Hartebeeste en hoofweeé

No Abstrac

On trivial words in finitely presented groups

We propose a numerical method for studying the cogrowth of finitely presented groups. To validate our numerical results we compare them against the corresponding data from groups whose cogrowth series are known exactly. Further, we add to the set of such groups by finding the cogrowth series for Baumslag-Solitar groups $\mathrm{BS}(N,N) =$ and prove that their cogrowth rates are algebraic numbers.Comment: This article has been rewritten as two separate papers, with improved exposition. The new papers are arXiv:1309.4184 and arXiv:1312.572

Forces and pressures in adsorbing partially directed walks

journal_title: Journal of Physics A: Mathematical and Theoretical article_type: paper article_title: Forces and pressures in adsorbing partially directed walks copyright_information: © 2016 IOP Publishing Ltd date_received: 2015-10-02 date_accepted: 2016-03-18 date_epub: 2016-04-1

A simple model of a vesicle drop in a confined geometry

We present the exact solution of a two-dimensional directed walk model of a drop, or half vesicle, confined between two walls, and attached to one wall. This model is also a generalisation of a polymer model of steric stabilisation recently investigated. We explore the competition between a sticky potential on the two walls and the effect of a pressure-like term in the system. We show that a negative pressure ensures the drop/polymer is unaffected by confinement when the walls are a macroscopic distance apart

Levelling the playing field: an investigation into the translation of academic literacy tests

It is widely accepted that low levels of proficiency in the languages of learning and teaching (in this article, academic language proficiency refers to academic literacy and the terms will be used interchangeably), affect through-put rates negatively. This unsettling trend is confirmed by local and international literature, and can possibly be attributed to the language curriculum in secondary education that does not prepare students adequately for the higher-order language-thinking skills they need for study at university. By this we refer to Bloom’s taxonomy, especially the three higher-order skills of analysing, synthesising and evaluating, and the way language is used for these purposes. In order to address this problem, and as part of language-planning initiatives, some faculties at Stellenbosch University introduced the integration of academic literacy courses into the first-year curriculum. These courses are fully creditbearing and a system of continuous assessment was adopted. Semester tests form part of this assessment process, and led to the investigation done for this paper. Since both Afrikaans- and English-speaking students register for the same academic literacy module it is imperative that outcomes and assessments should be on the same level. However, the aggregate on the Afrikaans semester tests have continuously been lower than on the English test. The aggregate for the Afrikaans tests was, furthermore, on par with the weighted average for all other first-year courses, which was not always the case with the English tests. After an initial investigation, it was concluded that the Englishspeaking students were not necessarily academically stronger than their Afrikaans counterparts, but it seemed likely that the problem lay with the tests themselves. A first notion was that academic and spoken English are closer than academic and spoken Afrikaans. It was also possible that the level of difficulty of the English test was substantially lower than that of the Afrikaans test. It should, however, be noted that both the Afrikaans and English tests produced excellent reliability coefficients (alpha above 0.88) and most items discriminated adequately. A possible solution to the benchmarking problem was to translate the Afrikaans test into English. The translation framework, adopted for this study, was Nord’s functionalist model. This paper will elaborate on the translation procedure, and the variance in students’ performance on the translated version compared to previous administrations. Preliminary conclusions on bias in translated tests and the success and feasibility of such procedures are drawn.Daar word allerweë aanvaar dat lae vaardigheidsvlakke in die tale van onderrig en leer (in hierdie artikel verwys akademiese taalvaardigheid na akademiese geletterdheid en die twee terme word afwisselend met mekaar gebruik) deurvloeikoerse benadeel. Hierdie onrusbarende tendens word deur plaaslike én internasionale literatuur bevestig, en kan moontlik daaraan toegeskryf word dat die taalkurrikulum in hoërskoolonderrig nie daarin slaag om studente genoegsaam vir die hoërorde-taaldenkvaardighede van universiteitstudie toe te rus nie. Met hoërorde-taaldenkvaardighede word verwys na Bloom se taksonomie, en spesifiek die drie hoërorde-vaardighede van analise, sintese en evaluering, en die wyse waarop taal vir hierdie doel aangewend word. Om hierdie probleem te hanteer, en as deel van taalbeplanningsinisiatiewe, het sommige fakulteite aan die Universiteit Stellenbosch kursusse in Akademiese Geletterdheid by die eerstejaarskurrikulum begin integreer. Hierdie kursusse is ten volle kredietdraend en volg ‘n stelsel van voortgesette assessering. Semestertoetse maak deel uit van hierdie assesseringsproses en het tot die ondersoek vir hierdie navorsingstuk aanleiding gegee. Aangesien sowel Afrikaans- as Engelssprekende studente vir dieselfde module in Akademiese Geletterdheid registreer, is dit noodsaaklik dat uitkomste en assessering op gelyke vlak lê. Tog was die totale punt vir die Afrikaanse semestertoets deurgaans laer as dié vir die Engelse toets. Voorts was die totale punt vir die Afrikaanse toets in lyn met die geweegde gemiddelde vir alle ander eerstejaarskursusse, wat weer nie altyd die geval met die Engelse toets was nie. Ná ‘n aanvanklike ondersoek is afgelei dat die Engelssprekende studente nie noodwendig akademies sterker as hul Afrikaanse eweknieë is nie, maar dat die probleem waarskynlik by die toetse self lê. ‘n Eerste moontlikheid was dat akademiese en gesproke Engels nader aan mekaar is as akademiese en gesproke Afrikaans. Tweedens kon die moeilikheidsgraad van die Engelse toets ook aansienlik laer wees as dié van die Afrikaanse toets. Dit is egter belangrik om daarop te let dat die Afrikaanse én Engelse toetse albei uitstekende betroubaarheidskoëffisiënte (alfa bo 0.88) sowel as merendeels goeie diskrimineringskoëffisiënte opgelewer het. ‘n Moontlike oplossing vir die probleem van rigpuntstelling was om die Afrikaanse toets in Engels te vertaal. Die vertaalraamwerk wat vir hierdie studie aanvaar is, was Nord se funksionalistiese model. Hierdie navorsingstuk wei uit oor die vertaalprosedure sowel as die wisseling in studenteprestasie in die vertaalde toets in vergelyking met vorige toetse. Voorlopige gevolgtrekkings word ook gemaak oor sydigheid in vertaalde toetse, en die sukses en uitvoerbaarheid van sodanige prosedures.Keywords: academic literacy test; functionalist translation approach; back-translation; adaptation of testsThe article is in English

A model for improving knowledge generation in Design Science Research through reflective practice

Abstract : Epistemology refers to the philosophy of knowledge and aims to address central questions of how we create new knowledge. All research paradigms can be distinguished in terms of epistemological assumptions, that is, assumptions of how knowledge is produced in the respective paradigms. Design science research (DSR) is a research paradigm often used in technical disciplines for the creation of artefacts. DSR has roots in pragmatism, where beliefs and theories are evaluated based on the success of its practical application. New knowledge is produced in DSR when original artefacts are created to solve a problem. The epistemological assumption of D“‘ can then shortly be defined as 'knowledge through making'. At its core, DSR is goal-orientated and its practical approaches are focused on delivering the product according to straight- forward processes - without being affected by human factors. This process of acquiring new knowledge is efficient but not necessarily effective in terms of capturing all aspects of the experience of the practitioner. Frameworks exist for the creation of artefacts in DSR, but the process of knowledge generation is not explicit. The aim of the paper is to guide explicit knowledge generation in D“‘. The research question is "How can we make the process of obtaining knowledge in D“‘ more explicit?" DSR Frameworks are iterative in nature and focus on the creation and evaluation of artefacts. There is an implicit assumption that reflection takes place in these iterations. Schön, author of The Reflective Practitioner, writes that new knowledge is produced through reflection during and after an event has occurred. He also states that you can only have a complete understanding of a problem through the dual process of reflection-in-action and reflection-on-action. We argue that this also holds true for artefact design and development in DSR. A reflective DSR practitioner can explicitly indicate how knowledge is produced in the design science research cycle. The effective use of reflective practice changes each individual phase of a DSR framework from goal-orientated to problem-orientated. Epistemologically, knowledge is then produced through 'learning by doing', which gives D“‘ a worldview that supports reflective practice. The paper promotes the incorporation of reflective practice in DSR and provides a demonstration thereof in an example on the preparation of IT students for their chosen career

Forcing Adsorption of a Tethered Polymer by Pulling

We present an analysis of a partially directed walk model of a polymer which at one end is tethered to a sticky surface and at the other end is subjected to a pulling force at fixed angle away from the point of tethering. Using the kernel method, we derive the full generating function for this model in two and three dimensions and obtain the respective phase diagrams. We observe adsorbed and desorbed phases with a thermodynamic phase transition in between. In the absence of a pulling force this model has a second-order thermal desorption transition which merely gets shifted by the presence of a lateral pulling force. On the other hand, if the pulling force contains a non-zero vertical component this transition becomes first-order. Strikingly, we find that if the angle between the pulling force and the surface is beneath a critical value, a sufficiently strong force will induce polymer adsorption, no matter how large the temperature of the system. Our findings are similar in two and three dimensions, an additional feature in three dimensions being the occurrence of a reentrance transition at constant pulling force for small temperature, which has been observed previously for this model in the presence of pure vertical pulling. Interestingly, the reentrance phenomenon vanishes under certain pulling angles, with details depending on how the three-dimensional polymer is modeled

Creative strategies to support student learning through reflection

Reflective practice has become a key attribute of promoting quality teaching and learning. Learning is an active process and include reflective writing, visualising and verbalising to promote critical thinking. In our experience most often than not superficial reflective writing is used. We explored the design of opportunities for students to engage in critical reflection. Theoretical data were obtained through in-depth exploration of the literature to allow contextualisation while arguing a case. A qualitative approach was used. Judgements were not made about the measured quality of reported findings, but on the relevance of reflective strategies to support students, enhance critical reflection and transform practice. Combined with narration and dialogue, reflection can bridge the gap between theoretical ideals and realities of the practice context. Four reflective activities have been identified that could be used to engage students in critical reflection

Incidence of heat-labile enterotoxin-producing Escherichia coli detected by means of polymerase chain reaction amplification

CITATION: Winterbach, R. et al. 1994. Incidence of heat-labile enterotoxin-producing Escherichia coli detected by means of polymerase chain reaction amplification. South African Medical Journal, 84:85-87.The original publication is available at http://www.samj.org.zaDiarrhoea can be caused by many different organisms, some of which are notoriously difficult to identify. One of these is enterotoxin-producing Escherichia coli. Recently a new diagnostic technique that uses polymerase chain reaction DNA amplification was developed for detection of the 'A' subunit of the labile enterotoxin-producing E. coli gene. This technique was used to evaluate the incidence of heat-labile (LT+) enterotoxin-producing E. coli in the causation of diarrhoea. The results from this study showed that LT+ E. coli is a cause of diarrhoea in the western Cape and that 5,3% of non-diagnosed diarrhoea patients in Tygerberg Hospital were infected with this pathogen. This represented less than 1% of the total number of cases of diarrhoea investigated in this hospital. The peak coincides with the wetter months in this locality and the infection rate is lower than that reported in most other countries. Given the low incidence of occurrence of this organism we do not recommend routine implementation of the diagnostic procedure. However, this test may be useful at times, e.g. to ascertain the source of a diarrhoea epidemic.Publisher’s versio

The cogrowth series for BS(N, N) is D-finite

We compute the cogrowth series for Baumslag-Solitar groups BS(N, N) = (a,b aNb = baN), which we show to be D-finite. It follows that their cogrowth rates are algebraic numbers. © 2014 World Scientific Publishing Company