112 research outputs found
Some variables influencing academic achievement : reading, motivation, learning strategies, learning approaches
No full textThe low throughput and high drop-out rates at contact institutions are of concern as this leads to small percentages of qualified students available for the labour market. In order to address this problem, it is essential for higher education institutions to possess knowledge of factors that can potentially contribute to or improve academic success such as reading ability, motivational factors, learning strategies and learning approaches. These were investigated among a sample of 260 Economic and Management education students by using validated instruments in a quantitative study. The results revealed that students demonstrated an average reading speed comparable to that of a grade 8 learner and a comprehension level of only 60%. The motivational factor, namely expectancy for success, was rated highest and test anxiety lowest contributor while learning strategies such as critical thinking, organising, rehearsal and additional efforts as well as the deep learning approach correlated positively with academic achievemen
Hormonal regulation of tuberization of cassava (Manihot esculenta Crantz)
No full textThesis (Ph.D.)-University of Natal, Pietermaritzburg, 1984.The relative distribution of dry matter over shoot and
tuberous roots is an important factor in determining the yield of
cassava. Under sub-tropical conditions the dry matter distribution
pattern is not always efficient. During the summer the vegetative
growth is generally excessive due to long days and high temperatures.
Furthermore, it was found that a reduction of tuberous root mass
occurs shortly after the winter period when the new canopy is formed.
The role of endogenous hormones, in particular abscisic acid and
cytokinins, in dry matter distribution and tuberization was studied.
Furthermore, experiments were conducted on the effect of exogenous
applied plant growth regulators on the growth of cassava.
Inhibitor activity present in plant extracts, was tentatively
identified as cis-abscisic acid. A high level of inhibitor
activity, co-eluting with abscisic acid, was found throughout the
tuberous roots. The highest level of inhibitor activity was
detected under conditions which caused a high rate of tuberous root
growth, ego with a low level of nitrogen fertilization. Gibberellic
acid application to the leaves promoted shoot growth and led to a
decrease in inhibitor activity of the tuberous roots. Shoot
removal, however, stopped tuberous root growth without leading to
changes in inhibitor activity. No clear correlation was found
between inhibitor activity of tuberous roots and the rate of tuberous root growth of plants harvested from the field tentatively identified as the major cytokinins in tuberous root
extracts. Cytokinin activity was concentrated in the meristematic
region of the xylem. The level of cytokinin activity in the roots
was much higher than in primary roots of the same plants.
Gibberellic acid application to the leaves and shoot removal
resulted in a reduction of the cytokinin level of tuberous roots.
The nitrogen application to the plants had no clear effect on the
cytokinin levels. In field-grown plants the highest level of
cytokinin activity was found shortly after tuber initiation.
Applications of Alar caused satisfactory reduction of shoot
growth of young cassava plants grown in the greenhouse. The
internodes were shortened, the leaf area generally reduced, while a
relatively larger part of the dry matter was allocated to storage
roots. The effect of Alar was further studied in field experiments.
A growth analysis showed that a reduction of tuberous root mass
occured shortly after the winter period, in September. Later in the
second growing season, shoot and tuberous root mass increased at a
relatively constant rate. Alar application (up to 4,5 grammes per
Iitre) early in the second season failed to bring about major
changes in dry matter distribution. Shoot removal at the end of the
winter period was followed by excessive vegetative growth. Alar
application reduced the internode length but the reduction of shoot
growth was insufficient to cause a significant increase in yield. A
nitrogen topdressing at the start of the second season increased the
vegetative growth. However, Alar application, later in the season,
did not inhibit shoot growth at any of the nitrogen levels applied.
RSW 0411 which caused good reduction of shoot growth in the
greenhouse, was not effective in the field
Die adverbiale bepaling in die sin
No full textSkripsie (M.A.) -- Universiteit van Stellenbosch, 1968.Full text to be digitised and attached to bibliographic record
Micropropagation of Juniperus navicularis, an endemic and rare species from Portugal SW coast
No full textJuniperus navicularis Gand (= J. oxycedrus L. subsp. transtagana Franco) is an endemic dioecious shrub from the Plio-Plistocene transition sands of the west Portuguese coast line. It grows in sole or mixed stands along with Pinus pinea and P. pinaster and, more rarely, with Quercus lusitanica. In order to reduce fire incidence in these Mediterranean mixed stands, forest management practices of mechanical or chemical treatments, have drastically reduced J. navicularis populations. In addition, the fast expansion of touristic areas along with a low seed germination rate further endangers this species. In this study we developed a protocol for micropropagation of adult J. navicularis. Microcuttings were obtained from lateral and apical twigs of both female and male mature plants, and used as explants. Microcuttings with axillary buds were grown on different media and plant growth regulators combinations. Developmental parameters were evaluated to define the best medium and plant growth regulator concentration for shoot bud induction during the multiplication cycles. Olive Medium and Gupta and Durzan medium, both supplemented with 0.45 µM 6-benzyl-amino-purine, were the most favourable of all combinations tested achieving more than 3 new shoots per explant. The highest rooting (60%) was obtained in microshoots cultured in Olive Medium when supplemented with indole-3-butyric acid at 12.3 µM. With this multiplication protocol, it was possible to obtain more than 500 shoots from the initial 20, after three multiplication cycles in 3 months
Towards marker assisted selection for nematode resistance in soybean.
No full textThesis (Ph.D.)-University of Natal, Pietermaritzburg, 2000.Meloidogyne javanica is the most widely spread nematode pest on soybean in South Africa. Only a few registered cultivars have some resistance to this nematode and there is an urgent need for an efficient breeding programme for resistant cultivars of all maturity groups. However, breeding is hampered by
laborious screening procedures for selection of resistant lines. The objective of this study was to develop an economically viable molecular marker system for application in selection procedures. Three techniques of marker identification were investigated, i.e. RAPD, RFLP and AFLP analysis. The RAPD technique proved to be applicable in fingerprinting soybean varieties, but was too sensitive for interplant variation to
be used as an efficient system for identification of molecular markers linked to nematode resistance. Both RFLP and AFLP screening identified markers linked to gall index variation in a segregating population of 60 F₂ progeny from across between a resistant cultivar, Gazelle, and a highly susceptible variety, Prima. A codominant RFLP marker( B212) was linked significantly to resistance and explained 62% of the variation in gall index. Seven AFLP markers were linked significantly to the resistance trait, of which four were linked in repulsion phase and three in coupling phase. All seven AFLP markers mapped to LG-F on the public soybean molecular map. The QTL for resistance mapped between markers E-ACC/M-CTC2 linked in coupling phase, 8212 and E-AAC/M-CAT1, linked in repulsion phase. These two AFLP markers bracketing the major resistance QTL were successfully converted to SCARs. Marker E-ACC/M-CTC2 was converted to a codominant SCAR marker SOJA6, which acounted for 41% of variation in gall index in the
mapping population. Marker E-AAC/M-CAT1 was converted to a dominant SCAR marker (SOJA7) and explained 42% of gall index variation in the mapping population. These two markers mapped approximately 3.8 cM and 2.4 cM respectively from the resistance QTL. This study represents the first report of the development of PCR-based sequence specific markers linked to resistance to M. javanica in soybean
Comparison between measured and simulated activity using Gafchromic™ film with radionuclides
No full textIn this study, Gafchromic™ film XR-QA2 and RT-QA2 were used to characterise the film energy response against various radionuclides. The film response was investigated with respect to different backscatter materials. The sensitivity of the two types of films was compared, and a film stack method was tested to allow the user to obtain sequential, cumulative doses at different time points. Monte Carlo (MC) simulations were used to link optical density (OD) values from measurements to the absorbed dose in the film. This was achieved by using conversion factors obtained by BEAMDP, BEAMnrc and DOSXYZnrc simulations to get the absorbed dose in the film. A neutron depletion theoretical model was introduced that can describe film response as a function of cumulated activity and absorbed dose. Background: Gafchromic™ film has been used for quality assurance in various studies but not in nuclear medicine applications. Once the OD has been determined after film exposure to a radionuclide, it can be linked to the absorbed dose using the air kerma rate constant at distances that approximates point sources and the dose in water can be linked to the dose in film using MC simulations to get conversion factors. MC simulations are known as a gold standard to get the absorbed dose in materials. Materials and Methods: XR-QA2 and RT-QA2 Gafchromic™ film were irradiated with the following radionuclides: Am-241, Cs-137, Tc-99m and I-131. The OD was calculated, and a function describing the relationship between the OD and the time-activity was derived based on the neutron depletion model. Different backscatter materials such as Corrugated fibreboard carton (CFC) or air equivalent material, polystyrene, Polymethyl Methacrylate (PMMA or perspex) and lead were used to investigate the effect it has on film response. The sensitivity of each film was investigated and compared. BEAMDP, BEAMnrc and DOSXYZnrc simulations were used to link the film response, OD, to the absorbed dose. The MC simulations were done replicating the exact geometry as with the physical measurements to get the absorbed dose in the film. Results: The new neutron depletion model fitted the OD vs cumulative activity accurately as well as the OD vs absorbed dose. The XR-QA2 Gafchromic™ film has shown to be the most sensitive film when using air equivalent material with radionuclides, especially with low energy radionuclides such as Am-241. When using more than one layer, the OD sensitivity of the film can be increased as well. The film stack method investigated also showed to be less time consuming when relating stacked film data to single film data. The fluence obtained from BEAMDP confirmed that the radionuclide containers have an effect on the radionuclide spectra’s. Lead was also the backscatter material which showed higher OD change but lower absorbed dose values. Conclusions: The neutron depletion theoretical model is more accurate than higher-order polynomial fits because it contains less free parameters. The XR-QA2 Gafchromic™ is better to use in nuclear medicine because of its sensitivity at low energies and because the sensitivity can be increased by using multiple layers of film. Film stack methods can be used to decrease experiment times. BEAMnrc can be used to accurately model radionuclides within their containers to evaluate the container effects. Lead showed a higher induced OD with lower absorbed dose, and the air equivalent material showed the lower OD change but higher absorbed dose
Comparison between measured and simulated activity using Gafchromic™ film with radionuclides
No full textIn this study, Gafchromic™ film XR-QA2 and RT-QA2 were used to characterise the film energy response against various radionuclides. The film response was investigated with respect to different backscatter materials. The sensitivity of the two types of films was compared, and a film stack method was tested to allow the user to obtain sequential, cumulative doses at different time points. Monte Carlo (MC) simulations were used to link optical density (OD) values from measurements to the absorbed dose in the film. This was achieved by using conversion factors obtained by BEAMDP, BEAMnrc and DOSXYZnrc simulations to get the absorbed dose in the film. A neutron depletion theoretical model was introduced that can describe film response as a function of cumulated activity and absorbed dose. Background: Gafchromic ™ film has been used for quality assurance in various studies but not in nuclear medicine applications. Once the OD has been determined after film exposure to a radionuclide, it can be linked to the absorbed dose using the air kerma rate constant at distances that approximates point sources and the dose in water can be linked to the dose in film using MC simulations to get conversion factors. MC simulations are known as a gold standard to get the absorbed dose in materials. Materials and Methods: XR-QA2 and RT-QA2 Gafchromic ™film were irradiated with the following radionuclides: Am-241, Cs-137, Tc-99m and I-131. The OD was calculated, and a function describing the relationship between the OD and the time-activity was derived based on the neutron depletion model. Different backscatter materials such as Corrugated fibreboard carton (CFC) or air equivalent material, polystyrene, Polymethyl Methacrylate (PMMA or perspex) and lead were used to investigate the effect it has on film response. The sensitivity of each film was investigated and compared. BEAMDP, BEAMnrc and DOSXYZnrc simulations were used to link the film response, OD, to the absorbed dose. The MC simulations were done replicating the exact geometry as with the physical measurements to get the absorbed dose in the film. Results: The new neutron depletion model fitted the OD vs cumulative activity accurately as well as the OD vs absorbed dose. The XR-QA2 Gafchromic ™ film has shown to be the most sensitive film when using air equivalent material with radionuclides, especially with low energy radionuclides such as Am-241. When using more than one layer, the OD sensitivity of the film can be increased as well. The film stack method investigated also showed to be less time consuming when relating stacked film data to single film data. The fluence obtained from BEAMDP confirmed that the radionuclide containers have an effect on the radionuclide spectra’s. Lead was also the backscatter material which showed higher OD change but lower absorbed dose values. Conclusions: The neutron depletion theoretical model is more accurate than higher-order polynomial fits because it contains less free parameters. The XR-QA2 Gafchromic ™ is better to use in nuclear medicine because of its sensitivity at low energies and because the sensitivity can be increased by using multiple layers of film. Film stack methods can be used to decrease experiment times. BEAMnrc can be used to accurately model radionuclides within their containers to evaluate the container effects. Lead showed a higher induced OD with lower absorbed dose, and the air equivalent material showed the lower OD change but higher absorbed dose
Experiences of rural girls in a historically dominated organisation: scouts in Mpumalanga, Western Cape and Eastern Cape
No full textMagister Artium - MAThis study explores the experiences of young rural girls in scouting practices, who reside in the rural areas of Mpumalanga, Western and Eastern Cape provinces of South Africa. This exploratory study draws special reference to their participation in Scout programmes in what in observed as a predominantly male-dominated organisational alignment. This exploratory study uses a qualitative feminist investigation, through focus groups and semi structured interviews to investigate the impact of these organisational change initiatives on the experiences of girls in scouting. Although the aim of the study was to explore the experiences of rural girls, boys were included in the study to explore gender dynamics and to problematise how gender inequalities can be understood and addressed in scouting.South Afric
Experiences of rural girls in a historically dominated organisation: scouts in Mpumalanga, Western Cape and Eastern Cape
No full textMagister Artium - MAThis study explores the experiences of young rural girls in scouting practices, who reside in the rural areas of Mpumalanga, Western and Eastern Cape provinces of South Africa. This exploratory study draws special reference to their participation in Scout programmes in what in observed as a predominantly male-dominated organisational alignment. This exploratory study uses a qualitative feminist investigation, through focus groups and semi structured interviews to investigate the impact of these organisational change initiatives on the experiences of girls in scouting. Although the aim of the study was to explore the experiences of rural girls, boys were included in the study to explore gender dynamics and to problematise how gender inequalities can be understood and addressed in scouting.South Afric
Low-literate consumers' use of clothing labels amidst personal and product related challenges
No full textLow-literate consumers experience various challenges in the marketplace. This quantitative study focused on low-literate female consumers' use of clothing labels amidst personal and product-related challenges in the marketplace. An interviewer-administered questionnaire was used among black African female consumers (n = 450) with literacy levels ranging from Grades 5 to 8 (on average, 11–14 years old), residing in the Emfuleni Local Municipality area, Gauteng, South Africa. Personal challenges experienced involved reading and numeracy skills, as well as concrete and pictographic thinking. Although respondents indicated that they read and understand clothing labels, results revealed problems experienced when attempting to use the information provided. Their numeracy skills were average and related abstract thinking skills were fair. Product-related challenges were related to the format of labels, care-label knowledge and evaluation of clothing quality. Respondents' preference for symbolic and graphic presentation of size format provided evidence of pictographic thinking. Care label understanding was poor, and clothing products were evaluated concretely. Some of the older respondents were inclined to follow the peripheral route of elaboration when reading clothing-label information. We conclude that low-literate consumers' use of clothing label information can improve if provided in a format that they can read and understan
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