11613 research outputs found
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Synthetic, electrochemical, spectroscopic and computational aspects of ferrocene derivatives coordinated to subphthalocyanines
No full textA series of six ferrocene derivatives, namely the ferrocenylcarboxylic acid dyads (Fc(CH2)nCO2H (n = 0 – 3), Fc(CH)2CO2H and FcCO(CH2)2CO2H) were synthesized and coordinated to subphthalocyanines (SubPcs) in the axial position to form seven novel (Fc(CH2)nCO2BSubPc(H)12 (n = 1 – 3), FcCO(CH2)2CO2BSubPc(H)12, (Fc-CH=CHCOO)BSubPc(H)12 and Y-BSubPc(F)12 with Y = (Fc-CH2-CH2-COO) or (Fc-CH=CH-COO)) and one known (Fc(CH2)nCO2BSubPc(H)12) ferrocenylcarboxylic acid subphthalocyanines dyads. In addition a novel subphthalocyanine HOBSubPc(C12H25)6(H)6 with a hydroxy group in the axial position and alkyl ligands (C12H25) on the non-peripheral positions, as well as the known ClBSubPc(F)12 and the mother compound ClBSubPc(H)12 were synthesized. UV/vis analysis of the SubPcs revealed that both the donor (C12H25) non-peripheral substituents and the acceptor (F) ring substituents shifted the Q band of SubPcs toward longer wavelengths compared to the unsubstituted ClBSubPc. However, the different ferrocenylcarboxylic acid dyads in the axial position did not have any influence on the position of the Q band of the SubPcs. An electrochemical study of the SubPcs showed that peripheral substitution generally has a smaller influence (ca 0.1 V shift) on the shift of the oxidation and reduction potential of a SubPc than non-peripheral substitution (ca 0.3 V shift). It was found that the novel SubPc HOBSubPc(C12H25)6(H)6 had the lowest macrocycle-based oxidation potential and that novel SubPc Fc(CH2)3CO2BSubPc(H)12 has the lowest first ring-based reduction potential reported for SubPcs to date. The experimental conditions used for the electrochemical study made it possible for the first time to obtain chemically reversible ring-based oxidation with peak current ratios approaching 1 and peak current separation ΔEp < 0.086 V for SubPcs. The cyclic voltammetry data of the seven new ferrocenylsubphthalocyanine dyads, in agreement with the character of DFT calculated molecular orbitals, showed that Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second ring based oxidation. All reductions are localised on the subphthalocyanine ligand. The fluorine ring substituents of the electron-withdrawing SubPcs Y-BSubPc(F)12, caused the ferrocenyl oxidation to shift with ca. 0.1 V more positive compared to electron-rich Y-BSubPc(H)12. Furthermore, the CV data revealed that the formal reduction potential of Fe(II/III) of the axial ferrocenyl moiety of the eight ferrocenylcarboxylic acid containing SubPc dyads followed the same trend than the free ferrocenylcarboxylic acid dyads, but shifted to a lower oxidation potential compared to free ferrocenylcarboxylic acid dyads. The carboxylic group in the free ferrocenylcarboxylic acid dyads is directly connected to ferrocenyl, or by an ethene group, or by an alkyl chain of varying length. The length of the alkyl chain separating the two groups affected the formal reduction potential of Fe of the ferrocenyl group. The formal reduction potential of Fe was also affected by the electron withdrawing carbonyl group. The extent of the effect depended on whether the carbonyl group was directly bound to a ferrocenyl moiety or isolated by an sp3 hybridised carbon atom backbone (-CH2-CH2- with no π-communication) or a non-isolated sp2 hybridised carbon atom backbone (-CH=CH- with π-communication between Fc and the carbonyl group possible). Density functional theory (DFT) calculations gave further insight into the redox properties of the novel dyads. A linear relationship between the formal reduction potential of these ferrocenyl carboxylic acid derivatives and DFT calculated HOMO (highest occupied molecular orbital) energies were obtained. The DFT study also provided linear relationships between the first oxidation potential and HOMO energies, as well as between the first reduction potential and LUMO (lowest unoccupied molecular orbital) energies for a series of non-ferrocene-containing SubPcs with peripheral and non-peripheral substituents = H, F or (C12H25) and axial substituent = Cl or an alkoxy group. The neutral ferrocenylcarboxylic acid subphthalocyanines dyads have LUMOs and HOMOs of mainly -ring and iron-d character respectively, confirming ring-based reduction and Fe(II) to Fe(III) oxidation. Optimisation of the cation (oxidised) species was essential to verify the locus of the second ring-based oxidation, since the frontier orbitals rearranged upon oxidation.National Research Foundation (NRF)University of the Free State (UFS
Reconceptualising urban public open spaces: a case of Freedom Square in Mangaung, South Africa
No full textUrban public open spaces play a critical part in sustainable neighbourhoods. In recent years, urban public open spaces are gradually disappearing, and this affect the spatial patterns of urban land use. Enabling extensive interaction of all urban stakeholders has been described as a panacea for curbing the incidence of encroachment. However, the existence of different perceptions by these stakeholders concerning the value and usefulness of these spaces poses a challenge to effective management. This has resulted in planning, economic, environmental, recreational, and housing value conflicts. Also, available evidence indicates that the value of urban public open spaces has been neglected by urban stakeholders as the focus is on planning for other land uses. To bridge this gap, the study sought to reconceptualise urban public open spaces in order to maximise its value, as well as to develop a framework for managing value conflicts, thereby enabling effective urban open space management in Mangaung, Free State province in South Africa. This study adopted a case study research design and deployed a variety of techniques such as focus group discussions, face-to face semi-structured interviews and personal observation for data elicitation at different intervals. Individual semi-structured interviews were conducted with purposively recruited town planning, human settlements and environmental management professionals from local government. The focus group discussants included community members who have encroached upon urban public open spaces and those owning properties around open spaces. Also, observations were conducted around the study area. The data was then analysed thematically, and the findings were used to test the propositions through intracase and cross-case study analysis. The study identified barriers in planning and management of urban public open spaces in Mangaung. These included lack of understanding of the value and utilisation of urban public open space; lack of planning and implementation, education and empowerment as well as communication to engender community participation; evidence of the varying value conflicts among the urban stakeholders; and absence of the management of the variety of perspectives during the planning and management of urban public open spaces. It was observed that lack of understanding of the value and usefulness of urban public open spaces led to urban public open space encroachment. The findings gave rise to the development of an Urban Public Open Space Management Framework. This framework indicates that effective community participation and effective value conflict management can lead to effective urban public open space management that will help to curb the incidence of urban public open space encroachment. It is expected that the framework would guide planning professionals, other professionals and policymakers involved in urban planning to plan and manage urban public open spaces effectively within the province and beyond
Assessing climate-related fire danger across the central Grassland Biome of South Africa
No full textThe grasslands of the South African interior plateau are subject to seasonal wildfires that occasionally inflict serious damage to livestock production systems and infrastructure. Recent and future projected changes in the climate imply long-term changes in the fire regime, which may pose challenges to fire managers and exceed the current suppression capacity. The aim of this study was thus to assess historical and future fire danger across the central grassland biome of South Africa. Both actual observed fires (i.e. total burned area obtained through satellite remote sensing) and climatological fire danger (i.e. fire danger indices calculated from reanalysis climate data) were considered over the historical period (1981 – 2010). Self-organizing map (SOM) analysis was also used to identify the 850 hPa synoptic weather patterns related to increased climatological fire danger over the historical period, while projections from six ensemble members were used in evaluating climate-related fire danger under the A2 scenario over three future periods (i.e. 2011 – 2040, 2041 – 2070 and 2071 – 2100). Results showed that enhanced rainfall during the antecedent mid-summer season lead to increased burning due to higher fuel loads. There was a large inter-annual variability in the total burned area, ranging from 478 000 to 1.6 million ha per annum, with a significant decreasing trend of about 34 000 ha per annum over the historical period. This was in contrast to the significant increase in climatological fire danger, particularly during the last decade. Climatological fire danger was shown to be considerably higher in the south-western part of the central grassland, where extreme days occurred on 5 – 9 days during the fire season. SOM analysis revealed that very dangerous fire conditions were mostly associated with the warm, dry and windy conditions typically experienced to the east of a well-developed frontal trough over the subcontinent. Projections from various ensemble members did not support a continued increase in climate-related fire danger over the current climate epoch and had broadly inconsistent spatial patterns of change in very dangerous occurrences. The bulk of the ensemble members projected relatively small changes in fire danger over the southern Highveld, while the largest increases occurred in the north-west. An increase of between 5 – 15 very dangerous days was predicted for the near-future climate epoch, and 5 – 45 days for the distant future epoch (double these values for FFDI under MIROC3.2). The pattern and magnitude of change generally corresponded to different degrees of warming. The shift towards higher fire danger seemed to be more prominent from mid-century onwards. The projections from two ensemble members, CSIRO Mk3.5 and GFDL-CM2.1, differed considerably from the others. They predicted a decrease of between 5 – 15 very dangerous days over the central and southern parts of the study area for the current and near-future climate epochs, and decreases of less than 5 days for the distant future epoch. Discrepancies among future climate scenarios and unrepresented processes (e.g. vegetation dynamics), contribute to uncertainty about the accuracy of these predictions. Nonetheless, the results of this study underscore the potentially large impacts of climate change on the central grassland biome.Inkaba yeAfrica (now Iphakade
An assessment of economic (in)security challenges faced by migrant women in Madibeng Local Municipality area
No full textThis study set out to explore the economic security challenges of international migrant women in Madibeng Local Municipality in the North West province of South Africa. The study adopted human security as its conceptual framework. A qualitative research design was used. The snowball sampling method was used to select a study sample of 19 international migrant women. Data were collected using semi- structured interviews. The study found that all the interviewed international migrant women (19) were experiencing chronic economic insecurity although they were economically active. Thirteen (13) of the participants were in wage labour and 6 were self-employed. Participants had access to an income, but the monthly income was not equal through-out the year. The wages were seasondependent. Most participants (17) were employed in fixed-term contracts; with two in verbal and ambiguous contracts. Entrepreneurship by the international migrant women was not by choice but a means to survive. The women preferred formal employment to running small businesses. Accessing a wage/salary does not necessarily equate to economic security. Seasonal work, contracts of not more than a year and lack of documentation from the Department of Home Affairs, were some of the main economic security challenges that international migrant women experienced. Economic (in)security is a condition that changes with time. The economic insecurity of most women worsened en-route to South Africa while for others it worsened as soon as they arrived in South Africa. However, the economic security for all the international migrant women improved with length of stay in South Africa. Lastly, recommendations for future research were suggested. Economic reasons were the main push factors while social networks were the main pull factors, for the interviewed international migrants to come to South Africa. The research also found out that “stokvels” and “saving clubs” were some of the devised plans to help the women to save their income. Social networks were important for saving and also helped the migrant women to secure jobs around the area.Canon Collins Educational and Legal Assistanc
Yield linkage drag in quality protein maize inbred lines and hybrids
No full textThe development of high yielding and stable quality protein maize (QPM) hybrids is important for increasing grain yield output per unit area, to support the fight against hunger and malnutrition in sub-Saharan Africa (SSA), as well as for feed supplement formulation for the animal and poultry industries. Despite the development of QPM genotypes with increased lysine and tryptophan content, important information is lacking on the yield potential of QPM genotypes compared to non-QPM (normal) genotypes. The main objective of this study was to quantify grain yield reduction (if any) due to the QPM trait. The specific objectives were to: (i) compare QPM and non-QPM inbred lines for yield and yield related traits, as well as quality traits, and determine stability for grain yield, (ii) compare QPM and non-QPM hybrids for yield and yield stability, (iii) estimate the combining ability for grain yield and quality traits of QPM and non-QPM inbred lines (iv) estimate the heritability, variance components, principal components, correlation coefficients, and do path analysis of grain yield, and agronomic and quality traits. In this study, 130 single cross hybrids were developed from 33 QPM and non-QPM inbred lines and four testers (two QPM and two non-QPM). Five hybrid checks (two QPM and three non-QPM, all single cross hybrids) were included, obtained from the International Maize and Wheat Improvement Center, Zimbabwe. The 135 hybrids together with the 40 inbred lines were evaluated in South Africa and Zimbabwe during the 2017/2018 and 2018/2019 cropping seasons. The inbred lines were evaluated at seven locations using a 5 x 16 alpha lattice design, while the hybrids were evaluated at 13 locations using a 5 x 27 alpha lattice design with two replications. In the field experiments, two plants per plot were selfpollinated for the determination of zein, tryptophan, amylose and starch, protein, oil, moisture and fibre contents. In the inbred line trials, the top six performing lines outyielded the best yielding check by 15%. Although the top two inbred lines were non-QPM, three of the six top yielding inbred lines were QPM. The QPM inbred line average yield was 0.29 ton ha-1 higher than for non-QPM inbreds. Inbred lines 39, 27 and 10 had protein content above 9%, while lines 2, 5 and 16 had tryptophan concentrations above 0.09%. The best performing hybrids were a QPM cross of line 11 x CZL15049 (entry 41) followed by a non-QPM hybrid involving line 28 x CZL15049 (entry 108). The best QPM hybrid outperformed the best non-QPM hybrid by 8.81%. In addition, the best QPM hybrid, genotype 41, outperformed the best non-QPM check (Pioneer) and best QPM check (CBI) by 50.45 and 52.24%, respectively. Despite this, QPM hybrids yielded 13.90% lower than non-QPM genotypes on average. The additive main effects and multiplicative interaction (AMMI) and genotype main effect plus genotype by environment interaction (GGE) biplots identified genotypes 108 and 12 as the most stable and high yielding hybrids. QPM hybrid 41 and non-QPM hybrids 108 and 12 were the highest yielding genotypes. Both additive and non-additive genetic effects were important in the expression of measured traits, with non-additive gene action controlling the inheritance of grain yield. Inbred lines 11, 14 and 28 and non-QPM tester CML444 showed desirable general combining ability effects for grain yield. Based on the specific combining ability values, crosses 41, 85, 99, 105, 105 and 121 were identified as the best hybrids across the 13 locations for grain yield. Hybrids 45, 69 and 6 had a high quality index, while hybrids 45 and 57 had high tryptophan content. Hybrids 51 and 37 had high values for starch and oil contents, respectively. Additive genetic effects were predominant in the control of the quality traits. Broad sense heritability estimates were higher than 80% for the traits measured. Most of the hybrids displayed heterosis for grain yield, with some having very high values. In conclusion, QPM inbred lines yielded higher than non-QPM lines, but QPM hybrids yielded 13.9% less than
non-QPM hybrids. So it would seem that there is yield drag associated with increased protein quality in hybrids in this specific set of material. There were, however, specific QPM hybrids that had excellent and stable yield, which can be considered for commercial release
Battle for the heart: how (not) to transform church and society
No full textThe battle of the heart can be seen as the core problem of the Christian religion in modern culture. According to Augustine, the complex mixture of longings are the driving forces of human lives. These longings are not an intellectual puzzle, but rather a craving for sustenance. The contributions locate the battle for the heart and transformation of society and church in the context of an ethnic, multi-religious, socio-economical divided Africa. Where are the authentic voices of leaders who can change the heart? How to mend a 'broken' heart? How to transform congregations towards inclusion of difference? Can we embrace the dignity of difference as attitudes that enable transformation of church and society
Identifying wetland soil properties aiding the dormancy of Rift Valley fever vectors in central South Africa
No full textRift Valley fever (RVF) is a vector-borne zoonotic disease caused by the Rift Valley fever virus (RVFV). This virus is considered one of the largest emerging diseases in Africa and the Middle East, affecting public and livestock health and causing economic loss. RVF causes a high mortality rate in young animals and 100% abortion. The RVF outbreaks are triggered by favourable environmental and flooding conditions, which enable mosquitoes to proliferate and spread the virus. Although environmental factors such as soil, geology and vegetation play a crucial role in the maintenance and survival of the virus, the specifics of these environmental factors are still uncertain and therefore in dire need for more intensive research. Large epidemics are reported to occur in central South Africa. This study was conducted in the Free State and Northern Cape Provinces of South Africa. The study was initially conducted using 22 selected seasonal and temporary wetland sites (depressions/pans). Of those 22, 12 sites were classified as sites with mortalities and 10 sites were classified as sites without mortalities. The study was subsequently expanded to include eight (8) additional sites, all classified as sites without mortalities. Soil surveys were conducted: soil classification and soil samples were collected to besubjected to chemical, physical, biological and mineralogical laboratory analysis. Three analyses were per formed, which included descriptive analysis, non-parametric van der Waerden test and discriminant analyses. Soil water content was measured at selected sites using level loggers, EM 50, and watermark loggers. The results from the study indicated that only the cations (exchangeable Ca2+, K+, Mg2+, soluble Ca2+ and K+) of all chemical analyses indicated significant differences, with sites without mortalities having higher mean values than sites with mortalities. Coarse silt was the only physical property that differed significantly, with sites without mortalities recording higher mean silt content than sites with mortalities. Coarse silt has a lower water holding capacity than clay and can thus result in drier environments that do not favour mosquito eggs aestivation. Mortality sites and new sites without mortalities were characterised by soils that indicate longer periods of water saturation. This coincided with soil morphological indicators of water saturation, including low chroma colours, presence of mottles and concretions, and lime precipitation. Ni, Y, Zn and Ba were the only four elements that were found to be significantly different. Thefirst three elements are repo rted to be toxic and therefore might have suppressed the mosquito eggs aestivation in soils without mortalities. Conversely, Ba was high in the mortality sites. The microbial activity was inconsistent between the two years of sampling at all sites. The inconsistency was due to various reasons including vastly differing weather conditions between the two years, possible differing sampling methods and other unknown natural variations. The hatching of Aedes mosquito eggs is promoted by above-normal rainfall that results in flooding of wetlands and thus creates a conducive environment for hatching. In winter months, the hatching of mosquitoes is normally minimal due to lower rainfall, cold temperatures and windy conditions. In some sites, the abundance of mosquitoes was minimal even during flooding, due to 90% of mosquitoes hatching during the first inundation than subsequent flooding. The discriminant function previously developed was used to classify the (8) new sites without mortalities. Based on this classification, seven sites were erroneously classified as sites with mortalities, while only one site was correctly classified as a site without mortalities. A new discriminant function was subsequently developed using all available data. The identified RVF outbreak-prone areas coupled with mosquito surveillance and climate data can be used to develop RVF risk maps and thus contribute to the prevention and control of outbreaks. Future research needs to include the collection of Aedes mosquito to be tested for the virus, sampling should be expanded to other provinces as this allows for a larger sample to clearly define sites with mortalities and sites without mortalities.EcoHealth Alliance/DTRAAgricultural Research Council (ARC)Department of Science and Technology (DST
Novel synthesis and characterization of SiO2 nanopowders doped with Sr2+ and co-doped withTb3+ dispersed in PLA for application in light emitting material.
No full textThe immobilization of the phosphor particles in a polymer matrix helps to overcome the problem of emitter layer thickness and thus the reproducibility of the emitted light experienced when phosphors are immobilized in glues such as polyurethane or epoxy resin. In this study composites of SiO2:0.4 mol% Sr2+:x mol% Tb3+ (with x = 0.02, 0.06, 0.1, 0.3, 0.4, 0.5) nano-powders dispersed in PLA polymer matrix were successfully prepared through melt mixing. The challenge as shown by the TEM images is that the filler particles tend to agglomerate in the polymer matrix. The XRD results showed broad peaks for all samples, which meant the samples were amorphous. The introduction of the nano-powders into the polymer matrix did not result in the change in the morphology of the samples. The emission peaks that can be associated with the Tb3+ transitions were observed with the dispersion of the nano-powders into the PLA. The SiO2 based phosphors used in this study were prepared using the sol-gel technique and characterized by SEM, TEM, XRD, UV and PL. The SiO2 doped with Sr2+ samples showed an increase in crystallinity with increasing Sr2+ concentration. These singly doped samples showed the highest luminescence at 0.4 mol% Sr2+ concentration, and the CIE analysis showed that the colour coordinates of SiO2:0.4 mol% Sr2+ were related to white light emission. This SiO2:0.4 mol% Sr2+ sample that showed the highest luminescence was co-doped with different mol% Tb3+. The co-doped samples were found to be amorphous with the co-doping and not having any significance on the shape of the particles. The addition of Tb3+ tuned the colour of the phosphors from blue to green.National Research Foundation (NRF
The strategy to enhance teaching and learning of work, energy and power concepts in Grade 12 physical sciences class
No full textThe study aimed to develop a strategy for the teaching and learning of work, energy and power concepts in the physical sciences Grade 12 class. Different reports from the Department of Basic Education (DBE) and other educational researchers expressed their concern about the poor performance of learners in physical sciences, especially in work, energy and power concepts. It is from the reason mentioned above that I undertook the research to develop a strategy for enhancing teaching and learning of work, energy and power concepts. The study was conducted at Mthavuma high school, which is one of the high schools in Newcastle. The following were selected to participate in my study, two physical science teachers from two different schools, one mathematics teacher who taught physical science in previous years, the school principal, Grade 12 physical science learners, a physical science subject advisor and the chairperson of the School Governing Body (SGB), who was also a motor mechanic. The selection of the co-researchers was based on my intentions to build a hybrid team with different expertise and experience on this topic. Different methods were used to generate the data. These methods included workshops, focus team discussions, Free Attitude Interview (FAI) and teacher presentations. Various factors, which contributed to the poor performance in work, energy and power, were discussed. Bricolage was used as a theoretical framework to achieve the aims of the study. Participatory Action Research (PAR) was used as a research methodology. PAR was preferred for this study because it is democratic and involve co-researchers in finding the solution to the problem. Critical Discourse Analysis (CDA) was used in presenting, analysing and interpreting the data generated from the research field
Factors affecting performance management at First National Bank Lesotho
No full textDissertation (MBA (Business Administration))--University of the Free State, 2020The main aim of this study is to analyse the factors affecting performance management at FNB Lesotho. It has come to the realisation that the bank’s performance management systems suffer from the lack of transparency in promotions, ineffective performance feedback mechanisms from managers, management’s lack of support for continuous process improvement initiatives and lack of recognition for high-performing staff. To achieve the objectives of this study, a stratified random sampling technique was adopted in which data was collected from a sample size of 60 respondents from FNB Lesotho. Data was collected using a questionnaire and it was analysed using SPPS. The study found that performance management at FNB is influenced by organisational culture, involvement of stakeholders, constant monitoring, feedback, distribution and learning from results and leadership assurance. The study recommends that FNB Lesotho continue to expand the involvement of its stakeholders so that they can contribute with their input to enhance all-inclusive policy decisions. The study further recommends that the bank ensure regular training of its employees to improve their skills, which in turn will boost their performance. The bank should also improve on its leadership commitment by making sure that the leadership is at the forefront of resource endowment, goals setting and leading the organisation towards the attainment of its overall objectives