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Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction
(stellenbosch University, 2023-12) Le Roux, Samantha Gailene
Fine-tuning properties using external stimuli is essential for the development of functional materials with dynamic properties. High pressure is an exciting and exceptionally useful stimulant in the field of supramolecular chemistry. High pressure can produce large changes in crystal and molecular structures, that consequently affect the physical properties of the materials. This dissertation reports the effect of high pressure, as an external stimulant, on the crystal and molecular structures of small organic molecules.
We firstly describe the effect of pressure on the pancake bonding in 4-phenyl-1,2,3,5-dithiadiazolyl (1). 1 orders as dimers in the solid state with strong intermolecular interactions between the S atoms. The strong interactions between the heterocyclic rings, containing the delocalized radical electron, are known as pancake bonds. The study on 1 looks at the highpressure crystallographic structures and uses complementary density functional theory (DFT) to better understand the behavior of 1 under pressure. Quantum Theory of Atoms In Molecules (QTAIM) and Electron Localization Function (ELF) formalisms are used to rationalize the degree of charge-shift bonding character of the pancake bonding with increasing pressure. The second study looked at the effect of pressure on both polymorphs of 4-cyanotetrafluorophenyl-1,2,3,5-dithiadiazolyl (2). 2 is a widely studied dithiadiazolyl (DTDA) with supramolecular chains of radicals in the solid state. The application of pressure to both polymorphs has a significant effect on the magnetic exchange interaction, J, as determined by unrestricted DFT. 2α initially becomes more ferromagnetically coupled with increasing pressure, but eventually becomes antiferromagnetically coupled. 2β becomes more antiferromagnetically coupled under pressure and experiences a phase change at 0.97 GPa. This study shows how high pressure can be used as a suitable stimulant for magnetic property changes. The third and final study looks at using high pressure for achieving solid-state reactions. Cinnamic acid (3) undergoes [2+2] cycloaddition under ultra-violet (UV) irradiation. 3 undergoes isothermal compression with pressure but does not undergo [2+2] cycloaddition. A combination of UV irradiation and pressure is successful in achieving complete reaction in significantly reduced irradiation times. An inverse relationship between pressure and irradiation time necessary for complete reaction is identified. This study eloquently illustrates how high pressure can be used as an additional stimulus for solid-state reactions to proceed in a single-crystal to single-crystal fashion under drastically reduced reaction times. These studies clearly illustrate how high pressure can be used to enhance existing intermolecular interactions and synthons. This ultimately affects the physical properties of the crystals studied, making high pressure a successful stimulant for physical property switching in the solid state.
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Climate change & epidemics 2023: climade consortium report; summary for policymakers COP28
(Centre for Epidemic Response and Innovation, 2023) The Core Writing Team
; De Oliveira, Tulio; Baxter, Cheryl; Huguet, Alexis
INTRODUCTION: As the world endeavours to recover from the COVID-19 pandemic, it is crucial to recognize that another crisis, unfolding at an alarming pace, demands our immediate attention. Climate change has assumed a dominant role our lives, causing unprecedented levels of distress. Populations across the globe are grappling with the devastating consequences of extreme climatic events, necessitating efforts to control wildfires, rebuild infrastructure damaged by floods, and adapt to a progressively hotter and more perilous environment. Regrettably, amidst these challenges, there is a looming threat that is being overlooked—the intricate interaction between climate change and infectious diseases. A review has revealed that climate change has the potential to aggravate over 50% of known human pathogens. This distressing phenomenon is not a distant projection but a stark reality currently unfolding before us.
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Conversations reflecting boundary-objects-related details of a teacher’s local practices with spreadsheet algebra programs on variables
(AOSIS (Pty) Ltd., 2023-11-30) Gierdien M. Faaiz; Daher Wajeeh; Abu-Saman Awni M.
The ways teachers converse about their work in relation to information and communications technologies (ICTs) are worth studying. We analyse how a teacher converses about her local practices in relation to two spreadsheet algebra programs (SAPs) on variables. During the conversations we noticed that the teacher keeps different policy documents – boundary objects – firmly in view, in relation to the design of the two other boundary objects, namely the two SAPs. The policy documents provide details on the operative curricula which entail the intended, implemented and examined curricula. Of these curricula, the teacher regarded the examined curriculum and associated examinations as most important. Also, she conversed about how she intends to align the design features of the two SAPs with particular policy documents, especially in the context of the South African high-stakes National Senior Certificate examinations and the attendant examination pressure. Our results confirm current professional development (PD) literature suggestions that emphasise fostering coherence, for example between policy boundary objects details and what university-based PD providers do when they interact with school teachers.
Contribution: The results provide guidelines for university-based PD providers to integrate SAPs or other ICTs related to algebra and variables by keeping teachers’ local practices in view. These providers should note that different policy-related boundary objects shape the ways teachers understand and converse about their local practices, namely their work at the classroom level.
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Examiner’s persception of grade 10 English second language “errors” in Namibia
(Stellenbosch : Stellenbosch University, 2018-12) Asheeke, Josefina; Van der Walt, Christa; Ruiters, John; Stellenbosch University. Faculty of Education. Dept. of Curriculum Studies.
This study was conducted to explore examiners’ perceptions of Grade 10 English Second Language (ESL) at Junior Secondary Certificate (JSC) level and to increase awareness of varieties of English. The study is situated in the Namibian context. An interpretive approach was employed to understand how examiners perceive Grade 10 English second language learners' ‘errors’. Semi-structured interviews were used to obtain information from six participants who are national markers of Grade 10 ESL papers in the Omusati region. The data were compared to the national examiners' reports for 2012–2016. The study was a qualitative case study. The unit of analysis in this case study was the perceptions of six examiners from the Omusati region of Namibia. This study was based on a sociolinguistic approach to the language. The replies of the six respondents and the examiners’ reports revealed that the Grade 10 learners’ level of proficiency in English is not at the level or grade they are in. In other words, they do not meet the requirements of the Grade 10 level. Both datasets revealed a perceived gap between learners from rural and urban schools. Learners from rural schools were perceived to be disadvantaged in terms of English proficiency compared to those in urban schools. Furthermore, the language spoken in certain areas influences learners' production of language. According to the examiners, learners have difficulty with interpreting questions correctly and as a result, they write off-topic. The findings revealed that 80% of learners do not keep to the word limit. This negatively affects the marks allocated because the examiners have to stop marking at the number of words expected. Most interestingly, the study revealed that learners were creating new forms of English which were seen by examiners as a direct translation from learners' home language into English. These types of translation mostly occur when learners translate idioms into English and when they write about things that relate to their culture. This led examiners to consider the possibility that an indigenous variety of English, colloquially referred to as ‘Namlish’, may be emerging in Namibia. Although this kind of English has not yet been standardised, it was acknowledged to exist in Namibia alongside the preferred British English.
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Research supervision as praxis: A need to speak back in dangerous ways
(Journal of Praxis in Higher Education, 2023-09-05) Hopwood Nick; Frick Liezel
Viewing research supervision as praxis offers alternative perspectives on this crucial aspect of academic work. In this paper, we consider the contributions in this Special Issue as counterpoints to dominant discourses on research supervision by drawing on the idea of praxis as morally committed and history-making action. This brings insights from Swedish research into dialogue with literature from across the world, particularly the Global South. We thematize these contributions by highlighting issues of complexity; considering how history, future and positionality shape supervision praxis; challenging narrow production-oriented discourses in favour of creativity as a foundation for supervision as praxis; and reflecting on how a shift from precarity to nuance may enable us to view supervision as praxis as enablement towards a better future. Our consideration of research supervision as praxis necessitates a stance that does not conform to the status quo, thus provoking further debate and action to think, and supervise, in non-routine, future-changing ways. As supervisors, we do not need to be resigned to futures where neoliberal regimes of surveillance, measurement and accountability shape our practices as strongly as they do today. We argue that there is a need to speak back to supervision as praxis in dangerous ways.