A comparison of simple low-power wedge-type X-band waveguide absorbing load implementations

The original publication is available at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4401506Stander, T., Van der Walt, P.W. & Meyer, P. 2007. A comparison of simple low-power wedge-type X-band waveguide absorbing load implementations, AFRICON 2007, Windhoek, September 26-28, doi:10.1109/AFRCON.2007.4401506.Two inexpensive waveguide absorbing loads are constructed and measured, each using a single thin resistive sheet absorber supported by styrofoam walls, and 50mm in length. It is found that a V-cut wedge displays less reflection than a tapered wedge, with -30 dB reflection across a band 8.5 - 12.4 GHz.Post-prin

Analytical condition monitoring system for liquid-immersed transformers

Abstract: Transformers form an integral part of the electrical power grid are widely employed in a variety of power-system applications inter alia power generation and distribution systems, and arc- and induction-furnace applications. Transformers are among the most expensive components in power systems but the protection and health requirements thereof are still catered for by traditional auxiliary protective devices and cooling control systems. This paper reports the development of an IoT-based condition monitoring system that offers advanced protection and control features. The condition monitoring system is intended to directly contribute to enhancing the lifespan of the transformer by detecting fault conditions at an early stage before catastrophic failure can occur and by ensuring that the quality of the transformer’s insulation is preserved for a greater period through improved cooling techniques

The burden of depression and anxiety among medical students in South Africa: A cross-sectional survey at the University of Cape Town

Background. Depressive and anxiety disorders occur at very high rates among medical students. For instance, an international review and meta-analysis estimated the overall pooled crude prevalence of depression or depressive symptoms at 27.2%. However, South African (SA) data are very limited.Objectives. To determine rates of depression and anxiety among medical students and to examine the associations with various sociodemographic variables (biological sex, gender identity, household income, ethnicity, and clinical v. pre-clinical students). We also examined whether the ‘mini-semester’ of 2017 resulting from the 2016 ‘Fees Must Fall’ student protests was associated with increased depression/anxiety.Methods. The study was a cross-sectional electronic survey conducted in the Faculty of Health Sciences, University of Cape Town, using an anonymous, self-administered online questionnaire. The questionnaire included basic sociodemographic questions, the Patient Health Questionnaire-9 and the Hospital Anxiety and Depression Scale.Results. The sample consisted of 473 medical students, 333 (70.4%) female and 140 (29.6%) male. Based on ethnic self-identification, 165 (35.6%) were black, 144 (31.1%) white, 88 (19%) coloured, 52 (11.2%) Indian and 8 (1.7%) Asian. There were 239 pre-clinical students (50.5%) and 234 clinical students (49.5%). Of the sample, 36.4% were above the cut-off for major depressive disorder and 45.9% for anxiety disorder. Reported rates of disorders diagnosed by a health professional were 25.0% for depressive disorder and 20.5% for anxiety disorder, and 28.1% of all students were receiving psychotropic medication. Female sex was associated with both depression (prevalence ratio (PR) 3.7; p<0.001) and anxiety diagnoses (PR 4.7; p<0.001). None of the other sociodemographic characteristics showed significant associations. Interestingly, students who undertook the 2017 mini-semester showed an increased rate of depression (PR 2.1; p<0.05) and anxiety diagnoses (PR 2.1; p<0.05).Conclusions. Nearly one in four students reported depression/anxiety diagnoses and were on psychotropic medication, significantly more than age-based expectations. Even more screened positive for risk of depression/anxiety. Our findings indicate that medical students, particularly females, are at a significantly increased risk of depression and anxiety disorders. Results suggest that the 2016 student protests may have had a direct impact on the mental state of students. Multidisciplinary efforts should be targeted at initiatives to strengthen mental wellbeing and institutional culture around mental health. These efforts may help build resilience in the next generation of health professionals in SA ahead of work in an overburdened health and health education system.

Progressive familial heart block type I : clinical and pathological observations

CITATION: 1991: .Van der Merwe, P.-L. et al. 1991. Progressive familial heart block type I : clinical and pathological observations. South African Medical Journal, 80:34-38.The original publication is available at http://www.samj.org.zaProgressive familial heart block type I (PFHB-I) is an autosomal inherited disease. It was previously postulated that the disease is limited to the cardiac conduction tissue. The presentation of a patient with dilated cardiomyopathy focused on the possibility that this might be part of PFHB-I. This observation led to routine echocardiographic examination of patients with complete heart block, who belonged to PFHB-I families, and another 5 cases with signs of dilated cardiomyopathy were identified. This is the first time, to our knowledge, that the histological picture of PFHB-I has been described. From these case reports it is clear that in the presence of a dilated cardiomyopathy the prognosis in PFHB-I tends to be poor.Publisher’s versio

Salmonella isolated from crocodiles and other reptiles during the period 1985-1994 in South Africa

Over a 10-year period, 173 isolates of Salmonella were obtained during routine isolation from reptiles. Of the 173 isolates, 92 different Salmonella serovars were identified. Of them, 61 (66%) belonged to subspecies I, nine to subspecies II and 21 to subspecies Ill (lIla and lllb), and one to subspecies IV. The majority of isolates were from farmed Nile crocodiles (145), three from wild-caught African dwarf crocodiles, 11 from captive snakes, 13 from lizards and one from a tortoise. The isolates from the tortoise and lizards were subspecies I isolates (Zaire and Tsevie, respectively). Of the snakes, nine isolates were S.lll. The serovars isolated most often from the crocodiles were of subspecies I (32 serovars). Eight were from subspecies II, seven from subspecies Ill and one from subspecies IV. The most frequently identified serovars were Typhimurium (seven), Tsevie (six), Duval (six), Schwerin (six), Tinda (six), and Tallahassee (six). On two commercial crocodile breeding farms that had experienced ongoing problems for about two years, many isolates of Salmonella were made. Some of these serovars were isolated more than once, and also months apart. No single Salmonella serovar predominated, nor did a single pathological condition. These salmonellas were predominantly of subspecies I.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat X Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

On the Identification of High Mass Star Forming Regions using IRAS: Contamination by Low-Mass Protostars

We present the results of a survey of a small sample (14) of low-mass protostars (L_IR < 10^3 Lsun) for 6.7 GHz methanol maser emission performed using the ATNF Parkes radio telescope. No new masers were discovered. We find that the lower luminosity limit for maser emission is near 10^3 Lsun, by comparison of the sources in our sample with previously detected methanol maser sources. We examine the IRAS properties of our sample and compare them with sources previously observed for methanol maser emission, almost all of which satisfy the Wood & Churchwell criterion for selecting candidate UCHII regions. We find that about half of our sample satisfy this criterion, and in addition almost all of this subgroup have integrated fluxes between 25 and 60 microns that are similar to sources with detectable methanol maser emission. By identifying a number of low-mass protostars in this work and from the literature that satisfy the Wood & Churchwell criterion for candidate UCHII regions, we show conclusively for the first time that the fainter flux end of their sample is contaminated by lower-mass non-ionizing sources, confirming the suggestion by van der Walt and Ramesh & Sridharan.Comment: 8 pages with 2 figures. Accepted by Ap

Differentially regulated pathways by endogenous vitamin D in multiple sclerosis identified by transcriptomics of immune cell subsets

Introduction: Vitamin D deficiency is a risk factor for MS. Apart from its role in skeletal health, vitamin D is also recognised to have immunomodulatory effects, which have predominantly been determined by in vitro studies. It remains unclear how vitamin D regulates immune cells in an in vivo setting. Objectives: We used transcriptomic datasets from immune cell subsets and aimed to identify pathways regulated by vitamin D in vivo, and whether there are differences in pathway regulation between people with MS and healthy controls. Methods: 73 MS cases and 102 healthy controls had microarray transcriptomic datasets available for at least one immune subset (monocyte, B, CD4, CD8, NK cell), and an independent cohort of 35 MS cases and 33 healthy controls had RNAseq datasets available. Latent variables were identified by RUV-4 or RUVg. Gene expression was corelated with serum 25(OH)D level (LIAISON 25 OH Vitamin D TOTAL assay) using Limma or edgeR. Gene set enrichment analysis (GSEA) was performed using ClusterProfiler and MSigDB. To identify differences in vitamin D-regulated pathways between MS cases and controls, genes whose expressions were correlated differently with 25(OH)D level by case/control status were determined and then used in GSEA. Results: Vitamin D-related pathways seen across multiple cell types were involved in RNA processing and splicing, mitochondrial function and oxidative phosphorylation, and immune signalling (FDR<0.05). In monocytes, the Gene Ontology term “vitamin D metabolic process” was enriched by genes downregulated with increasing 25(OH)D level in MS cases compared to controls. The Hallmark gene set “TNF-alpha signalling via NFKB” was enriched by genes downregulated in controls relative to cases. In CD4 cells, interleukin and TNF-alpha signalling gene sets were enriched by genes whose expressions were overall downregulated with increasing 25(OH)D level in cases relative to controls. Conclusions: Our pathway analyses identified signals for vitamin D regulation of immune function in vivo. These inferred differences in pathway regulation by vitamin D in MS cases and controls suggest differences in response to endogenous vitamin D

A rapid and reproducible picture of open access health facility data in Africa to support the COVID-19 response

Background: Open data on the locations and services provided by health facilities in some countries have allowed the development of software tools contributing to COVID-19 response. The UN and WHO encourage countries to make health facility location data open, to encourage use and improvement. We provide a summary of open access health facility location data in Africa using re-useable code. We aim to support data analysts developing software tools to address COVID-19 response in individual countries. In Africa there are currently three main sources of such data; 1) direct from national ministries of health, 2) a database for sub-Saharan Africa collated and published by a team from KEMRI-Wellcome Trust Research Programme and now hosted by WHO, and 3) The Global Healthsites Mapping Project in collaboration with OpenStreetMap. Methods: We searched for and documented official national facility location data that were openly available. We developed re-useable open-source R code to summarise and visualise facility location data by country from the three sources. This re-useable code is used to provide a web user interface allowing data exploration through maps and plots of facility type. Results: Out of 53 African countries, seven provide an official open facility list that can be downloaded and analysed reproducibly. Considering all three sources, there are over 185,000 health facility locations available for Africa. However, there are differences and overlaps between sources and a lack of data on capacities and service provision. Conclusions: We suggest that these summaries and tools will encourage greater use of existing health facility location data, incentivise further improvements in the provision of those data by national suppliers, and encourage collaboration within wider data communities. The tools are a part of the afrimapr project, actively developing R building blocks to facilitate the use of health data in Africa

A parsec-scale outflow from the luminous YSO IRAS 17527-2439

Imaging observations of IRAS 17527-2439 are obtained in the near-IR JHK photometric bands and in a narrow-band filter centred at the wavelength of the H_2 1-0 S(1) line. The continuum-subtracted H_2 image is used to identify outflows. The data obtained in this study are used in conjunction with Spitzer, AKARI, and IRAS data. A parsec-scale bipolar outflow is discovered in our H_2 line image, which is supported by the detection in the archival Spitzer images. The H_2 image exhibits signs of precession of the main jet and shows tentative evidence for a second outflow. These suggest the possibility of a companion to the outflow source. There is a strong component of continuum emission in the direction of the outflow, which supports the idea that the outflow cavity provides a path for radiation to escape, thereby reducing the radiation pressure on the accreted matter. The bulk of the emission observed close to the outflow in the WFCAM and Spitzer bands is rotated counter clockwise with respect to the outflow traced in H_2, which may be due to precession. The YSO driving the outflow is identified in the Spitzer images. The spectral energy distribution (SED) of the YSO is studied using available radiative transfer models. A model fit to the SED of the central source tells us that the YSO has a mass of 12.23 M_sun and that it is in an early stage of evolution.Comment: 6 Pages, 5 figures, accepted for publication by Astronomy and Astrophysic

A Hidden Population of Massive Stars with Circumstellar Shells Discovered with the Spitzer Space Telescope

We have discovered a large number of circular and elliptical shells at 24 microns around luminous central sources with the MIPS instrument on-board the Spitzer Space Telescope. Our archival follow-up effort has revealed 90% of these circumstellar shells to be previously unknown. The majority of the shells is only visible at 24 microns, but many of the central stars are detected at multiple wavelengths from the mid- to the near-IR regime. The general lack of optical counterparts, however, indicates that these sources represent a population of highly obscured objects. We obtained optical and near-IR spectroscopic observations of the central stars and find most of these objects to be massive stars. In particular, we identify a large population of sources that we argue represents a narrow evolutionary phase, closely related or identical to the LBV stage of massive stellar evolution.Comment: 23 pages, 9 figures, accepted for publication in A