Design and development of a low-voltage DC domestic power supply system

Thesis (Master of Engineering (Electrical)) -- Central University of Technology, Free State, 2018Much effort is spent in regulating the power quality in alternating current power supplies for electronic devices. Many electronic devices, however, do not use alternating current, but rather direct current. The output of most small scale renewable energy systems are also direct current, so it can be connected to the loads more efficiently by eliminating the inverter stage. In a circuit with a number of rectification stages the conversion losses can add up to a significant amount. By reducing the number of conversion stages or possibly eliminating some of the stages the overall system could be more efficient. The purpose of this dissertation is to present the simulation design and results of a direct current distribution system, containing common household appliances connected to a direct current grid supply and a renewable energy source. A bottom-up design approach is used where a list of household appliances with their voltage needs is identified and the distribution voltage is then selected based on the voltage needs. The distribution system is modelled using Matlab and Simulink software. Results show that common household loads can be supplied directly with direct current, from either a main direct current grid supply, or a renewable energy system with direct current output. This direct current distribution system is compared to two other systems: (1) Existing alternating current system and (2) Hybrid system (converting alternating current to direct current for distribution in the house). The three systems are compared to each other in terms of power efficiency and material cost. The existing alternating current system is shown to be the most efficient, with an average power efficiency of 87.85 %. The second most efficient system is the hybrid system with average power efficiency of 86.95 %, and the least efficient of the three is the direct current distribution system with 86.45 %. The main reason why the direct current system is less efficient is because of the high input power of the microwave oven when connected to a direct current supply. The direct current system is more efficient than the alternating current system if the microwave oven load is taken out of both. Future work will involve more detailed operational and transient state simulations of the loads in the direct current system. Another recommendation is to find a direct current design for supplying the microwave oven load that does not incur large losses. A final recommendation is to build a practical test set-up of the direct current system in order to analyse the practical aspects of a residential direct current distribution system

The Vaccine and Cervical Cancer Screen project 2 (VACCS 2): Linking cervical cancer screening to a two-dose HPV vaccination schedule in the South-West District of Tshwane, Gauteng, South Africa

BACKGROUND : Cervical cancer is preventable, but still highly prevalent in South Africa (SA). Screening strategies in the country have been ineffective, and new ways to prevent the disease are needed. OBJECTIVES : To investigate the feasibility of linking cervical cancer screening in adult women to human papillomavirus (HPV) vaccination in schoolgirls. METHODS : Ten primary schools in the South-West District of Tshwane, Gauteng Province, SA, took part in the study. Cervical cancer and HPV vaccine information was provided to schoolgirls and their parents. Consented schoolgirls were vaccinated and their female parents were invited to participate in self-screening. RESULTS : Among 1 654 girls invited for vaccination, the consented and invited uptake rates were 99.4% and 64.0%, respectively. Vaccine completion rates were higher in schools where the vaccination programme was completed in the same calendar year than in those where it was administered over two calendar years. Of 569 adult females invited, 253 (44.5%) returned screen tests; 169 (66.8%) tested negative and 75 (29.6%) positive for any high-risk HPV (hrHPV). There were no differences in level of education, employment status or access to healthcare between women with positive and those with negative screen results. CONCLUSIONS : Implementation of HPV vaccination in a primary school-based programme was successful, with high vaccine uptake and completion rates. Self-screening reached the ideal target group, and it is possible to link cervical cancer screening to the cervical cancer vaccine by giving women the opportunity of self-sampling for hrHPV testing. This is a novel and feasible approach that would require some adaptive strategies.http://www.samj.org.zahb201

The Vaccine and Cervical Cancer Screen (VACCS) project : linking cervical cancer screening to HPV vaccination in the South-West District of Tshwane, Gauteng, South Africa

BACKGROUND : Cervical cancer is preventable, but still highly prevalent in South Africa (SA). Screening strategies in the country have been ineffective, and new ways to prevent the disease are needed. OBJECTIVES : To investigate the feasibility of linking cervical cancer screening in adult women to human papillomavirus (HPV) vaccination in schoolgirls. METHODS : Ten primary schools in the South-West District of Tshwane, Gauteng Province, SA, took part in the study. Cervical cancer and HPV vaccine information was provided to schoolgirls and their parents. Consented schoolgirls were vaccinated and their female parents were invited to participate in self-screening. RESULTS : Among 1 654 girls invited for vaccination, the consented and invited uptake rates were 99.4% and 64.0%, respectively. Vaccine completion rates were higher in schools where the vaccination programme was completed in the same calendar year than in those where it was administered over two calendar years. Of 569 adult females invited, 253 (44.5%) returned screen tests; 169 (66.8%) tested negative and 75 (29.6%) positive for any high-risk HPV (hrHPV). There were no differences in level of education, employment status or access to healthcare between women with positive and those with negative screen results. CONCLUSIONS : Implementation of HPV vaccination in a primary school-based programme was successful, with high vaccine uptake and completion rates. Self-screening reached the ideal target group, and it is possible to link cervical cancer screening to the cervical cancer vaccine by giving women the opportunity of self-sampling for hrHPV testing. This is a novel and feasible approach that would require some adaptive strategies.http://www.samj.org.zahb201

Utility of extended HPV genotyping as primary cervical screen in an unscreened population with high HIV co-infection rate

OBJECTIVE : Screening with primary human papillomavirus (HPV) testing has been evaluated in highly prescreened populations with lower HPV and HIV prevalence than what is the case in South Africa. High prevalence of HPV and underlying precancer in women living with HIV (WLWH) affect the clinical performance of screening tests significantly. This study investigates the utility and performance of an extended genotyping HPV test in detection of precancer in a population with a high coinfection rate with HIV. METHODS : A total of 1,001 women aged 25 to 65 years with no cervical cancer screening in the preceding 5 years were tested with cytology and primary extended genotyping HPV testing. The cohort of 1,001 women included 430 WLWH (43.0%) and 564 HIV-negative (56.3%) women. RESULTS : Abnormal cytology (atypical squamous cells of undetermined significance or higher) was significantly higher in WLWH (37.2% vs 15.9%) and high-grade squamous intraepithelial lesion or above (23.5% vs 5.2%). The WLWH also tested positive more often for any HPV type (44.3% vs 19.6%; p < .0001) The specificity for cervical intraepithelial neoplasia 2+ at 91.2% of a combination of HPV types, 16/18/45 (very high risk) and 31/33/58/52 (moderate risk), performed better than cytology or any HPV-positive result to predict cervical intraepithelial neoplasia 3+ on histology. The additional genotype information supports direct referral to treatment or colposcopy in a larger proportion of the screen-positive population. CONCLUSIONS : The potential contribution of extended genotyping is demonstrated. The ideal choice of sensitivity and specificity ultimately depends on the health budget. More information will allow a screening algorithm, guiding management according to risk.https://journals.lww.com/jlgtd/pages/default.aspx2024-04-22hj2024Obstetrics and GynaecologySDG-03:Good heatlh and well-bein

A retrospective analysis of nickel exposure data at a South African base metal refinery

This study aimed to analyze historical soluble nickel exposure data from a South African base metal refinery and to identify trends in the soluble nickel exposure from 1981 until 2014 in the electrowinning department. Exposure data were presented in an exposure matrix, which described exposure profiles for both area and personal exposures inside two tankhouses. Exposure data were standardized by converting total nickel aerosol concentrations to inhalable nickel concentrations (correction factor 3.0). One-way analyses of variances (ANOVA) were conducted to identify significant differences in log-transformed area and personal exposures from 1982 until 2014, and the trends were assessed with linear regression. Differences were evaluated in area exposure between sections inside the tankhouses, i.e., East, West, and Center bays and in personal exposure between occupations, i.e., cell workers, crane drivers, and supervisors. Area exposure in Tankhouse 1 declined significantly (p ≤ 0.0001) between 1982 and 1986 with a factor of 29. However, after 1986 no significant downward trend in area exposure was evident in Tankhouse 1. Personal exposures in Tankhouse 1 significantly (p ≤ 0.0001) decreased with a factor of three between 1991 and 2014. No significant trends were evident in area and personal exposure in Tankhouse 2. Downward exposure trends were evident in Tankhouse 1 and may be ascribed to the implementation of various control measures and process changes, e.g., increasing polypropylene bead load. Limited data were available for Tankhouse 2, therefore, no trend in exposure could be established. Retrospective analyses may be used to identify trends and anomalies in exposure which might not have been identified during daily exposure monitorin

Combining cervical cancer screening for mothers with schoolgirl vaccination during human papillomavirus (HPV) vaccine implementation in South Africa : results from the VACCS1 and VACCS2 trials

OBJECTIVE : The platform provided by human papillomavirus (HPV) vaccination for linked public health interventions to improve cervical cancer prevention remains incompletely explored. The Vaccine And Cervical Cancer Screen (VACCS) cross-sectional observation trials aimed to evaluate the efficacy of school-based HPV vaccination linked with maternal cervical cancer screening. METHODS : Girls from 29 schools in two provinces in South Africa were invited in writing to receive HPV vaccination. Two approaches to informed consent were compared, namely an audiovisual presentation (VACCS1) and in written format (VACCS2). Markers of vaccine uptake and coverage were calculated, namely uptake among the invited and consented cohorts, and rates of completion and sufficient vaccination. Mothers and female guardians received educational material about cervical cancer, and either a self-sampling device or an invitation to attend existing screening facilities. Knowledge was assessed via structured questionnaires (before and after), and screening uptake was self-reported and directly assessed and compared between these approaches. RESULTS : Vaccine acceptance among 5137 invited girls was similar for the two methods of consent; 99.3% of consented girls received a first dose; overall completion rate was 90.5%. More girls were vaccinated using a two-dose (974/1016 (95.9%)) than a three-dose regimen (1859/2030 (91.6%)). The questionnaire (n=906) showed poor maternal knowledge which improved significantly (p<0.05) after health education; only 54% of mothers reported any previous screening. The offer of a self-sampling device (n=2247) was accepted by 43.9% of mothers, but only 26% of those invited to screen at existing facilities (n=396) reported subsequent screening. CONCLUSIONS : Successful linking of primary health interventions to control cervical cancer was demonstrated. School-based HPV vaccination, linked to health education, self-sampling, and molecular screening resulted in significant improvements in knowledge and screening.The Cancer Research Initiative of South Africa (CARISA), the South African Medical Research Council (MRC), and Cancer Association of South Africa (CANSA): financial support; vaccine manufacturing companies GlaxoSmithKline/Aspen SA and MSD: vaccine donations; the First for Women Foundation: funds for screening.https://ijgc.bmj.comhj2023Obstetrics and Gynaecolog