication in MNRAS. The data release is live and links can be found in the Data Availability Statement in the paper
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- 2023
21. HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey -- II. The Local Void and its substructure
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Kurapati, Sushma, Kraan-Korteweg, Renée C., Pisano, D. J., Chen, Hao, Rajohnson, Sambatriniaina H. A., Steyn, Nadia, Frank, Bradley, Serra, Paolo, Goedhart, Sharmila, and Camilo, Fernando
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Astrophysics - Astrophysics of Galaxies - Abstract
The Local Void is one of the nearest large voids, located at a distance of 23 Mpc. It lies largely behind the Galactic Bulge and is therefore extremely difficult to observe. We use HI 21 cm emission observations from the SARAO MeerKAT Galactic Plane Survey (SMGPS) to study the Local Void and its surroundings over the Galactic longitude range 329$^{\circ}< \ell <$ 55$^{\circ}$, Galactic latitude $|b| <$ 1.5$^{\circ}$, and redshift $cz <$ 7500 km/s. We have detected 291 galaxies to median rms sensitivity of 0.44 mJy per beam per 44 km/s channel. We find 17 galaxies deep inside the Void, 96 at the border of the Void, while the remaining 178 galaxies are in average density environments. The extent of the Void is ~ 58 Mpc. It is severely under-dense for the longitude range 350$^{\circ}< \ell <$ 35$^{\circ}$ up to redshift $z <$ 4500 km/s. The galaxies in the Void tend to have \HI masses that are lower (by approximately 0.25 dex) than their average density counterparts. We find several potential candidates for small groups of galaxies, of which two groups (with 3 members and 5 members) in the Void show signs of filamentary substructure within the Void., Comment: Accepted for publication in MNRAS; 16 pages, 14 figures, Supplementary data are available online at MNRAS
- Published
- 2023
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22. HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey $-$ I. Probing the richness of the Great Attractor Wall across the inner Zone of Avoidance
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Steyn, Nadia, Kraan-Korteweg, Renée C., Rajohnson, Sambatriniaina H. A., Kurapati, Sushma, Chen, Hao, Frank, Bradley, Serra, Paolo, Staveley-Smith, Lister, Camilo, Fernando, and Goedhart, Sharmila
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
This paper presents the first HI results extracted from the SARAO MeerKAT Galactic Plane Survey (SMGPS) $-$ a narrow strip ($b \sim 3^\circ$) along the southern Milky Way. The primary goal consisted in tracing the Great Attractor (GA) Wall across the innermost Zone of Avoidance. We reduced a segment spanning the longitude range $302^\circ \leq \ell \leq 332^\circ$ for the redshift range $z \leq 0.08$. The superb SMGPS sensitivity (rms = 0.3-0.5 mJy beam$^{-1}$ per 44 kms$^{-1}$ channel) and angular resolution ($\sim$ 31" $\times$ 26") lead to a detection limit of log$(M_{\rm HI}/$M$_\odot) \geq$ 8.5 at the GA distance ($V_{\rm hel} \sim 3500 - 6500$ kms$^{-1}$). A total of 477 galaxy candidates were identified over the full redshift range. A comparison of the few HI detections with counterparts in the literature (mostly HIZOA) found the HI fluxes and other HI parameters to be highly consistent. The continuation of the GA Wall is confirmed through a prominent overdensity of $N = 214$ detections in the GA distance range. At higher latitudes, the wall moves to higher redshifts, supportive of a possible link with the Ophiuchus cluster located behind the Galactic Bulge. This deep interferometric HI survey demonstrates the power of the SMGPS in improving our insight of large-scale structures at these extremely low latitudes, despite the high obscuration and continuum background., Comment: 5 pages, 7 figures, 2 appendices of 12 pages. Journal reference: MNRAS Letters, accepted
- Published
- 2023
23. Proton-unbound states in $^{24}{\rm Al}$ relevant for the $^{23}{\rm Mg}(p,\gamma)$ reaction in novae
- Author
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Vyfers, E. C., Pesudo, V., Triambak, S., Kamil, M., Adsley, P., Brown, B. A., Jivan, H., Marin-Lambarri, D. J., Neveling, R., Ondze, J. C. Nzobadila, Papka, P., Pellegri, L., Rebeiro, B. M., Singh, B., Smit, F. D., and Steyn, G. F.
- Subjects
Nuclear Experiment - Abstract
Background: The nucleosynthesis of several proton-rich nuclei is determined by radiative proton-capture reactions on unstable nuclei in nova explosions. One such reaction is $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$, which links the NeNa and MgAl cycles in oxygen-neon (ONe) novae. Purpose: To extract $^{23}{\rm Mg}(p,\gamma)$ resonance strengths from a study of proton-unbound states in $^{24}{\rm Al}$, produced via the $^{24}$Mg($^{3}$He,$t$) reaction. Methods: A beam of $^3 {\rm He}^{2+}$ ions at 50.7 MeV was used to produce the states of interest in $^{24}$Al. Proton-triton angular correlations were measured with a $K=600$ QDD magnetic spectrometer and a silicon detector array, located at iThemba LABS, South Africa. Results: We measured the excitation energies of the four lowest proton-unbound states in $^{24}$Al and place lower-limits on $\Gamma_p/\Gamma$ values for these four states. Together with shell-model calculations of partial gamma widths, the experimental data are also used to determine resonance strengths for the three lowest $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonances. Conclusions: The energy of the dominant first $^{23}{\rm Mg}(p,\gamma)$ resonance is determined to be $E_{r} = 478 \pm 4$ keV, with a resonance strength $\omega \gamma = 19 \pm 9$ meV., Comment: Accepted for Publication in Physical Review C
- Published
- 2023
24. Displaced left-turn intersection informational guide
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Steyn, Hermanus
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Left-turn lanes -- Design and construction. ,Roads -- Interchanges and intersections. -- United States - Published
- 2014
25. The role of freight forwarding companies in detecting and investigating trade-based money laundering
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Makkink, Ilse Maritha, Steyn, Blanche, and Bezuidenhout, Hannes Christo
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- 2024
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26. Revisiting the people of Whitcher's Cave, Eastern Cape, South Africa: An osteobiographic analysis
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Steyn, Maryna, Meyer, Anja, and Lombard, Marlize
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- 2024
27. Dental health and diet of the people of Whitcher's Cave, Eastern Cape, South Africa
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Steyn, Maryna, Lombard, Marlize, and Meyer, Anja
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- 2024
28. Phenotypic Diversity of Released South African Bred Potato Varieties for Tuber Yield and Processing Quality
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Mbuma, Ntombokulunga W., Steyn, Philippus J., Laurie, Sunette M., Labuschagne, Maryke T., and Bairu, Michael W.
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- 2024
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29. Prioritising quality: investigating the influence of image quality on forensic facial comparison
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Bacci, Nicholas, Briers, Nanette, and Steyn, Maryna
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- 2024
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30. Spectroscopic Imaging of the Sun with MeerKAT: Opening a New Frontier in Solar Physics
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Kansabanik, Devojyoti, Mondal, Surajit, Oberoi, Divya, Chibueze, James O., Engelbrecht, N. E., Strauss, R. D., Kontar, Eduard P., Botha, Gert J. J., Steyn, P. J., and Nel, Amore E.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
Solar radio emissions provide several unique diagnostics to estimate different physical parameters of the solar corona, which are otherwise simply inaccessible. However, imaging the highly dynamic solar coronal emissions spanning a large range of angular scales at radio wavelengths is extremely challenging. At GHz frequencies, MeerKAT radio telescope is possibly globally the best-suited instrument at present for providing high-fidelity spectroscopic snapshot solar images. Here, we present the first published spectroscopic images of the Sun made using the observations with MeerKAT in the 880-1670 MHz band. This work demonstrates the high fidelity of spectroscopic snapshot MeerKAT solar images through a comparison with simulated radio images at MeerKAT frequencies. The observed images show extremely good morphological similarities with the simulated images. Our analysis shows that below ~900 MHz MeerKAT images can recover essentially the entire flux density from the large angular scale solar disc. Not surprisingly, at higher frequencies, the missing flux density can be as large as ~50%. However, it can potentially be estimated and corrected for. We believe once solar observation with MeerKAT is commissioned, it will enable a host of novel studies, open the door to a large unexplored phase space with significant discovery potential, and also pave the way for solar science with the upcoming Square Kilometre Array-Mid telescope, for which MeerKAT is a precursor., Comment: Published at the Astrophysical Journal, 15 pages, 9 figures
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- 2023
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31. Death, Conflict and Scandal. A Practical Theological Study of the Role of Rituals in Congregations Following the Loss of the Minister
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Marileen Steyn
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Philosophy. Psychology. Religion - Abstract
Summary of PhD Thesis. This thesis was defended on October 23, 2023 at Stellenbosch University (South-Africa). Supervisors: prof. dr. Cas Wepener (Stellenbosch University, South-Africa) and prof. dr. Christo Thesnaar (Stellenbosch University, South-Africa). The Pastoral Office of the Western Cape Synod of the Dutch Reformed Church in South Africa acted as the problem owner and the funder of the research.
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- 2024
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32. Computer vision applications for the detection or analysis of tuberculosis using digitised human lung tissue images - a systematic review
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Kapongo D. Lumamba, Gordon Wells, Delon Naicker, Threnesan Naidoo, Adrie J. C. Steyn, and Mandlenkosi Gwetu
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Human lung tissue ,Tuberculosis ,Image analysis ,Deep learning ,Medical technology ,R855-855.5 - Abstract
Abstract Objective To conduct a systematic review of the computer vision applications that detect, diagnose, or analyse tuberculosis (TB) pathology or bacilli using digitised human lung tissue images either through automatic or semi-automatic methods. We categorised the computer vision platform into four technologies: image processing, object/pattern recognition, computer graphics, and deep learning. In this paper, the focus is on image processing and deep learning (DL) applications for either 2D or 3D digitised human lung tissue images. This review is useful for establishing a common practice in TB analysis using human lung tissue as well as identifying opportunities for further research in this space. The review brings attention to the state-of-art techniques for detecting TB, with emphasis on the challenges and limitations of the current techniques. The ultimate goal is to promote the development of more efficient and accurate algorithms for the detection or analysis of TB, and raise awareness about the importance of early detection. Design We searched five databases and Google Scholar for articles published between January 2017 and December 2022 that focus on Mycobacterium tuberculosis detection, or tuberculosis pathology using digitised human lung tissue images. Details regarding design, image processing and computer-aided techniques, deep learning models, and datasets were collected and summarised. Discussions, analysis, and comparisons of state-of-the-art methods are provided to help guide future research. Further, a brief update on the relevant techniques and their performance is provided. Results Several studies have been conducted to develop automated and AI-assisted methods for diagnosing Mtb and TB pathology from digitised human lung tissue images. Some studies presented a completely automated method of diagnosis, while other studies developed AI-assisted diagnostic methods. Low-level focus areas included the development of a novel $$\upmu$$ μ CT scanner for soft tissue image contract, and use of multiresolution computed tomography to analyse the 3D structure of the human lung. High-level focus areas included the investigation the effects of aging on the number and size of small airways in the lungs using CT and whole lung high-resolution $$\upmu$$ μ CT, and the 3D microanatomy characterisation of human tuberculosis lung using $$\upmu$$ μ CT in conjunction with histology and immunohistochemistry. Additionally, a novel method for acquiring high-resolution 3D images of human lung structure and topology is also presented. Conclusion The literature indicates that post 1950s, TB was predominantly studied using animal models even though no animal model reflects the full spectrum of human pulmonary TB disease and does not reproducibly transmit Mtb infection to other animals (Hunter, 2011). This explains why there are very few studies that used human lung tissue for detection or analysis of Mtb. Nonetheless, we found 10 studies that used human tissues (predominately lung) of which five studies proposed machine learning (ML) models for the detection of bacilli and the other five used CT on human lung tissue scanned ex-vivo.
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- 2024
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33. All-optical reporting of inhibitory receptor driving force in the nervous system
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Joshua S. Selfe, Teresa J. S. Steyn, Eran F. Shorer, Richard J. Burman, Kira M. Düsterwald, Ariel Z. Kraitzick, Ahmed S. Abdelfattah, Eric R. Schreiter, Sarah E. Newey, Colin J. Akerman, and Joseph V. Raimondo
- Subjects
Science - Abstract
Abstract Ionic driving forces provide the net electromotive force for ion movement across receptors, channels, and transporters, and are a fundamental property of all cells. In the nervous system, fast synaptic inhibition is mediated by chloride permeable GABAA and glycine receptors, and single-cell intracellular recordings have been the only method for estimating driving forces across these receptors (DFGABAA). Here we present a tool for quantifying inhibitory receptor driving force named ORCHID: all-Optical Reporting of CHloride Ion Driving force. We demonstrate ORCHID’s ability to provide accurate, high-throughput measurements of resting and dynamic DFGABAA from genetically targeted cell types over multiple timescales. ORCHID confirms theoretical predictions about the biophysical mechanisms that establish DFGABAA, reveals differences in DFGABAA between neurons and astrocytes, and affords the first in vivo measurements of intact DFGABAA. This work extends our understanding of inhibitory synaptic transmission and demonstrates the potential for all-optical methods to assess ionic driving forces.
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- 2024
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34. Gender emancipation and its impact on happiness: An examination of the happy wife, happy life formula
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Renier Steyn
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gender emancipation ,happiness ,world values survey ,longitudinal data ,Social Sciences ,Education (General) ,L7-991 - Abstract
The adage "happy wife, happy life" implies that women's gender emancipation could contribute to the overall societal quality of life. However, it raises at least two questions: Does advancing women's rights lead to increased happiness for women? Is it possible that advancing women’s rights occurs at the expense of men? The study examines the relationship between gender emancipation and happiness, aiming to determine whether gender emancipation genuinely enhances the happiness of both women and men, and whether the focus on women’s well-being might negatively impact men. Data from the World Values Survey were used to conduct cross-sectional and longitudinal analyses. The cross-sectional analysis focused on the relationship between emancipation and happiness, while the longitudinal analysis explored trends in gender emancipation and happiness from the 3rd cohort (1995-1998) to the 7th cohort (2017-2022). Women had higher gender emancipation scores, but the genders did not differ significantly in happiness scores. Surprisingly, there was no significant correlation between gender emancipation and happiness, whether analysing the entire sample or each gender separately. Longitudinal data revealed increasing gender emancipation and happiness over time. This similarity in trends was interpreted as a spurious relationship. It was hypothesised that happiness could stem from gender emancipation. However, despite longitudinal data revealing growing gender emancipation and happiness for both sexes, the cross-sectional analysis showed no such correlations. Gender emancipation and happiness, as measured by the World Values Survey, were not related. Emancipation does not necessarily equate to a happy life.
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- 2024
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35. The role of feedback in the development of managers
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Shelley Cook and Renier Steyn
- Subjects
feedback ,mangement development ,conceptualisation ,literature review ,Social Sciences - Abstract
The landscape in which modern organisations operate is rapidly changing and requires managerial agility. This necessitates a frequent review of how managers are developed. The aim of this article is to examine the role of workplace feedback in employee development. This will be achieved by developing a contemporary and comprehensive definition of feedback and specifying the elements of feedback that are associated with managerial development. Employing a qualitative, non-systematic literature review approach, journal articles and textbooks published after 2015, with feedback as their primary theme, were systematically selected and analysed for their content as well as the seminal works they referred to. The analysed literature suggests that feedback forms part of a dynamic communication and learning process. Development-driven feedback is information presented to recipients regarding their behaviour and/or performance in executing work tasks, as assessed by supervisors, subordinates, peers, coworkers, or the recipients themselves, with the intent to enhance work relationships and job performance. The elements central to structuring feedback were identified as purpose, content, source, frequency, timing, and delivery. These elements are customised to meet workplace performance requirements, also taking individual skill sets and personalised needs into account. A broad base of academic literature was captured and integrated to reach a comprehensive understanding of feedback as a development intervention. It was concluded that, although complex, literature on feedback can be consolidated to present both an inclusive definition of the concept and the elements associated with it.
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- 2024
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36. An Analysis of the Support Roles and Responsibilities of Circuit Managers to Principals during Transformation in the South African Basic Education System
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CMvA Steyn and Mp Fuller
- Abstract
The purpose of the study was to analyze the support roles and responsibilities of Circuit Managers' (CM) as middle tier managers to principals during education change in South Africa. Change management theories were used as theoretical frameworks to underpin this study. Using semistructured individual interviews data was collected from four CM and thirteen secondary school principals. Principals expressed that they are not effectively nor adequately supported within their specific challenging context by the Circuit Manager that is appointed to support them during education change. The study reveals that CM dictate more time toward administrative obligations and mostly assume accountability and responsibility for tasks outside of their purview or job description. Principals who are not effectively supported by CM find it difficult to provide quality leadership and management during education change as well as ensure school improvement. Change strategies are recommended for CM's, districts and stakeholders in the basic education system.
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- 2024
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37. Psychological Transformation of the 'Self' towards Eco-Sensitivity through High-Risk Nature-Based Sports: A South African Context
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Nicolette Human and Barend Johannes Marthinus Steyn
- Abstract
Mindless actions in the form of environmentally degrading behaviour constantly threaten the sustainability of healthy ecosystems. In this paper, the intrinsic value of strengthening the bond between humanity and nature through high-risk nature-based sports participation is explored. This interpretative phenomenological analytical study considers lived experiences of 10 skilled South African high-risk nature-based sports participants who take calculated risks through precautionary measures. Participant's activities are performed in the wilderness in isolation from civilisation with minimal availability of human and medical resources in case of an emergency, which give rise to the term 'high-risk.' Phenomenological traditions from Heidegger and Merleau-Ponty navigate a hermeneutical understanding of their-bodily-being-towards-death. Evidence of meaningful psychological transformation towards an eco-sensitivity by way of high-risk nature-based sports participation is analysed, through first-hand narratives via semi-structured interviews. The sensitizing process of the 'self' can be effectively articulated in the synchronous relationship between the Eigenwelt, Mitwelt and Umwelt.
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- 2024
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38. The Effect of a Walking, Dancing, and Strength Training Program on the Functional Fitness of Adults with Intellectual Disability: A Randomised Controlled Trial
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E. Steyn, P.H. Boer, and G. Joubert
- Abstract
Background: Many adults with intellectual disabilities live a sedentary lifestyle, have low levels of functional fitness and are overweight. The purpose of this study was to determine whether an exercise intervention with activities which are simple, fun, accessible and adapted for socialising in a group would elicit significant improvements in various parameters associated with functional fitness for adults with intellectual disabilities. Methods: Forty-two adults with intellectual disability (44.5 ± 11.5 years) were randomly located to an exercise group (n = 19) and a control group (n = 23). The program consisted of walking, dancing, and resistance training exercises and was implemented, three times a week for 6 weeks. Results: Significant ameliorations (p < 0.05) were reported for body mass, hip circumference, aerobic capacity, functional ability, muscular strength, balance, and flexibility with varying degrees of effect sizes. p Conclusions: The combined exercise training program showed a significant positive impact on various parameters associated with functional fitness for adults with intellectual disability.
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- 2024
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39. A Longitudinal Descriptive Assessment of US College COVID-19 Dashboards
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Katerina A. Jones, Frank D. Steyn, and Lorraine S. Wallace
- Abstract
Background: The purposes of this study were to (1) longitudinally examine US college and university COVID-19 dashboard content and (2) explore county-level population health and COVID-19 community indicators where colleges with large undergraduate enrollments were located. Methods: We identified 10 colleges with the largest undergraduate enrollments. Next, we located all public and private two- and four-year nonprofit colleges (n = 58) in each respective county. We assessed active COVID-19 dashboards using established criteria from "We Rate COVID Dashboards" in March 2021 and February 2022. Results: In 2021 and 2022, two-thirds (n = 38/58) of colleges had an active COVID-19 dashboard. While most COVID-19 dashboards were easy to read, they were less likely to include updated daily infection rates and testing frequency details. Conclusion: Overall quality, content, and features of COVID-19 dashboards varied greatly across colleges. Future COVID-19 dashboard designs should focus on providing evidence-based information with the goal of promoting and supporting informed decision making.
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- 2024
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40. Passively administered fluoxetine reaches the juvenile brain of FSL rats and reduces antioxidant defences, without altering serotonin turnover
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Steyn, Stephan F., Rheeders, Malie, Viljoen, Francois P., and Brand, Linda
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- 2024
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41. Jointly estimating epidemiological dynamics of Covid-19 from case and wastewater data in Aotearoa New Zealand
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Watson, Leighton M., Plank, Michael J., Armstrong, Bridget A., Chapman, Joanne R., Hewitt, Joanne, Morris, Helen, Orsi, Alvaro, Bunce, Michael, Donnelly, Christl A., and Steyn, Nicholas
- Published
- 2024
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42. Liver and pancreatic-targeted interleukin-22 as a therapeutic for metabolic dysfunction-associated steatohepatitis
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Sajiir, Haressh, Keshvari, Sahar, Wong, Kuan Yau, Borg, Danielle J., Steyn, Frederik J., Fercher, Christian, Taylor, Karin, Taylor, Breten, Barnard, Ross T., Müller, Alexandra, Moniruzzaman, Md, Miller, Gregory, Wang, Ran, Fotheringham, Amelia, Schreiber, Veronika, Sheng, Yong Hua, Hancock, Janelle Louise, Loo, Dorothy, Burr, Lucy, Huynh, Tony, Lockett, Jack, Ramm, Grant A., Macdonald, Graeme A., Prins, Johannes B., McGuckin, Michael A., and Hasnain, Sumaira Z.
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- 2024
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43. B cell heterogeneity in human tuberculosis highlights compartment-specific phenotype and functional roles
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Krause, Robert, Ogongo, Paul, Tezera, Liku, Ahmed, Mohammed, Mbano, Ian, Chambers, Mark, Ngoepe, Abigail, Magnoumba, Magalli, Muema, Daniel, Karim, Farina, Khan, Khadija, Lumamba, Kapongo, Nargan, Kievershen, Madansein, Rajhmun, Steyn, Adrie, Shalek, Alex K., Elkington, Paul, and Leslie, Al
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- 2024
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44. Gastric perforation biopsy: is it obsolete?
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Steyn, Petre Francois and Karusseit, Otto
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- 2024
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45. LiLA: lipid lung-based ATLAS built through a comprehensive workflow designed for an accurate lipid annotation
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Fernández Requena, Belén, Nadeem, Sajid, Reddy, Vineel P., Naidoo, Vanessa, Glasgow, Joel N., Steyn, Adrie J. C., Barbas, Coral, and Gonzalez-Riano, Carolina
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- 2024
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46. Teachers' Attitudes towards the Amendments in the Design Curriculum: A Critical Overview of the Approach and Findings of the Study
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van Deventer, Anriët and Steyn, Raïta
- Abstract
This article refers to the South African Design teachers' attitudes towards the implementation of the 2020 Section 4 amendments of the Design Curriculum and Assessment Policy Statement (CAPS). The purpose of the article is twofold: first to establish the necessity for "awareness" of the teachers' attitudes towards curriculum changes, especially when they are unexpected and abrupt. Secondly, to demonstrate the importance of "awareness" among educational authorities about the role of transparent discussions on the nature, purpose, and consequences of their relevant decisions before their final implementation. To this end, the article discusses the amendments and their differences to the former curriculum. The role of the Design teachers' positive attitude towards curriculum changes, especially in dealing with challenging pedagogical issues and communicating creative motivation to learners, is critically assessed. Theoretically, the study was guided by "Ubuntu" philosophy and the South African democratic principles while methodologically, based on a qualitative data collection process, the "attitudes" of Design teachers from seven selected schools have been individually examined. In conclusion, the teachers' heterogeneous responses have indicated that their opinions do not reflect the "à priori" governmental acceptance of the amendments.
- Published
- 2022
47. Probing Quasar Viewing Angle with the Variability Structure Function
- Author
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Tang, Ji-Jia, Wolf, Christian, Tonry, John, Lai, Samuel, Yong, Suk Yee, and Steyn, Zachary
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
Given the anisotropic emission from quasar accretion discs, their viewing angle affects estimates of the quasar luminosity, black-hole mass and Eddington ratio. Discs appear overluminous when viewed pole-on and underluminous when viewed at high inclination. In radio-quiet quasars, the viewing angle is usually unknown, although spectroscopic indicators have been proposed. Here, we use a recently discovered universality in the variability structure function (SF) of quasar light curves (LCs), where all quasars show the same SF when clocks run in units of orbital timescale. As an offset from the mean relation can be caused by incorrect orbital timescales and thus incorrect luminosities, we correlate these offsets with suggested inclination indicators. We derive SFs from NASA/ATLAS LCs spanning $\sim 6$ years of observation, using a sample of 183 luminous quasars with measured H$\beta$ lines as well as 753 quasars with CIV and MgII lines. Starting from the proposed orientation indicators, we expect quasars with narrower H$\beta$ lines and with more blueshifted CIV lines to be viewed more pole-on and thus appear overluminous. In contrast, our SF analysis finds that presumed pole-on discs appear underluminous, consistently for both line indicators. We discuss possible explanations for the behaviour of quasars with highly blueshifted CIV lines irrespective of inclination angle, including dusty outflows that might render the accretion disc underluminous and flatter disc temperature profiles with longer orbital timescales than in thin-disc models but reach no satisfying conclusion., Comment: 15 pages, 10 figures, Accepted for publication in MNRAS
- Published
- 2023
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48. A Boltzmann generator for the isobaric-isothermal ensemble
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van Leeuwen, Steyn, Ortíz, Alberto Pérez de Alba, and Dijkstra, Marjolein
- Subjects
Condensed Matter - Statistical Mechanics - Abstract
Boltzmann generators (BGs) are now recognized as forefront generative models for sampling equilibrium states of many-body systems in the canonical ensemble, as well as for calculating the corresponding Helmholtz free energy. Furthermore, BGs can potentially provide a notable improvement in efficiency compared to conventional techniques such as molecular dynamics (MD) and Monte Carlo (MC) methods. By sampling from a clustered latent space, BGs can circumvent free-energy barriers and overcome the rare-event problem. However, one major limitation of BGs is their inability to sample across phase transitions between ordered phases. This is due to the fact that new phases may not be commensurate with the box dimensions, which remain fixed in the canonical ensemble. In this work, we present a novel BG model for the isothermal-isobaric (NPT) ensemble, which can successfully overcome this limitation. This unsupervised machine-learning model can sample equilibrium states at various pressures, as well as pressure-driven phase transitions. We demonstrate that the samples generated by this model are in good agreement with those obtained through MD simulations of two model systems. Additionally, we derive an estimate of the Gibbs free energy using samples generated by the NPT BG.
- Published
- 2023
49. On the onset delays of solar energetic electrons and protons: Evidence for a common accelerator
- Author
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Strauss, R. D., Dresing, N., Richardson, I. G., Berg, J. P. van den, and Steyn, P. J.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Physics - Plasma Physics ,Physics - Space Physics - Abstract
The processes responsible for the acceleration of solar energetic particles (SEPs) are still not well understood, including whether SEP electrons and protons are accelerated by common or separate processes. Using a numerical particle transport model that includes both pitch-angle and perpendicular spatial diffusion, we simulate, amongst other quantities, the onset delay for MeV electrons and protons and compare the results to observations of SEPs from widely-separated spacecraft. Such observations have previously been interpreted, in a simple scenario assuming no perpendicular diffusion, as evidence for different electron and proton sources. We show that, by assuming a common particle source together with perpendicular diffusion, we are able to simultaneously reproduce the onset delays for both electrons and protons. We argue that this points towards a common accelerator for these particles. Moreover, a relatively broad particle source is required in the model to correctly describe the observations. This is suggestive of diffusive shock acceleration occurring at large shock structures playing a significant role in the acceleration of these SEPs., Comment: Accepted to ApJ
- Published
- 2023
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50. Corrigendum: Longitudinal mitochondrial bioenergetic signatures of blood monocytes and lymphocytes improve during treatment of drug-susceptible pulmonary tuberculosis patients
- Author
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Bridgette M. Cumming, Kelvin W. Addicott, Fernanda Maruri, Vanessa Pillay, Rukaya Asmal, Sashen Moodley, Beatriz Barreto-Durate, Mariana Araújo-Pereira, Matilda Mazibuko, Zoey Mhlane, Nikiwe Mbatha, Khadija Khan, Senamile Makhari, Farina Karim, Lauren Peetluk, Alexander S. Pym, Mahomed Yunus S. Moosa, Yuri F. van der Heijden, Timothy S. Sterling, Bruno B. Andrade, Alasdair Leslie, and Adrie J. C. Steyn
- Subjects
tuberculosis ,bioenergetic metabolism ,lymphocytes ,monocytes ,TB treatment ,cytokines ,Immunologic diseases. Allergy ,RC581-607 - Published
- 2025
- Full Text
- View/download PDF
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