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Aim: The variability in regional species richness is determined by the balance between speciation, extinction, and migration, but the underlying causes of high species richness in some regions (e.g. tropics, Mediterranean ecosystems) are challenging to explain. Species richness variability may be amplified by biotic feedbacks that promote species richness in some areas, while decreasing elsewhere. Following the example of species abundance, we speculated that species richness per area in arbitrary geographic units (e.g. quarter‐degree squares) follows a hollow‐shaped curve with the ranks of species richness to yield a species richness rank (SRR) curve. The hollowness of such an SRR curve may indicate biotic feedbacks. Location: South Africa, South West Australia, and global. Materials and Methods: We used vascular plant (VP) and bird data from distinct geographic regions and global syntheses of VP, bird, mammal, and amphibian species richness. These data were subdivided into geographic grids and the deviation from normality of the species richness quantified using skewness and kurtosis and the values ranked to yield SRR curves. Results: These SRR curves all had a consistent hollow shape (corresponding skewness 1.08–3.4, kurtosis 0.23–18.40) distinct from a normal distribution arising if species were allocated randomly to geographic units. The SRR curves indicate that relatively species‐rich regions are rare, while species‐poor areas are common. Main Conclusions: Neutral processes, abiotic determinants, environmental heterogeneity, historical factors (e.g. climate stability), and biotic feedbacks all likely play a role in contributing to the shapes of the curves. Although these curves for diverse taxa and regions integrate these multiple drivers of species richness, they indicate an acceleration of species richness as a function of species richness as a result of speciation and/or immigration, limited by increasing extinction likelihood. Biotic feedbacks provide a parsimonious explanation for the shapes of the SRR curves across taxa and regions. [ABSTRACT FROM AUTHOR]

This study investigated first‐year undergraduate statistics students' statistical problem‐solving skills on the probability of the union of two events, conditional probability, binomial probability distribution, probabilities for x‐limits using the z‐distribution, x‐limit associated with a given probability for a normal distribution, estimating the y‐value using a regression equation, and hypothesis testing for a single population mean when a population standard deviation is unknown. The study was a descriptive case study and employed a mixed‐method research approach. Data were collected through content analysis of a statistics course examination script of 120 first‐year undergraduate students of statistics in an open distance‐learning university in South Africa. Polya's Model of Problem Solving was used as the framework of analysis. The study revealed that the students, in general, had poor statistical problem‐solving skills. [ABSTRACT FROM AUTHOR]

Background: Haemoglobinopathies are one of the most common inherited diseases worldwide. Quantification of haemoglobin A2 is necessary for the diagnosis of the beta thalassaemia trait. In this context, it is important to have a reliable reference interval for haemoglobin A2 and a local reference range for South Africa has not been established. Objective: This study aimed to establish reference intervals for haemoglobin A2 using stored patient laboratory data. Methods: This descriptive study used retrospective data to evaluate haemoglobin A2 levels determined using high-performance liquid chromatography at the National Health Laboratory Service haematology laboratory in Pretoria, South Africa. All tests performed from 01 October 2012 to 31 December 2020 were screened for inclusion; of these, 144 patients' data met the selection criteria. The reference interval was calculated using descriptive statistics (mean and standard deviation) with a 95% confidence interval. Results: Analysed data from enrolled patients showed a normal distribution. The mean age of the patients was 40 years (range: 3–84 years). The reference interval for haemoglobin A2 calculated from this data was 2.3% – 3.6%. The minimum haemoglobin A2 was 2.3% and the maximum was 3.9% with a mean of 2.95% and a standard deviation of 0.357%. Conclusion: A normal reference interval has been established for the population served by the laboratory that will assist with accurate diagnosis of the beta thalassaemia trait. This reference interval may also be useful to other laboratories that employ the same technology, especially smaller laboratories where obtaining a sufficiently large number of normal controls may be challenging. [ABSTRACT FROM AUTHOR]

A comprehensive study about the spread of COVID-19 cases in Turkey and South Africa has been presented in this paper. An exhaustive statistical analysis was performed using data collected from Turkey and South Africa within the period of 11 March 2020 to 3 May 2020 and 05 March and 3 of May, respectively. It was observed that in the case of Turkey, a negative Spearman correlation for the number of infected class and a positive Spearman correlation for both the number of deaths and recoveries were obtained. This implied that the daily infections could decrease, while the daily deaths and number of recovered people could increase under current conditions. In the case of South Africa, a negative Spearman correlation for both daily deaths and daily infected people were obtained, indicating that these numbers may decrease if the current conditions are maintained. The utilization of a statistical technique predicted the daily number of infected, recovered, and dead people for each country; and three results were obtained for Turkey, namely an upper boundary, a prediction from current situation and lower boundary. The histograms of the daily number of newly infected, recovered and death showed a sign of lognormal and normal distribution, which is presented using the Bell curving method parameters estimation. A new mathematical model COVID-19 comprised of nine classes was suggested; of which a formula of the reproductive number, well-poseness of the solutions and the stability analysis were presented in detail. The suggested model was further extended to the scope of nonlocal operators for each case; whereby a numerical method was used to provide numerical solutions, and simulations were performed for different non-integer numbers. Additionally, sections devoted to control optimal and others dedicated to compare cases between Turkey and South Africa with the aim to comprehend why there are less numbers of deaths and infected people in South Africa than Turkey were presented in detail. [ABSTRACT FROM AUTHOR]

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Total IgE levels are usually elevated in allergic diseases, being highest in atopic eczema, followed by atopic asthma and allergic rhinitis. Genetic factors are believed to play a role in total IgE levels, with higher levels seen in Black African subjects. Total IgE is also raised in parasite infection. Thus, the higher total IgE levels in Black Africans could be because of environmental rather than genetic factors. Few studies have investigated the usefulness of total IgE levels in the evaluation of atopy in Black Africans. The objective of this study was to determine the total IgE levels in unselected urban Black African high school children and to correlate this with atopy and ascaris sensitization. Atopic status was assessed by means of specific allergen sensitization (skin prick tests to eight inhalant and four food allergens), self-reported asthma and bronchial hyper-responsiveness measured by methacholine challenge. Ascaris sensitization was assessed by means of ascaris IgE measured by CAP-RAST. Total IgE levels were markedly skewed toward the left and were not distributed in a Gaussian or a log-normal distribution. Skin prick tests were positive for aeroallergens in 32.3% of subjects. Thirty four percent had elevated ascaris IgE. Total IgE was higher in atopic vs. non-atopic subjects and correlated with the number of positive skin prick tests, self-reported asthma and bronchial hyper-responsiveness. Subjects without allergy (or) atopy had a median total IgE of 80–90 kU/I. In addition total IgE correlated with ascaris IgE. Subjects with no ascaris sensitization had median total IgE of 77.1 kU/l. Subjects with neither atopy/asthma nor ascaris sensitisation had a median total IgE of 69.9 kU/I, similar to the levels seen in people of other genetic origins. This study suggests that helminthic infection rather than genetic differences, may be the major determining factor of IgE levels in certain populations. [ABSTRACT FROM AUTHOR]

Geomechanical analysis and integrity assessment of hydrocarbon reservoirs upon depletion and injection are crucial to ensure that CO 2 storage projects can be safely implemented. The Bredasdorp basin in South Africa has a great potential for CO 2 storage given its hugely available exploration data. However, there has not been any geomechanical characterization carried out on this basin to determine its integrity issues. The aim of this study is to provide a guideline as to how geomechanical analysis of depleted fields can be done for a safe CO 2 sequestration practice. The results obtained from the geomechanical model constructed for the depth of 2570 m indicated that the magnitude of the principal vertical, minimum and maximum horizontal stresses in the field are respectively 57 MPa, 41 MPa and 42–46 MPa, indicating the presence of a normal faulting regime in the caprock and the reservoir. However, according to the pore pressure-stress coupling assessment, this normal faulting is much severe in compartment C3 of the reservoir. Fault reactivation and fracture stability were also investigated after depletion and it was found that faults in the compartments C1 and C2 are stable after depletion. However, normal faults (FNS8 and FNS9) in compartment C3 dipping SW were critically stressed and may be reactivated without a proper injection planning. Fractures in compartment C3 were also critically stressed, highlighting a great potential of leakage from this compartment upon injection. It was also revealed that the sustainable maximum fluid pressure of 25 MPa would not induce any fractures in the reservoir during CO 2 storage. • Stress distribution of a normal faulting regime is in both caprock and the reservoir. • Pore pressure -stress coupling analysis reveals that depletion decreases both S hmin and S Hmax. • Fault reactivation and fracture stability were also investigated after depletion. • The maximum CO 2 sustainable pressure should be lower than 25 MPa. [ABSTRACT FROM AUTHOR]

• A breakdown of the location accuracy of the SALDN and ALDIS per year, indicating that rare large location errors still occur even as performance improves. • A methodology to fit statistical models to geographical lightning data and evaluate the quality of the fit. • The methodology is applied to lightning location system data time-correlated with ground-truth lightning events - tall tower lightning in both South Africa and Austria. • It is shown that the bivariate Students' t-distribution is a better statistical model for lightning location system errors than the bivariate Gaussian distribution. Lightning location systems geolocate lightning strokes. Given assumptions made in the geolocation models, errors in the reported locations can occur. Modelling these errors as a bivariate Gaussian distribution of historic stroke detections has found success in the form of confidence ellipses. However, the presence of outliers - strokes with large location errors - indicate that there is a better model for these errors. The Students' t-distribution is a "heavier" tailed distribution. This paper investigates whether the bivariate Students' t-distribution is a better model for such errors. A methodology for modelling and evaluating the distribution of location errors using maximum likelihood estimation, expectation-maximization and a Mahalanobis distance quality-of-fit test is described. This method is applied to stroke reports from the South African Lightning Detection Network and the Austrian Lightning Detection and Information System time-correlated with photographed lightning events to the Brixton Tower, South Africa and current measurements to the Gaisberg Tower, Austria respectively. In both cases, we find outliers in the distribution of location errors - even as the performance of the networks increase. Using the Mahalanobis test, we find the bivariate Students' t-distribution to be a better statistical model for both the South African and the Austrian events. [ABSTRACT FROM AUTHOR]

Birthweight is strongly associated with infant mortality and is a major determinant of infant survival. Several factors such as maternal, environmental, clinical, and social factors influence birthweight, and these vary geographically, including across low, middle, and economically advanced countries. The aim of the study was to investigate the geographical modification of the effect of oxides of nitrogen exposure on birthweight adjusted for clinical and socio-demographic factors. Data for the study was obtained from the Mother and Child in the Environment birth cohort study in Durban, South Africa. Pregnant females were selected from public sector antenatal clinics in low socioeconomic neighborhoods. Land use regression models were used to determine household level antenatal exposure to oxides of nitrogen (NOx). Six hundred and seventy-seven births were analysed, using the geoadditive model with Gaussian distribution and identity link function. The newborns in the cohort had a mean birthweight of 3106.5 g (standard deviation (SD): 538.2 g and the maternal mean age was 26.1 years (SD: 5.7). A spatially modified NOx exposure-related effect on birthweight was found across two geographic regions in Durban. Prenatal exposure to NOx was also found to have a non-linear effect on the birthweight of infants. The study suggested that incorporating spatial variability is important to understand and design appropriate policies to reduce air pollution in order to prevent risks associated with birthweight., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Non-esterified fatty acid (NEFA) levels are an important diagnostic tool in the investigation of neonatal hypoglycaemia. NEFA reference intervals have not been reported for neonates previously. Methods: The objective of this study was to determine an NEFA reference interval for neonates. Results: Heparinized plasma obtained from 106 healthy neonates in the first week of life was analysed using the Roche "Free fatty acid, Half-micro test" kit. Results were then analysed statistically for normality (Shapiro-Wilk test) and reference interval determined non-parametrically (bootstrap method). Conclusions: NEFA levels displayed a non-Gaussian distribution and the reference interval (2.5th and 97.5th percentiles) was 0.2-1.5 mmol/L (90% confidence intervals 0.1-0.3 and 1.4-2.0 mmol/L, respectively). The NEFA reference interval in South African neonates less than a week old is similar to that described in infants (1-12 months), indicating that this reference range can be used over the entire neonatal period. [ABSTRACT FROM AUTHOR]