bluuebunny/crossref_metadata_2025 huggingface dataset:
Die meting van die suurstofbindingseienskappe van hemosianien met die hulp van ’n dunlaag optiese sel
Authors: Van Aardt W. J.
Published: July 2013

The merits of the thin-layer method of Dolman and Gill to study the oxygen binding of haemocyanin were experimentally tested with haemocyanin obtained from arthropods and molluscs. The results show that, spectrophotometrically, oxyhaemocyanin from both arthropods and molluscs has a prominent absorption peak between 335 and 345 nm. Haemocyanin is more stable in the thin- layer preparation when compared with haemoglobin. At 35 °C a decrease in the initial absorbance value of less than 2% was found after three hours. For haemoglobin the initial value decreases nearly 10% during the same period. For a high-affinity haemocyanin such as Marisa cornuarietis (P⁵⁰ = 1,07 mmHg) the thin-layer method of Dolman and Gill (1978) shows better PO₂ resolution than other methods. The reason for this is that the dilution valve, which is absent in other thin-layer methods, intrinsically measures the resultant PO₂ values at very low tensions more accurately. In this study a step-by-step explanation of the technique is given. The calculations have been explained using real figures and examples. It is hoped that this detailed description will make this technique more readily available for use by respiratory physiologists.
Genetiese manipulering van die gis Saccharomyces cerevisiae betreffende polisakkariedbenutting
Authors: Pretoruis I. S.
Published: July 2013

Die gis Saccharomyces cerevisiae word wêreldwyd as die belangrikste kommersiële mikro-organisme bestempel en geniet sogenaamde ABAV-status (Algemeen Beskou As Veilig) weens dié gis se eeue lange verbintenis met voedselproduksie (bv. brood, wyn, bier, proteienaanvulling en geurstowwe).
Die effek van heksavalente chroom by 'n variërende water-pH op die koolhidraatmetabolisme van Tilapia sparrmanii (Cichlidae)
Authors: Wepener V. , Van Vuuren J. H. J. , Du Preez H. H.
Published: July 2013

The effect of hexavalent chromium at different pH values on the carbohydrate metabolism of Tilapia sparrmanii was investigated. The indicator organisms were exposed to Cr(V1) for short and long-term exposures, after which the blood glucose levels and activities of pyruvate kinase, isocitrate dehydrogenase and glucose-6-phosphate dehydrogenase were determined. It was found that short-term exposures of Cr(V1) at an acidic medium caused an increase in energy production and glucose concentrations. Long­ term exposures led to exhaustion of carbohydrate reserves, which necessitated the formation of additional energy compounds.
'n Vergelykende studie van die kariotipes van Tilapia rendalli, Tilapia sparrmanii en Oreochromis mossambicus (Cichlidae)
Authors: Swanepoel A.
Published: July 2013

Optimal chromosome preparations were obtained from stimulated lymphocyte cultures with a new method based on a combination and modification of several techniques. Tilapia rendalli, T. sparrmanii and Oreochromis mossambicus have somatic chromosome numbers of 44, 42 and 44, respectively. Chromosome pairs L1 and L2 are easily identified in all the karyotypes and distinctive of the tilapias. Tilapia sparrmanii has one additional large metacentric chromosome pair(L3), which occurs concurrently with the reduction of two in the total chromosome number. The F chromosomes were divided into two groups, viz a submetacentric (sm) and a telocentric (t) group. T. rendalli has 8 sm chromosomes, while both T. sparrmanii and O. mossambicus have 6 chromosomes in the sm group. The rest of the F chromosomes were telocentric. The identification of the sex chromosomes in the karyotypes of tilapia has thus far not been possible using standard techniques.
Agoniste en reseptore verantwoordelik vir die aktivering van bloedplaatjies: 'n kort oorsig
Authors: Van Rijswijk A. W. , Du Toit A. E.
Published: July 2013

Few fields of physiology have been so intensely studied in the past decade as the function of platelets. This interest is partly due to the increasing realization of the important role of platelets in the body, not only during hemostasis but in other physiological processes such as phagocytosis, inflammation, immunological reactions and interaction with tumor cells. Platelet activation is regulated by specific mechanisms, many of which are unknown.
Die implementering van 'n akwatiese toksisiteitsindeks in die monitering van die Olifantsrivier (Nasionale Krugerwildtuin)
Authors: Wepener V. , Van Vuuren J. H. J. , Du Preez H. H.
Published: July 2013

No absract
Sirkadiese fluktuasies in serumserotonienkonsentrasies van normale gesonde mans
Authors: Office Editorial
Published: July 2013

The biogenic amine, serotonin (5-HT), is synthesized from tryptophan (an essential amino acid) and acts multipotent as neurotransmitter/neuromodulator/hormone/precursor for methoxy-indole compounds such as N-acetyl-5-methoxytryptamine (melatonin). The circadian secretion pattern of melatonin is well known. Circadian fluctuations in pineal gland (“central”) concentrations of 5-HT have already been reported in literature. Since information with regard to possible circadian fluctuations in “peripheral" (plasma/serum) serotonin concentrations is scanty, the main objective of this study was to ascertain whether such fluctuations do in fact occur. Serum serotonin concentrations were determined in blood samples obtained hourly from twelve healthy male subjects during a period of 24 hours. The results clearly suggest a triphasic secretion pattern for serum serotonin. (The said circadian secretion tendency does not correspond with that of any determinable 5-HT metabolite).
Die bepaling van die kragverspreiding in die drakabel van ’n sweefspoor
Authors: Vermeulen P. J.
Published: July 2013

The analysis of the forces in the uniform carrying cable of a cableway, used for conveying ore to an enrichment plant, is described. For the purpose of the analysis the problem is considered as a static equilibruim problem. The elasticity of the cable, its motion relative to the pylon supports after loading with carts, the weights of the loaded ore carts, and the forces exerted by the towing rope are taken into consideration. Since the cable is pulled taut the influence of bending moments is negligible and consequently the cable may be considered as a perfectly flexible cable that may be modelled by discrete modelling. In particular, use is made of a point mass model. The analysis gives the maximum tensile force and the corresponding position of this force for different representative positions of the loaded carts along the carrying cable. This enables the computation of safety factors for different types of cables.
Die berekening van die stukrag van ’n vuurpylmotor
Authors: Knoetze J. H.
Published: July 2013

Traditionally the thrust of a rocket motor is calculated by first calculating the thrust coefficient and then multiplying it by the product of the throat area and pressure. The thrust coefficient is calculated using a standard gas dynamics equation. This equation assumes that the combustion products are a single component, non-reacting ideal gas and that the flow through the nozzle is isentropic. The thrust coefficient is a function of the ratio of specific heats, y, the area ratio of the nozzle and the motor and ambient pressures. Standard methods exist for calculating the tosses due to deviations from the assumed flow. The combustion products of modern composite propellants contain a significant portion of condensed species (primarily A1₂O₃), while the composition of the combustion products changes continuously as the products move throught the nozzle. Some uncertainty therefore exists with regard to which value of y to use and how to handle the condensed species. The assumption o f an ideat, non-reacting gas can be el iminated hy as.mming the process to he isentropic and to calculate the thrust hy using the thermodynamic state and composition of the combustion products in the motor and nozzle exit. This can be achieved by using any of the standard thermochemistry programs available in the rocket industry. It is thus possible to use the results of a standard thermochemistry program directly in an alternative method for calculating thrust. Using this method only the mass flow rate (which is a function of pressure, throat area and effective caracteristic velocity) and the results from the thermochemistry program are needed to calculate the thrust. The advantages of the alternative method are illustrated by comparing the results of the two methods with a measured thrust curve.
Benutting van landbouneweprodukte en gesuiwerde rioolwater in akwakultuur in ontwikkelende gebiede van Suid-Afrika
Authors: Prinsloo J. F.
Published: July 2013

The serious shortage of potable water supplies for domestic, agricultural and industrial requirements necessitates an investigation into the optimal utilization of this scarce commodity in South Africa. The multipurpose use of water in agriculture through its effective utilization in integrated aquaculture-agriculture food production systems is one way of optimising the application of such water. In the present series of investigations, agricultural wastes such as chicken, cattle and duck manure were applied as organic nutrient in freshwaterfish ponds with and without supplementary feeds. Fish used in polyculture production for the optimal utilization of the various trophic levels in manured fishpond ecosystems included the European and Chinese carp species and the sharptooth catfish. Supplementary food consisted of 18-45% protein fish pellets. As an alternative to organic manures, treated sewage effluent with fish pellets was used to evaluate its fish-production potential. Fish species used in monoculture and polyculture production included the European common carp and the sharptooth catfish. The role of water temperature on the fish-production potential of these systems was also investigated. The possible value of integrated aquaculture-agriculture systems in protein production in rural community development in South Africa is discussed.
Korrespondensie
Authors: Office Editorial
Published: July 2013

No abstract
’n Toetskriterium vir kategorieel kompakte ringe
Authors: Office Editorial
Published: July 2013

The Kuratowski-Mrowka theorem - a topological space X is compact if and only if for each space Y the second projection map ∏₂:X x Y → Y is a closed map - provides for a categorical interpretation of compactness once a suitable notion of closure is obtained. In this article we study a general notion of compactness with respect to a class F of ring’s that is either hereditary semisimple or quotient reflective. We show that to test for categorical compactness of a ring R we need only check R R F, where R F = ∩{D D is an ideal of R and RD є F} , and to test ∏₂:(RRF)x H → H for rings H belonging to F as opposed to arbitrary H.
Die subletale effekte van die organochloriede dieldrien en lindaan op groei en voortplanting van Eudrilus eugeniae en Eisenia fetida (Oligochaeta)
Authors: Office Editorial
Published: July 2013

Experimental exposure of the earthworm species Eudrilus eugeniae to organochlorines showed that dieldrin causes damage to sperm ultrastructure when viewed electronmicroscopically. Worms containing concentrations of 7,27 mg/kg dieldrin and higher showed more than 10% sperm damage. Exposure of Eisenia fetida to sublethal concentrations of lindane did not result in sperm damage but demonstrated an increase in growth and reproductive activity. It is argued that quantification of sperm damage and correlation with pesticide concentration could provide a useful tool for evaluating environmental quality. Furthermore, the effects of sublethal concentrations of pesticides that manifest themselves in increased growth and reproductive activity could affect ecological balances.
Die gebruik van lasers in geneeskunde
Authors: Roux P.
Published: July 2013

The acronym laser stands for “light amplification by stimulated emission of radiation”. The basic principles by which light energy from a laser is generated is discussed briefly. The different types of lasers are mentioned. The diagnostic and therapeutic uses of lasers in medicine are discussed in greater detail.
’n ⁹⁹ᴹTc-verbinding vir miokardiale perfusiebeelding
Authors: Office Editorial
Published: July 2013

Imaging of the myocardium with ⁹⁹ᴹTc labelled methoxy isobutyl isocyanide (MIBI) is an important examination in the management of patients with coronary artery disease. In this study MIBI (UVHART) was locally synthesised, evaluated in baboons and clinically used. The synthesis was a three-step process, after which UVHART kits were prepared, freeze dried and tested for pyrogenity and sterility.
Die byniere van die Afrika-olifant (Loxodonta africana): enkele waarnemings. 1. Die kapsel, zona glomerulosa en zona fasciculata
Authors: Strassberger F. G. W. , Nel M. M. , Nel P. P. C.
Published: July 2013

The structure of the capsule, zona glomerulosa and zona fasciculata of the African elephant (Loxodonta africana) is described. The gland is surrounded by a connective tissue capsule from which connective tissue trabeculae extend towards the medulla. The arrangement of the cells in the zona glomerulosa and the zona fasciculata are similar to that described for other mammals. Two types of cells are found in the zona glomerulosa and three types in the zona fasciculata. Organelles in these two zones are as described for other cells that secrete steroids. Unidentified structures were observed in the zona fasciculata.
Gradogramme - ’n nuwe hulpmiddel vir kladistiese taksonomie
Authors: Burger I. C. , Heidema J. , Labuschagne W. A. , Meyer T. A. , Van Wyk B. E.
Published: July 2013

Cladistic taxonomists classify organisms with the aid of cladograms. A method is proposed that will serve as an aid to the cladistic taxonomist in drawing up the final most confirmed cladogram. The method is based on the construction of composite preference relations.
Die invloed van die neshope van die graanvretende mier Messor capensis op Karoo-plantegroei
Authors: Dean W. R. J.
Published: July 2013

The influence of harvester ant Messor capensis nest-mounds on plants in arid shrubland was investigated at Tierberg, Prince Albert, Cape Province, during 1991. Nest-mound soils contained significantly more phosphorus, potassium, nitrogen and organic matter than surrounding soils. Nest-mound soils also contained more viable seeds than the soil of inter-mound spaces, and more seedlings germinated on nest-mounds than in inter-mound spaces.
Elektronpresipitasie in die bo-atmosfeer te Sanae
Authors: Stoker P. H.
Published: July 2013

Auroral light emissions are due to collisional processes of electrons with atmospheric constituents and occur primarily above 100 km in the ionospheric E- and F-layers, according to studies on excitation of emission lines. The absorption of about ten metre wavelength cosmic radio noise energy, as observed by riometers, occurs mainly below 90 km due to an increase of electron concentration in the ionospheric D-layer. Because auroral luminosity and auroral absorption are produced mainly by electrons in different energy regions, simultaneous observations will provide information on the energy spectrum of the incident electrons and on spectral changes of these precipitating electrons during auroral events.
Die invloed van haelnette op die prestasie van tafeldruiwe Vitis vinifera (L.) in die somer- reëngebied
Authors: Avenant J. H.
Published: July 2013

The long term effect of black hail netting (20% shading) on budding percentage, but fertility, cane mass, yield, bunch mass, berry mass and berry cracking as well as sugar concentration (total soluble solids), acid concentration (titratable acidity) and pH of the berry juice of table grapes (cultivars Pirobella, Bien Donne, Ronelle and Italia) was evaluated. Budding percentage and bud fertility were significantly reduced by hail netting. Reproductive growth in terms of yield and bunch mass seemed to be higher under hail netting compared to direct sunlight, while berry mass was not affected. Berry cracking tended to decrease under hail netting. Berry sugar concentration and pH decreased significantly under hail netting, while the acid concentration increased.
’n ln vitro - vloeikamer as model om die hemostatiese funksie van lewende in situ-endoteelselle te bepaal
Authors: Meiring S. M. , Kotzé H. F. , Pretorius G. H. J. , Badenhorst P. N.
Published: July 2013

Cultured human umbilical cord endothelial cells are mostly used to study the response of endothelium to various stimuli. The effect of the culture process on cell function is however, not known and the function of endothelial cells from different anatomical loci differs. In view of this we developed a flow chamber to study the function of fresh endothelium. The flow chamber was designed to accommodate a five cm piece of baboon aorta in a closed circuit where six hours of perfusion of the aorta with Ringer’s lactate/dextrose buffer at 37 °C was maintained by a peristaltic pump.
Die voorspellingswaarde van basale follikel - stimuIerende hormoonvlakke gedurende geassisteerde reproduksie
Authors: Huyser C. , Fourie F. Le R. , Pentz J.
Published: July 2013

No abstract
Sperms verklap omgewingsbesoedeling
Authors: Reinecke A. J.
Published: July 2013

No abstract
Getuienis dat termoïnhibering en die opheffing daarvan deur suurstof plus kinetien by Great Lakes - slaaisaad verband hou met mitochondriale funksie
Authors: Small J. G. C.
Published: July 2013

Thermoinhibition of Lactuca sativa L.cv. Great Lakes 659 seeds occurred at 36 ˚C. Thermoinhibition was alleviated by a combi­nation of 100% O₂ and kinetin (10 mg dm⁻³). Chloramphenicol nullified the effect of O₂ plus kinetin. A number of mitochondrial activities (respiration, coupling, certain matrix enzyme activities and incorporation of [³⁵S]- methionine in mitochondrial proteins) were lower in thermoinhibited than in seeds imbibed at 25 ˚C. Treating seeds with plus kinetin at 36 °C restored these mitochondrial activities to the same or in some cases, to higher levels than in 25 °C control seeds.
Die implementering van ’n kleinste-kwadrate- algoritme vir die frekwensiebepaling van ’n protonpresessiesein
Authors: Office Editorial
Published: July 2013

An advantageous signal processing technique for estimating the frequency of a time-limited noisy sinusoidal signal has been implemented. The method is a least squares technique and is especially powerful when the estimation has to be done in the shortest possible time measured in terms of signal period, as is the case with the precession signal present in a proton magnetometer. The criterion for evaluating the performance is the minimum measuring time for a given error or the minimum error for a given measuring time. This technique is compared with the accepted way of measuring and the results show a considerable improve­ment.
Die Zebra-battery - ’n Suid-Afrikaanse aanspraakmaker in die elektriesevoertuigbedryf
Authors: Coertzer J. , Nolte M. J.
Published: July 2013

The Zebra battery is one of the most promising power sources for electric vehicles which might be on sale before the year 2000. It is a South African development which started at the CSIR and is at present jointly managed by the Anglo American Corpora­tion of S.A. and the German company A.E.G. The chemical reaction converts common salt and nickel to nickel chloride and sodium during the charging phase.
Enkele voorbeelde van die wisselwerking tussen samestellers en gebruikers van vakwoordeboeke
Authors: De Villiers W. Van Z.
Published: July 2013

No abstract
Faktore wat die fenologie van Ursinia cakilefolia, ’n efemeer van Namakwaland, beïnvloed
Authors: Steyn H. M.
Published: July 2013

The aim of this study was to investigate the effect of temperature and sowing date on the phenology of Ursinia cakilefolia, a Namaqualand ephemeral species. Seeds were sown on different dates and plants were subjected to various temperature treatments. Sowing date had a distinct effect on the growth and phenology of the plants. From the results it seems that temperature plays an important role in the timing of phenological stages. However, the effect of temperature differed between sowing dates. The plant's response to temperature is apparently modified by the prevailing photoperiod, although it may also be due to an endogenous rhythm. Generally it seems as if plants require cold temperatures from sowing until the initiation of flower buds, after which the plants need heat for anthesis and further development.
Masjienvisie in die landbou
Authors: Gouws J.
Published: July 2013

This paper provides an overview of the use of machine vision in agriculture. Agriculture is practised in a more natural environment than most industrial undertakings, implying that agricultural automation requires robotic systems with well developed sensory abili­ties. For such systems, machine vision is an essential component. In this paper examples are used to show that the use of machine vision is already widespread in agriculture, and that there are many more potential applications for this technology. It is also indicated that machine vision in agriculture does not only hold potential financial advantages, but that it can also contribute to improved quality of life for agricultural workers, and even for farm animals.
Tegnieke vir die verbetering van die akkuraattieid van frekwensiemetings op protonpresessieseine
Authors: Office Editorial
Published: July 2013

A statistical data processing technique has been implemented by which a significant improvement in accuracy can be achieved when measuring the frequency of noisy sinusoidal signals with an exponential amplitude decay as is the case with free proton precession signals (originating from a proton magnetometer sensor), where the highest accuracy is desired for the shortest observation time. A least square error curve fit method was used and weighing factors were introduced to compensate for the exponential decay of the signal into the noise floor. Additionally, a hardware demodulation process was implemented, enabling a higher quantizing accuracy to be achieved using the same frequency counter clock. Both techniques were realised with appropriate hardware and software and the results confirm the improvement in accuracy.
Epididimis: van hoofspeler tot bysaak?
Authors: Fourie M. H. , Bornman M. S. , Oosthuizen J. M. C.
Published: July 2013

During epididymal transit, sperm acquire the capacity for fertilization and progressive motility. The epididymis is functionally and mechanically indispensable for in vivo fertilization, but technology has progressed rapidly in the field of in vitro fertilization. Modern sperm-injection techniques have dispensed with the epididymis as a necessity in the treatment of individual infertile couples.
Die verband tussen zona pellucida(ZP)-afmetings en sekere geassisteerde bevrugtingsparameters tydens die behandeling van pasiënte
Authors: Du Plessis A.
Published: July 2013

Verskeie navorsers beweer dat ’n verdikte ZP moontliklik ’n negatiewe invloed op bevrugting, blastosistuitbreking, implantasie van die embrio en sodoende swangerskapsuitkoms het.
Ranteveldplantegroei van Klerksdorp, Noordwes Provinsie, Suid-Afrika
Authors: Van Wyk E.
Published: July 2013

This project investigates the vegetation of the fragmented ridges in the Klerksdorp Municipal area. Motivation for this study lies in the fact that these areas are being threatened by development, e.g. new residential areas, industrial sites and oilier disturbances. This vegetation study forms part of a proposed base plan for the development and conservation of this area.
Elektromagnetiese modelle vir elektriese spoorbaanstelsels
Authors: Steyn B. M. , Van Wyk J. D.
Published: July 2013

The use of electromagnetic models is very expedient when railway track circuits are designed or when their operation is being studied. These electromagnetic models include models for performance analysis of the different types of track circuits as well as models used to study the effect of electromagnetic interference. Before these models can produce useful results they all require accurate input parameters. These parameters include the transmission line parameters of the track and the traction current distribution along the length of the track. Models that have been developed for these parameters are presented in this paper, together with an overview of the available track circuit models.
’n Geochemiese en geofisiese ondersoek van ’n groep kors - en bomantel - insluitsels van die Venetia - kimberlietpype, Limpopo - gordel, Suid-Afrika
Authors: Pretorius W.
Published: July 2013

No abstract
Vervaardiging en karakterisering van CuInSe₂/CdS/ZnO-dunlagiesonselle
Authors: Alberts V.
Published: July 2013

Efficient thin film solar cells were fabricated using CulnSe absorber fi lm s obtained from the selenization (in H,Se/Ar atmosphere) o f InSe/Cu and InSe/Cu/lnSe metallic alloys. The material properties o f the CuInSe₂ layers and efficiencies of completed devices were critically influenced by the nature of the metallic alloys before the selenization step. Optimum material properties were obtained when InSe/Cu/InSe alloys were selenized in H₂Se/Ar while ramping the temperature between 200 °C and 400 °C.
Ontwikkeling van ’n studie-oriëntasievraelys in wiskunde
Authors: Maree J. G. , Schoeman W. J.
Published: July 2013

The aim of this study was to standardize a study orientation questionnaire in mathematics for learners from all language groups in South Africa. The population was defined as all learners taking mathematics in Grades 8 and 9, and in Grades 10 and 11 in high schools in South Africa. A stratified, random, two stage sample was then drawn. Statistical analyses included determining of reliabil­ity, intercorrelations (with a view to establishing criterion-related validity), norm determining and intercorrelations between factors. The data obtained were analysed by means of statistical techniques including MANOVA, ANOVA and the Scheffé test. Results are discussed. It is concluded that the questionnaire could be a useful instrument for use in classrooms in South Africa.
Oriëntering en navigering by voëls
Authors: Bouwman H.
Published: July 2013

How birds orientate and navigate over long distances, remains one of the subjects of ornithology eliciting much interest. Birds use combinations of different sources of information to find direction and position. Some of these are the geomagnetic field, celestial bodies, mosaic and gradient maps, sound, smell, idiotetic information and others. Different species use different combinations of sources. This ability is partially inherent and partially learned.
Die rol van die natuurwetenskaplike in samelewingsontwikkeling - uitdagings vir Suid-Afrika
Authors: Van Eldik P.
Published: July 2013

International and local trends and experiences confirm the importance of reassessing; the role and responsibilities of scientists in South Africa. Revised strategies for human resource development, equipped with scientific and technological expertise and skills, offer tremendous challenges to scientists and the higher education system of the country. Simultaneously the contributions of scien­tists, through their involvement in research and development, to new knowledge as well as the application and utilisation of knowledge in new processes, products and technology transfer, is of vital importance for the economic development of South Africa.
Reaktor - optimering vir die vervaardiging van homogene grootoppervlak amorfe silikon-sonselle
Authors: Saunderson J. D.
Published: July 2013

Results are presented on the optimisation of the configuration of a large area pilot plant for the production of thin films of hydrogen­ated amorphous silicon (a-Si:H). The basic design of the reactor is discussed, and the correlation between the configuration inside the reactor and the resulting homogeneity of the material is demonstrated. It is indicated that the homogeneity is mainly determined by the shape of the antenna, the distance between the antenna and the substrate, the direction and position of the gas inlet and the dilution of the reactive gasses with hydrogen. A homogeneity factor of 2,5% was obtained across a substrate area of 320 mm x 300 mm.
Die moontlikhede van ’n gedifferensieerde modulêre wiskundekurrikulum vir die RSA se sekondêre skole
Authors: Maree J. G. , Kriek C. G.
Published: July 2013

The scientifically orientated teacher of mathematics is constantly trying to refine and improve the existing practice of teaching and learning mathematics. This is achieved by implementing the scientific insights, which are gained by research. The field of curriculum development in mathematics represents one possible field for research concerning mathematics. In this article, guidelines with regard to the possibility of a differentiated, modular mathematics curriculum for secondary schools in the RSA are given.
Van Seaborg tot sokkerballe: nuwe chemiese elemente en verbindings
Authors: De Villiers W. Van Z.
Published: July 2013

In hierdie bydrae word ’n aantal nuwe elementname en chemie - terme bcspreek, en ’n groepie ou terme weer behandel.
Kompensasie vir die invloed van die elektriese veldsterkte op die bepaling van die bewegingshoek van ’n vliegtuig
Authors: Office Editorial
Published: July 2013

During flight large voltage differences can develop between isolated sensors on the wingtips of an aircraft. This is as a result of charge differences in the atmosphere under the influence of the earth's electrostatic field. These charge differences can be utilised for aircraft attitude measurements. An electrostatic sensor has been developed to measure these charge differences.
Hoe om ’n vakkundige verslag saam te stel
Authors: Pienaar W. J.
Published: July 2013

Guidelines are supplied for the effective structuring of reports on specialist research conducted for a client. The requirements for a report's title, abstract, table of contents, body (introduction, subject under discussion, conclusions and recommendations) are discussed. Advice is given on the sensible use of appendices and illustrations (tables, figures, maps and photographs) to enhance readability and intelligibility. Eight methods of selecting a subject for each chapter and the sequence in which they should appear in order to enhance impact are discussed.
Modelle in die onderrig van fisika
Authors: Smit J. J. A.
Published: July 2013

The role of models in the teaching of physics has been recognised since die early eighties. At present the emphasis in teaching is on the quantitative aspects of physics. Insufficient attention is paid to the qualitative aspects. The consequence is that high school pupils university students and even teachers have problems to understand physics.
Meertalige Terminologielys: HIV/VIGS
Authors: Alberts M.
Published: July 2013

No abstract
Hoe om ’n vakkundige verslag te skryf
Authors: Pienaar W. J.
Published: July 2013

Guidelines are supplied for effective report writing on specialised research conducted for a client.
Die effek van subletale dosisse mangaan op die getal witbloedseltipes van die bloukurper Oreochromis mossambicus
Authors: Barnhoorn I. , Van Vuren J. H. J. , Du Preez H. H.
Published: July 2013

Metal ions have become an increasing source of pollution in the natural waters of South Africa. This phenomenon is related to the increasing industrial, mining and agricultural activity along rivers.
Die Kruidfontein Karbonatietkompleks, Suid-Afrika: geologic, petrologie, geochemie en ekonomiese potensiaal
Authors: Office Editorial
Published: July 2013

The Kruidfontein Carbonatite Complex (1243 ± 171 Ma) is an example of an intracontinental caldera system which is related to carbonatite activity and mineralisation.
Die weidingekosisteem in ’n vinnig veranderende omgewing
Authors: Snyman H. A.
Published: July 2013

The requirements in managing the grassland ecosystem for sustainability are evaluated.
Die evaluering van ’n visgesondheidsindeks in die Olifantsrivieropvanggebied
Authors: Watson R. M. , Avenant-Oldewage A.
Published: July 2013

No abstract
’n Dekade jaarkongresse van die Suid-Afrikaanse Vereniging vir Atmosferiese Wetenskappe
Authors: Lutjeharms J. R. E. , Roos D. V.d. S.
Published: July 2013

The establishment of a national society for the furtherance of a specific scientific discipline is an important milestone for the development of such a discipline in any country.
Die Hubble-Ruimteteleskoop: ’n Kort Oorsig
Authors: Koen C.
Published: July 2013

Telescopes are placed in orbit around the earth in order to avoid the adverse influence of the earth's atmosphere on radiation from outer space.
Die gebruik van ordeningstegnieke vir die evaluering van rehabiliteringsukses op asdamme geassosieer met steenkoolgedrewe kragstasies
Authors: Morgenthal T. L. , Cilliers S. S. , Kellner K.
Published: July 2013

Ecological monitoring of rehabilitated plant communities can be useful to improve the management of rehabililated areas.
Waterkwaliteit van die Modderrivier
Authors: Koning N.
Published: July 2013

Seasonal and spatial patterns in the Modder River system, the influence of Botshabelo's sewage outflow’ on the water quality of the river, as well as the presence of any toxic compounds were determined. The Modder and Klein Modder Rivers do not follow distinctive seasonal patterns in terms of chemical parameters.
Opleiding van elektriese en elektroniese ingenieurs met groter klem op inligtingstegnologie
Authors: Gouws J.
Published: July 2013

This paper focuses on the question whether, or not, more components of information technology should be included in the curricula for training of electrical and electronic engineers. Foreign trends are briefly analysed, based on 61 advertisements of vacancies at academic institutions and in the American government and industry.
P.B.B. Vosloo — Wetenskaplike en Wateringenieur
Authors: Haarhof J.
Published: July 2013

Piet Vosloo was ’n merkwaardige mens wat ’n breë spoor op die Suid-Afrikaanse watergemeenskap gelaat het, en ’n onuitwisbare indruk op vele kollegas, eweknieë en vriende gemaak het.
Histopatologiese veranderinge in die testis van Oreochromis mossambicus (Ciehlidae) na blootstelling aan koper
Authors: Pieterse G. M.
Published: July 2013

Koper is een van die swaar metale wat algemeen inmynbou-, industriële, landbou- en stedelike uitvloeisels voorkom. In hoë konsentrasies is koper ’n potensiële besoedelstof wat ’n nadelige invloed op die akwatiese ekosisteem kan hé.
Lugvloeipatrone in en rondom ’n vlak vallei in die oostelike Hoëveld
Authors: Pretorius R. W.
Published: July 2013

The surface air-flow patterns in and around a shallow valley at Secunda in the eastern Highveld (Mpumalanga) were investigated in order to identify the regulators of the surface air flow and to determine to what extent the local and/or regional circulation is apparent in the long-term air-flow pattern.
Vroue in ingenieurswese — ’n geleentheid
Authors: Visser-Uys P. E.
Published: July 2013

In view of the under-representation of women in the field of engineering and the legislation concerning the employment and education of previously disadvantaged groups, an investigation was conducted to determine which factors are likely to promote an interest in engineering amongst women. Current statistics provided by the University of Pretoria are analysed.
Die plantfamilie Asteraceae: 2. Die blomme
Authors: Herman P. P. J.
Published: July 2013

Ray florets are the outermost, conspicuous flowers in the Asteraceae capitulum and can be arranged in one or more whorls. They are long, short or reduced, and the number of flowers per whorl varies. They can be white, yellow, orange, blue or purple in colour, and sometimes the colours of the upper and lower surfaces differ.
Genetiese variasie in mopanie
Authors: Brand L.
Published: July 2013

Colophospermum mopane (mopanie) het baie kommersiële toepassings, maar het veral bekendheid verwerf vanweë die mopaniewurms wat die blare vreet.
A collection of Book reviews for Volume 19, Number 3&4
Authors: Office Editorial
Published: July 2013

The Weather and Climate of Southern Africa.
Die rol van ’n plantkundige in Parke en Ontspanning
Authors: Smith G. F.
Published: July 2013

The exceptional wealth of the flora of Southern Africa has been known internationally since the early seventeenth century. However, our floral heritage has been subjected to ever increasing pressure resulting from industrial, urban and agricultural development. Research primarily aimed at conserving our indigenous flora, making rare species available to nurseries as well as establishing a meaningful tree planting programme can, however, be undertaken by Departments of Parks and Recre­ation. Educational programmes ranging from formal to non-formal botanical education can play an important role in making the public aware of our unique flora. A graduate presenting botany as one major subject can assist Departments of Parks and Recreation in utilizing these opportunities, not only to conserve, but also to develop the natural resources currently under their control.
Vliegintensiteite van kransduiwe (Columba guinea) en sonneblomskade
Authors: Kok O. B. , Kok A. C.
Published: July 2013

Daily flight patterns of rock pigeons (Columba guinea) in the Bloemfontein area are characterised by prominent peaks in early morning and late afternoon. During the middle of the day the birds usually rest in shady places of buildings situated en route to and from field crops in the immediate vicinity of the city. Sunflower is damaged mainly by rock pigeons of which the local population was estimated to be at least 6000. Investigations of bird damage to sunflower within a radius of 20 km from the city centre amounts to between 1 and 7% of the potential seed yield. The regular hunting of rock pigeons is recom­mended as a deterrent.
Nuwe verwikkelinge in die elektromagnetiese, nie-destruktiewe toetsing van staalmynhystoue
Authors: Bredenkamp G. L.
Published: July 2013

Potential fractures should be predicted in advance, but with the minimum disruption of mining activities. Existing as well as newly developed techniques are integrated into a single compact system to measure the three most relevant rope parameters, which are: cross sectional area, number of broken wires and the ohmic contact between wires. These parame­ters are measured simultaneously, in situ, in a non destructive manner.
Kompakte natuurlik-veilige kernkragreaktore
Authors: Schuman W. A.
Published: July 2013

The present need and marketing problems of small commercial reactors as welt as advantages and costs of these small naturally safe systems are highlighted against the background of a specific example of a modular high temperature gas cooled reactor.
Simposia en konferensies
Authors: Alant T. G.
Published: July 2013

Die tegnologiese rewolusie wat ons vandag beleef, is nie uniek aan enige bedryfsektor nie. Dit raak elke sektor. Wat meer verstommend is, is die snelle pas waarteen verandering en innovasie plaasvind, of waarteen nuwe produkte in die mark geplaas word. Die rekenaareeu is met ons en het ongekende, nuwe dimensies tot die mens se skeppende vermoe toegevoeg.
Chromelosporium fulvum in die sampioenbedryf: ’n Oorsig
Authors: Coetzee J. C.
Published: July 2013

The peat mould, Chromelosporium fulvum (Link) McGinty, Hennebert and Korf is a cosmopolitan fungus commonly occur­ring in greenhouses and on mushroom beds. In South Africa, however, this fungus remains relatively poorly known. In this paper the sometimes conflicting literature concerning the role of the peat mould in the mushroom industry is reviewed. Vari­ous aspects, including the characteristics and detrimental effects of the fungus on mushroom beds, as well as control meas­ures, are discussed.
Suurstoftoksisiteit
Authors: Van der Westhuizen C. A. , Viljoen M. , Pitout M. J. , Van Papendorp P. H.
Published: July 2013

Oxygen has been discovered about 200 years ago. Since then the vital physiological involvement of oxygen in various biologi­cal processes, mainly energy production, has been established. However, in the body molecular oxygen can be converted to toxic oxygen metabolites such as superoxide anion, hydrogen peroxide, the hydroxyl radical and singlet oxygen. These toxic metabolites are produced mainly in the mitochondria, plasma membranes and endoplasmic reticulum.
Die evaluering van erdwurmmeel as ’n proteïenbron in braaikuikendíëte
Authors: Reinecke A. J.
Published: July 2013

This study was undertaken to evaluate the earthworm meal as protein source by monitoring the growth of broiler chickens in a feeding trial. Earthworms were reared outdoors on cow manure. The harvested worms were sun dried and ground to produce a meal that was used as protein source in feeding trials. Three different diets were compared over a period of 56 days. Growth, food consumption, efficiency of food conversion and production efficiency factor were determined. It is con­cluded that earthworm meal has the potential to be utilized as a protein source in diets for broilers. Special density production systems would have to he developed to make the concept economically viable. Therefore these preliminary findings must be interpreted with due care.
Elektromagnetiese pulskompressor met gelyktydige oordrag in aangrensende lusse en verminderde magnetiese kernvolume
Authors: Bredenkamp G. L.
Published: July 2013

The inductor core volume of any loop in a Melville line pulse compressor may be reduced by allowing the inductor to saturate prior to complete charge transfer of the preceding loop. Two loops are thus active simultaneously and interactively, con­stituting a fifth order system. Hereby the core volume can be reduced to less than 30% of that of a comparable Melville line. The behaviour and design parameters of such a simultaneous transfer compressor are investigated by means of a theoreti­cal analysis, numerical simulation and physical modelling of the system.
Krimp - en termiese vervorming by furfurielalkohol-polimeerbeton
Authors: Kruger D.
Published: July 2013

In this study attention is given to the deformation performance of furfuryl alcohol polymer concrete during and directly after polymerisation. The deformation equations of ordinary Portland cement concrete are used as a model, while the appropriate adjustment is made to bring the effect of polymerisation shrinkage into consideration. Experimental work was done to deter­mine the deformation characteristics of material samples which were exposed to various temperature conditions, while being kept free from external stresses. These conditions of varying temperature are simulations of practical applications, where the material is exposed to high and low temperatures on a cyclic basis. Results show a different deformation curve for each of the temperature conditions, which will have a definite impact on the lifecycle of the material.
High spectral resolution ozone absorption cross-sections – Part 1: Measurements, data analysis and comparison with previous measurements around 293 K
Authors: Gorshelev V. , Serdyuchenko A. , Weber M. , Chehade W. , Burrows J. P.
Published: July 2013

Abstract. In this paper we discuss the methodology of taking broadband relative and absolute measurements of ozone cross-sections including uncertainty budget, experimental set-ups, and methods for data analysis. We report on new ozone absorption cross-section measurements in the solar spectral region using a combination of Fourier transform and echelle spectrometers. The new cross-sections cover the spectral range 213–1100 nm at a spectral resolution of 0.02–0.06 nm in the UV-vis and 0.12–0.24 nm in the IR at eleven temperatures from 193 to 293 K in steps of 10 K. The absolute accuracy is better than three percent for most parts of the spectral region and wavelength calibration accuracy is better than 0.005 nm. The new room temperature cross-sections data are compared in detail with previously available literature data. The temperature dependence of our cross-sections is described in a companion paper.
High spectral resolution ozone absorption cross-sections – Part 2: Temperature dependence
Authors: Serdyuchenko A. , Gorshelev V. , Weber M. , Chehade W. , Burrows J. P.
Published: July 2013

Abstract. We report on the temperature dependence of ozone absorption cross-sections measured in our laboratory in the spectral range 213–1100 nm with a spectral resolution of 0.02–0.24 nm (Full Width Half Maximum, FWHM) in the atmospherically relevant temperature range from 193 to 293 K. The temperature dependence of ozone absorption cross-sections was established using measurements at eleven temperatures. The methodology of the absolute broadband measurements, experimental procedures and spectra processing were described in our companion paper together with the associated error budget. In this paper, we report in detail on our data below room temperature and compare them with literature data using direct comparisons as well as the standard approach using a quadratic polynomial in temperature fitted to the cross-section data.
Benthic buffers and boosters of ocean acidification on coral reefs
Authors: Anthony K. R. N. , Diaz-Pulido G. , Verlinden N. , Tilbrook B. , Andersson A. J.
Published: July 2013

Abstract. Ocean acidification is a threat to marine ecosystems globally. In shallow-water systems, however, ocean acidification can be masked by benthic carbon fluxes, depending on community composition, seawater residence time, and the magnitude and balance of net community production (NCP) and calcification (NCC). Here, we examine how six benthic groups from a coral reef environment on Heron Reef (Great Barrier Reef, Australia) contribute to changes in the seawater aragonite saturation state (Ωa). Results of flume studies using intact reef habitats (1.2 m by 0.4 m), showed a hierarchy of responses across groups, depending on CO2 level, time of day and water flow. At low CO2 (350–450 μatm), macroalgae (Chnoospora implexa), turfs and sand elevated Ωa of the flume water by around 0.10 to 1.20 h−1 – normalised to contributions from 1 m2 of benthos to a 1 m deep water column. The rate of Ωa increase in these groups was doubled under acidification (560–700 μatm) and high flow (35 compared to 8 cm s−1). In contrast, branching corals (Acropora aspera) increased Ωa by 0.25 h−1 at ambient CO2 (350–450 μatm) during the day, but reduced Ωa under acidification and high flow. Nighttime changes in Ωa by corals were highly negative (0.6–0.8 h−1) and exacerbated by acidification. Calcifying macroalgae (Halimeda spp.) raised Ωa by day (by around 0.13 h−1), but lowered Ωa by a similar or higher amount at night. Analyses of carbon flux contributions from benthic communities with four different compositions to the reef water carbon chemistry across Heron Reef flat and lagoon indicated that the net lowering of Ωa by coral-dominated areas can to some extent be countered by long water-residence times in neighbouring areas dominated by turfs, macroalgae and carbonate sand.
Explosive demographic expansion by dreissenid bivalves as a possible result of astronomical forcing
Authors: Harzhauser M. , Mandic O. , Kern A. K. , Piller W. E. , Neubauer T. A. , Albrecht C. , Wilke T.
Published: July 2013

Abstract. Human induced range expansions of invasive dreissenid bivalves are of great concern. However, the underlying biological processes are only poorly understood, partly due to the lack of information on natural expansion events. Here we use the extinct bivalve species Sinucongeria primiformis as a model organism for testing natural (i.e. non-Anthropocene) blooms of dreissenid species in a lacustrine system of Lake Pannon during the Tortonian (~10.5 Myr; Late Miocene). 600 samples from a consecutive core were evaluated for the relative abundance of this pavement-forming mollusc, which cover about 8 millennia of Late Miocene time with a decadal resolution. Our data indicate that the settlement by bivalves in the offshore environment was limited mainly by bottom water oxygenation, which follows predictable and repetitive patterns through time. These population fluctuations might be related to solar cycles: successful dreissenid settlement is re-occurring in a frequency known as the lower and upper Gleissberg cycles with a 50–80 and 90–120 yr period. These cycles appear to control regional wind patterns, which are directly linked to water mixing of the lake. This is modulated by the even more prominent 500 yr cycle, which seems to be the most important pacemaker for Lake Pannon hydrology.