Performance Evaluation of a Simplified Multi-Function Current Transformer for High Frequency Power Converters

Abstract A multi-function current transformer introduced some years ago is revisited in an effort to improve its manufacturability. The original current sensor has the ability to accurately represent load and phase-arm currents in single phase full-bridge dc-dc-converter topologies under normal operating conditions. In the event of a phase-arm fault the shoot-through current can also be detected and the information used in the protection scheme. This sensor is however very complex to manufacture and this work presents a simplified version of the sensor, which still gives the most important information with a far less complex structure. This paper briefly discusses the original current sensor, proposes a simplified sensor and evaluates the new sensor in terms of performance

Enzootic geophagia of calves and lambs in Northern Cape and Northwest and the possible role of chronic manganese poisoning

(South African J of Animal Science, 2000, 30, Supplement 1: 105-106

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 a preventable disease with a high prevalence in South Africa (SA), where screening is opportunistic. Primary prevention is now possible through HPV vaccination. In VACCS 1 the feasibility of linking cervical cancer with HPV vaccination was demonstrated. OBJECTIVES : To investigate the feasibility of linking HPV self-testing with a two-dose HPV vaccination schedule and to compare results with VACCS 1. METHODS : The project was conducted in five schools in the South-West District of Tshwane, Gauteng, SA. Leaflet information on cervical cancer and screening was provided, with requests for consent and assent for a two-dose HPV vaccination of schoolgirls. Female caregivers were invited to take part in HPV self-screening. RESULTS : Of 965 girls invited for vaccination, 519 (53.7%) had full consent and 518 (99.8%) received at least one vaccine dose. The invited uptake rate was 53.7% and 495 girls received both doses, giving a completion rate of 95.4% v. 82.6% in VACCS 1. Of 1 135 self-screen kits handed out, 560 (49.3%) were not returned. The mean age (standard deviation) of the 160 women who participated in self-screening was 38.7 (7.7) years. HPV testing was negative in 116 women (72.5%), 15 women (9.4%) tested positive for HPV 16 and/or 18, and 27 (16.9%) were positive for non-16/18 oncogenic HPV. CONCLUSION : Data from the VACCS projects suggest that school-based vaccine programmes can be successfully implemented. A two-dose schedule allowed for higher completion rates. Linking self-collected HPV screening to HPV vaccination is feasible, is a promising and viable screening strategy, and reached the appropriate age group for screening.Cancer Research Initiative of South Africa,South African Medical Research Council and the Cancer Association of South Africa.First for Women Insurance.GlaxoSmithKline Biologicals SA (117280).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

Phase I of the DiaVACCS screening trial : study design, methods, population demographics and baseline results

BACKGROUND. Human papillomavirus (HPV)-based primary screening guidelines are based on screening test performance and prevalence data generated in high-resource areas with low HIV infection rates. There is an urgent need for local data on infection and disease prevalence, as well as screening test performance, among both HIV-positive and HIV-negative South African (SA) women, in order to inform updated screening guidelines. OBJECTIVES. This study describes the baseline characteristics of participants in the cross-sectional phase of the multicentric DIAgnosis in Vaccine And Cervical Cancer Screen (DiaVACCS) screening trial. The objective was to determine the prevalence of positive screening and pre-invasive disease using different tests and strategies in the SA HIV-positive and HIV-negative population. METHODS. A total of 1 104 women aged 25 - 65 years and eligible for screening were included, 465 HIV positive and 639 HIV negative. Visual inspection and molecular and cytological screening tests were done on self-sampled and healthcare worker-collected specimens. All participants who screened positive and 49.1% of those who screened negative were invited for colposcopy and biopsy, and those qualifying for treatment were recalled for large loop excision of the transformation zone as part of the trial. The worst histology result for each participant was used, and for untested women, multiple imputation was used to estimate verification biasadjusted histology values. RESULTS. Visual inspection was positive in 50.4% of HIV-positive v. 20.9% of HIV-negative women, cytology (atypical squamous cells of undetermined significance) in 39.9% v. 17.0%, and high-risk HPV DNA in 41.2% v. 19.6%. Overall, high-grade squamous intraepithelial lesion-positive cytology peaked in the age group 30 - 39 years at 16.7%. After adjustment for verification bias, histological diagnosis of cervical intraepithelial neoplasia (CIN)2+ was suspected in 44.7% v. 23.5% and CIN3+ in 23.3% v. 10.2% of HIV-positive and negative women, respectively. Invasive cancer was diagnosed in 15 women (1.95% of histological studies performed), and verification bias adjustment suggested 20 cases (1.8% of the study population). CONCLUSION. The baseline findings from the DiaVACCS trial confirm a high prevalence of HPV-related cervical pathology in the SA HIV-negative screening population, showing a clear need to reach these women with a screening programme. Among HIV-positive women, prevalence values were almost doubled. The prevalence of existing invasive cervical cancer was 1 - 2% of all women. Further analysis of the performance of single and multiple screening tests between the two subgroups will contribute to the choice of the most effective strategies to identify women at risk of developing invasive cancer.http://www.samj.org.zadm2022Medical VirologyObstetrics and Gynaecolog

Female genital tuberculosis

Mycobacterium tuberculosis has been identified as the aetiological agent of tuberculosis for many centuries. Genital tuberculosis is a chronic disease and often has low-grade symptomatology, with very few specific complaints. A study from South Africa found an incidence of 6% of culture-positive tuberculosis in an infertile population. The fallopian tubes are involved in most cases of genital tuberculosis and, together with endometrial involvement, cause infertility in patients. Many patients present with a symptom complex similar to that of ovarian carcinoma, i.e. abdominal distension, pelvic tumour and ascites, which may easily be confused with ovarian carcinoma. Biopsies should be obtained by either laparoscopy or laparotomy if examination of the ascitic fluid could not confirm the diagnosis. Genital tuberculosis is an elusive diagnosis and requires a high index of suspicion as a first step in the diagnostic process. Excellent cure rates are reported on all of the standard treatment regimens.Articl

The use of semen parameters to identify the subfertile male in the general population

Aims: To present a structured review of the literature published on semen parameters and in vivo fertility potential and to establish fertility/ subfertility thresholds for sperm morphology using Tygerberg strict criteria, sperm concentration, and sperm motility. Method: The published literature comparing fertile and subfertile populations between 1983 and 2002 was reviewed. Results: A total of 265 articles were identified by the sourcing methodology, but only four articles provided data that could be tabulated and analyzed. Using receiver-operating characteristics curves, morphology proved to be the best predictor of subfertility in 2 of the 4 articles, with concentration and motility also showing good predictive power. The thresholds calculated ranged between 4 and 10% for morphology, between 13.5 × 106/ml and 34 × 106/ml for concentration, and between 32 and 52% for motility. A second set of much lower thresholds was calculated in three of the articles using either a 15 or 50% prevalence of subfertility in the population or the tenth percentile of the fertile population. The adjusted thresholds were between 3 and 5% for morphology, between 9 × 106/ml and 20 × 106/ml for concentration, and between 20 and 30% for motility. Conclusions: Because these lower thresholds have a much higher positive predictive value, we suggest that thresholds of <5% normal sperm morphology, a concentration <15 × 106/ml, and a motility <30% should be used to identify the subfertile male. The lower threshold for morphology also fits in vitro fertilization and intrauterine insemination data calculated previously. Using the parameters in combination increases the clinical value of semen analysis. Copyright © 2005 S. Karger AG.Revie

Effect of limestone particle size on bone quality characteristics of hens at end-of-lay

A study was conducted to determine the effect of different limestone particle sizes in layer diets on bone quality characteristics at end-of-lay hens. Calcitic limestone (360 g Ca/kg DM) that is extensively used in commercial poultry diets was obtained from a specific South African source. Limestone particles were graded as small (1.0 mm) have a beneficial effect on improving the mechanical properties of bone of older laying hens

Effect of limestone particle size on egg production and eggshell quality of hens during late production

A study was conducted to determine the influence of different particle size limestone in layer diets on egg production and eggshell quality during the later stages of egg production (>54 weeks of age). Calcitic limestone (360 g Ca/kg), consisting of small

Influence of dietary lipid sources on carcass traits of broilers

A study was conducted to determine the influence of different dietary lipid sources on dressing percentage, breast meat yield and breast weight of male broiler birds. Four isoenergetic (15.1 MJ AME/kg DM) and isonitrogenous (222.3 g CP/kg DM) diets were formulated, using high oleic sunflower oil (HO), sunflower oil (SO), fish oil (FO) and tallow (T) at a 60 g/kg dietary inclusion level. Four hundred, day-old Ross 788 broiler males were randomly allocated to the four treatments (n = 100) and further subdivided into four replicates/treatment (n = 25). All birds receive a standard commercial diet for the first 14 days, where-after the experimental diets were fed for another 28 days. At 42 days of age, three birds/replicate (n = 12/treatment) were randomly selected, weighed and slaughtered at a commercial abattoir. Chilled carcasses (4 °C) were weighed to determine dressing percentage. Breast muscles were removed from the chilled carcasses, skinned and weighed for the calculation of breast meat yield. Breast meat yield were expressed as a percentage of the live body weight as well as carcass weight. This study showed that the broilers fed a diet supplemented with 60 g/kg tallow had a better dressing percentage, breast meat yield and breast weight compared to other treatments. These results suggested that dietary lipid sources could be used to improve certain carcass traits of broilers