49 research outputs found
Retention of radiotranslucent foreign bodies in the oesophagus as a cause of stridor
Two infants who presented with stridor were found to have radiotranslucent plastic objects impacted in the oesophagus at the level of the cricoid cartilage. From these 2 cases the lessons to be learnt are that oesophageal foreign bodies retained for even a short period may be a cause of stridor and that when these foreign bodies are not radiographically visible investigation must include the swallowing of contrast medium in which the foreign body should be visible as a translucency.S. Afr. Med. J., 48, 831 (1974)
Water erosion risk assessment in South Africa : a proposed methodological framework
With the increase in human impacts on the
environment, especially in terms of agricultural intensification
and climate change, erosion processes need to be
assessed and continually monitored. In many countries, but
particularly in developing countries such as South Africa,
standardized methodological frameworks that deliver comparable
results across large areas as a baseline for regional
scale monitoring are absent. Due to limitations of scale at
which techniques can be applied and erosion processes
assessed, this study describes a multi-process and multiscale
approach for soil erosion risk assessment under South
African conditions. The framework includes assessment of
sheet-rill erosion at a national scale based on the principles
and components defined in the Universal Soil Loss Equation;
gully erosion in a large catchment located in the Eastern
Cape Province by integrating 11 important factors into a
GIS; and sediment migration for a research catchment near
Wartburg in KwaZulu-Natal by means of the Soil andWater
Assessment Tool. Three hierarchical levels are presented in
the framework, illustrating the most feasible erosion assessment
techniques and input datasets that are required for
application at a regional scale with proper incorporation of
the most important erosion contributing factors. The methodological
framework is not interpreted as a single assessment
technique but rather as an approach that guides the
selection of appropriate techniques and datasets according to
scale dependency and modelled complexity of the erosion
processes.National Research Foundationhttp://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1468-0459hb201
Factors controlling gully development : comparing continuous and discontinuous gullies
Gully erosion is a degradation process affecting soils in many parts of theWorld. Despite the complexity of a series of collective factors across
different spatial scales, previous research has not yet explicitly quantified factor dominance between different sized gullies. This factorial
analysis quantifies the differences in factor dominance between continuous gullies (cgs) and discontinuous gullies (dgs). First, gullies (totaling
5273 ha) visible from SPOT 5 imagery were mapped for a catchment (nearly 5000 km2) located in the Eastern Cape Province of South Africa.
Eleven important factors were integrated into a geographical information system including topographical variables, parent material-soil
associations and land use–cover interactions. These were utilized in a zonal approach in order to determine the extent factors differ between
cgs and dgs. Factors leading to the development of cgs are gentle footslopes in zones of saturation along drainage paths with a large
contributing area, erodible duplex soils derived from mudstones and poor vegetation cover due to overgrazing. Compared to cgs conditions,
more dgs occur on rolling slopes where the surface becomes less frequently saturated with a smaller contributing area, soils are more stable
and shallow. Factorial analysis further illustrates that differences in factor dominance between the two groups of gullies is most apparent for
soil factors. A combination of overgrazing and susceptible mudstones proves to be key factors that consistently determine the development of
cgs and dgs.The ARC-ISCW, as well as Mr. D. J. Pretorius and his
colleagues at the Department of Agriculture Forestry and
Fisheries (DAFF), Directorate Land Use and Soil Management.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145X
Weak convergence of finite element approximations of linear stochastic evolution equations with additive noise II. Fully discrete schemes
We present an abstract framework for analyzing the weak error of fully
discrete approximation schemes for linear evolution equations driven by
additive Gaussian noise. First, an abstract representation formula is derived
for sufficiently smooth test functions. The formula is then applied to the wave
equation, where the spatial approximation is done via the standard continuous
finite element method and the time discretization via an I-stable rational
approximation to the exponential function. It is found that the rate of weak
convergence is twice that of strong convergence. Furthermore, in contrast to
the parabolic case, higher order schemes in time, such as the Crank-Nicolson
scheme, are worthwhile to use if the solution is not very regular. Finally we
apply the theory to parabolic equations and detail a weak error estimate for
the linearized Cahn-Hilliard-Cook equation as well as comment on the stochastic
heat equation
Parenchymal brain oxygen monitoring in the neurocritical care unit.
Patients admitted to the neurocritical care unit (NCCU) often have serious conditions that can be associated with high morbidity and mortality. Pharmacologic agents or neuroprotectants have disappointed in the clinical environment. Current NCCU management therefore is directed toward identification, prevention, and treatment of secondary cerebral insults that evolve over time and are known to aggravate outcome. This strategy is based on a variety of monitoring techniques including use of intraparenchymal monitors. This article reviews parenchymal brain oxygen monitors, including the available technologies, practical aspects of use, the physiologic rationale behind their use, and patient management based on brain oxygen
Experiances in resection for pulmonary tuberculosis in the South African Non-European
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Monitoring soil erosion in South Africa at a regional scale : review and recommendations
Loss of topsoil is one of the principal soil degradation problems confronting agriculture throughout South Africa and receives special attention by policy-makers. For effective prevention and remediation, the spatial extent of the problem has to be established and monitored. Recent developments in the application of remote sensing and GIS to the study of soil erosion offer considerable potential in this regard. This paper outlines key technologies available for monitoring, and highlights the problems to be solved at a regional scale. The status of the technologies used in South Africa are reviewed and the more recent studies related to soil erosion are presented in a comparative context. Spatial, temporal and measurement variabilities are major constraints in erosion assessment. Previous erosion studies conducted in South Africa at the regional scale have disregarded important erosion factors and have overvalued less important ones. Different processes and interactions are likely to emerge as dominant when crossing scale boundaries. Such considerations highlight the need to establish a methodological framework to guide and standardize future regional soil loss monitoring efforts
Anemia and brain oxygen after severe traumatic brain injury.
PURPOSE: To investigate the relationship between hemoglobin (Hgb) and brain tissue oxygen tension (PbtO(2)) after severe traumatic brain injury (TBI) and to examine its impact on outcome.
METHODS: This was a retrospective analysis of a prospective cohort of severe TBI patients whose PbtO(2) was monitored. The relationship between Hgb-categorized into four quartiles (≤9; 9-10; 10.1-11; >11 g/dl)-and PbtO(2) was analyzed using mixed-effects models. Anemia with compromised PbtO(2) was defined as episodes of Hgb ≤ 9 g/dl with simultaneous PbtO(2) < 20 mmHg. Outcome was assessed at 30 days using the Glasgow outcome score (GOS), dichotomized as favorable (GOS 4-5) vs. unfavorable (GOS 1-3).
RESULTS: We analyzed 474 simultaneous Hgb and PbtO(2) samples from 80 patients (mean age 44 ± 20 years, median GCS 4 (3-7)). Using Hgb > 11 g/dl as the reference level, and controlling for important physiologic covariates (CPP, PaO(2), PaCO(2)), Hgb ≤ 9 g/dl was the only Hgb level that was associated with lower PbtO(2) (coefficient -6.53 (95 % CI -9.13; -3.94), p < 0.001). Anemia with simultaneous PbtO(2) < 20 mmHg, but not anemia alone, increased the risk of unfavorable outcome (odds ratio 6.24 (95 % CI 1.61; 24.22), p = 0.008), controlling for age, GCS, Marshall CT grade, and APACHE II score.
CONCLUSIONS: In this cohort of severe TBI patients whose PbtO(2) was monitored, a Hgb level no greater than 9 g/dl was associated with compromised PbtO(2). Anemia with simultaneous compromised PbtO(2), but not anemia alone, was a risk factor for unfavorable outcome, irrespective of injury severity
Are initial radiographic and clinical scales associated with subsequent intracranial pressure and brain oxygen levels after severe traumatic brain injury?
BACKGROUND: Prediction of clinical course and outcome after severe traumatic brain injury (TBI) is important.
OBJECTIVE: To examine whether clinical scales (Glasgow Coma Scale [GCS], Injury Severity Score [ISS], and Acute Physiology and Chronic Health Evaluation II [APACHE II]) or radiographic scales based on admission computed tomography (Marshall and Rotterdam) were associated with intensive care unit (ICU) physiology (intracranial pressure [ICP], brain tissue oxygen tension [PbtO2]), and clinical outcome after severe TBI.
METHODS: One hundred one patients (median age, 41.0 years; interquartile range [26-55]) with severe TBI who had ICP and PbtO2 monitoring were identified. The relationship between admission GCS, ISS, APACHE II, Marshall and Rotterdam scores and ICP, PbtO2, and outcome was examined by using mixed-effects models and logistic regression.
RESULTS: Median (25%-75% interquartile range) admission GCS and APACHE II without GCS scores were 3.0 (3-7) and 11.0 (8-13), respectively. Marshall and Rotterdam scores were 3.0 (3-5) and 4.0 (4-5). Mean ICP and PbtO2 during the patients' ICU course were 15.5 ± 10.7 mm Hg and 29.9 ± 10.8 mm Hg, respectively. Three-month mortality was 37.6%. Admission GCS was not associated with mortality. APACHE II (P = .003), APACHE-non-GCS (P = .004), Marshall (P < .001), and Rotterdam scores (P < .001) were associated with mortality. No relationship between GCS, ISS, Marshall, or Rotterdam scores and subsequent ICP or PbtO2 was observed. The APACHE II score was inversely associated with median PbtO2 (P = .03) and minimum PbtO2 (P = .008) and had a stronger correlation with amount of time of reduced PbtO2.
CONCLUSION: Following severe TBI, factors associated with outcome may not always predict a patient's ICU course and, in particular, intracranial physiology