Showing papers by "University of the Witwatersrand published in 1985"
TL;DR: In this paper, it is shown that if ideal observations are available, they are insufficient to determine the space-time structure on the past light cone of the observer; however, in the cosmological case they are precisely necessary and sufficient to determine a spacetime geometry on the light cone and in its causal past (down to where caustics or curps first occur).
287 citations
TL;DR: The findings support the hypotheses that condensed tannins function to protect plant cell walls against microbial attack; and hydrolyzable tannin function to inactivate the digestive enzymes of insect herbivores.
Abstract: The palatability of 14 species of woody plant was assessed for three species of browsing ruminant, namely kudus, impalas and goats. Results show that palatability was most clearly related to leaf contents of condensed tannins. The effect was a threshold one, with all plants containing more than 5% condensed tannins being rejected as food during the wet season period. In contrast palatability was not influenced by concentrations of protein-precipitating polyphenols, and only weakly related to contents of nitrogen, phosphorus, cations, fibre components and other secondary metabolites. Insect herbivory shows a different pattern. These findings support the hypotheses that (i) condensed tannins function to protect plant cell walls against microbial attack; (ii) hydrolyzable tannins function to inactivate the digestive enzymes of insect herbivores. Large mammalian herbivores are influenced by condensed tannins due to their dependance upon microbial fermentation of plant cell walls for part of their energy needs.
285 citations
TL;DR: HBV integration was accompanied by a deletion of at least 13.5 kilobases of cellular sequences in a human hepatocellular carcinoma, and the viral DNA integration and deletion occurred on the short arm of chromosome 11 at location 11p13-11p14.
Abstract: Hepatitis B virus (HBV), a virus with known carcinogenic potential, integrates into cellular DNA during long-term persistent infection in man. Hepatocellular carcinomas isolated from viral carriers often contain clonally propagated viral DNA integrations. As small chromosomal deletions are associated with several types of carcinomas, the occurrence of chromosomal deletions in association with HBV integration in hepatocellular carcinoma was studied. HBV integration was accompanied by a deletion of at least 13.5 kilobases of cellular sequences in a human hepatocellular carcinoma. The viral DNA integration and deletion of cellular sequences occurred on the short arm of chromosome 11 at location 11p13-11p14. The cellular sequences that were deleted at the site of HBV integration were lost from the tumor cells, leaving only a single copy of the remaining cellular allele.
194 citations
TL;DR: The efficacy of recombinant leukocyte interferon therapy is restricted, but it may be of benefit in a proportion of carriers, if these carriers can be precisely identified.
153 citations
01 Jan 1985
134 citations
Journal Article•
TL;DR: A nosocomial outbreak of Crimean-Congo haemorrhagic fever occurred in Tygerberg Hospital near Cape Town in September 1984 when 7 medical personnel became ill after admission of an index patient.
Abstract: A nosocomial outbreak of Crimean-Congo haemorrhagic fever occurred in Tygerberg Hospital near Cape Town in September 1984 when 7 medical personnel became ill after admission of an index patient.
108 citations
TL;DR: Presidential address delivered at the Second Meeting of the International Association of Oral Pathologists, The Netherlands, June 4th – 7th 1984.
Abstract: Presidential address delivered at the Second Meeting of the International Association of Oral Pathologists, The Netherlands, June 4th – 7th 1984.
97 citations
TL;DR: In this article, the concept of the "secular trend" is discussed and a number of environmental causative factors are proposed, which can explain the historical development of the secular trend and the observed changes in its direction on a world-wide scale.
90 citations
83 citations
TL;DR: The notion of parental oppression is undermined by the complete loss of the meen caste, while the nature of the breeding system of this ant leads to the prediction of low relatedness between nestmates.
Abstract: Colonies of the ponerine Ophthalmopone berthoudi were collected throughout the year. The queen caste is absent. Dissection of large numbers of workers revealed that many of them (up to 100 in one nest) are inseminated and produce eggs. The ovaries are small and contain very few mature oocytes, indicating that there is a slow rate of egg-laying. Workers are produced throughout the year, and all are capable of becoming functional reproductives. However, only those that are sexually-attractive during the limited period of male activity become mated. Thus the percentages of mated laying workers (=gamergates) fluctuate seasonally (Fig. 2). Successive generations of gamergates do not overlap. Observation of nests in the field and in the laboratory indicated that gamergates were never active above ground. There is no aggression between them, and their numbers are not socially regulated. There are few interactions between gamergates and non-reproductive workers, and the former do not acquire more food during termite meals. The notion of parental oppression is undermined by the complete loss of the meen caste, while the nature of the breeding system of this ant leads to the prediction of low relatedness between nestmates.
83 citations
TL;DR: The Lie point symmetries of the non-linear differential equation [qdot] + 3qq + q3 = 0 which arises in the study of the modified Emden equation are shown to have an unexpectedly rich algebra associated with them, a feature which enables the above non linear differential equation to be transformed into the simplest linear second order ordinary differential equation.
Abstract: The Lie point symmetries of the non-linear differential equation [qdot] + 3qq + q3 = 0 which arises in the study of the modified Emden equation are shown to have an unexpectedly rich algebra associated with them, a feature which enables the above non-linear differential equation to be transformed into the simplest linear second order ordinary differential equation.
TL;DR: Ocymyrmex barbiger is a diurnal scavenger of arthropods in which the number of successful foraging excursions per colony per day increases with daily vapour pressure deficit and it appears that the ants make use of prey items which succumb to thermal and desiccation stress.
Abstract: Ocymyrmex barbiger is a diurnal scavenger of arthropods in which the number of successful foraging excursions per colony per day increases with daily vapour pressure deficit. It appears that the ants make use of prey items which succumb to thermal and desiccation stress. Running speed is a function of surface temperature but progressively less time is spent searching for prey beyond a critical surface temperature with the result that the optimal search temperature for individual foragers is about 52°C. Maximal foraging activity of colonies occurs at surface temperatures corresponding to this optimal search temperature.
TL;DR: Histologically, cysts in varying stages of development were lined by proliferating non-keratinized stratified squamous epithelium and caries was the most common etiologic factor in the formation of the cysts.
TL;DR: The Generalized Inverse Gaussian‐Poisson Distribution is suggested as an all‐embracing mathematical model for bibliometric frequency distributions and Twelve examples are given which show that the new model cannot be rejected by virtue of an objective chi‐squared test.
Abstract: The Generalized Inverse Gaussian-Poisson Distribution is suggested as an all-embracing mathematical model for bibliometric frequency distributions. Twelve examples are given which show that the new model cannot be rejected by virtue of an objective chi-squared test.
TL;DR: Dysplastic changes immediately adjacent to established squamous carcinomas are looked at in an attempt to determine whether any predictors can be identified in this way.
Abstract: A number of workers have attempted to identify dysplastic features which may be predictors of malignant change, by prospective studies of dysplastic lesions. In the present study we have looked at dysplastic changes immediately adjacent to established squamous carcinomas in an attempt to determine whether any predictors can be identified in this way. Eighty cases were included in the study for whom information on tobacco usage was known. Clinical details were recorded. Histological features in epithelium immediately adjacent to the carcinoma were studied in representative sections. Eighteen specific histological characteristics were noted as present or absent. Data were transferred by Conversational Monitoring System (CMS) terminal, processed and analyzed by the Statistical Analysis System (SAS) Computer package. Only 8 patients were non-smokers (10%). Dysplastic changes in adjacent epithelium were frequently multicentric. Changes appear to occur first in the basal layer in the form of disturbance of polarity or basal cell hyperplasia, while other dysplastic features are absent. The feature referred to as basal cell hyperplasia appears, in fact, to represent disturbed epithelial maturation. In 80% of cases increased nucleo-cytoplasmic ratio appears to result from a decrease in cytoplasmic volume rather than increased nuclear size. A defect in RNA synthesis may be a factor. A sharp decrease in inflammatory cells in the lamina propria of adjacent epithelium, compared with that of the carcinoma, was observed. Russell bodies were noted in 5 of the 8 lesions in non-smokers (63%) and in 16 of 72 lesions in smokers (22%) (p less than 0.001; Chi2 17.65).
TL;DR: Frequency and severity of nausea and of vomiting during pregnancy, and of pronounced dietary cravings and aversions, were determined in a series of South African rural and urban black, Indian, coloured (European‐African‐Malay) and white women.
TL;DR: At a corrected age of 3 months, 80 low birth-weight infants were assigned to normal or at-risk groups on the basis of a neurodevelopmental assessment scale and tested at 12 months by an independent psychologist blinded for infant group.
TL;DR: This case demonstrates the huge growth potential of the nasolabial cyst.
TL;DR: In this paper, a computational scheme using the technique of control parameterization is developed for solving a class of optimal control problems involving nonlinear hereditary systems with linear control constraints, and several examples have been solved to test the efficiency of the technique.
Abstract: In this paper, a computational scheme using the technique of control parameterization is developed for solving a class of optimal control problems involving nonlinear hereditary systems with linear control constraints. Several examples have been solved to test the efficiency of the technique.
TL;DR: The stiffest and strongest specimens were those of the conventional acrylic and all the reinforced specimens were significantly weaker; the reason appears to be failure to achieve true adhesion between the fibre and the matrix resulting in the layers of fibre separating the matrix into layers of narrow cross-section.
TL;DR: Both transient depression of cell-mediated immunity and loss of ciliary function in the tracheobronchial tree occurs during acute influenzal illness and may predispose to fungal superinfection.
TL;DR: A 44-year-old man with severe deficiency of alpha 1-antitrypsin associated with diffuse vasculitis involving skin, kidney, and colon is described.
TL;DR: Results suggest that Cosmesil has improved mechanical properties over commonly used facial prosthetic silicone elastomers, including tensile strength, tear resistance, and hardness.
Abstract: The tensile strength, tear resistance, and hardness of four silicone elastomers were compared. Results suggest that Cosmesil has improved mechanical properties over commonly used facial prosthetic silicone elastomers.
TL;DR: The possible effect on the infant of dopamine antagonists used to promote lactation is cause for concern, but domperidone (Motilium) may be safer than other drugs in this group as it does not cross the blood‐brain barrier.
TL;DR: In this paper, a smooth homotopy of diffeomorphisms between two symplectic manifolds is defined such that the timedependent vector field ξt defined byd/dt(φt-ξtoφT) is a globally hamiltonian vector field for allt, i.e. there exists a smooth real-valued timedependent Hamiltonian functionh(x, t) on X x [0, 1] such thatξt⌋ω=dht, whereht=h(ex,t).
Abstract: Two symplectic diffeomorphisms,φ0,φ1 of a symplectic manifold (X, ω) are said to be homologous if there exists a smooth homotopyφ1,t∋[0, 1] of symplectic diffeomorphisms between them such that the timedependent vector fieldξt defined byd/dt(φt-ξtoφt is a globally hamiltonian vector field for allt, i.e. there exists a smooth real-valued timedependent hamiltonian functionh(x, t) onX x [0, 1] such thatξt⌋ω=dht, whereht=h(x,t).
01 Jan 1985-The South African journal of communication disorders. Die Suid-Afrikaanse tydskrif vir Kommunikasieafwykings
TL;DR: Results suggesting that patient groupings on a newly developed profile for the characterisation of pragmatics could be predicted in terms of severity but not of type of aphasia are suggested.
Abstract: The Profile of Communicative Appropriateness — a newly developed profile for the characterisation of pragmatics is described. The theoretical background to this profile is covered as well as its main components. Its application to a group of eighteen aphasic patients is outlined, results suggesting that patient groupings on the profile could be predicted in terms of severity but not in terms of type of aphasia. Explanations for this finding are discussed and the potential utility of this profile is suggested.
TL;DR: In this article, the authors introduced the concept of a J-symmetric operator, which is defined as a linear operator whose domain is dense in 2 and whose coefficients satisfy the spectral theory of selfadjoint operators.
TL;DR: Limnological principles of the Northern Hemisphere are applicable to aquatic macrophytes in the Southern Hemisphere but there is a particular need for research into the effects of biotic variables and water level fluctuations on aquatic plants and communities in the latter.
Abstract: The term aseasonality is used in this paper to describe environmental conditions which either lack annual seasonal change or have periodicities of change which are longer or shorter than the seasons. Environmental factors act on plants either as stresses or disturbances and changes in environment can signal the onset of conditions which are favourable or unfavourable to plant growth and reproduction. Plant life-histories are thus adapted to these environmental factors and respond to them with both seasonal and aseasonal periodicities, depending on their manner of occurrence and effect on the plants. A review of pertinent studies from the Southern Hemisphere shows that plants of the same life-form (submerged, floating, emergent) might differ in the types of adaptation and response to environmental conditions according to latitude but that the periodicity of response could be seasonal or aseasonal regardless of latitude. The concept of seasonality versus aseasonality is therefore misleading and an oversimplification of the variety of periodicities with which the environment acts on plant genotypes. Limnological principles of the Northern Hemisphere are applicable to aquatic macrophytes in the Southern Hemisphere but there is a particular need for research into the effects of biotic variables and water level fluctuations on aquatic plants and communities in the latter.
TL;DR: Former clinical observations that have linked bulimics with low self-esteem, high anxiety, external locus of control, and a high incidence of maternal and family obesity are confirmed.
Abstract: This study compared (1) purging bulimics (those who terminate binging with self-induced vomiting and/or excessive use of laxatives), N = 26; (2) non-purging bulimics, N = 24; and (3) control subjects (in whom no eating problems were apparent), N = 24. These groups were examined empirically on several personality and demographic variables. Additionally, procedures were taken to control for the effects that being overweight may have had on the personality characteristics, which surprisingly has not been undertaken in previous research on bulimia. The comparison of the bulimics (purging and non-purging bulimics grouped together) with the controls empirically confirmed former clinical observations that have linked bulimics with low self-esteem, high anxiety, external locus of control, and a high incidence of maternal and family obesity. With regard to the comparison between the purging and non-purging bulimics, no significant differences between them appeared on any of the dimensions examined here.
TL;DR: A role for a gene (? oncogene) on chromosome 3q in thrombopoietin production is postulated and abnormalities of 3q may assist in delineating a subgroup of acute nonlymphocytic leukaemia, namely acute megakaryoblasticLeukaemia.
Abstract: Summary. A patient with acute megakaryoblastic leukaemia is described in whom exactly the same paracentric inversion of 3q was detected as in three previously documented cases. The patient's serum thrombopoietin (TSF) was significantly raised. Based on these findings we postulate a role for a gene (? oncogene) on chromosome 3q in thrombopoietin production. Abnormalities of 3q may assist in delineating a subgroup of acute nonlymphocytic leukaemia, namely acute megakaryoblastic leukaemia.