Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Maintaining constant high yields in „Abate Fetel‟ and „Forelle‟ orchards in South Africa is challenging. Improving productivity in these orchards could be achieved by increasing fruit set and fruit size. Fruit size is an important marketing and quality parameter and has a significant effect on the economic value of fruit. Various protocols to improve fruit set are used by South African producers but these are not well researched. We therefore evaluated different combinations of plant growth regulators including gibberellic acid (GA3), gibberellins 4+7 (GA4+7), GA4+7 combined with 6-benzyladenine (6-BA), aminoethoxyvinylglycine (AVG) and prohexadione-calcium (P-Ca) in combination with trunk girdling during flowering on „Forelle‟ and „Abate Fetel‟ to determine the best fruit set strategy. All applied growth regulators improved fruit set relative to an untreated control over two consecutive seasons, but GA3 and P-Ca reduced return bloom and AVG resulted in smaller fruit size relative to the other treatments. The application of synthetic cytokinins are believed to enhance fruit size by stimulating and extending the cell division period in fruit when applied at the correct stage of fruit growth. In addition, combination of P-Ca with GA4+7 was used successfully on Japanese pear (Pyrus pyrifolia Nakai) and „Bing‟ sweet cherry to improve fruit size. This combination of GA4+7 and P-Ca was evaluated and combined with 6-BA treatments on European pear (Pyrus communis L.) cultivars, Forelle and Abate Fetel, to see if a similar effect on fruit size could be achieved under South African growing conditions. On both „Forelle‟ and „Abate Fetel‟ the combination of GA4+7 and P-Ca increased fruit size, but was more pronounced in „Abate Fetel‟. Growth regulators N-phenyl-N‟ -1,2,3-thiadiazol-5-ylurea (TDZ), N (2-chloro-4-pyridyl)-N‟ -phenylurea (CPPU), 6-BA and 2,4-dichlorophenoxyacetic acid (2,4-D) successfully increased fruit size in pear cultivars Coscia and Spadona in Israel. These growth regulators were applied to „Forelle‟ and „Abate Fetel‟ to determine if a similar effect could be achieved. None of the synthetic cytokinins applied had a significant effect on increasing fruit size in these two cultivars over two consecutive seasons although 6-BA increased return bloom and 2,4-D application resulted in increased fruit set. The stage when the cell division period in „Forelle‟ and „Abate Fetel‟ ends was also determined as 34 and 45 days after full bloom respectively, which can be used in the future to better plan the timing of fruit size enhancement treatments. Based on results from various fruit set and fruit size improvement trials, it can be recommended to use GA4+7 or AVG to increase fruit set on „Forelle‟ and „Abate Fetel‟, depending on the fruit set history of the orchard. Results from fruit size improvement trials were variable, and emphasises the fact that a balance between yield and fruit size must be determined for an orchard to achieve good fruit size and maximum return. / AFRIKAANSE OPSOMMING: Die handhawing van konstante, hoë opbrengste in „Abate Fetel‟ en „Forelle‟ boorde in Suid-Afrika is 'n uitdaging. Produktiwiteit in hierdie boorde kan verhoog word deur vrugset en vruggrootte te verbeter. Vruggrootte is 'n belangrike bemarkings- en kwaliteitsparameter en het 'n betekenisvolle effek op die ekonomiese waarde van vrugte. 'n Verskeidenheid protokolle om vrugset te verbeter word deur Suid-Afrikaanse produsente gevolg, maar hierdie protokolle is nog nie goed nagevors nie. Verskillende kombinasies van plantgroeireguleerders insluitend gibberelliensuur (GA3), gibberellien 4+7 (GA4+7), GA4+7 in kombinasie met 6-bensieladenien (6-BA), aminoetoksievinielglisien (AVG) en prohexadioon-kalsium (P-Ca) in kombinasie met stamringelering is aan „Forelle‟ en „Abate Fetel‟ bome gedurende blomtyd toegedien om die beste vrugsetstrategie te bepaal. Alle plantgroeireguleerdes wat toegedien is het vrugset verbeter relatief tot 'n onbehandelde kontrole oor twee opeenvolgende seisoene, maar GA3 en P-Ca het die aantal blomme in die daaropvolgende seisoen verlaag en AVG het kleiner vruggrootte gelewer relatief tot alle ander behandelings. Dit is wel bekend dat die toediening van sintetiese sitokiniene vruggrootte verbeter deur die stimulering en bevordering van seldeling in vrugte wanneer dit in die regte groeifase toegedien word. Die kombinasie van P-Ca en GA4+7 was suksesvol om vruggrootte te verbeter toe dit aan Japanese pere (Pyrus pyrifolia Nakai) en „Bing‟ kersies toegedien is. Hierdie kombinasie van GA4+7 en P-Ca is geëvalueer en gekombineer met 6-BA-behandelings op die Europese peer (Pyrus communis L.) kultivars, Forelle en Abate Fetel, om te bepaal of dieselfde effek op vruggrootte bereik kan word onder Suid-Afrikaanse groei kondisies. Op beide „Forelle‟ en „Abate Fetel‟ het die kombinasies van GA4+7 en P-Ca vruggrootte verbeter, maar dit was meer opmerklik in die geval van „Abate Fetel‟. Die groeireguleerders N-feniel-N‟ -1,2,3-thiadiazol-5-ylurea (TDZ), N (2-chloro-4-piridiel)-N‟ -fenielurea (CPPU), 6-BA en 2,4- dichloorfenoksieasynsuur (2,4-D) het vruggrootte verbeter in „Coscia‟ en „Spadona‟ pere in Israel. Hierdie plantgroeireguleerders is toegedien aan „Forelle‟ en „Abate Fetel‟ om vas te stel of dieselfde effek verkry kon word. Nie enige van die sintetiese sitokiniene wat toegedien is het 'n betekenisvolle effek op die verbetering van vruggrootte in hierdie twee kultivars oor twee opeenvolgende seisoene getoon nie, alhoewel 6-BA die verbetering van blom in die daaropvolgende seisoen tot gevolg gehad en 2,4-D vrugset verbeter het. Die stadium waar seldeling in „Forelle‟ en „Abate Fetel‟ eindig is vasgestel as 34 en 45 dae na volblom, onderskeidelik, wat in die toekoms gebruik kan word om die beplanning en tydsberekening van vruggrootte behandelings te verbeter. Na verskeie vrugset en vruggroote verbeterings proewe, kan aanbeveel word dat GA4+7 of AVG gebruik kan word om vrugset in „Forelle‟ en „Abate Fetel‟ te verbeter, afhangende van die vrugset geskiedenis van die boord. Resultate van vruggrootte verbeterings proewe het gevarieër en beklemtoon net weer die feit dat 'n balans tussen opbrengs en vruggrootte bepaal moet word om optimale vruggrootte te handhaaf en so hoë winste te verseker. / SAAPPA

The following full-factorial study compared fungal activity on lignocellulosic biomass that was inoculated with three different amounts of fungus, and grown using three different airflow rates. These treatments were compared to a control which consisted of biomass that was not inoculated but was exposed to the same growth conditions in the environmental chamber. The objectives of the following experiment were to determine the inoculum density and airflow rate required to optimize Phanerochaete chrysosporium lignin degradation. Additionally, this study quantifies the saccharification yield from the pretreated switchgrass. The impact of substrate bulk density and substrate particle size on fungal growth were compared to determine if the particle size or the substrate bulk density has the predominant influence on the growth of the fungus, and subsequent pretreatment effectiveness quantified as an increase in glucose yields and lignin degradation. The particle size tests were controlled for bulk density; all three particle sizes were tested at a bulk density of 80 kg/m3. To test the density, three different bale densities were prepared controlling for particle size. The density tests were performed on small-scale bales made of 4 inch cut pieces of switchgrass compressed to the correct density. Therefore; density tests had the same particle size throughout all treatments, and particle size tests had the same density through all treatments. Carbohydrate accessibility post-pretreatment was examined through enzymatic saccharification and determination of glucose yields in the treatments and controls.

O presente estudo visa dar luz sobre fenômenos ainda pouco explorados que ocorrem durante a estratificação em leitos de jigagem, bem como sobre novas possibilidades de aplicação da técnica. Por meio de testes com misturas de agregados em jigues hidráulico e pneumático descontínuos, foi pela primeira vez examinada a ocorrência de convecção granular em jigues. Os fatores envolvidos em sua formação e a influência sobre a estratificação foram analisados em detalhes. Do mesmo modo, foi examinada a influência da granulometria do leito sobre a estratificação em jigues pneumáticos e a possibilidade de uso do mesmo como um equipamento multi-separador. Os resultados revelam a existência de um fluxo ordenado e estacionário de partículas durante a pulsação do leito, ascendente na porção central e descendente nas bordas do jigue, de modo similar ao fluxo convectivo descritos na literatura para leitos vibrados mecanicamente. Este fluxo convectivo gerou uma distorção no rearranjo do leito estratificado, dando origem a um perfil horizontal de estratificação no qual as partículas leves se concentraram nas bordas e as partículas densas se concentraram preferencialmente na zona central dos estratos. Com base nos resultados, um mecanismo de formação do fluxo convectivo e um modelo preditivo do rearranjo do leito foram propostos. Observou-se também que a diminuição da granulometria e o aumento da distribuição de tamanho dos constituintes do leito teve um efeito positivo sobre a estratificação. Os resultados sugerem que isto pode estar em parte relacionado a maior compactação do leito quando da presença de partículas de menor tamanho. Também, resultados experimentais demonstraram a possibilidade de uso do jigue pneumático para realizar a operação conjunta de separação de materiais rochosos e não rochosos em um único estágio. O desempenho global na remoção de contaminantes não-rochosos foi similar ao de separadores pneumáticos e sistemas de "sorting" automático descritos na literatura. Ainda, a quantidade inicial de contaminantes no sistema teve um efeito desprezível sobre o desempenho. Os resultados obtidos, em particular aqueles relacionados à convecção granular, fornecem novas perspectivas a respeito dos fenômenos envolvidos na estratificação em jigues. Ainda, benefícios práticos podem ser extraídos a partir dos resultados da análise do efeito da granulometria sobre a estratificação e do uso de jigues pneumáticos como multi-separadores. / This study aims to shed some light on some unclear phenomena that occurs during particle stratification in jigs as well as on new possibilities of application of jigging technique. For the first time, the occurrence of granular convection in jigging beds was analyzed by considering the case of hydraulic and pneumatic jigs operating with mixtures of aggregates. The elements involved in the pattern formation and its influence on bed stratification were analyzed in detail. The influence of particle size distribution on bed stratification and the possibility of using pneumatic jigging as a multi-separator were also examined. The experimental results reveal the existence of a steady, ordered flow of particles over bed pulsation, in which particles move upward in the center of the jig bed and downward along the walls of the jig container, similarly to the circulation patterns reported in the literature. The convection gave rise to a distortion in the particle rearrangement, engendering the formation of a horizontal stratification profile in which light particles tended to be concentrated along the walls while dense particles tended to be concentrated preferentially in the center portion of the strata. On the basis of the experimental results, a mechanism of pattern formation and a prediction model were proposed. The results also revealed that the decrease of the particle size and the increase in the particle size distribution had a positive influence on stratification extent. It was suggested by the results that this behavior can be related to the higher bed compaction due to the presence of smaller particles in the bed. Also, experimental results indicated the technical feasibility of the combined use of pneumatic jigging for the removal undesired non-stony materials together with the bed stratification in only one single stage. The reported separation efficiency in the removal of low-density materials was comparable to those of air classifiers and automatic sorting systems. Also, the initial content of contaminants seemed to have a negligible effect on the separation performance. The results obtained, in particular those related to the granular convection, provides new perspectives about the phenomena involved in stratification by jigging. Moreover, practical benefits can be obtained from the results about the influence of particle size on bed stratification and about the usage of pneumatic jigging for multi-separation.

Master of Science / Genetics Interdepartmental Program / Eduard D. Akhunov / The CRISPR/Cas9-based genome editing system holds a great promise to accelerate wheat improvement by helping us to understand the molecular basis of agronomic traits and providing means to modify genes controlling these traits. CRISPR/Cas9 is based on a synthetic guide-RNA (gRNA) that can guide Cas9 nuclease to specific targets in the genome and create double strand breaks (DSB). The DSB are repaired through the error-prone non-homologous end joining process causing insertions or deletions that may result in loss-of-function mutations. Here, we have developed an effective wheat genome editing pipeline. We used next-generation sequencing (NGS) data to estimate genome editing efficiency of many gRNAs using the wheat protoplast assay and choose the most efficient gRNAs for plant transformation. We successfully applied this pipeline to five wheat orthologs of the rice yield component genes that have been identified previously. We obtained edited plants for all these genes and validated the effect of the mutations in TaGW7 on wheat traits, which showed trends similar to those in rice. These results suggest that transferring discoveries made in rice to improve wheat is a feasible and effective strategy to accelerate breeding.

The effects of habitat complexity and predation risk on community assembly in small standing waters are reviewed. Both lethal and nonlethal predator effects are discussed. Emphasis is put on the role of omnivorous predators which do not fit into the standard food chain model. The review is complemented by a manuscript intended for publication in Freshwater Biology. It reports the results of a mesocosm experiment focusing on the effects of both lethal and nonlethal predation risk, induced by the invasive crayfish species Orconectes limosus, and habitat complexity on the abundance and biomass of macroinvertebrates in a naturally assembled community.

Over 60% of the adult population in the United Kingdom is now overweight or obese or classed as plus size . This is higher than almost all other developed countries in the world. Even with numerous public health interventions, the incidence of being plus size continues to rise potentially changing the demographics of the working population. This presents a challenge to those involved in workplace design as the design process relies upon the utilization of appropriate anthropometric data to establish the percentage of the user population that will be accommodated by the design. The aim of this thesis is to identify issues affecting plus size people in the working environment, not previously explored within the literature. Furthermore, by understanding the size and shape of this population via the collection of key anthropometric data, this will help inform the design of safe, comfortable, inclusive and productive working environments for plus size people within the United Kingdom. A first stage Scoping Study (n=135) found that fit (equipment, tools, furniture, uniforms and personal protective equipment) and space (circulation and shared spaces within the working environment) were issues of concern to plus size people. This suggests that aspects of the current design of the workplace are not suitable, and may even exclude plus size people. A better understanding of the anthropometric requirements of plus size workers is therefore required. Self-reported anthropometric data is an acceptable way of studying large and geographically diverse populations and may assist in accessing the hard to reach plus size working population. A validation study (n=20) established that self measurement of 14 key anthropometric measurements, using a self measurement instruction guide, was a feasible and acceptable data collection method for a larger scale anthropometric study to further understand the body size and shape of plus size people at work. A unique measure of knee splay (for a non-pregnant population) was included. Defined as the distance between the outer borders of the knees whilst seated in the preferred sitting position it represents the observed sitting postures of plus size individuals not captured in existing anthropometric data sources. The larger scale Plus Size Anthropometry Study (n=101) collected anthropometric data of plus size working age people via self measurement. The findings indicated that the study population was substantially larger in circumference, depth and breadth measurements than the population of existing anthropometric data sources. Knee splay was also identified as a key anthropometric variable for plus size people, however, it is not included in any datasets or literature relating to plus size people at work. These factors may contribute to high exclusion rates from current design practices that seek to accommodate the 5th to 95th or 99th percentile of users and may explain the high incidence of fit and space issues reported by participants with a BMI over 35kg/m2 . Finally, semi structured interviews with stakeholders (n=10) explored how they would like the data from the plus size anthropometry study communicated and any additional requirements of a resource aimed at supporting stakeholders in meeting the needs of plus size people within the working environment. The primary concern from stakeholders was the lack of existing data on the size and shape of the plus size working population and the importance of access to such data in whatever format. A range of ideas were suggested including case studies, guidance and access to training which may assist them in understanding the needs of their end users ultimately supporting the inclusion of plus size people in workplace design.

Gold nanoparticles (AuNPs) have garnered considerable attention for their interesting size-dependent properties. These properties have fueled applications that span a continuum ranging from simple to sophisticated. Applications for these materials have grown more complex as syntheses for these materials have improved. For simple applications, current synthetic processes are sufficient. However, development of syntheses that generate well-defined particle sizes with specifically tailored surface functionalities is an on-going challenge for chemists. The aim of this dissertation is to improve upon current AuNP syntheses to produce sophisticated materials needed to discover new material properties, and provide efficient access to materials to develop new advanced applications. The research described in this dissertation improves upon current methods for AuNP production by using a microreactor to provide enhanced mixing and synthetic control, and small angle X-ray scattering (SAXS) as a precise, rapid, solution-based method for size distribution determination. Using four ligand-stabilized AuNP samples as reference materials, SAXS analysis was compared to traditional microscopic size determination. SAXS analysis provided similar average diameters while avoiding deposition artifacts, probing a larger number of particles, and reducing analysis time. Next, the limits of SAXS size analysis was evaluated, focusing on identifying multiple distributions in solution. Utilizing binary and ternary mixtures of well-defined AuNP reference samples, SAXS analysis was shown to be effective at identifying multiple distributions. While microscopy has limited ability to differentiate these modes, SAXS analysis is more rapid and introduces less researcher bias. Because AuNP size and ligand functionality are interdependent, accessing desired core sizes with varied functionality is challenging. To address this, a new microfluidic synthetic method was developed to produce thiolate-passivated AuNPs with targeted core sizes from 1.5 - 12 nm with tailored functionality. This ability to control size while independently varying surface functionality is unprecedented. Lastly, AuNP core formation was probed by simultaneous in situ SAXS and UV/visible spectroscopy. A coalescence mechanism for AuNP growth was observed when using Bunte salt ligands. This finding compares well to observed coalescence in other systems using weakly-passivating ligands, and supports the hypothesis that Bunte salts passivate ionically during particle growth while resulting in covalent linkages. / 2015-10-10

In this qualitative study, the phenomenon of large class teaching in South African secondary schools is investigated. It was concluded that since large classes will be a feature of the South African teaching context for many years to come due to financial constraints, educators and educational planners should explore and implement coping strategies instead of becoming demoralised by the situation. The study provides several instructional guidelines for implementation in large classes in the South African context. The focus of these guidelines is on large class management and effective teaching in large classes. The possibilities of strategies such as whole group instruction, cooperative learning, peer teaching, groupwork and the proper organisation of classroom space are investigated. / Educational Studies / M. Ed. (Didactics)

Made available in DSpace on 2014-06-11T19:35:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2003Bitstream added on 2014-06-13T18:46:11Z : No. of bitstreams: 1 andrade_avc_dr_araiq.pdf: 5138584 bytes, checksum: bbedecd07acf7ed59aafdb0934ad7d94 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Métodos de determinação de tamanho de cristalito e microdeformação da rede cristalina utilizando difratometria de raios X por pó foram discutidos e aplicados em três sistemas cerâmicos de interesse tecnológico: LiCoO2 preparado por combustão ou pelo método de Pechini; SnO2 não dopado e dopado com 5% de cério ou 5% de ítrio ou 5% de lantânio, tratados termicamente a 550oC, 720oC, 820oC, 920oC, 1000oC e 1100oC; e hidroxiapatita preparada pelo método da emulsão. Foram discutidas (i) as análises qualitativas de tamanho de cristalito-deformação (td) utilizando gráficos da largura-total-a-meia-altura (fwhm) em função do ângulo de difração 2θ; (ii) a análise isotrópica pelo método de Rietveld utilizando a função Thompson-Cox-Hastings, modificada por Young e Desai (TCHZ); (iii) o gráfico de Williamson-Hall (iv) o método “double-Voigt” e (v) o método fenomenológico de Peter Stephens aplicado ao método de Rietveld. Foram desenvolvidos dois programas escritos para o programa MathCad® 7.0 que calculam o tamanho de cristalito e a microdeformação utilizando o gráfico de Williamson-Hall e o método “double-Voigt”, respectivamente. O método da máxima entropia foi utilizado neste trabalho como complementar ao método de Rietveld para a obtenção dos mapas de densidades eletrônicas da hidroxiapatita. A análise qualitativa de tamanho de cristalito e microdeformação da rede cristalina foi aplicada ao sistema LiCoO2. Este estudo revelou que a fase LiCoO2 trigonal predomina, acompanhada de uma pequena quantidade da fase espinélio Co3O4 cúbica. Observou-se que tanto os cristalitos quanto as microdeformações são maiores quando se utiliza o método de Pechini. Nas análises utilizando o método de Rietveld e a TCHZ nas amostras de SnO2, observou-se que enquanto os cristalitos aumentam com o aumento da temperatura de tratamento, as microdeformações diminuem... / Methods for crystallite size and microstrain determination using x-ray powder diffractometry are discussed and applied to three interesting technological ceramics systems: LiCoO2 prepared by combustion or Pechini methods, SnO2 non doped and doped with 5% of cerium or 5% of yttrium or 5% of lanthanum, heat-treated at 550oC, 720oC, 820oC, 920oC, 1000oC and 1100oC, and hydroxylapatite prepared by emulsion method. Are discussed (i) the crystallite size-deformation (td) qualitative analyses using fwhm as 2θ function; (ii) the isotropic analysis by Rietveld method using the modified Young and Desai Thompson-Cox-Hastings function (TCHZ); (iii) the Williamson-Hall plot, (iv) the double-Voigt method and (v) Peter Stephens' phenomenological method applied to the Rietveld method. Two programs to calculate the crystallite size and the microstrains are developed to be used in the MathCad® 7.0 program, using the Williamson-Hall plot and double-Voigt method, respectively. The maximum entropy method was used in this work as complemental to the Rietveld method for obtaining the electron densities maps of hydroxyapatite. The size-strain qualitative analysis was applied to the LiCoO2 system. This study revealed that LiCoO2 trigonal phase prevails, followed by of a small amount of spinel Co3O4 cubic phase. It is observed that crystallites and microstrains are larger when the Pechini method is used. Analysis using the Rietveld method and TCHZ function in SnO2 samples, allow to observe that, while crystallite size increases when the temperature treatment increase, the microstrains decreases. The non doped samples show greater sizes and smaller strains. The hydroxyapatite size and strain analysis showed differences among the used methods. The Rietveld method using the Peter Stephens' model showed cristallite sizes between 918 Å and 869 Å, in the parallel and perpendicular directions of broadening axis...(Complete abstract click electronic access below)

Urban greenspace has an important role in supporting biodiversity and providing structural and functional connectivity between natural habitats. However, the mapping of vegetation in urban areas presents challenges, as urban vegetation is highly fragmented and heterogeneous. This study compared maps with respect to their strengths and weaknesses in providing ecologically relevant information in an urban area with the purpose to find how useful they are for local planning. The study took place in the urban part of Dún Laoghaire-Rathdown County, Ireland. The maps analysed were the Urban Atlas 2012 provided by Copernicus, the Prime 2 database provided by the Ordnance Survey Ireland, and two maps that were generated by this project from Sentinel 2 satellite imagery, one which showed vegetation based on calculated NDVI and one with four land cover classes calculated with a supervised classification. These maps were compared from three points of view: correspondence of vegetation classes, structural connectivity, and quality of vegetated areas. Analyses of structural connectivity were based on several landscape metrics, one of them was the degree of coherence (Cm) which reflects how connected the vegetation patches are in the landscape. Definition of quality was based on contextual indicators, such as the proximity to streams and areas with high conservation value, and vegetation present on a historical map from the 1830s. The results showed that the overlap of vegetation between the datasets varies between 27.0-89.1%. The different datasets definitions of vegetation affect how well they correspond in terms of where vegetation can be found. Resolution is also an important factor, as urban vegetation patches tend to be small and thus a coarse minimum mapping unit – as is the case for the Urban Atlas – masks important information on the configuration of vegetated areas in the urban area. The structural connectivity of vegetation differed little between Prime 2 (Cm = 7.95×10-2%) and the Urban Atlas (Cm = 5.87×10-2%). However, the distance between vegetated patches was on average shorter in Prime 2. This suggests that the Prime 2 dataset, because of its higher spatial resolution, contains more information on potential stepping stones for species to move around the landscape. The distribution of vegetated areas with higher contextual quality was mainly close to the boundaries of the urban area. Connectivity in a fragmented landscape like this urban study area plays a crucial role in maintaining populations of flora and fauna. It is therefore important to consider in the management of urban vegetation and in planning for development. This study offers a first insight in the structural connectivity of Dún Laoghaire-Rathdown County, which can be used to make more informed decisions that will sustain urban biodiversity.