164 research outputs found
Effects of dietary changes on heat stress in broiler and Kampung chickens
No full text Poultry meat production has increased drastically over the last 35 years. Most developing countries are in the tropics and often have high ambient temperatures. At high ambient temperatures, chickens exhibit a slower growth rate due to a reduced feed intake. In order to limit the reduction in feed intake, a feeding strategy should be applied which decreases the level of heat production and/or increases the possibilities for heat dissipation. Such a feeding strategy can be based on feed that gives less heat because of lower energy costs of digestion or provides fewer nutrients that lead to a high heat production. This thesis studied how birds subjected to chronic heat stress change feed intake of especially crude protein and total energy. In addition, a wet feeding strategy that might alleviate the adverse effects of heat stress on performance was applied. Chickens exposed to choice feeding responded similarly at normal and at high ambient temperatures. They composed from a choice of a control diet, an energy rich diet and a protein rich diet a diet with a higher energy (HE) content and a lower protein content compared to the standard control diet. At high temperatures, chickens will reduce feed intake because they want to avoid or reduce a high body temperature. When the chickens were fed a wet-HE diet, feed intake and BW gain were higher in broiler chickens compared with feeding a dry-HE diet. The most beneficial effects of a wet diet occurred with a high energy diet. The indigenous Kampung chickens have been acclimatized to a high ambient temperature and did not benefit from a wet diet. In the present study, temperature had a major effect on relative lengths and empty weights of gastrointestinal tract segments in broiler chickens on day 42. Relative lengths of most gastrointestinal tract segments were affected by diet formulation at day 21 and 42, but not relative empty weight. Control-fed birds had shorter relative lengths than HE-fed birds, suggesting that the higher BW gain of control-fed birds were not accompanied by a similar increase in length of the gastrointestinal tract. Wetting the diet did not increase empty weights of intestines both at days 21 and 42. In Kampung chickens, effects of diet formulation on gastrointestinal tract development disappeared when the birds grew older, suggesting that this type of bird adapts easily to changes in dietary nutrient content. A positive effect of the relative weight of the intestine of birds fed a wet diet was observed in Kampung chickens. In general, it seems that the Kampung chickens grow proportionally but broiler carcass is growing faster than its gastrointestinal tract in control- and wet-fed birds. Key words: Self-selection, temperature, wet diet, broiler, indigenous chicken </p
Koos Kombuis: Ikonoklas na ikoon
No full textDie Afrikaanse skrywer en musikant Koos Kombuis word vandag wyd as \u27n ikoon beskou. In die 1980\u27s was hy egter \u27n randfiguur van die Afrikaner-establishment. Hoe het hierdie transformasie van ikonoklas na ikoon oor tyd plaasgevind? Kombuis het sy loopbaan as digter en skrywer in die 1980\u27s begin. Hy het homself aan die spits van die sogenaamde Tagtigerbeweging in die letterkunde bevind, en in 1989 het hy aan die berugte Voëlvry-toer deelgeneem wat sy status as dwarstrekker verskans het. Sy letterkunde en musiek van dié dekade het gepoog om die waardes en norme van die heersende Afrikaner-establishment omver te gooi. Die vroeë 1990\u27s het bepaalde veranderinge in sowel die breër sosio-politieke konteks van Suid-Afrika as Kombuis persoonlik gesien. Sy beeld onder Afrikaners het stelselmatig begin verander, en soos sy loopbaan in die jare sedertdien ontwikkel het, het hy algaande ikoonstatus bekom. Hierdie artikel stel ondersoek in na Koos Kombuis se transformasie van ikonoklas na ikoon binne Afrikaner geledere.
The Afrikaans author and musician, Koos Kombuis, is widely regarded as an icon today. In the 1980s, however, he was a fringe figure, arguably even an iconoclast of the Afrikaner establishment. How did this transformation from iconoclast to icon happen over time? Kombuis began his career as poet and author in the 1980s. He found himself as a leading figure of the so-called Tagtiger movement in Afrikaans literature, and in 1989 he participated in the Voëlvry tour which entrenched his image as an Afrikaner iconoclast. His literature and music of this particular decade attempted to overthrow the accepted norms and values of the reigning Afrikaner establishment. The early 1990s saw certain changes in the broader South African socio-political context as well as in Kombuis personally. His image among Afrikaners started changing and as his career developed in the years since, he gradually obtained icon status. This article investigates Koos Kombuis\u27s transformation from iconoclast to icon within Afrikaner society
Dawie de Villiers met Chris Schoeman, My Lewensreis: Springbok, Politikus, Diplomaat
No full textDawie de Villiers het deur die loop van sy lewe groot spore in die Suid-Afrikaanse samelewing getrap. Hy het bekendheid verwerf as Springbok rugbyspeler en kaptein in die 1960’s en vroeë 1970’s, waarna hy die politiek betree het. Na bykans ’n dekade op dieNasionale Party (NP) se banke in die parlement, is hy in 1979 na Londen as Suid-Afrika se ambassadeur daar. Met sy terugkeer na Suid-Afrika was De Villiers ’n sleutelspeler in die onderhandelings vir ’n nuwe, demokratiese Suid-Afrika. Sy outobiografie het dus die potensiaal om diep insigte oor ’n noemenswaardige Suid-Afrikaner se lewe te deel
An Experimental Approach to Study Drainage in Relation to Geometrical Features of Artificial Adhesives
No full textWith growing interest in wet adhesion, animals such as tree frogs are often used as paradigm for creating grippers in wet environments. Tree frogs are capable of attaching to surfaces under several conditions (smooth, rough, dry, wet, and flooded) due to the microstructure of their toe pads. This microstructure consists of pillar-shaped hexagonal cells separated by thin and deep channels. Drainage is an important phenomenon to consider, since too much liquid between the toe pad and surface results in a low adhesive force. Therefore, understanding the relationship between pillar-shaped microstructures and drainage can lead to the creation of adhesive pads that are functional in wet conditions and to other drainage related applications. Adhesives with a pillar-shaped microstructure were fabricated and their drainage speed was experimentally studied against a glass substrate. Gathering experimental data was accomplished by using Particle Image Velocimetry, and by using fluid velocity as a proxy for drainage. A custom-made set-up was built to accurately control the speed at which the adhesive and the substrate approached each other. Adhesives with various pillar diameters, pillar spacings, and pillar alignments were tested with fluids of various viscosities. It was found that the pillar diameter most likely has a significant effect on drainage, whereas the effect of pillar spacing and the effect of fluid type could not be determined. Pillar alignment did not have a significant effect on drainage. In future work, it is recommended to complement the findings of this thesis with adhesion and friction measurements to understand how drainage associates to adhesive force
On the analysis of refinable functions with respect to mask factorisation, regularity and corresponding subdivision convergence
No full textThesis (PhD (Mathematical Sciences))--University of Stellenbosch, 2007.We study refinable functions where the dilation factor is not always assumed to be 2. In
our investigation, the role of convolutions and refinable step functions is emphasized as a
framework for understanding various previously published results. Of particular importance
is a class of polynomial factors, which was first introduced for dilation factor 2 by
Berg and Plonka and which we generalise to general integer dilation factors.
We obtain results on the existence of refinable functions corresponding to certain reduced
masks which generalise similar results for dilation factor 2, where our proofs do not
rely on Fourier methods as those in the existing literature do.
We also consider subdivision for general integer dilation factors. In this regard, we extend
previous results of De Villiers on refinable function existence and subdivision convergence
in the case of positive masks from dilation factor 2 to general integer dilation factors.
We also obtain results on the preservation of subdivision convergence, as well as on the
convergence rate of the subdivision algorithm, when generalised Berg-Plonka polynomial
factors are added to the mask symbol.
We obtain sufficient conditions for the occurrence of polynomial sections in refinable
functions and construct families of related refinable functions.
We also obtain results on the regularity of a refinable function in terms of the mask
symbol factorisation. In this regard, we obtain much more general sufficient conditions
than those previously published, while for dilation factor 2, we obtain a characterisation of
refinable functions with a given number of continuous derivatives.
We also study the phenomenon of subsequence convergence in subdivision, which explains
some of the behaviour that we observed in non-convergent subdivision processes
during numerical experimentation. Here we are able to establish different sets of sufficient
conditions for this to occur, with some results similar to standard subdivision convergence,
e.g. that the limit function is refinable. These results provide generalisations of the corresponding
results for subdivision, since subsequence convergence is a generalisation of
subdivision convergence. The nature of this phenomenon is such that the standard subdivision
algorithm can be extended in a trivial manner to allow it to work in instances where
it previously failed.
Lastly, we show how, for masks of length 3, explicit formulas for refinable functions can
be used to calculate the exact values of the refinable function at rational points.
Various examples with accompanying figures are given throughout the text to illustrate
our results.Doctora
Estimates of Radiation Exposures to Crews on Missions in Cis-Lunar Space and on the Lunar Surface from the August 1972 SEP Event
No full textLawrence Townsend, University of Tennessee, USAWouter de Wet, University of New Hampshire, USAFahad Zaman, University of Tennessee, USAICES503: Radiation Issues for Space FlightThe 49th International Conference on Environmental Systems as held in Boston, Massachusetts, USA on 07 July 2019 through 11 July 2019.In work reported at the 2018 Intercontinental Conference on Environmental Systems, radiation doses in cis-lunar space for the August 1972 event, using the NASA design standard King spectrum, were compared with doses from the summed spectrum of the October 1989 series of events, recently-proposed as a new NASA design standard replacing the August 1972 event [1]. In this work we compare estimates of organ doses and effective doses, shielded by aluminum, for three representations of the August 1972 event spectrum: (1) King spectrum; (2) Langley Research Center spectrum; and (3) Band function representation. The estimates are made for missions in cis-lunar space and on the surface of Earth’s moon. Comparisons of organ doses will be made with NASA short-term exposure limits.
[1] Townsend, L.W.; Adams, J.H.; Blattnig, S.R.; Clowdsley, M.S.; Fry, D.J.; Jun, I.;, McLeod, C.D.; Minow, J.I.; Moore, D.F.; Norbury, J.W.; Norman, R.B.; Reames, D.V.; Schwadron, N.A.; Semones, E.; Singleterry, R.C.; Slaba, T.C.;Werneth, C.M.; Xapsos, M.A.: Solar Particle Event Storm Shelter Requirements for Missions Beyond Low Earth Orbit, Life Sciences in Space Research, Vol 17, May 2018, pp. 32-39. Doi.org/ 10.1016/j.lssr.2018.02.00
Estimates of Radiation Exposures to Crews on Missions in Cis-Lunar Space from the October 1989 Series of Solar Particle Events
No full textLawrence Townsend, The University of TennesseeWouter de Wet, The University of TennesseeFahad Zaman, The University of TennesseeICES503: Radiation Issues for Space FlightThe 48th International Conference on Environmental Systems was held in Albuquerque, New Mexico, USA on 08 July 2018 through 12 July 2018.In its 2008 report, the National Research Council recommended against the use of the King spectrum August 1972 solar energetic particle event as the design standard [1]. It was stated in the Council report that radiation exposures from other events in the historical record could exceed those from the 1972 event. Instead, the Council recommended that other events, such as the October 1989 event, be used in place of the 1972 event. In this work we present estimates of radiation exposures to male and female crew members in cis-lunar space from the summed spectrum of the October 1989 series of events and from the August 1972 King spectrum. These estimates are obtained for both aluminum and polyethylene shields, and compared to NASA short-term exposure limits.
[1] National Research Council. 2008. Managing Space Radiation Risk in the New Era of Space Exploration. Washington, DC: The National Academies Press. https://doi.org/10.17226/1204
Tendense in populêre werke oor Suid-Afrikaanse rugby,1948-1995: ’n Historiografiese studie
No full textAfrikaans
Die hervatting van internasionale rugby na die Tweede Wêreldoorlog het nuwe belangstelling onder rugby ondersteuners wêreldwyd gekweek. Tientalle populêre rugbyboeke het in die daaropvolgende jare in Suid-Afrika verskyn en rugby het een van die land se grootste sporte geword. Rugbyboeke het algemene items op Suid-Afrikaanse boekrakke geword. Hierdie artikel stel ondersoek in na die ontwikkeling van tendense in populêre Suid-Afrikaanse rugbygeskiedskrywing tussen 1948 en 1995. Tendense word geïdentifiseer en binne kontekstuele verband nagevolg deur middel van ’n noukeurige studie van die inhoud en stilistiese aspekte van die boeke. Daar word gekyk na wat in populêre rugbyboeke geskryf is, hoe daar geskryf is, en gevra waarom daar so geskryf is. Dit word duidelik dat hierdie tendense deur die veranderende politieke- en sosiale landskap van die twintigste eeu beïnvloed is. Die polities gemotiveerde betogings teen die Springbokke op oorsese toere, die uiteindelike internasionale sportboikot van die Springbokke, asook die koms van televisie in 1976 het elk ’n merkbare impak op Suid-Afrikaanse rugbygeskiedskrywing gehad.
English
The resumption of international rugby after the Second World War sparked a renewed interest in sport among supporters worldwide. In South Africa dozens of popular rugby books were published in subsequent years and rugby grew to be one of the country’s biggest sports. These rugby books became popular items on the South African bookshelf. This article investigates the tendencies in popular South African rugby historiography. Trends are identified in the changing political context from 1948 to 1995 and studied by means of an in-depth analysis of their content and stylistic aspects. Questions relating to what was written in popular rugby books, how it was written, as well as why it was written, are explored. It becomes apparent that these trends were influenced by the changing socio-political landscape of twentiethcentury South Africa. The politically motivated protests against the Springboks on tours overseas, the eventual boycott of the Springboks and the introduction of television to the country in 1976 all had a noticeable influence on popular South African rugby historiography. 
Tendense en tematologie in populêre werke oor Suid- Afrikaanse rugby, 1948-1995 : ’n historiografiese studie
No full textThesis (MA)-- Stellenbosch University, 2013.ENGLISH ABSTRACT: This is a historiographical study of popular rugby history covering the years 1948 to 1995.
The aim of this study is to show how this sport is portrayed in popular history writing. This
research will focus on the two forms of popular history during this time, namely general
rugby history books and biographical works. In order to fulfil its goals, this thesis will
identify tendencies and thematology in popular rugby history, as well as explore its
development over the years. This work lies on the edge between a study of history and that of
literature. By studying the content and literary aspects of the popular works, light will be shed
on its ever changing tendencies and thematology. Throughout this thesis, there will be
constant use of quotations in order to explain the development of popular rugby
historiography over time. By exploring the aforementioned complexities, this study aims to
make a contribution to the developing domain of South African sports history.AFRIKAANSE OPSOMMING: Hierdie studie is ’n historiografiese studie van populêre rugby geskiedskrywing, en dek die
jare 1948 tot 1995. Die doel is om te dui op hoe dié sport in populêre skrywes uitgebeeld is.
Die fokus gaan val op die twee vorme van populêre geskiedskrywing in hierdie tydperk,
naamlik algemene rugbygeskiedenisboeke en biografiese werke. Die manier hoe hierdie
verhandeling te werk gaan, is om tendense en tematologie in hierdie werke te identifiseer en
die verandering daarvan oor die jare, na te volg. Hierdie werk lê op die breekvlak tussen ’n
studie van die geskiedenis en die letterkunde. Deur die gewilde rugby skrywes inhoudelik en
letterkundig in fyn detail te bestudeer, gaan lig op die veranderende tendense en tematologie
gewerp word. Aanhalings word deurgans ingesluit en bespreek om die ontwikkeling van die
populêre rugby geskiedskrywing oor die jare te verduidelik. Deur op hierdie kompleksiteite
klem te lê, poog die studie om ’n bydrae te lewer tot die steeds ontwikkelende veld van Suid-
Afrikaanse sportgeskiedenis.Master
Knowledge, attitude and perception of private practitioners based in Gauteng, South Africa, regarding evidence-based practice
No full textBackground
Evidence-based medicine (EBM) involves the care of patients using the best available evidence from the results of good quality clinical research to guide clinical decision making 1 – 3. By incorporating the principles of Evidence-based Medicine (EBM), the family practitioner would be able to treat a patient according to the best clinical research available. This principle is implemented widely in the USA, Canada, the United Kingdom and Europe. In South Africa, however, EBM is not yet as widely incorporated into family practice. This is so despite the plethora of websites available to practitioners and the relative ease with which applicable research evidence can be found.
Very few published studies are available regarding EBM or Evidence–based Practice (EBP) in the South African context. The findings of this study would thus highlight reasons and/ or barriers preventing family practitioners from implementing EBM in their respective practices. This could also lead to further research into possible methods of implementation of EBM into South African family practices.
Aim:
The aim of the study was to describe the perceptions, knowledge and attitudes of private practitioners regarding evidence based practice and to identify the barriers encountered in evidence based practice.
Methods
A questionnaire survey of general practitioners in Gauteng, South Africa, was conducted. Questionnaires were distributed to a random sample of practitioners in the Gauteng region. Two hundred and twenty one (221) practitioners participated in the survey and responded to questionnaires mailed to them. The questionnaire was mailed, faxed or e-mailed to the practitioners, which they then completed and returned for statistical analysis.
Study design
The study design is that of quantitative, statistical analysis (descriptive cross-sectional survey).
Setting
General practitioners were randomly selected from a list of practitioners in the Gauteng Province. Doing a nationwide survey would have been a mammoth undertaking. It was therefore decided to limit the research to one province and therefore it was only concentrated on practitioners practicing in the Gauteng area.
Results
It is interesting to note that of the two hundred and twenty one participants in this study; only 10% of the practitioners were against using EBM in their practices. This, however, stands in stark contrast to the 56% of practitioners who do not implement EBM in their practices or make use of the EBM principle at all. The major barriers preventing practitioners from implementing EBM is depicted in the following graph: Lack of time and the training in aspects of Evidence-based medicine were the main barriers preventing the full scale implementation of EBM in family practices in Gauteng.
Conclusion
Participating Gauteng doctors were in principle, very positive towards the implementation of EBM in their respective practices. Most of the participants agreed that EBM would benefit their patients’ care and treatment. Very few of the participants, however, make use of EBM in practice. A lack of training and time constraints were the main barriers with regards to the implementation of EBM. Proper training of medical students at undergraduate level at faculties of health sciences, would go a long way assisting prospective doctors in mastering the concept of EBM and increasing their overall awareness of EBM. Further definitive research would assist in establishing whether such awareness would be associated with improved implementation of evidence in the form of evidence based guidelines in practice.AFRIKAANSE OPSOMMING: Geen opsomming beskikbaa
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