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End date: 2019Has files: Yes

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Now showing 1 - 10 of 182
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    Minimising the risk of thermally induced cracking in mass concrete structures through suitable materials selection and processing
    (Springer, 2018) Ballim, Yunus
    The hydration of cement is an exothermic reaction which generates around 300 kJ/kg of cement hydrated. In mass concrete structures such as dams and large foundations, this heat of hydration causes a significant rise in temperature in the internal sections of the concrete. If thermal gradients between the internal sections and the near-surface zone of the concrete element are sufficiently large, the thermal stress can cause cracking of the concrete. This cracking may cause functional or structural problems in the operation of the structure. In order to minimise the potential for such cracking, it is necessary to minimise the rate and amount of heat that is evolved, particularly during the early period of the hydration process. This can be achieved by design engineers and concrete technologists through judicious selection and processing of concrete-making materials. This paper presents the observations and results obtained over a number of years from adiabatic testing of concretes, computational modelling of temperature development in large concrete structures and direct temperature measurements in actual structures, with a view to understanding the effects of concrete-making materials on temperature development in concrete. The paper considers the effects of different types of rock aggregates, different types of Portland cement, fineness of grinding of the cement, the addition of supplementary cementitious materials and variations in the concrete starting temperature on temperature development in a large concrete element over time. The results indicate that using a coarser ground cement, adding significant amounts of supplementary cementitious materials and cooling the concrete mixture before placing has a more significant effect in reducing the risk of cracking than varying the aggregate type of the Portland cement type.
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    Aphallia: a review to standardize management
    (2018-04) Gabler, Tarryn; Charlton, Robyn; Loveland, Jerome; Mapunda, Ellen
    Congenital aphallia is a rare anomaly with little supporting literature and controversial management. The aim of this review is to assess the most recent literature with a focus on staged management of these cases. We performed a PubMed search of all English literature in the past 10 years using the term aphallia. Twenty-three articles were identified of which six were excluded. A further three papers meeting our criteria were found in the references to papers initially identified. We found that management can be staged in three phases: short, intermediate and long-term. We conclude that optimal short-term management centers on resuscitation and urinary diversion as necessary, intermediate-term management entails urethrorectal fistula division, urethrostomy and neophallus creation and long-term management results in successful neophalloplasty, urethroplasty, prosthetic implant and continued protection of the upper urinary tracts with a Mitrofanoff. All this within a multidisciplinary team ensuring shared decision-making with the patient and their family
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    Different adiposity indices and their association with blood pressure and hypertension in middle-aged urban black South African men and women: findings from the AWI-GEN South African Soweto Site
    (BioMed Central, 2018-04) Pisa, Pedro T.; Micklesfield, Lisa K.; Kagura, Juliana; Ramsay, Michele; Crowther, Nigel J.
    Background: To report associations between different adiposity indices [anthropometric and dual-energy X-ray absorptiometry (DXA) measures] and blood pressure (BP) and hypertension in urban black South African adults. Methods: Anthropometric and DXA whole body measures were performed on 1026 men and 982 women. Participants were classified as being hypertensive if they had a systolic BP (SBP) ≥ 140 mmHg and/or diastolic (DBP) ≥ 90 mmHg. Within each gender the relationship of adiposity with BP and hypertension risk was assessed using linear and logistic regression models respectively. Bivariate models were computed for each body composition variable. Furthermore, we computed a multiple regression model to illustrates how body composition parameters are associated with the outcome variables independent of each other. Results: The males were significantly taller and had a higher fat free soft tissue mass (FFSTM), DBP and socio-economic status, and were more likely to use tobacco and be hypertensive (48.0% vs. 38.8%). The females had higher body mass index (BMI), waist circumference (WC), fat mass (FM), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), FM/ FFSTM ratio and body fat % than males. All body composition parameters were positively associated with hypertension. In both males and females, the FM/FFSTM ratio associated the strongest with hypertension illustrating the following odds ratios [males: 70.37 (18.47, 268.16) p ≤ 0.001; females 2.48 (0.86,7.21) p = 0.09]. The multiple regression model, indicated that the VAT and WC significantly associated with both SBP and DBP in the men and women respectively, whilst WC was the only significant predictor for hypertension. Conclusions: All body composition parameters were associated with hypertension and FM/FFSTM ratio showed the strongest relationship. It was reassuring that WC remains a useful measure of central adiposity that can be used as a risk indicator for hypertension if more sophisticated measures are not available. Furthermore, our data in part, implies that reducing abdominal adiposity in aging adults could contribute to reducing the risk of elevated blood pressure and hypertension.
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    “People look and ask lots of questions”: caregivers’ perceptions of healthcare provision and support for children born with cleft lip and palate
    (BioMed Central, 2018-04) Hlongwa, Phumzile; Rispel, Laetitia C.
    Background: Clefting of the lip and/or palate (CL/P) is amongst the five most common birth defects reported in South Africa. The emotional impact on parents at the birth of their new-born with CL/P could affect parent-child relationships. In light of insufficient scholarly attention parental experiences and perceptions, this study reports on caregivers’ perceptions of health service provision and support for children born with cleft lip and palate in South Africa. Methods: The study setting consisted of 11 academic hospital centres situated in six of South Africa’s nine provinces. At each of the academic centres cleft clinic, five to ten parents or caregivers were selected purposively. Participants were interviewed, using a semi-structured interview schedule that elicited socio-demographic information, explored the family experiences of having a child with CL/P, and their perceptions of care provision and support services available. The interviews were analysed using thematic content analysis. Results: Seventy-nine participants were interviewed. Their mean age was 33.3 years (range 17–68 years). The majority of the parents were black African (72%), unemployed (72%), single (67%) and with only primary school education (58%). The majority of the children were male, with a mean age of 3.8 (SD = ±4.3) years. Five broad themes emerged from the interviews: emotional experiences following the birth of a child with cleft lip and palate; reactions from family, friends or the public; the burden of care provision; health system responsiveness; and social support services. Caregivers reported feelings of shock, anxiety, and sadness, exacerbated by the burden of care provision, health system deficiencies, lack of public awareness and insufficient social support services. Conclusions: The findings have implications for the integrated management of children with cleft lip and/or palate, including information to parents, the education and training of healthcare providers, raising public awareness of birth defects, and social support.
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    Neurodevelopmental assessment of HIV-exposed uninfected and early-treated HIV-infected children: study protocol
    (BioMed Central, 2018-04) Strehlau, Renate; van Aswegen, Tamryn; Potterton, Joanne
    Objective: Sub-Saharan Africa has the highest prevalence of children at risk of not achieving their developmental potential, attributable largely to the human immunodefciency virus (HIV) pandemic coupled with negative environmental factors. Childhood developmental stimulation programmes can mitigate adverse outcomes. Methods: Neonates testing HIV positive at birth will be initiated on antiretroviral treatment (ART) and receive an ageappropriate stimulation program, updated at 3 monthly intervals through the frst year of life. Neurodevelopment at 12 months of age will be assessed using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Outcomes will be compared with HIV-infected and HIV-exposed uninfected children (HEU) not having received the stimulatory intervention. Associations between neurodevelopmental outcomes, environmental factors, and parental stress will be investigated. The study will take place at a single site in Johannesburg, South Africa. This non-randomised controlled intervention study, with a single non-blinded comparative intervention group, aims to investigate whether an early childhood stimulation programme used in conjunction with ART initiated at birth can positively impact neurodevelopmental outcomes at 1 year of age in children infected with HIV.
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    Evidence for igneous differentiation in Sudbury Igneous Complex and impact-driven evolution of terrestrial planet proto-crusts
    (Nature Research, 2019-01) Latypov, Rais; Chistyakova, Sofya; Grieve, Richard; Huhma, Hannu
    Bolide impact is a ubiquitous geological process in the Solar System, which produced craters and basins filled with impact melt sheets on the terrestrial planets. However, it remains controversial whether these sheets were able to undergo large-scale igneous differentiation, or not. Here, we report on the discovery of large discrete bodies of melanorites that occur throughout almost the entire stratigraphy of the 1.85-billion-year-old Sudbury Igneous Complex (SIC) – the best exposed impact melt sheet on Earth – and use them to reaffirm that conspicuous norite-gabbro-granophyre stratigraphy of the SIC is produced by fractional crystallization of an originally homogeneous impact melt of granodioritic composition. This implies that more ancient and compositionally primitive Hadean impact melt sheets on the Earth and other terrestrial planets also underwent large-volume igneous differentiation. The near-surface differentiation of these giant impact melt sheets may therefore have contributed to the evolution and lithological diversity of the proto-crust on terrestrial planets.
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    Assessing runs of Homozygosity: a comparison of SNP Array and whole genome sequence low coverage data
    (BMC, 2018-01) Ceballos, Francisco C.; Hazelhurst, Scott; Ramsay, Michèle
    Background: Runs of Homozygosity (ROH) are genomic regions where identical haplotypes are inherited from each parent. Since their first detection due to technological advances in the late 1990s, ROHs have been shedding light on human population history and deciphering the genetic basis of monogenic and complex traits and diseases. ROH studies have predominantly exploited SNP array data, but are gradually moving to whole genome sequence (WGS) data as it becomes available. WGS data, covering more genetic variability, can add value to ROH studies, but require additional considerations during analysis. Results: Using SNP array and low coverage WGS data from 1885 individuals from 20 world populations, our aims were to compare ROH from the two datasets and to establish software conditions to get comparable results, thus providing guidelines for combining disparate datasets in joint ROH analyses. By allowing heterozygous SNPs per window, using the PLINK homozygosity function and non-parametric analysis, we were able to obtain non-significant differences in number ROH, mean ROH size and total sum of ROH between data sets using the different technologies for almost all populations. Conclusions: By allowing 3 heterozygous SNPs per ROH when dealing with WGS low coverage data, it is possible to establish meaningful comparisons between data using SNP array and WGS low coverage technologies
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    The effect of a ketogenic diet versus a high-carbohydrate, low-fat diet on sleep, cognition, thyroid function, and cardiovascular health independent of weight loss: study protocol for a randomized controlled trial
    (BMC, 2018-01) Iacovides, Stella; Meiring, Rebecca M.
    Background: Many physiological health benefits observed after following a ketogenic diet (KD) can be attributed to the associated weight loss. The KD has become more prominent as a popular health choice, not only in obese/ overweight individuals, but also in healthy adults. The study aims to determine the effects of a KD, independent of weight loss, on various aspects of physiological health including: sleep, thyroid function, cognition, and cardiometabolic health. The study will also aim to determine whether a change in basal metabolic rate may be associated with any changes observed. Methods: Twenty healthy men and women between 18 and 50 years of age will take part in this study. In a randomized controlled, cross-over design, participants will follow two isocaloric diets: a high-carbohydrate, low-fat diet (55% CHO, 20% fat, 25% protein) and a KD (15% CHO, 60% fat, 25% protein). Each dietary intervention will last for a minimum of 3 weeks, with a 1-week washout period in between. Before and after each diet, participants will be assessed for sleep quality, cognitive function, thyroid function, and basal metabolic rate. A blood sample will also be taken for the measurement of cardio-metabolic and immune markers. Discussion: The present study will help in understanding the potential effects of a KD on aspects of physiological health in healthy adults, without the confounding factor of weight loss. The study aims to fill a significant void in the academic literature with regards to the benefits and/or risks of a KD in a healthy population, but will also explore whether diet-related metabolic changes may be responsible for the changes observed in physiological health.
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    The importance of morphological identification of African anopheline mosquitoes (Diptera: Culicidae) for malaria control programmes
    (BMC, 2018-01) Erlank, Erica; Koekemoer, Lizette L.; Coetzee, Maureen
    Background: The correct identification of disease vectors is the first step towards implementing an effective control programme. Traditionally, for malaria control, this was based on the morphological differences observed in the adults and larvae between different mosquito species. However, the discovery of species complexes meant that genetic tools were needed to separate the sibling species and today there are standard molecular techniques that are used to identify the two major malaria vector groups of mosquitoes. On the assumption that species-diagnostic DNA polymerase chain reaction (PCR) assays are highly species-specific, experiments were conducted to investigate what would happen if non-vector species were randomly included in the molecular assays. Methods: Morphological keys for the Afrotropical Anophelinae were used to provide the a priori identifications. All mosquito specimens were then subjected to the standard PCR assays for members of the Anopheles gambiae complex and Anopheles funestus group. Results: One hundred and fifty mosquitoes belonging to 11 morphological species were processed. Three species (Anopheles pretoriensis, Anopheles rufipes and Anopheles rhodesiensis) amplified members of the An. funestus group and four species (An. pretoriensis, An. rufipes, Anopheles listeri and Anopheles squamosus) amplified members of the An. gambiae complex. Conclusions: Morphological identification of mosquitoes prior to PCR assays not only saves time and money in the laboratory, but also ensures that data received by malaria vector control programmes are useful for targeting the major vectors.
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    The shift to outcomes based frameworks: key problems from a critical perspective
    (The Federal Institute for Adult Education (bifeb), 2011) Michael, Young; Allais, Stephanie Matseleng
    This paper takes a step back from the discussions and debates about qualifications frameworks per se, to think more broadly about the role of „qualifications“ in educational reform. The aims of the paper are to locate the reform of qualifications in its broader social and institutional context, to propose a way of conceptualizing the change from qualification systems as they have emerged historically to qualifications frameworks andoutcomes-based qualifications and to explore the tensions involved in the different goals that the introduction of a (National) Qualifications Framework – (N)QF will achieve. We argue that what is at stake in current reforms is the role of educational institutions in the education and training of the next generation, the balance between institution-based education and informal (in some cases work-based) learning, and the ways in which trust in qualifications is established and maintained. Our two-model analysis explores the balance between an emphasis on institutions and outcomes. This paper was written to provoke debate, and help all involved in researching qualifications frameworks to think more clearly about the issues.