Sabinet | Volume 23, Issue 1_2
Volume 23, Issue 1_2, 2004
Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Volume 23, Issue 1_2, March 2004
Volume 23, Issue 1_2, March 2004
Die voorgeskiedenis van kwantumberekening : research and review article
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 23, pp 2 –6 (2004)
Die hoofidees wat tans gestalte vind in die teorie en tegnologie van kwantumberekening is in die laat 1970's en vroeg 1980's deur fisici in die Weste en 'n wiskundige in die voormalige Sowjetunie neergelê. Dat dié teorie ook wortels in die Russiestalige vakliteratuur het, is nie algemeen bekend in die Weste nie. Daar word kortliks gekyk na die idee soos deur Benioff en (veral) Feynman in die Weste versprei, asook die voorstel van dié rekengrondslag deur Manin in die Russiese literatuur. Die outeur hoop om hiermee so 'n onpartydig moontlike sintese van die vroeë gedagtegeskiedenis rondom kwantumberekening aan te bied. Die rol van omkeerbare en onomkeerbare berekeningsprosesse word vlugtig bekyk soos dit verband hou met die ontstaan van kwantumberekening, asook die sogenaamde Inligtingsparadoks in die fisika. Die inligtingsteorie en die fisika het heelwat met mekaar te kommunikeer, soos hierdie paradoks uitwys.
<b>The pre-history of quantum computation</b> <br>The main ideas behind developments in the theory and technology of quantum computation were formulated in the late 1970s and early 1980s by two physicists in the West and a mathematician in the former Soviet Union. It is not generally known in the West that the subject has roots in the Russian technical literature. The idea, as propagated by Benioff and (especially) Feynman, is reviewed along with the proposition of a foundation for this kind of computation by Manin in the Russian literature. The author hopes to present as impartial a synthesis as possible of the early history of thought on this subject. The role of reversible and irreversible computational processes will be examined briefly as it relates to the origins of quantum computing and the so-called Information Paradox in physics. Information theory and physics, as this paradox shows, have much to communicate to each other.
Oogknipbeheerde rekenaarmuis : ontwerp en evaluering : research and review article
Authors: S. Viljoen, T. Hanekom and P.J. Cilliers
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 23, pp 7 –12 (2004)
Motories gestremde persone vind dit moeilik om 'n rekenaar te gebruik vanweë die feit dat hulle nie 'n muis kan beheer nie. In hierdie artikel word die ontwerp, implementering en evaluering van 'n oogknipbeheerde rekenaarmuis vir gebruik deur gestremde persone beskryf. Die deteksie van willekeurige oogknippe word deur middel van die weerkaatsing van infrarooi- (IR-) lig vanaf die vel langs die oog bewerkstellig, terwyl onwillekeurige knippe verwerp word. Dit stel motories gestremde persone, wat nie meer die gebruik van hul arms het nie, in staat om 'n rekenaar te bedryf. Al die funksies van 'n PS2-muis word geëmuleer.
<b>Eye-blink controlled computer mouse : design and evaluation</b> <br>Physically disabled people who do not have the use of their limbs have difficulty operating a computer, since they cannot use a mouse. In this article the design, implementation and evaluation of an eye-blink controlled computer mouse to be used by handicapped people are described. Detection of voluntary blinks is established by the reflection of infrared light from the skin on the side of the eye, while involuntary blinks are ignored. This enables people who do not have the use of their limbs to operate a computer. All the functions of a PS2 mouse are emulated.
Die gebruik van 'n reologiese tegniek in die bepaling van die verhardingsreaksiekinetika van 'n reaktiewe poliësterpoeierdeklaag : research and review article
Authors: O.C. Vorster and L. Halasz
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 23, pp 13 –21 (2004)
Die studie van die verhardingsreaksiekinetika van deklae word bemoeilik deur die aanwesigheid van vlugtige stowwe, pigmente en bypigmente. In hierdie studie word die verhardingsreaksiekinetika van 'n karboksielgetermineerde poliëstertriglisediel-isosianuraat deur middel van parallelplaatspanningsreometrie bepaal. Jeltye is verkry en skaleringseksponente bepaal. 'n Nuwe metode vir die voorspelling van die verloop van die reaksie word voorgestel en vergelyk met resultate verkry deur middel van differensiële skanderingskalorimetrie.
<b>The use of a rheological technique in the determination of the curing kinetics of a reactive polyester powder coating</b> <br>In this article a study of the curing process of carboxyl terminated polyester-triglycidyl isocyanurate systems is reported. A comparison is made between the generally used Differential Scanning Calorimetric methods and rheokinetic methods, using a parallel plate oscillating stress rheometer. Gel times were determined and scaling exponents calculated. A new method for the estimation of the extent of reaction is presented and compared with results obtained by means of differential scanning calorimetry
Die effek van probiotika op die simptome en immunoglobulienvlakke van prikkelbare dermsindroom : research and review article
Authors: M. Viljoen, M. Panzer, A. Koorts, P. Henn, J.B. Van den Bogaerde and E. Horn
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 23, pp 22 –24 (2004)
Die medisinale gebruik van natuurlike plantmateriaal en voedselaanvullings is vinnig besig om veld te wen. Probiotika word deur die Voedseldirektoraat van die Departement van Gesondheid as voedselaanvulling beskou en van hierdie preparate is reeds geregistreer. In hierdie dubbelblinde studie is die invloed van probiotika (Lactobacillus acidophilus en Bifidobacterium longum en bifidum) op die simptome en sirkulerende immunoglobulienvlakke van pasiënte met prikkelbare dermsindroom (PDS) ondersoek. Vier en twintig pasiënte wat aan die Drossman-kriteria vir die diagnose van PDS voldoen het, is gerandomiseer om óf probiotika óf plasebo vir 28 dae te ontvang. Die serumvlakke van die immunoglobuliene IgG, IgA en IgM, sowel as die gastrointestinale simptome, is voor en na behandeling bepaal. Die simptome is beoordeel volgens 'n klinies erkende skaal vir gastrointestinale versteurings. Die nabehandelingimmunoglobulienvlakke het nie betekenisvol van die voorbehandelingvlakke verskil nie. Al 12 pasiënte op probiotika het die 28 dae-behandeling voltooi en die verbetering in simptome was hoogs betekenisvol (p=0.0001). Van die plasebogroeppasiënte het gedurende die proeftydperk besluit dat die preparaat geen resultate lewer nie en die neem daarvan gestaak. Daar was 'n kleiner maar steeds betekenisvolle verbetering in die simptome van die van die 7 pasiënte wat die 28 dae-behandeling op plasebo voltooi het (p=0.0473). 'n Opvolgstudie word aangedui deur die resultate.
<b>The effects of probiotics on symptoms and immunoglobulin levels of patients with irritable bowel syndrome</b> <br>The medicinal use of natural plant materials and food supplements is gaining in popularity. The Food Directorate of the Department of Health considers probiotics as a food supplement. In this double blind controlled pilot study the effects of probiotic treatment (Lactobacillus acidophilus and Bifidobacterium longum and bifidum) were evaluated on the symptoms and immunoglobulin levels of patients with Irritable Bowel Syndrome (IBS). Twenty-four patients who fulfilled the Drossman criteria for the diagnosis of IBS were randomised to receive either probiotics or a placebo for 28 days. Immunoglobulins IgG, IgA and IgM were measured and symptoms were rated (according to a clinically recognised questionnaire serving as a rating scale for gastrointestinal symptoms in patients with IBS) before and after treatment. The improvement in symptoms was statistically highly significant in the probiotic group (p = 0.0001, paired t-test). Some patients treated with placebo decided that the treatment was ineffective and stopped taking it. The 7 who completed the trial showed an improvement in symptoms, but this was only marginally significant (p = 0.0473, paired t-test). Serum immunoglobulin levels did not differ significantly. Larger studies to confirm the beneficial effects of probiotic bacteria on the symptoms of patients with IBS are indicated.
Die impak van tutoriale op die wiskundeprestasie van eerstejaarstudente : research and review article
Authors: J.G. Maree, C.J. Louw and S. Millard
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 23, pp 25 –34 (2004)
Studente uit histories-agtergeblewe gemeenskappe in Suid-Afrika onderpresteer dikwels in wiskunde vanweë 'n verskeidenheid faktore. Aksienavorsing wat aan die (voormalige) Technikon Noord-Gauteng uitgevoer is, om ondersoek in te stel na wyses waarop hierdie studente se wiskundeprestasie verbeter kan word, het die implementering van 'n tutoriaalstelsel behels. Kwantitatiewe en kwalitatiewe data is deur middel van 'n verskeidenheid instrumente ingesamel. Die resultate het sekere tendense in tersiêre wiskundeonderrig, wat in 'n tweede of derde taal geskied, uitgewys.
<b>The impact of tutorials on achievement in mathematics of first year students</b> <br>Historically disadvantaged students in South Africa often underachieve in mathematics due to a number of factors. Action research that was conducted at the (former) Technikon Northern Gauteng to investigate ways in which these students' achievements in mathematics could be improved comprised the implementation of tutorial sessions. Quantitative and qualitative data were gathered by means of a variety of instruments. The results revealed certain trends in tertiary mathematics education where learning takes place in a second or third language.
Die plantfamilie ASTERACEAE : 6. Die subfamilie Asteroideae : general article
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 23, pp 35 –41 (2004)
Die tribusse van die subfamilie &lt;I&gt;Asteroideae&lt;/I&gt; word meer volledig in hierdie artikel beskryf. Die genusse wat aan dié tribusse behoort word gelys en hulle verspreiding aangedui.
<b>The plant family &lt;I&gt;Asteraceae&lt;/I&gt; : 6. The subfamily <I>Asteroideae</I></b> <br>The tribes of the subfamily Asteroideae are described in this article. Genera belonging to the different tribes are listed and their distribution given.