420 research outputs found
Utilisation of semi-arid scrubland by goats in the dry season
(South African J of Animal Science, 2000, 30, Supplement 1: 93-94
Design of a DC overcurrent fault detection and protection scheme for DC collectors of a photovoltaic plant
Abstract: Faults in the DC collector circuits of a photovoltaic plant are a cause for major concern due to the damage they may cause to equipment. Fault protection is required for ground faults, line-to-line faults and arc faults. Typically, the magnitude of short-circuit currents of PV modules are similar to that of load currents which makes fault detection and protection difficult to carry out on the DC system. The DC collectors of a PV plant consist of combiner boxes where PV arrays are connected and inverter DC buses where combiner boxes are connected. This paper investigates the fault contribution from the PV modules on the combiner boxes and inverter DC buses in relation to typical PV module data on an isolated section of the DC network of a plant using the ETAP simulation tool. A fault detection and protection scheme for the main faults in a DC PV system is proposed based on previous research, for complete protection of the DC collector circuits
Selection and coordination of surge arresters for switching transient mitigation in photovoltaic power plants
Abstract: Photovoltaic energy generation has become a popular renewable alternative to conventional energy generation that utilise fossil fuels. However, given the diversity and complexity of these PV plants, it is imperative that such plant equipment be protected against the greatest contributor to equipment failure; surges. Software simulation using EMTP-RV version 3.3, this paper implements a proposed methodology for the insulation coordination study of a PV plant. The overvoltages associated with the opening of vacuum circuit breakers, at various test points along the network are considered in order to recommend possible selection criteria of surge arresters as well as location thereof. The study finds that for a reduction of surge magnitudes from 8 p.u to within 1.2 p.u would require surge arrester energy capabilities to be greater than 2.8 kJ/kV for the medium voltage (MV) arresters , and capabilities exceeding 259kJ/kV for the low voltage (LV) arrester. For the high voltage (HV) section of the plant, no surge propagation was identified thus exempting it from the insulation coordination. The above mentioned, along with surge current and overvoltage levels comprise the findings of the study providing parameter guidelines for arrester selection
Intestinal growth and function of broiler chicks fed sorghum based diets differing in condensed tannin levels
The effect of feeding sorghum condensed tannins on intestinal growth, function and histology was investigated in an 8-week broiler growth trial. Four sorghum varieties of different proanthocyanidins (PA) content; DC75 (DC - 2.48 A550nm/g DM) Chirimaugute (CH - 1.68 A550nm/g DM), Brown Tsweta (BT - 0.2 A550nm/g DM), SV2 (SV - 0.07 A550nm/g DM) and maize (MA) were used to formulate four diets each with one sorghum variety (CH, BT and SV) and maize included as the principal energy source. DC75 was used to replace 50 (DC50) and 100% (DC100) w/w maize to form the other two treatment diets. Relative weights of the small intestine differed significantly at 21 days of age. However, the decrease in weight did not correspond to the increase in PA level in a linear manner. Villus height and crypt depth were reduced at seven (7%) and 14 days (15%) in broilers fed DC and CH diets and thereafter was similar to MA and SV fed birds. The liver total and esterified cholesterol was reduced in DC100, DC50 and CH fed birds. Grain sorghum contains other phytochemicals such as policosanols and sterols besides PA which compound the observations in the liver. The effect of age on the severity of local liver lesions was not significant. The DC100 fed chicks showed mild crypt necrosis and/or sub-acute crypt distortion. There was a significant increase in the goblet cell number/mm2 measured in the jejunum of chicks fed CH, DC50 and DC100 diets. Sucrase but not maltase activity was significantly reduced with increased PA content in the 7-, 14- and 21-days age groups. From the results it appears that the dietary PA levels are not limiting factors in the development of the gastrointestinal tract of broiler chicks. Keywords: Sorghum; condensed tannins; intestinal adaptation; villus height; goblet cell density South African Journal of Animal Science Vol. 37 (3) 2007: pp.202-21
Presentation patterns of invasive cancer of the cervix: results from Parirenyatwa Oncology and Radiotherapy Centre, Harare, Zimbabwe 1998-2010
A research paper on cancer of the cervix in Zimbabwe.Cancer of the uterine cervix is the second most common cancer among women worldwide with a high incidence in Sub-Saharan Africa.1 In developing countries such as Zimbabwe invasive cancer of the cervix (CaCx) is the most common cancer in females and also the leading cause of cancer related deaths in women.2 The American Cancer Society3 estimated that 12.710 million new cases of invasive CaCx were going to be diagnosed in 2011 and about 4.290 million women were going to die with invasive CaCx. The same author reported that there is a significant decrease in incidence and mortality rate of invasive CaCx in developed countries over the past three decades as compared to the developing countries. This was attributed to available options of disease prevention with the possibility of early diagnosis of the disease due to effective screening and accessibility to effective treatment procedures in developed countries. To this end it has been noted that women living in developed countries have a 208% greater chance of being successfully treated when compared with women in less developed countries
Examining the classroom practices of physical science educators: a case study in four secondary schools in the Pietermaritzburg area, KwaZulu-Natal.
Thesis (M.Ed.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.The purpose of this study was to examine the classroom practices of the Physical Science educators and analyze how these practices influence deep conceptual learning and understanding. Four secondary schools in the Pietermaritzburg area, in the province of KwaZulu-Natal were selected as cases for in-depth qualitative study. All the schools were African schools servicing a working class community. From each school only one educator
participated, and each educator was observed teaching one of his/her classes. Two educators were observed teaching Grade 12 learners and the other two taught Grade 11 learners. The study utilized participant observation, interviews and relevant documents as source of data. The main findings of the study suggest that educator practices were predominantly traditional. They were characterized by lack of effective interactions with learners, dealing with surface
features of the content without probing for depth necessary for understanding. It was also found that schools lack a culture of resource development. Though resources were inadequate, the little that educators had was not effectively utilized. The educators seemed to be shifting towards employing a variety of assessment methods, but the difference was still superficial. The findings have implications for policy, practice and in-service training of educators (INSET). Evidence suggests that educators' beliefs have a major influence on how they teach, and that unsound beliefs about teaching and learning are a threat to the
implementation of policy. INSET programmes need to target the beliefs of educators about science teaching and learning
Understanding India - South Africa tourism: The Impact of Food Tourism on the Socio-Cultural and Economic Fabrics in Durban.
India-Africa relations is distinct and owes its origins to a common past that the countries share. In this paper the researchers attempt to trace India’s engagement in South Africa and its socio-cultural and economic impact in the coastal city of Durban. In order to gain an insight on the socio-economic activities and the cultural dynamics, a qualitative research design was used. Twenty key informant interviews were conducted. The results show that eating food is not just what we enjoy but it is additionally a medium of cultural exchange and experience. For Africans from other African countries based in Durban, the presence and availability of Indian food, fulfils a cultural and emotional gap by creating a space to their ‘remembered places’. The paper concludes that Indo-Africa engagement has accelerated growth on investment and culinary tourism. The paper recommends the development of culinary itineraries and the expansion of socio-economic and cultural programmes in South Africa
The Effect of Black Tax on Employee Engagement: The Mediating Role of Idiocentrism-Allocentrism-A Case of Pharmaceutical Industry in Zimbabwe
Employees in the Pharmaceutical industry are coming late to work and knocking off early. These actions unveiled by the employees are likely to incur economic costs on the employer, occasioned by low employee productivity. Owners of production have expressed concern over the general low staff morale in the pharmaceutical sector. While most studies have concentrated on internal job-related factors as drivers of employee engagement, this study seeks to assess employee engagement as being influenced by black tax, an external factor. The main aim of the research was to establish the influence of black tax on employee engagement, being mediated by idiocentrism-allocentrism, particularly focussing on the pharmaceutical manufacturing and retailing industry in Bulawayo, Zimbabwe. The study employed the philosophical approach of pragmatism to guide the whole research. The researcher adopted a multi-stage sampling technique supported by the census technique to pick participants from the population. Closed and open-ended questionnaires were used to collect data from qualified pharmacists who are working in both the manufacturing and retailing industry in Bulawayo. Statistical Package for Social Sciences v23 (Process v3.5 by Andrew F. Hayes) was used to test the hypothesized relationship among variables. Qualitative data were analyzed using thematic analysis. The results suggest that black tax directly influence employee engagement in the presence of a mediator (idiocentrism-allocentrism). Furthermore, the results indicate that the indirect coefficient was partially significant, which means that idiocentrism-allocentrism has a partial influence on employee engagement. The researchers recommend that management should ensure that employees are motivated all the time. They should implement an open-door policy so that employees can share their issues that affect their engagement level at work
Influence of season and other factors on avian Trypanosoma spp. and microfilarial prevalence in the Lowveld, South Africa
To comprehend the effects of emerging infectious diseases on both human and animal health, it is necessary to understand the ecology of pathogens that have wildlife reservoirs. In this study, we determined the prevalence of the parasites Trypanosoma spp. and filarial nematodes in the bloodstream of birds in and around the Kruger National Park, South Africa, partly to test the hypothesis that season influences parasitaemia. Other factors considered were foraging habits, gregariousness or solitariness, and whether location might facilitate contact between birds and parasite vectors. Microscopy was used to screen stained blood smears prepared from 685 captured birds of 87 species. It was found that 3.9% of the birds were infected with filarial nematodes (as reflected by the presence of microfilariae) and 3.1% with Trypanosoma spp. No cases of coinfection with both types of parasite were encountered. Ground-foraging and solitary birds had the highest parasite prevalences compared to other birds. Infections were recorded throughout the year at all six sites. The respective percentages of birds harbouring the two parasite types in the dry season were the same (both 2.3%), whereas microfilariae dominated in the wet season (6.9%) and the prevalence of Trypanosoma spp. then was 1.4%. These findings represent new knowledge concerning avian haemoparasite prevalence in an Afrotropical setting – something that has so far been poorly studied.
Significance:
• The determination by microscopy of the prevalence of microfilariae of filarial nematodes (3.9%) and Trypanosoma (3.1%) in the peripheral blood of 685 birds of 87 species provides new knowledge on birds in Africa.
• Unexpectedly, ground-foraging and solitary birds had the highest parasite prevalences.
• The possibility of human infection with these two types of avian parasites is considered
Clinical mentorship of midwifery students: The perceptions of registered midwives
Background:Â Clinical mentors are experienced practitioners who play an important role in encouraging the professional development of students in clinical areas. The responsibility of clinical mentorship in nursing is often difficult to maintain. However, there is a dire need for clinical mentorship in maternity units, especially in South African hospitals were high maternal mortality rates remain alarmingly high.
Aim:Â This study aimed to describe the perceptions of registered midwives regarding the clinical mentorship of midwifery students.
Setting:Â The study occurred in a semi-rural state regional hospital in the eThekwini district, KwaZulu-Natal.
Methods:Â A qualitative exploratory and descriptive design was conducted using in-depth individual interviews with midwives in maternity units. A purposive and convenient sampling method recruited 17 registered midwives from 3 maternity care areas within a single setting. Interviews were audio-recorded and all data were analysed using qualitative content analysis.
Results:Â Five categories emanated from this study namely, sharing knowledge and skills; encouraging role model behaviour; promoting self-worth; Is a challenging task; and requiring additional support.
Conclusion:Â Clinical mentorship has a reciprocal effect on teaching and learning in maternity care areas and encouraged registered midwives to lead as role-models. The process demands competence, professionalism, and leading by example. Despite the confidence, satisfaction and interest in clinical mentorship, registered midwives often find the process challenged by patient care priorities. Therefore, registered midwives require additional support to mentor students in clinical practice.
Contribution:Â This article shows that clinical mentorship places various challenges on registered midwives and formal mentorship training could be beneficial
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